SAM C20/C21 Family Data
Sheet
32-bit ARM Cortex-M0+ with 5V Support, CAN-FD, PTC,
and Advanced Analog
Features
Operating Conditions
• 2.7V – 5.5V, -40°C to +125°C, DC to 48 MHz
Core
• ARM® Cortex®-M0+ CPU running at up to 48 MHz
– Single-cycle hardware multiplier
– Micro Trace Buffer
– Memory Protection Unit (MPU)
Memories
• 32/64/128/256 KB in-system self-programmable Flash
• 1/2/4/8 KB independent self-programmable Flash for EEPROM emulation
• 4/8/16/32 KB SRAM Main Memory
System
• Power-on Reset (POR) and Brown-out Detection (BOD)
• Internal and external clock options with 48 MHz to 96 MHz Fractional Digital Phase Locked Loop
(FDPLL96M)
• External Interrupt Controller (EIC) (Interrupt pin debouncing is only available in SAM C21N)
• 16 external interrupts
– Hardware debouncing (only on the 100Pin TQFP)
• One non-maskable interrupt
• Two-pin Serial Wire Debug (SWD) programming, test, and debugging interface
Low-Power
• Idle and Standby Sleep modes
• SleepWalking peripherals
Peripherals
• Hardware Divide and Square Root Accelerator (DIVAS)
• 12-channel Direct Memory Access Controller (DMAC)
• 12-channel Event System
• Up to eight 16-bit Timer/Counters (TC), configurable as either (see Note):
Note:  Maximum and minimum capture is only available in SAM C21N devices.
– One 16-bit TC with compare/capture channels
– One 8-bit TC with compare/capture channels
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1
– One 32-bit TC with compare/capture channels, by using two TCs
• Two 24-bit Timer/Counters and one 16-bit Timer/Counter for Control (TCC), with extended functions:
– Up to four compare channels with optional complementary output
– Generation of synchronized pulse width modulation (PWM) pattern across port pins
– Deterministic fault protection, fast decay and configurable dead-time between complementary
output
– Dithering that increase resolution with up to 5 bit and reduce quantization error
• Frequency Meter (The division reference clock is only available in the SAM C21N)
• 32-bit Real Time Counter (RTC) with clock/calendar function
• Watchdog Timer (WDT)
• CRC-32 generator
• Up to two Controller Area Network (CAN) interfaces:
– CAN 2.0A/B and CAN-FD (ISO 11898-1:2015)
• Each CAN interface have two selectable pin locations to switch between two external CAN
transceivers (without the need for an external switch)
• Up to eight Serial Communication Interfaces (SERCOM), each configurable to operate as either:
– USART with full-duplex and single-wire half-duplex configuration
– I2C up to 3.4 MHz (Except SERCOM6 and SERCOM7)
– SPI
– LIN master/slave
– RS-485
– PMBus
• One Configurable Custom Logic (CCL)
• Up to Two 12-bit, 1 Msps Analog-to-Digital Converter (ADC) with up to 12 channels each (20 unique
channels)
– Differential and single-ended input
– Automatic offset and gain error compensation
– Oversampling and decimation in hardware to support 13-, 14-, 15- or 16-bit resolution
• One 16-bit Sigma-Delta Analog-to-Digital Converter (SDADC) with up to 3 differential channels
• 10-bit, 350 ksps Digital-to-Analog Converter (DAC)
• Up to four Analog Comparators (AC) with Window Compare function
• Integrated Temperature Sensor
• Peripheral Touch Controller (PTC)
– 256-Channel capacitive touch and proximity sensing
I/O
• Up to 84 programmable I/O pins
Qualification
• AEC-Q100 Grade 1 (-40°C to 125°C)
Packages
• 100-pin TQFP
• 64-pin TQFP, VQFN
• 56-pin WLCSP
SAM C20/C21 Family Data Sheet
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 2
• 48-pin TQFP, VQFN
• 32-pin TQFP, VQFN
General
• Drop in compatible with SAM D20 and SAM D21 (see Note)
Note:  Only applicable for 32-pin, 48-pin, and 64-pin TQFP and VQFN packages.
SAM C20/C21 Family Data Sheet
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Table of Contents
Features.......................................................................................................................... 1
1. Configuration Summary...........................................................................................14
2. Ordering Information................................................................................................19
3. Block Diagram......................................................................................................... 20
4. Pinout...................................................................................................................... 22
4.1. SAM C21E / SAM C20E.............................................................................................................22
4.2. SAM C21G / SAM C20G............................................................................................................ 23
4.3. SAM C21J / SAM C20J.............................................................................................................. 24
4.4. SAM C21N / SAM C20N............................................................................................................ 26
5. Signal Descriptions List........................................................................................... 27
6. I/O Multiplexing and Considerations........................................................................29
6.1. Multiplexed Signals.................................................................................................................... 29
6.2. Other Functions..........................................................................................................................35
7. Power Supply and Start-Up Considerations............................................................ 38
7.1. Power Domain Overview............................................................................................................38
7.2. Power Supply Considerations.................................................................................................... 39
7.3. Power-Up................................................................................................................................... 41
7.4. Power-On Reset and Brown-Out Detector................................................................................. 42
8. Product Mapping..................................................................................................... 43
9. Memories.................................................................................................................47
9.1. Embedded Memories................................................................................................................. 47
9.2. Physical Memory Map................................................................................................................ 47
9.3. NVM User Row Mapping............................................................................................................48
9.4. NVM Software Calibration Area Mapping...................................................................................49
9.5. NVM Temperature Calibration Area Mapping, SAM C21........................................................... 50
9.6. Serial Number............................................................................................................................ 50
10. Processor and Architecture..................................................................................... 52
10.1. Cortex M0+ Processor............................................................................................................... 52
10.2. Nested Vector Interrupt Controller..............................................................................................54
10.3. Micro Trace Buffer......................................................................................................................57
10.4. High-Speed Bus System............................................................................................................ 58
11. PAC - Peripheral Access Controller.........................................................................61
11.1. Overview.................................................................................................................................... 61
11.2. Features..................................................................................................................................... 61
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11.3. Block Diagram............................................................................................................................ 61
11.4. Product Dependencies...............................................................................................................61
11.5. Functional Description................................................................................................................63
11.6. Register Summary......................................................................................................................66
11.7. Register Description................................................................................................................... 67
12. Peripherals Configuration Summary........................................................................87
12.1. SAM C20/C21 N.........................................................................................................................88
12.2. SAM C20/C21 E/G/J.................................................................................................................. 93
13. DSU - Device Service Unit...................................................................................... 97
13.1. Overview.................................................................................................................................... 97
13.2. Features..................................................................................................................................... 97
13.3. Block Diagram............................................................................................................................ 98
13.4. Signal Description...................................................................................................................... 98
13.5. Product Dependencies............................................................................................................... 98
13.6. Debug Operation........................................................................................................................99
13.7. Chip Erase................................................................................................................................101
13.8. Programming............................................................................................................................102
13.9. Intellectual Property Protection................................................................................................ 102
13.10. Device Identification.................................................................................................................104
13.11. Functional Description..............................................................................................................105
13.12. Register Summary....................................................................................................................110
13.13. Register Description................................................................................................................. 112
14. DIVAS – Divide and Square Root Accelerator.......................................................135
14.1. Overview.................................................................................................................................. 135
14.2. Features................................................................................................................................... 135
14.3. Block Diagram.......................................................................................................................... 135
14.4. Signal Description.................................................................................................................... 135
14.5. Product Dependencies.............................................................................................................135
14.6. Functional Description..............................................................................................................136
14.7. Register Summary....................................................................................................................139
14.8. Register Description................................................................................................................. 139
15. Clock System.........................................................................................................147
15.1. Clock Distribution..................................................................................................................... 147
15.2. Synchronous and Asynchronous Clocks..................................................................................148
15.3. Register Synchronization......................................................................................................... 148
15.4. Enabling a Peripheral...............................................................................................................150
15.5. On-demand, Clock Requests................................................................................................... 150
15.6. Power Consumption vs. Speed................................................................................................ 151
15.7. Clocks after Reset.................................................................................................................... 151
16. GCLK - Generic Clock Controller.......................................................................... 152
16.1. Overview.................................................................................................................................. 152
16.2. Features................................................................................................................................... 152
16.3. Block Diagram.......................................................................................................................... 152
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16.4. Signal Description.................................................................................................................... 153
16.5. Product Dependencies.............................................................................................................153
16.6. Functional Description..............................................................................................................154
16.7. Register Summary....................................................................................................................160
16.8. Register Description................................................................................................................. 161
17. MCLK – Main Clock...............................................................................................171
17.1. Overview.................................................................................................................................. 171
17.2. Features................................................................................................................................... 171
17.3. Block Diagram.......................................................................................................................... 171
17.4. Signal Description.................................................................................................................... 171
17.5. Product Dependencies.............................................................................................................171
17.6. Functional Description..............................................................................................................173
17.7. Register Summary....................................................................................................................178
17.8. Register Description................................................................................................................. 178
18. RSTC – Reset Controller.......................................................................................194
18.1. Overview.................................................................................................................................. 194
18.2. Features................................................................................................................................... 194
18.3. Block Diagram.......................................................................................................................... 194
18.4. Signal Description.................................................................................................................... 194
18.5. Product Dependencies............................................................................................................. 194
18.6. Functional Description..............................................................................................................195
18.7. Register Summary....................................................................................................................198
18.8. Register Description................................................................................................................. 198
19. PM – Power Manager............................................................................................200
19.1. Overview.................................................................................................................................. 200
19.2. Features................................................................................................................................... 200
19.3. Block Diagram.......................................................................................................................... 200
19.4. Signal Description.................................................................................................................... 200
19.5. Product Dependencies.............................................................................................................200
19.6. Functional Description..............................................................................................................201
19.7. Register Summary....................................................................................................................205
19.8. Register Description................................................................................................................. 205
20. OSCCTRL – Oscillators Controller........................................................................208
20.1. Overview.................................................................................................................................. 208
20.2. Features................................................................................................................................... 208
20.3. Block Diagram.......................................................................................................................... 209
20.4. Signal Description.................................................................................................................... 209
20.5. Product Dependencies.............................................................................................................209
20.6. Functional Description..............................................................................................................210
20.7. Register Summary....................................................................................................................220
20.8. Register Description................................................................................................................. 221
21. OSC32KCTRL – 32KHz Oscillators Controller......................................................247
21.1. Overview.................................................................................................................................. 247
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21.2. Features................................................................................................................................... 247
21.3. Block Diagram.......................................................................................................................... 248
21.4. Signal Description.................................................................................................................... 248
21.5. Product Dependencies.............................................................................................................248
21.6. Functional Description..............................................................................................................250
21.7. Register Summary....................................................................................................................256
21.8. Register Description................................................................................................................. 256
22. SUPC – Supply Controller.....................................................................................272
22.1. Overview.................................................................................................................................. 272
22.2. Features................................................................................................................................... 272
22.3. Block Diagram.......................................................................................................................... 273
22.4. Signal Description.................................................................................................................... 273
22.5. Product Dependencies.............................................................................................................273
22.6. Functional Description..............................................................................................................274
22.7. Register Summary....................................................................................................................279
22.8. Register Description................................................................................................................. 279
23. WDT – Watchdog Timer........................................................................................ 293
23.1. Overview.................................................................................................................................. 293
23.2. Features................................................................................................................................... 293
23.3. Block Diagram.......................................................................................................................... 294
23.4. Signal Description.................................................................................................................... 294
23.5. Product Dependencies............................................................................................................. 294
23.6. Functional Description..............................................................................................................295
23.7. Register Summary....................................................................................................................301
23.8. Register Description................................................................................................................. 301
24. RTC – Real-Time Counter..................................................................................... 311
24.1. Overview...................................................................................................................................311
24.2. Features................................................................................................................................... 311
24.3. Block Diagram.......................................................................................................................... 311
24.4. Signal Description.................................................................................................................... 312
24.5. Product Dependencies.............................................................................................................312
24.6. Functional Description..............................................................................................................314
24.7. Register Summary - Mode 0 - 32-Bit Counter.......................................................................... 320
24.8. Register Description - Mode 0 - 32-Bit Counter....................................................................... 320
24.9. Register Summary - Mode 1 - 16-Bit Counter.......................................................................... 334
24.10. Register Description - Mode 1 - 16-Bit Counter....................................................................... 334
24.11. Register Summary - Mode 2 - Clock/Calendar.........................................................................349
24.12. Register Description - Mode 2 - Clock/Calendar......................................................................349
25. DMAC – Direct Memory Access Controller........................................................... 364
25.1. Overview.................................................................................................................................. 364
25.2. Features................................................................................................................................... 364
25.3. Block Diagram.......................................................................................................................... 366
25.4. Signal Description.................................................................................................................... 366
25.5. Product Dependencies.............................................................................................................366
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25.6. Functional Description..............................................................................................................367
25.7. Register Summary....................................................................................................................389
25.8. Register Description................................................................................................................. 390
25.9. Register Summary - SRAM...................................................................................................... 423
25.10. Register Description - SRAM................................................................................................... 423
26. EIC – External Interrupt Controller........................................................................ 430
26.1. Overview.................................................................................................................................. 430
26.2. Features................................................................................................................................... 430
26.3. Block Diagram.......................................................................................................................... 430
26.4. Signal Description.................................................................................................................... 431
26.5. Product Dependencies.............................................................................................................431
26.6. Functional Description..............................................................................................................433
26.7. Register Summary....................................................................................................................440
26.8. Register Description................................................................................................................. 441
27. NVMCTRL – Nonvolatile Memory Controller.........................................................456
27.1. Overview.................................................................................................................................. 456
27.2. Features................................................................................................................................... 456
27.3. Block Diagram.......................................................................................................................... 456
27.4. Signal Description.................................................................................................................... 457
27.5. Product Dependencies............................................................................................................. 457
27.6. Functional Description..............................................................................................................458
27.7. Register Summary....................................................................................................................466
27.8. Register Description................................................................................................................. 467
28. PORT - I/O Pin Controller......................................................................................482
28.1. Overview.................................................................................................................................. 482
28.2. Features................................................................................................................................... 482
28.3. Block Diagram.......................................................................................................................... 483
28.4. Signal Description.................................................................................................................... 483
28.5. Product Dependencies.............................................................................................................483
28.6. Functional Description..............................................................................................................485
28.7. Register Summary....................................................................................................................491
28.8. Register Description................................................................................................................. 492
29. EVSYS – Event System........................................................................................ 512
29.1. Overview.................................................................................................................................. 512
29.2. Features................................................................................................................................... 512
29.3. Block Diagram.......................................................................................................................... 512
29.4. Signal Description.................................................................................................................... 513
29.5. Product Dependencies.............................................................................................................513
29.6. Functional Description..............................................................................................................514
29.7. Register Summary....................................................................................................................518
29.8. Register Description................................................................................................................. 520
30. SERCOM – Serial Communication Interface.........................................................537
30.1. Overview.................................................................................................................................. 537
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30.2. Features................................................................................................................................... 537
30.3. Block Diagram.......................................................................................................................... 538
30.4. Signal Description.................................................................................................................... 538
30.5. Product Dependencies.............................................................................................................538
30.6. Functional Description..............................................................................................................540
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and
Transmitter.............................................................................................................546
31.1. Overview.................................................................................................................................. 546
31.2. USART Features...................................................................................................................... 546
31.3. Block Diagram.......................................................................................................................... 547
31.4. Signal Description.................................................................................................................... 547
31.5. Product Dependencies.............................................................................................................547
31.6. Functional Description..............................................................................................................549
31.7. Register Summary....................................................................................................................563
31.8. Register Description................................................................................................................. 564
32. SERCOM SPI – SERCOM Serial Peripheral Interface..........................................587
32.1. Overview.................................................................................................................................. 587
32.2. Features................................................................................................................................... 587
32.3. Block Diagram.......................................................................................................................... 588
32.4. Signal Description.................................................................................................................... 588
32.5. Product Dependencies............................................................................................................. 588
32.6. Functional Description..............................................................................................................590
32.7. Register Summary....................................................................................................................599
32.8. Register Description................................................................................................................. 600
33. SERCOM I2C – Inter-Integrated Circuit.................................................................618
33.1. Overview.................................................................................................................................. 618
33.2. Features................................................................................................................................... 618
33.3. Block Diagram.......................................................................................................................... 619
33.4. Signal Description.................................................................................................................... 619
33.5. Product Dependencies.............................................................................................................619
33.6. Functional Description..............................................................................................................621
33.7. Register Summary - I2C Slave.................................................................................................640
33.8. Register Description - I2C Slave...............................................................................................640
33.9. Register Summary - I2C Master...............................................................................................656
33.10. Register Description - I2C Master............................................................................................ 657
34. CAN - Control Area Network................................................................................. 674
34.1. Overview.................................................................................................................................. 674
34.2. Features................................................................................................................................... 674
34.3. Block Diagram.......................................................................................................................... 675
34.4. Signal Description.................................................................................................................... 675
34.5. Product Dependencies.............................................................................................................675
34.6. Functional Description..............................................................................................................677
34.7. Register Summary....................................................................................................................698
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34.8. Register Description................................................................................................................. 702
34.9. Message RAM..........................................................................................................................771
35. TC – Timer/Counter...............................................................................................781
35.1. Overview.................................................................................................................................. 781
35.2. Features................................................................................................................................... 781
35.3. Block Diagram.......................................................................................................................... 782
35.4. Signal Description.................................................................................................................... 782
35.5. Product Dependencies.............................................................................................................783
35.6. Functional Description..............................................................................................................784
35.7. Register Description................................................................................................................. 800
36. TCC – Timer/Counter for Control Applications...................................................... 869
36.1. Overview.................................................................................................................................. 869
36.2. Features................................................................................................................................... 869
36.3. Block Diagram.......................................................................................................................... 870
36.4. Signal Description.................................................................................................................... 871
36.5. Product Dependencies............................................................................................................. 871
36.6. Functional Description..............................................................................................................873
36.7. Register Summary....................................................................................................................907
36.8. Register Description................................................................................................................. 909
37. CCL – Configurable Custom Logic........................................................................954
37.1. Overview.................................................................................................................................. 954
37.2. Features................................................................................................................................... 954
37.3. Block Diagram.......................................................................................................................... 955
37.4. Signal Description.................................................................................................................... 955
37.5. Product Dependencies.............................................................................................................955
37.6. Functional Description..............................................................................................................957
37.7. Register Summary....................................................................................................................968
37.8. Register Description................................................................................................................. 968
38. ADC – Analog-to-Digital Converter........................................................................973
38.1. Overview.................................................................................................................................. 973
38.2. Features................................................................................................................................... 973
38.3. Block Diagram.......................................................................................................................... 974
38.4. Signal Description.................................................................................................................... 974
38.5. Product Dependencies.............................................................................................................975
38.6. Functional Description..............................................................................................................976
38.7. Register Summary....................................................................................................................991
38.8. Register Description................................................................................................................. 992
39. SDADC – Sigma-Delta Analog-to-Digital Converter............................................1020
39.1. Overview................................................................................................................................ 1020
39.2. Features................................................................................................................................. 1020
39.3. Block Diagram........................................................................................................................ 1021
39.4. Signal Description.................................................................................................................. 1021
39.5. Product Dependencies........................................................................................................... 1022
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39.6. Functional Description............................................................................................................1023
39.7. Register Summary..................................................................................................................1031
39.8. Register Description............................................................................................................... 1032
40. AC – Analog Comparators...................................................................................1057
40.1. Overview................................................................................................................................ 1057
40.2. Features................................................................................................................................. 1057
40.3. Block Diagram........................................................................................................................ 1058
40.4. Signal Description.................................................................................................................. 1059
40.5. Product Dependencies...........................................................................................................1059
40.6. Functional Description............................................................................................................1061
40.7. Register Summary..................................................................................................................1071
40.8. Register Description............................................................................................................... 1071
41. DAC – Digital-to-Analog Converter......................................................................1088
41.1. Overview................................................................................................................................ 1088
41.2. Features................................................................................................................................. 1088
41.3. Block Diagram........................................................................................................................ 1088
41.4. Signal Description.................................................................................................................. 1088
41.5. Product Dependencies...........................................................................................................1088
41.6. Functional Description............................................................................................................1090
41.7. Register Summary..................................................................................................................1095
41.8. Register Description............................................................................................................... 1095
42. Peripheral Touch Controller (PTC).......................................................................1108
42.1. Overview.................................................................................................................................1108
42.2. Features................................................................................................................................. 1108
42.3. Block Diagram........................................................................................................................ 1108
42.4. Signal Description...................................................................................................................1109
42.5. System Dependencies............................................................................................................1109
42.6. Functional Description.............................................................................................................1111
43. TSENS – Temperature Sensor.............................................................................1112
43.1. Overview.................................................................................................................................1112
43.2. Features..................................................................................................................................1112
43.3. Block Diagram.........................................................................................................................1112
43.4. Signal Description...................................................................................................................1112
43.5. Product Dependencies............................................................................................................1113
43.6. Functional Description............................................................................................................ 1114
43.7. Register Summary.................................................................................................................. 1118
43.8. Register Description................................................................................................................1118
44. FREQM – Frequency Meter.................................................................................1137
44.1. Overview.................................................................................................................................1137
44.2. Features................................................................................................................................. 1137
44.3. Block Diagram........................................................................................................................ 1137
44.4. Signal Description...................................................................................................................1137
44.5. Product Dependencies........................................................................................................... 1137
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44.6. Functional Description............................................................................................................ 1139
44.7. Register Summary..................................................................................................................1142
44.8. Register Description............................................................................................................... 1142
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)........................................ 1152
45.1. Disclaimer...............................................................................................................................1152
45.2. Absolute Maximum Ratings....................................................................................................1152
45.3. General Operating Ratings.....................................................................................................1152
45.4. Injection Current..................................................................................................................... 1153
45.5. Supply Characteristics............................................................................................................1154
45.6. Maximum Clock Frequencies................................................................................................. 1155
45.7. Power Consumption............................................................................................................... 1156
45.8. Wake-Up Time........................................................................................................................1158
45.9. I/O Pin Characteristics............................................................................................................1158
45.10. Analog Characteristics........................................................................................................... 1159
45.11. NVM Characteristics...............................................................................................................1177
45.12. Oscillator Characteristics........................................................................................................1178
45.13. Timing Characteristics............................................................................................................1186
46. Electrical Characteristics 105°C (SAM C20/C21 E/G/J)......................................1190
46.1. Disclaimer...............................................................................................................................1190
46.2. General Operating Ratings.....................................................................................................1190
46.3. Power Consumption............................................................................................................... 1190
46.4. Analog Characteristics............................................................................................................1191
46.5. NVM Characteristics...............................................................................................................1196
46.6. Oscillator Characteristics........................................................................................................1197
47. Electrical Characteristics 105°C (SAM C20/C21 N)............................................ 1200
47.1. Disclaimer...............................................................................................................................1200
47.2. General Operating Ratings.....................................................................................................1200
47.3. Power Consumption............................................................................................................... 1201
47.4. Analog Characteristics........................................................................................................... 1202
47.5. NVM Characteristics...............................................................................................................1212
47.6. Oscillator Characteristics........................................................................................................1212
48. AEC Q-100 Grade 1, 125°C Electrical Characteristics (SAM C20/C21 E/G/J)... 1217
48.1. Electrical Characteristics at 125°C Disclaimer....................................................................... 1217
48.2. General Operating Ratings.....................................................................................................1217
48.3. Supply Characteristics............................................................................................................1217
48.4. Power Consumption............................................................................................................... 1217
48.5. I/O Pin Characteristics............................................................................................................1220
48.6. Analog Characteristics........................................................................................................... 1220
48.7. NVM Characteristics...............................................................................................................1231
48.8. Oscillator Characteristics........................................................................................................1232
48.9. Timing Characteristics............................................................................................................1236
49. Packaging Information.........................................................................................1238
49.1. Package Marking Information.................................................................................................1238
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49.2. Thermal Considerations......................................................................................................... 1242
49.3. Package Drawings................................................................................................................. 1243
49.4. Soldering Profile.....................................................................................................................1265
50. Schematic Checklist............................................................................................ 1266
50.1. Introduction.............................................................................................................................1266
50.2. Operation in Noisy Environment.............................................................................................1266
50.3. Power Supply......................................................................................................................... 1266
50.4. External Analog Reference Connections............................................................................... 1268
50.5. External Reset Circuit.............................................................................................................1270
50.6. Unused or Unconnected Pins.................................................................................................1270
50.7. Clocks and Crystal Oscillators................................................................................................1271
50.8. Programming and Debug Ports..............................................................................................1274
51. Revision History...................................................................................................1278
51.1. Revision C - 01/2019..............................................................................................................1278
51.2. Revision B - 06/2017 .............................................................................................................1279
51.3. Revision A - 03/2017..............................................................................................................1279
51.4. Rev KJ - 11/2016....................................................................................................................1280
51.5. Rev J - 10/2016......................................................................................................................1280
51.6. Rev I - 09/2016.......................................................................................................................1280
51.7. Rev H - 05/2016..................................................................................................................... 1283
51.8. Rev G - 04/2015.....................................................................................................................1283
51.9. Rev F - 02/2015......................................................................................................................1285
51.10. Rev E - 12/2015..................................................................................................................... 1286
51.11. Rev D - 09/2015..................................................................................................................... 1287
51.12. Rev C - 09/2015.....................................................................................................................1287
51.13. Rev B - 06/2015..................................................................................................................... 1287
51.14. Rev A - 04/2015..................................................................................................................... 1288
The Microchip Web Site............................................................................................ 1289
Customer Change Notification Service......................................................................1289
Customer Support..................................................................................................... 1289
Product Identification System....................................................................................1290
Microchip Devices Code Protection Feature............................................................. 1290
Legal Notice...............................................................................................................1291
Trademarks............................................................................................................... 1291
Quality Management System Certified by DNV.........................................................1292
Worldwide Sales and Service....................................................................................1293
SAM C20/C21 Family Data Sheet
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1. Configuration Summary
Table 1-1. SAM C20 Device-specific Features
Device Flash (KB) SRAM (KB)
ATSAMC20E15 32 4
ATSAMC20E16 64 8
ATSAMC20E17 128 16
ATSAMC20E18 256 32
ATSAMC20G15 32 4
ATSAMC20G16 64 8
ATSAMC20G17 128 16
ATSAMC20G18 256 32
ATSAMC20J15 32 4
ATSAMC20J16 64 8
ATSAMC20J17 128 16
ATSAMC20J18 256 32
ATSAMC20N17 128 16
ATSAMC20N18 256 32
Table 1-2. SAM C21 Device-specific Features
Device Flash (KB) SRAM (KB)
ATSAMC21E15 32 4
ATSAMC21E16 64 8
ATSAMC21E17 128 16
ATSAMC21E18 256 32
ATSAMC21G15 32 4
ATSAMC21G16 64 8
ATSAMC21G17 128 16
ATSAMC21G18 256 32
ATSAMC21J15 32 4
ATSAMC21J16 64 8
ATSAMC21J17 128 16
ATSAMC21J18 256 32
ATSAMC21N17 128 16
SAM C20/C21 Family Data Sheet
Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 14
...........continued
Device Flash (KB) SRAM (KB)
ATSAMC21N18 256 32
Table 1-3. SAM C21 Family Features
SAM C21N SAM C21J SAM C21G SAM C21E
Pins 100 64 (56 for WLCSP) 48 32
General Purpose I/O-pins
(GPIOs)
84 52 (44 for WLCSP) 38 26
Flash 256/128 KB 256/128/64/32 KB 256/128/64/32 KB 256/128/64/32 KB
Flash RWW section 8/4 KB 8/4/2/1 KB 8/4/2/1 KB 8/4/2/1 KB
System SRAM 32/16 KB 32/16/8/4 KB 32/16/8/4 KB 32/16/8/4 KB
Timer Counter (TC) instances 8 5 5 5
Waveform output channels per
TC instance
2 2 2 2
TC Maximum and Minimum
Capture
Yes No No No
Timer Counter for Control (TCC)
instances
3 3 3 3
Waveform output channels per
TCC
8/4/2 8/4/2 8/4/2 6/4/2
DMA channels 12 12 12 12
CAN interface 2 2 2 1
Configurable Custom Logic
(CCL) (LUTs)
4 4 4 4
Serial Communication Interface
(SERCOM) instances
8 6 6 4
Divide and Square Root
Accelerator (DIVAS)
Yes Yes Yes Yes
Analog-to-Digital Converter
(ADC) channels
20 20 14 10
Analog-to-Digital Converter
(ADC) instances
2 2 2 2
Sigma-Delta Analog-to-Digital
Converter (SDADC) channels
3 3 2 1
Analog Comparators (AC) 4 4 4 4
Digital-to-Analog Converter
(DAC) channels
1 1 1 1
SAM C20/C21 Family Data Sheet
Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 15
...........continued
SAM C21N SAM C21J SAM C21G SAM C21E
Temperature Sensor (TSENS)(1) 1 1 1 1
Real-Time Counter (RTC) Yes Yes Yes Yes
RTC alarms 1 1 1 1
RTC compare values One 32-bit value or
two 16-bit values
One 32-bit value or
two 16-bit values
One 32-bit value or
two 16-bit values
One 32-bit value or
two 16-bit values
External Interrupt lines 16 with HW
debouncing
16 16 16
Peripheral Touch Controller
(PTC)
Number of self-capacitance
channels (Y-lines)
32 32 22 16
Peripheral Touch Controller
(PTC)
Number of mutual-capacitance
channels (X x Y lines)
256 (16x16) 256 (16x16) 121 (11x11) 64 (8x8)
Frequency Meter (FREQM)
reference clock divider
Yes Yes Yes Yes
Maximum CPU frequency 48 MHz
Packages TQFP VQFN
TQFP
WLCSP
VQFN
TQFP
VQFN
TQFP
Oscillators 32.768 kHz crystal oscillator (XOSC32K)
0.4-32 MHz crystal oscillator (XOSC)
32.768 kHz internal oscillator (OSC32K)
32 kHz ultra low-power internal oscillator (OSCULP32K)
48 MHz high-accuracy internal oscillator (OSC48M)
96 MHz Fractional Digital Phased Locked Loop (FDPLL96M)
Event System channels 12 12 12 12
SW Debug Interface Yes Yes Yes Yes
Watchdog Timer (WDT) Yes Yes Yes Yes
Note: 
1. TSENS is not available in AEC Q-100 qualified device part numbers.
SAM C20/C21 Family Data Sheet
Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 16
Table 1-4. SAM C20 Family Features
SAM C20N SAM C20J SAM C20G SAM C20E
Pins 100 64 (56 for WLCSP) 48 (44 for WLCSP) 32
General Purpose I/O-pins
(GPIOs)
84 52 38 26
Flash 256/128 KB 256/128/64/32 KB 256/128/64/32 KB 256/128/64/32 KB
Flash RWW section 8/4 KB 8/4/2/1 KB 8/4/2/1 KB 8/4/2/1 KB
System SRAM 32/16 KB 32/16/8/4 KB 32/16/8/4 KB 32/16/8/4 KB
Timer Counter (TC) instances 8 5 5 5
Waveform output channels per
TC instance
2 2 2 2
TC Maximum and Minimum
Capture
Yes No No No
Timer Counter for Control (TCC)
instances
3 3 3 3
Waveform output channels per
TCC
8/4/2 8/4/2 8/4/2 6/4/2
DMA channels 12 6 6 6
Configurable Custom Logic
(CCL) (LUTs)
4 4 4 4
Serial Communication Interface
(SERCOM) instances
8 4 4 4
Divide and Square Root
Accelerator (DIVAS)
Yes Yes Yes Yes
Analog-to-Digital Converter
(ADC) channels
12 12 12 10
Analog-to-Digital Converter
(ADC) instances
1 1 1 1
Analog Comparators (AC) 4 2 2 2
Real-Time Counter (RTC) Yes Yes Yes Yes
RTC alarms 1 1 1 1
RTC compare values One 32-bit value or
two 16-bit values
One 32-bit value or
two 16-bit values
One 32-bit value or
two 16-bit values
One 32-bit value or
two 16-bit values
External Interrupt lines 16 with HW debouncing 16 16 16
SAM C20/C21 Family Data Sheet
Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 17
...........continued
SAM C20N SAM C20J SAM C20G SAM C20E
Peripheral Touch Controller
(PTC)
Number of self-capacitance
channels (Y-lines)
32 32 22 16
Peripheral Touch Controller
(PTC)
Number of mutual-capacitance
channels (X x Y lines)
256 (16x16) 256 (16x16) 120 (12x10) 60 (10x6)
Frequency Meter (FREQM)
reference clock divider
Yes Yes Yes Yes
Maximum CPU frequency 48 MHz
Packages TQFP VQFN
TQFP
WLCSP
VQFN
TQFP
VQFN
TQFP
Oscillators 32.768 kHz crystal oscillator (XOSC32K)
0.4-32 MHz crystal oscillator (XOSC)
32.768 kHz internal oscillator (OSC32K)
32 kHz ultra low-power internal oscillator (OSCULP32K)
48 MHz high-accuracy internal oscillator (OSC48M)
96 MHz Fractional Digital Phased Locked Loop (FDPLL96M)
Event System channels 6 6 6 6
SW Debug Interface Yes Yes Yes Yes
Watchdog Timer (WDT) Yes Yes Yes Yes
Related Links
6. I/O Multiplexing and Considerations
SAM C20/C21 Family Data Sheet
Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 18
2. Ordering Information
ATSAMC 21 N 18 A - M U T
Product Family
E = 32 Pins
G = 48 Pins
J = 64 Pins
N = 100 Pins
No character = Tray (Default)
T = Tape and Reel
U = -40 - 85°C Matte Sn Plating
N = -40 - 105°C Matte Sn Plating
Z = -40°C - 125°C Matte Sn
Plating (AEC-Q100 Qualified)
A = TQFP
M = VQFN
U = WLCSP
21 = Cortex M0+ CPU, DMA, CAN,
16-bit SDADC
SAMC = 5V Microcontroller
Product Series
Flash Memory Density
Device Variant
A = Default Variant
Pin Count
Package Carrier
Package Grade
Package Type
18 = 256KB
17 = 128KB
16 = 64KB
15 = 32KB
20 = Cortex M0+ CPU, DMA
(3)
(4)(5)
Note: 
1. Not all combinations are valid. The available ordering numbers are listed in the Configuration
Summary.
2. SAM C2xN product is available only for the 105°C temperature grade.
3. The AEC-Q100 Grade 1 qualified version is only offered for SAM C20/C21 E/G/J in the TQFP and
VQFN packages. The VQFN package will have wettable flanks, and both TQFP and VQFN
packages are assembled with gold bond wires.
4. Devices in the WLCSP package include a factory programmed Bootloader. Please contact your
local Microchip sales office for more information.
5. The WLCSP package type is available only with the package Grade U.
SAM C20/C21 Family Data Sheet
Ordering Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 19
3. Block Diagram
Figure 3-1. System Block Diagram for SAM C20/C21
6 x SERCOM
8 x Timer Counter
AHB-APB
BRIDGE C
M
M
HIGH SPEED
BUS MATRIX
PORT
PORT
SERIAL
WIRE
SWDIO
S
CORTEX-M0+
PROCESSOR
Fmax 48 MHz
SWCLK
DEVICE
SERVICE
UNIT
AHB-APB
BRIDGE A
2x 12-CHANNEL
12-bit ADC 1MSPS
AIN[11..0]
VREFA
AIN[7..0]
S
SRAM
CONTROLLER
32/16KB
RAM
M
5x TIMER / COUNTER
EVENT SYSTEM
S
6x SERCOM
4 ANALOG
COMPARATORS
X[15..0]
Y[15..0]
PERIPHERAL
TOUCH
CONTROLLER
AHB-APB
BRIDGE B
VREFA
VOUT
10-bit DAC
PERIPHERAL
ACCESS CONTROLLER
S
PAD0
WO1
PAD1
PAD2
PAD3
WO0
256/128KB
RWW
NVM
NVM
CONTROLLER
Cache
M
DMA
2x CAN
3x TIMER / COUNTER
FOR CONTROL
WOn
IOBUS
DMA
DMA
DMA
DMA
DMA
MICRO
TRACE BUFFER
S
WO0
WO1
TxD
RxD
3-CHANNEL
16-bit SDADC 3KSPS
AIN[5..0]
VREFB
DMA
REAL TIME
COUNTER
WATCHDOG
TIMER
RESETN
OSCILLATORS CONTROLLER
XOUT
XIN
XOUT32
XIN32
OSCULP32K
OSC32K
OSC48M
XOSC32K
XOSC
EXTERNAL INTERRUPT
CONTROLLER
MAIN CLOCKS
CONTROLLER
EXTINT[15..0]
NMI
GCLK_IO[7..0]
FDPLL96M
GENERIC CLOCK
CONTROLLER
POWER
MANAGER
RESET
CONTROLLER
OSC32K CONTROLLER
SUPPLY CONTROLLER
VREF
BOD55
VREG
DivideAccellerator S
DMA
TEMPERATURE
SENSOR
FREQUENCY
METER
6 x SERCOM
3x TIMER / COUNTER
2x SERCOM
PAD0
WO1
PAD1
PAD2
PAD3
WO0
DMA
DMA
AHB-APB
BRIDGE D
S
3.3V VREG
SAM C20/C21 Family Data Sheet
Block Diagram
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 20
Note:  Not all features are available for all devices. Please refer to Table 1-3 and Table 1-4 to determine
feature availability for the particular device.
Related Links
6.2.5 TCC Configurations
6.1 Multiplexed Signals
SAM C20/C21 Family Data Sheet
Block Diagram
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 21
4. Pinout
4.1 SAM C21E / SAM C20E
4.1.1 VQFN32/TQFP32
PA00 1
PA01 2
PA02 3
PA03 4
PA04 5
PA05 6
PA06 7
PA07 8
VDDANA 9
GND 10
PA08 11
PA09 12
PA10 13
PA11 14
PA14 15
PA15 16
PA25
24
PA24
23
PA23
22
PA22
21
PA19
20
PA18
19
PA17
18
PA16
17
PA27
25
RESETN
26
PA28
27
GND
28
VDDCORE
29
VDDIN
30
PA30
31
PA31
32
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
SAM C20/C21 Family Data Sheet
Pinout
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 22
4.2 SAM C21G / SAM C20G
4.2.1 VQFN48 / TQFP48
PA21
PA00 1
PA01 2
PA02 3
PA03 4
GNDANA 5
VDDANA 6
PB08 7
PB09 8
PA04 9
PA05 10
PA06 11
PA07 12
PA08 13
PA09 14
PA10 15
PA11 16
VDDIO 17
GND 18
PB10 19
PB11 20
PA12 21
PA13 22
PA14 23
PA15 24
VDDIO36
GND35
PA2534
PA2433
PA2332
PA2231
30
PA2029
PA1928
PA1827
PA1726
PA1625
PB22
37
PB23
38
PA27
39
RESETN
40
PA28
41
GND
42
VDDCORE
43
VDDIN
44
PA30
45
PA31
46
PB02
47
PB03
48
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
SAM C20/C21 Family Data Sheet
Pinout
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 23
4.3 SAM C21J / SAM C20J
4.3.1 VQFN64/TQFP64
PA00 1
PA01 2
PA02 3
PA03 4
PB04 5
PB05 6
GNDANA 7
VDDANA 8
PB06 9
PB07 10
PB08 11
PB09 12
PA04 13
PA05 14
PA06 15
PA07 16
PA08 17
PA09 18
PA10 19
PA11 20
VDDIO 21
GND 22
PB10 23
PB11
24
PB12 25
PB13 26
PB14 27
PB15 28
PA12 29
PA13 30
PA14 31
PA15 32
VDDIO48
GND47
PA2546
PA2445
PA2344
PA2243
PA2142
PA2041
PB1740
PB1639
PA1938
PA1837
PA1736
PA1635
VDDIO34
GND33
PB22
49
PB23
50
PA27
51
RESETN
52
PA28
53
GND
54
VDDCORE
55
VDDIN
56
PA30
57
PA31
58
PB30
59
PB31
60
PB00
61
PB01
62
PB02
63
PB03
64
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
SAM C20/C21 Family Data Sheet
Pinout
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 24
4.3.2 WLCSP56
1
2
3
4
5
6
7
ABCDEFGH
PA00
PA01
PA03
PB08
PB09
PA04
PA06
PB01
PB02
PA02
PA09
PA05
PA07
PA08
PA31
PB00
PB03
VDDANA
VDDIO
PA10
PA11
PA30
VDDIN
GNDANA
GND
PB12
PB11
PB10
VDDCORE
GND
VDDIO
GND
PB15
PB14
PB13
PA28
PA23
VDDIO
GND
PA13
PA12
PB23
PA27
PA24
PA20
PA18
PA14
PA15
PB22
PA25
PA22
PA21
PA19
PA17
PA16
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
RESETN
SAM C20/C21 Family Data Sheet
Pinout
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 25
4.4 SAM C21N / SAM C20N
4.4.1 TQFP100
1
2
3
4
44
43
42
41
40
39
38
5
6
7
8
9
10
11
33
32
31
30
29
28
27
26
25
24
23
37
36
35
34
12
13
14
15
16
17
18
19
20
21
22
45
46
47
48
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
70
69
68
67
66
65
74
73
72
71
75
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
RESETN
VDDIN
GND
PA28
VDDIO
GND
VDDANA
PB01
PB00
PB03
PB02
PB30
PB31
PC05
PA07
PA06
PA04
PA05
PB08
PB09
PA12
PA13
PA14
PA15
PC08
PC09
PC12
PC13
PC10
PC11
PB25
PB24
PC07
PB23
PB22
PA01
PA00
PC26
PC24
PC25
PC06
PC27
PA31
PA30
VDDCORE
PA27
PA08
PA09
PA10
PA11
PA16
PA17
PA18
PA19
VDDIO
PA24
PA25
PA21
PA22
PA20
PA23
PB18
PB19
PB16
PB17
PC21
PC20
PC18
PC19
PC17
PC16
PC14
PB12
PB11
PB10
PC15
PB15
PB13
PB14
GND
VDDIO
VDDIO
GND
PB05
PB04
PA02
PA03
PB07
PB06
PC02
PC03
PC01
PC00
GND
VDDIO
PC28
GND
PB20
GND
PB21
DIGITAL PIN
ANALOG PIN
OSCILLATOR
GROUND
INPUT SUPPLY
REGULATED OUTPUT SUPPLY
RESET PIN
SAM C20/C21 Family Data Sheet
Pinout
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 26
5. Signal Descriptions List
The following tables provide the details on signal names classified by peripheral.
Table 5-1. Signal Descriptions List - SAM C20/C21
Signal Name Function Type Active Level
Analog Comparators - AC
AIN[7:0] AC Analog Inputs Analog
CMP[2:0] AC Comparator Outputs Digital
Analog Digital Converter - ADCx
AIN[19:0] ADC Analog Inputs Analog
VREFA ADC Voltage External Reference A Analog
Digital Analog Converter - DAC
VOUT[1:0] DAC Voltage output Analog
VREFA DAC Voltage External Reference Analog
Sigma-Delta Analog Digital Converter - SDADC
INN[2:0] SDADC Analog Negative Inputs Analog
INP[2:0] SDADC Analog Positive Inputs Analog
VREFB SDADC Voltage External Reference B Analog
External Interrupt Controller - EIC
EXTINT[15:0] External Interrupts inputs Digital
NMI External Non-Maskable Interrupt input Digital
Generic Clock Generator - GCLK
GCLK_IO[7:0] Generic Clock (source clock inputs or generic clock generator
output)
Digital
Custom Control Logic - CCL
IN[11:0] Logic Inputs Digital
OUT[3:0] Logic Outputs Digital
Power Manager - PM
RESETN Reset input Digital Low
Serial Communication Interface - SERCOMx
PAD[3:0] SERCOM Inputs/Outputs Pads Digital
Oscillators Control - OSCCTRL
XIN Crystal or external clock Input Analog/Digital
XOUT Crystal Output Analog
32 kHz Oscillators Control - OSC32KCTRL
XIN32 32 kHz Crystal or external clock Input Analog/Digital
XOUT32 32 kHz Crystal Output Analog
Timer Counter - TCx
SAM C20/C21 Family Data Sheet
Signal Descriptions List
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 27
...........continued
Signal Name Function Type Active Level
WO[1:0] Waveform Outputs Digital
Timer Counter - TCCx
WO[1:0] Waveform Outputs Digital
Peripheral Touch Controller - PTC
X[15:0] PTC Input Analog
Y[15:0] PTC Input Analog
General Purpose I/O - PORT
PA25 - PA00 Parallel I/O Controller I/O Port A Digital
PA28 - PA27 Parallel I/O Controller I/O Port A Digital
PA31 - PA30 Parallel I/O Controller I/O Port A Digital
PB17 - PB00 Parallel I/O Controller I/O Port B Digital
PB21 - PB19 Parallel I/O Controller I/O Port B Digital
PB25 - PB22 Parallel I/O Controller I/O Port B Digital
PB31 - PB30 Parallel I/O Controller I/O Port B Digital
PC03 - PC-00 Parallel I/O Controller I/O Port C Digital
PC21 - PC05 Parallel I/O Controller I/O Port C Digital
PC28 - PC24 Parallel I/O Controller I/O Port C Digital
Controller Area Network - CAN
TX CAN Transmit Line Digital
RX CAN Receive Line Digital
SAM C20/C21 Family Data Sheet
Signal Descriptions List
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 28
6. I/O Multiplexing and Considerations
6.1 Multiplexed Signals
Each pin is by default controlled by the PORT as a general purpose I/O, and alternatively it can be
assigned to one of the peripheral functions, such as A, B, C, D, E, F, G, H, or I. To enable a peripheral
function on a pin, the Peripheral Multiplexer Enable bit in the Pin Configuration register corresponding to
that pin (PINCFGn.PMUXEN, n = 0-31) in the PORT must be written to one. The selection of peripheral
function A to H is done by writing to the Peripheral Multiplexing Odd and Even bits in the Peripheral
Multiplexing register (PMUXn.PMUXE/O) in the PORT.
Table 6-1. PORT Function Multiplexing for SAM C21 N
Pin I/O Pin Supply A B B(1,2) C D E F G H I
EIC REF ADC0 ADC1 SDADC AC PTC DAC SERCOM SERCOM-ALT TC TCC COM AC/GCLK CCL
1 PA00 VDDANA EXTINT[0] SERCOM1/PAD[0] TC2/WO[0] CMP[2]
2 PA01 VDDANA EXTINT[1] SERCOM1/PAD[1] TC2/WO[1] CMP[3]
3 PC00 VDDANA EXTINT[8] AIN[8]
4 PC01 VDDANA EXTINT[9] AIN[9]
5 PC02 VDDANA EXTINT[10] AIN[10]
6 PC03 VDDIO EXTINT[11] AIN[11] SERCOM7/PAD[0] TCC2/WO[0]
7 PA02 VDDANA EXTINT[2] AIN[0] AIN[4] Y[0] VOUT
8 PA03 VDDANA EXTINT[3] ADC/VREFA
DAC/VREFB
AIN[1] Y[1]
9 PB04 VDDANA EXTINT[4] AIN[6] AIN[5] Y[10]
10 PB05 VDDANA EXTINT[5] AIN[7] AIN[6] Y[11]
13 PB06 VDDIO EXTINT[6] AIN[8] INN[2] AIN[7] Y[12] SERCOM7/PAD[1] CCL2/IN[6]
14 PB07 VDDIO EXTINT[7] AIN[9] INP[2] Y[13] SERCOM7/PAD[3] SERCOM7/PAD[2] CCL2/IN[7]
15 PB08 VDDIO EXTINT[8] AIN[2] AIN[4] INN[1] Y[14] SERCOM7/PAD[2] SERCOM7/PAD[3] TC4/WO[0] CCL2/IN[8]
16 PB09 VDDANA EXTINT[9] AIN[3] AIN[5] INP[1] Y[15] SERCOM4/PAD[1] TC4/WO[1] CCL2/OUT[2]
17 PA04 VDDANA EXTINT[4] SDADC/VREFB AIN[4] AIN[0] Y[2] SERCOM0/PAD[0] TC0/WO[0] CCL0/IN[0]
18 PA05 VDDANA EXTINT[5] AIN[5] AIN[1] Y[3] SERCOM0/PAD[1] TC0/WO[1] CCL0/IN[1]
19 PA06 VDDANA EXTINT[6] AIN[6] INN[0] AIN[2] Y[4] SERCOM0/PAD[2] TC1/WO[0] CCL0/IN[2]
20 PA07 VDDANA EXTINT[7] AIN[7] INP[0] AIN[3] Y[5] SERCOM0/PAD[3] TC1/WO[1] CCL0/OUT[0]
21 PC05 VDDANA EXTINT[13] SERCOM6/PAD[3] TCC2/WO[1]
22 PC06 VDDANA EXTINT[14] SERCOM6/PAD[0]
23 PC07 VDDANA EXTINT[15] SERCOM6/PAD[1]
26 PA08 VDDIO NMI AIN[10] X[0]/Y[16] SERCOM0/PAD[0] SERCOM2/PAD[0] TC0/WO[0] TCC0/WO[0] CCL1/IN[3]
27 PA09 VDDIO EXTINT[9] AIN[11] X[1]/Y[17] SERCOM0/PAD[1] SERCOM2/PAD[1] TC0/WO[1] TCC0/WO[1] CCL1/IN[4]
28 PA10 VDDIO EXTINT[10] X[2]/Y[18] SERCOM0/PAD[2] SERCOM2/PAD[2] TC1/WO[0] TCC0/WO[2] GCLK_IO[4] CCL1/IN[5]
29 PA11 VDDIO EXTINT[11] X[3]/Y[19] SERCOM0/PAD[3] SERCOM2/PAD[3] TC1/WO[1] TCC0/WO[3] GCLK_IO[5] CCL1/OUT[1]
30 PB10 VDDIO EXTINT[10] SERCOM4/PAD[2] TC5/WO[0] TCC0_WO4 GCLK_IO[4] CCL1/IN[5]
31 PB11 VDDIO EXTINT[11] SERCOM4/PAD[3] TC5/WO[1] TCC0_WO5 GCLK_IO[5] CCL1/OUT[1]
32 PB12 VDDIO EXTINT[12] X[12]/Y[28] SERCOM4/PAD[0] TC4/WO[0] TCC0_WO6 CAN1/TX GCLK_IO[6]
33 PB13 VDDIO EXTINT[13] X[13]/Y[29] SERCOM4/PAD[1] TC4/WO[1] TCC0_WO7 CAN1/RX GCLK_IO[7]
34 PB14 VDDIO EXTINT[14] X[14]/Y[30] SERCOM4/PAD[2] TC5/WO[0] CAN1/TX GCLK_IO[0] CCL3/IN[9]
35 PB15 VDDIO EXTINT[15] X[15]/Y[31] SERCOM4/PAD[3] TC5/WO[1] CAN1/RX GCLK_IO[1] CCL3/IN[10]
38 PC08 VDDIO EXTINT[0] SERCOM6/PAD[0] SERCOM7/PAD[0]
39 PC09 VDDIO EXTINT[1] SERCOM6/PAD[1] SERCOM7/PAD[1]
40 PC10 VDDIO EXTINT[2] SERCOM6/PAD[2] SERCOM7/PAD[2]
41 PC11 VDDIO EXTINT[3] SERCOM6/PAD[3] SERCOM7/PAD[3]
42 PC12 VDDIO EXTINT[4] SERCOM7/PAD[0]
43 PC13 VDDIO EXTINT[5] SERCOM7/PAD[1]
44 PC14 VDDIO EXTINT[6] SERCOM7/PAD[2]
45 PC15 VDDIO EXTINT[7] SERCOM7/PAD[3]
46 PA12 VDDIO EXTINT[12] SERCOM2/PAD[0] SERCOM4/PAD[0] TC2/WO[0] TCC0_WO6 CMP[0]
47 PA13 VDDIO EXTINT[13] SERCOM2/PAD[1] SERCOM4/PAD[1] TC2/WO[1] TCC0_WO7 CMP[1]
48 PA14 VDDIO EXTINT[14] SERCOM2/PAD[2] SERCOM4/PAD[2] TC3/WO[0] GCLK_IO[0]
49 PA15 VDDIO EXTINT[15] SERCOM2/PAD[3] SERCOM4/PAD[3] TC3/WO[1] GCLK_IO[1]
52 PA16 VDDIO EXTINT[0] X[4]/Y[20] SERCOM1/PAD[0] SERCOM3/PAD[0] TC2/WO[0] TCC1/WO[0] GCLK_IO[2] CCL0/IN[0]
53 PA17 VDDIO EXTINT[1] X[5]/Y[21] SERCOM1/PAD[1] SERCOM3/PAD[1] TC2/WO[1] TCC1/WO[1] GCLK_IO[3] CCL0/IN[1]
54 PA18 VDDIO EXTINT[2] X[6]/Y[22] SERCOM1/PAD[2] SERCOM3/PAD[2] TC3/WO[0] TCC1/WO[2] CMP[0] CCL0/IN[2]
55 PA19 VDDIO EXTINT[3] X[7]/Y[23] SERCOM1/PAD[3] SERCOM3/PAD[3] TC3/WO[1] TCC1/WO[3] CMP[1] CCL0/OUT[0]
56 PC16 VDDIO EXTINT[8] SERCOM6/PAD[0]
57 PC17 VDDIO EXTINT[9] SERCOM6/PAD[1]
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 29
...........continued
Pin I/O Pin Supply A B B(1,2) C D E F G H I
EIC REF ADC0 ADC1 SDADC AC PTC DAC SERCOM SERCOM-ALT TC TCC COM AC/GCLK CCL
58 PC18 VDDIO EXTINT[10] SERCOM6/PAD[2]
59 PC19 VDDIO EXTINT[11] SERCOM6/PAD[3]
60 PC20 VDDIO EXTINT[12] CCL3/IN[9]
61 PC21 VDDIO EXTINT[13] CCL3/IN[10]
64 PB16 VDDIO EXTINT[0] SERCOM5/PAD[0] TC6/WO[0] GCLK_IO[2] CCL3/IN[11]
65 PB17 VDDIO EXTINT[1] SERCOM5/PAD[1] TC6/WO[1] GCLK_IO[3] CCL3/OUT[3]
66 PB18 VDDIO EXTINT[2] SERCOM5/PAD[2] SERCOM3/PAD[2] GCLK_IO[4]
67 PB19 VDDIO EXTINT[3] SERCOM5/PAD[3] SERCOM3/PAD[3] GCLK_IO[5]
68 PB20 VDDIO EXTINT[4] SERCOM3/PAD[0] SERCOM2/PAD[0] GCLK_IO[6]
69 PB21 VDDIO EXTINT[5] SERCOM3/PAD[1] SERCOM2/PAD[1] GCLK_IO[7]
70 PA20 VDDIO EXTINT[4] X[8]/Y[24] SERCOM5/PAD[2] SERCOM3/PAD[2] TC7/WO[0] TCC2/WO[0] GCLK_IO[4]
71 PA21 VDDIO EXTINT[5] X[9]/Y[25] SERCOM5/PAD[3] SERCOM3/PAD[3] TC7/WO[1] TCC2/WO[1] GCLK_IO[5]
72 PA22 VDDIO EXTINT[6] X[10]/Y[26] SERCOM3/PAD[0] SERCOM5/PAD[0] TC4/WO[0] TCC1/WO[0] CAN0/TX GCLK_IO[6] CCL2/IN[6]
73 PA23 VDDIO EXTINT[7] X[11]/Y[27] SERCOM3/PAD[1] SERCOM5/PAD[1] TC4/WO[1] TCC1/WO[1] CAN0/RX GCLK_IO[7] CCL2/IN[7]
74 PA24 VDDIO EXTINT[12] SERCOM3/PAD[2] SERCOM5/PAD[2] TC5/WO[0] TCC2/WO[0] CAN0/TX CMP[2] CCL2/IN[8]
75 PA25 VDDIO EXTINT[13] SERCOM3/PAD[3] SERCOM5/PAD[3] TC5/WO[1] TCC2/WO[1] CAN0/RX CMP[3] CCL2/OUT[2]
78 PB22 VDDIO EXTINT[6] SERCOM0/PAD[2] SERCOM5/PAD[2] TC7/WO[0] TCC1/WO[2] GCLK_IO[0] CCL0/IN[0]
79 PB23 VDDIO EXTINT[7] SERCOM0/PAD[3] SERCOM5/PAD[3] TC7/WO[1] TCC1/WO[3] GCLK_IO[1] CCL0/OUT[0]
80 PB24 VDDIO EXTINT[8] SERCOM0/PAD[0] SERCOM4/PAD[0] CMP[0]
81 PB25 VDDIO EXTINT[9] SERCOM0/PAD[1] SERCOM4/PAD[1] CMP[1]
82 PC24 VDDIO EXTINT[0] SERCOM0/PAD[2] SERCOM4/PAD[2]
83 PC25 VDDIO EXTINT[1] SERCOM0/PAD[3] SERCOM4/PAD[3]
84 PC26 VDDIO EXTINT[2]
85 PC27 VDDIO EXTINT[3] SERCOM1/PAD[0] CCL1/IN[4]
86 PC28 VDDIO EXTINT[4] SERCOM1/PAD[1] CCL1/IN[5]
87 PA27 VDDIN EXTINT[15] GCLK_IO[0]
89 PA28 VDDIN EXTINT[8] GCLK_IO[0]
93 PA30 VDDIN EXTINT[10] SERCOM1/PAD[2] TC1/WO[0] CORTEX_M0P/SWCLK GCLK_IO[0] CCL1/IN[3]
94 PA31 VDDIN EXTINT[11] SERCOM1/PAD[3] TC1/WO[1] CORTEX_M0P/SWDIO CCL1/OUT[1]
95 PB30 VDDIN EXTINT[14] SERCOM1/PAD[0] SERCOM5/PAD[0] TC0/WO[0] CMP[2]
96 PB31 VDDIN EXTINT[15] SERCOM1/PAD[1] SERCOM5/PAD[1] TC0/WO[1] CMP[3]
97 PB00 VDDANA EXTINT[0] AIN[0] Y[6] SERCOM5/PAD[2] TC7/WO[0] CCL0/IN[1]
98 PB01 VDDANA EXTINT[1] AIN[1] Y[7] SERCOM5/PAD[3] TC7/WO[1] CCL0/IN[2]
99 PB02 VDDANA EXTINT[2] AIN[2] Y[8] SERCOM5/PAD[0] TC6/WO[0] CCL0/OUT[0]
100 PB03 VDDANA EXTINT[3] AIN[3] Y[9] SERCOM5/PAD[1] TC6/WO[1]
Note: 
1. All analog pin functions are on peripheral function B. Peripheral function B must be selected to
disable the digital control of the pin.
2. Only some pins can be used in SERCOM I2C mode. For additional information, refer to 6.2.3
SERCOM I2C Pins.
Table 6-2.  PORT Function Multiplexing for SAM C21 E/G/J
Pin(1) I/O Pin Supply A B(2,3) C D E F G H I
SAM C21E SAM C21G SAM C21J EIC REF ADC0 ADC1 AC PTC DAC SDADC SERCOM(2,3,4) SERCOM-ALT(4) TC
TCC
TCC COM AC/GCLK CCL
1 1 1 PA00 VDDANA EXTINT[0] SERCOM1/
PAD[0]
TCC2/WO[0] CMP[2]
2 2 2 PA01 VDDANA EXTINT[1] SERCOM1/
PAD[1]
TCC2/WO[1] CMP[3]
3 3 3 PA02 VDDANA EXTINT[2] AIN[0] AIN[4] Y[0] VOUT
4 4 4 PA03 VDDANA EXTINT[3] ADC/VREFA AIN[1] AIN[5] Y[1]
5 PB04 VDDANA EXTINT[4] AIN[6] Y[10]
6 PB05 VDDANA EXTINT[5] AIN[7] AIN[6] Y[11]
9 PB06 VDDANA EXTINT[6] AIN[8] AIN[7] Y[12] INN[2] CCL2/
IN[6]
10 PB07 VDDANA EXTINT[7] AIN[9] Y[13] INP[2] CCL2/
IN[7]
7 11 PB08 VDDANA EXTINT[8] AIN[2] AIN[4] Y[14] INN[1] SERCOM4/
PAD[0]
TC0/WO[0] CCL2/
IN[8]
8 12 PB09 VDDANA EXTINT[9] AIN[3] AIN[5] Y[15] INP[1] SERCOM4/
PAD[1]
TC0WO[1] CCL2/
OUT[2]
5 9 13 PA04 VDDANA EXTINT[4] SDADC / VREFB AIN[4] AIN[0] Y[2] SERCOM0/
PAD[0]
TCC0/WO[0] CCL0/
IN[0]
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 30
...........continued
Pin(1) I/O Pin Supply A B(2,3) C D E F G H I
SAM C21E SAM C21G SAM C21J EIC REF ADC0 ADC1 AC PTC DAC SDADC SERCOM(2,3,4) SERCOM-ALT(4) TC
TCC
TCC COM AC/GCLK CCL
6 10 14 PA05 VDDANA EXTINT[5] AIN[5] AIN[1] Y[3] SERCOM0/
PAD[1]
TCC0/WO[1] CCL0/
IN[1]
7 11 15 PA06 VDDANA EXTINT[6] AIN[6] AIN[2] Y[4] INN[0] SERCOM0/
PAD[2]
TCC1/WO[0] CCL0/
IN[2]
8 12 16 PA07 VDDANA EXTINT[7] AIN[7] AIN[3] Y[5] INP[0] SERCOM0/
PAD[3]
TCC1/WO[1] CCL0/
OUT[0]
11 13 17 PA08 VDDIO NMI AIN[8] AIN[10] X[0]/Y[16] SERCOM0/
PAD[0]
SERCOM2/
PAD[0]
TCC0/WO[0] TCC1/
WO[2]
CCL1/
IN[3]
12 14 18 PA09 VDDIO EXTINT[9] AIN[9] AIN[11] X[1]/Y[17] SERCOM0/
PAD[1]
SERCOM2/
PAD[1]
TCC0/WO[1] TCC1/
WO[3]
CCL1/
IN[4]
13 15 19 PA10 VDDIO EXTINT[10] AIN[10] X[2]/Y[18] SERCOM0/
PAD[2]
SERCOM2/
PAD[2]
TCC1/WO[0] TCC0/
WO[2]
GCLK_IO[4] CCL1/
IN[5]
14 16 20 PA11 VDDIO EXTINT[11] AIN[11] X[3]/Y[19] SERCOM0/
PAD[3]
SERCOM2/
PAD[3]
TCC1/WO[1] TCC0/
WO[3]
GCLK_IO[5] CCL1/
OUT[1]
19 23 PB10 VDDIO EXTINT[10] SERCOM4/
PAD[2]
TC1/WO[0] TCC0/
WO[4]
CAN1/TX GCLK_IO[4] CCL1/
IN[5]
20 24 PB11 VDDIO EXTINT[11] SERCOM4/
PAD[3]
TC1/WO[1] TCC0/
WO[5]
CAN1/RX GCLK_IO[5] CCL1/
OUT[1]
25 PB12 VDDIO EXTINT[12] X[12]/Y[28] SERCOM4/
PAD[0]
TC0/WO[0] TCC0/
WO[6]
GCLK_IO[6]
26 PB13 VDDIO EXTINT[13] X[13]/Y[29] SERCOM4/
PAD[1]
TC0/WO[1] TCC0/
WO[7]
GCLK_IO[7]
27 PB14 VDDIO EXTINT[14] X[14]/Y[30] SERCOM4/
PAD[2]
TC1/WO[0] CAN1/TX GCLK_IO[0] CCL3/
IN[9]
28 PB15 VDDIO EXTINT[15] X[15]/Y[31] SERCOM4/
PAD[3]
TC1/WO[1] CAN1/RX GCLK_IO[1] CCL3/
IN[10]
21 29 PA12 VDDIO EXTINT[12] SERCOM2/
PAD[0]
SERCOM4/
PAD[0]
TCC2/WO[0] TCC0/
WO[6]
AC/CMP[0]
22 30 PA13 VDDIO EXTINT[13] SERCOM2/
PAD[1]
SERCOM4/
PAD[1]
TCC2/WO[1] TCC0/
WO[7]
AC/CMP[1]
15 23 31 PA14 VDDIO EXTINT[14] SERCOM2/
PAD[2]
SERCOM4/
PAD[2]
TC4/WO[0] TCC0/
WO[4]
GCLK_IO[0]
16 24 32 PA15 VDDIO EXTINT[15] SERCOM2/
PAD[3]
SERCOM4/
PAD[3]
TC4/WO[1] TCC0/
WO[5]
GCLK_IO[1]
17 25 35 PA16 VDDIO EXTINT[0] X[4]/Y[20] SERCOM1/
PAD[0]
SERCOM3/
PAD[0]
TCC2/WO[0] TCC0/
WO[6]
GCLK_IO[2] CCL0/
IN[0]
18 26 36 PA17 VDDIO EXTINT[1] X[5]/Y[21] SERCOM1/
PAD[1]
SERCOM3/
PAD[1]
TCC2/WO[1] TCC0/
WO[7]
GCLK_IO[3] CCL0/
IN[1]
19 27 37 PA18 VDDIO EXTINT[2] X[6]/Y[22] SERCOM1/
PAD[2]
SERCOM3/
PAD[2]
TC4/WO[0] TCC0/
WO[2]
AC/CMP[0] CCL0/
IN[2]
20 28 38 PA19 VDDIO EXTINT[3] X[7]/Y[23] SERCOM1/
PAD[3]
SERCOM3/
PAD[3]
TC4/WO[1] TCC0/
WO[3]
AC/CMP[1] CCL0/
OUT[0]
39 PB16 VDDIO EXTINT[0] SERCOM5/
PAD[0]
TC2/WO[0] TCC0/
WO[4]
GCLK_IO[2] CCL3/
IN[11]
40 PB17 VDDIO EXTINT[1] SERCOM5/
PAD[1]
TC2/WO[1] TCC0/
WO[5]
GCLK_IO[3] CCL3/
OUT[3]
29 41 PA20 VDDIO EXTINT[4] X[8]/Y[24] SERCOM5/
PAD[2]
SERCOM3/
PAD[2]
TC3/WO[0] TCC0/
WO[6]
GCLK_IO[4]
30 42 PA21 VDDIO EXTINT[5] X[9]/Y[25] SERCOM5/
PAD[3]
SERCOM3/
PAD[3]
TC3/WO[1] TCC0/
WO[7]
GCLK_IO[5]
21 31 43 PA22 VDDIO EXTINT[6] X[10]/Y[26] SERCOM3/
PAD[0]
SERCOM5/
PAD[0]
TC0/WO[0] TCC0/
WO[4]
GCLK_IO[6] CCL2/
IN[6]
22 32 44 PA23 VDDIO EXTINT[7] X[11]/Y[27] SERCOM3/
PAD[1]
SERCOM5/
PAD[1]
TC0/WO[1] TCC0/
WO[5]
GCLK_IO[7] CCL2/
IN[7]
23 33 45 PA24 VDDIO EXTINT[12] SERCOM3/
PAD[2]
SERCOM5/
PAD[2]
TC1/WO[0] TCC1/
WO[2]
CAN0/TX AC/CMP[2] CCL2/
IN[8]
24 34 46 PA25 VDDIO EXTINT[13] SERCOM3/
PAD[3]
SERCOM5/
PAD[3]
TC1/WO[1] TCC1/
WO[3]
CAN0/RX AC/CMP[3] CCL2/
OUT[2]
37 49 PB22 VDDIO EXTINT[6] SERCOM5/
PAD[2]
TC3/WO[0] CAN0/TX GCLK_IO[0] CCL0/
IN[0]
38 50 PB23 VDDIO EXTINT[7] SERCOM5/
PAD[3]
TC3/WO[1] CAN0/RX GCLK_IO[1] CCL0/
OUT[0]
25 39 51 PA27 VDDIN EXTINT[15] GCLK_IO[0]
27 41 53 PA28 VDDIN EXTINT[8] GCLK_IO[0]
31 45 57 PA30 VDDIN EXTINT[10] SERCOM1/
PAD[2]
TCC1/WO[0] CORTEX_M0P/
SWCLK
GCLK_IO[0] CCL1/
IN[3]
32 46 58 PA31 VDDIN EXTINT[11] SERCOM1/
PAD[3]
TCC1/WO[1] CORTEX_M0P/
SWDIO
CCL1/
OUT[1]
59 PB30 VDDIN EXTINT[14] SERCOM5/
PAD[0]
TCC0/WO[0] TCC1/
WO[2]
AC/CMP[2]
60 PB31 VDDIN EXTINT[15] SERCOM5/
PAD[1]
TCC0/WO[1] TCC1/
WO[3]
AC/CMP[3]
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 31
...........continued
Pin(1) I/O Pin Supply A B(2,3) C D E F G H I
SAM C21E SAM C21G SAM C21J EIC REF ADC0 ADC1 AC PTC DAC SDADC SERCOM(2,3,4) SERCOM-ALT(4) TC
TCC
TCC COM AC/GCLK CCL
61 PB00 VDDANA EXTINT[0] AIN[0] Y[6] SERCOM5/
PAD[2]
TC3/WO[0] CCL0/
IN[1]
62 PB01 VDDANA EXTINT[1] AIN[1] Y[7] SERCOM5/
PAD[3]
TC3/WO[1] CCL0/
IN[2]
47 63 PB02 VDDANA EXTINT[2] AIN[2] Y[8] SERCOM5/
PAD[0]
TC2/WO[0] CCL0/
OUT[0]
48 64 PB03 VDDANA EXTINT[3] AIN[3] Y[9] SERCOM5/
PAD[1]
TC2/WO[1]
Note: 
1. Use the SAM C21J pinout muxing for the WLCSP56 package.
2. All analog pin functions are on peripheral function B. Peripheral function B must be selected to
disable the digital control of the pin.
3. Only some pins can be used in SERCOM I2C mode. For additional information, refer to 6.2.3
SERCOM I2C Pins.
4. SERCOM4 and SERCOM5 are not supported on SAM C21E.
Table 6-3. PORT Function Multiplexing for SAM C20 N
Pin I/O Pin Supply A B B(1,2) C D E F G H I
EIC REF ADC0 AC PTC SERCOM SERCOM-ALT TC TCC COM AC/GCLK CCL
1 PA00 VDDANA EXTINT[0] SERCOM1/PAD[0] TC2/WO[0] CMP[2]
2 PA01 VDDANA EXTINT[1] SERCOM1/PAD[1] TC2/WO[1] CMP[3]
3 PC00 VDDANA EXTINT[8] AIN[8]
4 PC01 VDDANA EXTINT[9] AIN[9]
5 PC02 VDDANA EXTINT[10] AIN[10]
6 PC03 VDDIO EXTINT[11] AIN[11] SERCOM7/PAD[0] TCC2/WO[0]
7 PA02 VDDANA EXTINT[2] AIN[0] AIN[4] Y[0]
8 PA03 VDDANA EXTINT[3] ADC/VREFA AIN[1] Y[1]
9 PB04 VDDANA EXTINT[4] AIN[5] Y[10]
10 PB05 VDDANA EXTINT[5] AIN[6] Y[11]
13 PB06 VDDIO EXTINT[6] AIN[7] Y[12] SERCOM7/PAD[1] CCL2/IN[6]
14 PB07 VDDIO EXTINT[7] Y[13] SERCOM7/PAD[3] SERCOM7/PAD[2] CCL2/IN[7]
15 PB08 VDDIO EXTINT[8] AIN[2] Y[14] SERCOM7/PAD[2] SERCOM7/PAD[3] TC4/WO[0] CCL2/IN[8]
16 PB09 VDDANA EXTINT[9] AIN[3] Y[15] SERCOM4/PAD[1] TC4/WO[1] CCL2/OUT[2]
17 PA04 VDDANA EXTINT[4] AIN[4] AIN[0] Y[2] SERCOM0/PAD[0] TC0/WO[0] CCL0/IN[0]
18 PA05 VDDANA EXTINT[5] AIN[5] AIN[1] Y[3] SERCOM0/PAD[1] TC0/WO[1] CCL0/IN[1]
19 PA06 VDDANA EXTINT[6] AIN[6] AIN[2] Y[4] SERCOM0/PAD[2] TC1/WO[0] CCL0/IN[2]
20 PA07 VDDANA EXTINT[7] AIN[7] AIN[3] Y[5] SERCOM0/PAD[3] TC1/WO[1] CCL0/OUT[0]
21 PC05 VDDANA EXTINT[13] SERCOM6/PAD[3] TCC2/WO[1]
22 PC06 VDDANA EXTINT[14] SERCOM6/PAD[0]
23 PC07 VDDANA EXTINT[15] SERCOM6/PAD[1]
26 PA08 VDDIO NMI X[0]/Y[16] SERCOM0/PAD[0] SERCOM2/PAD[0] TC0/WO[0] TCC0/WO[0] CCL1/IN[3]
27 PA09 VDDIO EXTINT[9] X[1]/Y[17] SERCOM0/PAD[1] SERCOM2/PAD[1] TC0/WO[1] TCC0/WO[1] CCL1/IN[4]
28 PA10 VDDIO EXTINT[10] X[2]/Y[18] SERCOM0/PAD[2] SERCOM2/PAD[2] TC1/WO[0] TCC0/WO[2] GCLK_IO[4] CCL1/IN[5]
29 PA11 VDDIO EXTINT[11] X[3]/Y[19] SERCOM0/PAD[3] SERCOM2/PAD[3] TC1/WO[1] TCC0/WO[3] GCLK_IO[5] CCL1/OUT[1]
30 PB10 VDDIO EXTINT[10] SERCOM4/PAD[2] TC5/WO[0] TCC0_WO4 GCLK_IO[4] CCL1/IN[5]
31 PB11 VDDIO EXTINT[11] SERCOM4/PAD[3] TC5/WO[1] TCC0_WO5 GCLK_IO[5] CCL1/OUT[1]
32 PB12 VDDIO EXTINT[12] X[12]/Y[28] SERCOM4/PAD[0] TC4/WO[0] TCC0_WO6 GCLK_IO[6]
33 PB13 VDDIO EXTINT[13] X[13]/Y[29] SERCOM4/PAD[1] TC4/WO[1] TCC0_WO7 GCLK_IO[7]
34 PB14 VDDIO EXTINT[14] X[14]/Y[30] SERCOM4/PAD[2] TC5/WO[0] GCLK_IO[0] CCL3/IN[9]
35 PB15 VDDIO EXTINT[15] X[15]/Y[31] SERCOM4/PAD[3] TC5/WO[1] GCLK_IO[1] CCL3/IN[10]
38 PC08 VDDIO EXTINT[0] SERCOM6/PAD[0] SERCOM7/PAD[0]
39 PC09 VDDIO EXTINT[1] SERCOM6/PAD[1] SERCOM7/PAD[1]
40 PC10 VDDIO EXTINT[2] SERCOM6/PAD[2] SERCOM7/PAD[2]
41 PC11 VDDIO EXTINT[3] SERCOM6/PAD[3] SERCOM7/PAD[3]
42 PC12 VDDIO EXTINT[4] SERCOM7/PAD[0]
43 PC13 VDDIO EXTINT[5] SERCOM7/PAD[1]
44 PC14 VDDIO EXTINT[6] SERCOM7/PAD[2]
45 PC15 VDDIO EXTINT[7] SERCOM7/PAD[3]
46 PA12 VDDIO EXTINT[12] SERCOM2/PAD[0] SERCOM4/PAD[0] TC2/WO[0] TCC0_WO6 CMP[0]
47 PA13 VDDIO EXTINT[13] SERCOM2/PAD[1] SERCOM4/PAD[1] TC2/WO[1] TCC0_WO7 CMP[1]
48 PA14 VDDIO EXTINT[14] SERCOM2/PAD[2] SERCOM4/PAD[2] TC3/WO[0] GCLK_IO[0]
49 PA15 VDDIO EXTINT[15] SERCOM2/PAD[3] SERCOM4/PAD[3] TC3/WO[1] GCLK_IO[1]
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 32
...........continued
Pin I/O Pin Supply A B B(1,2) C D E F G H I
EIC REF ADC0 AC PTC SERCOM SERCOM-ALT TC TCC COM AC/GCLK CCL
52 PA16 VDDIO EXTINT[0] X[4]/Y[20] SERCOM1/PAD[0] SERCOM3/PAD[0] TC2/WO[0] TCC1/WO[0] GCLK_IO[2] CCL0/IN[0]
53 PA17 VDDIO EXTINT[1] X[5]/Y[21] SERCOM1/PAD[1] SERCOM3/PAD[1] TC2/WO[1] TCC1/WO[1] GCLK_IO[3] CCL0/IN[1]
54 PA18 VDDIO EXTINT[2] X[6]/Y[22] SERCOM1/PAD[2] SERCOM3/PAD[2] TC3/WO[0] TCC1/WO[2] CMP[0] CCL0/IN[2]
55 PA19 VDDIO EXTINT[3] X[7]/Y[23] SERCOM1/PAD[3] SERCOM3/PAD[3] TC3/WO[1] TCC1/WO[3] CMP[1] CCL0/OUT[0]
56 PC16 VDDIO EXTINT[8] SERCOM6/PAD[0]
57 PC17 VDDIO EXTINT[9] SERCOM6/PAD[1]
58 PC18 VDDIO EXTINT[10] SERCOM6/PAD[2]
59 PC19 VDDIO EXTINT[11] SERCOM6/PAD[3]
60 PC20 VDDIO EXTINT[12] CCL3/IN[9]
61 PC21 VDDIO EXTINT[13] CCL3/IN[10]
64 PB16 VDDIO EXTINT[0] SERCOM5/PAD[0] TC6/WO[0] GCLK_IO[2] CCL3/IN[11]
65 PB17 VDDIO EXTINT[1] SERCOM5/PAD[1] TC6/WO[1] GCLK_IO[3] CCL3/OUT[3]
66 PB18 VDDIO EXTINT[2] SERCOM5/PAD[2] SERCOM3/PAD[2] GCLK_IO[4]
67 PB19 VDDIO EXTINT[3] SERCOM5/PAD[3] SERCOM3/PAD[3] GCLK_IO[5]
68 PB20 VDDIO EXTINT[4] SERCOM3/PAD[0] SERCOM2/PAD[0] GCLK_IO[6]
69 PB21 VDDIO EXTINT[5] SERCOM3/PAD[1] SERCOM2/PAD[1] GCLK_IO[7]
70 PA20 VDDIO EXTINT[4] X[8]/Y[24] SERCOM5/PAD[2] SERCOM3/PAD[2] TC7/WO[0] TCC2/WO[0] GCLK_IO[4]
71 PA21 VDDIO EXTINT[5] X[9]/Y[25] SERCOM5/PAD[3] SERCOM3/PAD[3] TC7/WO[1] TCC2/WO[1] GCLK_IO[5]
72 PA22 VDDIO EXTINT[6] X[10]/Y[26] SERCOM3/PAD[0] SERCOM5/PAD[0] TC4/WO[0] TCC1/WO[0] GCLK_IO[6] CCL2/IN[6]
73 PA23 VDDIO EXTINT[7] X[11]/Y[27] SERCOM3/PAD[1] SERCOM5/PAD[1] TC4/WO[1] TCC1/WO[1] GCLK_IO[7] CCL2/IN[7]
74 PA24 VDDIO EXTINT[12] SERCOM3/PAD[2] SERCOM5/PAD[2] TC5/WO[0] TCC2/WO[0] CMP[2] CCL2/IN[8]
75 PA25 VDDIO EXTINT[13] SERCOM3/PAD[3] SERCOM5/PAD[3] TC5/WO[1] TCC2/WO[1] CMP[3] CCL2/OUT[2]
78 PB22 VDDIO EXTINT[6] SERCOM0/PAD[2] SERCOM5/PAD[2] TC7/WO[0] TCC1/WO[2] GCLK_IO[0] CCL0/IN[0]
79 PB23 VDDIO EXTINT[7] SERCOM0/PAD[3] SERCOM5/PAD[3] TC7/WO[1] TCC1/WO[3] GCLK_IO[1] CCL0/OUT[0]
80 PB24 VDDIO EXTINT[8] SERCOM0/PAD[0] SERCOM4/PAD[0] CMP[0]
81 PB25 VDDIO EXTINT[9] SERCOM0/PAD[1] SERCOM4/PAD[1] CMP[1]
82 PC24 VDDIO EXTINT[0] SERCOM0/PAD[2] SERCOM4/PAD[2]
83 PC25 VDDIO EXTINT[1] SERCOM0/PAD[3] SERCOM4/PAD[3]
84 PC26 VDDIO EXTINT[2]
85 PC27 VDDIO EXTINT[3] SERCOM1/PAD[0] CCL1/IN[4]
86 PC28 VDDIO EXTINT[4] SERCOM1/PAD[1] CCL1/IN[5]
87 PA27 VDDIN EXTINT[15] GCLK_IO[0]
89 PA28 VDDIN EXTINT[8] GCLK_IO[0]
93 PA30 VDDIN EXTINT[10] SERCOM1/PAD[2] TC1/WO[0] CORTEX_M0P/SWCLK GCLK_IO[0] CCL1/IN[3]
94 PA31 VDDIN EXTINT[11] SERCOM1/PAD[3] TC1/WO[1] CORTEX_M0P/SWDIO CCL1/OUT[1]
95 PB30 VDDIN EXTINT[14] SERCOM1/PAD[0] SERCOM5/PAD[0] TC0/WO[0] CMP[2]
96 PB31 VDDIN EXTINT[15] SERCOM1/PAD[1] SERCOM5/PAD[1] TC0/WO[1] CMP[3]
97 PB00 VDDANA EXTINT[0] Y[6] SERCOM5/PAD[2] TC7/WO[0] CCL0/IN[1]
98 PB01 VDDANA EXTINT[1] Y[7] SERCOM5/PAD[3] TC7/WO[1] CCL0/IN[2]
99 PB02 VDDANA EXTINT[2] Y[8] SERCOM5/PAD[0] TC6/WO[0] CCL0/OUT[0]
100 PB03 VDDANA EXTINT[3] Y[9] SERCOM5/PAD[1] TC6/WO[1]
Note: 
1. All analog pin functions are on peripheral function B. Peripheral function B must be selected to
disable the digital control of the pin.
2. Only some pins can be used in SERCOM I2C mode. For additional information, refer to 6.2.3
SERCOM I2C Pins.
Table 6-4.  PORT Function Multiplexing for SAM C20 E/G/J
Pin(1) I/O Pin Supply A B(2,3) C D E F G H I
SAM C20E SAM C20G SAM C20J EIC REF ADC0 AC PTC SERCOM(2,3) SERCOM-ALT TC
TCC
TCC COM AC/GCLK CCL
1 1 1 PA00 VDDANA EXTINT[0] SERCOM1/
PAD[0]
TCC2/WO[0] CMP[2]
2 2 2 PA01 VDDANA EXTINT[1] SERCOM1/
PAD[1]
TCC2/WO[1] CMP[3]
3 3 3 PA02 VDDANA EXTINT[2] AIN[0] AIN[4] Y[0]
4 4 4 PA03 VDDANA EXTINT[3] ADC/VREFA AIN[1] AIN[5] Y[1]
5 PB04 VDDANA EXTINT[4] Y[10]
6 PB05 VDDANA EXTINT[5] AIN[6] Y[11]
9 PB06 VDDANA EXTINT[6] AIN[7] Y[12] CCL2/
IN[6]
10 PB07 VDDANA EXTINT[7] Y[13] CCL2/
IN[7]
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 33
...........continued
Pin(1) I/O Pin Supply A B(2,3) C D E F G H I
SAM C20E SAM C20G SAM C20J EIC REF ADC0 AC PTC SERCOM(2,3) SERCOM-ALT TC
TCC
TCC COM AC/GCLK CCL
7 11 PB08 VDDANA EXTINT[8] AIN[2] Y[14] - TC0/WO[0] CCL2/
IN[8]
8 12 PB09 VDDANA EXTINT[9] AIN[3] Y[15] - TC0WO[1] CCL2/
OUT[2]
5 9 13 PA04 VDDANA EXTINT[4] AIN[4] AIN[0] Y[2] SERCOM0/
PAD[0]
TCC0/WO[0] CCL0/
IN[0]
6 10 14 PA05 VDDANA EXTINT[5] AIN[5] AIN[1] Y[3] SERCOM0/
PAD[1]
TCC0/WO[1] CCL0/
IN[1]
7 11 15 PA06 VDDANA EXTINT[6] AIN[6] AIN[2] Y[4] SERCOM0/
PAD[2]
TCC1/WO[0] CCL0/
IN[2]
8 12 16 PA07 VDDANA EXTINT[7] AIN[7] AIN[3] Y[5] SERCOM0/
PAD[3]
TCC1/WO[1] CCL0/
OUT[0]
11 13 17 PA08 VDDIO NMI AIN[8] X[0]/Y[16] SERCOM0/
PAD[0]
SERCOM2/
PAD[0]
TCC0/WO[0] TCC1/
WO[2]
CCL1/
IN[3]
12 14 18 PA09 VDDIO EXTINT[9] AIN[9] X[1]/Y[17] SERCOM0/
PAD[1]
SERCOM2/
PAD[1]
TCC0/WO[1] TCC1/
WO[3]
CCL1/
IN[4]
13 15 19 PA10 VDDIO EXTINT[10] AIN[10] X[2]/Y[18] SERCOM0/
PAD[2]
SERCOM2/
PAD[2]
TCC1/WO[0] TCC0/
WO[2]
GCLK_IO[4] CCL1/
IN[5]
14 16 20 PA11 VDDIO EXTINT[11] AIN[11] X[3]/Y[19] SERCOM0/
PAD[3]
SERCOM2/
PAD[3]
TCC1/WO[1] TCC0/
WO[3]
GCLK_IO[5] CCL1/
OUT[1]
19 23 PB10 VDDIO EXTINT[10] - TC1/WO[0] TCC0/
WO[4]
GCLK_IO[4] CCL1/
IN[5]
20 24 PB11 VDDIO EXTINT[11] - TC1/WO[1] TCC0/
WO[5]
GCLK_IO[5] CCL1/
OUT[1]
25 PB12 VDDIO EXTINT[12] X[12]/Y[28] - TC0/WO[0] TCC0/
WO[6]
GCLK_IO[6]
26 PB13 VDDIO EXTINT[13] X[13]/Y[29] - TC0/WO[1] TCC0/
WO[7]
GCLK_IO[7]
27 PB14 VDDIO EXTINT[14] X[14]/Y[30] - TC1/WO[0] GCLK_IO[0] CCL3/
IN[9]
28 PB15 VDDIO EXTINT[15] X[15]/Y[31] - TC1/WO[1] GCLK_IO[1] CCL3/
IN[10]
21 29 PA12 VDDIO EXTINT[12] SERCOM2/
PAD[0]
- TCC2/WO[0] TCC0/
WO[6]
AC/CMP[0]
22 30 PA13 VDDIO EXTINT[13] SERCOM2/
PAD[1]
- TCC2/WO[1] TCC0/
WO[7]
AC/CMP[1]
15 23 31 PA14 VDDIO EXTINT[14] SERCOM2/
PAD[2]
- TC4/WO[0] TCC0/
WO[4]
GCLK_IO[0]
16 24 32 PA15 VDDIO EXTINT[15] SERCOM2/
PAD[3]
- TC4/WO[1] TCC0/
WO[5]
GCLK_IO[1]
17 25 35 PA16 VDDIO EXTINT[0] X[4]/Y[20] SERCOM1/
PAD[0]
SERCOM3/
PAD[0]
TCC2/WO[0] TCC0/
WO[6]
GCLK_IO[2] CCL0/
IN[0]
18 26 36 PA17 VDDIO EXTINT[1] X[5]/Y[21] SERCOM1/
PAD[1]
SERCOM3/
PAD[1]
TCC2/WO[1] TCC0/
WO[7]
GCLK_IO[3] CCL0/
IN[1]
19 27 37 PA18 VDDIO EXTINT[2] X[6]/Y[22] SERCOM1/
PAD[2]
SERCOM3/
PAD[2]
TC4/WO[0] TCC0/
WO[2]
AC/CMP[0] CCL0/
IN[2]
20 28 38 PA19 VDDIO EXTINT[3] X[7]/Y[23] SERCOM1/
PAD[3]
SERCOM3/
PAD[3]
TC4/WO[1] TCC0/
WO[3]
AC/CMP[1] CCL0/
OUT[0]
39 PB16 VDDIO EXTINT[0] - TC2/WO[0] TCC0/
WO[4]
GCLK_IO[2] CCL3/
IN[11]
40 PB17 VDDIO EXTINT[1] - TC2/WO[1] TCC0/
WO[5]
GCLK_IO[3] CCL3/
OUT[3]
29 41 PA20 VDDIO EXTINT[4] X[8]/Y[24] - SERCOM3/
PAD[2]
TC3/WO[0] TCC0/
WO[6]
GCLK_IO[4]
30 42 PA21 VDDIO EXTINT[5] X[9]/Y[25] - SERCOM3/
PAD[3]
TC3/WO[1] TCC0/
WO[7]
GCLK_IO[5]
21 31 43 PA22 VDDIO EXTINT[6] X[10]/Y[26] SERCOM3/
PAD[0]
- TC0/WO[0] TCC0/
WO[4]
GCLK_IO[6] CCL2/
IN[6]
22 32 44 PA23 VDDIO EXTINT[7] X[11]/Y[27] SERCOM3/
PAD[1]
- TC0/WO[1] TCC0/
WO[5]
GCLK_IO[7] CCL2/
IN[7]
23 33 45 PA24 VDDIO EXTINT[12] SERCOM3/
PAD[2]
- TC1/WO[0] TCC1/
WO[2]
AC/CMP[2] CCL2/
IN[8]
24 34 46 PA25 VDDIO EXTINT[13] SERCOM3/
PAD[3]
- TC1/WO[1] TCC1/
WO[3]
AC/CMP[3] CCL2/
OUT[2]
37 49 PB22 VDDIN EXTINT[6] - TC3/WO[0] GCLK_IO[0] CCL0/
IN[0]
38 50 PB23 VDDIN EXTINT[7] - TC3/WO[1] GCLK_IO[1] CCL0/
OUT[0]
25 39 51 PA27 VDDIN EXTINT[15] GCLK_IO[0]
27 41 53 PA28 VDDIN EXTINT[8] GCLK_IO[0]
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 34
...........continued
Pin(1) I/O Pin Supply A B(2,3) C D E F G H I
SAM C20E SAM C20G SAM C20J EIC REF ADC0 AC PTC SERCOM(2,3) SERCOM-ALT TC
TCC
TCC COM AC/GCLK CCL
31 45 57 PA30 VDDIN EXTINT[10] SERCOM1/
PAD[2]
TCC1/WO[0] CORTEX_M0P/
SWCLK
GCLK_IO[0] CCL1/
IN[3]
32 46 58 PA31 VDDIN EXTINT[11] SERCOM1/
PAD[3]
TCC1/WO[1] CORTEX_M0P/
SWDIO
CCL1/
OUT[1]
59 PB30 VDDIN EXTINT[14] - TCC0/WO[0] TCC1/
WO[2]
AC/CMP[2]
60 PB31 VDDIN EXTINT[15] - TCC0/WO[1] TCC1/
WO[3]
AC/CMP[3]
61 PB00 VDDANA EXTINT[0] Y[6] - TC3/WO[0] CCL0/
IN[1]
62 PB01 VDDANA EXTINT[1] Y[7] - TC3/WO[1] CCL0/
IN[2]
47 63 PB02 VDDANA EXTINT[2] Y[8] - TC2/WO[0] CCL0/
OUT[0]
48 64 PB03 VDDANA EXTINT[3] Y[9] - TC2/WO[1]
Note: 
1. Use the SAM C21J pinout muxing for the WLCSP56 package.
2. All analog pin functions are on peripheral function B. Peripheral function B must be selected to
disable the digital control of the pin.
3. Only some pins can be used in SERCOM I2C mode. For additional information, refer to 6.2.3
SERCOM I2C Pins.
Related Links
6.2.3 SERCOM I2C Pins
6.2 Other Functions
6.2.1 Oscillator Pinout
The oscillators are not mapped to the normal PORT functions and their multiplexing are controlled by
registers in the Oscillators Controller (OSCCTRL) and in the 32K Oscillators Controller (OSC32KCTRL).
Table 6-5. Oscillator Pinout
Oscillator Supply Signal I/O pin
XOSC VDDIO XIN PA14
XOUT PA15
XOSC32K VDDANA XIN32 PA00
XOUT32 PA01
6.2.2 Serial Wire Debug Interface Pinout
Only the SWCLK pin is mapped to the normal PORT functions. A debugger cold-plugging or hot-plugging
detection will automatically switch the SWDIO port to the SWDIO function.
Table 6-6. Serial Wire Debug Interface Pinout
Signal Supply I/O pin
SWCLK VDDIN PA30
SWDIO VDDIN PA31
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 35
6.2.3 SERCOM I2C Pins
Table 6-7. SERCOM Pins Supporting I2C
Package Pins Supporting I2C
32-pin PA08, PA09, PA16, PA17, PA22, PA23
48-pin PA08, PA09, PA12, PA13, PA16, PA17, PA22, PA23
64-pin PA08, PA09, PA12, PA13, PA16, PA17, PA22, PA23, PB12, PB13, PB16, PB17,
PB30, PB31
100-pin PA08, PA09, PA16, PA17, PB12, PB13, PB16, PB17
6.2.4 GPIO Clusters
Table 6-8. GPIO Clusters
Package Cluster GPIO Supplies Pin connected to the cluster
100 pins 1 PB31 PB30 PA31 PA30 PA28 PA27 VDDIN (92) GND (90)
2 PC28 PC27 PC26 PC25 PC24 PB25
PB24 PB23 PB22
VDDIO (77) GND( 76 )
3 PA25 PA24 PA23 PA22 PA21 PA20 PB21
PB20 PB19 PB18 PB17 PB16
VDDIO(63+77) GND(62+76)
4 PC21 PC20 PC19 PC18 PC17 PC16
PA19 PA18 PA17 PA16
VDDIO(51+63) GND(50+62)
5 PA15 PA14 PA13 PA12 PC14 PC13 PC12
PC11 PC10 PC09 PC08
VDDIO(36+51) GND(37+50)
6 PB15 PB13 PB12 PB11 PB10 PA11 PA10
PA09 PA08
VDDIO(25+36) GND(24+37)
7 PC07 PC06 PC05 PA07 PA06 PA05 PA04
PB09 PB05 PB04 PA03 PA02 PC02 PC01
PC00 PA01 PA00 PB03 PB02 PB01 PB00
VDDANA (12) GNDANA (11)
8 PC15 VDDIO(25) GND(37+50)
9 PB14 VDDIO(25) GND(24+37)
10 PB08 PB07 PB06 PC03 VDDIO(25) GNDANA (11)
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 36
...........continued
Package Cluster GPIO Supplies Pin connected to the cluster
64 pins 1 PB31 PB30 PA31 PA30 PA28 PA27 VDDIN (56) GND (54)
2 PB23 PB22 VDDIO (48) GND (54+47)
3 PA25 PA24 PA23 PA22 PA21 PA20 PB17
PB16 PA19 PA18 PA17 PA16
VDDIO (48+34) GND (47+33)
4 PA15 PA14 PA13 PA12 PB15 PB14 PB13
PB12 PB11 PB10
VDDIO (34+21) GND (33+22)
5 PA11 PA10 PA08 PA09 VDDIO (21) GND (22)
6 PA07 PA06 PA05 PA04 PB09 PB08 PB07
PB06 PB05 PB04 PA03 PA02 PA01 PA00
PB03 PB02 PB01 PB00
VDDANA (8) GNDANA (7)
48 pins 1 PA31 PA30 PA28 PA27 VDDIN (44) GND (42)
2 PB23 PB22 VDDIO (36) GND (42+35)
3 PA25 PA24 PA23 PA22 PA21 PA20 PA19
PA18 PA17 PA16 PA15 PA14 PA13 PA12
PB11 PB10
VDDIO (36+17) GND (35+18)
4 PA11 PA10 PA08 PA09 VDDIO (17) GND (18)
5 PA07 PA06 PA05 PA04 PB09 PB08 PA03
PA02 PA01 PA00 PB03 PB02
VDDANA (6) GNDANA (5)
32 pins 1 PA31 PA30 PA28 PA27 VDDIN (30) GND (28)
2 PA25 PA24 PA23 PA22 PA19 PA18 PA17
PA16 PA15 PA14 PA11 PA10 PA08 PA09
VDDANA (9) GND (28+10)
3 PA07 PA06 PA05 PA04 PA03 PA02 PA01
PA00
VDDANA (9) GND (28+10)
6.2.5 TCC Configurations
The SAM C20/C21 devices have three instances of the Timer/Counter for Control applications (TCC)
peripheral, , TCC[2:0]. The following table lists the features for each TCC instance.
Table 6-9. TCC Configuration Summary
TCC# Channels
(CC_NUM)
Waveform
Output
(WO_NUM)
Counter
size
Fault Dithering Output
matrix
Dead Time
Insertion
(DTI)
SWAP Pattern
generation
0 4 8 24-bit Yes Yes Yes Yes Yes Yes
1 2 4 24-bit Yes Yes Yes
2 2 2 16-bit Yes
Note:  The number of CC registers (CC_NUM) for each TCC corresponds to the number of compare/
capture channels, therefore a TCC can have more Waveform Outputs (WO_NUM) than CC registers.
SAM C20/C21 Family Data Sheet
I/O Multiplexing and Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 37
7. Power Supply and Start-Up Considerations
7.1 Power Domain Overview
Figure 7-1. Power Domain Overview, SAM C20/C21 E/G/J
PD1
Digital Logic
SERCOM[4:0],
TCC[2:0]
TC[3:0], DAC,
I2S, AES, TRNG
PAC, DMAC
LOW POWER
RAM
LOW POWER
RAM
PA[7:2]
PB[9:0]
PA[1:0]
PB[17:10]
PA[25:8]
PA[31:30]
PB[31:30]
VDDIO
VDDIN
GND
VDDCORE
GNDANA
VDDANA
ADC0
AC
DAC
PTC
SDADC
POR
BOD50
OSCULP32K
OSC32K
XOSC32K
Voltage
Regulator
OSC48M TOSC
BODCORE
POR
XOSC
Digital Logic
(CPU, Peripherals)
DPLL
NVM
HIGH SPEED
RAM
ADC1
PA[28:27]
PB[23:22]
SAM C20/C21 Family Data Sheet
Power Supply and Start-Up Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 38
Figure 7-2. Power Domain Overview, SAM C20/C21 N
PD1
Digital Logic
SERCOM[4:0],
TCC[2:0]
TC[3:0], DAC,
I2S, AES, TRNG
PAC, DMAC
LOW POWER
RAM
LOW POWER
RAM
PA[7:2]
PB[5:0]
PA[1:0]
PB[25:10]
PA[25:8]
PA[31:30]
PB[31:30]
VDDIO
VDDIN
GND
VDDCORE
GNDANA
VDDANA
ADC0
AC
DAC
PTC
SDADC
POR
BOD50
OSCULP32K
OSC32K
XOSC32K
Voltage
Regulator
OSC48M TOSC
BODCORE
POR
XOSC
Digital Logic
(CPU, Peripherals)
DPLL
NVM
HIGH SPEED
RAM
ADC1
PC[2:0]
PC3,PB14
PC[15:8]
PB[8:6]
PC[21:16]
PC[28:24]
PA[28:27]
PC[7:5]
PB[9]
7.2 Power Supply Considerations
7.2.1 Power Supplies, SAM C21/SAM C20
The SAM C21 has the following power supply pins:
• VDDIO: Powers I/O lines and XOSC. Voltage is 2.70V to 5.50V.
• VDDIN: Powers I/O lines and the OSC48M, TOSC and internal regulator. Voltage is 2.70V to 5.50V.
• VDDANA: Powers I/O lines and the ADC, AC, DAC, PTC, SDADC, OSCULP32K, OSC32K, and
XOSC32K. Voltage is 2.70V to 5.50V.
• VDDCORE: Internal regulated voltage output. Powers the core, memories, peripherals, and
FDPLL96M. Voltage is 1.2V typical.
The same voltage must be applied to both the VDDIN and VDDANA pins. This common voltage is
referred to as VDD in the datasheet. VDDIO must always be less than or equal to VDDIN.
The ground pins, GND, are common to VDDCORE, VDDIO and VDDIN. The ground pin for VDDANA is
GNDANA.
For decoupling recommendations for the different power supplies, refer to the schematic checklist.
The SAM C20 has the following power supply pins:
• VDDIO: Powers I/O lines and XOSC. Voltage is 2.70V to 5.50V.
• VDDIN: Powers I/O lines and the OSC48M, TOSC and internal regulator. Voltage is 2.70V to 5.50V.
SAM C20/C21 Family Data Sheet
Power Supply and Start-Up Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 39
• VDDANA: Powers I/O lines and the ADC, AC, PTC, OSCULP32K, OSC32K, and XOSC32K. Voltage
is 2.70V to 5.50V.
• VDDCORE: Internal regulated voltage output. Powers the core, memories, peripherals, and
FDPLL96M. Voltage is 1.2V typical.
The same voltage must be applied to both VDDIN and VDDANA. This common voltage is referred to as
VDD in the datasheet. VDDIO must always be less than or equal to VDDIN.
The ground pins, GND, are common to VDDCORE, VDDIO and VDDIN. The ground pin for VDDANA is
GNDANA.
For decoupling recommendations for the different power supplies, refer to the schematic checklist.
7.2.2 Voltage Regulator
The SAM C20/C21 voltage regulators have these two modes:
• Normal mode: This is the default mode when CPU and peripherals are running.
• Low Power (LP) mode: This default mode is used when the chip is in standby mode.
7.2.3 Typical Powering Schematics
The SAM C20/C21 use a single supply from 2.70V to 5.50V or dual supply mode where VDDIO is
supplied separately from VDDIN.
The following figures show the recommended power supply connections.
Figure 7-3. Power Supply Connection for single supply mode only
VDDIO
VDDANA
VDDIN
VDDCORE
GND
Main Supply
(2.70V - 5.50V)
SAM C20/C21 Family Data Sheet
Power Supply and Start-Up Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 40
Power Supply Connection for dual supply mode
Main Supply
(2.70V - 5.50V)
IO Supply
(2.70V - 5.50V)
7.2.4 Power-Up Sequence
7.2.4.1 Minimum Rise Rate
The integrated Power-on Reset (POR) circuitry monitoring the VDDIN power supply requires a minimum
rise rate.
7.2.4.2 Maximum Rise Rate
The rise rate of the power supply must not exceed the values described in Electrical Characteristics.
7.3 Power-Up
This section summarizes the power-up sequence of the SAM C20/C21. The behavior after power-up is
controlled by the Power Manager.
7.3.1 Starting of Clocks
After power-up, the device is set to its initial state and kept in reset, until the power has stabilized
throughout the device. Once the power has stabilized, the device will use a 4MHz clock. This clock is
derived from the 48MHz Internal Oscillator (OSC48M), which is configured to provide a 4MHz clock and
used as a clock source for generic clock generator 0. Generic clock generator 0 is the main clock for the
Power Manager (PM).
Some synchronous system clocks are active, allowing software execution.
Refer to the “Clock Mask Register” in the Power Manager for the list of default peripheral clocks running.
Synchronous system clocks that are running are by default not divided and receive a 4MHz clock through
generic clock generator 0. Other generic clocks are disabled.
7.3.2 I/O Pins
After power-up, the I/O pins are tri-stated.
SAM C20/C21 Family Data Sheet
Power Supply and Start-Up Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 41
7.3.3 Fetching of Initial Instructions
After reset has been released, the CPU starts fetching PC and SP values from the reset address, which
is 0x00000000. This address points to the first executable address in the internal flash. The code read
from the internal flash is free to configure the clock system and clock sources. Refer to the ARM
Architecture Reference Manual for more information on CPU startup (http://www.arm.com).
7.4 Power-On Reset and Brown-Out Detector
The SAM C20/C21 embed three features to monitor, warn, and/or reset the device:
• POR: Power-on reset on VDDIN and VDDIO
• BODVDD: Brown-out detector on VDDIN
• BODCORE: Voltage Regulator Internal Brown-out detector on VDDCORE. The Voltage Regulator
Internal BOD is calibrated in production and its calibration configuration is stored in the NVM User
Row. This configuration should not be changed if the user row is written to assure the correct
behavior of the BODCORE.
7.4.1 Power-On Reset on VDDIN
POR monitors VDDIN. It is always activated and monitors voltage at startup and also during all the sleep
modes. If VDDIN goes below the threshold voltage, the entire chip is reset.
7.4.2 Power-On Reset on VDDIO
POR monitors VDDIO. It is always activated and monitors voltage at startup and also during all the sleep
modes. If VDDIO goes below the threshold voltage, all IOs supplied by VDDIO are reset.
7.4.3 Brown-Out Detector on VDDIN
BODVDD monitors VDDIN.
7.4.4 Brown-Out Detector on VDDCORE
Once the device has started up, BODCORE monitors the internal VDDCORE.
SAM C20/C21 Family Data Sheet
Power Supply and Start-Up Considerations
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 42
8. Product Mapping
Figure 8-1. SAM C21 N Product Mapping
SAM C20/C21 Family Data Sheet
Product Mapping
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 43
Figure 8-2. SAM C20 N Product Mapping
SAM C20/C21 Family Data Sheet
Product Mapping
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 44
Figure 8-3. SAM C21 E/G/J Product Mapping
Code
SRAM
Undefined
Peripherals
Reserved
IOBUS
Reserved
Internal SRAM
Internal Flash
Reserved
CAN0
EVSYS
SERCOM0
SERCOM1
SERCOM2
SERCOM3
SERCOM4
SERCOM5
TC3
CAN1
TCC0
TCC1
TCC2
TC0
TC1
TC2
TC4
ADC0
0x42000400
0x42000800
0x42000C00
0x42001000
0x42001400
0x42001800
0x42002000
0x42001C00
0x42003000
0x42003400
0x42003800
0x42003C00
0x42004000
0x42004400
0x42004800
ADC1
0x42004C00
0x42002400
0x42002800
0x42002C00
SDADC
0x42005400
0x42005000
AC
Reserved
PORT
DSU
NVMCTRL
DMAC
MTB
PAC
PM
MCLK
RSTC
OSCCTRL
OSC32KCTRL
SUPC
Reserved
GCLK
WDT
RTC
EIC
FREQM
TSENS
Reserved
0x42FFFFFF
DAC
0x42005800
PTC
0x42006000
0x42005C00
CCL
AHB-APB
Bridge A
AHB-APB
Bridge B
AHB-APB
Bridge C
Reserved
AHB
DIVAS
0x42000000
0x00000000
0x20000000
0x22008000
0x40000000
0x48000200
0x60000000
0x60000400
0xFFFFFFFF
0x00000000
0x00400000
0x1FFFFFFF
0x20000000
0x20008000
AHB-APB Bridge C
Code
Global Memory Space
AHB-APB Bridge A
SRAM
AHB-APB
AHB-APB Bridge B
0x40000000
0x41000000
0x42000000
0x43000000
0x48000000
0x480001FF
0x41000000
0x41002000
0x41004000
0x41006000
0x41008000
0x41009000
0x41FFFFFF
0x40000000
0x40000400
0x40000800
0x40000C00
0x40001000
0x40001400
0x40001800
0x40001C00
0x40FFFFFF
0x40002000
0x40002800
0x40002C00
0x40003000
0x40003400
0x40002400
SAM C20/C21 Family Data Sheet
Product Mapping
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 45
Figure 8-4. SAM C20 E/G/J Product Mapping
Code
SRAM
Undefined
Peripherals
Reserved
IOBUS
Reserved
Global Memory Space
0x00000000
0x20000000
0x22008000
0x40000000
0x48000200
0x60000000
0x60000400
0xFFFFFFFF
Internal SRAM
SRAM
AHB-APB
Internal Flash
Reserved
Code
0x00000000
0x00400000
0x1FFFFFFF
0x20000000
0x20008000
0x40000000
0x41000000
0x42000000
0x43000000
Reserved
EVSYS
SERCOM0
SERCOM1
SERCOM2
SERCOM3
Reserved
Reserved
AHB-APB Bridge C
TC3
Reserved
TCC0
TC0
TC1
TC2
TC4
ADC0
0x42000000
0x42000400
0x42000800
0x42000C00
0x42001000
0x42001400
0x42001800
0x42002000
0x42001C00
0x42003000
0x42003400
0x42003800
0x42003C00
0x42004000
0x42004400
0x42004800
Reserved
0x42004C00
0x42002400
0x42002800
0x42002C00
Reserved
0x42005400
0x42005000
AC
AHB-APB Bridge B
Reserved
PORT
DSU
NVMCTRL
DMAC
0x41000000
0x41002000
0x41004000
0x41006000
MTB
0x41008000
0x41009000
0x41FFFFFF
PAC
PM
MCLK
RSTC
OSCCTRL
OSC32KCTRL
SUPC
AHB-APB Bridge A
0x40000000
0x40000400
0x40000800
0x40000C00
0x40001000
0x40001400
0x40001800
0x40001C00
Reserved
0x40FFFFFF
GCLK
WDT
RTC
EIC
FREQM
Reserved
0x40002000
0x40002800
0x40002C00
0x40003000
0x40003400
Reserved
0x42FFFFFF
Reserved
0x42005800
PTC
0x42006000
0x42005C00
CCL
0x48000000
0x480001FF
AHB-APB
Bridge A
AHB-APB
Bridge B
AHB-APB
Bridge C
Reserved
AHB
DIVAS
0x40002400
TCC1
TCC2
SAM C20/C21 Family Data Sheet
Product Mapping
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 46
9. Memories
9.1 Embedded Memories
• Internal high-speed Flash with read-while-write capability on section of the array
• Internal high-speed RAM, single-cycle access at full speed
9.2 Physical Memory Map
The High-Speed bus is implemented as a bus matrix. All High-Speed bus addresses are fixed, and they
are never remapped in any way, even during boot. The 32-bit physical address space is mapped as
follows:
Table 9-1. SAM C20/C21 Physical Memory Map(1)
Memory Start address Size Size Size Size
x18 x17 x16 x15
Embedded Flash 0x00000000 256 Kbytes 128 Kbytes 64 Kbytes 32 Kbytes
Embedded RWW section 0x00400000 8 Kbytes 4 Kbytes 2 Kbytes 1 Kbytes
Embedded high-speed SRAM 0x20000000 32 Kbytes 16 Kbytes 8 Kbytes 4 Kbytes
AHB-APB Bridge A 0x40000000 64 Kbytes 64 Kbytes 64 Kbytes 64 Kbytes
AHB-APB Bridge B 0x41000000 64 Kbytes 64 Kbytes 64 Kbytes 64 Kbytes
AHB-APB Bridge C 0x42000000 64 Kbytes 64 Kbytes 64 Kbytes 64 Kbytes
AHB-APB Bridge D 0x43000000 64 Kbytes - - -
AHB DIVAS 0x48000000 64 Kbytes 64 Kbytes 64 Kbytes 64 Kbytes
IOBUS 0x60000000 64 Kbytes 64 Kbytes 64 Kbytes 64 Kbytes
Note: 1. x = SAM C20/C21 G/J/E/N. The N-series (100-pin devices) does not include x16 and x15 option.
Table 9-2. SAM C20/C21 Flash Memory Parameters(1)
Device Flash size (FLASH_PM) Number of pages (FLASH_P) Page size (FLASH_W)
x18 256Kbytes 4096 64 bytes
x17 128Kbytes 2048 64 bytes
x16 64Kbytes 1024 64 bytes
x15 32Kbytes 512 64 bytes
Note: 1. x = SAM C20/C21 G/J/E/N. The N-series (100-pin devices) does not include x16 and x15 option.
SAM C20/C21 Family Data Sheet
Memories
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 47
Table 9-3. SAM C20/C21 RWW Section Parameters(1)
Device Flash size (FLASH_PM) Number of pages (FLASH_P) Page size (FLASH_W)
x18 8Kbytes 128 64 bytes
x17 4Kbytes 64 64 bytes
x16 2Kbytes 32 64 bytes
x15 1Kbytes 16 64 bytes
Note: 1. x = SAM C20/C21 G/J/E/N. The N-series (100-pin devices) does not include x16 and x15 option.
9.3 NVM User Row Mapping
The first two 32-bit words of the NVM User Row contains calibration data that are automatically read at
device power on.
The NVM User Row can be read at address 0x804000.
To write the NVM User Row, refer to the NVMCTRL - Non-Volatile Memory Controller.
Note that when writing to the user row the values do not get loaded by the other modules on the device
until a device reset occurs.
Table 9-4. NVM User Row Mapping
Bit Position Name Usage Production
setting
Related Peripheral
Register
2:0 BOOTPROT Used to select one of eight
different bootloader sizes.
7 NVMCTRL
3 Reserved - 1 -
6:4 EEPROM Used to select one of eight
different EEPROM sizes.
7 NVMCTRL
7 Reserved - 1 -
13:8 BODVDD Level BODVDD Threshold Level at
power on.
8 SUPC.BODVDD
14 BODVDD Disable BODVDD Disable at power on. 0 SUPC.BODVDD
16:15 BODVDD Action BODVDD Action at power on. 1 SUPC.BODVDD
25:17 Reserved Voltage Regulator Internal
BOD (BODCORE)
configuration. These bits are
written in production and must
not be changed.
0xA8 -
26 WDT Enable WDT Enable at power on. 0 WDT.CTRLA
27 WDT Always-On WDT Always-On at power on. 0 WDT.CTRLA
31:28 WDT Period WDT Period at power on. 0xB WDT.CONFIG
SAM C20/C21 Family Data Sheet
Memories
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 48
...........continued
Bit Position Name Usage Production
setting
Related Peripheral
Register
35:32 WDT Window WDT Window mode time-out
at power on.
0xB WDT.CONFIG
39:36 WDT
EWOFFSET
WDT Early Warning Interrupt
Time Offset at power on.
0xB WDT.EWCTRL
40 WDT WEN WDT Timer Window Mode
Enable at power on.
0 WDT.CTRLA
41 BODVDD
Hysteresis
BODVDD Hysteresis
configuration at power on.
0 SUPC.BODVDD
42 Reserved Voltage Regulator Internal
BOD (BODCORE)
configuration. These bits are
written in production and must
not be changed.
0 -
47:43 Reserved - 0x1F -
63:48 LOCK NVM Region Lock Bits. 0xFFFF NVMCTRL
Related Links
27. NVMCTRL – Nonvolatile Memory Controller
23.8.1 CTRLA
23.8.2 CONFIG
23.8.3 EWCTRL
22.8.5 BODVDD
9.4 NVM Software Calibration Area Mapping
The NVM Software Calibration Area contains calibration data that are measured and written during
production test. These calibration values should be read by the application software and written back to
the corresponding register.
The NVM Software Calibration Area can be read at address 0x806020.
The NVM Software Calibration Area can not be written.
Table 9-5. SAM CA1 NVM Software Calibration Area Mapping
Bit Position Name Description
2:0 ADC0 LINEARITY ADC0 Linearity Calibration. Should be written to the CALIB register.
5:3 ADC0 BIASCAL ADC0 Bias Calibration. Should be written to the CALIB register.
8:6 ADC1 LINEARITY ADC1 Linearity Calibration. Should be written to the CALIB register.
11:9 ADC1 BIASCAL ADC1 Bias Calibration. Should be written to the CALIB register.
18:12 OSC32K CAL OSC32K Calibration. Should be written to OSC32K register.
SAM C20/C21 Family Data Sheet
Memories
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 49
...........continued
Bit Position Name Description
40:19 CAL48M 5V OSC48M Calibration: VDD range 3.6V to 5.5V. Should be written to
the CAL48M register.
62:41 CAL48M 3V3 OSC48M Calibration: VDD range 2.7V to 3.6V. Should be written to
the CAL48M register.
63 Reserved
Related Links
20.8.18 CAL48M
9.5 NVM Temperature Calibration Area Mapping, SAM C21
The NVM Temperature Calibration Area contains calibration data that are measured and written during
production test. These calibration values should be read by the application software and written back to
the corresponding register.
The NVM Temperature Calibration Area can be read at address 0x806030.
The NVM Temperature Calibration Area can not be written.
Table 9-6. NVM Temperature Calibration Area Mapping, SAM C21
Bit Position Name Description
5:0 TSENS TCAL TSENS Temperature Calibration. Should be written to the TSENS CAL
register.
11:6 TSENS FCAL TSENS Frequency Calibration. Should be written to the TSENS CAL
register.
35:12 TSENS GAIN TSENS Gain Calibration. Should be written to the TSENS GAIN
register.
59:36 TSENS OFFSET TSENS Offset Calibration. Should be written to TSENS OFFSET
register.
63:60 Reserved
Related Links
43.8.15 CAL
43.8.13 GAIN
43.8.14 OFFSET
9.6 Serial Number
Each device has a unique 128-bit serial number which is a concatenation of four 32-bit words contained
at the following addresses:
Word 0: 0x0080A00C
Word 1: 0x0080A040
SAM C20/C21 Family Data Sheet
Memories
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 50
Word 2: 0x0080A044
Word 3: 0x0080A048
The uniqueness of the serial number is guaranteed only when using all 128 bits.
SAM C20/C21 Family Data Sheet
Memories
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 51
10. Processor and Architecture
10.1 Cortex M0+ Processor
The SAM C20/C21 implement the ARM® Cortex™-M0+ processor, based on the ARMv6 Architecture and
Thumb®-2 ISA. The Cortex M0+ is 100% instruction set compatible with its predecessor, the Cortex-M0
core, and upward compatible to Cortex-M3 and M4 cores. The implemented ARM Cortex-M0+ is revision
r0p1. For more information refer to http://www.arm.com.
10.1.1 Cortex M0+ Configuration
Table 10-1. Cortex M0+ Configuration
Features Cortex-M0+ options SAM C20/C21 configurations
Interrupts External interrupts 0-32 32
Data endianness Little-endian or big-endian Little-endian
SysTick timer Present or absent Present
Number of watchpoint comparators 0, 1, 2 2
Number of breakpoint comparators 0, 1, 2, 3, 4 4
Halting debug support Present or absent Present
Multiplier Fast or small Fast (single cycle)
Single-cycle I/O port Present or absent Present
Wake-up interrupt controller Supported or not supported Not supported
Vector Table Offset Register Present or absent Present
Unprivileged/Privileged support Present or absent Present
Memory Protection Unit Not present or 8-region 8-region
Reset all registers Present or absent Absent
Instruction fetch width 16-bit only or mostly 32-bit 32-bit
The ARM Cortex-M0+ core has two bus interfaces:
• Single 32-bit AMBA-3 AHB-Lite system interface that provides connections to peripherals and all
system memory, which includes flash and RAM.
• Single 32-bit I/O port bus interfacing to the PORT and DIVAS with 1-cycle loads and stores.
10.1.2 Cortex-M0+ Peripherals
• System Control Space (SCS)
– The processor provides debug through registers in the SCS. Refer to the Cortex-M0+ Technical
Reference Manual for details (http://www.arm.com).
• Nested Vectored Interrupt Controller (NVIC)
– External interrupt signals connect to the NVIC, and the NVIC prioritizes the interrupts. Software
can set the priority of each interrupt. The NVIC and the Cortex-M0+ processor core are closely
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 52
coupled, providing low latency interrupt processing and efficient processing of late arriving
interrupts. Refer to 10.2 Nested Vector Interrupt Controller and the Cortex-M0+ Technical
Reference Manual for details (http://www.arm.com).
• System Timer (SysTick)
– The System Timer is a 24-bit timer clocked by CLK_CPU that extends the functionality of both
the processor and the NVIC. Refer to the Cortex-M0+ Technical Reference Manual for details
(http://www.arm.com).
• System Control Block (SCB)
– The System Control Block provides system implementation information, and system control. This
includes configuration, control, and reporting of the system exceptions. Refer to the Cortex-M0+
Devices Generic User Guide for details (http://www.arm.com).
• Micro Trace Buffer (MTB)
– The CoreSight MTB-M0+ (MTB) provides a simple execution trace capability to the Cortex-M0+
processor. Refer to section 10.3 Micro Trace Buffer and the CoreSight MTB-M0+ Technical
Reference Manual for details (http://www.arm.com).
• Memory Protection Unit (MPU)
– The Memory Protection Unit divides the memory map into a number of regions, and defines the
location, size, access permissions and memory attributes of each region. Refer to the Cortex-
M0+ Devices Generic User Guide for details (http://www.arm.com)
10.1.3 Cortex-M0+ Address Map
Table 10-2. Cortex-M0+ Address Map
Address Peripheral
0xE000E000 System Control Space (SCS)
0xE000E010 System Timer (SysTick)
0xE000E100 Nested Vectored Interrupt Controller (NVIC)
0xE000ED00 System Control Block (SCB)
0x41008000 Micro Trace Buffer (MTB)
Related Links
8. Product Mapping
10.1.4 I/O Interface
10.1.4.1 Overview
Because accesses to the AMBA® AHB-Lite™ and the single cycle I/O interface can be made concurrently,
the Cortex-M0+ processor can fetch the next instructions while accessing the I/Os. This enables single
cycle I/O accesses to be sustained for as long as needed.
10.1.4.2 Description
Direct access to PORT registers and DIVAS registers.
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 53
10.2 Nested Vector Interrupt Controller
10.2.1 Overview
The Nested Vectored Interrupt Controller (NVIC) in the SAM C20/C21 supports 32 interrupt lines with four
different priority levels. For more details, refer to the Cortex-M0+ Technical Reference Manual (http://
www.arm.com).
10.2.2 Interrupt Line Mapping
Each of the interrupt lines is connected to one peripheral instance, as shown in the table below. Each
peripheral can have one or more interrupt flags, located in the peripheral’s Interrupt Flag Status and Clear
(INTFLAG) register.
The interrupt flag is set when the interrupt condition occurs. Each interrupt in the peripheral can be
individually enabled by writing a one to the corresponding bit in the peripheral’s Interrupt Enable Set
(INTENSET) register, and disabled by writing a one to the corresponding bit in the peripheral’s Interrupt
Enable Clear (INTENCLR) register.
An interrupt request is generated from the peripheral when the interrupt flag is set and the corresponding
interrupt is enabled.
The interrupt requests for one peripheral are ORed together on system level, generating one interrupt
request for each peripheral. An interrupt request will set the corresponding interrupt pending bit in the
NVIC interrupt pending registers (SETPEND/CLRPEND bits in ISPR/ICPR).
For the NVIC to activate the interrupt, it must be enabled in the NVIC interrupt enable register (SETENA/
CLRENA bits in ISER/ICER). The NVIC interrupt priority registers IPR0-IPR7 provide a priority field for
each interrupt.
Table 10-3. Interrupt Line Mapping, SAM C21
Peripheral Source NVIC Line
EIC NMI – External Interrupt Controller NMI
PM – Power Manager
MCLK - Main Clock
OSCCTRL - Oscillators Controller
OSC32KCTRL - 32kHz Oscillators Controller
SUPC - Supply Controller
PAC - Protection Access Controller
0
WDT – Watchdog Timer 1
RTC – Real Time Clock 2
EIC – External Interrupt Controller 3
FREQM – Frequency Meter 4
TSENS – Temperature Sensor 5
NVMCTRL – Non-Volatile Memory Controller 6
DMAC - Direct Memory Access Controller 7
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 54
...........continued
Peripheral Source NVIC Line
EVSYS – Event System 8
SERCOM0 – Serial Communication Controller 0
SERCOM6 – Serial Communication Controller 6
9
SERCOM1 – Serial Communication Controller 1
SERCOM7 – Serial Communication Controller 7
10
SERCOM2 – Serial Communication Controller 2 11
SERCOM3 – Serial Communication Controller 3 12
SERCOM4 – Serial Communication Controller 4 13
SERCOM5 – Serial Communication Controller 5 14
CAN0 – Controller Area Network 0 15
CAN1 – Controller Area Network 1 16
TCC0 – Timer Counter for Control 0 17
TCC1 – Timer Counter for Control 1 18
TCC2 – Timer Counter for Control 2 19
TC0 – Timer Counter 0
TC5 – Timer Counter 5
20
TC1 – Timer Counter 1
TC6 – Timer Counter 6
21
TC2 – Timer Counter 2
TC7 – Timer Counter 7
22
TC3 – Timer Counter 3Reserved 23
TC4 – Timer Counter 4Reserved 24
ADC0 – Analog-to-Digital Converter 0 25
ADC1 – Analog-to-Digital Converter 1Reserved 26
AC – Analog Comparator 27
DAC – Digital-to-Analog Converter 28
SDADC – Sigma-Delta Analog-to-Digital Converter 1 29
PTC – Peripheral Touch Controller 30
Reserved 31
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 55
Table 10-4. Interrupt Line Mapping, SAM C20
Peripheral Source NVIC Line
EIC NMI – External Interrupt Controller NMI
PM – Power Manager
MCLK - Main Clock
OSCCTRL - Oscillators Controller
OSC32KCTRL - 32kHz Oscillators Controller
SUPC - Supply Controller
PAC - Protection Access Controller
0
WDT – Watchdog Timer 1
RTC – Real Time Clock 2
EIC – External Interrupt Controller 3
FREQM – Frequency Meter 4
Reserved 5
NVMCTRL – Non-Volatile Memory Controller 6
DMAC - Direct Memory Access Controller 7
EVSYS – Event System 8
SERCOM0 – Serial Communication Controller 0
SERCOM6 – Serial Communication Controller 6
9
SERCOM1 – Serial Communication Controller 1
SERCOM7 – Serial Communication Controller 7
10
SERCOM2 – Serial Communication Controller 2 11
SERCOM3 – Serial Communication Controller 3 12
SERCOM4 – Serial Communication Controller 4 13
SERCOM5 – Serial Communication Controller 5 14
Reserved 15
Reserved 16
TCC0 – Timer Counter for Control 0 17
TCC1 – Timer Counter for Control 1 18
TCC2 – Timer Counter for Control 2 19
TC0 – Timer Counter 0
TC5 – Timer Counter 5
20
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 56
...........continued
Peripheral Source NVIC Line
TC1 – Timer Counter 1
TC6 – Timer Counter 6
21
TC2 – Timer Counter 2
TC7 – Timer Counter 7
22
TC3 – Timer Counter 3Reserved 23
TC4 – Timer Counter 4Reserved 24
ADC0 – Analog-to-Digital Converter 0 25
Reserved 26
AC – Analog Comparator 27
Reserved 28
Reserved 29
PTC – Peripheral Touch Controller 30
Reserved 31
10.3 Micro Trace Buffer
10.3.1 Features
• Program flow tracing for the Cortex-M0+ processor
• MTB SRAM can be used for both trace and general purpose storage by the processor
• The position and size of the trace buffer in SRAM is configurable by software
• CoreSight compliant
10.3.2 Overview
When enabled, the MTB records changes in program flow, reported by the Cortex-M0+ processor over
the execution trace interface shared between the Cortex-M0+ processor and the CoreSight MTB-M0+.
This information is stored as trace packets in the SRAM by the MTB. An off-chip debugger can extract the
trace information using the Debug Access Port to read the trace information from the SRAM. The
debugger can then reconstruct the program flow from this information.
The MTB simultaneously stores trace information into the SRAM, and gives the processor access to the
SRAM. The MTB ensures that trace write accesses have priority over processor accesses.
The execution trace packet consists of a pair of 32-bit words that the MTB generates when it detects the
processor PC value changes non-sequentially. A non-sequential PC change can occur during branch
instructions or during exception entry. See the CoreSight MTB-M0+ Technical Reference Manual for more
details on the MTB execution trace packet format.
Tracing is enabled when the MASTER.EN bit in the Master Trace Control Register is 1. There are various
ways to set the bit to 1 to start tracing, or to 0 to stop tracing. See the CoreSight Cortex-M0+ Technical
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 57
Reference Manual for more details on the Trace start and stop and for a detailed description of the MTB’s
MASTER register. The MTB can be programmed to stop tracing automatically when the memory fills to a
specified watermark level or to start or stop tracing by writing directly to the MASTER.EN bit. If the
watermark mechanism is not being used and the trace buffer overflows, then the buffer wraps around
overwriting previous trace packets.
The base address of the MTB registers is 0x41008000; this address is also written in the CoreSight ROM
Table. The offset of each register from the base address is fixed and as defined by the CoreSight MTB-
M0+ Technical Reference Manual. The MTB has 4 programmable registers to control the behavior of the
trace features:
• POSITION: Contains the trace write pointer and the wrap bit,
• MASTER: Contains the main trace enable bit and other trace control fields,
• FLOW: Contains the WATERMARK address and the AUTOSTOP and AUTOHALT control bits,
• BASE: Indicates where the SRAM is located in the processor memory map. This register is provided
to enable auto discovery of the MTB SRAM location, by a debug agent.
See the CoreSight MTB-M0+ Technical Reference Manual for a detailed description of these registers.
10.4 High-Speed Bus System
10.4.1 Features
High-Speed Bus Matrix has the following features:
• Symmetric crossbar bus switch implementation
• Allows concurrent accesses from different masters to different slaves
• 32-bit data bus
• Operation at a 1-to-1 clock frequency with the bus masters
10.4.2 Configuration
Figure 10-1. Master-Slave Relation High-Speed Bus Matrix, SAM C20/C21
DSU
DSU
High-Speed Bus SLAVES
FlexRAM
MASTER ID
SLAVE ID
FlexRAM PORT ID
Internal Flash
AHB-APB Bridge A
AHB-APB Bridge B
AHB-APB Bridge C
DIVAS
03457
9 8 7 5-6 3-4 2 1 0
12
6
Multi-Slave
MASTERS
Priviledged FlexRAM-access
MASTERS
CM0+
DSU
DMAC Data
MTB
CAN 1
CAN 0
DMAC WB
DMAC Fetch
0
1
2
MTB
CAN 1
CAN 0
DMAC WB
DMAC Fetch
DSU
CM0+
DMAC Data
AHB-APB Bridge D
8
(2)
(2)
1. The AHB-APB bridge D is available only on C21N and C20N.
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 58
2. The CAN peripheral is available only on C21.
Table 10-5. Bus Matrix Masters
Bus Matrix Masters Master ID
CM0+ - Cortex M0+ Processor 0
DSU - Device Service Unit 1
DMAC - Direct Memory Access Controller / Data Access 2
Table 10-6. Bus Matrix Slaves
Bus Matrix Slaves Slave ID
Internal Flash Memory 0
SRAM Port 4 - CM0+ Access 1
SRAM Port 6 - DSU Access 2
AHB-APB Bridge A 3
AHB-APB Bridge B 4
AHB-APB Bridge C 5
SRAM Port 5 - DMAC Data Access 6
DIVAS - Divide Accelerator 7
Table 10-7. SRAM Port Connections
SRAM Port Connection Port ID Connection Type
CM0+ - Cortex M0+ Processor 0 Bus Matrix
DSU - Device Service Unit 1 Bus Matrix
DMAC - Direct Memory Access Controller - Data Access 2 Bus Matrix
DMAC - Direct Memory Access Controller - Fetch Access 0 3 Direct
DMAC - Direct Memory Access Controller - Fetch Access 1 4 Direct
DMAC - Direct Memory Access Controller - Write-Back Access 0 5 Direct
DMAC - Direct Memory Access Controller - Write-Back Access 1 6 Direct
CAN0 - Controller Area Network 0 7 Direct
Reserved 8 Reserved
MTB - Micro Trace Buffer 9 Direct
10.4.3 SRAM Quality of Service
To ensure that masters with latency requirements get sufficient priority when accessing RAM, the different
masters can be configured to have a given priority for different type of access.
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 59
The Quality of Service (QoS) level is independently selected for each master accessing the RAM. For any
access to the RAM the RAM also receives the QoS level. The QoS levels and their corresponding bit
values for the QoS level configuration is shown in below.
Table 10-8. Quality of Service Level Configuration
Value Name Description
0x0 DISABLE Background (no sensitive operation)
0x1 LOW Sensitive Bandwidth
0x2 MEDIUM Sensitive Latency
0x3 HIGH Critical Latency
If a master is configured with QoS level DISABLE (0x0) or LOW (0x1) there will be minimum latency of
one cycle for the RAM access.
The priority order for concurrent accesses are decided by two factors. First, the QoS level for the master
and second, a static priority given by Table 10-7. The lowest port ID has the highest static priority.
The MTB has fixed QoS level HIGH (0x3) and the DSU has fixed QoS level LOW (0x1).
The CPU QoS level can be written/read at address 0x41007110, bits [1:0]. Its reset value is 0x0.
Refer to different master QOSCTRL registers for configuring QoS for the other masters (for SAM C21:
CAN, DMAC; for SAM C20: DMAC).
SAM C20/C21 Family Data Sheet
Processor and Architecture
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 60
11. PAC - Peripheral Access Controller
11.1 Overview
The Peripheral Access Controller provides an interface for the locking and unlocking of peripheral
registers within the device. It reports all violations that could happen when accessing a peripheral: write
protected access, illegal access, enable protected access, access when clock synchronization or
software reset is on-going. These errors are reported in a unique interrupt flag for a peripheral. The PAC
module also reports errors occurring at the slave bus level, when an access to a non-existing address is
detected.
11.2 Features
• Manages write protection access and reports access errors for the peripheral modules or bridges.
11.3 Block Diagram
Figure 11-1. PAC Block Diagram
INTFLAG
PERIPHERAL m
PERIPHERAL 0
BUSn
BUS0
Peripheral ERROR
Peripheral ERROR
WRITE CONTROL
WRITE CONTROL
PAC CONTROL
PERIPHERAL m
PERIPHERAL 0
SLAVEs
PAC
IRQ
APB
Slave ERROR
11.4 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
11.4.1 IO Lines
Not applicable.
11.4.2 Power Management
The PAC can continue to operate in any Sleep mode where the selected source clock is running. The
PAC interrupts can be used to wake up the device from Sleep modes. The events can trigger other
operations in the system without exiting sleep modes.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 61
Related Links
19. PM – Power Manager
11.4.3 Clocks
The PAC bus clock (CLK_PAC_APB) can be enabled and disabled in the Main Clock module. The default
state of CLK_PAC_APB can be found in the related links.
Related Links
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
11.4.4 DMA
Not applicable.
11.4.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the PAC interrupt requires the
Interrupt Controller to be configured first.
Table 11-1. Interrupt Lines
Instances NVIC Line
PAC PACERR
Related Links
10.2 Nested Vector Interrupt Controller
11.4.6 Events
The events are connected to the Event System, which may need configuration.
Related Links
29. EVSYS – Event System
11.4.7 Debug Operation
When the CPU is halted in debug mode, write protection of all peripherals is disabled and the PAC
continues normal operation.
11.4.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Write Control (WRCTRL) register
• AHB Slave Bus Interrupt Flag Status and Clear (INTFLAGAHB) register
• Peripheral Interrupt Flag Status and Clear n (INTFLAG A/B/C...) registers
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 62
11.5 Functional Description
11.5.1 Principle of Operation
The Peripheral Access Control module allows the user to set a write protection on peripheral modules
and generate an interrupt in case of a peripheral access violation. The peripheral’s protection can be set,
cleared or locked at the user discretion. A set of Interrupt Flag and Status registers informs the user on
the status of the violation in the peripherals. In addition, slaves bus errors can be also reported in the
cases where reserved area is accessed by the application.
11.5.2 Basic Operation
11.5.2.1 Initialization
After reset, the PAC is enabled.
11.5.2.2 Initialization, Enabling and Resetting
The PAC is always enabled after reset.
Only a hardware reset will reset the PAC module.
11.5.2.3 Operations
The PAC module allows the user to set, clear or lock the write protection status of all peripherals on all
Peripheral Bridges.
If a peripheral register violation occurs, the Peripheral Interrupt Flag n registers (INTFLAGn) are updated
to inform the user on the status of the violation in the peripherals connected to the Peripheral Bridge n (n
= A,B,C ...). The corresponding Peripheral Write Control Status n register (STATUSn) gives the state of
the write protection for all peripherals connected to the corresponding Peripheral Bridge n. Refer to
11.5.2.4 Peripheral Access Errors for details.
The PAC module also report the errors occurring at slave bus level when an access to reserved area is
detected. AHB Slave Bus Interrupt Flag register (INTFLAGAHB) informs the user on the status of the
violation in the corresponding slave. Refer to the 11.5.2.7 AHB Slave Bus Errors for details.
11.5.2.4 Peripheral Access Errors
The following events will generate a Peripheral Access Error:
• Protected write: To avoid unexpected writes to a peripheral's registers, each peripheral can be write
protected. Only the registers denoted as “PAC Write-Protection” in the module’s datasheet can be
protected. If a peripheral is not write protected, write data accesses are performed normally. If a
peripheral is write protected and if a write access is attempted, data will not be written and peripheral
returns an access error. The corresponding interrupt flag bit in the INTFLAGn register will be set.
• Illegal access: Access to an unimplemented register within the module.
• Synchronized write error: For write-synchronized registers an error will be reported if the register is
written while a synchronization is ongoing.
When any of the INTFLAGn registers bit are set, an interrupt will be requested if the PAC interrupt enable
bit is set.
11.5.2.5 Write Access Protection Management
Peripheral access control can be enabled or disabled by writing to the WRCTRL register.
The data written to the WRCTRL register is composed of two fields; WRCTRL.PERID and WRCTRL.KEY.
The WRCTRL.PERID is an unique identifier corresponding to a peripheral. The WRCTRL.KEY is a key
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 63
value that defines the operation to be done on the control access bit. These operations can be “clear
protection”, “set protection” and “set and lock protection bit”.
The “clear protection” operation will remove the write access protection for the peripheral selected by
WRCTRL.PERID. Write accesses are allowed for the registers in this peripheral.
The “set protection” operation will set the write access protection for the peripheral selected by
WRCTRL.PERID. Write accesses are not allowed for the registers with write protection property in this
peripheral.
The “set and lock protection” operation will set the write access protection for the peripheral selected by
WRCTRL.PERID and locks the access rights of the selected peripheral registers. The write access
protection will only be cleared by a hardware reset.
The peripheral access control status can be read from the corresponding STATUSn register.
11.5.2.6 Write Access Protection Management Errors
Only word-wise writes to the WRCTRL register will effectively change the access protection. Other type of
accesses will have no effect and will cause a PAC write access error. This error is reported in the
INTFLAGn.PAC bit corresponding to the PAC module.
PAC also offers an additional safety feature for correct program execution with an interrupt generated on
double write clear protection or double write set protection. If a peripheral is write protected and a
subsequent set protection operation is detected then the PAC returns an error, and similarly for a double
clear protection operation.
In addition, an error is generated when writing a “set and lock” protection to a write-protected peripheral
or when a write access is done to a locked set protection. This can be used to ensure that the application
follows the intended program flow by always following a write protect with an unprotect and conversely.
However in applications where a write protected peripheral is used in several contexts, e.g. interrupt, care
should be taken so that either the interrupt can not happen while the main application or other interrupt
levels manipulates the write protection status or when the interrupt handler needs to unprotect the
peripheral based on the current protection status by reading the STATUS register.
The errors generated while accessing the PAC module registers (eg. key error, double protect error...) will
set the INTFLAGn.PAC flag.
11.5.2.7 AHB Slave Bus Errors
The PAC module reports errors occurring at the AHB Slave bus level. These errors are generated when
an access is performed at an address where no slave (bridge or peripheral) is mapped . These errors are
reported in the corresponding bits of the INTFLAGAHB register.
11.5.2.8 Generating Events
The PAC module can also generate an event when any of the Interrupt Flag registers bit are set. To
enable the PAC event generation, the control bit EVCTRL.ERREO must be set a '1'.
11.5.3 DMA Operation
Not applicable.
11.5.4 Interrupts
The PAC has the following interrupt source:
• Error (ERR): Indicates that a peripheral access violation occurred in one of the peripherals controlled
by the PAC module, or a bridge error occurred in one of the bridges reported by the PAC
– This interrupt is a synchronous wake-up source.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 64
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAGAHB and INTFLAGn) registers is set when the interrupt condition occurs. Each
interrupt can be individually enabled by writing a '1' to the corresponding bit in the Interrupt Enable Set
(INTENSET) register, and disabled by writing a '1' to the corresponding bit in the Interrupt Enable Clear
(INTENCLR) register. An interrupt request is generated when the interrupt flag is set and the
corresponding interrupt is enabled. The interrupt request remains active until the interrupt flag is cleared,
the interrupt is disabled, or the PAC is reset. All interrupt requests from the peripheral are ORed together
on system level to generate one combined interrupt request to the NVIC. The user must read the
INTFLAGAHB and INTFLAGn registers to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
19.6.3.3 Sleep Mode Controller
11.5.5 Events
The PAC can generate the following output event:
• Error (ERR): Generated when one of the interrupt flag registers bits is set
Writing a '1' to an Event Output bit in the Event Control Register (EVCTRL.ERREO) enables the
corresponding output event. Writing a '0' to this bit disables the corresponding output event.
11.5.6 Sleep Mode Operation
In Sleep mode, the PAC is kept enabled if an available bus master (CPU, DMA) is running. The PAC will
continue to catch access errors from the module and generate interrupts or events.
11.5.7 Synchronization
Not applicable.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 65
11.6 Register Summary
Offset Name Bit Pos.
0x00 WRCTRL
7:0 PERID[7:0]
15:8 PERID[15:8]
23:16 KEY[7:0]
31:24
0x04 EVCTRL 7:0 ERREO
0x05
...
0x07
Reserved
0x08 INTENCLR 7:0 ERR
0x09 INTENSET 7:0 ERR
0x0A
...
0x0F
Reserved
0x10 INTFLAGAHB
7:0 DIVAS LPRAMDMAC HPB2 HPB0 HPB1 HSRAMDSU HSRAMCM0P FLASH
15:8 HPB3
23:16
31:24
0x14 INTFLAGA
7:0 GCLK SUPC OSC32KCTR
LOSCCTRL RSTC MCLK PM PAC
15:8 TSENS FREQM EIC RTC WDT
23:16
31:24
0x18 INTFLAGB
7:0 MTB DMAC NVMCTRL DSU PORT
15:8
23:16
31:24
0x1C INTFLAGC
7:0 CAN0 SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
15:8 TC3 TC2 TC1 TC0 TCC2 TCC1 TCC0 CAN1
23:16 CCL DAC AC SDADC ADC1 ADC0 TC4
31:24
0x20 INTFLAGD
7:0 TC7 TC6 TC5 SERCOM7 SERCOM6
15:8
23:16
31:24
0x24
...
0x33
Reserved
0x34 STATUSA
7:0 GCLK SUPC OSC32KCTR
LOSCCTRL MCLK PM
15:8 TSENS FREQM EIC RTC WDT
23:16
31:24
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 66
...........continued
Offset Name Bit Pos.
0x38 STATUSB
7:0 MTB DMAC NVMCTRL DSU PORT
15:8
23:16
31:24
0x3C STATUSC
7:0 CAN0 SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
15:8 TC3 TC2 TC1 TC0 TCC2 TCC1 TCC0 CAN1
23:16 CCL DAC AC SDADC ADC1 ADC0 TC4
31:24
0x40 STATUSD
7:0 TC7 TC6 TC5 SERCOM7 SERCOM6
15:8
23:16
31:24
11.7 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to the related links.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 67
11.7.1 Write Control
Name:  WRCTRL
Offset:  0x00
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
KEY[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
PERID[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PERID[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 23:16 – KEY[7:0] Peripheral Access Control Key
These bits define the peripheral access control key:
Value Name Description
0x0 OFF No action
0x1 CLEAR Clear the peripheral write control
0x2 SET Set the peripheral write control
0x3 LOCK Set and lock the peripheral write control until the next hardware reset
Bits 15:0 – PERID[15:0] Peripheral Identifier
The PERID represents the peripheral whose control is changed using the WRCTRL.KEY. The Peripheral
Identifier is calculated following formula:
 = 32*BridgeNumber+N
Where BridgeNumber represents the Peripheral Bridge Number (0 for Peripheral Bridge A, 1 for
Peripheral Bridge B, etc). N represents the peripheral index from the respective Bridge Number:
Table 11-2. PERID Values
Periph. Bridge Name BridgeNumber PERID Values
A 0 0+N
B 1 32+N
C 2 64+N
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 68
...........continued
Periph. Bridge Name BridgeNumber PERID Values
D 3 96+N
E 4 128+N
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 69
11.7.2 Event Control
Name:  EVCTRL
Offset:  0x04
Reset:  0x00
Bit 7 6 5 4 3 2 1 0
ERREO
Access RW
Reset 0
Bit 0 – ERREO Peripheral Access Error Event Output
This bit indicates if the Peripheral Access Error Event Output is enabled or disabled. When enabled, an
event will be generated when one of the interrupt flag registers bits (INTFLAGAHB, INTFLAGn) is set:
Value Description
0Peripheral Access Error Event Output is disabled.
1Peripheral Access Error Event Output is enabled.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 70
11.7.3 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x08
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
ERR
Access RW
Reset 0
Bit 0 – ERR Peripheral Access Error Interrupt Disable
This bit indicates that the Peripheral Access Error Interrupt is disabled and an interrupt request will be
generated when one of the interrupt flag registers bits (INTFLAGAHB, INTFLAGn) is set:
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Peripheral Access Error interrupt Enable bit and disables the
corresponding interrupt request.
Value Description
0Peripheral Access Error interrupt is disabled.
1Peripheral Access Error interrupt is enabled.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 71
11.7.4 Interrupt Enable Set
Name:  INTENSET
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
ERR
Access RW
Reset 0
Bit 0 – ERR Peripheral Access Error Interrupt Enable
This bit indicates that the Peripheral Access Error Interrupt is enabled and an interrupt request will be
generated when one of the interrupt flag registers bits (INTFLAGAHB, INTFLAGn) is set:
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Peripheral Access Error interrupt Enable bit and enables the
corresponding interrupt request.
Value Description
0Peripheral Access Error interrupt is disabled.
1Peripheral Access Error interrupt is enabled.
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 72
11.7.5 AHB Slave Bus Interrupt Flag Status and Clear
Name:  INTFLAGAHB
Offset:  0x10
Reset:  0x000000
Property:  –
This flag is cleared by writing a '1' to the flag.
This flag is set when an access error is detected by the SLAVE n, and will generate an interrupt request if
INTENCLR/SET.ERR is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the corresponding INTFLAGAHB interrupt flag.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
HPB3
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
DIVAS LPRAMDMAC HPB2 HPB0 HPB1 HSRAMDSU HSRAMCM0P FLASH
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 8 – HPB3 Interrupt Flag for SLAVE HPB3
Bit 7 – DIVAS Interrupt Flag for SLAVE DIVAS
Bit 6 – LPRAMDMAC Interrupt Flag for SLAVE LPRAMDMAC
Bit 5 – HPB2 Interrupt Flag for SLAVE HPB2
Bit 4 – HPB0 Interrupt Flag for SLAVE HPB0
Bit 3 – HPB1 Interrupt Flag for SLAVE HPB1
Bit 2 – HSRAMDSU Interrupt Flag for SLAVE HSRAMDSU
Bit 1 – HSRAMCM0P Interrupt Flag for SLAVE HSRAMCM0P
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 73
Bit 0 – FLASH Interrupt Flag for SLAVE FLASH
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 74
11.7.6 Peripheral Interrupt Flag Status and Clear A
Name:  INTFLAGA
Offset:  0x14
Reset:  0x000000
Property:  –
This flag is cleared by writing a one to the flag.
This flag is set when a Peripheral Access Error occurs while accessing the peripheral associated with the
respective INTFLAGA bit, and will generate an interrupt request if INTENCLR/SET.ERR is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the corresponding INTFLAGA interrupt flag.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TSENS FREQM EIC RTC WDT
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
GCLK SUPC OSC32KCTRL OSCCTRL RSTC MCLK PM PAC
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 12 – TSENS Interrupt Flag for TSENS
Bit 11 – FREQM Interrupt Flag for FREQM
Bit 10 – EIC Interrupt Flag for EIC
Bit 9 – RTC Interrupt Flag for RTC
Bit 8 – WDT Interrupt Flag for WDT
Bit 7 – GCLK Interrupt Flag for GCLK
Bit 6 – SUPC Interrupt Flag for SUPC
Bit 5 – OSC32KCTRL Interrupt Flag for OSC32KCTRL
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 75
Bit 4 – OSCCTRL Interrupt Flag for OSCCTRL
Bit 3 – RSTC Interrupt Flag for RSTC
Bit 2 – MCLK Interrupt Flag for MCLK
Bit 1 – PM Interrupt Flag for PM
Bit 0 – PAC Interrupt Flag for PAC
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 76
11.7.7 Peripheral Interrupt Flag Status and Clear B
Name:  INTFLAGB
Offset:  0x18
Reset:  0x000000
Property:  –
This flag is cleared by writing a '1' to the flag.
This flag is set when a Peripheral Access Error occurs while accessing the peripheral associated with the
respective INTFLAGB bit, and will generate an interrupt request if INTENCLR/SET.ERR is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the corresponding INTFLAGB interrupt flag.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
MTB DMAC NVMCTRL DSU PORT
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 4 – MTB Interrupt Flag for MTB
Bit 3 – DMAC Interrupt Flag for DMAC
Bit 2 – NVMCTRL Interrupt Flag for NVMCTRL
Bit 1 – DSU Interrupt Flag for DSU
Bit 0 – PORT Interrupt Flag for PORT
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 77
11.7.8 Peripheral Interrupt Flag Status and Clear C
Name:  INTFLAGC
Offset:  0x1C
Reset:  0x000000
Property:  –
This flag is cleared by writing a one to the flag.
This flag is set when a Peripheral Access Error occurs while accessing the peripheral associated with the
respective INTFLAGC bit, and will generate an interrupt request if INTENCLR/SET.ERR is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the corresponding INTFLAGC interrupt flag.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CCL DAC AC SDADC ADC1 ADC0 TC4
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TC3 TC2 TC1 TC0 TCC2 TCC1 TCC0 CAN1
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CAN0 SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 – CCL Interrupt Flag for CCL
Bit 21 – DAC Interrupt Flag for DAC
Bit 20 – AC Interrupt Flag for AC
Bit 19 – SDADC Interrupt Flag for SDADC
Bits 17, 18 – ADC Interrupt Flag for ADCn [n=1..0]
Bits 12, 13, 14, 15, 16 – TC Interrupt Flag for TCn [n = 4..0]
Bits 9, 10, 11 – TCC Interrupt Flag for TCCn [n = 2..0]
Bits 7, 8 – CAN Interrupt Flag for CAN
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 78
Bits 1, 2, 3, 4, 5, 6 – SERCOM Interrupt Flag for SERCOMn [n = 5..0]
Bit 0 – EVSYS Interrupt Flag for EVSYS
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 79
11.7.9 Peripheral Interrupt Flag Status and Clear D
Name:  INTFLAGD
Offset:  0x20
Reset:  0x000000
Property:  –
This flag is cleared by writing a one to the flag.
This flag is set when a Peripheral Access Error occurs while accessing the peripheral associated with the
respective INTFLAGD bit, and will generate an interrupt request if INTENCLR/SET.ERR is one.
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the corresponding INTFLAGD interrupt flag.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TC7 TC6 TC5 SERCOM7 SERCOM6
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bits 2, 3, 4 – TC Interrupt Flag for TCn [n = 7..5]
Bits 0, 1 – SERCOM Interrupt Flag for SERCOMn [n = 7..6]
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 80
11.7.10 Peripheral Write Protection Status A
Name:  STATUSA
Offset:  0x34
Reset:  0x000000
Property:  –
Writing to this register has no effect.
Reading STATUS register returns peripheral write protection status:
Value Description
0 Peripheral is not write protected.
1 Peripheral is write protected.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TSENS FREQM EIC RTC WDT
Access R R R R R
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
GCLK SUPC OSC32KCTRL OSCCTRL MCLK PM
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 12 – TSENS Peripheral TSENS Write Protection Status
Bit 11 – FREQM Peripheral FREQM Write Protection Status
Bit 10 – EIC Peripheral EIC Write Protection Status
Bit 9 – RTC Peripheral RTC Write Protection Status
Bit 8 – WDT Peripheral WDT Write Protection Status
Bit 7 – GCLK Peripheral GCLK Write Protection Status
Bit 6 – SUPC Peripheral SUPC Write Protection Status
Bit 5 – OSC32KCTRL Peripheral OSC32KCTRL Write Protection Status
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 81
Bit 4 – OSCCTRL Peripheral OSCCTRL Write Protection Status
Bit 2 – MCLK Peripheral MCLK Write Protection Status
Bit 1 – PM Peripheral PM Write Protection Status
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 82
11.7.11 Peripheral Write Protection Status B
Name:  STATUSB
Offset:  0x38
Reset:  0x000000
Property:  –
Writing to this register has no effect.
Reading STATUS register returns peripheral write protection status:
Value Description
0 Peripheral is not write protected.
1 Peripheral is write protected.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
MTB DMAC NVMCTRL DSU PORT
Access R R R R R
Reset 0 0 0 0 0
Bit 4 – MTB Peripheral MTB Write Protection Status
Bit 3 – DMAC Peripheral DMAC Write Protection Status
Bit 2 – NVMCTRL Peripheral NVMCTRL Write Protection Status
Bit 1 – DSU Peripheral DSU Write Protection Status
Bit 0 – PORT Peripheral PORt Write Protection Status
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 83
11.7.12 Peripheral Write Protection Status C
Name:  STATUSC
Offset:  0x3C
Reset:  0x000000
Property:  –
Writing to this register has no effect.
Reading STATUS register returns peripheral write protection status:
Value Description
0 Peripheral is not write protected.
1 Peripheral is write protected.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CCL DAC AC SDADC ADC1 ADC0 TC4
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TC3 TC2 TC1 TC0 TCC2 TCC1 TCC0 CAN1
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CAN0 SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 – CCL Peripheral CCL Write Protection Status
Bit 21 – DAC Peripheral DAC Write Protection Status
Bit 20 – AC Peripheral AC Write Protection Status
Bit 19 – SDADC Peripheral SDADC Write Protection Status
Bits 17, 18 – ADC Peripheral ADCn [n=1..0] Write Protection Status
Bits 12, 13, 14, 15, 16 – TC Peripheral TCn Write Protection Status [n = 4..0]
Bits 9, 10, 11 – TCC Peripheral TCCn [n = 2..0] Write Protection Status TCCn [n = 2..0]
Bits 7, 8 – CAN Peripheral CAN Write Protection Status
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 84
Bits 1, 2, 3, 4, 5, 6 – SERCOM Peripheral SERCOMn Write Protection Status [n = 5..0]
Bit 0 – EVSYS Peripheral EVSYS Write Protection Status
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 85
11.7.13 Peripheral Write Protection Status D
Name:  STATUSD
Offset:  0x40
Reset:  0x000000
Property:  –
Writing to this register has no effect.
Reading STATUS register returns peripheral write protection status:
Value Description
0 Peripheral is not write protected.
1 Peripheral is write protected.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TC7 TC6 TC5 SERCOM7 SERCOM6
Access R R R R R
Reset 0 0 0 0 0
Bits 2, 3, 4 – TC Peripheral TCn Write Protection Status [n = 7..5]
Bits 0, 1 – SERCOM Peripheral SERCOMn Write Protection Status [n = 7..6]
SAM C20/C21 Family Data Sheet
PAC - Peripheral Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 86
12. Peripherals Configuration Summary
Table 12-1. Peripherals Configuration Summary SAM C20/C21 E
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
AHB-APB
Bridge A
0x40000000 0 Y N/A
PAC 0x44000000 0 10 Y 0 Y 0 N 85 : ACCERR N/A
PM 0x40000400 0 1 Y 1 N N/A
MCLK 0x40000800 0 2 Y 2 N Y
RSTC 0x40000C00 3 Y 3 N N/A
OSCCTRL 0x40001000 0 4 Y 0: FDPLL96M
clk source
1: FDPLL96M
32kHz
4 N 0: XOSC_FAIL Y
OSC32KCTRL 0x40001400 0 5 Y 5 N 1: XOSC32K_FAIL Y
SUPC 0x40001800 0 6 Y 6 N N/A
GCLK 0x40001C00 7 Y 7 N N/A
WDT 0x40002000 1 8 Y 8 N Y
RTC 0x40002400 2 9 Y 9 N 2: CMP0/ALARM0
3: CMP1
4: OVF
5-12: PER0-7
Y
EIC 0x40002800 3,
NMI
10 Y 2 10 N 13-28: EXTINT0-15 Y
FREQM 0x40002C00 4 11 Y 3: Measure
4: Reference
11 N N/A
TSENS 0x40003000 5 12 N 5 12 N 0: START 29: WINMON 1: RESRDY A
AHB-APB
Bridge B
0x41000000 1 Y N/A
PORT 0x41000000 0 Y 0 N 1-4 : EV0-3 Y
DSU 0x41002000 3 Y 1 Y 1 Y N/A
NVMCTRL 0x41004000 6 5 Y 2 Y 39 2 N Y
DMAC 0x41006000 7 7 Y 3 N 5-8: CH0-3 30-33: CH0-3 Y
MTB 0x41008000 N 44: START
45: STOP
N/A
AHB-APB
Bridge C
0x42000000 2 Y N/A
EVSYS 0x42000000 8 0 N 6-17: one per
CHANNEL
0 N Y
SERCOM0 0x42000400 9 1 N 19: CORE
18: SLOW
1 N 2: RX
3: TX
Y
SERCOM1 0x42000800 10 2 N 20: CORE
18: SLOW
2 N 4: RX
5: TX
Y
SERCOM2 0x42000C00 11 3 N 21: CORE
18: SLOW
3 N 6: RX
7: TX
Y
SERCOM3 0x42001000 12 4 N 22: CORE
18: SLOW
4 N 8: RX
9: TX
Y
CAN0 0x42001C00 15 8 N 26 14: DEBUG N/A
CAN1 0x42002000 16 9 N 27 15: DEBUG N/A
TCC0 0x42002400 17 9 N 28 9 N 9-10: EV0-1
11-14: MC0-3
34: OVF
35: TRG
36: CNT
37-40: MC0-3
16: OVF
17-20: MC0-3
Y
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 87
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
TCC1 0x42002800 18 10 N 28 10 N 15-16: EV0-1
17-18: MC0-1
41: OVF
42: TRG
43: CNT
44-45: MC0-1
21: OVF
22-23: MC0-1
Y
TCC2 0x42002C00 19 11 N 29 11 N 19-20: EV0-1
21-22: MC0-1
46: OVF
47: TRG
48: CNT
49-50: MC0-1
24: OVF
25-26: MC0-1
Y
TC0 0x42003000 20 12 N 30 12 N 23: EVU 51: OVF
52-53: MC0-1
27: OVF
28-29: MC0-1
Y
TC1 0x42003400 21 13 N 30 13 N 24: EVU 54: OVF
55-56: MC0-1
30: OVF
21-32: MC0-1
Y
TC2 0x42003800 22 14 N 31 14 N 25: EVU 57: OVF
58-59: MC0-1
33: OVF
23-35: MC0-1
Y
TC3 0x42003C00 23 15 N 31 15 N 26: EVU 60: OVF
61-62: MC0-1
36: OVF
37-38: MC0-1
Y
TC4 0x42004000 24 16 N 32 16 N 27: EVU 63: OVF
64-65: MC0-1
39: OVF
40-41: MC0-1
Y
ADC0 0x42004400 25 17 N 33 17 N 28: START
29: SYNC
66: RESRDY
67: WINMON
42: RESRDY Y
ADC1 0x42004800 26 18 N 34 18 N 30: START
31: SYNC
68: RESRDY
69: WINMON
43: RESRDY Y
SDADC 0x42004C00 29 19 N 35 19 N 32: START
33: FLUSH
70: RESRDY
71: WINMON
44: RESRDY Y
AC 0x42005000 27 20 N 34 20 N 34:37
SOC0-3
72-75: COMP0-3
76-77: WIN0-1
Y
DAC 0x42005400 28 21 N 36 21 N 38: START 78: EMPTY 45: EMPTY Y
PTC 0x42005800 30 22 N 37 22 N 39: STCONV 79: EOC
80: WCOMP
EOC: 46
WCOMP: 47
SEQ: 48
CCL 0x42005C00 23 N 38 23 N 40-43 :
LUTIN0-3
781-84: LUTOUT0-3 Y
DIVAS 0x48000000 12 Y N/A
12.1 SAM C20/C21 N
Table 12-2. Peripherals Configuration Summary SAM C21 N
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
AHB-APB
Bridge A
0x40000000 0 Y N/A
PAC 0x40000000 0 10 Y 0 Y 0 N 85 : ACCERR N/A
PM 0x40000400 0 1 Y 1 N N/A
MCLK 0x40000800 0 2 Y 2 N Y
RSTC 0x40000C00 3 Y 3 N N/A
OSCCTRL 0x40001000 0 4 Y 0: FDPLL96M
clk source
1: FDPLL96M
32kHz
4 N 0: XOSC_FAIL Y
OSC32KCTRL 0x40001400 0 5 Y 5 N 1: XOSC32K_FAIL Y
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 88
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
SUPC 0x40001800 0 6 Y 6 N N/A
GCLK 0x40001C00 7 Y 7 N N/A
WDT 0x40002000 1 8 Y 8 N Y
RTC 0x40002400 2 9 Y 9 N 2: CMP0/ALARM0
3: CMP1
4: OVF5-1
5:12: PER0-7
Y
EIC 0x40002800 3,
NMI
10 Y 2 10 N 13-28: EXTINT0-15 Y
FREQM 0x40002C00 4 11 Y 3: Measure
4: Reference
11 N N/A
TSENS 0x40003000 5 12 N 5 12 N 0: START 29: WINMON 1: RESRDY A
AHB-APB
Bridge B
0x41000000 1 Y N/A
PORT 0x41000000 0 Y 0 N 1-4 : EV0-3 Y
DSU 0x41002000 3 Y 1 Y 1 Y N/A
NVMCTRL 0x41004000 6 5 Y 2 Y 39 2 N Y
DMAC 0x41006000 7 7 Y 3 N 5-8: CH0-3 30-33: CH0-3 Y
MTB 0x41008000 N 45: START
46: STOP
N/A
AHB-APB
Bridge C
0x42000000 2 Y N/A
EVSYS 0x42000000 8 0 N 6-17: one per
CHANNEL
0 N Y
SERCOM0 0x42000400 9 1 N 19: CORE
18: SLOW
1 N 2: RX
3: TX
Y
SERCOM1 0x42000800 10 2 N 20: CORE
18: SLOW
2 N 4: RX
5: TX
Y
SERCOM2 0x42000C00 11 3 N 21: CORE
18: SLOW
3 N 6: RX
7: TX
Y
SERCOM3 0x42001000 12 4 N 22: CORE
18: SLOW
4 N 8: RX
9: TX
Y
SERCOM4 0x42001400 13 5 N 23: CORE
18: SLOW
5 N 10: RX
11: TX
Y
SERCOM5 0x42001800 14 6 N 25: CORE
24: SLOW
6 N 12: RX
13: TX
Y
CAN0 0x42001C00 15 8 N 26 7 14: DEBUG N/A
CAN1 0x42002000 16 9 N 27 8 15: DEBUG N/A
TCC0 0x42002400 17 9 N 28 9 N 9-10: EV0-1
11-14: MC0-3
34: OVF
35: TRG
36: CNT
37-40: MC0-3
16: OVF
17-20: MC0-3
Y
TCC1 0x42002800 18 10 N 28 10 N 15-16: EV0-1
17-18:
MC0-1
41: OVF
42: TRG
43: CNT
44-45: MC0-1
21: OVF
22-23: MC0-1
Y
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 89
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
TCC2 0x42002C00 19 11 N 29 11 N 19-20: EV0-1
21-22:
MC0-1
46: OVF
47: TRG
48: CNT
49-50: MC0-1
24: OVF
25-26: MC0-1
Y
TC0 0x42003000 20 12 N 30 12 N 23: EVU 51: OVF
52-53: MC0-1
27: OVF
28-29: MC0-1
Y
TC1 0x42003400 21 13 N 30 13 N 24: EVU 54: OVF
55-56: MC0-1
30: OVF
31-32: MC0-1
Y
TC2 0x42003800 22 14 N 31 14 N 25: EVU 57: OVF
58-59: MC0-1
33: OVF
34-35: MC0-1
Y
TC3 0x42003C00 23 15 N 31 15 N 26: EVU 60: OVF
61-62: MC0-1
36: OVF
37-38: MC0-1
Y
TC4 0x42004000 24 16 N 32 16 N 27: EVU 63: OVF
64-65: MC0-1
39: OVF
40-41: MC0-1
Y
ADC0 0x42004400 25 17 N 33 17 N 28: START
29: SYNC
66: RESRDY
67: WINMON
42: RESRDY Y
ADC1 0x42004800 26 18 N 34 18 N 30: START
31: SYNC
68: RESRDY
69: WINMON
43: RESRDY Y
SDADC 0x42004C00 29 19 N 35 19 N 32: START
33: FLUSH
70: RESRDY
71: WINMON
44: RESRDY Y
AC 0x42005000 27 20 N 40 20 N 34-37:
SOC0-3
72-75: COMP0-3
76-77: WIN0-1
Y
DAC 0x42005400 28 21 N 36 21 N 38: START 78: EMPTY 45: EMPTY Y
PTC 0x42005800 30 22 N 37 22 N 39: STCONV 79: EOC
80: WCOMP
EOC: 46
WCOMP: 47
SEQ: 48
CCL 0x42005C00 23 N 38 23 N 40-43 :
LUTIN0-3
81-84: LUTOUT0-3 Y
AHB-APB
Bridge D
0x43000000 13 Y 0 N/A
SERCOM6 0x43000000 9 0 N 41: CORE
18: SLOW
0 N 49: RX
50: TX
Y
SERCOM7 0x43000400 10 1 N 42: CORE
18: SLOW
1 N 51: RX
52: TX
Y
TC5 0x43000800 20 2 N 43 2 N 47: EVU 87: OVF
88-89: MC0-1
53: OVF
54-55: MC0-1
Y
TC6 0x43000C00 21 3 N 44 3 N 48:EVU 90: OVF
91-92: MC0-1
56: OVF
57-58: MC0-1
Y
TC7 0x43001000 22 4 N 45 4 N 49:EVU 93: OVF
94-95: MC0-1
59: OVF
60-61: MC0-1
Y
DIVAS 0x48000000 12 Y N/A
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 90
Table 12-3. Peripherals Configuration Summary SAM C20 N
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
AHB-APB
Bridge A
0x40000000 0 Y N/A
PAC 0x40000000 0 10 Y 0 Y 0 N 85 : ACCERR N/A
PM 0x40000400 0 1 Y 1 N N/A
MCLK 0x40000800 0 2 Y 2 N Y
RSTC 0x40000C00 3 Y 3 N N/A
OSCCTRL 0x40001000 0 4 Y 0: FDPLL96M
clk source
1: FDPLL96M
32kHz
4 N 0: XOSC_FAIL Y
OSC32KCTRL 0x40001400 0 5 Y 5 N 1: XOSC32K_FAIL Y
SUPC 0x40001800 0 6 Y 6 N N/A
GCLK 0x40001C00 7 Y 7 N N/A
WDT 0x40002000 1 8 Y 8 N Y
RTC 0x40002400 2 9 Y 9 N 2: CMP0/ALARM0
3: CMP1
4: OVF5-1
5:12: PER0-7
Y
EIC 0x40002800 3,
NMI
10 Y 2 10 N 13-28: EXTINT0-15 Y
FREQM 0x40002C00 4 11 Y 3: Measure
4: Reference
11 N N/A
AHB-APB
Bridge B
0x41000000 1 Y N/A
PORT 0x41000000 0 Y 0 N 1-4 : EV0-3 Y
DSU 0x41002000 3 Y 1 Y 1 Y N/A
NVMCTRL 0x41004000 6 5 Y 2 Y 39 2 N Y
DMAC 0x41006000 7 7 Y 3 N 5-8: CH0-3 30-33: CH0-3 Y
MTB 0x41008000 N 45: START
46: STOP
N/A
AHB-APB
Bridge C
0x42000000 2 Y N/A
EVSYS 0x42000000 8 0 N 6-17: one per
CHANNEL
0 N Y
SERCOM0 0x42000400 9 1 N 19: CORE
18: SLOW
1 N 2: RX
3: TX
Y
SERCOM1 0x42000800 10 2 N 20: CORE
18: SLOW
2 N 4: RX
5: TX
Y
SERCOM2 0x42000C00 11 3 N 21: CORE
18: SLOW
3 N 6: RX
7: TX
Y
SERCOM3 0x42001000 12 4 N 22: CORE
18: SLOW
4 N 8: RX
9: TX
Y
SERCOM4 0x42001400 13 5 N 23: CORE
18: SLOW
5 N 10: RX
11: TX
Y
SERCOM5 0x42001800 14 6 N 25: CORE
24: SLOW
6 N 12: RX
13: TX
Y
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 91
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
TCC0 0x42002400 17 9 N 28 9 N 9-10: EV0-1
11-14:
MC0-3
34: OVF
35: TRG
36: CNT
37-40: MC0-3
16: OVF
17-20: MC0-3
Y
TCC1 0x42002800 18 10 N 28 10 N 15-16: EV0-1
17-18:
MC0-1
41: OVF
42: TRG
43: CNT
44-45: MC0-1
21: OVF
22-23: MC0-1
Y
TCC2 0x42002C00 19 11 N 29 11 N 19-20: EV0-1
21-22:
MC0-1
46: OVF
47: TRG
48: CNT
49-50: MC0-1
24: OVF
25-26: MC0-1
Y
TC0 0x42003000 20 12 N 30 12 N 23: EVU 51: OVF
52-53: MC0-1
27: OVF
28-29: MC0-1
Y
TC1 0x42003400 21 13 N 30 13 N 24: EVU 54: OVF
55-56: MC0-1
30: OVF
31-32: MC0-1
Y
TC2 0x42003800 22 14 N 31 14 N 25: EVU 57: OVF
58-59: MC0-1
33: OVF
34-35: MC0-1
Y
TC3 0x42003C00 23 15 N 31 15 N 26: EVU 60: OVF
61-62: MC0-1
36: OVF
37-38: MC0-1
Y
TC4 0x42004000 24 16 N 32 16 N 27: EVU 63: OVF
64-65: MC0-1
39: OVF
40-41: MC0-1
Y
ADC0 0x42004400 25 17 N 33 17 N 28: START
29: SYNC
66: RESRDY
67: WINMON
42: RESRDY Y
AC 0x42005000 27 20 N 40 20 N 34-37:
SOC0-3
72-75: COMP0-3
76-77: WIN0-1
Y
PTC 0x42005800 30 22 N 37 22 N 39: STCONV 79: EOC
80: WCOMP
EOC: 46
WCOMP: 47
SEQ: 48
CCL 0x42005C00 23 N 38 23 N 40-43 :
LUTIN0-3
81-84: LUTOUT0-3 Y
AHB-APB
Bridge D
0x43000000 13 Y 0 N/A
SERCOM6 0x43000000 9 0 N 41: CORE
18: SLOW
0 N 49: RX
50: TX
Y
SERCOM7 0x43000400 10 1 N 42: CORE
18: SLOW
1 N 51: RX
52: TX
Y
TC5 0x43000800 20 2 N 43 2 N 47: EVU 87: OVF
88-89: MC0-1
53: OVF
54-55: MC0-1
Y
TC6 0x43000C00 21 3 N 44 3 N 48:EVU 90: OVF
91-92: MC0-1
56: OVF
57-58: MC0-1
Y
TC7 0x43001000 22 4 N 45 4 N 49:EVU 93: OVF
94-95: MC0-1
59: OVF
60-61: MC0-1
Y
DIVAS 0x48000000 12 Y N/A
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 92
12.2 SAM C20/C21 E/G/J
Table 12-4. Peripherals Configuration Summary SAM C21 E/G/J
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
AHB-APB
Bridge A
0x40000000 0 Y N/A
PAC 0x44000000 0 10 Y 0 Y 0 N 85 : ACCERR N/A
PM 0x40000400 0 1 Y 1 N N/A
MCLK 0x40000800 0 2 Y 2 N Y
RSTC 0x40000C00 3 Y 3 N N/A
OSCCTRL 0x40001000 0 4 Y 0: FDPLL96M
clk source
1: FDPLL96M
32kHz
4 N 0: XOSC_FAIL Y
OSC32KCTRL 0x40001400 0 5 Y 5 N 1: XOSC32K_FAIL Y
SUPC 0x40001800 0 6 Y 6 N N/A
GCLK 0x40001C00 7 Y 7 N N/A
WDT 0x40002000 1 8 Y 8 N Y
RTC 0x40002400 2 9 Y 9 N 2: CMP0/ALARM0
3: CMP1
4: OVF
5-12: PER0-7
Y
EIC 0x40002800 3,
NMI
10 Y 2 10 N 13-28: EXTINT0-15 Y
FREQM 0x40002C00 4 11 Y 3: Measure
4: Reference
11 N N/A
TSENS 0x40003000 5 12 N 5 12 N 0: START 29: WINMON 1: RESRDY A
AHB-APB
Bridge B
0x41000000 1 Y N/A
PORT 0x41000000 0 Y 0 N 1-4 : EV0-3 Y
DSU 0x41002000 3 Y 1 Y 1 Y N/A
NVMCTRL 0x41004000 6 5 Y 2 Y 39 2 N Y
DMAC 0x41006000 7 7 Y 3 N 5-8: CH0-3 30-33: CH0-3 Y
MTB 0x41008000 N 44: START
45: STOP
N/A
AHB-APB
Bridge C
0x42000000 2 Y N/A
EVSYS 0x42000000 8 0 N 6-17: one per
CHANNEL
0 N Y
SERCOM0 0x42000400 9 1 N 19: CORE
18: SLOW
1 N 2: RX
3: TX
Y
SERCOM1 0x42000800 10 2 N 20: CORE
18: SLOW
2 N 4: RX
5: TX
Y
SERCOM2 0x42000C00 11 3 N 21: CORE
18: SLOW
3 N 6: RX
7: TX
Y
SERCOM3 0x42001000 12 4 N 22: CORE
18: SLOW
4 N 8: RX
9: TX
Y
SERCOM4 0x42001400 13 5 N 23: CORE
18: SLOW
5 N 10: RX
11: TX
Y
SERCOM5 0x42001800 14 6 N 25: CORE
24: SLOW
6 N 12: RX
13: TX
Y
CAN0 0x42001C00 15 8 N 26 14: DEBUG N/A
CAN1 0x42002000 16 9 N 27 15: DEBUG N/A
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 93
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
TCC0 0x42002400 17 9 N 28 9 N 9-10: EV0-1
11-14: MC0-3
34: OVF
35: TRG
36: CNT
37-40: MC0-3
16: OVF
17-20: MC0-3
Y
TCC1 0x42002800 18 10 N 28 10 N 15-16: EV0-1
17-18:
MC0-1
41: OVF
42: TRG
43: CNT
44-45: MC0-1
21: OVF
22-23: MC0-1
Y
TCC2 0x42002C00 19 11 N 29 11 N 19-20: EV0-1
21-22:
MC0-1
46: OVF
47: TRG
48: CNT
49-50: MC0-1
24: OVF
25-26: MC0-1
Y
TC0 0x42003000 20 12 N 30 12 N 23: EVU 51: OVF
52-53: MC0-1
27: OVF
28-29: MC0-1
Y
TC1 0x42003400 21 13 N 30 13 N 24: EVU 54: OVF
55-56: MC0-1
30: OVF
21-32: MC0-1
Y
TC2 0x42003800 22 14 N 31 14 N 25: EVU 57: OVF
58-59: MC0-1
33: OVF
23-35: MC0-1
Y
TC3 0x42003C00 23 15 N 31 15 N 26: EVU 60: OVF
61-62: MC0-1
36: OVF
37-38: MC0-1
Y
TC4 0x42004000 24 16 N 32 16 N 27: EVU 63: OVF
64-65: MC0-1
39: OVF
40-41: MC0-1
Y
ADC0 0x42004400 25 17 N 33 17 N 28: START
29: SYNC
66: RESRDY
67: WINMON
42: RESRDY Y
ADC1 0x42004800 26 18 N 34 18 N 30: START
31: SYNC
68: RESRDY
69: WINMON
43: RESRDY Y
SDADC 0x42004C00 29 19 N 35 19 N 32: START
33: FLUSH
70: RESRDY
71: WINMON
44: RESRDY Y
AC 0x42005000 27 20 N 34 20 N 34-37:
SOC0-3
72-75: COMP0-3
76-77: WIN0-1
Y
DAC 0x42005400 28 21 N 36 21 N 38: START 78: EMPTY 45: EMPTY Y
PTC 0x42005800 30 22 N 37 22 N 39: STCONV 79: EOC
80: WCOMP
EOC: 46
WCOMP: 47
SEQ: 48
CCL 0x42005C00 23 N 38 23 N 40-43 :
LUTIN0-3
781-84: LUTOUT0-3 Y
DIVAS 0x48000000 12 Y N/A
Table 12-5. Peripherals Configuration Summary SAM C20 E/G/J
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
AHB-APB
Bridge A
0x40000000 0 Y N/A
PAC 0x44000000 0 10 Y 0 Y 0 N 85 : ACCERR N/A
PM 0x40000400 0 1 Y 1 N N/A
MCLK 0x40000800 0 2 Y 2 N Y
RSTC 0x40000C00 3 Y 3 N N/A
OSCCTRL 0x40001000 0 4 Y 0: FDPLL96M
clk source
1: FDPLL96M
32kHz
4 N 0: XOSC_FAIL Y
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 94
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
OSC32KCTRL 0x40001400 0 5 Y 5 N 1: XOSC32K_FAIL Y
SUPC 0x40001800 0 6 Y 6 N N/A
GCLK 0x40001C00 7 Y 7 N N/A
WDT 0x40002000 1 8 Y 8 N Y
RTC 0x40002400 2 9 Y 9 N 2: CMP0/ALARM0
3: CMP1
4: OVF
5-12: PER0-7
Y
EIC 0x40002800 3,
NMI
10 Y 2 10 N 13-28: EXTINT0-15 Y
FREQM 0x40002C00 4 11 Y 3: Measure
4: Reference
11 N N/A
AHB-APB
Bridge B
0x41000000 1 Y N/A
PORT 0x41000000 0 Y 0 N 1-4 : EV0-3 Y
DSU 0x41002000 3 Y 1 Y 1 Y N/A
NVMCTRL 0x41004000 6 5 Y 2 Y 39 2 N Y
DMAC 0x41006000 7 7 Y 3 N 5-8: CH0-3 30-33: CH0-3 Y
MTB 0x41008000 N 44: START
45: STOP
N/A
AHB-APB
Bridge C
0x42000000 2 Y N/A
EVSYS 0x42000000 8 0 N 6-17: one per
CHANNEL
0 N Y
SERCOM0 0x42000400 9 1 N 19: CORE
18: SLOW
1 N 2: RX
3: TX
Y
SERCOM1 0x42000800 10 2 N 20: CORE
18: SLOW
2 N 4: RX
5: TX
Y
SERCOM2 0x42000C00 11 3 N 21: CORE
18: SLOW
3 N 6: RX
7: TX
Y
SERCOM3 0x42001000 12 4 N 22: CORE
18: SLOW
4 N 8: RX
9: TX
Y
SERCOM4 0x42001400 13 5 N 23: CORE
18: SLOW
5 N 10: RX
11: TX
Y
SERCOM5 0x42001800 14 6 N 25: CORE
24: SLOW
6 N 12: RX
13: TX
Y
TCC0 0x42002400 17 9 N 28 9 N 9-10: EV0-1
11-14:
MC0-3
34: OVF
35: TRG
36: CNT
37-40: MC0-3
16: OVF
17-20: MC0-3
Y
TCC1 0x42002800 18 10 N 28 10 N 15-16: EV0-1
17-18:
MC0-1
41: OVF
42: TRG
43: CNT
44-45: MC0-1
21: OVF
22-23: MC0-1
Y
TCC2 0x42002C00 19 11 N 29 11 N 19-20: EV0-1
21-22:
MC0-1
46: OVF
47: TRG
48: CNT
49-50: MC0-1
24: OVF
25-26: MC0-1
Y
TC0 0x42003000 20 12 N 30 12 N 23: EVU 51: OVF
52-53: MC0-1
27: OVF
28-29: MC0-1
Y
TC1 0x42003400 21 13 N 30 13 N 24: EVU 54: OVF
55-56: MC0-1
30: OVF
21-32: MC0-1
Y
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 95
...........continued
Peripheral Name Base Address IRQ
Line
AHB Clock APB Clock Generic Clock PAC Events DMA
Index Enabled
at Reset
Index Enabled at
Reset
Index Index Prot at
Reset
User Generator Index Sleep
Walking
TC2 0x42003800 22 14 N 31 14 N 25: EVU 57: OVF
58-59: MC0-1
33: OVF
23-35: MC0-1
Y
TC3 0x42003C00 23 15 N 31 15 N 26: EVU 60: OVF
61-62: MC0-1
36: OVF
37-38: MC0-1
Y
TC4 0x42004000 24 16 N 32 16 N 27: EVU 63: OVF
64-65: MC0-1
39: OVF
40-41: MC0-1
Y
ADC0 0x42004400 25 17 N 33 17 N 28: START
29: SYNC
66: RESRDY
67: WINMON
42: RESRDY Y
AC 0x42005000 27 20 N 34 20 N 34-37:
SOC0-3
72-75: COMP0-3
76-77: WIN0-1
Y
PTC 0x42005800 30 22 N 37 22 N 39: STCONV 79: EOC
80: WCOMP
EOC: 46
WCOMP: 47
SEQ: 48
CCL 0x42005C00 23 N 38 23 N 40-43 :
LUTIN0-3
781-84: LUTOUT0-3 Y
DIVAS 0x48000000 12 Y N/A
SAM C20/C21 Family Data Sheet
Peripherals Configuration Summary
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 96
13. DSU - Device Service Unit
13.1 Overview
The Device Service Unit (DSU) provides a means of detecting debugger probes. It enables the ARM
Debug Access Port (DAP) to have control over multiplexed debug pads and CPU reset. The DSU also
provides system-level services to debug adapters in an ARM debug system. It implements a CoreSight
Debug ROM that provides device identification as well as identification of other debug components within
the system. Hence, it complies with the ARM Peripheral Identification specification. The DSU also
provides system services to applications that need memory testing, as required for IEC60730 Class B
compliance, for example. The DSU can be accessed simultaneously by a debugger and the CPU, as it is
connected on the High-Speed Bus Matrix. For security reasons, some of the DSU features will be limited
or unavailable when the device is protected by the NVMCTRL security bit.
Related Links
13.11.6 System Services Availability when Accessed Externally and Device is Protected
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.2 Features
• CPU reset extension
• Debugger probe detection (Cold- and Hot-Plugging)
• Chip-Erase command and status
• 32-bit cyclic redundancy check (CRC32) of any memory accessible through the bus matrix
• ARM® CoreSight™ compliant device identification
• Two debug communications channels with DMA connection
• Debug access port security filter
• Onboard memory built-in self-test (MBIST)
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 97
13.3 Block Diagram
Figure 13-1. DSU Block Diagram
DSU
SWCLK
CORESIGHT ROM
DAP SECURITY FILTER
CRC-32
MBIST
CHIP ERASE
RESET
cpu_reset_extension
CPU
DAP
SWDIO
NVMCTRL
DBG
M
HIGH-SPEED
BUS MATRIX
M
S
debugger_present
DEBUGGER PROBE
INTERFACE
AHB-AP
DMA
S
DMA request
PORT
13.4 Signal Description
The DSU uses three signals to function.
Signal Name Type Description
RESET Digital Input External reset
SWCLK Digital Input SW clock
SWDIO Digital I/O SW bidirectional data pin
Related Links
6. I/O Multiplexing and Considerations
13.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
13.5.1 I/O Lines
The SWCLK pin is by default assigned to the DSU module to allow debugger probe detection and to
stretch the CPU reset phase. For more information, refer to 13.6.3 Debugger Probe Detection. The Hot-
Plugging feature depends on the PORT configuration. If the SWCLK pin function is changed in the PORT
or if the PORT_MUX is disabled, the Hot-Plugging feature is disabled until a power-reset or an external
reset is performed.
13.5.2 Power Management
The DSU will continue to operate in Idle mode.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 98
Related Links
19. PM – Power Manager
13.5.3 Clocks
The DSU bus clocks (CLK_DSU_APB and CLK_DSU_AHB) can be enabled and disabled by the Main
Clock Controller.
Related Links
19. PM – Power Manager
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
13.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). In order to use DMA requests with
this peripheral the DMAC must be configured first. Refer to DMAC – Direct Memory Access Controller for
details.
13.5.5 Interrupts
Not applicable.
13.5.6 Events
Not applicable.
13.5.7 Register Access Protection
Registers with write-access can be optionally write-protected by the Peripheral Access Controller (PAC),
except for the following:
• Debug Communication Channel 0 register (DCC0)
• Debug Communication Channel 1 register (DCC1)
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
13.5.8 Analog Connections
Not applicable.
13.6 Debug Operation
13.6.1 Principle of Operation
The DSU provides basic services to allow on-chip debug using the ARM Debug Access Port and the
ARM processor debug resources:
• CPU reset extension
• Debugger probe detection
For more details on the ARM debug components, refer to the ARM Debug Interface v5 Architecture
Specification.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 99
13.6.2 CPU Reset Extension
“CPU reset extension” refers to the extension of the reset phase of the CPU core after the external reset
is released. This ensures that the CPU is not executing code at startup while a debugger is connects to
the system. The debugger is detected on a RESET release event when SWCLK is low. At startup,
SWCLK is internally pulled up to avoid false detection of a debugger if the SWCLK pin is left
unconnected. When the CPU is held in the reset extension phase, the CPU Reset Extension bit of the
Status A register (STATUSA.CRSTEXT) is set. To release the CPU, write a '1' to STATUSA.CRSTEXT.
STATUSA.CRSTEXT will then be set to '0'. Writing a '0' to STATUSA.CRSTEXT has no effect. For
security reasons, it is not possible to release the CPU reset extension when the device is protected by the
NVMCTRL security bit. Trying to do so sets the Protection Error bit (PERR) of the Status A register
(STATUSA.PERR).
Figure 13-2. Typical CPU Reset Extension Set and Clear Timing Diagram
DSU CRSTEXT
Clear
SWCLK
CPU reset
extension
CPU_STATE reset running
RESET
Related Links
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.6.3 Debugger Probe Detection
13.6.3.1 Cold Plugging
Cold-Plugging is the detection of a debugger when the system is in reset. Cold-Plugging is detected when
the CPU reset extension is requested, as described above.
13.6.3.2 Hot Plugging
Hot-Plugging is the detection of a debugger probe when the system is not in reset. Hot-Plugging is not
possible under reset because the detector is reset when POR or RESET are asserted. Hot-Plugging is
active when a SWCLK falling edge is detected. The SWCLK pad is multiplexed with other functions and
the user must ensure that its default function is assigned to the debug system. If the SWCLK function is
changed, the Hot-Plugging feature is disabled until a power-reset or external reset occurs. Availability of
the Hot-Plugging feature can be read from the Hot-Plugging Enable bit of the Status B register
(STATUSB.HPE).
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 100
Figure 13-3. Hot-Plugging Detection Timing Diagram
SWCLK
Hot-Plugging
CPU_STATE reset running
RESET
The presence of a debugger probe is detected when either Hot-Plugging or Cold-Plugging is detected.
Once detected, the Debugger Present bit of the Status B register (STATUSB.DBGPRES) is set. For
security reasons, Hot-Plugging is not available when the device is protected by the NVMCTRL security
bit.
This detection requires that pads are correctly powered. Thus, at cold startup, this detection cannot be
done until POR is released. If the device is protected, Cold-Plugging is the only way to detect a debugger
probe, and so the external reset timing must be longer than the POR timing. If external reset is
deasserted before POR release, the user must retry the procedure above until it gets connected to the
device.
Related Links
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.7 Chip Erase
Chip-Erase consists of removing all sensitive information stored in the chip and clearing the NVMCTRL
security bit. Therefore, all volatile memories and the Flash memory (including the EEPROM emulation
area) will be erased. The Flash auxiliary rows, including the user row, will not be erased.
When the device is protected, the debugger must first reset the device in order to be detected. This
ensures that internal registers are reset after the protected state is removed. The Chip-Erase operation is
triggered by writing a '1' to the Chip-Erase bit in the Control register (CTRL.CE). This command will be
discarded if the DSU is protected by the Peripheral Access Controller (PAC). Once issued, the module
clears volatile memories prior to erasing the Flash array. To ensure that the Chip-Erase operation is
completed, check the Done bit of the Status A register (STATUSA.DONE).
The Chip-Erase operation depends on clocks and power management features that can be altered by the
CPU. For that reason, it is recommended to issue a Chip- Erase after a Cold-Plugging procedure to
ensure that the device is in a known and safe state.
The recommended sequence is as follows:
1. Issue the Cold-Plugging procedure (refer to 13.6.3.1 Cold Plugging). The device then:
1.1. Detects the debugger probe.
1.2. Holds the CPU in reset.
2. Issue the Chip-Erase command by writing a '1' to CTRL.CE. The device then:
2.1. Clears the system volatile memories.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 101
2.2. Erases the whole Flash array (including the EEPROM emulation area, not including
auxiliary rows).
2.3. Erases the lock row, removing the NVMCTRL security bit protection.
3. Check for completion by polling STATUSA.DONE (read as '1' when completed).
4. Reset the device to let the NVMCTRL update the fuses.
13.8 Programming
Programming the Flash or RAM memories is only possible when the device is not protected by the
NVMCTRL security bit. The programming procedure is as follows:
1. At power up, RESET is driven low by a debugger. The on-chip regulator holds the system in a POR
state until the input supply is above the POR threshold (refer to Powe-On Reset (POR)
characteristics). The system continues to be held in this static state until the internally regulated
supplies have reached a safe operating state.
2. The PM starts, clocks are switched to the slow clock (Core Clock, System Clock, Flash Clock and
any Bus Clocks that do not have clock gate control). Internal resets are maintained due to the
external reset.
3. The debugger maintains a low level on SWCLK. RESET is released, resulting in a debugger Cold-
Plugging procedure.
4. The debugger generates a clock signal on the SWCLK pin, the Debug Access Port (DAP) receives
a clock.
5. The CPU remains in Reset due to the Cold-Plugging procedure; meanwhile, the rest of the system
is released.
6. A Chip-Erase is issued to ensure that the Flash is fully erased prior to programming.
7. Programming is available through the AHB-AP.
8. After the operation is completed, the chip can be restarted either by asserting RESET or toggling
power. Make sure that the SWCLK pin is high when releasing RESET to prevent extending the
CPU reset.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.9 Intellectual Property Protection
Intellectual property protection consists of restricting access to internal memories from external tools
when the device is protected, and this is accomplished by setting the NVMCTRL security bit. This
protected state can be removed by issuing a Chip-Erase (refer to 13.7 Chip Erase). When the device is
protected, read/write accesses using the AHB-AP are limited to the DSU address range and DSU
commands are restricted. When issuing a Chip-Erase, sensitive information is erased from volatile
memory and Flash.
The DSU implements a security filter that monitors the AHB transactions inside the DAP. If the device is
protected, then AHB-AP read/write accesses outside the DSU external address range are discarded,
causing an error response that sets the ARM AHB-AP sticky error bits (refer to the ARM Debug Interface
v5 Architecture Specification on http://www.arm.com).
The DSU is intended to be accessed either:
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 102
• Internally from the CPU, without any limitation, even when the device is protected
• Externally from a debug adapter, with some restrictions when the device is protected
For security reasons, DSU features have limitations when used from a debug adapter. To differentiate
external accesses from internal ones, the first 0x100 bytes of the DSU register map has been mirrored at
offset 0x100:
• The first 0x100 bytes form the internal address range
• The next 0x100 bytes form the external address range
When the device is protected, the DAP can only issue MEM-AP accesses in the DSU range
0x0100-0x2000.
The DSU operating registers are located in the 0x0000-0x00FF area and remapped in 0x0100-0x01FF to
differentiate accesses coming from a debugger and the CPU. If the device is protected and an access is
issued in the region 0x0100-0x01FF, it is subject to security restrictions. For more information, refer to the
Table 13-1.
Figure 13-4. APB Memory Mapping
0x0000
0x00FF
0x0100
0x01FF
0x1000
0x1FFF
DSU operating
registers
Mirrored
DSU operating
registers
DSU CoreSight
ROM
Empty
Internal address range
(cannot be accessed from debug tools when the device is
protected by the NVMCTRL security bit)
External address range
(can be accessed from debug tools with some restrictions)
Some features not activated by APB transactions are not available when the device is protected:
Table 13-1. Feature Availability Under Protection
Features Availability when the device is protected
CPU Reset Extension Yes
Clear CPU Reset Extension No
Debugger Cold-Plugging Yes
Debugger Hot-Plugging No
Related Links
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 103
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.10 Device Identification
Device identification relies on the ARM CoreSight component identification scheme, which allows the chip
to be identified as a SAM device implementing a DSU. The DSU contains identification registers to
differentiate the device.
13.10.1 CoreSight Identification
A system-level ARM® CoreSight™ ROM table is present in the device to identify the vendor and the chip
identification method. Its address is provided in the MEM-AP BASE register inside the ARM Debug
Access Port. The CoreSight ROM implements a 64-bit conceptual ID composed as follows from the PID0
to PID7 CoreSight ROM Table registers:
Figure 13-5. Conceptual 64-bit Peripheral ID
Table 13-2. Conceptual 64-Bit Peripheral ID Bit Descriptions
Field Size Description Location
JEP-106 CC code 4 Continuation code: 0x0 PID4
JEP-106 ID code 7 Device ID: 0x1F PID1+PID2
4KB count 4 Indicates that the CoreSight component is a ROM: 0x0 PID4
RevAnd 4 Not used; read as 0 PID3
CUSMOD 4 Not used; read as 0 PID3
PARTNUM 12 Contains 0xCD0 to indicate that DSU is present PID0+PID1
REVISION 4 DSU revision (starts at 0x0 and increments by 1 at both major
and minor revisions). Identifies DSU identification method
variants. If 0x0, this indicates that device identification can be
completed by reading the Device Identification register (DID)
PID2
For more information, refer to the ARM Debug Interface Version 5 Architecture Specification.
13.10.2 Chip Identification Method
The DSU DID register identifies the device by implementing the following information:
• Processor identification
• Product family identification
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 104
• Product series identification
• Device select
13.11 Functional Description
13.11.1 Principle of Operation
The DSU provides memory services, such as CRC32 or MBIST that require almost the same interface.
Hence, the Address, Length and Data registers (ADDR, LENGTH, DATA) are shared. These shared
registers must be configured first; then a command can be issued by writing the Control register. When a
command is ongoing, other commands are discarded until the current operation is completed. Hence, the
user must wait for the STATUSA.DONE bit to be set prior to issuing another one.
13.11.2 Basic Operation
13.11.2.1 Initialization
The module is enabled by enabling its clocks. For more details, refer to 13.5.3 Clocks. The DSU registers
can be PAC write-protected.
Related Links
11. PAC - Peripheral Access Controller
13.11.2.2 Operation From a Debug Adapter
Debug adapters should access the DSU registers in the external address range 0x100 – 0x2000. If the
device is protected by the NVMCTRL security bit, accessing the first 0x100 bytes causes the system to
return an error. Refer to 13.9 Intellectual Property Protection.
Related Links
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.11.2.3 Operation From the CPU
There are no restrictions when accessing DSU registers from the CPU. However, the user should access
DSU registers in the internal address range (0x0 – 0x100) to avoid external security restrictions. Refer to
13.9 Intellectual Property Protection.
13.11.3 32-bit Cyclic Redundancy Check CRC32
The DSU unit provides support for calculating a cyclic redundancy check (CRC32) value for a memory
area (including Flash and AHB RAM).
When the CRC32 command is issued from:
• The internal range, the CRC32 can be operated at any memory location
• The external range, the CRC32 operation is restricted; DATA, ADDR, and LENGTH values are forced
(see below)
Table 13-3. AMOD Bit Descriptions when Operating CRC32
AMOD[1:0] Short name External range restrictions
0 ARRAY CRC32 is restricted to the full Flash array area (EEPROM emulation area not
included) DATA forced to 0xFFFFFFFF before calculation (no seed)
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...........continued
AMOD[1:0] Short name External range restrictions
1 EEPROM CRC32 of the whole EEPROM emulation area DATA forced to 0xFFFFFFFF
before calculation (no seed)
2-3 Reserved
The algorithm employed is the industry standard CRC32 algorithm using the generator polynomial
0xEDB88320 (reversed representation).
13.11.3.1 Starting CRC32 Calculation
CRC32 calculation for a memory range is started after writing the start address into the Address register
(ADDR) and the size of the memory range into the Length register (LENGTH). Both must be word-
aligned.
The initial value used for the CRC32 calculation must be written to the Data register (DATA). This value
will usually be 0xFFFFFFFF, but can be, for example, the result of a previous CRC32 calculation if
generating a common CRC32 of separate memory blocks.
Once completed, the calculated CRC32 value can be read out of the Data register. The read value must
be complemented to match standard CRC32 implementations or kept non-inverted if used as starting
point for subsequent CRC32 calculations.
The actual test is started by writing a '1' in the 32-bit Cyclic Redundancy Check bit of the Control register
(CTRL.CRC). A running CRC32 operation can be canceled by resetting the module (writing '1' to
CTRL.SWRST).
Related Links
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.11.3.2 Interpreting the Results
The user should monitor the Status A register. When the operation is completed, STATUSA.DONE is set.
Then the Bus Error bit of the Status A register (STATUSA.BERR) must be read to ensure that no bus
error occurred.
13.11.4 Debug Communication Channels
The Debug Communication Channels (DCCO and DCC1) consist of a pair of registers with associated
handshake logic, accessible by both CPU and debugger even if the device is protected by the NVMCTRL
security bit. The registers can be used to exchange data between the CPU and the debugger, during run
time as well as in debug mode. This enables the user to build a custom debug protocol using only these
registers.
The DCC0 and DCC1 registers are accessible when the protected state is active. When the device is
protected, however, it is not possible to connect a debugger while the CPU is running
(STATUSA.CRSTEXT is not writable and the CPU is held under Reset).
Two Debug Communication Channel status bits in the Status B registers (STATUS.DCCDx) indicate
whether a new value has been written in DCC0 or DCC1. These bits, DCC0D and DCC1D, are located in
the STATUSB registers. They are automatically set on write and cleared on read.
Note:  The DCC0 and DCC1 registers are shared with the on-board memory testing logic (MBIST).
Accordingly, DCC0 and DCC1 must not be used while performing MBIST operations.
SAM C20/C21 Family Data Sheet
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Related Links
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
13.11.5 Testing of On-Board Memories MBIST
The DSU implements a feature for automatic testing of memory, also known as MBIST (memory built-in
self test). This is primarily intended for production test of on-board memories. MBIST cannot be operated
from the external address range when the device is protected by the NVMCTRL security bit. If an MBIST
command is issued when the device is protected, a protection error is reported in the Protection Error bit
in the Status A register (STATUSA.PERR).
1. Algorithm
The algorithm used for testing is a type of March algorithm called "March LR". This algorithm is able
to detect a wide range of memory defects, while still keeping a linear run time. The algorithm is:
1.1. Write entire memory to '0', in any order.
1.2. Bit by bit read '0', write '1', in descending order.
1.3. Bit by bit read '1', write '0', read '0', write '1', in ascending order.
1.4. Bit by bit read '1', write '0', in ascending order.
1.5. Bit by bit read '0', write '1', read '1', write '0', in ascending order.
1.6. Read '0' from entire memory, in ascending order.
The specific implementation used as a run time which depends on the CPU clock frequency and
the number of bytes tested in the RAM. The detected faults are:
– Address decoder faults
– Stuck-at faults
– Transition faults
– Coupling faults
– Linked Coupling faults
2. Starting MBIST
To test a memory, you need to write the start address of the memory to the ADDR.ADDR bit field,
and the size of the memory into the Length register.
For best test coverage, an entire physical memory block should be tested at once. It is possible to
test only a subset of a memory, but the test coverage will then be somewhat lower.
The actual test is started by writing a '1' to CTRL.MBIST. A running MBIST operation can be
canceled by writing a '1' to CTRL.SWRST.
3. Interpreting the Results
The tester should monitor the STATUSA register. When the operation is completed,
STATUSA.DONE is set. There are two different modes:
– ADDR.AMOD=0: exit-on-error (default)
In this mode, the algorithm terminates either when a fault is detected or on successful
completion. In both cases, STATUSA.DONE is set. If an error was detected, STATUSA.FAIL
will be set. User then can read the DATA and ADDR registers to locate the fault.
– ADDR.AMOD=1: pause-on-error
In this mode, the MBIST algorithm is paused when an error is detected. In such a situation,
only STATUSA.FAIL is asserted. The state machine waits for user to clear STATUSA.FAIL by
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writing a '1' in STATUSA.FAIL to resume. Prior to resuming, user can read the DATA and
ADDR registers to locate the fault.
4. Locating Faults
If the test stops with STATUSA.FAIL set, one or more bits failed the test. The test stops at the first
detected error. The position of the failing bit can be found by reading the following registers:
– ADDR: Address of the word containing the failing bit
– DATA: contains data to identify which bit failed, and during which phase of the test it failed. The
DATA register will in this case contains the following bit groups:
Figure 13-6. DATA bits Description When MBIST Operation Returns an Error
Bit
Bit
Bit
Bit
phase
bit_index
31 30 29 28 27 26 25 24
23 22 21 20 19 18 17 16
15 14 13 12 11 10 9 8
76 5 432 1 0
• bit_index: contains the bit number of the failing bit
• phase: indicates which phase of the test failed and the cause of the error, as listed in the following
table.
Table 13-4. MBIST Operation Phases
Phase Test actions
0 Write all bits to zero. This phase cannot fail.
1 Read '0', write '1', increment address
2 Read '1', write '0'
3 Read '0', write '1', decrement address
4 Read '1', write '0', decrement address
5 Read '0', write '1'
6 Read '1', write '0', decrement address
7 Read all zeros. bit_index is not used
Table 13-5. AMOD Bit Descriptions for MBIST
AMOD[1:0] Description
0x0 Exit on Error
0x1 Pause on Error
SAM C20/C21 Family Data Sheet
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...........continued
AMOD[1:0] Description
0x2, 0x3 Reserved
Related Links
27. NVMCTRL – Nonvolatile Memory Controller
27.6.6 Security Bit
8. Product Mapping
13.11.6 System Services Availability when Accessed Externally and Device is Protected
External access: Access performed in the DSU address offset 0x200-0x1FFF range.
Internal access: Access performed in the DSU address offset 0x000-0x100 range.
Table 13-6. Available Features when Operated From The External Address Range and Device is
Protected
Features Availability From The External Address Range
and Device is Protected
Chip-Erase command and status Yes
CRC32 Yes, only full array or full EEPROM
CoreSight Compliant Device identification Yes
Debug communication channels Yes
Testing of onboard memories (MBIST) No
STATUSA.CRSTEXT clearing No (STATUSA.PERR is set when attempting to do
so)
SAM C20/C21 Family Data Sheet
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13.12 Register Summary
Offset Name Bit Pos.
0x00 CTRL 7:0 CE MBIST CRC SWRST
0x01 STATUSA 7:0 PERR FAIL BERR CRSTEXT DONE
0x02 STATUSB 7:0 HPE DCCD1 DCCD0 DBGPRES PROT
0x03 Reserved
0x04 ADDR
7:0 ADDR[5:0] AMOD[1:0]
15:8 ADDR[13:6]
23:16 ADDR[21:14]
31:24 ADDR[29:22]
0x08 LENGTH
7:0 LENGTH[5:0]
15:8 LENGTH[13:6]
23:16 LENGTH[21:14]
31:24 LENGTH[29:22]
0x0C DATA
7:0 DATA[7:0]
15:8 DATA[15:8]
23:16 DATA[23:16]
31:24 DATA[31:24]
0x10 DCC0
7:0 DATA[7:0]
15:8 DATA[15:8]
23:16 DATA[23:16]
31:24 DATA[31:24]
0x14 DCC1
7:0 DATA[7:0]
15:8 DATA[15:8]
23:16 DATA[23:16]
31:24 DATA[31:24]
0x18 DID
7:0 DEVSEL[7:0]
15:8 DIE[3:0] REVISION[3:0]
23:16 FAMILY[0:0] SERIES[5:0]
31:24 PROCESSOR[3:0] FAMILY[4:1]
0x1C
...
0x0FFF
Reserved
0x1000 ENTRY0
7:0 FMT EPRES
15:8 ADDOFF[3:0]
23:16 ADDOFF[11:4]
31:24 ADDOFF[19:12]
0x1004 ENTRY1
7:0 FMT EPRES
15:8 ADDOFF[3:0]
23:16 ADDOFF[11:4]
31:24 ADDOFF[19:12]
0x1008 END
7:0 END[7:0]
15:8 END[15:8]
23:16 END[23:16]
31:24 END[31:24]
SAM C20/C21 Family Data Sheet
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...........continued
Offset Name Bit Pos.
0x100C
...
0x1FCB
Reserved
0x1FCC MEMTYPE
7:0 SMEMP
15:8
23:16
31:24
0x1FD0 PID4
7:0 FKBC[3:0] JEPCC[3:0]
15:8
23:16
31:24
0x1FD4
...
0x1FDF
Reserved
0x1FE0 PID0
7:0 PARTNBL[7:0]
15:8
23:16
31:24
0x1FE4 PID1
7:0 JEPIDCL[3:0] PARTNBH[3:0]
15:8
23:16
31:24
0x1FE8 PID2
7:0 REVISION[3:0] JEPU JEPIDCH[2:0]
15:8
23:16
31:24
0x1FEC PID3
7:0 REVAND[3:0] CUSMOD[3:0]
15:8
23:16
31:24
0x1FF0 CID0
7:0 PREAMBLEB0[7:0]
15:8
23:16
31:24
0x1FF4 CID1
7:0 CCLASS[3:0] PREAMBLE[3:0]
15:8
23:16
31:24
0x1FF8 CID2
7:0 PREAMBLEB2[7:0]
15:8
23:16
31:24
SAM C20/C21 Family Data Sheet
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...........continued
Offset Name Bit Pos.
0x1FFC CID3
7:0 PREAMBLEB3[7:0]
15:8
23:16
31:24
13.13 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 13.5.7 Register Access Protection.
SAM C20/C21 Family Data Sheet
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13.13.1 Control
Name:  CTRL
Offset:  0x0000
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CE MBIST CRC SWRST
Access W W W W
Reset 0 0 0 0
Bit 4 – CE Chip-Erase
Writing a '0' to this bit has no effect.
Writing a '1' to this bit starts the Chip-Erase operation.
Bit 3 – MBIST Memory Built-In Self-Test
Writing a '0' to this bit has no effect.
Writing a '1' to this bit starts the memory BIST algorithm.
Bit 1 – CRC 32-bit Cyclic Redundancy Check
Writing a '0' to this bit has no effect.
Writing a '1' to this bit starts the cyclic redundancy check algorithm.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets the module.
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13.13.2 Status A
Name:  STATUSA
Offset:  0x0001
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
PERR FAIL BERR CRSTEXT DONE
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 4 – PERR Protection Error
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Protection Error bit.
This bit is set when a command that is not allowed in protected state is issued.
Bit 3 – FAIL Failure
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Failure bit.
This bit is set when a DSU operation failure is detected.
Bit 2 – BERR Bus Error
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Bus Error bit.
This bit is set when a bus error is detected.
Bit 1 – CRSTEXT CPU Reset Phase Extension
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the CPU Reset Phase Extension bit.
This bit is set when a debug adapter Cold-Plugging is detected, which extends the CPU reset phase.
Bit 0 – DONE Done
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Done bit.
This bit is set when a DSU operation is completed.
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13.13.3 Status B
Name:  STATUSB
Offset:  0x0002
Reset:  0x1X
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
HPE DCCD1 DCCD0 DBGPRES PROT
Access R R R R R
Reset 1 0 0 0 0
Bit 4 – HPE Hot-Plugging Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit has no effect.
This bit is set when Hot-Plugging is enabled.
This bit is cleared when Hot-Plugging is disabled. This is the case when the SWCLK function is changed.
Only a power-reset or a external reset can set it again.
Bits 2, 3 – DCCDx Debug Communication Channel x Dirty [x=1..0]
Writing a '0' to this bit has no effect.
Writing a '1' to this bit has no effect.
This bit is set when DCCx is written.
This bit is cleared when DCCx is read.
Bit 1 – DBGPRES Debugger Present
Writing a '0' to this bit has no effect.
Writing a '1' to this bit has no effect.
This bit is set when a debugger probe is detected.
This bit is never cleared.
Bit 0 – PROT Protected
Writing a '0' to this bit has no effect.
Writing a '1' to this bit has no effect.
This bit is set at power-up when the device is protected.
This bit is never cleared.
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13.13.4 Address
Name:  ADDR
Offset:  0x0004
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
ADDR[29:22]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
ADDR[21:14]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ADDR[13:6]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ADDR[5:0] AMOD[1:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:2 – ADDR[29:0] Address
Initial word start address needed for memory operations.
Bits 1:0 – AMOD[1:0] Access Mode
The functionality of these bits is dependent on the operation mode.
Bit description when operating CRC32: refer to 13.11.3 32-bit Cyclic Redundancy Check CRC32
Bit description when testing onboard memories (MBIST): refer to 13.11.5 Testing of On-Board Memories
MBIST
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13.13.5 Length
Name:  LENGTH
Offset:  0x0008
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
LENGTH[29:22]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
LENGTH[21:14]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
LENGTH[13:6]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
LENGTH[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 31:2 – LENGTH[29:0] Length
Length in words needed for memory operations.
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13.13.6 Data
Name:  DATA
Offset:  0x000C
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
DATA[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DATA[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DATA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DATA[31:0] Data
Memory operation initial value or result value.
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13.13.7 Debug Communication Channel 0
Name:  DCC0
Offset:  0x0010
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
DATA[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DATA[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DATA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DATA[31:0] Data
Data register.
SAM C20/C21 Family Data Sheet
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13.13.8 Debug Communication Channel 1
Name:  DCC1
Offset:  0x0014
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
DATA[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DATA[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DATA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DATA[31:0] Data
Data register.
SAM C20/C21 Family Data Sheet
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13.13.9 Device Identification
Name:  DID
Offset:  0x0018
Property:  PAC Write-Protection
The information in this register is related to the Ordering Information.
Bit 31 30 29 28 27 26 25 24
PROCESSOR[3:0] FAMILY[4:1]
Access R R R R R R R R
Reset p p p p f f f f
Bit 23 22 21 20 19 18 17 16
FAMILY[0:0] SERIES[5:0]
Access R R R R R R R
Reset f s s s s s s
Bit 15 14 13 12 11 10 9 8
DIE[3:0] REVISION[3:0]
Access R R R R R R R R
Reset d d d d r r r r
Bit 7 6 5 4 3 2 1 0
DEVSEL[7:0]
Access R R R R R R R R
Reset x x x x x x x x
Bits 31:28 – PROCESSOR[3:0] Processor
The value of this field defines the processor used on the device.
Bits 27:23 – FAMILY[4:0] Product Family
The value of this field corresponds to the product family part of the ordering code.
Bits 21:16 – SERIES[5:0] Product Series
The value of this field corresponds to the product series part of the ordering code.
Bits 15:12 – DIE[3:0] Die Number
Identifies the die family.
Bits 11:8 – REVISION[3:0] Revision Number
Identifies the die revision number. 0x0=rev.A, 0x1=rev.B etc.
Note:  The device variant (last letter of the ordering number) is independent of the die revision
(DSU.DID.REVISION): The device variant denotes functional differences, whereas the die revision marks
evolution of the die.
Bits 7:0 – DEVSEL[7:0] Device Selection
This bit field identifies a device within a product family and product series.
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13.13.10 CoreSight ROM Table Entry 0
Name:  ENTRY0
Offset:  0x1000
Reset:  0xXXXXX00X
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
ADDOFF[19:12]
Access R R R R R R R R
Reset x x x x x x x x
Bit 23 22 21 20 19 18 17 16
ADDOFF[11:4]
Access R R R R R R R R
Reset x x x x x x x x
Bit 15 14 13 12 11 10 9 8
ADDOFF[3:0]
Access R R R R
Reset x x x x
Bit 7 6 5 4 3 2 1 0
FMT EPRES
Access R R
Reset 1 x
Bits 31:12 – ADDOFF[19:0] Address Offset
The base address of the component, relative to the base address of this ROM table.
Bit 1 – FMT Format
Always reads as '1', indicating a 32-bit ROM table.
Bit 0 – EPRES Entry Present
This bit indicates whether an entry is present at this location in the ROM table.
This bit is set at power-up if the device is not protected indicating that the entry is not present.
This bit is cleared at power-up if the device is not protected indicating that the entry is present.
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13.13.11 CoreSight ROM Table Entry 1
Name:  ENTRY1
Offset:  0x1004
Reset:  0xXXXXX00X
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
ADDOFF[19:12]
Access R R R R R R R R
Reset x x x x x x x x
Bit 23 22 21 20 19 18 17 16
ADDOFF[11:4]
Access R R R R R R R R
Reset x x x x x x x x
Bit 15 14 13 12 11 10 9 8
ADDOFF[3:0]
Access R R R R
Reset x x x x
Bit 7 6 5 4 3 2 1 0
FMT EPRES
Access R R
Reset 1 x
Bits 31:12 – ADDOFF[19:0] Address Offset
The base address of the component, relative to the base address of this ROM table.
Bit 1 – FMT Format
Always read as '1', indicating a 32-bit ROM table.
Bit 0 – EPRES Entry Present
This bit indicates whether an entry is present at this location in the ROM table.
This bit is set at power-up if the device is not protected indicating that the entry is not present.
This bit is cleared at power-up if the device is not protected indicating that the entry is present.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 123
13.13.12 CoreSight ROM Table End
Name:  END
Offset:  0x1008
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
END[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
END[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
END[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
END[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – END[31:0] End Marker
Indicates the end of the CoreSight ROM table entries.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 124
13.13.13 CoreSight ROM Table Memory Type
Name:  MEMTYPE
Offset:  0x1FCC
Reset:  0x0000000x
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
SMEMP
Access R
Reset x
Bit 0 – SMEMP System Memory Present
This bit indicates whether system memory is present on the bus that connects to the ROM table.
This bit is set at power-up if the device is not protected, indicating that the system memory is accessible
from a debug adapter.
This bit is cleared at power-up if the device is protected, indicating that the system memory is not
accessible from a debug adapter.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 125
13.13.14 Peripheral Identification 4
Name:  PID4
Offset:  0x1FD0
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
FKBC[3:0] JEPCC[3:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 7:4 – FKBC[3:0] 4KB Count
These bits will always return zero when read, indicating that this debug component occupies one 4KB
block.
Bits 3:0 – JEPCC[3:0] JEP-106 Continuation Code
These bits will always return zero when read.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 126
13.13.15 Peripheral Identification 0
Name:  PID0
Offset:  0x1FE0
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
PARTNBL[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – PARTNBL[7:0] Part Number Low
These bits will always return 0xD0 when read, indicating that this device implements a DSU module
instance.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 127
13.13.16 Peripheral Identification 1
Name:  PID1
Offset:  0x1FE4
Reset:  0x000000FC
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
JEPIDCL[3:0] PARTNBH[3:0]
Access R R R R R R R R
Reset 1 1 1 1 1 1 0 0
Bits 7:4 – JEPIDCL[3:0] Low part of the JEP-106 Identity Code
These bits will always return 0xF when read (JEP-106 identity code is 0x1F).
Bits 3:0 – PARTNBH[3:0] Part Number High
These bits will always return 0xC when read, indicating that this device implements a DSU module
instance.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 128
13.13.17 Peripheral Identification 2
Name:  PID2
Offset:  0x1FE8
Reset:  0x00000009
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
REVISION[3:0] JEPU JEPIDCH[2:0]
Access R R R R R R R R
Reset 0 0 0 0 1 0 0 1
Bits 7:4 – REVISION[3:0] Revision Number
Revision of the peripheral. Starts at 0x0 and increments by one at both major and minor revisions.
Bit 3 – JEPU JEP-106 Identity Code is used
This bit will always return one when read, indicating that JEP-106 code is used.
Bits 2:0 – JEPIDCH[2:0] JEP-106 Identity Code High
These bits will always return 0x1 when read, (JEP-106 identity code is 0x1F).
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 129
13.13.18 Peripheral Identification 3
Name:  PID3
Offset:  0x1FEC
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
REVAND[3:0] CUSMOD[3:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 7:4 – REVAND[3:0] Revision Number
These bits will always return 0x0 when read.
Bits 3:0 – CUSMOD[3:0] ARM CUSMOD
These bits will always return 0x0 when read.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 130
13.13.19 Component Identification 0
Name:  CID0
Offset:  0x1FF0
Reset:  0x0000000D
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
PREAMBLEB0[7:0]
Access R R R R R R R R
Reset 0 0 0 0 1 1 0 1
Bits 7:0 – PREAMBLEB0[7:0] Preamble Byte 0
These bits will always return 0x0000000D when read.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 131
13.13.20 Component Identification 1
Name:  CID1
Offset:  0x1FF4
Reset:  0x00000010
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CCLASS[3:0] PREAMBLE[3:0]
Access R R R R R R R R
Reset 0 0 0 1 0 0 0 0
Bits 7:4 – CCLASS[3:0] Component Class
These bits will always return 0x1 when read indicating that this ARM CoreSight component is ROM table
(refer to the ARM Debug Interface v5 Architecture Specification at http://www.arm.com).
Bits 3:0 – PREAMBLE[3:0] Preamble
These bits will always return 0x00 when read.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 132
13.13.21 Component Identification 2
Name:  CID2
Offset:  0x1FF8
Reset:  0x00000005
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
PREAMBLEB2[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 1 0 1
Bits 7:0 – PREAMBLEB2[7:0] Preamble Byte 2
These bits will always return 0x00000005 when read.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 133
13.13.22 Component Identification 3
Name:  CID3
Offset:  0x1FFC
Reset:  0x000000B1
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
PREAMBLEB3[7:0]
Access R R R R R R R R
Reset 1 0 1 1 0 0 0 1
Bits 7:0 – PREAMBLEB3[7:0] Preamble Byte 3
These bits will always return 0x000000B1 when read.
SAM C20/C21 Family Data Sheet
DSU - Device Service Unit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 134
14. DIVAS – Divide and Square Root Accelerator
14.1 Overview
The Divide and Square Root Accelerator (DIVAS) is a programmable 32-bit signed or unsigned hardware
divider and a 32-bit unsigned square root hardware engine. The DIVAS is connected to the high-speed
bus matrix and may also be accessed using the low-latency CPU local bus (IOBUS; ARM® single-cycle
I/O port). The DIVAS takes dividend and divisor values and returns the quotient and remainder when it is
used as divider. The DIVAS takes unsigned input value and returns its square root and remainder when it
is used as square root function.
14.2 Features
• Division accelerator for Cortex-M0+ systems
• 32-bit signed or unsigned integer division
• 32-bit unsigned square root
• 32-bit division in 2-16 cycles
• Programmable leading zero optimization
• Result includes quotient and remainder
• Result includes square root and remainder
• Busy and Divide-by-zero status
• Automatic start of operation when divisor or square root input is loaded
14.3 Block Diagram
Figure 14-1. DIVAS Block Diagram
DIVAS
DEVIDE ENGINE
INTERFACE
AHB
IOBUS
QUOTIENT
REMAINDER
DIVIDEND
DIVISOR
CTRLA
14.4 Signal Description
Not applicable
14.5 Product Dependencies
In order to use this peripherial, other parts of the system must be configured correctly, as described
below.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 135
14.5.1 I/O Lines
Not applicable
14.5.2 Power Management
The DIVAS will not operate in any sleep mode .
14.5.3 Clocks
The DIVAS bus clock (CLK_DIVAS_AHB) can be enabled and disabled in the power manager, and the
default state of CLK_DIVAS_AHB can be found in the Peripheral Clock Masking section in the Power
Manager chapter.
14.5.4 DMA
Not applicable
14.5.5 Interrupts
Not applicable
14.5.6 Events
Not applicable
14.5.7 Debug Operation
Not applicable
14.5.8 Register Access Protection
Certain registers cannot be modified while DIVAS is busy. The following registers are write-protected
while busy:
• Control A (14.8.1 CTRLA)
• Dividend (14.8.3 DIVIDEND)
• Divisor (14.8.4 DIVISOR)
• Square Root Input (14.8.7 SQRNUM)
Accessing these registers while protected will result in an error.
14.5.9 Analog Connections
Not applicable
14.5.10 CPU Local Bus
The CPU local bus (IOBUS) is an interface that connects the CPU directly to the DIVAS. It is a single-
cycle bus interface, and does not support wait states. It supports byte, half word and word sizes. This bus
is generally used for low latency. All registers can be read and written using this bus.
Since the IOBUS cannot wait for DIVAS to complete operation, the Quotient and Remainder registers
must be only be read via the IOBUS while the Busy bit in the Status register (STATUS.BUSY) is zero to
prevent incorrect data from being read.
14.6 Functional Description
14.6.1 Principle of Operation
The Divide and Square Root Accelerator (DIVAS) supports signed or unsigned hardware division of 32-bit
values and unsigned square root of 32-bit value. It is accessible from the CPU via both the AHB bus and
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 136
IOBUS. When the dividend and divide registers are programmed, the division starts and the result will be
stored in the Result and Remainder registers. The Busy and Divide-by-zero status can be read from
STATUS register.
When the square root input register (14.8.7 SQRNUM) is programmed, the square root function starts
and the result will be stored in the Result and Remainder registers. The Busy status can be read from
STATUS register.
14.6.2 Basic Operation
14.6.2.1 Initialization
The DIVAS configuration cannot be modified while a divide operation is ongoing. The following bits must
be written prior to starting a division:
• Sign selection bit in Control A register (14.8.1 CTRLA.SIGNED)
• Leading zero mode bit in Control A register (14.8.1 CTRLA.DLZ)
14.6.2.2 Performing Division
First write the dividend to DIVIDEND register. Writing the divisor to DIVISOR register starts the division
and sets the busy bit in the Status register (STATUS.BUSY). When the division has completed, the
STATUS.BUSY bit is cleared and the result will be stored in RESULT and REMAINDER registers.
The RESULT and REMAINDER registers can be read directly via the high-speed bus without checking
first STATUS.BUSY. Wait states will be inserted on the high-speed bus until the operation is complete.
The IOBUS does not support wait states. For accesses via the IOBUS, the STATUS.BUSY bit must be
polled before reading the result from the RESULTand REMAINDER registers.
14.6.2.3 Operand Size
Divide
The DIVAS can perform 32-bit signed and unsigned division and the operation follows the equation as
below.
 31: 0 =  31:0 / 31: 0
 31:0 =  31:0 %  31:0
DIVAS completes 32-bit division in 2-16 cycles.
Square Root
The DIVAS can perform 32-bit unsigned division and the operation follows the equation as below.
 31: 0 =  31: 0
 31:0 =  31:0  31:0 2
14.6.2.4 Signed Division
When CTRLA.SIGNED is one, both the input and the result will be in 2’s complement format. The results
of signed division are such that the remainder and dividend have the same sign and the quotient is
negative if the dividend and divisor have opposite signs. 16-bit results are sign extended to 32-bits. Note
that when the maximum negative number is divided by the minimum negative number, the resulting
quotient overflows the signed integer range and will return the maximum negative number with no
indication of the overflow. This occurs for 0x80000000 / 0xFFFFFFFF in 32-bit operation and 0x8000 /
0xFFFF in 16-bit operation.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 137
14.6.2.5 Divide By Zero
A divide by zero fault occurs if the DIVISOR is programmed to zero. QUOTIENT will be zero and the
REMAINDER is equal to DIVIDEND. Divide by zero sets the Divide-by-zero bit in the Status register
(STATUS.DBZ) to one. STATUS.DBZ must be cleared by writing a one to it.
14.6.2.6 Leading Zero Optimization
Leading zero optimization can reduce the time it takes to complete a division by skipping leading zeros in
the DIVIDEND (or leading ones in signed mode). Leading zero optimization is enabled by default and can
be disabled by the Disable Leading Zero bit in the Control A register (CTRLA.DLZ). When CTRLA.DLZ is
zero, 16-bit division completes in 2-8 cycles and 32-bit division completes in 2-16 cycles, depending on
the dividend value. If deterministic timing is required, setting CTRLA.DLZ to one forces 16-bit division to
always take 8 cycles and 32-bit division to always take 16 cycles.
14.6.2.7 Unsigned Square Root
When the square root input register (14.8.7 SQRNUM) is programmed, the square root function starts
and the result will be stored in the Result and Remainder registers. The Busy status can be read from
STATUS register.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 138
14.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 DLZ SIGNED
0x01
...
0x03
Reserved
0x04 STATUS 7:0 DBZ BUSY
0x05
...
0x07
Reserved
0x08 DIVIDEND
7:0 DIVIDEND[7:0]
15:8 DIVIDEND[15:8]
23:16 DIVIDEND[23:16]
31:24 DIVIDEND[31:24]
0x0C DIVISOR
7:0 DIVISOR[7:0]
15:8 DIVISOR[15:8]
23:16 DIVISOR[23:16]
31:24 DIVISOR[31:24]
0x10 RESULT
7:0 RESULT[7:0]
15:8 RESULT[15:8]
23:16 RESULT[23:16]
31:24 RESULT[31:24]
0x14 REMAINDER
7:0 REMAINDER[7:0]
15:8 REMAINDER[15:8]
23:16 REMAINDER[23:16]
31:24 REMAINDER[31:24]
0x18 SQRNUM
7:0 SQRNUM[7:0]
15:8 SQRNUM[15:8]
23:16 SQRNUM[23:16]
31:24 SQRNUM[31:24]
14.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 139
14.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
DLZ SIGNED
Access R/W R/W
Reset 0 0
Bit 1 – DLZ Disable Leading Zero Optimization
Value Description
0Enable leading zero optimization; 32-bit division takes 2-16 cycles.
1Disable leading zero optimization; 32-bit division takes 16 cycles.
Bit 0 – SIGNED Signed Division Enable
Value Description
0Unsigned division.
1Signed division.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 140
14.8.2 Status
Name:  STATUS
Offset:  0x04
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
DBZ BUSY
Access R/W R/W
Reset 0 0
Bit 1 – DBZ Disable-By-Zero
Writing a zero to this bit has no effect.
Writing a one to this bit clears DBZ to zero.
Value Description
0A divide-by-zero fault has not occurred
1A divide-by-zero fault has occurred
Bit 0 – BUSY DIVAS Accelerator Busy
This bit is set when a value is written to the 14.8.4 DIVISOR or 14.8.7 SQRNUM registers.
This bit is cleared when either division or square root function completes and results are ready in the
14.8.5 RESULT and 14.8.6 REMAINDER registers.
Value Description
0DIVAS is idle
1DIVAS is busy with an ongoing division
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 141
14.8.3 Dividend
Name:  DIVIDEND
Offset:  0x08
Reset:  0x0000
Property:  -
Bit 31 30 29 28 27 26 25 24
DIVIDEND[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIVIDEND[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DIVIDEND[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DIVIDEND[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DIVIDEND[31:0] Dividend Value
Holds the 32-bit dividend for the divide operation. If the Signed bit in Control A register (CTRLA.SIGNED)
is zero, DIVIDEND is unsigned. If CTRLA.SIGNED = 1, DIVIDEND is signed two’s complement. Refer to
14.6.2.2 Performing Division, 14.6.2.3 Operand Size and 14.6.2.4 Signed Division.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 142
14.8.4 Divisor
Name:  DIVISOR
Offset:  0x0C
Reset:  0x0000
Property:  -
Bit 31 30 29 28 27 26 25 24
DIVISOR[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIVISOR[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DIVISOR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DIVISOR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DIVISOR[31:0] Divisor Value
Holds the 32-bit divisor for the divide operation. If the Signed bit in Control A register (CTRLA.SIGNED) is
zero, DIVISOR is unsigned. If CTRLA.SIGNED = 1, DIVISOR is signed two’s complement. Writing the
DIVISOR register will start the divide function. Refer to 14.6.2.2 Performing Division, 14.6.2.3 Operand
Size and 14.6.2.4 Signed Division.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 143
14.8.5 Result
Name:  RESULT
Offset:  0x10
Reset:  0x0000
Property:  -
Bit 31 30 29 28 27 26 25 24
RESULT[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
RESULT[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
RESULT[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RESULT[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – RESULT[31:0] Result of Operation
Holds the 32-bit result of the last performed operation. For a divide operation this is the quotient. If the
Signed bit in Control A register (CTRLA.SIGNED) is zero, the quotient is unsigned. If CTRLA.SIGNED =
1, the quotient is signed two’s complement. For a square root operation this is the square root. Refer to
14.6.2.2 Performing Division, 14.6.2.3 Operand Size and 14.6.2.4 Signed Division.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 144
14.8.6 Remainder
Name:  REMAINDER
Offset:  0x14
Reset:  0x0000
Property:  -
Bit 31 30 29 28 27 26 25 24
REMAINDER[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
REMAINDER[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
REMAINDER[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
REMAINDER[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – REMAINDER[31:0] Remainder of Operation
Holds the 32-bit remainder of the last performed operation. For a divide operation this is the division
remainder. If the Signed bit in Control A register (CTRLA.SIGNED) is zero, the quotient is unsigned. If
CTRLA.SIGNED = 1, the quotient is signed two’s complement. For a square root operation this is the
square root remainder. Refer to 14.6.2.2 Performing Division, 14.6.2.3 Operand Size and 14.6.2.4
Signed Division.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 145
14.8.7 Square Root Input
Name:  SQRNUM
Offset:  0x18
Reset:  0x0000
Property:  -
Bit 31 30 29 28 27 26 25 24
SQRNUM[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
SQRNUM[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
SQRNUM[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
SQRNUM[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – SQRNUM[31:0] Square Root Input
Holds the 32-bit unsigned input for the square root operation. Writing the SQRNUM register will start the
square root function. Refer to 14.6.2.7 Unsigned Square Root.
SAM C20/C21 Family Data Sheet
DIVAS – Divide and Square Root Accelerator
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 146
15. Clock System
This chapter only aims to summarize the clock distribution and terminology in the SAM C20/C21 device. It
will not explain every detail of its configuration. For in-depth documentation, see the referenced module
chapters.
15.1 Clock Distribution
Figure 15-1. Clock distribution
OSCCTRL GCLK
GCLK Generator 1
GCLK Generator x
Peripheral Channel 0
Peripheral Channel 1
(FDPLL96M Reference)
Peripheral z
Peripheral 0
Syncronous Clock
Controller
MCLK
AHB/APB System Clocks
GCLK_MAIN
OSC48M
XOSC
Generic
Clocks
OSCK32CTRL
OSC32K
OSCULP32K
XOSC32K
FDPLL96M
Peripheral Channel 3
GCLK_DPLL
Peripheral Channel y
GCLK_DPLL_32K
GCLK_DPLL
GCLK_DPLL_32K
RTC
CLK_RTC_OSC
CLK_WDT_OSC
Peripheral Channel 2
(FDPLL96M Reference)
WDT
32kHz
1kHz
32kHz
1kHz
32kHz
1kHz
CLK_ULP32K
EIC
GCLK Generator 0
The clock system on the SAM C20/C21 consists of:
• Clock sources, controlled by OSCCTRL and OSC32KCTRL
– A Clock source is the base clock signal used in the system. Example clock sources are the
internal 48MHz oscillator (OSC48M), External crystal oscillator (XOSC) and the Digital phase
locked loop (FDPLL96M).
• Generic Clock Controller (GCLK) which controls the clock distribution system, made up of:
– Generic Clock generators: A programmable prescaler, that can use any of the system clock
sources as its source clock. The Generic Clock Generator 0, also called GCLK_MAIN, is the
clock feeding the Power Manager used to generate synchronous clocks.
– Generic Clocks: Typically the clock input of a peripheral on the system. The generic clocks,
through the Generic Clock Multiplexer, can use any of the Generic Clock generators as its clock
source. Multiple instances of a peripheral will typically have a separate generic clock for each
instance.
• Main Clock controller (MCLK)
– The MCLK controls synchronous clocks on the system. This includes the CPU, bus clocks (APB,
AHB) as well as the synchronous (to the CPU) user interfaces of the peripherals. It contains
clock masks that can turn on/off the user interface of a peripheral as well as prescalers for the
CPU and bus clocks.
SAM C20/C21 Family Data Sheet
Clock System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 147
The figure below shows an example where SERCOM0 is clocked by the OSC48M. The OSC48M is
enabled, the Generic Clock Generator 1 uses the OSCLL48M as its clock source, and the generic clock
19, also called GCLK_SERCOM0_CORE, that is connected to SERCOM0 uses generator 1 as its
source. The SERCOM0 interface, clocked by CLK_SERCOM0_APB, has been unmasked in the APBC
Mask register in the MCLK.
Figure 15-2. Example of SERCOM clock
OSCCTRL
OSC48 Generic Clock
Generator 1
Peripheral
Channel 19 SERCOM 0
Syncronous Clock
Controller
MCLK
CLK_SERCOM0_APB
GCLK_SERCOM0_CORE
GCLK
15.2 Synchronous and Asynchronous Clocks
As the CPU and the peripherals can be clocked from different clock sources, possibly with widely different
clock speeds, some peripheral accesses by the CPU needs to be synchronized between the different
clock domains. In these cases the peripheral includes a SYNCBUSY status register that can be used to
check if a sync operation is in progress. As the nature of the synchronization might vary between different
peripherals, detailed description for each peripheral can be found in the sub-chapter “synchronization” for
each peripheral where this is necessary.
In the datasheet references to synchronous clocks are referring to the CPU and bus clocks, while
asynchronous clocks are clock generated by generic clocks.
15.3 Register Synchronization
15.3.1 Overview
All peripherals are composed of one digital bus interface, which is connected to the APB or AHB bus and
clocked using a corresponding synchronous clock, and one core clock, which is clocked using a generic
clock. Access between these clock domains must be synchronized. As this mechanism is implemented in
hardware the synchronization process takes place even if the different clocks domains are clocked from
the same source and on the same frequency. All registers in the bus interface are accessible without
synchronization. All core registers in the generic clock domain must be synchronized when written. Some
core registers must be synchronized when read. Registers that need synchronization has this denoted in
each individual register description.
15.3.2 General Write-Synchronization
Inside the same module, each core register, denoted by the Write-Synchronized property, use its own
synchronization mechanism so that writing to different core registers can be done without waiting for the
end of synchronization of previous core register access.
However a second write access to the same core register, while synchronization is on going, is discarded
and an error is reported through the PAC. To write again to the same core register in the same module,
user must wait for the end of synchronization.
For each core register, that can be written, a synchronization status bit is associated
SAM C20/C21 Family Data Sheet
Clock System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 148
Example:
REGA, REGB are 8-bit core registers. REGC is 16-bit core register.
Offset Register
0x00 REGA
0x01 REGB
0x02
REGC
0x03
Since synchronization is per register, user can write REGA (8-bit access) then immediately write REGB
(8-bit access) without error.
User can write REGC (16-bit access) without affecting REGA or REGB. But if user writes REGC in two
consecutive 8-bit accesses, second write will be discarded and generate an error.
When user makes a 32-bit access to offset 0x00, all registers are written but REGA, REGB, REGC can
be updated at a different time because of independent write synchronization
15.3.3 General Read-Synchronization
Before any read of a core register, the user must check that the related bit in SYNCBUSY register is
cleared.
Read access to core register is always immediate but the return value is reliable only if a synchronization
of this core register is not going.
15.3.4 Completion of Synchronization
The user can either poll SYNCBUSY register or use the Synchronization Ready interrupt (if available) to
check when the synchronization is complete.
15.3.5 Enable Write-Synchronization
Writing to the Enable bit in the Control register (CTRL.ENABLE) will also trigger write-synchronization and
set SYNCBUSY.ENABLE. CTRL.ENABLE will read its new value immediately after being written. The
Synchronisation Ready interrupt (if available) cannot be used for Enable write-synchronization.
15.3.6 Software Reset Write-Synchronization
Writing a one to the Software Reset bit in CTRL (CTRL.SWRST) will also trigger write-synchronization
and set SYNCBUSY.SWRST. When writing a one to the CTRL.SWRST bit it will immediately read as one.
CTRL.SWRST and SYNCBUSY.SWRST will be cleared by hardware when the peripheral has been reset.
Writing a zero to the CTRL.SWRST bit has no effect. The Synchronisation Ready interrupt (if available)
cannot be used for Software Reset write-synchronization.
15.3.7 Synchronization Delay
The synchronization will delay the write or read access duration by a delay D, given by the equation:
5 GCLK +2 APB << 6 GCLK +3 APB
Where GCLK is the period of the generic clock and APB is the period of the peripheral bus clock. A
normal peripheral bus register access duration is 2 APB.
SAM C20/C21 Family Data Sheet
Clock System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 149
15.4 Enabling a Peripheral
To enable a peripheral clocked by a generic clock, the following parts of the system needs to be
configured:
• A running clock source.
• A clock from the Generic Clock Generator must be configured to use one of the running clock
sources, and the generator must be enabled.
• The generic clock, through the Generic Clock Multiplexer, that connects to the peripheral needs to be
configured with a running clock from the Generic Clock Generator, and the generic clock must be
enabled.
• The user interface of the peripheral needs to be unmasked in the PM. If this is not done the
peripheral registers will read as all 0’s and any writes to the peripheral will be discarded.
15.5 On-demand, Clock Requests
Figure 15-3. Clock request routing
OSC48 Generic Clock
Generator
Clock request Generic Clock
Periph. Channel
Clock request
Peripheral
Clock request
ENABLE
RUNSTDBY
ONDEMAND
CLKEN
RUNSTDBY
ENABLE
RUNSTDBY
GENEN
All the clock sources in the system can be run in an on-demand mode, where the clock source is in a
stopped state when no peripherals are requesting the clock source. Clock requests propagate from the
peripheral, via the GCLK, to the clock source. If one or more peripheral is using a clock source, the clock
source will be started/kept running. As soon as the clock source is no longer needed and no peripheral
have an active request the clock source will be stopped until requested again. For the clock request to
reach the clock source, the peripheral, the generic clock and the clock from the Generic Clock Generator
in-between must be enabled. The time taken from a clock request being asserted to the clock source
being ready is dependent on the clock source startup time, clock source frequency as well as the divider
used in the Generic Clock Generator. The total startup time from a clock request to the clock is available
for the peripheral is:
Delay_start_max = Clock source startup time + 2 * clock source periods + 2 * divided clock
source periods
Delay_start_min = Clock source startup time + 1 * clock source period + 1 * divided clock
source periodDelay_start_min = Clock source startup time + 1 * clock source period + 1 *
divided clock source period
The delay for shutting down the clock source when there is no longer an active request is:
Delay_stop_min = 1 * divided clock source period + 1 * clock source period
Delay_stop_max = 2 * divided clock source periods + 2 * clock source periods
The On-Demand principle can be disabled individually for each clock source by clearing the ONDEMAND
bit located in each clock source controller. The clock is always running whatever is the clock request. This
has the effect to remove the clock source startup time at the cost of the power consumption.
In standby mode, the clock request mechanism is still working if the modules are configured to run in
standby mode (RUNSTDBY bit).
SAM C20/C21 Family Data Sheet
Clock System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 150
15.6 Power Consumption vs. Speed
Due to the nature of the asynchronous clocking of the peripherals there are some considerations that
needs to be taken if either targeting a low-power or a fast-acting system. If clocking a peripheral with a
very low clock, the active power consumption of the peripheral will be lower. At the same time the
synchronization to the synchronous (CPU) clock domain is dependent on the peripheral clock speed, and
will be longer with a slower peripheral clock; giving lower response time and more time waiting for the
synchronization to complete.
15.7 Clocks after Reset
On any reset the synchronous clocks start to their initial state:
• OSC48M is enabled and divided by 12
• GCLK_MAIN uses OSC48M as source
• CPU and BUS clocks are undivided
On a power reset the GCLK starts to their initial state:
• All generic clock generators disabled except:
– The generator 0 (GCLK_MAIN) using OSC48M as source, with no division
• All generic clocks disabled
On a user reset the GCLK starts to their initial state, except for:
• Generic clocks that are write-locked (WRTLOCK is written to one prior to reset)
On any reset the clock sources are reset to their initial state except the 32KHz clock sources which are
reset only by a power reset.
SAM C20/C21 Family Data Sheet
Clock System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 151
16. GCLK - Generic Clock Controller
16.1 Overview
Depending on the application, peripherals may require specific clock frequencies to operate correctly. The
Generic Clock controller (GCLK) features 9 Generic Clock Generators 0..8 that can provide a wide range
of clock frequencies.
Generators can be set to use different external and internal oscillators as source. The clock of each
Generator can be divided. The outputs from the Generators are used as sources for the Peripheral
Channels, which provide the Generic Clock (GCLK_PERIPH) to the peripheral modules, as shown in
Figure 16-2. The number of Peripheral Clocks depends on how many peripherals the device has.
Note:  The Generator 0 is always the direct source of the GCLK_MAIN signal.
16.2 Features
• Provides a device-defined, configurable number of Peripheral Channel clocks
• Wide frequency range:
– Various clock sources
– Embedded dividers
16.3 Block Diagram
The generation of Peripheral Clock signals (GCLK_PERIPH) and the Main Clock (GCLK_MAIN) can be
seen in Device Clocking Diagram.
Figure 16-1. Device Clocking Diagram
GCLK_IO
Generic Clock Generator
OSC48M
OSCCTRL
Clock
Divider &
Masker
Clock
Gate
Peripheral Channel
GCLK_PERIPH
PERIPHERAL
GENERIC CLOCK CONTROLLER
MCLK
GCLK_MAIN
XOSC
OSC32CTRL
OSC32K
OSCULP32K
XOSC32K
FDPLL96M
The GCLK block diagram is shown below:
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 152
Figure 16-2. Generic Clock Controller Block Diagram
Generic Clock Generator 0
GCLK_IO[0]
(I/O input)
Clock
Divider &
Masker
Clock Sources GCLKGEN[0]
GCLK_IO[1]
(I/O input)
GCLKGEN[1]
GCLK_IO[n]
(I/O input)
GCLKGEN[n]
Clock
Gate
Peripheral Channel 0
GCLK_PERIPH[0]
Clock
Gate
Peripheral Channel 1
Clock
Gate
Peripheral Channel n
GCLKGEN[n:0]
GCLK_MAIN
GCLK_IO[1]
(I/O output)
GCLK_IO[0]
(I/O output)
GCLK_IO[n]
(I/O output)
Generic Clock Generator 1
Clock
Divider &
Masker
Generic Clock Generator n
Clock
Divider &
Masker
GCLK_PERIPH[1]
GCLK_PERIPH[n]
16.4 Signal Description
Table 16-1. GCLK Signal Description
Signal Name Type Description
GCLK_IO[7:0] Digital I/O Clock source for Generators
when input
Generic Clock signal when output
Note:  One signal can be mapped on several pins.
Related Links
6. I/O Multiplexing and Considerations
16.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
16.5.1 I/O Lines
Using the GCLK I/O lines requires the I/O pins to be configured.
Related Links
28. PORT - I/O Pin Controller
16.5.2 Power Management
The GCLK can operate in sleep modes, if required. Refer to the sleep mode description in the Power
Manager (PM) section.
Related Links
19. PM – Power Manager
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 153
16.5.3 Clocks
The GCLK bus clock (CLK_GCLK_APB) can be enabled and disabled in the Main Clock Controller.
Related Links
17.6.2.6 Peripheral Clock Masking
21. OSC32KCTRL – 32KHz Oscillators Controller
16.5.4 DMA
Not applicable.
16.5.5 Interrupts
Not applicable.
16.5.6 Events
Not applicable.
16.5.7 Debug Operation
When the CPU is halted in debug mode the GCLK continues normal operation. If the GCLK is configured
in a way that requires it to be periodically serviced by the CPU through interrupts or similar, improper
operation or data loss may result during debugging.
16.5.8 Register Access Protection
All registers with write-access can be optionally write-protected by the Peripheral Access Controller
(PAC).
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
16.5.9 Analog Connections
Not applicable.
16.6 Functional Description
16.6.1 Principle of Operation
The GCLK module is comprised of nine Generic Clock Generators (Generators) sourcing up to 64
Peripheral Channels and the Main Clock signal GCLK_MAIN.
A clock source selected as input to a Generator can either be used directly, or it can be prescaled in the
Generator. A generator output is used by one or more Peripheral Channels to provide a peripheral
generic clock signal (GCLK_PERIPH) to the peripherals.
16.6.2 Basic Operation
16.6.2.1 Initialization
Before a Generator is enabled, the corresponding clock source should be enabled. The Peripheral clock
must be configured as outlined by the following steps:
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 154
1. The Generator must be enabled (GENCTRLn.GENEN=1) and the division factor must be set
(GENTRLn.DIVSEL and GENCTRLn.DIV) by performing a single 32-bit write to the Generator
Control register (GENCTRLn).
2. The Generic Clock for a peripheral must be configured by writing to the respective Peripheral
Channel Control register (PCHCTRLm). The Generator used as the source for the Peripheral Clock
must be written to the GEN bit field in the Peripheral Channel Control register (PCHCTRLm.GEN).
Note:  Each Generator n is configured by one dedicated register GENCTRLn.
Note:  Each Peripheral Channel m is configured by one dedicated register PCHCTRLm.
16.6.2.2 Enabling, Disabling, and Resetting
The GCLK module has no enable/disable bit to enable or disable the whole module.
The GCLK is reset by setting the Software Reset bit in the Control A register (CTRLA.SWRST) to 1. All
registers in the GCLK will be reset to their initial state, except for Peripheral Channels and associated
Generators that have their Write Lock bit set to 1 (PCHCTRLm.WRTLOCK). For further details, refer to
16.6.3.4 Configuration Lock.
16.6.2.3 Generic Clock Generator
Each Generator (GCLK_GEN) can be set to run from one of nine different clock sources except
GCLK_GEN[1], which can be set to run from one of eight sources. GCLK_GEN[1] is the only Generator
that can be selected as source to others Generators.
Each generator GCLK_GEN[x] can be connected to one specific pin GCLK_IO[x]. A pin GCLK_IO[x] can
be set either to act as source to GCLK_GEN[x] or to output the clock signal generated by GCLK_GEN[x].
The selected source can be divided. Each Generator can be enabled or disabled independently.
Each GCLK_GEN clock signal can then be used as clock source for Peripheral Channels. Each
Generator output is allocated to one or several Peripherals.
GCLK_GEN[0] is used as GCLK_MAIN for the synchronous clock controller inside the Main Clock
Controller. Refer to the Main Clock Controller description for details on the synchronous clock generation.
Figure 16-3. Generic Clock Generator
Related Links
17. MCLK – Main Clock
16.6.2.4 Enabling a Generator
A Generator is enabled by writing a '1' to the Generator Enable bit in the Generator Control register
(GENCTRLn.GENEN=1).
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 155
16.6.2.5 Disabling a Generator
A Generator is disabled by writing a '0' to GENCTRLn.GENEN. When GENCTRLn.GENEN=0, the
GCLK_GEN[n] clock is disabled and gated.
16.6.2.6 Selecting a Clock Source for the Generator
Each Generator can individually select a clock source by setting the Source Select bit group in the
Generator Control register (GENCTRLn.SRC).
Changing from one clock source, for example A, to another clock source, B, can be done on the fly: If
clock source B is not ready, the Generator will continue using clock source A. As soon as source B is
ready, the Generator will switch to it. During the switching operation, the Generator maintains clock
requests to both clock sources A and B, and will release source A as soon as the switch is done. The
according bit in SYNCBUSY register (SYNCBUSY.GENCTRLn) will remain '1' until the switch operation is
completed.
Before switching the Generic Clock Generator 0 (GCLKGEN0) from a clock source A to another clock
source B, enable the ONDEMAND feature of the clock source A to ensure a proper transition from clock
source A to clock source B.
The available clock sources are device dependent (usually the oscillators, RC oscillators, and DPLL).
Only Generator 1 can be used as a common source for all other generators.
16.6.2.7 Changing the Clock Frequency
The selected source for a Generator can be divided by writing a division value in the Division Factor bit
field of the Generator Control register (GENCTRLn.DIV). How the actual division factor is calculated is
depending on the Divide Selection bit (GENCTRLn.DIVSEL).
If GENCTRLn.DIVSEL=0 and GENCTRLn.DIV is either 0 or 1, the output clock will be undivided.
Note:  The number of available DIV bits may vary from Generator to Generator.
16.6.2.8 Duty Cycle
When dividing a clock with an odd division factor, the duty-cycle will not be 50/50. Setting the Improve
Duty Cycle bit of the Generator Control register (GENCTRLn.IDC) will result in a 50/50 duty cycle.
16.6.2.9 External Clock
The output clock (GCLK_GEN) of each Generator can be sent to I/O pins (GCLK_IO).
If the Output Enable bit in the Generator Control register is set (GENCTRLn.OE = 1) and the generator is
enabled (GENCTRLn.GENEN=1), the Generator requests its clock source and the GCLK_GEN clock is
output to an I/O pin.
Note:  The I/O pin (GCLK/IO[n]) must first be configured as output by writing the corresponding PORT
registers.
If GENCTRLn.OE is 0, the according I/O pin is set to an Output Off Value, which is selected by
GENCTRLn.OOV: If GENCTRLn.OOV is '0', the output clock will be low. If this bit is '1', the output clock
will be high.
In Standby mode, if the clock is output (GENCTRLn.OE=1), the clock on the I/O pin is frozen to the OOV
value if the Run In Standby bit of the Generic Control register (GENCTRLn.RUNSTDBY) is zero. If
GENCTRLn.RUNSTDBY is '1', the GCLKGEN clock is kept running and output to the I/O pin.
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 156
16.6.3 Peripheral Clock
Figure 16-4. Peripheral Clock
16.6.3.1 Enabling a Peripheral Clock
Before a Peripheral Clock is enabled, one of the Generators must be enabled (GENCTRLn.GENEN) and
selected as source for the Peripheral Channel by setting the Generator Selection bits in the Peripheral
Channel Control register (PCHCTRL.GEN). Any available Generator can be selected as clock source for
each Peripheral Channel.
When a Generator has been selected, the peripheral clock is enabled by setting the Channel Enable bit in
the Peripheral Channel Control register, PCHCTRLm.CHEN = 1. The PCHCTRLm.CHEN bit must be
synchronized to the generic clock domain. PCHCTRLm.CHEN will continue to read as its previous state
until the synchronization is complete.
16.6.3.2 Disabling a Peripheral Clock
A Peripheral Clock is disabled by writing PCHCTRLm.CHEN=0. The PCHCTRLm.CHEN bit must be
synchronized to the Generic Clock domain. PCHCTRLm.CHEN will stay in its previous state until the
synchronization is complete. The Peripheral Clock is gated when disabled.
Related Links
16.8.4 PCHCTRLm
16.6.3.3 Selecting the Clock Source for a Peripheral
When changing a peripheral clock source by writing to PCHCTRLm.GEN, the peripheral clock must be
disabled before re-enabling it with the new clock source setting. This prevents glitches during the
transition:
1. Disable the Peripheral Channel by writing PCHCTRLm.CHEN=0
2. Assert that PCHCTRLm.CHEN reads '0'
3. Change the source of the Peripheral Channel by writing PCHCTRLm.GEN
4. Re-enable the Peripheral Channel by writing PCHCTRLm.CHEN=1
Related Links
16.8.4 PCHCTRLm
16.6.3.4 Configuration Lock
The peripheral clock configuration can be locked for further write accesses by setting the Write Lock bit in
the Peripheral Channel Control register PCHCTRLm.WRTLOCK=1). All writing to the PCHCTRLm
register will be ignored. It can only be unlocked by a Power Reset.
The Generator source of a locked Peripheral Channel will be locked, too: The corresponding GENCTRLn
register is locked, and can be unlocked only by a Power Reset.
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 157
There is one exception concerning the Generator 0. As it is used as GCLK_MAIN, it cannot be locked. It
is reset by any Reset and will start up in a known configuration. The software reset (CTRLA.SWRST) can
not unlock the registers.
In case of an external Reset, the Generator source will be disabled. Even if the WRTLOCK bit is written to
'1' the peripheral channels are disabled (PCHCTRLm.CHEN set to '0') until the Generator source is
enabled again. Then, the PCHCTRLm.CHEN are set to '1' again.
Related Links
16.8.1 CTRLA
16.6.4 Additional Features
16.6.4.1 Peripheral Clock Enable after Reset
The Generic Clock Controller must be able to provide a generic clock to some specific peripherals after a
Reset. That means that the configuration of the Generators and Peripheral Channels after Reset is
device-dependent.
Refer to GENCTRLn.SRC for details on GENCTRLn reset.
Refer to PCHCTRLm.SRC for details on PCHCTRLm reset.
16.6.5 Sleep Mode Operation
16.6.5.1 SleepWalking
The GCLK module supports the SleepWalking feature.
If the system is in a sleep mode where the Generic Clocks are stopped, a peripheral that needs its clock
in order to execute a process must request it from the Generic Clock Controller.
The Generic Clock Controller receives this request, determines which Generic Clock Generator is
involved and which clock source needs to be awakened. It then wakes up the respective clock source,
enables the Generator and Peripheral Channel stages successively, and delivers the clock to the
peripheral.
The RUNSTDBY bit in the Generator Control register controls clock output to pin during standby sleep
mode. If the bit is cleared, the Generator output is not available on pin. When set, the GCLK can
continuously output the generator output to GCLK_IO. Refer to 16.6.2.9 External Clock for details.
Related Links
19. PM – Power Manager
16.6.5.2 Minimize Power Consumption in Standby
The following table identifies when a Clock Generator is off in Standby Mode, minimizing the power
consumption:
Table 16-2. Clock Generator n Activity in Standby Mode
Request for Clock n present GENCTRLn.RUNSTDBY GENCTRLn.OE Clock Generator n
yes - - active
no 1 1 active
no 1 0 OFF
no 0 1 OFF
no 0 0 OFF
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 158
16.6.5.3 Entering Standby Mode
There may occur a delay when the device is put into Standby, until the power is turned off. This delay is
caused by running Clock Generators: if the Run in Standby bit in the Generator Control register
(GENCTRLn.RUNSTDBY) is '0', GCLK must verify that the clock is turned of properly. The duration of this
verification is frequency-dependent.
Related Links
19. PM – Power Manager
16.6.6 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
An exception is the Channel Enable bit in the Peripheral Channel Control registers (PCHCTRLm.CHEN).
When changing this bit, the bit value must be read-back to ensure the synchronization is complete and to
assert glitch free internal operation. Note that changing the bit value under ongoing synchronization will
not generate an error.
The following registers are synchronized when written:
• Generic Clock Generator Control register (GENCTRLn)
• Control A register (CTRLA)
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
16.8.1 CTRLA
15.3 Register Synchronization
16.8.4 PCHCTRLm
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 159
16.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 SWRST
0x01
...
0x03
Reserved
0x04 SYNCBUSY
7:0 GENCTRL5 GENCTRL4 GENCTRL3 GENCTRL2 GENCTRL1 GENCTRL0 SWRST
15:8 GENCTRL7 GENCTRL6
23:16
31:24
0x08
...
0x1F
Reserved
0x20 GENCTRL0
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x24 GENCTRL1
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x28 GENCTRL2
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x2C GENCTRL3
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x30 GENCTRL4
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x34 GENCTRL5
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x38 GENCTRL6
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x3C GENCTRL7
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 160
...........continued
Offset Name Bit Pos.
0x40 GENCTRL8
7:0 SRC[4:0]
15:8 RUNSTDBY DIVSEL OE OOV IDC GENEN
23:16 DIV[7:0]
31:24 DIV[15:8]
0x44
...
0x7F
Reserved
0x80 PCHCTRL0
7:0 WRTLOCK CHEN GEN[3:0]
15:8
23:16
31:24
...
0x0134 PCHCTRL45
7:0 WRTLOCK CHEN GEN[3:0]
15:8
23:16
31:24
16.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 16.5.8 Register Access Protection.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to 16.6.6 Synchronization.
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 161
16.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
SWRST
Access R/W
Reset 0
Bit 0 – SWRST Software Reset
Writing a zero to this bit has no effect.
Setting this bit to 1 will reset all registers in the GCLK to their initial state after a Power Reset, except for
generic clocks and associated Generators that have their WRTLOCK bit in PCHCTRLm set to 1.
Refer to GENCTRL Reset Value for details on GENCTRL register reset.
Refer to PCHCTRL Reset Value for details on PCHCTRL register reset.
Due to synchronization, there is a waiting period between setting CTRLA.SWRST and a completed
Reset. CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
Value Description
0There is no Reset operation ongoing.
1A Reset operation is ongoing.
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 162
16.8.2 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x04
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
GENCTRL7 GENCTRL6
Access R R
Reset 0 0
Bit 7 6 5 4 3 2 1 0
GENCTRL5 GENCTRL4 GENCTRL3 GENCTRL2 GENCTRL1 GENCTRL0 SWRST
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bits 2, 3, 4, 5, 6, 7, 8, 9 – GENCTRL Generator Control n Synchronization Busy
This bit is cleared when the synchronization of the Generator Control n register (GENCTRLn) between
clock domains is complete, or when clock switching operation is complete.
This bit is set when the synchronization of the Generator Control n register (GENCTRLn) between clock
domains is started.
Bit 0 – SWRST Software Reset Synchronization Busy
This bit is cleared when the synchronization of the CTRLA.SWRST register bit between clock domains is
complete.
This bit is set when the synchronization of the CTRLA.SWRST register bit between clock domains is
started.
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 163
16.8.3 Generator Control
Name:  GENCTRLn
Offset:  0x20 + n*0x04 [n=0..8]
Reset:  0x00000106
Property:  PAC Write-Protection, Write-Synchronized
GENCTRLn controls the settings of Generic Generator n (n=0..8). The reset value is 0x00000106 for
Generator n=0, else 0x00000000
Bit 31 30 29 28 27 26 25 24
DIV[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIV[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
RUNSTDBY DIVSEL OE OOV IDC GENEN
Access
Reset 0 0 0 0 0 1
Bit 7 6 5 4 3 2 1 0
SRC[4:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bits 31:16 – DIV[15:0] Division Factor
These bits represent a division value for the corresponding Generator. The actual division factor is
dependent on the state of DIVSEL. The number of relevant DIV bits for each Generator can be seen in
this table. Written bits outside of the specified range will be ignored.
Table 16-3. Division Factor Bits
Generic Clock Generator Division Factor Bits
Generator 0 8 division factor bits - DIV[7:0]
Generator 1 16 division factor bits - DIV[15:0]
Generator 2-9 8 division factor bits - DIV[4:0]
Bit 13 – RUNSTDBY Run in Standby
This bit is used to keep the Generator running in Standby as long as it is configured to output to a
dedicated GCLK_IO pin. If GENCTRLn.OE is zero, this bit has no effect and the generator will only be
running if a peripheral requires the clock.
Value Description
0The Generator is stopped in Standby and the GCLK_IO pin state (one or zero) will be
dependent on the setting in GENCTRL.OOV.
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 164
Value Description
1The Generator is kept running and output to its dedicated GCLK_IO pin during Standby
mode.
Bit 12 – DIVSEL Divide Selection
This bit determines how the division factor of the clock source of the Generator will be calculated from
DIV. If the clock source should not be divided, DIVSEL must be 0 and the GENCTRLn.DIV value must be
either 0 or 1.
Value Description
0The Generator clock frequency equals the clock source frequency divided by
GENCTRLn.DIV.
1The Generator clock frequency equals the clock source frequency divided by 2^(N+1), where
N is the Division Factor Bits for the selected generator (refer to GENCTRLn.DIV).
Bit 11 – OE Output Enable
This bit is used to output the Generator clock output to the corresponding pin (GCLK_IO), as long as
GCLK_IO is not defined as the Generator source in the GENCTRLn.SRC bit field.
Value Description
0No Generator clock signal on pin GCLK_IO.
1The Generator clock signal is output on the corresponding GCLK_IO, unless GCLK_IO is
selected as a generator source in the GENCTRLn.SRC bit field.
Bit 10 – OOV Output Off Value
This bit is used to control the clock output value on pin (GCLK_IO) when the Generator is turned off or the
OE bit is zero, as long as GCLK_IO is not defined as the Generator source in the GENCTRLn.SRC bit
field.
Value Description
0The GCLK_IO will be LOW when generator is turned off or when the OE bit is zero.
1The GCLK_IO will be HIGH when generator is turned off or when the OE bit is zero.
Bit 9 – IDC Improve Duty Cycle
This bit is used to improve the duty cycle of the Generator output to 50/50 for odd division factors.
Value Description
0Generator output clock duty cycle is not balanced to 50/50 for odd division factors.
1Generator output clock duty cycle is 50/50.
Bit 8 – GENEN Generator Enable
This bit is used to enable and disable the Generator.
Value Description
0Generator is disabled.
1Generator is enabled.
Bits 4:0 – SRC[4:0] Generator Clock Source Selection
These bits select the Generator clock source, as shown in this table.
Table 16-4. Generator Clock Source Selection
Value Name Description
0x00 XOSC XOSC oscillator output
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 165
...........continued
Value Name Description
0x01 GCLK_IN Generator input pad (GCLK_IO)
0x02 GCLK_GEN1 Generic clock generator 1 output
0x03 OSCULP32K OSCULP32K oscillator output
0x04 OSC32K OSC32K oscillator output
0x05 XOSC32K XOSC32K oscillator output
0x06 OSC48M OSC48M oscillator output
0x07 DPLL96M DPLL96M output
0x08-0x1F Reserved Reserved for future use
A Power Reset will reset all GENCTRLn registers. the Reset values of the GENCTRLn registers are
shown in table below.
Table 16-5. GENCTRLn Reset Value after a Power Reset
GCLK Generator Reset Value after a Power Reset
0 0x00000106
others 0x00000000
A User Reset will reset the associated GENCTRL register unless the Generator is the source of a locked
Peripheral Channel (PCHCTRLm.WRTLOCK=1). The reset values of the GENCTRL register are as
shown in the table below.
Table 16-6. GENCTRLn Reset Value after a User Reset
GCLK Generator Reset Value after a User Reset
0 0x00000106
others No change if the generator is used by a Peripheral Channel m with
PCHCTRLm.WRTLOCK=1
else 0x00000000
Related Links
16.8.4 PCHCTRLm
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 166
16.8.4 Peripheral Channel Control
Name:  PCHCTRLm
Offset:  0x80 + m*0x04 [m=0..45]
Reset:  0x00000000
Property:  PAC Write-Protection
PCHTRLm controls the settings of Peripheral Channel number m (m=0..45).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
WRTLOCK CHEN GEN[3:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 – WRTLOCK Write Lock
After this bit is set to '1', further writes to the PCHCTRLm register will be discarded. The control register of
the corresponding Generator n (GENCTRLn), as assigned in PCHCTRLm.GEN, will also be locked. It can
only be unlocked by a Power Reset.
Note that Generator 0 cannot be locked.
Value Description
0The Peripheral Channel register and the associated Generator register are not locked
1The Peripheral Channel register and the associated Generator register are locked
Bit 6 – CHEN Channel Enable
This bit is used to enable and disable a Peripheral Channel.
Value Description
0The Peripheral Channel is disabled
1The Peripheral Channel is enabled
Bits 3:0 – GEN[3:0] Generator Selection
This bit field selects the Generator to be used as the source of a peripheral clock, as shown in the table
below:
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 167
Table 16-7. Generator Selection
Value Description
0x0 Generic Clock Generator 0
0x1 Generic Clock Generator 1
0x2 Generic Clock Generator 2
0x3 Generic Clock Generator 3
0x4 Generic Clock Generator 4
0x5 Generic Clock Generator 5
0x6 Generic Clock Generator 6
0x7 Generic Clock Generator 7
0x8 Generic Clock Generator 8
0x9 - 0xF Reserved
Table 16-8. Reset Value after a User Reset or a Power Reset
Reset PCHCTRLm.GEN PCHCTRLm.CHEN PCHCTRLm.WRTLOCK
Power Reset 0x0 0x0 0x0
User Reset If WRTLOCK = 0
: 0x0
If WRTLOCK = 1: no change
If WRTLOCK = 0
: 0x0
If WRTLOCK = 1: no change
No change
A Power Reset will reset all the PCHCTRLm registers.
A User Reset will reset a PCHCTRL if WRTLOCK=0, or else, the content of that PCHCTRL remains
unchanged.
PCHCTRL register Reset values are shown in the table PCHCTRLm Mapping.
Table 16-9. PCHCTRLm Mapping
index(m) Name Description
0 GCLK_DPLL FDPLL96M input clock source for reference
1 GCLK_DPLL_32K FDPLL96M 32kHz clock for FDPLL96M internal clock
timer
2 GCLK_EIC EIC
3 GCLK_FREQM_MSR FREQM Measure
4 GCLK_FREQM_REF FREQM Reference
5 GCLK_TSENS TSENS
6 GCLK_EVSYS_CHANNEL_0 EVSYS_CHANNEL_0
7 GCLK_EVSYS_CHANNEL_1 EVSYS_CHANNEL_1
8 GCLK_EVSYS_CHANNEL_2 EVSYS_CHANNEL_2
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 168
...........continued
index(m) Name Description
9 GCLK_EVSYS_CHANNEL_3 EVSYS_CHANNEL_3
10 GCLK_EVSYS_CHANNEL_4 EVSYS_CHANNEL_4
11 GCLK_EVSYS_CHANNEL_5 EVSYS_CHANNEL_5
12 GCLK_EVSYS_CHANNEL_6 EVSYS_CHANNEL_6
13 GCLK_EVSYS_CHANNEL_7 EVSYS_CHANNEL_7
14 GCLK_EVSYS_CHANNEL_8 EVSYS_CHANNEL_8
15 GCLK_EVSYS_CHANNEL_9 EVSYS_CHANNEL_9
16 GCLK_EVSYS_CHANNEL_10 EVSYS_CHANNEL_10
17 GCLK_EVSYS_CHANNEL_11 EVSYS_CHANNEL_11
18 GCLK_SERCOM[0,1,2,3]_SLOW SERCOM[0,1,2,3]_SLOW
19 GCLK_SERCOM0_CORE SERCOM0_CORE
20 GCLK_SERCOM1_CORE SERCOM1_CORE
21 GCLK_SERCOM2_CORE SERCOM2_CORE
22 GCLK_SERCOM3_CORE SERCOM3_CORE
23
24 GCLK_SERCOM5_SLOW
25 GCLK_SERCOM5_CORE SERCOM5_CORE
26 GCLK_CAN0 CAN0
27 GCLK_CAN1 CAN1
28 GCLK_TCC0, GCLK_TCC1 TCC0,TCC1
29 GCLK_TCC2 TCC2
30 GCLK_TC0, GCLK_TC1 TC0,TC1
31 GCLK_TC2, GCLK_TC3 TC2,TC3
32 GCLK_TC4 TC4
33 GCLK_ADC0 ADC0
34 GCLK_ADC1 ADC1
35 GCLK_SDADC SDADC
36 GCLK_DAC DAC
37 GCLK_PTC PTC
38 GCLK_CCL CCL
39 - Reserved
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 169
...........continued
index(m) Name Description
40 GCLK_AC AC
41 GCLK_SERCOM6_CORE SERCOM6_CORE
42 GCLK_SERCOM7_CORE SERCOM7_CORE
43 GCLK_TC5 TC5
44 GCLK_TC6 TC6
45 GCLK_TC7 TC7
SAM C20/C21 Family Data Sheet
GCLK - Generic Clock Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 170
17. MCLK – Main Clock
17.1 Overview
The Main Clock (MCLK) controls the synchronous clock generation of the device.
Using a clock provided by the Generic Clock Module (GCLK_MAIN), the Main Clock Controller provides
synchronous system clocks to the CPU and the modules connected to the AHBx and the APBx bus. The
synchronous system clocks are divided into a number of clock domains. Each clock domain can run at
different frequencies, enabling the user to save power by running peripherals at a relatively low clock
frequency, while maintaining high CPU performance or vice versa. In addition, the clock can be masked
for individual modules, enabling the user to minimize power consumption.
17.2 Features
• Generates CPU, AHB, and APB system clocks
– Clock source and division factor from GCLK
– Clock prescaler with 1x to 128x division
• Safe run-time clock switching from GCLK
• Module-level clock gating through maskable peripheral clocks
17.3 Block Diagram
Figure 17-1. MCLK Block Diagram
MAIN
CLOCK CONTROLLER
CPU
GCLK GCLK_MAIN PERIPHERALS
CLK_APBx
CLK_AHBx
CLK_CPU
17.4 Signal Description
Not applicable.
17.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
17.5.1 I/O Lines
Not applicable.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 171
17.5.2 Power Management
The MCLK will operate in all sleep modes if a synchronous clock is required in these modes.
Related Links
19. PM – Power Manager
17.5.3 Clocks
The MCLK bus clock (CLK_MCLK_APB) can be enabled and disabled in the Main Clock module, and the
default state of CLK_MCLK_APB can be found in the Peripheral Clock Masking section. If this clock is
disabled, it can only be re-enabled by a reset.
The Generic Clock GCLK_MAIN is required to generate the Main Clocks. GCLK_MAIN is configured in
the Generic Clock Controller, and can be re-configured by the user if needed.
Related Links
16. GCLK - Generic Clock Controller
17.6.2.6 Peripheral Clock Masking
17.5.3.1 Main Clock
The main clock GCLK_MAIN is the common source for the synchronous clocks. This is fed into the
common 8-bit prescaler that is used to generate synchronous clocks to the CPU, AHBx, and APBx
modules.
17.5.3.2 CPU Clock
The CPU clock (CLK_CPU) is routed to the CPU. Halting the CPU clock inhibits the CPU from executing
instructions.
17.5.3.3 APBx and AHBx Clock
The APBx clocks (CLK_APBx) and the AHBx clocks (CLK_AHBx) are the root clock source used by
modules requiring a clock on the APBx and the AHBx bus. These clocks are always synchronous to the
CPU clock, and can run even when the CPU clock is turned off in sleep mode. A clock gater is inserted
after the common APB clock to gate any APBx clock of a module on APBx bus, as well as the AHBx
clock.
17.5.3.4 Clock Domains
The device has these synchronous clock domains:
• CPU synchronous clock domain (CPU Clock Domain). Frequency is fCPU.
See also the related links for the clock domain partitioning.
Related Links
17.6.2.6 Peripheral Clock Masking
17.5.4 DMA
Not applicable.
17.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the MCLK interrupt requires the
Interrupt Controller to be configured first.
17.5.6 Events
Not applicable.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 172
17.5.7 Debug Operation
When the CPU is halted in debug mode, the MCLK continues normal operation. In sleep mode, the
clocks generated from the MCLK are kept running to allow the debugger accessing any module. As a
consequence, power measurements are incorrect in debug mode.
17.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Flag register (INTFLAG)
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
17.5.9 Analog Connections
Not applicable.
17.6 Functional Description
17.6.1 Principle of Operation
The GCLK_MAIN clock signal from the GCLK module is the source for the main clock, which in turn is the
common root for the synchronous clocks for the CPU, APBx, and AHBx modules. The GCLK_MAIN is
divided by an 8-bit prescaler. Each of the derived clocks can run from any divided or undivided main
clock, ensuring synchronous clock sources for each clock domain. The clock domain (CPU) can be
changed on the fly to respond to variable load in the application. The clocks for each module in a clock
domain can be masked individually to avoid power consumption in inactive modules. Depending on the
sleep mode, some clock domains can be turned off.
17.6.2 Basic Operation
17.6.2.1 Initialization
After a Reset, the default clock source of the GCLK_MAIN clock is started and calibrated before the CPU
starts running. The GCLK_MAIN clock is selected as the main clock without any prescaler division.
By default, only the necessary clocks are enabled.
Related Links
17.6.2.6 Peripheral Clock Masking
17.6.2.2 Enabling, Disabling, and Resetting
The MCLK module is always enabled and cannot be reset.
17.6.2.3 Selecting the Main Clock Source
Refer to the Generic Clock Controller description for details on how to configure the clock source of the
GCLK_MAIN clock.
Related Links
16. GCLK - Generic Clock Controller
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 173
17.6.2.4 Selecting the Synchronous Clock Division Ratio
The main clock GCLK_MAIN feeds an 8-bit prescaler, which can be used to generate the synchronous
clocks. By default, the synchronous clocks run on the undivided main clock. The user can select a
prescaler division for the CPU clock domain by writing the Division (DIV) bits in the CPU Clock Division
register CPUDIV, resulting in a CPU clock domain frequency determined by this equation:
 =

If the application attempts to write forbidden values in CPUDIV register, registers are written but these
bad values are not used and a violation is reported to the PAC module.
Division bits (DIV) can be written without halting or disabling peripheral modules. Writing DIV bits allows a
new clock setting to be written to all synchronous clocks belonging to the corresponding clock domain at
the same time.
Figure 17-2. Synchronous Clock Selection and Prescaler
Sleep Controller Sleep mode
CPUDIV
CLK_CPU
GCLK
GCLKMAIN Clock
gate
Clock gate
Clock gate
CLK_AHB_HS
clk_ahb_ip0
clk_ahb_ip1
clk_ahb_ipn
Clock
gate Clock
gate
CLK_APB_HS
clk_apb_ip0
clk_apb_ip1
clk_apb_ipn
Clock
gate Clock
gate
PERIPHERALS
CPU
CPU
Clock Domain: fCPU
MASK
MASK
Prescaler
17.6.2.5 Clock Ready Flag
There is a slight delay between writing to CPUDIV until the new clock settings become effective.
During this interval, the Clock Ready flag in the Interrupt Flag Status and Clear register
(INTFLAG.CKRDY) will return zero when read. If CKRDY in the INTENSET register is set to '1', the Clock
Ready interrupt will be triggered when the new clock setting is effective. The clock settings (CLKCFG)
must not be re-written while INTFLAG. CKRDY reads '0'. The system may become unstable or hang, and
a violation is reported to the PAC module.
Related Links
11. PAC - Peripheral Access Controller
17.6.2.6 Peripheral Clock Masking
It is possible to disable/enable the AHB or APB clock for a peripheral by writing the corresponding bit in
the Clock Mask registers (APBxMASK) to '0'/'1'. The default state of the peripheral clocks is shown here.
Table 17-1. Peripheral Clock Default State
CPU Clock Domain
Peripheral Clock Default State
CLK_AC_APB Disabled
CLK_ADC0_APB Disabled
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 174
...........continued
CPU Clock Domain
Peripheral Clock Default State
CLK_ADC1_APB Disabled
CLK_BRIDGE_A_AHB Enabled
CLK_BRIDGE_B_AHB Enabled
CLK_BRIDGE_C_AHB Enabled
CLK_BRIDGE_D_AHB Enabled
CLK_CAN0_AHB Disabled
CLK_CAN1_AHB Disabled
CLK_CCL_APB Disabled
CLK_DAC_APB Disabled
CLK_DIVAS_AHB Enabled
CLK_DMAC_AHB Enabled
CLK_DMAC_APB Enabled
CLK_DSU_AHB Enabled
CLK_DSU_APB Enabled
CLK_EIC_APB Enabled
CLK_EVSYS_APB Disabled
CLK_FREQM_APB Enabled
CLK_GCLK_AHB Enabled
CLK_HAMATRIX_APB Disabled
CLK_MCLK_APB Enabled
CLK_MTB_APB Enabled
CLK_NVMCTRL_AHB Enabled
CLK_NVMCTRL_APB Enabled
CLK_OSCCTRL_APB Enabled
CLK_OSC32CTRL_APB Enabled
CLK_PAC_AHB Enabled
CLK_PAC_APB Enabled
CLK_PORT_APB Enabled
CLK_PTC_APB Disabled
CLK_SDADC_APB Disabled
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 175
...........continued
CPU Clock Domain
Peripheral Clock Default State
CLK_SERCOM0_APB Disabled
CLK_SERCOM1_AHB Disabled
CLK_SERCOM2_APB Disabled
CLK_SERCOM3_APB Disabled
CLK_SERCOM4_APB Disabled
CLK_SERCOM5_APB Disabled
CLK_SERCOM6_APB Disabled
CLK_SERCOM7_APB Disabled
CLK_TCC0_APB Disabled
CLK_TCC1_APB Disabled
CLK_TCC2_APB Disabled
CLK_TC0_APB Disabled
CLK_TC1_APB Disabled
CLK_TC2_APB Disabled
CLK_TC3_APB Disabled
CLK_TC4_APB Disabled
CLK_TC5_APB Disabled
CLK_TC6_APB Disabled
CLK_TC7_APB Disabled
CLK_TSENS_APB Disabled
CLK_WDT_APB Enabled
Backup Clock Domain
Peripheral Clock Default State
CLK_OSC32KCTRL_APB Enabled
CLK_PM_APB Enabled
CLK_SUPC_APB Enabled
CLK_RSTC_APB Enabled
CLK_RTC_APB Enabled
When the APB clock is not provided to a module, its registers cannot be read or written. The module can
be re-enabled later by writing the corresponding mask bit to '1'.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 176
A module may be connected to several clock domains (for instance, AHB and APB), in which case it will
have several mask bits.
Note that clocks should only be switched off if it is certain that the module will not be used: Switching off
the clock for the NVM Controller (NVMCTRL) will cause a problem if the CPU needs to read from the
Flash Memory. Switching off the clock to the MCLK module (which contains the mask registers) or the
corresponding APBx bridge, will make it impossible to write the mask registers again. In this case, they
can only be re-enabled by a system reset.
17.6.3 DMA Operation
Not applicable.
17.6.4 Interrupts
The peripheral has the following interrupt sources:
• Clock Ready (CKRDY): indicates that CPU clocks are ready. This interrupt is a synchronous wake-up
source.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be enabled
individually by writing a '1' to the corresponding enabling bit in the Interrupt Enable Set (INTENSET)
register, and disabled by writing a '1' to the corresponding clearing bit in the Interrupt Enable Clear
(INTENCLR) register.
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled or the
peripheral is reset. An interrupt flag is cleared by writing a '1' to the corresponding bit in the INTFLAG
register. Each peripheral can have one interrupt request line per interrupt source or one common interrupt
request line for all the interrupt sources.If the peripheral has one common interrupt request line for all the
interrupt sources, the user must read the INTFLAG register to determine which interrupt condition is
present.
Related Links
10.2.1 Overview
19.6.3.3 Sleep Mode Controller
19. PM – Power Manager
17.6.5 Events
Not applicable.
17.6.6 Sleep Mode Operation
In IDLE sleep mode, the MCLK is still running on the selected main clock.
In STANDBY sleep mode, the MCLK is frozen if no synchronous clock is required.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 177
17.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0
0x01 INTENCLR 7:0 CKRDY
0x02 INTENSET 7:0 CKRDY
0x03 INTFLAG 7:0 CKRDY
0x04 Reserved
0x05 CPUDIV 7:0 CPUDIV[7:0]
0x06
...
0x0F
Reserved
0x10 AHBMASK
7:0 DMAC HSRAM NVMCTRL HMATRIXHS DSU APBC APBB APBA
15:8 PAC CAN1 CAN0
23:16
31:24
0x14 APBAMASK
7:0 GCLK SUPC OSC32KCTR
LOSCCTRL RSTC MCLK PM PAC
15:8 TSENS FREQM EIC RTC WDT
23:16
31:24
0x18 APBBMASK
7:0 HMATRIXHS NVMCTRL DSU PORT
15:8
23:16
31:24
0x1C APBCMASK
7:0 SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
15:8 TC3 TC2 TC1 TC0 TCC2 TCC1 TCC0
23:16 CCL TC DAC AC SDADC ADC1 ADC0 TC4
31:24
0x20 APBDMASK
7:0 TC7 TC6 TC5 SERCOM7 SERCOM6
15:8
23:16
31:24
17.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers can be write-protected optionally by the Peripheral Access Controller (PAC). This is
denoted by the property "PAC Write-Protection" in each individual register description. Refer to the
17.5.8 Register Access Protection for details.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 178
17.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection
All bits in this register are reserved.
Bit 7 6 5 4 3 2 1 0
Access
Reset
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 179
17.8.2 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 7 6 5 4 3 2 1 0
CKRDY
Access R/W
Reset 0
Bit 0 – CKRDY Clock Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Clock Ready Interrupt Enable bit and the corresponding interrupt
request.
Value Description
0The Clock Ready interrupt is enabled and will generate an interrupt request when the Clock
Ready Interrupt Flag is set.
1The Clock Ready interrupt is disabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 180
17.8.3 Interrupt Enable Set
Name:  INTENSET
Offset:  0x02
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 7 6 5 4 3 2 1 0
CKRDY
Access R/W
Reset 0
Bit 0 – CKRDY Clock Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Clock Ready Interrupt Enable bit and enable the Clock Ready interrupt.
Value Description
0The Clock Ready interrupt is disabled.
1The Clock Ready interrupt is enabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 181
17.8.4 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x03
Reset:  0x01
Property:  –
Bit 7 6 5 4 3 2 1 0
CKRDY
Access R/W
Reset 1
Bit 0 – CKRDY Clock Ready
This flag is cleared by writing a '1' to the flag.
This flag is set when the synchronous CPU, APBx, and AHBx clocks have frequencies as indicated in the
CLKCFG registers and will generate an interrupt if INTENCLR/SET.CKRDY is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Clock Ready interrupt flag.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 182
17.8.5 CPU Clock Division
Name:  CPUDIV
Offset:  0x05
Reset:  0x01
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CPUDIV[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 1
Bits 7:0 – CPUDIV[7:0] CPU Clock Division Factor
These bits define the division ratio of the main clock prescaler related to the CPU clock domain.
Frequencies must never exceed the specified maximum frequency for each clock domain.
Value Name Description
0x01 DIV1 Divide by 1
0x02 DIV2 Divide by 2
0x04 DIV4 Divide by 4
0x08 DIV8 Divide by 8
0x10 DIV16 Divide by 16
0x20 DIV32 Divide by 32
0x40 DIV64 Divide by 64
0x80 DIV128 Divide by 128
others - Reserved
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 183
17.8.6 AHB Mask
Name:  AHBMASK
Offset:  0x10
Reset:  0x000003CFF
Property:  PAC Write-Protection
Note:  This register is only available for SAMC2x "N" series devices.
Bit 31 30 29 28 27 26 25 24
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
PAC CAN1 CAN0
Access R R R R R R/W R/W R/W
Reset 0 0 0 0 1 1 0 0
Bit 7 6 5 4 3 2 1 0
DMAC HSRAM NVMCTRL HMATRIXHS DSU APBC APBB APBA
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 13 – APBD APBD AHB Clock Enable
Value Description
0The AHB clock for the APBD is stopped.
1The AHB clock for the APBD is enabled.
Bit 12 – DIVAS DIVAS AHB Clock Enable
Value Description
0The AHB clock for the DIVAS is stopped.
1The AHB clock for the DIVAS is enabled.
Bit 10 – PAC PAC AHB Clock Enable
Value Description
0The AHB clock for the PAC is stopped.
1The AHB clock for the PAC is enabled.
Bit 9 – CAN1 CAN1 AHB Clock Enable
Value Description
0The AHB clock for the CAN1 is stopped.
1The AHB clock for the CAN1 is enabled.
Bit 8 – CAN0 CAN0 AHB Clock Enable
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 184
Value Description
0The AHB clock for the CAN0 is stopped.
1The AHB clock for the CAN0 is enabled.
Bit 7 – DMAC DMAC AHB Clock Enable
Value Description
0The AHB clock for the DMAC is stopped.
1The AHB clock for the DMAC is enabled.
Bit 6 – HSRAM HSRAM AHB Clock Enable
Value Description
0The AHB clock for the HSRAM is stopped.
1The AHB clock for the HSRAM is enabled.
Bit 5 – NVMCTRL NVMCTRL AHB Clock Enable
Value Description
0The AHB clock for the NVMCTRL is stopped.
1The AHB clock for the NVMCTRL is enabled.
Bit 4 – HMATRIXHS HMATRIXHS AHB Clock Enable
Value Description
0The AHB clock for the HMATRIXHS is stopped.
1The AHB clock for the HMATRIXHS is enabled.
Bit 3 – DSU DSU AHB Clock Enable
Value Description
0The AHB clock for the DSU is stopped.
1The AHB clock for the DSU is enabled.
Bit 2 – APBC APBC AHB Clock Enable
Value Description
0The AHB clock for the APBC is stopped.
1The AHB clock for the APBC is enabled
Bit 1 – APBB APBB AHB Clock Enable
Value Description
0The AHB clock for the APBB is stopped.
1The AHB clock for the APBB is enabled.
Bit 0 – APBA APBA AHB Clock Enable
Value Description
0The AHB clock for the APBA is stopped.
1The AHB clock for the APBA is enabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 185
17.8.7 APBA Mask
Name:  APBAMASK
Offset:  0x14
Reset:  0x00000FFF
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TSENS FREQM EIC RTC WDT
Access R/W R/W R/W R/W R/W
Reset 0 1 1 1 1
Bit 7 6 5 4 3 2 1 0
GCLK SUPC OSC32KCTRL OSCCTRL RSTC MCLK PM PAC
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 12 – TSENS TSENS APBA Clock Enable
Value Description
0The APBA clock for the TSENS is stopped.
1The APBA clock for the TSENS is enabled.
Bit 11 – FREQM FREQM APBA Clock Enable
Value Description
0The APBA clock for the FREQM is stopped.
1The APBA clock for the FREQM is enabled.
Bit 10 – EIC EIC APBA Clock Enable
Value Description
0The APBA clock for the EIC is stopped.
1The APBA clock for the EIC is enabled.
Bit 9 – RTC RTC APBA Clock Enable
Value Description
0The APBA clock for the RTC is stopped.
1The APBA clock for the RTC is enabled.
Bit 8 – WDT WDT APBA Clock Enable
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 186
Value Description
0The APBA clock for the WDT is stopped.
1The APBA clock for the WDT is enabled.
Bit 7 – GCLK GCLK APBA Clock Enable
Value Description
0The APBA clock for the GCLK is stopped.
1The APBA clock for the GCLK is enabled.
Bit 6 – SUPC SUPC APBA Clock Enable
Value Description
0The APBA clock for the SUPC is stopped.
1The APBA clock for the SUPC is enabled.
Bit 5 – OSC32KCTRL OSC32KCTRL APBA Clock Enable
Value Description
0The APBA clock for the OSC32KCTRL is stopped.
1The APBA clock for the OSC32KCTRL is enabled.
Bit 4 – OSCCTRL OSCCTRL APBA Clock Enable
Value Description
0The APBA clock for the OSCCTRL is stopped.
1The APBA clock for the OSCCTRL is enabled.
Bit 3 – RSTC RSTC APBA Clock Enable
Value Description
0The APBA clock for the RSTC is stopped.
1The APBA clock for the RSTC is enabled.
Bit 2 – MCLK MCLK APBA Clock Enable
Value Description
0The APBA clock for the MCLK is stopped.
1The APBA clock for the MCLK is enabled.
Bit 1 – PM PM APBA Clock Enable
Value Description
0The APBA clock for the PM is stopped.
1The APBA clock for the PM is enabled.
Bit 0 – PAC PAC APBA Clock Enable
Value Description
0The APBA clock for the PAC is stopped.
1The APBA clock for the PAC is enabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 187
17.8.8 APBB Mask
Name:  APBBMASK
Offset:  0x18
Reset:  0x00000007
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
HMATRIXHS NVMCTRL DSU PORT
Access R/W R/W R/W R/W
Reset 0 1 1 1
Bit 5 – HMATRIXHS HMATRIXHS APBB Clock Enable
Value Description
0The APBB clock for the HMATRIXHS is stopped
1The APBB clock for the HMATRIXHS is enabled
Bit 2 – NVMCTRL NVMCTRL APBB Clock Enable
Value Description
0The APBB clock for the NVMCTRL is stopped
1The APBB clock for the NVMCTRL is enabled
Bit 1 – DSU DSU APBB Clock Enable
Value Description
0The APBB clock for the DSU is stopped
1The APBB clock for the DSU is enabled
Bit 0 – PORT PORT APBB Clock Enable
Value Description
0The APBB clock for the PORT is stopped.
1The APBB clock for the PORT is enabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 188
17.8.9 APBC Mask
Name:  APBCMASK
Offset:  0x1C
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CCL PTC DAC AC SDADC ADC1 ADC0 TC4
Access R/W R/W R R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TC3 TC2 TC1 TC0 TCC2 TCC1 TCC0
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
SERCOM5 SERCOM4 SERCOM3 SERCOM2 SERCOM1 SERCOM0 EVSYS
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 23 – CCL CCL APBC Clock Enable
Value Description
0The APBC clock for the CCL is stopped.
1The APBC clock for the CCL is enabled.
Bit 22 – PTC PTC APBC Mask Clock Enable
Value Description
0The APBC clock for the PTC is stopped.
1The APBC clock for the PTC is enabled.
Bit 21 – DAC DAC APBC Mask Clock Enable
Value Description
0The APBC clock for the DAC is stopped.
1The APBC clock for the DAC is enabled.
Bit 20 – AC AC APBC Clock Enable
Value Description
0The APBC clock for the AC is stopped.
1The APBC clock for the AC is enabled.
Bit 19 – SDADC SDADC APBC Clock Enable
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 189
Value Description
0The APBC clock for the SDADC is stopped.
1The APBC clock for the SDADC is enabled.
Bit 18 – ADC1 ADC1 APBC Clock Enable
Value Description
0The APBC clock for the ADC1 is stopped.
1The APBC clock for the ADC1 is enabled.
Bit 17 – ADC0 ADC0 APBC Clock Enable
Value Description
0The APBC clock for the ADC0 is stopped.
1The APBC clock for the ADC0 is enabled.
Bit 16 – TC4 TC4 APBC Mask Clock Enable
Bit 15 – TC3 TC3 APBC Mask Clock Enable
Value Description
0The APBC clock for the TC3 is stopped.
1The APBC clock for the TC3 is enabled.
Bit 14 – TC2 TC2 APBC Mask Clock Enable
Value Description
0The APBC clock for the TC2 is stopped.
1The APBC clock for the TC2 is enabled.
Bit 13 – TC1 TC1 APBC Mask Clock Enable
Value Description
0The APBC clock for the TC1 is stopped.
1The APBC clock for the TC1 is enabled.
Bit 12 – TC0 TC0 APBC Mask Clock Enable
Value Description
0The APBC clock for the TC0 is stopped.
1The APBC clock for the TC0 is enabled.
Bit 11 – TCC2 TCC2 APBC Mask Clock Enable
Value Description
0The APBC clock for the TCC2 is stopped.
1The APBC clock for the TCC2 is enabled.
Bit 10 – TCC1 TCC1 APBC Mask Clock Enable
Value Description
0The APBC clock for the TCC1 is stopped.
1The APBC clock for the TCC1 is enabled.
Bit 9 – TCC0 TCC0 APBC Mask Clock Enable
Value Description
0The APBC clock for the TCC0 is stopped.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 190
Value Description
1The APBC clock for the TCC0 is enabled.
Bit 6 – SERCOM5 SERCOM5 APBC Mask Clock Enable
Value Description
0The APBC clock for the SERCOM5 is stopped.
1The APBC clock for the SERCOM5 is enabled.
Bit 5 – SERCOM4 SERCOM4 APBC Mask Clock Enable
Value Description
0The APBC clock for the SERCOM4 is stopped.
1The APBC clock for the SERCOM4 is enabled.
Bit 4 – SERCOM3 SERCOM3 APBC Mask Clock Enable
Value Description
0The APBC clock for the SERCOM3 is stopped.
1The APBC clock for the SERCOM3 is enabled.
Bit 3 – SERCOM2 SERCOM2 APBC Mask Clock Enable
Value Description
0The APBC clock for the SERCOM2 is stopped.
1The APBC clock for the SERCOM2 is enabled.
Bit 2 – SERCOM1 SERCOM1 APBC Mask Clock Enable
Value Description
0The APBC clock for the SERCOM1 is stopped.
1The APBC clock for the SERCOM1 is enabled.
Bit 1 – SERCOM0 SERCOM0 APBC Mask Clock Enable
Value Description
0The APBC clock for the SERCOM0 is stopped.
1The APBC clock for the SERCOM0 is enabled.
Bit 0 – EVSYS EVSYS APBC Clock Enable
Value Description
0The APBC clock for the EVSYS is stopped.
1The APBC clock for the EVSYS is enabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 191
17.8.10 APBD Mask
Name:  APBDMASK
Offset:  0x20
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TC7 TC6 TC5 SERCOM7 SERCOM6
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 4 – TC7 TC7 APBD Mask Clock Enable
Value Description
0The APBD clock for the TC7 is stopped.
1The APBD clock for the TC7 is enabled.
Bit 3 – TC6 TC6 APBD Mask Clock Enable
Value Description
0The APBD clock for the TC6 is stopped.
1The APBD clock for the TC6 is enabled.
Bit 2 – TC5 TC5 APBd Mask Clock Enable
Value Description
0The APBD clock for the TC5 is stopped.
1The APBD clock for the TC5 is enabled.
Bit 1 – SERCOM7 SERCOM7 APBD Mask Clock Enable
Value Description
0The APBD clock for the SERCOM7 is stopped.
1The APBD clock for the SERCOM7 is enabled.
Bit 0 – SERCOM6 SERCOM6 APBD Mask Clock Enable
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 192
Value Description
0The APBD clock for the SERCOM6 is stopped.
1The APBD clock for the SERCOM6 is enabled.
SAM C20/C21 Family Data Sheet
MCLK – Main Clock
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 193
18. RSTC – Reset Controller
18.1 Overview
The Reset Controller (RSTC) manages the reset of the microcontroller. It issues a microcontroller reset,
sets the device to its initial state and allows the reset source to be identified by software.
18.2 Features
• Reset the microcontroller and set it to an initial state according to the reset source
• Reset cause register for reading the reset source from the application code
• Multiple reset sources
– Power supply reset sources: POR, BODCORE, BODVDD
– User reset sources: External reset (RESET), Watchdog reset, and System Reset Request
18.3 Block Diagram
Figure 18-1. Reset System
RESET CONTROLLER
BODCORE
BODVDD
POR
WDT
RESET
RESET SOURCES RTC
32kHz clock sources
WDT with ALWAYSON
GCLK with WRTLOCK
Debug Logic
Other Modules
CPU
RCAUSE
18.4 Signal Description
Signal Name Type Description
RESET Digital input External reset
One signal can be mapped on several pins.
Related Links
6. I/O Multiplexing and Considerations
18.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
SAM C20/C21 Family Data Sheet
RSTC – Reset Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 194
18.5.1 I/O Lines
Not applicable.
18.5.2 Power Management
The Reset Controller module is always on.
18.5.3 Clocks
The RSTC bus clock (CLK_RSTC_APB) can be enabled and disabled in the Main Clock Controller.
Related Links
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
18.5.4 DMA
Not applicable.
18.5.5 Interrupts
Not applicable.
18.5.6 Events
Not applicable.
18.5.7 Debug Operation
When the CPU is halted in debug mode, the RSTC continues normal operation.
18.5.8 Register Access Protection
All registers with write-access can be optionally write-protected by the Peripheral Access Controller
(PAC).
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
18.5.9 Analog Connections
Not applicable.
18.6 Functional Description
18.6.1 Principle of Operation
The Reset Controller collects the various Reset sources and generates Reset for the device.
18.6.2 Basic Operation
18.6.2.1 Initialization
After a power-on Reset, the RSTC is enabled and the Reset Cause (RCAUSE) register indicates the
POR source.
18.6.2.2 Enabling, Disabling, and Resetting
The RSTC module is always enabled.
SAM C20/C21 Family Data Sheet
RSTC – Reset Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 195
18.6.2.3 Reset Causes and Effects
The latest Reset cause is available in RCAUSE register, and can be read during the application boot
sequence in order to determine proper action.
These are the groups of Reset sources:
• Power supply Reset: Resets caused by an electrical issue. It covers POR and BODs Resets
• User Reset: Resets caused by the application. It covers external Resets, system Reset requests and
watchdog Resets
The following table lists the parts of the device that are reset, depending on the Reset type.
Table 18-1. Effects of the Different Reset Causes
Power Supply Reset User Reset
POR, BODVDD,
BODCORE
External Reset WDT Reset, System
Reset Request
RTC, OSC32KCTRL, RSTC Y N N
GCLK with WRTLOCK Y N N
Debug logic Y Y N
Others Y Y Y
The external Reset is generated when pulling the RESET pin low.
The POR, BODCORE, and BODVDD Reset sources are generated by their corresponding module in the
Supply Controller Interface (SUPC).
The WDT Reset is generated by the Watchdog Timer.
The System Reset Request is a Reset generated by the CPU when asserting the SYSRESETREQ bit
located in the Reset Control register of the CPU (for details refer to the ARM® Cortex™ Technical
Reference Manual on http://www.arm.com).
Note:  Refer to the External Reset Characteristics table in the Timing Characteristics section of the
Electrical Characteristics chapter.
Related Links
23. WDT – Watchdog Timer
22. SUPC – Supply Controller
18.6.3 Additional Features
Not applicable.
18.6.4 DMA Operation
Not applicable.
18.6.5 Interrupts
Not applicable.
18.6.6 Events
Not applicable.
SAM C20/C21 Family Data Sheet
RSTC – Reset Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 196
18.6.7 Sleep Mode Operation
The RSTC module is active in all sleep modes.
SAM C20/C21 Family Data Sheet
RSTC – Reset Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 197
18.7 Register Summary
Offset Name Bit Pos.
0x00 RCAUSE 7:0 SYST WDT EXT BODVDD BODCORE POR
18.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 18.5.8 Register Access Protection.
SAM C20/C21 Family Data Sheet
RSTC – Reset Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 198
18.8.1 Reset Cause
Name:  RCAUSE
Offset:  0x00
Property:  –
When a Reset occurs, the bit corresponding to the Reset source is set to '1' and all other bits are written
to '0'.
Bit 7 6 5 4 3 2 1 0
SYST WDT EXT BODVDD BODCORE POR
Access R R R R R R
Reset x x x x x x
Bit 6 – SYST System Reset Request
This bit is set if a System Reset Request has occurred. Refer to the Cortex processor documentation for
more details.
Bit 5 – WDT Watchdog Reset
This bit is set if a Watchdog Timer Reset has occurred.
Bit 4 – EXT External Reset
This bit is set if an external Reset has occurred.
Bit 2 – BODVDD  Brown Out VDD Detector Reset
This bit is set if a BODVDD Reset has occurred.
Bit 1 – BODCORE  Brown Out CORE Detector Reset
This bit is set if a BODCORE Reset has occurred.
Bit 0 – POR Power On Reset
This bit is set if a POR has occurred.
SAM C20/C21 Family Data Sheet
RSTC – Reset Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 199
19. PM – Power Manager
Related Links
34.6.9 Sleep Mode Operation
19.1 Overview
The Power Manager (PM) controls the sleep modes of the device.
Various sleep modes are provided in order to fit power consumption requirements. This enables the PM
to stop unused modules in order to save power. In active mode, the CPU is executing application code.
When the device enters a sleep mode, program execution is stopped and some modules and clock
domains are automatically switched off by the PM according to the sleep mode. The application code
decides which sleep mode to enter and when. Interrupts from enabled peripherals and all enabled reset
sources can restore the device from a sleep mode to active mode.
19.2 Features
• Power management control
– Sleep modes: Idle, Standby
19.3 Block Diagram
Figure 19-1. PM Block Diagram
SLEEP MODE
CONTROLLER
POWER MANAGER
SUPPLY
CONTROLLER
MAIN CLOCK
CONTROLLER
SLEEPCFG
POWER DOMAIN
CONTROLLER
STDBYCFG
19.4 Signal Description
Not applicable.
19.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
19.5.1 I/O Lines
Not applicable.
19.5.2 Clocks
The PM bus clock (CLK_PM_APB) can be enabled and disabled in the Main Clock module. If this clock is
disabled, it can only be re-enabled by a system reset.
SAM C20/C21 Family Data Sheet
PM – Power Manager
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 200
19.5.3 DMA
Not applicable.
19.5.4 Interrupts
The interrupt request line is connected to the interrupt controller. Using the PM interrupt requires the
interrupt controller to be configured first.
19.5.5 Events
Not applicable.
19.5.6 Debug Operation
When the CPU is halted in debug mode, the PM continues normal operation. If standby sleep mode is
requested by the system while in debug mode, the power domains are not turned off. As a consequence,
power measurements while in debug mode are not relevant.
Hot plugging in standby mode is supported.
19.5.7 Register Access Protection
Registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Write-protection does not apply to accesses through an external debugger.
19.5.8 Analog Connections
Not applicable.
19.6 Functional Description
19.6.1 Terminology
The following is a list of terms used to describe the Power Managemement features of this
microcontroller.
19.6.1.1 Sleep Modes
The device can be set in a sleep mode. In sleep mode, the CPU is stopped and the peripherals are either
active or idle, according to the sleep mode depth:
• Idle sleep mode: The CPU is stopped. Synchronous clocks are stopped except when requested. The
logic is retained.
• Standby sleep mode: The CPU is stopped as well as the peripherals.
19.6.2 Principle of Operation
In active mode, all clock domains and power domains are active, allowing software execution and
peripheral operation. The PM Sleep Mode Controller allows to save power by choosing between different
sleep modes depending on application requirements, see 19.6.3.3 Sleep Mode Controller.
The PM Power Domain Controller allows to reduce the power consumption in standby mode even further.
19.6.3 Basic Operation
19.6.3.1 Initialization
After a power-on reset, the PM is enabled, the device is in ACTIVE mode.
SAM C20/C21 Family Data Sheet
PM – Power Manager
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 201
19.6.3.2 Enabling, Disabling and Resetting
The PM is always enabled and can not be reset.
19.6.3.3 Sleep Mode Controller
A Sleep mode is entered by executing the Wait For Interrupt instruction (WFI). The Sleep Mode bits in the
Sleep Configuration register (SLEEPCFG.SLEEPMODE) select the level of the sleep mode.
Note:  A small latency happens between the store instruction and actual writing of the SLEEPCFG
register due to bridges. Software must ensure that the SLEEPCFG register reads the desired value
before issuing a WFI instruction.
Table 19-1. Sleep Mode Entry and Exit Table
Mode Mode Entry Wake-Up Sources
IDLE SLEEPCFG.SLEEPMODE = IDLE Synchronous (2) (APB, AHB),
asynchronous (1)
STANDBY SLEEPCFG.SLEEPMODE = STANDBY Synchronous(3), Asynchronous
Note: 
1. Asynchronous: interrupt generated on generic clock, external clock, or external event.
2. Synchronous: interrupt generated on the APB clock.
3. Synchronous interrupt only for peripherals configured to run in standby.
Note:  The type of wake-up sources (synchronous or asynchronous) is given in each module interrupt
section.
The sleep modes (idle, standby) and their effect on the clocks activity, the regulator and the NVM state
are described in the table and the sections below.
Table 19-2. Sleep Mode Overview
Mode CPU
clock
AHB
clock
APB clock Main
clock
GCLK
clocks
Oscillators Regulator RAM
ONDEMAND = 0 ONDEMAND = 1
IDLE Stop Stop(2) Stop(2) Run Run(1) Run Run if requested Main Normal
STANDBY Stop Stop(2) Stop(2) Stop Stop(2) Run if requested
or RUNSTDBY=1
Run if requested LPVREG(3) Low power(4)
Note: 
1. Running if requested by peripheral.
2. Running during SleepWalking.
3. Regulator state is programmable by using STDBYCFG.VREGSMOD bits.
4. RAM state is programmable by using STDBYCFG.BBIASHS bit.
19.6.3.3.1 IDLE Mode
The IDLE mode allows power optimization with the fastest wake-up time.
The CPU is stopped. To further reduce power consumption, the user can disable the clocking of modules
and clock sources by configuring the SLEEPCFG bit group to IDLE. The peripheral will be halted
regardless of the bit settings of the mask registers in the MCLK (MCLK.AHBMASK, MCLK.APBxMASK).
• Entering IDLE mode: The IDLE mode is entered by executing the WFI instruction. Additionally, if the
SLEEPONEXIT bit in the ARM Cortex System Control register (SCR) is set, the IDLE mode will also
be entered when the CPU exits the lowest priority ISR. This mechanism can be useful for
SAM C20/C21 Family Data Sheet
PM – Power Manager
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 202
applications that only require the processor to run when an interrupt occurs. Before entering the IDLE
mode, the user must configure the Sleep Configuration register.
• Exiting IDLE mode: The processor wakes the system up when it detects any non-masked interrupt
with sufficient priority to cause exception entry. The system goes back to the ACTIVE mode. The
CPU and affected modules are restarted.
Regulator operates in normal mode.
19.6.3.3.2 STANDBY Mode
The STANDBY mode is the lowest power configuration while keeping the state of the logic and the
content of the RAM.
In this mode, all clocks are stopped except those which are kept running if requested by a running
peripheral or have the ONDEMAND bit written to "0". For example, the RTC can operate in STANDBY
mode. In this case, its GCLK clock source will also be enabled.
All features that don’t require CPU intervention are supported in STANDBY mode. Here are examples:
• Autonomous peripherals features.
• Features relying on Event System allowing autonomous communication between peripherals.
• Features relying on on-demand clock.
• DMA transfers.
• Entering STANDBY mode: This mode is entered by executing the WFI instruction with the
SLEEPCFG register written to STANDBY. The SLEEPONEXIT feature is also available as in IDLE
mode.
• Exiting STANDBY mode: Any peripheral able to generate an asynchronous interrupt can wake up the
system. For example, a peripheral running on a GCLK clock can trigger an interrupt. When the
enabled asynchronous wake-up event occurs and the system is woken up, the device will either
execute the interrupt service routine or continue the normal program execution according to the
Priority Mask Register (PRIMASK) configuration of the CPU.
Depending on the configuration of these modules, the current consumption of the device in STANDBY
mode can be slightly different.
The regulator operates in low-power mode (LP VREG) by default and can switch automatically to the
main regulator if a task required by a peripheral requires more power. It returns automatically in the low
power mode as soon as the task is completed.
19.6.4 Advanced Features
19.6.4.1 RAM Automatic Low Power Mode
The RAM is by default put in low power mode (back-biased) if the device is in standby sleep mode.
This behavior can be changed by configuring the Back Bias bit in the Standby Configuration register
(STDBYCFG.BBIASHS), refer to the table below for details.
Note:  In standby sleep mode, the RAM is put in low-power mode by default. This means that the RAM is
back-biased, and the DMAC cannot access it. The DMAC can only access the RAM when it is not back
biased (PM.STDBYCFG.BBIASxx=0x0).
Table 19-3. RAM Back-Biasing Mode
STBYCDFG.BBIASHS RAM
0x0 No Back Biasing RAM is not back-biased if the device is in standby sleep mode.
SAM C20/C21 Family Data Sheet
PM – Power Manager
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 203
...........continued
STBYCDFG.BBIASHS RAM
0x1 Standby Back Biasing mode RAM is back-biased if the device is in standby sleep mode.
19.6.4.2 Regulator Automatic Low Power Mode
In standby mode, the PM selects either the main or the low power voltage regulator to supply the
VDDCORE. By default the low power voltage regulator is used.
If a sleepwalking task is working on either asynchronous clocks (generic clocks) or synchronous clock
(APB/AHB clocks), the main voltage regulator is used. This behavior can be changed by writing the
Voltage Regulator Standby Mode bits in the Standby Configuration register (STDBYCFG.VREGSMOD).
Refer to the following table for details.
Table 19-4. Regulator State in Sleep Mode
Sleep
Mode
STDBYCFG.
VREGSMOD
SleepWalking Regulator state for VDDCORE
Active - - main voltage regulator
Idle - - main voltage regulator
Standby 0x0: AUTO NO low power regulator
YES main voltage regulator
0x1: PERFORMANCE - main voltage regulator
0x2: LP - low power regulator
19.6.5 DMA Operation
Not applicable.
19.6.6 Interrupts
Not applicable.
19.6.7 Events
Not applicable.
19.6.8 Sleep Mode Operation
The Power Manager is always active.
SAM C20/C21 Family Data Sheet
PM – Power Manager
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19.7 Register Summary
Offset Name Bit Pos.
0x01 SLEEPCFG 7:0 SLEEPMODE[2:0]
0x02
...
0x07
Reserved
0x08 STDBYCFG
7:0 VREGSMOD[1:0]
15:8 BBIASHS
19.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 19.5.7 Register Access Protection.
SAM C20/C21 Family Data Sheet
PM – Power Manager
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19.8.1 Sleep Configuration
Name:  SLEEPCFG
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
SLEEPMODE[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – SLEEPMODE[2:0] Sleep Mode
Note:  A small latency happens between the store instruction and actual writing of the SLEEPCFG
register due to bridges. Software has to make sure the SLEEPCFG register reads the wanted value
before issuing Wait For Interrupt (WFI) instruction.
Value Name Definition
0x0
0x1
0x2 IDLE
0x3 Reserved Reserved
0x4 STANDBY
0x5 - 0x7 Reserved Reserved
SAM C20/C21 Family Data Sheet
PM – Power Manager
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 206
19.8.2 Standby Configuration
Name:  STDBYCFG
Offset:  0x08
Reset:  0x0400
Property:  PAC Write-Protection
Bit 15 14 13 12 11 10 9 8
BBIASHS
Access R/W
Reset 1
Bit 7 6 5 4 3 2 1 0
VREGSMOD[1:0]
Access R/W R/W
Reset 0 0
Bit 10 – BBIASHS Back Bias for HMCRAMCHS
Refer to 19.6.4.1 RAM Automatic Low Power Mode for details.
Value Description
0No Back Biasing Mode
1Standby Back Biasing Mode
Bits 7:6 – VREGSMOD[1:0] VREG Switching Mode
Refer to for 19.6.4.2 Regulator Automatic Low Power Mode details.
Value Name Description
0x0 AUTO Automatic Mode
0x1 PERFORMANCE Performance oriented
0x2 LP Low Power consumption oriented
0x9 Reserved Reserved
SAM C20/C21 Family Data Sheet
PM – Power Manager
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 207
20. OSCCTRL – Oscillators Controller
20.1 Overview
The Oscillators Controller (OSCCTRL) provides a user interface to the XOSC, OSC48M and FDPLL96M.
Through the interface registers, it is possible to enable, disable, calibrate, and monitor the OSCCTRL
oscillators.
All oscillators statuses are collected in the Status register (STATUS). They can additionally trigger
interrupts upon status changes via the INTENSET, INTENCLR, and INTFLAG registers.
Related Links
20.8.1 INTENCLR
20.8.2 INTENSET
20.8.3 INTFLAG
20.8.4 STATUS
20.2 Features
• 0.4-32MHz Crystal Oscillator (XOSC)
– Tunable gain control
– Programmable start-up time
– Crystal or external input clock on XIN I/O
– Clock failure detection with safe clock switch
– Clock failure event output
• 48MHz Internal Oscillator (OSC48M)
– Fast start-up
– Programmable start-up time
– 4-bit linear divider available
• Fractional Digital Phase Locked Loop (FDPLL96M)
– 48MHz to 96MHz output frequency
– 32kHz to 2MHz reference clock
– A selection of sources for the reference clock
– Adjustable proportional integral controller
– Fractional part used to achieve 1/16th of reference clock step
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 208
20.3 Block Diagram
Figure 20-1. OSCCTRL Block Diagram
OSCILLATORS
CONTROL
STATUS
INTERRUPTS
GENERATOR Interrupts
OSCCTRL
XINXOUT
XOSC
DPLL96M
OSC48M
CLK_XOSC
CLK_DPLL
CLK_OSC48M
CFD CFD Event
register
20.4 Signal Description
Signal Description Type
XIN Multipurpose Crystal Oscillator or external clock generator input Analog input
XOUT Multipurpose Crystal Oscillator output Analog output
The I/O lines are automatically selected when XOSC is enabled.
20.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
20.5.1 I/O Lines
I/O lines are configured by OSCCTRL when XOSC is enabled, and need no user configuration.
20.5.2 Power Management
The OSCCTRL can continue to operate in any sleep mode where the selected source clock is running.
The OSCCTRL interrupts can be used to wake up the device from sleep modes. The events can trigger
other operations in the system without exiting sleep modes.
Related Links
19. PM – Power Manager
20.5.3 Clocks
The OSCCTRL gathers controls for all device oscillators and provides clock sources to the Generic Clock
Controller (GCLK). The available clock sources are: XOSC, OSC48M and FDPLL96M.
The OSCCTRL bus clock (CLK_OSCCTRL_APB) can be enabled and disabled in the Main Clock module
(MCLK).
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 209
The OSC48M control logic uses the oscillator output, which is also asynchronous to the user interface
clock (CLK_OSCCTRL_APB). Due to this asynchronicity, writes to certain registers will require
synchronization between the clock domains. Refer to 20.6.9 Synchronization for further details.
Related Links
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
20.5.4 DMA
Not applicable.
20.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the OSCCTRL interrupts requires
the interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
20.8.3 INTFLAG
19.6.3.3 Sleep Mode Controller
20.5.6 Events
The events of this peripheral are connected to the Event System.
Related Links
29. EVSYS – Event System
20.5.7 Debug Operation
When the CPU is halted in debug mode the OSCCTRL continues normal operation. If the OSCCTRL is
configured in a way that requires it to be periodically serviced by the CPU through interrupts or similar,
improper operation or data loss may result during debugging.
20.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Flag Status and Clear register (INTFLAG)
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
20.5.9 Analog Connections
The 0.4-32MHz crystal must be connected between the XIN and XOUT pins, along with any required load
capacitors.
20.6 Functional Description
20.6.1 Principle of Operation
XOSC, OSC48M, and FDPLL96M. are configured via OSCCTRL control registers. Through this interface,
the oscillators are enabled, disabled, or have their calibration values updated.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 210
The Status register gathers different status signals coming from the oscillators controlled by the
OSCCTRL. The status signals can be used to generate system interrupts, and in some cases wake the
system from Sleep mode, provided the corresponding interrupt is enabled.
20.6.2 External Multipurpose Crystal Oscillator (XOSC) Operation
The XOSC can operate in two different modes:
• External clock, with an external clock signal connected to the XIN pin
• Crystal oscillator, with an external 0.4-32MHz crystal
The XOSC can be used as a clock source for generic clock generators. This is configured by the Generic
Clock Controller.
At reset, the XOSC is disabled, and the XIN/XOUT pins can be used as General Purpose I/O (GPIO) pins
or by other peripherals in the system. When XOSC is enabled, the operating mode determines the GPIO
usage. When in crystal oscillator mode, the XIN and XOUT pins are controlled by the OSCCTRL, and
GPIO functions are overridden on both pins. When in external clock mode, only the XIN pin will be
overridden and controlled by the OSCCTRL, while the XOUT pin can still be used as a GPIO pin.
The XOSC is enabled by writing a '1' to the Enable bit in the External Multipurpose Crystal Oscillator
Control register (XOSCCTRL.ENABLE).
To enable XOSC as an external crystal oscillator, the XTAL Enable bit (XOSCCTRL.XTALEN) must be
written to '1'. If XOSCCTRL.XTALEN is zero, the external clock input on XIN will be enabled.
When in crystal oscillator mode (XOSCCTRL.XTALEN=1), the External Multipurpose Crystal Oscillator
Gain (XOSCCTRL.GAIN) must be set to match the external crystal oscillator frequency. If the External
Multipurpose Crystal Oscillator Automatic Amplitude Gain Control (XOSCCTRL.AMPGC) is '1', the
oscillator amplitude will be automatically adjusted, and in most cases result in a lower power
consumption.
The XOSC will behave differently in different sleep modes, based on the settings of
XOSCCTRL.RUNSTDBY, XOSCCTRL.ONDEMAND, and XOSCCTRL.ENABLE. If
XOSCCTRL.ENABLE=0, the XOSC will be always stopped. For XOSCCTRL.ENABLE=1, this table is
valid:
Table 20-1. XOSC Sleep Behavior
CPU Mode XOSCCTRL.RUNST
DBY
XOSCCTRL.ONDEM
AND
Sleep Behavior
Active or Idle - 0 Always run
Active or Idle - 1 Run if requested by peripheral
Standby 1 0 Always run
Standby 1 1 Run if requested by peripheral
Standby 0 - Run if requested by peripheral
After a hard reset, or when waking up from a sleep mode where the XOSC was disabled, the XOSC will
need a certain amount of time to stabilize on the correct frequency. This start-up time can be configured
by changing the Oscillator Start-Up Time bit group (XOSCCTRL.STARTUP) in the External Multipurpose
Crystal Oscillator Control register. During the start-up time, the oscillator output is masked to ensure that
no unstable clock propagates to the digital logic.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 211
The External Multipurpose Crystal Oscillator Ready bit in the Status register (STATUS.XOSCRDY) is set
once the external clock or crystal oscillator is stable and ready to be used as a clock source. An interrupt
is generated on a zero-to-one transition on STATUS.XOSCRDY if the External Multipurpose Crystal
Oscillator Ready bit in the Interrupt Enable Set register (INTENSET.XOSCRDY) is set.
Related Links
16. GCLK - Generic Clock Controller
20.6.3 Clock Failure Detection Operation
The Clock Failure Detector (CFD) allows the user to monitor the external clock or crystal oscillator signal
provided by the external oscillator (XOSC). The CFD detects failing operation of the XOSC clock with
reduced latency, and allows to switch to a safe clock source in case of clock failure. The user can also
switch from the safe clock back to XOSC in case of recovery. The safe clock is derived from the OSC48M
oscillator with a configurable prescaler. This allows to configure the safe clock in order to fulfill the
operative conditions of the microcontroller.
In sleep modes, CFD operation is automatically disabled when the external oscillator is not requested to
run by a peripheral. See the Sleep Behavior table above when this is the case.
The user interface registers allow to enable, disable, and configure the CFD. The Status register provides
status flags on failure and clock switch conditions. The CFD can optionally trigger an interrupt or an event
when a failure is detected.
Clock Failure Detection
The CFD is disabled at reset. The CFD does not monitor the XOSC clock when the oscillator is disabled
(XOSCCTRL.ENABLE=0).
Before starting CFD operation, the user must start and enable the safe clock source (OSC48M oscillator).
CFD operation is started by writing a '1' to the CFD Enable bit in the External Oscillator Control register
(XOCCTRL.CFDEN). After starting or restarting the XOSC, the CFD does not detect failure until the start-
up time has elapsed. The start-up time is configured by the Oscillator Start-Up Time in the External
Multipurpose Crystal Oscillator Control register (XOSCCTRL.STARTUP). Once the XOSC Start-Up Time
is elapsed, the XOSC clock is constantly monitored.
During a period of 4 safe clocks (monitor period), the CFD watches for a clock activity from the XOSC.
There must be at least one rising and one falling XOSC clock edge during 4 safe clock periods to meet
non-failure conditions. If no or insufficient activity is detected, the failure status is asserted: The Clock
Failure Detector status bit in the Status register (STATUS.CLKFAIL) and the Clock Failure Detector
interrupt flag bit in the Interrupt Flag register (INTFLAG.CLKFAIL) are set. If the CLKFAIL bit in the
Interrupt Enable Set register (INTENSET.CLKFAIL) is set, an interrupt is generated as well. If the Event
Output enable bit in the Event Control register (EVCTRL.CFDEO) is set, an output event is generated,
too.
After a clock failure was issued the monitoring of the XOSC clock is continued, and the Clock Failure
Detector status bit in the Status register (STATUS.CLKFAIL) reflects the current XOSC activity.
Clock Switch
When a clock failure is detected, the XOSC clock is replaced by the safe clock in order to maintain an
active clock during the XOSC clock failure. The safe clock source is the OSC48M oscillator clock. The
safe clock source can be scaled down by a configurable prescaler to ensure that the safe clock frequency
does not exceed the operating conditions selected by the application. When the XOSC clock is switched
to the safe clock, the Clock Switch bit in the Status register (STATUS.CLKSW) is set.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 212
When the CFD has switched to the safe clock, the XOSC is not disabled. If desired, the application must
take the necessary actions to disable the oscillator. The application must also take the necessary actions
to configure the system clocks to continue normal operations.
In the case the application can recover the XOSC, the application can switch back to the XOSC clock by
writing a '1' to Switch Back Enable bit in the Clock Failure Control register (XOSCCTRL.SWBACK). Once
the XOSC clock is switched back, the Switch Back bit (XOSCCTRL.SWBACK) is cleared by hardware.
Prescaler
The CFD has an internal configurable prescaler to generate the safe clock from the OSC48M oscillator.
The prescaler size allows to scale down the OSC48M oscillator so the safe clock frequency is not higher
than the XOSC clock frequency monitored by the CFD. The division factor is 2^P, with P being the value
of the CFD Prescaler bits in the CFD Prescaler Register (CFDPRESC.CFDPRESC).
Example 20-1. Example
For an external crystal oscillator at 0.4MHz and the OSC48M frequency at 16MHz, the
CFDPRESC.CFDPRESC value should be set scale down by more than factor 16/0.4=80,
e.g. to 128, for a safe clock of adequate frequency.
Event
If the Event Output Enable bit in the Event Control register (EVCTRL.CFDEO) is set, the CFD clock
failure will be output on the Event Output. When the CFD is switched to the safe clock, the CFD clock
failure will not be output on the Event Output.
Sleep Mode
The CFD is halted depending on configuration of the XOSC and the peripheral clock request. For further
details, refer to the Sleep Behavior table above. The CFD interrupt can be used to wake up the device
from sleep modes.
20.6.4 48MHz Internal Oscillator (OSC48M) Operation
The OSC48M is an internal oscillator operating in open-loop mode and generating 48MHz frequency. The
OSC48M frequency is selected by writing to the Division Factor field in the OSC48MDIV register
(OSC48MDIV.DIV). OSC48M is enabled by writing '1' to the Oscillator Enable bit in the OSC48M Control
register (OSC48MCTRL.ENABLE), and disabled by writing a '0' to this bit.
After enabling OSC48M, the OSC48M clock is output as soon as the oscillator is ready
(STATUS.OSC48MRDY=1). User must ensure that the OSC48M is fully disabled before enabling it by
reading STATUS.OSC48MRDY=0.
After reset, OSC48M is enabled and serves as the default clock source at 4MHz.
OSC48M will behave differently in different sleep modes based on the settings of
OSC48MCTRL.RUNSTDBY, OSC48MCTRL.ONDEMAND, and OSC48MCTRL.ENABLE. If
OSC48MCTRL.ENABLE=0, the OSC48M will be always stopped. For OSC48MCTRL.ENABLE=1, this
table is valid:
Table 20-2. OSC48M Sleep Behavior
CPU Mode OSC48MCTRL.RUN
STDBY
OSC48MCTRL.OND
EMAND
Sleep Behavior
Active or Idle - 0 Always run
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 213
...........continued
CPU Mode OSC48MCTRL.RUN
STDBY
OSC48MCTRL.OND
EMAND
Sleep Behavior
Active or Idle - 1 Run if requested by peripheral
Standby 1 0 Always run
Standby 1 1 Run if requested by peripheral
Standby 0 - Run if requested by peripheral
After a hard reset, or when waking up from a sleep mode where the OSC48M was disabled, the OSC48M
will need a certain amount of time to stabilize on the correct frequency. This start-up time can be
configured by changing the Oscillator Start-Up Delay bit group (OSC48MSTUP.STARTUP) in the
OSC48M Startup register. During the start-up time, the oscillator output is masked to ensure that no
unstable clock propagates to the digital logic. The OSC48M Ready bit in the Status register
(STATUS.OSC48MRDY) is set when the oscillator is stable and ready to be used as a clock source. An
interrupt is generated on a zero-to-one transition on STATUS.OSC48MRDY if the OSC48M Ready bit in
the Interrupt Enable Set register (INTENSET.OSC48MRDY) is set.
Faster start-up times are achievable by selecting shorter delays. However, the oscillator frequency may
not stabilize within tolerances when short delays are used. If a fast start-up time is desired at the expense
of initial accuracy, the division factor should be set to two or higher (OSC48MDIV.DIV > 0).
The OSC48M is used as a clock source for the generic clock generators.
Related Links
16. GCLK - Generic Clock Controller
20.6.5 Digital Phase Locked Loop (DPLL) Operation
The task of the DPLL is to maintain coherence between the input (reference) signal and the respective
output frequency, CLK_DPLL, via phase comparison. The DPLL controller supports three independent
sources of reference clocks:
• XOSC32K: this clock is provided by the 32K External Crystal Oscillator (XOSC32K).
• XOSC: this clock is provided by the External Multipurpose Crystal Oscillator (XOSC).
• GCLK: this clock is provided by the Generic Clock Controller.
When the controller is enabled, the relationship between the reference clock frequency and the output
clock frequency is:
CK =CKR × LDR + 1 + LDRFRAC
16 ×1
2PRESC
Where fCK is the frequency of the DPLL output clock, LDR is the loop divider ratio integer part, LDRFRAC
is the loop divider ratio fractional part, fCKR is the frequency of the selected reference clock, and PRESC
is the output prescaler value.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 214
Figure 20-2. DPLL Block Diagram
XIN
XOUT
XOSC
XIN32
XOUT32
XOSC32K
GCLK
DIVIDER
DPLLCTRLB.DIV
DPLLCTRLB.REFCLK
DIGITAL FILTER
TDC
DPLLCTRLB.FILTER
DCO
CKDIV4
CKDIV2
CKDIV1
DPLLPRESC
CLK_DPLL
RATIO
DPLLRATIO
CK
CKR
CG
When the controller is disabled, the output clock is low. If the Loop Divider Ratio Fractional part bit field in
the DPLL Ratio register (DPLLRATIO.LDRFRAC) is zero, the DPLL works in integer mode. Otherwise,
the fractional mode is activated. Note that the fractional part has a negative impact on the jitter of the
DPLL.
Example (integer mode only): assuming FCKR = 32kHz and FCK = 48MHz, the
multiplication ratio is 1500. It means that LDR shall be set to 1499.
Example (fractional mode): assuming FCKR = 32kHz and FCK = 48.006MHz, the
multiplication ratio is 1500.1875 (1500 + 3/16). Thus LDR is set to 1499 and LDRFRAC
to 3.
Related Links
16. GCLK - Generic Clock Controller
21. OSC32KCTRL – 32KHz Oscillators Controller
20.6.5.1 Basic Operation
20.6.5.1.1 Initialization, Enabling, Disabling, and Resetting
The DPLLC is enabled by writing a '1' to the Enable bit in the DPLL Control A register
(DPLLCTRLA.ENABLE). The DPLLC is disabled by writing a zero to this bit.
The DPLLSYNCBUSY.ENABLE is set when the DPLLCTRLA.ENABLE bit is modified. It is cleared when
the DPLL output clock CK has sampled the bit at the high level after enabling the DPLL. When disabling
the DPLL, DPLLSYNCBUSY.ENABLE is cleared when the output clock is no longer running.
Figure 20-3. Enable Synchronization Busy Operation
ENABLE
CK
SYNCBUSY.ENABLE
CLK_APB_OSCCTRL
The frequency of the DPLL output clock CK is stable when the module is enabled and when the Lock bit
in the DPLL Status register is set (DPLLSTATUS.LOCK).
When the Lock Time bit field in the DPLL Control B register (DPLLCTRLB.LTIME) is non-zero, a user
defined lock time is used to validate the lock operation. In this case the lock time is constant. If
DPLLCTRLB.LTIME=0, the lock signal is linked with the status bit of the DPLL, and the lock time varies
depending on the filter selection and the final target frequency.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 215
When the Wake Up Fast bit (DPLLCTRLB.WUF) is set, the wake up fast mode is activated. In this mode
the clock gating cell is enabled at the end of the startup time. At this time the final frequency is not stable,
as it is still during the acquisition period, but it allows to save several milliseconds. After first acquisition,
the Lock Bypass bit (DPLLCTRLB.LBYPASS) indicates if the lock signal is discarded from the control of
the clock gater (CG) generating the output clock CLK_DPLL.
Table 20-3. CLK_DPLL Behavior from Startup to First Edge Detection
WUF LTIME CLK_DPLL Behavior
0 0 Normal Mode: First Edge when lock is asserted
0 Not Equal To Zero Lock Timer Timeout mode: First Edge when the timer down-counts to 0.
1 X Wake Up Fast Mode: First Edge when CK is active (startup time)
Table 20-4. CLK_DPLL Behavior after First Edge Detection
LBYPASS CLK_DPLL Behavior
0 Normal Mode: the CLK_DPLL is turned off when lock signal is low.
1 Lock Bypass Mode: the CLK_DPLL is always running, lock is irrelevant.
Figure 20-4. CK and CLK_DPLL Output from DPLL Off Mode to Running Mode
CKR
ENABLE
CK
LOCK
CK STABLEtstartup_time tlock_time
CLK_DPLL
20.6.5.1.2 Reference Clock Switching
When a software operation requires reference clock switching, the recommended procedure is to turn the
DPLL into the standby mode, modify the DPLLCTRLB.REFCLK to select the desired reference source,
and activate the DPLL again.
20.6.5.1.3 Output Clock Prescaler
The DPLL controller includes an output prescaler. This prescaler provides three selectable output clocks
CK, CKDIV2 and CKDIV4. The Prescaler bit field in the DPLL Prescaler register (DPLLPRESC.PRESC)
is used to select a new output clock prescaler. When the prescaler field is modified, the
DPLLSYNCBUSY.DPLLPRESC bit is set. It will be cleared by hardware when the synchronization is over.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 216
Figure 20-5. Output Clock Switching Operation
CKR
PRESC
CLK_DPLL
DPLL_LOCK
01
CK STABLECK STABLE CK SWITCHING
SYNCBUSY.PRESC
CK
CKDIV2
20.6.5.1.4 Loop Divider Ratio Updates
The DPLL Controller supports on-the-fly update of the DPLL Ratio Control (DPLLRATIO) register,
allowing to modify the loop divider ratio and the loop divider ratio fractional part when the DPLL is
enabled.
STATUS.DPLLLDRTO is set when the DPLLRATIO register has been modified and the DPLL analog cell
has successfully sampled the updated value. At that time the DPLLSTATUS.LOCK bit is cleared and set
again by hardware when the output frequency reached a stable state.
Figure 20-6. RATIOCTRL register update operation
CKR
LDR
LDRFRAC
CK
CLK_DPLL
mult0 mult1
LOCK
LOCKL
20.6.5.1.5 Digital Filter Selection
The PLL digital filter (PI controller) is automatically adjusted in order to provide a good compromise
between stability and jitter. Nevertheless a software operation can override the filter setting using the
Filter bit field in the DPLL Control B register (DPLLCTRLB.FILTER). The Low Power Enable bit
(DPLLCTRLB.LPEN) can be use to bypass the Time to Digital Converter (TDC) module.
20.6.6 DMA Operation
Not applicable.
20.6.7 Interrupts
The OSCCTRL has the following interrupt sources:
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 217
• XOSCRDY - Multipurpose Crystal Oscillator Ready: A 0-to-1 transition on the STATUS.XOSCRDY bit
is detected
• CLKFAIL - Clock Failure. A 0-to-1 transition on the STATUS.CLKFAIL bit is detected
• OSC48MRDY - 48MHz Internal Oscillator Ready: A 0-to-1 transition on the STATUS.OSC48MRDY
bit is detected
• DPLL-related:
– DPLLLOCKR - DPLL Lock Rise: A 0-to-1 transition of the STATUS.DPLLLOCKR bit is detected
– DPLLLOCKF - DPLL Lock Fall: A 0-to-1 transition of the STATUS.DPLLLOCKF bit is detected
– DPLLLTTO - DPLL Lock Timer Time-out: A 0-to-1 transition of the STATUS.DPLLLTTO bit is
detected
– DPLLLDRTO - DPLL Loop Divider Ratio Update Complete. A 0-to-1 transition of the
STATUS.DPLLLDRTO bit is detected
All these interrupts are synchronous wake-up source.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG) is set when the interrupt condition occurs.
Each interrupt can be individually enabled by writing a '1' to the corresponding bit in the Interrupt Enable
Set register (INTENSET), and disabled by writing a '1' to the corresponding bit in the Interrupt Enable
Clear register (INTENCLR).
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or the
OSCCTRL is reset. See the INTFLAG register for details on how to clear interrupt flags.
The OSCCTRL has one common interrupt request line for all the interrupt sources. The user must read
the INTFLAG register to determine which interrupt condition is present. Refer to the INTFLAG register for
details.
Note:  The interrupts must be globally enabled for interrupt requests to be generated.
20.6.8 Events
The CFD can generate the following output event:
• Clock Failure (CLKFAIL): Generated when the Clock Failure status bit is set in the Status register
(STATUS.CLKFAIL). The CFD event is not generated when the Clock Switch bit (STATUS.CLKSW)
in the Status register is set.
Writing a '1' to an Event Output bit in the Event Control register (EVCTRL.CFDEO) enables the CFD
output event. Writing a '0' to this bit disables the CFD output event. Refer to the Event System chapter for
details on configuring the event system.
20.6.9 Synchronization
OSC48M
Due to the multiple clock domains, values in the OSC48M control registers need to be synchronized to
other clock domains.
When executing an operation that requires synchronization, the relevant synchronization bit in the
Synchronization Busy register (OSC48MSYNCBUSY) will be set immediately, and cleared when
synchronization is complete.
The following registers need synchronization when written:
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 218
• OSC48M Divider register (OSC48MDIV)
DPLL96M
Due to the multiple clock domains, some registers in the DPLL96M must be synchronized when
accessed.
When executing an operation that requires synchronization, the relevant synchronization bit in the
Synchronization Busy register (DPLLSYNCBUSY) will be set immediately, and cleared when
synchronization is complete.
The following bits need synchronization when written:
• Enable bit in control register A (DPLLCTRLA.ENABLE)
• DPLL Ratio register (DPLLRATIO)
• DPLL Prescaler register (DPLLPRESC)
Related Links
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 219
20.7 Register Summary
Offset Name Bit Pos.
0x00 INTENCLR
7:0 OSC48MRDY CLKFAIL XOSCRDY
15:8 DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
23:16
31:24
0x04 INTENSET
7:0 OSC48MRDY CLKFAIL XOSCRDY
15:8 DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
23:16
31:24
0x08 INTFLAG
7:0 OSC48MRDY CLKFAIL XOSCRDY
15:8 DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
23:16
31:24
0x0C STATUS
7:0 OSC48MRDY CLKSW CLKFAIL XOSCRDY
15:8 DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
23:16
31:24
0x10 XOSCCTRL
7:0 ONDEMAND RUNSTDBY SWBACK CFDEN XTALEN ENABLE
15:8 STARTUP[3:0] AMPGC GAIN[2:0]
0x12 CFDPRESC 7:0 CFDPRESC[2:0]
0x13 EVCTRL 7:0 CFDEO
0x14 OSC48MCTRL 7:0 ONDEMAND RUNSTDBY ENABLE
0x15 OSC48MDIV 7:0 DIV[3:0]
0x16 OSC48MSTUP 7:0 STARTUP[2:0]
0x17 Reserved
0x18 OSC48MSYNCBUS
Y
7:0 OSC48MDIV
15:8
23:16
31:24
0x1C DPLLCTRLA 7:0 ONDEMAND RUNSTDBY ENABLE
0x1D
...
0x1F
Reserved
0x20 DPLLRATIO
7:0 LDR[7:0]
15:8 LDR[11:8]
23:16 LDRFRAC[3:0]
31:24
0x24 DPLLCTRLB
7:0 REFCLK[1:0] WUF LPEN FILTER[1:0]
15:8 LBYPASS LTIME[2:0]
23:16 DIV[7:0]
31:24 DIV[10:8]
0x28 DPLLPRESC 7:0 PRESC[1:0]
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 220
...........continued
Offset Name Bit Pos.
0x29
...
0x2B
Reserved
0x2C DPLLSYNCBUSY 7:0 DPLLPRESC DPLLRATIO ENABLE
0x2D
...
0x2F
Reserved
0x30 DPLLSTATUS 7:0 CLKRDY LOCK
0x31
...
0x37
Reserved
0x38 CAL48M
7:0 FCAL[5:0]
15:8 FRANGE[1:0]
23:16 TCAL[5:0]
31:24
20.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection
is denoted by the "PAC Write-Protection" property in each individual register description. Refer to the
20.5.8 Register Access Protection section and the PAC - Peripheral Access Controller chapter for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" or "Write-Synchronized" property in each individual register description. Refer to
the section on Synchronization for details.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 221
20.8.1 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OSC48MRDY CLKFAIL XOSCRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 11 – DPLLLDRTO DPLL Loop Divider Ratio Update Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the DPLL Loop Divider Ratio Update Complete Interrupt Enable bit, which
disables the DPLL Loop Divider Ratio Update Complete interrupt.
Value Description
0The DPLL Loop Divider Ratio Update Complete interrupt is disabled.
1The DPLL Loop Divider Ratio Update Complete interrupt is enabled, and an interrupt request
will be generated when the DPLL Loop Divider Ratio Update Complete Interrupt flag is set.
Bit 10 – DPLLLTO DPLL Lock Timeout Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the DPLL Lock Timeout Interrupt Enable bit, which disables the DPLL Lock
Timeout interrupt.
Value Description
0The DPLL Lock Timeout interrupt is disabled.
1The DPLL Lock Timeout interrupt is enabled, and an interrupt request will be generated
when the DPLL Lock Timeout Interrupt flag is set.
Bit 9 – DPLLLCKF DPLL Lock Fall Interrupt Enable
Writing '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 222
Writing '1' to this bit will clear the DPLL Lock Fall Interrupt Enable bit, which disables the DPLL Lock Fall
interrupt.
Value Description
0The DPLL Lock Fall interrupt is disabled.
1The DPLL Lock Fall interrupt is enabled, and an interrupt request will be generated when the
DPLL Lock Fall Interrupt flag is set.
Bit 8 – DPLLLCKR DPLL Lock Rise Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the DPLL Lock Rise Interrupt Enable bit, which disables the DPLL Lock Rise
interrupt.
Value Description
0The DPLL Lock Rise interrupt is disabled.
1The DPLL Lock Rise interrupt is enabled, and an interrupt request will be generated when
the DPLL Lock Rise Interrupt flag is set.
Bit 4 – OSC48MRDY OSC48M Ready Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the OSC48M Ready Interrupt Enable bit, which disables the OSC48M
Ready interrupt.
Value Description
0The OSC48M Ready interrupt is disabled.
1The OSC48M Ready interrupt is enabled, and an interrupt request will be generated when
the OSC48M Ready Interrupt flag is set.
Bit 1 – CLKFAIL Clock Failure Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the XOSC Clock Failure Interrupt Enable bit, which disables the XOSC
Clock Failure interrupt.
Value Description
0The XOSC Clock Failure interrupt is disabled.
1The XOSC Clock Failure interrupt is enabled, and an interrupt request will be generated
when the XOSC Clock Failure Interrupt flag is set.
Bit 0 – XOSCRDY XOSC Ready Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the XOSC Ready Interrupt Enable bit, which disables the XOSC Ready
interrupt.
Value Description
0The XOSC Ready interrupt is disabled.
1The XOSC Ready interrupt is enabled, and an interrupt request will be generated when the
XOSC Ready Interrupt flag is set.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 223
20.8.2 Interrupt Enable Set
Name:  INTENSET
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OSC48MRDY CLKFAIL XOSCRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 11 – DPLLLDRTO DPLL Loop Divider Ratio Update Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the DPLL Loop Ratio Update Complete Interrupt Enable bit, which enables
the DPLL Loop Ratio Update Complete interrupt.
Value Description
0The DPLL Loop Divider Ratio Update Complete interrupt is disabled.
1The DPLL Loop Ratio Update Complete interrupt is enabled, and an interrupt request will be
generated when the DPLL Loop Ratio Update Complete Interrupt flag is set.
Bit 10 – DPLLLTO DPLL Lock Timeout Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the DPLL Lock Timeout Interrupt Enable bit, which enables the DPLL Lock
Timeout interrupt.
Value Description
0The DPLL Lock Timeout interrupt is disabled.
1The DPLL Lock Timeout interrupt is enabled, and an interrupt request will be generated
when the DPLL Lock Timeout Interrupt flag is set.
Bit 9 – DPLLLCKF DPLL Lock Fall Interrupt Enable
Writing '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 224
Writing '1' to this bit will set the DPLL Lock Fall Interrupt Enable bit, which enables the DPLL Lock Fall
interrupt.
Value Description
0The DPLL Lock Fall interrupt is disabled.
1The DPLL Lock Fall interrupt is enabled, and an interrupt request will be generated when the
DPLL Lock Fall Interrupt flag is set.
Bit 8 – DPLLLCKR DPLL Lock Rise Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the DPLL Lock Rise Interrupt Enable bit, which enables the DPLL Lock Rise
interrupt.
Value Description
0The DPLL Lock Rise interrupt is disabled.
1The DPLL Lock Rise interrupt is enabled, and an interrupt request will be generated when
the DPLL Lock Rise Interrupt flag is set.
Bit 4 – OSC48MRDY OSC48M Ready Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the OSC48M Ready Interrupt Enable bit, which enables the OSC48M Ready
interrupt.
Value Description
0The OSC48M Ready interrupt is disabled.
1The OSC48M Ready interrupt is enabled, and an interrupt request will be generated when
the OSC48M Ready Interrupt flag is set.
Bit 1 – CLKFAIL XOSC Clock Failure Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the XOSC Clock Failure Interrupt Enable bit, which enables the XOSC Clock
Failure Interrupt.
Value Description
0The XOSC Clock Failure Interrupt is disabled.
1The XOSC Clock Failure Interrupt is enabled, and an interrupt request will be generated
when the XOSC Clock Failure Interrupt flag is set.
Bit 0 – XOSCRDY XOSC Ready Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the XOSC Ready Interrupt Enable bit, which enables the XOSC Ready
interrupt.
Value Description
0The XOSC Ready interrupt is disabled.
1The XOSC Ready interrupt is enabled, and an interrupt request will be generated when the
XOSC Ready Interrupt flag is set.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 225
20.8.3 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x08
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OSC48MRDY CLKFAIL XOSCRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 11 – DPLLLDRTO DPLL Loop Divider Ratio Update Complete
This flag is cleared by writing '1' to it.
This flag is set on 0-to-1 transition of the DPLL Loop Divider Ratio Update Complete bit in the Status
register (STATUS.DPLLLDRTO) and will generate an interrupt request if INTENSET.DPLLLDRTO is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the DPLL Loop Divider Ratio Update Complete interrupt flag.
Bit 10 – DPLLLTO DPLL Lock Timeout
This flag is cleared by writing '1' to it.
This flag is set on 0-to-1 transition of the DPLL Lock Timeout bit in the Status register
(STATUS.DPLLLTO) and will generate an interrupt request if INTENSET.DPLLLTO is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the DPLL Lock Timeout interrupt flag.
Bit 9 – DPLLLCKF DPLL Lock Fall
This flag is cleared by writing '1' to it.
This flag is set on 0-to-1 transition of the DPLL Lock Fall bit in the Status register (STATUS.DPLLLCKF)
and will generate an interrupt request if INTENSET.DPLLLCKF is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the DPLL Lock Fall interrupt flag.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 226
Bit 8 – DPLLLCKR DPLL Lock Rise
This flag is cleared by writing '1' to it.
This flag is set on 0-to-1 transition of the DPLL Lock Rise bit in the Status register (STATUS.DPLLLCKR)
and will generate an interrupt request if INTENSET.DPLLLCKR is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the DPLL Lock Rise interrupt flag.
Bit 4 – OSC48MRDY OSC48M Ready
This flag is cleared by writing '1' to it.
This flag is set on 0-to-1 transition of the OSC48M Ready bit in the Status register
(STATUS.OSC48MRDY) and will generate an interrupt request if INTENSET.OSC48MRDY is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the OSC48M Ready interrupt flag.
Bit 1 – CLKFAIL XOSC Failure Detection
This flag is cleared by writing '1' to it.
This flag is set on a 0-to-1 transition of the XOSC Clock Failure bit in the Status register
(STATUS.CLKFAIL) and will generate an interrupt request if INTENSET.CLKFAIL is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the XOSC Clock Fail interrupt flag.
Bit 0 – XOSCRDY XOSC Ready
This flag is cleared by writing '1' to it.
This flag is set on a 0-to-1 transition of the XOSC Ready bit in the Status register (STATUS.XOSCRDY)
and will generate an interrupt request if INTENSET.XOSCRDY is '1'.
Writing '0' to this bit has no effect.
Writing '1' to this bit clears the XOSC Ready interrupt flag.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 227
20.8.4 Status
Name:  STATUS
Offset:  0x0C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
DPLLLDRTO DPLLLTO DPLLLCKF DPLLLCKR
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OSC48MRDY CLKSW CLKFAIL XOSCRDY
Access R R R R
Reset 0 0 0 0
Bit 11 – DPLLLDRTO DPLL Loop Divider Ratio Update Complete
Value Description
0DPLL Loop Divider Ratio Update Complete not detected.
1DPLL Loop Divider Ratio Update Complete detected.
Bit 10 – DPLLLTO DPLL Lock Timeout
Value Description
0DPLL Lock time-out not detected.
1DPLL Lock time-out detected.
Bit 9 – DPLLLCKF DPLL Lock Fall
Value Description
0DPLL Lock fall edge not detected.
1DPLL Lock fall edge detected.
Bit 8 – DPLLLCKR DPLL Lock Rise
Value Description
0DPLL Lock rise edge not detected.
1DPLL Lock fall edge detected.
Bit 4 – OSC48MRDY OSC48M Ready
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 228
Value Description
0OSC48M is not ready.
1OSC48M is stable and ready to be used as a clock source.
Bit 2 – CLKSW XOSC Clock Switch
Value Description
0XOSC is not switched and provides the external clock or crystal oscillator clock.
1XOSC is switched and provides the safe clock.
Bit 1 – CLKFAIL XOSC Clock Failure
Value Description
0No XOSC failure detected.
1A XOSC failure was detected.
Bit 0 – XOSCRDY XOSC Ready
Value Description
0XOSC is not ready.
1XOSC is stable and ready to be used as a clock source.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 229
20.8.5 External Multipurpose Crystal Oscillator (XOSC) Control
Name:  XOSCCTRL
Offset:  0x10
Reset:  0x0080
Property:  PAC Write-Protection
Bit 15 14 13 12 11 10 9 8
STARTUP[3:0] AMPGC GAIN[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY SWBACK CFDEN XTALEN ENABLE
Access R/W R/W R/W R/W R/W R/W
Reset 1 0 0 0 0 0
Bits 15:12 – STARTUP[3:0] Start-Up Time
These bits select start-up time for the oscillator.
The OSCULP32K oscillator is used to clock the start-up counter.
Table 20-5. Start-Up Time for External Multipurpose Crystal Oscillator
STARTUP[3:0] Number of OSCULP32K
Clock Cycles
Number of XOSC
Clock Cycles
Approximate Equivalent
Time [µs]
0x0 1 3 31
0x1 2 3 61
0x2 4 3 122
0x3 8 3 244
0x4 16 3 488
0x5 32 3 977
0x6 64 3 1953
0x7 128 3 3906
0x8 256 3 7813
0x9 512 3 15625
0xA 1024 3 31250
0xB 2048 3 62500µs
0xC 4096 3 125000
0xD 8192 3 250000
0xE 16384 3 500000
0xF 32768 3 1000000
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 230
Note: 
1. Actual startup time is 1 OSCULP32K cycle + 3 XOSC cycles.
2. The given time neglects the three XOSC cycles before OSCULP32K cycle.
Bit 11 – AMPGC Automatic Amplitude Gain Control
Note:  This bit must be set only after the XOSC has settled, indicated by the XOSC Ready flag in the
Status register (STATUS.XOSCRDY).
Value Description
0The automatic amplitude gain control is disabled.
1The automatic amplitude gain control is enabled. Amplitude gain will be automatically
adjusted during Crystal Oscillator operation.
Bits 10:8 – GAIN[2:0] Oscillator Gain
These bits select the gain for the oscillator. The listed maximum frequencies are recommendations, and
might vary based on capacitive load and crystal characteristics. Those bits must be properly configured
even when the Automatic Amplitude Gain Control is active.
Value Recommended Max Frequency [MHz]
0x0 2
0x1 4
0x2 8
0x3 16
0x4 30
0x5-0x7 Reserved
Bit 7 – ONDEMAND On Demand Control
The On Demand operation mode allows the oscillator to be enabled or disabled, depending on peripheral
clock requests.
If the ONDEMAND bit has been previously written to '1', the oscillator will be running only when requested
by a peripheral. If there is no peripheral requesting the oscillator’s clock source, the oscillator will be in a
disabled state.
If On Demand is disabled, the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active.
Value Description
0The oscillator is always on, if enabled.
1The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock
source. The oscillator is disabled if no peripheral is requesting the clock source.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the XOSC behaves during standby sleep mode, together with the ONDEMAND bit:
Value Description
0The XOSC is not running in Standby sleep mode if no peripheral requests the clock.
1The XOSC is running in Standby sleep mode. If ONDEMAND=1, the XOSC will be running
when a peripheral is requesting the clock. If ONDEMAND=0, the clock source will always be
running in Standby sleep mode.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 231
Bit 4 – SWBACK Clock Switch Back
This bit controls the XOSC output switch back to the external clock or crystal oscillator in case of clock
recovery:
Value Description
0The clock switch back is disabled.
1The clock switch back is enabled. This bit is reset once the XOSC putput clock is switched
back to the external clock or crystal oscillator.
Bit 3 – CFDEN Clock Failure Detector Enable
This bit controls the clock failure detector:
Value Description
0The Clock Failure Detector is disabled.
1the Clock Failure Detector is enabled.
Bit 2 – XTALEN Crystal Oscillator Enable
This bit controls the connections between the I/O pads and the external clock or crystal oscillator:
Value Description
0External clock connected on XIN. XOUT can be used as general-purpose I/O.
1Crystal connected to XIN/XOUT.
Bit 1 – ENABLE Oscillator Enable
Value Description
0The oscillator is disabled.
1The oscillator is enabled.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 232
20.8.6 Clock Failure Detector Prescaler
Name:  CFDPRESC
Offset:  0x12
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CFDPRESC[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – CFDPRESC[2:0] Clock Failure Detector Prescaler
These bits select the prescaler for the clock failure detector.
The OSC48M oscillator is used to clock the CFD prescaler. The CFD safe clock frequency is the
OSC48M frequency divided by 2^CFDPRESC.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 233
20.8.7 Event Control
Name:  EVCTRL
Offset:  0x13
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CFDEO
Access R/W
Reset 0
Bit 0 – CFDEO Clock Failure Detector Event Output Enable
This bit indicates whether the Clock Failure detector event output is enabled or not and an output event
will be generated when the Clock Failure detector detects a clock failure
Value Description
0Clock Failure detector event output is disabled and no event will be generated.
1Clock Failure detector event output is enabled and an event will be generated.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 234
20.8.8 48MHz Internal Oscillator (OSC48M) Control
Name:  OSC48MCTRL
Offset:  0x14
Reset:  0x82
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY ENABLE
Access R/W R/W R/W
Reset 1 0 1
Bit 7 – ONDEMAND On Demand Control
The On Demand operation mode allows the oscillator to be enabled or disabled depending on peripheral
clock requests.
If the ONDEMAND bit has been previously written to '1', the oscillator will only be running when requested
by a peripheral. If there is no peripheral requesting the oscillator’s clock source, the oscillator will be in a
disabled state.
If On Demand is disabled the oscillator will always be running when enabled.
In standby sleep mode, the On Demand operation is still active.
Value Description
0The oscillator is always on, if enabled.
1The oscillator is enabled when a peripheral is requesting the oscillator to be used as a clock
source. The oscillator is disabled if no peripheral is requesting the clock source.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the OSC48M behaves during standby sleep mode.
Value Description
0The OSC48M is disabled in standby sleep mode if no peripheral requests the clock.
1The OSC48M is not stopped in standby sleep mode. If ONDEMAND=1, the OSC48M will be
running when a peripheral is requesting the clock. If ONDEMAND=0, the clock source will
always be running in standby sleep mode.
Bit 1 – ENABLE Oscillator Enable
Value Description
0The oscillator is disabled.
1The oscillator is enabled.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 235
20.8.9 OSC48M Divider
Name:  OSC48MDIV
Offset:  0x15
Reset:  0x0B
Property:  -
Bit 7 6 5 4 3 2 1 0
DIV[3:0]
Access R/W R/W R/W R/W
Reset 1 0 1 1
Bits 3:0 – DIV[3:0] Oscillator Divider Selection
These bits control the oscillator frequency range by adjusting the division ratio. The oscillator frequency is
48MHz divided by DIV+1.
Value Description
0000 48MHz
0001 24MHz
0010 16MHz
0011 12MHz
0100 9.6MHz
0101 8MHz
0110 6.86MHz
0111 6MHz
1000 5.33MHz
1001 4.8MHz
1010 4.36MHz
1011 4MHz
1100 3.69MHz
1101 3.43MHz
1110 3.2MHz
1111 3MHz
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 236
20.8.10 OSC48M Startup
Name:  OSC48MSTUP
Offset:  0x16
Reset:  0x07
Property:  -
Bit 7 6 5 4 3 2 1 0
STARTUP[2:0]
Access R/W R/W R/W
Reset 1 1 1
Bits 2:0 – STARTUP[2:0] Oscillator Startup Delay
These bits select the oscillator start-up delay in oscillator cycles.
Table 20-6. Oscillator Divider Selection
STARTUP[2:0] Number of OSCM48M Clock
Cycles
Approximate Equivalent Time
0x0 8 166ns
0x1 16 333ns
0x2 32 667ns
0x3 64 1.333μs
0x4 128 2.667μs
0x5 256 5.333μs
0x6 512 10.667μs
0x7 1024 21.333μs
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 237
20.8.11 OSC48M Synchronization Busy
Name:  OSC48MSYNCBUSY
Offset:  0x18
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
OSC48MDIV
Access R/W
Reset 1
Bit 2 – OSC48MDIV Oscillator Divider Synchronization Status
This bit is set when OSC48MDIV register is written.
This bit is cleared when OSC48MDIV synchronization is completed.
Value Description
0No synchronized access.
1Synchronized access is ongoing.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 238
20.8.12 DPLL Control A
Name:  DPLLCTRLA
Offset:  0x1C
Reset:  0x80
Property:  PAC Write-Protection, Write-Synchronized (ENABLE)
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY ENABLE
Access R/W R/W R/W
Reset 1 0 0
Bit 7 – ONDEMAND On Demand Clock Activation
The On Demand operation mode allows the DPLL to be enabled or disabled depending on peripheral
clock requests.
If the ONDEMAND bit has been previously written to '1', the DPLL will only be running when requested by
a peripheral. If there is no peripheral requesting the DPLL’s clock source, the DPLL will be in a disabled
state.
If On Demand is disabled the DPLL will always be running when enabled.
In standby sleep mode, the On Demand operation is still active.
Value Description
0The DPLL is always on, if enabled.
1The DPLL is enabled when a peripheral is requesting the DPLL to be used as a clock
source. The DPLL is disabled if no peripheral is requesting the clock source.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the DPLL behaves during standby sleep mode:
Value Description
0The DPLL is disabled in standby sleep mode if no peripheral requests the clock.
1The DPLL is not stopped in standby sleep mode. If ONDEMAND=1, the DPLL will be running
when a peripheral is requesting the clock. If ONDEMAND=0, the clock source will always be
running in standby sleep mode.
Bit 1 – ENABLE DPLL Enable
The software operation of enabling or disabling the DPLL takes a few clock cycles, so the
DPLLSYNCBUSY.ENABLE status bit indicates when the DPLL is successfully enabled or disabled.
Value Description
0The DPLL is disabled.
1The DPLL is enabled.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 239
20.8.13 DPLL Ratio Control
Name:  DPLLRATIO
Offset:  0x20
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
LDRFRAC[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
LDR[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
LDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 19:16 – LDRFRAC[3:0] Loop Divider Ratio Fractional Part
Writing these bits selects the fractional part of the frequency multiplier. Due to synchronization there is a
delay between writing these bits and the effect on the DPLL output clock. The value written will read back
immediately and the DPLLRATIO bit in the DPLL Synchronization Busy register
(DPLLSYNCBUSY.DPLLRATIO) will be set. DPLLSYNCBUSY.DPLLRATIO will be cleared when the
operation is completed.
Bits 11:0 – LDR[11:0] Loop Divider Ratio
Writing these bits selects the integer part of the frequency multiplier. The value written to these bits will
read back immediately, and the DPLLRATIO bit in the DPLL Synchronization busy register
(DPLLSYNCBUSY.DPLLRATIO), will be set. DPLLSYNCBUSY.DPLLRATIO will be cleared when the
operation is completed.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 240
20.8.14 DPLL Control B
Name:  DPLLCTRLB
Offset:  0x24
Reset:  0x00
Property:  Enable-Protected, PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
DIV[10:8]
Access R/W R/W R/W
Reset 0 0 0
Bit 23 22 21 20 19 18 17 16
DIV[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
LBYPASS LTIME[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
REFCLK[1:0] WUF LPEN FILTER[1:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 26:16 – DIV[10:0] Clock Divider
These bits set the XOSC clock division factor and can be calculated with following formula:
f =
2 + 1
Bit 12 – LBYPASS Lock Bypass
Value Description
0DPLL Lock signal drives the DPLL controller internal logic.
1DPLL Lock signal is always asserted.
Bits 10:8 – LTIME[2:0] Lock Time
These bits select the lock time-out value:
Value Name Description
0x0 Default No time-out. Automatic lock.
0x1 Reserved
0x2 Reserved
0x3 Reserved
0x4 8MS Time-out if no lock within 8ms
0x5 9MS Time-out if no lock within 9ms
0x6 10MS Time-out if no lock within 10ms
0x7 11MS Time-out if no lock within 11ms
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 241
Bits 5:4 – REFCLK[1:0] Reference Clock Selection
Write these bits to select the DPLL clock reference:
Value Name Description
0x0 XOSC32K XOSC32K clock reference
0x1 XOSC XOSC clock reference
0x2 GCLK GCLK clock reference
0x3 Reserved
Bit 3 – WUF Wake Up Fast
Value Description
0DPLL clock is output after startup and lock time.
1DPLL clock is output after startup time.
Bit 2 – LPEN Low-Power Enable
Value Description
0The low-power mode is disabled. Time to Digital Converter is enabled.
1The low-power mode is enabled. Time to Digital Converter is disabled. This will improve
power consumption but increase the output jitter.
Bits 1:0 – FILTER[1:0] Proportional Integral Filter Selection
These bits select the DPLL filter type:
Value Name Description
0x0 DEFAULT Default filter mode
0x1 LBFILT Low bandwidth filter
0x2 HBFILT High bandwidth filter
0x3 HDFILT High damping filter
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 242
20.8.15 DPLL Prescaler
Name:  DPLLPRESC
Offset:  0x28
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
PRESC[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – PRESC[1:0] Output Clock Prescaler
These bits define the output clock prescaler setting.
Value Name Description
0x0 DIV1 DPLL output is divided by 1
0x1 DIV2 DPLL output is divided by 2
0x2 DIV4 DPLL output is divided by 4
0x3 Reserved
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 243
20.8.16 DPLL Synchronization Busy
Name:  DPLLSYNCBUSY
Offset:  0x2C
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
DPLLPRESC DPLLRATIO ENABLE
Access R R R
Reset 0 0 0
Bit 3 – DPLLPRESC DPLL Prescaler Synchronization Status
Value Description
0The DPLLRESC register has been synchronized.
1The DPLLRESC register value has changed and its synchronization is in progress.
Bit 2 – DPLLRATIO DPLL Loop Divider Ratio Synchronization Status
Value Description
0The DPLLRATIO register has been synchronized.
1The DPLLRATIO register value has changed and its synchronization is in progress.
Bit 1 – ENABLE DPLL Enable Synchronization Status
Value Description
0The DPLLCTRLA.ENABLE bit has been synchronized.
1The DPLLCTRLA.ENABLE bit value has changed and its synchronization is in progress.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 244
20.8.17 DPLL Status
Name:  DPLLSTATUS
Offset:  0x30
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
CLKRDY LOCK
Access R R
Reset 0 0
Bit 1 – CLKRDY Output Clock Ready
Value Description
0The DPLL output clock is off.
1The DPLL output clock in on.
Bit 0 – LOCK DPLL Lock status bit
Value Description
0The DPLL Lock signal is cleared, when the DPLL is disabled or when the DPLL is trying to
reach the target frequency.
1The DPLL Lock signal is asserted when the desired frequency is reached.
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 245
20.8.18 OSC48M Calibration
Name:  CAL48M
Offset:  0x38
Reset:  Calibrated value for VDD range 3.6 V to 5.5 V
Property:  PAC Write-Protection
This register (bits 0 to 21) must be updated with the corresponding data in the NVM Software Calibration
Area: CAL48M 5V or CAL48M 3V3, depending on the VDD range. Refer to 9.4 NVM Software
Calibration Area Mapping.
Note:  This register is only available for Rev D silicon.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
TCAL[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset x x x x x x
Bit 15 14 13 12 11 10 9 8
FRANGE[1:0]
Access R/W R/W
Reset x x
Bit 7 6 5 4 3 2 1 0
FCAL[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset x x x x x x
Bits 21:16 – TCAL[5:0] Temperature Calibration
Bits 9:8 – FRANGE[1:0] Frequency Range
Bits 5:0 – FCAL[5:0] Frequency Calibration
Related Links
9.4 NVM Software Calibration Area Mapping
SAM C20/C21 Family Data Sheet
OSCCTRL – Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 246
21. OSC32KCTRL – 32KHz Oscillators Controller
21.1 Overview
The 32KHz Oscillators Controller (OSC32KCTRL) provides a user interface to the 32.768kHz oscillators:
XOSC32K, OSC32K, and OSCULP32K.
The OSC32KCTRL sub-peripherals can be enabled, disabled, calibrated, and monitored through
interface registers.
All sub-peripheral statuses are collected in the Status register (STATUS). They can additionally trigger
interrupts upon status changes via the INTENSET, INTENCLR, and INTFLAG registers.
21.2 Features
• 32.768kHz Crystal Oscillator (XOSC32K)
– Programmable start-up time
– Crystal or external input clock on XIN32 I/O
– Clock failure detection with safe clock switch
– Clock failure event output
• 32.768kHz High Accuracy Internal Oscillator (OSC32K)
– Frequency fine tuning
– Programmable start-up time
• 32.768kHz Ultra Low Power Internal Oscillator (OSCULP32K)
– Ultra low power, always-on oscillator
– Frequency fine tuning
• Calibration value loaded from Flash factory calibration at reset
• 1.024kHz clock outputs available
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 247
21.3 Block Diagram
Figure 21-1. OSC32KCTRL Block Diagram
STATUS
register
INTERRUPTS
GENERATOR Interrupts
OSC32KCTRL
32K OSCILLATORS
CONTROL
XOUT32 XIN32
CLK_XOSC32K
CLK_OSC32K
CLK_OSCULP32K
CFD Event
XOSC32K
OSCULP32K
OSC32K
CFD
21.4 Signal Description
Signal Description Type
XIN32 Analog Input 32.768 kHz Crystal Oscillator or external clock input
XOUT32 Analog Output 32.768 kHz Crystal Oscillator output
The I/O lines are automatically selected when XOSC32K is enabled.
Note:  The signal of the external crystal oscillator may affect the jitter of neighboring pads.
21.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
21.5.1 I/O Lines
I/O lines are configured by OSC32KCTRL when XOSC32K is enabled, and need no user configuration.
21.5.2 Power Management
The OSC32KCTRL will continue to operate in any sleep mode where a 32KHz oscillator is running as
source clock. The OSC32KCTRL interrupts can be used to wake up the device from sleep modes.
Related Links
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 248
19. PM – Power Manager
21.5.3 Clocks
The OSC32KCTRL gathers controls for all 32KHz oscillators and provides clock sources to the Generic
Clock Controller (GCLK), Real-Time Counter (RTC), and Watchdog Timer (WDT).
The available clock sources are: XOSC32K, OSC32K, and OSCULP32K.
The OSC32KCTRL bus clock (CLK_OSC32KCTRL_APB) can be enabled and disabled in the Main Clock
module (MCLK).
Related Links
17.6.2.6 Peripheral Clock Masking
21.5.4 Interrupts
The interrupt request lines are connected to the interrupt controller. Using the OSC32KCTRL interrupts
requires the interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
21.5.5 Events
The events of this peripheral are connected to the Event System.
Related Links
29. EVSYS – Event System
21.5.6 Debug Operation
When the CPU is halted in debug mode, OSC32KCTRL will continue normal operation. If OSC32KCTRL
is configured in a way that requires it to be periodically serviced by the CPU through interrupts or similar,
improper operation or data loss may result during debugging.
21.5.7 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Flag Status and Clear (INTFLAG) register
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
21.5.8 Analog Connections
The external 32.768kHz crystal must be connected between the XIN32 and XOUT32 pins, along with any
required load capacitors. For details on recommended oscillator characteristics and capacitor load, refer
to the related links.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 249
21.5.9 Calibration
The OSC32K calibration value from the production test must be loaded from the NVM Software
Calibration Area into the OSC32K register (OSC32K.CALIB) by software to achieve specified accuracy.
Related Links
9.4 NVM Software Calibration Area Mapping
21.6 Functional Description
21.6.1 Principle of Operation
XOSC32K, OSC32K, and OSCULP32K are configured via OSC32KCTRL control registers. Through this
interface, the sub-peripherals are enabled, disabled, or have their calibration values updated.
The STATUS register gathers different status signals coming from the sub-peripherals of OSC32KCTRL.
The status signals can be used to generate system interrupts, and in some cases wake up the system
from standby mode, provided the corresponding interrupt is enabled.
21.6.2 32KHz External Crystal Oscillator (XOSC32K) Operation
The XOSC32K can operate in two different modes:
• External clock, with an external clock signal connected to XIN32
• Crystal oscillator, with an external 32.768kHz crystal connected between XIN32 and XOUT32
At reset, the XOSC32K is disabled, and the XIN32/XOUT32 pins can either be used as General Purpose
I/O (GPIO) pins or by other peripherals in the system.
When XOSC32K is enabled, the operating mode determines the GPIO usage. When in crystal oscillator
mode, the XIN32 and XOUT32 pins are controlled by the OSC32KCTRL, and GPIO functions are
overridden on both pins. When in external clock mode, the only XIN32 pin will be overridden and
controlled by the OSC32KCTRL, while the XOUT32 pin can still be used as a GPIO pin.
The XOSC32K is enabled by writing a '1' to the Enable bit in the 32KHz External Crystal Oscillator
Control register (XOSC32K.ENABLE=1). The XOSC32K is disabled by writing a '0' to the Enable bit in the
32KHz External Crystal Oscillator Control register (XOSC32K.ENABLE=0).
To enable the XOSC32K as a crystal oscillator, the XTALEN bit in the 32KHz External Crystal Oscillator
Control register must be set (XOSC32K.XTALEN=1). If XOSC32K.XTALEN is '0', the external clock input
will be enabled.
The XOSC32K 32.768kHz output is enabled by setting the 32KHz Output Enable bit in the 32KHz
External Crystal Oscillator Control register (XOSC32K.EN32K=1). The XOSC32K also has a 1.024kHz
clock output. This is enabled by setting the 1KHz Output Enable bit in the 32KHz External Crystal
Oscillator Control register (XOSC32K.EN1K=1).
It is also possible to lock the XOSC32K configuration by setting the Write Lock bit in the 32KHz External
Crystal Oscillator Control register (XOSC32K.WRTLOCK=1). If set, the XOSC32K configuration is locked
until a Power-On Reset (POR) is detected.
The XOSC32K will behave differently in different sleep modes based on the settings of
XOSC32K.RUNSTDBY, XOSC32K.ONDEMAND, and XOSC32K.ENABLE. If
XOSC32KCTRL.ENABLE=0, the XOSC32K will be always stopped. For XOS32KCTRL.ENABLE=1, this
table is valid:
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 250
Table 21-1. XOSC32K Sleep Behavior
CPU Mode XOSC32K.
RUNSTDBY
XOSC32K.
ONDEMAND
Sleep Behavior of XOSC32K and CFD
Active or Idle - 0 Always run
Active or Idle - 1 Run if requested by peripheral
Standby 1 0 Always run
Standby 1 1 Run if requested by peripheral
Standby 0 - Run if requested by peripheral
As a crystal oscillator usually requires a very long start-up time, the 32KHz External Crystal Oscillator will
keep running across resets when XOSC32K.ONDEMAND=0, except for power-on reset (POR). After a
reset or when waking up from a sleep mode where the XOSC32K was disabled, the XOSC32K will need
a certain amount of time to stabilize on the correct frequency. This start-up time can be configured by
changing the Oscillator Start-Up Time bit group (XOSC32K.STARTUP) in the 32KHz External Crystal
Oscillator Control register. During the start-up time, the oscillator output is masked to ensure that no
unstable clock propagates to the digital logic.
Once the external clock or crystal oscillator is stable and ready to be used as a clock source, the
XOSC32K Ready bit in the Status register is set (STATUS.XOSC32KRDY=1). The transition of
STATUS.XOSC32KRDY from '0' to '1' generates an interrupt if the XOSC32K Ready bit in the Interrupt
Enable Set register is set (INTENSET.XOSC32KRDY=1).
The XOSC32K can be used as a source for Generic Clock Generators (GCLK) or for the Real-Time
Counter (RTC). Before enabling the GCLK or the RTC module, the corresponding oscillator output must
be enabled (XOSC32K.EN32K or XOSC32K.EN1K) in order to ensure proper operation. In the same way,
the GCLK or RTC modules must be disabled before the clock selection is changed. For details on RTC
clock configuration, refer also to 21.6.7 Real-Time Counter Clock Selection.
Related Links
16. GCLK - Generic Clock Controller
24. RTC – Real-Time Counter
21.6.3 Clock Failure Detection Operation
The Clock Failure Detector (CFD) allows the user to monitor the external clock or crystal oscillator signal
provided by the external oscillator (XOSC32K). The CFD detects failing operation of the XOSC32K clock
with reduced latency, and allows to switch to a safe clock source in case of clock failure. The user can
also switch from the safe clock back to XOSC32K in case of recovery. The safe clock is derived from the
OSCULP32K oscillator with a configurable prescaler. This allows to configure the safe clock in order to
fulfill the operative conditions of the microcontroller.
In sleep modes, CFD operation is automatically disabled when the external oscillator is not requested to
run by a peripheral. See the Sleep Behavior table above when this is the case.
The user interface registers allow to enable, disable, and configure the CFD. The Status register provides
status flags on failure and clock switch conditions. The CFD can optionally trigger an interrupt or an event
when a failure is detected.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 251
Clock Failure Detection
The CFD is reset only at power-on (POR). The CFD does not monitor the XOSC32K clock when the
oscillator is disabled (XOSC32K.ENABLE=0).
Before starting CFD operation, the user must start and enable the safe clock source (OSCULP32K
oscillator).
CFD operation is started by writing a '1' to the CFD Enable bit in the External Oscillator Control register
(CFDCTRL.CFDEN). After starting or restarting the XOSC32K, the CFD does not detect failure until the
start-up time has elapsed. The start-up time is configured by the Oscillator Start-Up Time in the External
Multipurpose Crystal Oscillator Control register (XOSC32K.STARTUP). Once the XOSC32K Start-Up
Time is elapsed, the XOSC32K clock is constantly monitored.
During a period of 4 safe clocks (monitor period), the CFD watches for a clock activity from the
XOSC32K. There must be at least one rising and one falling XOSC32K clock edge during 4 safe clock
periods to meet non-failure conditions. If no or insufficient activity is detected, the failure status is
asserted: The Clock Failure Detector status bit in the Status register (STATUS.CLKFAIL) and the Clock
Failure Detector interrupt flag bit in the Interrupt Flag register (INTFLAG.CLKFAIL) are set. If the CLKFAIL
bit in the Interrupt Enable Set register (INTENSET.CLKFAIL) is set, an interrupt is generated as well. If
the Event Output enable bit in the Event Control register (EVCTRL.CFDEO) is set, an output event is
generated, too.
After a clock failure was issued the monitoring of the XOSC32K clock is continued, and the Clock Failure
Detector status bit in the Status register (STATUS.CLKFAIL) reflects the current XOSC32K activity.
Clock Switch
When a clock failure is detected, the XOSC32K clock is replaced by the safe clock in order to maintain an
active clock during the XOSC32K clock failure. The safe clock source is the OSCULP32K oscillator clock.
Both 32KHz and 1KHz outputs of the XOSC32K are replaced by the respective OSCULP32K 32KHz and
1KHz outputs. The safe clock source can be scaled down by a configurable prescaler to ensure that the
safe clock frequency does not exceed the operating conditions selected by the application. When the
XOSC32K clock is switched to the safe clock, the Clock Switch bit in the Status register
(STATUS.CLKSW) is set.
When the CFD has switched to the safe clock, the XOSC32K is not disabled. If desired, the application
must take the necessary actions to disable the oscillator. The application must also take the necessary
actions to configure the system clocks to continue normal operations. In the case the application can
recover the XOSC32K, the application can switch back to the XOSC32K clock by writing a '1' to Switch
Back Enable bit in the Clock Failure Control register (CFDCTRL.SWBACK). Once the XOSC32K clock is
switched back, the Switch Back bit (CFDCTRL.SWBACK) is cleared by hardware.
Prescaler
The CFD has an internal configurable prescaler to generate the safe clock from the OSCULP32K
oscillator. The prescaler size allows to scale down the OSCULP32K oscillator so the safe clock frequency
is not higher than the XOSC32K clock frequency monitored by the CFD. The maximum division factor is
2.
The prescaler is applied on both outputs (32KHz and 1KHz) of the safe clock.
Example 21-1. Example
For an external crystal oscillator at 32KHz and the OSCULP32K frequency is 32KHz, the
XOSC32K.CFDPRESC should be set to 0 for a safe clock of equal frequency.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 252
Event
If the Event Output Enable bit in the Event Control register (EVCTRL.CFDEO) is set, the CFD clock
failure will be output on the Event Output. When the CFD is switched to the safe clock, the CFD clock
failure will not be output on the Event Output.
Sleep Mode
The CFD is halted depending on configuration of the XOSC32K and the peripheral clock request. For
further details, refer to the Sleep Behavior table above. The CFD interrupt can be used to wake up the
device from sleep modes.
21.6.4 32KHz Internal Oscillator (OSC32K) Operation
The OSC32K provides a tunable, low-speed, and low-power clock source.
At reset, the OSC32K is disabled. It can be enabled by setting the Enable bit in the 32KHz Internal
Oscillator Control register (OSC32K.ENABLE=1). The OSC32K is disabled by clearing the Enable bit in
the 32KHz Internal Oscillator Control register (OSC32K.ENABLE=0).
The frequency of the OSC32K oscillator is controlled by OSC32K.CALIB, which is a calibration value in
the 32KHz Internal Oscillator Calibration bits in the 32KHz Internal Oscillator Control register. The CALIB
value must be must be loaded with production calibration values from the NVM Software Calibration
Area. When writing the Calibration bits, the user must wait for the STATUS.OSC32KRDY bit to go high
before the new value is committed to the oscillator.
The OSC32K has a 32.768kHz output which is enabled by setting the 32KHz Output Enable bit in the
32KHz Internal Oscillator Control register (OSC32K.EN32K=1). The OSC32K also has a 1.024kHz clock
output. This is enabled by setting the 1KHz Output Enable bit in the 32KHz Internal Oscillator Control
register (OSC32K.EN1K).
Before using the OSC32K, the Calibration field in the OSC32K register (OSC32K.CALIB) must be loaded
with production calibration values from the NVM Software Calibration Area.
The OSC32K will behave differently in different sleep modes based on the settings of
OSC32K.RUNSTDBY, OSC32K.ONDEMAND, and OSC32K.ENABLE. If OSC32KCTRL.ENABLE=0, the
OSC32K will be always stopped. For OS32KCTRL.ENABLE=1, this table is valid:
Table 21-2. OSC32K Sleep Behavior
CPU Mode OSC32KCTRL.RUN
STDBY
OSC32KCTRL.OND
EMAND
Sleep Behavior
Active or Idle - 0 Always run
Active or Idle - 1 Run if requested by peripheral
Standby 1 0 Always run
Standby 1 1 Run if requested by peripheral
Standby 0 - Run if requested by peripheral
The OSC32K requires a start-up time. For this reason, OSC32K will keep running across resets when
OSC32K.ONDEMAND=0, except for power-on reset (POR).
After such a reset, or when waking up from a sleep mode where the OSC32K was disabled, the OSC32K
will need a certain amount of time to stabilize on the correct frequency.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 253
This startup time can be configured by changing the Oscillator Start-Up Time bit group
(OSC32K.STARTUP) in the OSC32K Control register. During the start-up time, the oscillator output is
masked to ensure that no unstable clock propagates to the digital logic.
Once the external clock or crystal oscillator is stable and ready to be used as a clock source, the
OSC32K Ready bit in the Status register is set (STATUS.OSC32KRDY=1). The transition of
STATUS.OSC32KRDY from '0' to '1' generates an interrupt if the OSC32K Ready bit in the Interrupt
Enable Set register is set (INTENSET.OSC32KRDY=1).
The OSC32K can be used as a source for Generic Clock Generators (GCLK) or for the Real-Time
Counter (RTC). Before enabling the GCLK or the RTC module, the corresponding oscillator output must
be enabled (OSC32K.EN32K or OSC32K.EN1K) in order to ensure proper operation. In the same way,
the GCLK or RTC modules must be disabled before the clock selection is changed.
Related Links
9.4 NVM Software Calibration Area Mapping
24. RTC – Real-Time Counter
21.6.7 Real-Time Counter Clock Selection
21.6.5 32 kHz Ultra-Low-Power Internal Oscillator (OSCULP32K) Operation
The OSCULP32K provides a tunable, low-speed, and ultra-low-power clock source. The OSCULP32K is
factory-calibrated under typical voltage and temperature conditions. The OSCULP32K should be
preferred to the OSC32K whenever the power requirements are prevalent over frequency stability and
accuracy.
The OSCULP32K is enabled by default after a power-on reset (POR) and will always run except during
POR. The frequency of the OSCULP32K Oscillator is controlled by the value in the Calibration bits in the
32 kHz Ultra-Low-Power Internal Oscillator Control register (OSCULP32K.CALIB). This data is used to
compensate for process variations.
OSCULP32K.CALIB is automatically loaded from Flash Factory Calibration during start-up. The
calibration value can be overridden by the user by writing to OSCULP32K.CALIB.
It is also possible to lock the OSCULP32K configuration by setting the Write Lock bit in the 32 kHz Ultra-
Low-Power Internal Oscillator Control register (OSCULP32K.WRTLOCK = 1). If set, the OSCULP32K
configuration is locked until a Power-on Reset (POR) is detected.
The OSCULP32K can be used as a source for Generic Clock Generators (GCLK) or for the Real-Time
Counter (RTC). To ensure proper operation, the GCLK or RTC modules must be disabled before the
clock selection is changed.
Related Links
24. RTC – Real-Time Counter
21.6.7 Real-Time Counter Clock Selection
16. GCLK - Generic Clock Controller
21.6.6 Watchdog Timer Clock Selection
The Watchdog Timer (WDT) uses the internal 1.024kHz OSCULP32K output clock. This clock is running
all the time and internally enabled when requested by the WDT module.
Related Links
23. WDT – Watchdog Timer
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 254
21.6.7 Real-Time Counter Clock Selection
Before enabling the RTC module, the RTC clock must be selected first. All oscillator outputs are valid as
RTC clock. The selection is done in the RTC Control register (RTCCTRL). To ensure a proper operation,
it is highly recommended to disable the RTC module first, before the RTC clock source selection is
changed.
Related Links
24. RTC – Real-Time Counter
21.6.8 Interrupts
The OSC32KCTRL has the following interrupt sources:
• XOSC32KRDY - 32KHz Crystal Oscillator Ready: A 0-to-1 transition on the STATUS.XOSC32KRDY
bit is detected
• CLKFAIL - Clock Failure Detector: A 0-to-1 transition on the STATUS.CLKFAIL bit is detected
• OSC32KRDY - 32KHz Internal Oscillator Ready: A 0-to-1 transition on the STATUS.OSC32KRDY bit
is detected
All these interrupts are synchronous wake-up source.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be enabled
individually by setting the corresponding bit in the Interrupt Enable Set register (INTENSET), and disabled
by setting the corresponding bit in the Interrupt Enable Clear register (INTENCLR). An interrupt request is
generated when the interrupt flag is set and the corresponding interrupt is enabled. The interrupt request
remains active until the interrupt flag is cleared, the interrupt is disabled or the OSC32KCTRL is reset.
See the INTFLAG register for details on how to clear interrupt flags.
The OSC32KCTRL has one common interrupt request line for all the interrupt sources. The user must
read the INTFLAG register to determine which interrupt condition is present. Refer to the INTFLAG
register for details.
Note:  Interrupts must be globally enabled for interrupt requests to be generated.
Related Links
19. PM – Power Manager
10.2 Nested Vector Interrupt Controller
21.6.9 Events
The CFD can generate the following output event:
• Clock Failure Detector (CLKFAIL): Generated when the Clock Failure Detector status bit is set in the
Status register (STATUS.CLKFAIL). The CFD event is not generated when the Clock Switch bit
(STATUS.SWBACK) in the Status register is set.
Writing a '1' to an Event Output bit in the Event Control register (EVCTRL.CFDEO) enables the CFD
output event. Writing a '0' to this bit disables the CFD output event. Refer to the Event System chapter for
details on configuring the event system.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 255
21.7 Register Summary
Offset Name Bit Pos.
0x00 INTENCLR
7:0 CLKFAIL OSC32KRDY XOSC32KRD
Y
15:8
23:16
31:24
0x04 INTENSET
7:0 CLKFAIL OSC32KRDY XOSC32KRD
Y
15:8
23:16
31:24
0x08 INTFLAG
7:0 CLKFAIL OSC32KRDY XOSC32KRD
Y
15:8
23:16
31:24
0x0C STATUS
7:0 CLKSW CLKFAIL OSC32KRDY XOSC32KRD
Y
15:8
23:16
31:24
0x10 RTCCTRL
7:0 RTCSEL[2:0]
15:8
23:16
31:24
0x14 XOSC32K
7:0 ONDEMAND RUNSTDBY EN1K EN32K XTALEN ENABLE
15:8 WRTLOCK STARTUP[2:0]
0x16 CFDCTRL 7:0 CFDPRESC SWBACK CFDEN
0x17 EVCTRL 7:0 CFDEO
0x18 OSC32K
7:0 ONDEMAND RUNSTDBY EN1K EN32K ENABLE
15:8 WRTLOCK STARTUP[2:0]
23:16 CALIB[6:0]
31:24
0x1C OSCULP32K
7:0
15:8 WRTLOCK CALIB[4:0]
23:16
31:24
21.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register and the 8-bit halves of a 16-bit register can be
accessed directly.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 256
All registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
Optional Write-Protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in the register description. Write-protection does not apply to accesses through an
external debugger.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 257
21.8.1 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CLKFAIL OSC32KRDY XOSC32KRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – CLKFAIL XOSC32K Clock Failure Detection Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the XOSC32K Clock Failure Interrupt Enable bit, which disables the
XOSC32K Clock Failure interrupt.
Value Description
0The XOSC32K Clock Failure Detection is disabled.
1The XOSC32K Clock Failure Detection is enabled. An interrupt request will be generated
when the XOSC32K Clock Failure Detection interrupt flag is set.
Bit 1 – OSC32KRDY OSC32K Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the OSC32K Ready Interrupt Enable bit, which disables the OSC32K
Ready interrupt.
Value Description
0The OSC32K Ready interrupt is disabled.
1The OSC32K Ready interrupt is enabled.
Bit 0 – XOSC32KRDY XOSC32K Ready Interrupt Enable
Writing a '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 258
Writing a '1' to this bit will clear the XOSC32K Ready Interrupt Enable bit, which disables the XOSC32K
Ready interrupt.
Value Description
0The XOSC32K Ready interrupt is disabled.
1The XOSC32K Ready interrupt is enabled.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 259
21.8.2 Interrupt Enable Set
Name:  INTENSET
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CLKFAIL OSC32KRDY XOSC32KRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – CLKFAIL XOSC32K Clock Failure Detection Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the XOSC32K Clock Failure Interrupt Enable bit, which enables the
XOSC32K Clock Failure interrupt.
Value Description
0The XOSC32K Clock Failure Detection is disabled.
1The XOSC32K Clock Failure Detection is enabled. An interrupt request will be generated
when the XOSC32K Clock Failure Detection interrupt flag is set.
Bit 1 – OSC32KRDY OSC32K Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the OSC32K Ready Interrupt Enable bit, which enables the OSC32K Ready
interrupt.
Value Description
0The OSC32K Ready interrupt is disabled.
1The OSC32K Ready interrupt is enabled.
Bit 0 – XOSC32KRDY XOSC32K Ready Interrupt Enable
Writing a '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 260
Writing a '1' to this bit will set the XOSC32K Ready Interrupt Enable bit, which enables the XOSC32K
Ready interrupt.
Value Description
0The XOSC32K Ready interrupt is disabled.
1The XOSC32K Ready interrupt is enabled.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 261
21.8.3 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x08
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CLKFAIL OSC32KRDY XOSC32KRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – CLKFAIL XOSC32K Clock Failure Detection
This flag is cleared by writing a '1' to it.
This flag is set on a zero-to-one transition of the XOSC32K Clock Failure Detection bit in the Status
register (STATUS.CLKFAIL) and will generate an interrupt request if INTENSET.CLKFAIL is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the XOSC32K Clock Failure Detection flag.
Bit 1 – OSC32KRDY OSC32K Ready
This flag is cleared by writing a '1' to it.
This flag is set by a zero-to-one transition of the OSC32K Ready bit in the Status register
(STATUS.OSC32KRDY), and will generate an interrupt request if INTENSET.OSC32KRDY=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the OSC32K Ready interrupt flag.
Bit 0 – XOSC32KRDY XOSC32K Ready
This flag is cleared by writing a '1' to it.
This flag is set by a zero-to-one transition of the XOSC32K Ready bit in the Status register
(STATUS.XOSC32KRDY), and will generate an interrupt request if INTENSET.XOSC32KRDY=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the XOSC32K Ready interrupt flag.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 262
21.8.4 Status
Name:  STATUS
Offset:  0x0C
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CLKSW CLKFAIL OSC32KRDY XOSC32KRDY
Access R R R R
Reset 0 0 0 0
Bit 3 – CLKSW XOSC32K Clock Switch
Value Description
0XOSC32K is not switched and provided the crystal oscillator.
1XOSC32K is switched to be provided by the safe clock.
Bit 2 – CLKFAIL XOSC32K Clock Failure Detector
Value Description
0XOSC32K is passing failure detection.
1XOSC32K is not passing failure detection.
Bit 1 – OSC32KRDY OSC32K Ready
Value Description
0OSC32K is not ready.
1OSC32K is stable and ready to be used as a clock source.
Bit 0 – XOSC32KRDY XOSC32K Ready
Value Description
0XOSC32K is not ready.
1XOSC32K is stable and ready to be used as a clock source.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 263
21.8.5 RTC Clock Selection Control
Name:  RTCCTRL
Offset:  0x10
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
RTCSEL[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – RTCSEL[2:0] RTC Clock Source Selection
These bits select the source for the RTC.
Value Name Description
0x0 ULP1K 1.024 kHz from 32 kHz internal ULP oscillator
0x1 ULP32K 32.768 kHz from 32 kHz internal ULP oscillator
0x2 OSC1K 1.024 kHz from 32 kHz internal oscillator
0x3 OSC32K 32.768 kHz from 32 kHz internal oscillator
0x4 XOSC1K 1.024 kHz from 32 kHz external oscillator
0x5 XOSC32K 32.768 kHz from 32 kHz external crystal oscillator
0x6 Reserved
0x7 Reserved
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 264
21.8.6 32KHz External Crystal Oscillator (XOSC32K) Control
Name:  XOSC32K
Offset:  0x14
Reset:  0x00000080
Property:  PAC Write-Protection
Bit 15 14 13 12 11 10 9 8
WRTLOCK STARTUP[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY EN1K EN32K XTALEN ENABLE
Access R/W R/W R/W R/W R/W R/W
Reset 1 0 0 0 0 0
Bit 12 – WRTLOCK Write Lock
This bit locks the XOSC32K register for future writes, effectively freezing the XOSC32K configuration.
Value Description
0The XOSC32K configuration is not locked.
1The XOSC32K configuration is locked.
Bits 10:8 – STARTUP[2:0] Oscillator Start-Up Time
These bits select the start-up time for the oscillator.
The OSCULP32K oscillator is used to clock the start-up counter.
Table 21-3. Start-Up Time for 32KHz External Crystal Oscillator
STARTUP[2:0] Number of OSCULP32K
Clock Cycles
Number of XOSC32K
Clock Cycles
Approximate Equivalent
Time
[s]
0x0 2048 3 0.06
0x1 4096 3 0.13
0x2 16384 3 0.5
0x3 32768 3 1
0x4 65536 3 2
0x5 131072 3 4
0x6 262144 3 8
0x7 - - Reserved
Note: 
1. Actual Start-Up time is 1 OSCULP32K cycle + 3 XOSC32K cycles.
2. The given time assumes an XTAL frequency of 32.768kHz.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 265
Bit 7 – ONDEMAND On Demand Control
This bit controls how the XOSC32K behaves when a peripheral clock request is detected. For details,
refer to XOSC32K Sleep Behavior.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the XOSC32K behaves during standby sleep mode. For details, refer to XOSC32K
Sleep Behavior.
Bit 4 – EN1K 1KHz Output Enable
Value Description
0The 1KHz output is disabled.
1The 1KHz output is enabled, and available internally only for RTC.
Bit 3 – EN32K 32KHz Output Enable
Value Description
0The 32KHz output is disabled.
1The 32KHz output is enabled, and can be routed to GCLK/GCLK_IO.
Bit 2 – XTALEN Crystal Oscillator Enable
This bit controls the connections between the I/O pads and the external clock or crystal oscillator.
Value Description
0External clock connected on XIN32. XOUT32 can be used as general-purpose I/O.
1Crystal connected to XIN32/XOUT32.
Bit 1 – ENABLE Oscillator Enable
Value Description
0The oscillator is disabled.
1The oscillator is enabled.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 266
21.8.7 Clock Failure Detector Control
Name:  CFDCTRL
Offset:  0x16
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CFDPRESC SWBACK CFDEN
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – CFDPRESC Clock Failure Detector Prescaler
This bit selects the prescaler for the Clock Failure Detector.
Value Description
0The CFD safe clock frequency is the OSCULP32K frequency
1The CFD safe clock frequency is the OSCULP32K frequency divided by 2
Bit 1 – SWBACK Clock Switch Back
This bit clontrols the XOSC32K output switch back to the external clock or crystal scillator in case of clock
recovery.
Value Description
0The clock switch is disabled.
1The clock switch is enabled. This bit is reset when the XOSC32K output is switched back to
the external clock or crystal oscillator.
Bit 0 – CFDEN Clock Failure Detector Enable
This bit selects the Clock Failure Detector state.
Value Description
0The CFD is disabled.
1The CFD is enabled.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 267
21.8.8 Event Control
Name:  EVCTRL
Offset:  0x17
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CFDEO
Access R/W
Reset 0
Bit 0 – CFDEO Clock Failure Detector Event Out Enable
This bit controls whether the Clock Failure Detector event output is enabled and an event will be
generated when the CFD detects a clock failure.
Value Description
0Clock Failure Detector Event output is disabled, no event will be generated.
1Clock Failure Detector Event output is enabled, an event will be generated.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 268
21.8.9 32KHz Internal Oscillator (OSC32K) Control
Name:  OSC32K
Offset:  0x18
Reset:  0x0000 0080 (Writing action by User required)
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CALIB[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
WRTLOCK STARTUP[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY EN1K EN32K ENABLE
Access R/W R/W R/W R/W R/W
Reset 1 0 0 0 0
Bits 22:16 – CALIB[6:0] Oscillator Calibration
These bits control the oscillator calibration. The calibration values must be loaded by the user from the
NVM Software Calibration Area.
Bit 12 – WRTLOCK Write Lock
This bit locks the OSC32K register for future writes, effectively freezing the OSC32K configuration.
Value Description
0The OSC32K configuration is not locked.
1The OSC32K configuration is locked.
Bits 10:8 – STARTUP[2:0] Oscillator Start-Up Time
These bits select start-up time for the oscillator.
The OSCULP32K oscillator is used as input clock to the start-up counter.
Table 21-4. Start-Up Time for 32KHz Internal Oscillator
STARTUP[2:0] Number of OSC32K clock cycles Approximate Equivalent Time [ms]
0x0 3 0.092
0x1 4 0.122
0x2 6 0.183
0x3 10 0.305
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 269
...........continued
STARTUP[2:0] Number of OSC32K clock cycles Approximate Equivalent Time [ms]
0x4 18 0.549
0x5 34 1.038
0x6 66 2.014
0x7 130 3.967
Note: 
1. Start-up time is given by STARTUP + three OSC32K cycles.
2. The given time assumes an XTAL frequency of 32.768kHz.
Bit 7 – ONDEMAND On Demand Control
This bit controls how the OSC32K behaves when a peripheral clock request is detected. For details, refer
to OSC32K Sleep Behavior.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the OSC32K behaves during standby sleep mode. For details, refer to OSC32K
Sleep Behavior.
Bit 3 – EN1K 1KHz Output Enable
Value Description
0The 1KHz output is disabled.
1The 1KHz output is enabled, and available internally only for RTC.
Bit 2 – EN32K 32KHz Output Enable
Value Description
0The 32KHz output is disabled.
1The 32KHz output is enabled, and can be routed to GCLK/GCLK_IO.
Bit 1 – ENABLE Oscillator Enable
Value Description
0The oscillator is disabled.
1The oscillator is enabled.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 270
21.8.10 32KHz Ultra Low Power Internal Oscillator (OSCULP32K) Control
Name:  OSCULP32K
Offset:  0x1C
Reset:  0x0000XX06
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
WRTLOCK CALIB[4:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 x x x x x
Bit 7 6 5 4 3 2 1 0
Access
Reset
Bit 15 – WRTLOCK Write Lock
This bit locks the OSCULP32K register for future writes to fix the OSCULP32K configuration.
Value Description
0The OSCULP32K configuration is not locked.
1The OSCULP32K configuration is locked.
Bits 12:8 – CALIB[4:0] Oscillator Calibration
These bits control the oscillator calibration.
These bits are loaded from Flash Calibration at startup.
SAM C20/C21 Family Data Sheet
OSC32KCTRL – 32KHz Oscillators Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 271
22. SUPC – Supply Controller
22.1 Overview
The Supply Controller (SUPC) manages the voltage reference and power supply of the device.
The SUPC controls the voltage regulators for the core (VDDCORE) domain. It sets the voltage regulators
according to the sleep modes, or the user configuration.
The SUPC embeds two Brown-Out Detectors. BODVDD monitors the voltage applied to the device (VDD)
and BODCORE monitors the internal voltage to the core (VDDCORE). The BOD can monitor the supply
voltage continuously (continuous mode) or periodically (sampling mode).
The SUPC generates also a selectable reference voltage and a voltage dependent on the temperature
which can be used by analog modules like the ADC, SDADC or DAC.
22.2 Features
• Voltage Regulator System
– Main voltage regulator: LDO in active mode (MAINVREG)
– Low Power voltage regulator in standby mode (LPVREG)
• Voltage Reference System
– Reference voltage for ADC, SDADC and DAC
– Temperature sensor
• VDD Brown-Out Detector (BODVDD)
– Programmable threshold
– Threshold value loaded from NVM User Row at startup
– Triggers resets or interrupts. Action loaded from NVM User Row
– Operating modes:
• Continuous mode
• Sampled mode for low power applications with programmable sample frequency
– Hysteresis value from Flash User Calibration
• VDDCORE Brown-Out Detector (BODCORE)
– Internal non-configurable Brown-Out Detector
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 272
22.3 Block Diagram
Figure 22-1. SUPC Block Diagram
LDO
LP VREG
VDDCORE
BODCORE
VDD
BODVDD BODVDD
BODCORE
VREG
Core
domain
PM
sleep mode
VREF
VREF
temperature sensor
reference voltage
Main VREG
22.4 Signal Description
Not appclicable.
Related Links
6. I/O Multiplexing and Considerations
22.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
22.5.1 I/O Lines
Not applicable.
22.5.2 Power Management
The SUPC can operate in all sleep modes.
Related Links
19. PM – Power Manager
22.5.3 Clocks
The SUPC bus clock (CLK_SUPC_APB) can be enabled and disabled in the Main Clock module.
A 32KHz clock, asynchronous to the user interface clock (CLK_SUPC_APB), is required to run BODVDD
and BODCORE in sampled mode. Due to this asynchronicity, writing to certain registers will require
synchronization between the clock domains. Refer to 22.6.5 Synchronization for further details.
Related Links
21. OSC32KCTRL – 32KHz Oscillators Controller
17.6.2.6 Peripheral Clock Masking
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 273
22.5.4 DMA
Not applicable.
22.5.5 Interrupts
The interrupt request lines are connected to the interrupt controller. Using the SUPC interrupts requires
the interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
22.5.6 Events
Not applicable.
22.5.7 Debug Operation
When the CPU is halted in debug mode, the SUPC continues normal operation. If the SUPC is configured
in a way that requires it to be periodically serviced by the CPU through interrupts or similar, improper
operation or data loss may result during debugging.
If debugger cold-plugging is detected by the system, BODVDD and BODCORE resets will be masked.
The BOD resets keep running under hot-plugging. This allows to correct a BODVDD user level too high
for the available supply.
22.5.8 Register Access Protection
Registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
Note:  Not all registers with write-access can be write-protected.
PAC Write-Protection is not available for the following registers:
• Interrupt Flag Status and Clear register (INTFLAG)
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Related Links
11. PAC - Peripheral Access Controller
22.5.9 Analog Connections
Not applicable.
22.6 Functional Description
22.6.1 Voltage Regulator System Operation
22.6.1.1 Enabling, Disabling, and Resetting
The LDO main voltage regulator is enabled after any Reset. The main voltage regulator (MAINVREG)
can be disabled by writing the Enable bit in the VREG register (VREG.ENABLE) to zero. The main
voltage regulator output supply level is automatically defined by the sleep mode selected in the Power
Manager module.
Related Links
19. PM – Power Manager
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 274
22.6.1.2 Initialization
After a Reset, the LDO voltage regulator supplying VDDCORE is enabled.
22.6.1.3 Sleep Mode Operation
In standby mode, the low power voltage regulator (LPVREG) is used to supply VDDCORE.
When the Run in Standby bit in the VREG register (VREG.RUNSTDBY) is written to '1', VDDCORE is
supplied by the main voltage regulator. The VDDCORE level is set to the active mode voltage level.
Related Links
19.6.3.3 Sleep Mode Controller
22.6.2 Voltage Reference System Operation
The reference voltages are generated by a functional block DETREF inside of the SUPC. DETREF is
providing a fixed-voltage source, BANDGAP=1.1V, and a variable voltage, INTREF.
22.6.2.1 Initialization
The voltage reference output and the temperature sensor are disabled after any Reset.
22.6.2.2 Enabling, Disabling, and Resetting
The voltage reference output is enabled/disabled by setting/clearing the Voltage Reference Output
Enable bit in the Voltage Reference register (VREF.VREFOE).
The temperature sensor is enabled/disabled by setting/clearing the Temperature Sensor Enable bit in the
Voltage Reference register (VREF.TSEN).
Note:  When VREF.ONDEMAND=0, it is not recommended to enable both voltage reference output and
temperature sensor at the same time - only the voltage reference output will be present at both ADC
inputs.
22.6.2.3 Selecting a Voltage Reference
The Voltage Reference Selection bit field in the VREF register (VREF.SEL) selects the voltage of INTREF
to be applied to analog modules, e.g. the ADC.
22.6.2.4 Sleep Mode Operation
The Voltage Reference output and the Temperature Sensor output behavior during sleep mode can be
configured using the Run in Standby bit and the On Demand bit in the Voltage Reference register
(VREF.RUNSTDBY, VREF.ONDEMAND), see the following table:
Table 22-1. VREF Sleep Mode Operation
VREF.ONDEMAND VREF.RUNSTDBY Voltage Reference Sleep behavior
- - Disable
0 0 Always run in all sleep modes except standby sleep mode
0 1 Always run in all sleep modes including standby sleep mode
1 0 Only run if requested by the ADC, in all sleep modes except
standby sleep mode
1 1 Only run if requested by the ADC, in all sleep modes including
standby sleep mode
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 275
22.6.3 Brown-Out Detectors
22.6.3.1 Initialization
Before a Brown-Out Detector (BODVDD) is enabled, it must be configured, as outlined by the following:
• Set the BOD threshold level (BODVDD.LEVEL)
• Set the configuration in Active, Standby (BODVDD.ACTION, BODVDD.STDBYCFG)
• Set the prescaling value if the BOD will run in sampling mode (BODVDD.PSEL)
• Set the action and hysteresis (BODVDD.ACTION and BODVDD.HYST)
The BODVDD register is Enable-Protected, meaning that they can only be written when the BOD is
disabled (BODVDD.ENABLE=0 and STATUS.BVDDSRDY=0). As long as the Enable bit is '1', any writes
to Enable-Protected registers will be discarded, and an APB error will be generated. The Enable bits are
not Enable-Protected.
22.6.3.2 Enabling, Disabling, and Resetting
After power or user reset, the BODVDD and BODCORE register values are loaded from the NVM User
Page.
The BODVDD is enabled by writing a '1' to the Enable bit in the BOD control register
(BODVDD.ENABLE). The BOD is disabled by writing a '0' to the BODVDD.ENABLE.
Related Links
9.3 NVM User Row Mapping
22.6.3.3 VDD Brown-Out Detector (BODVDD)
The VDD Brown-Out Detector (BODVDD) is able to monitor the VDD supply and compares the voltage
with the brown-out threshold level set in the BODVDD Level field (BODVDD.LEVEL) in the BODVDD
register.
When VDD crosses below the brown-out threshold level, the BODVDD can generate either an interrupt or
a Reset, depending on the BODVDD Action bit field (BODVDD.ACTION).
The BODVDD detection status can be read from the BODVDD Detection bit in the Status register
(STATUS.BODVDDDET).
At start-up or at Power-On Reset (POR), the BODVDD register values are loaded from the NVM User
Row.
Related Links
9.3 NVM User Row Mapping
45.10.2 Brown Out Detectors Characteristics
22.6.3.4 VDDCORE Brown-Out Detector (BODCORE)
The BODCORE is calibrated in production and its calibration configuration is stored in the NVM User
Row. This configuration must not be changed to assure the correct behavior of the BODCORE. The
BODCORE generates a reset when VDDCORE crosses below the preset brown-out level. The
BODCORE is always disabled in Standby Sleep mode.
Related Links
9.3 NVM User Row Mapping
22.6.3.5 Continuous Mode
Continuous mode is the default mode for BODVDD.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 276
The BODVDD is continuously monitoring the VDD supply voltage if it is enabled (BODVDD.ENABLE=1)
and if the BODVDD Configuration bit in the BODVDD register is cleared (BODVDD.ACTCFG=0 for active
mode, BODVDD.STDBYCFG=0 for standby mode).
22.6.3.6 Sampling Mode
The Sampling Mode is a low-power mode where the BODVDD is being repeatedly enabled on a sampling
clock’s ticks. The BODVDD will monitor the supply voltage for a short period of time and then go to a low-
power disabled state until the next sampling clock tick.
Sampling mode is enabled in Active mode for BODVDD by writing the ACTCFG bit
(BODVDD.ACTCFG=1). Sampling mode is enabled in Standby mode by writing to the STDBYCFG bit
(BODVDD.STBYCFG=1). The frequency of the clock ticks (Fclksampling) is controlled by the Prescaler
Select bit groups in the BODVDD register (BODVDD.PSEL).
 =
2PSEL + 1
The prescaler signal (Fclkprescaler) is a 1KHz clock, output by the 32KHz Ultra Low Power Oscillator
OSCULP32K.
As the sampling clock is different from the APB clock domain, synchronization among the clocks is
necessary. See also 22.6.5 Synchronization.
22.6.3.7 Hysteresis
A hysteresis on the trigger threshold of a BOD will reduce the sensitivity to ripples on the monitored
voltage: instead of switching RESET at each crossing of VBOD, the thresholds for switching RESET on
and off are separated (VBOD- and VBOD+, respectively).
Figure 22-2. BOD Hysteresis Principle
Hysteresis OFF:
VCC
RESET
VBOD
Hysteresis ON:
VCC
RESET
VBOD-
VBOD+
Enabling the BODVDD hysteresis by writing the Hysteresis bit in the BODVDD register (BODVDD.HYST)
to '1' will add hysteresis to the BODVDD threshold level.
The hysteresis functionality can be used in both Continuous and Sampling Mode.
22.6.3.8 Sleep Mode Operation
22.6.3.8.1 Standby Mode
The BODVDD can be used in standby mode if the BOD is enabled and the corresponding Run in Standby
bit is written to '1' (BODVDD.RUNSTDBY).
The BODVDD can be configured to work in either Continuous or Sampling Mode by writing a '1' to the
Configuration in Standby Sleep Mode bit (BODVDD.STDBYCFG).
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 277
22.6.4 Interrupts
The SUPC has the following interrupt sources, which are either synchronous or asynchronous wake-up
sources:
• BODVDD Ready (BODVDDRDY), synchronous
• BODVDD Detection (BODVDDDET), asynchronous
• BODVDD Synchronization Ready (BVDDSRDY), synchronous
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG) is set when the interrupt condition occurs.
Each interrupt can be individually enabled by writing a '1' to the corresponding bit in the Interrupt Enable
Set register (INTENSET), and disabled by writing a '1' to the corresponding bit in the Interrupt Enable
Clear register (INTENCLR).
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until either the interrupt flag is cleared, the interrupt is disabled, or
the SUPC is reset. See the INTFLAG register for details on how to clear interrupt flags. The SUPC has
one common interrupt request line for all the interrupt sources. The user must read the INTFLAG register
to determine which interrupt condition is present.
Note:  Interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
19.6.3.3 Sleep Mode Controller
22.6.5 Synchronization
The prescaler counters that are used to trigger brown-out detections operate asynchronously from the
peripheral bus. As a consequence, the BODVDD Enable bit (BODVDD.ENABLE) need synchronization
when written.
The Write-Synchronization of the Enable bit is triggered by writing a '1' to the Enable bit of the BODVDD
Control register. The Synchronization Ready bit (STATUS.BVDDSRDY) in the STATUS register will be
cleared when the Write-Synchronization starts, and set again when the Write-Synchronization is
complete. Writing to the same register while the Write-Synchronization is ongoing (STATUS.BVDDSRDY
is '0') will generate a PAC error without stalling the APB bus.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 278
22.7 Register Summary
Offset Name Bit Pos.
0x00 INTENCLR
7:0 BVDDSRDY BODVDDDET BODVDDRDY
15:8
23:16
31:24
0x04 INTENSET
7:0 BVDDSRDY BODVDDDET BODVDDRDY
15:8
23:16
31:24
0x08 INTFLAG
7:0 BVDDSRDY BODVDDDET BODVDDRDY
15:8
23:16
31:24
0x0C STATUS
7:0 BVDDSRDY BODVDDDET BODVDDRDY
15:8
23:16
31:24
0x10 BODVDD
7:0 RUNSTDBY STDBYCFG ACTION[1:0] HYST ENABLE
15:8 PSEL[3:0] ACTCFG
23:16 LEVEL[5:0]
31:24
0x14
...
0x17
Reserved
0x18 VREG
7:0 RUNSTDBY ENABLE
15:8
23:16
31:24
0x1C VREF
7:0 ONDEMAND RUNSTDBY VREFOE
15:8
23:16 SEL[3:0]
31:24
22.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). PAC Write-
protection is denoted by the "PAC Write-Protection" property in each individual register description. Refer
to 22.5.8 Register Access Protection for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Write-Synchronized" or the "Read-Synchronized" property in each individual register description. Refer
to 22.6.5 Synchronization for details.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 279
22.8.1 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
BVDDSRDY BODVDDDET BODVDDRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – BVDDSRDY  BODVDD Synchronization Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the BODVDD Synchronization Ready Interrupt Enable bit, which disables
the BODVDD Synchronization Ready interrupt.
Value Description
0The BODVDD Synchronization Ready interrupt is disabled.
1The BODVDD Synchronization Ready interrupt is enabled, and an interrupt request will be
generated when the BODVDD Synchronization Ready Interrupt flag is set.
Bit 1 – BODVDDDET  BODVDD Detection Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the BODVDD Detection Interrupt Enable bit, which disables the BODVDD
Detection interrupt.
Value Description
0The BODVDD Detection interrupt is disabled.
1The BODVDD Detection interrupt is enabled, and an interrupt request will be generated
when the BODVDD Detection Interrupt flag is set.
Bit 0 – BODVDDRDY  BODVDD Ready Interrupt Enable
Writing a '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 280
Writing a '1' to this bit will clear the BODVDD Ready Interrupt Enable bit, which disables the BODVDD
Ready interrupt.
Value Description
0The BODVDD Ready interrupt is disabled.
1The BODVDD Ready interrupt is enabled, and an interrupt request will be generated when
the BODVDD Ready Interrupt flag is set.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 281
22.8.2 Interrupt Enable Set
Name:  INTENSET
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
BVDDSRDY BODVDDDET BODVDDRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – BVDDSRDY  BODVDD Synchronization Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the BODVDD Synchronization Ready Interrupt Enable bit, which enables
the BODVDD Synchronization Ready interrupt.
Value Description
0The BODVDD Synchronization Ready interrupt is disabled.
1The BODVDD Synchronization Ready interrupt is enabled, and an interrupt request will be
generated when the BODVDD Synchronization Ready Interrupt flag is set.
Bit 1 – BODVDDDET  BODVDD Detection Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the BODVDD Detection Interrupt Enable bit, which enables the BODVDD
Detection interrupt.
Value Description
0The BODVDD Detection interrupt is disabled.
1The BODVDD Detection interrupt is enabled, and an interrupt request will be generated
when the BODVDD Detection Interrupt flag is set.
Bit 0 – BODVDDRDY  BODVDD Ready Interrupt Enable
Writing a '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 282
Writing a '1' to this bit will set the BODVDD Ready Interrupt Enable bit, which enables the BODVDD
Ready interrupt.
Value Description
0The BODVDD Ready interrupt is disabled.
1The BODVDD Ready interrupt is enabled, and an interrupt request will be generated when
the BODVDD Ready Interrupt flag is set.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 283
22.8.3 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x08
Reset:  X determined from NVM User Row
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
BVDDSRDY BODVDDDET BODVDDRDY
Access R/W R/W R/W
Reset 0 0 x
Bit 2 – BVDDSRDY  BODVDD Synchronization Ready
This flag is cleared by writing a '1' to it.
This flag is set on a zero-to-one transition of the BODVDD Synchronization Ready bit in the Status
register (STATUS.BVDDSRDY) and will generate an interrupt request if INTENSET.BVDDSRDY=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the BODVDD Synchronization Ready interrupt flag.
Bit 1 – BODVDDDET  BODVDD Detection
This flag is cleared by writing a '1' to it.
This flag is set on a zero-to-one transition of the BODVDD Detection bit in the Status register
(STATUS.BODVDDDET) and will generate an interrupt request if INTENSET.BODVDDDET=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the BODVDD Detection interrupt flag.
Bit 0 – BODVDDRDY  BODVDD Ready
This flag is cleared by writing a '1' to it.
This flag is set on a zero-to-one transition of the BODVDD Ready bit in the Status register
(STATUS.BODVDDRDY) and will generate an interrupt request if INTENSET.BODVDDRDY=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the BODVDD Ready interrupt flag.
The BODVDD can be enabled.
Related Links
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 284
9.3 NVM User Row Mapping
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 285
22.8.4 Status
Name:  STATUS
Offset:  0x0C
Reset:  Determined from NVM User Row
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
BVDDSRDY BODVDDDET BODVDDRDY
Access R R R
Reset 0 0 y
Bit 2 – BVDDSRDY  BODVDD Synchronization Ready
Value Description
0BODVDD synchronization is ongoing.
1BODVDD synchronization is complete.
Bit 1 – BODVDDDET  BODVDD Detection
Value Description
0No BODVDD detection.
1BODVDD has detected that the I/O power supply is going below the BODVDD reference
value.
Bit 0 – BODVDDRDY  BODVDD Ready
The BODVDD can be enabled at start-up from NVM User Row.
Value Description
0BODVDD is not ready.
1BODVDD is ready.
Related Links
9.3 NVM User Row Mapping
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 286
22.8.5 VDD Brown-Out Detector (BODVDD) Control
Name:  BODVDD
Offset:  0x10
Reset:  X determined from NVM User Row
Property:  Write-Synchronized, Enable-Protected, PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
LEVEL[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset x x x x x x
Bit 15 14 13 12 11 10 9 8
PSEL[3:0] ACTCFG
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RUNSTDBY STDBYCFG ACTION[1:0] HYST ENABLE
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 x x x x
Bits 21:16 – LEVEL[5:0]  BODVDD Threshold Level on VDD
These bits set the triggering voltage threshold for the BODVDD when the BODVDD monitors the VDD.
These bits are loaded from NVM User Row at start-up.
This bit field is not synchronized.
Bits 15:12 – PSEL[3:0] Prescaler Select
Selects the prescaler divide-by output for the BODVDD sampling mode. The input clock comes from the
OSCULP32K 1KHz output.
Value Name Description
0x0 DIV2 Divide clock by 2
0x1 DIV4 Divide clock by 4
0x2 DIV8 Divide clock by 8
0x3 DIV16 Divide clock by 16
0x4 DIV32 Divide clock by 32
0x5 DIV64 Divide clock by 64
0x6 DIV128 Divide clock by 128
0x7 DIV256 Divide clock by 256
0x8 DIV512 Divide clock by 512
0x9 DIV1024 Divide clock by 1024
0xA DIV2048 Divide clock by 2048
0xB DIV4096 Divide clock by 4096
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 287
Value Name Description
0xC DIV8192 Divide clock by 8192
0xD DIV16384 Divide clock by 16384
0xE DIV32768 Divide clock by 32768
0xF DIV65536 Divide clock by 65536
Bit 8 – ACTCFG  BODVDD Configuration in Active Sleep Mode
This bit is not synchronized.
Value Description
0In active mode, the BODVDD operates in continuous mode.
1In active mode, the BODVDD operates in sampling mode.
Bit 6 – RUNSTDBY Run in Standby
This bit is not synchronized.
Value Description
0In standby sleep mode, the BODVDD is disabled.
1In standby sleep mode, the BODVDD is enabled.
Bit 5 – STDBYCFG  BODVDD Configuration in Standby Sleep Mode
If the RUNSTDBY bit is set to '1', the STDBYCFG bit sets the BODVDD configuration in standby sleep
mode.
This bit is not synchronized.
Value Description
0In standby sleep mode, the BODVDD is enabled and configured in continuous mode.
1In standby sleep mode, the BODVDD is enabled and configured in sampling mode.
Bits 4:3 – ACTION[1:0]  BODVDD Action
These bits are used to select the BODVDD action when the supply voltage crosses below the BODVDD
threshold.
These bits are loaded from NVM User Row at start-up.
This bit field is not synchronized.
Value Name Description
0x0 NONE No action
0x1 RESET The BODVDD generates a reset
0x2 INT The BODVDD generates an interrupt
0x3 - Reserved
Bit 2 – HYST Hysteresis
This bit indicates whether hysteresis is enabled for the BODVDD threshold voltage.
This bit is loaded from NVM User Row at start-up.
This bit is not synchronized.
Value Description
0No hysteresis.
1Hysteresis enabled.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 288
Bit 1 – ENABLE Enable
This bit is loaded from NVM User Row at start-up.
This bit is not enable-protected.
Value Description
0BODVDD is disabled.
1BODVDD is enabled.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
9.3 NVM User Row Mapping
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 289
22.8.6 Voltage Regulator System (VREG) Control
Name:  VREG
Offset:  0x18
Reset:  0x00000002
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RUNSTDBY ENABLE
Access R R/W R R R R R/W R
Reset 0 0 0 0 0 0 1 0
Bit 6 – RUNSTDBY Run in Standby
Value Description
0The voltage regulator is in Low-Power mode in Standby-Sleep mode.
1The voltage regulator is in normal mode in Standby-Sleep mode.
Bit 1 – ENABLE Must be set to 1.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 290
22.8.7 Voltage References System (VREF) Control
Name:  VREF
Offset:  0x1C
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
SEL[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY VREFOE
Access R/W R/W R/W
Reset 0 0 0
Bits 19:16 – SEL[3:0] Voltage Reference Selection
These bits select the Voltage Reference for the ADC/ SDADC/DAC.
Value Description
0x0 1.024V voltage reference typical value
0x2 2.048V voltage reference typical value
0x3 4.096V voltage reference typical value
Others Reserved
Bit 7 – ONDEMAND On Demand Control
The On Demand operation mode allows to enable or disable the voltage reference depending on
peripheral requests.
Value Description
0The voltage reference is always on, if enabled.
1The voltage reference is enabled when a peripheral is requesting it. The voltage reference is
disabled if no peripheral is requesting it.
Bit 6 – RUNSTDBY Run In Standby
The bit controls how the voltage reference behaves during Standby Sleep mode.
Value Description
0The voltage reference is halted during Standby Sleep mode.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 291
Value Description
1The voltage reference is not stopped in Standby Sleep mode. If VREF.ONDEMAND=1, the
voltage reference will be running when a peripheral is requesting it. If VREF.ONDEMAND=0,
the voltage reference will always be running in Standby Sleep mode.
Bit 2 – VREFOE Voltage Reference Output Enable
Value Description
0The Voltage Reference output is not available as an ADC input channel.
1The Voltage Reference output is routed to an ADC input channel.
SAM C20/C21 Family Data Sheet
SUPC – Supply Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 292
23. WDT – Watchdog Timer
23.1 Overview
The Watchdog Timer (WDT) is a system function for monitoring correct program operation. It makes it
possible to recover from error situations such as runaway or deadlocked code. The WDT is configured to
a predefined time-out period, and is constantly running when enabled. If the WDT is not cleared within the
time-out period, it will issue a system reset. An early-warning interrupt is available to indicate an
upcoming watchdog time-out condition.
The window mode makes it possible to define a time slot (or window) inside the total time-out period
during which the WDT must be cleared. If the WDT is cleared outside this window, either too early or too
late, a system reset will be issued. Compared to the normal mode, this can also catch situations where a
code error causes the WDT to be cleared frequently.
When enabled, the WDT will run in active mode and all sleep modes. It is asynchronous and runs from a
CPU-independent clock source. The WDT will continue operation and issue a system reset or interrupt
even if the main clocks fail.
23.2 Features
• Issues a system reset if the Watchdog Timer is not cleared before its time-out period
• Early Warning interrupt generation
• Asynchronous operation from dedicated oscillator
• Two types of operation
– Normal
– Window mode
• Selectable time-out periods
– From 8 cycles to 16,384 cycles in Normal mode
– From 16 cycles to 32,768 cycles in Window mode
• Always-On capability
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 293
23.3 Block Diagram
Figure 23-1. WDT Block Diagram
0xA5
CLEAR
COUNT
0
CLK_WDT_OSC
OSC32KCTRL
PER/WINDOWS/EWOFFSET
Early Warning Interrupt
Reset
23.4 Signal Description
Not applicable.
23.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
23.5.1 I/O Lines
Not applicable.
23.5.2 Power Management
The WDT can continue to operate in any sleep mode where the selected source clock is running. The
WDT interrupts can be used to wake up the device from sleep modes. The events can trigger other
operations in the system without exiting sleep modes.
Related Links
19. PM – Power Manager
23.5.3 Clocks
The WDT bus clock (CLK_WDT_APB) can be enabled and disabled (masked) in the Main Clock module
(MCLK).
A 1 kHz oscillator clock (CLK_WDT_OSC) is required to clock the WDT internal counter.
CLK_WDT_OSC is sourced from the clock of the internal ultra-low-power oscillator, OSCULP32K. Due to
the ultra-low-power design, the oscillator is not very accurate, and so the exact time-out period may vary
from device to device. This variation must be kept in mind when designing software that uses the WDT to
ensure that the time-out periods used are valid for all devices.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 294
The counter clock CLK_WDT_OSC is asynchronous to the bus clock (CLK_WDT_APB). Due to this
asynchronicity, writing to certain registers will require synchronization between the clock domains. Refer
to 23.6.7 Synchronization for further details.
Related Links
17.6.2.6 Peripheral Clock Masking
21. OSC32KCTRL – 32KHz Oscillators Controller
23.5.4 DMA
Not applicable.
23.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the WDT interrupt(s) requires the
interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
10.2.1 Overview
10.2.2 Interrupt Line Mapping
23.5.6 Events
Not applicable.
23.5.7 Debug Operation
When the CPU is halted in debug mode the WDT will halt normal operation.
23.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Flag Status and Clear (INTFLAG) register
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
23.5.9 Analog Connections
Not applicable.
23.6 Functional Description
23.6.1 Principle of Operation
The Watchdog Timer (WDT) is a system for monitoring correct program operation, making it possible to
recover from error situations such as runaway code, by issuing a Reset. When enabled, the WDT is a
constantly running timer that is configured to a predefined time-out period. Before the end of the time-out
period, the WDT should be set back, or else, a system Reset is issued.
The WDT has two modes of operation, Normal mode and Window mode. Both modes offer the option of
Early Warning interrupt generation. The description for each of the basic modes is given below. The
settings in the Control A register (CTRLA) and the Interrupt Enable register (handled by INTENCLR/
INTENSET) determine the mode of operation:
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 295
Table 23-1. WDT Operating Modes
CTRLA.ENABLE CTRLA.WEN Interrupt Enable Mode
0 x x Stopped
1 0 0 Normal mode
1 0 1 Normal mode with Early Warning interrupt
1 1 0 Window mode
1 1 1 Window mode with Early Warning interrupt
23.6.2 Basic Operation
23.6.2.1 Initialization
The following bits are enable-protected, meaning that they can only be written when the WDT is disabled
(CTRLA.ENABLE=0):
• Control A register (CTRLA), except the Enable bit (CTRLA.ENABLE)
• Configuration register (CONFIG)
• Early Warning Interrupt Control register (EWCTRL)
Enable-protected bits in the CTRLA register can be written at the same time as CTRLA.ENABLE is
written to '1', but not at the same time as CTRLA.ENABLE is written to '0'.
The WDT can be configured only while the WDT is disabled. The WDT is configured by defining the
required Time-Out Period bits in the Configuration register (CONFIG.PER). If Window mode operation is
desired, the Window Enable bit in the Control A register must be set (CTRLA.WEN=1) and the Window
Period bits in the Configuration register (CONFIG.WINDOW) must be defined.
Enable-protection is denoted by the "Enable-Protected" property in the register description.
23.6.2.2 Configurable Reset Values
After a Power-on Reset, some registers will be loaded with initial values from the NVM User Row.
This includes the following bits and bit groups:
• Enable bit in the Control A register, CTRLA.ENABLE
• Always-On bit in the Control A register, CTRLA.ALWAYSON
• Watchdog Timer Windows Mode Enable bit in the Control A register, CTRLA.WEN
• Watchdog Timer Windows Mode Time-Out Period bits in the Configuration register,
CONFIG.WINDOW
• Time-Out Period bits in the Configuration register, CONFIG.PER
• Early Warning Interrupt Time Offset bits in the Early Warning Interrupt Control register,
EWCTRL.EWOFFSET
Related Links
9.3 NVM User Row Mapping
23.6.2.3 Enabling, Disabling, and Resetting
The WDT is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The
WDT is disabled by writing a '0' to CTRLA.ENABLE.
The WDT can be disabled only if the Always-On bit in the Control A register (CTRLA.ALWAYSON) is '0'.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 296
23.6.2.4 Normal Mode
In Normal mode operation, the length of a time-out period is configured in CONFIG.PER. The WDT is
enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). Once enabled, the
WDT will issue a system reset if a time-out occurs. This can be prevented by clearing the WDT at any
time during the time-out period.
The WDT is cleared and a new WDT time-out period is started by writing 0xA5 to the Clear register
(CLEAR). Writing any other value than 0xA5 to CLEAR will issue an immediate system reset.
There are 12 possible WDT time-out (TOWDT) periods, selectable from 8ms to 16s.
By default, the early warning interrupt is disabled. If it is desired, the Early Warning Interrupt Enable bit in
the Interrupt Enable register (INTENSET.EW) must be written to '1'. The Early Warning Interrupt is
disabled again by writing a '1' to the Early Warning Interrupt bit in the Interrupt Enable Clear register
(INTENCLR.EW).
If the Early Warning Interrupt is enabled, an interrupt is generated prior to a WDT time-out condition. In
Normal mode, the Early Warning Offset bits in the Early Warning Interrupt Control register,
EWCTRL.EWOFFSET, define the time when the early warning interrupt occurs. The Normal mode
operation is illustrated in the figure Normal-Mode Operation.
Figure 23-2. Normal-Mode Operation
5 10 15 20 25 30 35
WDT Timeout
Early Warning Interrupt
Timely WDT Clear
t[ms]
TOWDT
System Reset
WDT Count
PER[3:0] = 1
EWOFFSET[3:0] = 0
23.6.2.5 Window Mode
In Window mode operation, the WDT uses two different time specifications: the WDT can only be cleared
by writing 0xA5 to the CLEAR register after the closed window time-out period (TOWDTW), during the
subsequent Normal time-out period (TOWDT). If the WDT is cleared before the time window opens (before
TOWDTW is over), the WDT will issue a system reset.
Both parameters TOWDTW and TOWDT are periods in a range from 8ms to 16s, so the total duration of the
WDT time-out period is the sum of the two parameters.
The closed window period is defined by the Window Period bits in the Configuration register
(CONFIG.WINDOW), and the open window period is defined by the Period bits in the Configuration
register (CONFIG.PER).
By default, the Early Warning interrupt is disabled. If it is desired, the Early Warning Interrupt Enable bit in
the Interrupt Enable register (INTENSET.EW) must be written to '1'. The Early Warning Interrupt is
disabled again by writing a '1' to the Early Warning Interrupt bit in the Interrupt Enable Clear
(INTENCLR.EW) register.
If the Early Warning interrupt is enabled in Window mode, the interrupt is generated at the start of the
open window period, i.e. after TOWDTW. The Window mode operation is illustrated in figure Window-Mode
Operation.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 297
Figure 23-3. Window-Mode Operation
5 10 15 20 25 30 35
WDT Timeout
Early Warning Interrupt
Timely WDT Clear
t[ms]
TOWDT
System Reset
WDT Count
PER[3:0] = 0
WINDOW[3:0] = 0
TOWDTW
Early WDT Clear
Closed Open
23.6.3 DMA Operation
Not applicable.
23.6.4 Interrupts
The WDT has the following interrupt source:
• Early Warning (EW): Indicates that the counter is approaching the time-out condition.
– This interrupt is an asynchronous wake-up source.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs.
Each interrupt can be individually enabled by writing a '1' to the corresponding bit in the Interrupt Enable
Set (INTENSET) register, and disabled by writing a '1' to the corresponding bit in the Interrupt Enable
Clear (INTENCLR) register.
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or the
WDT is reset. See the 23.8.6 INTFLAG register description for details on how to clear interrupt flags. All
interrupt requests from the peripheral are ORed together on system level to generate one combined
interrupt request to the NVIC. The user must read the INTFLAG register to determine which interrupt
condition is present.
Note:  Interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
10.2.1 Overview
10.2.2 Interrupt Line Mapping
19. PM – Power Manager
19.6.3.3 Sleep Mode Controller
23.6.5 Events
Not applicable.
23.6.6 Sleep Mode Operation
Related Links
23.8.1 CTRLA
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 298
23.6.7 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following registers are synchronized when written:
• Enable bit in Control A register (CTRLA.ENABLE)
• Window Enable bit in Control A register (CTRLA.WEN)
• Always-On bit in control Control A (CTRLA.ALWAYSON)
• Watchdog Clear register (CLEAR)
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Required read-synchronization is denoted by the "Read-Synchronized" property in the register
description.
23.6.8 Additional Features
23.6.8.1 Always-On Mode
The Always-On mode is enabled by setting the Always-On bit in the Control A register
(CTRLA.ALWAYSON=1). When the Always-On mode is enabled, the WDT runs continuously, regardless
of the state of CTRLA.ENABLE. Once written, the Always-On bit can only be cleared by a power-on
reset. The Configuration (CONFIG) and Early Warning Control (EWCTRL) registers are read-only
registers while the CTRLA.ALWAYSON bit is set. Thus, the time period configuration bits (CONFIG.PER,
CONFIG.WINDOW, EWCTRL.EWOFFSET) of the WDT cannot be changed.
Enabling or disabling Window mode operation by writing the Window Enable bit (CTRLA.WEN) is allowed
while in Always-On mode, but note that CONFIG.PER cannot be changed.
The Interrupt Clear and Interrupt Set registers are accessible in the Always-On mode. The Early Warning
interrupt can still be enabled or disabled while in the Always-On mode, but note that
EWCTRL.EWOFFSET cannot be changed.
Table WDT Operating Modes With Always-On shows the operation of the WDT for
CTRLA.ALWAYSON=1.
Table 23-2. WDT Operating Modes With Always-On
WEN Interrupt Enable Mode
0 0 Always-on and normal mode
0 1 Always-on and normal mode with Early Warning interrupt
1 0 Always-on and window mode
1 1 Always-on and window mode with Early Warning interrupt
23.6.8.2 Early Warning
The Early Warning interrupt notifies that the WDT is approaching its time-out condition. The Early
Warning interrupt behaves differently in Normal mode and in Window mode.
In Normal mode, the Early Warning interrupt generation is defined by the Early Warning Offset in the
Early Warning Control register (EWCTRL.EWOFFSET). The Early Warning Offset bits define the number
of CLK_WDT_OSC clocks before the interrupt is generated, relative to the start of the watchdog time-out
period.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 299
The user must take caution when programming the Early Warning Offset bits. If these bits define an Early
Warning interrupt generation time greater than the watchdog time-out period, the watchdog time-out
system reset is generated prior to the Early Warning interrupt. Consequently, the Early Warning interrupt
will never be generated.
In window mode, the Early Warning interrupt is generated at the start of the open window period. In a
typical application where the system is in sleep mode, the Early Warning interrupt can be used to wake
up and clear the Watchdog Timer, after which the system can perform other tasks or return to sleep
mode.
If the WDT is operating in Normal mode with CONFIG.PER = 0x2 and
EWCTRL.EWOFFSET = 0x1, the Early Warning interrupt is generated 16
CLK_WDT_OSC clock cycles after the start of the time-out period. The time-out system
reset is generated 32 CLK_WDT_OSC clock cycles after the start of the watchdog time-
out period.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 300
23.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 ALWAYSON WEN ENABLE
0x01 CONFIG 7:0 WINDOW[3:0] PER[3:0]
0x02 EWCTRL 7:0 EWOFFSET[3:0]
0x03 Reserved
0x04 INTENCLR 7:0 EW
0x05 INTENSET 7:0 EW
0x06 INTFLAG 7:0 EW
0x07 Reserved
0x08 SYNCBUSY
7:0 WEN ENABLE
15:8
23:16
31:24
0x0C CLEAR 7:0 CLEAR[7:0]
23.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 23.5.8 Register Access Protection.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to 23.6.7 Synchronization.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 301
23.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  X determined from NVM User Row
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
ALWAYSON WEN ENABLE
Access R/W R/W R/W
Reset x x x
Bit 7 – ALWAYSON Always-On
This bit allows the WDT to run continuously. After being set, this bit cannot be written to '0', and the WDT
will remain enabled until a power-on Reset is received. When this bit is '1', the Control A register
(CTRLA), the Configuration register (CONFIG) and the Early Warning Control register (EWCTRL) will be
read-only, and any writes to these registers are not allowed.
Writing a '0' to this bit has no effect.
This bit is not Enable-Protected.
This bit is loaded from NVM User Row at start-up.
Value Description
0The WDT is enabled and disabled through the ENABLE bit.
1The WDT is enabled and can only be disabled by a power-on reset (POR).
Bit 2 – WEN Watchdog Timer Window Mode Enable
This bit enables Window mode. It can only be written if the peripheral is disabled unless
CTRLA.ALWAYSON=1. The initial value of this bit is loaded from Flash Calibration.
This bit is loaded from NVM User Row at startup.
Value Description
0Window mode is disabled (normal operation).
1Window mode is enabled.
Bit 1 – ENABLE Enable
This bit enables or disables the WDT. It can only be written if CTRLA.ALWAYSON=0.
Due to synchronization, there is delay between writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately, and the Enable bit in the
Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared
when the operation is complete.
This bit is not Enable-Protected.
This bit is loaded from NVM User Row at startup.
Value Description
0The WDT is disabled.
1The WDT is enabled.
Related Links
9.3 NVM User Row Mapping
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 302
23.8.2 Configuration
Name:  CONFIG
Offset:  0x01
Reset:  X determined from NVM User Row
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
WINDOW[3:0] PER[3:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset x x x x x x x x
Bits 7:4 – WINDOW[3:0] Window Mode Time-Out Period
In Window mode, these bits determine the watchdog closed window period as a number of cycles of the
1.024kHz CLK_WDT_OSC clock.
These bits are loaded from NVM User Row at start-up.
Value Name Description
0x0 CYC8 8 clock cycles
0x1 CYC16 16 clock cycles
0x2 CYC32 32 clock cycles
0x3 CYC64 64 clock cycles
0x4 CYC128 128 clock cycles
0x5 CYC256 256 clock cycles
0x6 CYC512 512 clock cycles
0x7 CYC1024 1024 clock cycles
0x8 CYC2048 2048 clock cycles
0x9 CYC4096 4096 clock cycles
0xA CYC8192 8192 clock cycles
0xB -
0xF
- Reserved
Bits 3:0 – PER[3:0]  Time-Out Period
These bits determine the watchdog time-out period as a number of 1.024kHz CLK_WDTOSC clock
cycles. In Window mode operation, these bits define the open window period.
These bits are loaded from NVM User Row at startup.
Value Name Description
0x0 CYC8 8 clock cycles
0x1 CYC16 16 clock cycles
0x2 CYC32 32 clock cycles
0x3 CYC64 64 clock cycles
0x4 CYC128 128 clock cycles
0x5 CYC256 256 clock cycles
0x6 CYC512 512 clock cycles
0x7 CYC1024 1024 clock cycles
0x8 CYC2048 2048 clock cycles
0x9 CYC4096 4096 clock cycles
0xA CYC8192 8192 clock cycles
0xB CYC16384 16384 clock cycles
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 303
Value Name Description
0xC -
0xF
- Reserved
Related Links
9.3 NVM User Row Mapping
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 304
23.8.3 Early Warning Control
Name:  EWCTRL
Offset:  0x02
Reset:  X determined from NVM User Row
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
EWOFFSET[3:0]
Access R/W R/W R/W R/W
Reset x x x x
Bits 3:0 – EWOFFSET[3:0] Early Warning Interrupt Time Offset
These bits determine the number of GCLK_WDT clock cycles between the start of the watchdog time-out
period and the generation of the Early Warning interrupt. These bits are loaded from NVM User Row at
start-up.
Value Name Description
0x0 CYC8 8 clock cycles
0x1 CYC16 16 clock cycles
0x2 CYC32 32 clock cycles
0x3 CYC64 64 clock cycles
0x4 CYC128 128 clock cycles
0x5 CYC256 256 clock cycles
0x6 CYC512 512 clock cycles
0x7 CYC1024 1024 clock cycles
0x8 CYC2048 2048 clock cycles
0x9 CYC4096 4096 clock cycles
0xA CYC8192 8192 clock cycles
0xB CYC16384 16384 clock cycles
0xC -
0xF
- Reserved
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 305
23.8.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 7 6 5 4 3 2 1 0
EW
Access R/W
Reset 0
Bit 0 – EW Early Warning Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Early Warning Interrupt Enable bit, which disables the Early Warning
interrupt.
Value Description
0The Early Warning interrupt is disabled.
1The Early Warning interrupt is enabled.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 306
23.8.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 7 6 5 4 3 2 1 0
EW
Access R/W
Reset 0
Bit 0 – EW Early Warning Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit sets the Early Warning Interrupt Enable bit, which enables the Early Warning
interrupt.
Value Description
0The Early Warning interrupt is disabled.
1The Early Warning interrupt is enabled.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 307
23.8.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x06
Reset:  0x00
Property:  N/A
Bit 7 6 5 4 3 2 1 0
EW
Access R/W
Reset 0
Bit 0 – EW Early Warning
This flag is cleared by writing a '1' to it.
This flag is set when an Early Warning interrupt occurs, as defined by the EWOFFSET bit group in
EWCTRL.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Early Warning interrupt flag.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 308
23.8.7 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x08
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
WEN ENABLE
Access R R
Reset 0 0
Bit 2 – WEN Window Enable Synchronization Busy
Value Description
0Write synchronization of the CTRLA.WEN bit is complete.
1Write synchronization of the CTRLA.WEN bit is ongoing.
Bit 1 – ENABLE Enable Synchronization Busy
Value Description
0Write synchronization of the CTRLA.ENABLE bit is complete.
1Write synchronization of the CTRLA.ENABLE bit is ongoing.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 309
23.8.8 Clear
Name:  CLEAR
Offset:  0x0C
Reset:  0x00
Property:  Write-Synchronized
Bit 7 6 5 4 3 2 1 0
CLEAR[7:0]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – CLEAR[7:0] Watchdog Clear
In Normal mode, writing 0xA5 to this register during the watchdog time-out period will clear the Watchdog
Timer and the watchdog time-out period is restarted.
In Window mode, any writing attempt to this register before the time-out period started (i.e., during
TOWDTW) will issue an immediate system Reset. Writing 0xA5 during the time-out period TOWDT will clear
the Watchdog Timer and the complete time-out sequence (first TOWDTW then TOWDT) is restarted.
In both modes, writing any other value than 0xA5 will issue an immediate system Reset.
SAM C20/C21 Family Data Sheet
WDT – Watchdog Timer
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 310
24. RTC – Real-Time Counter
24.1 Overview
The Real-Time Counter (RTC) is a 32-bit counter with a 10-bit programmable prescaler that typically runs
continuously to keep track of time. The RTC can wake up the device from sleep modes using the alarm/
compare wake up, periodic wake up, or overflow wake up mechanisms.
The RTC can generate periodic peripheral events from outputs of the prescaler, as well as alarm/compare
interrupts and peripheral events, which can trigger at any counter value. Additionally, the timer can trigger
an overflow interrupt and peripheral event, and can be reset on the occurrence of an alarm/compare
match. This allows periodic interrupts and peripheral events at very long and accurate intervals.
The 10-bit programmable prescaler can scale down the clock source. By this, a wide range of resolutions
and time-out periods can be configured. With a 32.768kHz clock source, the minimum counter tick
interval is 30.5µs, and time-out periods can range up to 36 hours. For a counter tick interval of 1s, the
maximum time-out period is more than 136 years.
24.2 Features
• 32-bit counter with 10-bit prescaler
• Multiple clock sources
• 32-bit or 16-bit counter mode
• One 32-bit or two 16-bit compare values
• Clock/Calendar mode
– Time in seconds, minutes, and hours (12/24)
– Date in day of month, month, and year
– Leap year correction
• Digital prescaler correction/tuning for increased accuracy
• Overflow, alarm/compare match and prescaler interrupts and events
– Optional clear on alarm/compare match
24.3 Block Diagram
Figure 24-1. RTC Block Diagram (Mode 0 — 32-Bit Counter)
OVF
MATCHCLR
CMPn
OSC32KCTRL
CLK_RTC_OSC PRESCALER CLK_RTC_CNT
Periodic Events
COUNT
COMPn
=
0x00000000
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 311
Figure 24-2. RTC Block Diagram (Mode 1 — 16-Bit Counter)
CLK_RTC_OSC CLK_RTC_CNT
OSC32KCTRL PRESCALER
COMPn
PER
COUNT
0x0000
Periodic Events
=
=CMPn
OVF
Figure 24-3. RTC Block Diagram (Mode 2 — Clock/Calendar)
CLK_RTC_CNT
CLK_RTC_OSC
OSC32KCTRL PRESCALER
Periodic Events MASKn
CLOCK
ALARMn
=
0x00000000
OVF
MATCHCLR
ALARMn
Related Links
24.6.2.3 32-Bit Counter (Mode 0)
24.6.2.4 16-Bit Counter (Mode 1)
24.6.2.5 Clock/Calendar (Mode 2)
24.4 Signal Description
Not applicable.
24.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
24.5.1 I/O Lines
For more information on I/O configurations, refer to the "RTC Pinout" section.
Related Links: 6. I/O Multiplexing and Considerations
24.5.2 Power Management
The RTC will continue to operate in any sleep modes where the selected source clock is running. The
RTC interrupts can be used to wake up the device from sleep modes. Events connected to the event
system can trigger other operations in the system without exiting sleep modes. Refer to the Power
Manager for details on the different sleep modes.
The RTC will be reset only at power-on (POR) or by setting the Software Reset bit in the Control A
register (CTRLA.SWRST=1).
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 312
Related Links
19. PM – Power Manager
24.5.3 Clocks
The RTC bus clock (CLK_RTC_APB) can be enabled and disabled in the Main Clock module MCLK, and
the default state of CLK_RTC_APB can be found in Peripheral Clock Masking section.
A 32KHz or 1KHz oscillator clock (CLK_RTC_OSC) is required to clock the RTC. This clock must be
configured and enabled in the 32KHz oscillator controller (OSC32KCTRL) before using the RTC.
This oscillator clock is asynchronous to the bus clock (CLK_RTC_APB). Due to this asynchronicity,
writing to certain registers will require synchronization between the clock domains. Refer to 24.6.7
Synchronization for further details.
Related Links
21. OSC32KCTRL – 32KHz Oscillators Controller
17.6.2.6 Peripheral Clock Masking
24.5.4 DMA
Not applicable.
Related Links
25. DMAC – Direct Memory Access Controller
24.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the RTC interrupt requires the
Interrupt Controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
24.5.6 Events
The events are connected to the Event System.
Related Links
29. EVSYS – Event System
24.5.7 Debug Operation
When the CPU is halted in debug mode the RTC will halt normal operation. The RTC can be forced to
continue operation during debugging. Refer to 24.8.6 DBGCTRL for details.
24.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC),
except the following registers:
• Interrupt Flag Status and Clear (INTFLAG) register
Write-protection is denoted by the "PAC Write-Protection" property in the register description.
Write-protection does not apply to accesses through an external debugger. Refer to the PAC - Peripheral
Access Controller for details.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 313
24.5.9 Analog Connections
A 32.768kHz crystal can be connected to the XIN32 and XOUT32 pins, along with any required load
capacitors. See Electrical Characteristics for details on recommended crystal characteristics and load
capacitors.
24.6 Functional Description
24.6.1 Principle of Operation
The RTC keeps track of time in the system and enables periodic events, as well as interrupts and events
at a specified time. The RTC consists of a 10-bit prescaler that feeds a 32-bit counter. The actual format
of the 32-bit counter depends on the RTC operating mode.
The RTC can function in one of these modes:
• Mode 0 - COUNT32: RTC serves as 32-bit counter
• Mode 1 - COUNT16: RTC serves as 16-bit counter
• Mode 2 - CLOCK: RTC serves as clock/calendar with alarm functionality
24.6.2 Basic Operation
24.6.2.1 Initialization
The following bits are enable-protected, meaning that they can only be written when the RTC is disabled
(CTRLA.ENABLE=0):
• Operating Mode bits in the Control A register (CTRLA.MODE)
• Prescaler bits in the Control A register (CTRLA.PRESCALER)
• Clear on Match bit in the Control A register (CTRLA.MATCHCLR)
• Clock Representation bit in the Control A register (CTRLA.CLKREP)
The following registers are enable-protected:
• Event Control register (EVCTRL)
Enable-protected bits and registers can be changed only when the RTC is disabled (CTRLA.ENABLE=0).
If the RTC is enabled (CTRLA.ENABLE=1), these operations are necessary: first write
CTRLA.ENABLE=0 and check whether the write synchronization has finished, then change the desired
bit field value. Enable-protected bits in CTRLA register can be written at the same time as
CTRLA.ENABLE is written to '1', but not at the same time as CTRLA.ENABLE is written to '0'.
Enable-protection is denoted by the "Enable-Protected" property in the register description.
The RTC prescaler divides the source clock for the RTC counter.
Note:  In Clock/Calendar mode, the prescaler must be configured to provide a 1Hz clock to the counter
for correct operation.
The frequency of the RTC clock (CLK_RTC_CNT) is given by the following formula:
CLK_RTC_CNT =CLK_RTC_OSC
2PRESCALER
The frequency of the oscillator clock, CLK_RTC_OSC, is given by fCLK_RTC_OSC, and fCLK_RTC_CNT is the
frequency of the internal prescaled RTC clock, CLK_RTC_CNT.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 314
24.6.2.2 Enabling, Disabling, and Resetting
The RTC is enabled by setting the Enable bit in the Control A register (CTRLA.ENABLE=1). The RTC is
disabled by writing CTRLA.ENABLE=0.
The RTC is reset by setting the Software Reset bit in the Control A register (CTRLA.SWRST=1). All
registers in the RTC, except DEBUG, will be reset to their initial state, and the RTC will be disabled. The
RTC must be disabled before resetting it.
24.6.2.3 32-Bit Counter (Mode 0)
When the RTC Operating Mode bits in the Control A register (CTRLA.MODE) are written to 0x0, the
counter operates in 32-bit Counter mode. The block diagram of this mode is shown in Figure 24-1. When
the RTC is enabled, the counter will increment on every 0-to-1 transition of CLK_RTC_CNT. The counter
will increment until it reaches the top value of 0xFFFFFFFF, and then wrap to 0x00000000. This sets the
Overflow Interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.OVF).
The RTC counter value can be read from or written to the Counter Value register (COUNT) in 32-bit
format.
The counter value is continuously compared with the 32-bit Compare register (COMP0). When a compare
match occurs, the Compare 0 Interrupt flag in the Interrupt Flag Status and Clear register
(INTFLAG.CMP0) is set on the next 0-to-1 transition of CLK_RTC_CNT.
If the Clear on Match bit in the Control A register (CTRLA.MATCHCLR) is '1', the counter is cleared on
the next counter cycle when a compare match with COMP0 occurs. This allows the RTC to generate
periodic interrupts or events with longer periods than the prescaler events. Note that when
CTRLA.MATCHCLR is '1', INTFLAG.CMP0 and INTFLAG.OVF will both be set simultaneously on a
compare match with COMP0.
24.6.2.4 16-Bit Counter (Mode 1)
When the RTC Operating Mode bits in the Control A register (CTRLA.MODE) are written to 0x1, the
counter operates in 16-bit Counter mode as shown in Figure 24-2. When the RTC is enabled, the counter
will increment on every 0-to-1 transition of CLK_RTC_CNT. In 16-bit Counter mode, the 16-bit Period
register (PER) holds the maximum value of the counter. The counter will increment until it reaches the
PER value, and then wrap to 0x0000. This sets the Overflow Interrupt flag in the Interrupt Flag Status and
Clear register (INTFLAG.OVF).
The RTC counter value can be read from or written to the Counter Value register (COUNT) in 16-bit
format.
The counter value is continuously compared with the 16-bit Compare registers (COMPn, n=0..1). When a
compare match occurs, the Compare n Interrupt flag in the Interrupt Flag Status and Clear register
(INTFLAG.CMPn, n=0..1) is set on the next 0-to-1 transition of CLK_RTC_CNT.
24.6.2.5 Clock/Calendar (Mode 2)
When the RTC Operating Mode bits in the Control A register (CTRLA.MODE) are written to 0x2, the
counter operates in Clock/Calendar mode, as shown in Figure 24-3. When the RTC is enabled, the
counter will increment on every 0-to-1 transition of CLK_RTC_CNT. The selected clock source and RTC
prescaler must be configured to provide a 1Hz clock to the counter for correct operation in this mode.
The time and date can be read from or written to the Clock Value register (CLOCK) in a 32-bit time/date
format. Time is represented as:
• Seconds
• Minutes
• Hours
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 315
Hours can be represented in either 12- or 24-hour format, selected by the Clock Representation bit in the
Control A register (CTRLA.CLKREP). This bit can be changed only while the RTC is disabled.
The date is represented in this form:
• Day as the numeric day of the month (starting at 1)
• Month as the numeric month of the year (1 = January, 2 = February, etc.)
• Year as a value from 0x00 to 0x3F. This value must be added to a user-defined reference year. The
reference year must be a leap year (2016, 2020 etc). Example: the year value 0x2D, added to a
reference year 2016, represents the year 2061.
The RTC will increment until it reaches the top value of 23:59:59 December 31 of year value 0x3F, and
then wrap to 00:00:00 January 1 of year value 0x00. This will set the Overflow Interrupt flag in the
Interrupt Flag Status and Clear registers (INTFLAG.OVF).
The clock value is continuously compared with the 32-bit Alarm register (ALARM0). When an alarm
match occurs, the Alarm 0 Interrupt flag in the Interrupt Flag Status and Clear registers
(INTFLAG.ALARM0) is set on the next 0-to-1 transition of CLK_RTC_CNT. E.g. For a 1Hz clock counter,
it means the Alarm 0 Interrupt flag is set with a delay of 1s after the occurrence of alarm match.
A valid alarm match depends on the setting of the Alarm Mask Selection bits in the Alarm 0 Mask register
(MASK0.SEL). These bits determine which time/date fields of the clock and alarm values are valid for
comparison and which are ignored.
If the Clear on Match bit in the Control A register (CTRLA.MATCHCLR) is set, the counter is cleared on
the next counter cycle when an alarm match with ALARM0 occurs. This allows the RTC to generate
periodic interrupts or events with longer periods than it would be possible with the prescaler events only
(see 24.6.8.1 Periodic Intervals).
Note:  When CTRLA.MATCHCLR is 1, INTFLAG.ALARM0 and INTFLAG.OVF will both be set
simultaneously on an alarm match with ALARM0.
24.6.3 DMA Operation
Not applicable.
24.6.4 Interrupts
The RTC has the following interrupt sources:
• Overflow (OVF): Indicates that the counter has reached its top value and wrapped to zero.
• Compare (CMPn): Indicates a match between the counter value and the compare register.
• Alarm (ALARM): Indicates a match between the clock value and the alarm register.
• Period n (PERn): The corresponding bit in the prescaler has toggled. Refer to 24.6.8.1 Periodic
Intervals for details.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be
individually enabled by setting the corresponding bit in the Interrupt Enable Set register (INTENSET=1),
and disabled by setting the corresponding bit in the Interrupt Enable Clear register (INTENCLR=1).
An interrupt request is generated when the interrupt flag is raised and the corresponding interrupt is
enabled. The interrupt request remains active until either the interrupt flag is cleared, the interrupt is
disabled or the RTC is reset. See the description of the INTFLAG registers for details on how to clear
interrupt flags.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 316
All interrupt requests from the peripheral are ORed together on system level to generate one combined
interrupt request to the NVIC. Refer to the Nested Vector Interrupt Controller for details. The user must
read the INTFLAG register to determine which interrupt condition is present.
Note:  Interrupts must be globally enabled for interrupt requests to be generated. Refer to the Nested
Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
24.6.5 Events
The RTC can generate the following output events:
• Overflow (OVF): Generated when the counter has reached its top value and wrapped to zero.
• Compare (CMPn): Indicates a match between the counter value and the compare register.
• Alarm (ALARM): Indicates a match between the clock value and the alarm register.
• Period n (PERn): The corresponding bit in the prescaler has toggled. Refer to 24.6.8.1 Periodic
Intervals for details.
• Periodic Daily (PERD): Generated when the COUNT/CLOCK has incremented at a fixed period of
time.
Setting the Event Output bit in the Event Control Register (EVCTRL.xxxEO=1) enables the corresponding
output event. Writing a zero to this bit disables the corresponding output event. Refer to the EVSYS -
Event System for details on configuring the event system.
Related Links
29. EVSYS – Event System
24.6.6 Sleep Mode Operation
The RTC will continue to operate in any sleep mode where the source clock is active. The RTC interrupts
can be used to wake up the device from a sleep mode. RTC events can trigger other operations in the
system without exiting the sleep mode.
An interrupt request will be generated after the wake-up if the Interrupt Controller is configured
accordingly. Otherwise the CPU will wake up directly, without triggering any interrupt. In this case, the
CPU will continue executing right from the first instruction that followed the entry into sleep.
24.6.7 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in Control A register, CTRLA.SWRST
• Enable bit in Control A register, CTRLA.ENABLE
The following registers are synchronized when written:
• Counter Value register, COUNT
• Clock Value register, CLOCK
• Counter Period register, PER
• Compare n Value registers, COMPn
• Alarm n Value registers, ALARMn
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 317
• Frequency Correction register, FREQCORR
• Alarm n Mask register, MASKn
The following registers are synchronized when read:
• The Counter Value register, COUNT, if the Counter Read Sync Enable bit in CTRLA
(CTRLA.COUNTSYNC) is '1'
• The Clock Value register, CLOCK, if the Clock Read Sync Enable bit in CTRLA
(CTRLA.CLOCKSYNC) is '1'
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Required read-synchronization is denoted by the "Read-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
24.6.8 Additional Features
24.6.8.1 Periodic Intervals
The RTC prescaler can generate interrupts and events at periodic intervals, allowing flexible system tick
creation. Any of the upper eight bits of the prescaler (bits 2 to 9) can be the source of an interrupt/event.
When one of the eight Periodic Event Output bits in the Event Control register (EVCTRL.PEREO[n=0..7])
is '1', an event is generated on the 0-to-1 transition of the related bit in the prescaler, resulting in a
periodic event frequency of:
PERIODIC(n) =CLK_RTC_OSC
2n+3
fCLK_RTC_OSC is the frequency of the internal prescaler clock CLK_RTC_OSC, and n is the position of the
EVCTRL.PEREOn bit. For example, PER0 will generate an event every eight CLK_RTC_OSC cycles,
PER1 every 16 cycles, etc. This is shown in the figure below.
Periodic events are independent of the prescaler setting used by the RTC counter, except if
CTRLA.PRESCALER is zero. Then, no periodic events will be generated.
Figure 24-4. Example Periodic Events
CLK_RTC_OSC
PER0
PER1
PER2
PER3
24.6.8.2 Frequency Correction
The RTC Frequency Correction module employs periodic counter corrections to compensate for a too-
slow or too-fast oscillator. Frequency correction requires that CTRLA.PRESCALER is greater than 1.
The digital correction circuit adds or subtracts cycles from the RTC prescaler to adjust the frequency in
approximately 1ppm steps. Digital correction is achieved by adding or skipping a single count in the
prescaler once every 4096 CLK_RTC_OSC cycles. The Value bit group in the Frequency Correction
register (FREQCORR.VALUE) determines the number of times the adjustment is applied over 240 of
these periods. The resulting correction is as follows:
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 318
Correctioninppm = FREQCORR.VALUE
4096 240 106ppm
This results in a resolution of 1.017ppm.
The Sign bit in the Frequency Correction register (FREQCORR.SIGN) determines the direction of the
correction. A positive value will add counts and increase the period (reducing the frequency), and a
negative value will reduce counts per period (speeding up the frequency).
Digital correction also affects the generation of the periodic events from the prescaler. When the
correction is applied at the end of the correction cycle period, the interval between the previous periodic
event and the next occurrence may also be shortened or lengthened depending on the correction value.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 319
24.7 Register Summary - Mode 0 - 32-Bit Counter
Offset Name Bit Pos.
0x00 CTRLA
7:0 MATCHCLR MODE[1:0] ENABLE SWRST
15:8 COUNTSYNC PRESCALER[3:0]
0x02
...
0x03
Reserved
0x04 EVCTRL
7:0 PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
15:8 OVFEO CMPEO0
23:16
31:24
0x08 INTENCLR
7:0 PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
15:8 OVF CMP0
0x0A INTENSET
7:0 PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
15:8 OVF CMP0
0x0C INTFLAG
7:0 PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
15:8 OVF CMP0
0x0E DBGCTRL 7:0 DBGRUN
0x0F Reserved
0x10 SYNCBUSY
7:0 COMP0 COUNT FREQCORR ENABLE SWRST
15:8 COUNTSYNC
23:16
31:24
0x14 FREQCORR 7:0 SIGN VALUE[6:0]
0x15
...
0x17
Reserved
0x18 COUNT
7:0 COUNT[7:0]
15:8 COUNT[15:8]
23:16 COUNT[23:16]
31:24 COUNT[31:24]
0x1C
...
0x1F
Reserved
0x20 COMP
7:0 COMP[7:0]
15:8 COMP[15:8]
23:16 COMP[23:16]
31:24 COMP[31:24]
24.8 Register Description - Mode 0 - 32-Bit Counter
This Register Description section is valid if the RTC is in COUNT32 mode (CTRLA.MODE=0).
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 320
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 321
24.8.1 Control A in COUNT32 mode (CTRLA.MODE=0)
Name:  CTRLA
Offset:  0x00
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
COUNTSYNC PRESCALER[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MATCHCLR MODE[1:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 15 – COUNTSYNC COUNT Read Synchronization Enable
The COUNT register requires synchronization when reading. Disabling the synchronization will prevent
reading valid values from the COUNT register.
This bit is not enable-protected.
Value Description
0COUNT read synchronization is disabled
1COUNT read synchronization is enabled
Bits 11:8 – PRESCALER[3:0] Prescaler
These bits define the prescaling factor for the RTC clock source (GCLK_RTC) to generate the counter
clock (CLK_RTC_CNT). Periodic events and interrupts are not available when the prescaler is off. These
bits are not synchronized.
Value Name Description
0x0 OFF CLK_RTC_CNT = GCLK_RTC/1
0x1 DIV1 CLK_RTC_CNT = GCLK_RTC/1
0x2 DIV2 CLK_RTC_CNT = GCLK_RTC/2
0x3 DIV4 CLK_RTC_CNT = GCLK_RTC/4
0x4 DIV8 CLK_RTC_CNT = GCLK_RTC/8
0x5 DIV16 CLK_RTC_CNT = GCLK_RTC/16
0x6 DIV32 CLK_RTC_CNT = GCLK_RTC/32
0x7 DIV64 CLK_RTC_CNT = GCLK_RTC/64
0x8 DIV128 CLK_RTC_CNT = GCLK_RTC/128
0x9 DIV256 CLK_RTC_CNT = GCLK_RTC/256
0xA DIV512 CLK_RTC_CNT = GCLK_RTC/512
0xB DIV1024 CLK_RTC_CNT = GCLK_RTC/1024
0xC-0xF - Reserved
Bit 7 – MATCHCLR Clear on Match
This bit defines if the counter is cleared or not on a match.
This bit is not synchronized.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 322
Value Description
0The counter is not cleared on a Compare/Alarm 0 match
1The counter is cleared on a Compare/Alarm 0 match
Bits 3:2 – MODE[1:0] Operating Mode
This bit group defines the operating mode of the RTC.
This bit is not synchronized.
Value Name Description
0x0 COUNT32 Mode 0: 32-bit counter
0x1 COUNT16 Mode 1: 16-bit counter
0x2 CLOCK Mode 2: Clock/calendar
0x3 - Reserved
Bit 1 – ENABLE Enable
Due to synchronization there is a delay between writing CTRLA.ENABLE and until the peripheral is
enabled/disabled. The value written to CTRLA.ENABLE will read back immediately and the Enable bit in
the Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be
cleared when the operation is complete.
Value Description
0The peripheral is disabled
1The peripheral is enabled
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the RTC (except DBGCTRL) to their initial state, and the RTC
will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay between writing CTRLA.SWRST and until the reset is complete.
CTRLA.SWRST will be cleared when the reset is complete.
Value Description
0There is not reset operation ongoing
1The reset operation is ongoing
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 323
24.8.2 Event Control in COUNT32 mode (CTRLA.MODE=0)
Name:  EVCTRL
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
OVFEO CMPEO0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVFEO Overflow Event Output Enable
Value Description
0Overflow event is disabled and will not be generated.
1Overflow event is enabled and will be generated for every overflow.
Bit 8 – CMPEO0 Compare 0 Event Output Enable
Value Description
0Compare 0 event is disabled and will not be generated.
1Compare 0 event is enabled and will be generated for every compare match.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PEREOn Periodic Interval n Event Output Enable [n = 7..0]
Value Description
0Periodic Interval n event is disabled and will not be generated.
1Periodic Interval n event is enabled and will be generated.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 324
24.8.3 Interrupt Enable Clear in COUNT32 mode (CTRLA.MODE=0)
Name:  INTENCLR
Offset:  0x08
Reset:  0x0000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 15 14 13 12 11 10 9 8
OVF CMP0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Overflow Interrupt Enable bit, which disables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bit 8 – CMP0 Compare 0 Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Compare 0 Interrupt Enable bit, which disables the Compare 0
interrupt.
Value Description
0The Compare 0 interrupt is disabled.
1The Compare 0 interrupt is enabled.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n Interrupt Enable [n = 7..0]
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Periodic Interval n Interrupt Enable bit, which disables the Periodic
Interval n interrupt.
Value Description
0Periodic Interval n interrupt is disabled.
1Periodic Interval n interrupt is enabled.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 325
24.8.4 Interrupt Enable Set in COUNT32 mode (CTRLA.MODE=0)
Name:  INTENSET
Offset:  0x0A
Reset:  0x0000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 15 14 13 12 11 10 9 8
OVF CMP0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Overflow Interrupt Enable bit, which enables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bit 8 – CMP0 Compare 0 Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Compare 0 Interrupt Enable bit, which enables the Compare 0 interrupt.
Value Description
0The Compare 0 interrupt is disabled.
1The Compare 0 interrupt is enabled.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n Interrupt Enable [n = 7..0]
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Periodic Interval n Interrupt Enable bit, which enables the Periodic
Interval n interrupt.
Value Description
0Periodic Interval n interrupt is disabled.
1Periodic Interval n interrupt is enabled.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 326
24.8.5 Interrupt Flag Status and Clear in COUNT32 mode (CTRLA.MODE=0)
Name:  INTFLAG
Offset:  0x0C
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
OVF CMP0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow
This flag is cleared by writing a '1' to the flag.
This flag is set on the next CLK_RTC_CNT cycle after an overflow condition occurs, and an interrupt
request will be generated if INTENCLR/SET.OVF is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
Bit 8 – CMP0 Compare 0
This flag is cleared by writing a '1' to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with the compare condition, and an
interrupt request will be generated if INTENCLR/SET.COMP0 is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Compare 0 interrupt flag.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n [n = 7..0]
This flag is cleared by writing a '1' to the flag.
This flag is set on the 0-to-1 transition of prescaler bit [n+2], and an interrupt request will be generated if
INTENCLR/SET.PERn is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Periodic Interval n interrupt flag.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 327
24.8.6 Debug Control
Name:  DBGCTRL
Offset:  0x0E
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bit controls the functionality when the CPU is halted by an external debugger.
Value Description
0The RTC is halted when the CPU is halted by an external debugger.
1The RTC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 328
24.8.7 Synchronization Busy in COUNT32 mode (CTRLA.MODE=0)
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
COUNTSYNC
Access R
Reset 0
Bit 7 6 5 4 3 2 1 0
COMP0 COUNT FREQCORR ENABLE SWRST
Access R R R R R
Reset 0 0 0 0 0
Bit 15 – COUNTSYNC Count Read Sync Enable Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.COUNTSYNC bit is complete.
1Write synchronization for CTRLA.COUNTSYNC bit is ongoing.
Bit 5 – COMP0 Compare 0 Synchronization Busy Status
Value Description
0Write synchronization for COMP0 register is complete.
1Write synchronization for COMP0 register is ongoing.
Bit 3 – COUNT Count Value Synchronization Busy Status
Value Description
0Read/write synchronization for COUNT register is complete.
1Read/write synchronization for COUNT register is ongoing.
Bit 2 – FREQCORR Frequency Correction Synchronization Busy Status
Value Description
0Write synchronization for FREQCORR register is complete.
1Write synchronization for FREQCORR register is ongoing.
Bit 1 – ENABLE Enable Synchronization Busy Status
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 329
Value Description
0Write synchronization for CTRLA.ENABLE bit is complete.
1Write synchronization for CTRLA.ENABLE bit is ongoing.
Bit 0 – SWRST Software Reset Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.SWRST bit is complete.
1Write synchronization for CTRLA.SWRST bit is ongoing.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 330
24.8.8 Frequency Correction
Name:  FREQCORR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
SIGN VALUE[6:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 – SIGN Correction Sign
Value Description
0The correction value is positive, i.e., frequency will be decreased.
1The correction value is negative, i.e., frequency will be increased.
Bits 6:0 – VALUE[6:0] Correction Value
These bits define the amount of correction applied to the RTC prescaler.
Value Description
0Correction is disabled and the RTC frequency is unchanged.
1 - 127 The RTC frequency is adjusted according to the value.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 331
24.8.9 Counter Value in COUNT32 mode (CTRLA.MODE=0)
Name:  COUNT
Offset:  0x18
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Bit 31 30 29 28 27 26 25 24
COUNT[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
COUNT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – COUNT[31:0] Counter Value
These bits define the value of the 32-bit RTC counter in mode 0.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 332
24.8.10 Compare 0 Value in COUNT32 mode (CTRLA.MODE=0)
Name:  COMP
Offset:  0x20
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
COMP[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
COMP[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
COMP[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COMP[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – COMP[31:0] Compare Value
The 32-bit value of COMP0 is continuously compared with the 32-bit COUNT value. When a match
occurs, the Compare 0 interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMP0) is
set on the next counter cycle, and the counter value is cleared if CTRLA.MATCHCLR is '1'.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 333
24.9 Register Summary - Mode 1 - 16-Bit Counter
Offset Name Bit Pos.
0x00 CTRLA
7:0 MODE[1:0] ENABLE SWRST
15:8 COUNTSYNC PRESCALER[3:0]
0x02
...
0x03
Reserved
0x04 EVCTRL
7:0 PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
15:8 OVFEO CMPEO1 CMPEO0
23:16
31:24
0x08 INTENCLR
7:0 PER7 PER6 PER5 PER4 PER3 PER2 CMP1 CMP0
15:8 OVF
0x0A INTENSET
7:0 PER7 PER6 PER5 PER4 PER3 PER2 CMP1 CMP0
15:8 OVF
0x0C INTFLAG
7:0 PER7 PER6 PER5 PER4 PER3 PER2 CMP1 CMP0
15:8 OVF
0x0E DBGCTRL 7:0 DBGRUN
0x0F Reserved
0x10 SYNCBUSY
7:0 COMP1 COMP0 PER COUNT FREQCORR ENABLE SWRST
15:8 COUNTSYNC
23:16
31:24
0x14 FREQCORR 7:0 SIGN VALUE[6:0]
0x15
...
0x17
Reserved
0x18 COUNT
7:0 COUNT[7:0]
15:8 COUNT[15:8]
0x1A
...
0x1B
Reserved
0x1C PER
7:0 PER[7:0]
15:8 PER[15:8]
0x1E
...
0x1F
Reserved
0x20 COMP0
7:0 COMP[7:0]
15:8 COMP[15:8]
0x22 COMP1
7:0 COMP[7:0]
15:8 COMP[15:8]
24.10 Register Description - Mode 1 - 16-Bit Counter
This Register Description section is valid if the RTC is in COUNT16 mode (CTRLA.MODE=1).
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 334
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 335
24.10.1 Control A in COUNT16 mode (CTRLA.MODE=1)
Name:  CTRLA
Offset:  0x00
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
COUNTSYNC PRESCALER[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MODE[1:0] ENABLE SWRST
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 – COUNTSYNC COUNT Read Synchronization Enable
The COUNT register requires synchronization when reading. Disabling the synchronization will prevent
reading valid values from the COUNT register.
This bit is not enable-protected.
Value Description
0COUNT read synchronization is disabled
1COUNT read synchronization is enabled
Bits 11:8 – PRESCALER[3:0] Prescaler
These bits define the prescaling factor for the RTC clock source (GCLK_RTC) to generate the counter
clock (CLK_RTC_CNT). Periodic events and interrupts are not available when the prescaler is off. These
bits are not synchronized.
Value Name Description
0x0 OFF CLK_RTC_CNT = GCLK_RTC/1
0x1 DIV1 CLK_RTC_CNT = GCLK_RTC/1
0x2 DIV2 CLK_RTC_CNT = GCLK_RTC/2
0x3 DIV4 CLK_RTC_CNT = GCLK_RTC/4
0x4 DIV8 CLK_RTC_CNT = GCLK_RTC/8
0x5 DIV16 CLK_RTC_CNT = GCLK_RTC/16
0x6 DIV32 CLK_RTC_CNT = GCLK_RTC/32
0x7 DIV64 CLK_RTC_CNT = GCLK_RTC/64
0x8 DIV128 CLK_RTC_CNT = GCLK_RTC/128
0x9 DIV256 CLK_RTC_CNT = GCLK_RTC/256
0xA DIV512 CLK_RTC_CNT = GCLK_RTC/512
0xB DIV1024 CLK_RTC_CNT = GCLK_RTC/1024
0xC-0xF - Reserved
Bits 3:2 – MODE[1:0] Operating Mode
This field defines the operating mode of the RTC. This bit is not synchronized.
Value Name Description
0x0 COUNT32 Mode 0: 32-bit counter
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 336
Value Name Description
0x1 COUNT16 Mode 1: 16-bit counter
0x2 CLOCK Mode 2: Clock/calendar
0x3 - Reserved
Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the Enable bit in the
Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared
when the operation is complete.
Value Description
0The peripheral is disabled
1The peripheral is enabled
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the RTC (except DBGCTRL) to their initial state, and the RTC
will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST will be cleared when the reset is complete.
Value Description
0There is not reset operation ongoing
1The reset operation is ongoing
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 337
24.10.2 Event Control in COUNT16 mode (CTRLA.MODE=1)
Name:  EVCTRL
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
OVFEO CMPEO1 CMPEO0
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVFEO Overflow Event Output Enable
Value Description
0Overflow event is disabled and will not be generated.
1Overflow event is enabled and will be generated for every overflow.
Bits 8, 9 – CMPEOn Compare n Event Output Enable [n = 1..0]
Value Description
0Compare n event is disabled and will not be generated.
1Compare n event is enabled and will be generated for every compare match.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PEREOn Periodic Interval n Event Output Enable [n = 7..0]
Value Description
0Periodic Interval n event is disabled and will not be generated.
1Periodic Interval n event is enabled and will be generated.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 338
24.10.3 Interrupt Enable Clear in COUNT16 mode (CTRLA.MODE=1)
Name:  INTENCLR
Offset:  0x08
Reset:  0x0000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 15 14 13 12 11 10 9 8
OVF
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 CMP1 CMP0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect. Writing a '1' to this bit will clear the Overflow Interrupt Enable bit,
which disables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bits 0, 1 – CMPn Compare n Interrupt Enable [n = 1..0]
Writing a '0' to this bit has no effect. Writing a '1' to this bit will clear the Compare n Interrupt Enable bit,
which disables the Compare n interrupt.
Value Description
0The Compare n interrupt is disabled.
1The Compare n interrupt is enabled.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n Interrupt Enable [n = 7..0]
Writing a '0' to this bit has no effect. Writing a '1' to this bit will clear the Periodic Interval n Interrupt
Enable bit, which disables the Periodic Interval n interrupt.
Value Description
0Periodic Interval n interrupt is disabled.
1Periodic Interval n interrupt is enabled.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 339
24.10.4 Interrupt Enable Set in COUNT16 mode (CTRLA.MODE=1)
Name:  INTENSET
Offset:  0x0A
Reset:  0x0000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 15 14 13 12 11 10 9 8
OVF
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 CMP1 CMP0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect. Writing a '1' to this bit will set the Overflow Interrupt Enable bit, which
enables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bits 0, 1 – CMPn Compare n Interrupt Enable [n = 1..0]
Writing a '0' to this bit has no effect. Writing a '1' to this bit will set the Compare n Interrupt Enable bit,
which and enables the Compare n interrupt.
Value Description
0The Compare n interrupt is disabled.
1The Compare n interrupt is enabled.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n Interrupt Enable [n = 7..0]
Writing a '0' to this bit has no effect. Writing a '1' to this bit will set the Periodic Interval n Interrupt Enable
bit, which enables the Periodic Interval n interrupt.
Value Description
0Periodic Interval n interrupt is disabled.
1Periodic Interval n interrupt is enabled.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 340
24.10.5 Interrupt Flag Status and Clear in COUNT16 mode (CTRLA.MODE=1)
Name:  INTFLAG
Offset:  0x0C
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
OVF
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 CMP1 CMP0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow
This flag is cleared by writing a '1' to the flag.
This flag is set on the next CLK_RTC_CNT cycle after an overflow condition occurs, and an interrupt
request will be generated if INTENCLR/SET.OVF is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
Bits 0, 1 – CMPn Compare n [n = 1..0]
This flag is cleared by writing a '1' to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with the compare condition, and an
interrupt request will be generated if INTENCLR/SET.COMPn is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Compare n interrupt flag.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n [n = 7..0]
This flag is cleared by writing a '1' to the flag.
This flag is set on the 0-to-1 transition of prescaler bit [n+2], and an interrupt request will be generated if
INTENCLR/SET.PERx is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Periodic Interval n interrupt flag.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 341
24.10.6 Debug Control
Name:  DBGCTRL
Offset:  0x0E
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bit controls the functionality when the CPU is halted by an external debugger.
Value Description
0The RTC is halted when the CPU is halted by an external debugger.
1The RTC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 342
24.10.7 Synchronization Busy in COUNT16 mode (CTRLA.MODE=1)
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
COUNTSYNC
Access R
Reset 0
Bit 7 6 5 4 3 2 1 0
COMP1 COMP0 PER COUNT FREQCORR ENABLE SWRST
Access R/W R/W R R R R R
Reset 0 0 0 0 0 0 0
Bit 15 – COUNTSYNC Count Read Sync Enable Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.COUNTSYNC bit is complete.
1Write synchronization for CTRLA.COUNTSYNC bit is ongoing.
Bits 5, 6 – COMPn Compare n Synchronization Busy Status [n = 1..0]
Value Description
0Write synchronization for COMPn register is complete.
1Write synchronization for COMPn register is ongoing.
Bit 4 – PER Period Synchronization Busy Status
Value Description
0Write synchronization for PER register is complete.
1Write synchronization for PER register is ongoing.
Bit 3 – COUNT Count Value Synchronization Busy Status
Value Description
0Read/write synchronization for COUNT register is complete.
1Read/write synchronization for COUNT register is ongoing.
Bit 2 – FREQCORR Frequency Correction Synchronization Busy Status
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
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Value Description
0Write synchronization for FREQCORR register is complete.
1Write synchronization for FREQCORR register is ongoing.
Bit 1 – ENABLE Enable Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.ENABLE bit is complete.
1Write synchronization for CTRLA.ENABLE bit is ongoing.
Bit 0 – SWRST Software Reset Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.SWRST bit is complete.
1Write synchronization for CTRLA.SWRST bit is ongoing.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 344
24.10.8 Frequency Correction
Name:  FREQCORR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
SIGN VALUE[6:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 – SIGN Correction Sign
Value Description
0The correction value is positive, i.e., frequency will be decreased.
1The correction value is negative, i.e., frequency will be increased.
Bits 6:0 – VALUE[6:0] Correction Value
These bits define the amount of correction applied to the RTC prescaler.
Value Description
0Correction is disabled and the RTC frequency is unchanged.
1 - 127 The RTC frequency is adjusted according to the value.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 345
24.10.9 Counter Value in COUNT16 mode (CTRLA.MODE=1)
Name:  COUNT
Offset:  0x18
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Bit 15 14 13 12 11 10 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – COUNT[15:0] Counter Value
These bits define the value of the 16-bit RTC counter in COUNT16 mode (CTRLA.MODE=1).
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 346
24.10.10 Counter Period in COUNT16 mode (CTRLA.MODE=1)
Name:  PER
Offset:  0x1C
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
PER[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PER[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – PER[15:0] Counter Period
These bits define the value of the 16-bit RTC period in COUNT16 mode (CTRLA.MODE=1).
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 347
24.10.11 Compare n Value in COUNT16 mode (CTRLA.MODE=1)
Name:  COMP
Offset:  0x20 + n*0x02 [n=0..1]
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
COMP[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COMP[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – COMP[15:0] Compare Value
The 16-bit value of COMPn is continuously compared with the 16-bit COUNT value. When a match
occurs, the Compare n interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.CMPn) is
set on the next counter cycle.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 348
24.11 Register Summary - Mode 2 - Clock/Calendar
Offset Name Bit Pos.
0x00 CTRLA
7:0 MATCHCLR CLKREP MODE[1:0] ENABLE SWRST
15:8 CLOCKSYNC PRESCALER[3:0]
0x02
...
0x03
Reserved
0x04 EVCTRL
7:0 PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
15:8 OVFEO ALARMEO
23:16
31:24
0x08 INTENCLR
7:0 PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
15:8 OVF ALARM0
0x0A INTENSET
7:0 PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
15:8 OVF ALARM0
0x0C INTFLAG
7:0 PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
15:8 OVF ALARM0
0x0E DBGCTRL 7:0 DBGRUN
0x0F Reserved
0x10 SYNCBUSY
7:0 ALARM0 CLOCK FREQCORR ENABLE SWRST
15:8 CLOCKSYNC MASK0
23:16
31:24
0x14 FREQCORR 7:0 SIGN VALUE[6:0]
0x15
...
0x17
Reserved
0x18 CLOCK
7:0 MINUTE[1:0] SECOND[5:0]
15:8 HOUR[3:0] MINUTE[5:2]
23:16 MONTH[1:0] DAY[4:0] HOUR[4:4]
31:24 YEAR[5:0] MONTH[3:2]
0x1C
...
0x1F
Reserved
0x20 ALARM
7:0 MINUTE[1:0] SECOND[5:0]
15:8 HOUR[3:0] MINUTE[5:2]
23:16 MONTH[1:0] DAY[4:0] HOUR[4:4]
31:24 YEAR[5:0] MONTH[3:2]
0x24 MASK 7:0 SEL[2:0]
24.12 Register Description - Mode 2 - Clock/Calendar
This Register Description section is valid if the RTC is in Clock/Calendar mode (CTRLA.MODE=2).
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 349
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 350
24.12.1 Control A in Clock/Calendar mode (CTRLA.MODE=2)
Name:  CTRLA
Offset:  0x00
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
CLOCKSYNC PRESCALER[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MATCHCLR CLKREP MODE[1:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 15 – CLOCKSYNC CLOCK Read Synchronization Enable
The CLOCK register requires synchronization when reading. Disabling the synchronization will prevent
reading valid values from the CLOCK register.
This bit is not enable-protected.
Value Description
0CLOCK read synchronization is disabled
1CLOCK read synchronization is enabled
Bits 11:8 – PRESCALER[3:0] Prescaler
These bits define the prescaling factor for the RTC clock source (GCLK_RTC) to generate the counter
clock (CLK_RTC_CNT). Periodic events and interrupts are not available when the prescaler is off. These
bits are not synchronized.
Value Name Description
0x0 OFF CLK_RTC_CNT = GCLK_RTC/1
0x1 DIV1 CLK_RTC_CNT = GCLK_RTC/1
0x2 DIV2 CLK_RTC_CNT = GCLK_RTC/2
0x3 DIV4 CLK_RTC_CNT = GCLK_RTC/4
0x4 DIV8 CLK_RTC_CNT = GCLK_RTC/8
0x5 DIV16 CLK_RTC_CNT = GCLK_RTC/16
0x6 DIV32 CLK_RTC_CNT = GCLK_RTC/32
0x7 DIV64 CLK_RTC_CNT = GCLK_RTC/64
0x8 DIV128 CLK_RTC_CNT = GCLK_RTC/128
0x9 DIV256 CLK_RTC_CNT = GCLK_RTC/256
0xA DIV512 CLK_RTC_CNT = GCLK_RTC/512
0xB DIV1024 CLK_RTC_CNT = GCLK_RTC/1024
0xC-0xF - Reserved
Bit 7 – MATCHCLR Clear on Match
This bit is valid only in Mode 0 (COUNT32) and Mode 2 (CLOCK). This bit can be written only when the
peripheral is disabled. This bit is not synchronized.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
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Value Description
0The counter is not cleared on a Compare/Alarm 0 match
1The counter is cleared on a Compare/Alarm 0 match
Bit 6 – CLKREP Clock Representation
This bit is valid only in Mode 2 and determines how the hours are represented in the Clock Value
(CLOCK) register. This bit can be written only when the peripheral is disabled. This bit is not
synchronized.
Value Description
024 Hour
112 Hour (AM/PM)
Bits 3:2 – MODE[1:0] Operating Mode
This field defines the operating mode of the RTC. This bit is not synchronized.
Value Name Description
0x0 COUNT32 Mode 0: 32-bit counter
0x1 COUNT16 Mode 1: 16-bit counter
0x2 CLOCK Mode 2: Clock/calendar
0x3 - Reserved
Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the Enable bit in the
Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared
when the operation is complete.
Value Description
0The peripheral is disabled
1The peripheral is enabled
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the RTC, except DBGCTRL, to their initial state, and the RTC
will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST will be cleared when the reset is complete.
Value Description
0There is not reset operation ongoing
1The reset operation is ongoing
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 352
24.12.2 Event Control in Clock/Calendar mode (CTRLA.MODE=2)
Name:  EVCTRL
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
OVFEO ALARMEO
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PEREO7 PEREO6 PEREO5 PEREO4 PEREO3 PEREO2 PEREO1 PEREO0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVFEO Overflow Event Output Enable
Value Description
0Overflow event is disabled and will not be generated.
1Overflow event is enabled and will be generated for every overflow.
Bit 8 – ALARMEO Alarm 0 Event Output Enable
Value Description
0Alarm 0 event is disabled and will not be generated.
1Alarm 0 event is enabled and will be generated for every compare match.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PEREOn Periodic Interval n Event Output Enable [n = 7..0]
Value Description
0Periodic Interval n event is disabled and will not be generated.
1Periodic Interval n event is enabled and will be generated.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 353
24.12.3 Interrupt Enable Clear in Clock/Calendar mode (CTRLA.MODE=2)
Name:  INTENCLR
Offset:  0x08
Reset:  0x0000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 15 14 13 12 11 10 9 8
OVF ALARM0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect. Writing a '1' to this bit will clear the Overflow Interrupt Enable bit,
which disables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bit 8 – ALARM0 Alarm 0 Interrupt Enable
Writing a '0' to this bit has no effect. Writing a '1' to this bit will clear the Alarm 0 Interrupt Enable bit, which
disables the Alarm interrupt.
Value Description
0The Alarm 0 interrupt is disabled.
1The Alarm 0 interrupt is enabled.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n Interrupt Enable [n = 7..0]
Writing a '0' to this bit has no effect. Writing a '1' to this bit will clear the Periodic Interval n Interrupt
Enable bit, which disables the Periodic Interval n interrupt.
Value Description
0Periodic Interval n interrupt is disabled.
1Periodic Interval n interrupt is enabled.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 354
24.12.4 Interrupt Enable Set in Clock/Calendar mode (CTRLA.MODE=2)
Name:  INTENSET
Offset:  0x0A
Reset:  0x0000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 15 14 13 12 11 10 9 8
OVF ALARM0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect. Writing a '1' to this bit will set the Overflow Interrupt Enable bit, which
enables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bit 8 – ALARM0 Alarm 0 Interrupt Enable
Writing a '0' to this bit has no effect. Writing a '1' to this bit will set the Alarm 0 Interrupt Enable bit, which
enables the Alarm 0 interrupt.
Value Description
0The Alarm 0 interrupt is disabled.
1The Alarm 0 interrupt is enabled.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n Interrupt Enable [n = 7..0]
Writing a '0' to this bit has no effect. Writing a '1' to this bit will set the Periodic Interval n Interrupt Enable
bit, which enables the Periodic Interval n interrupt.
Value Description
0Periodic Interval n interrupt is disabled.
1Periodic Interval n interrupt is enabled.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 355
24.12.5 Interrupt Flag Status and Clear in Clock/Calendar mode (CTRLA.MODE=2)
Name:  INTFLAG
Offset:  0x0C
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
OVF ALARM0
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
PER7 PER6 PER5 PER4 PER3 PER2 PER1 PER0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – OVF Overflow
This flag is cleared by writing a '1' to the flag.
This flag is set on the next CLK_RTC_CNT cycle after an overflow condition occurs, and an interrupt
request will be generated if INTENCLR/SET.OVF is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
Bit 8 – ALARM0 Alarm 0
This flag is cleared by writing a '1' to the flag.
This flag is set on the next CLK_RTC_CNT cycle after a match with the compare condition, and an
interrupt request will be generated if INTENCLR/SET.ALARM0 is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Alarm 0 interrupt flag.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – PERn Periodic Interval n [n = 7..0]
This flag is cleared by writing a '1' to the flag.
This flag is set on the 0-to-1 transition of prescaler bit [n+2], and an interrupt request will be generated if
INTENCLR/SET.PERx is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Periodic Interval n interrupt flag.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 356
24.12.6 Debug Control
Name:  DBGCTRL
Offset:  0x0E
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bit controls the functionality when the CPU is halted by an external debugger.
Value Description
0The RTC is halted when the CPU is halted by an external debugger.
1The RTC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
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24.12.7 Synchronization Busy in Clock/Calendar mode (CTRLA.MODE=2)
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
CLOCKSYNC MASK0
Access R R
Reset 0 0
Bit 7 6 5 4 3 2 1 0
ALARM0 CLOCK FREQCORR ENABLE SWRST
Access R R R R R
Reset 0 0 0 0 0
Bit 15 – CLOCKSYNC Clock Read Sync Enable Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.CLOCKSYNC bit is complete.
1Write synchronization for CTRLA.CLOCKSYNC bit is ongoing.
Bit 11 – MASK0 Mask 0 Synchronization Busy Status
Value Description
0Write synchronization for MASK0 register is complete.
1Write synchronization for MASK0 register is ongoing.
Bit 5 – ALARM0 Alarm 0 Synchronization Busy Status
Value Description
0Write synchronization for ALARM0 register is complete.
1Write synchronization for ALARM0 register is ongoing.
Bit 3 – CLOCK Clock Register Synchronization Busy Status
Value Description
0Read/write synchronization for CLOCK register is complete.
1Read/write synchronization for CLOCK register is ongoing.
Bit 2 – FREQCORR Frequency Correction Synchronization Busy Status
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
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Value Description
0Write synchronization for FREQCORR register is complete.
1Write synchronization for FREQCORR register is ongoing.
Bit 1 – ENABLE Enable Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.ENABLE bit is complete.
1Write synchronization for CTRLA.ENABLE bit is ongoing.
Bit 0 – SWRST Software Reset Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.SWRST bit is complete.
1Write synchronization for CTRLA.SWRST bit is ongoing.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
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24.12.8 Frequency Correction
Name:  FREQCORR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
SIGN VALUE[6:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 – SIGN Correction Sign
Value Description
0The correction value is positive, i.e., frequency will be decreased.
1The correction value is negative, i.e., frequency will be increased.
Bits 6:0 – VALUE[6:0] Correction Value
These bits define the amount of correction applied to the RTC prescaler.
Value Description
0Correction is disabled and the RTC frequency is unchanged.
1 - 127 The RTC frequency is adjusted according to the value.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 360
24.12.9 Clock Value in Clock/Calendar mode (CTRLA.MODE=2)
Name:  CLOCK
Offset:  0x18
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Bit 31 30 29 28 27 26 25 24
YEAR[5:0] MONTH[3:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
MONTH[1:0] DAY[4:0] HOUR[4:4]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
HOUR[3:0] MINUTE[5:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MINUTE[1:0] SECOND[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:26 – YEAR[5:0] Year
The year offset with respect to the reference year (defined in software).
The year is considered a leap year if YEAR[1:0] is zero.
Bits 25:22 – MONTH[3:0] Month
1 – January
2 – February
...
12 – December
Bits 21:17 – DAY[4:0] Day
Day starts at 1 and ends at 28, 29, 30, or 31, depending on the month and year.
Bits 16:12 – HOUR[4:0] Hour
When CTRLA.CLKREP=0, the Hour bit group is in 24-hour format, with values 0-23. When
CTRLA.CLKREP=1, HOUR[3:0] has values 1-12, and HOUR[4] represents AM (0) or PM (1).
Bits 11:6 – MINUTE[5:0] Minute
0 – 59
Bits 5:0 – SECOND[5:0] Second
0 – 59
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 361
24.12.10 Alarm Value in Clock/Calendar mode (CTRLA.MODE=2)
Name:  ALARM
Offset:  0x20
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized
The 32-bit value of ALARM is continuously compared with the 32-bit CLOCK value, based on the
masking set by MASK.SEL. When a match occurs, the Alarm n interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG.ALARM) is set on the next counter cycle, and the counter is cleared if
CTRLA.MATCHCLR is '1'.
Bit 31 30 29 28 27 26 25 24
YEAR[5:0] MONTH[3:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
MONTH[1:0] DAY[4:0] HOUR[4:4]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
HOUR[3:0] MINUTE[5:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MINUTE[1:0] SECOND[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:26 – YEAR[5:0] Year
The alarm year. Years are only matched if MASK.SEL is 6
Bits 25:22 – MONTH[3:0] Month
The alarm month. Months are matched only if MASK.SEL is greater than 4.
Bits 21:17 – DAY[4:0] Day
The alarm day. Days are matched only if MASK.SEL is greater than 3.
Bits 16:12 – HOUR[4:0] Hour
The alarm hour. Hours are matched only if MASK.SEL is greater than 2.
Bits 11:6 – MINUTE[5:0] Minute
The alarm minute. Minutes are matched only if MASK.SEL is greater than 1.
Bits 5:0 – SECOND[5:0] Second
The alarm second. Seconds are matched only if MASK.SEL is greater than 0.
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 362
24.12.11 Alarm Mask in Clock/Calendar mode (CTRLA.MODE=2)
Name:  MASK
Offset:  0x24
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
SEL[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – SEL[2:0] Alarm Mask Selection
These bits define which bit groups of ALARM are valid.
Value Name Description
0x0 OFF Alarm Disabled
0x1 SS Match seconds only
0x2 MMSS Match seconds and minutes only
0x3 HHMMSS Match seconds, minutes, and hours only
0x4 DDHHMMSS Match seconds, minutes, hours, and days only
0x5 MMDDHHMMSS Match seconds, minutes, hours, days, and months only
0x6 YYMMDDHHMMSS Match seconds, minutes, hours, days, months, and years
0x7 - Reserved
SAM C20/C21 Family Data Sheet
RTC – Real-Time Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 363
25. DMAC – Direct Memory Access Controller
25.1 Overview
The Direct Memory Access Controller (DMAC) contains both a Direct Memory Access engine and a
Cyclic Redundancy Check (CRC) engine. The DMAC can transfer data between memories and
peripherals, and thus off-load these tasks from the CPU. It enables high data transfer rates with minimum
CPU intervention, and frees up CPU time. With access to all peripherals, the DMAC can handle
automatic transfer of data between communication modules.
The DMA part of the DMAC has several DMA channels which all can receive different types of transfer
triggers to generate transfer requests from the DMA channels to the arbiter, see also the Block Diagram.
The arbiter will grant one DMA channel at a time to act as the active channel. When an active channel
has been granted, the fetch engine of the DMAC will fetch a transfer descriptor from the SRAM and store
it in the internal memory of the active channel, which will execute the data transmission.
An ongoing data transfer of an active channel can be interrupted by a higher prioritized DMA channel.
The DMAC will write back the updated transfer descriptor from the internal memory of the active channel
to SRAM, and grant the higher prioritized channel to start transfer as the new active channel. Once a
DMA channel is done with its transfer, interrupts and events can be generated optionally.
The DMAC has four bus interfaces:
• The data transfer bus is used for performing the actual DMA transfer.
• The AHB/APB Bridge bus is used when writing and reading the I/O registers of the DMAC.
• The descriptor fetch bus is used by the fetch engine to fetch transfer descriptors before data transfer
can be started or continued.
• The write-back bus is used to write the transfer descriptor back to SRAM.
All buses are AHB master interfaces but the AHB/APB Bridge bus, which is an APB slave interface.
The CRC engine can be used by software to detect an accidental error in the transferred data and to take
corrective action, such as requesting the data to be sent again or simply not using the incorrect data.
25.2 Features
• Data transfer from:
– Peripheral to peripheral
– Peripheral to memory
– Memory to peripheral
– Memory to memory
• Transfer trigger sources
– Software
– Events from Event System
– Dedicated requests from peripherals
• SRAM based transfer descriptors
– Single transfer using one descriptor
– Multi-buffer or circular buffer modes by linking multiple descriptors
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 364
• Up to 12 channels
– Enable 12 independent transfers
– Automatic descriptor fetch for each channel
– Suspend/resume operation support for each channel
• Flexible arbitration scheme
– 4 configurable priority levels for each channel
– Fixed or round-robin priority scheme within each priority level
• From 1 to 256KB data transfer in a single block transfer
• Multiple addressing modes
– Static
– Configurable increment scheme
• Optional interrupt generation
– On block transfer complete
– On error detection
– On channel suspend
• 4 event inputs
– One event input for each of the 4 least significant DMA channels
– Can be selected to trigger normal transfers, periodic transfers or conditional transfers
– Can be selected to suspend or resume channel operation
• 4 event outputs
– One output event for each of the 4 least significant DMA channels
– Selectable generation on AHB, block, or transaction transfer complete
• Error management supported by write-back function
– Dedicated Write-Back memory section for each channel to store ongoing descriptor transfer
• CRC polynomial software selectable to
– CRC-16 (CRC-CCITT)
– CRC-32 (IEEE® 802.3)
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 365
25.3 Block Diagram
Figure 25-1. DMAC Block Diagram
HIGH SPEED
BUS MATRIX
AHB/APB
Bridge
CPU
SRAM
S
S
M
M
Events
Channel 0
Channel 1
Channel n
Arbiter
DMA Channels
MASTER
Active
Channel
CRC
Engine
n
Fetch
Engine
Interrupt /
Events
DMAC
Interrupts
Transfer
Triggers n
Data Transfer
Write-back
Descriptor Fetch
25.4 Signal Description
Not applicable.
25.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
25.5.1 I/O Lines
Not applicable.
25.5.2 Power Management
The DMAC will continue to operate in any sleep mode where the selected source clock is running. The
DMAC’s interrupts can be used to wake up the device from sleep modes. Events connected to the event
system can trigger other operations in the system without exiting sleep modes. On hardware or software
reset, all registers are set to their reset value.
Related Links
19. PM – Power Manager
25.5.3 Clocks
The DMAC bus clock (CLK_DMAC_APB) must be configured and enabled in the Main Clock module
before using the DMAC.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 366
This bus clock (CLK_DMAC_APB) is always synchronous to the module clock (CLK_DMAC_AHB), but
can be divided by a prescaler and may run even when the module clock is turned off.
Related Links
17.6.2.6 Peripheral Clock Masking
25.5.4 DMA
Not applicable.
25.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the DMAC interrupt requires the
interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
25.5.6 Events
The events are connected to the event system.
Related Links
29. EVSYS – Event System
25.5.7 Debug Operation
When the CPU is halted in debug mode the DMAC will halt normal operation. The DMAC can be forced
to continue operation during debugging. Refer to 25.8.6 DBGCTRL for details.
25.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Pending register (INTPEND)
• Channel ID register (CHID)
• Channel Interrupt Flag Status and Clear register (CHINTFLAG)
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
25.5.9 Analog Connections
Not applicable.
25.6 Functional Description
25.6.1 Principle of Operation
The DMAC consists of a DMA module and a CRC module.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 367
25.6.1.1 DMA
The DMAC can transfer data between memories and peripherals without interaction from the CPU. The
data transferred by the DMAC are called transactions, and these transactions can be split into smaller
data transfers. The following figure shows the relationship between the different transfer sizes:
Figure 25-2. DMA Transfer Sizes
DMA transaction
Block transfer
Link Enabled
Burst transfer
Link EnabledLink Enabled
Beat transfer
• Beat transfer: The size of one data transfer bus access, and the size is selected by writing the Beat
Size bit group in the Block Transfer Control register (BTCTRL.BEATSIZE)
• Block transfer: The amount of data one transfer descriptor can transfer, and the amount can range
from 1 to 64k beats. A block transfer can be interrupted.
• Transaction: The DMAC can link several transfer descriptors by having the first descriptor pointing to
the second and so forth, as shown in the figure above. A DMA transaction is the complete transfer of
all blocks within a linked list.
A transfer descriptor describes how a block transfer should be carried out by the DMAC, and it must
remain in SRAM. For further details on the transfer descriptor refer to 25.6.2.3 Transfer Descriptors.
The figure above shows several block transfers linked together, which are called linked descriptors. For
further information about linked descriptors, refer to 25.6.3.1 Linked Descriptors.
A DMA transfer is initiated by an incoming transfer trigger on one of the DMA channels. This trigger can
be configured to be either a software trigger, an event trigger, or one of the dedicated peripheral triggers.
The transfer trigger will result in a DMA transfer request from the specific channel to the arbiter. If there
are several DMA channels with pending transfer requests, the arbiter chooses which channel is granted
access to become the active channel. The DMA channel granted access as the active channel will carry
out the transaction as configured in the transfer descriptor. A current transaction can be interrupted by a
higher prioritized channel, but will resume the block transfer when the according DMA channel is granted
access as the active channel again.
For each beat transfer, an optional output event can be generated. For each block transfer, optional
interrupts and an optional output event can be generated. When a transaction is completed, dependent of
the configuration, the DMA channel will either be suspended or disabled.
25.6.1.2 CRC
The internal CRC engine supports two commonly used CRC polynomials: CRC-16 (CRC-CCITT) and
CRC-32 (IEEE 802.3). It can be used on a selectable DMA channel, or on the I/O interface. Refer to
25.6.3.7 CRC Operation for details.
25.6.2 Basic Operation
25.6.2.1 Initialization
The following DMAC registers are enable-protected, meaning that they can only be written when the
DMAC is disabled (CTRL.DMAENABLE=0):
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 368
• Descriptor Base Memory Address register (BASEADDR)
• Write-Back Memory Base Address register (WRBADDR)
The following DMAC bit is enable-protected, meaning that it can only be written when both the DMAC and
CRC are disabled (CTRL.DMAENABLE=0 and CTRL.CRCENABLE=0):
• Software Reset bit in Control register (CTRL.SWRST)
The following DMA channel register is enable-protected, meaning that it can only be written when the
corresponding DMA channel is disabled (CHCTRLA.ENABLE=0):
• Channel Control B (CHCTRLB) register, except the Command bit (CHCTRLB.CMD) and the Channel
Arbitration Level bit (CHCTRLB.LVL)
The following DMA channel bit is enable-protected, meaning that it can only be written when the
corresponding DMA channel is disabled:
• Channel Software Reset bit in Channel Control A register (CHCTRLA.SWRST)
The following CRC registers are enable-protected, meaning that they can only be written when the CRC
is disabled (CTRL.CRCENABLE=0):
• CRC Control register (CRCCTRL)
• CRC Checksum register (CRCCHKSUM)
Enable-protection is denoted by the "Enable-Protected" property in the register description.
Before the DMAC is enabled it must be configured, as outlined by the following steps:
• The SRAM address of where the descriptor memory section is located must be written to the
Description Base Address (BASEADDR) register
• The SRAM address of where the write-back section should be located must be written to the Write-
Back Memory Base Address (WRBADDR) register
• Priority level x of the arbiter can be enabled by setting the Priority Level x Enable bit in the Control
register (CTRL.LVLENx=1)
Before a DMA channel is enabled, the DMA channel and the corresponding first transfer descriptor must
be configured, as outlined by the following steps:
• DMA channel configurations
– The channel number of the DMA channel to configure must be written to the Channel ID (CHID)
register
– Trigger action must be selected by writing the Trigger Action bit group in the Channel Control B
register (CHCTRLB.TRIGACT)
– Trigger source must be selected by writing the Trigger Source bit group in the Channel Control B
register (CHCTRLB.TRIGSRC)
• Transfer Descriptor
– The size of each access of the data transfer bus must be selected by writing the Beat Size bit
group in the Block Transfer Control register (BTCTRL.BEATSIZE)
– The transfer descriptor must be made valid by writing a one to the Valid bit in the Block Transfer
Control register (BTCTRL.VALID)
– Number of beats in the block transfer must be selected by writing the Block Transfer Count
(BTCNT) register
– Source address for the block transfer must be selected by writing the Block Transfer Source
Address (SRCADDR) register
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 369
– Destination address for the block transfer must be selected by writing the Block Transfer
Destination Address (DSTADDR) register
If CRC calculation is needed, the CRC engine must be configured before it is enabled, as outlined by the
following steps:
• The CRC input source must selected by writing the CRC Input Source bit group in the CRC Control
register (CRCCTRL.CRCSRC)
• The type of CRC calculation must be selected by writing the CRC Polynomial Type bit group in the
CRC Control register (CRCCTRL.CRCPOLY)
• If I/O is selected as input source, the beat size must be selected by writing the CRC Beat Size bit
group in the CRC Control register (CRCCTRL.CRCBEATSIZE)
Related Links
25.8.15 BASEADDR
25.8.18 CHCTRLA
25.8.19 CHCTRLB
25.8.4 CRCCHKSUM
25.8.2 CRCCTRL
25.8.1 CTRL
25.8.16 WRBADDR
25.10.1 BTCTRL
25.10.2 BTCNT
25.10.4 DSTADDR
25.10.3 SRCADDR
25.6.2.2 Enabling, Disabling, and Resetting
The DMAC is enabled by writing the DMA Enable bit in the Control register (CTRL.DMAENABLE) to '1'.
The DMAC is disabled by writing a '0' to CTRL.DMAENABLE.
A DMA channel is enabled by writing the Enable bit in the Channel Control A register
(CHCTRLA.ENABLE) to '1', after writing the corresponding channel id to the Channel ID bit group in the
Channel ID register (CHID.ID). A DMA channel is disabled by writing a '0' to CHCTRLA.ENABLE.
The CRC is enabled by writing a '1' to the CRC Enable bit in the Control register (CTRL.CRCENABLE).
The CRC is disabled by writing a '0' to CTRL.CRCENABLE.
The DMAC is reset by writing a '1' to the Software Reset bit in the Control register (CTRL.SWRST) while
the DMAC and CRC are disabled. All registers in the DMAC except DBGCTRL will be reset to their initial
state.
A DMA channel is reset by writing a '1' to the Software Reset bit in the Channel Control A register
(CHCTRLA.SWRST), after writing the corresponding channel id to the Channel ID bit group in the
Channel ID register (CHID.ID). The channel registers will be reset to their initial state. The corresponding
DMA channel must be disabled in order for the reset to take effect.
25.6.2.3 Transfer Descriptors
Together with the channel configurations the transfer descriptors decides how a block transfer should be
executed. Before a DMA channel is enabled (CHCTRLA.ENABLE is written to one), and receives a
transfer trigger, its first transfer descriptor has to be initialized and valid (BTCTRL.VALID). The first
transfer descriptor describes the first block transfer of a transaction.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 370
All transfer descriptors must reside in SRAM. The addresses stored in the Descriptor Memory Section
Base Address (BASEADDR) and Write-Back Memory Section Base Address (WRBADDR) registers tell
the DMAC where to find the descriptor memory section and the write-back memory section.
The descriptor memory section is where the DMAC expects to find the first transfer descriptors for all
DMA channels. As BASEADDR points only to the first transfer descriptor of channel 0 (see figure below),
all first transfer descriptors must be stored in a contiguous memory section, where the transfer descriptors
must be ordered according to their channel number. For further details on linked descriptors, refer to
25.6.3.1 Linked Descriptors.
The write-back memory section is the section where the DMAC stores the transfer descriptors for the
ongoing block transfers. WRBADDR points to the ongoing transfer descriptor of channel 0. All ongoing
transfer descriptors will be stored in a contiguous memory section where the transfer descriptors are
ordered according to their channel number. The figure below shows an example of linked descriptors on
DMA channel 0. For further details on linked descriptors, refer to 25.6.3.1 Linked Descriptors.
Figure 25-3. Memory Sections
Channel 0 – Descriptor n-1
Channel 0 – Last Descriptor
DESCADDR
DESCADDR
Device Memory Space
BASEADDR Channel 0 – First Descriptor
Channel 1 – First Descriptor
Channel 2 – First Descriptor
Channel n – First Descriptor
Descriptor Section
WRBADDR Channel 0 Ongoing Descriptor
Channel 1 Ongoing Descriptor
Channel 2 Ongoing Descriptor
Channel n Ongoing Descriptor
Write-Back Section
Undefined
Undefined
Undefined
Undefined
Undefined
SRCADDR
DSTADDR
BTCTRL
DESCADDR
BTCNT
SRCADDR
DSTADDR
BTCTRL
DESCADDR
BTCNT
SRCADDR
DSTADDR
BTCTRL
0x00000000
BTCNT
The size of the descriptor and write-back memory sections is dependent on the number of the most
significant enabled DMA channel m, as shown below:
 = 128bits + 1
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 371
For memory optimization, it is recommended to always use the less significant DMA channels if not all
channels are required.
The descriptor and write-back memory sections can either be two separate memory sections, or they can
share memory section (BASEADDR=WRBADDR). The benefit of having them in two separate sections, is
that the same transaction for a channel can be repeated without having to modify the first transfer
descriptor. The benefit of having descriptor memory and write-back memory in the same section is that it
requires less SRAM. In addition, the latency from fetching the first descriptor of a transaction to the first
burst transfer is executed, is reduced.
25.6.2.4 Arbitration
If a DMA channel is enabled and not suspended when it receives a transfer trigger, it will send a transfer
request to the arbiter. When the arbiter receives the transfer request it will include the DMA channel in the
queue of channels having pending transfers, and the corresponding Pending Channel x bit in the Pending
Channels registers (PENDCH.PENDCHx) will be set. Depending on the arbitration scheme, the arbiter
will choose which DMA channel will be the next active channel. The active channel is the DMA channel
being granted access to perform its next burst transfer. When the arbiter has granted a DMA channel
access to the DMAC, the corresponding bit PENDCH.PENDCHx will be cleared. See also the following
figure.
If the upcoming burst transfer is the first for the transfer request, the corresponding Busy Channel x bit in
the Busy Channels register will be set (BUSYCH.BUSYCHx=1), and it will remain '1' for the subsequent
granted burst transfers.
When the channel has performed its granted burst transfer(s) it will be either fed into the queue of
channels with pending transfers, set to be waiting for a new transfer trigger, suspended, or disabled. This
depends on the channel and block transfer configuration. If the DMA channel is fed into the queue of
channels with pending transfers, the corresponding BUSYCH.BUSYCHx will remain '1'. If the DMA
channel is set to wait for a new transfer trigger, suspended, or disabled, the corresponding
BUSYCH.BUSYCHx will be cleared.
If a DMA channel is suspended while it has a pending transfer, it will be removed from the queue of
pending channels, but the corresponding PENDCH.PENDCHx will remain set. When the same DMA
channel is resumed, it will be added to the queue of pending channels again.
If a DMA channel gets disabled (CHCTRLA.ENABLE=0) while it has a pending transfer, it will be removed
from the queue of pending channels, and the corresponding PENDCH.PENDCHx will be cleared.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 372
Figure 25-4. Arbiter Overview
Channel 0
Channel N
Active
Channel
Priority
decoder
Active.LVLEXx
PRICTRLx.LVLPRI
Arbiter
CTRL.LVLENx
Burst Done
Transfer Request
Channel Number
Level Enable
Channel Burst Done
Channel Priority Level
Channel Pending
Channel Suspend
Channel Burst Done
Channel Priority Level
Channel Pending
Channel Suspend
Priority Levels
When a channel level is pending or the channel is transferring data, the corresponding Level Executing
bit is set in the Active Channel and Levels register (ACTIVE.LVLEXx).
Each DMA channel supports a 4-level priority scheme. The priority level for a channel is configured by
writing to the Channel Arbitration Level bit group in the Channel Control B register (CHCTRLB.LVL). As
long as all priority levels are enabled, a channel with a higher priority level number will have priority over
a channel with a lower priority level number. Each priority level x is enabled by setting the corresponding
Priority Level x Enable bit in the Control register (CTRL.LVLENx=1).
Within each priority level the DMAC's arbiter can be configured to prioritize statically or dynamically:
Static Arbitration within a priority level is selected by writing a '0' to the Level x Round-Robin Scheduling
Enable bit in the Priority Control 0 register (PRICTRL0.RRLVLENx).
When static arbitration is selected, the arbiter will prioritize a low channel number over a high channel
number as shown in the figure below. When using the static arbitration there is a risk of high channel
numbers never being granted access as the active channel. This can be avoided using a dynamic
arbitration scheme.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 373
Figure 25-5. Static Priority Scheduling
Highest Channel
Lowest Channel Highest Priority
Lowest Priority
Channel N
Channel 0
Channel x+1
Channel x
.
.
.
.
.
.
Dynamic Arbitration within a priority level is selected by writing a '1' to PRICTRL0.RRLVLENx.
The dynamic arbitration scheme in the DMAC is round-robin. With the round-robin scheme, the channel
number of the last channel being granted access will have the lowest priority the next time the arbiter has
to grant access to a channel within the same priority level, as shown in Figure 25-6. The channel number
of the last channel being granted access as the active channel is stored in the Level x Channel Priority
Number bit group in the Priority Control 0 register (PRICTRL0.LVLPRIx) for the corresponding priority
level.
Figure 25-6. Dynamic (Round-Robin) Priority Scheduling
Channel N Channel N
Channel 0
Channel x
Channel x+1
Channel x last acknowledge request Channel (x+1) last acknowledge request
Channel 0
Channel x
Channel x+1
Channel x+2
Lowest Priority
Highest Priority
Highest Priority
Lowest Priority
.
.
.
.
.
.
25.6.2.5 Data Transmission
Before the DMAC can perform a data transmission, a DMA channel has to be configured and enabled, its
corresponding transfer descriptor has to be initialized, and the arbiter has to grant the DMA channel
access as the active channel.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 374
Once the arbiter has granted a DMA channel access as the active channel (refer to DMA Block Diagram
section) the transfer descriptor for the DMA channel will be fetched from SRAM using the fetch bus, and
stored in the internal memory for the active channel. For a new block transfer, the transfer descriptor will
be fetched from the descriptor memory section (BASEADDR); For an ongoing block transfer, the
descriptor will be fetched from the write-back memory section (WRBADDR). By using the data transfer
bus, the DMAC will read the data from the current source address and write it to the current destination
address. For further details on how the current source and destination addresses are calculated, refer to
the section on Addressing.
The arbitration procedure is performed after each burst transfer. If the current DMA channel is granted
access again, the block transfer counter (BTCNT) of the internal transfer descriptor will be decremented
by the number of beats in a burst transfer, the optional output event Beat will be generated if configured
and enabled, and the active channel will perform a new burst transfer. If a different DMA channel than the
current active channel is granted access, the block transfer counter value will be written to the write-back
section before the transfer descriptor of the newly granted DMA channel is fetched into the internal
memory of the active channel.
When a block transfer has come to its end (BTCNT is zero), the Valid bit in the Block Transfer Control
register will be cleared (BTCTRL.VALID=0) before the entire transfer descriptor is written to the write-
back memory. The optional interrupts, Channel Transfer Complete and Channel Suspend, and the
optional output event Block, will be generated if configured and enabled. After the last block transfer in a
transaction, the Next Descriptor Address register (DESCADDR) will hold the value 0x00000000, and the
DMA channel will either be suspended or disabled, depending on the configuration in the Block Action bit
group in the Block Transfer Control register (BTCTRL.BLOCKACT). If the transaction has further block
transfers pending, DESCADDR will hold the SRAM address to the next transfer descriptor to be fetched.
The DMAC will fetch the next descriptor into the internal memory of the active channel and write its
content to the write-back section for the channel, before the arbiter gets to choose the next active
channel.
25.6.2.6 Transfer Triggers and Actions
A DMA transfer through a DMA channel can be started only when a DMA transfer request is detected,
and the DMA channel has been granted access to the DMA. A transfer request can be triggered from
software, from a peripheral, or from an event. There are dedicated Trigger Source selections for each
DMA Channel Control B (CHCTRLB.TRIGSRC).
The trigger actions are available in the Trigger Action bit group in the Channel Control B register
(CHCTRLB.TRIGACT). By default, a trigger generates a request for a block transfer operation. If a single
descriptor is defined for a channel, the channel is automatically disabled when a block transfer has been
completed. If a list of linked descriptors is defined for a channel, the channel is automatically disabled
when the last descriptor in the list is executed. If the list still has descriptors to execute, the channel will
be waiting for the next block transfer trigger. When enabled again, the channel will wait for the next block
transfer trigger. The trigger actions can also be configured to generate a request for a beat transfer
(CHCTRLB.TRIGACT=0x2) or transaction transfer (CHCTRLB.TRIGACT=0x3) instead of a block transfer
(CHCTRLB.TRIGACT=0x0).
Figure 25-7 shows an example where triggers are used with two linked block descriptors.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 375
Figure 25-7. Trigger Action and Transfers
CHENn
Trigger
PENDCHn
BUSYCHn
Data Transfer
CHENn
Trigger
PENDCHn
BUSYCHn
Data Transfer
CHENn
Trigger
PENDCHn
BUSYCHn
Data Transfer
Block Transfer
Block Transfer
Block Transfer
Block Transfer
Block Transfer
Block Transfer
Trigger Lost
Trigger Lost
Trigger Lost
Transaction Trigger Action
Block Trigger Action
Beat Trigger Action
BEAT
BEAT BEAT BEAT BEATBEAT
BEAT
BEAT BEAT BEAT BEATBEAT
BEAT
BEAT BEAT BEAT BEATBEAT
If the trigger source generates a transfer request for a channel during an ongoing transfer, the new
transfer request will be kept pending (CHSTATUS.PEND=1), and the new transfer can start after the
ongoing one is done. Only one pending transfer can be kept per channel. If the trigger source generates
more transfer requests while one is already pending, the additional ones will be lost. All channels pending
status flags are also available in the Pending Channels register (PENDCH).
When the transfer starts, the corresponding Channel Busy status flag is set in Channel Status register
(CHSTATUS.BUSY). When the trigger action is complete, the Channel Busy status flag is cleared. All
channel busy status flags are also available in the Busy Channels register (BUSYCH) in DMAC.
25.6.2.7 Addressing
Each block transfer needs to have both a source address and a destination address defined. The source
address is set by writing the Transfer Source Address (SRCADDR) register, the destination address is set
by writing the Transfer Destination Address (SRCADDR) register.
The addressing of this DMAC module can be static or incremental, for either source or destination of a
block transfer, or both.
Incrementation for the source address of a block transfer is enabled by writing the Source Address
Incrementation Enable bit in the Block Transfer Control register (BTCTRL.SRCINC=1). The step size of
the incrementation is configurable and can be chosen by writing the Step Selection bit in the Block
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 376
Transfer Control register (BTCTRL.STEPSEL=1) and writing the desired step size in the Address
Increment Step Size bit group in the Block Transfer Control register (BTCTRL.STEPSIZE). If
BTCTRL.STEPSEL=0, the step size for the source incrementation will be the size of one beat.
When source address incrementation is configured (BTCTRL.SRCINC=1), SRCADDR is calculated as
follows:
If BTCTRL.STEPSEL=1:
SRCADDR = SRCADDR +  + 1 2STEPSIZE
If BTCTRL.STEPSEL=0:
SRCADDR = SRCADDR +  + 1
• SRCADDRSTART is the source address of the first beat transfer in the block transfer
• BTCNT is the initial number of beats remaining in the block transfer
• BEATSIZE is the configured number of bytes in a beat
• STEPSIZE is the configured number of beats for each incrementation
The following figure shows an example where DMA channel 0 is configured to increment the source
address by one beat after each beat transfer (BTCTRL.SRCINC=1), and DMA channel 1 is configured to
increment the source address by two beats (BTCTRL.SRCINC=1, BTCTRL.STEPSEL=1, and
BTCTRL.STEPSIZE=0x1). As the destination address for both channels are peripherals, destination
incrementation is disabled (BTCTRL.DSTINC=0).
Figure 25-8. Source Address Increment
SRC Data Buffer
a
b
c
d
e
f
Incrementation for the destination address of a block transfer is enabled by setting the Destination
Address Incrementation Enable bit in the Block Transfer Control register (BTCTRL.DSTINC=1). The step
size of the incrementation is configurable by clearing BTCTRL.STEPSEL=0 and writing
BTCTRL.STEPSIZE to the desired step size. If BTCTRL.STEPSEL=1, the step size for the destination
incrementation will be the size of one beat.
When the destination address incrementation is configured (BTCTRL.DSTINC=1), DSTADDR must be
set and calculated as follows:
 = + • + 1 • 2 where BTCTRL.STEPSEL is zero
 = + • + 1 where BTCTRL.STEPSEL is one
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 377
• DSTADDRSTART is the destination address of the first beat transfer in the block transfer
• BTCNT is the initial number of beats remaining in the block transfer
• BEATSIZE is the configured number of bytes in a beat
• STEPSIZE is the configured number of beats for each incrementation
The followiong figure shows an example where DMA channel 0 is configured to increment destination
address by one beat (BTCTRL.DSTINC=1) and DMA channel 1 is configured to increment destination
address by two beats (BTCTRL.DSTINC=1, BTCTRL.STEPSEL=0, and BTCTRL.STEPSIZE=0x1). As
the source address for both channels are peripherals, source incrementation is disabled
(BTCTRL.SRCINC=0).
Figure 25-9. Destination Address Increment
DST Data Buffer
a
b
c
d
25.6.2.8 Error Handling
If a bus error is received from an AHB slave during a DMA data transfer, the corresponding active
channel is disabled and the corresponding Channel Transfer Error Interrupt flag in the Channel Interrupt
Status and Clear register (CHINTFLAG.TERR) is set. If enabled, the optional transfer error interrupt is
generated. The transfer counter will not be decremented and its current value is written-back in the write-
back memory section before the channel is disabled.
When the DMAC fetches an invalid descriptor (BTCTRL.VALID=0) or when the channel is resumed and
the DMA fetches the next descriptor with null address (DESCADDR=0x00000000), the corresponding
channel operation is suspended, the Channel Suspend Interrupt Flag in the Channel Interrupt Flag Status
and Clear register (CHINTFLAG.SUSP) is set, and the Channel Fetch Error bit in the Channel Status
register (CHSTATUS.FERR) is set. If enabled, the optional suspend interrupt is generated.
25.6.3 Additional Features
25.6.3.1 Linked Descriptors
A transaction can consist of either a single block transfer or of several block transfers. When a
transaction consists of several block transfers it is done with the help of linked descriptors.
Figure 25-3 illustrates how linked descriptors work. When the first block transfer is completed on DMA
channel 0, the DMAC fetches the next transfer descriptor, which is pointed to by the value stored in the
Next Descriptor Address (DESCADDR) register of the first transfer descriptor. Fetching the next transfer
descriptor (DESCADDR) is continued until the last transfer descriptor. When the block transfer for the last
transfer descriptor is executed and DESCADDR=0x00000000, the transaction is terminated. For further
details on how the next descriptor is fetched from SRAM, refer to section 25.6.2.5 Data Transmission.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 378
25.6.3.1.1 Adding Descriptor to the End of a List
To add a new descriptor at the end of the descriptor list, create the descriptor in SRAM, with
DESCADDR=0x00000000 indicating that it is the new last descriptor in the list, and modify the
DESCADDR value of the current last descriptor to the address of the newly created descriptor.
25.6.3.1.2 Modifying a Descriptor in a List
In order to add descriptors to a linked list, the following actions must be performed:
1. Enable the Suspend interrupt for the DMA channel.
2. Enable the DMA channel.
3. Reserve memory space in SRAM to configure a new descriptor.
4. Configure the new descriptor:
– Set the next descriptor address (DESCADDR)
– Set the destination address (DSTADDR)
– Set the source address (SRCADDR)
– Configure the block transfer control (BTCTRL) including
• Optionally enable the Suspend block action
• Set the descriptor VALID bit
5. Clear the VALID bit for the existing list and for the descriptor which has to be updated.
6. Read DESCADDR from the Write-Back memory.
– If the DMA has not already fetched the descriptor which requires changes (i.e., DESCADDR is
wrong):
• Update the DESCADDR location of the descriptor from the List
• Optionally clear the Suspend block action
• Set the descriptor VALID bit to '1'
• Optionally enable the Resume software command
– If the DMA is executing the same descriptor as the one which requires changes:
• Set the Channel Suspend software command and wait for the Suspend interrupt
• Update the next descriptor address (DESCRADDR) in the write-back memory
• Clear the interrupt sources and set the Resume software command
• Update the DESCADDR location of the descriptor from the List
• Optionally clear the Suspend block action
• Set the descriptor VALID bit to '1'
7. Go to step 4 if needed.
25.6.3.1.3 Adding a Descriptor Between Existing Descriptors
To insert a new descriptor 'C' between two existing descriptors ('A' and 'B'), the descriptor currently
executed by the DMA must be identified.
1. If DMA is executing descriptor B, descriptor C cannot be inserted.
2. If DMA has not started to execute descriptor A, follow the steps:
2.1. Set the descriptor A VALID bit to '0'.
2.2. Set the DESCADDR value of descriptor A to point to descriptor C instead of descriptor B.
2.3. Set the DESCADDR value of descriptor C to point to descriptor B.
2.4. Set the descriptor A VALID bit to '1'.
3. If DMA is executing descriptor A:
3.1. Apply the software suspend command to the channel and
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DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 379
3.2. Perform steps 2.1 through 2.4.
3.3. Apply the software resume command to the channel.
25.6.3.2 Channel Suspend
The channel operation can be suspended at any time by software by writing a '1' to the Suspend
command in the Command bit field of Channel Control B register (CHCTRLB.CMD). After the ongoing
burst transfer is completed, the channel operation is suspended and the suspend command is
automatically cleared.
When suspended, the Channel Suspend Interrupt flag in the Channel Interrupt Status and Clear register
is set (CHINTFLAG.SUSP=1) and the optional suspend interrupt is generated.
By configuring the block action to suspend by writing Block Action bit group in the Block Transfer Control
register (BTCTRL.BLOCKACT is 0x2 or 0x3), the DMA channel will be suspended after it has completed
a block transfer. The DMA channel will be kept enabled and will be able to receive transfer triggers, but it
will be removed from the arbitration scheme.
If an invalid transfer descriptor (BTCTRL.VALID=0) is fetched from SRAM, the DMA channel will be
suspended, and the Channel Fetch Error bit in the Channel Status register(CHASTATUS.FERR) will be
set.
Note:  Only enabled DMA channels can be suspended. If a channel is disabled when it is attempted to
be suspended, the internal suspend command will be ignored.
For more details on transfer descriptors, refer to section 25.6.2.3 Transfer Descriptors.
Related Links
25.8.19 CHCTRLB
25.8.22 CHINTFLAG
25.10.1 BTCTRL
25.6.3.3 Channel Resume and Next Suspend Skip
A channel operation can be resumed by software by setting the Resume command in the Command bit
field of the Channel Control B register (CHCTRLB.CMD). If the channel is already suspended, the
channel operation resumes from where it previously stopped when the Resume command is detected.
When the Resume command is issued before the channel is suspended, the next suspend action is
skipped and the channel continues the normal operation.
Figure 25-10. Channel Suspend/Resume Operation
CHENn
Memory Descriptor
Transfer
Resume Command
Descriptor 0
(suspend disabled)
Fetch Block
Transfer 0
Descriptor 1
(suspend enabled)
Block
Transfer 1
Suspend skipped
Descriptor 2
(suspend enabled)
Block
Transfer 2
Channel
suspended
Descriptor 3
(last)
Block
Transfer 3
Related Links
25.8.19 CHCTRLB
25.6.3.4 Event Input Actions
The event input actions are available only on the least significant DMA channels. For details on channels
with event input support, refer to the in the Event system documentation.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 380
Before using event input actions, the event controller must be configured first according to the following
table, and the Channel Event Input Enable bit in the Channel Control B register (CHCTRLB.EVIE) must
be written to '1'. Refer also to 25.6.6 Events.
Table 25-1. Event Input Action
Action CHCTRLB.EVACT CHCTRLB.TRGSRC
None NOACT -
Normal Transfer TRIG DISABLE
Conditional Transfer on Strobe TRIG any peripheral
Conditional Transfer CTRIG
Conditional Block Transfer CBLOCK
Channel Suspend SUSPEND
Channel Resume RESUME
Skip Next Block Suspend SSKIP
Normal Transfer
The event input is used to trigger a beat or burst transfer on peripherals.
The event is acknowledged as soon as the event is received. When received, both the Channel Pending
status bit in the Channel Status register (CHSTATUS.PEND) and the corresponding Channel n bit in the
Pending Channels register (25.8.13 PENDCH.PENDCHn) are set. If the event is received while the
channel is pending, the event trigger is lost.
The figure below shows an example where beat transfers are enabled by internal events.
Figure 25-11. Beat Event Trigger Action
CHENn
Peripheral Trigger
Event
PENDCHn
BUSYCHn
Data Transfer
Trigger Lost
Block Transfer
BEAT BEAT BEAT BEAT BEAT BEAT
Block Transfer
Conditional Transfer on Strobe
The event input is used to trigger a transfer on peripherals with pending transfer requests. This event
action is intended to be used with peripheral triggers, e.g. for timed communication protocols or periodic
transfers between peripherals: only when the peripheral trigger coincides with the occurrence of a
(possibly cyclic) event the transfer is issued.
The event is acknowledged as soon as the event is received. The peripheral trigger request is stored
internally when the previous trigger action is completed (i.e. the channel is not pending) and when an
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 381
active event is received. If the peripheral trigger is active, the DMA will wait for an event before the
peripheral trigger is internally registered. When both event and peripheral transfer trigger are active, both
CHSTATUS.PEND and 25.8.13 PENDCH.PENDCHn are set. A software trigger will now trigger a
transfer.
The figure below shows an example where the peripheral beat transfer is started by a conditional strobe
event action.
Figure 25-12. Periodic Event with Beat Peripheral Triggers
Event
Peripheral Trigger
PENDCHn
Data Transfer
Trigger Lost Trigger Lost
Block Transfer
BEAT
Conditional Transfer
The event input is used to trigger a conditional transfer on peripherals with pending transfer requests. For
example, this type of event can be used for peripheral-to-peripheral transfers, where one peripheral is the
source of event and the second peripheral is the source of the trigger.
Each peripheral trigger is stored internally when the event is received. When the peripheral trigger is
stored internally, the Channel Pending status bit is set (CHSTATUS.PEND), the respective Pending
Channel n Bit in the Pending Channels register is set (25.8.13 PENDCH.PENDCHn), and the event is
acknowledged. A software trigger will now trigger a transfer.
The figure below shows an example where conditional event is enabled with peripheral beat trigger
requests.
Figure 25-13. Conditional Event with Beat Peripheral Triggers
Event
Peripheral Trigger
PENDCHn
Data Transfer
Block Transfer
BEAT BEAT
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
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Conditional Block Transfer
The event input is used to trigger a conditional block transfer on peripherals.
Before starting transfers within a block, an event must be received. When received, the event is
acknowledged when the block transfer is completed. A software trigger will trigger a transfer.
The figure below shows an example where conditional event block transfer is started with peripheral beat
trigger requests.
Figure 25-14. Conditional Block Transfer with Beat Peripheral Triggers
BEAT BEAT
Block Transfer
BEAT BEAT
Block Transfer
Data Transfer
Peripheral Trigger
Event
PENDCHn
Channel Suspend
The event input is used to suspend an ongoing channel operation. The event is acknowledged when the
current AHB access is completed. For further details on Channel Suspend, refer to 25.6.3.2 Channel
Suspend.
Channel Resume
The event input is used to resume a suspended channel operation. The event is acknowledged as soon
as the event is received and the Channel Suspend Interrupt Flag (CHINTFLAG.SUSP) is cleared. For
further details refer to 25.6.3.2 Channel Suspend.
Skip Next Block Suspend
This event can be used to skip the next block suspend action. If the channel is suspended before the
event rises, the channel operation is resumed and the event is acknowledged. If the event rises before a
suspend block action is detected, the event is kept until the next block suspend detection. When the block
transfer is completed, the channel continues the operation (not suspended) and the event is
acknowledged.
25.6.3.5 Event Output Selection
Event output selection is available only for the least significant DMA channels. The pulse width of an
event output from a channel is one AHB clock cycle.
The output of channel events is enabled by writing a '1' to the Channel Event Output Enable bit in the
Control B register (CHCTRLB.EVOE). The event output cause is selected by writing to the Event Output
Selection bits in the Block Transfer Control register (BTCTRL.EVOSEL). It is possible to generate events
after each block transfer (BTCTRL.EVOSEL=0x1) or beat transfer (BTCTRL.EVOSEL=0x3). To enable an
event being generated when a transaction is complete, the block event selection must be set in the last
transfer descriptor only.
Figure 25-15 shows an example where the event output generation is enabled in the first block transfer,
and disabled in the second block.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 383
Figure 25-15. Event Output Generation
Beat Event Output
Data Transfer
Event Output
Data Transfer
Event Output
Block Transfer
BEAT
Block Event Output
Block Transfer
Block Transfer
Block Transfer
BEAT BEAT
BEAT
BEAT BEAT BEAT BEAT
Related Links
25.8.19 CHCTRLB
25.10.1 BTCTRL
25.6.3.6 Aborting Transfers
Transfers on any channel can be aborted gracefully by software by disabling the corresponding DMA
channel. It is also possible to abort all ongoing or pending transfers by disabling the DMAC.
When a DMA channel disable request or DMAC disable request is detected:
• Ongoing transfers of the active channel will be disabled when the ongoing beat transfer is completed
and the write-back memory section is updated. This prevents transfer corruption before the channel
is disabled.
• All other enabled channels will be disabled in the next clock cycle.
The corresponding Channel Enable bit in the Channel Control A register is cleared
(CHCTRLA.ENABLE=0) when the channel is disabled.
The corresponding DMAC Enable bit in the Control register is cleared (CTRL.DMAENABLE=0) when the
entire DMAC module is disabled.
25.6.3.7 CRC Operation
A cyclic redundancy check (CRC) is an error detection technique used to find errors in data. It is
commonly used to determine whether the data during a transmission, or data present in data and
program memories has been corrupted or not. A CRC takes a data stream or a block of data as input and
generates a 16- or 32-bit output that can be appended to the data and used as a checksum.
When the data is received, the device or application repeats the calculation: If the new CRC result does
not match the one calculated earlier, the block contains a data error. The application will then detect this
and may take a corrective action, such as requesting the data to be sent again or simply not using the
incorrect data.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 384
The CRC engine in DMAC supports two commonly used CRC polynomials: CRC-16 (CRC-CCITT) and
CRC-32 (IEEE 802.3). Typically, applying CRC-n (CRC-16 or CRC-32) to a data block of arbitrary length
will detect any single alteration that is ≤n bits in length, and will detect the fraction 1-2-n of all longer error
bursts.
• CRC-16:
– Polynomial: x16+ x12+ x5+ 1
– Hex value: 0x1021
• CRC-32:
– Polynomial: x32+x26+ x23+ x22+x16+ x12+ x11+ x10+ x8+ x7+ x5+ x4+ x2+ x + 1
– Hex value: 0x04C11DB7
The data source for the CRC engine can either be one of the DMA channels or the APB bus interface,
and must be selected by writing to the CRC Input Source bits in the CRC Control register
(CRCCTRL.CRCSRC). The CRC engine then takes data input from the selected source and generates a
checksum based on these data. The checksum is available in the CRC Checksum register
(CRCCHKSUM). When CRC-32 polynomial is used, the final checksum read is bit reversed and
complemented, as shown in Figure 25-16.
The CRC polynomial is selected by writing to the CRC Polynomial Type bit in the CRC Control register
(CRCCTRL.CRCPOLY), the default is CRC-16. The CRC engine operates on byte only. When the DMA is
used as data source for the CRC engine, the DMA channel beat size setting will be used. When used
with APB bus interface, the application must select the CRC Beat Size bit field of CRC Control register
(CRCCTRL.CRCBEATSIZE). 8-, 16-, or 32-bit bus transfer access type is supported. The corresponding
number of bytes will be written in the CRCDATAIN register and the CRC engine will operate on the input
data in a byte by byte manner.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 385
Figure 25-16. CRC Generator Block Diagram
168 8 32
Checksum
read
crc32
CRCCTRL
CHECKSUM
bit-reverse +
complement
CRC-16 CRC-32
DMAC
Channels
CRCDATAIN
CRC on
DMA
data
CRC-16 or CRC-32 calculations can be performed on data passing through any DMA
channel. Once a DMA channel is selected as the source, the CRC engine will continuously
generate the CRC on the data passing through the DMA channel. The checksum is available
for readout once the DMA transaction is completed or aborted. A CRC can also be generated
on SRAM, Flash, or I/O memory by passing these data through a DMA channel. If the latter is
done, the destination register for the DMA data can be the data input (CRCDATAIN) register in
the CRC engine.
CRC using the I/O
interface
Before using the CRC engine with the I/O interface, the application must set the
CRC Beat Size bits in the CRC Control register (CRCCTRL.CRCBEATSIZE).
8/16/32-bit bus transfer type can be selected.
CRC can be performed on any data by loading them into the CRC engine using the CPU and writing the
data to the CRCDATAIN register. Using this method, an arbitrary number of bytes can be written to the
register by the CPU, and CRC is done continuously for each byte. This means if a 32-bit data is written to
the CRCDATAIN register the CRC engine takes four cycles to calculate the CRC. The CRC complete is
signaled by a set CRCBUSY bit in the CRCSTATUS register. New data can be written only when
CRCBUSY flag is not set.
25.6.4 DMA Operation
Not applicable.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 386
25.6.5 Interrupts
The DMAC channels have the following interrupt sources:
• Transfer Complete (TCMPL): Indicates that a block transfer is completed on the corresponding
channel. Refer to 25.6.2.5 Data Transmission for details.
• Transfer Error (TERR): Indicates that a bus error has occurred during a burst transfer, or that an
invalid descriptor has been fetched. Refer to 25.6.2.8 Error Handling for details.
• Channel Suspend (SUSP): Indicates that the corresponding channel has been suspended. Refer to
25.6.3.2 Channel Suspend and 25.6.2.5 Data Transmission for details.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Channel Interrupt
Flag Status and Clear (CHINTFLAG) register is set when the interrupt condition occurs. Each interrupt
can be individually enabled by setting the corresponding bit in the Channel Interrupt Enable Set register
(CHINTENSET=1), and disabled by setting the corresponding bit in the Channel Interrupt Enable Clear
register (CHINTENCLR=1).
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, the DMAC
is reset or the corresponding DMA channel is reset. See CHINTFLAG for details on how to clear interrupt
flags. All interrupt requests are ORed together on system level to generate one combined interrupt
request to the NVIC.
The user must read the Channel Interrupt Status (INTSTATUS) register to identify the channels with
pending interrupts and must read the Channel Interrupt Flag Status and Clear (CHINTFLAG) register to
determine which interrupt condition is present for the corresponding channel. It is also possible to read
the Interrupt Pending register (INTPEND), which provides the lowest channel number with pending
interrupt and the respective interrupt flags.
Note:  Interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
25.6.6 Events
The DMAC can generate the following output events:
• Channel (CH): Generated when a block transfer for a given channel has been completed, or when a
beat transfer within a block transfer for a given channel has been completed. Refer to Event Output
Selection for details.
Setting the Channel Event Output Enable bit (CHEVCTRLx.EVOE = 1) enables the corresponding output
event configured in the Event Output Selection bit group in the Block Transfer Control register
(BTCTRL.EVOSEL). Clearing CHEVCTRLx.EVOE = 0 disables the corresponding output event.
The DMAC can take the following actions on an input event:
• Transfer and Periodic Transfer Trigger (TRIG): normal transfer or periodic transfers on peripherals
are enabled
• Conditional Transfer Trigger (CTRIG): conditional transfers on peripherals are enabled
• Conditional Block Transfer Trigger (CBLOCK): conditional block transfers on peripherals are enabled
• Channel Suspend Operation (SUSPEND): suspend a channel operation
• Channel Resume Operation (RESUME): resume a suspended channel operation
• Skip Next Block Suspend Action (SSKIP): skip the next block suspend transfer condition
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 387
• Increase Priority (INCPRI): increase channel priority
Setting the Channel Event Input Enable bit (CHEVCTRLx.EVIE = 1) enables the corresponding action on
input event. Clearing this bit disables the corresponding action on input event. Note that several actions
can be enabled for incoming events. If several events are connected to the peripheral, any enabled action
will be taken for any of the incoming events. For further details on event input actions, refer to Event Input
Actions.
Note:  Event input and outputs are not available for every channel. Refer to the Features section for
more information.
Related Links
29. EVSYS – Event System
25.8.19 CHCTRLB
25.10.1 BTCTRL
25.6.7 Sleep Mode Operation
Each DMA channel can be configured to operate in any sleep mode. To be able to run in standby, the
RUNSTDBY bit in Channel Control A register (CHCTRLA.RUNSTDBY) must be written to '1'. The DMAC
can wake up the device using interrupts from any sleep mode or perform actions through the Event
System.
For channels with CHCTRLA.RUNSTDBY = 0, it is up to software to stop DMA transfers on these
channels and wait for completion before going to standby mode using the following sequence:
1. Suspend the DMAC channels for which CHCTRLA.RUNSTDBY = 0.
2. Check the SYNCBUSY bits of registers accessed by the DMAC channels being suspended.
3. Go to sleep.
4. When the device wakes up, resume the suspended channels.
Note:  In Stand-by Sleep mode, the DMAC can only access RAM when it is not back biased
(PM.STDBYCFG.BBIASxx = 0x0)
25.6.8 Synchronization
Not applicable.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 388
25.7 Register Summary
Offset Name Bit Pos.
0x00 CTRL
7:0 CRCENABLE DMAENABLE SWRST
15:8 LVLENx3 LVLENx2 LVLENx1 LVLENx0
0x02 CRCCTRL
7:0 CRCPOLY[1:0] CRCBEATSIZE[1:0]
15:8 CRCSRC[5:0]
0x04 CRCDATAIN
7:0 CRCDATAIN[7:0]
15:8 CRCDATAIN[15:8]
23:16 CRCDATAIN[23:16]
31:24 CRCDATAIN[31:24]
0x08 CRCCHKSUM
7:0 CRCCHKSUM[7:0]
15:8 CRCCHKSUM[15:8]
23:16 CRCCHKSUM[23:16]
31:24 CRCCHKSUM[31:24]
0x0C CRCSTATUS 7:0 CRCZERO CRCBUSY
0x0D DBGCTRL 7:0 DBGRUN
0x0E QOSCTRL 7:0 DQOS[1:0] FQOS[1:0] WRBQOS[1:0]
0x0F Reserved
0x10 SWTRIGCTRL
7:0 SWTRIGn[7:0]
15:8 SWTRIGn[11:8]
23:16
31:24
0x14 PRICTRL0
7:0 RRLVLEN0 LVLPRI0[3:0]
15:8 RRLVLEN1 LVLPRI1[3:0]
23:16 RRLVLEN2 LVLPRI2[3:0]
31:24 RRLVLEN3 LVLPRI3[3:0]
0x18
...
0x1F
Reserved
0x20 INTPEND
7:0 ID[3:0]
15:8 PEND BUSY FERR SUSP TCMPL TERR
0x22
...
0x23
Reserved
0x24 INTSTATUS
7:0 CHINTn[7:0]
15:8 CHINTn[11:8]
23:16
31:24
0x28 BUSYCH
7:0 BUSYCHn[7:0]
15:8 BUSYCHn[11:8]
23:16
31:24
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 389
...........continued
Offset Name Bit Pos.
0x2C PENDCH
7:0 PENDCH7 PENDCH6 PENDCH5 PENDCH4 PENDCH3 PENDCH2 PENDCH1 PENDCH0
15:8 PENDCH11 PENDCH10 PENDCH9 PENDCH8
23:16
31:24
0x30 ACTIVE
7:0 LVLEXx LVLEXx LVLEXx LVLEXx
15:8 ABUSY ID[4:0]
23:16 BTCNT[7:0]
31:24 BTCNT[15:8]
0x34 BASEADDR
7:0
15:8
23:16
31:24
0x38 WRBADDR
7:0
15:8
23:16
31:24
0x3C
...
0x3E
Reserved
0x3F CHID 7:0 ID[3:0]
0x40 CHCTRLA 7:0 RUNSTDBY ENABLE SWRST
0x41
...
0x43
Reserved
0x44 CHCTRLB
7:0 LVL[1:0] EVOE EVIE EVACT[2:0]
15:8 TRIGSRC[5:0]
23:16 TRIGACT[1:0]
31:24 CMD[1:0]
0x48
...
0x4B
Reserved
0x4C CHINTENCLR 7:0 SUSP TCMPL TERR
0x4D CHINTENSET 7:0 SUSP TCMPL TERR
0x4E CHINTFLAG 7:0 SUSP TCMPL TERR
0x4F CHSTATUS 7:0 FERR BUSY PEND
25.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 25.5.8 Register Access Protection.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 390
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 391
25.8.1 Control
Name:  CTRL
Offset:  0x00
Reset:  0x00X0
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
LVLENx3 LVLENx2 LVLENx1 LVLENx0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CRCENABLE DMAENABLE SWRST
Access R/W R/W R/W
Reset 0 0 0
Bits 8, 9, 10, 11 – LVLENx Priority Level x Enable
When this bit is set, all requests with the corresponding level will be fed into the arbiter block. When
cleared, all requests with the corresponding level will be ignored.
For details on arbitration schemes, refer to the Arbitration section.
These bits are not enable-protected.
Value Description
0Transfer requests for Priority level x will not be handled.
1Transfer requests for Priority level x will be handled.
Bit 2 – CRCENABLE CRC Enable
Writing a '0' to this bit will disable the CRC calculation when the CRC Status Busy flag is cleared
(CRCSTATUS. CRCBUSY). The bit is zero when the CRC is disabled.
Writing a '1' to this bit will enable the CRC calculation.
Value Description
0The CRC calculation is disabled.
1The CRC calculation is enabled.
Bit 1 – DMAENABLE DMA Enable
Setting this bit will enable the DMA module.
Writing a '0' to this bit will disable the DMA module. When writing a '0' during an ongoing transfer, the bit
will not be cleared until the internal data transfer buffer is empty and the DMA transfer is aborted. The
internal data transfer buffer will be empty once the ongoing burst transfer is completed.
This bit is not enable-protected.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit when both the DMAC and the CRC module are disabled (DMAENABLE and
CRCENABLE are '0') resets all registers in the DMAC (except DBGCTRL) to their initial state. If either the
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 392
DMAC or CRC module is enabled, the Reset request will be ignored and the DMAC will return an access
error.
Value Description
0There is no Reset operation ongoing.
1A Reset operation is ongoing.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 393
25.8.2 CRC Control
Name:  CRCCTRL
Offset:  0x02
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
CRCSRC[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CRCPOLY[1:0] CRCBEATSIZE[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 13:8 – CRCSRC[5:0] CRC Input Source
These bits select the input source for generating the CRC, as shown in the table below. The selected
source is locked until either the CRC generation is completed or the CRC module is disabled. This means
the CRCSRC cannot be modified when the CRC operation is ongoing. The lock is signaled by the
CRCBUSY status bit. CRC generation complete is generated and signaled from the selected source
when used with the DMA channel.
Value Name Description
0x00 NOACT No action
0x01 IO I/O interface
0x02-0x
1F
- Reserved
0x20 CHN DMA channel 0
0x21 CHN DMA channel 1
0x22 CHN DMA channel 2
0x23 CHN DMA channel 3
0x24 CHN DMA channel 4
0x25 CHN DMA channel 5
0x26 CHN DMA channel 6
0x27 CHN DMA channel 7
0x28 CHN DMA channel 8
0x29 CHN DMA channel 9
0x2A CHN DMA channel 10
0x2B CHN DMA channel 11
0x2C CHN DMA channel 12
0x2D CHN DMA channel 13
0x2E CHN DMA channel 14
0x2F CHN DMA channel 15
0x30 CHN DMA channel 16
0x31 CHN DMA channel 17
0x32 CHN DMA channel 18
0x33 CHN DMA channel 19
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 394
Value Name Description
0x34 CHN DMA channel 20
0x35 CHN DMA channel 21
0x36 CHN DMA channel 22
0x37 CHN DMA channel 23
0x38 CHN DMA channel 24
0x39 CHN DMA channel 25
0x3A CHN DMA channel 26
0x3B CHN DMA channel 27
0x3C CHN DMA channel 28
0x3D CHN DMA channel 29
0x3E CHN DMA channel 30
0x3F CHN DMA channel 31
Bits 3:2 – CRCPOLY[1:0] CRC Polynomial Type
These bits define the size of the data transfer for each bus access when the CRC is used with I/O
interface, as shown in the table below.
Value Name Description
0x0 CRC16 CRC-16 (CRC-CCITT)
0x1 CRC32 CRC32 (IEEE 802.3)
0x2-0x3 Reserved
Bits 1:0 – CRCBEATSIZE[1:0] CRC Beat Size
These bits define the size of the data transfer for each bus access when the CRC is used with I/O
interface.
Value Name Description
0x0 BYTE 8-bit bus transfer
0x1 HWORD 16-bit bus transfer
0x2 WORD 32-bit bus transfer
0x3 Reserved
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 395
25.8.3 CRC Data Input
Name:  CRCDATAIN
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
CRCDATAIN[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CRCDATAIN[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CRCDATAIN[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CRCDATAIN[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CRCDATAIN[31:0] CRC Data Input
These bits store the data for which the CRC checksum is computed. A new CRC Checksum is ready
(CRCBEAT+ 1) clock cycles after the CRCDATAIN register is written.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 396
25.8.4 CRC Checksum
Name:  CRCCHKSUM
Offset:  0x08
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
The CRCCHKSUM represents the 16- or 32-bit checksum value and the generated CRC. The register is
reset to zero by default, but it is possible to reset all bits to one by writing the CRCCHKSUM register
directly. It is possible to write this register only when the CRC module is disabled. If CRC-32 is selected
and the CRC Status Busy flag is cleared (i.e., CRC generation is completed or aborted), the bit reversed
(bit 31 is swapped with bit 0, bit 30 with bit 1, etc.) and complemented result will be read from
CRCCHKSUM. If CRC-16 is selected or the CRC Status Busy flag is set (i.e., CRC generation is
ongoing), CRCCHKSUM will contain the actual content.
Bit 31 30 29 28 27 26 25 24
CRCCHKSUM[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CRCCHKSUM[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CRCCHKSUM[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CRCCHKSUM[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CRCCHKSUM[31:0] CRC Checksum
These bits store the generated CRC result. The 16 MSB bits are always read zero when CRC-16 is
enabled.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 397
25.8.5 CRC Status
Name:  CRCSTATUS
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
CRCZERO CRCBUSY
Access R R/W
Reset 0 0
Bit 1 – CRCZERO CRC Zero
This bit is cleared when a new CRC source is selected.
This bit is set when the CRC generation is complete and the CRC Checksum is zero.
When running CRC-32 and appending the checksum at the end of the packet (as little endian), the final
checksum should be 0x2144df1c, and not zero. However, if the checksum is complemented before it is
appended (as little endian) to the data, the final result in the checksum register will be zero. See the
description of CRCCHKSUM to read out different versions of the checksum.
Bit 0 – CRCBUSY CRC Module Busy
This flag is cleared by writing a one to it when used with I/O interface. When used with a DMA channel,
the bit is set when the corresponding DMA channel is enabled, and cleared when the corresponding DMA
channel is disabled. This register bit cannot be cleared by the application when the CRC is used with a
DMA channel.
This bit is set when a source configuration is selected and as long as the source is using the CRC
module.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 398
25.8.6 Debug Control
Name:  DBGCTRL
Offset:  0x0D
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bit controls the functionality when the CPU is halted by an external debugger.
Value Description
0The DMAC is halted when the CPU is halted by an external debugger.
1The DMAC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 399
25.8.7 Quality of Service Control
Name:  QOSCTRL
Offset:  0x0E
Reset:  0x2A
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DQOS[1:0] FQOS[1:0] WRBQOS[1:0]
Access R/W R/W R/W R/W R/W R/W
Reset 1 0 1 0 1 0
Bits 5:4 – DQOS[1:0] Data Transfer Quality of Service
These bits define the memory priority access during the data transfer operation.
DQOS[1:0] Name Description
0x0 DISABLE Background (no sensitive operation)
0x1 LOW Sensitive Bandwidth
0x2 MEDIUM Sensitive Latency
0x3 HIGH Critical Latency
Bits 3:2 – FQOS[1:0] Fetch Quality of Service
These bits define the memory priority access during the fetch operation.
FQOS[1:0] Name Description
0x0 DISABLE Background (no sensitive operation)
0x1 LOW Sensitive Bandwidth
0x2 MEDIUM Sensitive Latency
0x3 HIGH Critical Latency
Bits 1:0 – WRBQOS[1:0] Write-Back Quality of Service
These bits define the memory priority access during the write-back operation.
WRBQOS[1:0] Name Description
0x0 DISABLE Background (no sensitive operation)
0x1 LOW Sensitive Bandwidth
0x2 MEDIUM Sensitive Latency
0x3 HIGH Critical Latency
Related Links
10.4.3 SRAM Quality of Service
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 400
25.8.8 Software Trigger Control
Name:  SWTRIGCTRL
Offset:  0x10
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
SWTRIGn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
SWTRIGn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 11:0 – SWTRIGn[11:0] Channel n Software Trigger [n = 11..0]
This bit is cleared when the Channel Pending bit in the Channel Status register (CHSTATUS.PEND) for
the corresponding channel is either set, or by writing a '1' to it.
This bit is set if CHSTATUS.PEND is already '1' when writing a '1' to that bit.
Writing a '0' to this bit will clear the bit.
Writing a '1' to this bit will generate a DMA software trigger on channel x, if CHSTATUS.PEND=0 for
channel x. CHSTATUS.PEND will be set and SWTRIGn will remain cleared.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 401
25.8.9 Priority Control 0
Name:  PRICTRL0
Offset:  0x14
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
RRLVLEN3 LVLPRI3[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
RRLVLEN2 LVLPRI2[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
RRLVLEN1 LVLPRI1[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RRLVLEN0 LVLPRI0[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 31 – RRLVLEN3 Level 3 Round-Robin Arbitration Enable
This bit controls which arbitration scheme is selected for DMA channels with priority level 3. For details on
arbitration schemes, refer to 25.6.2.4 Arbitration.
Value Description
0Static arbitration scheme for channels with level 3 priority.
1Round-robin arbitration scheme for channels with level 3 priority.
Bits 27:24 – LVLPRI3[3:0] Level 3 Channel Priority Number
When round-robin arbitration is enabled (PRICTRL0.RRLVLEN3=1) for priority level 3, this register holds
the channel number of the last DMA channel being granted access as the active channel with priority
level 3.
When static arbitration is enabled (PRICTRL0.RRLVLEN3=0) for priority level 3, and the value of this bit
group is non-zero, it will not affect the static priority scheme.
This bit group is not reset when round-robin arbitration gets disabled (PRICTRL0.RRLVLEN3 written to
'0').
Bit 23 – RRLVLEN2 Level 2 Round-Robin Arbitration Enable
This bit controls which arbitration scheme is selected for DMA channels with priority level 2. For details on
arbitration schemes, refer to 25.6.2.4 Arbitration.
Value Description
0Static arbitration scheme for channels with level 2 priority.
1Round-robin arbitration scheme for channels with level 2 priority.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 402
Bits 19:16 – LVLPRI2[3:0] Level 2 Channel Priority Number
When round-robin arbitration is enabled (PRICTRL0.RRLVLEN2=1) for priority level 2, this register holds
the channel number of the last DMA channel being granted access as the active channel with priority
level 2.
When static arbitration is enabled (PRICTRL0.RRLVLEN2=0) for priority level 2, and the value of this bit
group is non-zero, it will not affect the static priority scheme.
This bit group is not reset when round-robin arbitration gets disabled (PRICTRL0.RRLVLEN2 written to
'0').
Bit 15 – RRLVLEN1 Level 1 Round-Robin Scheduling Enable
For details on arbitration schemes, refer to 25.6.2.4 Arbitration.
Value Description
0Static arbitration scheme for channels with level 1 priority.
1Round-robin arbitration scheme for channels with level 1 priority.
Bits 11:8 – LVLPRI1[3:0] Level 1 Channel Priority Number
When round-robin arbitration is enabled (PRICTRL0.RRLVLEN1=1) for priority level 1, this register holds
the channel number of the last DMA channel being granted access as the active channel with priority
level 1.
When static arbitration is enabled (PRICTRL0.RRLVLEN1=0) for priority level 1, and the value of this bit
group is non-zero, it will not affect the static priority scheme.
This bit group is not reset when round-robin arbitration gets disabled (PRICTRL0.RRLVLEN1 written to
'0').
Bit 7 – RRLVLEN0 Level 0 Round-Robin Scheduling Enable
For details on arbitration schemes, refer to 25.6.2.4 Arbitration.
Value Description
0Static arbitration scheme for channels with level 0 priority.
1Round-robin arbitration scheme for channels with level 0 priority.
Bits 3:0 – LVLPRI0[3:0] Level 0 Channel Priority Number
When round-robin arbitration is enabled (PRICTRL0.RRLVLEN0=1) for priority level 0, this register holds
the channel number of the last DMA channel being granted access as the active channel with priority
level 0.
When static arbitration is enabled (PRICTRL0.RRLVLEN0=0) for priority level 0, and the value of this bit
group is non-zero, it will not affect the static priority scheme.
This bit group is not reset when round-robin arbitration gets disabled (PRICTRL0.RRLVLEN0 written to
'0').
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 403
25.8.10 Interrupt Pending
Name:  INTPEND
Offset:  0x20
Reset:  0x0000
Property:  -
This register allows the user to identify the lowest DMA channel with pending interrupt.
Bit 15 14 13 12 11 10 9 8
PEND BUSY FERR SUSP TCMPL TERR
Access R R R R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ID[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 – PEND Pending
This bit will read '1' when the channel selected by Channel ID field (ID) is pending.
Bit 14 – BUSY Busy
This bit will read '1' when the channel selected by Channel ID field (ID) is busy.
Bit 13 – FERR Fetch Error
This bit will read '1' when the channel selected by Channel ID field (ID) fetched an invalid descriptor.
Bit 10 – SUSP Channel Suspend
This bit will read '1' when the channel selected by Channel ID field (ID) has pending Suspend interrupt.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel ID (ID) Suspend interrupt flag.
Bit 9 – TCMPL Transfer Complete
This bit will read '1' when the channel selected by Channel ID field (ID) has pending Transfer Complete
interrupt.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel ID (ID) Transfer Complete interrupt flag.
Bit 8 – TERR Transfer Error
This bit is read one when the channel selected by Channel ID field (ID) has pending Transfer Error
interrupt.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel ID (ID) Transfer Error interrupt flag.
Bits 3:0 – ID[3:0] Channel ID
These bits store the lowest channel number with pending interrupts. The number is valid if Suspend
(SUSP), Transfer Complete (TCMPL) or Transfer Error (TERR) bits are set. The Channel ID field is
refreshed when a new channel (with channel number less than the current one) with pending interrupts is
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 404
detected, or when the application clears the corresponding channel interrupt sources. When no pending
channels interrupts are available, these bits will always return zero value when read.
When the bits are written, indirect access to the corresponding Channel Interrupt Flag register is enabled.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 405
25.8.11 Interrupt Status
Name:  INTSTATUS
Offset:  0x24
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
CHINTn[11:8]
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CHINTn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 11:0 – CHINTn[11:0] Channel n Pending Interrupt [n=11..0]
This bit is set when Channel n has a pending interrupt/the interrupt request is received.
This bit is cleared when the corresponding Channel n interrupts are disabled or the interrupts sources are
cleared.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 406
25.8.12 Busy Channels
Name:  BUSYCH
Offset:  0x28
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
BUSYCHn[11:8]
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
BUSYCHn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 11:0 – BUSYCHn[11:0] Busy Channel n [x=11..0]
This bit is cleared when the channel trigger action for DMA channel n is complete, when a bus error for
DMA channel n is detected, or when DMA channel n is disabled.
This bit is set when DMA channel n starts a DMA transfer.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 407
25.8.13 Pending Channels
Name:  PENDCH
Offset:  0x2C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
PENDCH11 PENDCH10 PENDCH9 PENDCH8
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PENDCH7 PENDCH6 PENDCH5 PENDCH4 PENDCH3 PENDCH2 PENDCH1 PENDCH0
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 – PENDCH Pending Channel n [n=11..0]
This bit is cleared when trigger execution defined by channel trigger action settings for DMA channel n is
started, when a bus error for DMA channel n is detected or when DMA channel n is disabled. For details
on trigger action settings, refer to CHCTRLB.TRIGACT.
This bit is set when a transfer is pending on DMA channel n.
Related Links
25.8.19 CHCTRLB
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 408
25.8.14 Active Channel and Levels
Name:  ACTIVE
Offset:  0x30
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
BTCNT[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
BTCNT[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ABUSY ID[4:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
LVLEXx LVLEXx LVLEXx LVLEXx
Access R R R R
Reset 0 0 0 0
Bits 31:16 – BTCNT[15:0] Active Channel Block Transfer Count
These bits hold the 16-bit block transfer count of the ongoing transfer. This value is stored in the active
channel and written back in the corresponding Write-Back channel memory location when the arbiter
grants a new channel access. The value is valid only when the active channel active busy flag (ABUSY)
is set.
Bit 15 – ABUSY Active Channel Busy
This bit is cleared when the active transfer count is written back in the write-back memory section.
This bit is set when the next descriptor transfer count is read from the write-back memory section.
Bits 12:8 – ID[4:0] Active Channel ID
These bits hold the channel index currently stored in the active channel registers. The value is updated
each time the arbiter grants a new channel transfer access request.
Bits 3,2,1,0 – LVLEXx Level x Channel Trigger Request Executing [x=3..0]
This bit is set when a level-x channel trigger request is executing or pending.
This bit is cleared when no request is pending or being executed.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 409
25.8.15 Descriptor Memory Section Base Address
Name:  BASEADDR
Offset:  0x34
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
Access
Reset
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 410
25.8.16 Write-Back Memory Section Base Address
Name:  WRBADDR
Offset:  0x38
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
Access
Reset
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 411
25.8.17 Channel ID
Name:  CHID
Offset:  0x3F
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
ID[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – ID[3:0] Channel ID
These bits define the channel number that will be affected by the channel registers (CH*). Before reading
or writing a channel register, the channel ID bit group must be written first.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 412
25.8.18 Channel Control A
Name:  CHCTRLA
Offset:  0x40
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
This register affects the DMA channel that is selected in the Channel ID register (CHID.ID).
Bit 7 6 5 4 3 2 1 0
RUNSTDBY ENABLE SWRST
Access R R/W R R R R R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 6 – RUNSTDBY Channel run in standby
This bit is used to keep the DMAC channel running in standby mode.
This bit is not enable-protected.
Value Description
0The DMAC channel is halted in standby.
1The DMAC channel continues to run in standby.
Bit 1 – ENABLE Channel Enable
Writing a '0' to this bit during an ongoing transfer, the bit will not be cleared until the internal data transfer
buffer is empty and the DMA transfer is aborted. The internal data transfer buffer will be empty once the
ongoing burst transfer is completed.
Writing a '1' to this bit will enable the DMA channel.
This bit is not enable-protected.
Value Description
0DMA channel is disabled.
1DMA channel is enabled.
Bit 0 – SWRST Channel Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets the channel registers to their initial state. The bit can be set when the
channel is disabled (ENABLE=0). Writing a '1' to this bit will be ignored as long as ENABLE=1. This bit is
automatically cleared when the reset is completed.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 413
25.8.19 Channel Control B
Name:  CHCTRLB
Offset:  0x44
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
This register affects the DMA channel that is selected in the Channel ID register (CHID.ID).
Bit 31 30 29 28 27 26 25 24
CMD[1:0]
Access R/W R/W
Reset 0 0
Bit 23 22 21 20 19 18 17 16
TRIGACT[1:0]
Access R/W R/W
Reset 0 0
Bit 15 14 13 12 11 10 9 8
TRIGSRC[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
LVL[1:0] EVOE EVIE EVACT[2:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 25:24 – CMD[1:0] Software Command
These bits define the software commands. Refer to 25.6.3.2 Channel Suspend and 25.6.3.3 Channel
Resume and Next Suspend Skip.
These bits are not enable-protected.
CMD[1:0] Name Description
0x0 NOACT No action
0x1 SUSPEND Channel suspend operation
0x2 RESUME Channel resume operation
0x3 - Reserved
Bits 23:22 – TRIGACT[1:0] Trigger Action
These bits define the trigger action used for a transfer.
TRIGACT[1:0] Name Description
0x0 BLOCK One trigger required for each block transfer
0x1 - Reserved
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
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...........continued
TRIGACT[1:0] Name Description
0x2 BEAT One trigger required for each beat transfer
0x3 TRANSACTION One trigger required for each transaction
Bits 13:8 – TRIGSRC[5:0] Trigger Source
These bits define the peripheral trigger which is source of the transfer. For details on trigger selection and
trigger modes, refer to Transfer Triggers and Actions and CHCTRLB.TRIGACT.
Table 25-2. Peripheral Trigger Source
Value Name Description
0x00 DISABLE Only software/event triggers
0x01 TSENS TSENS Result Ready Trigger
0x02 SERCOM0 RX SERCOM0 RX Trigger
0x03 SERCOM0 TX SERCOM0TX Trigger
0x04 SERCOM1 RX SERCOM1 RX Trigger
0x05 SERCOM1 TX SERCOM1 TX Trigger
0x06 SERCOM2 RX SERCOM2 RX Trigger
0x07 SERCOM2 TX SERCOM2 TX Trigger
0x08 SERCOM3 RX SERCOM3 RX Trigger
0x09 SERCOM3 TX SERCOM3 TX Trigger
0x0A SERCOM4 RX- SERCOM4 RX TriggerReserved
0x0B SERCOM4 TX- SERCOM4 TX TriggerReserved
0x0C SERCOM5 RX- SERCOM5 RX TriggerReserved
0x0D SERCOM5 TX- SERCOM5 TX TriggerReserved
0x0E CAN0 DEBUG- CAN0 Debug TriggerReserved
0x0F CAN1 DEBUG- CAN1 Debug TriggerReserved
0x10 TCC0 OVF TCC0 Overflow Trigger
0x11 TCC0 MC0 TCC0 Match/Compare 0 Trigger
0x12 TCC0 MC1 TCC0 Match/Compare 1 Trigger
0x13 TCC0 MC2 TCC0 Match/Compare 2 Trigger
0x14 TCC0 MC3 TCC0 Match/Compare 3 Trigger
0x15 TCC1 OVF TCC1 Overflow Trigger
0x16 TCC1 MC0 TCC1 Match/Compare 0 Trigger
0x17 TCC1 MC1 TCC1 Match/Compare 1 Trigger
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
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...........continued
Value Name Description
0x18 TCC2 OVF TCC2 Overflow Trigger
0x19 TCC2 MC0 TCC2 Match/Compare 0 Trigger
0x1A TCC2 MC1 TCC2 Match/Compare 1 Trigger
0x1B TC0 OVF TC0 Overflow Trigger
0x1C TC0 MC0 TC0 Match/Compare 0 Trigger
0x1D TC0 MC1 TC0 Match/Compare 1 Trigger
0x1E TC1 OVF TC1 Overflow Trigger
0x1F TC1 MC0 TC1 Match/Compare 0 Trigger
0x20 TC1 MC1 TC1 Match/Compare 1 Trigger
0x21 TC2 OVF TC2 Overflow Trigger
0x22 TC2 MC0 TC2 Match/Compare 0 Trigger
0x23 TC2 MC1 TC2 Match/Compare 1 Trigger
0x24 TC3 OVF TC3 Overflow Trigger
0x25 TC3 MC0 TC3 Match/Compare 0 Trigger
0x26 TC3 MC1 TC3 Match/Compare 1 Trigger
0x27 TC4 OVF TC4 Overflow Trigger
0x28 TC4 MC0 TC4 Match/Compare 0 Trigger
0x29 TC4 MC1 TC4 Match/Compare 1 Trigger
0x2A ADC0 RESRDY ADC0 Result Ready Trigger
0x2B ADC1 RESRDY ADC1 Result Ready Trigger
0x2C SDADC RESRDY SDADC Result Ready Trigger
0x2D DAC EMPTY DAC Empty Trigger
0x2E PTC EOC PTC End of Conversion Trigger
0x2F PTC WCOMP PTC Window Compare Trigger
0x30 PTC SEQ PTC Sequence Trigger
0x31 SERCOM6 RX SERCOM6 RX Trigger
0x32 SERCOM6 TX SERCOM6 TX Trigger
0x33 SERCOM7 RX SERCOM6 RX Trigger
0x34 SERCOM7 TX SERCOM6 TX Trigger
0x35 TC5 OVF TC5 Overflow Trigger
0x36 TC5 MC0 TC5 Match/Compare 0 Trigger
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 416
...........continued
Value Name Description
0x37 TC5 MC1 TC5 Match/Compare 1 Trigger
0x38 TC6 OVF TC6 Overflow Trigger
0x39 TC6 MC0 TC6 Match/Compare 0 Trigger
0x3A TC6 MC1 TC6 Match/Compare 1 Trigger
0x3B TC7 OVF TC7 Overflow Trigger
0x3C TC7 MC0 TC7 Match/Compare 0 Trigger
0x3D TC7MC1 TC7 Match/Compare 1 Trigger
Bits 6:5 – LVL[1:0] Channel Arbitration Level
These bits define the arbitration level used for the DMA channel, where a high level has priority over a
low level. For further details on arbitration schemes, refer to 25.6.2.4 Arbitration.
These bits are not enable-protected.
TRIGACT[1:0] Name Description
0x0 LVL0 Channel Priority Level 0
0x1 LVL1 Channel Priority Level 1
0x2 LVL2 Channel Priority Level 2
0x3 LVL3 Channel Priority Level 3
Bit 4 – EVOE Channel Event Output Enable
This bit indicates if the Channel event generation is enabled. The event will be generated for every
condition defined in the descriptor Event Output Selection (BTCTRL.EVOSEL).
This bit is available only for the least significant DMA channels. Refer to table: User Multiplexer Selection
and Event Generator Selection of the Event System for details.
Value Description
0Channel event generation is disabled.
1Channel event generation is enabled.
Bit 3 – EVIE Channel Event Input Enable
This bit is available only for the least significant DMA channels. Refer to table: User Multiplexer Selection
and Event Generator Selection of the Event System for details.
Value Description
0Channel event action will not be executed on any incoming event.
1Channel event action will be executed on any incoming event.
Bits 2:0 – EVACT[2:0] Event Input Action
These bits define the event input action, as shown below. The action is executed only if the
corresponding EVIE bit in CHCTRLB register of the channel is set.
These bits are available only for the least significant DMA channels. Refer to table: User Multiplexer
Selection and Event Generator Selection of the Event System for details.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 417
EVACT[2:0] Name Description
0x0 NOACT No action
0x1 TRIG Normal Transfer and Conditional Transfer on Strobe trigger
0x2 CTRIG Conditional transfer trigger
0x3 CBLOCK Conditional block transfer
0x4 SUSPEND Channel suspend operation
0x5 RESUME Channel resume operation
0x6 SSKIP Skip next block suspend action
0x7 - Reserved
Related Links
29.8.7 CHANNELn
29.7.3 USERm
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 418
25.8.20 Channel Interrupt Enable Clear
Name:  CHINTENCLR
Offset:  0x4C
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Channel Interrupt Enable Set (CHINTENSET) register.
This register affects the DMA channel that is selected in the Channel ID register (CHID.ID).
Bit 7 6 5 4 3 2 1 0
SUSP TCMPL TERR
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – SUSP Channel Suspend Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel Suspend Interrupt Enable bit, which disables the Channel
Suspend interrupt.
Value Description
0The Channel Suspend interrupt is disabled.
1The Channel Suspend interrupt is enabled.
Bit 1 – TCMPL Channel Transfer Complete Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel Transfer Complete Interrupt Enable bit, which disables the
Channel Transfer Complete interrupt.
Value Description
0The Channel Transfer Complete interrupt is disabled. When block action is set to none, the
TCMPL flag will not be set when a block transfer is completed.
1The Channel Transfer Complete interrupt is enabled.
Bit 0 – TERR Channel Transfer Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel Transfer Error Interrupt Enable bit, which disables the
Channel Transfer Error interrupt.
Value Description
0The Channel Transfer Error interrupt is disabled.
1The Channel Transfer Error interrupt is enabled.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 419
25.8.21 Channel Interrupt Enable Set
Name:  CHINTENSET
Offset:  0x4D
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Channel Interrupt Enable Clear (CHINTENCLR) register.
This register affects the DMA channel that is selected in the Channel ID register (CHID.ID).
Bit 7 6 5 4 3 2 1 0
SUSP TCMPL TERR
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – SUSP Channel Suspend Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Channel Suspend Interrupt Enable bit, which enables the Channel
Suspend interrupt.
Value Description
0The Channel Suspend interrupt is disabled.
1The Channel Suspend interrupt is enabled.
Bit 1 – TCMPL Channel Transfer Complete Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Channel Transfer Complete Interrupt Enable bit, which enables the
Channel Transfer Complete interrupt.
Value Description
0The Channel Transfer Complete interrupt is disabled.
1The Channel Transfer Complete interrupt is enabled.
Bit 0 – TERR Channel Transfer Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Channel Transfer Error Interrupt Enable bit, which enables the Channel
Transfer Error interrupt.
Value Description
0The Channel Transfer Error interrupt is disabled.
1The Channel Transfer Error interrupt is enabled.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
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25.8.22 Channel Interrupt Flag Status and Clear
Name:  CHINTFLAG
Offset:  0x4E
Reset:  0x00
Property:  -
This register affects the DMA channel that is selected in the Channel ID register (CHID.ID).
Bit 7 6 5 4 3 2 1 0
SUSP TCMPL TERR
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – SUSP Channel Suspend
This flag is cleared by writing a '1' to it.
This flag is set when a block transfer with suspend block action is completed, when a software suspend
command is executed, when a suspend event is received or when an invalid descriptor is fetched by the
DMA.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Channel Suspend interrupt flag for the corresponding channel.
For details on available software commands, refer to CHCTRLB.CMD.
For details on available event input actions, refer to CHCTRLB.EVACT.
For details on available block actions, refer to BTCTRL.BLOCKACT.
Bit 1 – TCMPL Channel Transfer Complete
This flag is cleared by writing a '1' to it.
This flag is set when a block transfer is completed and the corresponding interrupt block action is
enabled.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Transfer Complete interrupt flag for the corresponding channel.
Bit 0 – TERR Channel Transfer Error
This flag is cleared by writing a '1' to it.
This flag is set when a bus error is detected during a beat transfer or when the DMAC fetches an invalid
descriptor.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Transfer Error interrupt flag for the corresponding channel.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 421
25.8.23 Channel Status
Name:  CHSTATUS
Offset:  0x4F
Reset:  0x00
Property:  -
This register affects the DMA channel that is selected in the Channel ID register (CHID.ID).
Bit 7 6 5 4 3 2 1 0
FERR BUSY PEND
Access R R R
Reset 0 0 0
Bit 2 – FERR Channel Fetch Error
This bit is cleared when a software resume command is executed.
This bit is set when an invalid descriptor is fetched.
Bit 1 – BUSY Channel Busy
This bit is cleared when the channel trigger action is completed, when a bus error is detected or when the
channel is disabled.
This bit is set when the DMA channel starts a DMA transfer.
Bit 0 – PEND Channel Pending
This bit is cleared when the channel trigger action is started, when a bus error is detected or when the
channel is disabled. For details on trigger action settings, refer to CHCTRLB.TRIGACT.
This bit is set when a transfer is pending on the DMA channel, as soon as the transfer request is
received.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 422
25.9 Register Summary - SRAM
Offset Name Bit Pos.
0x00 BTCTRL
7:0 BLOCKACT[1:0] EVOSEL[1:0] VALID
15:8 STEPSIZE[2:0] STEPSEL DSTINC SRCINC BEATSIZE[1:0]
0x02 BTCNT
7:0 BTCNT[7:0]
15:8 BTCNT[15:8]
0x04 SRCADDR
7:0 SRCADDR[7:0]
15:8 SRCADDR[15:8]
23:16 SRCADDR[23:16]
31:24 SRCADDR[31:24]
0x08 DSTADDR
7:0 DSTADDR[7:0]
15:8 DSTADDR[15:8]
23:16 DSTADDR[23:16]
31:24 DSTADDR[31:24]
0x0C DESCADDR
7:0 DESCADDR[7:0]
15:8 DESCADDR[15:8]
23:16 DESCADDR[23:16]
31:24 DESCADDR[31:24]
25.10 Register Description - SRAM
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 25.5.8 Register Access Protection.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 423
25.10.1 Block Transfer Control
Name:  BTCTRL
Offset:  0x00
Property:  -
The BTCTRL register offset is relative to (BASEADDR or WRBADDR) + Channel Number * 0x10
Bit 15 14 13 12 11 10 9 8
STEPSIZE[2:0] STEPSEL DSTINC SRCINC BEATSIZE[1:0]
Access
Reset
Bit 7 6 5 4 3 2 1 0
BLOCKACT[1:0] EVOSEL[1:0] VALID
Access
Reset
Bits 15:13 – STEPSIZE[2:0] Address Increment Step Size
These bits select the address increment step size. The setting apply to source or destination address,
depending on STEPSEL setting.
Value Name Description
0x0 X1 Next ADDR = ADDR + (Beat size in byte) * 1
0x1 X2 Next ADDR = ADDR + (Beat size in byte) * 2
0x2 X4 Next ADDR = ADDR + (Beat size in byte) * 4
0x3 X8 Next ADDR = ADDR + (Beat size in byte) * 8
0x4 X16 Next ADDR = ADDR + (Beat size in byte) * 16
0x5 X32 Next ADDR = ADDR + (Beat size in byte) * 32
0x6 X64 Next ADDR = ADDR + (Beat size in byte) * 64
0x7 X128 Next ADDR = ADDR + (Beat size in byte) * 128
Bit 12 – STEPSEL Step Selection
This bit selects if source or destination addresses are using the step size settings.
Value Name Description
0x0 DST Step size settings apply to the destination address
0x1 SRC Step size settings apply to the source address
Bit 11 – DSTINC Destination Address Increment Enable
Writing a '0' to this bit will disable the destination address incrementation. The address will be kept fixed
during the data transfer.
Writing a '1' to this bit will enable the destination address incrementation. By default, the destination
address is incremented by 1. If the STEPSEL bit is cleared, flexible step-size settings are available in the
STEPSIZE register.
Value Description
0The Destination Address Increment is disabled.
1The Destination Address Increment is enabled.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
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Bit 10 – SRCINC Source Address Increment Enable
Writing a '0' to this bit will disable the source address incrementation. The address will be kept fixed
during the data transfer.
Writing a '1' to this bit will enable the source address incrementation. By default, the source address is
incremented by 1. If the STEPSEL bit is set, flexible step-size settings are available in the STEPSIZE
register.
Value Description
0The Source Address Increment is disabled.
1The Source Address Increment is enabled.
Bits 9:8 – BEATSIZE[1:0] Beat Size
These bits define the size of one beat. A beat is the size of one data transfer bus access, and the setting
apply to both read and write accesses.
Value Name Description
0x0 BYTE 8-bit bus transfer
0x1 HWORD 16-bit bus transfer
0x2 WORD 32-bit bus transfer
other Reserved
Bits 4:3 – BLOCKACT[1:0] Block Action
These bits define what actions the DMAC should take after a block transfer has completed.
BLOCKACT[1:0] Name Description
0x0 NOACT Channel will be disabled if it is the last block transfer in the transaction
0x1 INT Channel will be disabled if it is the last block transfer in the transaction
and block interrupt
0x2 SUSPEND Channel suspend operation is completed
0x3 BOTH Both channel suspend operation and block interrupt
Bits 2:1 – EVOSEL[1:0] Event Output Selection
These bits define the event output selection.
EVOSEL[1:0] Name Description
0x0 DISABLE Event generation disabled
0x1 BLOCK Event strobe when block transfer complete
0x2 Reserved
0x3 BEAT Event strobe when beat transfer complete
Bit 0 – VALID Descriptor Valid
Writing a '0' to this bit in the Descriptor or Write-Back memory will suspend the DMA channel operation
when fetching the corresponding descriptor.
The bit is automatically cleared in the Write-Back memory section when channel is aborted, when an
error is detected during the block transfer, or when the block transfer is completed.
Value Description
0The descriptor is not valid.
1The descriptor is valid.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 425
25.10.2 Block Transfer Count
Name:  BTCNT
Offset:  0x02
Property:  -
The BTCNT register offset is relative to (BASEADDR or WRBADDR) + Channel Number * 0x10
Bit 15 14 13 12 11 10 9 8
BTCNT[15:8]
Access
Reset
Bit 7 6 5 4 3 2 1 0
BTCNT[7:0]
Access
Reset
Bits 15:0 – BTCNT[15:0] Block Transfer Count
This bit group holds the 16-bit block transfer count.
During a transfer, the internal counter value is decremented by one after each beat transfer. The internal
counter is written to the corresponding write-back memory section for the DMA channel when the DMA
channel loses priority, is suspended or gets disabled. The DMA channel can be disabled by a complete
transfer, a transfer error or by software.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 426
25.10.3 Block Transfer Source Address
Name:  SRCADDR
Offset:  0x04
Property:  -
The SRCADDR register offset is relative to (BASEADDR or WRBADDR) + Channel Number * 0x10
Bit 31 30 29 28 27 26 25 24
SRCADDR[31:24]
Access
Reset
Bit 23 22 21 20 19 18 17 16
SRCADDR[23:16]
Access
Reset
Bit 15 14 13 12 11 10 9 8
SRCADDR[15:8]
Access
Reset
Bit 7 6 5 4 3 2 1 0
SRCADDR[7:0]
Access
Reset
Bits 31:0 – SRCADDR[31:0] Transfer Source Address
This bit group holds the source address corresponding to the last beat transfer address in the block
transfer.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 427
25.10.4 Block Transfer Destination Address
Name:  DSTADDR
Offset:  0x08
Property:  -
The DSTADDR register offset is relative to (BASEADDR or WRBADDR) + Channel Number * 0x10
Bit 31 30 29 28 27 26 25 24
DSTADDR[31:24]
Access
Reset
Bit 23 22 21 20 19 18 17 16
DSTADDR[23:16]
Access
Reset
Bit 15 14 13 12 11 10 9 8
DSTADDR[15:8]
Access
Reset
Bit 7 6 5 4 3 2 1 0
DSTADDR[7:0]
Access
Reset
Bits 31:0 – DSTADDR[31:0] Transfer Destination Address
This bit group holds the destination address corresponding to the last beat transfer address in the block
transfer.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 428
25.10.5 Next Descriptor Address
Name:  DESCADDR
Offset:  0x0C
Property:  -
The DESCADDR register offset is relative to (BASEADDR or WRBADDR) + Channel Number * 0x10
Bit 31 30 29 28 27 26 25 24
DESCADDR[31:24]
Access
Reset
Bit 23 22 21 20 19 18 17 16
DESCADDR[23:16]
Access
Reset
Bit 15 14 13 12 11 10 9 8
DESCADDR[15:8]
Access
Reset
Bit 7 6 5 4 3 2 1 0
DESCADDR[7:0]
Access
Reset
Bits 31:0 – DESCADDR[31:0] Next Descriptor Address
This bit group holds the SRAM address of the next descriptor. The value must be 128-bit aligned. If the
value of this SRAM register is 0x00000000, the transaction will be terminated when the DMAC tries to
load the next transfer descriptor.
SAM C20/C21 Family Data Sheet
DMAC – Direct Memory Access Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 429
26. EIC – External Interrupt Controller
26.1 Overview
The External Interrupt Controller (EIC) allows external pins to be configured as interrupt lines. Each
interrupt line can be individually masked and can generate an interrupt on rising, falling, or both edges, or
on high or low levels. Each external pin has a configurable filter to remove spikes. Each external pin can
also be configured to be asynchronous in order to wake up the device from sleep modes where all clocks
have been disabled. External pins can also generate an event.
A separate non-maskable interrupt (NMI) is also supported. It has properties similar to the other external
interrupts, but is connected to the NMI request of the CPU, enabling it to interrupt any other interrupt
mode.
26.2 Features
• Up to 16 external pins (EXTINTx), plus one non-maskable pin (NMI)
• Dedicated, individually maskable interrupt for each pin
• Interrupt on rising, falling, or both edges
• Synchronous or asynchronous edge detection mode
• Interrupt pin debouncing
• Interrupt on high or low levels
• Asynchronous interrupts for sleep modes without clock
• Filtering of external pins
• Event generation from EXTINTx
26.3 Block Diagram
Figure 26-1. EIC Block Diagram
Filter Edge/Level
Detection
Interrupt
Wake
Event
FILTENx
EXTINTx
intreq_extint
inwake_extint
evt_extint
Filter Edge/Level
Detection
Interrupt
Wake
NMIFILTEN NMISENSE[2:0]
NMI
intreq_nmi
inwake_nmi
SENSEx[2:0]
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 430
26.4 Signal Description
Signal Name Type Description
EXTINT[15..0] Digital Input External interrupt pin
NMI Digital Input Non-maskable interrupt pin
One signal may be available on several pins.
Related Links
6. I/O Multiplexing and Considerations
26.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
26.5.1 I/O Lines
Using the EIC’s I/O lines requires the I/O pins to be configured.
Related Links
28. PORT - I/O Pin Controller
26.5.2 Power Management
All interrupts are available down to STANDBY sleep mode, but the EIC can be configured to automatically
mask some interrupts in order to prevent device wake-up.
The EIC will continue to operate in any sleep mode where the selected source clock is running. The EIC’s
interrupts can be used to wake up the device from sleep modes. Events connected to the Event System
can trigger other operations in the system without exiting sleep modes.
Related Links
19. PM – Power Manager
26.5.3 Clocks
The EIC bus clock (CLK_EIC_APB) can be enabled and disabled by the Main Clock Controller, the
default state of CLK_EIC_APB can be found in the Peripheral Clock Masking section.
Some optional functions need a peripheral clock, which can either be a generic clock (GCLK_EIC, for
wider frequency selection) or a Ultra Low Power 32KHz clock (CLK_ULP32K, for highest power
efficiency). One of the clock sources must be configured and enabled before using the peripheral:
GCLK_EIC is configured and enabled in the Generic Clock Controller.
CLK_ULP32K is provided by the internal ultra-low-power (OSCULP32K) oscillator in the OSC32KCTRL
module.
Both GCLK_EIC and CLK_ULP32K are asynchronous to the user interface clock (CLK_EIC_APB). Due
to this asynchronicity, writes to certain registers will require synchronization between the clock domains.
Refer to Synchronization for further details.
Related Links
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 431
16. GCLK - Generic Clock Controller
21. OSC32KCTRL – 32KHz Oscillators Controller
26.5.4 DMA
Not applicable.
26.5.5 Interrupts
There are several interrupt request lines, at least one for the external interrupts (EXTINT) and one for
non-maskable interrupt (NMI).
The EXTINT interrupt request line is connected to the interrupt controller. Using the EIC interrupt requires
the interrupt controller to be configured first.
The NMI interrupt request line is also connected to the interrupt controller, but does not require the
interrupt to be configured.
Related Links
10.2 Nested Vector Interrupt Controller
26.5.6 Events
The events are connected to the Event System. Using the events requires the Event System to be
configured first.
Related Links
29. EVSYS – Event System
26.5.7 Debug Operation
When the CPU is halted in debug mode, the EIC continues normal operation. If the EIC is configured in a
way that requires it to be periodically serviced by the CPU through interrupts or similar, improper
operation or data loss may result during debugging.
26.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Flag Status and Clear register (INTFLAG)
• Non-Maskable Interrupt Flag Status and Clear register (NMIFLAG)
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
26.5.9 Analog Connections
Not applicable.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 432
26.6 Functional Description
26.6.1 Principle of Operation
The EIC detects edge or level condition to generate interrupts to the CPU interrupt controller or events to
the Event System. Each external interrupt pin (EXTINT) can be filtered using majority vote filtering,
clocked by GCLK_EIC or by CLK_ULP32K.
Related Links
26.6.3 External Pin Processing
26.6.2 Basic Operation
26.6.2.1 Initialization
The EIC must be initialized in the following order:
1. Enable CLK_EIC_APB
2. If required, configure the NMI by writing the Non-Maskable Interrupt Control register (NMICTRL)
3. Enable GCLK_EIC or CLK_ULP32K when one of the following configuration is selected:
– the NMI uses edge detection or filtering.
– one EXTINT uses filtering.
– one EXTINT uses synchronous edge detection.
– one EXTINT uses debouncing.
GCLK_EIC is used when a frequency higher than 32KHz is required for filtering.
CLK_ULP32K is recommended when power consumption is the priority. For CLK_ULP32K write a
'1' to the Clock Selection bit in the Control A register (CTRLA.CKSEL).
4. Configure the EIC input sense and filtering by writing the Configuration n register (CONFIG).
5. Optionally, enable the asynchronous mode.
6. Optionally, enable the debouncer mode.
7. Enable the EIC by writing a ‘1’ to CTRLA.ENABLE.
The following bits are enable-protected, meaning that it can only be written when the EIC is disabled
(CTRLA.ENABLE=0):
• Clock Selection bit in Control A register (CTRLA.CKSEL)
The following registers are enable-protected:
• Event Control register (EVCTRL)
• Configuration n register (CONFIG).
• External Interrupt Asynchronous Mode register (26.8.9 ASYNCH)
• Debouncer Enable register (26.8.11 DEBOUNCEN)
• Debounce Prescaler register (26.8.12 DPRESCALER)
Enable-protected bits in the CTRLA register can be written at the same time when setting
CTRLA.ENABLE to '1', but not at the same time as CTRLA.ENABLE is being cleared.
Enable-protection is denoted by the "Enable-Protected" property in the register description.
Related Links
26.8.10 CONFIG
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 433
26.6.2.2 Enabling, Disabling, and Resetting
The EIC is enabled by writing a '1' the Enable bit in the Control A register (CTRLA.ENABLE). The EIC is
disabled by writing CTRLA.ENABLE to '0'.
The EIC is reset by setting the Software Reset bit in the Control register (CTRLA.SWRST). All registers in
the EIC will be reset to their initial state, and the EIC will be disabled.
Refer to the CTRLA register description for details.
26.6.3 External Pin Processing
Each external pin can be configured to generate an interrupt/event on edge detection (rising, falling or
both edges) or level detection (high or low). The sense of external interrupt pins is configured by writing
the Input Sense x bits in the Config n register (CONFIG.SENSEx). The corresponding interrupt flag
(INTFLAG.EXTINT[x]) in the Interrupt Flag Status and Clear register (26.8.8 INTFLAG) is set when the
interrupt condition is met.
When the interrupt flag has been cleared in edge-sensitive mode, INTFLAG.EXTINT[x] will only be set if a
new interrupt condition is met.
In level-sensitive mode, when interrupt has been cleared, INTFLAG.EXTINT[x] will be set immediately if
the EXTINTx pin still matches the interrupt condition.
Each external pin can be filtered by a majority vote filtering, clocked by GCLK_EIC or CLK_ULP32K.
Filtering is enabled if bit Filter Enable x in the Configuration n register (CONFIG.FILTENx) is written to '1'.
The majority vote filter samples the external pin three times with GCLK_EIC or CLK_ULP32K and outputs
the value when two or more samples are equal.
Table 26-1. Majority Vote Filter
Samples [0, 1, 2] Filter Output
[0,0,0] 0
[0,0,1] 0
[0,1,0] 0
[0,1,1] 1
[1,0,0] 0
[1,0,1] 1
[1,1,0] 1
[1,1,1] 1
When an external interrupt is configured for level detection and when filtering is disabled, detection is
done asynchronously. Level detection and asynchronous edge detection does not require GCLK_EIC or
CLK_ULP32K, but interrupt and events can still be generated.
If filtering or synchronous edge detection or debouncing is enabled, the EIC automatically requests
GCLK_EIC or CLK_ULP32K to operate. The selection between these two clocks is done by writing the
Clock Selection bits in the Control A register (CTRLA.CKSEL). GCLK_EIC must be enabled in the GCLK
module. In these modes the external pin is sampled at the EIC clock rate, thus pulses with duration lower
than two EIC clock periods may not be properly detected.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 434
Figure 26-2. Interrupt Detection Latency by modes (Rising Edge)
intreq_extint[x]
(edge detection / filter)
intreq_extint[x]
(edge detection / no filter)
intreq_extint[x]
(level detection / filter)
intreq_extint[x]
(level detection / no filter)
EXTINTx
CLK_EIC_APB
GCLK_EIC
clear INTFLAG.EXTINT[x]
No interrupt
No interrupt
The detection latency depends on the detection mode.
Table 26-2. Detection Latency
Detection mode Latency (worst case)
Level without filter Five CLK_EIC_APB periods
Level with filter Four GCLK_EIC/CLK_ULP32K periods + five CLK_EIC_APB periods
Edge without filter Four GCLK_EIC/CLK_ULP32K periods + five CLK_EIC_APB periods
Edge with filter Six GCLK_EIC/CLK_ULP32K periods + five CLK_EIC_APB periods
Related Links
16. GCLK - Generic Clock Controller
26.8.10 CONFIG
26.6.4 Additional Features
26.6.4.1 Non-Maskable Interrupt (NMI)
The non-maskable interrupt pin can also generate an interrupt on edge or level detection, but it is
configured with the dedicated NMI Control register (NMICTRL). To select the sense for NMI, write to the
NMISENSE bit group in the NMI Control register (NMICTRL.NMISENSE). NMI filtering is enabled by
writing a '1' to the NMI Filter Enable bit (NMICTRL.NMIFILTEN).
If edge detection or filtering is required, enable GCLK_EIC or CLK_ULP32K.
NMI detection is enabled only by the NMICTRL.NMISENSE value, and the EIC is not required to be
enabled.
When an NMI is detected, the non-maskable interrupt flag in the NMI Flag Status and Clear register is set
(NMIFLAG.NMI). NMI interrupt generation is always enabled, and NMIFLAG.NMI generates an interrupt
request when set.
26.6.4.2 Asynchronous Edge Detection Mode (No Debouncing)
The EXTINT edge detection can be operated synchronously or asynchronously, selected by the
Asynchronous Control Mode bit for external pin x in the External Interrupt Asynchronous Mode register
(ASYNCH.ASYNCH[x]). The EIC edge detection is operated synchronously when the Asynchronous
Control Mode bit (ASYNCH.ASYNCH[x]) is '0' (default value). It is operated asynchronously when
ASYNCH.ASYNCH[x] is written to '1'.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 435
In Synchronous Edge Detection Mode, the external interrupt (EXTINT) or the non-maskable interrupt
(NMI) pins are sampled using the EIC clock as defined by the Clock Selection bit in the Control A register
(CTRLA.CKSEL). The External Interrupt flag (INTFLAG.EXTINT[x]) or Non-Maskable Interrupt flag
(NMIFLAG.NMI) is set when the last sampled state of the pin differs from the previously sampled state. In
this mode, the EIC clock is required.
The Synchronous Edge Detection Mode can be used in Idle and Standby sleep modes.
In Asynchronous Edge Detection Mode, the external interrupt (EXTINT) pins or the non-maskable
interrupt (NMI) pins set the External Interrupt flag or Non-Maskable Interrupt flag (INTFLAG.EXTINT[x] or
NMIFLAG) directly. In this mode, the EIC clock is not requested.
The asynchronous edge detection mode can be used in Idle and Standby sleep modes.
26.6.4.3 Interrupt Pin Debouncing
The external interrupt pin (EXTINT) edge detection can use a debouncer to improve input noise immunity.
When selected, the debouncer can work in the synchronous mode or the asynchronous mode, depending
on the configuration of the ASYNCH.ASYNCH[x] bit for the pin. The debouncer uses the EIC clock as
defined by the bit CTRLA.CKSEL to clock the debouncing circuitry. The debouncing time frame is set with
the debouncer prescaler DPRESCALER.DPRESCALERn, which provides the low frequency clock tick
that is used to reject higher frequency signals.
The debouncing mode for pin EXTINT x can be selected only if the Sense bits in the Configuration y
register (CONFIGy.SENSEx) are set to RISE, FALL or BOTH. If the debouncing mode for pin EXTINT x is
selected, the filter mode for that pin (CONFIGy.FILTENx) can not be selected.
The debouncer manages an internal “valid pin state” that depends on the external interrupt (EXTINT) pin
transitions, the debouncing mode and the debouncer prescaler frequency. The valid pin state reflects the
pin value after debouncing. The external interrupt pin (EXTINT) is sampled continously on EIC clock. The
sampled value is evaluated on each low frequency clock tick to detect a transitional edge when the
sampled value is different of the current valid pin state. The sampled value is evaluated on each EIC
clock when DPRESCALER.TICKON=0 or on each low frequency clock tick when
DPRESCALER.TICKON=1, to detect a bounce when the sampled value is equal to the current valid pin
state. Transitional edge detection increments the transition counter of the EXTINT pin, while bounce
detection resets the transition counter. The transition counter must exceed the transition count threshold
as defined by the DPRESCALER.STATESn bitfield. In the synchronous mode the threshold is 4 when
DPRESCALER.STATESn=0 or 8 when DPRESCALER.STATESn=1. In the asynchronous mode the
threshold is 4.
The valid pin state for the pins can be accessed by reading the register PINSTATE for both synchronous
or asynchronous debouncing mode.
Synchronous edge detection In this mode the external interrupt (EXTINT) pin is sampled continously on
EIC clock.
1. A pin edge transition will be validated when the sampled value is consistently different of the
current valid pin state for 4 (or 8 depending on bit DPRESCALER.STATESn) consecutive ticks of
the low frequency clock.
2. Any pin sample, at the low frequency clock tick rate, with a value opposite to the current valid pin
state will increment the transition counter.
3. Any pin sample, at EIC clock rate (when DPRESCALER.TICKON=0) or the low frequency clock tick
(when DPRESCALER.TICKON=1), with a value identical to the current valid pin state will return the
transition counter to zero.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 436
4. When the transition counter meets the count threshold, the pin edge transition is validated and the
pin state PINSTATE.PINSTATE[x] is changed to the detected level.
5. The external interrupt flag (INTFLAG.EXTINT[x]) is set when the pin state PINSTATE.PINSTATE[x]
is changed.
Figure 26-3. EXTINT Pin Synchronous Debouncing (Rising Edge)
CLK_EIC
CLK_PRESCALER
EXTINTx
PIN_STATE
INTGLAG
TRANSITIONLOW HIGH
Set INTFLAG
In the synchronous edge detection mode, the EIC clock is required. The synchronous edge detection
mode can be used in Idle and Standby sleep modes.
Asynchronous edge detection In this mode, the external interrupt (EXTINT) pin directly drives an
asynchronous edges detector which triggers any rising or falling edge on the pin:
1. Any edge detected that indicates a transition from the current valid pin state will immediately set the
valid pin state PINSTATE.PINSTATE[x] to the detected level.
2. The external interrupt flag (INTFLAG.EXTINT[x] is immediately changed.
3. The edge detector will then be idle until no other rising or falling edge transition is detected during 4
consecutive ticks of the low frequency clock.
4. Any rising or falling edge transition detected during the idle state will return the transition counter to
0.
5. After 4 consecutive ticks of the low frequency clock without bounce detected, the edge detector is
ready for a new detection.
Figure 26-4. EXTINT Pin Asynchronous Debouncing (Rising Edge)
CLK_EIC
CLK_PRESCALER
EXTINTx
PIN_STATE
INTGLAG
TRANSITION
LOW HIGH
Set INTFLAG
In this mode, the EIC clock is requested. The asynchronous edge detection mode can be used in Idle and
Standby sleep modes.
26.6.5 DMA Operation
Not applicable.
26.6.6 Interrupts
The EIC has the following interrupt sources:
• External interrupt pins (EXTINTx). See 26.6.2 Basic Operation.
• Non-maskable interrupt pin (NMI). See 26.6.4 Additional Features.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 437
Each interrupt source has an associated interrupt flag. The interrupt flag in the Interrupt Flag Status and
Clear register (INTFLAG) is set when an interrupt condition occurs (NMIFLAG for NMI). Each interrupt,
except NMI, can be individually enabled by setting the corresponding bit in the Interrupt Enable Set
register (INTENSET=1), and disabled by setting the corresponding bit in the Interrupt Enable Clear
register (INTENCLR=1).
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or the EIC
is reset. See the INTFLAG register for details on how to clear interrupt flags. The EIC has one interrupt
request line for each external interrupt (EXTINTx) and one line for NMI. The user must read the INTFLAG
(or NMIFLAG) register to determine which interrupt condition is present.
Note: 
1. Interrupts must be globally enabled for interrupt requests to be generated.
2. If an external interrupts (EXTINT) is common on two or more I/O pins, only one will be active (the
first one programmed).
Related Links
10. Processor and Architecture
26.6.7 Events
The EIC can generate the following output events:
• External event from pin (EXTINTx).
Setting an Event Output Control register (EVCTRL.EXTINTEO) enables the corresponding output event.
Clearing this bit disables the corresponding output event. Refer to Event System for details on configuring
the Event System.
When the condition on pin EXTINTx matches the configuration in the CONFIGn register, the
corresponding event is generated, if enabled.
Related Links
29. EVSYS – Event System
26.6.8 Sleep Mode Operation
In sleep modes, an EXTINTx pin can wake up the device if the corresponding condition matches the
configuration in the CONFIG register, and the corresponding bit in the Interrupt Enable Set register
(26.8.7 INTENSET) is written to '1'.
Figure 26-5. Wake-up Operation Example (High-Level Detection, No Filter, Interrupt Enable Set)
CLK_EIC_APB
EXTINTx
intwake_extint[x]
intreq_extint[x]
clear INTFLAG.EXTINT[x]
wake from sleep mode
Related Links
26.8.10 CONFIG
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 438
26.6.9 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in control register (CTRLA.SWRST)
• Enable bit in control register (CTRLA.ENABLE)
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 439
26.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 CKSEL ENABLE SWRST
0x01 NMICTRL 7:0 NMIASYNCH NMIFILTEN NMISENSE[2:0]
0x02 NMIFLAG
7:0 NMI
15:8
0x04 SYNCBUSY
7:0 ENABLE SWRST
15:8
23:16
31:24
0x08 EVCTRL
7:0 EXTINTEO[7:0]
15:8 EXTINTEO[15:8]
23:16
31:24
0x0C INTENCLR
7:0 EXTINT[7:0]
15:8 EXTINT[15:8]
23:16
31:24
0x10 INTENSET
7:0 EXTINT[7:0]
15:8 EXTINT[15:8]
23:16
31:24
0x14 INTFLAG
7:0 EXTINT[7:0]
15:8 EXTINT[15:8]
23:16
31:24
0x18 ASYNCH
7:0 ASYNCH[7:0]
15:8 ASYNCH[15:8]
23:16
31:24
0x1C CONFIG0
7:0 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
15:8 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
23:16 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
31:24 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
0x20 CONFIG1
7:0 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
15:8 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
23:16 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
31:24 FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
0x24
...
0x2F
Reserved
0x30 DEBOUNCEN
7:0 DEBOUNCEN[7:0]
15:8 DEBOUNCEN[15:8]
23:16
31:24
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 440
...........continued
Offset Name Bit Pos.
0x34 DPRESCALER
7:0 STATESx PRESCALERx[2:0] STATESx PRESCALERx[2:0]
15:8
23:16 TICKON
31:24
0x38 PINSTATE
7:0 PINSTATE[7:0]
15:8 PINSTATE[15:8]
23:16
31:24
26.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 441
26.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
CKSEL ENABLE SWRST
Access RW RW W
Reset 0 0 0
Bit 4 – CKSEL Clock Selection
The EIC can be clocked either by GCLK_EIC (when a frequency higher than 32KHz is required for
filtering) or by CLK_ULP32K (when power consumption is the priority).
This bit is not Write-Synchronized.
Value Description
0The EIC is clocked by GCLK_EIC.
1The EIC is clocked by CLK_ULP32K.
Bit 1 – ENABLE Enable
Due to synchronization there is a delay between writing to CTRLA.ENABLE until the peripheral is
enabled/disabled. The value written to CTRLA.ENABLE will read back immediately and the Enable bit in
the Synchronization Busy register will be set (SYNCBUSY.ENABLE=1). SYNCBUSY.ENABLE will be
cleared when the operation is complete.
This bit is not Enable-Protected.
This bit is Write-Synchronized.
Value Description
0The EIC is disabled.
1The EIC is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the EIC to their initial state, and the EIC will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the Reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the Reset is complete.
This bit is not Enable-Protected.
This bit is Write-Synchronized.
Value Description
0There is no ongoing reset operation.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 442
26.8.2 Non-Maskable Interrupt Control
Name:  NMICTRL
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
NMIASYNCH NMIFILTEN NMISENSE[2:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 4 – NMIASYNCH Asynchronous Edge Detection Mode
The NMI edge detection can be operated synchronously or asynchronously to the EIC clock.
Value Description
0The NMI edge detection is synchronously operated.
1The NMI edge detection is asynchronously operated.
Bit 3 – NMIFILTEN Non-Maskable Interrupt Filter Enable
Value Description
0NMI filter is disabled.
1NMI filter is enabled.
Bits 2:0 – NMISENSE[2:0] Non-Maskable Interrupt Sense Configuration
These bits define on which edge or level the NMI triggers.
Value Name Description
0x0 NONE No detection
0x1 RISE Rising-edge detection
0x2 FALL Falling-edge detection
0x3 BOTH Both-edge detection
0x4 HIGH High-level detection
0x5 LOW Low-level detection
0x6 -
0x7
- Reserved
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 443
26.8.3 Non-Maskable Interrupt Flag Status and Clear
Name:  NMIFLAG
Offset:  0x02
Reset:  0x0000
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
NMI
Access RW
Reset 0
Bit 0 – NMI Non-Maskable Interrupt
This flag is cleared by writing a '1' to it.
This flag is set when the NMI pin matches the NMI sense configuration, and will generate an interrupt
request.
Writing a '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 444
26.8.4 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x04
Reset:  0x00000000
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ENABLE SWRST
Access R R
Reset 0 0
Bit 1 – ENABLE Enable Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.ENABLE bit is complete.
1Write synchronization for CTRLA.ENABLE bit is ongoing.
Bit 0 – SWRST Software Reset Synchronization Busy Status
Value Description
0Write synchronization for CTRLA.SWRST bit is complete.
1Write synchronization for CTRLA.SWRST bit is ongoing.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 445
26.8.5 Event Control
Name:  EVCTRL
Offset:  0x08
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
EXTINTEO[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EXTINTEO[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – EXTINTEO[15:0] External Interrupt Event Output Enable
The bit x of EXTINTEO enables the event associated with the EXTINTx pin.
Value Description
0Event from pin EXTINTx is disabled.
1Event from pin EXTINTx is enabled and will be generated when EXTINTx pin matches the
external interrupt sensing configuration.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 446
26.8.6 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x0C
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
EXTINT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EXTINT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – EXTINT[15:0] External Interrupt Enable
The bit x of EXTINT disables the interrupt associated with the EXTINTx pin.
Writing a '0' to bit x has no effect.
Writing a '1' to bit x will clear the External Interrupt Enable bit x, which disables the external interrupt
EXTINTx.
Value Description
0The external interrupt x is disabled.
1The external interrupt x is enabled.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 447
26.8.7 Interrupt Enable Set
Name:  INTENSET
Offset:  0x10
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
EXTINT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EXTINT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – EXTINT[15:0] External Interrupt Enable
The bit x of EXTINT enables the interrupt associated with the EXTINTx pin.
Writing a '0' to bit x has no effect.
Writing a '1' to bit x will set the External Interrupt Enable bit x, which enables the external interrupt
EXTINTx.
Value Description
0The external interrupt x is disabled.
1The external interrupt x is enabled.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 448
26.8.8 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x14
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
EXTINT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EXTINT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – EXTINT[15:0] External Interrupt
The flag bit x is cleared by writing a '1' to it.
This flag is set when EXTINTx pin matches the external interrupt sense configuration and will generate an
interrupt request if INTENCLR/SET.EXTINT[x] is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the External Interrupt x flag.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 449
26.8.9 External Interrupt Asynchronous Mode
Name:  ASYNCH
Offset:  0x18
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
ASYNCH[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ASYNCH[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – ASYNCH[15:0] Asynchronous Edge Detection Mode
The bit x of ASYNCH set the Asynchronous Edge Detection Mode for the interrupt associated with the
EXTINTx pin.
Value Description
0The EXTINT x edge detection is synchronously operated.
1The EXTINT x edge detection is asynchronously operated.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 450
26.8.10 External Interrupt Sense Configuration n
Name:  CONFIG
Offset:  0x1C + n*0x04 [n=0..1]
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
FILTENx SENSEx[2:0] FILTENx SENSEx[2:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 3,7,11,15,19,23,27,31 – FILTENx Filter Enable x [x=7..0]
Note:  The filter must be disabled if the asynchronous detection is enabled.
Value Description
0Filter is disabled for EXTINT[n*8+x] input.
1Filter is enabled for EXTINT[n*8+x] input.
Bits 0:2,4:6,8:10,12:14,16:18,20:22,24:26,28:30 – SENSEx Input Sense Configuration x [x=7..0]
These bits define on which edge or level the interrupt or event for EXTINT[n*8+x] will be generated.
Value Name Description
0x0 NONE No detection
0x1 RISE Rising-edge detection
0x2 FALL Falling-edge detection
0x3 BOTH Both-edge detection
0x4 HIGH High-level detection
0x5 LOW Low-level detection
0x6 -
0x7
- Reserved
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 451
26.8.11 Debouncer Enable
Name:  DEBOUNCEN
Offset:  0x30
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
DEBOUNCEN[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DEBOUNCEN[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – DEBOUNCEN[15:0] Debouncer Enable
The bit x of DEBOUNCEN set the Debounce mode for the interrupt associated with the EXTINTx pin.
Value Description
0The EXTINT x edge input is not debounced.
1The EXTINT x edge input is debounced.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 452
26.8.12 Debouncer Prescaler
Name:  DPRESCALER
Offset:  0x34
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
TICKON
Access RW
Reset 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
STATESx PRESCALERx[2:0] STATESx PRESCALERx[2:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 16 – TICKON Pin Sampler frequency selection
This bit selects the clock used for the sampling of bounce during transition detection.
Value Description
0The bounce sampler is using GCLK_EIC.
1The bounce sampler is using the low frequency clock.
Bits 3,7 – STATESx Debouncer number of states x
This bit selects the number of samples by the debouncer low frequency clock needed to validate a
transition from current pin state to next pin state in synchronous debouncing mode for pins
EXTINT[7+(8x):8x].
Value Description
0The number of low frequency samples is 3.
1The number of low frequency samples is 7.
Bits 2:0, 6:4 – PRESCALERx Debouncer Prescaler x
These bits select the debouncer low frequency clock for pins EXTINT[7+(8x):8x].
Value Name Description
0x0 F/2 EIC clock divided by 2
0x1 F/4 EIC clock divided by 4
0x2 F/8 EIC clock divided by 8
0x3 F/16 EIC clock divided by 16
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 453
Value Name Description
0x4 F/32 EIC clock divided by 32
0x5 F/64 EIC clock divided by 64
0x6 F/128 EIC clock divided by 128
0x7 F/256 EIC clock divided by 256
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 454
26.8.13 Pin State
Name:  PINSTATE
Offset:  0x38
Reset:  0x00000000
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
PINSTATE[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PINSTATE[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – PINSTATE[15:0] Pin State
These bits return the valid pin state of the debounced external interrupt pin EXTINTx.
SAM C20/C21 Family Data Sheet
EIC – External Interrupt Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 455
27. NVMCTRL – Nonvolatile Memory Controller
27.1 Overview
Nonvolatile Memory (NVM) is a reprogrammable Flash memory that retains program and data storage
even with power off. It embeds a main array and a separate smaller array intended for EEPROM
emulation (RWWEE) that can be programmed while reading the main array. The NVM Controller
(NVMCTRL) connects to the AHB and APB bus interfaces for system access to the NVM block. The AHB
interface is used for reads and writes to the NVM block, while the APB interface is used for commands
and configuration.
27.2 Features
• 32-bit AHB interface for reads and writes
• Read-While-Write DATA Flash
• All NVM sections are memory mapped to the AHB, including calibration and system configuration
• 32-bit APB interface for commands and control
• Programmable wait states for read optimization
• 16 regions can be individually protected or unprotected
• Additional protection for bootloader
• Supports device protection through a security bit
• Interface to Power Manager for power-down of Flash blocks in sleep modes
• Can optionally wake up on exit from sleep or on first access
• Direct-mapped cache
Note:  A register with property "Enable-Protected" may contain bits that are not enable-protected.
27.3 Block Diagram
Figure 27-1. Block Diagram
Command and
Control
NVM Interface
Cache
NVM Block
NVMCTRL
AHB
APB
main array
RWWEE array
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 456
27.4 Signal Description
Not applicable.
27.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described in the
following sections.
27.5.1 Power Management
The NVMCTRL will continue to operate in any sleep mode where the selected source clock is running.
The NVMCTRL interrupts can be used to wake up the device from sleep modes.
The Power Manager will automatically put the NVM block into a low-power state when entering sleep
mode. This is based on the Control B register (CTRLB) SLEEPPRM bit setting. Refer to the 27.8.2
CTRLB. SLEEPPRM register description for more details. The NVM block goes into low-power mode
automatically when the device enters STANDBY mode regardless of SLEEPPRM. The NVM Page Buffer
is lost when the NVM goes into low power mode therefore a write command must be issued prior entering
the NVM low power mode. NVMCTRL SLEEPPRM can be disabled to avoid such loss when the CPU
goes into sleep except if the device goes into STANDBY mode for which there is no way to retain the
Page Buffer.
Related Links
19. PM – Power Manager
27.5.2 Clocks
Two synchronous clocks are used by the NVMCTRL. One is provided by the AHB bus
(CLK_NVMCTRL_AHB) and the other is provided by the APB bus (CLK_NVMCTRL_APB). For higher
system frequencies, a programmable number of wait states can be used to optimize performance. When
changing the AHB bus frequency, the user must ensure that the NVM Controller is configured with the
proper number of wait states. Refer to the Electrical Characteristics for the exact number of wait states to
be used for a particular frequency range.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
27.5.3 Interrupts
The NVM Controller interrupt request line is connected to the interrupt controller. Using the NVMCTRL
interrupt requires the interrupt controller to be programmed first.
27.5.4 Debug Operation
When an external debugger forces the CPU into debug mode, the peripheral continues normal operation.
Access to the NVM block can be protected by the security bit. In this case, the NVM block will not be
accessible. See the section on the NVMCTRL 27.6.6 Security Bit for details.
27.5.5 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC),
except the following registers:
• Interrupt Flag Status and Clear register (INTFLAG)
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 457
• Status register (STATUS)
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Related Links
11. PAC - Peripheral Access Controller
27.5.6 Analog Connections
Not applicable.
27.6 Functional Description
27.6.1 Principle of Operation
The NVM Controller is a slave on the AHB and APB buses. It responds to commands, read requests and
write requests, based on user configuration.
27.6.1.1 Initialization
After power up, the NVM Controller goes through a power-up sequence. During this time, access to the
NVM Controller from the AHB bus is halted. Upon power-up completion, the NVM Controller is
operational without any need for user configuration.
27.6.2 Memory Organization
Refer to the Physical Memory Map for memory sizes and addresses for each device.
The NVM is organized into rows, where each row contains four pages, as shown in the NVM Row
Organization figure. The NVM has a row-erase granularity, while the write granularity is by page. In other
words, a single row erase will erase all four pages in the row, while four write operations are used to write
the complete row.
Figure 27-2. NVM Row Organization
Page (n*4) + 3 Page (n*4) + 2 Page (n*4) + 1 Page (n*4) + 0
Row n
The NVM block contains a calibration and auxiliary space plus a dedicated EEPROM emulation space
that are memory mapped. Refer to the NVM Organization figure below for details.
The calibration and auxiliary space contains factory calibration and system configuration information.
These spaces can be read from the AHB bus in the same way as the main NVM main address space.
In addition, a boot loader section can be allocated at the beginning of the main array, and an EEPROM
section can be allocated at the end of the NVM main address space.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 458
Figure 27-3. NVM Memory Organization
Calibration and
Auxillary Space
RWWEE
Address Space
NVM Main
Address Space
NVM Base Address + 0x00800000
NVM Base Address + 0x00400000
NVM Base Address + NVM Size
NVM Base Address
The lower rows in the NVM main address space can be allocated as a boot loader section by using the
BOOTPROT fuses, and the upper rows can be allocated to EEPROM, as shown in the figure below.
The boot loader section is protected by the lock bit(s) corresponding to this address space and by the
BOOTPROT[2:0] fuse. The EEPROM rows can be written regardless of the region lock status.
The number of rows protected by BOOTPROT is given in Boot Loader Size, the number of rows allocated
to the EEPROM are given in EEPROM Size.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 459
Figure 27-4. EEPROM and Boot Loader Allocation
Related Links
9.2 Physical Memory Map
27.6.3 Region Lock Bits
The NVM block is grouped into 16 equally sized regions. The region size is dependent on the Flash
memory size, and is given in the table below. Each region has a dedicated lock bit preventing writing and
erasing pages in the region. After production, all regions will be unlocked.
Table 27-1. Region Size
Memory Size [KB] Region Size [KB]
256 16
128 8
64 4
32 2
To lock or unlock a region, the Lock Region and Unlock Region commands are provided. Writing one of
these commands will temporarily lock/unlock the region containing the address loaded in the ADDR
register. ADDR can be written by software, or the automatically loaded value from a write operation can
be used. The new setting will stay in effect until the next Reset, or until the setting is changed again using
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 460
the Lock and Unlock commands. The current status of the lock can be determined by reading the LOCK
register.
To change the default lock/unlock setting for a region, the user configuration section of the auxiliary space
must be written using the Write Auxiliary Page command. Writing to the auxiliary space will take effect
after the next Reset. Therefore, a boot of the device is needed for changes in the lock/unlock setting to
take effect. Refer to the Physical Memory Map for calibration and auxiliary space address mapping.
Related Links
9.2 Physical Memory Map
27.6.4 Command and Data Interface
The NVM Controller is addressable from the APB bus, while the NVM main address space is addressable
from the AHB bus. Read and automatic page write operations are performed by addressing the NVM
main address space or the RWWEE address space directly, while other operations such as manual page
writes and row erases must be performed by issuing commands through the NVM Controller.
To issue a command, the CTRLA.CMD bits must be written along with the CTRLA.CMDEX value. When a
command is issued, INTFLAG.READY will be cleared until the command has completed. Any commands
written while INTFLAG.READY is low will be ignored.
The CTRLB register must be used to control the power reduction mode, read wait states, and the write
mode.
27.6.4.1 NVM Read
Reading from the NVM main address space is performed via the AHB bus by addressing the NVM main
address space or auxiliary address space directly. Read data is available after the configured number of
read wait states (CTRLB.RWS) set in the NVM Controller.
The number of cycles data are delayed to the AHB bus is determined by the read wait states. Examples
of using zero and one wait states are shown in the following figure.
Reading the NVM main address space while a programming or erase operation is ongoing on the NVM
main array results in an AHB bus stall until the end of the operation. Reading the NVM main array does
not stall the bus when the RWWEE array is being programmed or erased.
Figure 27-5. Read Wait State Examples
0 Wait States
1 Wait States
AHB Command
AHB Slave Ready
AHB Slave Data
AHB Command
AHB Slave Ready
AHB Slave Data
Rd 0 Rd 1 Idle
Rd 0 Rd 1 Idle
Data 0 Data 1
Data 0 Data 1
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 461
27.6.4.2 RWWEE Read
Reading from the RWW EEPROM address space is performed via the AHB bus by addressing the
RWWEE address space directly.
Read timings are similar to regular NVM read timings when access size is Byte or half-Word. The AHB
data phase is twice as long in case of full-Word-size access.
It is not possible to read the RWWEE area while the NVM main array is being written or erased, whereas
the RWWEE area can be written or erased while the main array is being read.
The RWWEE address space is not cached, therefore it is recommended to limit access to this area for
performance and power consumption considerations.
27.6.4.3 NVM Write
The NVM Controller requires that an erase must be done before programming. The entire NVM main
address space and the RWWEE address space can be erased by a debugger Chip Erase command.
Alternatively, rows can be individually erased by the Erase Row command or the RWWEE Erase Row
command to erase the NVM main address space or the RWWEE address space, respectively.
After programming the NVM main array, the region that the page resides in can be locked to prevent
spurious write or erase sequences. Locking is performed on a per-region basis, and so, locking a region
will lock all pages inside the region.
Data to be written to the NVM block are first written to and stored in an internal buffer called the page
buffer. The page buffer contains the same number of bytes as an NVM page. Writes to the page buffer
must be 16 or 32 bits. 8-bit writes to the page buffer are not allowed and will cause a system exception.
Internally, writes to the page buffer are on a 64-bit basis through the page buffer load data register
(PBLDATA1 and PBLDATA0). The PBLDATA register is a holding register for writes to the same 64-bit
page buffer section. Data within a 64-bit section can be written in any order. Crossing a 64-bit boundary
will reset the PBLDATA register to all ones. The following example assumes startup from reset where the
current address is 0 and PBLDATA is all ones. Only 64 bits of the page buffer are written at a time, but
128 bits are shown for reference.
Sequential 32-bit Write Example:
• 32-bit 0x1 written to address 0
– Page buffer[127:0] = {0xFFFFFFFF_FFFFFFFF, PBLDATA[63:32], 0x00000001}
– PBLDATA[63:0] = {PBLDATA[63:32], 0x00000001}
• 32-bit 0x2 written to address 1
– Page buffer[127:0] = {0xFFFFFFFF_FFFFFFFF, 0x00000002, PBLDATA[31:0]
– PBLDATA[63:0] = 0x00000002, PBLDATA[31:0]}
• 32-bit 0x3 written to address 2 (crosses 64-bit boundary)
– Page buffer[127:0] = 0xFFFFFFFF_00000003_00000002_00000001
– PBLDATA[63:0] = 0xFFFFFFFF_00000003
Random access writes to 32-bit words within the page buffer will overwrite the opposite word within the
same 64-bit section with ones. In the following example, notice that 0x00000001 is overwritten with
0xFFFFFFFF from the third write due to the 64-bit boundary crossing. Only 64 bits of the page buffer are
written at a time, but 128 bits are shown for reference.
Random Access 32-bit Write Example:
• 32-bit 0x1 written to address 2
– Page buffer[127:0] = 0xFFFFFFFF_00000001_FFFFFFFF_FFFFFFFF
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 462
– PBLDATA[63:0] = 0xFFFFFFFF_00000001
• 32-bit 0x2 written to address 1
– Page buffer[127:0] = 0xFFFFFFFF_00000001_00000002_FFFFFFFF
– PBLDATA[63:0] = 0x00000002_FFFFFFFF
• 32-bit 0x3 written to address 3
– Page buffer[127:0] = 0x00000003_FFFFFFFF_00000002_FFFFFFFF
– PBLDATA[63:0] = 0x00000003_0xFFFFFFFF
Both the NVM main array and the RWWEE array share the same page buffer. Writing to the NVM block
via the AHB bus is performed by a load operation to the page buffer. For each AHB bus write, the address
is stored in the ADDR register. After the page buffer has been loaded with the required number of bytes,
the page can be written to the NVM main array or the RWWEE array by setting CTRLA.CMD to 'Write
Page' or 'RWWEE Write Page', respectively, and setting the key value to CMDEX. The LOAD bit in the
STATUS register indicates whether the page buffer has been loaded or not. Before writing the page to
memory, the accessed row must be erased.
Automatic page writes are enabled by writing the manual write bit to zero (CTRLB.MANW=0). This will
trigger a write operation to the page addressed by ADDR when the last location of the page is written.
Because the address is automatically stored in ADDR during the I/O bus write operation, the last given
address will be present in the ADDR register. There is no need to load the ADDR register manually,
unless a different page in memory is to be written.
27.6.4.3.1 Procedure for Manual Page Writes (CTRLB.MANW=1)
The row to be written to must be erased before the write command is given.
• Write to the page buffer by addressing the NVM main address space directly
• Write the page buffer to memory: CTRL.CMD='Write Page' and CMDEX
• The READY bit in the INTFLAG register will be low while programming is in progress, and access
through the AHB will be stalled
27.6.4.3.2 Procedure for Automatic Page Writes (CTRLB.MANW=0)
The row to be written to must be erased before the last write to the page buffer is performed.
Note that partially written pages must be written with a manual write.
• Write to the page buffer by addressing the NVM main address space directly.
When the last location in the page buffer is written, the page is automatically written to NVM main
address space.
• INTFLAG.READY will be zero while programming is in progress and access through the AHB will be
stalled.
27.6.4.4 Page Buffer Clear
The page buffer is automatically set to all '1' after a page write is performed. If a partial page has been
written and it is desired to clear the contents of the page buffer, the Page Buffer Clear command can be
used.
27.6.4.5 Erase Row
Before a page can be written, the row containing that page must be erased. The Erase Row command
can be used to erase the desired row in the NVM main address space. The RWWEE Erase Row can be
used to erase the desired row in the RWWEE array. Erasing the row sets all bits to '1'. If the row resides
in a region that is locked, the erase will not be performed and the Lock Error bit in the Status register
(STATUS.LOCKE) will be set.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 463
27.6.4.5.1 Procedure for Erase Row
• Write the address of the row to erase to ADDR. Any address within the row can be used.
• Issue an Erase Row command.
Note:  The NVM Address bit field in the Address register (ADDR.ADDR) uses 16-bit addressing.
27.6.4.6 Lock and Unlock Region
These commands are used to lock and unlock regions as detailed in section 27.6.3 Region Lock Bits.
27.6.4.7 Set and Clear Power Reduction Mode
The NVM Controller and block can be taken in and out of power reduction mode through the Set and
Clear Power Reduction Mode commands. When the NVM Controller and block are in power reduction
mode, the Power Reduction Mode bit in the Status register (STATUS.PRM) is set.
27.6.5 NVM User Configuration
The NVM user configuration resides in the auxiliary space. Refer to the Physical Memory Map of the
device for calibration and auxiliary space address mapping.
The bootloader resides in the main array starting at offset zero. The allocated boot loader section is write-
protected.
Table 27-2. Boot Loader Size
BOOTPROT [2:0] Rows Protected by BOOTPROT Boot Loader Size in Bytes
0x7(1)None 0
0x6 2 512
0x5 4 1024
0x4 8 2048
0x3 16 4096
0x2 32 8192
0x1 64 16384
0x0 128 32768
Note:  1) Default value is 0x7.
The EEPROM[2:0] bits indicate the EEPROM size, see the table below. The EEPROM resides in the
upper rows of the NVM main address space and is writable, regardless of the region lock status.
Table 27-3. EEPROM Size
EEPROM[2:0] Rows Allocated to EEPROM EEPROM Size in Bytes
7 None 0
6 1 256
5 2 512
4 4 1024
3 8 2048
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 464
...........continued
EEPROM[2:0] Rows Allocated to EEPROM EEPROM Size in Bytes
2 16 4096
1 32 8192
0 64 16384
Related Links
9.2 Physical Memory Map
27.6.6 Security Bit
The security bit allows the entire chip to be locked from external access for code security. The security bit
can be written by a dedicated command, Set Security Bit (SSB). Once set, the only way to clear the
security bit is through a debugger Chip Erase command. After issuing the SSB command, the PROGE
error bit can be checked.
In order to increase the security level it is recommended to enable the internal BODVDD when the
security bit is set.
Related Links
13. DSU - Device Service Unit
27.6.7 Cache
The NVM Controller cache reduces the device power consumption and improves system performance
when wait states are required. Only the NVM main array address space is cached. It is a direct-mapped
cache that implements 8 lines of 64 bits (i.e., 64 Bytes). NVM Controller cache can be enabled by writing
a '0' to the Cache Disable bit in the Control B register (CTRLB.CACHEDIS).
The cache can be configured to three different modes using the Read Mode bit group in the Control B
register (CTRLB.READMODE).
The INVALL command can be issued using the Command bits in the Control A register to invalidate all
cache lines (CTRLA.CMD=INVALL). Commands affecting NVM content automatically invalidate cache
lines.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 465
27.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA
7:0 CMD[6:0]
15:8 CMDEX[7:0]
0x02
...
0x03
Reserved
0x04 CTRLB
7:0 MANW RWS[3:0]
15:8 SLEEPPRM[1:0]
23:16 CACHEDIS READMODE[1:0]
31:24
0x08 PARAM
7:0 NVMP[7:0]
15:8 NVMP[15:8]
23:16 RWWEEP[3:0] PSZ[2:0]
31:24 RWWEEP[11:4]
0x0C INTENCLR 7:0 ERROR READY
0x0D
...
0x0F
Reserved
0x10 INTENSET 7:0 ERROR READY
0x11
...
0x13
Reserved
0x14 INTFLAG 7:0 ERROR READY
0x15
...
0x17
Reserved
0x18 STATUS
7:0 NVME LOCKE PROGE LOAD PRM
15:8 SB
0x1A
...
0x1B
Reserved
0x1C ADDR
7:0 ADDR[7:0]
15:8 ADDR[15:8]
23:16 ADDR[20:16]
31:24
0x20 LOCK
7:0 LOCK[7:0]
15:8 LOCK[15:8]
0x22
...
0x27
Reserved
0x28 PBLDATA0
7:0 PBLDATA[7:0]
15:8 PBLDATA[15:8]
23:16 PBLDATA[23:16]
31:24 PBLDATA[31:24]
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 466
...........continued
Offset Name Bit Pos.
0x2C PBLDATA1
7:0 PBLDATA[7:0]
15:8 PBLDATA[15:8]
23:16 PBLDATA[23:16]
31:24 PBLDATA[31:24]
27.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 467
27.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x0000
Property:  PAC Write-Protection
Bit 15 14 13 12 11 10 9 8
CMDEX[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CMD[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 15:8 – CMDEX[7:0] Command Execution
When this bit group is written to the key value 0xA5, the command written to CMD will be executed. If a
value different from the key value is tried, the write will not be performed and the Programming Error bit in
the Status register (STATUS.PROGE) will be set. PROGE is also set if a previously written command is
not completed yet.
The key value must be written at the same time as CMD. If a command is issued through the APB bus on
the same cycle as an AHB bus access, the AHB bus access will be given priority. The command will then
be executed when the NVM block and the AHB bus are idle.
INTFLAG.READY must be '1' when the command is issued.
Bit 0 of the CMDEX bit group will read back as '1' until the command is issued.
Note:  The NVM Address bit field in the Address register (ADDR.ADDR) uses 16-bit addressing.
Bits 6:0 – CMD[6:0] Command
These bits define the command to be executed when the CMDEX key is written.
CMD[6:0] Group
Configuration
Description
0x00-0x01 - Reserved
0x02 ER Erase Row - Erases the row addressed by the ADDR register in the
NVM main array.
0x03 - Reserved
0x04 WP Write Page - Writes the contents of the page buffer to the page
addressed by the ADDR register.
0x05 EAR Erase Auxiliary Row - Erases the auxiliary row addressed by the
ADDR register. This command can be given only when the Security
bit is not set and only to the User Configuration Row.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 468
...........continued
CMD[6:0] Group
Configuration
Description
0x06 WAP Write Auxiliary Page - Writes the contents of the page buffer to the
page addressed by the ADDR register. This command can be given
only when the Security bit is not set and only to the User
Configuration Row.
0x07-0x0E - Reserved
0x0F - Reserved
0x1A-0x19 - Reserved
0x1A RWWEEER RWWEE Erase Row - Erases the row addressed by the ADDR
register in the RWWEE array.
0x1B - Reserved
0x1C RWWEEWP RWWEE Write Page - Writes the contents of the page buffer to the
page addressed by the ADDR register in the RWWEE array.
0x1D-0x3F - Reserved
0x40 LR Lock Region - Locks the region containing the address location in
the ADDR register.
0x41 UR Unlock Region - Unlocks the region containing the address location
in the ADDR register.
0x42 SPRM Sets the Power Reduction mode.
0x43 CPRM Clears the Power Reduction mode.
0x44 PBC Page Buffer Clear - Clears the page buffer.
0x45 SSB Set Security Bit - Sets the Security bit by writing 0x00 to the first
byte in the lockbit row.
0x46 INVALL Invalidates all cache lines.
0x47 LDR Lock Data Region - Locks the data region containing the address
location in the ADDR register.
When the security extension is enabled, only secure access can
lock secure regions.
0x48 UDR Unlock Data Region - Unlocks the data region containing the
address location in the ADDR register.
When the security extension is enabled, only secure access can
unlock secure regions.
0x47-0x7F - Reserved
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 469
27.8.2 Control B
Name:  CTRLB
Offset:  0x04
Reset:  0x00000080
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CACHEDIS READMODE[1:0]
Access R/W R/W R/W
Reset 0 0 0
Bit 15 14 13 12 11 10 9 8
SLEEPPRM[1:0]
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
MANW RWS[3:0]
Access R/W R/W R/W R/W R/W
Reset 1 0 0 0 0
Bit 18 – CACHEDIS Cache Disable
This bit is used to disable the cache.
Value Description
0The cache is enabled
1The cache is disabled
Bits 17:16 – READMODE[1:0] NVMCTRL Read Mode
Value Name Description
0x0 NO_MISS_PENALTY The NVM Controller (cache system) does not insert wait states on a
cache miss. Gives the best system performance.
0x1 LOW_POWER Reduces power consumption of the cache system, but inserts a wait
state each time there is a cache miss. This mode may not be relevant
if CPU performance is required, as the application will be stalled and
may lead to increased run time.
0x2 DETERMINISTIC The cache system ensures that a cache hit or miss takes the same
amount of time, determined by the number of programmed Flash wait
states. This mode can be used for real-time applications that require
deterministic execution timings.
0x3 Reserved
Bits 9:8 – SLEEPPRM[1:0] Power Reduction Mode during Sleep
Indicates the Power Reduction Mode during sleep.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 470
Value Name Description
0x0 WAKEUPACCESS NVM block enters low-power mode when entering sleep.
NVM block exits low-power mode upon first access.
0x1 WAKEUPINSTANT NVM block enters low-power mode when entering sleep.
NVM block exits low-power mode when exiting sleep.
0x2 Reserved
0x3 DISABLED Auto power reduction disabled.
Bit 7 – MANW Manual Write
Note that reset value of this bit is '1'.
Value Description
0Writing to the last word in the page buffer will initiate a write operation to the page addressed
by the last write operation. This includes writes to memory and auxiliary rows.
1Write commands must be issued through the CTRLA.CMD register.
Bits 4:1 – RWS[3:0] NVM Read Wait States
These bits control the number of wait states for a read operation. '0' indicates zero wait states, '1'
indicates one wait state, etc., up to 15 wait states.
This register is initialized to 0 wait states. Software can change this value based on the NVM access time
and system frequency.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 471
27.8.3 NVM Parameter
Name:  PARAM
Offset:  0x08
Reset:  0x000XXXXX
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
RWWEEP[11:4]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
RWWEEP[3:0] PSZ[2:0]
Access R R R R R R R
Reset 0 0 0 0 x x x
Bit 15 14 13 12 11 10 9 8
NVMP[15:8]
Access R R R R R R R R
Reset x x x x x x x x
Bit 7 6 5 4 3 2 1 0
NVMP[7:0]
Access R R R R R R R R
Reset x x x x x x x x
Bits 31:20 – RWWEEP[11:0] Read While Write EEPROM emulation area Pages
Indicates the number of pages in the RWW EEPROM emulation address space.
Bits 18:16 – PSZ[2:0] Page Size
Indicates the page size. Not all devices of the device families will provide all the page sizes indicated in
the table.
Value Name Description
0x0 8 8 bytes
0x1 16 16 bytes
0x2 32 32 bytes
0x3 64 64 bytes
0x4 128 128 bytes
0x5 256 256 bytes
0x6 512 512 bytes
0x7 1024 1024 bytes
Bits 15:0 – NVMP[15:0] NVM Pages
Indicates the number of pages in the NVM main address space.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 472
27.8.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
ERROR READY
Access R/W R/W
Reset 0 0
Bit 1 – ERROR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the ERROR interrupt enable.
This bit will read as the current value of the ERROR interrupt enable.
Bit 0 – READY NVM Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the READY interrupt enable.
This bit will read as the current value of the READY interrupt enable.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 473
27.8.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x10
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
ERROR READY
Access R/W R/W
Reset 0 0
Bit 1 – ERROR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit sets the ERROR interrupt enable.
This bit will read as the current value of the ERROR interrupt enable.
Bit 0 – READY NVM Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit sets the READY interrupt enable.
This bit will read as the current value of the READY interrupt enable.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 474
27.8.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x14
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
ERROR READY
Access R/W R
Reset 0 0
Bit 1 – ERROR Error
This flag is set on the occurrence of an NVME, LOCKE or PROGE error.
This bit can be cleared by writing a '1' to its bit location.
Value Description
0No errors have been received since the last clear.
1At least one error has occurred since the last clear.
Bit 0 – READY NVM Ready
Value Description
0The NVM controller is busy programming or erasing.
1The NVM controller is ready to accept a new command.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 475
27.8.7 Status
Name:  STATUS
Offset:  0x18
Reset:  0x0X00
Property:  –
Bit 15 14 13 12 11 10 9 8
SB
Access R
Reset x
Bit 7 6 5 4 3 2 1 0
NVME LOCKE PROGE LOAD PRM
Access R/W R/W R/W R/W R
Reset 0 0 0 0 0
Bit 8 – SB Security Bit Status
Value Description
0The Security bit is inactive.
1The Security bit is active.
Bit 4 – NVME NVM Error
This bit can be cleared by writing a '1' to its bit location.
Value Description
0No programming or erase errors have been received from the NVM controller since this bit
was last cleared.
1At least one error has been registered from the NVM Controller since this bit was last
cleared.
Bit 3 – LOCKE Lock Error Status
This bit can be cleared by writing a '1' to its bit location.
Value Description
0No programming of any locked lock region has happened since this bit was last cleared.
1Programming of at least one locked lock region has happened since this bit was last cleared.
Bit 2 – PROGE Programming Error Status
This bit can be cleared by writing a '1' to its bit location.
Value Description
0No invalid commands or bad keywords were written in the NVM Command register since this
bit was last cleared.
1An invalid command and/or a bad keyword was/were written in the NVM Command register
since this bit was last cleared.
Bit 1 – LOAD NVM Page Buffer Active Loading
This bit indicates that the NVM page buffer has been loaded with one or more words. Immediately after
an NVM load has been performed, this flag is set. It remains set until a page write or a page buffer clear
(PBCLR) command is given.
This bit can be cleared by writing a '1' to its bit location.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 476
Bit 0 – PRM Power Reduction Mode
This bit indicates the current NVM power reduction state. The NVM block can be set in power reduction
mode in two ways: through the command interface or automatically when entering sleep with SLEEPPRM
set accordingly.
PRM can be cleared in three ways: through AHB access to the NVM block, through the command
interface (SPRM and CPRM) or when exiting sleep with SLEEPPRM set accordingly.
Value Description
0NVM is not in power reduction mode.
1NVM is in power reduction mode.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 477
27.8.8 Address
Name:  ADDR
Offset:  0x1C
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
ADDR[20:16]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ADDR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ADDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 20:0 – ADDR[20:0] NVM Address
ADDR drives the hardware (16-bit) address to the NVM when a command is executed using CMDEX.
This register is also automatically updated when writing to the page buffer.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 478
27.8.9 Lock Section
Name:  LOCK
Offset:  0x20
Reset:  0xXXXX
Property:  –
Bit 15 14 13 12 11 10 9 8
LOCK[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
LOCK[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 x
Bits 15:0 – LOCK[15:0] Region Lock Bits
To set or clear these bits, the CMD register must be used.
Default state after erase will be unlocked (0x0000).
Value Description
0The corresponding lock region is locked.
1The corresponding lock region is not locked.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 479
27.8.10 Page Buffer Load Data 0
Name:  PBLDATA0
Offset:  0x28
Reset:  0xFFFFFFFF
Property:  -
Bit 31 30 29 28 27 26 25 24
PBLDATA[31:24]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bit 23 22 21 20 19 18 17 16
PBLDATA[23:16]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bit 15 14 13 12 11 10 9 8
PBLDATA[15:8]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bit 7 6 5 4 3 2 1 0
PBLDATA[7:0]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bits 31:0 – PBLDATA[31:0] Page Buffer Load Data
The PBLDATA register is a holding register for partial AHB writes to the same 64-bit page buffer section.
Page buffer loads are performed on a 64-bit basis.
This is a read only register.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 480
27.8.11 Page Buffer Load Data 1
Name:  PBLDATA1
Offset:  0x2C
Reset:  0xFFFFFFFF
Property:  -
Bit 31 30 29 28 27 26 25 24
PBLDATA[31:24]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bit 23 22 21 20 19 18 17 16
PBLDATA[23:16]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bit 15 14 13 12 11 10 9 8
PBLDATA[15:8]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bit 7 6 5 4 3 2 1 0
PBLDATA[7:0]
Access R R R R R R R R
Reset 1 1 1 1 1 1 1 1
Bits 31:0 – PBLDATA[31:0] Page Buffer Load Data (Bits 63:32])
The PBLDATA register is a holding register for partial AHB writes to the same 64-bit page buffer section.
Page buffer loads are performed on a 64-bit basis.
This is a read only register.
SAM C20/C21 Family Data Sheet
NVMCTRL – Nonvolatile Memory Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 481
28. PORT - I/O Pin Controller
28.1 Overview
The IO Pin Controller (PORT) controls the I/O pins of the device. The I/O pins are organized in a series of
groups, collectively referred to as a PORT group. Each PORT group can have up to 32 pins that can be
configured and controlled individually or as a group. The number of PORT groups on a device may
depend on the package/number of pins. Each pin may either be used for general-purpose I/O under
direct application control or be assigned to an embedded device peripheral. When used for general-
purpose I/O, each pin can be configured as input or output, with highly configurable driver and pull
settings.
All I/O pins have true read-modify-write functionality when used for general-purpose I/O; the direction or
the output value of one or more pins may be changed (set, reset or toggled) explicitly without
unintentionally changing the state of any other pins in the same port group by a single, atomic 8-, 16- or
32-bit write.
The PORT is connected to the high-speed bus matrix through an AHB/APB bridge.
28.2 Features
• Selectable input and output configuration for each individual pin
• Software-controlled multiplexing of peripheral functions on I/O pins
• Flexible pin configuration through a dedicated Pin Configuration register
• Configurable output driver and pull settings:
– Totem-pole (push-pull)
– Pull configuration
– Driver strength
• Configurable input buffer and pull settings:
– Internal pull-up or pull-down
– Input sampling criteria
– Input buffer can be disabled if not needed for lower power consumption
– Read-Modify-Write support for output value (OUTCLR/OUTSET/OUTGL) and pin direction
(DIRCLR/DIRSET/DIRTGL)
• Input event:
– Up to four input event pins for each PORT group
– SET/CLEAR/TOGGLE event actions for each event input on output value of a pin
– Can be output to pin
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 482
28.3 Block Diagram
Figure 28-1. PORT Block Diagram
ANALOG
BLOCKS
PERIPHERALS
Digital Controls of Analog Blocks
Analog Pad
Connections
I/O
PADS
Port Line
Bundles
IP Line Bundles
Peripheral Mux Select
PORT
Control
and
Status
Pad Line
Bundles
PORTMUX
28.4 Signal Description
Table 28-1. Signal description for PORT
Signal name Type Description
Pxy Digital I/O General-purpose I/O pin y in group x
Refer to the I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One
signal can be mapped on several pins.
Related Links
6. I/O Multiplexing and Considerations
28.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly as follows.
28.5.1 I/O Lines
The I/O lines of the PORT are mapped to pins of the physical device. The following naming scheme is
used:
Each line bundle with up to 32 lines is assigned an identifier 'xy', with letter x=A, B, C… and two-digit
number y=00, 01, …31. Examples: A24, C03.
PORT pins are labeled 'Pxy' accordingly, for example PA24, PC03. This identifies each pin in the device
uniquely.
Each pin may be controlled by one or more peripheral multiplexer settings, which allow the pad to be
routed internally to a dedicated peripheral function. When the setting is enabled, the selected peripheral
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 483
has control over the output state of the pad, as well as the ability to read the current physical pad state.
Refer to I/O Multiplexing and Considerations for details.
Device-specific configurations may cause some lines (and the corresponding Pxy pin) not to be
implemented.
Related Links
6. I/O Multiplexing and Considerations
28.5.2 Power Management
During Reset, all PORT lines are configured as inputs with input buffers, output buffers and pull disabled.
The PORT peripheral will continue operating in any sleep mode where its source clock is running.
28.5.3 Clocks
The PORT bus clock (CLK_PORT_APB) can be enabled and disabled in the Main Clock module, and the
default state of CLK_PORT_APB can be found in the Peripheral Clock Masking section in MCLK – Main
Clock.
The PORT requires an APB clock, which may be divided from the CPU main clock and allows the CPU to
access the registers of PORT through the high-speed matrix and the AHB/APB bridge.
One clock cycle latency can be observed on the APB access in case of concurrent PORT accesses.
Related Links
17. MCLK – Main Clock
28.5.4 DMA
Not applicable.
28.5.5 Interrupts
Not applicable.
28.5.6 Events
The events of this peripheral are connected to the Event System.
Related Links
29. EVSYS – Event System
28.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation.
28.5.8 Register Access Protection
All registers with write-access can be optionally write-protected by the Peripheral Access Controller
(PAC).
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 484
28.5.9 Analog Connections
Analog functions are connected directly between the analog blocks and the I/O pads using analog buses.
However, selecting an analog peripheral function for a given pin will disable the corresponding digital
features of the pad.
28.6 Functional Description
Figure 28-2. Overview of the PORT
PULLENx
OUTx
DIRx
INENx
PORT PAD
VDD
INEN
OE
OUT
PULLEN
PAD
Pull
Resistor
PG
NG
Input to Other Modules Analog Input/Output
IN
INx
APB Bus
Synchronizer
Q D
R
R
DQ
DRIVEx
DRIVE
28.6.1 Principle of Operation
Each PORT group of up to 32 pins is controlled by the registers in PORT, as described in the figure.
These registers in PORT are duplicated for each PORT group, with increasing base addresses. The
number of PORT groups may depend on the package/number of pins.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 485
Figure 28-3. Overview of the peripheral functions multiplexing
Port y PINCFG
Port y
Periph Signal 0
PORT bit y
PMUXEN
Data+Config
Periph Signal 1
Periph Signal 15
Port y
PMUX[3:0]
Port y PMUX Select
Port y Line Bundle
PAD y
Pad y
Peripheral Signals to
be muxed to Pad y
Port y Peripheral
Mux Enable
15
1
0
0
1
Line Bundle
PORTMUX
The I/O pins of the device are controlled by PORT peripheral registers. Each port pin has a corresponding
bit in the Data Direction (DIR) and Data Output Value (OUT) registers to enable that pin as an output and
to define the output state.
The direction of each pin in a PORT group is configured by the DIR register. If a bit in DIR is set to '1', the
corresponding pin is configured as an output pin. If a bit in DIR is set to '0', the corresponding pin is
configured as an input pin.
When the direction is set as output, the corresponding bit in the OUT register will set the level of the pin.
If bit y in OUT is written to '1', pin y is driven HIGH. If bit y in OUT is written to '0', pin y is driven LOW. Pin
configuration can be set by Pin Configuration (PINCFGy) registers, with y=00, 01, ..31 representing the
bit position.
The Data Input Value (IN) is set as the input value of a port pin with resynchronization to the PORT clock.
To reduce power consumption, these input synchronizers can be clocked only when system requires
reading the input value, as specified in the SAMPLING field of the Control register (CTRL). The value of
the pin can always be read, whether the pin is configured as input or output. If the Input Enable bit in the
Pin Configuration registers (PINCFGy.INEN) is '0', the input value will not be sampled.
In PORT, the Peripheral Multiplexer Enable bit in the PINCFGy register (PINCFGy.PMUXEN) can be
written to '1' to enable the connection between peripheral functions and individual I/O pins. The
Peripheral Multiplexing n (PMUXn) registers select the peripheral function for the corresponding pin. This
will override the connection between the PORT and that I/O pin, and connect the selected peripheral
signal to the particular I/O pin instead of the PORT line bundle.
28.6.2 Basic Operation
28.6.2.1 Initialization
After reset, all standard function device I/O pads are connected to the PORT with outputs tri-stated and
input buffers disabled, even if there is no clock running.
However, specific pins, such as those used for connection to a debugger, may be configured differently,
as required by their special function.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 486
28.6.2.2 Operation
Each I/O pin Pxy can be controlled by the registers in PORT. Each PORT group x has its own set of
PORT registers, with a base address at byte address (PORT + 0x80 * group index) (A corresponds to
group index 0, B to 1, etc...). Within that set of registers, the pin index is y, from 0 to 31.
Refer to I/O Multiplexing and Considerations for details on available pin configuration and PORT groups.
Configuring Pins as Output
To use pin Pxy as an output, write bit y of the DIR register to '1'. This can also be done by writing bit y in
the DIRSET register to '1' - this will avoid disturbing the configuration of other pins in that group. The y bit
in the OUT register must be written to the desired output value.
Similarly, writing an OUTSET bit to '1' will set the corresponding bit in the OUT register to '1'. Writing a bit
in OUTCLR to '1' will set that bit in OUT to zero. Writing a bit in OUTTGL to '1' will toggle that bit in OUT.
Configuring Pins as Input
To use pin Pxy as an input, bit y in the DIR register must be written to '0'. This can also be done by writing
bit y in the DIRCLR register to '1' - this will avoid disturbing the configuration of other pins in that group.
The input value can be read from bit y in register IN as soon as the INEN bit in the Pin Configuration
register (PINCFGy.INEN) is written to '1'.
By default, the input synchronizer is clocked only when an input read is requested. This will delay the
read operation by two cycles of the PORT clock. To remove the delay, the input synchronizers for each
PORT group of eight pins can be configured to be always active, but this will increase power
consumption. This is enabled by writing '1' to the corresponding SAMPLINGn bit field of the CTRL
register, see CTRL.SAMPLING for details.
Using Alternative Peripheral Functions
To use pin Pxy as one of the available peripheral functions, the corresponding PMUXEN bit of the
PINCFGy register must be '1'. The PINCFGy register for pin Pxy is at byte offset (PINCFG0 + y).
The peripheral function can be selected by setting the PMUXO or PMUXE in the PMUXn register. The
PMUXO/PMUXE is at byte offset PMUX0 + (y/2). The chosen peripheral must also be configured and
enabled.
Related Links
6. I/O Multiplexing and Considerations
28.6.3 I/O Pin Configuration
The Pin Configuration register (PINCFGy) is used for additional I/O pin configuration. A pin can be set in
a totem-pole or pull configuration.
As pull configuration is done through the Pin Configuration register, all intermediate PORT states during
switching of pin direction and pin values are avoided.
The I/O pin configurations are described further in this chapter, and summarized in Table 28-2.
28.6.3.1 Pin Configurations Summary
Table 28-2. Pin Configurations Summary
DIR INEN PULLEN OUT Configuration
0 0 0 X Reset or analog I/O: all digital disabled
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 487
...........continued
DIR INEN PULLEN OUT Configuration
0 0 1 0 Pull-down; input disabled
0 0 1 1 Pull-up; input disabled
0 1 0 X Input
0 1 1 0 Input with pull-down
0 1 1 1 Input with pull-up
1 0 X X Output; input disabled
1 1 X X Output; input enabled
28.6.3.2 Input Configuration
Figure 28-4. I/O configuration - Standard Input
PULLEN
DIR
OUT
IN
INEN
PULLEN INEN DIR
0 1 0
Figure 28-5. I/O Configuration - Input with Pull
PULLEN
DIR
OUT
IN
INEN
PULLEN INEN DIR
1 1 0
Note:  When pull is enabled, the pull value is defined by the OUT value.
28.6.3.3 Totem-Pole Output
When configured for totem-pole (push-pull) output, the pin is driven low or high according to the
corresponding bit setting in the OUT register. In this configuration there is no current limitation for sink or
source other than what the pin is capable of. If the pin is configured for input, the pin will float if no
external pull is connected.
Note:  Enabling the output driver will automatically disable pull.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 488
Figure 28-6. I/O Configuration - Totem-Pole Output with Disabled Input
PULLEN
DIR
OUT
IN
INEN
PULLEN INEN DIR
0 0 1
Figure 28-7. I/O Configuration - Totem-Pole Output with Enabled Input
PULLEN
DIR
OUT
IN
INEN
PULLEN INEN DIR
0 1 1
Figure 28-8. I/O Configuration - Output with Pull
PULLEN
DIR
OUT
IN
INEN
PULLEN INEN DIR
1 0 0
28.6.3.4 Digital Functionality Disabled
Neither Input nor Output functionality are enabled.
Figure 28-9. I/O Configuration - Reset or Analog I/O: Digital Output, Input and Pull Disabled
PULLEN
DIR
OUT
IN
INEN
PULLEN INEN DIR
0 0 0
28.6.4 Events
The PORT allows input events to control individual I/O pins. These input events are generated by the
EVSYS module and can originate from a different clock domain than the PORT module.
The PORT can perform the following actions:
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 489
• Output (OUT): I/O pin will be set when the incoming event has a high level ('1') and cleared when the
incoming event has a low-level ('0').
• Set (SET): I/O pin will be set when an incoming event is detected.
• Clear (CLR): I/O pin will be cleared when an incoming event is detected.
• Toggle (TGL): I/O pin will toggle when an incoming event is detected.
The event is output to pin without any internal latency. For SET, CLEAR and TOGGLE event actions, the
action will be executed up to three clock cycles after a rising edge.
The event actions can be configured with the Event Action m bit group in the Event Input Control
register( EVCTRL.EVACTm). Writing a '1' to a PORT Event Enable Input m of the Event Control register
(EVCTRL.PORTEIm) enables the corresponding action on input event. Writing '0' to this bit disables the
corresponding action on input event. Note that several actions can be enabled for incoming events. If
several events are connected to the peripheral, any enabled action will be taken for any of the incoming
events. Refer to EVSYS – Event System. for details on configuring the Event System.
Each event input can address one and only one I/O pin at a time. The selection of the pin is indicated by
the PORT Event Pin Identifier of the Event Input Control register (EVCTR.PIDn). On the other hand, one
I/O pin can be addressed by up to four different input events. To avoid action conflict on the output value
of the register (OUT) of this particular I/O pin, only one action is performed according to the table below.
Note that this truth table can be applied to any SET/CLR/TGL configuration from two to four active input
events.
Table 28-3. Priority on Simultaneous SET/CLR/TGL Event Actions
EVACT0 EVACT1 EVACT2 EVACT3 Executed Event Action
SET SET SET SET SET
CLR CLR CLR CLR CLR
All Other Combinations TGL
Be careful when the event is output to pin. Due to the fact the events are received asynchronously, the
I/O pin may have unpredictable levels, depending on the timing of when the events are received. When
several events are output to the same pin, the lowest event line will get the access. All other events will
be ignored.
Related Links
29. EVSYS – Event System
28.6.5 PORT Access Priority
The PORT is accessed by different systems:
• The ARM® CPU through the high-speed matrix and the AHB/APB bridge (APB)
• EVSYS through four asynchronous input events
The following priority is adopted:
1. APB
2. EVSYS input events, except for events with EVCTRL.EVACTn=OUT, where the output pin directly
follows the event input signal, independently of the OUT register value.
For input events that require different actions on the same I/O pin, refer to 28.6.4 Events.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 490
28.7 Register Summary
The I/O pins are assembled in pin groups with up to 32 pins. Group 0 consists of the PA pins, and group 1
is for the PB pins, etc. Each pin group has its own PORT registers, with a 0x80 address spacing. For
example, the register address offset for the Data Direction (DIR) register for group 0 (PA00 to PA31) is
0x00, and the register address offset for the DIR register for group 1 (PB00 to PB31) is 0x80.
Offset Name Bit Pos.
0x00 DIR
7:0 DIR[7:0]
15:8 DIR[15:8]
23:16 DIR[23:16]
31:24 DIR[31:24]
0x04 DIRCLR
7:0 DIRCLR[7:0]
15:8 DIRCLR[15:8]
23:16 DIRCLR[23:16]
31:24 DIRCLR[31:24]
0x08 DIRSET
7:0 DIRSET[7:0]
15:8 DIRSET[15:8]
23:16 DIRSET[23:16]
31:24 DIRSET[31:24]
0x0C DIRTGL
7:0 DIRTGL[7:0]
15:8 DIRTGL[15:8]
23:16 DIRTGL[23:16]
31:24 DIRTGL[31:24]
0x10 OUT
7:0 OUT[7:0]
15:8 OUT[15:8]
23:16 OUT[23:16]
31:24 OUT[31:24]
0x14 OUTCLR
7:0 OUTCLR[7:0]
15:8 OUTCLR[15:8]
23:16 OUTCLR[23:16]
31:24 OUTCLR[31:24]
0x18 OUTSET
7:0 OUTSET[7:0]
15:8 OUTSET[15:8]
23:16 OUTSET[23:16]
31:24 OUTSET[31:24]
0x1C OUTTGL
7:0 OUTTGL[7:0]
15:8 OUTTGL[15:8]
23:16 OUTTGL[23:16]
31:24 OUTTGL[31:24]
0x20 IN
7:0 IN[7:0]
15:8 IN[15:8]
23:16 IN[23:16]
31:24 IN[31:24]
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 491
...........continued
Offset Name Bit Pos.
0x24 CTRL
7:0 SAMPLING[7:0]
15:8 SAMPLING[15:8]
23:16 SAMPLING[23:16]
31:24 SAMPLING[31:24]
0x28 WRCONFIG
7:0 PINMASK[7:0]
15:8 PINMASK[15:8]
23:16 DRVSTR PULLEN INEN PMUXEN
31:24 HWSEL WRPINCFG WRPMUX PMUX[3:0]
0x2C EVCTRL
7:0 PORTEIx EVACTx[1:0] PIDx[4:0]
15:8 PORTEIx EVACTx[1:0] PIDx[4:0]
23:16 PORTEIx EVACTx[1:0] PIDx[4:0]
31:24 PORTEIx EVACTx[1:0] PIDx[4:0]
0x30 PMUX0 7:0 PMUXO[3:0] PMUXE[3:0]
...
0x3F PMUX15 7:0 PMUXO[3:0] PMUXE[3:0]
0x40 PINCFG0 7:0 DRVSTR PULLEN INEN PMUXEN
...
0x5F PINCFG31 7:0 DRVSTR PULLEN INEN PMUXEN
28.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 28.5.8 Register Access Protection.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 492
28.8.1 Data Direction
Name:  DIR
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to configure one or more I/O pins as an input or output. This register can be
manipulated without doing a read-modify-write operation by using the Data Direction Toggle (DIRTGL),
Data Direction Clear (DIRCLR) and Data Direction Set (DIRSET) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
DIR[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIR[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DIR[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DIR[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DIR[31:0] Port Data Direction
These bits set the data direction for the individual I/O pins in the PORT group.
Value Description
0The corresponding I/O pin in the PORT group is configured as an input.
1The corresponding I/O pin in the PORT group is configured as an output.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 493
28.8.2 Data Direction Clear
Name:  DIRCLR
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to set one or more I/O pins as an input, without doing a read-modify-write
operation. Changes in this register will also be reflected in the Data Direction (DIR), Data Direction Toggle
(DIRTGL) and Data Direction Set (DIRSET) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
DIRCLR[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIRCLR[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DIRCLR[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DIRCLR[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DIRCLR[31:0] Port Data Direction Clear
Writing a '0' to a bit has no effect.
Writing a '1' to a bit will clear the corresponding bit in the DIR register, which configures the I/O pin as an
input.
Value Description
0The corresponding I/O pin in the PORT group will keep its configuration.
1The corresponding I/O pin in the PORT group is configured as input.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 494
28.8.3 Data Direction Set
Name:  DIRSET
Offset:  0x08
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to set one or more I/O pins as an output, without doing a read-modify-write
operation. Changes in this register will also be reflected in the Data Direction (DIR), Data Direction Toggle
(DIRTGL) and Data Direction Clear (DIRCLR) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
DIRSET[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIRSET[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DIRSET[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DIRSET[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DIRSET[31:0] Port Data Direction Set
Writing '0' to a bit has no effect.
Writing '1' to a bit will set the corresponding bit in the DIR register, which configures the I/O pin as an
output.
Value Description
0The corresponding I/O pin in the PORT group will keep its configuration.
1The corresponding I/O pin in the PORT group is configured as an output.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 495
28.8.4 Data Direction Toggle
Name:  DIRTGL
Offset:  0x0C
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to toggle the direction of one or more I/O pins, without doing a read-modify-
write operation. Changes in this register will also be reflected in the Data Direction (DIR), Data Direction
Set (DIRSET) and Data Direction Clear (DIRCLR) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
DIRTGL[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIRTGL[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DIRTGL[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DIRTGL[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – DIRTGL[31:0] Port Data Direction Toggle
Writing '0' to a bit has no effect.
Writing '1' to a bit will toggle the corresponding bit in the DIR register, which reverses the direction of the
I/O pin.
Value Description
0The corresponding I/O pin in the PORT group will keep its configuration.
1The direction of the corresponding I/O pin is toggled.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 496
28.8.5 Data Output Value
Name:  OUT
Offset:  0x10
Reset:  0x00000000
Property:  PAC Write-Protection
This register sets the data output drive value for the individual I/O pins in the PORT.
This register can be manipulated without doing a read-modify-write operation by using the Data Output
Value Clear (OUTCLR), Data Output Value Set (OUTSET), and Data Output Value Toggle (OUTTGL)
registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
OUT[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
OUT[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OUT[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OUT[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – OUT[31:0] PORT Data Output Value
For pins configured as outputs via the Data Direction register (DIR), these bits set the logical output drive
level.
For pins configured as inputs via the Data Direction register (DIR) and with pull enabled via the Pull
Enable bit in the Pin Configuration register (PINCFG.PULLEN), these bits will set the input pull direction.
Value Description
0The I/O pin output is driven low, or the input is connected to an internal pull-down.
1The I/O pin output is driven high, or the input is connected to an internal pull-up.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 497
28.8.6 Data Output Value Clear
Name:  OUTCLR
Offset:  0x14
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to set one or more output I/O pin drive levels low, without doing a read-
modify-write operation. Changes in this register will also be reflected in the Data Output Value (OUT),
Data Output Value Toggle (OUTTGL) and Data Output Value Set (OUTSET) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
OUTCLR[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
OUTCLR[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OUTCLR[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OUTCLR[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – OUTCLR[31:0] PORT Data Output Value Clear
Writing '0' to a bit has no effect.
Writing '1' to a bit will clear the corresponding bit in the OUT register. Pins configured as outputs via the
Data Direction register (DIR) will be set to low output drive level. Pins configured as inputs via DIR and
with pull enabled via the Pull Enable bit in the Pin Configuration register (PINCFG.PULLEN) will set the
input pull direction to an internal pull-down.
Value Description
0The corresponding I/O pin in the PORT group will keep its configuration.
1The corresponding I/O pin output is driven low, or the input is connected to an internal pull-
down.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 498
28.8.7 Data Output Value Set
Name:  OUTSET
Offset:  0x18
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to set one or more output I/O pin drive levels high, without doing a read-
modify-write operation. Changes in this register will also be reflected in the Data Output Value (OUT),
Data Output Value Toggle (OUTTGL) and Data Output Value Clear (OUTCLR) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
OUTSET[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
OUTSET[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OUTSET[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OUTSET[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – OUTSET[31:0] PORT Data Output Value Set
Writing '0' to a bit has no effect.
Writing '1' to a bit will set the corresponding bit in the OUT register, which sets the output drive level high
for I/O pins configured as outputs via the Data Direction register (DIR). For pins configured as inputs via
Data Direction register (DIR) with pull enabled via the Pull Enable register (PULLEN), these bits will set
the input pull direction to an internal pull-up.
Value Description
0The corresponding I/O pin in the group will keep its configuration.
1The corresponding I/O pin output is driven high, or the input is connected to an internal pull-
up.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 499
28.8.8 Data Output Value Toggle
Name:  OUTTGL
Offset:  0x1C
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to toggle the drive level of one or more output I/O pins, without doing a read-
modify-write operation. Changes in this register will also be reflected in the Data Output Value (OUT),
Data Output Value Set (OUTSET) and Data Output Value Clear (OUTCLR) registers.
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
OUTTGL[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
OUTTGL[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OUTTGL[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OUTTGL[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – OUTTGL[31:0] PORT Data Output Value Toggle
Writing '0' to a bit has no effect.
Writing '1' to a bit will toggle the corresponding bit in the OUT register, which inverts the output drive level
for I/O pins configured as outputs via the Data Direction register (DIR). For pins configured as inputs via
Data Direction register (DIR) with pull enabled via the Pull Enable register (PULLEN), these bits will
toggle the input pull direction.
Value Description
0The corresponding I/O pin in the PORT group will keep its configuration.
1The corresponding OUT bit value is toggled.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 500
28.8.9 Data Input Value
Name:  IN
Offset:  0x20
Reset:  0x00000000
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
IN[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
IN[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
IN[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
IN[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – IN[31:0] PORT Data Input Value
These bits are cleared when the corresponding I/O pin input sampler detects a logical low level on the
input pin.
These bits are set when the corresponding I/O pin input sampler detects a logical high level on the input
pin.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 501
28.8.10 Control
Name:  CTRL
Offset:  0x24
Reset:  0x00000000
Property:  PAC Write-Protection
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
Bit 31 30 29 28 27 26 25 24
SAMPLING[31:24]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
SAMPLING[23:16]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
SAMPLING[15:8]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
SAMPLING[7:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – SAMPLING[31:0] Input Sampling Mode
Configures the input sampling functionality of the I/O pin input samplers, for pins configured as inputs via
the Data Direction register (DIR).
The input samplers are enabled and disabled in sub-groups of eight. Thus if any pins within a byte
request continuous sampling, all pins in that eight pin sub-group will be continuously sampled.
Value Description
0On demand sampling of I/O pin is enabled.
1Continuous sampling of I/O pin is enabled.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 502
28.8.11 Write Configuration
Name:  WRCONFIG
Offset:  0x28
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Only
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
This write-only register is used to configure several pins simultaneously with the same configuration
and/or peripheral multiplexing.
In order to avoid side effect of non-atomic access, 8-bit or 16-bit writes to this register will have no effect.
Reading this register always returns zero.
Bit 31 30 29 28 27 26 25 24
HWSEL WRPINCFG WRPMUX PMUX[3:0]
Access W W W W W W W
Reset 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DRVSTR PULLEN INEN PMUXEN
Access W W W W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
PINMASK[15:8]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PINMASK[7:0]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bit 31 – HWSEL Half-Word Select
This bit selects the half-word field of a 32-PORT group to be reconfigured in the atomic write operation.
This bit will always read as zero.
Value Description
0The lower 16 pins of the PORT group will be configured.
1The upper 16 pins of the PORT group will be configured.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 503
Bit 30 – WRPINCFG Write PINCFG
This bit determines whether the atomic write operation will update the Pin Configuration register
(PINCFGy) or not for all pins selected by the WRCONFIG.PINMASK and WRCONFIG.HWSEL bits.
Writing '0' to this bit has no effect.
Writing '1' to this bit updates the configuration of the selected pins with the written WRCONFIG.DRVSTR,
WRCONFIG.PULLEN, WRCONFIG.INEN, WRCONFIG.PMUXEN, and WRCONFIG.PINMASK values.
This bit will always read as zero.
Value Description
0The PINCFGy registers of the selected pins will not be updated.
1The PINCFGy registers of the selected pins will be updated.
Bit 28 – WRPMUX Write PMUX
This bit determines whether the atomic write operation will update the Peripheral Multiplexing register
(PMUXn) or not for all pins selected by the WRCONFIG.PINMASK and WRCONFIG.HWSEL bits.
Writing '0' to this bit has no effect.
Writing '1' to this bit updates the pin multiplexer configuration of the selected pins with the written
WRCONFIG. PMUX value.
This bit will always read as zero.
Value Description
0The PMUXn registers of the selected pins will not be updated.
1The PMUXn registers of the selected pins will be updated.
Bits 27:24 – PMUX[3:0] Peripheral Multiplexing
These bits determine the new value written to the Peripheral Multiplexing register (PMUXn) for all pins
selected by the WRCONFIG.PINMASK and WRCONFIG.HWSEL bits, when the WRCONFIG.WRPMUX
bit is set.
These bits will always read as zero.
Bit 22 – DRVSTR Output Driver Strength Selection
This bit determines the new value written to PINCFGy.DRVSTR for all pins selected by the
WRCONFIG.PINMASK and WRCONFIG.HWSEL bits, when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
Bit 18 – PULLEN Pull Enable
This bit determines the new value written to PINCFGy.PULLEN for all pins selected by the
WRCONFIG.PINMASK and WRCONFIG.HWSEL bits, when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
Bit 17 – INEN Input Enable
This bit determines the new value written to PINCFGy.INEN for all pins selected by the
WRCONFIG.PINMASK and WRCONFIG.HWSEL bits, when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
Bit 16 – PMUXEN Peripheral Multiplexer Enable
This bit determines the new value written to PINCFGy.PMUXEN for all pins selected by the
WRCONFIG.PINMASK and WRCONFIG.HWSEL bits, when the WRCONFIG.WRPINCFG bit is set.
This bit will always read as zero.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 504
Bits 15:0 – PINMASK[15:0] Pin Mask for Multiple Pin Configuration
These bits select the pins to be configured within the half-word group selected by the
WRCONFIG.HWSEL bit.
These bits will always read as zero.
Value Description
0The configuration of the corresponding I/O pin in the half-word group will be left unchanged.
1The configuration of the corresponding I/O pin in the half-word PORT group will be updated.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 505
28.8.12 Event Input Control
Name:  EVCTRL
Offset:  0x2C
Reset:  0x00000000
Property:  PAC Write-Protection
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
There are up to four input event pins for each PORT group. Each byte of this register addresses one
Event input pin.
Bit 31 30 29 28 27 26 25 24
PORTEIx EVACTx[1:0] PIDx[4:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
PORTEIx EVACTx[1:0] PIDx[4:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
PORTEIx EVACTx[1:0] PIDx[4:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PORTEIx EVACTx[1:0] PIDx[4:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 31,23,15,7 – PORTEIx PORT Event Input Enable x [x = 3..0]
Value Description
0The event action x (EVACTx) will not be triggered on any incoming event.
1The event action x (EVACTx) will be triggered on any incoming event.
Bits 30:29, 22:21,14:13,6:5 – EVACTx PORT Event Action x [x = 3..0]
These bits define the event action the PORT will perform on event input x. See also Table 28-4.
Bits 28:24,20:16,12:8,4:0 – PIDx PORT Event Pin Identifier x [x = 3..0]
These bits define the I/O pin on which the event action will be performed, according to Table 28-5.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 506
Table 28-4. PORT Event x Action ( x = [3..0] )
Value Name Description
0x0 OUT Output register of pin will be set
to level of event.
0x1 SET Set output register of pin on
event.
0x2 CLR Clear output register of pin on
event.
0x3 TGL Toggle output register of pin on
event.
Table 28-5. PORT Event x Pin Identifier ( x = [3..0] )
Value Name Description
0x0 PIN0 Event action to be executed on
PIN 0.
0x1 PIN1 Event action to be executed on
PIN 1.
... ... ...
0x31 PIN31 Event action to be executed on
PIN 31.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 507
28.8.13 Peripheral Multiplexing n
Name:  PMUX
Offset:  0x30 + n*0x01 [n=0..15]
Property:  PAC Write-Protection
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
There are up to 16 Peripheral Multiplexing registers in each group, one for every set of two subsequent
I/O lines. The n denotes the number of the set of I/O lines.
Bit 7 6 5 4 3 2 1 0
PMUXO[3:0] PMUXE[3:0]
Access RW RW RW RW RW RW RW RW
Reset 0 0 0 0 0 0 0 0
Bits 7:4 – PMUXO[3:0] Peripheral Multiplexing for Odd-Numbered Pin
These bits select the peripheral function for odd-numbered pins (2*n + 1) of a PORT group, if the
corresponding PINCFGy.PMUXEN bit is '1'.
Not all possible values for this selection may be valid. For more details, refer to the I/O Multiplexing and
Considerations.
PMUXO[3:0] Name Description
0x0 A Peripheral function A selected
0x1 B Peripheral function B selected
0x2 C Peripheral function C selected
0x3 D Peripheral function D selected
0x4 E Peripheral function E selected
0x5 F Peripheral function F selected
0x6 G Peripheral function G selected
0x7 H Peripheral function H selected
0x8 I Peripheral function I selected
0x9 - Reserved
0xA - Reserved
0xB - Reserved
0xC - Reserved
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 508
...........continued
PMUXO[3:0] Name Description
0xD - Reserved
0xE-0xF - Reserved
Bits 3:0 – PMUXE[3:0] Peripheral Multiplexing for Even-Numbered Pin
These bits select the peripheral function for even-numbered pins (2*n) of a PORT group, if the
corresponding PINCFGy.PMUXEN bit is '1'.
Not all possible values for this selection may be valid. For more details, refer to the I/O Multiplexing and
Considerations.
PMUXE[3:0] Name Description
0x0 A Peripheral function A selected
0x1 B Peripheral function B selected
0x2 C Peripheral function C selected
0x3 D Peripheral function D selected
0x4 E Peripheral function E selected
0x5 F Peripheral function F selected
0x6 G Peripheral function G selected
0x7 H Peripheral function H selected
0x8 I Peripheral function I selected
0x9 - Reserved
0xA - Reserved
0xB - Reserved
0xC - Reserved
0xD - Reserved
0xE-0xF - Reserved
Related Links
6. I/O Multiplexing and Considerations
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 509
28.8.14 Pin Configuration
Name:  PINCFG
Offset:  0x40 + n*0x01 [n=0..31]
Reset:  0x00
Property:  PAC Write-Protection
Tip:  The I/O pins are assembled in pin groups (”PORT groups”) with up to 32 pins. Group 0
consists of the PA pins, group 1 is for the PB pins, etc. Each pin group has its own PORT
registers, with a 0x80 address spacing. For example, the register address offset for the Data
Direction (DIR) register for group 0 (PA00 to PA31) is 0x00, and the register address offset for
the DIR register for group 1 (PB00 to PB31) is 0x80.
There are up to 32 Pin Configuration registers in each PORT group, one for each I/O line.
Bit 7 6 5 4 3 2 1 0
DRVSTR PULLEN INEN PMUXEN
Access RW RW RW RW
Reset 0 0 0 0
Bit 6 – DRVSTR Output Driver Strength Selection
This bit controls the output driver strength of an I/O pin configured as an output.
Value Description
0Pin drive strength is set to normal drive strength.
1Pin drive strength is set to stronger drive strength.
Bit 2 – PULLEN Pull Enable
This bit enables the internal pull-up or pull-down resistor of an I/O pin configured as an input.
Value Description
0Internal pull resistor is disabled, and the input is in a high-impedance configuration.
1Internal pull resistor is enabled, and the input is driven to a defined logic level in the absence
of external input.
Bit 1 – INEN Input Enable
This bit controls the input buffer of an I/O pin configured as either an input or output.
Writing a zero to this bit disables the input buffer completely, preventing read-back of the physical pin
state when the pin is configured as either an input or output.
Value Description
0Input buffer for the I/O pin is disabled, and the input value will not be sampled.
1Input buffer for the I/O pin is enabled, and the input value will be sampled when required.
Bit 0 – PMUXEN Peripheral Multiplexer Enable
This bit enables or disables the peripheral multiplexer selection set in the Peripheral Multiplexing register
(PMUXn) to enable or disable alternative peripheral control over an I/O pin direction and output drive
value.
Writing a zero to this bit allows the PORT to control the pad direction via the Data Direction register (DIR)
and output drive value via the Data Output Value register (OUT). The peripheral multiplexer value in
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 510
PMUXn is ignored. Writing '1' to this bit enables the peripheral selection in PMUXn to control the pad. In
this configuration, the physical pin state may still be read from the Data Input Value register (IN) if
PINCFGn.INEN is set.
Value Description
0The peripheral multiplexer selection is disabled, and the PORT registers control the direction
and output drive value.
1The peripheral multiplexer selection is enabled, and the selected peripheral function controls
the direction and output drive value.
SAM C20/C21 Family Data Sheet
PORT - I/O Pin Controller
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 511
29. EVSYS – Event System
29.1 Overview
The Event System (EVSYS) allows autonomous, low-latency and configurable communication between
peripherals.
Several peripherals can be configured to generate and/or respond to signals known as events. The exact
condition to generate an event, or the action taken upon receiving an event, is specific to each peripheral.
Peripherals that respond to events are called event users. Peripherals that generate events are called
event generators. A peripheral can have one or more event generators and can have one or more event
users.
Communication is made without CPU intervention and without consuming system resources such as bus
or RAM bandwidth. This reduces the load on the CPU and other system resources, compared to a
traditional interrupt-based system.
29.2 Features
• 12 configurable event channels, where each channel can:
– Be connected to any event generator.
– Provide a pure asynchronous, resynchronized or synchronous path
• 87 event generators.
• 47 event users.
• Configurable edge detector.
• Peripherals can be event generators, event users, or both.
• SleepWalking and interrupt for operation in sleep modes.
• Software event generation.
• Each event user can choose which channel to respond to.
29.3 Block Diagram
Figure 29-1. Event System Block Diagram
USER x+1
Event Channel m
Event Channel 1
Event Channel 0 USER x
DQ
R
Synchronized Path
Asynchronous Path
Edge Detector
CHANNEL0.EDGSEL
CHANNEL0.PATH
EVT
DQ
R
DQ
R
DQ
R
Resynchronized Path
DQ
R
DQ
R
DQ
R
SWEVT.CHANNEL0
PERIPHERAL n
PERIPHERAL0
CHANNEL0.EVGEN
USER.CHANNELx
Channel_EVT_0
EVT ACK
Channel_EVT_m
Clock Request [m:0]
To Peripheral x
Peripheral x
GCLK_EVSYS_0
SleepWalking
Detector
Event Acknowledge
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 512
29.4 Signal Description
Not applicable.
29.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
29.5.1 I/O Lines
Not applicable.
29.5.2 Power Management
The EVSYS can be used to wake up the CPU from all sleep modes, even if the clock used by the EVSYS
channel and the EVSYS bus clock are disabled. Refer to the PM – Power Manager for details on the
different sleep modes.
Although the clock for the EVSYS is stopped, the device still can wake up the EVSYS clock. Some event
generators can generate an event when their clocks are stopped. The generic clock for the channel
(GCLK_EVSYS_CHANNEL_n) will be restarted if that channel uses a synchronized path or a
resynchronized path. It does not need to wake the system from sleep.
Related Links
19. PM – Power Manager
29.5.3 Clocks
The EVSYS bus clock (CLK_EVSYS_APB) can be enabled and disabled in the Main Clock module, and
the default state of CLK_EVSYS_APB can be found in Peripheral Clock Masking.
Each EVSYS channel has a dedicated generic clock (GCLK_EVSYS_CHANNEL_n). These are used for
event detection and propagation for each channel. These clocks must be configured and enabled in the
generic clock controller before using the EVSYS. Refer to GCLK - Generic Clock Controller for details.
Related Links
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
29.5.4 DMA
Not applicable.
29.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. Using the EVSYS interrupts requires
the interrupt controller to be configured first. Refer to Nested Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
29.5.6 Events
Not applicable.
29.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 513
data loss may result during debugging. This peripheral can be forced to halt operation during debugging -
refer to the Debug Control (DBGCTRL) register for details.
29.5.8 Register Access Protection
Registers with write-access can be optionally write-protected by the Peripheral Access Controller (PAC),
except for the following:
• Channel Status (CHSTATUS)
• Interrupt Flag Status and Clear register (INTFLAG)
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
29.5.9 Analog Connections
Not applicable.
29.6 Functional Description
29.6.1 Principle of Operation
The Event System consists of several channels which route the internal events from peripherals
(generators) to other internal peripherals or I/O pins (users). Each event generator can be selected as
source for multiple channels, but a channel cannot be set to use multiple event generators at the same
time.
A channel path can be configured in asynchronous, synchronous or resynchronized mode of operation.
The mode of operation must be selected based on the requirements of the application.
When using synchronous or resynchronized path, the Event System includes options to transfer events to
users when rising, falling or both edges are detected on event generators.
For further details, refer to the Channel Path section of this chapter.
29.6.2 Basic Operation
29.6.2.1 Initialization
Before enabling event routing within the system, the Event Users Multiplexer and Event Channels must
be selected in the Event System (EVSYS), and the two peripherals that generate and use the event have
to be configured. The recommended sequence is:
1. In the event generator peripheral, enable output of event by writing a '1' to the respective Event
Output Enable bit ("EO") in the peripheral's Event Control register (e.g., TCC.EVCTRL.MCEO1,
AC.EVCTRL.WINEO0, RTC.EVCTRL.OVFEO).
2. Configure the EVSYS:
2.1. Configure the Event User multiplexer by writing the respective EVSYS.USERm register,
see also 29.6.2.3 User Multiplexer Setup.
2.2. Configure the Event Channel by writing the respective EVSYS.CHANNELn register, see
also 29.6.2.4 Event System Channel.
3. Configure the action to be executed by the event user peripheral by writing to the Event Action bits
(EVACT) in the respective Event control register (e.g., TC.EVCTRL.EVACT,
PDEC.EVCTRL.EVACT). Note: not all peripherals require this step.
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 514
4. In the event user peripheral, enable event input by writing a '1' to the respective Event Input Enable
bit ("EI") in the peripheral's Event Control register (e.g., AC.EVCTRL.IVEI0,
ADC.EVCTRL.STARTEI).
29.6.2.2 Enabling, Disabling, and Resetting
The EVSYS is always enabled.
The EVSYS is reset by writing a ‘1’ to the Software Reset bit in the Control A register (CTRLA.SWRST).
All registers in the EVSYS will be reset to their initial state and all ongoing events will be canceled.
Refer to CTRLA.SWRST register for details.
29.6.2.3 User Multiplexer Setup
The user multiplexer defines the channel to be connected to which event user. Each user multiplexer is
dedicated to one event user. A user multiplexer receives all event channels output and must be
configured to select one of these channels, as shown in Block Diagram section. The channel is selected
with the Channel bit group in the User register (USERm.CHANNEL).
The user multiplexer must always be configured before the channel. A list of all user multiplexers is found
in the User (USERm) register description.
Related Links
29.8.8 USERm
29.6.2.4 Event System Channel
An event channel can select one event from a list of event generators. Depending on configuration, the
selected event could be synchronized, resynchronized or asynchronously sent to the users. When
synchronization or resynchronization is required, the channel includes an internal edge detector, allowing
the Event System to generate internal events when rising, falling or both edges are detected on the
selected event generator.
An event channel is able to generate internal events for the specific software commands. A channel block
diagram is shown in Block Diagram section.
29.6.2.5 Event Generators
Each event channel can receive the events form all event generators. All event generators are listed in
the Event Generator bit field in the Channel n register (CHANNELn.EVGEN). For details on event
generation, refer to the corresponding module chapter. The channel event generator is selected by the
Event Generator bit group in the Channel register (CHANNELn.EVGEN). By default, the channels are not
connected to any event generators (ie, CHANNELn.EVGEN = 0)
29.6.2.6 Channel Path
There are three different ways to propagate the event from an event generator:
• Asynchronous path
• Synchronous path
• Resynchronized path
The path is decided by writing to the Path Selection bit group of the Channel register (CHANNELn.PATH).
Asynchronous Path
When using the asynchronous path, the events are propagated from the event generator to the event
user without intervention from the Event System. The GCLK for this channel
(GCLK_EVSYS_CHANNEL_n) is not mandatory, meaning that an event will be propagated to the user
without any clock latency.
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 515
When the asynchronous path is selected, the channel cannot generate any interrupts, and the Channel
Status register (CHSTATUS) is always zero. The edge detection is not required and must be disabled by
software. Each peripheral event user has to select which event edge must trigger internal actions. For
further details, refer to each peripheral chapter description.
Synchronous Path
The synchronous path should be used when the event generator and the event channel share the same
generator for the generic clock. If they do not share the same clock, a logic change from the event
generator to the event channel might not be detected in the channel, which means that the event will not
be propagated to the event user. For details on generic clock generators, refer to GCLK - Generic Clock
Controller.
When using the synchronous path, the channel is able to generate interrupts. The channel busy n bit in
the Channel Status register (CHSTATUS.CHBUSYn) are also updated and available for use.
Resynchronized Path
The resynchronized path are used when the event generator and the event channel do not share the
same generator for the generic clock. When the resynchronized path is used, resynchronization of the
event from the event generator is done in the channel. For details on generic clock generators, refer to
GCLK - Generic Clock Controller.
When the resynchronized path is used, the channel is able to generate interrupts. The channel busy n
bits in the Channel Status register (CHSTATUS.CHBUSYn) are also updated and available for use.
Related Links
16. GCLK - Generic Clock Controller
29.6.2.7 Edge Detection
When synchronous or resynchronized paths are used, edge detection must be enabled. The event
system can execute edge detection in three different ways:
• Generate an event only on the rising edge
• Generate an event only on the falling edge
• Generate an event on rising and falling edges.
Edge detection is selected by writing to the Edge Selection bit group of the Channel register
(CHANNELn.EDGSEL).
29.6.2.8 Event Latency
An event from an event generator is propagated to an event user with different latency, depending on
event channel configuration.
• Asynchronous Path: The maximum routing latency of an external event is related to the internal
signal routing and it is device dependent.
• Synchronous Path: The maximum routing latency of an external event is one
GCLK_EVSYS_CHANNEL_n clock cycle.
• Resynchronized Path: The maximum routing latency of an external event is three
GCLK_EVSYS_CHANNEL_n clock cycles.
The maximum propagation latency of a user event to the peripheral clock core domain is three peripheral
clock cycles.
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 516
The event generators, event channel and event user clocks ratio must be selected in relation with the
internal event latency constraints. Events propagation or event actions in peripherals may be lost if the
clock setup violates the internal latencies.
29.6.2.9 The Overrun Channel n Interrupt
The Overrun Channel n interrupt flag in the Interrupt Flag Status and Clear register (CHINTFLAGn.OVR)
will be set, and the optional interrupt will be generated in the following cases:
• One or more event users on channel n is not ready when there is a new event.
• An event occurs when the previous event on channel m has not been handled by all event users
connected to that channel.
The flag will only be set when using synchronous or resynchronized paths. In the case of asynchronous
path, the CHINTFLAGn.OVR is always read as zero.
29.6.2.10 The Event Detected Channel n Interrupt
The Event Detected Channel n interrupt flag in the Interrupt Flag Status and Clear register
(CHINTFLAGn.EVD) is set when an event coming from the event generator configured on channel n is
detected.
The flag will only be set when using a synchronous or resynchronized path. In the case of asynchronous
path, the CHINTFLAGn.EVD is always zero.
29.6.2.11 Channel Status
The Channel Status register (CHSTATUS) shows the status of the channels when using a synchronous or
resynchronized path. There are two different status bits in CHSTATUS for each of the available channels:
• The CHSTATUSn.BUSYCH bit will be set when an event on the corresponding channel n has not
been handled by all event users connected to that channel.
• The CHSTATUSn.RDYUSR bit will be set when all event users connected to the corresponding
channel are ready to handle incoming events on that channel.
29.6.2.12 Software Event
A software event can be initiated on a channel by setting the Channel n bit in the Software Event register
(SWEVT.CHANNELn) to ‘1’. Then the software event can be serviced as any event generator; i.e., when
the bit is set to ‘1’, an event will be generated on the respective channel.
29.6.3 Interrupts
The EVSYS has the following interrupt sources:
• Overrun Channel n interrupt (OVRn): for details, refer to 29.6.2.9 The Overrun Channel n Interrupt.
• Event Detected Channel n interrupt (EVDn): for details, refer to 29.6.2.10 The Event Detected
Channel n Interrupt.
These interrupts events are asynchronous wake-up sources. See Sleep Mode Controller. Each interrupt
source has an interrupt flag which is in the Interrupt Flag Status and Clear (INTFLAG) register. The flag is
set when the interrupt is issued. Each interrupt event can be individually enabled by setting a ‘1’ to the
corresponding bit in the Interrupt Enable Set (INTENSET) register, and disabled by setting a ‘1’ to the
corresponding bit in the Interrupt Enable Clear (INTENCLR) register. An interrupt event is generated
when the interrupt flag is set and the corresponding interrupt is enabled. The interrupt event works until
the interrupt flag is cleared, the interrupt is disabled, or the Event System is reset. See 29.8.5 INTFLAG
for details on how to clear interrupt flags.
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 517
All interrupt events from the peripheral are ORed together on system level to generate one combined
interrupt request to the NVIC. Refer to the Nested Vector Interrupt Controller for details. The event user
must read the INTFLAG register to determine what the interrupt condition is.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to Nested
Vector Interrupt Controller for details.
Related Links
19.6.3.3 Sleep Mode Controller
29.6.4 Sleep Mode Operation
The EVSYS can generate interrupts to wake up the device from any sleep mode.
To be able to run in standby, the Run in Standby bit in the Channel register (CHANNELn.RUNSTDBY)
must be set to ‘1’. When the Generic Clock On Demand bit in Channel register
(CHANNELn.ONDEMAND) is set to ‘1’ and the event generator is detected, the event channel will
request its clock (GCLK_EVSYS_CHANNEL_n). The event latency for a resynchronized channel path will
increase by two GCLK_EVSYS_CHANNEL_n clock (i.e., up to five GCLK_EVSYS_CHANNEL_n clock
cycles).
A channel will behave differently in different sleep modes regarding to CHANNELn.RUNSTDBY and
CHANNELn.ONDEMAND, as shown in the table below:
Table 29-1. Event Channel Sleep Behavior
CHANNELn.ONDEMAN
D
CHANNELn.RUNSTDB
Y
Sleep Behavior
0 0 Only run in IDLE sleep mode if an event must be
propagated. Disabled in STANDBY sleep mode.
0 1 Always run in IDLE and STANDBY sleep modes.
1 0 Only run in IDLE sleep mode if an event must be
propagated. Disabled in STANDBY sleep mode.
Two GCLK_EVSYS_n latency added in RESYNC
path before the event is propagated internally.
1 1 Always run in IDLE and STANDBY sleep modes.
Two GCLK_EVSYS_n latency added in RESYNC
path before the event is propagated internally.
29.7 Register Summary
29.7.1 Common Registers
Offset Name Bit Pos.
0x00 CTRLA 7:0 SWRST
0x01..0x0B Reserved
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 518
...........continued
Offset Name Bit Pos.
0x0C
CHSTATUS
7:0 USRRDY7 USRRDY6 USRRDY5 USRRDY4 USRRDY3 USRRDY2 USRRDY1 USRRDY0
0x0D 15:8 USRRDY11 USRRDY10 USRRDY9 USRRDY8
0x0E 23:16 CHBUSY7 CHBUSY6 CHBUSY5 CHBUSY4 CHBUSY3 CHBUSY2 CHBUSY1 CHBUSY0
0x0F 31:24 CHBUSY11 CHBUSY10 CHBUSY9 CHBUSY8
0x10
INTENCLR
7:0 OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
0x11 15:8 OVR11 OVR10 OVR9 OVR8
0x12 23:16 EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
0x13 31:24 EVD11 EVD10 EVD9 EVD8
0x14
INTENSET
7:0 OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
0x15 15:8 OVR11 OVR10 OVR9 OVR8
0x16 23:16 EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
0x17 31:24 EVD11 EVD10 EVD9 EVD9
0x18
INTFLAG
7:0 OVR7 OVR6 OVR5 OVR4 OVR3 OVR2 OVR1 OVR0
0x19 15:8 OVR11 OVR10 OVR9 OVR8
0x1A 23:16 EVD7 EVD6 EVD5 EVD4 EVD3 EVD2 EVD1 EVD0
0x1B 31:24 EVD11 EVD10 EVD9 EVD9
0x1C
SWEVT
7:0 CHANNEL[7:0]
0x1D 15:8 CHANNEL[11:8]
0x1E 23:16
0x1F 31:24
29.7.2 CHANNELn
Offset Name Bit
Pos.
0x20
+ 0x4*n
29.8.7 CHANNELn
7:0 EVGEN[7:0]
0x21
+ 0x4*n 15:8 ONDEMAND RUNSTDBY EDGSEL[1:0] PATH[1:0]
0x22
+ 0x4*n 23:16
0x23
+ 0x4*n 31:24
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 519
29.7.3 USERm
Offset Name Bit
Pos.
0x80
+ 0x4*m
29.8.8 USERm
7:0 CHANNEL[7:0]
0x81
+ 0x4*m 15:8
0x82
+ 0x4*m 23:16
0x83
+ 0x4*m 31:24
29.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Refer to Register Access Protection and PAC - Peripheral Access Controller.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 520
29.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
SWRST
Access W
Reset 0
Bit 0 – SWRST Software Reset
Writing '0' to this bit has no effect.
Writing '1' to this bit resets all registers in the EVSYS to their initial state.
Note:  Before applying a Software Reset it is recommended to disable the event generators.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 521
29.8.2 Channel Status
Name:  CHSTATUS
Offset:  0x0C
Reset:  0x000000FF
Property:  –
Bit 31 30 29 28 27 26 25 24
CHBUSYn[11:8]
Access R R R R
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CHBUSYn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
USRRDYn[11:8]
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
USRRDYn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 1
Bits 27:16 – CHBUSYn[11:0] Channel Busy n [n = 11..0]
This bit is cleared when channel n is idle.
This bit is set if an event on channel n has not been handled by all event users connected to channel n.
Bits 11:0 – USRRDYn[11:0] User Ready for Channel n [n = 11..0]
This bit is cleared when at least one of the event users connected to the channel is not ready.
This bit is set when all event users connected to channel n are ready to handle incoming events on
channel n.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 522
29.8.3 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x10
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 31 30 29 28 27 26 25 24
EVDn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EVDn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OVRn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OVRn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 27:16 – EVDn[11:0] Event Detected Channel n Interrupt Enable [n = 11..0]
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Event Detected Channel n Interrupt Enable bit, which disables the Event
Detected Channel n interrupt.
Value Description
0The Event Detected Channel n interrupt is disabled.
1The Event Detected Channel n interrupt is enabled.
Bits 11:0 – OVRn[11:0] Overrun Channel n Interrupt Enable[n = 11..0]
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Overrun Channel n Interrupt Enable bit, which disables the Overrun
Channel n interrupt.
Value Description
0The Overrun Channel n interrupt is disabled.
1The Overrun Channel n interrupt is enabled.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 523
29.8.4 Interrupt Enable Set
Name:  INTENSET
Offset:  0x14
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 31 30 29 28 27 26 25 24
EVDn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EVDn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OVRn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OVRn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 27:16 – EVDn[11:0] Event Detected Channel n Interrupt Enable [n = 11..0]
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Event Detected Channel n Interrupt Enable bit, which enables the Event
Detected Channel n interrupt.
Value Description
0The Event Detected Channel n interrupt is disabled.
1The Event Detected Channel n interrupt is enabled.
Bits 11:0 – OVRn[11:0] Overrun Channel n Interrupt Enable [n = 11..0]
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Overrun Channel n Interrupt Enable bit, which disables the Overrun
Channel n interrupt.
Value Description
0The Overrun Channel n interrupt is disabled.
1The Overrun Channel n interrupt is enabled.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 524
29.8.5 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x18
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
EVDn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EVDn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OVRn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OVRn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 27:16 – EVDn[11:0] Event Detected Channel n [n=11..0]
This flag is set on the next CLK_EVSYS_APB cycle when an event is being propagated through the
channel, and an interrupt request will be generated if INTENCLR/SET.EVDn is '1'.
When the event channel path is asynchronous, the EVDn interrupt flag will not be set.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Event Detected Channel n interrupt flag.
Bits 11:0 – OVRn[11:0] Overrun Channel n [n=11..0]
This flag is set on the next CLK_EVSYS_APB cycle after an overrun channel condition occurs, and an
interrupt request will be generated if INTENCLR/SET.OVRn is '1'.
There are two possible overrun channel conditions:
• One or more of the event users on channel n are not ready when a new event occurs.
• An event happens when the previous event on channel n has not yet been handled by all event
users.
When the event channel path is asynchronous, the OVRn interrupt flag will not be set.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Overrun Detected Channel n interrupt flag.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 525
29.8.6 Software Event
Name:  SWEVT
Offset:  0x1C
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
CHANNELn[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CHANNELn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 11:0 – CHANNELn[11:0] Channel n Software [n=11..0] Selection
Writing '0' to this bit has no effect.
Writing '1' to this bit will trigger a software event for the channel n.
These bits will always return zero when read.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 526
29.8.7 Channel
Name:  CHANNELn
Offset:  0x20+n*0x4 [0..11n=0..11]
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to configure channel n. To write to this register, do a single, 32-bit write of all
the configuration data.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
ONDEMAND RUNSTDBY EDGSEL[1:0] PATH[1:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EVGEN[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – ONDEMAND Generic Clock On Demand
Value Description
0Generic clock for a channel is always on, if the channel is configured and generic clock
source is enabled.
1Generic clock is requested on demand while an event is handled
Bit 14 – RUNSTDBY Run in Standby
This bit is used to define the behavior during standby sleep mode.
Value Description
0The channel is disabled in standby sleep mode.
1The channel is not stopped in standby sleep mode and depends on the
CHANNEL.ONDEMAND
Bits 11:10 – EDGSEL[1:0] Edge Detection Selection
These bits set the type of edge detection to be used on the channel.
These bits must be written to zero when using the asynchronous path.
Value Name Description
0x0 NO_EVT_OUTPUT No event output when using the resynchronized or synchronous path
0x1 RISING_EDGE Event detection only on the rising edge of the signal from the event
generator
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 527
Value Name Description
0x2 FALLING_EDGE Event detection only on the falling edge of the signal from the event
generator
0x3 BOTH_EDGES Event detection on rising and falling edges of the signal from the event
generator
Bits 9:8 – PATH[1:0] Path Selection
These bits are used to choose which path will be used by the selected channel.
The path choice can be limited by the channel source, see the table in 29.8.8 USERm.
Value Name Description
0x0 SYNCHRONOUS Synchronous path
0x1 RESYNCHRONIZED Resynchronized path
0x2 ASYNCHRONOUS Asynchronous path
0x3 - Reserved
Bits 7:0 – EVGEN[7:0] Event Generator
These bits are used to choose the event generator to connect to the selected channel.
Table 29-2. Event Generators
Value Event Generator Description
0x00 NONE No event generator selected
0x01 OSCCTRL FAIL XOSC Clock Failure
0x02 OSC32KCTRL FAIL XOSC32K Clock Failure
0x03 RTC CMP0 Compare 0 (mode 0 and 1) or
Alarm 0 (mode 2)
0x04 RTC CMP1 Compare 1
0x05 RTC OVF Overflow
0x06 RTC PER0 Period 0
0x07 RTC PER1 Period 1
0x08 RTC PER2 Period 2
0x09 RTC PER3 Period 3
0x0A RTC PER4 Period 4
0x0B RTC PER5 Period 5
0x0C RTC PER6 Period 6
0x0D RTC PER7 Period 7
0x0E EIC EXTINT0 External Interrupt 0
0x0F EIC EXTINT1 External Interrupt 1
0x10 EIC EXTINT2 External Interrupt 2
0x11 EIC EXTINT3 External Interrupt 3
0x12 EIC EXTINT4 External Interrupt 4
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 528
...........continued
Value Event Generator Description
0x13 EIC EXTINT5 External Interrupt 5
0x14 EIC EXTINT6 External Interrupt 6
0x15 EIC EXTINT7 External Interrupt 7
0x16 EIC EXTINT8 External Interrupt 8
0x17 EIC EXTINT9 External Interrupt 9
0x18 EIC EXTINT10 External Interrupt 10
0x19 EIC EXTINT11 External Interrupt 11
0x1A EIC EXTINT12 External Interrupt 12
0x1B EIC EXTINT13 External Interrupt 13
0x1C EIC EXTINT14 External Interrupt 14
0x1D EIC EXTINT15 External Interrupt 15
0x1E TSENS WINMON- Window Monitor
0x1F DMAC CH0 Channel 0
0x20 DMAC CH1 Channel 1
0x21 DMAC CH2 Channel 2
0x22 DMAC CH3 Channel 3
0x23 TCC0 OVF Overflow
0x24 TCC0 TRG Trig
0x25 TCC0 CNT Counter
0x26 TCC0 MC0 Match/Capture 1
0x27 TCC0 MC1 Match/Capture 1
0x28 TCC0 MC2 Match/Capture 2
0x29 TCC0 MC3 Match/Capture 3
0x2A TCC1 OVF Overflow
0x2B TCC1 TRG Trig
0x2C TCC1 CNT Counter
0x2D TCC1 MC0 Match/Capture 0
0x2E TCC1 MC1 Match/Capture 1
0x2F TCC2 OVF Overflow
0x30 TCC2 TRG Trig
0x31 TCC2 CNT Counter
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 529
...........continued
Value Event Generator Description
0x32 TCC2 MC0 Match/Capture 0
0x33 TCC2 MC1 Match/Capture 1
0x34 TC0 OVF Overflow/Underflow
0x35 TC0 MC0 Match/Capture 0
0x36 TC0 MC1 Match/Capture 1
0x37 TC1 OVF Overflow/Underflow
0x38 TC1 MC0 Match/Capture 0
0x39 TC1 MC1 Match/Capture 1
0x3A TC2 OVF Overflow/Underflow
0x3B TC2 MC1 Match/Capture 0
0x3C TC2 MC0 Match/Capture 1
0x3D TC3 OVF Overflow/Underflow
0x3E TC3 MC0 Match/Capture 0
0x3F TC3 MC1 Match/Capture 1
0x40 TC4 OVF Overflow/Underflow
0x41 TC4 MC0 Match/Capture 0
0x42 TC4 MC1 Match/Capture 1
0x43 ADC0 RESRDY Result Ready
0x44 ADC0 WINMON Window Monitor
0x45 ADC1 RESRDY Result Ready
0x46 ADC1 WINMON Window Monitor
0x47 SDADC RESRDY Result Ready
0x48 SDADC WINMON Window Monitor
0x49 AC COMP0 Comparator 0
0x4A AC COMP1 Comparator 1
0x4B AC COMP2 Comparator 2
0x4C AC COMP3 Comparator 3
0x4D AC WIN0 Window 0
0x4E AC WIN1 Window 1
0x4F DAC EMPTY Data Buffer Empty
0x50 PTC EOC End of Conversion
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 530
...........continued
Value Event Generator Description
0x51 PTC WCOMP Window Comparator
0x52 CCL LUTOUT0 CCL output
0x53 CCL LUTOUT1 CCL output
0x54 CCL LUTOUT2 CCL output
0x55 CCL LUT3 CCL output
0x56 PAC ACCERR Access Error
0x57 - Reserved
0x58 TC5 OVF Overflow/Underflow
0x59 TC5 MC0 Match/Capture 0
0x5A TC5 MC1 Match/Capture 1
0x5B TC6 OVF Overflow/Underflow
0x5C TC6 MC0 Match/Capture 0
0x5D TC6 MC1 Match/Capture 1
0x5E TC7 OVF Overflow/Underflow
0x5F TC7 MC0 Match/Capture 0
0x60 TC7 MC1 Match/Capture 1
0x61 - 0xFF - Reserved
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 531
29.8.8 Event User m
Name:  USERm
Offset:  0x80+m*0x4 [m=0..460..46]
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CHANNEL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – CHANNEL[7:0] Channel Event Selection
These bits are used to select the channel to connect to the event user.
Note that to select channel m, the value (m+1) must be written to the USER.CHANNEL bit group.
Value Channel Number
0x00 No channel output selected
0x01 0
0x02 1
0x03 2
0x04 3
0x05 4
0x06 5
0x07 6
0x08 7
0x09 8
0x0A 9
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 532
...........continued
Value Channel Number
0x0B 10
0x0C 11
0x0D-0xFF Reserved
Table 29-3. User Multiplexer Number
USERm User Multiplexer Description Path Type
m = 0 TSENS
STARTReserved
Start measurement- Asynchronous,
synchronous, and
resynchronized
pathsReserved
m = 1 PORT EV0 Event 0 Asynchronous path only
m = 2 PORT EV1 Event 1 Asynchronous path only
m = 3 PORT EV2 Event 2 Asynchronous path only
m = 4 PORT EV3 Event 3 Asynchronous path only
m = 5 DMAC CH0 Channel 0 Asynchronous,
synchronous, and
resynchronized paths
m = 6 DMAC CH1 Channel 1 Asynchronous,
synchronous, and
resynchronized paths
m = 7 DMAC CH2 Channel 2 Asynchronous,
synchronous, and
resynchronized paths
m = 8 DMAC CH3 Channel 3 Asynchronous,
synchronous, and
resynchronized paths
m = 9 TCC0 EV0 - Asynchronous,
synchronous, and
resynchronized paths
m = 10 TCC0 EV1 - Asynchronous,
synchronous, and
resynchronized paths
m = 11 TCC0 MC0 Match/Capture 0 Asynchronous,
synchronous, and
resynchronized paths
m = 12 TCC0 MC1 Match/Capture 1 Asynchronous,
synchronous, and
resynchronized paths
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 533
...........continued
USERm User Multiplexer Description Path Type
m = 13 TCC0 MC2 Match/Capture 2 Asynchronous,
synchronous, and
resynchronized paths
m = 14 TCC0 MC3 Match/Capture 3 Asynchronous,
synchronous, and
resynchronized paths
m = 15 TCC1 EV0 - Asynchronous,
synchronous, and
resynchronized paths
m = 16 TCC1 EV1 - Asynchronous,
synchronous, and
resynchronized paths
m = 17 TCC1 MC0 Match/Capture 0 Asynchronous,
synchronous, and
resynchronized paths
m = 18 TCC1 MC1 Match/Capture 1 Asynchronous,
synchronous, and
resynchronized paths
m = 19 TCC2 EV0 - Asynchronous,
synchronous, and
resynchronized paths
m = 20 TCC2 EV1 - Asynchronous,
synchronous, and
resynchronized paths
m = 21 TCC2 MC0 Match/Capture 0 Asynchronous,
synchronous, and
resynchronized paths
m = 22 TCC2 MC1 Match/Capture 1 Asynchronous,
synchronous, and
resynchronized paths
m = 23 TC0 - Asynchronous,
synchronous, and
resynchronized paths
m = 24 TC1 - Asynchronous,
synchronous, and
resynchronized paths
m = 25 TC2 - Asynchronous,
synchronous, and
resynchronized paths
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 534
...........continued
USERm User Multiplexer Description Path Type
m = 26 TC3 - Asynchronous,
synchronous, and
resynchronized paths
m = 27 TC4 - Asynchronous,
synchronous, and
resynchronized paths
m = 28 ADC0 START ADC start conversion Asynchronous,
synchronous, and
resynchronized paths
m = 29 ADC0 SYNC Flush ADC Asynchronous,
synchronous, and
resynchronized paths
m = 30 ADC1 START ADC start conversion Asynchronous,
synchronous, and
resynchronized paths
m = 31 ADC1 SYNC Flush ADC Asynchronous,
synchronous, and
resynchronized paths
m = 32 SDADC START SADC start conversion Asynchronous path only
m = 33 SDADC FLUSH Flush SADC Asynchronous path only
m=30 to 33 Reserved - Reserved
m = 34 AC COMP0 Start comparator 0 Asynchronous path only
m = 35 AC COMP1 Start comparator 1 Asynchronous path only
m = 36 AC COMP2 Start comparator 2 Asynchronous path only
m = 37 AC COMP3 Start comparator 3 Asynchronous path only
m = 38 DAC START DAC start conversion Asynchronous path only
m=36 to 38 Reserved - Reserved
m = 39 PTC STCONC PTC start conversion Asynchronous path only
m = 40 CCL LUTIN 0 CCL input Asynchronous path only
m = 41 CCL LUTIN 1 CCL input Asynchronous path only
m = 42 CCL LUTIN 2 CCL input Asynchronous path only
m = 43 CCL LUTIN 3 CCL input Asynchronous path only
m=44 to 46 Reserved - Reserved
m=47 TC5 - Asynchronous,
synchronous, and
resynchronized paths
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 535
...........continued
USERm User Multiplexer Description Path Type
m=48 TC6 - Asynchronous,
synchronous, and
resynchronized paths
m=49 TC7 - Asynchronous,
synchronous, and
resynchronized paths
others Reserved - Reserved
SAM C20/C21 Family Data Sheet
EVSYS – Event System
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 536
30. SERCOM – Serial Communication Interface
30.1 Overview
There are up to eight instances of the serial communication interface (SERCOM) peripheral.
A SERCOM can be configured to support a number of modes: I2C, SPI, and USART. When an instance
of SERCOM is configured and enabled, all of the resources of that SERCOM instance will be dedicated
to the selected mode.
The SERCOM serial engine consists of a transmitter and receiver, baud-rate generator and address
matching functionality. It can use the internal generic clock or an external clock. Using an external clock
allows the SERCOM to be operated in all Sleep modes.
Related Links
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and Transmitter
32. SERCOM SPI – SERCOM Serial Peripheral Interface
33. SERCOM I2C – Inter-Integrated Circuit
30.2 Features
• Interface for configuring into one of the following:
– Inter-Integrated Circuit (I2C) Two-wire Serial Interface
– System Management Bus (SMBus™) compatible
– Serial Peripheral Interface (SPI)
– Universal Synchronous/Asynchronous Receiver/Transmitter (USART)
• Single transmit buffer and double receive buffer
• Baud-rate generator
• Address match/mask logic
• Operational in all Sleep modes with an external clock source
• Can be used with DMA
See the Related Links for full feature lists of the interface configurations.
Related Links
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and Transmitter
32. SERCOM SPI – SERCOM Serial Peripheral Interface
33. SERCOM I2C – Inter-Integrated Circuit
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 537
30.3 Block Diagram
Figure 30-1. SERCOM Block Diagram
TX/RX DATA
CONTROL/STATUS
Mode n
SERCOM
BAUD/ADDR
Transmitter
Register Interface
Serial Engine
Receiver
Mode 0
Mode 1
Baud Rate
Generator
Address
Match
Mode Specific
PAD[3:0]
30.4 Signal Description
See the respective SERCOM mode chapters for details.
Related Links
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and Transmitter
32. SERCOM SPI – SERCOM Serial Peripheral Interface
33. SERCOM I2C – Inter-Integrated Circuit
30.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
30.5.1 I/O Lines
Using the SERCOM I/O lines requires the I/O pins to be configured using port configuration (PORT).
The SERCOM has four internal pads, PAD[3:0], and the signals from I2C, SPI and USART are routed
through these SERCOM pads through a multiplexer. The configuration of the multiplexer is available from
the different SERCOM modes. Refer to the mode specific chapters for additional information.
Related Links
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and Transmitter
32. SERCOM SPI – SERCOM Serial Peripheral Interface
33. SERCOM I2C – Inter-Integrated Circuit
28. PORT - I/O Pin Controller
31.3 Block Diagram
30.5.2 Power Management
The SERCOM can operate in any Sleep mode provided the selected clock source is running. SERCOM
interrupts can be configured to wake the device from sleep modes.
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 538
Related Links
19. PM – Power Manager
30.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB) can be enabled and disabled in the Main Clock
Controller. Refer to Peripheral Clock Masking for details and default status of this clock.
The SERCOM uses two generic clocks: GCLK_SERCOMx_CORE and GCLK_SERCOMx_SLOW. The
core clock (GCLK_SERCOMx_CORE) is required to clock the SERCOM while working as a master. The
slow clock (GCLK_SERCOMx_SLOW) is only required for certain functions. See specific mode chapters
for details.
These clocks must be configured and enabled in the Generic Clock Controller (GCLK) before using the
SERCOM.
The generic clocks are asynchronous to the user interface clock (CLK_SERCOMx_APB). Due to this
asynchronicity, writing to certain registers will require synchronization between the clock domains. Refer
to 30.6.8 Synchronization for details.
Related Links
16. GCLK - Generic Clock Controller
17. MCLK – Main Clock
30.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). The DMAC must be configured
before the SERCOM DMA requests are used.
Related Links
25. DMAC – Direct Memory Access Controller
30.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller (NVIC). The NVIC must be configured
before the SERCOM interrupts are used.
Related Links
10.2 Nested Vector Interrupt Controller
30.5.6 Events
Not applicable.
30.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
data loss may result during debugging. This peripheral can be forced to halt operation during debugging -
refer to the Debug Control (DBGCTRL) register for details.
30.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Interrupt Flag Clear and Status register (INTFLAG)
• Status register (STATUS)
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 539
• Data register (DATA)
• Address register (ADDR)
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
30.5.9 Analog Connections
Not applicable.
30.6 Functional Description
30.6.1 Principle of Operation
The basic structure of the SERCOM serial engine is shown in Figure 30-2. Labels in capital letters are
synchronous to the system clock and accessible by the CPU; labels in lowercase letters can be
configured to run on the GCLK_SERCOMx_CORE clock or an external clock.
Figure 30-2. SERCOM Serial Engine
Transmitter
Baud Rate Generator
Equal
Selectable
Internal Clk
(GCLK)
Ext Clk
Receiver
Address Match
Baud Rate Generator
TX Shift Register
RX Shift Register
RX BufferStatus
BAUD TX DATA ADDR/ADDRMASK
RX DATASTATUS
1/- /2- /16
The transmitter consists of a single write buffer and a shift register.
The receiver consists of a one-level (I2C), two-level (USART, SPI) receive buffer and a shift register.
The baud-rate generator is capable of running on the GCLK_SERCOMx_CORE clock or an external
clock.
Address matching logic is included for SPI and I2C operation.
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 540
30.6.2 Basic Operation
30.6.2.1 Initialization
The SERCOM must be configured to the desired mode by writing the Operating Mode bits in the Control
A register (CTRLA.MODE). Refer to table SERCOM Modes for details.
Table 30-1. SERCOM Modes
CTRLA.MODE Description
0x0 USART with external clock
0x1 USART with internal clock
0x2 SPI in slave operation
0x3 SPI in master operation
0x4 I2C slave operation
0x5 I2C master operation
0x6-0x7 Reserved
For further initialization information, see the respective SERCOM mode chapters:
Related Links
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and Transmitter
32. SERCOM SPI – SERCOM Serial Peripheral Interface
33. SERCOM I2C – Inter-Integrated Circuit
30.6.2.2 Enabling, Disabling, and Resetting
This peripheral is enabled by writing '1' to the Enable bit in the Control A register (CTRLA.ENABLE), and
disabled by writing '0' to it.
Writing ‘1’ to the Software Reset bit in the Control A register (CTRLA.SWRST) will reset all registers of
this peripheral to their initial states, except the DBGCTRL register, and the peripheral is disabled.
Refer to the CTRLA register description for details.
30.6.2.3 Clock Generation – Baud-Rate Generator
The baud-rate generator, as shown in Figure 30-3, generates internal clocks for asynchronous and
synchronous communication. The output frequency (fBAUD) is determined by the Baud register (BAUD)
setting and the baud reference frequency (fref). The baud reference clock is the serial engine clock, and it
can be internal or external.
For asynchronous communication, the /16 (divide-by-16) output is used when transmitting, whereas
the /1 (divide-by-1) output is used while receiving.
For synchronous communication, the /2 (divide-by-2) output is used.
This functionality is automatically configured, depending on the selected operating mode.
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 541
Figure 30-3. Baud Rate Generator
Base
Period
Selectable
Internal Clk
(GCLK)
Ext Clk
CTRLA.MODE[0]
0
1
0
1
0
1
0
1
fref
Clock
Recovery
Tx Clk
Rx Clk
CTRLA.MODE
/2 /8
/1 /2 /16
Baud Rate Generator
Table 30-2 contains equations for the baud rate (in bits per second) and the BAUD register value for each
operating mode.
For asynchronous operation, the BAUD register value is 16 bits (0 to 65,535).
For synchronous operation, the BAUD register value is 8 bits (0 to 255).
Table 30-2. Baud Rate Equations
Operating Mode Condition Baud Rate (Bits Per Second) BAUD Register Value Calculation
Asynchronous
Arithmetic  
16  =
16 1
65536  = 65536 116 

Synchronous  
2 =
2 + 1  =
2 
1
The baud rate error is represented by the following formula:
Error = 1 ExpectedBaudRate
ActualBaudRate
30.6.2.3.1 Asynchronous Arithmetic Mode BAUD Value Selection
The formula given for fBAUD calculates the average frequency over 65536 fref cycles. Although the BAUD
register can be set to any value between 0 and 65536, the actual average frequency of fBAUD over a
single frame is more granular. The BAUD register values that will affect the average frequency over a
single frame lead to an integer increase in the cycles per frame (CPF)
 =

+
where
•D represent the data bits per frame
•S represent the sum of start and first stop bits, if present.
Table 30-3 shows the BAUD register value versus baud frequency fBAUD at a serial engine frequency of
48MHz. This assumes a D value of 8 bits and an S value of 2 bits (10 bits, including start and stop bits).
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 542
Table 30-3. BAUD Register Value vs. Baud Frequency
BAUD Register Value Serial Engine CPF fBAUD at 48MHz Serial Engine Frequency (fREF)
0 – 406 160 3MHz
407 – 808 161 2.981MHz
809 – 1205 162 2.963MHz
... ... ...
65206 31775 15.11kHz
65207 31871 15.06kHz
65208 31969 15.01kHz
30.6.3 Additional Features
30.6.3.1 Address Match and Mask
The SERCOM address match and mask feature is capable of matching either one address, two unique
addresses, or a range of addresses with a mask, based on the mode selected. The match uses seven or
eight bits, depending on the mode.
30.6.3.1.1 Address With Mask
An address written to the Address bits in the Address register (ADDR.ADDR), and a mask written to the
Address Mask bits in the Address register (ADDR.ADDRMASK) will yield an address match. All bits that
are masked are not included in the match. Note that writing the ADDR.ADDRMASK to 'all zeros' will
match a single unique address, while writing ADDR.ADDRMASK to 'all ones' will result in all addresses
being accepted.
Figure 30-4. Address With Mask
rx shift register
ADDRMASK
ADDR
== Match
30.6.3.1.2 Two Unique Addresses
The two addresses written to ADDR and ADDRMASK will cause a match.
Figure 30-5. Two Unique Addresses
ADDRMASK
rx shift register
ADDR
==
Match
==
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 543
30.6.3.1.3 Address Range
The range of addresses between and including ADDR.ADDR and ADDR.ADDRMASK will cause a match.
ADDR.ADDR and ADDR.ADDRMASK can be set to any two addresses, with ADDR.ADDR acting as the
upper limit and ADDR.ADDRMASK acting as the lower limit.
Figure 30-6. Address Range
ADDRMASK rx shift register ADDR
==
Match
30.6.4 DMA Operation
The available DMA interrupts and their depend on the operation mode of the SERCOM peripheral. Refer
to the Functional Description sections of the respective SERCOM mode.
Related Links
31. SERCOM USART - SERCOM Synchronous and Asynchronous Receiver and Transmitter
32. SERCOM SPI – SERCOM Serial Peripheral Interface
33. SERCOM I2C – Inter-Integrated Circuit
30.6.5 Interrupts
Interrupt sources are mode-specific. See the respective SERCOM mode chapters for details.
Each interrupt source has its own interrupt flag.
The interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG) will be set when the interrupt
condition is met.
Each interrupt can be individually enabled by writing '1' to the corresponding bit in the Interrupt Enable
Set register (INTENSET), and disabled by writing '1' to the corresponding bit in the Interrupt Enable Clear
register (INTENCLR).
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until either the interrupt flag is cleared, the interrupt is disabled, or
the SERCOM is reset. For details on clearing interrupt flags, refer to the INTFLAG register description.
The value of INTFLAG indicates which interrupt condition occurred. The user must read the INTFLAG
register to determine which interrupt condition is present.
Note:  Interrupts must be globally enabled for interrupt requests.
Related Links
10.2 Nested Vector Interrupt Controller
30.6.6 Events
Not applicable.
30.6.7 Sleep Mode Operation
The peripheral can operate in any sleep mode where the selected serial clock is running. This clock can
be external or generated by the internal baud-rate generator.
The SERCOM interrupts can be used to wake up the device from sleep modes. Refer to the different
SERCOM mode chapters for details.
30.6.8 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 544
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Required read-synchronization is denoted by the "Read-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
SERCOM – Serial Communication Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 545
31. SERCOM USART - SERCOM Synchronous and Asynchronous
Receiver and Transmitter
31.1 Overview
The Universal Synchronous and Asynchronous Receiver and Transmitter (USART) is one of the available
modes in the Serial Communication Interface (SERCOM).
The USART uses the SERCOM transmitter and receiver, see 31.3 Block Diagram. Labels in uppercase
letters are synchronous to CLK_SERCOMx_APB and accessible for CPU. Labels in lowercase letters can
be programmed to run on the internal generic clock or an external clock.
The transmitter consists of a single write buffer, a shift register, and control logic for different frame
formats. The write buffer support data transmission without any delay between frames. The receiver
consists of a two-level receive buffer and a shift register. Status information of the received data is
available for error checking. Data and clock recovery units ensure robust synchronization and noise
filtering during asynchronous data reception.
Related Links
30. SERCOM – Serial Communication Interface
31.2 USART Features
• Full-duplex operation
• Asynchronous (with clock reconstruction) or synchronous operation
• Internal or external clock source for asynchronous and synchronous operation
• Baud-rate generator
• Supports serial frames with 5, 6, 7, 8 or 9 data bits and 1 or 2 stop bits
• Odd or even parity generation and parity check
• Selectable LSB- or MSB-first data transfer
• Buffer overflow and frame error detection
• Noise filtering, including false start-bit detection and digital low-pass filter
• Collision detection
• Can operate in all sleep modes
• Operation at speeds up to half the system clock for internally generated clocks
• Operation at speeds up to the system clock for externally generated clocks
• RTS and CTS flow control
• IrDA modulation and demodulation up to 115.2kbps
• LIN master support
• RS485 Support
• Start-of-frame detection
• Can work with DMA
Related Links
30.2 Features
SAM C20/C21 Family Data Sheet
SERCOM USART - SERCOM Synchronous and Asyn...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 546
31.3 Block Diagram
Figure 31-1. USART Block Diagram
GCLK
(internal)
XCK
BAUD
Baud Rate Generator
TX DATA
TX Shift Register
RX Shift Register
STATUS
Status
RX DATA
RX Buffer
TxD
RxD
CTRLA.MODE /1 - /2 - /16
CTRLA.MODE
31.4 Signal Description
Table 31-1. SERCOM USART Signals
Signal Name Type Description
PAD[3:0] Digital I/O General SERCOM pins
One signal can be mapped to one of several pins.
Related Links
6. I/O Multiplexing and Considerations
31.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
31.5.1 I/O Lines
Using the USART’s I/O lines requires the I/O pins to be configured using the I/O Pin Controller (PORT).
When the SERCOM is used in USART mode, the SERCOM controls the direction and value of the I/O
pins according to the table below. Both PORT control bits PINCFGn.PULLEN and PINCFGn.DRVSTR are
still effective. If the receiver or transmitter is disabled, these pins can be used for other purposes.
Table 31-2. USART Pin Configuration
Pin Pin Configuration
TxD Output
RxD Input
XCK Output or input
SAM C20/C21 Family Data Sheet
SERCOM USART - SERCOM Synchronous and Asyn...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 547
The combined configuration of PORT and the Transmit Data Pinout and Receive Data Pinout bit fields in
the Control A register (CTRLA.TXPO and CTRLA.RXPO, respectively) will define the physical position of
the USART signals in Table 31-2.
Related Links
28. PORT - I/O Pin Controller
31.5.2 Power Management
This peripheral can continue to operate in any sleep mode where its source clock is running. The
interrupts can wake up the device from sleep modes.
Related Links
19. PM – Power Manager
31.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB) can be enabled and disabled in the Main Clock
Controller. Refer to Peripheral Clock Masking for details and default status of this clock.
A generic clock (GCLK_SERCOMx_CORE) is required to clock the SERCOMx_CORE. This clock must
be configured and enabled in the Generic Clock Controller before using the SERCOMx_CORE. Refer to
GCLK - Generic Clock Controller for details.
This generic clock is asynchronous to the bus clock (CLK_SERCOMx_APB). Therefore, writing to certain
registers will require synchronization to the clock domains. Refer to Synchronization for further details.
Related Links
17.6.2.6 Peripheral Clock Masking
31.6.6 Synchronization
16. GCLK - Generic Clock Controller
31.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). In order to use DMA requests with
this peripheral the DMAC must be configured first. Refer to DMAC – Direct Memory Access Controller for
details.
Related Links
25. DMAC – Direct Memory Access Controller
31.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. In order to use interrupt requests of this
peripheral, the Interrupt Controller (NVIC) must be configured first. Refer to Nested Vector Interrupt
Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
31.5.6 Events
Not applicable.
31.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
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data loss may result during debugging. This peripheral can be forced to halt operation during debugging -
refer to the Debug Control (DBGCTRL) register for details.
Related Links
31.8.12 DBGCTRL
31.5.8 Register Access Protection
Registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
PAC Write-Protection is not available for the following registers:
• Interrupt Flag Clear and Status register (INTFLAG)
• Status register (STATUS)
• Data register (DATA)
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
31.5.9 Analog Connections
Not applicable.
31.6 Functional Description
31.6.1 Principle of Operation
The USART uses the following lines for data transfer:
• RxD for receiving
• TxD for transmitting
• XCK for the transmission clock in synchronous operation
USART data transfer is frame based. A serial frame consists of:
• 1 start bit
• From 5 to 9 data bits (MSB or LSB first)
• No, even or odd parity bit
• 1 or 2 stop bits
A frame starts with the start bit followed by one character of data bits. If enabled, the parity bit is inserted
after the data bits and before the first stop bit. After the stop bit(s) of a frame, either the next frame can
follow immediately, or the communication line can return to the idle (high) state. The figure below
illustrates the possible frame formats. Brackets denote optional bits.
Figure 31-2. Frame Formats
Frame
(IDLE) St 0 1 2 3 4 [5] [6] [7] [8] [P] Sp1 [Sp2] [St/IDL]
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St Start bit. Signal is always low.
n, [n] Data bits. 0 to [5..9]
[P] Parity bit. Either odd or even.
Sp, [Sp] Stop bit. Signal is always high.
IDLE No frame is transferred on the communication line. Signal is always high in this state.
31.6.2 Basic Operation
31.6.2.1 Initialization
The following registers are enable-protected, meaning they can only be written when the USART is
disabled (CTRL.ENABLE=0):
• Control A register (CTRLA), except the Enable (ENABLE) and Software Reset (SWRST) bits.
• Control B register (CTRLB), except the Receiver Enable (RXEN) and Transmitter Enable (TXEN)
bits.
• Baud register (BAUD)
When the USART is enabled or is being enabled (CTRLA.ENABLE=1), any writing attempt to these
registers will be discarded. If the peripheral is being disabled, writing to these registers will be executed
after disabling is completed. Enable-protection is denoted by the "Enable-Protection" property in the
register description.
Before the USART is enabled, it must be configured by these steps:
1. Select either external (0x0) or internal clock (0x1) by writing the Operating Mode value in the
CTRLA register (CTRLA.MODE).
2. Select either asynchronous (0) or or synchronous (1) communication mode by writing the
Communication Mode bit in the CTRLA register (CTRLA.CMODE).
3. Select pin for receive data by writing the Receive Data Pinout value in the CTRLA register
(CTRLA.RXPO).
4. Select pads for the transmitter and external clock by writing the Transmit Data Pinout bit in the
CTRLA register (CTRLA.TXPO).
5. Configure the Character Size field in the CTRLB register (CTRLB.CHSIZE) for character size.
6. Set the Data Order bit in the CTRLA register (CTRLA.DORD) to determine MSB- or LSB-first data
transmission.
7. To use parity mode:
7.1. Enable parity mode by writing 0x1 to the Frame Format field in the CTRLA register
(CTRLA.FORM).
7.2. Configure the Parity Mode bit in the CTRLB register (CTRLB.PMODE) for even or odd
parity.
8. Configure the number of stop bits in the Stop Bit Mode bit in the CTRLB register
(CTRLB.SBMODE).
9. When using an internal clock, write the Baud register (BAUD) to generate the desired baud rate.
10. Enable the transmitter and receiver by writing '1' to the Receiver Enable and Transmitter Enable
bits in the CTRLB register (CTRLB.RXEN and CTRLB.TXEN).
SAM C20/C21 Family Data Sheet
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31.6.2.2 Enabling, Disabling, and Resetting
This peripheral is enabled by writing '1' to the Enable bit in the Control A register (CTRLA.ENABLE), and
disabled by writing '0' to it.
Writing ‘1’ to the Software Reset bit in the Control A register (CTRLA.SWRST) will reset all registers of
this peripheral to their initial states, except the DBGCTRL register, and the peripheral is disabled.
Refer to the CTRLA register description for details.
31.6.2.3 Clock Generation and Selection
For both synchronous and asynchronous modes, the clock used for shifting and sampling data can be
generated internally by the SERCOM baud-rate generator or supplied externally through the XCK line.
The synchronous mode is selected by writing a '1' to the Communication Mode bit in the Control A
register (CTRLA.CMODE), the asynchronous mode is selected by writing a zero to CTRLA.CMODE.
The internal clock source is selected by writing 0x1 to the Operation Mode bit field in the Control A
register (CTRLA.MODE), the external clock source is selected by writing 0x0 to CTRLA.MODE.
The SERCOM baud-rate generator is configured as in the figure below.
In asynchronous mode (CTRLA.CMODE=0), the 16-bit Baud register value is used.
In synchronous mode (CTRLA.CMODE=1), the eight LSBs of the Baud register are used. Refer to Clock
Generation – Baud-Rate Generator for details on configuring the baud rate.
Figure 31-3. Clock Generation
XCK
CTRLA.MODE[0]
1
0
XCKInternal Clk
(GCLK) Baud Rate Generator
Base
Period /2 /8
/2 /8/1
1
0
1
0
0
1
Tx Clk
Rx Clk
CTRLA.CMODE
Related Links
30.6.2.3 Clock Generation – Baud-Rate Generator
30.6.2.3.1 Asynchronous Arithmetic Mode BAUD Value Selection
31.6.2.3.1 Synchronous Clock Operation
In synchronous mode, the CTRLA.MODE bit field determines whether the transmission clock line (XCK)
serves either as input or output. The dependency between clock edges, data sampling, and data change
is the same for internal and external clocks. Data input on the RxD pin is sampled at the opposite XCK
clock edge when data is driven on the TxD pin.
The Clock Polarity bit in the Control A register (CTRLA.CPOL) selects which XCK clock edge is used for
RxD sampling, and which is used for TxD change:
When CTRLA.CPOL is '0', the data will be changed on the rising edge of XCK, and sampled on the falling
edge of XCK.
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When CTRLA.CPOL is '1', the data will be changed on the falling edge of XCK, and sampled on the rising
edge of XCK.
Figure 31-4. Synchronous Mode XCK Timing
XCK
RxD / TxD
CTRLA.CPOL=1
Change
Sample
XCK
RxD / TxD
CTRLA.CPOL=0
Change
Sample
When the clock is provided through XCK (CTRLA.MODE=0x0), the shift registers operate directly on the
XCK clock. This means that XCK is not synchronized with the system clock and, therefore, can operate at
frequencies up to the system frequency.
31.6.2.4 Data Register
The USART Transmit Data register (TxDATA) and USART Receive Data register (RxDATA) share the
same I/O address, referred to as the Data register (DATA). Writing the DATA register will update the
TxDATA register. Reading the DATA register will return the contents of the RxDATA register.
31.6.2.5 Data Transmission
Data transmission is initiated by writing the data to be sent into the DATA register. Then, the data in
TxDATA will be moved to the shift register when the shift register is empty and ready to send a new
frame. After the shift register is loaded with data, the data frame will be transmitted.
When the entire data frame including stop bit(s) has been transmitted and no new data was written to
DATA, the Transmit Complete interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.TXC)
will be set, and the optional interrupt will be generated.
The Data Register Empty flag in the Interrupt Flag Status and Clear register (INTFLAG.DRE) indicates
that the register is empty and ready for new data. The DATA register should only be written to when
INTFLAG.DRE is set.
31.6.2.5.1 Disabling the Transmitter
The transmitter is disabled by writing '0' to the Transmitter Enable bit in the CTRLB register
(CTRLB.TXEN).
Disabling the transmitter will complete only after any ongoing and pending transmissions are completed,
i.e., there is no data in the transmit shift register and TxDATA to transmit.
31.6.2.6 Data Reception
The receiver accepts data when a valid start bit is detected. Each bit following the start bit will be sampled
according to the baud rate or XCK clock, and shifted into the receive shift register until the first stop bit of
a frame is received. The second stop bit will be ignored by the receiver.
When the first stop bit is received and a complete serial frame is present in the receive shift register, the
contents of the shift register will be moved into the two-level receive buffer. Then, the Receive Complete
interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.RXC) will be set, and the optional
interrupt will be generated.
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The received data can be read from the DATA register when the Receive Complete interrupt flag is set.
31.6.2.6.1 Disabling the Receiver
Writing '0' to the Receiver Enable bit in the CTRLB register (CTRLB.RXEN) will disable the receiver, flush
the two-level receive buffer, and data from ongoing receptions will be lost.
31.6.2.6.2 Error Bits
The USART receiver has three error bits in the Status (STATUS) register: Frame Error (FERR), Buffer
Overflow (BUFOVF), and Parity Error (PERR). Once an error happens, the corresponding error bit will be
set until it is cleared by writing ‘1’ to it. These bits are also cleared automatically when the receiver is
disabled.
There are two methods for buffer overflow notification, selected by the Immediate Buffer Overflow
Notification bit in the Control A register (CTRLA.IBON):
When CTRLA.IBON=1, STATUS.BUFOVF is raised immediately upon buffer overflow. Software can then
empty the receive FIFO by reading RxDATA, until the receiver complete interrupt flag (INTFLAG.RXC) is
cleared.
When CTRLA.IBON=0, the buffer overflow condition is attending data through the receive FIFO. After the
received data is read, STATUS.BUFOVF will be set along with INTFLAG.RXC.
31.6.2.6.3 Asynchronous Data Reception
The USART includes a clock recovery and data recovery unit for handling asynchronous data reception.
The clock recovery logic can synchronize the incoming asynchronous serial frames at the RxD pin to the
internally generated baud-rate clock.
The data recovery logic samples and applies a low-pass filter to each incoming bit, thereby improving the
noise immunity of the receiver.
31.6.2.6.4 Asynchronous Operational Range
The operational range of the asynchronous reception depends on the accuracy of the internal baud-rate
clock, the rate of the incoming frames, and the frame size (in number of bits). In addition, the operational
range of the receiver is depending on the difference between the received bit rate and the internally
generated baud rate. If the baud rate of an external transmitter is too high or too low compared to the
internally generated baud rate, the receiver will not be able to synchronize the frames to the start bit.
There are two possible sources for a mismatch in baud rate: First, the reference clock will always have
some minor instability. Second, the baud-rate generator cannot always do an exact division of the
reference clock frequency to get the baud rate desired. In this case, the BAUD register value should be
set to give the lowest possible error. Refer to Clock Generation – Baud-Rate Generator for details.
Recommended maximum receiver baud-rate errors for various character sizes are shown in the table
below.
Table 31-3. Asynchronous Receiver Error for 16-fold Oversampling
D
(Data bits+Parity)
RSLOW [%] RFAST [%] Max. total error [%] Recommended max. Rx error [%]
5 94.12 107.69 +5.88/-7.69 ±2.5
6 94.92 106.67 +5.08/-6.67 ±2.0
7 95.52 105.88 +4.48/-5.88 ±2.0
8 96.00 105.26 +4.00/-5.26 ±2.0
SAM C20/C21 Family Data Sheet
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...........continued
D
(Data bits+Parity)
RSLOW [%] RFAST [%] Max. total error [%] Recommended max. Rx error [%]
9 96.39 104.76 +3.61/-4.76 ±1.5
10 96.70 104.35 +3.30/-4.35 ±1.5
The following equations calculate the ratio of the incoming data rate and internal receiver baud rate:
SLOW =+ 1
1+ +
,FAST =+ 2
+ 1 +
•RSLOW is the ratio of the slowest incoming data rate that can be accepted in relation to the receiver
baud rate
•RFAST is the ratio of the fastest incoming data rate that can be accepted in relation to the receiver
baud rate
•D is the sum of character size and parity size (D = 5 to 10 bits)
•S is the number of samples per bit (S = 16, 8 or 3)
•SF is the first sample number used for majority voting (SF = 7, 3, or 2) when CTRLA.SAMPA=0.
•SM is the middle sample number used for majority voting (SM = 8, 4, or 2) when CTRLA.SAMPA=0.
The recommended maximum Rx Error assumes that the receiver and transmitter equally divide the
maximum total error. Its connection to the SERCOM Receiver error acceptance is depicted in this figure:
Figure 31-5. USART Rx Error Calculation
+
+
Error Max (%)
Error Min (%)
Baud Rate
SERCOM Receiver error acceptance
from RSLOW and RFAST formulas
Baud Generator offset error
depends on BAUD register value
+
Clock source error
Recommended max. Rx Error (%)
The recommendation values in the table above accommodate errors of the clock source and the baud
generator. The following figure gives an example for a baud rate of 3Mbps:
Figure 31-6. USART Rx Error Calculation Example
+
+
Error Max 3.3%
Error Min -4.35%
Baud Rate 3Mbps
SERCOM Receiver error acceptance
sampling = x16
data bits = 10
parity = 0
start bit = stop bit = 1
No baud generator offset error
Fbaud(3Mbps) = 48MHz *1(BAUD=0) /16
+
Clock Source at 3MHz
+/-0.3%
Recommended
max. Rx Error +/-1.5%
(example)
Error Max 3.3%
Error Min -4.35%
+
Error Max 3.0%
Error Min -4.05%
Transmitter Error*
Accepted
Receiver Error
security margin
*Transmitter Error depends on the external transmitter used in the application.
It is advised that it is within the Recommended max. Rx Error (+/-1.5% in this example).
Larger Transmitter Errors are acceptable but must lie within the Accepted Receiver Error.
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Related Links
30.6.2.3 Clock Generation – Baud-Rate Generator
30.6.2.3.1 Asynchronous Arithmetic Mode BAUD Value Selection
31.6.3 Additional Features
31.6.3.1 Parity
Even or odd parity can be selected for error checking by writing 0x1 to the Frame Format bit field in the
Control A register (CTRLA.FORM).
If even parity is selected (CTRLB.PMODE=0), the parity bit of an outgoing frame is '1' if the data contains
an odd number of bits that are '1', making the total number of '1' even.
If odd parity is selected (CTRLB.PMODE=1), the parity bit of an outgoing frame is '1' if the data contains
an even number of bits that are '0', making the total number of '1' odd.
When parity checking is enabled, the parity checker calculates the parity of the data bits in incoming
frames and compares the result with the parity bit of the corresponding frame. If a parity error is detected,
the Parity Error bit in the Status register (STATUS.PERR) is set.
31.6.3.2 Hardware Handshaking
The USART features an out-of-band hardware handshaking flow control mechanism, implemented by
connecting the RTS and CTS pins with the remote device, as shown in the figure below.
Figure 31-7. Connection with a Remote Device for Hardware Handshaking
RXD
CTS
RTS
USART
TXD
RTS
CTS
Remote
Device
TXD RXD
Hardware handshaking is only available in the following configuration:
• USART with internal clock (CTRLA.MODE=1),
• Asynchronous mode (CTRLA.CMODE=0),
• and Flow control pinout (CTRLA.TXPO=2).
When the receiver is disabled or the receive FIFO is full, the receiver will drive the RTS pin high. This
notifies the remote device to stop transfer after the ongoing transmission. Enabling and disabling the
receiver by writing to CTRLB.RXEN will set/clear the RTS pin after a synchronization delay. When the
receive FIFO goes full, RTS will be set immediately and the frame being received will be stored in the
shift register until the receive FIFO is no longer full.
Figure 31-8. Receiver Behavior when Operating with Hardware Handshaking
RTS
Rx FIFO Full
RXD
RXEN
The current CTS Status is in the STATUS register (STATUS.CTS). Character transmission will start only if
STATUS.CTS=0. When CTS is set, the transmitter will complete the ongoing transmission and stop
transmitting.
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Figure 31-9. Transmitter Behavior when Operating with Hardware Handshaking
CTS
TXD
31.6.3.3 IrDA Modulation and Demodulation
Transmission and reception can be encoded IrDA compliant up to 115.2 kb/s. IrDA modulation and
demodulation work in the following configuration:
• IrDA encoding enabled (CTRLB.ENC=1),
• Asynchronous mode (CTRLA.CMODE=0),
• and 16x sample rate (CTRLA.SAMPR[0]=0).
During transmission, each low bit is transmitted as a high pulse. The pulse width is 3/16 of the baud rate
period, as illustrated in the figure below.
Figure 31-10. IrDA Transmit Encoding
IrDA encoded TXD
TXD
1 baud clock
3/16 baud clock
The reception decoder has two main functions.
The first is to synchronize the incoming data to the IrDA baud rate counter. Synchronization is performed
at the start of each zero pulse.
The second main function is to decode incoming Rx data. If a pulse width meets the minimum length set
by configuration (RXPL.RXPL), it is accepted. When the baud rate counter reaches its middle value (1/2
bit length), it is transferred to the receiver.
Note:  Note that the polarity of the transmitter and receiver are opposite: During transmission, a '0' bit is
transmitted as a '1' pulse. During reception, an accepted '0' pulse is received as a '0' bit.
Example: The figure below illustrates reception where RXPL.RXPL is set to 19. This
indicates that the pulse width should be at least 20 SE clock cycles. When using
BAUD=0xE666 or 160 SE cycles per bit, this corresponds to 2/16 baud clock as
minimum pulse width required. In this case the first bit is accepted as a '0', the second bit
is a '1', and the third bit is also a '1'. A low pulse is rejected since it does not meet the
minimum requirement of 2/16 baud clock.
Figure 31-11. IrDA Receive Decoding
IrDA encoded RXD
RXD
Baud clock
20 SE clock cycles
0 0.5 11.5 2 2.5
31.6.3.4 Break Character Detection and Auto-Baud
Break character detection and auto-baud are available in this configuration:
• Auto-baud frame format (CTRLA.FORM = 0x04 or 0x05),
• Asynchronous mode (CTRLA.CMODE = 0),
SAM C20/C21 Family Data Sheet
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• and 16x sample rate using fractional baud rate generation (CTRLA.SAMPR = 1).
The USART uses a break detection threshold of greater than 11 nominal bit times at the configured baud
rate. At any time, if more than 11 consecutive dominant bits are detected on the bus, the USART detects
a Break Field. When a Break Field has been detected, the Receive Break interrupt flag
(INTFLAG.RXBRK) is set and the USART expects the Sync Field character to be 0x55. This field is used
to update the actual baud rate in order to stay synchronized. If the received Sync character is not 0x55,
then the Inconsistent Sync Field error flag (STATUS.ISF) is set along with the Error interrupt flag
(INTFLAG.ERROR), and the baud rate is unchanged.
After a break field is detected and the start bit of the Sync Field is detected, a counter is started. The
counter is then incremented for the next 8 bit times of the Sync Field. At the end of these 8 bit times, the
counter is stopped. At this moment, the 13 most significant bits of the counter (value divided by 8) give
the new clock divider (BAUD.BAUD), and the 3 least significant bits of this value (the remainder) give the
new Fractional Part (BAUD.FP).
When the Sync Field has been received, the clock divider (BAUD.BAUD) and the Fractional Part
(BAUD.FP) are updated after a synchronization delay. After the Break and Sync Fields are received,
multiple characters of data can be received.
31.6.3.5 LIN Master
LIN master is available with the following configuration:
• LIN master format (CTRLA.FORM = 0x02)
• Asynchronous mode (CTRLA.CMODE = 0)
• 16x sample rate using fractional baud rate generation (CTRLA.SAMPR = 1)
LIN frames start with a header transmitted by the master. The header consists of the break, sync, and
identifier fields. After the master transmits the header, the addressed slave will respond with 1-8 bytes of
data plus checksum.
Figure 31-12. LIN Frame Format
Header
Slave response
Break Sync ID
1-8 Data bytes Checksum
TxD
RxD
Using the LIN command field (CTRLB.LINCMD), the complete header can be automatically transmitted,
or software can control transmission of the various header components.
When CTRLB.LINCMD=0x1, software controls transmission of the LIN header. In this case, software
uses the following sequence.
• CTRLB.LINCMD is written to 0x1.
• DATA register written to 0x00. This triggers transmission of the break field by hardware. Note that
writing the DATA register with any other value will also result in the transmission of the break field by
hardware.
• DATA register written to 0x55. The 0x55 value (sync) is transmitted.
• DATA register written to the identifier. The identifier is transmitted.
When CTRLB.LINCMD=0x2, hardware controls transmission of the LIN header. In this case, software
uses the following sequence.
• CTRLB.LINCMD is written to 0x2.
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• DATA register written to the identifier. This triggers transmission of the complete header by hardware.
First the break field is transmitted. Next, the sync field is transmitted, and finally the identifier is
transmitted.
In LIN master mode, the length of the break field is programmable using the break length field
(CTRLC.BRKLEN). When the LIN header command is used (CTRLB.LINCMD=0x2), the delay between
the break and sync fields, in addition to the delay between the sync and ID fields are configurable using
the header delay field (CTRLC.HDRDLY). When manual transmission is used (CTRLB.LINCMD=0x1),
software controls the delay between break and sync.
Figure 31-13. LIN Header Generation
Configurable
Break Field Length Sync Field Identifier Field
LIN Header
Configurable delay using CTRLC.HDRDLY
After header transmission is complete, the slave responds with 1-8 data bytes plus checksum.
31.6.3.6 RS485
RS485 is available with the following configuration:
• USART frame format (CTRLA.FORM = 0x00 or 0x01)
• RS485 pinout (CTRLA.TXPO=0x3).
The RS485 feature enables control of an external line driver as shown in the figure below. While
operating in RS485 mode, the transmit enable pin (TE) is driven high when the transmitter is active.
Figure 31-14. RS485 Bus Connection
TXD
TE
USART
RXD
Differential
Bus
The TE pin will remain high for the complete frame including stop bit(s). If a Guard Time is programmed in
the Control C register (CTRLC.GTIME), the line will remain driven after the last character completion. The
following figure shows a transfer with one stop bit and CTRLC.GTIME=3.
Figure 31-15. Example of TE Drive with Guard Time
TXD
Start StopData GTIME=3
TE
The Transmit Complete interrupt flag (INTFLAG.TXC) will be raised after the guard time is complete and
TE goes low.
31.6.3.7 Collision Detection
When the receiver and transmitter are connected either through pin configuration or externally, transmit
collision can be detected after selecting the Collision Detection Enable bit in the CTRLB register
(CTRLB.COLDEN=1). To detect collision, the receiver and transmitter must be enabled (CTRLB.RXEN=1
and CTRLB.TXEN=1).
SAM C20/C21 Family Data Sheet
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Collision detection is performed for each bit transmitted by comparing the received value with the transmit
value, as shown in the figure below. While the transmitter is idle (no transmission in progress), characters
can be received on RxD without triggering a collision.
Figure 31-16. Collision Checking
8-bit character, single stop bit
Collision checked
TXD
RXD
The next figure shows the conditions for a collision detection. In this case, the start bit and the first data
bit are received with the same value as transmitted. The second received data bit is found to be different
than the transmitted bit at the detection point, which indicates a collision.
Figure 31-17. Collision Detected
Collision checked and ok
TXD
RXD
Collision detected
Tri-state
TXEN
When a collision is detected, the USART follows this sequence:
1. Abort the current transfer.
2. Flush the transmit buffer.
3. Disable transmitter (CTRLB.TXEN=0)
– This is done after a synchronization delay. The CTRLB Synchronization Busy bit
(SYNCBUSY.CTRLB) will be set until this is complete.
– After disabling, the TxD pin will be tri-stated.
4. Set the Collision Detected bit (STATUS.COLL) along with the Error interrupt flag
(INTFLAG.ERROR).
5. Set the Transmit Complete interrupt flag (INTFLAG.TXC), since the transmit buffer no longer
contains data.
After a collision, software must manually enable the transmitter again before continuing, after assuring
that the CTRLB Synchronization Busy bit (SYNCBUSY.CTRLB) is not set.
31.6.3.8 Loop-Back Mode
For loop-back mode, configure the Receive Data Pinout (CTRLA.RXPO) and Transmit Data Pinout
(CTRLA.TXPO) to use the same data pins for transmit and receive. The loop-back is through the pad, so
the signal is also available externally.
31.6.3.9 Start-of-Frame Detection
The USART start-of-frame detector can wake up the CPU when it detects a start bit. In standby sleep
mode, the internal fast startup oscillator must be selected as the GCLK_SERCOMx_CORE source.
When a 1-to-0 transition is detected on RxD, the 8MHz Internal Oscillator is powered up and the USART
clock is enabled. After startup, the rest of the data frame can be received, provided that the baud rate is
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slow enough in relation to the fast startup internal oscillator start-up time. Refer to Electrical
Characteristics for details. The start-up time of this oscillator varies with supply voltage and temperature.
The USART start-of-frame detection works both in asynchronous and synchronous modes. It is enabled
by writing ‘1’ to the Start of Frame Detection Enable bit in the Control B register (CTRLB.SFDE).
If the Receive Start Interrupt Enable bit in the Interrupt Enable Set register (INTENSET.RXS) is set, the
Receive Start interrupt is generated immediately when a start is detected.
When using start-of-frame detection without the Receive Start interrupt, start detection will force the
8MHz Internal Oscillator and USART clock active while the frame is being received. In this case, the CPU
will not wake up until the Receive Complete interrupt is generated.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
31.6.3.10 Sample Adjustment
In asynchronous mode (CTRLA.CMODE=0), three samples in the middle are used to determine the value
based on majority voting. The three samples used for voting can be selected using the Sample
Adjustment bit field in Control A register (CTRLA.SAMPA). When CTRLA.SAMPA=0, samples 7-8-9 are
used for 16x oversampling, and samples 3-4-5 are used for 8x oversampling.
31.6.4 DMA, Interrupts and Events
Table 31-4. Module Request for SERCOM USART
Condition Request
DMA Interrupt Event
Data Register Empty (DRE) Yes
(request cleared when data is written)
Yes NA
Receive Complete (RXC) Yes
(request cleared when data is read)
Yes
Transmit Complete (TXC) NA Yes
Receive Start (RXS) NA Yes
Clear to Send Input Change (CTSIC) NA Yes
Receive Break (RXBRK) NA Yes
Error (ERROR) NA Yes
31.6.4.1 DMA Operation
The USART generates the following DMA requests:
• Data received (RX): The request is set when data is available in the receive FIFO. The request is
cleared when DATA is read.
• Data transmit (TX): The request is set when the transmit buffer (TX DATA) is empty. The request is
cleared when DATA is written.
31.6.4.2 Interrupts
The USART has the following interrupt sources. These are asynchronous interrupts, and can wake up the
device from any sleep mode:
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• Data Register Empty (DRE)
• Receive Complete (RXC)
• Transmit Complete (TXC)
• Receive Start (RXS)
• Clear to Send Input Change (CTSIC)
• Received Break (RXBRK)
• Error (ERROR)
Each interrupt source has its own interrupt flag. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) will be set when the interrupt condition is met. Each interrupt can be individually
enabled by writing '1' to the corresponding bit in the Interrupt Enable Set register (INTENSET), and
disabled by writing '1' to the corresponding bit in the Interrupt Enable Clear register (INTENCLR).
An interrupt request is generated when the interrupt flag is set and if the corresponding interrupt is
enabled. The interrupt request remains active until either the interrupt flag is cleared, the interrupt is
disabled, or the USART is reset. For details on clearing interrupt flags, refer to the INTFLAG register
description.
The value of INTFLAG indicates which interrupt is executed. Note that interrupts must be globally
enabled for interrupt requests. Refer to Nested Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
31.6.4.3 Events
Not applicable.
31.6.5 Sleep Mode Operation
The behavior in sleep mode is depending on the clock source and the Run In Standby bit in the Control A
register (CTRLA.RUNSTDBY):
• Internal clocking, CTRLA.RUNSTDBY=1: GCLK_SERCOMx_CORE can be enabled in all sleep
modes. Any interrupt can wake up the device.
• External clocking, CTRLA.RUNSTDBY=1: The Receive Start and the Receive Complete interrupt(s)
can wake up the device.
• Internal clocking, CTRLA.RUNSTDBY=0: Internal clock will be disabled, after any ongoing transfer
was completed. The Receive Start and the Receive Complete interrupt(s) can wake up the device.
• External clocking, CTRLA.RUNSTDBY=0: External clock will be disconnected, after any ongoing
transfer was completed. All reception will be dropped.
31.6.6 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in the CTRLA register (CTRLA.SWRST)
• Enable bit in the CTRLA register (CTRLA.ENABLE)
• Receiver Enable bit in the CTRLB register (CTRLB.RXEN)
• Transmitter Enable bit in the Control B register (CTRLB.TXEN)
Note:  CTRLB.RXEN is write-synchronized somewhat differently. See also 31.8.2 CTRLB for details.
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Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
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31.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA
7:0 RUNSTDBY MODE[2:0] ENABLE SWRST
15:8 SAMPR[2:0] IBON
23:16 SAMPA[1:0] RXPO[1:0] TXPO[1:0]
31:24 DORD CPOL CMODE FORM[3:0]
0x04 CTRLB
7:0 SBMODE CHSIZE[2:0]
15:8 PMODE ENC SFDE COLDEN
23:16 RXEN TXEN
31:24 LINCMD[1:0]
0x08 CTRLC
7:0 GTIME[2:0]
15:8 HDRDLY[1:0] BRKLEN[1:0]
23:16
31:24
0x0C BAUD
7:0 BAUD[7:0]
15:8 BAUD[15:8]
0x0E RXPL 7:0 RXPL[7:0]
0x0F
...
0x13
Reserved
0x14 INTENCLR 7:0 ERROR RXBRK CTSIC RXS RXC TXC DRE
0x15 Reserved
0x16 INTENSET 7:0 ERROR RXBRK CTSIC RXS RXC TXC DRE
0x17 Reserved
0x18 INTFLAG 7:0 ERROR RXBRK CTSIC RXS RXC TXC DRE
0x19 Reserved
0x1A STATUS
7:0 TXE COLL ISF CTS BUFOVF FERR PERR
15:8
0x1C SYNCBUSY
7:0 CTRLB ENABLE SWRST
15:8
23:16
31:24
0x20
...
0x27
Reserved
0x28 DATA
7:0 DATA[7:0]
15:8 DATA[8:8]
0x2A
...
0x2F
Reserved
0x30 DBGCTRL 7:0 DBGSTOP
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31.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
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31.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
DORD CPOL CMODE FORM[3:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
SAMPA[1:0] RXPO[1:0] TXPO[1:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
SAMPR[2:0] IBON
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RUNSTDBY MODE[2:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 30 – DORD Data Order
This bit selects the data order when a character is shifted out from the Data register.
This bit is not synchronized.
Value Description
0MSB is transmitted first.
1LSB is transmitted first.
Bit 29 – CPOL Clock Polarity
This bit selects the relationship between data output change and data input sampling in synchronous
mode.
This bit is not synchronized.
CPOL TxD Change RxD Sample
0x0 Rising XCK edge Falling XCK edge
0x1 Falling XCK edge Rising XCK edge
Bit 28 – CMODE Communication Mode
This bit selects asynchronous or synchronous communication.
This bit is not synchronized.
Value Description
0Asynchronous communication.
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Value Description
1Synchronous communication.
Bits 27:24 – FORM[3:0] Frame Format
These bits define the frame format.
These bits are not synchronized.
FORM[3:0] Description
0x0 USART frame
0x1 USART frame with parity
0x2 LIN Master - Break and sync generation. See LIN Command (CTRLB.LINCMD).
0x3 Reserved
0x4 Auto-baud (LIN Slave) - break detection and auto-baud.
0x5 Auto-baud - break detection and auto-baud with parity
0x6-0xF Reserved
Bits 23:22 – SAMPA[1:0] Sample Adjustment
These bits define the sample adjustment.
These bits are not synchronized.
SAMPA[1:0] 16x Over-sampling (CTRLA.SAMPR=0 or
1)
8x Over-sampling (CTRLA.SAMPR=2 or
3)
0x0 7-8-9 3-4-5
0x1 9-10-11 4-5-6
0x2 11-12-13 5-6-7
0x3 13-14-15 6-7-8
Bits 21:20 – RXPO[1:0] Receive Data Pinout
These bits define the receive data (RxD) pin configuration.
These bits are not synchronized.
RXPO[1:0] Name Description
0x0 PAD[0] SERCOM PAD[0] is used for data reception
0x1 PAD[1] SERCOM PAD[1] is used for data reception
0x2 PAD[2] SERCOM PAD[2] is used for data reception
0x3 PAD[3] SERCOM PAD[3] is used for data reception
Bits 17:16 – TXPO[1:0] Transmit Data Pinout
These bits define the transmit data (TxD) and XCK pin configurations.
This bit is not synchronized.
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TXPO TxD Pin Location XCK Pin Location (When
Applicable)
RTS/TE CTS
0x0 SERCOM PAD[0] SERCOM PAD[1] N/A N/A
0x1 SERCOM PAD[2] SERCOM PAD[3] N/A N/A
0x2 SERCOM PAD[0] N/A SERCOM PAD[2] SERCOM PAD[3]
0x3 SERCOM_PAD[0] SERCOM_PAD[1] SERCOM_PAD[2] N/A
Bits 15:13 – SAMPR[2:0] Sample Rate
These bits select the sample rate.
These bits are not synchronized.
SAMPR[2:0] Description
0x0 16x over-sampling using arithmetic baud rate generation.
0x1 16x over-sampling using fractional baud rate generation.
0x2 8x over-sampling using arithmetic baud rate generation.
0x3 8x over-sampling using fractional baud rate generation.
0x4 3x over-sampling using arithmetic baud rate generation.
0x5-0x7 Reserved
Bit 8 – IBON Immediate Buffer Overflow Notification
This bit controls when the buffer overflow status bit (STATUS.BUFOVF) is asserted when a buffer
overflow occurs.
Value Description
0STATUS.BUFOVF is asserted when it occurs in the data stream.
1STATUS.BUFOVF is asserted immediately upon buffer overflow.
Bit 7 – RUNSTDBY Run In Standby
This bit defines the functionality in standby sleep mode.
This bit is not synchronized.
RUNSTDBY External Clock Internal Clock
0x0 External clock is disconnected
when ongoing transfer is
finished. All reception is
dropped.
Generic clock is disabled when ongoing transfer is
finished. The device will not wake up on either Receive
Start or Transfer Complete interrupt unless the
appropriate ONDEMAND bits are set in the clocking
chain.
0x1 Wake on Receive Start or
Receive Complete interrupt.
Generic clock is enabled in all sleep modes. Any
interrupt can wake up the device.
Bits 4:2 – MODE[2:0] Operating Mode
These bits select the USART serial communication interface of the SERCOM.
These bits are not synchronized.
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Value Description
0x0 USART with external clock
0x1 USART with internal clock
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the Enable
Synchronization Busy bit in the Synchronization Busy register (SYNCBUSY.ENABLE) will be set.
SYNCBUSY.ENABLE is cleared when the operation is complete.
This bit is not enable-protected.
Value Description
0The peripheral is disabled or being disabled.
1The peripheral is enabled or being enabled.
Bit 0 – SWRST Software Reset
Writing '0' to this bit has no effect.
Writing '1' to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the
SERCOM will be disabled.
Writing '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded. Any register write access during the ongoing reset will result in an APB
error. Reading any register will return the reset value of the register.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable-protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
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31.8.2 Control B
Name:  CTRLB
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
LINCMD[1:0]
Access R/W R/W
Reset 0 0
Bit 23 22 21 20 19 18 17 16
RXEN TXEN
Access R/W R/W
Reset 0 0
Bit 15 14 13 12 11 10 9 8
PMODE ENC SFDE COLDEN
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
SBMODE CHSIZE[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 25:24 – LINCMD[1:0] LIN Command
These bits define the LIN header transmission control. This field is only valid in LIN master mode
(CTRLA.FORM= LIN Master).
These are strobe bits and will always read back as zero.
These bits are not enable-protected.
Value Description
0x0 Normal USART transmission.
0x1 Break field is transmitted when DATA is written.
0x2 Break, sync and identifier are automatically transmitted when DATA is written with the
identifier.
0x3 Reserved
Bit 17 – RXEN Receiver Enable
Writing '0' to this bit will disable the USART receiver. Disabling the receiver will flush the receive buffer
and clear the FERR, PERR and BUFOVF bits in the STATUS register.
Writing '1' to CTRLB.RXEN when the USART is disabled will set CTRLB.RXEN immediately. When the
USART is enabled, CTRLB.RXEN will be cleared, and SYNCBUSY.CTRLB will be set and remain set
until the receiver is enabled. When the receiver is enabled, CTRLB.RXEN will read back as '1'.
Writing '1' to CTRLB.RXEN when the USART is enabled will set SYNCBUSY.CTRLB, which will remain
set until the receiver is enabled, and CTRLB.RXEN will read back as '1'.
This bit is not enable-protected.
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Value Description
0The receiver is disabled or being enabled.
1The receiver is enabled or will be enabled when the USART is enabled.
Bit 16 – TXEN Transmitter Enable
Writing '0' to this bit will disable the USART transmitter. Disabling the transmitter will not become effective
until ongoing and pending transmissions are completed.
Writing '1' to CTRLB.TXEN when the USART is disabled will set CTRLB.TXEN immediately. When the
USART is enabled, CTRLB.TXEN will be cleared, and SYNCBUSY.CTRLB will be set and remain set until
the transmitter is enabled. When the transmitter is enabled, CTRLB.TXEN will read back as '1'.
Writing '1' to CTRLB.TXEN when the USART is enabled will set SYNCBUSY.CTRLB, which will remain
set until the transmitter is enabled, and CTRLB.TXEN will read back as '1'.
This bit is not enable-protected.
Value Description
0The transmitter is disabled or being enabled.
1The transmitter is enabled or will be enabled when the USART is enabled.
Bit 13 – PMODE Parity Mode
This bit selects the type of parity used when parity is enabled (CTRLA.FORM is '1'). The transmitter will
automatically generate and send the parity of the transmitted data bits within each frame. The receiver
will generate a parity value for the incoming data and parity bit, compare it to the parity mode and, if a
mismatch is detected, STATUS.PERR will be set.
This bit is not synchronized.
Value Description
0Even parity.
1Odd parity.
Bit 10 – ENC Encoding Format
This bit selects the data encoding format.
This bit is not synchronized.
Value Description
0Data is not encoded.
1Data is IrDA encoded.
Bit 9 – SFDE Start of Frame Detection Enable
This bit controls whether the start-of-frame detector will wake up the device when a start bit is detected
on the RxD line.
This bit is not synchronized.
SFDE INTENSET.RXS INTENSET.RXC Description
0 X X Start-of-frame detection disabled.
1 0 0 Reserved
1 0 1 Start-of-frame detection enabled. RXC wakes up the device
from all sleep modes.
1 1 0 Start-of-frame detection enabled. RXS wakes up the device
from all sleep modes.
SAM C20/C21 Family Data Sheet
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...........continued
SFDE INTENSET.RXS INTENSET.RXC Description
1 1 1 Start-of-frame detection enabled. Both RXC and RXS wake
up the device from all sleep modes.
Bit 8 – COLDEN Collision Detection Enable
This bit enables collision detection.
This bit is not synchronized.
Value Description
0Collision detection is not enabled.
1Collision detection is enabled.
Bit 6 – SBMODE Stop Bit Mode
This bit selects the number of stop bits transmitted.
This bit is not synchronized.
Value Description
0One stop bit.
1Two stop bits.
Bits 2:0 – CHSIZE[2:0] Character Size
These bits select the number of bits in a character.
These bits are not synchronized.
CHSIZE[2:0] Description
0x0 8 bits
0x1 9 bits
0x2-0x4 Reserved
0x5 5 bits
0x6 6 bits
0x7 7 bits
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31.8.3 Control C
Name:  CTRLC
Offset:  0x08
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
HDRDLY[1:0] BRKLEN[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
GTIME[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 11:10 – HDRDLY[1:0] LIN Master Header Delay
These bits define the delay between break and sync transmission in addition to the delay between the
sync and identifier (ID) fields when in LIN master mode (CTRLA.FORM=0x2).
This field is only valid when using the LIN header command (CTRLB.LINCMD=0x2).
Value Description
0x0 Delay between break and sync transmission is 1 bit time.
Delay between sync and ID transmission is 1 bit time.
0x1 Delay between break and sync transmission is 4 bit time.
Delay between sync and ID transmission is 4 bit time.
0x2 Delay between break and sync transmission is 8 bit time.
Delay between sync and ID transmission is 4 bit time.
0x3 Delay between break and sync transmission is 14 bit time.
Delay between sync and ID transmission is 4 bit time.
Bits 9:8 – BRKLEN[1:0] LIN Master Break Length
These bits define the length of the break field transmitted when in LIN master mode
(CTRLA.FORM=0x2).
Value Description
0x0 Break field transmission is 13 bit times
0x1 Break field transmission is 17 bit times
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Value Description
0x2 Break field transmission is 21 bit times
0x3 Break field transmission is 26 bit times
Bits 2:0 – GTIME[2:0] Guard Time
These bits define the guard time when using RS485 mode (CTRLA.FORM=0x0 or CTRLA.FORM=0x1,
and CTRLA.TXPO=0x3).
For RS485 mode, the guard time is programmable from 0-7 bit times and defines the time that the
transmit enable pin (TE) remains high after the last stop bit is transmitted and there is no remaining data
to be transmitted.
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31.8.4 Baud
Name:  BAUD
Offset:  0x0C
Reset:  0x0000
Property:  Enable-Protected, PAC Write-Protection
Bit 15 14 13 12 11 10 9 8
BAUD[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
BAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – BAUD[15:0] Baud Value
Arithmetic Baud Rate Generation (CTRLA.SAMPR[0]=0):
These bits control the clock generation, as described in the SERCOM Baud Rate section.
If Fractional Baud Rate Generation (CTRLA.SAMPR[0]=1) bit positions 15 to 13 are replaced by FP[2:0]
Fractional Part:
•Bits 15:13 - FP[2:0]: Fractional Part
These bits control the clock generation, as described in the SERCOM Clock Generation – Baud-Rate
Generator section.
•Bits 12:0 - BAUD[12:0]: Baud Value
These bits control the clock generation, as described in the SERCOM Clock Generation – Baud-Rate
Generator section.
Related Links
30.6.2.3 Clock Generation – Baud-Rate Generator
30.6.2.3.1 Asynchronous Arithmetic Mode BAUD Value Selection
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31.8.5 Receive Pulse Length Register
Name:  RXPL
Offset:  0x0E
Reset:  0x00
Property:  Enable-Protected, PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
RXPL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – RXPL[7:0] Receive Pulse Length
When the encoding format is set to IrDA (CTRLB.ENC=1), these bits control the minimum pulse length
that is required for a pulse to be accepted by the IrDA receiver with regards to the serial engine clock
period .
 RXPL + 2 
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31.8.6 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
ERROR RXBRK CTSIC RXS RXC TXC DRE
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 5 – RXBRK Receive Break Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Receive Break Interrupt Enable bit, which disables the Receive Break
interrupt.
Value Description
0Receive Break interrupt is disabled.
1Receive Break interrupt is enabled.
Bit 4 – CTSIC Clear to Send Input Change Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Clear To Send Input Change Interrupt Enable bit, which disables the
Clear To Send Input Change interrupt.
Value Description
0Clear To Send Input Change interrupt is disabled.
1Clear To Send Input Change interrupt is enabled.
Bit 3 – RXS Receive Start Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Receive Start Interrupt Enable bit, which disables the Receive Start
interrupt.
Value Description
0Receive Start interrupt is disabled.
1Receive Start interrupt is enabled.
Bit 2 – RXC Receive Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Receive Complete Interrupt Enable bit, which disables the Receive
Complete interrupt.
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Value Description
0Receive Complete interrupt is disabled.
1Receive Complete interrupt is enabled.
Bit 1 – TXC Transmit Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Transmit Complete Interrupt Enable bit, which disables the Receive
Complete interrupt.
Value Description
0Transmit Complete interrupt is disabled.
1Transmit Complete interrupt is enabled.
Bit 0 – DRE Data Register Empty Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Data Register Empty Interrupt Enable bit, which disables the Data
Register Empty interrupt.
Value Description
0Data Register Empty interrupt is disabled.
1Data Register Empty interrupt is enabled.
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31.8.7 Interrupt Enable Set
Name:  INTENSET
Offset:  0x16
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
ERROR RXBRK CTSIC RXS RXC TXC DRE
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 5 – RXBRK Receive Break Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Receive Break Interrupt Enable bit, which enables the Receive Break
interrupt.
Value Description
0Receive Break interrupt is disabled.
1Receive Break interrupt is enabled.
Bit 4 – CTSIC Clear to Send Input Change Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Clear To Send Input Change Interrupt Enable bit, which enables the Clear
To Send Input Change interrupt.
Value Description
0Clear To Send Input Change interrupt is disabled.
1Clear To Send Input Change interrupt is enabled.
Bit 3 – RXS Receive Start Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Receive Start Interrupt Enable bit, which enables the Receive Start
interrupt.
Value Description
0Receive Start interrupt is disabled.
1Receive Start interrupt is enabled.
Bit 2 – RXC Receive Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Receive Complete Interrupt Enable bit, which enables the Receive
Complete interrupt.
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Value Description
0Receive Complete interrupt is disabled.
1Receive Complete interrupt is enabled.
Bit 1 – TXC Transmit Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Transmit Complete Interrupt Enable bit, which enables the Transmit
Complete interrupt.
Value Description
0Transmit Complete interrupt is disabled.
1Transmit Complete interrupt is enabled.
Bit 0 – DRE Data Register Empty Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Data Register Empty Interrupt Enable bit, which enables the Data Register
Empty interrupt.
Value Description
0Data Register Empty interrupt is disabled.
1Data Register Empty interrupt is enabled.
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31.8.8 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x18
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
ERROR RXBRK CTSIC RXS RXC TXC DRE
Access R/W R/W R/W R/W R R/W R
Reset 0 0 0 0 0 0 0
Bit 7 – ERROR Error
This flag is cleared by writing '1' to it.
This bit is set when any error is detected. Errors that will set this flag have corresponding status flags in
the STATUS register. Errors that will set this flag are COLL, ISF, BUFOVF, FERR, and PERR.Writing '0' to
this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 5 – RXBRK Receive Break
This flag is cleared by writing '1' to it.
This flag is set when auto-baud is enabled (CTRLA.FORM) and a break character is received.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 4 – CTSIC Clear to Send Input Change
This flag is cleared by writing a '1' to it.
This flag is set when a change is detected on the CTS pin.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 3 – RXS Receive Start
This flag is cleared by writing '1' to it.
This flag is set when a start condition is detected on the RxD line and start-of-frame detection is enabled
(CTRLB.SFDE is '1').
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Receive Start interrupt flag.
Bit 2 – RXC Receive Complete
This flag is cleared by reading the Data register (DATA) or by disabling the receiver.
This flag is set when there are unread data in DATA.
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
Bit 1 – TXC Transmit Complete
This flag is cleared by writing '1' to it or by writing new data to DATA.
This flag is set when the entire frame in the transmit shift register has been shifted out and there are no
new data in DATA.
Writing '0' to this bit has no effect.
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Writing '1' to this bit will clear the flag.
Bit 0 – DRE Data Register Empty
This flag is cleared by writing new data to DATA.
This flag is set when DATA is empty and ready to be written.
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
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31.8.9 Status
Name:  STATUS
Offset:  0x1A
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TXE COLL ISF CTS BUFOVF FERR PERR
Access R/W R/W R/W R R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 6 – TXE Transmitter Empty
When CTRLA.FORM is set to LIN master mode, this bit is set when any ongoing transmission is complete
and TxDATA is empty.
When CTRLA.FORM is not set to LIN master mode, this bit will always read back as zero.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
Bit 5 – COLL Collision Detected
This bit is cleared by writing '1' to the bit or by disabling the receiver.
This bit is set when collision detection is enabled (CTRLB.COLDEN) and a collision is detected.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
Bit 4 – ISF Inconsistent Sync Field
This bit is cleared by writing '1' to the bit or by disabling the receiver.
This bit is set when the frame format is set to auto-baud (CTRLA.FORM) and a sync field not equal to
0x55 is received.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
Bit 3 – CTS Clear to Send
This bit indicates the current level of the CTS pin when flow control is enabled (CTRLA.TXPO).
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
Bit 2 – BUFOVF Buffer Overflow
Reading this bit before reading the Data register will indicate the error status of the next character to be
read.
This bit is cleared by writing '1' to the bit or by disabling the receiver.
This bit is set when a buffer overflow condition is detected. A buffer overflow occurs when the receive
buffer is full, there is a new character waiting in the receive shift register and a new start bit is detected.
Writing '0' to this bit has no effect.
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Writing '1' to this bit will clear it.
Bit 1 – FERR Frame Error
Reading this bit before reading the Data register will indicate the error status of the next character to be
read.
This bit is cleared by writing '1' to the bit or by disabling the receiver.
This bit is set if the received character had a frame error, i.e., when the first stop bit is zero.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
Bit 0 – PERR Parity Error
Reading this bit before reading the Data register will indicate the error status of the next character to be
read.
This bit is cleared by writing '1' to the bit or by disabling the receiver.
This bit is set if parity checking is enabled (CTRLA.FORM is 0x1, 0x5) and a parity error is detected.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
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31.8.10 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x1C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CTRLB ENABLE SWRST
Access R R R
Reset 0 0 0
Bit 2 – CTRLB CTRLB Synchronization Busy
Writing to the CTRLB register when the SERCOM is enabled requires synchronization. When writing to
CTRLB the SYNCBUSY.CTRLB bit will be set until synchronization is complete. If CTRLB is written while
SYNCBUSY.CTRLB is asserted, an APB error will be generated.
Value Description
0CTRLB synchronization is not busy.
1CTRLB synchronization is busy.
Bit 1 – ENABLE SERCOM Enable Synchronization Busy
Enabling and disabling the SERCOM (CTRLA.ENABLE) requires synchronization. When written, the
SYNCBUSY.ENABLE bit will be set until synchronization is complete.
Value Description
0Enable synchronization is not busy.
1Enable synchronization is busy.
Bit 0 – SWRST Software Reset Synchronization Busy
Resetting the SERCOM (CTRLA.SWRST) requires synchronization. When written, the
SYNCBUSY.SWRST bit will be set until synchronization is complete.
Value Description
0SWRST synchronization is not busy.
1SWRST synchronization is busy.
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31.8.11 Data
Name:  DATA
Offset:  0x28
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
DATA[8:8]
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 8:0 – DATA[8:0] Data
Reading these bits will return the contents of the Receive Data register. The register should be read only
when the Receive Complete Interrupt Flag bit in the Interrupt Flag Status and Clear register
(INTFLAG.RXC) is set. The status bits in STATUS should be read before reading the DATA value in order
to get any corresponding error.
Writing these bits will write the Transmit Data register. This register should be written only when the Data
Register Empty Interrupt Flag bit in the Interrupt Flag Status and Clear register (INTFLAG.DRE) is set.
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31.8.12 Debug Control
Name:  DBGCTRL
Offset:  0x30
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGSTOP
Access R/W
Reset 0
Bit 0 – DBGSTOP Debug Stop Mode
This bit controls the baud-rate generator functionality when the CPU is halted by an external debugger.
Value Description
0The baud-rate generator continues normal operation when the CPU is halted by an external
debugger.
1The baud-rate generator is halted when the CPU is halted by an external debugger.
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32. SERCOM SPI – SERCOM Serial Peripheral Interface
32.1 Overview
The serial peripheral interface (SPI) is one of the available modes in the Serial Communication Interface
(SERCOM).
The SPI uses the SERCOM transmitter and receiver configured as shown in 32.3 Block Diagram. Each
side, master and slave, depicts a separate SPI containing a shift register, a transmit buffer and a two-level
receive buffer. In addition, the SPI master uses the SERCOM baud-rate generator, while the SPI slave
can use the SERCOM address match logic. Labels in capital letters are synchronous to
CLK_SERCOMx_APB and accessible by the CPU, while labels in lowercase letters are synchronous to
the SCK clock.
Related Links
30. SERCOM – Serial Communication Interface
32.2 Features
SERCOM SPI includes the following features:
• Full-duplex, four-wire interface (MISO, MOSI, SCK, SS)
• One-level transmit buffer, two-level receive buffer
• Supports all four SPI modes of operation
• Single data direction operation allows alternate function on MISO or MOSI pin
• Selectable LSB- or MSB-first data transfer
• Can be used with DMA
• Master operation:
– Serial clock speed, fSCK=1/tSCK(1)
– 8-bit clock generator
– Hardware controlled SS
• Slave Operation:
– Serial clock speed, fSCK=1/tSSCK(1)
– Optional 8-bit address match operation
– Operation in all sleep modes
– Wake on SS transition
1. For tSCK and tSSCK values, refer to SPI Timing Characteristics.
Related Links
45.13.1 SERCOM in SPI Mode Timing
30. SERCOM – Serial Communication Interface
30.2 Features
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32.3 Block Diagram
Figure 32-1. Full-Duplex SPI Master Slave Interconnection
BAUD
baud rate generator
Tx DATA
shift register
rx buffer
Rx DATA
Master Slave
Tx DATA
shift register
rx buffer
Rx DATA
SCK
_SS
MISO
MOSI
ADDR/ADDRMASK
==
Address Match
32.4 Signal Description
Table 32-1. SERCOM SPI Signals
Signal Name Type Description
PAD[3:0] Digital I/O General SERCOM pins
One signal can be mapped to one of several pins.
Related Links
6. I/O Multiplexing and Considerations
32.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
32.5.1 I/O Lines
In order to use the SERCOM’s I/O lines, the I/O pins must be configured using the IO Pin Controller
(PORT).
When the SERCOM is configured for SPI operation, the SERCOM controls the direction and value of the
I/O pins according to the table below. Both PORT control bits PINCFGn.PULLEN and PINCFGn.DRVSTR
are still effective. If the receiver is disabled, the data input pin can be used for other purposes. In master
mode, the slave select line (SS) is hardware controlled when the Master Slave Select Enable bit in the
Control B register (CTRLB.MSSEN) is '1'.
Table 32-2. SPI Pin Configuration
Pin Master SPI Slave SPI
MOSI Output Input
MISO Input Output
SCK Output Input
SS Output (CTRLB.MSSEN=1) Input
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The combined configuration of PORT, the Data In Pinout and the Data Out Pinout bit groups in the
Control A register (CTRLA.DIPO and CTRLA.DOPO) define the physical position of the SPI signals in the
table above.
Related Links
28. PORT - I/O Pin Controller
32.5.2 Power Management
This peripheral can continue to operate in any sleep mode where its source clock is running. The
interrupts can wake up the device from sleep modes.
Related Links
19. PM – Power Manager
32.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB) can be enabled and disabled in the Main Clock
Controller. Refer to Peripheral Clock Masking for details and default status of this clock.
A generic clock (GCLK_SERCOMx_CORE) is required to clock the SPI. This clock must be configured
and enabled in the Generic Clock Controller before using the SPI.
This generic clock is asynchronous to the bus clock (CLK_SERCOMx_APB). Therefore, writes to certain
registers will require synchronization to the clock domains.
Related Links
16. GCLK - Generic Clock Controller
17.6.2.6 Peripheral Clock Masking
32.6.6 Synchronization
32.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). In order to use DMA requests with
this peripheral the DMAC must be configured first. Refer to DMAC – Direct Memory Access Controller for
details.
Related Links
25. DMAC – Direct Memory Access Controller
32.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. In order to use interrupt requests of this
peripheral, the Interrupt Controller (NVIC) must be configured first. Refer to Nested Vector Interrupt
Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
32.5.6 Events
Not applicable.
32.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
data loss may result during debugging. This peripheral can be forced to halt operation during debugging -
refer to the Debug Control (DBGCTRL) register for details.
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32.5.8 Register Access Protection
Registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
PAC Write-Protection is not available for the following registers:
• Interrupt Flag Clear and Status register (INTFLAG)
• Status register (STATUS)
• Data register (DATA)
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
32.5.9 Analog Connections
Not applicable.
32.6 Functional Description
32.6.1 Principle of Operation
The SPI is a high-speed synchronous data transfer interface. It allows high-speed communication
between the device and peripheral devices.
The SPI can operate as master or slave. As master, the SPI initiates and controls all data transactions.
The SPI is single buffered for transmitting and double buffered for receiving.
When transmitting data, the Data register can be loaded with the next character to be transmitted during
the current transmission.
When receiving, the data is transferred to the two-level receive buffer, and the receiver is ready for a new
character.
The SPI transaction format is shown in SPI Transaction Format. Each transaction can contain one or
more characters. The character size is configurable, and can be either 8 or 9 bits.
Figure 32-2. SPI Transaction Format
Character
Transaction
MOSI/MISO
_SS
Character 0 Character 1 Character 2
The SPI master must pull the slave select line (SS) of the desired slave low to initiate a transaction. The
master and slave prepare data to send via their respective shift registers, and the master generates the
serial clock on the SCK line.
Data are always shifted from master to slave on the Master Output Slave Input line (MOSI); data is shifted
from slave to master on the Master Input Slave Output line (MISO).
Each time character is shifted out from the master, a character will be shifted out from the slave
simultaneously. To signal the end of a transaction, the master will pull the SS line high
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32.6.2 Basic Operation
32.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the SPI is
disabled (CTRL.ENABLE=0):
• Control A register (CTRLA), except Enable (CTRLA.ENABLE) and Software Reset (CTRLA.SWRST)
• Control B register (CTRLB), except Receiver Enable (CTRLB.RXEN)
• Baud register (BAUD)
• Address register (ADDR)
When the SPI is enabled or is being enabled (CTRLA.ENABLE=1), any writing to these registers will be
discarded.
when the SPI is being disabled, writing to these registers will be completed after the disabling.
Enable-protection is denoted by the Enable-Protection property in the register description.
Initialize the SPI by following these steps:
1. Select SPI mode in master / slave operation in the Operating Mode bit group in the CTRLA register
(CTRLA.MODE= 0x2 or 0x3 ).
2. Select transfer mode for the Clock Polarity bit and the Clock Phase bit in the CTRLA register
(CTRLA.CPOL and CTRLA.CPHA) if desired.
3. Select the Frame Format value in the CTRLA register (CTRLA.FORM).
4. Configure the Data In Pinout field in the Control A register (CTRLA.DIPO) for SERCOM pads of the
receiver.
5. Configure the Data Out Pinout bit group in the Control A register (CTRLA.DOPO) for SERCOM
pads of the transmitter.
6. Select the Character Size value in the CTRLB register (CTRLB.CHSIZE).
7. Write the Data Order bit in the CTRLA register (CTRLA.DORD) for data direction.
8. If the SPI is used in master mode:
8.1. Select the desired baud rate by writing to the Baud register (BAUD).
8.2. If Hardware SS control is required, write '1' to the Master Slave Select Enable bit in CTRLB
register (CTRLB.MSSEN).
9. Enable the receiver by writing the Receiver Enable bit in the CTRLB register (CTRLB.RXEN=1).
32.6.2.2 Enabling, Disabling, and Resetting
This peripheral is enabled by writing '1' to the Enable bit in the Control A register (CTRLA.ENABLE), and
disabled by writing '0' to it.
Writing ‘1’ to the Software Reset bit in the Control A register (CTRLA.SWRST) will reset all registers of
this peripheral to their initial states, except the DBGCTRL register, and the peripheral is disabled.
Refer to the CTRLA register description for details.
32.6.2.3 Clock Generation
In SPI master operation (CTRLA.MODE=0x3), the serial clock (SCK) is generated internally by the
SERCOM baud-rate generator.
In SPI mode, the baud-rate generator is set to synchronous mode. The 8-bit Baud register (BAUD) value
is used for generating SCK and clocking the shift register. Refer to Clock Generation – Baud-Rate
Generator for more details.
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In SPI slave operation (CTRLA.MODE is 0x2), the clock is provided by an external master on the SCK
pin. This clock is used to directly clock the SPI shift register.
Related Links
30.6.2.3 Clock Generation – Baud-Rate Generator
30.6.2.3.1 Asynchronous Arithmetic Mode BAUD Value Selection
32.6.2.4 Data Register
The SPI Transmit Data register (TxDATA) and SPI Receive Data register (RxDATA) share the same I/O
address, referred to as the SPI Data register (DATA). Writing DATA register will update the Transmit Data
register. Reading the DATA register will return the contents of the Receive Data register.
32.6.2.5 SPI Transfer Modes
There are four combinations of SCK phase and polarity to transfer serial data. The SPI data transfer
modes are shown in SPI Transfer Modes (Table) and SPI Transfer Modes (Figure).
SCK phase is configured by the Clock Phase bit in the CTRLA register (CTRLA.CPHA). SCK polarity is
programmed by the Clock Polarity bit in the CTRLA register (CTRLA.CPOL). Data bits are shifted out and
latched in on opposite edges of the SCK signal. This ensures sufficient time for the data signals to
stabilize.
Table 32-3. SPI Transfer Modes
Mode CPOL CPHA Leading Edge Trailing Edge
0 0 0 Rising, sample Falling, setup
1 0 1 Rising, setup Falling, sample
2 1 0 Falling, sample Rising, setup
3 1 1 Falling, setup Rising, sample
Note: 
Leading edge is the first clock edge in a clock cycle.
Trailing edge is the second clock edge in a clock cycle.
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Figure 32-3. SPI Transfer Modes
Bit 1
Bit 6
LSB
MSB
Mode 0
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
Mode 2
SS
MSB
LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
MSB first (DORD = 0)
LSB first (DORD = 1)
Mode 1
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
Mode 3
SS
MSB
LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
LSB
MSB
MSB first (DORD = 0)
LSB first (DORD = 1)
32.6.2.6 Transferring Data
32.6.2.6.1 Master
In master mode (CTRLA.MODE=0x3), when Master Slave Enable Select (CTRLB.MSSEN) is ‘1’,
hardware will control the SS line.
When Master Slave Select Enable (CTRLB.MSSEN) is '0', the SS line must be configured as an output.
SS can be assigned to any general purpose I/O pin. When the SPI is ready for a data transaction,
software must pull the SS line low.
When writing a character to the Data register (DATA), the character will be transferred to the shift register.
Once the content of TxDATA has been transferred to the shift register, the Data Register Empty flag in the
Interrupt Flag Status and Clear register (INTFLAG.DRE) will be set. And a new character can be written
to DATA.
Each time one character is shifted out from the master, another character will be shifted in from the slave
simultaneously. If the receiver is enabled (CTRLA.RXEN=1), the contents of the shift register will be
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transferred to the two-level receive buffer. The transfer takes place in the same clock cycle as the last
data bit is shifted in. And the Receive Complete Interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG.RXC) will be set. The received data can be retrieved by reading DATA.
When the last character has been transmitted and there is no valid data in DATA, the Transmit Complete
Interrupt flag in the Interrupt Flag Status and Clear register (INTFLAG.TXC) will be set. When the
transaction is finished, the master must pull the SS line high to notify the slave. If Master Slave Select
Enable (CTRLB.MSSEN) is set to '0', the software must pull the SS line high.
32.6.2.6.2 Slave
In slave mode (CTRLA.MODE=0x2), the SPI interface will remain inactive with the MISO line tri-stated as
long as the SS pin is pulled high. Software may update the contents of DATA at any time as long as the
Data Register Empty flag in the Interrupt Status and Clear register (INTFLAG.DRE) is set.
When SS is pulled low and SCK is running, the slave will sample and shift out data according to the
transaction mode set. When the content of TxDATA has been loaded into the shift register,
INTFLAG.DRE will be set, and new data can be written to DATA.
Similar to the master, the slave will receive one character for each character transmitted. A character will
be transferred into the two-level receive buffer within the same clock cycle its last data bit is received. The
received character can be retrieved from DATA when the Receive Complete interrupt flag
(INTFLAG.RXC) is set.
When the master pulls the SS line high, the transaction is done and the Transmit Complete Interrupt flag
in the Interrupt Flag Status and Clear register (INTFLAG.TXC) will be set.
After DATA is written it takes up to three SCK clock cycles until the content of DATA is ready to be loaded
into the shift register on the next character boundary. As a consequence, the first character transferred in
a SPI transaction will not be the content of DATA. This can be avoided by using the preloading feature.
Refer to 32.6.3.2 Preloading of the Slave Shift Register.
When transmitting several characters in one SPI transaction, the data has to be written into DATA register
with at least three SCK clock cycles left in the current character transmission. If this criteria is not met, the
previously received character will be transmitted.
Once the DATA register is empty, it takes three CLK_SERCOM_APB cycles for INTFLAG.DRE to be set.
32.6.2.7 Receiver Error Bit
The SPI receiver has one error bit: the Buffer Overflow bit (BUFOVF), which can be read from the Status
register (STATUS). Once an error happens, the bit will stay set until it is cleared by writing '1' to it. The bit
is also automatically cleared when the receiver is disabled.
There are two methods for buffer overflow notification, selected by the immediate buffer overflow
notification bit in the Control A register (CTRLA.IBON):
If CTRLA.IBON=1, STATUS.BUFOVF is raised immediately upon buffer overflow. Software can then
empty the receive FIFO by reading RxDATA until the receiver complete interrupt flag in the Interrupt Flag
Status and Clear register (INTFLAG.RXC) goes low.
If CTRLA.IBON=0, the buffer overflow condition travels with data through the receive FIFO. After the
received data is read, STATUS.BUFOVF and INTFLAG.ERROR will be set along with INTFLAG.RXC,
and RxDATA will be zero.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 594
32.6.3 Additional Features
32.6.3.1 Address Recognition
When the SPI is configured for slave operation (CTRLA.MODE=0x2) with address recognition
(CTRLA.FORM is 0x2), the SERCOM address recognition logic is enabled: the first character in a
transaction is checked for an address match.
If there is a match, the Receive Complete Interrupt flag in the Interrupt Flag Status and Clear register
(INTFLAG.RXC) is set, the MISO output is enabled, and the transaction is processed. If the device is in
sleep mode, an address match can wake up the device in order to process the transaction.
If there is no match, the complete transaction is ignored.
If a 9-bit frame format is selected, only the lower 8 bits of the shift register are checked against the
Address register (ADDR).
Preload must be disabled (CTRLB.PLOADEN=0) in order to use this mode.
Related Links
30.6.3.1 Address Match and Mask
32.6.3.2 Preloading of the Slave Shift Register
When starting a transaction, the slave will first transmit the contents of the shift register before loading
new data from DATA. The first character sent can be either the reset value of the shift register (if this is
the first transmission since the last reset) or the last character in the previous transmission.
Preloading can be used to preload data into the shift register while SS is high: this eliminates sending a
dummy character when starting a transaction. If the shift register is not preloaded, the current contents of
the shift register will be shifted out.
Only one data character will be preloaded into the shift register while the synchronized SS signal is high.
If the next character is written to DATA before SS is pulled low, the second character will be stored in
DATA until transfer begins.
For proper preloading, sufficient time must elapse between SS going low and the first SCK sampling
edge, as in Timing Using Preloading. See also Electrical Characteristics for timing details.
Preloading is enabled by writing '1' to the Slave Data Preload Enable bit in the CTRLB register
(CTRLB.PLOADEN).
Figure 32-4. Timing Using Preloading
_SS
_SS synchronized
to system domain
SCK
Synchronization
to system domain
MISO to SCK
setup time
Required _SS-to-SCK time
using PRELOADEN
32.6.3.3 Master with Several Slaves
Master with multiple slaves in parallel is only available when Master Slave Select Enable
(CTRLB.MSSEN) is set to zero and hardware SS control is disabled. If the bus consists of several SPI
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 595
slaves, an SPI master can use general purpose I/O pins to control the SS line to each of the slaves on
the bus, as shown in Multiple Slaves in Parallel. In this configuration, the single selected SPI slave will
drive the tri-state MISO line.
Figure 32-5. Multiple Slaves in Parallel
MOSI
MISO
SCK
_SS
MOSI
MISO
SCK
_SS[0]
MOSI
MISO
SCK
_SS
_SS[n-1]
shift register shift register
shift register
SPI Master
SPI Slave 0
SPI Slave n-1
Another configuration is multiple slaves in series, as in Multiple Slaves in Series. In this configuration, all
n attached slaves are connected in series. A common SS line is provided to all slaves, enabling them
simultaneously. The master must shift n characters for a complete transaction. Depending on the Master
Slave Select Enable bit (CTRLB.MSSEN), the SS line can be controlled either by hardware or user
software and normal GPIO.
Figure 32-6. Multiple Slaves in Series
MOSI
MISO
SCK
_SS
MOSI
MISO
SCK
_SS
MOSI
MISO
SCK
_SS
shift register shift register
shift register
SPI Master SPI Slave 0
SPI Slave n-1
32.6.3.4 Loop-Back Mode
For loop-back mode, configure the Data In Pinout (CTRLA.DIPO) and Data Out Pinout (CTRLA.DOPO) to
use the same data pins for transmit and receive. The loop-back is through the pad, so the signal is also
available externally.
32.6.3.5 Hardware Controlled SS
In master mode, a single SS chip select can be controlled by hardware by writing the Master Slave Select
Enable (CTRLB.MSSEN) bit to '1'. In this mode, the SS pin is driven low for a minimum of one baud cycle
before transmission begins, and stays low for a minimum of one baud cycle after transmission completes.
If back-to-back frames are transmitted, the SS pin will always be driven high for a minimum of one baud
cycle between frames.
In Hardware Controlled SS, the time T is between one and two baud cycles depending on the SPI
transfer mode.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 596
Figure 32-7. Hardware Controlled SS
_SS
SCK
T
T = 1 to 2 baud cycles
TTT
T
When CTRLB.MSSEN=0, the SS pin(s) is/are controlled by user software and normal GPIO.
32.6.3.6 Slave Select Low Detection
In slave mode, the SPI can wake the CPU when the slave select (SS) goes low. When the Slave Select
Low Detect is enabled (CTRLB.SSDE=1), a high-to-low transition will set the Slave Select Low interrupt
flag (INTFLAG.SSL) and the device will wake up if applicable.
32.6.4 DMA, Interrupts, and Events
Table 32-4. Module Request for SERCOM SPI
Condition Request
DMA Interrupt Event
Data Register Empty (DRE) Yes
(request cleared when data is written)
Yes NA
Receive Complete (RXC) Yes
(request cleared when data is read)
Yes
Transmit Complete (TXC) NA Yes
Slave Select low (SSL) NA Yes
Error (ERROR) NA Yes
32.6.4.1 DMA Operation
The SPI generates the following DMA requests:
• Data received (RX): The request is set when data is available in the receive FIFO. The request is
cleared when DATA is read.
• Data transmit (TX): The request is set when the transmit buffer (TX DATA) is empty. The request is
cleared when DATA is written.
32.6.4.2 Interrupts
The SPI has the following interrupt sources. These are asynchronous interrupts, and can wake up the
device from any sleep mode:
• Data Register Empty (DRE)
• Receive Complete (RXC)
• Transmit Complete (TXC)
• Slave Select Low (SSL)
• Error (ERROR)
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 597
Each interrupt source has its own interrupt flag. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) will be set when the interrupt condition is met. Each interrupt can be individually
enabled by writing '1' to the corresponding bit in the Interrupt Enable Set register (INTENSET), and
disabled by writing '1' to the corresponding bit in the Interrupt Enable Clear register (INTENCLR).
An interrupt request is generated when the interrupt flag is set and if the corresponding interrupt is
enabled. The interrupt request remains active until either the interrupt flag is cleared, the interrupt is
disabled, or the SPI is reset. For details on clearing interrupt flags, refer to the INTFLAG register
description.
The value of INTFLAG indicates which interrupt is executed. Note that interrupts must be globally
enabled for interrupt requests. Refer to Nested Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
32.6.4.3 Events
Not applicable.
32.6.5 Sleep Mode Operation
The behavior in sleep mode is depending on the master/slave configuration and the Run In Standby bit in
the Control A register (CTRLA.RUNSTDBY):
• Master operation, CTRLA.RUNSTDBY=1: The peripheral clock GCLK_SERCOM_CORE will
continue to run in idle sleep mode and in standby sleep mode. Any interrupt can wake up the device.
• Master operation, CTRLA.RUNSTDBY=0: GLK_SERCOMx_CORE will be disabled after the ongoing
transaction is finished. Any interrupt can wake up the device.
• Slave operation, CTRLA.RUNSTDBY=1: The Receive Complete interrupt can wake up the device.
• Slave operation, CTRLA.RUNSTDBY=0: All reception will be dropped, including the ongoing
transaction.
32.6.6 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in the CTRLA register (CTRLA.SWRST)
• Enable bit in the CTRLA register (CTRLA.ENABLE)
• Receiver Enable bit in the CTRLB register (CTRLB.RXEN)
Note:  CTRLB.RXEN is write-synchronized somewhat differently. See also CTRLB register for details.
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 598
32.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA
7:0 RUNSTDBY MODE[2:0] ENABLE SWRST
15:8 IBON
23:16 DIPO[1:0] DOPO[1:0]
31:24 DORD CPOL CPHA FORM[3:0]
0x04 CTRLB
7:0 PLOADEN CHSIZE[2:0]
15:8 AMODE[1:0] MSSEN SSDE
23:16 RXEN
31:24
0x08
...
0x0B
Reserved
0x0C BAUD 7:0 BAUD[7:0]
0x0D
...
0x13
Reserved
0x14 INTENCLR 7:0 ERROR SSL RXC TXC DRE
0x15 Reserved
0x16 INTENSET 7:0 ERROR SSL RXC TXC DRE
0x17 Reserved
0x18 INTFLAG 7:0 ERROR SSL RXC TXC DRE
0x19 Reserved
0x1A STATUS
7:0 BUFOVF
15:8
0x1C SYNCBUSY
7:0 CTRLB ENABLE SWRST
15:8
23:16
31:24
0x20
...
0x23
Reserved
0x24 ADDR
7:0 ADDR[7:0]
15:8
23:16 ADDRMASK[7:0]
31:24
0x28 DATA
7:0 DATA[7:0]
15:8 DATA[8:8]
0x2A
...
0x2F
Reserved
0x30 DBGCTRL 7:0 DBGSTOP
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 599
32.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Refer to 32.6.6 Synchronization
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Refer to 32.5.8 Register Access Protection.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 600
32.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
DORD CPOL CPHA FORM[3:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DIPO[1:0] DOPO[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
IBON
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
RUNSTDBY MODE[2:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 30 – DORD Data Order
This bit selects the data order when a character is shifted out from the shift register.
This bit is not synchronized.
Value Description
0MSB is transferred first.
1LSB is transferred first.
Bit 29 – CPOL Clock Polarity
In combination with the Clock Phase bit (CPHA), this bit determines the SPI transfer mode.
This bit is not synchronized.
Value Description
0SCK is low when idle. The leading edge of a clock cycle is a rising edge, while the trailing
edge is a falling edge.
1SCK is high when idle. The leading edge of a clock cycle is a falling edge, while the trailing
edge is a rising edge.
Bit 28 – CPHA Clock Phase
In combination with the Clock Polarity bit (CPOL), this bit determines the SPI transfer mode.
This bit is not synchronized.
SAM C20/C21 Family Data Sheet
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Mode CPOL CPHA Leading Edge Trailing Edge
0x0 0 0 Rising, sample Falling, change
0x1 0 1 Rising, change Falling, sample
0x2 1 0 Falling, sample Rising, change
0x3 1 1 Falling, change Rising, sample
Value Description
0The data is sampled on a leading SCK edge and changed on a trailing SCK edge.
1The data is sampled on a trailing SCK edge and changed on a leading SCK edge.
Bits 27:24 – FORM[3:0] Frame Format
This bit field selects the various frame formats supported by the SPI in slave mode. When the 'SPI frame
with address' format is selected, the first byte received is checked against the ADDR register.
FORM[3:0] Name Description
0x0 SPI SPI frame
0x1 - Reserved
0x2 SPI_ADDR SPI frame with address
0x3-0xF - Reserved
Bits 21:20 – DIPO[1:0] Data In Pinout
These bits define the data in (DI) pad configurations.
In master operation, DI is MISO.
In slave operation, DI is MOSI.
These bits are not synchronized.
DIPO[1:0] Name Description
0x0 PAD[0] SERCOM PAD[0] is used as data input
0x1 PAD[1] SERCOM PAD[1] is used as data input
0x2 PAD[2] SERCOM PAD[2] is used as data input
0x3 PAD[3] SERCOM PAD[3] is used as data input
Bits 17:16 – DOPO[1:0] Data Out Pinout
This bit defines the available pad configurations for data out (DO) and the serial clock (SCK). In slave
operation, the slave select line (SS) is controlled by DOPO, while in master operation the SS line is
controlled by the port configuration.
In master operation, DO is MOSI.
In slave operation, DO is MISO.
These bits are not synchronized.
DOPO DO SCK Slave SS Master SS
0x0 PAD[0] PAD[1] PAD[2] System configuration
0x1 PAD[2] PAD[3] PAD[1] System configuration
SAM C20/C21 Family Data Sheet
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...........continued
DOPO DO SCK Slave SS Master SS
0x2 PAD[3] PAD[1] PAD[2] System configuration
0x3 PAD[0] PAD[3] PAD[1] System configuration
Bit 8 – IBON Immediate Buffer Overflow Notification
This bit controls when the buffer overflow status bit (STATUS.BUFOVF) is set when a buffer overflow
occurs.
This bit is not synchronized.
Value Description
0STATUS.BUFOVF is set when it occurs in the data stream.
1STATUS.BUFOVF is set immediately upon buffer overflow.
Bit 7 – RUNSTDBY Run In Standby
This bit defines the functionality in standby sleep mode.
These bits are not synchronized.
RUNSTDBY Slave Master
0x0 Disabled. All reception is dropped,
including the ongoing transaction.
Generic clock is disabled when ongoing
transaction is finished. All interrupts can wake
up the device.
0x1 Ongoing transaction continues, wake on
Receive Complete interrupt.
Generic clock is enabled while in sleep modes.
All interrupts can wake up the device.
Bits 4:2 – MODE[2:0] Operating Mode
These bits must be written to 0x2 or 0x3 to select the SPI serial communication interface of the
SERCOM.
0x2: SPI slave operation
0x3: SPI master operation
These bits are not synchronized.
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRL.ENABLE will read back immediately and the Synchronization Enable
Busy bit in the Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE is
cleared when the operation is complete.
This bit is not enable-protected.
Value Description
0The peripheral is disabled or being disabled.
1The peripheral is enabled or being enabled.
Bit 0 – SWRST Software Reset
Writing '0' to this bit has no effect.
Writing '1' to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the
SERCOM will be disabled.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 603
Writing ''1' to CTRL.SWRST will always take precedence, meaning that all other writes in the same write-
operation will be discarded. Any register write access during the ongoing reset will result in an APB error.
Reading any register will return the reset value of the register.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY. SWRST will both be cleared when the reset is complete.
This bit is not enable-protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 604
32.8.2 Control B
Name:  CTRLB
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
RXEN
Access R/W
Reset 0
Bit 15 14 13 12 11 10 9 8
AMODE[1:0] MSSEN SSDE
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PLOADEN CHSIZE[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 17 – RXEN Receiver Enable
Writing '0' to this bit will disable the SPI receiver immediately. The receive buffer will be flushed, data from
ongoing receptions will be lost and STATUS.BUFOVF will be cleared.
Writing '1' to CTRLB.RXEN when the SPI is disabled will set CTRLB.RXEN immediately. When the SPI is
enabled, CTRLB.RXEN will be cleared, SYNCBUSY.CTRLB will be set and remain set until the receiver is
enabled. When the receiver is enabled CTRLB.RXEN will read back as '1'.
Writing '1' to CTRLB.RXEN when the SPI is enabled will set SYNCBUSY.CTRLB, which will remain set
until the receiver is enabled, and CTRLB.RXEN will read back as '1'.
This bit is not enable-protected.
Value Description
0The receiver is disabled or being enabled.
1The receiver is enabled or it will be enabled when SPI is enabled.
Bits 15:14 – AMODE[1:0] Address Mode
These bits set the slave addressing mode when the frame format (CTRLA.FORM) with address is used.
They are unused in master mode.
AMODE[1:0] Name Description
0x0 MASK ADDRMASK is used as a mask to the ADDR register
0x1 2_ADDRS The slave responds to the two unique addresses in ADDR and ADDRMASK
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 605
...........continued
AMODE[1:0] Name Description
0x2 RANGE The slave responds to the range of addresses between and including ADDR
and ADDRMASK. ADDR is the upper limit
0x3 - Reserved
Bit 13 – MSSEN Master Slave Select Enable
This bit enables hardware slave select (SS) control.
Value Description
0Hardware SS control is disabled.
1Hardware SS control is enabled.
Bit 9 – SSDE Slave Select Low Detect Enable
This bit enables wake up when the slave select (SS) pin transitions from high to low.
Value Description
0SS low detector is disabled.
1SS low detector is enabled.
Bit 6 – PLOADEN Slave Data Preload Enable
Setting this bit will enable preloading of the slave shift register when there is no transfer in progress. If the
SS line is high when DATA is written, it will be transferred immediately to the shift register.
Bits 2:0 – CHSIZE[2:0] Character Size
CHSIZE[2:0] Name Description
0x0 8BIT 8 bits
0x1 9BIT 9 bits
0x2-0x7 - Reserved
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 606
32.8.3 Baud Rate
Name:  BAUD
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
BAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – BAUD[7:0] Baud Register
These bits control the clock generation, as described in the SERCOM Clock Generation – Baud-Rate
Generator.
Related Links
30.6.2.3 Clock Generation – Baud-Rate Generator
30.6.2.3.1 Asynchronous Arithmetic Mode BAUD Value Selection
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 607
32.8.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without read-modify-write operation. Changes in this
register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
ERROR SSL RXC TXC DRE
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 3 – SSL Slave Select Low Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Slave Select Low Interrupt Enable bit, which disables the Slave Select
Low interrupt.
Value Description
0Slave Select Low interrupt is disabled.
1Slave Select Low interrupt is enabled.
Bit 2 – RXC Receive Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Receive Complete Interrupt Enable bit, which disables the Receive
Complete interrupt.
Value Description
0Receive Complete interrupt is disabled.
1Receive Complete interrupt is enabled.
Bit 1 – TXC Transmit Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Transmit Complete Interrupt Enable bit, which disable the Transmit
Complete interrupt.
Value Description
0Transmit Complete interrupt is disabled.
1Transmit Complete interrupt is enabled.
Bit 0 – DRE Data Register Empty Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Data Register Empty Interrupt Enable bit, which disables the Data
Register Empty interrupt.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 608
Value Description
0Data Register Empty interrupt is disabled.
1Data Register Empty interrupt is enabled.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 609
32.8.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x16
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without read-modify-write operation. Changes in this
register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
ERROR SSL RXC TXC DRE
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 3 – SSL Slave Select Low Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Slave Select Low Interrupt Enable bit, which enables the Slave Select Low
interrupt.
Value Description
0Slave Select Low interrupt is disabled.
1Slave Select Low interrupt is enabled.
Bit 2 – RXC Receive Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Receive Complete Interrupt Enable bit, which enables the Receive
Complete interrupt.
Value Description
0Receive Complete interrupt is disabled.
1Receive Complete interrupt is enabled.
Bit 1 – TXC Transmit Complete Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Transmit Complete Interrupt Enable bit, which enables the Transmit
Complete interrupt.
Value Description
0Transmit Complete interrupt is disabled.
1Transmit Complete interrupt is enabled.
Bit 0 – DRE Data Register Empty Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Data Register Empty Interrupt Enable bit, which enables the Data Register
Empty interrupt.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 610
Value Description
0Data Register Empty interrupt is disabled.
1Data Register Empty interrupt is enabled.
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 611
32.8.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x18
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
ERROR SSL RXC TXC DRE
Access R/W R/W R R/W R
Reset 0 0 0 0 0
Bit 7 – ERROR Error
This flag is cleared by writing '1' to it.
This bit is set when any error is detected. Errors that will set this flag have corresponding status flags in
the STATUS register. The BUFOVF error will set this interrupt flag.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 3 – SSL Slave Select Low
This flag is cleared by writing '1' to it.
This bit is set when a high to low transition is detected on the _SS pin in slave mode and Slave Select
Low Detect (CTRLB.SSDE) is enabled.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 2 – RXC Receive Complete
This flag is cleared by reading the Data (DATA) register or by disabling the receiver.
This flag is set when there are unread data in the receive buffer. If address matching is enabled, the first
data received in a transaction will be an address.
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
Bit 1 – TXC Transmit Complete
This flag is cleared by writing '1' to it or by writing new data to DATA.
In master mode, this flag is set when the data have been shifted out and there are no new data in DATA.
In slave mode, this flag is set when the _SS pin is pulled high. If address matching is enabled, this flag is
only set if the transaction was initiated with an address match.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 0 – DRE Data Register Empty
This flag is cleared by writing new data to DATA.
This flag is set when DATA is empty and ready for new data to transmit.
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 612
32.8.7 Status
Name:  STATUS
Offset:  0x1A
Reset:  0x0000
Property:  –
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
BUFOVF
Access R/W
Reset 0
Bit 2 – BUFOVF Buffer Overflow
Reading this bit before reading DATA will indicate the error status of the next character to be read.
This bit is cleared by writing '1' to the bit or by disabling the receiver.
This bit is set when a buffer overflow condition is detected. See also CTRLA.IBON for overflow handling.
When set, the corresponding RxDATA will be zero.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
Value Description
0No Buffer Overflow has occurred.
1A Buffer Overflow has occurred.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 613
32.8.8 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x1C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CTRLB ENABLE SWRST
Access R R R
Reset 0 0 0
Bit 2 – CTRLB CTRLB Synchronization Busy
Writing to the CTRLB when the SERCOM is enabled requires synchronization. Ongoing synchronization
is indicated by SYNCBUSY.CTRLB=1 until synchronization is complete. If CTRLB is written while
SYNCBUSY.CTRLB=1, an APB error will be generated.
Value Description
0CTRLB synchronization is not busy.
1CTRLB synchronization is busy.
Bit 1 – ENABLE SERCOM Enable Synchronization Busy
Enabling and disabling the SERCOM (CTRLA.ENABLE) requires synchronization. Ongoing
synchronization is indicated by SYNCBUSY.ENABLE=1 until synchronization is complete.
Value Description
0Enable synchronization is not busy.
1Enable synchronization is busy.
Bit 0 – SWRST Software Reset Synchronization Busy
Resetting the SERCOM (CTRLA.SWRST) requires synchronization. Ongoing synchronization is indicated
by SYNCBUSY.SWRST=1 until synchronization is complete.
Value Description
0SWRST synchronization is not busy.
1SWRST synchronization is busy.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 614
32.8.9 Address
Name:  ADDR
Offset:  0x24
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
ADDRMASK[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ADDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:16 – ADDRMASK[7:0] Address Mask
These bits hold the address mask when the transaction format with address is used (CTRLA.FORM,
CTRLB.AMODE).
Bits 7:0 – ADDR[7:0] Address
These bits hold the address when the transaction format with address is used (CTRLA.FORM,
CTRLB.AMODE).
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 615
32.8.10 Data
Name:  DATA
Offset:  0x28
Reset:  0x0000
Property:  –
Bit 15 14 13 12 11 10 9 8
DATA[8:8]
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 8:0 – DATA[8:0] Data
Reading these bits will return the contents of the receive data buffer. The register should be read only
when the Receive Complete Interrupt Flag bit in the Interrupt Flag Status and Clear register
(INTFLAG.RXC) is set.
Writing these bits will write the transmit data buffer. This register should be written only when the Data
Register Empty Interrupt Flag bit in the Interrupt Flag Status and Clear register (INTFLAG.DRE) is set.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 616
32.8.11 Debug Control
Name:  DBGCTRL
Offset:  0x30
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGSTOP
Access R/W
Reset 0
Bit 0 – DBGSTOP Debug Stop Mode
This bit controls the functionality when the CPU is halted by an external debugger.
Value Description
0The baud-rate generator continues normal operation when the CPU is halted by an external
debugger.
1The baud-rate generator is halted when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
SERCOM SPI – SERCOM Serial Peripheral Interface
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 617
33. SERCOM I2C – Inter-Integrated Circuit
33.1 Overview
The inter-integrated circuit ( I2C) interface is one of the available modes in the serial communication
interface (SERCOM).
The I2C interface uses the SERCOM transmitter and receiver configured as shown in Figure 33-1. Labels
in capital letters are registers accessible by the CPU, while lowercase labels are internal to the SERCOM.
A SERCOM instance can be configured to be either an I2C master or an I2C slave. Both master and slave
have an interface containing a shift register, a transmit buffer and a receive buffer. In addition, the I2C
master uses the SERCOM baud-rate generator, while the I2C slave uses the SERCOM address match
logic.
Related Links
30. SERCOM – Serial Communication Interface
33.2 Features
SERCOM I2C includes the following features:
• Master or slave operation
• Can be used with DMA
• Philips I2C compatible
• SMBus™ compatible
• PMBus compatible
• Support of 100kHz and 400kHz, 1MHz and 3.4MHz I2C mode
• 4-Wire operation supported
• Physical interface includes:
– Slew-rate limited outputs
– Filtered inputs
• Slave operation:
– Operation in all sleep modes
– Wake-up on address match
– 7-bit and 10-bit Address match in hardware for:
– • Unique address and/or 7-bit general call address
• Address range
• Two unique addresses can be used with DMA
Related Links
30.2 Features
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 618
33.3 Block Diagram
Figure 33-1. I2C Single-Master Single-Slave Interconnection
BAUD TxDATA
RxDATA
baud rate generator SCL hold low
shift register
TxDATA
RxDATA
shift register
0 0
0 0
SCL hold low
ADDR/ADDRMASK
==
SDA
SCL
Master Slave
33.4 Signal Description
Signal Name Type Description
PAD[0] Digital I/O SDA
PAD[1] Digital I/O SCL
PAD[2] Digital I/O SDA_OUT (4-wire operation)
PAD[3] Digital I/O SCL_OUT (4-wire operation)
One signal can be mapped on several pins.
Not all the pins are I2C pins.
Related Links
6. I/O Multiplexing and Considerations
33.6.3.3 4-Wire Mode
33.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
33.5.1 I/O Lines
In order to use the I/O lines of this peripheral, the I/O pins must be configured using the I/O Pin Controller
(PORT).
When the SERCOM is used in I2C mode, the SERCOM controls the direction and value of the I/O pins. If
the receiver or transmitter is disabled, these pins can be used for other purposes.
Related Links
28. PORT - I/O Pin Controller
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 619
33.5.2 Power Management
This peripheral can continue to operate in any sleep mode where its source clock is running. The
interrupts can wake up the device from sleep modes.
Related Links
19. PM – Power Manager
33.5.3 Clocks
The SERCOM bus clock (CLK_SERCOMx_APB) can be enabled and disabled in the Main Clock
Controller. Refer to Peripheral Clock Masking for details and default status of this clock.
Two generic clocks are used by SERCOM, GCLK_SERCOMx_CORE and GCLK_SERCOM_SLOW. The
core clock (GCLK_SERCOMx_CORE) can clock the I2C when working as a master. The slow clock
(GCLK_SERCOM_SLOW) is required only for certain functions, e.g. SMBus timing. These two clocks
must be configured and enabled in the Generic Clock Controller (GCLK) before using the I2C.
These generic clocks are asynchronous to the bus clock (CLK_SERCOMx_APB). Due to this
asynchronicity, writes to certain registers will require synchronization between the clock domains. Refer to
33.6.6 Synchronization for further details.
Related Links
16. GCLK - Generic Clock Controller
17.6.2.6 Peripheral Clock Masking
19. PM – Power Manager
33.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). In order to use DMA requests with
this peripheral the DMAC must be configured first. Refer to DMAC – Direct Memory Access Controller for
details.
Related Links
25. DMAC – Direct Memory Access Controller
33.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. In order to use interrupt requests of this
peripheral, the Interrupt Controller (NVIC) must be configured first. Refer to Nested Vector Interrupt
Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
33.5.6 Events
Not applicable.
33.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will continue normal operation. If the peripheral is
configured to require periodical service by the CPU through interrupts or similar, improper operation or
data loss may result during debugging. This peripheral can be forced to halt operation during debugging -
refer to the Debug Control (DBGCTRL) register for details.
33.5.8 Register Access Protection
Registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 620
PAC Write-Protection is not available for the following registers:
• Interrupt Flag Clear and Status register (INTFLAG)
• Status register (STATUS)
• Data register (DATA)
• Address register (ADDR)
Optional PAC Write-Protection is denoted by the "PAC Write-Protection" property in each individual
register description.
Write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
33.5.9 Analog Connections
Not applicable.
33.6 Functional Description
33.6.1 Principle of Operation
The I2C interface uses two physical lines for communication:
• Serial Data Line (SDA) for data transfer
• Serial Clock Line (SCL) for the bus clock
A transaction starts with the I2C master sending the start condition, followed by a 7-bit address and a
direction bit (read or write to/from the slave).
The addressed I2C slave will then acknowledge (ACK) the address, and data packet transactions can
begin. Every 9-bit data packet consists of 8 data bits followed by a one-bit reply indicating whether the
data was acknowledged or not.
If a data packet is not acknowledged (NACK), whether by the I2C slave or master, the I2C master takes
action by either terminating the transaction by sending the stop condition, or by sending a repeated start
to transfer more data.
The figure below illustrates the possible transaction formats and Transaction Diagram Symbols explains
the transaction symbols. These symbols will be used in the following descriptions.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 621
Figure 33-2. Transaction Diagram Symbols
S
Sr
A
A
R
W
P
START condition
repeated START condition
STOP condition
Master driving bus
Slave driving bus
Either Master or Slave driving bus
Acknowledge (ACK)
Not Acknowledge (NACK)
Master Read
Master Write
Bus Driver Special Bus Conditions
Data Package Direction Acknowledge
'1'
'0'
'0'
'1'
Figure 33-3. Basic I2C Transaction Diagram
SDA
SCL
SADDRESS R/W ACK DATA ACK DATA ACK/NACK
6..0 7..0 7..0
P
S ADDRESS R/W A DATA PA DATA A/A
Direction
Address Packet Data Packet #0 Data Packet #1
Transaction
33.6.2 Basic Operation
33.6.2.1 Initialization
The following registers are enable-protected, meaning they can be written only when the I2C interface is
disabled (CTRLA.ENABLE is ‘0’):
• Control A register (CTRLA), except Enable (CTRLA.ENABLE) and Software Reset (CTRLA.SWRST)
bits
• Control B register (CTRLB), except Acknowledge Action (CTRLB.ACKACT) and Command
(CTRLB.CMD) bits
• Baud register (BAUD)
• Address register (ADDR) in slave operation.
When the I2C is enabled or is being enabled (CTRLA.ENABLE=1), writing to these registers will be
discarded. If the I2C is being disabled, writing to these registers will be completed after the disabling.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 622
Enable-protection is denoted by the "Enable-Protection" property in the register description.
Before the I2C is enabled it must be configured as outlined by the following steps:
1. Select I2C Master or Slave mode by writing 0x4 (Slave mode) or 0x5 (Master mode) to the
Operating Mode bits in the CTRLA register (CTRLA.MODE).
2. If desired, select the SDA Hold Time value in the CTRLA register (CTRLA.SDAHOLD).
3. If desired, enable smart operation by setting the Smart Mode Enable bit in the CTRLB register
(CTRLB.SMEN).
4. If desired, enable SCL low time-out by setting the SCL Low Time-Out bit in the Control A register
(CTRLA.LOWTOUT).
5. In Master mode:
5.1. Select the inactive bus time-out in the Inactive Time-Out bit group in the CTRLA register
(CTRLA.INACTOUT).
5.2. Write the Baud Rate register (BAUD) to generate the desired baud rate.
In Slave mode:
5.1. Configure the address match configuration by writing the Address Mode value in the
CTRLB register (CTRLB.AMODE).
5.2. Set the Address and Address Mask value in the Address register (ADDR.ADDR and
ADDR.ADDRMASK) according to the address configuration.
33.6.2.2 Enabling, Disabling, and Resetting
This peripheral is enabled by writing '1' to the Enable bit in the Control A register (CTRLA.ENABLE), and
disabled by writing '0' to it.
Writing ‘1’ to the Software Reset bit in the Control A register (CTRLA.SWRST) will reset all registers of
this peripheral to their initial states, except the DBGCTRL register, and the peripheral is disabled.
33.6.2.3 I2C Bus State Logic
The bus state logic includes several logic blocks that continuously monitor the activity on the I2C bus lines
in all sleep modes with running GCLK_SERCOM_x clocks. The start and stop detectors and the bit
counter are all essential in the process of determining the current bus state. The bus state is determined
according to Bus State Diagram. Software can get the current bus state by reading the Master Bus State
bits in the Status register (STATUS.BUSSTATE). The value of STATUS.BUSSTATE in the figure is shown
in binary.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 623
Figure 33-4. Bus State Diagram
RESET
Write ADDR to generate
Start Condition
IDLE
(0b01)
Start Condition
BUSY
(0b11)
Timeout or Stop Condition
UNKNOWN
(0b00)
OWNER
(0b10)
Lost Arbitration
Repeated
Start Condition
Write ADDR to generate
Repeated Start Condition
Stop Condition
Timeout or Stop Condition
The bus state machine is active when the I2C master is enabled.
After the I2C master has been enabled, the bus state is UNKNOWN (0b00). From the UNKNOWN state,
the bus will transition to IDLE (0b01) by either:
• Forcing by writing 0b01 to STATUS.BUSSTATE
• A stop condition is detected on the bus
• If the inactive bus time-out is configured for SMBus compatibility (CTRLA.INACTOUT) and a time-out
occurs.
Note:  Once a known bus state is established, the bus state logic will not re-enter the UNKNOWN state.
When the bus is IDLE it is ready for a new transaction. If a start condition is issued on the bus by another
I2C master in a multi-master setup, the bus becomes BUSY (0b11). The bus will re-enter IDLE either
when a stop condition is detected, or when a time-out occurs (inactive bus time-out needs to be
configured).
If a start condition is generated internally by writing the Address bit group in the Address register
(ADDR.ADDR) while IDLE, the OWNER state (0b10) is entered. If the complete transaction was
performed without interference, i.e., arbitration was not lost, the I2C master can issue a stop condition,
which will change the bus state back to IDLE.
However, if a packet collision is detected while in OWNER state, the arbitration is assumed lost and the
bus state becomes BUSY until a stop condition is detected. A repeated start condition will change the bus
state only if arbitration is lost while issuing a repeated start.
Note:  Violating the protocol may cause the I2C to hang. If this happens it is possible to recover from this
state by a software reset (CTRLA.SWRST='1').
Related Links
33.10.1 CTRLA
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 624
33.6.2.4 I2C Master Operation
The I2C master is byte-oriented and interrupt based. The number of interrupts generated is kept at a
minimum by automatic handling of most incidents. The software driver complexity and code size are
reduced by auto-triggering of operations, and a special smart mode, which can be enabled by the Smart
Mode Enable bit in the Control A register (CTRLA.SMEN).
The I2C master has two interrupt strategies.
When SCL Stretch Mode (CTRLA.SCLSM) is '0', SCL is stretched before or after the acknowledge bit . In
this mode the I2C master operates according to Master Behavioral Diagram (SCLSM=0). The circles
labelled "Mn" (M1, M2..) indicate the nodes the bus logic can jump to, based on software or hardware
interaction.
This diagram is used as reference for the description of the I2C master operation throughout the
document.
Figure 33-5. I2C Master Behavioral Diagram (SCLSM=0)
IDLE SBUSYBUSY P
Sr
P
M3
M3
M2
M2
M1
M1
R DATA
Wait for
IDLE
ADDRESS
W
A/ADATA
APPLICATION
SW
SW
Sr
P
M3
M2
BUSY M4
A
SW
A/A
A/A
A/A
M4
A
IDLE
IDLE
Slave Bus INTERRUPT + SCL HOLD
Master Bus INTERRUPT + SCL HOLD
SW
SW
SW
BUSYR/W
SW Software interaction
A
A
R/W
BUSY M4
The master provides data on the bus
Addressed slave provides data on the bus
In the second strategy (CTRLA.SCLSM=1), interrupts only occur after the ACK bit, as in Master
Behavioral Diagram (SCLSM=1). This strategy can be used when it is not necessary to check DATA
before acknowledging.
Note:  I2C High-speed (Hs) mode requires CTRLA.SCLSM=1.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 625
Figure 33-6.  I2C Master Behavioral Diagram (SCLSM=1)
IDLE SBUSYBUSY P
Sr
P
M3
M3
M2
M2
M1
M1
R DATA
W
A/ADATA
APPLICATION
SW
SW
Sr
P
M3
M2
BUSY M4
SW
A/A
M4
A
IDLE
IDLE
Master Bus INTERRUPT + SCL HOLD
SW
SW
SW
BUSYR/W
A
A
R/W
BUSY M4
SW Software interaction
The master provides data on the bus
Addressed slave provides data on the bus
Slave Bus INTERRUPT + SCL HOLD
Wait for
IDLE
ADDRESS
33.6.2.4.1 Master Clock Generation
The SERCOM peripheral supports several I2C bidirectional modes:
• Standard mode (Sm) up to 100kHz
• Fast mode (Fm) up to 400kHz
• Fast mode Plus (Fm+) up to 1MHz
• High-speed mode (Hs) up to 3.4MHz
The Master clock configuration for Sm, Fm, and Fm+ are described in Clock Generation (Standard-Mode,
Fast-Mode, and Fast-Mode Plus). For Hs, refer to Master Clock Generation (High-Speed Mode).
Clock Generation (Standard-Mode, Fast-Mode, and Fast-Mode Plus)
In I2C Sm, Fm, and Fm+ mode, the Master clock (SCL) frequency is determined as described in this
section:
The low (TLOW) and high (THIGH) times are determined by the Baud Rate register (BAUD), while the rise
(TRISE) and fall (TFALL) times are determined by the bus topology. Because of the wired-AND logic of the
bus, TFALL will be considered as part of TLOW. Likewise, TRISE will be in a state between TLOW and THIGH
until a high state has been detected.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 626
Figure 33-7. SCL Timing
TSU;STO THD;STA
TBUF TFALL
TLOW
TRISE
THIGH
SCL
SDA
P S
TSU;STA
Sr
The following parameters are timed using the SCL low time period TLOW. This comes from the Master
Baud Rate Low bit group in the Baud Rate register (BAUD.BAUDLOW). When BAUD.BAUDLOW=0, or
the Master Baud Rate bit group in the Baud Rate register (BAUD.BAUD) determines it.
• TLOW – Low period of SCL clock
• TSU;STO – Set-up time for stop condition
• TBUF – Bus free time between stop and start conditions
• THD;STA – Hold time (repeated) start condition
• TSU;STA – Set-up time for repeated start condition
• THIGH is timed using the SCL high time count from BAUD.BAUD
• TRISE is determined by the bus impedance; for internal pull-ups. Refer to Electrical Characteristics.
• TFALL is determined by the open-drain current limit and bus impedance; can typically be regarded as
zero. Refer to Electrical Characteristics for details.
The SCL frequency is given by:
SCL =1
LOW +HIGH +RISE
When BAUD.BAUDLOW is zero, the BAUD.BAUD value is used to time both SCL high and SCL low. In
this case the following formula will give the SCL frequency:
SCL =GCLK
10 + 2 +GCLK RISE
When BAUD.BAUDLOW is non-zero, the following formula determines the SCL frequency:
SCL =GCLK
10 +  + +GCLK RISE
The following formulas can determine the SCL TLOW and THIGH times:
LOW = + 5
GCLK
HIGH = + 5
GCLK
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 627
Note:  The I2C standard Fm+ (Fast-mode plus) requires a nominal high to low SCL ratio of 1:2, and
BAUD should be set accordingly. At a minimum, BAUD.BAUD and/or BAUD.BAUDLOW must be non-
zero.
Startup Timing The minimum time between SDA transition and SCL rising edge is 6 APB cycles when
the DATA register is written in smart mode. If a greater startup time is required due to long rise times, the
time between DATA write and IF clear must be controlled by software.
Note:  When timing is controlled by user, the Smart Mode cannot be enabled.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
Master Clock Generation (High-Speed Mode)
For I2C Hs transfers, there is no SCL synchronization. Instead, the SCL frequency is determined by the
GCLK_SERCOMx_CORE frequency (fGCLK) and the High-Speed Baud setting in the Baud register
(BAUD.HSBAUD). When BAUD.HSBAUDLOW=0, the HSBAUD value will determine both SCL high and
SCL low. In this case the following formula determines the SCL frequency.
SCL =GCLK
2+2  
When HSBAUDLOW is non-zero, the following formula determines the SCL frequency.
SCL =GCLK
2+  +
Note:  The I2C standard Hs (High-speed) requires a nominal high to low SCL ratio of 1:2, and HSBAUD
should be set accordingly. At a minimum, BAUD.HSBAUD and/or BAUD.HSBAUDLOW must be non-
zero.
33.6.2.4.2 Transmitting Address Packets
The I2C master starts a bus transaction by writing the I2C slave address to ADDR.ADDR and the direction
bit, as described in 33.6.1 Principle of Operation. If the bus is busy, the I2C master will wait until the bus
becomes idle before continuing the operation. When the bus is idle, the I2C master will issue a start
condition on the bus. The I2C master will then transmit an address packet using the address written to
ADDR.ADDR. After the address packet has been transmitted by the I2C master, one of four cases will
arise according to arbitration and transfer direction.
Case 1: Arbitration lost or bus error during address packet transmission
If arbitration was lost during transmission of the address packet, the Master on Bus bit in the Interrupt
Flag Status and Clear register (INTFLAG.MB) and the Arbitration Lost bit in the Status register
(STATUS.ARBLOST) are both set. Serial data output to SDA is disabled, and the SCL is released, which
disables clock stretching. In effect the I2C master is no longer allowed to execute any operation on the
bus until the bus is idle again. A bus error will behave similarly to the arbitration lost condition. In this
case, the MB interrupt flag and Master Bus Error bit in the Status register (STATUS.BUSERR) are both
set in addition to STATUS.ARBLOST.
The Master Received Not Acknowledge bit in the Status register (STATUS.RXNACK) will always contain
the last successfully received acknowledge or not acknowledge indication.
In this case, software will typically inform the application code of the condition and then clear the interrupt
flag before exiting the interrupt routine. No other flags have to be cleared at this moment, because all
flags will be cleared automatically the next time the ADDR.ADDR register is written.
Case 2: Address packet transmit complete – No ACK received
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 628
If there is no I2C slave device responding to the address packet, then the INTFLAG.MB interrupt flag and
STATUS.RXNACK will be set. The clock hold is active at this point, preventing further activity on the bus.
The missing ACK response can indicate that the I2C slave is busy with other tasks or sleeping. Therefore,
it is not able to respond. In this event, the next step can be either issuing a stop condition (recommended)
or resending the address packet by a repeated start condition. When using SMBus logic, the slave must
ACK the address. If there is no response, it means that the slave is not available on the bus.
Case 3: Address packet transmit complete – Write packet, Master on Bus set
If the I2C master receives an acknowledge response from the I2C slave, INTFLAG.MB will be set and
STATUS.RXNACK will be cleared. The clock hold is active at this point, preventing further activity on the
bus.
In this case, the software implementation becomes highly protocol dependent. Three possible actions can
enable the I2C operation to continue:
• Initiate a data transmit operation by writing the data byte to be transmitted into DATA.DATA.
• Transmit a new address packet by writing ADDR.ADDR. A repeated start condition will automatically
be inserted before the address packet.
• Issue a stop condition, consequently terminating the transaction.
Case 4: Address packet transmit complete – Read packet, Slave on Bus set
If the I2C master receives an ACK from the I2C slave, the I2C master proceeds to receive the next byte of
data from the I2C slave. When the first data byte is received, the Slave on Bus bit in the Interrupt Flag
register (INTFLAG.SB) will be set and STATUS.RXNACK will be cleared. The clock hold is active at this
point, preventing further activity on the bus.
In this case, the software implementation becomes highly protocol dependent. Three possible actions can
enable the I2C operation to continue:
• Let the I2C master continue to read data by acknowledging the data received. ACK can be sent by
software, or automatically in smart mode.
• Transmit a new address packet.
• Terminate the transaction by issuing a stop condition.
Note:  An ACK or NACK will be automatically transmitted if smart mode is enabled. The Acknowledge
Action bit in the Control B register (CTRLB.ACKACT) determines whether ACK or NACK should be sent.
33.6.2.4.3 Transmitting Data Packets
When an address packet with direction Master Write (see Figure 33-3) was transmitted successfully ,
INTFLAG.MB will be set. The I2C master will start transmitting data via the I2C bus by writing to
DATA.DATA, and monitor continuously for packet collisions. I
If a collision is detected, the I2C master will lose arbitration and STATUS.ARBLOST will be set. If the
transmit was successful, the I2C master will receive an ACK bit from the I2C slave, and
STATUS.RXNACK will be cleared. INTFLAG.MB will be set in both cases, regardless of arbitration
outcome.
It is recommended to read STATUS.ARBLOST and handle the arbitration lost condition in the beginning
of the I2C Master on Bus interrupt. This can be done as there is no difference between handling address
and data packet arbitration.
STATUS.RXNACK must be checked for each data packet transmitted before the next data packet
transmission can commence. The I2C master is not allowed to continue transmitting data packets if a
NACK is received from the I2C slave.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 629
33.6.2.4.4 Receiving Data Packets (SCLSM=0)
When INTFLAG.SB is set, the I2C master will already have received one data packet. The I2C master
must respond by sending either an ACK or NACK. Sending a NACK may be unsuccessful when
arbitration is lost during the transmission. In this case, a lost arbitration will prevent setting INTFLAG.SB.
Instead, INTFLAG.MB will indicate a change in arbitration. Handling of lost arbitration is the same as for
data bit transmission.
33.6.2.4.5 Receiving Data Packets (SCLSM=1)
When INTFLAG.SB is set, the I2C master will already have received one data packet and transmitted an
ACK or NACK, depending on CTRLB.ACKACT. At this point, CTRLB.ACKACT must be set to the correct
value for the next ACK bit, and the transaction can continue by reading DATA and issuing a command if
not in the smart mode.
33.6.2.4.6 High-Speed Mode
High-speed transfers are a multi-step process, see High Speed Transfer.
First, a master code (0b00001nnn, where 'nnn' is a unique master code) is transmitted in Full-speed
mode, followed by a NACK since no slaveshould acknowledge. Arbitration is performed only during the
Full-speed Master Code phase. The master code is transmitted by writing the master code to the address
register (ADDR.ADDR) and writing the high-speed bit (ADDR.HS) to '0'.
After the master code and NACK have been transmitted, the master write interrupt will be asserted. In the
meanwhile, the slave address can be written to the ADDR.ADDR register together with ADDR.HS=1.
Now in High-speed mode, the master will generate a repeated start, followed by the slave address with
RW-direction. The bus will remain in High-speed mode until a stop is generated. If a repeated start is
desired, the ADDR.HS bit must again be written to '1', along with the new address ADDR.ADDR to be
transmitted.
Figure 33-8. High Speed Transfer
SAA/A
Sr PA DATA
N Data Packets
Master Code R/W
ADDRESS
Sr ADDRESS
Hs-mode continues
F/S-mode
Hs-mode
F/S-mode
Transmitting in High-speed mode requires the I2C master to be configured in High-speed mode
(CTRLA.SPEED=0x2) and the SCL clock stretch mode (CTRLA.SCLSM) bit set to '1'.
33.6.2.4.7 10-Bit Addressing
When 10-bit addressing is enabled by the Ten Bit Addressing Enable bit in the Address register
(ADDR.TENBITEN=1) and the Address bit field ADDR.ADDR is written, the two address bytes will be
transmitted, see 10-bit Address Transmission for a Read Transaction. The addressed slave
acknowledges the two address bytes, and the transaction continues. Regardless of whether the
transaction is a read or write, the master must start by sending the 10-bit address with the direction bit
(ADDR.ADDR[0]) being zero.
If the master receives a NACK after the first byte, the write interrupt flag will be raised and the
STATUS.RXNACK bit will be set. If the first byte is acknowledged by one or more slaves, then the master
will proceed to transmit the second address byte and the master will first see the write interrupt flag after
the second byte is transmitted. If the transaction direction is read-from-slave, the 10-bit address
transmission must be followed by a repeated start and the first 7 bits of the address with the read/write bit
equal to '1'.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 630
Figure 33-9. 10-bit Address Transmission for a Read Transaction
S AW addr[7:0] A
11110 addr[9:8] Sr AR
1
S
W
11110 addr[9:8]
MB INTERRUPT
This implies the following procedure for a 10-bit read operation:
1. Write the 10-bit address to ADDR.ADDR[10:1]. ADDR.TENBITEN must be '1', the direction bit
(ADDR.ADDR[0]) must be '0' (can be written simultaneously with ADDR).
2. Once the Master on Bus interrupt is asserted, Write ADDR[7:0] register to '11110 address[9:8]
1'. ADDR.TENBITEN must be cleared (can be written simultaneously with ADDR).
3. Proceed to transmit data.
33.6.2.5 I2C Slave Operation
The I2C slave is byte-oriented and interrupt-based. The number of interrupts generated is kept at a
minimum by automatic handling of most events. The software driver complexity and code size are
reduced by auto-triggering of operations, and a special smart mode, which can be enabled by the Smart
Mode Enable bit in the Control A register (CTRLA.SMEN).
The I2C slave has two interrupt strategies.
When SCL Stretch Mode bit (CTRLA.SCLSM) is '0', SCL is stretched before or after the acknowledge bit.
In this mode, the I2C slave operates according to I2C Slave Behavioral Diagram (SCLSM=0). The circles
labelled "Sn" (S1, S2..) indicate the nodes the bus logic can jump to, based on software or hardware
interaction.
This diagram is used as reference for the description of the I2C slave operation throughout the document.
Figure 33-10. I2C Slave Behavioral Diagram (SCLSM=0)
S
S3
ADDRESS
S2
A
S1
R
W
DATA A/A
DATA
P
S2
Sr
S3
P
S2
Sr
S3
A
S
W
S
W
S
W
S
W
AA/A
A
S1
S
W
Interrupt on STOP
Condition Enabled
S1
S
WSoftware interaction
The master provides data
on the bus
Addressed slave provides
data on the bus
AMATCH INTERRUPT DRDY INTERRUPT
PREC INTERRUPT
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 631
In the second strategy (CTRLA.SCLSM=1), interrupts only occur after the ACK bit is sent as shown in
Slave Behavioral Diagram (SCLSM=1). This strategy can be used when it is not necessary to check
DATA before acknowledging. For master reads, an address and data interrupt will be issued
simultaneously after the address acknowledge. However, for master writes, the first data interrupt will be
seen after the first data byte has been received by the slave and the acknowledge bit has been sent to
the master.
Note:  For I2C High-speed mode (Hs), SCLSM=1 is required.
Figure 33-11. I2C Slave Behavioral Diagram (SCLSM=1)
S
S3
ADDRESS
S2
R
W
DATA A/A
DATA
P
S2
Sr
S3
P
S2
Sr
S3
S
W
S
W
S
W
A/A
S
W
Interrupt on STOP
Condition Enabled
S1
S
WSoftware interaction
The master provides data
on the bus
Addressed slave provides
data on the bus
A/A
A/A
PREC INTERRUPT
AMATCH INTERRUPT (+ DRDY INTERRUPT in Master Read mode) DRDY INTERRUPT
33.6.2.5.1 Receiving Address Packets (SCLSM=0)
When CTRLA.SCLSM=0, the I2C slave stretches the SCL line according to Figure 33-10. When the I2C
slave is properly configured, it will wait for a start condition.
When a start condition is detected, the successive address packet will be received and checked by the
address match logic. If the received address is not a match, the packet will be rejected, and the I2C slave
will wait for a new start condition. If the received address is a match, the Address Match bit in the
Interrupt Flag register (INTFLAG.AMATCH) will be set.
SCL will be stretched until the I2C slave clears INTFLAG.AMATCH. As the I2C slave holds the clock by
forcing SCL low, the software has unlimited time to respond.
The direction of a transaction is determined by reading the Read / Write Direction bit in the Status register
(STATUS.DIR). This bit will be updated only when a valid address packet is received.
If the Transmit Collision bit in the Status register (STATUS.COLL) is set, this indicates that the last packet
addressed to the I2C slave had a packet collision. A collision causes the SDA and SCL lines to be
released without any notification to software. Therefore, the next AMATCH interrupt is the first indication
of the previous packet’s collision. Collisions are intended to follow the SMBus Address Resolution
Protocol (ARP).
After the address packet has been received from the I2C master, one of two cases will arise based on
transfer direction.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 632
Case 1: Address packet accepted – Read flag set
The STATUS.DIR bit is ‘1’, indicating an I2C master read operation. The SCL line is forced low, stretching
the bus clock. If an ACK is sent, I2C slave hardware will set the Data Ready bit in the Interrupt Flag
register (INTFLAG.DRDY), indicating data are needed for transmit. If a NACK is sent, the I2C slave will
wait for a new start condition and address match.
Typically, software will immediately acknowledge the address packet by sending an ACK/NACK bit. The
I2C slave Command bit field in the Control B register (CTRLB.CMD) can be written to '0x3' for both read
and write operations as the command execution is dependent on the STATUS.DIR bit. Writing ‘1’ to
INTFLAG.AMATCH will also cause an ACK/NACK to be sent corresponding to the CTRLB.ACKACT bit.
Case 2: Address packet accepted – Write flag set
The STATUS.DIR bit is cleared, indicating an I2C master write operation. The SCL line is forced low,
stretching the bus clock. If an ACK is sent, the I2C slave will wait for data to be received. Data, repeated
start or stop can be received.
If a NACK is sent, the I2C slave will wait for a new start condition and address match. Typically, software
will immediately acknowledge the address packet by sending an ACK/NACK. The I2C slave command
CTRLB.CMD = 3 can be used for both read and write operation as the command execution is dependent
on STATUS.DIR.
Writing ‘1’ to INTFLAG.AMATCH will also cause an ACK/NACK to be sent corresponding to the
CTRLB.ACKACT bit.
33.6.2.5.2 Receiving Address Packets (SCLSM=1)
When SCLSM=1, the I2C slave will stretch the SCL line only after an ACK, see Slave Behavioral Diagram
(SCLSM=1). When the I2C slave is properly configured, it will wait for a start condition to be detected.
When a start condition is detected, the successive address packet will be received and checked by the
address match logic.
If the received address is not a match, the packet will be rejected and the I2C slave will wait for a new
start condition.
If the address matches, the acknowledge action as configured by the Acknowledge Action bit Control B
register (CTRLB.ACKACT) will be sent and the Address Match bit in the Interrupt Flag register
(INTFLAG.AMATCH) is set. SCL will be stretched until the I2C slave clears INTFLAG.AMATCH. As the
I2C slave holds the clock by forcing SCL low, the software is given unlimited time to respond to the
address.
The direction of a transaction is determined by reading the Read/Write Direction bit in the Status register
(STATUS.DIR). This bit will be updated only when a valid address packet is received.
If the Transmit Collision bit in the Status register (STATUS.COLL) is set, the last packet addressed to the
I2C slave had a packet collision. A collision causes the SDA and SCL lines to be released without any
notification to software. The next AMATCH interrupt is, therefore, the first indication of the previous
packet’s collision. Collisions are intended to follow the SMBus Address Resolution Protocol (ARP).
After the address packet has been received from the I2C master, INTFLAG.AMATCH be set to ‘1’ to clear
it.
33.6.2.5.3 Receiving and Transmitting Data Packets
After the I2C slave has received an address packet, it will respond according to the direction either by
waiting for the data packet to be received or by starting to send a data packet by writing to DATA.DATA.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 633
When a data packet is received or sent, INTFLAG.DRDY will be set. After receiving data, the I2C slave
will send an acknowledge according to CTRLB.ACKACT.
Case 1: Data received
INTFLAG.DRDY is set, and SCL is held low, pending for SW interaction.
Case 2: Data sent
When a byte transmission is successfully completed, the INTFLAG.DRDY interrupt flag is set. If NACK is
received, indicated by STATUS.RXNACK=1, the I2C slave must expect a stop or a repeated start to be
received. The I2C slave must release the data line to allow the I2C master to generate a stop or repeated
start. Upon detecting a stop condition, the Stop Received bit in the Interrupt Flag register
(INTFLAG.PREC) will be set and the I2C slave will return to IDLE state.
33.6.2.5.4 High-Speed Mode
When the I2C slave is configured in High-speed mode (Hs, CTRLA.SPEED=0x2) and CTRLA.SCLSM=1,
switching between Full-speed and High-speed modes is automatic. When the slave recognizes a START
followed by a master code transmission and a NACK, it automatically switches to High-speed mode and
sets the High-speed status bit (STATUS.HS). The slave will then remain in High-speed mode until a
STOP is received.
33.6.2.5.5 10-Bit Addressing
When 10-bit addressing is enabled (ADDR.TENBITEN=1), the two address bytes following a START will
be checked against the 10-bit slave address recognition. The first byte of the address will always be
acknowledged, and the second byte will raise the address interrupt flag, see 10-bit Addressing.
If the transaction is a write, then the 10-bit address will be followed by N data bytes.
If the operation is a read, the 10-bit address will be followed by a repeated START and reception of '11110
ADDR[9:8] 1', and the second address interrupt will be received with the DIR bit set. The slave matches
on the second address as it it was addressed by the previous 10-bit address.
Figure 33-12. 10-bit Addressing
S AW addr[7:0] A
11110 addr[9:8] Sr R
S
W
S
W
11110 addr[9:8]
AMATCH INTERRUPT AMATCH INTERRUPT
33.6.2.5.6 PMBus Group Command
When the PMBus Group Command bit in the CTRLB register is set (CTRLB.GCMD=1) and 7-bit
addressing is used, INTFLAG.PREC will be set if the slave has been addressed since the last STOP
condition. When CTRLB.GCMD=0, a STOP condition without address match will not be set
INTFLAG.PREC.
The group command protocol is used to send commands to more than one device. The commands are
sent in one continuous transmission with a single STOP condition at the end. When the STOP condition
is detected by the slaves addressed during the group command, they all begin executing the command
they received.
PMBus Group Command Example shows an example where this slave, bearing ADDRESS 1, is
addressed after a repeated START condition. There can be multiple slaves addressed before and after
this slave. Eventually, at the end of the group command, a single STOP is generated by the master. At
this point a STOP interrupt is asserted.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 634
Figure 33-13. PMBus Group Command Example
A
SAn Bytes
W
ADDRESS 0
Command/Data
A
Sr An Bytes
W
ADDRESS 1
(this slave)
Command/Data
S
W
S
W
A
Sr An Bytes
W
ADDRESS 2
Command/Data
P
S
W
AMATCH INTERRUPT DRDY INTERRUPT
PREC INTERRUPT
33.6.3 Additional Features
33.6.3.1 SMBus
The I2C includes three hardware SCL low time-outs which allow a time-out to occur for SMBus SCL low
time-out, master extend time-out, and slave extend time-out. This allows for SMBus functionality These
time-outs are driven by the GCLK_SERCOM_SLOW clock. The GCLK_SERCOM_SLOW clock is used to
accurately time the time-out and must be configured to use a 32KHz oscillator. The I2C interface also
allows for a SMBus compatible SDA hold time.
• TTIMEOUT: SCL low time of 25..35ms – Measured for a single SCL low period. It is enabled by
CTRLA.LOWTOUTEN.
• TLOW:SEXT: Cumulative clock low extend time of 25 ms – Measured as the cumulative SCL low
extend time by a slave device in a single message from the initial START to the STOP. It is enabled
by CTRLA.SEXTTOEN.
• TLOW:MEXT: Cumulative clock low extend time of 10 ms – Measured as the cumulative SCL low
extend time by the master device within a single byte from START-to-ACK, ACK-to-ACK, or ACK-to-
STOP. It is enabled by CTRLA.MEXTTOEN.
33.6.3.2 Smart Mode
The I2C interface has a smart mode that simplifies application code and minimizes the user interaction
needed to adhere to the I2C protocol. The smart mode accomplishes this by automatically issuing an ACK
or NACK (based on the content of CTRLB.ACKACT) as soon as DATA.DATA is read.
33.6.3.3 4-Wire Mode
Writing a '1' to the Pin Usage bit in the Control A register (CTRLA.PINOUT) will enable 4-wire mode
operation. In this mode, the internal I2C tri-state drivers are bypassed, and an external I2C compliant tri-
state driver is needed when connecting to an I2C bus.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 635
Figure 33-14. I2C Pad Interface
SCL/SDA
pad
I2C
Driver
SCL_OUT/
SDA_OUT
pad
PINOUT
PINOUT
SCL_IN/
SDA_IN
SCL_OUT/
SDA_OUT
33.6.3.4 Quick Command
Setting the Quick Command Enable bit in the Control B register (CTRLB.QCEN) enables quick command.
When quick command is enabled, the corresponding interrupt flag (INTFLAG.SB or INTFLAG.MB) is set
immediately after the slave acknowledges the address. At this point, the software can either issue a stop
command or a repeated start by writing CTRLB.CMD or ADDR.ADDR.
33.6.4 DMA, Interrupts and Events
Each interrupt source has its own interrupt flag. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) will be set when the interrupt condition is meet. Each interrupt can be individually
enabled by writing ‘1’ to the corresponding bit in the Interrupt Enable Set register (INTENSET), and
disabled by writing ‘1’ to the corresponding bit in the Interrupt Enable Clear register (INTENCLR). An
interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request is active until the interrupt flag is cleared, the interrupt is disabled or the I2C is reset.
See the 33.8.5 INTFLAG (Slave) or 33.10.6 INTFLAG (Master) register for details on how to clear
interrupt flags.
Table 33-1. Module Request for SERCOM I2C Slave
Condition Request
DMA Interrupt Event
Data needed for transmit (TX)
(Slave transmit mode)
Yes
(request cleared
when data is
written)
NA
Data received (RX) (Slave receive
mode)
Yes
(request cleared
when data is
read)
Data Ready (DRDY) Yes
Address Match (AMATCH) Yes
Stop received (PREC) Yes
Error (ERROR) Yes
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 636
Table 33-2. Module Request for SERCOM I2C Master
Condition Request
DMA Interrupt Event
Data needed for transmit (TX)
(Master transmit mode)
Yes
(request cleared
when data is
written)
NA
Data needed for transmit (RX)
(Master transmit mode)
Yes
(request cleared
when data is
read)
Master on Bus (MB) Yes
Stop received (SB) Yes
Error (ERROR) Yes
33.6.4.1 DMA Operation
Smart mode must be enabled for DMA operation in the Control B register by writing CTRLB.SMEN=1.
33.6.4.1.1 Slave DMA
When using the I2C slave with DMA, an address match will cause the address interrupt flag
(INTFLAG.ADDRMATCH) to be raised. After the interrupt has been serviced, data transfer will be
performed through DMA.
The I2C slave generates the following requests:
• Write data received (RX): The request is set when master write data is received. The request is
cleared when DATA is read.
• Read data needed for transmit (TX): The request is set when data is needed for a master read
operation. The request is cleared when DATA is written.
33.6.4.1.2 Master DMA
When using the I2C master with DMA, the ADDR register must be written with the desired address
(ADDR.ADDR), transaction length (ADDR.LEN), and transaction length enable (ADDR.LENEN). When
ADDR.LENEN is written to 1 along with ADDR.ADDR, ADDR.LEN determines the number of data bytes
in the transaction from 0 to 255. DMA is then used to transfer ADDR.LEN bytes followed by an
automatically generated NACK (for master reads) and a STOP.
If a NACK is received by the slave for a master write transaction before ADDR.LEN bytes, a STOP will be
automatically generated and the length error (STATUS.LENERR) will be raised along with the
INTFLAG.ERROR interrupt.
The I2C master generates the following requests:
• Read data received (RX): The request is set when master read data is received. The request is
cleared when DATA is read.
• Write data needed for transmit (TX): The request is set when data is needed for a master write
operation. The request is cleared when DATA is written.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 637
33.6.4.2 Interrupts
The I2C slave has the following interrupt sources. These are asynchronous interrupts. They can wake-up
the device from any sleep mode:
• Error (ERROR)
• Data Ready (DRDY)
• Address Match (AMATCH)
• Stop Received (PREC)
The I2C master has the following interrupt sources. These are asynchronous interrupts. They can wake-
up the device from any sleep mode:
• Error (ERROR)
• Slave on Bus (SB)
• Master on Bus (MB)
Each interrupt source has its own interrupt flag. The interrupt flag in the Interrupt Flag Status and Clear
register (INTFLAG) will be set when the interrupt condition is meet. Each interrupt can be individually
enabled by writing ‘1’ to the corresponding bit in the Interrupt Enable Set register (INTENSET), and
disabled by writing ‘1’ to the corresponding bit in the Interrupt Enable Clear register (INTENCLR). An
interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request active until the interrupt flag is cleared, the interrupt is disabled or the I2C is reset.
See the INTFLAG register for details on how to clear interrupt flags.
The value of INTFLAG indicates which interrupt is executed. Note that interrupts must be globally
enabled for interrupt requests. Refer to Nested Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
33.6.4.3 Events
Not applicable.
33.6.5 Sleep Mode Operation
I2C Master Operation
The generic clock (GCLK_SERCOMx_CORE) will continue to run in idle sleep mode. If the Run In
Standby bit in the Control A register (CTRLA.RUNSTDBY) is '1', the GLK_SERCOMx_CORE will also run
in standby sleep mode. Any interrupt can wake up the device.
If CTRLA.RUNSTDBY=0, the GLK_SERCOMx_CORE will be disabled after any ongoing transaction is
finished. Any interrupt can wake up the device.
I2C Slave Operation
Writing CTRLA.RUNSTDBY=1 will allow the Address Match interrupt to wake up the device.
When CTRLA.RUNSTDBY=0, all receptions will be dropped.
33.6.6 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in the CTRLA register (CTRLA.SWRST)
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 638
• Enable bit in the CTRLA register (CTRLA.ENABLE)
• Command bits in CTRLB register (CTRLB.CMD)
• Write to Bus State bits in the Status register (STATUS.BUSSTATE)
• Address bits in the Address register (ADDR.ADDR) when in master operation.
The following registers are synchronized when written:
• Data (DATA) when in master operation
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 639
33.7 Register Summary - I2C Slave
Offset Name Bit Pos.
0x00 CTRLA
7:0 RUNSTDBY MODE[2:0] ENABLE SWRST
15:8
23:16 SEXTTOEN SDAHOLD[1:0] PINOUT
31:24 LOWTOUT SCLSM SPEED[1:0]
0x04 CTRLB
7:0
15:8 AMODE[1:0] AACKEN GCMD SMEN
23:16 ACKACT CMD[1:0]
31:24
0x08
...
0x13
Reserved
0x14 INTENCLR 7:0 ERROR DRDY AMATCH PREC
0x15 Reserved
0x16 INTENSET 7:0 ERROR DRDY AMATCH PREC
0x17 Reserved
0x18 INTFLAG 7:0 ERROR DRDY AMATCH PREC
0x19 Reserved
0x1A STATUS
7:0 CLKHOLD LOWTOUT SR DIR RXNACK COLL BUSERR
15:8 HS SEXTTOUT
0x1C SYNCBUSY
7:0 ENABLE SWRST
15:8
23:16
31:24
0x20
...
0x23
Reserved
0x24 ADDR
7:0 ADDR[6:0] GENCEN
15:8 TENBITEN ADDR[9:7]
23:16 ADDRMASK[6:0]
31:24 ADDRMASK[9:7]
0x28 DATA
7:0 DATA[7:0]
15:8
33.8 Register Description - I2C Slave
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 33.5.8 Register Access Protection.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 640
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to 33.6.6 Synchronization.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 641
33.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
LOWTOUT SCLSM SPEED[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
SEXTTOEN SDAHOLD[1:0] PINOUT
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
RUNSTDBY MODE[2:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 30 – LOWTOUT SCL Low Time-Out
This bit enables the SCL low time-out. If SCL is held low for 25ms-35ms, the slave will release its clock
hold, if enabled, and reset the internal state machine. Any interrupt flags set at the time of time-out will
remain set.
Value Description
0Time-out disabled.
1Time-out enabled.
Bit 27 – SCLSM SCL Clock Stretch Mode
This bit controls when SCL will be stretched for software interaction.
This bit is not synchronized.
Value Description
0SCL stretch according to Figure 33-10
1SCL stretch only after ACK bit according to Figure 33-11
Bits 25:24 – SPEED[1:0] Transfer Speed
These bits define bus speed.
These bits are not synchronized.
Value Description
0x0 Standard-mode (Sm) up to 100 kHz and Fast-mode (Fm) up to 400 kHz
0x1 Fast-mode Plus (Fm+) up to 1 MHz
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 642
Value Description
0x2 High-speed mode (Hs-mode) up to 3.4 MHz
0x3 Reserved
Bit 23 – SEXTTOEN Slave SCL Low Extend Time-Out
This bit enables the slave SCL low extend time-out. If SCL is cumulatively held low for greater than 25ms
from the initial START to a STOP, the slave will release its clock hold if enabled and reset the internal
state machine. Any interrupt flags set at the time of time-out will remain set. If the address was
recognized, PREC will be set when a STOP is received.
This bit is not synchronized.
Value Description
0Time-out disabled
1Time-out enabled
Bits 21:20 – SDAHOLD[1:0] SDA Hold Time
These bits define the SDA hold time with respect to the negative edge of SCL.
These bits are not synchronized.
Value Name Description
0x0 DIS Disabled
0x1 75 50-100ns hold time
0x2 450 300-600ns hold time
0x3 600 400-800ns hold time
Bit 16 – PINOUT Pin Usage
This bit sets the pin usage to either two- or four-wire operation:
This bit is not synchronized.
Value Description
04-wire operation disabled
14-wire operation enabled
Bit 7 – RUNSTDBY Run in Standby
This bit defines the functionality in standby sleep mode.
This bit is not synchronized.
Value Description
0Disabled – All reception is dropped.
1Wake on address match, if enabled.
Bits 4:2 – MODE[2:0] Operating Mode
These bits must be written to 0x04 to select the I2C slave serial communication interface of the SERCOM.
These bits are not synchronized.
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRL.ENABLE will read back immediately and the Enable Synchronization
Busy bit in the Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE
will be cleared when the operation is complete.
This bit is not enable-protected.
Value Description
0The peripheral is disabled or being disabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 643
Value Description
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing '0' to this bit has no effect.
Writing '1' to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the
SERCOM will be disabled.
Writing '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded. Any register write access during the ongoing reset will result in an APB
error. Reading any register will return the reset value of the register.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable-protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 644
33.8.2 Control B
Name:  CTRLB
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
ACKACT CMD[1:0]
Access R/W W W
Reset 0 0 0
Bit 15 14 13 12 11 10 9 8
AMODE[1:0] AACKEN GCMD SMEN
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
Access
Reset
Bit 18 – ACKACT Acknowledge Action
This bit defines the slave's acknowledge behavior after an address or data byte is received from the
master. The acknowledge action is executed when a command is written to the CMD bits. If smart mode
is enabled (CTRLB.SMEN=1), the acknowledge action is performed when the DATA register is read.
This bit is not enable-protected.
Value Description
0Send ACK
1Send NACK
Bits 17:16 – CMD[1:0] Command
This bit field triggers the slave operation as the below. The CMD bits are strobe bits, and always read as
zero. The operation is dependent on the slave interrupt flags, INTFLAG.DRDY and INTFLAG.AMATCH,
in addition to STATUS.DIR.
All interrupt flags (INTFLAG.DRDY, INTFLAG.AMATCH and INTFLAG.PREC) are automatically cleared
when a command is given.
This bit is not enable-protected.
Table 33-3. Command Description
CMD[1:0] DIR Action
0x0 X (No action)
0x1 X (Reserved)
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 645
...........continued
CMD[1:0] DIR Action
0x2 Used to complete a transaction in response to a data interrupt (DRDY)
0 (Master write) Execute acknowledge action succeeded by waiting for any start (S/Sr)
condition
1 (Master read) Wait for any start (S/Sr) condition
0x3 Used in response to an address interrupt (AMATCH)
0 (Master write) Execute acknowledge action succeeded by reception of next byte
1 (Master read) Execute acknowledge action succeeded by slave data interrupt
Used in response to a data interrupt (DRDY)
0 (Master write) Execute acknowledge action succeeded by reception of next byte
1 (Master read) Execute a byte read operation followed by ACK/NACK reception
Bits 15:14 – AMODE[1:0] Address Mode
These bits set the addressing mode.
These bits are not write-synchronized.
Value Name Description
0x0 MASK The slave responds to the address written in ADDR.ADDR masked by the value
in ADDR.ADDRMASK.
See SERCOM – Serial Communication Interface for additional information.
0x1 2_ADDRS The slave responds to the two unique addresses in ADDR.ADDR and
ADDR.ADDRMASK.
0x2 RANGE The slave responds to the range of addresses between and including
ADDR.ADDR and ADDR.ADDRMASK. ADDR.ADDR is the upper limit.
0x3 - Reserved.
Bit 10 – AACKEN Automatic Acknowledge Enable
This bit enables the address to be automatically acknowledged if there is an address match.
This bit is not write-synchronized.
Value Description
0Automatic acknowledge is disabled.
1Automatic acknowledge is enabled.
Bit 9 – GCMD PMBus Group Command
This bit enables PMBus group command support. When enabled, the Stop Recived interrupt flag
(INTFLAG.PREC) will be set when a STOP condition is detected if the slave has been addressed since
the last STOP condition on the bus.
This bit is not write-synchronized.
Value Description
0Group command is disabled.
1Group command is enabled.
Bit 8 – SMEN Smart Mode Enable
When smart mode is enabled, data is acknowledged automatically when DATA.DATA is read.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 646
This bit is not write-synchronized.
Value Description
0Smart mode is disabled.
1Smart mode is enabled.
Related Links
30. SERCOM – Serial Communication Interface
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 647
33.8.3 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
ERROR DRDY AMATCH PREC
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 2 – DRDY Data Ready Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Data Ready bit, which disables the Data Ready interrupt.
Value Description
0The Data Ready interrupt is disabled.
1The Data Ready interrupt is enabled.
Bit 1 – AMATCH Address Match Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Address Match Interrupt Enable bit, which disables the Address Match
interrupt.
Value Description
0The Address Match interrupt is disabled.
1The Address Match interrupt is enabled.
Bit 0 – PREC Stop Received Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Stop Received Interrupt Enable bit, which disables the Stop Received
interrupt.
Value Description
0The Stop Received interrupt is disabled.
1The Stop Received interrupt is enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 648
33.8.4 Interrupt Enable Set
Name:  INTENSET
Offset:  0x16
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
ERROR DRDY AMATCH PREC
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 2 – DRDY Data Ready Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Data Ready bit, which enables the Data Ready interrupt.
Value Description
0The Data Ready interrupt is disabled.
1The Data Ready interrupt is enabled.
Bit 1 – AMATCH Address Match Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Address Match Interrupt Enable bit, which enables the Address Match
interrupt.
Value Description
0The Address Match interrupt is disabled.
1The Address Match interrupt is enabled.
Bit 0 – PREC Stop Received Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Stop Received Interrupt Enable bit, which enables the Stop Received
interrupt.
Value Description
0The Stop Received interrupt is disabled.
1The Stop Received interrupt is enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 649
33.8.5 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x18
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
ERROR DRDY AMATCH PREC
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 – ERROR Error
This bit is set when any error is detected. Errors that will set this flag have corresponding status flags in
the STATUS register. The corresponding bits in STATUS are SEXTTOUT, LOWTOUT, COLL, and
BUSERR.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 2 – DRDY Data Ready
This flag is set when a I2C slave byte transmission is successfully completed.
The flag is cleared by hardware when either:
• Writing to the DATA register.
• Reading the DATA register with smart mode enabled.
• Writing a valid command to the CMD register.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Data Ready interrupt flag.
Bit 1 – AMATCH Address Match
This flag is set when the I2C slave address match logic detects that a valid address has been received.
The flag is cleared by hardware when CTRL.CMD is written.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Address Match interrupt flag. When cleared, an ACK/NACK will be sent
according to CTRLB.ACKACT.
Bit 0 – PREC Stop Received
This flag is set when a stop condition is detected for a transaction being processed. A stop condition
detected between a bus master and another slave will not set this flag, unless the PMBus Group
Command is enabled in the Control B register (CTRLB.GCMD=1).
This flag is cleared by hardware after a command is issued on the next address match.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Stop Received interrupt flag.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 650
33.8.6 Status
Name:  STATUS
Offset:  0x1A
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
HS SEXTTOUT
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
CLKHOLD LOWTOUT SR DIR RXNACK COLL BUSERR
Access R R/W R R R R/W R/W
Reset 0 0 0 0 0 0 0
Bit 10 – HS High-speed
This bit is set if the slave detects a START followed by a Master Code transmission.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the status. However, this flag is automatically cleared when a STOP is
received.
Bit 9 – SEXTTOUT Slave SCL Low Extend Time-Out
This bit is set if a slave SCL low extend time-out occurs.
This bit is cleared automatically if responding to a new start condition with ACK or NACK (write 3 to
CTRLB.CMD) or when INTFLAG.AMATCH is cleared.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the status.
Value Description
0No SCL low extend time-out has occurred.
1SCL low extend time-out has occurred.
Bit 7 – CLKHOLD Clock Hold
The slave Clock Hold bit (STATUS.CLKHOLD) is set when the slave is holding the SCL line low,
stretching the I2C clock. Software should consider this bit a read-only status flag that is set when
INTFLAG.DRDY or INTFLAG.AMATCH is set.
This bit is automatically cleared when the corresponding interrupt is also cleared.
Bit 6 – LOWTOUT SCL Low Time-out
This bit is set if an SCL low time-out occurs.
This bit is cleared automatically if responding to a new start condition with ACK or NACK (write 3 to
CTRLB.CMD) or when INTFLAG.AMATCH is cleared.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the status.
Value Description
0No SCL low time-out has occurred.
1SCL low time-out has occurred.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 651
Bit 4 – SR Repeated Start
When INTFLAG.AMATCH is raised due to an address match, SR indicates a repeated start or start
condition.
This flag is only valid while the INTFLAG.AMATCH flag is one.
Value Description
0Start condition on last address match
1Repeated start condition on last address match
Bit 3 – DIR Read / Write Direction
The Read/Write Direction (STATUS.DIR) bit stores the direction of the last address packet received from
a master.
Value Description
0Master write operation is in progress.
1Master read operation is in progress.
Bit 2 – RXNACK Received Not Acknowledge
This bit indicates whether the last data packet sent was acknowledged or not.
Value Description
0Master responded with ACK.
1Master responded with NACK.
Bit 1 – COLL Transmit Collision
If set, the I2C slave was not able to transmit a high data or NACK bit, the I2C slave will immediately
release the SDA and SCL lines and wait for the next packet addressed to it.
This flag is intended for the SMBus address resolution protocol (ARP). A detected collision in non-ARP
situations indicates that there has been a protocol violation, and should be treated as a bus error.
Note that this status will not trigger any interrupt, and should be checked by software to verify that the
data were sent correctly. This bit is cleared automatically if responding to an address match with an ACK
or a NACK (writing 0x3 to CTRLB.CMD), or INTFLAG.AMATCH is cleared.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the status.
Value Description
0No collision detected on last data byte sent.
1Collision detected on last data byte sent.
Bit 0 – BUSERR Bus Error
The Bus Error bit (STATUS.BUSERR) indicates that an illegal bus condition has occurred on the bus,
regardless of bus ownership. An illegal bus condition is detected if a protocol violating start, repeated
start or stop is detected on the I2C bus lines. A start condition directly followed by a stop condition is one
example of a protocol violation. If a time-out occurs during a frame, this is also considered a protocol
violation, and will set STATUS.BUSERR.
This bit is cleared automatically if responding to an address match with an ACK or a NACK (writing 0x3 to
CTRLB.CMD) or INTFLAG.AMATCH is cleared.
Writing a '1' to this bit will clear the status.
Writing a '0' to this bit has no effect.
Value Description
0No bus error detected.
1Bus error detected.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 652
33.8.7 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x1C
Reset:  0x00000000
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ENABLE SWRST
Access R R
Reset 0 0
Bit 1 – ENABLE SERCOM Enable Synchronization Busy
Enabling and disabling the SERCOM (CTRLA.ENABLE) requires synchronization. When written, the
SYNCBUSY.ENABLE bit will be set until synchronization is complete.
Value Description
0Enable synchronization is not busy.
1Enable synchronization is busy.
Bit 0 – SWRST Software Reset Synchronization Busy
Resetting the SERCOM (CTRLA.SWRST) requires synchronization. When written, the
SYNCBUSY.SWRST bit will be set until synchronization is complete.
Value Description
0SWRST synchronization is not busy.
1SWRST synchronization is busy.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 653
33.8.8 Address
Name:  ADDR
Offset:  0x24
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
ADDRMASK[9:7]
Access R/W R/W R/W
Reset 0 0 0
Bit 23 22 21 20 19 18 17 16
ADDRMASK[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TENBITEN ADDR[9:7]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ADDR[6:0] GENCEN
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 26:17 – ADDRMASK[9:0] Address Mask
These bits act as a second address match register, an address mask register or the lower limit of an
address range, depending on the CTRLB.AMODE setting.
Bit 15 – TENBITEN Ten Bit Addressing Enable
Value Description
010-bit address recognition disabled.
110-bit address recognition enabled.
Bits 10:1 – ADDR[9:0] Address
These bits contain the I2C slave address used by the slave address match logic to determine if a master
has addressed the slave.
When using 7-bit addressing, the slave address is represented by ADDR[6:0].
When using 10-bit addressing (ADDR.TENBITEN=1), the slave address is represented by ADDR[9:0]
When the address match logic detects a match, INTFLAG.AMATCH is set and STATUS.DIR is updated to
indicate whether it is a read or a write transaction.
Bit 0 – GENCEN General Call Address Enable
A general call address is an address consisting of all-zeroes, including the direction bit (master write).
Value Description
0General call address recognition disabled.
1General call address recognition enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 654
33.8.9 Data
Name:  DATA
Offset:  0x28
Reset:  0x0000
Property:  Write-Synchronized, Read-Synchronized
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – DATA[7:0] Data
The slave data register I/O location (DATA.DATA) provides access to the master transmit and receive
data buffers. Reading valid data or writing data to be transmitted can be successfully done only when
SCL is held low by the slave (STATUS.CLKHOLD is set). An exception occurs when reading the last data
byte after the stop condition has been received.
Accessing DATA.DATA auto-triggers I2C bus operations. The operation performed depends on the state
of CTRLB.ACKACT, CTRLB.SMEN and the type of access (read/write).
Writing or reading DATA.DATA when not in smart mode does not require synchronization.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 655
33.9 Register Summary - I2C Master
Offset Name Bit Pos.
0x00 CTRLA
7:0 RUNSTDBY MODE[2:0] ENABLE SWRST
15:8
23:16 SEXTTOEN MEXTTOEN SDAHOLD[1:0] PINOUT
31:24 LOWTOUT INACTOUT[1:0] SCLSM SPEED[1:0]
0x04 CTRLB
7:0
15:8 QCEN SMEN
23:16 ACKACT CMD[1:0]
31:24
0x08
...
0x0B
Reserved
0x0C BAUD
7:0 BAUD[7:0]
15:8 BAUDLOW[7:0]
23:16 HSBAUD[7:0]
31:24 HSBAUDLOW[7:0]
0x10
...
0x13
Reserved
0x14 INTENCLR 7:0 ERROR SB MB
0x15 Reserved
0x16 INTENSET 7:0 ERROR SB MB
0x17 Reserved
0x18 INTFLAG 7:0 ERROR SB MB
0x19 Reserved
0x1A STATUS
7:0 CLKHOLD LOWTOUT BUSSTATE[1:0] RXNACK ARBLOST BUSERR
15:8 LENERR SEXTTOUT MEXTTOUT
0x1C SYNCBUSY
7:0 SYSOP ENABLE SWRST
15:8
23:16
31:24
0x20
...
0x23
Reserved
0x24 ADDR
7:0 ADDR[7:0]
15:8 TENBITEN HS LENEN ADDR[10:8]
23:16 LEN[7:0]
31:24
0x28 DATA
7:0 DATA[7:0]
15:8
0x2A
...
0x2F
Reserved
0x30 DBGCTRL 7:0 DBGSTOP
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 656
33.10 Register Description - I2C Master
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 33.5.8 Register Access Protection.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to 33.6.6 Synchronization.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 657
33.10.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
LOWTOUT INACTOUT[1:0] SCLSM SPEED[1:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
SEXTTOEN MEXTTOEN SDAHOLD[1:0] PINOUT
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
RUNSTDBY MODE[2:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 30 – LOWTOUT SCL Low Time-Out
This bit enables the SCL low time-out. If SCL is held low for 25ms-35ms, the master will release its clock
hold, if enabled, and complete the current transaction. A stop condition will automatically be transmitted.
INTFLAG.SB or INTFLAG.MB will be set as normal, but the clock hold will be released. The
STATUS.LOWTOUT and STATUS.BUSERR status bits will be set.
This bit is not synchronized.
Value Description
0Time-out disabled.
1Time-out enabled.
Bits 29:28 – INACTOUT[1:0] Inactive Time-Out
If the inactive bus time-out is enabled and the bus is inactive for longer than the time-out setting, the bus
state logic will be set to idle. An inactive bus arise when either an I2C master or slave is holding the SCL
low.
Enabling this option is necessary for SMBus compatibility, but can also be used in a non-SMBus set-up.
Calculated time-out periods are based on a 100kHz baud rate.
These bits are not synchronized.
Value Name Description
0x0 DIS Disabled
0x1 55US 5-6 SCL cycle time-out (50-60µs)
0x2 105US 10-11 SCL cycle time-out (100-110µs)
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 658
Value Name Description
0x3 205US 20-21 SCL cycle time-out (200-210µs)
Bit 27 – SCLSM SCL Clock Stretch Mode
This bit controls when SCL will be stretched for software interaction.
This bit is not synchronized.
Value Description
0SCL stretch according to Figure 33-5.
1SCL stretch only after ACK bit, Figure 33-6.
Bits 25:24 – SPEED[1:0] Transfer Speed
These bits define bus speed.
These bits are not synchronized.
Value Description
0x0 Standard-mode (Sm) up to 100 kHz and Fast-mode (Fm) up to 400 kHz
0x1 Fast-mode Plus (Fm+) up to 1 MHz
0x2 High-speed mode (Hs-mode) up to 3.4 MHz
0x3 Reserved
Bit 23 – SEXTTOEN Slave SCL Low Extend Time-Out
This bit enables the slave SCL low extend time-out. If SCL is cumulatively held low for greater than 25ms
from the initial START to a STOP, the master will release its clock hold if enabled, and complete the
current transaction. A STOP will automatically be transmitted.
SB or MB will be set as normal, but CLKHOLD will be release. The MEXTTOUT and BUSERR status bits
will be set.
This bit is not synchronized.
Value Description
0Time-out disabled
1Time-out enabled
Bit 22 – MEXTTOEN Master SCL Low Extend Time-Out
This bit enables the master SCL low extend time-out. If SCL is cumulatively held low for greater than
10ms from START-to-ACK, ACK-to-ACK, or ACK-to-STOP the master will release its clock hold if
enabled, and complete the current transaction. A STOP will automatically be transmitted.
SB or MB will be set as normal, but CLKHOLD will be released. The MEXTTOUT and BUSERR status
bits will be set.
This bit is not synchronized.
Value Description
0Time-out disabled
1Time-out enabled
Bits 21:20 – SDAHOLD[1:0] SDA Hold Time
These bits define the SDA hold time with respect to the negative edge of SCL.
These bits are not synchronized.
Value Name Description
0x0 DIS Disabled
0x1 75NS 50-100ns hold time
0x2 450NS 300-600ns hold time
0x3 600NS 400-800ns hold time
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 659
Bit 16 – PINOUT Pin Usage
This bit set the pin usage to either two- or four-wire operation:
This bit is not synchronized.
Value Description
04-wire operation disabled.
14-wire operation enabled.
Bit 7 – RUNSTDBY Run in Standby
This bit defines the functionality in standby sleep mode.
This bit is not synchronized.
Value Description
0GCLK_SERCOMx_CORE is disabled and the I2C master will not operate in standby sleep
mode.
1GCLK_SERCOMx_CORE is enabled in all sleep modes.
Bits 4:2 – MODE[2:0] Operating Mode
These bits must be written to 0x5 to select the I2C master serial communication interface of the
SERCOM.
These bits are not synchronized.
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRL.ENABLE will read back immediately and the Synchronization Enable
Busy bit in the Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE
will be cleared when the operation is complete.
This bit is not enable-protected.
Value Description
0The peripheral is disabled or being disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing '0' to this bit has no effect.
Writing '1' to this bit resets all registers in the SERCOM, except DBGCTRL, to their initial state, and the
SERCOM will be disabled.
Writing '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded. Any register write access during the ongoing reset will result in an APB
error. Reading any register will return the reset value of the register.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable-protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 660
33.10.2 Control B
Name:  CTRLB
Offset:  0x04
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
ACKACT CMD[1:0]
Access R/W W W
Reset 0 0 0
Bit 15 14 13 12 11 10 9 8
QCEN SMEN
Access R/W R/W
Reset 0 0
Bit 7 6 5 4 3 2 1 0
Access
Reset
Bit 18 – ACKACT Acknowledge Action
This bit defines the I2C master's acknowledge behavior after a data byte is received from the I2C slave.
The acknowledge action is executed when a command is written to CTRLB.CMD, or if smart mode is
enabled (CTRLB.SMEN is written to one), when DATA.DATA is read.
This bit is not enable-protected.
This bit is not write-synchronized.
Value Description
0Send ACK.
1Send NACK.
Bits 17:16 – CMD[1:0] Command
Writing these bits triggers a master operation as described below. The CMD bits are strobe bits, and
always read as zero. The acknowledge action is only valid in master read mode. In master write mode, a
command will only result in a repeated start or stop condition. The CTRLB.ACKACT bit and the CMD bits
can be written at the same time, and then the acknowledge action will be updated before the command is
triggered.
Commands can only be issued when either the Slave on Bus interrupt flag (INTFLAG.SB) or Master on
Bus interrupt flag (INTFLAG.MB) is '1'.
If CMD 0x1 is issued, a repeated start will be issued followed by the transmission of the current address
in ADDR.ADDR. If another address is desired, ADDR.ADDR must be written instead of the CMD bits.
This will trigger a repeated start followed by transmission of the new address.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 661
Issuing a command will set the System Operation bit in the Synchronization Busy register
(SYNCBUSY.SYSOP).
Table 33-4. Command Description
CMD[1:0] Direction Action
0x0 X (No action)
0x1 X Execute acknowledge action succeeded by repeated Start
0x2 0 (Write) No operation
1 (Read) Execute acknowledge action succeeded by a byte read operation
0x3 X Execute acknowledge action succeeded by issuing a stop condition
These bits are not enable-protected.
Bit 9 – QCEN Quick Command Enable
This bit is not write-synchronized.
Value Description
0Quick Command is disabled.
1Quick Command is enabled.
Bit 8 – SMEN Smart Mode Enable
When smart mode is enabled, acknowledge action is sent when DATA.DATA is read.
This bit is not write-synchronized.
Value Description
0Smart mode is disabled.
1Smart mode is enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 662
33.10.3 Baud Rate
Name:  BAUD
Offset:  0x0C
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
HSBAUDLOW[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
HSBAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
BAUDLOW[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
BAUD[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:24 – HSBAUDLOW[7:0] High Speed Master Baud Rate Low
HSBAUDLOW non-zero: HSBAUDLOW indicates the SCL low time in High-speed mode according to
HSBAUDLOW = GCLK LOW 1
HSBAUDLOW equal to zero: The HSBAUD register is used to time TLOW, THIGH, TSU;STO, THD;STA and
TSU;STA.. TBUF is timed by the BAUD register.
Bits 23:16 – HSBAUD[7:0] High Speed Master Baud Rate
This bit field indicates the SCL high time in High-speed mode according to the following formula. When
HSBAUDLOW is zero, TLOW, THIGH, TSU;STO, THD;STA and TSU;STA are derived using this formula. TBUF is
timed by the BAUD register.
HSBAUD = GCLK HIGH 1
Bits 15:8 – BAUDLOW[7:0] Master Baud Rate Low
If this bit field is non-zero, the SCL low time will be described by the value written.
For more information on how to calculate the frequency, see SERCOM 30.6.2.3 Clock Generation –
Baud-Rate Generator.
Bits 7:0 – BAUD[7:0] Master Baud Rate
This bit field is used to derive the SCL high time if BAUD.BAUDLOW is non-zero. If BAUD.BAUDLOW is
zero, BAUD will be used to generate both high and low periods of the SCL.
For more information on how to calculate the frequency, see SERCOM 30.6.2.3 Clock Generation –
Baud-Rate Generator.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 663
33.10.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
ERROR SB MB
Access R/W R/W R/W
Reset 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 1 – SB Slave on Bus Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Slave on Bus Interrupt Enable bit, which disables the Slave on Bus
interrupt.
Value Description
0The Slave on Bus interrupt is disabled.
1The Slave on Bus interrupt is enabled.
Bit 0 – MB Master on Bus Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the Master on Bus Interrupt Enable bit, which disables the Master on Bus
interrupt.
Value Description
0The Master on Bus interrupt is disabled.
1The Master on Bus interrupt is enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 664
33.10.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x16
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
ERROR SB MB
Access R/W R/W R/W
Reset 0 0 0
Bit 7 – ERROR Error Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0Error interrupt is disabled.
1Error interrupt is enabled.
Bit 1 – SB Slave on Bus Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Slave on Bus Interrupt Enable bit, which enables the Slave on Bus
interrupt.
Value Description
0The Slave on Bus interrupt is disabled.
1The Slave on Bus interrupt is enabled.
Bit 0 – MB Master on Bus Interrupt Enable
Writing '0' to this bit has no effect.
Writing '1' to this bit will set the Master on Bus Interrupt Enable bit, which enables the Master on Bus
interrupt.
Value Description
0The Master on Bus interrupt is disabled.
1The Master on Bus interrupt is enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 665
33.10.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x18
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
ERROR SB MB
Access R/W R/W R/W
Reset 0 0 0
Bit 7 – ERROR Error
This flag is cleared by writing '1' to it.
This bit is set when any error is detected. Errors that will set this flag have corresponding status bits in the
STATUS register. These status bits are LENERR, SEXTTOUT, MEXTTOUT, LOWTOUT, ARBLOST, and
BUSERR.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear the flag.
Bit 1 – SB Slave on Bus
The Slave on Bus flag (SB) is set when a byte is successfully received in master read mode, i.e., no
arbitration lost or bus error occurred during the operation. When this flag is set, the master forces the
SCL line low, stretching the I2C clock period. The SCL line will be released and SB will be cleared on one
of the following actions:
• Writing to ADDR.ADDR
• Writing to DATA.DATA
• Reading DATA.DATA when smart mode is enabled (CTRLB.SMEN)
• Writing a valid command to CTRLB.CMD
Writing '1' to this bit location will clear the SB flag. The transaction will not continue or be terminated until
one of the above actions is performed.
Writing '0' to this bit has no effect.
Bit 0 – MB Master on Bus
This flag is set when a byte is transmitted in master write mode. The flag is set regardless of the
occurrence of a bus error or an arbitration lost condition. MB is also set when arbitration is lost during
sending of NACK in master read mode, or when issuing a start condition if the bus state is unknown.
When this flag is set and arbitration is not lost, the master forces the SCL line low, stretching the I2C clock
period. The SCL line will be released and MB will be cleared on one of the following actions:
• Writing to ADDR.ADDR
• Writing to DATA.DATA
• Reading DATA.DATA when smart mode is enabled (CTRLB.SMEN)
• Writing a valid command to CTRLB.CMD
Writing '1' to this bit location will clear the MB flag. The transaction will not continue or be terminated until
one of the above actions is performed.
Writing '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 666
33.10.7 Status
Name:  STATUS
Offset:  0x1A
Reset:  0x0000
Property:  Write-Synchronized
Bit 15 14 13 12 11 10 9 8
LENERR SEXTTOUT MEXTTOUT
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
CLKHOLD LOWTOUT BUSSTATE[1:0] RXNACK ARBLOST BUSERR
Access R R/W R/W R/W R R/W R/W
Reset 0 0 0 0 0 0 0
Bit 10 – LENERR Transaction Length Error
This bit is set when automatic length is used for a DMA transaction and the slave sends a NACK before
ADDR.LEN bytes have been written by the master.
Writing '1' to this bit location will clear STATUS.LENERR. This flag is automatically cleared when writing
to the ADDR register.
Writing '0' to this bit has no effect.
This bit is not write-synchronized.
Bit 9 – SEXTTOUT Slave SCL Low Extend Time-Out
This bit is set if a slave SCL low extend time-out occurs.
This bit is automatically cleared when writing to the ADDR register.
Writing '1' to this bit location will clear SEXTTOUT. Normal use of the I2C interface does not require the
SEXTTOUT flag to be cleared by this method.
Writing '0' to this bit has no effect.
This bit is not write-synchronized.
Bit 8 – MEXTTOUT Master SCL Low Extend Time-Out
This bit is set if a master SCL low time-out occurs.
Writing '1' to this bit location will clear STATUS.MEXTTOUT. This flag is automatically cleared when
writing to the ADDR register.
Writing '0' to this bit has no effect.
This bit is not write-synchronized.
Bit 7 – CLKHOLD Clock Hold
This bit is set when the master is holding the SCL line low, stretching the I2C clock. Software should
consider this bit when INTFLAG.SB or INTFLAG.MB is set.
This bit is cleared when the corresponding interrupt flag is cleared and the next operation is given.
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
This bit is not write-synchronized.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 667
Bit 6 – LOWTOUT SCL Low Time-Out
This bit is set if an SCL low time-out occurs.
Writing '1' to this bit location will clear this bit. This flag is automatically cleared when writing to the ADDR
register.
Writing '0' to this bit has no effect.
This bit is not write-synchronized.
Bits 5:4 – BUSSTATE[1:0] Bus State
These bits indicate the current I2C bus state.
When in UNKNOWN state, writing 0x1 to BUSSTATE forces the bus state into the IDLE state. The bus
state cannot be forced into any other state.
Writing BUSSTATE to idle will set SYNCBUSY.SYSOP.
Value Name Description
0x0 UNKNOWN The bus state is unknown to the I2C master and will wait for a stop condition to
be detected or wait to be forced into an idle state by software
0x1 IDLE The bus state is waiting for a transaction to be initialized
0x2 OWNER The I2C master is the current owner of the bus
0x3 BUSY Some other I2C master owns the bus
Bit 2 – RXNACK Received Not Acknowledge
This bit indicates whether the last address or data packet sent was acknowledged or not.
Writing '0' to this bit has no effect.
Writing '1' to this bit has no effect.
This bit is not write-synchronized.
Value Description
0Slave responded with ACK.
1Slave responded with NACK.
Bit 1 – ARBLOST Arbitration Lost
This bit is set if arbitration is lost while transmitting a high data bit or a NACK bit, or while issuing a start or
repeated start condition on the bus. The Master on Bus interrupt flag (INTFLAG.MB) will be set when
STATUS.ARBLOST is set.
Writing the ADDR.ADDR register will automatically clear STATUS.ARBLOST.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
This bit is not write-synchronized.
Bit 0 – BUSERR Bus Error
This bit indicates that an illegal bus condition has occurred on the bus, regardless of bus ownership. An
illegal bus condition is detected if a protocol violating start, repeated start or stop is detected on the I2C
bus lines. A start condition directly followed by a stop condition is one example of a protocol violation. If a
time-out occurs during a frame, this is also considered a protocol violation, and will set BUSERR.
If the I2C master is the bus owner at the time a bus error occurs, STATUS.ARBLOST and INTFLAG.MB
will be set in addition to BUSERR.
Writing the ADDR.ADDR register will automatically clear the BUSERR flag.
Writing '0' to this bit has no effect.
Writing '1' to this bit will clear it.
This bit is not write-synchronized.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 668
33.10.8 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x1C
Reset:  0x00000000
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
SYSOP ENABLE SWRST
Access R R R
Reset 0 0 0
Bit 2 – SYSOP System Operation Synchronization Busy
Writing CTRLB.CMD, STATUS.BUSSTATE, ADDR, or DATA when the SERCOM is enabled requires
synchronization. When written, the SYNCBUSY.SYSOP bit will be set until synchronization is complete.
Value Description
0System operation synchronization is not busy.
1System operation synchronization is busy.
Bit 1 – ENABLE SERCOM Enable Synchronization Busy
Enabling and disabling the SERCOM (CTRLA.ENABLE) requires synchronization. When written, the
SYNCBUSY.ENABLE bit will be set until synchronization is complete.
Value Description
0Enable synchronization is not busy.
1Enable synchronization is busy.
Bit 0 – SWRST Software Reset Synchronization Busy
Resetting the SERCOM (CTRLA.SWRST) requires synchronization. When written, the
SYNCBUSY.SWRST bit will be set until synchronization is complete.
Value Description
0SWRST synchronization is not busy.
1SWRST synchronization is busy.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 669
33.10.9 Address
Name:  ADDR
Offset:  0x24
Reset:  0x0000
Property:  Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
LEN[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TENBITEN HS LENEN ADDR[10:8]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ADDR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:16 – LEN[7:0] Transaction Length
These bits define the transaction length of a DMA transaction from 0 to 255 bytes. The Transfer Length
Enable (LENEN) bit must be written to '1' in order to use DMA.
Bit 15 – TENBITEN Ten Bit Addressing Enable
This bit enables 10-bit addressing. This bit can be written simultaneously with ADDR to indicate a 10-bit
or 7-bit address transmission.
Value Description
010-bit addressing disabled.
110-bit addressing enabled.
Bit 14 – HS High Speed
This bit enables High-speed mode for the current transfer from repeated START to STOP. This bit can be
written simultaneously with ADDR for a high speed transfer.
Value Description
0High-speed transfer disabled.
1High-speed transfer enabled.
Bit 13 – LENEN Transfer Length Enable
Value Description
0Automatic transfer length disabled.
1Automatic transfer length enabled.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 670
Bits 10:0 – ADDR[10:0] Address
When ADDR is written, the consecutive operation will depend on the bus state:
UNKNOWN: INTFLAG.MB and STATUS.BUSERR are set, and the operation is terminated.
BUSY: The I2C master will await further operation until the bus becomes IDLE.
IDLE: The I2C master will issue a start condition followed by the address written in ADDR. If the address
is acknowledged, SCL is forced and held low, and STATUS.CLKHOLD and INTFLAG.MB are set.
OWNER: A repeated start sequence will be performed. If the previous transaction was a read, the
acknowledge action is sent before the repeated start bus condition is issued on the bus. Writing ADDR to
issue a repeated start is performed while INTFLAG.MB or INTFLAG.SB is set.
STATUS.BUSERR, STATUS.ARBLOST, INTFLAG.MB and INTFLAG.SB will be cleared when ADDR is
written.
The ADDR register can be read at any time without interfering with ongoing bus activity, as a read access
does not trigger the master logic to perform any bus protocol related operations.
The I2C master control logic uses bit 0 of ADDR as the bus protocol’s read/write flag (R/W); 0 for write
and 1 for read.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 671
33.10.10 Data
Name:  DATA
Offset:  0x28
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – DATA[7:0] Data
The master data register I/O location (DATA) provides access to the master transmit and receive data
buffers. Reading valid data or writing data to be transmitted can be successfully done only when SCL is
held low by the master (STATUS.CLKHOLD is set). An exception is reading the last data byte after the
stop condition has been sent.
Accessing DATA.DATA auto-triggers I2C bus operations. The operation performed depends on the state
of CTRLB.ACKACT, CTRLB.SMEN and the type of access (read/write).
Writing or reading DATA.DATA when not in Smart mode does not require synchronization.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 672
33.10.11 Debug Control
Name:  DBGCTRL
Offset:  0x30
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGSTOP
Access R/W
Reset 0
Bit 0 – DBGSTOP Debug Stop Mode
This bit controls functionality when the CPU is halted by an external debugger.
Value Description
0The baud-rate generator continues normal operation when the CPU is halted by an external
debugger.
1The baud-rate generator is halted when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
SERCOM I2C – Inter-Integrated Circuit
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 673
34. CAN - Control Area Network
34.1 Overview
The Control Area Network (CAN) performs communication according to ISO 11898-1:2015 (Bosch CAN
specification 2.0 part A,B, ISO CAN FD). The message storage is intended to be a single- or dual-ported
Message RAM outside of the module.
34.2 Features
• Conform with CAN protocol version 2.0 part A, B and ISO 11898-1:2015
• Up to two Controller Area Network CAN
– Supporting CAN2.0 A/B and CAN-FD (ISO 11898-1:2015)
• CAN FD with up to 64 data bytes supported
• CAN Error Logging
• AUTOSAR optimized
• SAE J1939 optimized
• Two configurable Receive FIFOs
• Separate signaling on reception of High-Priority Messages
• Up to 64 dedicated Receive Buffers and up to 32 dedicated Transmit Buffers
• Configurable Transmit FIFO, Transmit Queue, Transmit Event FIFO
• Direct Message RAM access for CPU
• Programmable Loop-Back Test mode
• Maskable module interrupts
• Power-down support; Debug on CAN support
• Transfer rates:
– 1 Mb/s for CAN 2.0 mode
– 10 Mb/s for CAN-FD mode
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 674
34.3 Block Diagram
Figure 34-1. CAN Block Diagram
CAN
NVIC
GCLK
USER
INTF CAN CORE
CAN_TX
CAN_RX
GCLK_CAN
CAN interrupts
SRAM
High-Speed Bus
AHB
34.4 Signal Description
Table 34-1. Signal Description
Signal Description Type
CAN_TX CAN transmit Digital output
CAN_RX CAN receive Digital input
Refer to for details on the pin mapping for this peripheral. One signal can be mapped to one of several
pins.
Related Links
6. I/O Multiplexing and Considerations
34.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
34.5.1 I/O Lines
Using the CAN’s I/O lines requires the I/O pins to be configured.
Related Links
28. PORT - I/O Pin Controller
34.5.2 Power Management
The CAN will continue to operate in any Idle Sleep mode where the selected source clock is running. The
CAN interrupts can be used to wake up the device from sleep modes. Refer to the Power Manager
chapter for details on the different sleep modes.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 675
The CAN module has its own Low-Power mode. The clock sources cannot be halted while the CAN is
enabled unless this mode is used. Refer to the section "Sleep Mode Operation" for additional information.
Related Links
34.6.9 Sleep Mode Operation
34.5.3 Clocks
An AHB clock (CLK_CAN_AHB) is required to clock the CAN. This clock can be configured in the Main
Clock peripheral (MCLK) before using the CAN, and the default state of CLK_CAN_AHB can be found in
the MCLK.AHBMASK register.
A generic clock (GCLK_CAN) is required to clock the CAN. This clock must be configured and enabled in
the generic clock controller before using the CAN.
This generic clock is asynchronous to the bus clock (CLK_CAN_AHB). Due to this asynchronicity, writes
to certain registers will require synchronization between the clock domains.
Related Links
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
34.5.4 DMA
The CAN has a built-in Direct Memory Access (DMA) and will read/write data to/from the system RAM
when a CAN transaction takes place. No CPU or DMA Controller (DMAC) resources are required.
The DMAC can be used for debug messages functionality.
Related Links
25. DMAC – Direct Memory Access Controller
34.5.5 Interrupts
The interrupt request lines are connected to the interrupt controller. Using the CAN interrupts requires the
interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
34.5.6 Events
Not applicable.
34.5.7 Debug Operation
Not applicable.
34.5.8 Register Access Protection
Not applicable.
34.5.9 Analog Connections
No analog connections.
SAM C20/C21 Family Data Sheet
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34.6 Functional Description
34.6.1 Principle of Operation
The CAN performs communication according to ISO 11898-1:2015 (identical to Bosch CAN protocol
specification 2.0 part A,B, ISO CAN FD).
The message storage is intended to be a single- or dual-ported Message RAM outside the module. It is
connected to the CAN via AHB.
All functions concerning the handling of messages are implemented by the Rx Handler and the Tx
Handler. The Rx Handler manages message acceptance filtering, the transfer of received messages from
the CAN Core to the Message RAM as well as providing receive message status information. The Tx
Handler is responsible for the transfer of transmit messages from the Message RAM to the CAN Core as
well as providing transmit status information.
Acceptance filtering is implemented by a combination of up to 128 filter elements where each one can be
configured as a range, as a bit mask, or as a dedicated ID filter.
34.6.2 Operating Modes
34.6.2.1 Software Initialization
Software initialization is started by setting bit CCCR.INIT, either by software or by a hardware reset, when
an uncorrected bit error was detected in the Message RAM, or by going Bus_Off. While CCCR.INIT is
set, message transfer from and to the CAN bus is stopped, the status of the CAN bus output CAN_TX
is ”recessive” (HIGH). The counters of the Error Management Logic EML are unchanged. Setting
CCCR.INIT does not change any configuration register. Resetting CCCR.INIT finishes the software
initialization. Afterwards the Bit Stream Processor BSP synchronizes itself to the data transfer on the CAN
bus by waiting for the occurrence of a sequence of 11 consecutive ”recessive” bits (= Bus_Idle) before it
can take part in bus activities and start the message transfer.
Access to the CAN configuration registers is only enabled when both bits CCCR.INIT and CCCR.CCE are
set (protected write).
CCCR.CCE can only be set/reset while CCCR.INIT = ‘1’. CCCR.CCE is automatically reset when
CCCR.INIT is reset.
The following registers are reset when CCCR.CCE is set
• HPMS - High Priority Message Status
• RXF0S - Rx FIFO 0 Status
• RXF1S - Rx FIFO 1 Status
• TXFQS - Tx FIFO/Queue Status
• TXBRP - Tx Buffer Request Pending
• TXBTO - Tx Buffer Transmission Occurred
• TXBCF - Tx Buffer Cancellation Finished
• TXEFS - Tx Event FIFO Status
The Timeout Counter value TOCV.TOC is preset to the value configured by TOCC.TOP when
CCCR.CCE is set.
In addition the state machines of the Tx Handler and Rx Handler are held in idle state while CCCR.CCE =
‘1’.
The following registers are only writable while CCCR.CCE = ‘0’
SAM C20/C21 Family Data Sheet
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• TXBAR - Tx Buffer Add Request
• TXBCR - Tx Buffer Cancellation Request
CCCR.TEST and CCCR.MON can only be set by the CPU while CCCR.INIT = ‘1’ and CCR.CCE = ‘1’.
Both bits may be reset at any time. CCCR.DAR can only be set/reset while CCCR.INIT = ‘1’ and
CCCR.CCE = ‘1’.
34.6.2.2 Normal Operation
Once the CAN is initialized and CCCR.INIT is reset to ‘0’, the CAN synchronizes itself to the CAN bus
and is ready for communication.
After passing the acceptance filtering, received messages including Message ID and DLC are stored into
a dedicated Rx Buffer or into Rx FIFO0 or Rx FIFO1.
For messages to be transmitted dedicated Tx Buffers and/or a Tx FIFO or a Tx Queue can be initialized
or updated. Automated transmission on reception of remote frames is not implemented.
34.6.2.3 CAN FD Operation
There are two variants in the CAN FD frame format, first the CAN FD frame without bit rate switching
where the data field of a CAN frame may be longer than 8 bytes. The second variant is the CAN FD
frame where control field, data field, and CRC field of a CAN frame are transmitted with a higher bit rate
than the beginning and the end of the frame.
The previously reserved bit in CAN frames with 11-bit identifiers and the first previously reserved bit in
CAN frames with 29-bit identifiers will now be decoded as FDF bit. FDF = recessive signifies a CAN FD
frame, FDF = dominant signifies a Classic CAN frame. In a CAN FD frame, the two bits following FDF, res
and BRS, decide whether the bit rate inside of this CAN FD frame is switched. A CAN FD bit rate switch
is signified by res = dominant and BRS = recessive. The coding of res = recessive is reserved for future
expansion of the protocol. In case the CAN receives a frame with FDF = recessive and res = recessive, it
will signal a Protocol Exception Event by setting bit PSR.PXE. When Protocol Exception Handling is
enabled (CCCR.PXHD = ‘0’), this causes the operation state to change from Receiver (PSR.ACT = “10”)
to Integrating (PSR.ACT = “00”) at the next sample point. In case Protocol Exception Handling is disabled
(CCCR.PXHD = ‘1’), the CAN will treat a recessive res bit as a form error and will respond with an error
frame.
CAN FD operation is enabled by programming CCCR.FDOE. In case CCCR.FDOE = ‘1’, transmission
and reception of CAN FD frames is enabled. Transmission and reception of Classic CAN frames is
always possible. Whether a CAN FD frame or a Classic CAN frame is transmitted can be configured via
bit FDF in the respective Tx Buffer element. With CCCR.FDOE = ‘0’, received frames are interpreted as
Classic CAN frames, witch leads to the transmission of an error frame when receiving a CAN FD frame.
When CAN FD operation is disabled, no CAN FD frames are transmitted even if bit FDF of a Tx Buffer
element is set. CCCR.FDOE and CCCR.BRSE can only be changed while CCCR.INIT and CCCR.CCE
are both set.
With CCCR.FDOE = ‘0’, the setting of bits FDF and BRS is ignored and frames are transmitted in Classic
CAN format. With CCCR.FDOE = ‘1’ and CCCR.BRSE = ‘0’, only bit FDF of a Tx Buffer element is
evaluated. With CCCR.FDOE = ‘1’ and CCCR.BRSE = ‘1’, transmission of CAN FD frames with bit rate
switching is enabled. All Tx Buffer elements with bits FDF and BRS set are transmitted in CAN FD format
with bit rate switching.
A mode change during CAN operation is only recommended under the following conditions:
• The failure rate in the CAN FD data phase is significantly higher than in the CAN FD arbitration
phase. In this case disable the CAN FD bit rate switching option for transmissions.
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 678
• During system startup all nodes are transmitting Classic CAN messages until it is verified that they
are able to communicate in CAN FD format. If this is true, all nodes switch to CAN FD operation.
• Wake-up messages in CAN Partial Networking have to be transmitted in Classic CAN format.
• End-of-line programming in case not all nodes are CAN FD capable. Non CAN FD nodes are held in
silent mode until programming has completed. Then all nodes switch back to Classic CAN
communication.
In the CAN FD format, the coding of the DLC differs from the standard CAN format. The DLC codes 0 to 8
have the same coding as in standard CAN, the codes 9 to 15, which in standard CAN all code a data field
of 8 bytes, are coded according to the table below.
Table 34-2. Coding of DLC in CAN FD
DLC 9 10 11 12 13 14 15
Number of Data Bytes 12 16 20 24 32 48 64
In CAN FD frames, the bit timing will be switched inside the frame, after the BRS (Bit Rate Switch) bit, if
this bit is recessive. Before the BRS bit, in the CAN FD arbitration phase, the nominal CAN bit timing is
used as defined by the Nominal Bit Timing & Prescaler Register NBTP. In the following CAN FD data
phase, the fast CAN bit timing is used as defined by the Data Bit Timing & Prescaler Register DBTP. The
bit timing is switched back from the fast timing at the CRC delimiter or when an error is detected,
whichever occurs first.
The maximum configurable bit rate in the CAN FD data phase depends on the CAN clock frequency
(GCLK_CAN). Example: with a CAN clock frequency of 20MHz and the shortest configurable bit time of 4
tq, the bit rate in the data phase is 5 Mbit/s.
In both data frame formats, CAN FD long and CAN FD fast, the value of the bit ESI (Error Status
Indicator) is determined by the transmitter’s error state at the start of the transmission. If the transmitter is
error passive, ESI is transmitted recessive, else it is transmitted dominant.
34.6.2.4 Transceiver Delay Compensation
During the data phase of a CAN FD transmission only one node is transmitting, all others are receivers.
The length of the bus line has no impact. When transmitting via pin CAN_TX the CAN receives the
transmitted data from its local CAN transceiver via pin CAN_RX. The received data is delayed by the
CAN transceiver’s loop delay. In case this delay is greater than TSEG1 (time segment before sample
point), a bit error is detected. In order to enable a data phase bit time that is even shorter than the
transceiver loop delay, the delay compensation is introduced. Without transceiver delay compensation,
the bit rate in the data phase of a CAN FD frame is limited by the transceivers loop delay.
Description
The CAN’s protocol unit has implemented a delay compensation mechanism to compensate the
transmitter delay, thereby enabling transmission with higher bit rates during the CAN FD data phase
independent of the delay of a specific CAN transceiver.
To check for bit errors during the data phase of transmitting nodes, the delayed transmit data is compared
against the received data at the Secondary Sample Point SSP. If a bit error is detected, the transmitter
will react on this bit error at the next following regular sample point. During arbitration phase the delay
compensation is always disabled.
The transmitter delay compensation enables configurations where the data bit time is shorter than the
transmitter delay, it is described in detail in the new ISO11898-1. It is enabled by setting bit DBTP.TDC.
SAM C20/C21 Family Data Sheet
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The received bit is compared against the transmitted bit at the SSP. The SSP position is defined as the
sum of the measured delay from the CAN’s transmit output CAN_TX through the transceiver to the
receive input CAN_RX plus the transmitter delay compensation offset as configured by TDCR.TDCO. The
transmitter delay compensation offset is used to adjust the position of the SSP inside the received bit
(e.g. half of the bit time in the data phase). The position of the secondary sample point is rounded down
to the next integer number of mtq.
PSR.TDCV shows the actual transmitter delay compensation value. PSR.TDCV is cleared when
CCCR.INIT is set and is updated at each transmission of an FD frame while DBTP.TDC is set.
The following boundary conditions have to be considered for the transmitter delay compensation
implemented in the CAN:
• The sum of the measured delay from CAN_TX to CAN_RX and the configured transceiver delay
compensation offset FBTP.TDCO has to be less than 6 bit times in the data phase.
• The sum of the measured delay from CAN_TX to CAN_RX and the configured transceiver delay
compensation offset FBTP.TDCO has to be less or equal to 127 mtq. In case this sum exceeds 127
mtq, the maximum value of 127 mtq is used for transceiver delay compensation.
• The data phase ends at the sample point of the CRC delimiter, that stops checking of receive bits at
the SSPs.
Transmitter Delay Compensation Measurement
If transmitter delay compensation is enabled by programming DBTP.TDC = ‘1’, the measurement is
started within each transmitted CAN FD frame at the falling edge of bit FDF to bit res. The measurement
is stopped when this edge is seen at the receive input CAN_TX of the transmitter. The resolution of this
measurement is one mtq.
Figure 34-2. Transceiver delay measurement
Delay
+
Start Stop
Delay Counter
Delay Compensation Offset
SSP Position
CAN_TX
CAN_RX
GCLK_CAN
TDCR.TDCO
data phase
data phasearbitration phase
arbitration phase
Transmitter Delay
FDF res BRS ESI DLC
To avoid that a dominant glitch inside the received FDF bit ends the delay compensation measurement
before the falling edge of the received res bit, resulting in a too early SSP position, the use of a
transmitter delay compensation filter window can be enabled by programming TDCR.TDCF. This defines
a minimum value for the SSP position. Dominant edges of CAN_RX, that would result in an earlier SSP
position are ignored for transmitter delay measurement. The measurement is stopped when the SSP
position is at least TDCR.TDCF AND CAN _RX is low.
34.6.2.5 Restricted Operation Mode
In Restricted Operation Mode the node is able to receive data and remote frames and to give
acknowledge to valid frames, but it does not send data frames, remote frames, active error frames, or
overload frames. In case of an error condition or overload condition, it does not send dominant bits,
SAM C20/C21 Family Data Sheet
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instead it waits for the occurrence of bus idle condition to resynchronize itself to the CAN communication.
The error counters (ECR.REC, ECR.TEC) are frozen while Error Logging (ECR.CEL) is still incremented.
The CPU can set the CAN into Restricted Operation mode by setting bit CCCR.ASM. The bit can only be
set by the CPU when both CCCR.CCE and CCCR.INIT are set to ‘1’. The bit can be reset by the CPU at
any time.
Restricted Operation Mode is automatically entered when the Tx Handler was not able to read data from
the Message RAM in time. To leave Restricted Operation Mode, the CPU has to reset CCCR.ASM.
The Restricted Operation Mode can be used in applications that adapt themselves to different CAN bit
rates. In this case the application tests different bit rates and leaves the Restricted Operation Mode after it
has received a valid frame.
34.6.2.6 Bus Monitoring Mode
The CAN is set in Bus Monitoring Mode by programming CCCR.MON to ‘1’. In Bus Monitoring Mode (see
ISO 11898-1, 10.12 Bus monitoring), the CAN is able to receive valid data frames and valid remote
frames, but cannot start a transmission. In this mode, it sends only recessive bits on the CAN bus. If the
CAN is required to send a dominant bit (ACK bit, overload flag, active error flag), the bit is rerouted
internally so that the CAN monitors this dominant bit, although the CAN bus may remain in recessive
state. In Bus Monitoring Mode register TXBRP is held in reset state.
The Bus Monitoring Mode can be used to analyze the traffic on a CAN bus without affecting it by the
transmission of dominant bits. The figure below shows the connection of signals CAN_TX and CAN_RX
to the CAN in Bus Monitoring Mode.
Figure 34-3. Pin Control in Bus Monitoring Mode
CAN_TX CAN_RX
=1
TX
HANDLER
RX
HANDLER
CAN
Bus Monitoring Mode
34.6.2.7 Disabled Automatic Retransmission
According to the CAN Specification (see ISO 11898-1, 6.3.3 Recovery Management), the CAN provides
means for automatic retransmission of frames that have lost arbitration or that have been disturbed by
errors during transmission. By default automatic retransmission is enabled. To support time-triggered
communication as described in ISO 11898-1, chapter 9.2, the automatic retransmission may be disabled
via CCCR.DAR.
Frame Transmission in DAR Mode
In DAR mode all transmissions are automatically cancelled after they started on the CAN bus. A Tx
Buffer’s Tx Request Pending bit TXBRP.TRPx is reset after successful transmission, when a transmission
has not yet been started at the point of cancellation, has been aborted due to lost arbitration, or when an
error occurred during frame transmission.
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 681
• Successful transmission:
– Corresponding Tx Buffer Transmission Occurred bit TXBTO.TOx set
– Corresponding Tx Buffer Cancellation Finished bit TXBCF.CFx not set
• Successful transmission in spite of cancellation:
– Corresponding Tx Buffer Transmission Occurred bit TXBTO.TOx set
– Corresponding Tx Buffer Cancellation Finished bit TXBCF.CFx set
• Arbitration lost or frame transmission disturbed:
– Corresponding Tx Buffer Transmission Occurred bit TXBTO.TOx not set
– Corresponding Tx Buffer Cancellation Finished bit TXBCF.CFx set
In case of a successful frame transmission, and if storage of Tx events is enabled, a Tx Event FIFO
element is written with Event Type ET = “10” (transmission in spite of cancellation).
34.6.2.8 Test Modes
To enable write access to register TEST, bit CCCR.TEST has to be set to ‘1’. This allows the configuration
of the test modes and test functions.
Four output functions are available for the CAN transmit pin CAN_TX by programming TEST.TX.
Additionally to its default function – the serial data output – it can drive the CAN Sample Point signal to
monitor the CAN’s bit timing and it can drive constant dominant or recessive values. The actual value at
pin CAN_RX can be read from TEST.RX. Both functions can be used to check the CAN bus’ physical
layer.
Due to the synchronization mechanism between GCLK_CAN and GCLK_CAN_APB domains, there may
be a delay of several GCLK_CAN_APB periods between writing to TEST.TX until the new configuration is
visible at output pin CAN_TX. This applies also when reading input pin CAN_RX via TEST.RX.
Note: Test modes should be used for production tests or self test only. The software control for pin
CAN_TX interferes with all CAN protocol functions. It is not recommended to use test modes for
application.
External Loop Back Mode
The CAN can be set in External Loop Back Mode by programming TEST.LBCK to ‘1’. In Loop Back
Mode, the CAN treats its own transmitted messages as received messages and stores them (if they pass
acceptance filtering) into an Rx Buffer or an Rx FIFO. The figure below shows the connection of signals
CAN_TX and CAN_RX to the CAN in External Loop Back Mode.
This mode is provided for hardware self-test. To be independent from external stimulation, the CAN
ignores acknowledge errors (recessive bit sampled in the acknowledge slot of a data/remote frame) in
Loop Back Mode. In this mode the CAN performs an internal feedback from its Tx output to its Rx input.
The actual value of the CAN_RX input pin is disregarded by the CAN. The transmitted messages can be
monitored at the CAN_TX pin.
Internal Loop Back Mode
Internal Loop Back Mode is entered by programming bits TEST.LBCK and CCCR.MON to ‘1’. This mode
can be used for a “Hot Selftest”, meaning the CAN can be tested without affecting a running CAN system
connected to the pins CAN_TX and CAN_RX. In this mode pin CAN_RX is disconnected from the CAN
and pin CAN_TX is held recessive. The figure below shows the connection of CAN_TX and CAN_RX to
the CAN in case of Internal Loop Back Mode.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 682
Figure 34-4. Pin Control in Loop Back Modes
CAN_TX CAN_RX CAN_TX CAN_RX
TX
HANDLER
RX
HANDLER
TX
HANDLER
RX
HANDLER
CAN CAN
External Loop Back Mode Internal Loop Back Mode
=1
34.6.3 Timestamp Generation
For timestamp generation the CAN supplies a 16-bit wrap-around counter. A prescaler TSCC.TCP can be
configured to clock the counter in multiples of CAN bit times (1…16). The counter is readable via
TSCV.TSC. A write access to register TSCV resets the counter to zero. When the timestamp counter
wraps around interrupt flag IR.TSW is set.
On start of frame reception / transmission the counter value is captured and stored into the timestamp
section of an Rx Buffer / Rx FIFO (RXTS[15:0]) or Tx Event FIFO (TXTS[15:0]) element.
34.6.4 Timeout Counter
To signal timeout conditions for Rx FIFO 0, Rx FIFO 1, and the Tx Event FIFO the CAN supplies a 16-bit
Timeout Counter. It operates as down-counter and uses the same prescaler controlled by TSCC.TCP as
the Timestamp Counter. The Timeout Counter is configured via register TOCC. The actual counter value
can be read from TOCV.TOC. The Timeout Counter can only be started while CCCR.INIT = ‘0’. It is
stopped when CCCR.INIT = ‘1’, e.g. when the CAN enters Bus_Off state.
The operation mode is selected by TOCC.TOS. When operating in Continuous Mode, the counter starts
when CCCR.INIT is reset. A write to TOCV presets the counter to the value configured by TOCC.TOP
and continues down-counting.
When the Timeout Counter is controlled by one of the FIFOs, an empty FIFO presets the counter to the
value configured by TOCC.TOP. Down-counting is started when the first FIFO element is stored. Writing
to TOCV has no effect.
When the counter reaches zero, interrupt flag IR.TOO is set. In Continuous Mode, the counter is
immediately restarted at TOCC.TOP.
Note: The clock signal for the Timeout Counter is derived from the CAN Core’s sample point signal.
Therefore the point in time where the Timeout Counter is decremented may vary due to the
synchronization / re-synchronization mechanism of the CAN Core. If the baud rate switch feature in CAN
FD is used, the timeout counter is clocked differently in arbitration and data field.
34.6.5 Rx Handling
The Rx Handler controls the acceptance filtering, the transfer of received messages to the Rx Buffers or
to one of the two Rx FIFOs, as well as the Rx FIFO’s Put and Get Indices.
SAM C20/C21 Family Data Sheet
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34.6.5.1 Acceptance Filtering
The CAN offers the possibility to configure two sets of acceptance filters, one for standard identifiers and
one for extended identifiers. These filters can be assigned to an Rx Buffer or to Rx FIFO 0,1. For
acceptance filtering each list of filters is executed from element #0 until the first matching element.
Acceptance filtering stops at the first matching element. The following filter elements are not evaluated for
this message.
The main features are:
• Each filter element can be configured as
– range filter (from - to)
– filter for one or two dedicated IDs
– classic bit mask filter
• Each filter element is configurable for acceptance or rejection filtering
• Each filter element can be enabled / disabled individually
• Filters are checked sequentially, execution stops with the first matching filter element
Related configuration registers are:
• Global Filter Configuration GFC
• Standard ID Filter Configuration SIDFC
• Extended ID Filter Configuration XIDFC
• Extended ID AND Mask XIDAM
Depending on the configuration of the filter element (SFEC/EFEC) a match triggers one of the following
actions:
• Store received frame in FIFO 0 or FIFO 1
• Store received frame in Rx Buffer
• Store received frame in Rx Buffer and generate pulse at filter event pin
• Reject received frame
• Set High Priority Message interrupt flag IR.HPM
• Set High Priority Message interrupt flag IR.HPM and store received frame in FIFO 0 or FIFO 1
Acceptance filtering is started after the complete identifier has been received. After acceptance filtering
has completed, and if a matching Rx Buffer or Rx FIFO has been found, the Message Handler starts
writing the received message data in portions of 32 bit to the matching Rx Buffer or Rx FIFO. If the CAN
protocol controller has detected an error condition (e.g. CRC error), this message is discarded with the
following impact on the affected Rx Buffer or Rx FIFO:
Rx Buffer
New Data flag of matching Rx Buffer is not set, but Rx Buffer (partly) overwritten with received data. For
error type see PSR.LEC respectively PSR.FLEC.
Rx FIFO
Put index of matching Rx FIFO is not updated, but related Rx FIFO element (partly) overwritten with
received data. For error type see PSR.LEC respectively PSR.FLEC. In case the matching Rx FIFO is
operated in overwrite mode, the boundary conditions described in Rx FIFO Overwrite Mode have to be
considered.
Note: When an accepted message is written to one of the two Rx FIFOs, or into an Rx Buffer, the
unmodified received identifier is stored independent of the filter(s) used. The result of the acceptance
filter process is strongly depending on the sequence of configured filter elements.
SAM C20/C21 Family Data Sheet
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Range Filter
The filter matches for all received frames with Message IDs in the range defined by SF1ID/SF2ID for
standard frames or EF1ID/EF2ID for extended frames.
There are two possibilities when range filtering is used together with extended frames:
EFT = “00” The Message ID of received frames is AND’ed with the Extended ID AND Mask (XIDAM)
before the
range filter is applied
EFT = “11” The Extended ID AND Mask (XIDAM) is not used for range filtering
Filter for specific IDs
A filter element can be configured to filter for one or two specific Message IDs. To filter for one specific
Message ID, the filter element has to be configured with SF1ID = SF2ID resp. EF1ID = EF2ID.
Classic Bit Mask Filter
Classic bit mask filtering is intended to filter groups of Message IDs by masking single bits of a received
Message ID. With classic bit mask filtering SF1ID/EF1ID is used as Message ID filter, while SF2ID/EF2ID
is used as filter mask.
A zero bit at the filter mask will mask out the corresponding bit position of the configured ID filter, e.g. the
value of the received Message ID at that bit position is not relevant for acceptance filtering. Only those
bits of the received Message ID where the corresponding mask bits are one are relevant for acceptance
filtering.
In case all mask bits are one, a match occurs only when the received Message ID and the Message ID
filter are identical. If all mask bits are zero, all Message IDs match.
Standard Message ID Filtering
The figure below shows the flow for standard Message ID (11-bit Identifier) filtering. The Standard
Message ID Filter element is described in 34.9.5 Standard Message ID Filter Element.
Controlled by the Global Filter Configuration GFC and the Standard ID Filter Configuration SIDFC
Message ID, Remote Transmission Request bit (RTR), and the Identifier Extension bit (IDE) of received
frames are compared against the list of configured filter elements.
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 685
Figure 34-5. Standard Message ID Filtering
11 / 29 bit identifier
remote frame reject remote frames
receive filter list enabled
match filter element #0
match filter element #SIDFC.LSS
accept non-matching frames
acceptance / rejection
discard frame
valid frame received
target FIFO full (blocking)
or Rx Buffer ND = '1'
store frame
11-bit 29-bit
yes
no
GFC.RRFS = '1'
GFC.RRFS = '0'
yes
yes
no
GFC.ANFS[1] = '1'
GFC.ANFS[1] = '0'
accept
reject
yes
no
SIDFC.LSS[7:0] > 0
SIDFC.LSS[7:0] = 0
Extended Message ID Filtering
The figure below shows the flow for extended Message ID (29-bit Identifier) filtering. The Extended
Message ID Filter element is described in 34.9.6 Extended Message ID Filter Element.
Controlled by the Global Filter Configuration GFC and the Extended ID Filter Configuration XIDFC
Message ID, Remote Transmission Request bit (RTR), and the Identifier Extension bit (IDE) of received
frames are compared against the list of configured filter elements.
The Extended ID AND Mask XIDAM is AND’ed with the received identifier before the filter list is executed.
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 686
Figure 34-6. Extended Message ID Filtering
11 / 29 bit identifier
remote frame
reject remote frames
receive filter list enabled
match filter element #0
match filter element #XIDFC.LSE
accept non-matching frames
acceptance / rejection
discard frame
valid frame received
target FIFO full (blocking)
or Rx Buffer ND = '1'
store frame
11-bit 29-bit
yes
no
GFC.RRFE = '1'
GFC.RRFE = '0'
yes
yes
no
GFC.ANFE[1] = '1'
GFC.ANFE[1] = '0'
accept
reject
yes
no
XIDFC.LSE[6:0] > 0
XIDFC.LSE[6:0] = 0
34.6.5.2 Rx FIFOs
Rx FIFO 0 and Rx FIFO 1 can be configured to hold up to 64 elements each. Configuration of the two Rx
FIFOs is done via registers RXF0C and RXF1C.
Received messages that passed acceptance filtering are transferred to the Rx FIFO as configured by the
matching filter element. For a description of the filter mechanisms available for Rx FIFO 0 and Rx FIFO 1
see 34.6.5.1 Acceptance Filtering. The Rx FIFO element is described in 34.9.2 Rx Buffer and FIFO
Element.
To avoid an Rx FIFO overflow, the Rx FIFO watermark can be used. When the Rx FIFO fill level reaches
the Rx FIFO watermark configured by RXFnC.FnWM, interrupt flag IR.RFnW is set. When the Rx FIFO
Put Index reaches the Rx FIFO Get Index an Rx FIFO Full condition is signalled by RXFnS.FnF. In
addition interrupt flag IR.RFnF is set.
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Figure 34-7. Rx FIFO Status
0
1
2
3
4
5
6
7
Get Index
RXFnS.FnGI
Put Index
RXFnS.FnPI
Fill Level
RXFnS.FnFI
When reading from an Rx FIFO, Rx FIFO Get Index RXFnS.FnGI • FIFO Element Size has to be added
to the corresponding Rx FIFO start address RXFnC.FnSA.
Table 34-3. Rx Buffer / FIFO Element Size
RXESC.RBDS[2:0]
RXESC.FnDS[2:0]
Data Field
[bytes]
FIFO Element Size
[RAM words]
000 8 4
001 12 5
010 16 6
011 20 7
100 24 8
101 32 10
110 48 14
111 64 18
Rx FIFO Blocking Mode
The Rx FIFO blocking mode is configured by RXFnC.FnOM = ‘0’. This is the default operation mode for
the Rx FIFOs.
When an Rx FIFO full condition is reached (RXFnS.FnPI = RXFnS.FnGI), no further messages are
written to the corresponding Rx FIFO until at least one message has been read out and the Rx FIFO Get
Index has been incremented. An Rx FIFO full condition is signaled by RXFnS.FnF = ‘1’. In addition
interrupt flag IR.RFnF is set.
In case a message is received while the corresponding Rx FIFO is full, this message is discarded and the
message lost condition is signalled by RXFnS.RFnL = ‘1’. In addition interrupt flag IR.RFnL is set.
Rx FIFO Overwrite Mode
The Rx FIFO overwrite mode is configured by RXFnC.FnOM = ‘1’.
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When an Rx FIFO full condition (RXFnS.FnPI = RXFnS.FnGI) is signaled by RXFnS.FnF = ‘1’, the next
message accepted for the FIFO will overwrite the oldest FIFO message. Put and get index are both
incremented by one.
When an Rx FIFO is operated in overwrite mode and an Rx FIFO full condition is signaled, reading of the
Rx FIFO elements should start at least at get index + 1. The reason for that is, that it might happen, that a
received message is written to the Message RAM (put index) while the CPU is reading from the Message
RAM (get index). In this case inconsistent data may be read from the respective Rx FIFO element.
Adding an offset to the get index when reading from the Rx FIFO avoids this problem. The offset depends
on how fast the CPU accesses the Rx FIFO. The figure below shows an offset of two with respect to the
get index when reading the Rx FIFO. In this case the two messages stored in element 1 and 2 are lost.
Figure 34-8. Rx FIFO Overflow Handling
RXFnS.FnPI =
RXFnS.FnGI
read Get Index + 2
element 0 overwritten
RXFnS.FnPI =
RXFnS.FnGI
Rx FIFO Full
(RXFnS.FnF = '1')
Rx FIFO Overwrite
(RXFnS.FnF = '1')
1
0
2
3
4
5
6
7
1
0
2
3
4
5
6
7
After reading from the Rx FIFO, the number of the last element read has to be written to the Rx FIFO
Acknowledge Index RXFnA.FnA. This increments the get index to that element number. In case the put
index has not been incremented to this Rx FIFO element, the Rx FIFO full condition is reset (RXFnS.FnF
= ‘0’).
34.6.5.3 Dedicated Rx Buffers
The CAN supports up to 64 dedicated Rx Buffers. The start address of the dedicated Rx Buffer section is
configured via RXBC.RBSA.
For each Rx Buffer a Standard or Extended Message ID Filter Element with SFEC / EFEC = “111” and
SFID2 / EFID2[10:9] = “00” has to be configured (see 34.9.5 Standard Message ID Filter Element and
34.9.6 Extended Message ID Filter Element).
After a received message has been accepted by a filter element, the message is stored into the Rx Buffer
in the Message RAM referenced by the filter element. The format is the same as for an Rx FIFO element.
In addition the flag IR.DRX (Message stored in Dedicated Rx Buffer) in the interrupt register is set.
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Table 34-4. Example Filter Configuration for Rx Buffers
Filter Element SFID1[10:0] / EFID1[28:0] SFID2[10:9] / EFID2[10:9] SFID2[5:0] / EFID2[5:0]
0 ID message 1 00 00 0000
1 ID message 2 00 00 0001
2 ID message 3 00 00 0010
After the last word of a matching received message has been written to the Message RAM, the
respective New Data flag in register NDAT1, NDAT2 is set. As long as the New Data flag is set, the
respective Rx Buffer is locked against updates from received matching frames. The New Data flags have
to be reset by the CPU by writing a ‘1’ to the respective bit position.
While an Rx Buffer’s New Data flag is set, a Message ID Filter Element referencing this specific Rx Buffer
will not match, causing the acceptance filtering to continue. Following Message ID Filter Elements may
cause the received message to be stored into another Rx Buffer, or into an Rx FIFO, or the message may
be rejected, depending on filter configuration.
Rx Buffer Handling
• Reset interrupt flag IR.DRX
• Read New Data registers
• Read messages from Message RAM
• Reset New Data flags of processed messages
34.6.5.4 Debug on CAN Support
Debug messages are stored into Rx Buffers. For debug handling three consecutive Rx buffers (e.g. #61,
#62, #63) have to be used for storage of debug messages A, B, and C. The format is the same as for an
Rx Buffer or an Rx FIFO element (see 34.9.2 Rx Buffer and FIFO Element ).
Advantage: Fixed start address for the DMA transfers (relative to RXBC.RBSA), no additional
configuration required.
For filtering of debug messages Standard / Extended Filter Elements with SFEC / EFEC = “111” have to
be set up. Messages matching these filter elements are stored into the Rx Buffers addressed by SFID2 /
EFID2[5:0].
After message C has been stored, the DMA request output is activated and the three messages can be
read from the Message RAM under DMA control. The RAM words holding the debug messages will not
be changed by the CAN while DMA request is activated. The behavior is similar to that of an Rx Buffers
with its New Data flag set.
After the DMA has completed the DMA unit sets the DMA acknowledge. This resets DMA request. Now
the CAN is prepared to receive the next set of debug messages.
Filtering for Debug Messages
Filtering for debug messages is done by configuring one Standard / Extended Message ID Filter Element
for each of the three debug messages. To enable a filter element to filter for debug messages SFEC /
EFEC has to be programmed to “111”. In this case fields SFID1 / SFID2 and EFID1 / EFID2 have a
different meaning (see 34.9.5 Standard Message ID Filter Element and 34.9.6 Extended Message ID
Filter Element). While SFID2 / EFID2[10:9] controls the debug message handling state machine, SFID2 /
EFID2[5:0] controls the location for storage of a received debug message.
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When a debug message is stored, neither the respective New Data flag nor IR.DRX are set. The
reception of debug messages can be monitored via RXF1S.DMS.
Table 34-5. Example Filter Configuration for Debug Messages
Filter Element SFID1[10:0] / EFID1[28:0] SFID2[10:9] / EFID2[10:9] SFID2[5:0] / EFID2[5:0]
0 ID debug message A 01 11 1101
1 ID debug message B 10 11 1110
2 ID debug message C 11 11 1111
Debug Message Handling
The debug message handling state machine assures that debug messages are stored to three
consecutive Rx Buffers in correct order. In case of missing messages the process is restarted. The DMA
request is activated only when all three debug messages A, B, C have been received in correct order.
Figure 34-9. Debug Message Handling State Machine
T0
T1
T2
T3
T4
T5
T6
T7
T8
DMS = 00
DMS = 01
DMS = 10
DMS = 11
HW reset
or
Initial state
T0: Reset DMA request output, enable reception of debug message A, B, and C
T1: Reception of debug message A
T2: Reception of debug message A
T3: Reception of debug message C
T4: Reception of debug message B
T5: Reception of debug message A, B
T6: Reception of debug message C
T7: DMA transfer completed
T8: Reception of debug message A, B, C (message rejected)
34.6.6 Tx Handling
The Tx Handler handles transmission requests for the dedicated Tx Buffers, the Tx FIFO, and the Tx
Queue. It controls the transfer of transmit messages to the CAN Core, the Put and Get Indices, and the
Tx Event FIFO. Up to 32 Tx Buffers can be set up for message transmission. The CAN mode for
transmission (Classic CAN or CAN FD) can be configured separately for each Tx Buffer element. The Tx
Buffer element is described in 34.9.3 Tx Buffer Element. The table below describes the possible
configurations for frame transmission.
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Table 34-6. Possible Configurations for Frame Transmission
CCCR Tx Buffer Element Frame Transmission
BRSE FDOE FDF BRS
ignored 0 ignored ignored Classic CAN
0 1 0 ignored Classic CAN
0 1 1 ignored FD without bit rate switching
1 1 0 ignored Classic CAN
1 1 1 0 FD without bit rate switching
1 1 1 1 FD with bit rate switching
Note: AUTOSAR requires at least three Tx Queue Buffers and support of transmit cancellation
The Tx Handler starts a Tx scan to check for the highest priority pending Tx request (Tx Buffer with
lowest Message ID) when the Tx Buffer Request Pending register TXBRP is updated, or when a
transmission has been started.
34.6.6.1 Transmit Pause
The transmit pause feature is intended for use in CAN systems where the CAN message identifiers are
(permanently) specified to specific values and cannot easily be changed. These message identifiers may
have a higher CAN arbitration priority than other defined messages, while in a specific application their
relative arbitration priority should be inverse. This may lead to a case where one ECU sends a burst of
CAN messages that cause another ECU’s CAN messages to be delayed because that other messages
have a lower CAN arbitration priority.
If e.g. CAN ECU-1 has the transmit pause feature enabled and is requested by its application software to
transmit four messages, it will, after the first successful message transmission, wait for two CAN bit times
of bus idle before it is allowed to start the next requested message. If there are other ECUs with pending
messages, those messages are started in the idle time, they would not need to arbitrate with the next
message of ECU-1. After having received a message, ECU-1 is allowed to start its next transmission as
soon as the received message releases the CAN bus.
The transmit pause feature is controlled by bit CCCR.TXP. If the bit is set, the CAN will, each time it has
successfully transmitted a message, pause for two CAN bit times before starting the next transmission.
This enables other CAN nodes in the network to transmit messages even if their messages have lower
prior identifiers. Default is transmit pause disabled (CCCR.TXP = ‘0’).
This feature looses up burst transmissions coming from a single node and it protects against "babbling
idiot" scenarios where the application program erroneously requests too many transmissions.
34.6.6.2 Dedicated Tx Buffers
Dedicated Tx Buffers are intended for message transmission under complete control of the CPU. Each
Dedicated Tx Buffer is configured with a specific Message ID. In case that multiple Tx Buffers are
configured with the same Message ID, the Tx Buffer with the lowest buffer number is transmitted first.
If the data section has been updated, a transmission is requested by an Add Request via TXBAR.ARn.
The requested messages arbitrate internally with messages from an optional Tx FIFO or Tx Queue and
externally with messages on the CAN bus, and are sent out according to their Message ID.
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A Dedicated Tx Buffer allocates Element Size 32-bit words in the Message RAM (refer to table below).
Therefore the start address of a dedicated Tx Buffer in the Message RAM is calculated by adding transmit
buffer index (0…31) • Element Size to the Tx Buffer Start Address TXBC.TBSA.
Table 34-7. Tx Buffer / FIFO / Queue Element Size
TXESC.TBDS[2:0] Data Field [bytes] Element Size [RAM words]
000 8 4
001 12 5
010 16 6
011 20 7
100 24 8
101 32 10
110 48 14
111 64 18
34.6.6.3 Tx FIFO
Tx FIFO operation is configured by programming TXBC.TFQM to ‘0’. Messages stored in the Tx FIFO are
transmitted starting with the message referenced by the Get Index TXFQS.TFGI. After each transmission
the Get Index is incremented cyclically until the Tx FIFO is empty. The Tx FIFO enables transmission of
messages with the same Message ID from different Tx Buffers in the order these messages have been
written to the Tx FIFO. The CAN calculates the Tx FIFO Free Level TXFQS.TFFL as difference between
Get and Put Index. It indicates the number of available (free) Tx FIFO elements.
New transmit messages have to be written to the Tx FIFO starting with the Tx Buffer referenced by the
Put Index TXFQS.TFQPI. An Add Request increments the Put Index to the next free Tx FIFO element.
When the Put Index reaches the Get Index, Tx FIFO Full (TXFQS.TFQF = ‘1’) is signaled. In this case no
further messages should be written to the Tx FIFO until the next message has been transmitted and the
Get Index has been incremented.
When a single message is added to the Tx FIFO, the transmission is requested by writing a ‘1’ to the
TXBAR bit related to the Tx Buffer referenced by the Tx FIFO’s Put Index.
When multiple (n) messages are added to the Tx FIFO, they are written to n consecutive Tx Buffers
starting with the Put Index. The transmissions are then requested via TXBAR. The Put Index is then
cyclically incremented by n. The number of requested Tx buffers should not exceed the number of free Tx
Buffers as indicated by the Tx FIFO Free Level.
When a transmission request for the Tx Buffer referenced by the Get Index is canceled, the Get Index is
incremented to the next Tx Buffer with pending transmission request and the Tx FIFO Free Level is
recalculated. When transmission cancellation is applied to any other Tx Buffer, the Get Index and the
FIFO Free Level remain unchanged.
A Tx FIFO element allocates Element Size 32-bit words in the Message RAM (refer to Table 34-7).
Therefore the start address of the next available (free) Tx FIFO Buffer is calculated by adding Tx FIFO/
Queue Put Index TXFQS.TFQPI (0…31) • Element Size to the Tx Buffer Start Address TXBC.TBSA.
34.6.6.4 Tx Queue
Tx Queue operation is configured by programming TXBC.TFQM to ‘1’. Messages stored in the Tx Queue
are transmitted starting with the message with the lowest Message ID (highest priority). In case that
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multiple Queue Buffers are configured with the same Message ID, the Queue Buffer with the lowest buffer
number is transmitted first.
New messages have to be written to the Tx Buffer referenced by the Put Index TXFQS.TFQPI. An Add
Request cyclically increments the Put Index to the next free Tx Buffer. In case that the Tx Queue is full
(TXFQS.TFQF = ’1’), the Put Index is not valid and no further message should be written to the Tx Queue
until at least one of the requested messages has been sent out or a pending transmission request has
been canceled.
The application may use register TXBRP instead of the Put Index and may place messages to any Tx
Buffer without pending transmission request.
A Tx Queue Buffer allocates Element Size 32-bit words in the Message RAM (refer to Table 34-7).
Therefore the start address of the next available (free) Tx Queue Buffer is calculated by adding Tx FIFO/
Queue Put Index TXFQS.TFQPI (0…31) • Element Size to the Tx Buffer Start Address TXBC.TBSA.
34.6.6.5 Mixed Dedicated Tx Buffers / Tx FIFO
In this case the Tx Buffers section in the Message RAM is subdivided into a set of Dedicated Tx Buffers
and a Tx FIFO. The number of Dedicated Tx Buffers is configured by TXBC.NDTB. The number of Tx
Buffers assigned to the Tx FIFO is configured by TXBC.TFQS. In case TXBC.TFQS is programmed to
zero, only Dedicated Tx Buffers are used.
Figure 34-10. Example of mixed Configuration Dedicated Tx Buffers / Tx FIFO
Dedicated Tx Buffers Tx FIFO
Buffer Index
Tx Sequence
Get Index Put Index
1 2 345 6 78 9
1. 5. 4. 6. 2. 3.
ID3 ID15 ID8 ID4 ID2ID24
0
Tx prioritization:
• Scan Dedicated Tx Buffers and oldest pending Tx FIFO Buffer (referenced by TXFS.TFGI)
• Buffer with lowest Message ID gets highest priority and is transmitted next
34.6.6.6 Mixed Dedicated Tx Buffers / Tx Queue
In this case the Tx Buffers section in the Message RAM is subdivided into a set of Dedicated Tx Buffers
and a Tx Queue. The number of Dedicated Tx Buffers is configured by TXBC.NDTB. The number of Tx
Queue Buffers is configured by TXBC.TFQS. In case TXBC.TFQS is programmed to zero, only Dedicated
Tx Buffers are used.
Figure 34-11. Example of mixed Configuration Dedicated Tx Buffers / Tx Queue
Dedicated Tx Buffers Tx Queue
ID3 ID15 ID8 ID4 ID2ID24
01 2 345 6 78 9
Buffer Index
Tx Sequence 2. 5. 4. 6. 3. 1.
Put Index
Tx prioritization:
• Scan all Tx Buffers with activated transmission request
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• Tx Buffer with lowest Message ID gets highest priority and is transmitted next
34.6.6.7 Transmit Cancellation
The CAN supports transmit cancellation. This feature is especially intended for gateway applications and
AUTOSAR based applications. To cancel a requested transmission from a dedicated Tx Buffer or a Tx
Queue Buffer the CPU has to write a ‘1’ to the corresponding bit position (=number of Tx Buffer) of
register TXBCR. Transmit cancellation is not intended for Tx FIFO operation.
Successful cancellation is signaled by setting the corresponding bit of register TXBCF to ‘1’.
In case a transmit cancellation is requested while a transmission from a Tx Buffer is already ongoing, the
corresponding TXBRP bit remains set as long as the transmission is in progress. If the transmission was
successful, the corresponding TXBTO and TXBCF bits are set. If the transmission was not successful, it
is not repeated and only the corresponding TXBCF bit is set.
Note:  In case a pending transmission is canceled immediately before this transmission could have been
started, there follows a short time window where no transmission is started even if another message is
also pending in this node. This may enable another node to transmit a message which may have a lower
priority than the second message in this node.
34.6.6.8 Tx Event Handling
To support Tx event handling the CAN has implemented a Tx Event FIFO. After the CAN has transmitted
a message on the CAN bus, Message ID and timestamp are stored in a Tx Event FIFO element. To link a
Tx event to a Tx Event FIFO element, the Message Marker from the transmitted Tx Buffer is copied into
the Tx Event FIFO element.
The Tx Event FIFO can be configured to a maximum of 32 elements. The Tx Event FIFO element is
described in 34.9.4 Tx Event FIFO Element.
When a Tx Event FIFO full condition is signaled by IR.TEFF, no further elements are written to the Tx
Event FIFO until at least one element has been read out and the Tx Event FIFO Get Index has been
incremented. In case a Tx event occurs while the Tx Event FIFO is full, this event is discarded and
interrupt flag IR.TEFL is set.
To avoid a Tx Event FIFO overflow, the Tx Event FIFO watermark can be used. When the Tx Event FIFO
fill level reaches the Tx Event FIFO watermark configured by TXEFC.EFWM, interrupt flag IR.TEFW is
set.
When reading from the Tx Event FIFO, two times the Tx Event FIFO Get Index TXEFS.EFGI has to be
added to the Tx Event FIFO start address TXEFC.EFSA.
34.6.7 FIFO Acknowledge Handling
The Get Indexes of Rx FIFO 0, Rx FIFO 1 and the Tx Event FIFO are controlled by writing to the
corresponding FIFO Acknowledge Index (refer to 34.8.29 RXF0A, 34.8.33 RXF1A and 34.8.47 TXEFA).
Writing to the FIFO Acknowledge Index will set the FIFO Get Index to the FIFO Acknowledge Index plus
one and thereby updates the FIFO Fill Level. There are two use cases:
When only a single element has been read from the FIFO (the one being pointed to by the Get Index),
this Get Index value is written to the FIFO Acknowledge Index.
When a sequence of elements has been read from the FIFO, it is sufficient to write the FIFO
Acknowledge Index only once at the end of that read sequence (value: Index of the last element read), to
update the FIFO’s Get Index.
Due to the fact that the CPU has free access to the CAN’s Message RAM, special care has to be taken
when reading FIFO elements in an arbitrary order (Get Index not considered). This might be useful when
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reading a High Priority Message from one of the two Rx FIFOs. In this case the FIFO’s Acknowledge
Index should not be written because this would set the Get Index to a wrong position and also alters the
FIFO’s Fill Level. In this case some of the older FIFO elements would be lost.
Note:  The application has to ensure that a valid value is written to the FIFO Acknowledge Index. The
CAN does not check for erroneous values.
34.6.8 Interrupts
The CAN has the following interrupt sources:
• Access to Reserved Address
• Protocol Errors (Data Phase / Arbitration Phase)
• Watchdog Interrupt
• Bus_Off Status
• Error Warning & Passive
• Error Logging Overflow
• Message RAM Bit Errors (Uncorrected / Corrected)
• Message stored to Dedicated Rx Buffer
• Timeout Occurred
• Message RAM Access Failure
• Timestamp Wraparound
• Tx Event FIFO statuses (Element Lost / Full / Watermark Reached / New Entry)
• Tx FIFO Empty
• Transmission Cancellation Finished
• Timestamp Completed
• High Priority Message
• Rx FIFO 1 Statuses (Message Lost / Full / Watermark Reached / New Message)
• Rx FIFO 0 Statuses (Message Lost / Full / Watermark Reached / New Message)
Each interrupt source has an interrupt flag associated with it. The interrupt flag register (IR) is set when
the interrupt condition occurs. Each interrupt can be individually enabled by writing ‘1’ or disabled by
writing ‘0’ to the corresponding bit in the interrupt enable register (IE). Each interrupt flag can be assigned
to one of two interrupt service lines.
An interrupt request is generated when an interrupt flag is set, the corresponding interrupt enable is set,
and the corresponding service line enable assigned to the interrupt is set. The interrupt request remains
active until the interrupt flag is cleared, the interrupt is disabled, the service line is disabled, or the CAN is
reset. Refer to 34.8.16 IR for details on how to clear interrupt flags. All interrupt requests from the
peripheral are sent to the NVIC. The user must read the IR register to determine which interrupt condition
is present.
Note that interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
34.6.9 Sleep Mode Operation
The CAN can be configured to operate in any idle sleep mode. Tha CAN cannot operate in Standby sleep
mode.
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The CAN has its own low power mode that may be used at any time without disabling the CAN. It is also
mandatory to allow the CAN to complete all pending transactions before entering standby by activating
this low power mode. This is performed by writing one to the Clock Stop Request bit in the CC Control
register (CCCR.CSR = 1). Once all pending transactions are completed and the idle bus state is
detected, the CAN will automatically set the Clock Stop Acknowledge bit (CCCR.CSA = 1). The CAN then
reverts back to its initial state (CCCR.INIT = 1), blocking further transfers, and it is now safe for
CLK_CANx_APB and GCLK_CANx to be switched off and the system may go to standby.
To leave low power mode, CLK_CANx_APB and GCLK_CANx must be active before writing CCCR.CSR
to '0'. The CAN will acknowledge this by resetting CCCR.CSA = 0. Afterwards, the application can restart
CAN communication by resetting bit CCCR.INIT.
34.6.10 Synchronization
Due to the asynchronicity between the main clock domain (CLK_CAN_APB) and the peripheral clock
domain (GCLK_CAN) some registers are synchronized when written. When a write-synchronized register
is written, the read back value will not be updated until the register has completed synchronization.
The following bits and registers are write-synchronized:
l Initialization bit in CC Control register (CCCR.INIT)
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34.7 Register Summary
Offset Name Bit Pos.
0x00 CREL
7:0
15:8
23:16 SUBSTEP[3:0]
31:24 REL[3:0] STEP[3:0]
0x04 ENDN
7:0 ETV[7:0]
15:8 ETV[15:8]
23:16 ETV[23:16]
31:24 ETV[31:24]
0x08 MRCFG
7:0 DQOS[1:0]
15:8
23:16
31:24
0x0C DBTP
7:0 DTSEG2[3:0] DSJW[3:0]
15:8 DTSEG1[4:0]
23:16 TDC DBRP[4:0]
31:24
0x10 TEST
7:0 RX TX[1:0] LBCK
15:8
23:16
31:24
0x14 RWD
7:0 WDC[7:0]
15:8 WDV[7:0]
23:16
31:24
0x18 CCCR
7:0 TEST DAR MON CSR CSA ASM CCE INIT
15:8 TXP EFBI PXHD BRSE FDOE
23:16
31:24
0x1C NBTP
7:0 NTSEG2[6:0]
15:8 NTSEG1[7:0]
23:16 NBRP[7:0]
31:24 NSJW[6:0] NBRP[8:8]
0x20 TSCC
7:0 TSS[1:0]
15:8
23:16 TCP[3:0]
31:24
0x24 TSCV
7:0 TSC[7:0]
15:8 TSC[14:8]
23:16
31:24
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...........continued
Offset Name Bit Pos.
0x28 TOCC
7:0 TOS[1:0] ETOC
15:8
23:16 TOP[7:0]
31:24 TOP[15:8]
0x2C TOCV
7:0 TOC[7:0]
15:8 TOC[15:8]
23:16
31:24
0x30
...
0x3F
Reserved
0x40 ECR
7:0 TEC[7:0]
15:8 RP REC[6:0]
23:16 CEL[7:0]
31:24
0x44 PSR
7:0 BO EW EP ACT[1:0] LEC[2:0]
15:8 PXE RFDF RBRS RESI DLEC[2:0]
23:16 TDCV[6:0]
31:24
0x48 TDCR
7:0 TDCF[6:0]
15:8 TDCO[6:0]
23:16
31:24
0x4C
...
0x4F
Reserved
0x50 IR
7:0 RF1L RF1F RF1W RF1N RF0L RF0F RF0W RF0N
15:8 TEFL TEFF TEFW TEFN TFE TCF TC HPM
23:16 EP ELO BEU BEC DRX TOO MRAF TSW
31:24 ARA PED PEA WDI BO EW
0x54 IE
7:0 RF1LE RF1FE RF1WE RF1NE RF0LE RF0FE RF0WE RF0NE
15:8 TEFLE TEFFE TEFWE TEFNE TFEE TCFE TCE HPME
23:16 EPE ELOE BEUE BECE DRXE TOOE MRAFE TSWE
31:24 ARAE PEDE PEAE WDIE BOE EWE
0x58 ILS
7:0 RF1LL RF1FL RF1WL RF1NL RF0LL RF0FL RF0WL RF0NL
15:8 TEFLL TEFFL TEFWL TEFNL TFEL TCFL TCL HPML
23:16 EPL ELOL BEUL BECL DRXL TOOL MRAFL TSWL
31:24 ARAL PEDL PEAL WDIL BOL EWL
0x5C ILE
7:0 EINTn[1:0]
15:8
23:16
31:24
0x60
...
0x7F
Reserved
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 699
...........continued
Offset Name Bit Pos.
0x80 GFC
7:0 ANFS[1:0] ANFE[1:0] RRFS RRFE
15:8
23:16
31:24
0x84 SIDFC
7:0 FLSSA[7:0]
15:8 FLSSA[15:8]
23:16 LSS[7:0]
31:24
0x88 XIDFC
7:0 FLESA[7:0]
15:8 FLESA[15:8]
23:16 LSE[6:0]
31:24
0x8C
...
0x8F
Reserved
0x90 XIDAM
7:0 EIDM[7:0]
15:8 EIDM[15:8]
23:16 EIDM[23:16]
31:24 EIDM[28:24]
0x94 HPMS
7:0 MSI[1:0] BIDX[5:0]
15:8 FLST FIDX[6:0]
23:16
31:24
0x98 NDAT1
7:0 NDn[7:0]
15:8 NDn[15:8]
23:16 NDn[23:16]
31:24 NDn[31:24]
0x9C NDAT2
7:0 NDn[7:0]
15:8 NDn[15:8]
23:16 NDn[23:16]
31:24 NDn[31:24]
0xA0 RXF0C
7:0 F0SA[7:0]
15:8 F0SA[15:8]
23:16 F0S[6:0]
31:24 F0OM F0WM[6:0]
0xA4 RXF0S
7:0 F0FL[6:0]
15:8 F0GI[5:0]
23:16 F0PI[5:0]
31:24 RF0L F0F
0xA8 RXF0A
7:0 F0AI[5:0]
15:8
23:16
31:24
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 700
...........continued
Offset Name Bit Pos.
0xAC RXBC
7:0 RBSA[7:0]
15:8 RBSA[15:8]
23:16
31:24
0xB0 RXF1C
7:0 F1SA[7:0]
15:8 F1SA[15:8]
23:16 F1S[6:0]
31:24 F1OM F1WM[6:0]
0xB4 RXF1S
7:0 F1FL[6:0]
15:8 F1GI[5:0]
23:16 F1PI[5:0]
31:24 DMS[1:0] RF1L F1F
0xB8 RXF1A
7:0 F1AI[5:0]
15:8
23:16
31:24
0xBC RXESC
7:0 F1DS[2:0] F0DS[2:0]
15:8 RBDS[2:0]
23:16
31:24
0xC0 TXBC
7:0 TBSA[7:0]
15:8 TBSA[15:8]
23:16 NDTB[5:0]
31:24 TFQM TFQS[5:0]
0xC4 TXFQS
7:0 TFFL[5:0]
15:8 TFGI[4:0]
23:16 TFQF TFQPI[4:0]
31:24
0xC8 TXESC
7:0 TBDS[2:0]
15:8
23:16
31:24
0xCC TXBRP
7:0 TRPn[7:0]
15:8 TRPn[15:8]
23:16 TRPn[23:16]
31:24 TRPn[31:24]
0xD0 TXBAR
7:0 ARn[7:0]
15:8 ARn[15:8]
23:16 ARn[23:16]
31:24 ARn[31:24]
0xD4 TXBCR
7:0 CRn[7:0]
15:8 CRn[15:8]
23:16 CRn[23:16]
31:24 CRn[31:24]
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 701
...........continued
Offset Name Bit Pos.
0xD8 TXBTO
7:0 TOn[7:0]
15:8 TOn[15:8]
23:16 TOn[23:16]
31:24 TOn[31:24]
0xDC TXBCF
7:0 CFn[7:0]
15:8 CFn[15:8]
23:16 CFn[23:16]
31:24 CFn[31:24]
0xE0 TXBTIE
7:0 TIEn[7:0]
15:8 TIEn[15:8]
23:16 TIEn[23:16]
31:24 TIEn[31:24]
0xE4 TXBCIE
7:0 CFIEn[7:0]
15:8 CFIEn[15:8]
23:16 CFIEn[23:16]
31:24 CFIEn[31:24]
0xE8
...
0xEF
Reserved
0xF0 TXEFC
7:0 EFSA[7:0]
15:8 EFSA[15:8]
23:16 EFS[5:0]
31:24 EFWM[5:0]
0xF4 TXEFS
7:0 EFFI[4:0]
15:8 EFGI[4:0]
23:16 EFP[4:0]
31:24 TEFL EFF
0xF8 TXEFA
7:0 EFAI[4:0]
15:8
23:16
31:24
34.8 Register Description
Registers are 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the 8-bit
quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be accessed
directly.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 702
34.8.1 Core Release
Name:  CREL
Offset:  0x00
Reset:  0x32100000
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
REL[3:0] STEP[3:0]
Access R R R R R R R R
Reset 0 0 1 1 0 0 1 0
Bit 23 22 21 20 19 18 17 16
SUBSTEP[3:0]
Access R R R R
Reset 0 0 0 1
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
Access
Reset
Bits 31:28 – REL[3:0] Core Release
One digit, BCD-coded.
Bits 27:24 – STEP[3:0] Step of Core Release
One digit, BCD-coded.
Bits 23:20 – SUBSTEP[3:0]  Sub-step of Core Release
One digit, BCD-coded.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 703
34.8.2 Endian
Name:  ENDN
Offset:  0x04
Reset:  0x87654321
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
ETV[31:24]
Access R R R R R R R R
Reset 1 0 0 0 0 1 1 1
Bit 23 22 21 20 19 18 17 16
ETV[23:16]
Access R R R R R R R R
Reset 0 1 1 0 0 1 0 1
Bit 15 14 13 12 11 10 9 8
ETV[15:8]
Access R R R R R R R R
Reset 0 1 0 0 0 0 1 1
Bit 7 6 5 4 3 2 1 0
ETV[7:0]
Access R R R R R R R R
Reset 0 0 1 0 0 0 0 1
Bits 31:0 – ETV[31:0] Endianness Test Value
The endianness test value is 0x87654321
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 704
34.8.3 Message RAM Configuration
Name:  MRCFG
Offset:  0x08
Reset:  0x00000002
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
DQOS[1:0]
Access R/W R/W
Reset 1 0
Bits 1:0 – DQOS[1:0] Data Quality of Service
This field defines the memory priority access during the Message RAM read/write data operation.
Value Name Description
0x0 DISABLE Background (no sensitive operation)
0x1 LOW Sensitive bandwidth
0x2 MEDIUM Sensitive latency
0x3 HIGH Critical latency
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 705
34.8.4 Data Bit Timing and Prescaler
Name:  DBTP
Offset:  0x0C
Reset:  0x00000A33
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
The CAN bit time may be programmed in the range of 4 to 49 time quanta. The CAN time quantum may
be programmed in the range of 1 to 32 GCLK_CAN periods. tq = (DBRP + 1) mtq.
Note: 
With a GCLK_CAN of 8MHz, the reset value 0x00000A33 configures the CAN for a fast bit rate of 500
kBits/s.
The bit rate configured for the CAN FD data phase via DBTP must be higher or equal to the bit rate
configured for the arbitration phase via NBTP.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
TDC DBRP[4:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DTSEG1[4:0]
Access R/W R/W R/W R/W R/W
Reset 0 1 0 1 0
Bit 7 6 5 4 3 2 1 0
DTSEG2[3:0] DSJW[3:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 1 1 0 0 1 1
Bit 23 – TDC Transceiver Delay Compensation
Value Description
0Transceiver Delay Compensation disabled.
1Transceiver Delay Compensation enabled.
Bits 20:16 – DBRP[4:0] Data Baud Rate Prescaler
Value Description
0x00 -
0x1F
The value by which the oscillator frequency is divided for generating the bit time quanta. The
bit time is built up from a multiple of this quanta. Valid values for the Baud Rate Prescaler are
0 to 31. The actual interpretation by the hardware of this value is such that one more than
the value programmed here is used.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 706
Bits 12:8 – DTSEG1[4:0] Fast time segment before sample point
Value Description
0x00 -
0x1F
Valid values are 0 to 31. The actual interpretation by the hardware of this value is such that
one more than the programmed value is used. DTSEG1 is the sum of Prop_Seg and
Phase_Seg1.
Bits 7:4 – DTSEG2[3:0] Data time segment after sample point
Value Description
0x0 -
0xF
Valid values are 0 to 15. The actual interpretation by the hardware of this value is such that
one more than the programmed value is used. DTSEG2 is Phase_Seg2.
Bits 3:0 – DSJW[3:0] Data (Re)Syncronization Jump Width
Value Description
0x0 -
0xF
Valid values are 0 to 15. The actual interpretation by the hardware of this value is such that
one more than the programmed value is used.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 707
34.8.5 Test
Name:  TEST
Offset:  0x10
Reset:  0x00000000
Property:  Read-only, Write-restricted
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
RX TX[1:0] LBCK
Access R R/W R/W R/W
Reset 0 0 0 0
Bit 7 – RX Receive Pin
Monitors the actual value of pin CAN_RX
Value Description
0The CAN bus is dominant (CAN_RX = 0).
1The CAN bus is recessive (CAN_RX = 1).
Bits 6:5 – TX[1:0] Control of Transmit Pin
This field defines the control of the transmit pin.
Value Name Description
0x0 CORE Reset value, CAN_TX controlled by CAN core, updated at the end of CAN bit
time.
0x1 SAMPLE Sample Point can be monitored at pin CAN_TX.
0x2 DOMINANT Dominant (‘0’) level at pin CAN_TX.
0x3 RECESSIVE Recessive (‘1’) level at pin CAN_TX.
Bit 4 – LBCK Loop Back Mode
Value Description
0Loop Back Mode is disabled.
1Loop Back Mode is enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 708
34.8.6 RAM Watchdog
Name:  RWD
Offset:  0x14
Reset:  0x00000000
Property:  Read-only, Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
The RAM Watchdog monitors the READY output of the Message RAM. A Message RAM access via the
CAN’s AHB Master Interface starts the Message RAM Watchdog Counter with the value configured by
RWD.WDC. The counter is reloaded with RWD.WDC when the Message RAM signals successful
completion by activating its READY output. In case there is no response from the Message RAM until the
counter has counted down to zero, the counter stops and interrupt IR.WDI is set.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
WDV[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WDC[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 15:8 – WDV[7:0] Watchdog Value
Actual Message RAM Watchdog Counter Value.
Bits 7:0 – WDC[7:0] Watchdog Configuration
Start value of the Message RAM Watchdog Counter. With the reset value of 0x00 the counter is disabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 709
34.8.7 CC Control
Name:  CCCR
Offset:  0x18
Reset:  0x00000001
Property:  Read-only, Write-restricted
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TXP EFBI PXHD BRSE FDOE
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TEST DAR MON CSR CSA ASM CCE INIT
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 1
Bit 14 – TXP Transmit Pause
This bit field is write-restricted and only writable if bit fields CCE = 1 and INIT = 1.
Value Description
0Transmit pause disabled.
1Transmit pause enabled. The CAN pauses for two CAN bit times before starting the next
transmission after itself has successfully transmitted a frame.
Bit 13 – EFBI Edge Filtering during Bus Integration
Value Description
0Edge filtering is disabled.
1Two consecutive dominant tq required to detect an edge for hard synchronization.
Bit 12 – PXHD Protocol Exception Handling Disable
Note:  When protocol exception handling is disabled, the CAN will transmit an error frame when it
detects a protocol exception condition.
Value Description
0Protocol exception handling enabled.
1Protocol exception handling disabled.
Bit 9 – BRSE Bit Rate Switch Enable
Note:  When CAN FD operation is disabled FDOE = 0, BRSE is not evaluated.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 710
Value Description
0Bit rate switching for transmissions disabled.
1Bit rate switching for transmissions enabled.
Bit 8 – FDOE FD Operation Enable
Value Description
0FD operation disabled.
1FD operation enabled.
Bit 7 – TEST Test Mode Enable
This bit field is write-restricted.
Writing a 0 to this field is always allowed.
Writing a 1 to this field is only allowed if bit fields CCE = 1 and INIT = 1.
Value Description
0Normal operation. Register TEST holds reset values.
1Test Mode, write access to register TEST enabled.
Bit 6 – DAR Disable Automatic Retransmission
This bit field is write-restricted and only writable if bit fields CCE = 1 and INIT = 1.
Value Description
0Automatic retransmission of messages not transmitted successfully enabled.
1Automatic retransmission disabled.
Bit 5 – MON Bus Monitoring Mode
This bit field is write-restricted.
Writing a 0 to this field is always allowed.
Writing a 1 to this field is only allowed if bit fields CCE = 1 and INIT = 1.
Value Description
0Bus Monitoring Mode is disabled.
1Bus Monitoring Mode is enabled.
Bit 4 – CSR Clock Stop Request
Value Description
0No clock stop is requested.
1Clock stop requested. When clock stop is requested, first INIT and then CSA will be set after
all pending transfer requests have been completed and the CAN bus reached idle.
Bit 3 – CSA Clock Stop Acknowledge
Value Description
0No clock stop acknowledged.
1CAN may be set in power down by stopping CLK_CAN_APB and GCLK_CAN.
Bit 2 – ASM Restricted Operation Mode
This bit field is write-restricted.
Writing a 0 to this field is always allowed.
Writing a 1 to this field is only allowed if bit fields CCE = 1 and INIT = 1.
Value Description
0Normal CAN operation.
1Restricted Operation Mode active.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 711
Bit 1 – CCE Configuration Change Enable
This bit field is write-restricted and only writable if bit field INIT = 1.
Value Description
0The CPU has no write access to the protected configuration registers.
1The CPU has write access to the protected configuration registers (while CCCR.INIT = 1).
Bit 0 – INIT Initialization
Due to the synchronization mechanism between the two clock domains, there may be a delay until the
value written to INIT can be read back. The programmer has to assure that the previous value written to
INIT has been accepted by reading INIT before setting INIT to a new value.
Value Description
0Normal Operation.
1Initialization is started.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 712
34.8.8 Nominal Bit Timing and Prescaler
Name:  NBTP
Offset:  0x1C
Reset:  0x00000A33
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
The CAN bit time may be programmed in the range of 4 to 385 time quanta. The CAN time quantum may
be programmed in the range of 1 to 512 GCLK_CAN periods. tq = (NBRP + 1) mtq.
Note:  With a CAN clock (GCLK_CAN) of 8MHz, the reset value 0x06000A03 configures the CAN for a
bit rate of 500 kBits/s.
Bit 31 30 29 28 27 26 25 24
NSJW[6:0] NBRP[8:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 1 1 0
Bit 23 22 21 20 19 18 17 16
NBRP[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
NTSEG1[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 1 0 1 0
Bit 7 6 5 4 3 2 1 0
NTSEG2[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 1 1
Bits 31:25 – NSJW[6:0] Nominal (Re)Syncronization Jump Width
Value Description
0x00 -
0x7F
Valid values are 0 to 127. The actual interpretation by the hardware of this value is such that
one more than the programmed value is used.
Bits 24:16 – NBRP[8:0] Nominal Baud Rate Prescaler
Value Description
0x000 -
0x1FF
The value by which the oscillator frequency is divided for generating the bit time quanta. The
bit time is built up from a multiple of this quanta. Valid values for the Baud Rate Prescaler are
0 to 511. The actual interpretation by the hardware of this value is such that one more than
the value programmed here is used.
Bits 15:8 – NTSEG1[7:0] Nominal Time segment before sample point
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 713
Value Description
0x00 -
0x7F
Valid values are 1 to 255. The actual interpretation by the hardware of this value is such that
one more than the programmed value is used. NTSEG1 is the sum of Prop_Seg and
Phase_Seg1.
Bits 6:0 – NTSEG2[6:0] Time segment after sample point
Value Description
0x00 -
0x7F
Valid values are 0 to 127. The actual interpretation by the hardware of this value is such that
one more than the programmed value is used. NTSEG2 is Phase_Seg2.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 714
34.8.9 Timestamp Counter Configuration
Name:  TSCC
Offset:  0x20
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
TCP[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TSS[1:0]
Access R/W R/W
Reset 0 0
Bits 19:16 – TCP[3:0] Timestamp Counter Prescaler
Value Description
0x0 -
0xF
Configures the timestamp and timeout counters time unit in multiples of CAN bit times
[1...16]. The actual interpretation by the hardware of this value is such that one more than
the value programmed here is used.
Bits 1:0 – TSS[1:0] Timestamp Select
This field defines the timestamp counter selection.
Value Name Description
0x0 or
0x3
ZERO Timestamp counter value always 0x0000.
0x1 INC Timestamp counter value incremented by TCP.
0x2 - Reserved
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 715
34.8.10 Timestamp Counter Value
Name:  TSCV
Offset:  0x24
Reset:  0x00000000
Property:  Read-only
Note: 
1. A write access to TSCV while in internal mode clears the Timestamp Counter value. A write access
to TSCV while in external mode has no impact.
2. A “wrap around” is a change of the Timestamp Counter value from non-zero to zero not caused by
the write access to TSCV.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TSC[14:8]
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TSC[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 14:0 – TSC[14:0] Timestamp Counter
The internal Timestamp Counter value is captured on start of frame (both Rx and Tx). When TSCC.TSS =
0x1, the Timestamp Counter is incremented in multiples of CAN bit times [1...16] depending on the
configuration of TSCC.TCP. A wrap around sets interrupt flag IR.TSW.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 716
34.8.11 Timeout Counter Configuration
Name:  TOCC
Offset:  0x28
Reset:  0xFFFF0000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
TOP[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 23 22 21 20 19 18 17 16
TOP[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TOS[1:0] ETOC
Access R/W R/W R/W
Reset 0 0 0
Bits 31:16 – TOP[15:0] Timeout Period
Start value of the Timeout Counter (down-counter). Configures the Timeout Period.
Bits 2:1 – TOS[1:0] Timeout Select
When operating in Continuous mode, a write to TOCV presets the counter to the value configured by
TOCC.TOP and continues down-counting. When the Timeout Counter is controlled by one of the FIFOs,
an empty FIFO presets the counter to the value configured by TOCC.TOP. Down-counting is started
when the first FIFO element is stored.
Value Name Description
0x0 CONT Continuous operation.
0x1 TXEF Timeout controlled by TX Event FIFO.
0x2 RXF0 Timeout controlled by Rx FIFO 0.
0x3 RXF1 Timeout controlled by Rx FIFO 1.
Bit 0 – ETOC Enable Timeout Counter
Value Description
0Timeout Counter disabled.
1Timeout Counter enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 717
34.8.12 Timeout Counter Value
Name:  TOCV
Offset:  0x2C
Reset:  0x0000FFFF
Property:  Read-only
Note:  A write access to TOCV reloads the Timeout Counter with the value of TOCV.TOP.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TOC[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 7 6 5 4 3 2 1 0
TOC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bits 15:0 – TOC[15:0] Timeout Counter
The Timeout Counter is decremented in multiples of CAN bit times [1...16] depending on the configuration
of TSCC.TCP. When decremented to zero, interrupt flag IR.TOO is set and the Timeout Counter is
stopped. Start and reset/restart conditions are configured via TOCC.TOS.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 718
34.8.13 Error Counter
Name:  ECR
Offset:  0x40
Reset:  0x00000000
Property:  Read-only
Note:  When CCCR.ASM is set, the CAN protocol controller does not increment TECand REC when a
CAN protocol error is detected, but CEL is still incremented.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CEL[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
RP REC[6:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TEC[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 23:16 – CEL[7:0] CAN Error Logging
The counter is incremented each time when a CAN protocol error causes the Transmit Error Counter or
Receive Error Counter to be incremented. It is reset by read access to CEL. The counter stops at 0xFF;
the next increment of TEC or REC sets interrupt flag IR.ELO.
Bit 15 – RP Receive Error Passive
Bits 14:8 – REC[6:0] Receive Error Counter
Actual state of the Receive Error Counter, values between 0 and 127.
Bits 7:0 – TEC[7:0] Transmit Error Counter
Actual state of the Transmit Error Counter, values between 0 and 255.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 719
34.8.14 Protocol Status
Name:  PSR
Offset:  0x44
Reset:  0x00000707
Property:  Read-only
Note: 
1. When a frame in CAN FD format has reached the data phase with BRS flag set, the next CAN
event (error or valid frame) will be shown in FLEC instead of LEC. An error in a fixed stuff bit of a
CAN FD CRC sequence will be shown as a Form Error, not Stuff Error.
2. The Bus_Off recovery sequence (see CAN Specification Rev. 2.0 or ISO 11898-1) cannot be
shortened by setting or resetting CCCR.INIT. If the device goes Bus_Off, it will set CCCR.INIT of its
own accord, stopping all bus activities. Once CCCR.INIT has been cleared by the CPU, the device
will then wait for 129 occurrences of Bus Idle (129 * 11 consecutive recessive bits) before resuming
normal operation. At the end of the Bus_Off recovery sequence, the Error Management Counters
will be reset. During the waiting time after the resetting of CCCR.INIT, each time a sequence of 11
recessive bits has been monitored, a Bit0 Error code is written to PSR.LEC, enabling the CPU to
readily check up whether the CAN bus is stuck at dominant or continuously disturbed and to
monitor the Bus_Off recovery sequence. ECR.REC is used to count these sequences.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
TDCV[6:0]
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
PXE RFDF RBRS RESI DLEC[2:0]
Access R R R R R R R
Reset 0 0 0 0 1 1 1
Bit 7 6 5 4 3 2 1 0
BO EW EP ACT[1:0] LEC[2:0]
Access R R R R R R R R
Reset 0 0 0 0 0 1 1 1
Bits 22:16 – TDCV[6:0] Transmitter Delay Compensation Value
Value Description
0x00 -
0x7F
Position of the secondary sample point, defined by the sum of the measured delay from
CAN_TX to CAN_RX and TDCR.TDCO. The SSP position is, in the data phase, the number
of mtq between the start of the transmitted bit and the secondary sample point. Valid values
are 0 to 127 mtq.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 720
Bit 14 – PXE Protocol Exception Event
This field is cleared on read access.
Value Description
0No protocol exception event occurred since last read access.
1Protocol exception event occurred.
Bit 13 – RFDF Received a CAN FD Message
This field is cleared on read access.
Value Description
0Since this bit was reset by the CPU, no CAN FD message has been received.
1Message in CAN FD format with FDF flag set has been received. This bit is set independent
of acceptance filtering.
Bit 12 – RBRS BRS flag of last received CAN FD Message
This field is cleared on read access.
Value Description
0Last received CAN FD message did not have its BRS flag set.
1Last received CAN FD message had its BRS flag set. This bit is set together with RFDF,
independent of acceptance filtering.
Bit 11 – RESI ESI flag of last received CAN FD Message
This field is cleared on read access.
Value Description
0Last received CAN FD message did not have its ESI flag set.
1Last received CAN FD message had its ESI flag set.
Bits 10:8 – DLEC[2:0] Data Last Error Code
Type of last error that occurred in the data phase of a CAN FD format frame with its BRS flag set. Coding
is the same as for LEC. This field will be cleared to zero when a CAN FD format frame with its BRS flag
set has been transferred (reception or transmission) without error.
Bit 7 – BO Bus_Off Status
Value Description
0The CAN is not Bus_Off.
1The CAN is in Bus_Off state.
Bit 6 – EW Error Warning Status
Value Description
0Both error counters are below the Error_Warning limit of 96.
1At least one of the error counter has reached the Error_Warning limit of 96.
Bit 5 – EP Error Passive
Value Description
0The CAN is in the Error_Active state. It normally takes part in bus communication and sends
an active error flag when an error has been detected.
1The CAN is in the Error_Passive state.
Bits 4:3 – ACT[1:0] Activity
Monitors the module’s CAN communication state.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 721
Value Name Description
0x0 SYNC Node is synchronizing on CAN communication.
0x1 IDLE Node is neither receiver nor transmitter.
0x2 RX Node is operating as receiver.
0x3 TX Node is operating as transmitter.
Bits 2:0 – LEC[2:0] Last Error Code
The LEC indicates the type of the last error to occur on the CAN bus. This field will be cleared to ‘0’ when
a message has been transferred (reception or transmission) without error.
This field is set on read access.
Value Name Description
0x0 NONE No Error: No error occurred since LEC has been reset by successful reception or
transmission.
0x1 STUFF Stuff Error: More than 5 equal bits in a sequence have occurred in a part of a
received message where this is not allowed.
0x2 FORM Form Error: A fixed format part of a received frame has the wrong format.
0x3 ACK Ack Error: The message transmitted by the CAN was not acknowledged by another
node.
0x4 BIT1 Bit1 Error: During the transmission of a message (with the exception of the
arbitration field), the device wanted to send a recessive level (bit of logical value ‘1’),
but the monitored bus was dominant.
0x5 BIT0 Bit0 Error: During the transmission of a message (or acknowledge bit, or active
error flag, or overload flag), the device wanted to send a dominant level (data or
identifier bit logical value ‘0’), but the monitored bus value was recessive. During
Bus_Off recovery this status is set each time a sequence of 11 recessive bits have
been monitored. This enables the CPU to monitor the proceeding of the Bus_Off
recovery sequence (indicating the bus is not stuck at dominant or continuously
disturbed).
0x6 CRC CRC Error: The CRC checksum of a received message was incorrect. The CRC of
an incoming message does not match with the CRC calculated from the received
data.
0x7 NC No Change: Any read access to the Protocol Status Register re-initializes the LEC
to ‘7’. When the LEC shows the value ‘7’, no CAN bus event was detected since the
last CPU read access to the Protocol Status Register.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 722
34.8.15 Transmitter Delay Compensation
Name:  TDCR
Offset:  0x48
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TDCO[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TDCF[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 14:8 – TDCO[6:0] Transmitter Delay Compensation Offset
Value Description
0x00 -
0x7F
Offset value defining the distance between the measured delay from CAN_TX to CAN_RX
and the secondary sample point. Valid values are 0 to 127 mtq.
Bits 6:0 – TDCF[6:0] Transmitter Delay Compensation Filter Window Length
Value Description
0x00 -
0x7F
Defines the minimum value for the SSP position, dominant edges on CAN_RX that would
result in an earlier SSP position are ignored for transmitter delay measurement. The feature
is enabled when TDCF is configured to a value greater than TDCO. Valid values are 0 to 127
mtq.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 723
34.8.16 Interrupt
Name:  IR
Offset:  0x50
Reset:  0x00000000
Property:  -
The flags are set when one of the listed conditions is detected (edge-sensitive). A flag is cleared by
writing a 1 to the corresponding bit field. Writing a 0 has no effect. A hard reset will clear the register.
Bit 31 30 29 28 27 26 25 24
ARA PED PEA WDI BO EW
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EP ELO BEU BEC DRX TOO MRAF TSW
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TEFL TEFF TEFW TEFN TFE TCF TC HPM
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RF1L RF1F RF1W RF1N RF0L RF0F RF0W RF0N
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 29 – ARA Access to Reserved Address
Value Description
0No access to reserved address occurred.
1Access to reserved address occurred.
Bit 28 – PED Protocol Error in Data Phase
Value Description
0No protocol error in data phase.
1Protocol error in data phase detected (PSR.DLEC != 0,7).
Bit 27 – PEA Protocol Error in Arbitration Phase
Value Description
0No protocol error in arbitration phase.
1Protocol error in arbitration phase detected (PSR.LEC != 0,7).
Bit 26 – WDI Watchdog Interrupt
Value Description
0No Message RAM Watchdog event occurred.
1Message RAM Watchdog event due to missing READY.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 724
Bit 25 – BO Bus_Off Status
Value Description
0Bus_Off status unchanged.
1Bus_Off status changed.
Bit 24 – EW Error Warning Status
Value Description
0Error_Warning status unchanged.
1Error_Warning status changed.
Bit 23 – EP Error Passive
Value Description
0Error_Passive status unchanged.
1Error_Passive status changed.
Bit 22 – ELO Error Logging Overflow
Value Description
0CAN Error Logging Counter did not overflow.
1Overflow of CAN Error Logging Counter occurred.
Bit 21 – BEU Bit Error Uncorrected
Message RAM bit error detected, uncorrected. Generated by an optional external parity / ECC logic
attached to the Message RAM. An uncorrected Message RAM bit sets CCCR.INIT to 1. This is done to
avoid transmission of corrupted data.
Value Description
0Not bit error detected when reading from Message RAM.
1Bit error detected, uncorrected (e.g. parity logic).
Bit 20 – BEC Bit Error Corrected
Message RAM bit error detected and corrected. Generated by an optional external parity / ECC logic
attached to the Message RAM.
Value Description
0Not bit error detected when reading from Message RAM.
1Bit error detected and corrected (e.g. ECC).
Bit 19 – DRX Message stored to Dedicated Rx Buffer
The flag is set whenever a received message has been stored into a dedicated Rx Buffer.
Value Description
0No Rx Buffer updated.
1At least one received message stored into a Rx Buffer.
Bit 18 – TOO Timeout Occurred
Value Description
0No timeout.
1Timeout reached.
Bit 17 – MRAF Message RAM Access Failure
The flag is set, when the Rx Handler
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 725
• has not completed acceptance filtering or storage of an accepted message until the arbitration field of
the following message has been received. In this case acceptance filtering or message storage is
aborted and the Rx Handler starts processing of the following message.
• was not able to write a message to the Message RAM. In this case message storage is aborted.
In both cases the FIFO put index is not updated resp. the New Data flag for a dedicated Rx Buffer is not
set, a partly stored message is overwritten when the next message is stored to this location.
The flag is also set when the Tx Handler was not able to read a message from the Message RAM in time.
In this case message transmission is aborted. In case of a Tx Handler access failure the CAN is switched
into Restricted Operation Mode. To leave Restricted Operation Mode, the Host CPU has to reset
CCCR.ASM.
Value Description
0No Message RAM access failure occurred.
1Message RAM access failure occurred.
Bit 16 – TSW Timestamp Wraparound
Value Description
0No timestamp counter wrap-around.
1Timestamp counter wrapped around.
Bit 15 – TEFL Tx Event FIFO Element Lost
Value Description
0No Tx Event FIFO element lost.
1Tx Event FIFO element lost, also set after write attempt to Tx Event FIFO of size zero.
Bit 14 – TEFF Tx Event FIFO Full
Value Description
0Tx Event FIFO not full.
1Tx Event FIFO full.
Bit 13 – TEFW Tx Event FIFO Watermark Reached
Value Description
0Tx Event FIFO fill level below watermark.
1Tx Event FIFO fill level reached watermark.
Bit 12 – TEFN Tx Event FIFO New Entry
Value Description
0Tx Event FIFO unchanged.
1Tx Handler wrote Tx Event FIFO element.
Bit 11 – TFE Tx FIFO Empty
Value Description
0Tx FIFO non-empty.
1Tx FIFO empty.
Bit 10 – TCF Transmission Cancellation Finished
Value Description
0No transmission cancellation finished.
1Transmission cancellation finished.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 726
Bit 9 – TC Timestamp Completed
Value Description
0No transmission completed.
1Transmission completed.
Bit 8 – HPM High Priority Message
Value Description
0No high priority message received.
1High priority message received.
Bit 7 – RF1L Rx FIFO 1 Message Lost
Value Description
0No Rx FIFO 1 message lost.
1Rx FIFO 1 message lost. also set after write attempt to Rx FIFO 1 of size zero.
Bit 6 – RF1F Rx FIFO 1 Full
Value Description
0Rx FIFO 1 not full.
1Rx FIFO 1 full.
Bit 5 – RF1W Rx FIFO 1 Watermark Reached
Value Description
0Rx FIFO 1 fill level below watermark.
1Rx FIFO 1 fill level reached watermark.
Bit 4 – RF1N Rx FIFO 1 New Message
Value Description
0No new message written to Rx FIFO 1.
1New message written to Rx FIFO 1.
Bit 3 – RF0L Rx FIFO 0 Message Lost
Value Description
0No Rx FIFO 0 message lost.
1Rx FIFO 0 message lost. also set after write attempt to Rx FIFO 0 of size zero.
Bit 2 – RF0F Rx FIFO 0 Full
Value Description
0Rx FIFO 0 not full.
1Rx FIFO 0 full.
Bit 1 – RF0W Rx FIFO 0 Watermark Reached
Value Description
0Rx FIFO 0 fill level below watermark.
1Rx FIFO 0 fill level reached watermark.
Bit 0 – RF0N Rx FIFO 0 New Message
Value Description
0No new message written to Rx FIFO 0.
1New message written to Rx FIFO 0.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 727
34.8.17 Interrupt Enable
Name:  IE
Offset:  0x54
Reset:  0x00000000
Property:  -
The settings in the Interrupt Enable register determine which status changes in the Interrupt Register will
be signalled on an interrupt line.
Bit 31 30 29 28 27 26 25 24
ARAE PEDE PEAE WDIE BOE EWE
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EPE ELOE BEUE BECE DRXE TOOE MRAFE TSWE
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TEFLE TEFFE TEFWE TEFNE TFEE TCFE TCE HPME
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RF1LE RF1FE RF1WE RF1NE RF0LE RF0FE RF0WE RF0NE
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 29 – ARAE Access to Reserved Address Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 28 – PEDE Protocol Error in Data Phase Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 27 – PEAE Protocol Error in Arbitration Phase Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 26 – WDIE Watchdog Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 728
Bit 25 – BOE Bus_Off Status Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 24 – EWE Error Warning Status Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 23 – EPE Error Passive Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 22 – ELOE Error Logging Overflow Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 21 – BEUE Bit Error Uncorrected Interrupt Enable.
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 20 – BECE Bit Error Corrected Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 19 – DRXE Message stored to Dedicated Rx Buffer Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 18 – TOOE Timeout Occurred Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 17 – MRAFE Message RAM Access Failure Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 16 – TSWE Timestamp Wraparound Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 729
Bit 15 – TEFLE Tx Event FIFO Event Lost Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 14 – TEFFE Tx Event FIFO Full Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 13 – TEFWE Tx Event FIFO Watermark Reached Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 12 – TEFNE Tx Event FIFO New Entry Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 11 – TFEE Tx FIFO Empty Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 10 – TCFE Transmission Cancellation Finished Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 9 – TCE Transmission Completed Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 8 – HPME High Priority Message Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 7 – RF1LE Rx FIFO 1 Message Lost Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 6 – RF1FE Rx FIFO 1 Full Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 730
Bit 5 – RF1WE Rx FIFO 1 Watermark Reached Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 4 – RF1NE Rx FIFO 1 New Message Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 3 – RF0LE Rx FIFO 0 Message Lost Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 2 – RF0FE Rx FIFO 0 Full Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 1 – RF0WE Rx FIFO 0 Watermark Reached Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
Bit 0 – RF0NE Rx FIFO 0 New Message Interrupt Enable
Value Description
0Interrupt disabled.
1Interrupt enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 731
34.8.18 Interrupt Line Select
Name:  ILS
Offset:  0x58
Reset:  0x00000000
Property:  -
The Interrupt Line Select register assigns an interrupt generated by a specific interrupt flag from IR to one
of the two module interrupt lines.
Bit 31 30 29 28 27 26 25 24
ARAL PEDL PEAL WDIL BOL EWL
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EPL ELOL BEUL BECL DRXL TOOL MRAFL TSWL
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TEFLL TEFFL TEFWL TEFNL TFEL TCFL TCL HPML
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RF1LL RF1FL RF1WL RF1NL RF0LL RF0FL RF0WL RF0NL
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 29 – ARAL Access to Reserved Address Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 28 – PEDL Protocol Error in Data Phase Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 27 – PEAL Protocol Error in Arbitration Phase Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 26 – WDIL Watchdog Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 732
Bit 25 – BOL Bus_Off Status Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 24 – EWL Error Warning Status Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 23 – EPL Error Passive Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 22 – ELOL Error Logging Overflow Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 21 – BEUL Bit Error Uncorrected Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 20 – BECL Bit Error Corrected Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 19 – DRXL Message stored to Dedicated Rx Buffer Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 18 – TOOL Timeout Occurred Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 17 – MRAFL Message RAM Access Failure Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 16 – TSWL Timestamp Wraparound Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 733
Bit 15 – TEFLL Tx Event FIFO Event Lost Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 14 – TEFFL Tx Event FIFO Full Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 13 – TEFWL Tx Event FIFO Watermark Reached Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 12 – TEFNL Tx Event FIFO New Entry Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 11 – TFEL Tx FIFO Empty Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 10 – TCFL Transmission Cancellation Finished Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 9 – TCL Transmission Completed Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 8 – HPML High Priority Message Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 7 – RF1LL Rx FIFO 1 Message Lost Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 6 – RF1FL Rx FIFO 1 Full Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 734
Bit 5 – RF1WL Rx FIFO 1 Watermark Reached Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 4 – RF1NL Rx FIFO 1 New Message Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 3 – RF0LL Rx FIFO 0 Message Lost Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 2 – RF0FL Rx FIFO 0 Full Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 1 – RF0WL Rx FIFO 0 Watermark Reached Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
Bit 0 – RF0NL Rx FIFO 0 New Message Interrupt Line
Value Description
0Interrupt assigned to CAN interrupt line 0.
1Interrupt assigned to CAN interrupt line 1.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 735
34.8.19 Interrupt Line Enable
Name:  ILE
Offset:  0x5C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
EINTn[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – EINTn[1:0] Enable Interrupt Line n [n = 1,0]
Value Description
0CAN interrupt line n disabled.
1CAN interrupt line n enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 736
34.8.20 Global Filter Configuration
Name:  GFC
Offset:  0x80
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ANFS[1:0] ANFE[1:0] RRFS RRFE
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5:4 – ANFS[1:0] Accept Non-matching Frames Standard
Defines how received messages with 11-bit IDs that do not match any element of the filter list are treated.
Value Name Description
0x0 RXF0 Accept in Rx FIFO 0.
0x1 RXF1 Accept in Rx FIFO 1.
0x2 or
0x3
REJECT Reject
Bits 3:2 – ANFE[1:0] Accept Non-matching Frames Extended
Defines how received messages with 29-bit IDs that do not match any element of the filter list are treated.
Value Name Description
0x0 RXF0 Accept in Rx FIFO 0.
0x1 RXF1 Accept in Rx FIFO 1.
0x2 or
0x3
REJECT Reject
Bit 1 – RRFS Reject Remote Frames Standard
Value Description
0Filter remote frames with 11-bit standard IDs.
1Reject all remote frames with 11-bit standard IDs.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 737
Bit 0 – RRFE Reject Remote Frames Extended
Value Description
0Filter remote frames with 29-bit extended IDs.
1Reject all remote frames with 29-bit extended IDS.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 738
34.8.21 Standard ID Filter Configuration
Name:  SIDFC
Offset:  0x84
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
LSS[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FLSSA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
FLSSA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:16 – LSS[7:0] List Size Standard
Value Description
0No standard Message ID filter.
1 - 128 Number of standard Message ID filter elements.
> 128 Values greater than 128 are interpreted as 128.
Bits 15:0 – FLSSA[15:0] Filter List Standard Start Address
Start address of standard Message ID filter list. When the CAN module addresses the Message RAM it
addresses 32-bit words, not single bytes. The configurable start addresses are 32-bit word addresses, i.e.
only bits 15 to 2 are evaluated, the two least significant bits are ignored. Bits 1 to 0 will always be read
back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 739
34.8.22 Extended ID Filter Configuration
Name:  XIDFC
Offset:  0x88
Reset:  0x00000000
Property:  Write-restricted
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
LSE[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FLESA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
FLESA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 22:16 – LSE[6:0] List Size Extended
Value Description
0No extended Message ID filter.
1 - 64 Number of Extended Message ID filter elements.
> 64 Values greater than 64 are interpreted as 64.
Bits 15:0 – FLESA[15:0] Filter List Extended Start Address
Start address of extended Message ID filter list. When the CAN module addresses the Message RAM it
addresses 32-bit words, not single bytes. The configurable start addresses are 32-bit word addresses, i.e.
only bits 15 to 2 are evaluated, the two least significant bits are ignored. Bits 1 to 0 will always be read
back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 740
34.8.23 Extended ID AND Mask
Name:  XIDAM
Offset:  0x90
Reset:  0x1FFFFFFF
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
EIDM[28:24]
Access R/W R/W R/W R/W R/W
Reset 1 1 1 1 1
Bit 23 22 21 20 19 18 17 16
EIDM[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 15 14 13 12 11 10 9 8
EIDM[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 7 6 5 4 3 2 1 0
EIDM[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bits 28:0 – EIDM[28:0] Extended ID Mask
For acceptance filtering of extended frames the Extended ID AND Mask is ANDed with the Message ID of
a received frame. Intended for masking of 29-bit IDs in SAE J1939. With the reset value of all bits set to
one the mask is not active.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 741
34.8.24 High Priority Message Status
Name:  HPMS
Offset:  0x94
Reset:  0x00000000
Property:  Read-only
This register is updated every time a Message ID filter element configured to generate a priority event
matches. This can be used to monitor the status of incoming high priority messages and to enable fast
access to these messages.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
FLST FIDX[6:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MSI[1:0] BIDX[5:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 – FLST Filter List
Indicates the filter list of the matching filter element.
Value Description
0Standard Filter List.
1Extended Filter List.
Bits 14:8 – FIDX[6:0] Filter Index
Index of matching filter element. Range is 0 to SIDFC.LSS - 1 (standard) or XIDFC.LSE - 1 (extended).
Bits 7:6 – MSI[1:0] Message Storage Indicator
This field defines the message storage information to a FIFO.
Value Name Description
0x0 NONE No FIFO selected.
0x1 LOST FIFO message lost.
0x2 FIFO0 Message stored in FIFO 0.
0x3 FIFO1 Message stored in FIFO 1.
Bits 5:0 – BIDX[5:0] Buffer Index
Index of Rx FIFO element to which the message was stored. Only valid when MSI[1] = 1.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 742
34.8.25 New Data 1
Name:  NDAT1
Offset:  0x98
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
NDn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
NDn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
NDn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
NDn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – NDn[31:0] New Data n [n = 0..31]
The register holds the New Data flags of Rx Buffers 0 to 31. The flags are set when the respective Rx
Buffer has been updated from a received frame. The flags remain set until the Host clears them. A flag is
cleared by writing 1 to the corresponding bit position. Writing a 0 has no effect. A hard reset will clear the
register.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 743
34.8.26 New Data 2
Name:  NDAT2
Offset:  0x9C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
NDn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
NDn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
NDn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
NDn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – NDn[31:0] New Data [n = 32..64]
The register holds the New Data flags of Rx Buffers 32 to 63. The flags are set when the respective Rx
Buffer has been updated from a received frame. The flags remain set until the Host clears them. A flag is
cleared by writing 1 to the corresponding bit position. Writing a 0 has no effect. A hard reset will clear the
register.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 744
34.8.27 Rx FIFO 0 Configuration
Name:  RXF0C
Offset:  0xA0
Reset:  0x00000000
Property:  Write-restricted
Bit 31 30 29 28 27 26 25 24
F0OM F0WM[6:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
F0S[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
F0SA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
F0SA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 31 – F0OM FIFO 0 Operation Mode
FIFO 0 can be operated in blocking or in overwrite mode.
Value Description
0FIFO 0 blocking mode.
1FIFO 0 overwrite mode.
Bits 30:24 – F0WM[6:0] Rx FIFO 0 Watermark
Value Description
0Watermark interrupt disabled.
1 - 64 Level for Rx FIFO 0 watermark interrupt (IR.RF0W).
>64 Watermark interrupt disabled.
Bits 22:16 – F0S[6:0] Rx FIFO 0 Size
The Rx FIFO 0 elements are indexed from 0 to F0S - 1.
Value Description
0No Rx FIFO 0
1 - 64 Number of Rx FIFO 0 elements.
>64 Values greater than 64 are interpreted as 64.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 745
Bits 15:0 – F0SA[15:0] Rx FIFO 0 Start Address
Start address of Rx FIFO 0 in Message RAM. When the CAN module addresses the Message RAM it
addresses 32-bit words, not single bytes. The configurable start addresses are 32-bit word addresses, i.e.
only bits 15 to 2 are evaluated, the two least significant bits are ignored. Bits 1 to 0 will always be read
back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 746
34.8.28 Rx FIFO 0 Status
Name:  RXF0S
Offset:  0xA4
Reset:  0x00000000
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
RF0L F0F
Access R R
Reset 0 0
Bit 23 22 21 20 19 18 17 16
F0PI[5:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
F0GI[5:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
F0FL[6:0]
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bit 25 – RF0L Rx FIFO 0 Message Lost
This bit is a copy of interrupt flag IR.RF0L. When IR.RF0L is reset, this bit is also reset.
Overwriting the oldest message when RXF0C.F0OM = ‘1’ will not set this flag.
Value Description
0No Rx FIFO 0 message lost.
1Rx FIFO 0 message lost, also set after write attempt to Rx FIFO 0 of size zero.
Bit 24 – F0F Rx FIFO 0 Full
Value Description
0Rx FIFO 0 not full.
1Rx FIFO 0 full.
Bits 21:16 – F0PI[5:0] Rx FIFO 0 Put Index
Rx FIFO 0 write index pointer, range 0 to 63.
Bits 13:8 – F0GI[5:0] Rx FIFO 0 Get Index
Rx FIFO 0 read index pointer, range 0 to 63.
Bits 6:0 – F0FL[6:0] Rx FIFO 0 Fill Level
Number of elements stored in Rx FIFO 0, range 0 to 64.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 747
34.8.29 Rx FIFO 0 Acknowledge
Name:  RXF0A
Offset:  0xA8
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
F0AI[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5:0 – F0AI[5:0] Rx FIFO 0 Acknowledge Index
After the Host has read a message or a sequence of messages from Rx FIFO 0 it has to write the buffer
index of the last element read from Rx FIFO 0 to F0AI. This will set the Rx FIFO 0 Get Index RXF0S.F0GI
to F0AI + 1 and update the FIFO 0 Fill Level RXF0S.F0FL.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 748
34.8.30 Rx Buffer Configuration
Name:  RXBC
Offset:  0xAC
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
RBSA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RBSA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – RBSA[15:0] Rx Buffer Start Address
Configures the start address of the Rx Buffers section in the Message RAM. Also used to reference
debug message A,B,C. When the CAN module addresses the Message RAM it addresses 32-bit words,
not single bytes. The configurable start addresses are 32-bit word addresses, i.e. only bits 15 to 2 are
evaluated, the two least significant bits are ignored. Bits 1 to 0 will always be read back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 749
34.8.31 Rx FIFO 1 Configuration
Name:  RXF1C
Offset:  0xB0
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
F1OM F1WM[6:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
F1S[6:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
F1SA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
F1SA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 31 – F1OM FIFO 1 Operation Mode
FIFO 1 can be operated in blocking or in overwrite mode.
Value Description
0FIFO 1 blocking mode.
1FIFO 1 overwrite mode.
Bits 30:24 – F1WM[6:0] Rx FIFO 1 Watermark
Value Description
0Watermark interrupt disabled.
1 - 64 Level for Rx FIFO 1 watermark interrupt (IR.RF1W).
>64 Watermark interrupt disabled.
Bits 22:16 – F1S[6:0] Rx FIFO 1 Size
The Rx FIFO 1 elements are indexed from 0 to F1S - 1.
Value Description
0No Rx FIFO 1
1 - 64 Number of Rx FIFO 1 elements.
>64 Values greater than 64 are interpreted as 64.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 750
Bits 15:0 – F1SA[15:0] Rx FIFO 1 Start Address
Start address of Rx FIFO 1 in Message RAM. When the CAN module addresses the Message RAM it
addresses 32-bit words, not single bytes. The configurable start addresses are 32-bit word addresses, i.e.
only bits 15 to 2 are evaluated, the two least significant bits are ignored. Bits 1 to 0 will always be read
back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 751
34.8.32 Rx FIFO 1 Status
Name:  RXF1S
Offset:  0xB4
Reset:  0x00000000
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
DMS[1:0] RF1L F1F
Access R R R R
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
F1PI[5:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
F1GI[5:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
F1FL[6:0]
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bits 31:30 – DMS[1:0] Debug Message Status
This field defines the debug message status.
Value Name Description
0x0 IDLE Idle state, wait for reception of debug messages, DMA request is cleared.
0x1 DBGA Debug message A received.
0x2 DBGB Debug message A, B received.
0x3 DBGC Debug message A, B, C received, DMA request is set.
Bit 25 – RF1L Rx FIFO 1 Message Lost
This bit is a copy of interrupt flag IR.RF1L. When IR.RF1L is reset, this bit is also reset.
Overwriting the oldest message when RXF1C.F0OM = ‘1’ will not set this flag.
Value Description
0No Rx FIFO 1 message lost.
1Rx FIFO 1 message lost, also set after write attempt to Rx FIFO 1 of size zero.
Bit 24 – F1F Rx FIFO 1 Full
Value Description
0Rx FIFO 1 not full.
1Rx FIFO 1 full.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 752
Bits 21:16 – F1PI[5:0] Rx FIFO 1 Put Index
Rx FIFO 1 write index pointer, range 0 to 63.
Bits 13:8 – F1GI[5:0] Rx FIFO 1 Get Index
Rx FIFO 1 read index pointer, range 0 to 63.
Bits 6:0 – F1FL[6:0] Rx FIFO 1 Fill Level
Number of elements stored in Rx FIFO 1, range 0 to 64.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 753
34.8.33 Rx FIFO 1 Acknowledge
Name:  RXF1A
Offset:  0xB8
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
F1AI[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5:0 – F1AI[5:0] Rx FIFO 1 Acknowledge Index
After the Host has read a message or a sequence of messages from Rx FIFO 1 it has to write the buffer
index of the last element read from Rx FIFO 1 to F1AI. This will set the Rx FIFO 1 Get Index RXF1S.F0GI
to F1AI + 1 and update the FIFO 1 Fill Level RXF1S.F1FL.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 754
34.8.34 Rx Buffer / FIFO Element Size Configuration
Name:  RXESC
Offset:  0xBC
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Configures the number of data bytes belonging to an Rx Buffer / Rx FIFO element. Data field sizes >8
bytes are intended for CAN FD operation only.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
RBDS[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
F1DS[2:0] F0DS[2:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 10:8 – RBDS[2:0] Rx Buffer Data Field Size
In case the data field size of an accepted CAN frame exceeds the data field size configured for the
matching Rx Buffer, only the number of bytes as configured by RXESC are stored to the Rx Buffer
element. The rest of the frame’s data field is ignored.
Value Name Description
0x0 DATA8 8 byte data field.
0x1 DATA12 12 byte data field.
0x2 DATA16 16 byte data field.
0x3 DATA20 20 byte data field.
0x4 DATA24 24 byte data field.
0x5 DATA32 32 byte data field.
0x6 DATA48 48 byte data field.
0x7 DATA64 64 byte data field.
Bits 6:4 – F1DS[2:0] Rx FIFO 1 Data Field Size
In case the data field size of an accepted CAN frame exceeds the data field size configured for the
matching Rx FIFO 1, only the number of bytes as configured by RXESC are stored to the Rx FIFO 1
element. The rest of the frame’s data field is ignored.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 755
Value Name Description
0x0 DATA8 8 byte data field.
0x1 DATA12 12 byte data field.
0x2 DATA16 16 byte data field.
0x3 DATA20 20 byte data field.
0x4 DATA24 24 byte data field.
0x5 DATA32 32 byte data field.
0x6 DATA48 48 byte data field.
0x7 DATA64 64 byte data field.
Bits 2:0 – F0DS[2:0] Rx FIFO 0 Data Field Size
In case the data field size of an accepted CAN frame exceeds the data field size configured for the
matching Rx FIFO 0, only the number of bytes as configured by RXESC are stored to the Rx FIFO 0
element. The rest of the frame’s data field is ignored.
Value Name Description
0x0 DATA8 8 byte data field.
0x1 DATA12 12 byte data field.
0x2 DATA16 16 byte data field.
0x3 DATA20 20 byte data field.
0x4 DATA24 24 byte data field.
0x5 DATA32 32 byte data field.
0x6 DATA48 48 byte data field.
0x7 DATA64 64 byte data field.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 756
34.8.35 Tx Buffer Configuration
Name:  TXBC
Offset:  0xC0
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Note:  Be aware that the sum of TFQS and NDTB may not be greater than 32. There is no check for
erroneous configurations. The Tx Buffers section in the Message RAM starts with the dedicated Tx
Buffers.
Bit 31 30 29 28 27 26 25 24
TFQM TFQS[5:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
NDTB[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TBSA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TBSA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 30 – TFQM Tx FIFO/Queue Mode
Value Description
0Tx FIFO operation.
1Tx Queue operation.
Bits 29:24 – TFQS[5:0] Transmit FIFO/Queue Size
Value Description
0No Tx FIFO/Queue.
1 - 32 Number of Tx Buffers used for Tx FIFO/Queue.
>32 Values greater than 32 are interpreted as 32.
Bits 21:16 – NDTB[5:0] Number of Dedicated Transmit Buffers
Value Description
0No Tx FIFO/Queue.
1 - 32 Number of Tx Buffers used for Tx FIFO/Queue.
>32 Values greater than 32 are interpreted as 32.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 757
Bits 15:0 – TBSA[15:0] Tx Buffers Start Address
Start address of Tx Buffers section in Message RAM. When the CAN module addresses the Message
RAM it addresses 32-bit words, not single bytes. The configurable start addresses are 32-bit word
addresses, i.e. only bits 15 to 2 are evaluated, the two least significant bits are ignored. Bits 1 to 0 will
always be read back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 758
34.8.36 Tx FIFO/Queue Status
Name:  TXFQS
Offset:  0xC4
Reset:  0x00000000
Property:  Read-only
Note:  In case of mixed configurations where dedicated Tx Buffers are combined with a Tx FIFO or a Tx
Queue, the Put and Get Indexes indicate the number of the Tx Buffer starting with the first dedicated Tx
Buffers. Example: For a configuration of 12 dedicated Tx Buffers and a Tx FIFO of 20 Buffers a Put Index
of 15 points to the fourth buffer of the Tx FIFO.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
TFQF TFQPI[4:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TFGI[4:0]
Access R R R R R
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TFFL[5:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 21 – TFQF Tx FIFO/Queue Full
Value Description
0Tx FIFO/Queue not full.
1Tx FIFO/Queue full.
Bits 20:16 – TFQPI[4:0] Tx FIFO/Queue Put Index
Tx FIFO/Queue write index pointer, range 0 to 31.
Bits 12:8 – TFGI[4:0] Tx FIFO/Queue Get Index
Tx FIFO read index pointer, range 0 to 31. Read as zero when Tx Queue operation is configured
(TXBC.TFQM = ‘1’).
Bits 5:0 – TFFL[5:0] Tx FIFO Free Level
Number of consecutive free Tx FIFO elements starting from TFGI, range 0 to 32. Read as zero when Tx
Queue operation is configured (TXBC.TFQM = ‘1’).
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 759
34.8.37 Tx Buffer Element Size Configuration
Name:  TXESC
Offset:  0xC8
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Configures the number of data bytes belonging to a Tx Buffer element. Data field sizes >8 bytes are
intended for CAN FD operation only.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
TBDS[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – TBDS[2:0] Tx Buffer Data Field Size
In case the data length code DLC of a Tx Buffer element is configured to a value higher than the Tx
Buffer data field size TXESC.TBDS, the bytes not defined by the Tx Buffer are transmitted as “0xCC”
(padding bytes).
Value Name Description
0x0 DATA8 8 byte data field.
0x1 DATA12 12 byte data field.
0x2 DATA16 16 byte data field.
0x3 DATA20 20 byte data field.
0x4 DATA24 24 byte data field.
0x5 DATA32 32 byte data field.
0x6 DATA48 48 byte data field.
0x7 DATA64 64 byte data field.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 760
34.8.38 Tx Buffer Request Pending
Name:  TXBRP
Offset:  0xCC
Reset:  0x00000000
Property:  Read-only
Note:  TXBRP bits which are set while a Tx scan is in progress are not considered during this particular
Tx scan. In case a cancellation is requested for such a Tx Buffer, this Add Request is canceled
immediately, the corresponding TXBRP bit is reset.
Bit 31 30 29 28 27 26 25 24
TRPn[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
TRPn[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TRPn[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TRPn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – TRPn[31:0] Transmission Request Pending
Each Tx Buffer has its own Transmission Request Pending bit.
The bits are reset after a requested transmission has completed or has been cancelled via register
TXBCR.
TXBRP bits are set only for those Tx Buffers configured via TXBC. After a TXBRP bit has been set, a Tx
scan is started to check for the pending Tx request with the highest priority (Tx Buffer with lowest
Message ID).
A cancellation request resets the corresponding transmission request pending bit of register TXBRP. In
case a transmission has already been started when a cancellation is requested, this is done at the end of
the transmission, regardless whether the transmission was successful or not. The cancellation request
bits are reset directly after the corresponding TXBRP bit has been reset.
After a cancellation has been requested, a finished cancellation is signaled via TXBCF
• after successful transmission together with the corresponding TXBTO bit
• when the transmission has not yet been started at the point of cancellation
• when the transmission has been aborted due to lost arbitration
• when an error occurred during frame transmission
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 761
In DAR mode all transmissions are automatically canceled if they are not successful. The corresponding
TXBCF bit is set for all unsuccessful transmissions.
Value Description
0No transmission request pending.
1Transmission request pending.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 762
34.8.39 Tx Buffer Add Request
Name:  TXBAR
Offset:  0xD0
Reset:  0x00000000
Property:  -
Note:  If an add request is applied for a Tx Buffer with pending transmission request (corresponding
TXBRP bit is already set), this add request is ignored.
Bit 31 30 29 28 27 26 25 24
ARn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
ARn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ARn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ARn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – ARn[31:0] Add Request
Each Tx Buffer has its own Add Request bit.
Writing a ‘1’ will set the corresponding Add Request bit; writing a ‘0’ has no impact. This enables the Host
to set transmission requests for multiple Tx Buffers with one write to TXBAR. TXBAR bits are set only for
those Tx Buffers configured via TXBC. When no Tx scan is running, the bits are reset immediately, else
the bits remain set until the Tx scan process has completed.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 763
34.8.40 Tx Buffer Cancellation Request
Name:  TXBCR
Offset:  0xD4
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
CRn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CRn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CRn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CRn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CRn[31:0] Cancellation Request
Each Tx Buffer has its own Cancellation Request bit.
Writing a ‘1’ will set the corresponding Cancellation Request bit; writing a ‘0’ has no impact. This enables
the Host to set cancellation requests for multiple Tx Buffers with one write to TXBCR. TXBCR bits are set
only for those Tx Buffers configured via TXBC. The bits remain set until the corresponding bit of TXBRP
is reset.
Value Description
0No cancellation pending.
1Cancellation pending.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 764
34.8.41 Tx Buffer Transmission Occurred
Name:  TXBTO
Offset:  0xD8
Reset:  0x00000000
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
TOn[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
TOn[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TOn[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TOn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – TOn[31:0] Transmission Occurred
Each Tx Buffer has its own Transmission Occurred bit.
The bits are set when the corresponding TXBRP bit is cleared after a successful transmission.
The bits are reset when a new transmission is requested by writing ‘1’ to the corresponding bit of register
TXBAR.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 765
34.8.42 Tx Buffer Cancellation Finished
Name:  TXBCF
Offset:  0xDC
Reset:  0x00000000
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
CFn[31:24]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CFn[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CFn[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CFn[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CFn[31:0] Cancellation Finished
Each Tx Buffer has its own Cancellation Finished bit.
The bits are set when the corresponding TXBRP bit is cleared after a cancellation was requested via
TXBCR. In case the corresponding TXBRP bit was not set at the point of cancellation, CF is set
immediately.
The bits are reset when a new transmission is requested by writing ‘1’ to the corresponding bit of register
TXBAR.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 766
34.8.43 Tx Buffer Transmission Interrupt Enable
Name:  TXBTIE
Offset:  0xE0
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
TIEn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
TIEn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TIEn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
TIEn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – TIEn[31:0] Transmission Interrupt Enable
Each Tx Buffer has its own Transmission Interrupt Enable bit.
Value Description
0Transmission interrupt disabled.
1Transmission interrupt enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 767
34.8.44 Tx Buffer Cancellation Finished Interrupt Enable
Name:  TXBCIE
Offset:  0xE4
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
CFIEn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CFIEn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CFIEn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CFIEn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CFIEn[31:0] Cancellation Finished Interrupt Enable
Each Tx Buffer has its own Cancellation Finished Interrupt Enable bit.
Value Description
0Cancellation finished interrupt disabled.
1Cancellation finished interrupt enabled.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 768
34.8.45 Tx Event FIFO Configuration
Name:  TXEFC
Offset:  0xF0
Reset:  0x00000000
Property:  Write-restricted
This register is write-restricted and only writable if bit fields CCCR.CCE = 1 and CCCR.INIT = 1.
Bit 31 30 29 28 27 26 25 24
EFWM[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
EFS[5:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
EFSA[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EFSA[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 29:24 – EFWM[5:0] Event FIFO Watermark
Value Description
0Watermark interrupt disabled.
1 - 32 Level for Tx Event FIFO watermark interrupt (IR.TEFW).
>32 Watermark interrupt disabled.
Bits 21:16 – EFS[5:0] Event FIFO Size
The Tx Event FIFO elements are indexed from 0 to EFS - 1.
Value Description
0Tx Event FIFO disabled
1 - 32 Number of Tx Event FIFO elements.
>32 Values greater than 32 are interpreted as 32.
Bits 15:0 – EFSA[15:0] Event FIFO Start Address
Start address of Tx Event FIFO in Message RAM. When the CAN module addresses the Message RAM it
addresses 32-bit words, not single bytes. The configurable start addresses are 32-bit word addresses, i.e.
only bits 15 to 2 are evaluated, the two least significant bits are ignored. Bits 1 to 0 will always be read
back as “00”.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 769
34.8.46 Tx Event FIFO Status
Name:  TXEFS
Offset:  0xF4
Reset:  0x00000000
Property:  Read-only
Bit 31 30 29 28 27 26 25 24
TEFL EFF
Access R R
Reset 0 0
Bit 23 22 21 20 19 18 17 16
EFP[4:0]
Access R R R R R
Reset 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
EFGI[4:0]
Access R R R R R
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EFFI[4:0]
Access R R R R R
Reset 0 0 0 0 0
Bit 25 – TEFL Tx Event FIFO Element Lost
This bit is a copy of interrupt flag IR.TEFL. When IR.TEFL is reset, this bit is also reset.
Value Description
0No Tx Event FIFO element lost.
1Tx Event FIFO element lost, also set after write attempt to Tx Event FIFO of size zero.
Bit 24 – EFF Event FIFO Full
Value Description
0Tx Event FIFO not full.
1Tx Event FIFO full.
Bits 20:16 – EFP[4:0] Event FIFO Put Index
Tx Event FIFO write index pointer, range 0 to 31.
Bits 12:8 – EFGI[4:0] Event FIFO Get Index
Tx Event FIFO read index pointer, range 0 to 31.
Bits 4:0 – EFFI[4:0] Event FIFO Fill Level
Number of elements stored in Tx Event FIFO, range 0 to 32.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 770
34.8.47 Tx Event FIFO Acknowledge
Name:  TXEFA
Offset:  0xF8
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
EFAI[4:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bits 4:0 – EFAI[4:0] Event FIFO Acknowledge Index
After the Host has read an element or a sequence of elements from the Tx Event FIFO it has to write the
index of the last element read from Tx Event FIFO to EFAI. This will set the Tx Event FIFO Get Index
TXEFS.EFGI to EFAI + 1 and update the FIFO 0 Fill Level TXEFS.EFFL.
34.9 Message RAM
For storage of Rx/Tx messages and for storage of the filter configuration a single- or dual-ported
Message RAM has to be connected to the CAN module.
34.9.1 Message RAM Configuration
The Message RAM has a width of 32 bits. In case parity checking or ECC is used a respective number of
bits has to be added to each word. The CAN module can be configured to allocate up to 4352 words in
the Message RAM. It is not necessary to configure each of the sections listed in the figure below, nor is
there any restriction with respect to the sequence of the sections.
When operated in CAN FD mode the required Message RAM size strongly depends on the element size
configured for Rx FIFO 0, Rx FIFO 1, Rx Buffers, and Tx Buffers via RXESC.F0DS, RXESC.F1DS,
RXESC.RBDS, and TXESC.TBDS.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 771
Figure 34-12. Message RAM Configuration
11-bit Filter
29-bit Filter
Rx FIFO 0
Rx FIFO 1
Rx Buffers
Tx Event FIFO
Tx Buffers
0-128 elements / 0-128 words
0-64 elements / 0-128 words
0-64 elements / 0-1152 words
0-64 elements / 0-1152 words
0-64 elements / 0-1152 words
0-32 elements / 0-64 words
0-32 elements / 0-576 words
SIDFC.FLSSA
XIDFC.FLESA
RXF0C.F0SA
RXF1C.F1SA
RXBC.RBSA
TXEFC.EFSA
TXBC.TBSA
32 bit
max 4352 words
Start Address
When the CAN addresses the Message RAM it addresses 32-bit words, not single bytes. The
configurable start addresses are 32-bit word addresses (i.e. only bits 15 to 2 are evaluated and the two
LSBs are ignored).
WARNING
The CAN does not check for erroneous configuration of the Message RAM. Especially the
configuration of the start addresses of the different sections and the number of elements of
each section has to be done carefully to avoid falsification or loss of data.
34.9.2 Rx Buffer and FIFO Element
Up to 64 Rx Buffers and two Rx FIFOs can be configured in the Message RAM. Each Rx FIFO section
can be configured to store up to 64 received messages. The structure of a Rx Buffer / FIFO element is
shown in the table below. The element size can be configured for storage of CAN FD messages with up
to 64 bytes data field via register RXESC.
Table 34-8. Rx Buffer and FIFO Element
31 3
0
29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R0
E
S
I
X
T
D
R
T
R
ID[28:0]
R1
A
N
M
F
FIDX[6:0]
F
D
F
B
R
S
DLC[3:0] RXTS[15:0]
R2 DB3[7:0] DB2[7:0] DB1[7:0] DB0[7:0]
R3 DB7[7:0] DB6[7:0] DB5[7:0] DB4[7:0]
... ... ... ... ...
Rn DBm[7:0] DBm-1[7:0] DBm-2[7:0] DBm-3[7:0]
• R0 Bit 31 - ESI: Error State Indicator
SAM C20/C21 Family Data Sheet
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0 : Transmitting node is error active.
1 : Transmitting node is error passive.
• R0 Bit 30 - XTD: Extended Identifier
Signals to the Host whether the received frame has a standard or extended identifier.
0 : 11-bit standard identifier.
1 : 29-bit extended identifier.
• R0 Bit 29 - RTR: Remote Transmission Request
Signals to the Host whether the received frame is a data frame or a remote frame.
0 : Received frame is a data frame.
1 : Received frame is a remote frame.
Note:  There are no remote frames in CAN FD format. In case a CAN FD frame was received (EDL
= ‘1’), bit RTR reflects the state of the reserved bit r1.
• R0 Bits 28:0 - ID[28:0]: Identifier
Standard or extended identifier depending on bit XTD. A standard identifier is stored into ID[28:18].
• R1 Bit 31 - ANMF: Accepted Non-matching Frame
Acceptance of non-matching frames may be enabled via GFC.ANFS and GFC.ANFE.
0 : Received frame matching filter index FIDX.
1 : Received frame did not match any Rx filter element.
• R1 Bits 30:24 - FIDX[6:0]: Filter Index
0-127 : Index of matching Rx acceptance filter element (invalid if ANMF = ‘1’).
Note:  Range is 0 to SIDFC.LSS-1 for standard and 0 to XIDFC.LSE-1 for extended.
• R1 Bits 23:22 - Reserved
• R1 Bit 21 - FDF: FD Format
0 : Standard frame format.
1 : CAN FD frame format (new DLC-coding and CRC).
• R1 Bit 20 - BRS: Bit Rate Search
0 : Frame received without bit rate switching.
1 : Frame received with bit rate switching.
• R1 Bits 19:16 - DLC[3:0]: Data Length Code
0-8 : CAN + CAN FD: received frame has 0-8 data bytes.
9-15 : CAN: received frame has 8 data bytes.
9-15 : CAN FD: received frame has 12/16/20/24/32/48/64 data bytes.
• R1 Bits 15:0 - RXTS[15:0]: Rx Timestamp
Timestamp Counter value captured on start of frame reception. Resolution depending on
configuration of the Timestamp Counter Prescaler TSCC.TCP.
SAM C20/C21 Family Data Sheet
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• R2 Bits 31:24 - DB3[7:0]: Data Byte 3
• R2 Bits 23:16 - DB2[7:0]: Data Byte 2
• R2 Bits 15:8 - DB1[7:0]: Data Byte 1
• R2 Bits 7:0 - DB0[7:0]: Data Byte 0
• R3 Bits 31:24 - DB7[7:0]: Data Byte 7
• R3 Bits 23:16 - DB6[7:0]: Data Byte 6
• R3 Bits 15:8 - DB5[7:0]: Data Byte 5
• R3 Bits 7:0 - DB4[7:0]: Data Byte 4
...
• Rn Bits 31:24 - DBm[7:0]: Data Byte m
• Rn Bits 23:16 - DBm-1[7:0]: Data Byte m-1
• Rn Bits 15:8 - DBm-2[7:0]: Data Byte m-2
• Rn Bits 7:0 - DBm-3[7:0]: Data Byte m-3
WARNING
Depending on the configuration of RXESC, between two and sixteen 32-bit words (Rn = 3 ... 17)
are used for storage of a CAN message’s data field.
34.9.3 Tx Buffer Element
The Tx Buffers section can be configured to hold dedicated Tx Buffers as well as a Tx FIFO / Tx Queue.
In case that the Tx Buffers section is shared by dedicated Tx buffers and a Tx FIFO / Tx Queue, the
dedicated Tx Buffers start at the beginning of the Tx Buffers section followed by the buffers assigned to
the Tx FIFO or Tx Queue. The Tx Handler distinguishes between dedicated Tx Buffers and Tx FIFO / Tx
Queue by evaluating the Tx Buffer configuration TXBC.TFQS and TXBC.NDTB. The element size can be
configured for storage of CAN FD messages with up to 64 bytes data field via register TXESC.
Table 34-9. Tx Buffer Element
31 3
0
29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
T0
E
S
I
X
T
D
R
T
R
ID[28:0]
T1 MM[7:0]
E
F
C
F
D
F
B
R
S
DLC[3:0]
T2 DB3[7:0] DB2[7:0] DB1[7:0] DB0[7:0]
T3 DB7[7:0] DB6[7:0] DB5[7:0] DB4[7:0]
... ... ... ... ...
Tn DBm[7:0] DBm-1[7:0] DBm-2[7:0] DBm-3[7:0]
• T0 Bit 31 - ESI: Error State Indicator
0 : ESI bit in CAN FD format depends only on error passive flag.
1 : ESI bit in CAN FD format transmitted recessive.
SAM C20/C21 Family Data Sheet
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Note:  The ESI bit of the transmit buffer is OR’ed with the error passive flag to decide the value of
the ESI bit in the transmitted FD frame. As required by the CAN FD protocol specification, an error
active node may optionally transmit the ESI bit recessive, but an error passive node will always
transmit the ESI bit recessive.
• T0 Bit 30 - XTD: Extended Identifier
0 : 11-bit standard identifier.
1 : 29-bit extended identifier.
• T0 Bit 29 - RTR: Remote Transmission Request
0 : Transmit data frame.
1 : Transmit remote frame.
Note:  When RTR = ‘1’, the CAN transmits a remote frame according to ISO 11898-1, even if
CCCR.CME enables the transmission in CAN FD format.
• T0 Bits 28:0 - ID[28:0]: Identifier
Standard or extended identifier depending on bit XTD. A standard identifier is stored into ID[28:18].
• T1 Bits 31:24 - MM[7:0]: Message Marker
Written by CPU during Tx Buffer configuration. Copied into Tx Event FIFO element for identification
of Tx message status.
• T1 Bit 23 - EFC: Event FIFO Control
0 : Don’t store Tx events.
1 : Store Tx events.
• T1 Bit 22 - Reserved
• TR1 Bit 21 - FDF: FD Format
0 : Frame transmitted in Classic CAN format.
1 : Frame transmitted in CAN FD format.
• T1 Bit 20 - BRS: Bit Rate Search
0 : CAN FD frames transmitted without bit rate switching.
1 : CAN FD frames transmitted with bit rate switching.
Note:  Bits ESI, FDF, and BRS are only evaluated when CAN FD operation is enabled CCCR.FDOE
= ‘1’. Bit BRS is only evaluated when in addition CCCR.BRSE = ‘1’.
• T1 Bits 19:16 - DLC[3:0]: Data Length Code
0-8 : CAN + CAN FD: received frame has 0-8 data bytes.
9-15 : CAN: received frame has 8 data bytes.
9-15 : CAN FD: received frame has 12/16/20/24/32/48/64 data bytes.
• T1 Bits 15:0 - Reserved
• T2 Bits 31:24 - DB3[7:0]: Data Byte 3
• T2 Bits 23:16 - DB2[7:0]: Data Byte 2
• T2 Bits 15:8 - DB1[7:0]: Data Byte 1
• T2 Bits 7:0 - DB0[7:0]: Data Byte 0
• T3 Bits 31:24 - DB7[7:0]: Data Byte 7
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 775
• T3 Bits 23:16 - DB6[7:0]: Data Byte 6
• T3 Bits 15:8 - DB5[7:0]: Data Byte 5
• T3 Bits 7:0 - DB4[7:0]: Data Byte 4
...
• Tn Bits 31:24 - DBm[7:0]: Data Byte m
• Tn Bits 23:16 - DBm-1[7:0]: Data Byte m-1
• Tn Bits 15:8 - DBm-2[7:0]: Data Byte m-2
• Tn Bits 7:0 - DBm-3[7:0]: Data Byte m-3
Note:  Depending on the configuration of TXESC, between two and sixteen 32-bit words (Tn = 3 ... 17)
are used for storage of a CAN message’s data field.
34.9.4 Tx Event FIFO Element
Each element stores information about transmitted messages. By reading the Tx Event FIFO the Host
CPU gets this information in the order the messages were transmitted. Status information about the Tx
Event FIFO can be obtained from register TXEFS.
Table 34-10. Tx Event FIFO Element
31 3
0
29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
E0
E
S
I
X
T
D
R
T
R
ID[28:0]
E1 MM[7:0] ET
[1:0]
F
D
F
B
R
S
DLC[3:0] TXTS[15:0]
• E0 Bit 31 - ESI: Error State Indicator
0 : Transmitting node is error active.
1 : Transmitting node is error passive.
• E0 Bit 30 - XTD: Extended Identifier
0 : 11-bit standard identifier.
1 : 29-bit extended identifier.
• E0 Bit 29 - RTR: Remote Transmission Request
0 : Received frame is a data frame.
1 : Received frame is a remote frame.
• E0 Bits 28:0 - ID[28:0]: Identifier
Standard or extended identifier depending on bit XTD. A standard identifier is stored into ID[28:18].
• E1 Bits 31:24 - MM[7:0]: Message Marker
Copied from Tx Buffer into Tx Event FIFO element for identification of Tx message status.
• E1 Bits 23:22 - ET[1:0]: Event Type
This field defines the event type.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 776
Table 34-11. Event Type
Value Name Description
0x0 or 0x3 RES Reserved
0x1 TXE Tx event
0x2 TXC Transmission in spite of cancellation (always set for transmission in DAR mode)
• E1 Bit 21 - FDF: FD Format
0 : Standard frame format.
1 : CAN FD frame format (new DLC-coding and CRC).
• E1 Bit 20 - BRS: Bit Rate Search
0 : Frame received without bit rate switching.
1 : Frame received with bit rate switching.
• E1 Bits 19:16 - DLC[3:0]: Data Length Code
0-8 : CAN + CAN FD: received frame has 0-8 data bytes.
9-15 : CAN: received frame has 8 data bytes.
9-15 : CAN FD: received frame has 12/16/20/24/32/48/64 data bytes.
• E1 Bits 15:0 - TXTS[15:0]: Tx Timestamp
Timestamp Counter value captured on start of frame transmission. Resolution depending on
configuration of the Timestamp Counter Prescaler TSCC.TCP.
34.9.5 Standard Message ID Filter Element
Up to 128 filter elements can be configured for 11-bit standard IDs. When accessing a Standard Message
ID Filter element, its address is the Filter List Standard Start Address SIDFC.FLSSA plus the index of the
filter element (0 ... 127).
Table 34-12. Standard Message ID Filter Element
31 3
0
29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
S0 SFT
[1:0]
SFEC
[2:0] SFID1[10:0] SFID2[10:0]
• Bits 31:30 - SFT[1:0]: Standard Filter Type
This field defines the standard filter type.
Table 34-13. Standard Filter Type
Value Name Description
0x0 RANGE Range filter from SFID1 to SFID2 (SFID2 >= SFID1)
0x1 DUAL Dual ID filter for SFID1 or SFID2
0x2 CLASSIC Classic filter: SFID1 = filter, SFID2 = mask
0x3 RES Reserved
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 777
• Bits 29:27 - SFEC[2:0]: Standard Filter Element Configuration
All enabled filter elements are used for acceptance filtering of standard frames. Acceptance filtering
stops at the first matching enabled filter element or when the end of the filter list is reached. If SFEC
= “100”, “101”, or “110” a match sets interrupt flag IR.HPM and, if enabled, an interrupt is generated.
In this case register HPMS is updated with the status of the priority match.
Table 34-14. Standard Filter Element Configuration
Value Name Description
0x0 DISABLE Disable filter element
0x1 STF0M Store in Rx FIFO 0 if filter matches
0x2 STF1M Store in Rx FIFO 1 if filter matches
0x3 REJECT Reject ID if filter matches
0x4 PRIORITY Set priority if filter matches.
0x5 PRIF0M Set priority and store in FIFO 0 if filter matches.
0x6 PRIF1M Set priority and store in FIFO 1 if filter matches.
0x7 STRXBUF Store into Rx Buffer or as debug message, configuration of SFT[1:0] ignored.
• Bits 26:16 - SFID1[10:0]: Standard Filter ID 1
First ID of standard ID filter element.
When filtering for Rx Buffers or for debug messages this field defines the ID of a standard mesage to
be stored. The received identifiers must match exactly, no masking mechanism is used.
• Bits 15:11 - Reserved
• Bits 10:0 - SFID2[10:0]: Standard Filter ID 2
This bit field has a different meaning depending on the configuration of SFEC.
5.1. SFEC = “001” ... “110”: Second ID of standard ID filter element.
5.2. SFEC = “111”: Filter for Rx Buffers or for debug messages.
SFID2[10:9] decides whether the received message is stored into an Rx Buffer or treated as
message A, B, or C of the debug message sequence.
00 = Store message into an Rx Buffer
01 = Debug Message A
10 = Debug Message B
11 = Debug Message C
SFID2[8:6] is used to control the filter event pins at the Extension Interface. A ‘1’ at the respective bit
position enables generation of a pulse at the related filter event pin with the duration of one
CLK_CAN_APB period in case the filter matches.
SFID2[5:0] defines the offset to the Rx Buffer Start Address RXBC.RBSA for storage of a matching
message.
34.9.6 Extended Message ID Filter Element
Up to 64 filter elements can be configured for 29-bit extended IDs. When accessing an Extended
Message ID Filter element, its address is the Filter List Extended Start Address XIDFC.FLESA plus two
times the index of the filter element (0…63).
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 778
Table 34-15. Extended Message ID Filter Element
31 3
0
29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
F0 EFEC
[2:0] EFID1[28:0]
F1 EFT
[1:0] EFID2[28:0]
• F0 Bits 31:29 - EFEC[2:0]: Extended Filter Element Configuration
All enabled filter elements are used for acceptance filtering of extended frames. Acceptance filtering
stops at the first matching enabled filter element or when the end of the filter list is reached. If EFEC
= “100”, “101”, or “110” a match sets interrupt flag IR.HPM and, if enabled, an interrupt is generated.
In this case register HPMS is updated with the status of the priority match.
Table 34-16. Extended Filter Element Configuration
Value Name Description
0x0 DISABLE Disable filter element.
0x1 STF0M Store in Rx FIFO 0 if filter matches.
0x2 STF1M Store in Rx FIFO 1 if filter matches.
0x3 REJECT Reject ID if filter matches.
0x4 PRIORITY Set priority if filter matches.
0x5 PRIF0M Set priority and store in FIFO 0 if filter matches.
0x6 PRIF1M Set priority and store in FIFO 1 if filter matches.
0x7 STRXBUF Store into Rx Buffer or as debug message, configuration of EFT[1:0] ignored.
• F0 Bits 28:0 - EFID1[28:0]: Extended Filter ID 1
First ID of extended ID filter element.
When filtering for Rx Buffers or for debug messages this field defines the ID of a extended mesage to
be stored. The received identifiers must match exactly, only XIDAM masking mechanism is used.
• F1 Bits 31:30 - EFT[1:0]: Extended Filter Type
This field defines the extended filter type.
Table 34-17. Extended Filter Type
Value Name Description
0x0 RANGEM Range filter from EFID1 to EFID2 (EFID2 >= EFID1).
0x1 DUAL Dual ID filter for EFID1 or EFID2.
0x2 CLASSIC Classic filter: EFID1 = filter, EFID2 = mask.
0x3 RANGE Range filter from EFID1 to EFID2 (EFID2 >= EFID1), XIDAM mask not applied.
• F1 Bits 28:0 - EFID2[28:0]: Extended Filter ID 2
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 779
This bit field has a different meaning depending on the configuration of EFEC.
1) EFEC = “001” ... “110” Second ID of standard ID filter element.
2) EFEC = “111” Filter for Rx Buffers or for debug messages.
EFID2[10:9] decides whether the received message is stored into an Rx Buffer or treated as
message A, B, or C of the debug message sequence.
00 = Store message into an Rx Buffer
01 = Debug Message A
10 = Debug Message B
11 = Debug Message C
EFID2[8:6] is used to control the filter event pins at the Extension Interface. A ‘1’ at the respective bit
position enables generation of a pulse at the related filter event pin with the duration of one
CLK_CAN_APB period in case the filter matches.
EFID2[5:0] defines the offset to the Rx Buffer Start Address RXBC.RBSA for storage of a matching
message.
SAM C20/C21 Family Data Sheet
CAN - Control Area Network
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 780
35. TC – Timer/Counter
35.1 Overview
There are up to eight TC peripheral instances.
Each TC consists of a counter, a prescaler, compare/capture channels and control logic. The counter can
be set to count events, or clock pulses. The counter, together with the compare/capture channels, can be
configured to timestamp input events or IO pin edges, allowing for capturing of frequency and/or pulse
width.
A TC can also perform waveform generation, such as frequency generation and pulse-width modulation.
35.2 Features
• Selectable configuration
– 8-, 16- or 32-bit TC operation, with compare/capture channels
• 2 compare/capture channels (CC) with:
– Double buffered timer period setting (in 8-bit mode only)
– Double buffered compare channel
• Waveform generation
– Frequency generation
– Single-slope pulse-width modulation
• Input capture
– Event / IO pin edge capture
– Frequency capture
– Pulse-width capture
– Time-stamp capture
– Minimum and maximum capture
• One input event
• Interrupts/output events on:
– Counter overflow/underflow
– Compare match or capture
• Internal prescaler
• DMA support
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 781
35.3 Block Diagram
Figure 35-1. Timer/Counter Block Diagram
Base Counter
"count"
"clear"
"load"
"direction"
TOP
BOTTOM
"event"
UPDATE
=
OVF (INT/Event/DMA Req.)
ERR (INT Req.)
TC Input Event
PERBUF
Prescaler
PER
Compare/Capture
(Unit x = {0,1}
BUFV
"capture"
"match"
Control Logic
WO[1]
WO[0]
MCx (INT/Event/DMA Req.)
Counter
BUFV
= 0
Event
System
=
Waveform
Generation
Control Logic
COUNT
CCx
CCBUFx
35.4 Signal Description
Table 35-1. Signal Description for TC.
Signal Name Type Description
WO[1:0] Digital output Waveform output
Digital input Capture input
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 782
Related Links
6. I/O Multiplexing and Considerations
35.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
35.5.1 I/O Lines
In order to use the I/O lines of this peripheral, the I/O pins must be configured using the I/O Pin Controller
(PORT).
Related Links
28. PORT - I/O Pin Controller
35.5.2 Power Management
This peripheral can continue to operate in any sleep mode where its source clock is running. The
interrupts can wake up the device from sleep modes. Events connected to the event system can trigger
other operations in the system without exiting sleep modes.
Related Links
19. PM – Power Manager
35.5.3 Clocks
The TC bus clocks (CLK_TCx_APB) can be enabled and disabled in the Main Clock Module. The default
state of CLK_TCx_APB can be found in the Peripheral Clock Masking.
The generic clocks (GCLK_TCx) are asynchronous to the user interface clock (CLK_TCx_APB). Due to
this asynchronicity, accessing certain registers will require synchronization between the clock domains.
Refer to Synchronization for further details.
Note:  Two instances of the TC may share a peripheral clock channel. In this case, they cannot be set to
different clock frequencies. Refer to the peripheral clock channel mapping of the Generic Clock Controller
(GCLK.PCHTRLm) to identify shared peripheral clocks.
Related Links
16.8.4 PCHCTRLm
17.6.2.6 Peripheral Clock Masking
35.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). In order to use DMA requests with
this peripheral the DMAC must be configured first. Refer to DMAC – Direct Memory Access Controller for
details.
Related Links
25. DMAC – Direct Memory Access Controller
35.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. In order to use interrupt requests of this
peripheral, the Interrupt Controller (NVIC) must be configured first. Refer to Nested Vector Interrupt
Controller for details.
Related Links
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 783
10.2 Nested Vector Interrupt Controller
35.5.6 Events
The events of this peripheral are connected to the Event System.
Related Links
29. EVSYS – Event System
35.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will halt normal operation. This peripheral can be
forced to continue operation during debugging - refer to the Debug Control (DBGCTRL) register for
details.
Related Links
35.7.1.11 DBGCTRL
35.5.8 Register Access Protection
Registers with write-access can be optionally write-protected by the Peripheral Access Controller (PAC),
except for the following:
• Interrupt Flag Status and Clear register (INTFLAG)
• Status register (STATUS)
• Count register (COUNT)
• Period and Period Buffer registers (PER, PERBUF)
• Compare/Capture Value registers and Compare/Capture Value Buffer registers (CCx, CCBUFx)
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
35.5.9 Analog Connections
Not applicable.
35.6 Functional Description
35.6.1 Principle of Operation
The following definitions are used throughout the documentation:
Table 35-2. Timer/Counter Definitions
Name Description
TOP The counter reaches TOP when it becomes equal to the highest value in
the count sequence. The TOP value can be the same as Period (PER)
or the Compare Channel 0 (CC0) register value depending on the
waveform generator mode in 35.6.2.6.1 Waveform Output Operations.
ZERO The counter is ZERO when it contains all zeroes
MAX The counter reaches MAX when it contains all ones
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 784
...........continued
Name Description
UPDATE The timer/counter signals an update when it reaches ZERO or TOP,
depending on the direction settings.
Timer The timer/counter clock control is handled by an internal source
Counter The clock control is handled externally (e.g. counting external events)
CC For compare operations, the CC are referred to as “compare channels”
For capture operations, the CC are referred to as “capture channels.”
Each TC instance has up to two compare/capture channels (CC0 and CC1).
The counter in the TC can either count events from the Event System, or clock ticks of the GCLK_TCx
clock, which may be divided by the prescaler.
The counter value is passed to the CCx where it can be either compared to user-defined values or
captured.
For optimized timing the CCx and CCBUFx registers share a common resource. When writing into
CCBUFx, lock the access to the corresponding CCx register (SYNCBUSY.CCX = 1) till the CCBUFx
register value is not loaded into the CCx register (BUFVx == 1). Each buffer register has a buffer valid
(BUFV) flag that indicates when the buffer contains a new value.
The Counter register (COUNT) and the Compare and Capture registers with buffers (CCx and CCBUFx)
can be configured as 8-, 16- or 32-bit registers, with according MAX values. Mode settings
(CTRLA.MODE) determine the maximum range of the Counter register.
In 8-bit mode, a Period Value (PER) register and its Period Buffer Value (PERBUF) register are also
available. The counter range and the operating frequency determine the maximum time resolution
achievable with the TC peripheral.
The TC can be set to count up or down. Under normal operation, the counter value is continuously
compared to the TOP or ZERO value to determine whether the counter has reached that value. On a
comparison match the TC can request DMA transactions, or generate interrupts or events for the Event
System.
In compare operation, the counter value is continuously compared to the values in the CCx registers. In
case of a match the TC can request DMA transactions, or generate interrupts or events for the Event
System. In waveform generator mode, these comparisons are used to set the waveform period or pulse
width.
Capture operation can be enabled to perform input signal period and pulse width measurements, or to
capture selectable edges from an IO pin or internal event from Event System.
35.6.2 Basic Operation
35.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the TC is
disabled (CTRLA.ENABLE =0):
• Control A register (CTRLA), except the Enable (ENABLE) and Software Reset (SWRST) bits
• Drive Control register (DRVCTRL)
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 785
• Wave register (WAVE)
• Event Control register (EVCTRL)
Writing to Enable-Protected bits and setting the CTRLA.ENABLE bit can be performed in a single 32-bit
access of the CTRLA register. Writing to Enable-Protected bits and clearing the CTRLA.ENABLE bit
cannot be performed in a single 32-bit access.
Before enabling the TC, the peripheral must be configured by the following steps:
1. Enable the TC bus clock (CLK_TCx_APB).
2. Select 8-, 16- or 32-bit counter mode via the TC Mode bit group in the Control A register
(CTRLA.MODE). The default mode is 16-bit.
3. Select one wave generation operation in the Waveform Generation Operation bit group in the
WAVE register (WAVE.WAVEGEN).
4. If desired, the GCLK_TCx clock can be prescaled via the Prescaler bit group in the Control A
register (CTRLA.PRESCALER).
– If the prescaler is used, select a prescaler synchronization operation via the Prescaler and
Counter Synchronization bit group in the Control A register (CTRLA.PRESYNC).
5. If desired, select one-shot operation by writing a '1' to the One-Shot bit in the Control B Set register
(CTRLBSET.ONESHOT).
6. If desired, configure the counting direction 'down' (starting from the TOP value) by writing a '1' to
the Counter Direction bit in the Control B register (CTRLBSET.DIR).
7. For capture operation, enable the individual channels to capture in the Capture Channel x Enable
bit group in the Control A register (CTRLA.CAPTEN).
8. If desired, enable inversion of the waveform output or IO pin input signal for individual channels via
the Invert Enable bit group in the Drive Control register (DRVCTRL.INVEN).
35.6.2.2 Enabling, Disabling, and Resetting
The TC is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The TC is
disabled by writing a zero to CTRLA.ENABLE.
The TC is reset by writing a '1' to the Software Reset bit in the Control A register (CTRLA.SWRST). All
registers in the TC, except DBGCTRL, will be reset to their initial state. Refer to the CTRLA register for
details.
The TC should be disabled before the TC is reset in order to avoid undefined behavior.
35.6.2.3 Prescaler Selection
The GCLK_TCx is fed into the internal prescaler.
The prescaler consists of a counter that counts up to the selected prescaler value, whereupon the output
of the prescaler toggles.
If the prescaler value is higher than one, the counter update condition can be optionally executed on the
next GCLK_TCx clock pulse or the next prescaled clock pulse. For further details, refer to Prescaler
(CTRLA.PRESCALER) and Counter Synchronization (CTRLA.PRESYNC) description.
Prescaler outputs from 1 to 1/1024 are available. For a complete list of available prescaler outputs, see
the register description for the Prescaler bit group in the Control A register (CTRLA.PRESCALER).
Note:  When counting events, the prescaler is bypassed.
The joint stream of prescaler ticks and event action ticks is called CLK_TC_CNT.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 786
Figure 35-2. Prescaler
PRESCALER
GCLK_TC /
{1,2,4,8,64,256,1024}
GCLK_TC Prescaler
COUNT
CLK_TC_CNT
EVACT
EVENT
35.6.2.4 Counter Mode
The counter mode is selected by the Mode bit group in the Control A register (CTRLA.MODE). By default,
the counter is enabled in the 16-bit counter resolution. Three counter resolutions are available:
• COUNT8: The 8-bit TC has its own Period Value and Period Buffer Value registers (PER and
PERBUF).
• COUNT16: 16-bit is the default counter mode. There is no dedicated period register in this mode.
• COUNT32: This mode is achieved by pairing two 16-bit TC peripherals. TCn is paired with TCn+1.
TC2 does not support 32-bit resolution.
When paired, the TC peripherals are configured using the registers of the even-numbered TC. The
odd-numbered partner will act as a slave, and the Slave bit in the Status register (STATUS.SLAVE)
will be set. The register values of a slave will not reflect the registers of the 32-bit counter. Writing to
any of the slave registers will not affect the 32-bit counter. Normal access to the slave COUNT and
CCx registers is not allowed.
35.6.2.5 Counter Operations
Depending on the mode of operation, the counter is cleared, reloaded, incremented, or decremented at
each TC clock input (CLK_TC_CNT). A counter clear or reload marks the end of the current counter cycle
and the start of a new one.
The counting direction is set by the Direction bit in the Control B register (CTRLB.DIR). If this bit is zero
the counter is counting up, and counting down if CTRLB.DIR=1. The counter will count up or down for
each tick (clock or event) until it reaches TOP or ZERO. When it is counting up and TOP is reached, the
counter will be set to zero at the next tick (overflow) and the Overflow Interrupt Flag in the Interrupt Flag
Status and Clear register (INTFLAG.OVF) will be set. When it is counting down, the counter is reloaded
with the TOP value when ZERO is reached (underflow), and INTFLAG.OVF is set.
INTFLAG.OVF can be used to trigger an interrupt, a DMA request, or an event. An overflow/underflow
occurrence (i.e., a compare match with TOP/ZERO) will stop counting if the One-Shot bit in the Control B
register is set (CTRLBSET.ONESHOT).
It is possible to change the counter value (by writing directly in the COUNT register) even when the
counter is running. When starting the TC, the COUNT value will be either ZERO or TOP (depending on
the counting direction set by CTRLBSET.DIR or CTRLBCLR.DIR), unless a different value has been
written to it, or the TC has been stopped at a value other than ZERO. The write access has higher priority
than count, clear, or reload. The direction of the counter can also be changed when the counter is
running. See also the following figure.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 787
Figure 35-3. Counter Operation
DIR
COUNT
MAX
"reload" update
TOP
COUNT writtenDirection Change
Period (T)
ZERO
"clear" update
Due to asynchronous clock domains, the internal counter settings are written when the synchronization is
complete. Normal operation must be used when using the counter as timer base for the capture
channels.
35.6.2.5.1 Stop Command and Event Action
A Stop command can be issued from software by using Command bits in the Control B Set register
(CTRLBSET.CMD = 0x2, STOP). When a Stop is detected while the counter is running, the counter will
retain its current value. All waveforms are cleared and the Stop bit in the Status register is set
(STATUS.STOP).
35.6.2.5.2 Re-Trigger Command and Event Action
A re-trigger command can be issued from software by writing the Command bits in the Control B Set
register (CTRLBSET.CMD = 0x1, RETRIGGER), or from event when a re-trigger event action is
configured in the Event Control register (EVCTRL.EVACT = 0x1, RETRIGGER).
When the command is detected during counting operation, the counter will be reloaded or cleared,
depending on the counting direction (CTRLBSET.DIR or CTRLBCLR.DIR). When the re-trigger command
is detected while the counter is stopped, the counter will resume counting from the current value in the
COUNT register.
Note:  When a re-trigger event action is configured in the Event Action bits in the Event Control register
(EVCTRL.EVACT=0x1, RETRIGGER), enabling the counter will not start the counter. The counter will
start on the next incoming event and restart on corresponding following event.
35.6.2.5.3 Count Event Action
The TC can count events. When an event is received, the counter increases or decreases the value,
depending on direction settings (CTRLBSET.DIR or CTRLBCLR.DIR). The count event action can be
selected by the Event Action bit group in the Event Control register (EVCTRL.EVACT=0x2, COUNT).
Note:  If this operation mode is selected, PWM generation is not supported.
35.6.2.5.4 Start Event Action
The TC can start counting operation on an event when previously stopped. In this configuration, the event
has no effect if the counter is already counting. When the peripheral is enabled, the counter operation
starts when the event is received or when a re-trigger software command is applied.
The Start TC on Event action can be selected by the Event Action bit group in the Event Control register
(EVCTRL.EVACT=0x3, START).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 788
35.6.2.6 Compare Operations
By default, the Compare/Capture channel is configured for compare operations.
When using the TC and the Compare/Capture Value registers (CCx) for compare operations, the counter
value is continuously compared to the values in the CCx registers. This can be used for timer or for
waveform operation.
The Channel x Compare Buffer (CCBUFx) registers provide double buffer capability. The double buffering
synchronizes the update of the CCx register with the buffer value at the UPDATE condition or a forced
update command (CTRLBSET.CMD=UPDATE). For further details, refer to 35.6.2.7 Double Buffering.
The synchronization prevents the occurrence of odd-length, non-symmetrical pulses and ensures glitch-
free output.
35.6.2.6.1 Waveform Output Operations
The compare channels can be used for waveform generation on output port pins. To make the waveform
available on the connected pin, the following requirements must be fulfilled:
1. Choose a Waveform Generation mode in the Waveform Generation Operation bit in Waveform
register (WAVE.WAVEGEN).
2. Optionally invert the waveform output WO[x] by writing the corresponding Output Waveform x Invert
Enable bit in the Driver Control register (DRVCTRL.INVENx).
3. Configure the pins with the I/O Pin Controller. Refer to PORT - I/O Pin Controller for details.
Note:  Event must not be used when the compare channel is set in waveform output operating
mode.
The counter value is continuously compared with each CCx value. On a comparison match, the Match or
Capture Channel x bit in the Interrupt Flag Status and Clear register (INTFLAG.MCx) will be set on the
next zero-to-one transition of CLK_TC_CNT (see Normal Frequency Operation). An interrupt/and or
event can be generated on comparison match if enabled. The same condition generates a DMA request.
There are four waveform configurations for the Waveform Generation Operation bit group in the
Waveform register (WAVE.WAVEGEN). This will influence how the waveform is generated and impose
restrictions on the top value. The configurations are:
• Normal frequency (NFRQ)
• Match frequency (MFRQ)
• Normal pulse-width modulation (NPWM)
• Match pulse-width modulation (MPWM)
When using NPWM or NFRQ configuration, the TOP will be determined by the counter resolution. In 8-bit
Counter mode, the Period register (PER) is used as TOP, and the TOP can be changed by writing to the
PER register. In 16- and 32-bit Counter mode, TOP is fixed to the maximum (MAX) value of the counter.
Normal Frequency Generation (NFRQ)
For Normal Frequency Generation, the period time (T) is controlled by the period register (PER) for 8-bit
Counter mode and MAX for 16- and 32-bit mode. The waveform generation output (WO[x]) is toggled on
each compare match between COUNT and CCx, and the corresponding Match or Capture Channel x
Interrupt Flag (INTFLAG.MCx) will be set.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 789
Figure 35-4. Normal Frequency Operation
COUNT
MAX
TOP
ZERO
CCx
WO[x]
Direction ChangePeriod (T) COUNT Written
"reload" update
"clear" update
"match"
Match Frequency Generation (MFRQ)
For Match Frequency Generation, the period time (T) is controlled by the CC0 register instead of PER or
MAX. WO[0] toggles on each Update condition.
Figure 35-5. Match Frequency Operation
COUNT
MAX
CC0
COUNT WrittenDirection Change
Period (T)
ZERO
WO[0]
"reload" update
"clear" update
Normal Pulse-Width Modulation Operation (NPWM)
NPWM uses single-slope PWM generation.
For single-slope PWM generation, the period time (T) is controlled by the TOP value, and CCx controls
the duty cycle of the generated waveform output. When up-counting, the WO[x] is set at start or compare
match between the COUNT and TOP values, and cleared on compare match between COUNT and CCx
register values. When down-counting, the WO[x] is cleared at start or compare match between the
COUNT and ZERO values, and set on compare match between COUNT and CCx register values.
The following equation calculates the exact resolution for a single-slope PWM (RPWM_SS) waveform:
PWM_SS =log(TOP+1)
log(2)
The PWM frequency (fPWM_SS) depends on TOP value and the peripheral clock frequency (fGCLK_TC), and
can be calculated by the following equation:
PWM_SS =GCLK_TC
N(TOP+1)
Where N represents the prescaler divider used (1, 2, 4, 8, 16, 64, 256, 1024).
Match Pulse-Width Modulation Operation (MPWM)
In MPWM, the output of WO[1] is depending on CC1 as shown in the figure below. On every overflow/
underflow, a one-TC-clock-cycle negative pulse is put out on WO[0] (not shown in the figure).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 790
Figure 35-6. Match PWM Operation
COUNT
MAX
CC0
Period (T)
" match"
ZERO
CCx= Zero
CC1
CCx= TOP
" clear" update
WO[1]
The table below shows the Update Counter and Overflow Event/Interrupt Generation conditions in
different operation modes.
Table 35-3. Counter Update and Overflow Event/interrupt Conditions in TC
Name Operation TOP Update Output Waveform OVFIF/Event
On Match On Update Up Down
NFRQ Normal Frequency PER TOP/ ZERO Toggle Stable TOP ZERO
MFRQ Match Frequency CC0 TOP/ ZERO Toggle Stable TOP ZERO
NPWM Single-slope PWM PER TOP/ ZERO See description above. TOP ZERO
MPWM Single-slope PWM CC0 TOP/ ZERO Toggle Toggle TOP ZERO
Related Links
28. PORT - I/O Pin Controller
35.6.2.7 Double Buffering
The Compare Channels (CCx) registers, and the Period (PER) register in 8-bit mode are double buffered.
Each buffer register has a buffer valid bit (CCBUFVx or PERBUFV) in the STATUS register, which
indicates that the buffer register contains a new valid value that can be copied into the corresponding
register. As long as the respective buffer valid status flag (PERBUFV or CCBUFVx) are set to '1', related
syncbusy bits are set (SYNCBUSY.PER or SYNCBUSY.CCx), a write to the respective PER/PERBUF or
CCx/CCBUFx registers will generate a PAC error, and access to the respective PER or CCx register is
invalid.
When the buffer valid flag bit in the STATUS register is '1' and the Lock Update bit in the CTRLB register
is set to '0', (writing CTRLBCLR.LUPD to '1'), double buffering is enabled: the data from buffer registers
will be copied into the corresponding register under hardware UPDATE conditions, then the buffer valid
flags bit in the STATUS register are automatically cleared by hardware.
Note:  The software update command (CTRLBSET.CMD=0x3) is acting independently of the LUPD
value.
A compare register is double buffered as in the following figure.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 791
Figure 35-7. Compare Channel Double Buffering
CCBUFVx
UPDATE
"write enable" "data write"
=
COUNT
"match"
EN
EN CCBUFx
CCx
Both the registers (PER/CCx) and corresponding buffer registers (PERBUF/CCBUFx) are available in the
I/O register map, and the double buffering feature is not mandatory. The double buffering is disabled by
writing a '1' to CTRLBSET.LUPD.
Note:  In NFRQ, MFRQ or PWM down-counting counter mode (CTRLBSET.DIR=1), when double
buffering is enabled (CTRLBCLR.LUPD=1), PERBUF register is continously copied into the PER
independently of update conditions.
Changing the Period
The counter period can be changed by writing a new TOP value to the Period register (PER or CC0,
depending on the waveform generation mode), which is available in 8-bit mode. Any period update on
registers (PER or CCx) is effective after the synchronization delay.
Figure 35-8. Unbuffered Single-Slope Up-Counting Operation
COUNT
MAX
New TOP written to
PER that is higher
than current COUNT
Counter Wraparound
New TOP written to
PER that is lower
than current COUNT
"clear" update
"write"
ZERO
A counter wraparound can occur in any operation mode when up-counting without buffering, see Figure
35-8.
COUNT and TOP are continuously compared, so when a new TOP value that is lower than current
COUNT is written to TOP, COUNT will wrap before a compare match.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 792
Figure 35-9. Unbuffered Single-Slope Down-Counting Operation
COUNT
MAX
New TOP written to
PER that is higher
than current COUNT
New TOP written to
PER that is lower
than current COUNT
"reload" update
"write"
ZERO
When double buffering is used, the buffer can be written at any time and the counter will still maintain
correct operation. The period register is always updated on the update condition, as shown in Figure
35-10. This prevents wraparound and the generation of odd waveforms.
Figure 35-10. Changing the Period Using Buffering
COUNT
MAX
New TOP written to
PER that is higher
than current COUNT
" clear" update
" write"
ZERO
New TOP written to
PER that is lower
than current COUNT
35.6.2.8 Capture Operations
To enable and use capture operations, the corresponding Capture Channel x Enable bit in the Control A
register (CTRLA.CAPTENx) must be written to '1'.
A capture trigger can be provided by input event line TC_EV or by asynchronous IO pin WO[x] for each
capture channel or by a TC event. To enable the capture from input event line, Event Input Enable bit in
the Event Control register (EVCTRL.TCEI) must be written to '1'. To enable the capture from the IO pin,
the Capture On Pin x Enable bit in CTRLA register (CTRLA.COPENx) must be written to '1'.
Note: 
1. The RETRIGGER, COUNT and START event actions are available only on an event from the Event
System.
2. Event system channels must be configured to operate in asynchronous mode of operation when
used for capture operations.
By default, a capture operation is done when a rising edge is detected on the input signal. Capture on
falling edge is available, its activation is depending on the input source:
• When the channel is used with a IO pin, write a '1' to the corresponding Invert Enable bit in the Drive
Control register (DRVCTRL.INVENx).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 793
• When the channel is counting events from the Event System, write a '1' to the TC Event Input Invert
Enable bit in Event Control register (EVCTRL.TCINV).
Figure 35-11. Capture Double Buffering
BV
"capture"
IF
COUNT
CCBx
CCx
EN
EN
"INT/DMA
request" data read
For input capture, the buffer register and the corresponding CCx act like a FIFO. When CCx is empty or
read, any content in CCBUFx is transferred to CCx. The buffer valid flag is passed to set the CCx
interrupt flag (IF) and generate the optional interrupt, event or DMA request. The CCBUFx register value
can't be read, all captured data must be read from CCx register.
35.6.2.8.1 Event Capture Action
The compare/capture channels can be used as input capture channels to capture events from the Event
System and give them a timestamp. The following figure shows four capture events for one capture
channel.
Figure 35-12. Input Capture Timing
events
COUNT
TOP
ZERO
Capture 0 Capture 1 Capture 2 Capture 3
The TC can detect capture overflow of the input capture channels: When a new capture event is detected
while the Capture Interrupt flag (INTFLAG.MCx) is still set, the new timestamp will not be stored and
INTFLAG.ERR will be set.
35.6.2.8.2 Period and Pulse-Width (PPW) Capture Action
The TC can perform two input captures and restart the counter on one of the edges. This enables the TC
to measure the pulse width and period and to characterize the frequency f and duty cycle of an input
signal:
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 794
=1
dutyCycle =
Figure 35-13. PWP Capture
Period (T)
external signal
events
COUNT
MAX
ZERO
"capture"
Pulsewitdh (tp)
CC0 CC0 CC1CC1
Selecting PWP in the Event Action bit group in the Event Control register (EVCTRL.EVACT) enables the
TC to perform one capture action on the rising edge and the other one on the falling edge. The period T
will be captured into CC1 and the pulse width tp in CC0. EVCTRL.EVACT=PPW (period and pulse-width)
offers identical functionality, but will capture T into CC0 and tp into CC1.
The TC Event Input Invert Enable bit in the Event Control register (EVCTRL.TCINV) is used to select
whether the wraparound should occur on the rising edge or the falling edge. If EVCTRL.TCINV=1, the
wraparound will happen on the falling edge. In case pin capture is enabled, this can also be achieved by
modifying the value of the DRVCTRL.INVENx bit.
The TC can detect capture overflow of the input capture channels: When a new capture event is detected
while the Capture Interrupt flag (INTFLAG.MCx) is still set, the new timestamp will not be stored and
INTFLAG.ERR will be set.
Note:  The corresponding capture is working only if the channel is enabled in capture mode
(CTRLA.CAPTENx=1). If not, the capture action is ignored and the channel is enabled in compare mode
of operation. Consequently, both channels must be enabled in order to fully characterize the input.
35.6.2.8.3 Pulse-Width Capture Action
The TC performs the input capture on the falling edge of the input signal. When the edge is detected, the
counter value is cleared and the TC stops counting. When a rising edge is detected on the input signal,
the counter restarts the counting operation. To enable the operation on opposite edges, the input signal to
capture must be inverted (refer to DRVCTRL.INVEN or EVCTRL.TCEINV).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 795
Figure 35-14. Pulse-Width Capture on Channel 0
external signal
events
COUNT
MAX
ZERO
"capture"
Pulsewitdh (tp)
CC0 CC0
"restart"
The TC can detect capture overflow of the input capture channels: When a new capture event is detected
while the Capture Interrupt flag (INTFLAG.MCx) is still set, the new timestamp will not be stored and
INTFLAG.ERR will be set.
35.6.3 Additional Features
35.6.3.1 One-Shot Operation
When one-shot is enabled, the counter automatically stops on the next counter overflow or underflow
condition. When the counter is stopped, the Stop bit in the Status register (STATUS.STOP) is
automatically set and the waveform outputs are set to zero.
One-shot operation is enabled by writing a '1' to the One-Shot bit in the Control B Set register
(CTRLBSET.ONESHOT), and disabled by writing a '1' to CTRLBCLR.ONESHOT. When enabled, the TC
will count until an overflow or underflow occurs and stops counting operation. The one-shot operation can
be restarted by a re-trigger software command, a re-trigger event, or a start event. When the counter
restarts its operation, STATUS.STOP is automatically cleared.
35.6.3.2 Time-Stamp Capture
This feature is enabled when the Capture Time Stamp (STAMP) Event Action in Event Control register
(EVCTRL.EVACT) is selected. The counter TOP value must be smaller than MAX.
When a capture event is detected, the COUNT value is copied into the corresponding Channel x
Compare/Capture Value (CCx) register. In case of an overflow, the MAX value is copied into the
corresponding CCx register.
When a valid captured value is present in the capture channel register, the corresponding Capture
Channel x Interrupt Flag (INTFLAG.MCx) is set.
The timer/counter can detect capture overflow of the input capture channels: When a new capture event
is detected while the Capture Channel interrupt flag (INTFLAG.MCx) is still set, the new time-stamp will
not be stored and INTFLAG.ERR will be set.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 796
Figure 35-15. Time-Stamp
MAX
ZERO
COUNT
TOP
"capture"
"overflow"
Capture Events
CCx Value COUNT COUNTTOP MAXCOUNT
35.6.3.3 Minimum Capture
The minimum capture is enabled by writing the CAPTMIN mode in the Channel n Capture Mode bits in
the Control A register (CTRLA.CAPTMODEn = CAPTMIN).
CCx Content:
In CAPTMIN operations, CCx keeps the Minimum captured values. Before enabling this mode of capture,
the user must initialize the corresponding CCx register value to a value different from zero. If the CCx
register initial value is zero, no captures will be performed using the corresponding channel.
MCx Behaviour:
In CAPTMIN operation, capture is performed only when on capture event time, the counter value is lower
than the last captured value. The MCx interrupt flag is set only when on capture event time, the counter
value is upper or equal to the value captured on the previous event. So interrupt flag is set when a new
absolute local Minimum value has been detected.
35.6.3.4 Maximum Capture
The maximum capture is enabled by writing the CAPTMAX mode in the Channel n Capture Mode bits in
the Control A register (CTRLA.CAPTMODEn = CAPTMAX).
CCx Content:
In CAPTMAX operations, CCx keeps the Maximum captured values. Before enabling this mode of
capture, the user must initialize the corresponding CCx register value to a value different from TOP. If the
CCx register initial value is TOP, no captures will be performed using the corresponding channel.
MCx Behaviour:
In CAPTMAX operation, capture is performed only when on capture event time, the counter value is
upper than the last captured value. The MCx interrupt flag is set only when on capture event time, the
counter value is lower or equal to the value captured on the previous event. So interrupt flag is set when
a new absolute local Maximum value has been detected.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 797
Figure 35-16. Maximum Capture Operation with CC0 Initialized with ZERO Value
COUNT "match"
ZERO
"clear" update
Input event
TOP
CC0
CC0 Event/
Interrupt
35.6.4 DMA Operation
The TC can generate the following DMA requests:
• Overflow (OVF): the request is set when an update condition (overflow, underflow or re-trigger) is
detected, the request is cleared by hardware on DMA acknowledge.
• Match or Capture Channel x (MCx): for a compare channel, the request is set on each compare
match detection, the request is cleared by hardware on DMA acknowledge. For a capture channel,
the request is set when valid data is present in the CCx register, and cleared when CCx register is
read.
35.6.5 Interrupts
The TC has the following interrupt sources:
• Overflow/Underflow (OVF)
• Match or Capture Channel x (MCx)
• Capture Overflow Error (ERR)
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG) is set when the interrupt condition occurs.
Each interrupt can be individually enabled by writing a '1' to the corresponding bit in the Interrupt Enable
Set register (INTENSET), and disabled by writing a '1' to the corresponding bit in the Interrupt Enable
Clear register (INTENCLR).
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until either the interrupt flag is cleared, the interrupt is disabled, or
the TC is reset. See INTFLAG for details on how to clear interrupt flags.
The TC has one common interrupt request line for all the interrupt sources. The user must read the
INTFLAG register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to Nested
Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
35.6.6 Events
The TC can generate the following output events:
• Overflow/Underflow (OVF)
• Match or Capture Channel x (MCx)
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 798
Writing a '1' to an Event Output bit in the Event Control register (EVCTRL.MCEOx) enables the
corresponding output event. The output event is disabled by writing EVCTRL.MCEOx=0.
One of the following event actions can be selected by the Event Action bit group in the Event Control
register (EVCTRL.EVACT):
• Disable event action (OFF)
• Start TC (START)
• Re-trigger TC (RETRIGGER)
• Count on event (COUNT)
• Capture time stamp (STAMP)
• Capture Period (PPW and PWP)
• Capture Pulse Width (PW)
Writing a '1' to the TC Event Input bit in the Event Control register (EVCTRL.TCEI) enables input events
to the TC. Writing a '0' to this bit disables input events to the TC. The TC requires only asynchronous
event inputs. For further details on how configuring the asynchronous events, refer to EVSYS - Event
System.
Related Links
29. EVSYS – Event System
35.6.7 Sleep Mode Operation
The TC can be configured to operate in any sleep mode. To be able to run in standby, the RUNSTDBY bit
in the Control A register (CTRLA.RUNSTDBY) must be '1'. This peripheral can wake up the device from
any sleep mode using interrupts or perform actions through the Event System.
If the On Demand bit in the Control A register (CTRLA.ONDEMAND) is written to '1', the module stops
requesting its peripheral clock when the STOP bit in STATUS register (STATUS.STOP) is set to '1'. When
a re-trigger or start condition is detected, the TC requests the clock before the operation starts.
35.6.8 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset and Enable bits in Control A register (CTRLA.SWRST and CTRLA.ENABLE)
• Capture Channel Buffer Valid bit in STATUS register (STATUS.CCBUFVx)
The following registers are synchronized when written:
• Control B Clear and Control B Set registers (CTRLBCLR and CTRLBSET)
• Count Value register (COUNT)
• Period Value and Period Buffer Value registers (PER and PERBUF)
• Channel x Compare/Capture Value and Channel x Compare/Capture Buffer Value registers (CCx and
CCBUFx)
The following registers are synchronized when read:
• Count Value register (COUNT): synchronization is done on demand through READSYNC command
(CTRLBSET.CMD).
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 799
Required read-synchronization is denoted by the "Read-Synchronized" property in the register
description.
35.7 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to Register Access Protection.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to Synchronization.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 800
35.7.1 Register Summary - 8-bit Mode
Offset Name Bit Pos.
0x00 CTRLA
7:0 ONDEMAND RUNSTDBY PRESCSYNC[1:0] MODE[1:0] ENABLE SWRST
15:8 ALOCK PRESCALER[2:0]
23:16 COPEN1 COPEN0 CAPTEN1 CAPTEN0
31:24 CAPTMODE1[1:0] CAPTMODE0[1:0]
0x04 CTRLBCLR 7:0 CMD[2:0] ONESHOT LUPD DIR
0x05 CTRLBSET 7:0 CMD[2:0] ONESHOT LUPD DIR
0x06 EVCTRL
7:0 TCEI TCINV EVACT[2:0]
15:8 MCEO1 MCEO0 OVFEO
0x08 INTENCLR 7:0 MC1 MC0 ERR OVF
0x09 INTENSET 7:0 MC1 MC0 ERR OVF
0x0A INTFLAG 7:0 MC1 MC0 ERR OVF
0x0B STATUS 7:0 CCBUFV1 CCBUFV0 PERBUFV SLAVE STOP
0x0C WAVE 7:0 WAVEGEN[1:0]
0x0D DRVCTRL 7:0 INVEN1 INVEN0
0x0E Reserved
0x0F DBGCTRL 7:0 DBGRUN
0x10 SYNCBUSY
7:0 CC1 CC0 COUNT STATUS CTRLB ENABLE SWRST
15:8
23:16
31:24
0x14 COUNT 7:0 COUNT[7:0]
0x15
...
0x1B
Reserved
0x1C CC0 7:0 CC[7:0]
0x1D CC1 7:0 CC[7:0]
0x1E
...
0x2E
Reserved
0x2F PERBUF 7:0 PERBUF[7:0]
0x30 CCBUF0 7:0 CCBUF[7:0]
0x31 CCBUF1 7:0 CCBUF[7:0]
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 801
35.7.1.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized, Enable-Protected
Bit 31 30 29 28 27 26 25 24
CAPTMODE1[1:0] CAPTMODE0[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
COPEN1 COPEN0 CAPTEN1 CAPTEN0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ALOCK PRESCALER[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY PRESCSYNC[1:0] MODE[1:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W R/W W
Reset 0 0 0 0 0 0 0 0
Bits 28:27 – CAPTMODE1[1:0] Capture mode Channel 1
These bits select the channel 1 capture mode.
Value Name Description
0x0 DEFAULT Default capture
0x1 CAPTMIN Minimum capture
0x2 CAPTMAX Maximum capture
0x3 Reserved
Bits 25:24 – CAPTMODE0[1:0] Capture mode Channel 0
These bits select the channel 0 capture mode.
Value Name Description
0x0 DEFAULT Default capture
0x1 CAPTMIN Minimum capture
0x2 CAPTMAX Maximum capture
0x3 Reserved
Bits 20, 21 – COPENx Capture On Pin x Enable
Bit x of COPEN[1:0] selects the trigger source for capture operation, either events or I/O pin input.
Value Description
0Event from Event System is selected as trigger source for capture operation on channel x.
1I/O pin is selected as trigger source for capture operation on channel x.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 802
Bits 16, 17 – CAPTENx Capture Channel x Enable
Bit x of CAPTEN[1:0] selects whether channel x is a capture or a compare channel.
These bits are not synchronized.
Value Description
0CAPTEN disables capture on channel x.
1CAPTEN enables capture on channel x.
Bit 11 – ALOCK Auto Lock
When this bit is set, Lock bit update (LUPD) is set to '1' on each overflow/underflow or re-trigger event.
This bit is not synchronized.
Value Description
0The LUPD bit is not affected on overflow/underflow, and re-trigger event.
1The LUPD bit is set on each overflow/underflow or re-trigger event.
Bits 10:8 – PRESCALER[2:0] Prescaler
These bits select the counter prescaler factor.
These bits are not synchronized.
Value Name Description
0x0 DIV1 Prescaler: GCLK_TC
0x1 DIV2 Prescaler: GCLK_TC/2
0x2 DIV4 Prescaler: GCLK_TC/4
0x3 DIV8 Prescaler: GCLK_TC/8
0x4 DIV16 Prescaler: GCLK_TC/16
0x5 DIV64 Prescaler: GCLK_TC/64
0x6 DIV256 Prescaler: GCLK_TC/256
0x7 DIV1024 Prescaler: GCLK_TC/1024
Bit 7 – ONDEMAND Clock On Demand
This bit selects the clock requirements when the TC is stopped.
In standby mode, if the Run in Standby bit (CTRLA.RUNSTDBY) is '0', ONDEMAND is forced to '0'.
This bit is not synchronized.
Value Description
0The On Demand is disabled. If On Demand is disabled, the TC will continue to request the
clock when its operation is stopped (STATUS.STOP=1).
1The On Demand is enabled. When On Demand is enabled, the stopped TC will not request
the clock. The clock is requested when a software re-trigger command is applied or when an
event with start/re-trigger action is detected.
Bit 6 – RUNSTDBY Run in Standby
This bit is used to keep the TC running in standby mode.
This bit is not synchronized.
Value Description
0The TC is halted in standby.
1The TC continues to run in standby.
Bits 5:4 – PRESCSYNC[1:0] Prescaler and Counter Synchronization
These bits select whether the counter should wrap around on the next GCLK_TCx clock or the next
prescaled GCLK_TCx clock. It also makes it possible to reset the prescaler.
These bits are not synchronized.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 803
Value Name Description
0x0 GCLK Reload or reset the counter on next generic clock
0x1 PRESC Reload or reset the counter on next prescaler clock
0x2 RESYNC Reload or reset the counter on next generic clock. Reset the prescaler counter
0x3 - Reserved
Bits 3:2 – MODE[1:0] Timer Counter Mode
These bits select the counter mode.
These bits are not synchronized.
Value Name Description
0x0 COUNT16 Counter in 16-bit mode
0x1 COUNT8 Counter in 8-bit mode
0x2 COUNT32 Counter in 32-bit mode
0x3 - Reserved
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately, and the ENABLE
Synchronization Busy bit in the SYNCBUSY register (SYNCBUSY.ENABLE) will be set.
SYNCBUSY.ENABLE will be cleared when the operation is complete.
This bit is not enable protected.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the TC, except DBGCTRL, to their initial state, and the TC will
be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence; all other writes in the same write-operation
will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 804
35.7.1.2 Control B Clear
Name:  CTRLBCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection, Read-Synchronized, Write-Synchronized
This register allows the user to clear bits in the CTRLB register without doing a read-modify-write
operation. Changes in this register will also be reflected in the Control B Set register (CTRLBSET).
Bit 7 6 5 4 3 2 1 0
CMD[2:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] Command
These bits are used for software control of the TC. The commands are executed on the next prescaled
GCLK_TC clock cycle. When a command has been executed, the CMD bit group will be read back as
zero.
Writing 0x0 to these bits has no effect.
Writing a '1' to any of these bits will clear the pending command.
Bit 2 – ONESHOT One-Shot on Counter
This bit controls one-shot operation of the TC.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will disable one-shot operation.
Value Description
0The TC will wrap around and continue counting on an overflow/underflow condition.
1The TC will wrap around and stop on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TC buffered registers.
When CTRLB.LUPD is set, no any update of the registers with value of its buffered register is performed
on hardware UPDATE condition. Locking the update ensures that all buffer registers are valid before an
hardware update is performed. After all the buffer registers are loaded correctly, the buffered registers
can be unlocked.
This bit has no effect when input capture operation is enabled.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the LUPD bit.
Value Description
0The CCBUFx and PERBUF buffer registers value are copied into CCx and PER registers on
hardware update condition.
1The CCBUFx and PERBUF buffer registers value are not copied into CCx and PER registers
on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the bit and make the counter count up.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 805
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 806
35.7.1.3 Control B Set
Name:  CTRLBSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection, Read-synchronized, Write-Synchronized
This register allows the user to set bits in the CTRLB register without doing a read-modify-write operation.
Changes in this register will also be reflected in the Control B Clear register (CTRLBCLR).
Bit 7 6 5 4 3 2 1 0
CMD[2:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] Command
These bits are used for software control of the TC. The commands are executed on the next prescaled
GCLK_TC clock cycle. When a command has been executed, the CMD bit group will be read back as
zero.
Writing 0x0 to these bits has no effect.
Writing a value different from 0x0 to these bits will issue a command for execution.
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Force a start, restart or retrigger
0x2 STOP Force a stop
0x3 UPDATE Force update of double buffered registers
0x4 READSYNC Force a read synchronization of COUNT
Bit 2 – ONESHOT One-Shot on Counter
This bit controls one-shot operation of the TC.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will enable one-shot operation.
Value Description
0The TC will wrap around and continue counting on an overflow/underflow condition.
1The TC will wrap around and stop on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TC buffered registers.
When CTRLB.LUPD is set, no any update of the registers with value of its buffered register is performed
on hardware UPDATE condition. Locking the update ensures that all buffer registers are valid before an
hardware update is performed. After all the buffer registers are loaded correctly, the buffered registers
can be unlocked.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the LUPD bit.
This bit has no effect when input capture operation is enabled.
Value Description
0The CCBUFx and PERBUF buffer registers value are copied into CCx and PER registers on
hardware update condition.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 807
Value Description
1The CCBUFx and PERBUF buffer registers value are not copied into CCx and PER registers
on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will clear the bit and make the counter count up.
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 808
35.7.1.4 Event Control
Name:  EVCTRL
Offset:  0x06
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
MCEO1 MCEO0 OVFEO
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
TCEI TCINV EVACT[2:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 13 – MCEO1 Match or Capture Channel x Event Output Enable [x = 1..0]
These bits enable the generation of an event for every match or capture on channel x.
Value Description
0Match/Capture event on channel x is disabled and will not be generated.
1Match/Capture event on channel x is enabled and will be generated for every compare/
capture.
Bit 12 – MCEO0 Match or Capture Channel x Event Output Enable [x = 1..0]
These bits enable the generation of an event for every match or capture on channel x.
Value Description
0Match/Capture event on channel x is disabled and will not be generated.
1Match/Capture event on channel x is enabled and will be generated for every compare/
capture.
Bit 8 – OVFEO Overflow/Underflow Event Output Enable
This bit enables the Overflow/Underflow event. When enabled, an event will be generated when the
counter overflows/underflows.
Value Description
0Overflow/Underflow event is disabled and will not be generated.
1Overflow/Underflow event is enabled and will be generated for every counter overflow/
underflow.
Bit 5 – TCEI TC Event Enable
This bit is used to enable asynchronous input events to the TC.
Value Description
0Incoming events are disabled.
1Incoming events are enabled.
Bit 4 – TCINV TC Inverted Event Input Polarity
This bit inverts the asynchronous input event source.
Value Description
0Input event source is not inverted.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 809
Value Description
1Input event source is inverted.
Bits 2:0 – EVACT[2:0] Event Action
These bits define the event action the TC will perform on an event.
Value Name Description
0x0 OFF Event action disabled
0x1 RETRIGGER Start, restart or retrigger TC on event
0x2 COUNT Count on event
0x3 START Start TC on event
0x4 STAMP Time stamp capture
0x5 PPW Period captured in CC0, pulse width in CC1
0x6 PWP Period captured in CC1, pulse width in CC0
0x7 PW Pulse width capture
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 810
35.7.1.5 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x08
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will clear the corresponding Match or Capture Channel x Interrupt Enable bit, which
disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 4 – MC0 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will clear the corresponding Match or Capture Channel x Interrupt Enable bit, which
disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 1 – ERR Error Interrupt Disable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Disable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Overflow Interrupt Enable bit, which disables the Overflow interrupt
request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 811
35.7.1.6 Interrupt Enable Set
Name:  INTENSET
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which
enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 4 – MC0 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which
enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 1 – ERR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Overflow Interrupt Enable bit, which enables the Overflow interrupt
request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 812
35.7.1.7 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x0A
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x
This flag is set on a comparison match, or when the corresponding CCx register contains a valid capture
value. This flag is set on the next CLK_TC_CNT cycle, and will generate an interrupt request if the
corresponding Match or Capture Channel x Interrupt Enable bit in the Interrupt Enable Set register
(INTENSET.MCx) is '1'.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture operation, this flag is automatically cleared when CCx register is read.
Bit 4 – MC0 Match or Capture Channel x
This flag is set on a comparison match, or when the corresponding CCx register contains a valid capture
value. This flag is set on the next CLK_TC_CNT cycle, and will generate an interrupt request if the
corresponding Match or Capture Channel x Interrupt Enable bit in the Interrupt Enable Set register
(INTENSET.MCx) is '1'.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture operation, this flag is automatically cleared when CCx register is read.
Bit 1 – ERR Error Interrupt Flag
This flag is set when a new capture occurs on a channel while the corresponding Match or Capture
Channel x interrupt flag is set, in which case there is nowhere to store the new capture.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Error interrupt flag.
Bit 0 – OVF Overflow Interrupt Flag
This flag is set on the next CLK_TC_CNT cycle after an overflow condition occurs, and will generate an
interrupt request if INTENCLR.OVF or INTENSET.OVF is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 813
35.7.1.8 Status
Name:  STATUS
Offset:  0x0B
Reset:  0x01
Property:  Read-Synchronized
Bit 7 6 5 4 3 2 1 0
CCBUFV1 CCBUFV0 PERBUFV SLAVE STOP
Access R/W R/W R/W R R
Reset 0 0 0 0 1
Bits 4, 5 – CCBUFV Channel x Compare or Capture Buffer Valid
For a compare channel x, the bit x is set when a new value is written to the corresponding CCBUFx
register.
The bit x is cleared by writing a '1' to it when CTRLB.LUPD is set, or it is cleared automatically by
hardware on UPDATE condition.
For a capture channel x, the bit x is set when a valid capture value is stored in the CCBUFx register. The
bit x is cleared automatically when the CCx register is read.
Bit 3 – PERBUFV Period Buffer Valid
This bit is set when a new value is written to the PERBUF register. The bit is cleared by writing '1' to the
corresponding location when CTRLB.LUPD is set, or automatically cleared by hardware on UPDATE
condition. This bit is available only in 8-bit mode and will always read zero in 16- and 32-bit modes.
Bit 1 – SLAVE Slave Status Flag
This bit is only available in 32-bit mode on the slave TC (i.e., TC1 and/or TC3). The bit is set when the
associated master TC (TC0 and TC2, respectively) is set to run in 32-bit mode.
Bit 0 – STOP Stop Status Flag
This bit is set when the TC is disabled, on a Stop command, or on an overflow/underflow condition when
the One-Shot bit in the Control B Set register (CTRLBSET.ONESHOT) is '1'.
Value Description
0Counter is running.
1Counter is stopped.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 814
35.7.1.9 Waveform Generation Control
Name:  WAVE
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
WAVEGEN[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – WAVEGEN[1:0] Waveform Generation Mode
These bits select the waveform generation operation. They affect the top value, as shown in 35.6.2.6.1
Waveform Output Operations. They also control whether frequency or PWM waveform generation should
be used. The waveform generation operations are explained in 35.6.2.6.1 Waveform Output Operations.
These bits are not synchronized.
Value Name Operation Top Value Output
Waveform
on Match
Output Waveform
on Wraparound
0x0 NFRQ Normal frequency PER1 / Max Toggle No action
0x1 MFRQ Match frequency CC0 Toggle No action
0x2 NPWM Normal PWM PER1 / Max Set Clear
0x3 MPWM Match PWM CC0 Set Clear
1) This depends on the TC mode: In 8-bit mode, the top value is the Period Value register (PER). In 16-
and 32-bit mode it is the respective MAX value.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 815
35.7.1.10 Driver Control
Name:  DRVCTRL
Offset:  0x0D
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
INVEN1 INVEN0
Access R/W R/W
Reset 0 0
Bits 0, 1 – INVENx Output Waveform x Invert Enable
Bit x of INVEN[1:0] selects inversion of the output or capture trigger input of channel x.
Value Description
0Disable inversion of the WO[x] output and IO input pin.
1Enable inversion of the WO[x] output and IO input pin.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 816
35.7.1.11 Debug Control
Name:  DBGCTRL
Offset:  0x0F
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Run in Debug Mode
This bit is not affected by a software Reset, and should not be changed by software while the TC is
enabled.
Value Description
0The TC is halted when the device is halted in debug mode.
1The TC continues normal operation when the device is halted in debug mode.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 817
35.7.1.12 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CC1 CC0 COUNT STATUS CTRLB ENABLE SWRST
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bits 6, 7 – CCx Compare/Capture Channel x Synchronization Busy
For details on CC channels number, refer to each TC feature list.
This bit is set when the synchronization of CCx between clock domains is started.
This bit is also set when the CCBUFx is written, and cleared on update condition. The bit is automatically
cleared when the STATUS.CCBUFx bit is cleared.
Bit 4 – COUNT COUNT Synchronization Busy
This bit is cleared when the synchronization of COUNT between the clock domains is complete.
This bit is set when the synchronization of COUNT between clock domains is started.
Bit 3 – STATUS STATUS Synchronization Busy
This bit is cleared when the synchronization of STATUS between the clock domains is complete.
This bit is set when a '1' is written to the Capture Channel Buffer Valid status flags (STATUS.CCBUFVx)
and the synchronization of STATUS between clock domains is started.
Bit 2 – CTRLB CTRLB Synchronization Busy
This bit is cleared when the synchronization of CTRLB between the clock domains is complete.
This bit is set when the synchronization of CTRLB between clock domains is started.
Bit 1 – ENABLE ENABLE Synchronization Busy
This bit is cleared when the synchronization of ENABLE bit between the clock domains is complete.
This bit is set when the synchronization of ENABLE bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 818
Bit 0 – SWRST SWRST Synchronization Busy
This bit is cleared when the synchronization of SWRST bit between the clock domains is complete.
This bit is set when the synchronization of SWRST bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 819
35.7.1.13 Counter Value, 8-bit Mode
Name:  COUNT
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Note:  Prior to any read access, this register must be synchronized by user by writing the according TC
Command value to the Control B Set register (CTRLBSET.CMD=READSYNC).
Bit 7 6 5 4 3 2 1 0
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – COUNT[7:0]  Counter Value
These bits contain the current counter value.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 820
35.7.1.14 Channel x Compare/Capture Value, 8-bit Mode
Name:  CCx
Offset:  0x1C + x*0x01 [x=0..1]
Reset:  0x00
Property:  Write-Synchronized, Read-Synchronized
Bit 7 6 5 4 3 2 1 0
CC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – CC[7:0] Channel x Compare/Capture Value
These bits contain the compare/capture value in 8-bit TC mode. In Match frequency (MFRQ) or Match
PWM (MPWM) waveform operation (WAVE.WAVEGEN), the CC0 register is used as a period register.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 821
35.7.1.15 Period Buffer Value, 8-bit Mode
Name:  PERBUF
Offset:  0x2F
Reset:  0xFF
Property:  Write-Synchronized
Bit 7 6 5 4 3 2 1 0
PERBUF[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 1
Bits 7:0 – PERBUF[7:0] Period Buffer Value
These bits hold the value of the period buffer register. The value is copied to PER register on UPDATE
condition.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 822
35.7.1.16 Channel x Compare Buffer Value, 8-bit Mode
Name:  CCBUFx
Offset:  0x30 + x*0x01 [x=0..1]
Reset:  0x00
Property:  Write-Synchronized
Bit 7 6 5 4 3 2 1 0
CCBUF[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:0 – CCBUF[7:0] Channel x Compare Buffer Value
These bits hold the value of the Channel x Compare Buffer Value. When the buffer valid flag is '1' and
double buffering is enabled (CTRLBCLR.LUPD=1), the data from buffer registers will be copied into the
corresponding CCx register under UPDATE condition (CTRLBSET.CMD=0x3), including the software
update command.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 823
35.7.2 Register Summary - 16-bit Mode
Offset Name Bit Pos.
0x00 CTRLA
7:0 ONDEMAND RUNSTDBY PRESCSYNC[1:0] MODE[1:0] ENABLE SWRST
15:8 ALOCK PRESCALER[2:0]
23:16 COPEN1 COPEN0 CAPTEN1 CAPTEN0
31:24 CAPTMODE1[1:0] CAPTMODE0[1:0]
0x04 CTRLBCLR 7:0 CMD[2:0] ONESHOT LUPD DIR
0x05 CTRLBSET 7:0 CMD[2:0] ONESHOT LUPD DIR
0x06 EVCTRL
7:0 TCEI TCINV EVACT[2:0]
15:8 MCEO1 MCEO0 OVFEO
0x08 INTENCLR 7:0 MC1 MC0 ERR OVF
0x09 INTENSET 7:0 MC1 MC0 ERR OVF
0x0A INTFLAG 7:0 MC1 MC0 ERR OVF
0x0B STATUS 7:0 CCBUFV1 CCBUFV0 PERBUFV SLAVE STOP
0x0C WAVE 7:0 WAVEGEN[1:0]
0x0D DRVCTRL 7:0 INVEN1 INVEN0
0x0E Reserved
0x0F DBGCTRL 7:0 DBGRUN
0x10 SYNCBUSY
7:0 CC1 CC0 COUNT STATUS CTRLB ENABLE SWRST
15:8
23:16
31:24
0x14 COUNT
7:0 COUNT[7:0]
15:8 COUNT[15:8]
0x16
...
0x1B
Reserved
0x1C CC0
7:0 CC[7:0]
15:8 CC[15:8]
0x1E CC1
7:0 CC[7:0]
15:8 CC[15:8]
0x20
...
0x2F
Reserved
0x30 CCBUF0
7:0 CCBUF[7:0]
15:8 CCBUF[15:8]
0x32 CCBUF1
7:0 CCBUF[7:0]
15:8 CCBUF[15:8]
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 824
35.7.2.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized, Enable-Protected
Bit 31 30 29 28 27 26 25 24
CAPTMODE1[1:0] CAPTMODE0[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
COPEN1 COPEN0 CAPTEN1 CAPTEN0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ALOCK PRESCALER[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY PRESCSYNC[1:0] MODE[1:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W R/W W
Reset 0 0 0 0 0 0 0 0
Bits 28:27 – CAPTMODE1[1:0] Capture mode Channel 1
These bits select the channel 1 capture mode.
Value Name Description
0x0 DEFAULT Default capture
0x1 CAPTMIN Minimum capture
0x2 CAPTMAX Maximum capture
0x3 Reserved
Bits 25:24 – CAPTMODE0[1:0] Capture mode Channel 0
These bits select the channel 0 capture mode.
Value Name Description
0x0 DEFAULT Default capture
0x1 CAPTMIN Minimum capture
0x2 CAPTMAX Maximum capture
0x3 Reserved
Bits 20, 21 – COPENx Capture On Pin x Enable
Bit x of COPEN[1:0] selects the trigger source for capture operation, either events or I/O pin input.
Value Description
0Event from Event System is selected as trigger source for capture operation on channel x.
1I/O pin is selected as trigger source for capture operation on channel x.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 825
Bits 16, 17 – CAPTENx Capture Channel x Enable
Bit x of CAPTEN[1:0] selects whether channel x is a capture or a compare channel.
These bits are not synchronized.
Value Description
0CAPTEN disables capture on channel x.
1CAPTEN enables capture on channel x.
Bit 11 – ALOCK Auto Lock
When this bit is set, Lock bit update (LUPD) is set to '1' on each overflow/underflow or re-trigger event.
This bit is not synchronized.
Value Description
0The LUPD bit is not affected on overflow/underflow, and re-trigger event.
1The LUPD bit is set on each overflow/underflow or re-trigger event.
Bits 10:8 – PRESCALER[2:0] Prescaler
These bits select the counter prescaler factor.
These bits are not synchronized.
Value Name Description
0x0 DIV1 Prescaler: GCLK_TC
0x1 DIV2 Prescaler: GCLK_TC/2
0x2 DIV4 Prescaler: GCLK_TC/4
0x3 DIV8 Prescaler: GCLK_TC/8
0x4 DIV16 Prescaler: GCLK_TC/16
0x5 DIV64 Prescaler: GCLK_TC/64
0x6 DIV256 Prescaler: GCLK_TC/256
0x7 DIV1024 Prescaler: GCLK_TC/1024
Bit 7 – ONDEMAND Clock On Demand
This bit selects the clock requirements when the TC is stopped.
In standby mode, if the Run in Standby bit (CTRLA.RUNSTDBY) is '0', ONDEMAND is forced to '0'.
This bit is not synchronized.
Value Description
0The On Demand is disabled. If On Demand is disabled, the TC will continue to request the
clock when its operation is stopped (STATUS.STOP=1).
1The On Demand is enabled. When On Demand is enabled, the stopped TC will not request
the clock. The clock is requested when a software re-trigger command is applied or when an
event with start/re-trigger action is detected.
Bit 6 – RUNSTDBY Run in Standby
This bit is used to keep the TC running in standby mode.
This bit is not synchronized.
Value Description
0The TC is halted in standby.
1The TC continues to run in standby.
Bits 5:4 – PRESCSYNC[1:0] Prescaler and Counter Synchronization
These bits select whether the counter should wrap around on the next GCLK_TCx clock or the next
prescaled GCLK_TCx clock. It also makes it possible to reset the prescaler.
These bits are not synchronized.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 826
Value Name Description
0x0 GCLK Reload or reset the counter on next generic clock
0x1 PRESC Reload or reset the counter on next prescaler clock
0x2 RESYNC Reload or reset the counter on next generic clock. Reset the prescaler counter
0x3 - Reserved
Bits 3:2 – MODE[1:0] Timer Counter Mode
These bits select the counter mode.
These bits are not synchronized.
Value Name Description
0x0 COUNT16 Counter in 16-bit mode
0x1 COUNT8 Counter in 8-bit mode
0x2 COUNT32 Counter in 32-bit mode
0x3 - Reserved
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately, and the ENABLE
Synchronization Busy bit in the SYNCBUSY register (SYNCBUSY.ENABLE) will be set.
SYNCBUSY.ENABLE will be cleared when the operation is complete.
This bit is not enable protected.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the TC, except DBGCTRL, to their initial state, and the TC will
be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence; all other writes in the same write-operation
will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 827
35.7.2.2 Control B Clear
Name:  CTRLBCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection, Read-Synchronized, Write-Synchronized
This register allows the user to clear bits in the CTRLB register without doing a read-modify-write
operation. Changes in this register will also be reflected in the Control B Set register (CTRLBSET).
Bit 7 6 5 4 3 2 1 0
CMD[2:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] Command
These bits are used for software control of the TC. The commands are executed on the next prescaled
GCLK_TC clock cycle. When a command has been executed, the CMD bit group will be read back as
zero.
Writing 0x0 to these bits has no effect.
Writing a '1' to any of these bits will clear the pending command.
Bit 2 – ONESHOT One-Shot on Counter
This bit controls one-shot operation of the TC.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will disable one-shot operation.
Value Description
0The TC will wrap around and continue counting on an overflow/underflow condition.
1The TC will wrap around and stop on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TC buffered registers.
When CTRLB.LUPD is set, no any update of the registers with value of its buffered register is performed
on hardware UPDATE condition. Locking the update ensures that all buffer registers are valid before an
hardware update is performed. After all the buffer registers are loaded correctly, the buffered registers
can be unlocked.
This bit has no effect when input capture operation is enabled.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the LUPD bit.
Value Description
0The CCBUFx and PERBUF buffer registers value are copied into CCx and PER registers on
hardware update condition.
1The CCBUFx and PERBUF buffer registers value are not copied into CCx and PER registers
on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the bit and make the counter count up.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 828
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 829
35.7.2.3 Control B Set
Name:  CTRLBSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection, Read-synchronized, Write-Synchronized
This register allows the user to set bits in the CTRLB register without doing a read-modify-write operation.
Changes in this register will also be reflected in the Control B Clear register (CTRLBCLR).
Bit 7 6 5 4 3 2 1 0
CMD[2:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] Command
These bits are used for software control of the TC. The commands are executed on the next prescaled
GCLK_TC clock cycle. When a command has been executed, the CMD bit group will be read back as
zero.
Writing 0x0 to these bits has no effect.
Writing a value different from 0x0 to these bits will issue a command for execution.
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Force a start, restart or retrigger
0x2 STOP Force a stop
0x3 UPDATE Force update of double buffered registers
0x4 READSYNC Force a read synchronization of COUNT
Bit 2 – ONESHOT One-Shot on Counter
This bit controls one-shot operation of the TC.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will enable one-shot operation.
Value Description
0The TC will wrap around and continue counting on an overflow/underflow condition.
1The TC will wrap around and stop on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TC buffered registers.
When CTRLB.LUPD is set, no any update of the registers with value of its buffered register is performed
on hardware UPDATE condition. Locking the update ensures that all buffer registers are valid before an
hardware update is performed. After all the buffer registers are loaded correctly, the buffered registers
can be unlocked.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the LUPD bit.
This bit has no effect when input capture operation is enabled.
Value Description
0The CCBUFx and PERBUF buffer registers value are copied into CCx and PER registers on
hardware update condition.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 830
Value Description
1The CCBUFx and PERBUF buffer registers value are not copied into CCx and PER registers
on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will clear the bit and make the counter count up.
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 831
35.7.2.4 Event Control
Name:  EVCTRL
Offset:  0x06
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
MCEO1 MCEO0 OVFEO
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
TCEI TCINV EVACT[2:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 13 – MCEO1 Match or Capture Channel x Event Output Enable [x = 1..0]
These bits enable the generation of an event for every match or capture on channel x.
Value Description
0Match/Capture event on channel x is disabled and will not be generated.
1Match/Capture event on channel x is enabled and will be generated for every compare/
capture.
Bit 12 – MCEO0 Match or Capture Channel x Event Output Enable [x = 1..0]
These bits enable the generation of an event for every match or capture on channel x.
Value Description
0Match/Capture event on channel x is disabled and will not be generated.
1Match/Capture event on channel x is enabled and will be generated for every compare/
capture.
Bit 8 – OVFEO Overflow/Underflow Event Output Enable
This bit enables the Overflow/Underflow event. When enabled, an event will be generated when the
counter overflows/underflows.
Value Description
0Overflow/Underflow event is disabled and will not be generated.
1Overflow/Underflow event is enabled and will be generated for every counter overflow/
underflow.
Bit 5 – TCEI TC Event Enable
This bit is used to enable asynchronous input events to the TC.
Value Description
0Incoming events are disabled.
1Incoming events are enabled.
Bit 4 – TCINV TC Inverted Event Input Polarity
This bit inverts the asynchronous input event source.
Value Description
0Input event source is not inverted.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 832
Value Description
1Input event source is inverted.
Bits 2:0 – EVACT[2:0] Event Action
These bits define the event action the TC will perform on an event.
Value Name Description
0x0 OFF Event action disabled
0x1 RETRIGGER Start, restart or retrigger TC on event
0x2 COUNT Count on event
0x3 START Start TC on event
0x4 STAMP Time stamp capture
0x5 PPW Period captured in CC0, pulse width in CC1
0x6 PWP Period captured in CC1, pulse width in CC0
0x7 PW Pulse width capture
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 833
35.7.2.5 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x08
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will clear the corresponding Match or Capture Channel x Interrupt Enable bit, which
disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 4 – MC0 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will clear the corresponding Match or Capture Channel x Interrupt Enable bit, which
disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 1 – ERR Error Interrupt Disable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Disable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Overflow Interrupt Enable bit, which disables the Overflow interrupt
request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 834
35.7.2.6 Interrupt Enable Set
Name:  INTENSET
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which
enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 4 – MC0 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which
enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 1 – ERR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Overflow Interrupt Enable bit, which enables the Overflow interrupt
request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 835
35.7.2.7 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x0A
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x
This flag is set on a comparison match, or when the corresponding CCx register contains a valid capture
value. This flag is set on the next CLK_TC_CNT cycle, and will generate an interrupt request if the
corresponding Match or Capture Channel x Interrupt Enable bit in the Interrupt Enable Set register
(INTENSET.MCx) is '1'.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture operation, this flag is automatically cleared when CCx register is read.
Bit 4 – MC0 Match or Capture Channel x
This flag is set on a comparison match, or when the corresponding CCx register contains a valid capture
value. This flag is set on the next CLK_TC_CNT cycle, and will generate an interrupt request if the
corresponding Match or Capture Channel x Interrupt Enable bit in the Interrupt Enable Set register
(INTENSET.MCx) is '1'.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture operation, this flag is automatically cleared when CCx register is read.
Bit 1 – ERR Error Interrupt Flag
This flag is set when a new capture occurs on a channel while the corresponding Match or Capture
Channel x interrupt flag is set, in which case there is nowhere to store the new capture.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Error interrupt flag.
Bit 0 – OVF Overflow Interrupt Flag
This flag is set on the next CLK_TC_CNT cycle after an overflow condition occurs, and will generate an
interrupt request if INTENCLR.OVF or INTENSET.OVF is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 836
35.7.2.8 Status
Name:  STATUS
Offset:  0x0B
Reset:  0x01
Property:  Read-Synchronized
Bit 7 6 5 4 3 2 1 0
CCBUFV1 CCBUFV0 PERBUFV SLAVE STOP
Access R/W R/W R/W R R
Reset 0 0 0 0 1
Bits 4, 5 – CCBUFV Channel x Compare or Capture Buffer Valid
For a compare channel x, the bit x is set when a new value is written to the corresponding CCBUFx
register.
The bit x is cleared by writing a '1' to it when CTRLB.LUPD is set, or it is cleared automatically by
hardware on UPDATE condition.
For a capture channel x, the bit x is set when a valid capture value is stored in the CCBUFx register. The
bit x is cleared automatically when the CCx register is read.
Bit 3 – PERBUFV Period Buffer Valid
This bit is set when a new value is written to the PERBUF register. The bit is cleared by writing '1' to the
corresponding location when CTRLB.LUPD is set, or automatically cleared by hardware on UPDATE
condition. This bit is available only in 8-bit mode and will always read zero in 16- and 32-bit modes.
Bit 1 – SLAVE Slave Status Flag
This bit is only available in 32-bit mode on the slave TC (i.e., TC1 and/or TC3). The bit is set when the
associated master TC (TC0 and TC2, respectively) is set to run in 32-bit mode.
Bit 0 – STOP Stop Status Flag
This bit is set when the TC is disabled, on a Stop command, or on an overflow/underflow condition when
the One-Shot bit in the Control B Set register (CTRLBSET.ONESHOT) is '1'.
Value Description
0Counter is running.
1Counter is stopped.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 837
35.7.2.9 Waveform Generation Control
Name:  WAVE
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
WAVEGEN[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – WAVEGEN[1:0] Waveform Generation Mode
These bits select the waveform generation operation. They affect the top value, as shown in 35.6.2.6.1
Waveform Output Operations. They also control whether frequency or PWM waveform generation should
be used. The waveform generation operations are explained in 35.6.2.6.1 Waveform Output Operations.
These bits are not synchronized.
Value Name Operation Top Value Output
Waveform
on Match
Output Waveform
on Wraparound
0x0 NFRQ Normal frequency PER1 / Max Toggle No action
0x1 MFRQ Match frequency CC0 Toggle No action
0x2 NPWM Normal PWM PER1 / Max Set Clear
0x3 MPWM Match PWM CC0 Set Clear
1) This depends on the TC mode: In 8-bit mode, the top value is the Period Value register (PER). In 16-
and 32-bit mode it is the respective MAX value.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 838
35.7.2.10 Driver Control
Name:  DRVCTRL
Offset:  0x0D
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
INVEN1 INVEN0
Access R/W R/W
Reset 0 0
Bits 0, 1 – INVENx Output Waveform x Invert Enable
Bit x of INVEN[1:0] selects inversion of the output or capture trigger input of channel x.
Value Description
0Disable inversion of the WO[x] output and IO input pin.
1Enable inversion of the WO[x] output and IO input pin.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 839
35.7.2.11 Debug Control
Name:  DBGCTRL
Offset:  0x0F
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Run in Debug Mode
This bit is not affected by a software Reset, and should not be changed by software while the TC is
enabled.
Value Description
0The TC is halted when the device is halted in debug mode.
1The TC continues normal operation when the device is halted in debug mode.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 840
35.7.2.12 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CC1 CC0 COUNT STATUS CTRLB ENABLE SWRST
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bits 6, 7 – CCx Compare/Capture Channel x Synchronization Busy
For details on CC channels number, refer to each TC feature list.
This bit is set when the synchronization of CCx between clock domains is started.
This bit is also set when the CCBUFx is written, and cleared on update condition. The bit is automatically
cleared when the STATUS.CCBUFx bit is cleared.
Bit 4 – COUNT COUNT Synchronization Busy
This bit is cleared when the synchronization of COUNT between the clock domains is complete.
This bit is set when the synchronization of COUNT between clock domains is started.
Bit 3 – STATUS STATUS Synchronization Busy
This bit is cleared when the synchronization of STATUS between the clock domains is complete.
This bit is set when a '1' is written to the Capture Channel Buffer Valid status flags (STATUS.CCBUFVx)
and the synchronization of STATUS between clock domains is started.
Bit 2 – CTRLB CTRLB Synchronization Busy
This bit is cleared when the synchronization of CTRLB between the clock domains is complete.
This bit is set when the synchronization of CTRLB between clock domains is started.
Bit 1 – ENABLE ENABLE Synchronization Busy
This bit is cleared when the synchronization of ENABLE bit between the clock domains is complete.
This bit is set when the synchronization of ENABLE bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 841
Bit 0 – SWRST SWRST Synchronization Busy
This bit is cleared when the synchronization of SWRST bit between the clock domains is complete.
This bit is set when the synchronization of SWRST bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 842
35.7.2.13 Counter Value, 16-bit Mode
Name:  COUNT
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Note:  Prior to any read access, this register must be synchronized by user by writing the according TC
Command value to the Control B Set register (CTRLBSET.CMD=READSYNC).
Bit 15 14 13 12 11 10 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – COUNT[15:0]  Counter Value
These bits contain the current counter value.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 843
35.7.2.14 Channel x Compare/Capture Value, 16-bit Mode
Name:  CCx
Offset:  0x1C + x*0x02 [x=0..1]
Reset:  0x0000
Property:  Write-Synchronized
Bit 15 14 13 12 11 10 9 8
CC[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – CC[15:0] Channel x Compare/Capture Value
These bits contain the compare/capture value in 16-bit TC mode. In Match frequency (MFRQ) or Match
PWM (MPWM) waveform operation (WAVE.WAVEGEN), the CC0 register is used as a period register.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 844
35.7.2.15 Channel x Compare Buffer Value, 16-bit Mode
Name:  CCBUFx
Offset:  0x30 + x*0x02 [x=0..1]
Reset:  0x0000
Property:  Write-Synchronized
Bit 15 14 13 12 11 10 9 8
CCBUF[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CCBUF[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – CCBUF[15:0] Channel x Compare Buffer Value
These bits hold the value of the Channel x Compare Buffer Value. When the buffer valid flag is '1' and
double buffering is enabled (CTRLBCLR.LUPD=1), the data from buffer registers will be copied into the
corresponding CCx register under UPDATE condition (CTRLBSET.CMD=0x3), including the software
update command.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 845
35.7.3 Register Summary - 32-bit Mode
Offset Name Bit Pos.
0x00 CTRLA
7:0 ONDEMAND RUNSTDBY PRESCSYNC[1:0] MODE[1:0] ENABLE SWRST
15:8 ALOCK PRESCALER[2:0]
23:16 COPEN1 COPEN0 CAPTEN1 CAPTEN0
31:24 CAPTMODE1[1:0] CAPTMODE0[1:0]
0x04 CTRLBCLR 7:0 CMD[2:0] ONESHOT LUPD DIR
0x05 CTRLBSET 7:0 CMD[2:0] ONESHOT LUPD DIR
0x06 EVCTRL
7:0 TCEI TCINV EVACT[2:0]
15:8 MCEO1 MCEO0 OVFEO
0x08 INTENCLR 7:0 MC1 MC0 ERR OVF
0x09 INTENSET 7:0 MC1 MC0 ERR OVF
0x0A INTFLAG 7:0 MC1 MC0 ERR OVF
0x0B STATUS 7:0 CCBUFV1 CCBUFV0 PERBUFV SLAVE STOP
0x0C WAVE 7:0 WAVEGEN[1:0]
0x0D DRVCTRL 7:0 INVEN1 INVEN0
0x0E Reserved
0x0F DBGCTRL 7:0 DBGRUN
0x10 SYNCBUSY
7:0 CC1 CC0 COUNT STATUS CTRLB ENABLE SWRST
15:8
23:16
31:24
0x14 COUNT
7:0 COUNT[7:0]
15:8 COUNT[15:8]
23:16 COUNT[23:16]
31:24 COUNT[31:24]
0x18
...
0x1B
Reserved
0x1C CC0
7:0 CC[7:0]
15:8 CC[15:8]
23:16 CC[23:16]
31:24 CC[31:24]
0x20 CC1
7:0 CC[7:0]
15:8 CC[15:8]
23:16 CC[23:16]
31:24 CC[31:24]
0x24
...
0x2F
Reserved
0x30 CCBUF0
7:0 CCBUF[7:0]
15:8 CCBUF[15:8]
23:16 CCBUF[23:16]
31:24 CCBUF[31:24]
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 846
...........continued
Offset Name Bit Pos.
0x34 CCBUF1
7:0 CCBUF[7:0]
15:8 CCBUF[15:8]
23:16 CCBUF[23:16]
31:24 CCBUF[31:24]
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 847
35.7.3.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized, Enable-Protected
Bit 31 30 29 28 27 26 25 24
CAPTMODE1[1:0] CAPTMODE0[1:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
COPEN1 COPEN0 CAPTEN1 CAPTEN0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
ALOCK PRESCALER[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY PRESCSYNC[1:0] MODE[1:0] ENABLE SWRST
Access R/W R/W R/W R/W R/W R/W R/W W
Reset 0 0 0 0 0 0 0 0
Bits 28:27 – CAPTMODE1[1:0] Capture mode Channel 1
These bits select the channel 1 capture mode.
Value Name Description
0x0 DEFAULT Default capture
0x1 CAPTMIN Minimum capture
0x2 CAPTMAX Maximum capture
0x3 Reserved
Bits 25:24 – CAPTMODE0[1:0] Capture mode Channel 0
These bits select the channel 0 capture mode.
Value Name Description
0x0 DEFAULT Default capture
0x1 CAPTMIN Minimum capture
0x2 CAPTMAX Maximum capture
0x3 Reserved
Bits 20, 21 – COPENx Capture On Pin x Enable
Bit x of COPEN[1:0] selects the trigger source for capture operation, either events or I/O pin input.
Value Description
0Event from Event System is selected as trigger source for capture operation on channel x.
1I/O pin is selected as trigger source for capture operation on channel x.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 848
Bits 16, 17 – CAPTENx Capture Channel x Enable
Bit x of CAPTEN[1:0] selects whether channel x is a capture or a compare channel.
These bits are not synchronized.
Value Description
0CAPTEN disables capture on channel x.
1CAPTEN enables capture on channel x.
Bit 11 – ALOCK Auto Lock
When this bit is set, Lock bit update (LUPD) is set to '1' on each overflow/underflow or re-trigger event.
This bit is not synchronized.
Value Description
0The LUPD bit is not affected on overflow/underflow, and re-trigger event.
1The LUPD bit is set on each overflow/underflow or re-trigger event.
Bits 10:8 – PRESCALER[2:0] Prescaler
These bits select the counter prescaler factor.
These bits are not synchronized.
Value Name Description
0x0 DIV1 Prescaler: GCLK_TC
0x1 DIV2 Prescaler: GCLK_TC/2
0x2 DIV4 Prescaler: GCLK_TC/4
0x3 DIV8 Prescaler: GCLK_TC/8
0x4 DIV16 Prescaler: GCLK_TC/16
0x5 DIV64 Prescaler: GCLK_TC/64
0x6 DIV256 Prescaler: GCLK_TC/256
0x7 DIV1024 Prescaler: GCLK_TC/1024
Bit 7 – ONDEMAND Clock On Demand
This bit selects the clock requirements when the TC is stopped.
In standby mode, if the Run in Standby bit (CTRLA.RUNSTDBY) is '0', ONDEMAND is forced to '0'.
This bit is not synchronized.
Value Description
0The On Demand is disabled. If On Demand is disabled, the TC will continue to request the
clock when its operation is stopped (STATUS.STOP=1).
1The On Demand is enabled. When On Demand is enabled, the stopped TC will not request
the clock. The clock is requested when a software re-trigger command is applied or when an
event with start/re-trigger action is detected.
Bit 6 – RUNSTDBY Run in Standby
This bit is used to keep the TC running in standby mode.
This bit is not synchronized.
Value Description
0The TC is halted in standby.
1The TC continues to run in standby.
Bits 5:4 – PRESCSYNC[1:0] Prescaler and Counter Synchronization
These bits select whether the counter should wrap around on the next GCLK_TCx clock or the next
prescaled GCLK_TCx clock. It also makes it possible to reset the prescaler.
These bits are not synchronized.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 849
Value Name Description
0x0 GCLK Reload or reset the counter on next generic clock
0x1 PRESC Reload or reset the counter on next prescaler clock
0x2 RESYNC Reload or reset the counter on next generic clock. Reset the prescaler counter
0x3 - Reserved
Bits 3:2 – MODE[1:0] Timer Counter Mode
These bits select the counter mode.
These bits are not synchronized.
Value Name Description
0x0 COUNT16 Counter in 16-bit mode
0x1 COUNT8 Counter in 8-bit mode
0x2 COUNT32 Counter in 32-bit mode
0x3 - Reserved
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately, and the ENABLE
Synchronization Busy bit in the SYNCBUSY register (SYNCBUSY.ENABLE) will be set.
SYNCBUSY.ENABLE will be cleared when the operation is complete.
This bit is not enable protected.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the TC, except DBGCTRL, to their initial state, and the TC will
be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence; all other writes in the same write-operation
will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 850
35.7.3.2 Control B Clear
Name:  CTRLBCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection, Read-Synchronized, Write-Synchronized
This register allows the user to clear bits in the CTRLB register without doing a read-modify-write
operation. Changes in this register will also be reflected in the Control B Set register (CTRLBSET).
Bit 7 6 5 4 3 2 1 0
CMD[2:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] Command
These bits are used for software control of the TC. The commands are executed on the next prescaled
GCLK_TC clock cycle. When a command has been executed, the CMD bit group will be read back as
zero.
Writing 0x0 to these bits has no effect.
Writing a '1' to any of these bits will clear the pending command.
Bit 2 – ONESHOT One-Shot on Counter
This bit controls one-shot operation of the TC.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will disable one-shot operation.
Value Description
0The TC will wrap around and continue counting on an overflow/underflow condition.
1The TC will wrap around and stop on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TC buffered registers.
When CTRLB.LUPD is set, no any update of the registers with value of its buffered register is performed
on hardware UPDATE condition. Locking the update ensures that all buffer registers are valid before an
hardware update is performed. After all the buffer registers are loaded correctly, the buffered registers
can be unlocked.
This bit has no effect when input capture operation is enabled.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the LUPD bit.
Value Description
0The CCBUFx and PERBUF buffer registers value are copied into CCx and PER registers on
hardware update condition.
1The CCBUFx and PERBUF buffer registers value are not copied into CCx and PER registers
on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the bit and make the counter count up.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 851
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 852
35.7.3.3 Control B Set
Name:  CTRLBSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection, Read-synchronized, Write-Synchronized
This register allows the user to set bits in the CTRLB register without doing a read-modify-write operation.
Changes in this register will also be reflected in the Control B Clear register (CTRLBCLR).
Bit 7 6 5 4 3 2 1 0
CMD[2:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] Command
These bits are used for software control of the TC. The commands are executed on the next prescaled
GCLK_TC clock cycle. When a command has been executed, the CMD bit group will be read back as
zero.
Writing 0x0 to these bits has no effect.
Writing a value different from 0x0 to these bits will issue a command for execution.
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Force a start, restart or retrigger
0x2 STOP Force a stop
0x3 UPDATE Force update of double buffered registers
0x4 READSYNC Force a read synchronization of COUNT
Bit 2 – ONESHOT One-Shot on Counter
This bit controls one-shot operation of the TC.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will enable one-shot operation.
Value Description
0The TC will wrap around and continue counting on an overflow/underflow condition.
1The TC will wrap around and stop on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TC buffered registers.
When CTRLB.LUPD is set, no any update of the registers with value of its buffered register is performed
on hardware UPDATE condition. Locking the update ensures that all buffer registers are valid before an
hardware update is performed. After all the buffer registers are loaded correctly, the buffered registers
can be unlocked.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the LUPD bit.
This bit has no effect when input capture operation is enabled.
Value Description
0The CCBUFx and PERBUF buffer registers value are copied into CCx and PER registers on
hardware update condition.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 853
Value Description
1The CCBUFx and PERBUF buffer registers value are not copied into CCx and PER registers
on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will clear the bit and make the counter count up.
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 854
35.7.3.4 Event Control
Name:  EVCTRL
Offset:  0x06
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
MCEO1 MCEO0 OVFEO
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
TCEI TCINV EVACT[2:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 13 – MCEO1 Match or Capture Channel x Event Output Enable [x = 1..0]
These bits enable the generation of an event for every match or capture on channel x.
Value Description
0Match/Capture event on channel x is disabled and will not be generated.
1Match/Capture event on channel x is enabled and will be generated for every compare/
capture.
Bit 12 – MCEO0 Match or Capture Channel x Event Output Enable [x = 1..0]
These bits enable the generation of an event for every match or capture on channel x.
Value Description
0Match/Capture event on channel x is disabled and will not be generated.
1Match/Capture event on channel x is enabled and will be generated for every compare/
capture.
Bit 8 – OVFEO Overflow/Underflow Event Output Enable
This bit enables the Overflow/Underflow event. When enabled, an event will be generated when the
counter overflows/underflows.
Value Description
0Overflow/Underflow event is disabled and will not be generated.
1Overflow/Underflow event is enabled and will be generated for every counter overflow/
underflow.
Bit 5 – TCEI TC Event Enable
This bit is used to enable asynchronous input events to the TC.
Value Description
0Incoming events are disabled.
1Incoming events are enabled.
Bit 4 – TCINV TC Inverted Event Input Polarity
This bit inverts the asynchronous input event source.
Value Description
0Input event source is not inverted.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 855
Value Description
1Input event source is inverted.
Bits 2:0 – EVACT[2:0] Event Action
These bits define the event action the TC will perform on an event.
Value Name Description
0x0 OFF Event action disabled
0x1 RETRIGGER Start, restart or retrigger TC on event
0x2 COUNT Count on event
0x3 START Start TC on event
0x4 STAMP Time stamp capture
0x5 PPW Period captured in CC0, pulse width in CC1
0x6 PWP Period captured in CC1, pulse width in CC0
0x7 PW Pulse width capture
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 856
35.7.3.5 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x08
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will clear the corresponding Match or Capture Channel x Interrupt Enable bit, which
disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 4 – MC0 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will clear the corresponding Match or Capture Channel x Interrupt Enable bit, which
disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 1 – ERR Error Interrupt Disable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Error Interrupt Enable bit, which disables the Error interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Disable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Overflow Interrupt Enable bit, which disables the Overflow interrupt
request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 857
35.7.3.6 Interrupt Enable Set
Name:  INTENSET
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which
enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 4 – MC0 Match or Capture Channel x Interrupt Enable
Writing a '0' to these bits has no effect.
Writing a '1' to MCx will set the corresponding Match or Capture Channel x Interrupt Enable bit, which
enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 1 – ERR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Error Interrupt Enable bit, which enables the Error interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Overflow Interrupt Enable bit, which enables the Overflow interrupt
request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 858
35.7.3.7 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x0A
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
MC1 MC0 ERR OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 5 – MC1 Match or Capture Channel x
This flag is set on a comparison match, or when the corresponding CCx register contains a valid capture
value. This flag is set on the next CLK_TC_CNT cycle, and will generate an interrupt request if the
corresponding Match or Capture Channel x Interrupt Enable bit in the Interrupt Enable Set register
(INTENSET.MCx) is '1'.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture operation, this flag is automatically cleared when CCx register is read.
Bit 4 – MC0 Match or Capture Channel x
This flag is set on a comparison match, or when the corresponding CCx register contains a valid capture
value. This flag is set on the next CLK_TC_CNT cycle, and will generate an interrupt request if the
corresponding Match or Capture Channel x Interrupt Enable bit in the Interrupt Enable Set register
(INTENSET.MCx) is '1'.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In capture operation, this flag is automatically cleared when CCx register is read.
Bit 1 – ERR Error Interrupt Flag
This flag is set when a new capture occurs on a channel while the corresponding Match or Capture
Channel x interrupt flag is set, in which case there is nowhere to store the new capture.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Error interrupt flag.
Bit 0 – OVF Overflow Interrupt Flag
This flag is set on the next CLK_TC_CNT cycle after an overflow condition occurs, and will generate an
interrupt request if INTENCLR.OVF or INTENSET.OVF is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 859
35.7.3.8 Status
Name:  STATUS
Offset:  0x0B
Reset:  0x01
Property:  Read-Synchronized
Bit 7 6 5 4 3 2 1 0
CCBUFV1 CCBUFV0 PERBUFV SLAVE STOP
Access R/W R/W R/W R R
Reset 0 0 0 0 1
Bits 4, 5 – CCBUFV Channel x Compare or Capture Buffer Valid
For a compare channel x, the bit x is set when a new value is written to the corresponding CCBUFx
register.
The bit x is cleared by writing a '1' to it when CTRLB.LUPD is set, or it is cleared automatically by
hardware on UPDATE condition.
For a capture channel x, the bit x is set when a valid capture value is stored in the CCBUFx register. The
bit x is cleared automatically when the CCx register is read.
Bit 3 – PERBUFV Period Buffer Valid
This bit is set when a new value is written to the PERBUF register. The bit is cleared by writing '1' to the
corresponding location when CTRLB.LUPD is set, or automatically cleared by hardware on UPDATE
condition. This bit is available only in 8-bit mode and will always read zero in 16- and 32-bit modes.
Bit 1 – SLAVE Slave Status Flag
This bit is only available in 32-bit mode on the slave TC (i.e., TC1 and/or TC3). The bit is set when the
associated master TC (TC0 and TC2, respectively) is set to run in 32-bit mode.
Bit 0 – STOP Stop Status Flag
This bit is set when the TC is disabled, on a Stop command, or on an overflow/underflow condition when
the One-Shot bit in the Control B Set register (CTRLBSET.ONESHOT) is '1'.
Value Description
0Counter is running.
1Counter is stopped.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 860
35.7.3.9 Waveform Generation Control
Name:  WAVE
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
WAVEGEN[1:0]
Access R/W R/W
Reset 0 0
Bits 1:0 – WAVEGEN[1:0] Waveform Generation Mode
These bits select the waveform generation operation. They affect the top value, as shown in 35.6.2.6.1
Waveform Output Operations. They also control whether frequency or PWM waveform generation should
be used. The waveform generation operations are explained in 35.6.2.6.1 Waveform Output Operations.
These bits are not synchronized.
Value Name Operation Top Value Output
Waveform
on Match
Output Waveform
on Wraparound
0x0 NFRQ Normal frequency PER1 / Max Toggle No action
0x1 MFRQ Match frequency CC0 Toggle No action
0x2 NPWM Normal PWM PER1 / Max Set Clear
0x3 MPWM Match PWM CC0 Set Clear
1) This depends on the TC mode: In 8-bit mode, the top value is the Period Value register (PER). In 16-
and 32-bit mode it is the respective MAX value.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 861
35.7.3.10 Driver Control
Name:  DRVCTRL
Offset:  0x0D
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
INVEN1 INVEN0
Access R/W R/W
Reset 0 0
Bits 0, 1 – INVENx Output Waveform x Invert Enable
Bit x of INVEN[1:0] selects inversion of the output or capture trigger input of channel x.
Value Description
0Disable inversion of the WO[x] output and IO input pin.
1Enable inversion of the WO[x] output and IO input pin.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 862
35.7.3.11 Debug Control
Name:  DBGCTRL
Offset:  0x0F
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Run in Debug Mode
This bit is not affected by a software Reset, and should not be changed by software while the TC is
enabled.
Value Description
0The TC is halted when the device is halted in debug mode.
1The TC continues normal operation when the device is halted in debug mode.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 863
35.7.3.12 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
CC1 CC0 COUNT STATUS CTRLB ENABLE SWRST
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bits 6, 7 – CCx Compare/Capture Channel x Synchronization Busy
For details on CC channels number, refer to each TC feature list.
This bit is set when the synchronization of CCx between clock domains is started.
This bit is also set when the CCBUFx is written, and cleared on update condition. The bit is automatically
cleared when the STATUS.CCBUFx bit is cleared.
Bit 4 – COUNT COUNT Synchronization Busy
This bit is cleared when the synchronization of COUNT between the clock domains is complete.
This bit is set when the synchronization of COUNT between clock domains is started.
Bit 3 – STATUS STATUS Synchronization Busy
This bit is cleared when the synchronization of STATUS between the clock domains is complete.
This bit is set when a '1' is written to the Capture Channel Buffer Valid status flags (STATUS.CCBUFVx)
and the synchronization of STATUS between clock domains is started.
Bit 2 – CTRLB CTRLB Synchronization Busy
This bit is cleared when the synchronization of CTRLB between the clock domains is complete.
This bit is set when the synchronization of CTRLB between clock domains is started.
Bit 1 – ENABLE ENABLE Synchronization Busy
This bit is cleared when the synchronization of ENABLE bit between the clock domains is complete.
This bit is set when the synchronization of ENABLE bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 864
Bit 0 – SWRST SWRST Synchronization Busy
This bit is cleared when the synchronization of SWRST bit between the clock domains is complete.
This bit is set when the synchronization of SWRST bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 865
35.7.3.13 Counter Value, 32-bit Mode
Name:  COUNT
Offset:  0x14
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Note:  Prior to any read access, this register must be synchronized by user by writing the according TC
Command value to the Control B Set register (CTRLBSET.CMD=READSYNC).
Bit 31 30 29 28 27 26 25 24
COUNT[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
COUNT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – COUNT[31:0]  Counter Value
These bits contain the current counter value.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 866
35.7.3.14 Channel x Compare/Capture Value, 32-bit Mode
Name:  CCx
Offset:  0x1C + x*0x04 [x=0..1]
Reset:  0x00000000
Property:  Write-Synchronized
Bit 31 30 29 28 27 26 25 24
CC[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CC[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CC[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CC[31:0] Channel x Compare/Capture Value
These bits contain the compare/capture value in 32-bit TC mode. In Match frequency (MFRQ) or Match
PWM (MPWM) waveform operation (WAVE.WAVEGEN), the CC0 register is used as a period register.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 867
35.7.3.15 Channel x Compare Buffer Value, 32-bit Mode
Name:  CCBUFx
Offset:  0x30 + x*0x04 [x=0..1]
Reset:  0x00000000
Property:  Write-Synchronized
Bit 31 30 29 28 27 26 25 24
CCBUF[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CCBUF[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CCBUF[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CCBUF[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – CCBUF[31:0] Channel x Compare Buffer Value
These bits hold the value of the Channel x Compare Buffer Value. When the buffer valid flag is '1' and
double buffering is enabled (CTRLBCLR.LUPD=1), the data from buffer registers will be copied into the
corresponding CCx register under UPDATE condition (CTRLBSET.CMD=0x3), including the software
update command.
SAM C20/C21 Family Data Sheet
TC – Timer/Counter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 868
36. TCC – Timer/Counter for Control Applications
36.1 Overview
The device provides three instances of the Timer/Counter for Control applications (TCC) peripheral,
TCC[2:0].
Each TCC instance consists of a counter, a prescaler, compare/capture channels and control logic. The
counter can be set to count events or clock pulses. The counter together with the compare/capture
channels can be configured to time stamp input events, allowing capture of frequency and pulse-width. It
can also perform waveform generation, such as frequency generation and pulse-width modulation.
Waveform extensions are featured for motor control, ballast, LED, H-bridge, power converters, and other
types of power control applications. They allow for low-side and high-side output with optional dead-time
insertion. Waveform extensions can also generate a synchronized bit pattern across the waveform output
pins. The fault options enable fault protection for safe and deterministic handling, disabling and/or shut
down of external drivers.
Figure 36-1 shows all features in TCC.
Note:  The TCC configurations, such as channel numbers and features, may be reduced for some of the
TCC instances.
Related Links
6.2.5 TCC Configurations
36.2 Features
• Up to four compare/capture channels (CC) with:
– Double buffered period setting
– Double buffered compare or capture channel
– Circular buffer on period and compare channel registers
• Waveform generation:
– Frequency generation
– Single-slope pulse-width modulation (PWM)
– Dual-slope PWM with half-cycle reload capability
• Input capture:
– Event capture
– Frequency capture
– Pulse-width capture
• Waveform extensions:
– Configurable distribution of compare channels outputs across port pins
– Low-side and high-side output with programmable dead-time insertion
– Waveform swap option with double buffer support
– Pattern generation with double buffer support
– Dithering support
• Fault protection for safe disabling of drivers:
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 869
– Two recoverable fault sources
– Two non-recoverable fault sources
– Debugger can be a source of non-recoverable fault
• Input events:
– Two input events (EVx) for counter
– One input event (MCx) for each channel
• Output events:
– Three output events (Count, Re-Trigger and Overflow) are available for counter
– One Compare Match/Input Capture event output for each channel
• Interrupts:
– Overflow and Re-Trigger interrupt
– Compare Match/Input Capture interrupt
– Interrupt on fault detection
• Can be used with DMA and can trigger DMA transactions
36.3 Block Diagram
Figure 36-1. Timer/Counter for Control Applications - Block Diagram
Base Counter
Compare/Capture
(Unit x = {0,1,…,3})
Counter
=
CCx
CCBUFx
Waveform
Generation
BV
=
PER
COUNT
BV
= 0
"count"
"clear"
"direction"
"load" Control Logic
Prescaler
OVF (INT/Event/DMA Req.)
ERR (INT Req.)
TOP
"match" MCx (INT/Event/DMA Req.)
Control Logic
"capture"
UPDATE
BOTTOM
Recoverable
Faults
Output
Matrix
Dead-Time
Insertion
SWAP
Pattern
Generation
Non-recoverable
Faults
WO[0]
WO[1]
WO[2]
WO[3]
WO[4]
WO[5]
WO[6]
WO[7]
Event
System
"TCCx_EV0" (TCE0)
"TCCx_EV1" (TCE1)
"TCCx_MCx"
"event"
PERBUFx
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 870
36.4 Signal Description
Pin Name Type Description
TCCx/WO[0] Digital output Compare channel 0 waveform output
TCCx/WO[1] Digital output Compare channel 1 waveform output
… ... ...
TCCx/WO[WO_NUM-1] Digital output Compare channel n waveform output
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
Related Links
6. I/O Multiplexing and Considerations
36.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
36.5.1 I/O Lines
In order to use the I/O lines of this peripheral, the I/O pins must be configured using the I/O Pin Controller
(PORT).
Related Links
28. PORT - I/O Pin Controller
36.5.2 Power Management
This peripheral can continue to operate in any sleep mode where its source clock is running. The
interrupts can wake up the device from sleep modes. Events connected to the event system can trigger
other operations in the system without exiting sleep modes.
36.5.3 Clocks
The TCC bus clocks (CLK_TCCx_APB) can be enabled and disabled in the Main Clock module. The
default state of CLK_TCCx_APB can be found in the Peripheral Clock Masking section (see the Related
Links below).
A generic clock (GCLK_TCCx) is required to clock the TCC. This clock must be configured and enabled
in the generic clock controller before using the TCC. Note that TCC0 and TCC1 share a peripheral clock
generator.
The generic clocks (GCLK_TCCx) are asynchronous to the bus clock (CLK_TCCx_APB). Due to this
asynchronicity, writing certain registers will require synchronization between the clock domains. Refer to
36.6.7 Synchronization for further details.
Related Links
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 871
36.5.4 DMA
The DMA request lines are connected to the DMA Controller (DMAC). In order to use DMA requests with
this peripheral the DMAC must be configured first. Refer to DMAC – Direct Memory Access Controller for
details.
Related Links
25. DMAC – Direct Memory Access Controller
36.5.5 Interrupts
The interrupt request line is connected to the Interrupt Controller. In order to use interrupt requests of this
peripheral, the Interrupt Controller (NVIC) must be configured first. Refer to Nested Vector Interrupt
Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
36.5.6 Events
The events of this peripheral are connected to the Event System.
Related Links
29. EVSYS – Event System
36.5.7 Debug Operation
When the CPU is halted in debug mode, this peripheral will halt normal operation. This peripheral can be
forced to continue operation during debugging - refer to the Debug Control (DBGCTRL) register for
details.
Refer to 36.8.8 DBGCTRL register for details.
36.5.8 Register Access Protection
Registers with write-access can be optionally write-protected by the Peripheral Access Controller (PAC),
except for the following:
• Interrupt Flag register (INTFLAG)
• Status register (STATUS)
• Period and Period Buffer registers (PER, PERBUF)
• Compare/Capture and Compare/Capture Buffer registers (CCx, CCBUFx)
• Control Waveform register (WAVE)
• Control Waveform Buffer register (WAVEBUF)
• Pattern Generation Value and Pattern Generation Value Buffer registers (PATT, PATTBUF)
Note:  Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
Write-protection does not apply for accesses through an external debugger.
36.5.9 Analog Connections
Not applicable.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 872
36.6 Functional Description
36.6.1 Principle of Operation
The following definitions are used throughout the documentation:
Table 36-1. Timer/Counter for Control Applications - Definitions
Name Description
TOP The counter reaches TOP when it becomes equal to the highest value in
the count sequence. The TOP value can be the same as Period (PER)
or the Compare Channel 0 (CC0) register value depending on the
waveform generator mode in 36.6.2.5.1 Waveform Output Generation
Operations.
ZERO The counter reaches ZERO when it contains all zeroes.
MAX The counter reaches maximum when it contains all ones.
UPDATE The timer/counter signals an update when it reaches ZERO or TOP,
depending on the direction settings.
Timer The timer/counter clock control is handled by an internal source.
Counter The clock control is handled externally (e.g., counting external events).
CC For compare operations, the CC are referred to as "compare channels."
For capture operations, the CC are referred to as "capture channels."
Each TCC instance has up to four compare/capture channels (CCx).
The counter register (COUNT), period registers with buffer (PER and PERBUF), and compare and
capture registers with buffers (CCx and CCBUFx) are 16- or 24-bit registers, depending on each TCC
instance. Each buffer register has a buffer valid (BUFV) flag that indicates when the buffer contains a new
value.
Under normal operation, the counter value is continuously compared to the TOP or ZERO value to
determine whether the counter has reached TOP or ZERO. In either case, the TCC can generate
interrupt requests, request DMA transactions, or generate events for the Event System. In waveform
generator mode, these comparisons are used to set the waveform period or pulse width.
A prescaled generic clock (GCLK_TCCx) and events from the event system can be used to control the
counter. The event system is also used as a source to the input capture.
The Recoverable Fault Unit enables event controlled waveforms by acting directly on the generated
waveforms of the TCC compare channels output. These events can restart, halt the timer/counter period,
shorten the output pulse active time, or disable waveform output as long as the fault condition is present.
This can typically be used for current sensing regulation, and zero-crossing and demagnetization re-
triggering.
The MCE0 and MCE1 asynchronous event sources are shared with the Recoverable Fault Unit. Only
asynchronous events are used internally when fault unit extension is enabled. For further details on how
to configure asynchronous events routing, refer to EVSYS – Event System.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 873
Recoverable fault sources can be filtered and/or windowed to avoid false triggering, for example from I/O
pin glitches, by using digital filtering, input blanking, and qualification options. See also 36.6.3.5
Recoverable Faults.
In order to support applications with different types of motor control, ballast, LED, H-bridge, power
converter, and other types of power switching applications, the following independent units are
implemented in some of the TCC instances as optional and successive units:
• Recoverable faults and non-recoverable faults
• Output matrix
• Dead-time insertion
• Swap
• Pattern generation
See also Figure 36-1.
The output matrix (OTMX) can distribute and route out the TCC waveform outputs across the port pins in
different configurations, each optimized for different application types. The Dead-Time Insertion (DTI) unit
splits the four lower OTMX outputs into two non-overlapping signals: the non-inverted low side (LS) and
inverted high side (HS) of the waveform output with optional dead-time insertion between LS and HS
switching. The SWAP unit can swap the LS and HS pin outputs, and can be used for fast decay motor
control.
The pattern generation unit can be used to generate synchronized waveforms with constant logic level on
TCC UPDATE conditions. This is useful for easy stepper motor and full bridge control.
The non-recoverable fault module enables event controlled fault protection by acting directly on the
generated waveforms of the timer/counter compare channel outputs. When a non-recoverable fault
condition is detected, the output waveforms are forced to a preconfigured value that is safe for the
application. This is typically used for instant and predictable shut down and disabling high current or
voltage drives.
The count event sources (TCE0 and TCE1) are shared with the non-recoverable fault extension. The
events can be optionally filtered. If the filter options are not used, the non-recoverable faults provide an
immediate asynchronous action on waveform output, even for cases where the clock is not present. For
further details on how to configure asynchronous events routing, refer to section EVSYS – Event System.
Related Links
29. EVSYS – Event System
36.6.2 Basic Operation
36.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the TCC is
disabled(CTRLA.ENABLE=0):
• Control A (CTRLA) register, except Run Standby (RUNSTDBY), Enable (ENABLE) and Software
Reset (SWRST) bits
• Recoverable Fault n Control registers (FCTRLA and FCTRLB)
• Waveform Extension Control register (WEXCTRL)
• Drive Control register (DRVCTRL)
• Event Control register (EVCTRL)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 874
Enable-protected bits in the CTRLA register can be written at the same time as CTRLA.ENABLE is
written to '1', but not at the same time as CTRLA.ENABLE is written to '0'. Enable-protection is denoted
by the “Enable-Protected” property in the register description.
Before the TCC is enabled, it must be configured as outlined by the following steps:
1. Enable the TCC bus clock (CLK_TCCx_APB).
2. If Capture mode is required, enable the channel in capture mode by writing a '1' to the Capture
Enable bit in the Control A register (CTRLA.CPTEN).
Optionally, the following configurations can be set before enabling TCC:
1. Select PRESCALER setting in the Control A register (CTRLA.PRESCALER).
2. Select Prescaler Synchronization setting in Control A register (CTRLA.PRESCSYNC).
3. If down-counting operation is desired, write the Counter Direction bit in the Control B Set register
(CTRLBSET.DIR) to '1'.
4. Select the Waveform Generation operation in the WAVE register (WAVE.WAVEGEN).
5. Select the Waveform Output Polarity in the WAVE register (WAVE.POL).
6. The waveform output can be inverted for the individual channels using the Waveform Output Invert
Enable bit group in the Driver register (DRVCTRL.INVEN).
36.6.2.2 Enabling, Disabling, and Resetting
The TCC is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The
TCC is disabled by writing a zero to CTRLA.ENABLE.
The TCC is reset by writing '1' to the Software Reset bit in the Control A register (CTRLA.SWRST). All
registers in the TCC, except DBGCTRL, will be reset to their initial state, and the TCC will be disabled.
Refer to Control A (36.8.1 CTRLA) register for details.
The TCC should be disabled before the TCC is reset to avoid undefined behavior.
36.6.2.3 Prescaler Selection
The GCLK_TCCx clock is fed into the internal prescaler.
The prescaler consists of a counter that counts up to the selected prescaler value, whereupon the output
of the prescaler toggles.
If the prescaler value is higher than one, the counter update condition can be optionally executed on the
next GCLK_TCC clock pulse or the next prescaled clock pulse. For further details, refer to the Prescaler
(CTRLA.PRESCALER) and Counter Synchronization (CTRLA.PRESYNC) descriptions.
Prescaler outputs from 1 to 1/1024 are available. For a complete list of available prescaler outputs, see
the register description for the Prescaler bit group in the Control A register (CTRLA.PRESCALER).
Note:  When counting events, the prescaler is bypassed.
The joint stream of prescaler ticks and event action ticks is called CLK_TCC_COUNT.
Figure 36-2. Prescaler
TCCx EV0/1
COUNT
PRESCALER
PRESCALER EVACT 0/1
GCLK_TCC
GCLK_TCC /
{1,2,4,8,64,256,1024 } CLK_TCC_COUNT
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 875
36.6.2.4 Counter Operation
Depending on the mode of operation, the counter is cleared, reloaded, incremented, or decremented at
each TCC clock input (CLK_TCC_COUNT). A counter clear or reload mark the end of current counter
cycle and the start of a new one.
The counting direction is set by the Direction bit in the Control B register (CTRLB.DIR). If the bit is zero,
it's counting up and one if counting down.
The counter will count up or down for each tick (clock or event) until it reaches TOP or ZERO. When it's
counting up and TOP is reached, the counter will be set to zero at the next tick (overflow) and the
Overflow Interrupt Flag in the Interrupt Flag Status and Clear register (INTFLAG.OVF) will be set. When
down-counting, the counter is reloaded with the TOP value when ZERO is reached (underflow), and
INTFLAG.OVF is set.
INTFLAG.OVF can be used to trigger an interrupt, a DMA request, or an event. An overflow/underflow
occurrence (i.e. a compare match with TOP/ZERO) will stop counting if the One-Shot bit in the Control B
register is set (CTRLBSET.ONESHOT). The One-Shot feature is explained in the Additional Features
section.
Figure 36-3. Counter Operation
DIR
COUNT
MAX
"reload" update
TOP
COUNT writtenDirection Change
ZERO
"clear" update
It is possible to change the counter value (by writing directly in the COUNT register) even when the
counter is running. The COUNT value will always be ZERO or TOP, depending on direction set by
CTRLBSET.DIR or CTRLBCLR.DIR, when starting the TCC, unless a different value has been written to
it, or the TCC has been stopped at a value other than ZERO. The write access has higher priority than
count, clear, or reload. The direction of the counter can also be changed during normal operation. See
also Figure 36-3.
Stop Command
A stop command can be issued from software by using TCC Command bits in Control B Set register
(CTRLBSET.CMD=0x2, STOP).
Pause Event Action
A pause command can be issued when the stop event action is configured in the Input Event Action 1 bits
in Event Control register (EVCTRL.EVACT1=0x3, STOP).
Re-Trigger Command and Event Action
A re-trigger command can be issued from software by using TCC Command bits in Control B Set register
(CTRLBSET.CMD=0x1, RETRIGGER), or from event when the re-trigger event action is configured in the
Input Event 0/1 Action bits in Event Control register (EVCTRL.EVACTn=0x1, RETRIGGER).
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 876
When the command is detected during counting operation, the counter will be reloaded or cleared,
depending on the counting direction (CTRLBSET.DIR or CTRLBCLR.DIR). The Re-Trigger bit in the
Interrupt Flag Status and Clear register will be set (INTFLAG.TRG). It is also possible to generate an
event by writing a '1' to the Re-Trigger Event Output Enable bit in the Event Control register
(EVCTRL.TRGEO). If the re-trigger command is detected when the counter is stopped, the counter will
resume counting operation from the value in COUNT.
Note: 
When a re-trigger event action is configured in the Event Action bits in the Event Control register
(EVCTRL.EVACTn=0x1, RETRIGGER), enabling the counter will not start the counter. The counter will
start on the next incoming event and restart on corresponding following event.
Start Event Action
The start action can be selected in the Event Control register (EVCTRL.EVACT0=0x3, START) and can
start the counting operation when previously stopped. The event has no effect if the counter is already
counting. When the module is enabled, the counter operation starts when the event is received or when a
re-trigger software command is applied.
Note: 
When a start event action is configured in the Event Action bits in the Event Control register
(EVCTRL.EVACT0=0x3, START), enabling the counter will not start the counter. The counter will start on
the next incoming event, but it will not restart on subsequent events.
Count Event Action
The TCC can count events. When an event is received, the counter increases or decreases the value,
depending on direction settings (CTRLBSET.DIR or CTRLBCLR.DIR).
The count event action is selected by the Event Action 0 bit group in the Event Control register
(EVCTRL.EVACT0=0x5, COUNT).
Direction Event Action
The direction event action can be selected in the Event Control register (EVCTRL.EVACT1=0x2, DIR).
When this event is used, the asynchronous event path specified in the event system must be configured
or selected. The direction event action can be used to control the direction of the counter operation,
depending on external events level. When received, the event level overrides the Direction settings
(CTRLBSET.DIR or CTRLBCLR.DIR) and the direction bit value is updated accordingly.
Increment Event Action
The increment event action can be selected in the Event Control register (EVCTRL.EVACT0=0x4, INC)
and can change the counter state when an event is received. When the TCE0 event (TCCx_EV0) is
received, the counter increments, whatever the direction setting (CTRLBSET.DIR or CTRLBCLR.DIR) is.
Decrement Event Action
The decrement event action can be selected in the Event Control register (EVCTRL.EVACT1=0x4, DEC)
and can change the counter state when an event is received. When the TCE1 (TCCx_EV1) event is
received, the counter decrements, whatever the direction setting (CTRLBSET.DIR or CTRLBCLR.DIR) is.
Non-recoverable Fault Event Action
Non-recoverable fault actions can be selected in the Event Control register (EVCTRL.EVACTn=0x7,
FAULT). When received, the counter will be stopped and the output of the compare channels is
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 877
overridden according to the Driver Control register settings (DRVCTRL.NREx and DRVCTRL.NRVx).
TCE0 and TCE1 must be configured as asynchronous events.
Event Action Off
If the event action is disabled (EVCTRL.EVACTn=0x0, OFF), enabling the counter will also start the
counter.
Related Links
36.6.3.1 One-Shot Operation
36.6.2.5 Compare Operations
By default, the Compare/Capture channel is configured for compare operations. To perform capture
operations, it must be re-configured.
When using the TCC with the Compare/Capture Value registers (CCx) for compare operations, the
counter value is continuously compared to the values in the CCx registers. This can be used for timer or
for waveform operation.
The Channel x Compare/Capture Buffer Value (CCBUFx) registers provide double buffer capability. The
double buffering synchronizes the update of the CCx register with the buffer value at the UPDATE
condition or a force update command (CTRLBSET.CMD=0x3, UPDATE). For further details, refer to
36.6.2.6 Double Buffering. The synchronization prevents the occurrence of odd-length, non-symmetrical
pulses and ensures glitch-free output.
36.6.2.5.1 Waveform Output Generation Operations
The compare channels can be used for waveform generation on output port pins. To make the waveform
available on the connected pin, the following requirements must be fulfilled:
1. Choose a waveform generation mode in the Waveform Generation Operation bit in Waveform
register (WAVE.WAVEGEN).
2. Optionally invert the waveform output WO[x] by writing the corresponding Waveform Output x
Inversion bit in the Driver Control register (DRVCTRL.INVENx).
3. Configure the pins with the I/O Pin Controller. Refer to PORT - I/O Pin Controller for details.
The counter value is continuously compared with each CCx value. On a comparison match, the Match or
Capture Channel x bit in the Interrupt Flag Status and Clear register (INTFLAG.MCx) will be set on the
next zero-to-one transition of CLK_TCC_COUNT (see Normal Frequency Operation). An interrupt and/or
event can be generated on the same condition if Match/Capture occurs, i.e. INTENSET.MCx and/or
EVCTRL.MCEOx is '1'. Both interrupt and event can be generated simultaneously. The same condition
generates a DMA request.
There are seven waveform configurations for the Waveform Generation Operation bit group in the
Waveform register (WAVE.WAVEGEN). This will influence how the waveform is generated and impose
restrictions on the top value. The configurations are:
• Normal Frequency (NFRQ)
• Match Frequency (MFRQ)
• Normal Pulse-Width Modulation (NPWM)
• Dual-slope, interrupt/event at TOP (DSTOP)
• Dual-slope, interrupt/event at ZERO (DSBOTTOM)
• Dual-slope, interrupt/event at Top and ZERO (DSBOTH)
• Dual-slope, critical interrupt/event at ZERO (DSCRITICAL)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 878
When using MFRQ configuration, the TOP value is defined by the CC0 register value. For the other
waveform operations, the TOP value is defined by the Period (PER) register value.
For dual-slope waveform operations, the update time occurs when the counter reaches ZERO. For the
other waveforms generation modes, the update time occurs on counter wraparound, on overflow,
underflow, or re-trigger.
The table below shows the update counter and overflow event/interrupt generation conditions in different
operation modes.
Table 36-2. Counter Update and Overflow Event/interrupt Conditions
Name Operation TOP Update Output Waveform OVFIF/Event
On Match On Update Up Down
NFRQ Normal
Frequency
PER TOP/
ZERO
Toggle Stable TOP ZERO
MFRQ Match
Frequency
CC0 TOP/
ZERO
Toggle Stable TOP ZERO
NPWM Single-
slope PWM
PER TOP/
ZERO
See section 'Output
Polarity' below
TOP ZERO
DSCRITICAL Dual-slope
PWM
PER ZERO - ZERO
DSBOTTOM Dual-slope
PWM
PER ZERO - ZERO
DSBOTH Dual-slope
PWM
PER TOP(1) &
ZERO
TOP ZERO
DSTOP Dual-slope
PWM
PER ZERO TOP –
1. The UPDATE condition on TOP only will occur when circular buffer is enabled for the channel.
Related Links
36.6.3.2 Circular Buffer
28. PORT - I/O Pin Controller
36.6.2.5.2 Normal Frequency (NFRQ)
For Normal Frequency generation, the period time (T) is controlled by the period register (PER). The
waveform generation output (WO[x]) is toggled on each compare match between COUNT and CCx, and
the corresponding Match or Capture Channel x Interrupt Flag (EVCTRL.MCEOx) will be set.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 879
Figure 36-4. Normal Frequency Operation
COUNT
MAX
TOP
ZERO
CCx
WO[x]
Direction Change COUNT Written
"reload" update
"clear" update
"match"
Period (T)
36.6.2.5.3 Match Frequency (MFRQ)
For Match Frequency generation, the period time (T) is controlled by CC0 register instead of PER. WO[0]
toggles on each update condition.
Figure 36-5. Match Frequency Operation
COUNT
MAX
CC0
COUNT WrittenDirection Change
ZERO
WO[0]
"reload" update
"clear" update
36.6.2.5.4 Normal Pulse-Width Modulation (NPWM)
NPWM uses single-slope PWM generation.
36.6.2.5.5 Single-Slope PWM Operation
For single-slope PWM generation, the period time (T) is controlled by Top value, and CCx controls the
duty cycle of the generated waveform output. When up-counting, the WO[x] is set at start or compare
match between the COUNT and TOP values, and cleared on compare match between COUNT and CCx
register values. When down-counting, the WO[x] is cleared at start or compare match between the
COUNT and ZERO values, and set on compare match between COUNT and CCx register values.
Figure 36-6. Single-Slope PWM Operation
COUNT
MAX
TOP "match"
ZERO
CCx=ZERO
CCx
CCx=TOP
"clear" update
WO[x]
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 880
The following equation calculates the exact resolution for a single-slope PWM (RPWM_SS) waveform:
PWM_SS =log(TOP+1)
log(2)
The PWM frequency depends on the Period register value (PER) and the peripheral clock frequency
(fGCLK_TCC), and can be calculated by the following equation:
PWM_SS =GCLK_TCC
N(TOP+1)
Where N represents the prescaler divider used (1, 2, 4, 8, 16, 64, 256, 1024).
36.6.2.5.6 Dual-Slope PWM Generation
For dual-slope PWM generation, the period setting (TOP) is controlled by PER, while CCx control the
duty cycle of the generated waveform output. The figure below shows how the counter repeatedly counts
from ZERO to PER and then from PER to ZERO. The waveform generator output is set on compare
match when up-counting, and cleared on compare match when down-counting. An interrupt and/or event
is generated on TOP (when counting upwards) and/or ZERO (when counting up or down).
In DSBOTH operation, the circular buffer must be enabled to enable the update condition on TOP.
Figure 36-7. Dual-Slope Pulse Width Modulation
COUNT
CCx=ZERO
CCx
CCx=TOP
WO[x]
ZERO
TOP
MAX "match"
"update"
Using dual-slope PWM results in a lower maximum operation frequency compared to single-slope PWM
generation. The period (TOP) defines the PWM resolution. The minimum resolution is 1 bit
(TOP=0x00000001).
The following equation calculates the exact resolution for dual-slope PWM (RPWM_DS):
PWM_DS =log(PER+1)
log(2) .
The PWM frequency fPWM_DS depends on the period setting (TOP) and the peripheral clock frequency
fGCLK_TCC, and can be calculated by the following equation:
PWM_DS =GCLK_TCC
2 PER
N represents the prescaler divider used. The waveform generated will have a maximum frequency of half
of the TCC clock frequency (fGCLK_TCC) when TOP is set to 0x00000001 and no prescaling is used.
The pulse width (PPWM_DS) depends on the compare channel (CCx) register value and the peripheral
clock frequency (fGCLK_TCC), and can be calculated by the following equation:
PWM_DS =2 TOP CCx
GCLK_TCC
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 881
N represents the prescaler divider used.
Note:  In DSTOP, DSBOTTOM and DSBOTH operation, when TOP is lower than MAX/2, the CCx MSB
bit defines the ramp on which the CCx Match interrupt or event is generated. (Rising if CCx[MSB] = 0,
falling if CCx[MSB] = 1.)
Related Links
36.6.3.2 Circular Buffer
36.6.2.5.7 Dual-Slope Critical PWM Generation
Critical mode generation allows generation of non-aligned centered pulses. In this mode, the period time
is controlled by PER while CCx control the generated waveform output edge during up-counting and
CC(x+CC_NUM/2) control the generated waveform output edge during down-counting.
Figure 36-8. Dual-Slope Critical Pulse Width Modulation (N=CC_NUM)
COUNT
CCx
WO[x]
ZERO
TOP
MAX "match"
"reload" update
CC(x+N/2) CCx CC(x+N/2) CCx CC(x+N/2)
36.6.2.5.8 Output Polarity
The polarity (WAVE.POLx) is available in all waveform output generation. In single-slope and dual-slope
PWM operation, it is possible to invert the pulse edge alignment individually on start or end of a PWM
cycle for each compare channels. The table below shows the waveform output set/clear conditions,
depending on the settings of timer/counter, direction, and polarity.
Table 36-3. Waveform Generation Set/Clear Conditions
Waveform Generation
operation
DIR POLx Waveform Generation Output Update
Set Clear
Single-Slope PWM 0 0 Timer/counter matches TOP Timer/counter matches CCx
1 Timer/counter matches CC Timer/counter matches TOP
1 0 Timer/counter matches CC Timer/counter matches ZERO
1 Timer/counter matches ZERO Timer/counter matches CC
Dual-Slope PWM x 0 Timer/counter matches CC
when counting up
Timer/counter matches CC
when counting down
1 Timer/counter matches CC
when counting down
Timer/counter matches CC
when counting up
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 882
In Normal and Match Frequency, the WAVE.POLx value represents the initial state of the waveform
output.
36.6.2.6 Double Buffering
The Pattern (PATT), Waveform (WAVE), Period (PER) and Compare Channels (CCx) registers are all
double buffered. Each buffer register has a buffer valid (PATTBUFV, WAVEBUFV, PERBUFV and
CCBUFVx) bit in the STATUS register, which indicates that the buffer register contains a valid value that
can be copied into the corresponding register. .
When the buffer valid flag bit in the STATUS register is '1' and the Lock Update bit in the CTRLB register
is set to '0', (writing CTRLBCLR.LUPD to '1'), double buffering is enabled: the data from buffer registers
will be copied into the corresponding register under hardware UPDATE conditions, then the buffer valid
flags bit in the STATUS register are automatically cleared by hardware.
Note:  Software update command (CTRLBSET.CMD=0x3) act independently of LUPD value.
A compare register is double buffered as in the following figure.
Figure 36-9. Compare Channel Double Buffering
=
EN
EN
"APB write enable" "data write"
UPDATE
COUNT
"match"
CCBUFx
CCx
BV
Both the registers (PATT/WAVE/PER/CCx) and corresponding buffer registers (PATTBUF/WAVEBUFV/
PERBUF/CCBUFx) are available in the I/O register map, and the double buffering feature is not
mandatory. The double buffering is disabled by writing a '1' to CTRLSET.LUPD.
Note:  In NFRQ, MFRQ or PWM down-counting counter mode (CTRLBSET.DIR=1), when double
buffering is enabled (CTRLBCLR.LUPD=1), PERBUF register is continuously copied into the PER
independently of update conditions.
Changing the Period
The counter period can be changed by writing a new Top value to the Period register (PER or CC0,
depending on the waveform generation mode), any period update on registers (PER or CCx) is effective
after the synchronization delay, whatever double buffering enabling is.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 883
Figure 36-10. Unbuffered Single-Slope Up-Counting Operation
COUNT
MAX
New value written to
PER that is higher
than current COUNT
Counter Wraparound
New value written to
PER that is lower
than current COUNT
"clear" update
"write"
ZERO
Figure 36-11. Unbuffered Single-Slope Down-Counting Operation
COUNT
MAX
New value written to
PER that is higher
than current COUNT
New value written to
PER that is lower
than current COUNT
"reload" update
"write"
ZERO
A counter wraparound can occur in any operation mode when up-counting without buffering, see Figure
36-10. COUNT and TOP are continuously compared, so when a new value that is lower than the current
COUNT is written to TOP, COUNT will wrap before a compare match.
Figure 36-12. Unbuffered Dual-Slope Operation
COUNT
New value written to
PER that is higher
than current COUNT
New value written to
PER that is lower
than current COUNT
"reload" update
"write"
Counter Wraparound
MAX
ZERO
When double buffering is used, the buffer can be written at any time and the counter will still maintain
correct operation. The period register is always updated on the update condition, as shown in Figure
36-13. This prevents wraparound and the generation of odd waveforms.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 884
Figure 36-13. Changing the Period Using Buffering
COUNT
"reload" update
"write"
MAX
ZERO
New value written to
PERBUF that is higher
than current COUNT
New value written to
PERBUF that is lower
than current COUNT
PER is updated with
PERBUF value
36.6.2.7 Capture Operations
To enable and use capture operations, the Match or Capture Channel x Event Input Enable bit in the
Event Control register (EVCTRL.MCEIx) must be written to '1'. The capture channels to be used must
also be enabled in the Capture Channel x Enable bit in the Control A register (CTRLA.CPTENx) before
capturing can be performed.
Event Capture Action
The compare/capture channels can be used as input capture channels to capture events from the Event
System, and give them a timestamp. The following figure shows four capture events for one capture
channel.
Figure 36-14. Input Capture Timing
events
COUNT
MAX
ZERO
Capture 0 Capture 1 Capture 2 Capture 3
For input capture, the buffer register and the corresponding CCx act like a FIFO. When CCx is empty or
read, any content in CCBUFx is transferred to CCx. The buffer valid flag is passed to set the CCx
interrupt flag (IF) and generate the optional interrupt, event or DMA request. CCBUFx register value can't
be read, all captured data must be read from CCx register.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 885
Figure 36-15. Capture Double Buffering
BUFV
"capture"
IF
COUNT
CCx
EN
EN
"INT/DMA
request" data read
CCBUFx
The TCC can detect capture overflow of the input capture channels: When a new capture event is
detected while the Capture Buffer Valid flag (STATUS.CCBUFV) is still set, the new timestamp will not be
stored and INTFLAG.ERR will be set.
Period and Pulse-Width (PPW) Capture Action
The TCC can perform two input captures and restart the counter on one of the edges. This enables the
TCC to measure the pulse-width and period and to characterize the frequency f and dutyCycle of an input
signal:
=1
, =
Figure 36-16. PWP Capture
Period (T)
external
signal /event
capture times
COUNT
MAX
ZERO
"capture"
CC0 CC0 CC1CC1
Selecting PWP or PPW in the Timer/Counter Event Input 1 Action bit group in the Event Control register
(EVCTRL.EVACT1) enables the TCC to perform one capture action on the rising edge and the other one
on the falling edge. When using PPW (period and pulse-width) event action, period T will be captured into
CC0 and the pulse-width tp into CC1. The PWP (Pulse-width and Period) event action offers the same
functionality, but T will be captured into CC1 and tp into CC0.
The Timer/Counter Event x Invert Enable bit in Event Control register (EVCTRL.TCEINVx) is used for
event source x to select whether the wraparound should occur on the rising edge or the falling edge. If
EVCTRL.TCEINVx=1, the wraparound will happen on the falling edge.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 886
The corresponding capture is done only if the channel is enabled in capture mode (CTRLA.CPTENx=1). If
not, the capture action will be ignored and the channel will be enabled in compare mode of operation.
When only one of these channel is required, the other channel can be used for other purposes.
The TCC can detect capture overflow of the input capture channels: When a new capture event is
detected while the INTFLAG.MCx is still set, the new timestamp will not be stored and INTFLAG.ERR will
be set.
Note:  When up-counting (CTRLBSET.DIR=0), counter values lower than 1 cannot be captured in
Capture Minimum mode (FCTRLn.CAPTURE=CAPTMIN). To capture the full range including value 0, the
TCC must be configured in down-counting mode (CTRLBSET.DIR=0).
Note:  In dual-slope PWM operation, and when TOP is lower than MAX/2, the CCx MSB captures the
CTRLB.DIR state to identify the ramp on which the capture has been done. For rising ramps CCx[MSB] is
zero, for falling ramps CCx[MSB]=1.
36.6.3 Additional Features
36.6.3.1 One-Shot Operation
When one-shot is enabled, the counter automatically stops on the next counter overflow or underflow
condition. When the counter is stopped, the Stop bit in the Status register (STATUS.STOP) is set and the
waveform outputs are set to the value defined by DRVCTRL.NREx and DRVCTRL.NRVx.
One-shot operation can be enabled by writing a '1' to the One-Shot bit in the Control B Set register
(CTRLBSET.ONESHOT) and disabled by writing a '1' to CTRLBCLR.ONESHOT. When enabled, the TCC
will count until an overflow or underflow occurs and stop counting. The one-shot operation can be
restarted by a re-trigger software command, a re-trigger event or a start event. When the counter restarts
its operation, STATUS.STOP is automatically cleared.
36.6.3.2 Circular Buffer
The Period register (PER) and the compare channels register (CC0 to CC3) support circular buffer
operation. When circular buffer operation is enabled, the PER or CCx values are copied into the
corresponding buffer registers at each update condition. Circular buffering is dedicated to RAMP2,
RAMP2A, and DSBOTH operations.
Figure 36-17. Circular Buffer on Channel 0
BUFV
UPDATE
"write enable" "data write"
=
COUNT
"match"
EN
EN CCBUF0
CC0
UPDATE
CIRCC0EN
36.6.3.3 Dithering Operation
The TCC supports dithering on Pulse-width or Period on a 16, 32 or 64 PWM cycles frame.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 887
Dithering consists in adding some extra clocks cycles in a frame of several PWM cycles, and can improve
the accuracy of the average output pulse width and period. The extra clock cycles are added on some of
the compare match signals, one at a time, through a "blue noise" process that minimizes the flickering on
the resulting dither patterns.
Dithering is enabled by writing the corresponding configuration in the Enhanced Resolution bits in CTRLA
register (CTRLA.RESOLUTION):
• DITH4 enable dithering every 16 PWM frames
• DITH5 enable dithering every 32 PWM frames
• DITH6 enable dithering every 64 PWM frames
The DITHERCY bits of COUNT, PER and CCx define the number of extra cycles to add into the frame
(DITHERCY bits from the respective COUNT, PER or CCx registers). The remaining bits of COUNT, PER,
CCx define the compare value itself.
The pseudo code, giving the extra cycles insertion regarding the cycle is:
int extra_cycle(resolution, dithercy, cycle){
int MASK;
int value
switch (resolution){
DITH4: MASK = 0x0f;
DITH5: MASK = 0x1f;
DITH6: MASK = 0x3f;
}
value = cycle * dithercy;
if (((MASK & value) + dithercy) > MASK)
return 1;
return 0;
}
Dithering on Period
Writing DITHERCY in PER will lead to an average PWM period configured by the following formulas.
DITH4 mode:
 =DITHERCY
16 + PER 1
GCLK_TCC
Note:  If DITH4 mode is enabled, the last 4 significant bits from PER/CCx or COUNT register correspond
to the DITHERCY value, rest of the bits corresponds to PER/CCx or COUNT value.
DITH5 mode:
 =DITHERCY
32 + PER 1
GCLK_TCC
DITH6 mode:
 =DITHERCY
64 + PER 1
GCLK_TCC
Dithering on Pulse Width
Writing DITHERCY in CCx will lead to an average PWM pulse width configured by the following formula.
DITH4 mode:
ℎ = DITHERCY
16 + CCx 1
GCLK_TCC
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 888
DITH5 mode:
ℎ = DITHERCY
32 + CCx 1
GCLK_TCC
DITH6 mode:
ℎ = DITHERCY
64 + CCx 1
GCLK_TCC
Note:  The PWM period will remain static in this case.
36.6.3.4 Ramp Operations
Three ramp operation modes are supported. All of them require the timer/counter running in single-slope
PWM generation. The ramp mode is selected by writing to the Ramp Mode bits in the Waveform Control
register (WAVE.RAMP).
RAMP1 Operation
This is the default PWM operation, described in Single-Slope PWM Generation.
RAMP2 Operation
These operation modes are dedicated for power factor correction (PFC), Half-Bridge and Push-Pull
SMPS topologies, where two consecutive timer/counter cycles are interleaved, see Figure 36-18. In cycle
A, odd channel output is disabled, and in cycle B, even channel output is disabled. The ramp index
changes after each update, but can be software modified using the Ramp index command bits in Control
B Set register (CTRLBSET.IDXCMD).
Standard RAMP2 (RAMP2) Operation
Ramp A and B periods are controlled by the PER register value. The PER value can be different on each
ramp by the Circular Period buffer option in the Wave register (WAVE.CIPEREN=1). This mode uses a
two-channel TCC to generate two output signals, or one output signal with another CC channel enabled
in capture mode.
Figure 36-18. RAMP2 Standard Operation
COUNT
"match"
ZERO
"clear" update
A B A BRamp
WO[0]
WO[1]
TOP(A) TOP(B)
CC0 CC1
TOP(B)
CC0
CC1
Retrigger
on
FaultA
Keep on FaultB
CIPEREN = 1
POL0 = 1
POL1 = 1
FaultA input
FaultB input
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 889
Alternate RAMP2 (RAMP2A) Operation
Alternate RAMP2 operation is similar to RAMP2, but CC0 controls both WO[0] and WO[1] waveforms
when the corresponding circular buffer option is enabled (CIPEREN=1). The waveform polarity is the
same on both outputs. Channel 1 can be used in capture mode.
Figure 36-19. RAMP2 Alternate Operation
COUNT
"match"
ZERO
"clear" update
A B A BRamp
WO[0]
WO[1]
TOP(A)
TOP(B)
CC0(A)
CC0(B)
TOP(B)
CC0(A)
CC0(B)
Retrigger
on
FaultA
CIPEREN = 1
POL0 = 1
CICCEN0 = 1
FaultA input
Keep on FaultB
FaultB input
Critical RAMP2 (RAMP2C) Operation
Critical RAMP2 operation provides a way to cover RAMP2 operation requirements without the update
constraint associated with the use of circular buffers. In this mode, CC0 is controlling the period of ramp A
and PER is controlling the period of ramp B. When using more than two channels, WO[0] output is
controlled by CC2 (HIGH) and CC0 (LOW). On TCC with 2 channels, a pulse on WO[0] will last the entire
period of ramp A, if WAVE.POL0=0.
Figure 36-20. RAMP2 Critical Operation With More Than 2 Channels
COUNT
"match"
ZERO
"clear" update
A B A B
Ramp
WO[0]
WO[1]
CC0
TOP
CC2
CC1
TOP
CC2
CC1
Retrigger
on
FaultA
Keep on FaultB
POL2 = 1
POL1 = 1
FaultA input
FaultB input
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 890
Figure 36-21. RAMP2 Critical Operation With 2 Channels
COUNT
"match"
ZERO
"clear" update
A B A B
Ramp
WO[0]
WO[1]
CC0
TOP
CC1
TOP
CC1
Retrigger
on
FaultA
Keep on FaultB
POL0 = 0
POL1 = 1
FaultA input
FaultB input
36.6.3.5 Recoverable Faults
Recoverable faults can restart or halt the timer/counter. Two faults, called Fault A and Fault B, can trigger
recoverable fault actions on the compare channels CC0 and CC1 of the TCC. The compare channels'
outputs can be clamped to inactive state either as long as the fault condition is present, or from the first
valid fault condition detection on until the end of the timer/counter cycle.
Fault Inputs
The first two channel input events (TCCxMC0 and TCCxMC1) can be used as Fault A and Fault B inputs,
respectively. Event system channels connected to these fault inputs must be configured as
asynchronous. The TCC must work in a PWM mode.
Fault Filtering
There are three filters available for each input Fault A and Fault B. They are configured by the
corresponding Recoverable Fault n Configuration registers (FCTRLA and FCTRLB). The three filters can
either be used independently or in any combination.
Input
Filtering
By default, the event detection is asynchronous. When the event occurs, the fault system
will immediately and asynchronously perform the selected fault action on the compare
channel output, also in device power modes where the clock is not available. To avoid false
fault detection on external events (e.g. due to a glitch on an I/O port) a digital filter can be
enabled and configured by the Fault B Filter Value bits in the Fault n Configuration registers
(FCTRLn.FILTERVAL). If the event width is less than FILTERVAL (in clock cycles), the
event will be discarded. A valid event will be delayed by FILTERVAL clock cycles.
Fault
Blanking
This ignores any fault input for a certain time just after a selected waveform output edge.
This can be used to prevent false fault triggering due to signal bouncing, as shown in the
figure below. Blanking can be enabled by writing an edge triggering configuration to the
Fault n Blanking Mode bits in the Recoverable Fault n Configuration register
(FCTRLn.BLANK). The desired duration of the blanking must be written to the Fault n
Blanking Time bits (FCTRLn.BLANKVAL).
The blanking time tbis calculated by
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 891
=1 + BLANKVAL
GCLK_TCCx_PRESC
Here, fGCLK_TCCx_PRESC is the frequency of the prescaled peripheral clock frequency
fGCLK_TCCx.
The maximum blanking time (FCTRLn.BLANKVAL=
255) at fGCLK_TCCx=96MHz is 2.67µs (no prescaler) or 170µs (prescaling). For
fGCLK_TCCx=1MHz, the maximum blanking time is either 170µs (no prescaling) or 10.9ms
(prescaling enabled).
Figure 36-22. Fault Blanking in RAMP1 Operation with Inverted Polarity
COUNT
"match"
ZERO
"clear" update
FaultA Input
CC0
TOP
WO[0]
CMP0
FCTRLA.BLANKVAL = 0 FCTRLA.BLANKVAL > 0 FCTRLA.BLANKVAL > 0
- -FaultA Blanking
x x x x
"Fault input enabled"
-"Fault input disabled"
x
"Fault discarded"
Fault
Qualification
This is enabled by writing a '1' to the Fault n Qualification bit in the Recoverable Fault
n Configuration register (FCTRLn.QUAL). When the recoverable fault qualification is
enabled (FCTRLn.QUAL=1), the fault input is disabled all the time the corresponding
channel output has an inactive level, as shown in the figures below.
Figure 36-23. Fault Qualification in RAMP1 Operation
COUNT
MAX
TOP
ZERO
Fault Input A
CC0
- - - --
- - - -Fault B Input Qual - -
Fault Input B
x x x x x x x x x
x x x xx x x x x x xx x x x x
x x x
CC1
Fault A Input Qual
"match"
"clear" update
"Fault input enabled"
-"Fault input disabled"
x
"Fault discarded"
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 892
Figure 36-24. Fault Qualification in RAMP2 Operation with Inverted Polarity
COUNT
MAX
TOP
ZERO
Fault Input A
CC0
- - -Fault A Input Qual
- -
Fault B Input Qual -
Fault Input B
Cycle
CC1
xxx x x x xxxxxx
x x x x x x x x x xx x x x x
"match"
"clear" update
"Fault input enabled"
-"Fault input disabled"
x
"Fault discarded"
Fault Actions
Different fault actions can be configured individually for Fault A and Fault B. Most fault actions are not
mutually exclusive; hence two or more actions can be enabled at the same time to achieve a result that is
a combination of fault actions.
Keep
Action
This is enabled by writing the Fault n Keeper bit in the Recoverable Fault n Configuration
register (FCTRLn.KEEP) to '1'. When enabled, the corresponding channel output will be
clamped to zero as long as the fault condition is present. The clamp will be released on the
start of the first cycle after the fault condition is no longer present, see next Figure.
Figure 36-25. Waveform Generation with Fault Qualification and Keep Action
KEEP
KEEP
COUNT
MAX
TOP
ZERO
Fault Input A
CC0
-
- - -Fault A Input Qual
x x x x
-
WO[0]
"match"
"clear" update
"Fault input enabled"
-"Fault input disabled"
x
"Fault discarded"
Restart
Action
This is enabled by writing the Fault n Restart bit in Recoverable Fault n Configuration register
(FCTRLn.RESTART) to '1'. When enabled, the timer/counter will be restarted as soon as the
corresponding fault condition is present. The ongoing cycle is stopped and the timer/counter
starts a new cycle, see Figure 36-26. In Ramp 1 mode, when the new cycle starts, the
compare outputs will be clamped to inactive level as long as the fault condition is present.
Note:  For RAMP2 operation, when a new timer/counter cycle starts the cycle index will
change automatically, see Figure 36-27. Fault A and Fault B are qualified only during the
cycle A and cycle B respectively: Fault A is disabled during cycle B, and Fault B is disabled
during cycle A.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 893
Figure 36-26. Waveform Generation in RAMP1 mode with Restart Action
COUNT
MAX
TOP "match"
ZERO
"clear" update
Fault Input A
CC0
CC1
RestartRestart
WO[0]
WO[1]
Figure 36-27. Waveform Generation in RAMP2 mode with Restart Action
COUNT
MAX
TOP
"match"
ZERO
CCx=ZERO
CC0/CC1
CCx=TOP
"clear" update
Fault Input A
Cycle
Restart
No fault A action
in cycle B
WO[1]
WO[0]
Capture
Action
Several capture actions can be selected by writing the Fault n Capture Action bits in the
Fault n Control register (FCTRLn.CAPTURE). When one of the capture operations is
selected, the counter value is captured when the fault occurs. These capture operations are
available:
• CAPT - the equivalent to a standard capture operation, for further details refer to
36.6.2.7 Capture Operations
• CAPTMIN - gets the minimum time stamped value: on each new local minimum
captured value, an event or interrupt is issued.
• CAPTMAX - gets the maximum time stamped value: on each new local maximum
captured value, an event or interrupt (IT) is issued, see Figure 36-28.
• LOCMIN - notifies by event or interrupt when a local minimum captured value is
detected.
• LOCMAX - notifies by event or interrupt when a local maximum captured value is
detected.
• DERIV0 - notifies by event or interrupt when a local extreme captured value is detected,
see Figure 36-29.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 894
CCx Content:
In CAPTMIN and CAPTMAX operations, CCx keeps the respective extremum captured
values, see Figure 36-28. In LOCMIN, LOCMAX or DERIV0 operation, CCx follows the
counter value at fault time, see Figure 36-29.
Before enabling CAPTMIN or CAPTMAX mode of capture, the user must initialize the
corresponding CCx register value to a value different from zero (for CAPTMIN) top (for
CAPTMAX). If the CCx register initial value is zero (for CAPTMIN) top (for CAPTMAX), no
captures will be performed using the corresponding channel.
MCx Behaviour:
In LOCMIN and LOCMAX operation, capture is performed on each capture event. The MCx
interrupt flag is set only when the captured value is above or equal (for LOCMIN) or below or
equal (for LOCMAX) to the previous captured value. So interrupt flag is set when a new
relative local Minimum (for CAPTMIN) or Maximum (for CAPTMAX) value has been
detected. DERIV0 is equivalent to an OR function of (LOCMIN, LOCMAX).
In CAPT operation, capture is performed on each capture event. The MCx interrupt flag is
set on each new capture.
In CAPTMIN and CAPTMAX operation, capture is performed only when on capture event
time, the counter value is lower (for CAPTMIN) or higher (for CAPMAX) than the last
captured value. The MCx interrupt flag is set only when on capture event time, the counter
value is higher or equal (for CAPTMIN) or lower or equal (for CAPTMAX) to the value
captured on the previous event. So interrupt flag is set when a new absolute local Minimum
(for CAPTMIN) or Maximum (for CAPTMAX) value has been detected.
Interrupt Generation
In CAPT mode, an interrupt is generated on each filtered Fault n and each dedicated CCx
channel capture counter value. In other modes, an interrupt is only generated on an extreme
captured value.
Figure 36-28. Capture Action “CAPTMAX”
COUNT
ZERO
"clear" update
FaultA Input
TOP
CC0
CC0 Event/
Interrupt
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 895
Figure 36-29. Capture Action “DERIV0”
COUNT "match"
ZERO
"update"
FaultA Input
TOP
CC0
CC0 Event/
Interrupt
WO[0]
Hardware
Halt Action
This is configured by writing 0x1 to the Fault n Halt mode bits in the Recoverable Fault n
Configuration register (FCTRLn.HALT). When enabled, the timer/counter is halted and the
cycle is extended as long as the corresponding fault is present.
The next figure ('Waveform Generation with Halt and Restart Actions') shows an example
where both restart action and hardware halt action are enabled for Fault A. The compare
channel 0 output is clamped to inactive level as long as the timer/counter is halted. The
timer/counter resumes the counting operation as soon as the fault condition is no longer
present. As the restart action is enabled in this example, the timer/counter is restarted
after the fault condition is no longer present.
The figure after that ('Waveform Generation with Fault Qualification, Halt, and Restart
Actions') shows a similar example, but with additionally enabled fault qualification. Here,
counting is resumed after the fault condition is no longer present.
Note that in RAMP2 and RAMP2A operations, when a new timer/counter cycle starts, the
cycle index will automatically change.
Figure 36-30. Waveform Generation with Halt and Restart Actions
HALT
COUNT
MAX
TOP "match"
ZERO
"clear" update
Fault Input A
CC0
RestartRestart
WO[0]
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 896
Figure 36-31. Waveform Generation with Fault Qualification, Halt, and Restart
Actions
KEEP
HALT
COUNT
MAX
TOP "match"
ZERO
"update"
Fault Input A
CC0
- - -Fault A Input Qual -
Resume
x x x
-
WO[0]
Software
Halt Action
This is configured by writing 0x2 to the Fault n Halt mode bits in the Recoverable Fault n
configuration register (FCTRLn.HALT). Software halt action is similar to hardware halt
action, but in order to restart the timer/counter, the corresponding fault condition must not
be present anymore, and the corresponding FAULT n bit in the STATUS register must be
cleared by software.
Figure 36-32. Waveform Generation with Software Halt, Fault Qualification, Keep and Restart
Actions
KEEP
HALT
COUNT
MAX
TOP "match"
ZERO
"update"
Fault Input A
CC0
-
-Fault A Input Qual -
Software Clear
NO
KEEP
Restart Restart
x x
-
WO[0]
FCTRLA.KEEP = 1 FCTRLA.KEEP = 0
36.6.3.6 Non-Recoverable Faults
The non-recoverable fault action will force all the compare outputs to a pre-defined level programmed into
the Driver Control register (DRVCTRL.NRE and DRVCTRL.NRV). The non-recoverable fault input (EV0
and EV1) actions are enabled in Event Control register (EVCTRL.EVACT0 and EVCTRL.EVACT1).
To avoid false fault detection on external events (e.g. a glitch on an I/O port) a digital filter can be enabled
using Non-Recoverable Fault Input x Filter Value bits in the Driver Control register
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 897
(DRVCTRL.FILTERVALn). Therefore, the event detection is synchronous, and event action is delayed by
the selected digital filter value clock cycles.
When the Fault Detection on Debug Break Detection bit in Debug Control register (DGBCTRL.FDDBD) is
written to '1', a non-recoverable Debug Faults State and an interrupt (DFS) is generated when the system
goes in debug operation.
In RAMP2, RAMP2A, or DSBOTH operation, when the Lock Update bit in the Control B register is set by
writing CTRLBSET.LUPD=1 and the ramp index or counter direction changes, a non-recoverable Update
Fault State and the respective interrupt (UFS) are generated.
36.6.3.7 Waveform Extension
Figure 36-33 shows a schematic diagram of actions of the four optional units that follow the recoverable
fault stage on a port pin pair: Output Matrix (OTMX), Dead-Time Insertion (DTI), SWAP and Pattern
Generation. The DTI and SWAP units can be seen as a four port pair slices:
• Slice 0 DTI0 / SWAP0 acting on port pins (WO[0], WO[WO_NUM/2 +0])
• Slice 1 DTI1 / SWAP1 acting on port pins (WO[1], WO[WO_NUM/2 +1])
And more generally:
• Slice n DTIx / SWAPx acting on port pins (WO[x], WO[WO_NUM/2 +x])
Figure 36-33. Waveform Extension Stage Details
OTMX[x]
DTIx
LS
HS
OTMX[x+WO_NUM/2]
DTIxEN SWAPx
PGO[x+WO_NUM/2]
PGO[x]
PGV[x+WO_NUM/2]
PGV[x]
INV[x+WO_NUM/2]
P[x+WO_NUM/2]
INV[x]
P[x]
PORTSWEX
OTMX
OTMX DTI SWAP PATTERN
The output matrix (OTMX) unit distributes compare channels, according to the selectable configurations
in Table 36-4.
Table 36-4. Output Matrix Channel Pin Routing Configuration
Value OTMX[x]
0x0 CC3 CC2 CC1 CC0 CC3 CC2 CC1 CC0
0x1 CC1 CC0 CC1 CC0 CC1 CC0 CC1 CC0
0x2 CC0 CC0 CC0 CC0 CC0 CC0 CC0 CC0
0x3 CC1 CC1 CC1 CC1 CC1 CC1 CC1 CC0
Notes on Table 36-4:
• Configuration 0x0 is the default configuration. The channel location is the default one, and channels
are distributed on outputs modulo the number of channels. Channel 0 is routed to the Output matrix
output OTMX[0], and Channel 1 to OTMX[1]. If there are more outputs than channels, then channel 0
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 898
is duplicated to the Output matrix output OTMX[CC_NUM], channel 1 to OTMX[CC_NUM+1] and so
on.
• Configuration 0x1 distributes the channels on output modulo half the number of channels. This
assigns twice the number of output locations to the lower channels than the default configuration.
This can be used, for example, to control the four transistors of a full bridge using only two compare
channels.
Using pattern generation, some of these four outputs can be overwritten by a constant level, enabling
flexible drive of a full bridge in all quadrant configurations.
• Configuration 0x2 distributes compare channel 0 (CC0) to all port pins. With pattern generation, this
configuration can control a stepper motor.
• Configuration 0x3 distributes the compare channel CC0 to the first output, and the channel CC1 to all
other outputs. Together with pattern generation and the fault extension, this configuration can control
up to seven LED strings, with a boost stage.
•Table 36-5. Example: four compare channels on four outputs
Value OTMX[3] OTMX[2] OTMX[1] OTMX[0]
0x0 CC3 CC2 CC1 CC0
0x1 CC1 CC0 CC1 CC0
0x2 CC0 CC0 CC0 CC0
0x3 CC1 CC1 CC1 CC0
The dead-time insertion (DTI) unit generates OFF time with the non-inverted low side (LS) and inverted
high side (HS) of the wave generator output forced at low level. This OFF time is called dead time. Dead-
time insertion ensures that the LS and HS will never switch simultaneously.
The DTI stage consists of four equal dead-time insertion generators; one for each of the first four
compare channels. Figure 36-34 shows the block diagram of one DTI generator. The four channels have
a common register which controls the dead time, which is independent of high side and low side setting.
Figure 36-34. Dead-Time Generator Block Diagram
Dead Time Generator
Edge Detect
D Q
= 0
"DTLS"
(To PORT)
"DTHS"
(To PORT)
Counter
EN
LOAD
OTMX output
DTLS DTHS
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 899
As shown in Figure 36-35, the 8-bit dead-time counter is decremented by one for each peripheral clock
cycle until it reaches zero. A non-zero counter value will force both the low side and high side outputs into
their OFF state. When the output matrix (OTMX) output changes, the dead-time counter is reloaded
according to the edge of the input. When the output changes from low to high (positive edge) it initiates a
counter reload of the DTLS register. When the output changes from high to low (negative edge) it reloads
the DTHS register.
Figure 36-35. Dead-Time Generator Timing Diagram
"dti_cnt"
"OTMX output"
"DTLS"
"DTHS"
t
DTILS
t
DTIHS
T
t
P
The pattern generator unit produces a synchronized bit pattern across the port pins it is connected to.
The pattern generation features are primarily intended for handling the commutation sequence in
brushless DC motors (BLDC), stepper motors, and full bridge control. See also Figure 36-36.
Figure 36-36. Pattern Generator Block Diagram
COUNT
UPDATE
BV BVPGEB[7:0]
PGE[7:0]
PGVB[7:0]
PGV[7:0]
SWAP output
ENEN
WOx[7:0]
As with other double-buffered timer/counter registers, the register update is synchronized to the UPDATE
condition set by the timer/counter waveform generation operation. If synchronization is not required by
the application, the software can simply access directly the PATT.PGE, PATT.PGV bits registers.
36.6.4 Master/Slave Operation
Two TCC instances sharing the same GCLK_TCC clock, can be linked to provide more synchronized CC
channels. The operation is enabled by setting the Master Synchronization bit in Control A register
(CTRLA.MSYNC) in the Slave instance. When the bit is set, the slave TCC instance will synchronize the
CC channels to the Master counter.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 900
Related Links
36.8.1 CTRLA
36.6.5 DMA, Interrupts, and Events
Table 36-6. Module Requests for TCC
Condition Interrupt
request
Event
output
Event
input
DMA
request
DMA request is
cleared
Overflow / Underflow Yes Yes Yes(1) On DMA acknowledge
Channel Compare
Match or Capture
Yes Yes Yes(2) Yes(3) For circular buffering:
on DMA acknowledge
For capture channel:
when CCx register is
read
Retrigger Yes Yes
Count Yes Yes
Capture Overflow Error Yes
Debug Fault State Yes
Recoverable Faults Yes
Non-Recoverable Faults Yes
TCCx Event 0 input Yes(4)
TCCx Event 1 input Yes(5)
Notes:
1. DMA request set on overflow, underflow or re-trigger conditions.
2. Can perform capture or generate recoverable fault on an event input.
3. In capture or circular modes.
4. On event input, either action can be executed:
– re-trigger counter
– control counter direction
– stop the counter
– decrement the counter
– perform period and pulse width capture
– generate non-recoverable fault
5. On event input, either action can be executed:
– re-trigger counter
– increment or decrement counter depending on direction
– start the counter
– increment or decrement counter based on direction
– increment counter regardless of direction
– generate non-recoverable fault
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 901
36.6.5.1 DMA Operation
The TCC can generate the following DMA requests:
Counter
overflow
(OVF)
If the Ones-shot Trigger mode in the control A register (CTRLA.DMAOS) is written to '0',
the TCC generates a DMA request on each cycle when an update condition (overflow,
underflow or re-trigger) is detected.
When an update condition (overflow, underflow or re-trigger) is detected while
CTRLA.DMAOS=1, the TCC generates a DMA trigger on the cycle following the DMA
One-Shot Command written to the Control B register (CTRLBSET.CMD=DMAOS).
In both cases, the request is cleared by hardware on DMA acknowledge.
Channel
Match (MCx)
A DMA request is set only on a compare match if CTRLA.DMAOS=0. The request is
cleared by hardware on DMA acknowledge.
When CTRLA.DMAOS=1, the DMA requests are not generated.
Channel
Capture
(MCx)
For a capture channel, the request is set when valid data is present in the CCx register,
and cleared once the CCx register is read.
In this operation mode, the CTRLA.DMAOS bit value is ignored.
DMA Operation with Circular Buffer
When circular buffer operation is enabled, the buffer registers must be written in a correct order and
synchronized to the update times of the timer. The DMA triggers of the TCC provide a way to ensure a
safe and correct update of circular buffers.
Note:  Circular buffer are intended to be used with RAMP2, RAMP2A and DSBOTH operation only.
DMA Operation with Circular Buffer in RAMP2 and RAMP2A Mode
When a CCx channel is selected as a circular buffer, the related DMA request is not set on a compare
match detection, but on start of ramp B.
If at least one circular buffer is enabled, the DMA overflow request is conditioned to the start of ramp A
with an effective DMA transfer on previous ramp B (DMA acknowledge).
The update of all circular buffer values for ramp A can be done through a DMA channel triggered on a MC
trigger. The update of all circular buffer values for ramp B, can be done through a second DMA channel
triggered by the overflow DMA request.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 902
Figure 36-37. DMA Triggers in RAMP and RAMP2 Operation Mode and Circular Buffer Enabled
"update"
ZERO
DMA Channel i
DMA Channel j
Update ramp A
Update ramp B
N-2 N-1 N
A B AAB B
COUNT
Cycle
STATUS.IDX
DMA_CCx_req
DMA_OVF_req
Ramp
DMA Operation with Circular Buffer in DSBOTH Mode
When a CC channel is selected as a circular buffer, the related DMA request is not set on a compare
match detection, but on start of down-counting phase.
If at least one circular buffer is enabled, the DMA overflow request is conditioned to the start of up-
counting phase with an effective DMA transfer on previous down-counting phase (DMA acknowledge).
When up-counting, all circular buffer values can be updated through a DMA channel triggered by MC
trigger. When down-counting, all circular buffer values can be updated through a second DMA channel,
triggered by the OVF DMA request.
Figure 36-38. DMA Triggers in DSBOTH Operation Mode and Circular Buffer Enabled
COUNT
Cycle
CTRLB.DIR
DMA_CCx_req
DMA_OVF_req
Old Parameter Set New Parameter Set
"update"
ZERO
DMA Channel i
DMA Channel j
Update Rising
Update Rising
N-2 N-1 N
36.6.5.2 Interrupts
The TCC has the following interrupt sources:
• Overflow/Underflow (OVF)
• Retrigger (TRG)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 903
• Count (CNT) - refer also to description of EVCTRL.CNTSEL.
• Capture Overflow Error (ERR)
• Non-Recoverable Update Fault (UFS)
• Debug Fault State (DFS)
• Recoverable Faults (FAULTn)
• Non-recoverable Faults (FAULTx)
• Compare Match or Capture Channels (MCx)
These interrupts are asynchronous wake-up sources. See Sleep Mode Entry and Exit Table in PM/Sleep
Mode Controller section for details.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be
individually enabled by writing a '1' to the corresponding bit in the Interrupt Enable Set (INTENSET)
register, and disabled by writing a '1' to the corresponding bit in the Interrupt Enable Clear (INTENCLR)
register. An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is
enabled. The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or
the TCC is reset. See 36.8.12 INTFLAG for details on how to clear interrupt flags. The TCC has one
common interrupt request line for all the interrupt sources. The user must read the INTFLAG register to
determine which interrupt condition is present.
Note: Interrupts must be globally enabled for interrupt requests to be generated. Refer to Nested Vector
Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
19.6.3.3 Sleep Mode Controller
36.6.5.3 Events
The TCC can generate the following output events:
• Overflow/Underflow (OVF)
• Trigger (TRG)
• Counter (CNT) For further details, refer to EVCTRL.CNTSEL description.
• Compare Match or Capture on compare/capture channels: MCx
Writing a '1' ('0') to an Event Output bit in the Event Control Register (EVCTRL.xxEO) enables (disables)
the corresponding output event. Refer also to EVSYS – Event System.
The TCC can take the following actions on a channel input event (MCx):
• Capture event
• Generate a recoverable or non-recoverable fault
The TCC can take the following actions on counter Event 1 (TCCx EV1):
• Counter re-trigger
• Counter direction control
• Stop the counter
• Decrement the counter on event
• Period and pulse width capture
• Non-recoverable fault
The TCC can take the following actions on counter Event 0 (TCCx EV0):
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 904
• Counter re-trigger
• Count on event (increment or decrement, depending on counter direction)
• Counter start - start counting on the event rising edge. Further events will not restart the counter; the
counter will keep on counting using prescaled GCLK_TCCx, until it reaches TOP or ZERO,
depending on the direction.
• Counter increment on event. This will increment the counter, irrespective of the counter direction.
• Count during active state of an asynchronous event (increment or decrement, depending on counter
direction). In this case, the counter will be incremented or decremented on each cycle of the
prescaled clock, as long as the event is active.
• Non-recoverable fault
The counter Event Actions are available in the Event Control registers (EVCTRL.EVACT0 and
EVCTRL.EVACT1). For further details, refer to EVCTRL.
Writing a '1' ('0') to an Event Input bit in the Event Control register (EVCTRL.MCEIx or EVCTRL.TCEIx)
enables (disables) the corresponding action on input event.
Note:  When several events are connected to the TCC, the enabled action will apply for each of the
incoming events. Refer to EVSYS – Event System for details on how to configure the event system.
Related Links
29. EVSYS – Event System
36.6.6 Sleep Mode Operation
The TCC can be configured to operate in any sleep mode. To be able to run in standby the RUNSTDBY
bit in the Control A register (CTRLA.RUNSTDBY) must be '1'. The MODULE can in any sleep mode wake
up the device using interrupts or perform actions through the Event System.
36.6.7 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset and Enable bits in Control A register (CTRLA.SWRST and CTRLA.ENABLE)
The following registers are synchronized when written:
• Control B Clear and Control B Set registers (CTRLBCLR and CTRLBSET)
• Status register (STATUS)
• Pattern and Pattern Buffer registers (PATT and PATTBUF)
• Waveform register (WAVE)
• Count Value register (COUNT)
• Period Value and Period Buffer Value registers (PER and PERBUF)
• Compare/Capture Channel x and Channel x Compare/Capture Buffer Value registers (CCx and
CCBUFx)
The following registers are synchronized when read:
• Control B Clear and Control B Set registers (CTRLBCLR and CTRLBSET)
• Count Value register (COUNT): synchronization is done on demand through READSYNC command
(CTRLBSET.CMD)
• Pattern and Pattern Buffer registers (PATT and PATTBUF)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 905
• Waveform register (WAVE)
• Period Value and Period Buffer Value registers (PER and PERBUF)
• Compare/Capture Channel x and Channel x Compare/Capture Buffer Value registers (CCx and
CCBUFx)
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Required read-synchronization is denoted by the "Read-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 906
36.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA
7:0 RESOLUTION[1:0] ENABLE SWRST
15:8 MSYNC ALOCK PRESCYNC[1:0] RUNSTDBY PRESCALER[2:0]
23:16
31:24 CPTEN3 CPTEN2 CPTEN1 CPTEN0
0x04 CTRLBCLR 7:0 CMD[2:0] IDXCMD[1:0] ONESHOT LUPD DIR
0x05 CTRLBSET 7:0 CMD[2:0] IDXCMD[1:0] ONESHOT LUPD DIR
0x06
...
0x07
Reserved
0x08 SYNCBUSY
7:0 PER WAVE PATT COUNT STATUS CTRLB ENABLE SWRST
15:8 CC3 CC2 CC1 CC0
23:16
31:24
0x0C FCTRLA
7:0 RESTART BLANK[1:0] QUAL KEEP SRC[1:0]
15:8 CAPTURE[2:0] CHSEL[1:0] HALT[1:0]
23:16 BLANKVAL[7:0]
31:24 FILTERVAL[3:0]
0x10 FCTRLBA
7:0 RESTART BLANK[1:0] QUAL KEEP SRC[1:0]
15:8 CAPTURE[2:0] CHSEL[1:0] HALT[1:0]
23:16 BLANKVAL[7:0]
31:24 FILTERVAL[3:0]
0x14 WEXCTRL
7:0 OTMX[1:0]
15:8 DTIEN3 DTIEN2 DTIEN1 DTIEN0
23:16 DTLS[7:0]
31:24 DTHS[7:0]
0x18 DRVCTRL
7:0 NRE7 NRE6 NRE5 NRE4 NRE3 NRE2 NRE1 NRE0
15:8 NRV7 NRV6 NRV5 NRV4 NRV3 NRV2 NRV1 NRV0
23:16 INVEN7 INVEN6 INVEN5 INVEN4 INVEN3 INVEN2 INVEN1 INVEN0
31:24 FILTERVAL1[3:0] FILTERVAL0[3:0]
0x1C
...
0x1D
Reserved
0x1E DBGCTRL 7:0 FDDBD DBGRUN
0x1F Reserved
0x20 EVCTRL
7:0 CNTSEL[1:0] EVACT1[2:0] EVACT0[2:0]
15:8 TCEI1 TCEI0 TCINV1 TCINV0 CNTEO TRGEO OVFEO
23:16 MCEI3 MCEI2 MCEI1 MCEI0
31:24 MCEO3 MCEO2 MCEO1 MCEO0
0x24 INTENCLR
7:0 ERR CNT TRG OVF
15:8 FAULT1 FAULT0 FAULTB FAULTA DFS UFS
23:16 MC3 MC2 MC1 MC0
31:24
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 907
...........continued
Offset Name Bit Pos.
0x28 INTENSET
7:0 ERR CNT TRG OVF
15:8 FAULT1 FAULT0 FAULTB FAULTA DFS UFS
23:16 MC3 MC2 MC1 MC0
31:24
0x2C INTFLAG
7:0 ERR CNT TRG OVF
15:8 FAULT1 FAULT0 FAULTB FAULTA DFS UFS
23:16 MC3 MC2 MC1 MC0
31:24
0x30 STATUS
7:0 PERBUFV WAVEBUFV PATTBUFV SLAVE DFS UFS IDX STOP
15:8 FAULT1 FAULT0 FAULTB FAULTA FAULT1IN FAULT0IN FAULTBIN FAULTAIN
23:16 CCBUFV3 CCBUFV2 CCBUFV1 CCBUFV0
31:24 CMP3 CMP2 CMP1 CMP0
0x34 COUNT
7:0 COUNT[7:0]
15:8 COUNT[15:8]
23:16 COUNT[23:16]
31:24
0x38 PATT
7:0 PGE0[7:0]
15:8 PGV0[7:0]
0x3A
...
0x3B
Reserved
0x3C WAVE
7:0 CIPEREN WAVEGEN[2:0]
15:8 CICCEN3 CICCEN2 CICCEN1 CICCEN0
23:16 POL3 POL2 POL1 POL0
31:24 SWAP3 SWAP2 SWAP1 SWAP0
0x40 PER
7:0 PER[1:0] DITHER[5:0]
15:8 PER[9:2]
23:16 PER[17:10]
31:24
0x44 CC0
7:0 CC[1:0] DITHER[5:0]
15:8 CC[9:2]
23:16 CC[17:10]
31:24
0x48 CC1
7:0 CC[1:0] DITHER[5:0]
15:8 CC[9:2]
23:16 CC[17:10]
31:24
0x4C CC2
7:0 CC[1:0] DITHER[5:0]
15:8 CC[9:2]
23:16 CC[17:10]
31:24
0x50 CC3
7:0 CC[1:0] DITHER[5:0]
15:8 CC[9:2]
23:16 CC[17:10]
31:24
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 908
...........continued
Offset Name Bit Pos.
0x54
...
0x63
Reserved
0x64 PATTBUF
7:0 PGEB0[7:0]
15:8 PGVB0[7:0]
0x66
...
0x67
Reserved
0x68 WAVEBUF
7:0 CIPERENB RAMPB[1:0] WAVEGENB[2:0]
15:8 CICCENB3 CICCENB2 CICCENB1 CICCENB0
23:16 POLB3 POLB2 POLB1 POLB0
31:24 SWAPB 3 SWAPB 2 SWAPB 1 SWAPB 0
0x6C PERBUF
7:0 PERBUF[1:0] DITHERBUF[5:0]
15:8 PERBUF[9:2]
23:16 PERBUF[17:10]
31:24
0x70 CCBUF0
7:0 CCBUF[1:0] DITHERBUF[5:0]
15:8 CCBUF[9:2]
23:16 CCBUF[17:10]
31:24
0x74 CCBUF1
7:0 CCBUF[1:0] DITHERBUF[5:0]
15:8 CCBUF[9:2]
23:16 CCBUF[17:10]
31:24
0x78 CCBUF2
7:0 CCBUF[1:0] DITHERBUF[5:0]
15:8 CCBUF[9:2]
23:16 CCBUF[17:10]
31:24
0x7C CCBUF3
7:0 CCBUF[1:0] DITHERBUF[5:0]
15:8 CCBUF[9:2]
23:16 CCBUF[17:10]
31:24
36.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 909
36.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected, Write-Synchronized (ENABLE, SWRST)
Bit 31 30 29 28 27 26 25 24
CPTEN3 CPTEN2 CPTEN1 CPTEN0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
MSYNC ALOCK PRESCYNC[1:0] RUNSTDBY PRESCALER[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RESOLUTION[1:0] ENABLE SWRST
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 24, 25, 26, 27 – CPTEN Capture Channel x Enable
These bits are used to select the capture or compare operation on channel x.
Writing a '1' to CPTENx enables capture on channel x.
Writing a '0' to CPTENx disables capture on channel x.
Bit 15 – MSYNC Master Synchronization (only for TCC slave instance)
This bit must be set if the TCC counting operation must be synchronized on its Master TCC.
This bit is not synchronized.
Value Description
0The TCC controls its own counter.
1The counter is controlled by its Master TCC.
Bit 14 – ALOCK Auto Lock
This bit is not synchronized.
Value Description
0The Lock Update bit in the Control B register (CTRLB.LUPD) is not affected by overflow/
underflow, and re-trigger events
1CTRLB.LUPD is set to '1' on each overflow/underflow or re-trigger event.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 910
Bits 13:12 – PRESCYNC[1:0] Prescaler and Counter Synchronization
These bits select if on re-trigger event, the Counter is cleared or reloaded on either the next GCLK_TCCx
clock, or on the next prescaled GCLK_TCCx clock. It is also possible to reset the prescaler on re-trigger
event.
These bits are not synchronized.
Value Name Description
Counter Reloaded Prescaler
0x0 GCLK Reload or reset Counter on next
GCLK
-
0x1 PRESC Reload or reset Counter on next
prescaler clock
-
0x2 RESYNC Reload or reset Counter on next
GCLK
Reset prescaler counter
0x3 Reserved
Bit 11 – RUNSTDBY Run in Standby
This bit is used to keep the TCC running in standby mode.
This bit is not synchronized.
Value Description
0The TCC is halted in standby.
1The TCC continues to run in standby.
Bits 10:8 – PRESCALER[2:0] Prescaler
These bits select the Counter prescaler factor.
These bits are not synchronized.
Value Name Description
0x0 DIV1 Prescaler: GCLK_TCC
0x1 DIV2 Prescaler: GCLK_TCC/2
0x2 DIV4 Prescaler: GCLK_TCC/4
0x3 DIV8 Prescaler: GCLK_TCC/8
0x4 DIV16 Prescaler: GCLK_TCC/16
0x5 DIV64 Prescaler: GCLK_TCC/64
0x6 DIV256 Prescaler: GCLK_TCC/256
0x7 DIV1024 Prescaler: GCLK_TCC/1024
Bits 6:5 – RESOLUTION[1:0] Dithering Resolution
These bits increase the TCC resolution by enabling the dithering options.
These bits are not synchronized.
Table 36-7. Dithering
Value Name Description
0x0 NONE The dithering is disabled.
0x1 DITH4 Dithering is done every 16 PWM frames. PER[3:0]
and CCx[3:0] contain dithering pattern selection.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 911
...........continued
Value Name Description
0x2 DITH5 Dithering is done every 32 PWM frames. PER[4:0]
and CCx[4:0] contain dithering pattern selection.
0x3 DITH6 Dithering is done every 64 PWM frames. PER[5:0]
and CCx[5:0] contain dithering pattern selection.
Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the ENABLE bit in the
SYNCBUSY register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared when the
operation is complete.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the TCC (except DBGCTRL) to their initial state, and the TCC
will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence; all other writes in the same write-operation
will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 912
36.8.2 Control B Clear
Name:  CTRLBCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
This register allows the user to change this register without doing a read-modify-write operation. Changes
in this register will also be reflected in the Control B Set (CTRLBSET) register.
Bit 7 6 5 4 3 2 1 0
CMD[2:0] IDXCMD[1:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] TCC Command
These bits can be used for software control of re-triggering and stop commands of the TCC. When a
command has been executed, the CMD bit field will read back zero. The commands are executed on the
next prescaled GCLK_TCC clock cycle.
Writing zero to this bit group has no effect.
Writing a '1' to any of these bits will clear the pending command.
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Clear start, restart or retrigger
0x2 STOP Force stop
0x3 UPDATE Force update of double buffered registers
0x4 READSYNC Force COUNT read synchronization
0x5 DMAOS One-shot DMA trigger
Bits 4:3 – IDXCMD[1:0] Ramp Index Command
These bits can be used to force cycle A and cycle B changes in RAMP2 and RAMP2A operation. On
timer/counter update condition, the command is executed, the IDX flag in STATUS register is updated
and the IDXCMD command is cleared.
Writing zero to these bits has no effect.
Writing a '1' to any of these bits will clear the pending command.
Value Name Description
0x0 DISABLE DISABLE Command disabled: IDX toggles between cycles A and B
0x1 SET Set IDX: cycle B will be forced in the next cycle
0x2 CLEAR Clear IDX: cycle A will be forced in next cycle
0x3 HOLD Hold IDX: the next cycle will be the same as the current cycle.
Bit 2 – ONESHOT One-Shot
This bit controls one-shot operation of the TCC. When one-shot operation is enabled, the TCC will stop
counting on the next overflow/underflow condition or on a stop command.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will disable the one-shot operation.
Value Description
0The TCC will update the counter value on overflow/underflow condition and continue
operation.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 913
Value Description
1The TCC will stop counting on the next underflow/overflow condition.
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TCC buffered registers.
When CTRLB.LUPD is cleared, the hardware UPDATE registers with value from their buffered registers is
enabled.
This bit has no effect when input capture operation is enabled.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will enable the registers updates on hardware UPDATE condition.
Value Description
0The CCBx, PERB, PGVB, PGOB, and SWAPBx buffer registers values are copied into the
corresponding CCx, PER, PGV, PGO and SWAPx registers on hardware update condition.
1The CCBx, PERB, PGVB, PGOB, and SWAPBx buffer registers values are not copied into
the corresponding CCx, PER, PGV, PGO and SWAPx registers on hardware update
condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will clear the bit and make the counter count up.
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 914
36.8.3 Control B Set
Name:  CTRLBSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
This register allows the user to change this register without doing a read-modify-write operation. Changes
in this register will also be reflected in the Control B Set (CTRLBCLR) register.
Bit 7 6 5 4 3 2 1 0
CMD[2:0] IDXCMD[1:0] ONESHOT LUPD DIR
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 7:5 – CMD[2:0] TCC Command
These bits can be used for software control of re-triggering and stop commands of the TCC. When a
command has been executed, the CMD bit field will be read back as zero. The commands are executed
on the next prescaled GCLK_TCC clock cycle.
Writing zero to this bit group has no effect
Writing a valid value to this bit group will set the associated command.
Value Name Description
0x0 NONE No action
0x1 RETRIGGER Force start, restart or retrigger
0x2 STOP Force stop
0x3 UPDATE Force update of double buffered registers
0x4 READSYNC Force a read synchronization of COUNT
0x5 DMAOS One-shot DMA trigger
Bits 4:3 – IDXCMD[1:0] Ramp Index Command
These bits can be used to force cycle A and cycle B changes in RAMP2 and RAMP2A operation. On
timer/counter update condition, the command is executed, the IDX flag in STATUS register is updated
and the IDXCMD command is cleared.
Writing a zero to these bits has no effect.
Writing a valid value to these bits will set a command.
Value Name Description
0x0 DISABLE Command disabled: IDX toggles between cycles A and B
0x1 SET Set IDX: cycle B will be forced in the next cycle
0x2 CLEAR Clear IDX: cycle A will be forced in next cycle
0x3 HOLD Hold IDX: the next cycle will be the same as the current cycle.
Bit 2 – ONESHOT One-Shot
This bit controls one-shot operation of the TCC. When in one-shot operation, the TCC will stop counting
on the next overflow/underflow condition or a stop command.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will enable the one-shot operation.
Value Description
0The TCC will count continuously.
1The TCC will stop counting on the next underflow/overflow condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 915
Bit 1 – LUPD Lock Update
This bit controls the update operation of the TCC buffered registers.
When CTRLB.LUPD is set, the hardware UPDATE registers with value from their buffered registers is
disabled. Disabling the update ensures that all buffer registers are valid before an hardware update is
performed. After all the buffer registers are loaded correctly, the buffered registers can be unlocked.
This bit has no effect when input capture operation is enabled.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will disable the registers updates on hardware UPDATE condition.
Value Description
0The CCBx, PERB, PGVB, PGOB, and SWAPBx buffer registers values are copied into the
corresponding CCx, PER, PGV, PGO and SWAPx registers on hardware update condition.
1The CCBx, PERB, PGVB, PGOB, and SWAPBx buffer registers values are not copied into
CCx, PER, PGV, PGO and SWAPx registers on hardware update condition.
Bit 0 – DIR Counter Direction
This bit is used to change the direction of the counter.
Writing a '0' to this bit has no effect
Writing a '1' to this bit will clear the bit and make the counter count up.
Value Description
0The timer/counter is counting up (incrementing).
1The timer/counter is counting down (decrementing).
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 916
36.8.4 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x08
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
CC3 CC2 CC1 CC0
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PER WAVE PATT COUNT STATUS CTRLB ENABLE SWRST
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 8, 9, 10, 11 – CC Compare/Capture Channel x Synchronization Busy
This bit is cleared when the synchronization of Compare/Capture Channel x register between the clock
domains is complete.
This bit is set when the synchronization of Compare/Capture Channel x register between clock domains
is started.
CCx bit is available only for existing Compare/Capture Channels. For details on CC channels number,
refer to each TCC feature list.
This bit is set when the synchronization of CCx register between clock domains is started.
Bit 7 – PER PER Synchronization Busy
This bit is cleared when the synchronization of PER register between the clock domains is complete.
This bit is set when the synchronization of PER register between clock domains is started.
Bit 6 – WAVE WAVE Synchronization Busy
This bit is cleared when the synchronization of WAVE register between the clock domains is complete.
This bit is set when the synchronization of WAVE register between clock domains is started.
Bit 5 – PATT PATT Synchronization Busy
This bit is cleared when the synchronization of PATTERN register between the clock domains is
complete.
This bit is set when the synchronization of PATTERN register between clock domains is started.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 917
Bit 4 – COUNT COUNT Synchronization Busy
This bit is cleared when the synchronization of COUNT register between the clock domains is complete.
This bit is set when the synchronization of COUNT register between clock domains is started.
Bit 3 – STATUS STATUS Synchronization Busy
This bit is cleared when the synchronization of STATUS register between the clock domains is complete.
This bit is set when the synchronization of STATUS register between clock domains is started.
Bit 2 – CTRLB CTRLB Synchronization Busy
This bit is cleared when the synchronization of CTRLB register between the clock domains is complete.
This bit is set when the synchronization of CTRLB register between clock domains is started.
Bit 1 – ENABLE ENABLE Synchronization Busy
This bit is cleared when the synchronization of ENABLE bit between the clock domains is complete.
This bit is set when the synchronization of ENABLE bit between clock domains is started.
Bit 0 – SWRST SWRST Synchronization Busy
This bit is cleared when the synchronization of SWRST bit between the clock domains is complete.
This bit is set when the synchronization of SWRST bit between clock domains is started.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 918
36.8.5 Fault Control A and B
Name:  FCTRLA, FCTRLB
Offset:  0x0C + n*0x04 [n=0..1]
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
FILTERVAL[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
BLANKVAL[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CAPTURE[2:0] CHSEL[1:0] HALT[1:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RESTART BLANK[1:0] QUAL KEEP SRC[1:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 27:24 – FILTERVAL[3:0] Recoverable Fault n Filter Value
These bits define the filter value applied on MCEx (x=0,1) event input line. The value must be set to zero
when MCEx event is used as synchronous event.
Bits 23:16 – BLANKVAL[7:0] Recoverable Fault n Blanking Value
These bits determine the duration of the blanking of the fault input source. Activation and edge selection
of the blank filtering are done by the BLANK bits (FCTRLn.BLANK).
When enabled, the fault input source is internally disabled for BLANKVAL* prescaled GCLK_TCC periods
after the detection of the waveform edge.
Bits 14:12 – CAPTURE[2:0] Recoverable Fault n Capture Action
These bits select the capture and Fault n interrupt/event conditions.
Table 36-8. Fault n Capture Action
Value Name Description
0x0 DISABLE Capture on valid recoverable Fault n is disabled
0x1 CAPT On rising edge of a valid recoverable Fault n, capture counter value on channel
selected by CHSEL[1:0]. INTFLAG.FAULTn flag rises on each new captured value.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 919
...........continued
Value Name Description
0x2 CAPTMIN On rising edge of a valid recoverable Fault n, capture counter value on channel
selected by CHSEL[1:0], if COUNT value is lower than the last stored capture
value (CC). INTFLAG.FAULTn flag rises on each local minimum detection.
0x3 CAPTMAX On rising edge of a valid recoverable Fault n, capture counter value on channel
selected by CHSEL[1:0], if COUNT value is higher than the last stored capture
value (CC). INTFLAG.FAULTn flag rises on each local maximun detection.
0x4 LOCMIN On rising edge of a valid recoverable Fault n, capture counter value on channel
selected by CHSEL[1:0]. INTFLAG.FAULTn flag rises on each local minimum
value detection.
0x5 LOCMAX On rising edge of a valid recoverable Fault n, capture counter value on channel
selected by CHSEL[1:0]. INTFLAG.FAULTn flag rises on each local maximun
detection.
0x6 DERIV0 On rising edge of a valid recoverable Fault n, capture counter value on channel
selected by CHSEL[1:0]. INTFLAG.FAULTn flag rises on each local maximun or
minimum detection.
0x7 CAPTMARK Capture with ramp index as MSB value.
Bits 11:10 – CHSEL[1:0] Recoverable Fault n Capture Channel
These bits select the channel for capture operation triggered by recoverable Fault n.
Value Name Description
0x0 CC0 Capture value stored into CC0
0x1 CC1 Capture value stored into CC1
0x2 CC2 Capture value stored into CC2
0x3 CC3 Capture value stored into CC3
Bits 9:8 – HALT[1:0] Recoverable Fault n Halt Operation
These bits select the halt action for recoverable Fault n.
Value Name Description
0x0 DISABLE Halt action disabled
0x1 HW Hardware halt action
0x2 SW Software halt action
0x3 NR Non-recoverable fault
Bit 7 – RESTART Recoverable Fault n Restart
Setting this bit enables restart action for Fault n.
Value Description
0Fault n restart action is disabled.
1Fault n restart action is enabled.
Bits 6:5 – BLANK[1:0] Recoverable Fault n Blanking Operation
These bits, select the blanking start point for recoverable Fault n.
Value Name Description
0x0 START Blanking applied from start of the Ramp period
0x1 RISE Blanking applied from rising edge of the waveform output
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 920
Value Name Description
0x2 FALL Blanking applied from falling edge of the waveform output
0x3 BOTH Blanking applied from each toggle of the waveform output
Bit 4 – QUAL Recoverable Fault n Qualification
Setting this bit enables the recoverable Fault n input qualification.
Value Description
0The recoverable Fault n input is not disabled on CMPx value condition.
1The recoverable Fault n input is disabled when output signal is at inactive level (CMPx == 0).
Bit 3 – KEEP Recoverable Fault n Keep
Setting this bit enables the Fault n keep action.
Value Description
0The Fault n state is released as soon as the recoverable Fault n is released.
1The Fault n state is released at the end of TCC cycle.
Bits 1:0 – SRC[1:0] Recoverable Fault n Source
These bits select the TCC event input for recoverable Fault n.
Event system channel connected to MCEx event input, must be configured to route the event
asynchronously, when used as a recoverable Fault n input.
Value Name Description
0x0 DISABLE Fault input disabled
0x1 ENABLE MCEx (x=0,1) event input
0x2 INVERT Inverted MCEx (x=0,1) event input
0x3 ALTFAULT Alternate fault (A or B) state at the end of the previous period.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 921
36.8.6 Waveform Extension Control
Name:  WEXCTRL
Offset:  0x14
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
DTHS[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
DTLS[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
DTIEN3 DTIEN2 DTIEN1 DTIEN0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OTMX[1:0]
Access R/W R/W
Reset 0 0
Bits 31:24 – DTHS[7:0] Dead-Time High Side Outputs Value
This register holds the number of GCLK_TCC clock cycles for the dead-time high side.
Bits 23:16 – DTLS[7:0] Dead-time Low Side Outputs Value
This register holds the number of GCLK_TCC clock cycles for the dead-time low side.
Bits 8, 9, 10, 11 – DTIEN Dead-time Insertion Generator x Enable
Setting any of these bits enables the dead-time insertion generator for the corresponding output matrix.
This will override the output matrix [x] and [x+WO_NUM/2], with the low side and high side waveform
respectively.
Value Description
0No dead-time insertion override.
1Dead time insertion override on signal outputs[x] and [x+WO_NUM/2], from matrix outputs[x]
signal.
Bits 1:0 – OTMX[1:0] Output Matrix
These bits define the matrix routing of the TCC waveform generation outputs to the port pins, according
to Table 36-4.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 922
36.8.7 Driver Control
Name:  DRVCTRL
Offset:  0x18
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
FILTERVAL1[3:0] FILTERVAL0[3:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
INVEN7 INVEN6 INVEN5 INVEN4 INVEN3 INVEN2 INVEN1 INVEN0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
NRV7 NRV6 NRV5 NRV4 NRV3 NRV2 NRV1 NRV0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
NRE7 NRE6 NRE5 NRE4 NRE3 NRE2 NRE1 NRE0
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:28 – FILTERVAL1[3:0] Non-Recoverable Fault Input 1 Filter Value
These bits define the filter value applied on TCE1 event input line. When the TCE1 event input line is
configured as a synchronous event, this value must be 0x0.
Bits 27:24 – FILTERVAL0[3:0] Non-Recoverable Fault Input 0 Filter Value
These bits define the filter value applied on TCE0 event input line. When the TCE0 event input line is
configured as a synchronous event, this value must be 0x0.
Bits 16, 17, 18, 19, 20, 21, 22, 23 – INVEN Waveform Output x Inversion
These bits are used to select inversion on the output of channel x.
Writing a '1' to INVENx inverts output from WO[x].
Writing a '0' to INVENx disables inversion of output from WO[x].
Bits 8, 9, 10, 11, 12, 13, 14, 15 – NRV NRVx Non-Recoverable State x Output Value
These bits define the value of the enabled override outputs, under non-recoverable fault condition.
Bits 0, 1, 2, 3, 4, 5, 6, 7 – NRE Non-Recoverable State x Output Enable
These bits enable the override of individual outputs by NRVx value, under non-recoverable fault
condition.
Value Description
0Non-recoverable fault tri-state the output.
1Non-recoverable faults set the output to NRVx level.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 923
36.8.8 Debug control
Name:  DBGCTRL
Offset:  0x1E
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
FDDBD DBGRUN
Access R/W R/W
Reset 0 0
Bit 2 – FDDBD Fault Detection on Debug Break Detection
This bit is not affected by software reset and should not be changed by software while the TCC is
enabled.
By default this bit is zero, and the on-chip debug (OCD) fault protection is disabled. When this bit is
written to ‘1’, OCD break request from the OCD system will trigger non-recoverable fault. When this bit is
set, OCD fault protection is enabled and OCD break request from the OCD system will trigger a non-
recoverable fault.
Value Description
0No faults are generated when TCC is halted in debug mode.
1A non recoverable fault is generated and FAULTD flag is set when TCC is halted in debug
mode.
Bit 0 – DBGRUN Debug Running State
This bit is not affected by software reset and should not be changed by software while the TCC is
enabled.
Value Description
0The TCC is halted when the device is halted in debug mode.
1The TCC continues normal operation when the device is halted in debug mode.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 924
36.8.9 Event Control
Name:  EVCTRL
Offset:  0x20
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
MCEO3 MCEO2 MCEO1 MCEO0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
MCEI3 MCEI2 MCEI1 MCEI0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
TCEI1 TCEI0 TCINV1 TCINV0 CNTEO TRGEO OVFEO
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CNTSEL[1:0] EVACT1[2:0] EVACT0[2:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 24, 25, 26, 27 – MCEO Match or Capture Channel x Event Output Enable
These bits control if the match/capture event on channel x is enabled and will be generated for every
match or capture.
Value Description
0Match/capture x event is disabled and will not be generated.
1Match/capture x event is enabled and will be generated for every compare/capture on
channel x.
Bits 16, 17, 18, 19 – MCEI Match or Capture Channel x Event Input Enable
These bits indicate if the match/capture x incoming event is enabled
These bits are used to enable match or capture input events to the CCx channel of TCC.
Value Description
0Incoming events are disabled.
1Incoming events are enabled.
Bits 14, 15 – TCEI Timer/Counter Event Input x Enable
This bit is used to enable input event x to the TCC.
Value Description
0Incoming event x is disabled.
1Incoming event x is enabled.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 925
Bits 12, 13 – TCINV Timer/Counter Event x Invert Enable
This bit inverts the event x input.
Value Description
0Input event source x is not inverted.
1Input event source x is inverted.
Bit 10 – CNTEO Timer/Counter Event Output Enable
This bit is used to enable the counter cycle event. When enabled, an event will be generated on begin or
end of counter cycle depending of CNTSEL[1:0] settings.
Value Description
0Counter cycle output event is disabled and will not be generated.
1Counter cycle output event is enabled and will be generated depend of CNTSEL[1:0] value.
Bit 9 – TRGEO Retrigger Event Output Enable
This bit is used to enable the counter retrigger event. When enabled, an event will be generated when the
counter retriggers operation.
Value Description
0Counter retrigger event is disabled and will not be generated.
1Counter retrigger event is enabled and will be generated for every counter retrigger.
Bit 8 – OVFEO Overflow/Underflow Event Output Enable
This bit is used to enable the overflow/underflow event. When enabled an event will be generated when
the counter reaches the TOP or the ZERO value.
Value Description
0Overflow/underflow counter event is disabled and will not be generated.
1Overflow/underflow counter event is enabled and will be generated for every counter
overflow/underflow.
Bits 7:6 – CNTSEL[1:0] Timer/Counter Interrupt and Event Output Selection
These bits define on which part of the counter cycle the counter event output is generated.
Value Name Description
0x0 BEGIN An interrupt/event is generated at begin of each counter cycle
0x1 END An interrupt/event is generated at end of each counter cycle
0x2 BETWEEN An interrupt/event is generated between each counter cycle.
0x3 BOUNDARY An interrupt/event is generated at begin of first counter cycle, and end of last
counter cycle.
Bits 5:3 – EVACT1[2:0] Timer/Counter Event Input 1 Action
These bits define the action the TCC will perform on TCE1 event input.
Value Name Description
0x0 OFF Event action disabled.
0x1 RETRIGGER Start, restart or re-trigger TC on event
0x2 DIR (asynch) Direction control
0x3 STOP Stop TC on event
0x4 DEC Decrement TC on event
0x5 PPW Period captured into CC0 Pulse Width on CC1
0x6 PWP Period captured into CC1 Pulse Width on CC0
0x7 FAULT Non-recoverable Fault
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 926
Bits 2:0 – EVACT0[2:0] Timer/Counter Event Input 0 Action
These bits define the action the TCC will perform on TCE0 event input 0.
Value Name Description
0x0 OFF Event action disabled.
0x1 RETRIGGER Start, restart or re-trigger TC on event
0x2 COUNTEV Count on event.
0x3 START Start TC on event
0x4 INC Increment TC on EVENT
0x5 COUNT (async) Count on active state of asynchronous event
0x6
0x7 FAULT Non-recoverable Fault
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 927
36.8.10 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x24
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
MC3 MC2 MC1 MC0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FAULT1 FAULT0 FAULTB FAULTA DFS UFS
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ERR CNT TRG OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 16, 17, 18, 19 – MC Match or Capture Channel x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the corresponding Match or Capture Channel x Interrupt Disable/Enable
bit, which disables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 15 – FAULT1 Non-Recoverable Fault x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Non-Recoverable Fault x Interrupt Disable/Enable bit, which disables
the Non-Recoverable Fault x interrupt.
Value Description
0The Non-Recoverable Fault x interrupt is disabled.
1The Non-Recoverable Fault x interrupt is enabled.
Bit 14 – FAULT0 Non-Recoverable Fault x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Non-Recoverable Fault x Interrupt Disable/Enable bit, which disables
the Non-Recoverable Fault x interrupt.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 928
Value Description
0The Non-Recoverable Fault x interrupt is disabled.
1The Non-Recoverable Fault x interrupt is enabled.
Bit 13 – FAULTB Recoverable Fault B Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Recoverable Fault B Interrupt Disable/Enable bit, which disables the
Recoverable Fault B interrupt.
Value Description
0The Recoverable Fault B interrupt is disabled.
1The Recoverable Fault B interrupt is enabled.
Bit 12 – FAULTA Recoverable Fault A Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Recoverable Fault A Interrupt Disable/Enable bit, which disables the
Recoverable Fault A interrupt.
Value Description
0The Recoverable Fault A interrupt is disabled.
1The Recoverable Fault A interrupt is enabled.
Bit 11 – DFS Non-Recoverable Debug Fault Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Debug Fault State Interrupt Disable/Enable bit, which disables the
Debug Fault State interrupt.
Value Description
0The Debug Fault State interrupt is disabled.
1The Debug Fault State interrupt is enabled.
Bit 10 – UFS Non-Recoverable Update Fault Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Non-Recoverable Update Fault Interrupt Disable/Enable bit, which
disables the Non-Recoverable Update Fault interrupt.
Note:  This bit is only available on variant L devices. Refer to the Configuration Summary for more
information.
Value Description
0The Non-Recoverable Update Fault interrupt is disabled.
1The Non-Recoverable Update Fault interrupt is enabled.
Bit 3 – ERR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Error Interrupt Disable/Enable bit, which disables the Compare
interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 2 – CNT Counter Interrupt Enable
Writing a '0' to this bit has no effect.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 929
Writing a '1' to this bit will clear the Counter Interrupt Disable/Enable bit, which disables the Counter
interrupt.
Value Description
0The Counter interrupt is disabled.
1The Counter interrupt is enabled.
Bit 1 – TRG Retrigger Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Retrigger Interrupt Disable/Enable bit, which disables the Retrigger
interrupt.
Value Description
0The Retrigger interrupt is disabled.
1The Retrigger interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Overflow Interrupt Disable/Enable bit, which disables the Overflow
interrupt request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 930
36.8.11 Interrupt Enable Set
Name:  INTENSET
Offset:  0x28
Reset:  0x00000000
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
MC3 MC2 MC1 MC0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FAULT1 FAULT0 FAULTB FAULTA DFS UFS
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ERR CNT TRG OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 16, 17, 18, 19 – MC Match or Capture Channel x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the corresponding Match or Capture Channel x Interrupt Disable/Enable bit,
which enables the Match or Capture Channel x interrupt.
Value Description
0The Match or Capture Channel x interrupt is disabled.
1The Match or Capture Channel x interrupt is enabled.
Bit 15 – FAULT1 Non-Recoverable Fault x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Non-Recoverable Fault x Interrupt Disable/Enable bit, which enables the
Non-Recoverable Fault x interrupt.
Value Description
0The Non-Recoverable Fault x interrupt is disabled.
1The Non-Recoverable Fault x interrupt is enabled.
Bit 14 – FAULT0 Non-Recoverable Fault x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Non-Recoverable Fault x Interrupt Disable/Enable bit, which disables
the Non-Recoverable Fault x interrupt.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 931
Value Description
0The Non-Recoverable Fault x interrupt is disabled.
1The Non-Recoverable Fault x interrupt is enabled.
Bit 13 – FAULTB Recoverable Fault B Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Recoverable Fault B Interrupt Disable/Enable bit, which enables the
Recoverable Fault B interrupt.
Value Description
0The Recoverable Fault B interrupt is disabled.
1The Recoverable Fault B interrupt is enabled.
Bit 12 – FAULTA Recoverable Fault A Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Recoverable Fault A Interrupt Disable/Enable bit, which enables the
Recoverable Fault A interrupt.
Value Description
0The Recoverable Fault A interrupt is disabled.
1The Recoverable Fault A interrupt is enabled.
Bit 11 – DFS Non-Recoverable Debug Fault Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Debug Fault State Interrupt Disable/Enable bit, which enables the
Debug Fault State interrupt.
Value Description
0The Debug Fault State interrupt is disabled.
1The Debug Fault State interrupt is enabled.
Bit 10 – UFS Non-Recoverable Update Fault Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Non-Recoverable Update Fault Interrupt Disable/Enable bit, which
enables the Non-Recoverable Update Fault interrupt.
Note:  This bit is only available on variant L devices. Refer to the Configuration Summary for more
information.
Value Description
0The Non-Recoverable Update Fault interrupt is disabled.
1The Non-Recoverable Update Fault interrupt is enabled.
Bit 3 – ERR Error Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Error Interrupt Disable/Enable bit, which enables the Compare interrupt.
Value Description
0The Error interrupt is disabled.
1The Error interrupt is enabled.
Bit 2 – CNT Counter Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Retrigger Interrupt Disable/Enable bit, which enables the Counter
interrupt.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 932
Value Description
0The Counter interrupt is disabled.
1The Counter interrupt is enabled.
Bit 1 – TRG Retrigger Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Retrigger Interrupt Disable/Enable bit, which enables the Retrigger
interrupt.
Value Description
0The Retrigger interrupt is disabled.
1The Retrigger interrupt is enabled.
Bit 0 – OVF Overflow Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Overflow Interrupt Disable/Enable bit, which enables the Overflow
interrupt request.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 933
36.8.12 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x2C
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
MC3 MC2 MC1 MC0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FAULT1 FAULT0 FAULTB FAULTA DFS UFS
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ERR CNT TRG OVF
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 16, 17, 18, 19 – MC Match or Capture Channel x Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after a match with the compare condition or once
CCx register contain a valid capture value.
Writing a '0' to one of these bits has no effect.
Writing a '1' to one of these bits will clear the corresponding Match or Capture Channel x interrupt flag
In Capture operation, this flag is automatically cleared when CCx register is read.
Bit 15 – FAULT1 Non-Recoverable Fault x Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after a Non-Recoverable Fault x occurs.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Non-Recoverable Fault x interrupt flag.
Bit 14 – FAULT0 Non-Recoverable Fault x Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Non-Recoverable Fault x Interrupt Disable/Enable bit, which disables
the Non-Recoverable Fault x interrupt.
Value Description
0The Non-Recoverable Fault x interrupt is disabled.
1The Non-Recoverable Fault x interrupt is enabled.
Bit 13 – FAULTB Recoverable Fault B Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after a Recoverable Fault B occurs.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 934
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Recoverable Fault B interrupt flag.
Bit 12 – FAULTA Recoverable Fault A Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after a Recoverable Fault B occurs.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Recoverable Fault B interrupt flag.
Bit 11 – DFS Non-Recoverable Debug Fault State Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after an Debug Fault State occurs.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Debug Fault State interrupt flag.
Bit 10 – UFS Non-Recoverable Update Fault
This flag is set when the RAMP index changes and the Lock Update bit is set (CTRLBSET.LUPD).
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Non-Recoverable Update Fault interrupt flag.
Note:  This bit is only available on variant L devices. Refer to the Configuration Summary for more
information.
Bit 3 – ERR Error Interrupt Flag
This flag is set if a new capture occurs on a channel when the corresponding Match or Capture Channel x
interrupt flag is one. In which case there is nowhere to store the new capture.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the error interrupt flag.
Bit 2 – CNT Counter Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after a counter event occurs.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the CNT interrupt flag.
Bit 1 – TRG Retrigger Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after a counter retrigger occurs.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the re-trigger interrupt flag.
Bit 0 – OVF Overflow Interrupt Flag
This flag is set on the next CLK_TCC_COUNT cycle after an overflow condition occurs.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overflow interrupt flag.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 935
36.8.13 Status
Name:  STATUS
Offset:  0x30
Reset:  0x00000001
Property:  -
Bit 31 30 29 28 27 26 25 24
CMP3 CMP2 CMP1 CMP0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
CCBUFV3 CCBUFV2 CCBUFV1 CCBUFV0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
FAULT1 FAULT0 FAULTB FAULTA FAULT1IN FAULT0IN FAULTBIN FAULTAIN
Access R/W R/W R/W R/W R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PERBUFV WAVEBUFV PATTBUFV SLAVE DFS UFS IDX STOP
Access R/W R/W R/W R R/W R/W R R
Reset 0 0 0 0 0 0 0 1
Bits 24, 25, 26, 27 – CMP Channel x Compare Value
This bit reflects the channel x output compare value.
Value Description
0Channel compare output value is 0.
1Channel compare output value is 1.
Bits 16, 17, 18, 19 – CCBUFV Channel x Compare or Capture Buffer Valid
For a compare channel, this bit is set when a new value is written to the corresponding CCBUFx register.
The bit is cleared either by writing a '1' to the corresponding location when CTRLB.LUPD is set, or
automatically on an UPDATE condition.
For a capture channel, the bit is set when a valid capture value is stored in the CCBUFx register. The bit
is automatically cleared when the CCx register is read.
Bits 14, 15 – FAULT Non-recoverable Fault x State
This bit is set by hardware as soon as non-recoverable Fault x condition occurs.
This bit is cleared by writing a one to this bit and when the corresponding FAULTxIN status bit is low.
Once this bit is clear, the timer/counter will restart from the last COUNT value. To restart the timer/counter
from BOTTOM, the timer/counter restart command must be executed before clearing the corresponding
STATEx bit. For further details on timer/counter commands, refer to available commands description
(36.8.3 CTRLBSET.CMD).
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 936
Bit 13 – FAULTB Recoverable Fault B State
This bit is set by hardware as soon as recoverable Fault B condition occurs.
This bit can be clear by hardware when Fault B action is resumed, or by writing a '1' to this bit when the
corresponding FAULTBIN bit is low. If software halt command is enabled (FAULTB.HALT=SW), clearing
this bit will release the timer/counter.
Bit 12 – FAULTA Recoverable Fault A State
This bit is set by hardware as soon as recoverable Fault A condition occurs.
This bit can be clear by hardware when Fault A action is resumed, or by writing a '1' to this bit when the
corresponding FAULTAIN bit is low. If software halt command is enabled (FAULTA.HALT=SW), clearing
this bit will release the timer/counter.
Bit 11 – FAULT1IN Non-Recoverable Fault 1 Input
This bit is set while an active Non-Recoverable Fault 1 input is present.
Bit 10 – FAULT0IN Non-Recoverable Fault 0 Input
This bit is set while an active Non-Recoverable Fault 0 input is present.
Bit 9 – FAULTBIN Recoverable Fault B Input
This bit is set while an active Recoverable Fault B input is present.
Bit 8 – FAULTAIN Recoverable Fault A Input
This bit is set while an active Recoverable Fault A input is present.
Bit 7 – PERBUFV Period Buffer Valid
This bit is set when a new value is written to the PERBUF register. This bit is automatically cleared by
hardware on UPDATE condition when CTRLB.LUPD is set, or by writing a '1' to this bit.
Bit 6 – WAVEBUFV Waveform Control Buffer Valid
This bit is set when a new value is written to the WAVEBUF register. This bit is automatically cleared by
hardware on UPDATE condition when CTRLB.LUPD is set, or by writing a '1' to this bit.
Bit 5 – PATTBUFV Pattern Generator Value Buffer Valid
This bit is set when a new value is written to the PATTBUF register. This bit is automatically cleared by
hardware on UPDATE condition when CTRLB.LUPD is set, or by writing a '1' to this bit.
Bit 4 – SLAVE Slave
This bit is set when TCC is set in Slave mode. This bit follows the CTRLA.MSYNC bit state.
Bit 3 – DFS Debug Fault State
This bit is set by hardware in Debug mode when DDBGCTRL.FDDBD bit is set. The bit is cleared by
writing a '1' to this bit and when the TCC is not in Debug mode.
When the bit is set, the counter is halted and the Waveforms state depend on DRVCTRL.NRE and
DRVCTRL.NRV registers.
Bit 2 – UFS Non-recoverable Update Fault State
This bit is set by hardware when the RAMP index changes and the Lock Update bit is set
(CTRLBSET.LUPD). The bit is cleared by writing a one to this bit.
When the bit is set, the waveforms state depend on DRVCTRL.NRE and DRVCTRL.NRV registers.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 937
Bit 1 – IDX Ramp Index
In RAMP2 and RAMP2A operation, the bit is cleared during the cycle A and set during the cycle B. In
RAMP1 operation, the bit always reads zero. For details on ramp operations, refer to 36.6.3.4 Ramp
Operations.
Bit 0 – STOP Stop
This bit is set when the TCC is disabled either on a STOP command or on an UPDATE condition when
One-Shot operation mode is enabled (CTRLBSET.ONESHOT=1).
This bit is clear on the next incoming counter increment or decrement.
Value Description
0Counter is running.
1Counter is stopped.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 938
36.8.14 Counter Value
Name:  COUNT
Offset:  0x34
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized, Read-Synchronized
Note:  Prior to any read access, this register must be synchronized by user by writing the according TCC
Command value to the Control B Set register (CTRLBSET.CMD=READSYNC).
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
COUNT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
COUNT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
COUNT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – COUNT[23:0] Counter Value
These bits hold the value of the counter register.
Note:  When the TCC is configured as 16-bit timer/counter, the excess bits are read zero.
Note:  This bit field occupies the MSB of the register, [23:m]. m is dependent on the Resolution bit in the
Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [23:m]
0x0 - NONE 23:0 (depicted)
0x1 - DITH4 23:4
0x2 - DITH5 23:5
0x3 - DITH6 23:6
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 939
36.8.15 Pattern
Name:  PATT
Offset:  0x38
Reset:  0x0000
Property:  Write-Synchronized
Bit 15 14 13 12 11 10 9 8
PGV0[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PGE0[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 8:15, 16:23, 24:31, 32:39, 40:47, 48:55, 56:63, 64:71 – PGV Pattern Generation Output Value
This register holds the values of pattern for each waveform output.
Bits 0:7, 8:15, 16:23, 24:31, 32:39, 40:47, 48:55, 56:63 – PGE Pattern Generation Output Enable
This register holds the enable status of pattern generation for each waveform output. A bit written to '1'
will override the corresponding SWAP output with the corresponding PGVn value.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 940
36.8.16 Waveform
Name:  WAVE
Offset:  0x3C
Reset:  0x00000000
Property:  Write-Synchronized
Bit 31 30 29 28 27 26 25 24
SWAP3 SWAP2 SWAP1 SWAP0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
POL3 POL2 POL1 POL0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CICCEN3 CICCEN2 CICCEN1 CICCEN0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CIPEREN WAVEGEN[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 24, 25, 26, 27 – SWAP Swap DTI Output Pair x
Setting these bits enables output swap of DTI outputs [x] and [x+WO_NUM/2]. Note the DTIxEN settings
will not affect the swap operation.
Bits 16, 17, 18, 19 – POL Channel Polarity x
Setting these bits enables the output polarity in single-slope and dual-slope PWM operations.
Value Name Description
0(single-slope PWM waveform
generation)
Compare output is initialized to ~DIR and set to DIR when
TCC counter matches CCx value
1(single-slope PWM waveform
generation)
Compare output is initialized to DIR and set to ~DIR when
TCC counter matches CCx value.
0(dual-slope PWM waveform
generation)
Compare output is set to ~DIR when TCC counter matches
CCx value
1(dual-slope PWM waveform
generation)
Compare output is set to DIR when TCC counter matches
CCx value.
Bits 8, 9, 10, 11 – CICCEN Circular CC Enable x
Setting this bits enables the compare circular buffer option on channel. When the bit is set, CCx register
value is copied-back into the CCx register on UPDATE condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 941
Bit 7 – CIPEREN Circular Period Enable
Setting this bits enable the period circular buffer option. When the bit is set, the PER register value is
copied-back into the PERB register on UPDATE condition.
These bits select Ramp operation (RAMP). These bits are not synchronized.
Value Name Description
0x0 RAMP1 RAMP1 operation
0x1 RAMP2A Alternative RAMP2 operation
0x2 RAMP2 RAMP2 operation
0x3 RAMP2C. This bit is only available in variant L devices. Refer
to Configuration Summary for more information.
Critical RAMP2 operation
0x4
Bits 2:0 – WAVEGEN[2:0] Waveform Generation Operation
These bits select the waveform generation operation. The settings impact the top value and control if
frequency or PWM waveform generation should be used. These bits are not synchronized.
Value Name Description
Operation Top Update Waveform Output
On Match
Waveform Output
On Update
OVFIF/Event
Up Down
0x0 NFRQ Normal Frequency PER TOP/Zero Toggle Stable TOP Zero
0x1 MFRQ Match Frequency CC0 TOP/Zero Toggle Stable TOP Zero
0x2 NPWM Normal PWM PER TOP/Zero Set Clear TOP Zero
0x3
0x4 DSCRITICAL Dual-slope PWM PER Zero ~DIR Stable – Zero
0x5 DSBOTTOM Dual-slope PWM PER Zero ~DIR Stable – Zero
0x6 DSBOTH Dual-slope PWM PER TOP & Zero ~DIR Stable TOP Zero
0x7 DSTOP Dual-slope PWM PER Zero ~DIR Stable TOP –
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 942
36.8.17 Period Value
Name:  PER
Offset:  0x40
Reset:  0xFFFFFFFF
Property:  Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
PER[17:10]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 15 14 13 12 11 10 9 8
PER[9:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 7 6 5 4 3 2 1 0
PER[1:0] DITHER[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bits 23:6 – PER[17:0] Period Value
These bits hold the value of the period buffer register.
Note:  When the TCC is configured as 16-bit timer/counter, the excess bits are read zero.
Note:  This bit field occupies the MSB of the register, [23:m]. m is dependent on the Resolution bit in the
Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [23:m]
0x0 - NONE 23:0
0x1 - DITH4 23:4
0x2 - DITH5 23:5
0x3 - DITH6 23:6 (depicted)
Bits 5:0 – DITHER[5:0] Dithering Cycle Number
These bits hold the number of extra cycles that are added on the PWM pulse period every 64 PWM
frames.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 943
Note:  This bit field consists of the n LSB of the register. n is dependent on the value of the Resolution
bits in the Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [n:0]
0x0 - NONE -
0x1 - DITH4 3:0
0x2 - DITH5 4:0
0x3 - DITH6 5:0 (depicted)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 944
36.8.18 Compare/Capture Channel x
Name:  CC
Offset:  0x44 + n*0x04 [n=0..3]
Reset:  0x00000000
Property:  Write-Synchronized, Read-Synchronized
The CCx register represents the 16-, 24- bit value, CCx. The register has two functions, depending of the
mode of operation.
For capture operation, this register represents the second buffer level and access point for the CPU and
DMA.
For compare operation, this register is continuously compared to the counter value. Normally, the output
form the comparator is then used for generating waveforms.
CCx register is updated with the buffer value from their corresponding CCBUFx register when an
UPDATE condition occurs.
In addition, in match frequency operation, the CC0 register controls the counter period.
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CC[17:10]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CC[9:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CC[1:0] DITHER[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:6 – CC[17:0] Channel x Compare/Capture Value
These bits hold the value of the Channel x compare/capture register.
Note:  When the TCC is configured as 16-bit timer/counter, the excess bits are read zero.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 945
Note:  This bit field occupies the m MSB of the register, [23:m]. m is dependent on the Resolution bit in
the Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [23:m]
0x0 - NONE 23:0
0x1 - DITH4 23:4
0x2 - DITH5 23:5
0x3 - DITH6 23:6 (depicted)
Bits 5:0 – DITHER[5:0] Dithering Cycle Number
These bits hold the number of extra cycles that are added on the PWM pulse width every 64 PWM
frames.
Note:  This bit field consists of the n LSB of the register. n is dependent on the value of the Resolution
bits in the Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [n:0]
0x0 - NONE -
0x1 - DITH4 3:0
0x2 - DITH5 4:0
0x3 - DITH6 5:0 (depicted)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 946
36.8.19 Pattern Buffer
Name:  PATTBUF
Offset:  0x64
Reset:  0x0000
Property:  Write-Synchronized, Read-Synchronized
Bit 15 14 13 12 11 10 9 8
PGVB0[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PGEB0[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 8:15, 16:23, 24:31, 32:39, 40:47, 48:55, 56:63, 64:71 – PGVB Pattern Generation Output Value
Buffer
This register is the buffer for the PGV register. If double buffering is used, valid content in this register is
copied to the PGV register on an UPDATE condition.
Bits 0:7, 8:15, 16:23, 24:31, 32:39, 40:47, 48:55, 56:63 – PGEB Pattern Generation Output Enable
Buffer
This register is the buffer of the PGE register. If double buffering is used, valid content in this register is
copied into the PGE register at an UPDATE condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 947
36.8.20 Waveform Buffer
Name:  WAVEBUF
Offset:  0x68
Reset:  0x00000000
Property:  Write-Synchronized, Read-Synchronized
Bit 31 30 29 28 27 26 25 24
SWAPB 3 SWAPB 2 SWAPB 1 SWAPB 0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 23 22 21 20 19 18 17 16
POLB3 POLB2 POLB1 POLB0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CICCENB3 CICCENB2 CICCENB1 CICCENB0
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CIPERENB RAMPB[1:0] WAVEGENB[2:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 24, 25, 26, 27 – SWAPB  Swap DTI output pair x Buffer
These register bits are the buffer bits for the SWAP register bits. If double buffering is used, valid content
in these bits is copied to the corresponding SWAPx bits on an UPDATE condition.
Bits 16, 17, 18, 19 – POLB Channel Polarity x Buffer
These register bits are the buffer bits for POLx register bits. If double buffering is used, valid content in
these bits is copied to the corresponding POBx bits on an UPDATE condition.
Bits 8, 9, 10, 11 – CICCENB Circular CCx Buffer Enable
These register bits are the buffer bits for CICCENx register bits. If double buffering is used, valid content
in these bits is copied to the corresponding CICCENx bits on a UPDATE condition.
Bit 7 – CIPERENB Circular Period Enable Buffer
This register bit is the buffer bit for CIPEREN register bit. If double buffering is used, valid content in this
bit is copied to the corresponding CIPEREN bit on a UPDATE condition.
Bits 5:4 – RAMPB[1:0] Ramp Operation Buffer
These register bits are the buffer bits for RAMP register bits. If double buffering is used, valid content in
these bits is copied to the corresponding RAMP bits on a UPDATE condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 948
Bits 2:0 – WAVEGENB[2:0] Waveform Generation Operation Buffer
These register bits are the buffer bits for WAVEGEN register bits. If double buffering is used, valid content
in these bits is copied to the corresponding WAVEGEN bits on a UPDATE condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 949
36.8.21 Period Buffer Value
Name:  PERBUF
Offset:  0x6C
Reset:  0xFFFFFFFF
Property:  Write-Synchronized, Read-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
PERBUF[17:10]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 15 14 13 12 11 10 9 8
PERBUF[9:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bit 7 6 5 4 3 2 1 0
PERBUF[1:0] DITHERBUF[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 1 1 1 1 1 1 1 1
Bits 23:6 – PERBUF[17:0] Period Buffer Value
These bits hold the value of the period buffer register. The value is copied to PER register on UPDATE
condition.
Note:  When the TCC is configured as 16-bit timer/counter, the excess bits are read zero.
Note:  This bit field occupies the MSB of the register, [23:m]. m is dependent on the Resolution bit in the
Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [23:m]
0x0 - NONE 23:0
0x1 - DITH4 23:4
0x2 - DITH5 23:5
0x3 - DITH6 23:6 (depicted)
Bits 5:0 – DITHERBUF[5:0] Dithering Buffer Cycle Number
These bits represent the PER.DITHER bits buffer. When the double buffering is enabled, the value of this
bit field is copied to the PER.DITHER bits on an UPDATE condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 950
Note:  This bit field consists of the n LSB of the register. n is dependent on the value of the Resolution
bits in the Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [n:0]
0x0 - NONE -
0x1 - DITH4 3:0
0x2 - DITH5 4:0
0x3 - DITH6 5:0 (depicted)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 951
36.8.22 Channel x Compare/Capture Buffer Value
Name:  CCBUF
Offset:  0x70 + n*0x04 [n=0..3]
Reset:  0x00000000
Property:  Write-Synchronized, Read-Synchronized
CCBUFx is copied into CCx at TCC update time
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
CCBUF[17:10]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
CCBUF[9:2]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
CCBUF[1:0] DITHERBUF[5:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:6 – CCBUF[17:0] Channel x Compare/Capture Buffer Value
These bits hold the value of the Channel x Compare/Capture Buffer Value register. The register serves as
the buffer for the associated compare or capture registers (CCx). Accessing this register using the CPU
or DMA will affect the corresponding CCBUFVx status bit.
Note:  When the TCC is configured as 16-bit timer/counter, the excess bits are read zero.
Note:  This bit field occupies the MSB of the register, [23:m]. m is dependent on the Resolution bit in the
Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [23:m]
0x0 - NONE 23:0
0x1 - DITH4 23:4
0x2 - DITH5 23:5
0x3 - DITH6 23:6 (depicted)
Bits 5:0 – DITHERBUF[5:0] Dithering Buffer Cycle Number
These bits represent the CCx.DITHER bits buffer. When the double buffering is enable, DITHERBUF bits
value is copied to the CCx.DITHER bits on an UPDATE condition.
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 952
Note:  This bit field consists of the n LSB of the register. n is dependent on the value of the Resolution
bits in the Control A register (CTRLA.RESOLUTION):
CTRLA.RESOLUTION Bits [n:0]
0x0 - NONE -
0x1 - DITH4 3:0
0x2 - DITH5 4:0
0x3 - DITH6 5:0 (depicted)
SAM C20/C21 Family Data Sheet
TCC – Timer/Counter for Control Applications
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 953
37. CCL – Configurable Custom Logic
37.1 Overview
The Configurable Custom Logic (CCL) is a programmable logic peripheral which can be connected to the
device pins, to events, or to other internal peripherals. This allows the user to eliminate logic gates for
simple glue logic functions on the PCB.
Each LookUp Table (LUT) consists of three inputs, a truth table, an optional synchronizer/filter, and an
optional edge detector. Each LUT can generate an output as a user programmable logic expression with
three inputs. Inputs can be individually masked.
The output can be combinatorially generated from the inputs, and can be filtered to remove spikes.
Optional sequential logic can be used. The inputs of the sequential module are individually controlled by
two independent, adjacent LUT (LUT0/LUT1, LUT2/LUT3 etc.) outputs, enabling complex waveform
generation.
37.2 Features
• Glue logic for general purpose PCB design
• Up to 4 programmable LookUp Tables (LUTs)
• Combinatorial logic functions:
AND, NAND, OR, NOR, XOR, XNOR, NOT
• Sequential logic functions:
Gated D Flip-Flop, JK Flip-Flop, gated D Latch, RS Latch
• Flexible LUT inputs selection:
– I/Os
– Events
– Internal peripherals
– Subsequent LUT output
• Output can be connected to the I/O pins or the Event System
• Optional synchronizer, filter, or edge detector available on each LUT output
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 954
37.3 Block Diagram
Figure 37-1. Configurable Custom Logic
Edge DetectorFilter / Synch
Truth Table 8
CLR CLR Sequential
CLR
Internal
Events
I/O
Peripherals
LUTCTRL0
(ENABLE)
LUTCTRL0
(EDGESEL)
LUTCTRL0
(FILTSEL)
LUTCTRL0
(INSEL)
SEQCTRL
(SEQSEL0)
CTRL
(ENABLE)
D Q
CLK_CCL_APB
GCLK_CCL
LUT0
Edge DetectorFilter / Synch
Truth Table 8
CLR CLR
Internal
Events
I/O
Peripherals
LUTCTRL1
(ENABLE)
LUTCTRL1
(EDGESEL)
LUTCTRL1
(FILTSEL)
LUTCTRL1
(INSEL)
D Q
CLK_CCL_APB
GCLK_CCL
LUT1
CTRL
(ENABLE)
UNIT 0
.....
OUT1
Event System
I/O
OUT0
Event System
I/O
UNIT x OUT2x-1
Event System
I/O
37.4 Signal Description
Pin Name Type Description
OUT[n:0] Digital output Output from lookup table
IN[3n+2:0] Digital input Input to lookup table
1. n is the number of CCL groups.
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
Related Links
6. I/O Multiplexing and Considerations
37.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
37.5.1 I/O Lines
The CCL can take inputs and generate output through I/O pins. For this to function properly, the I/O pins
must be configured to be used by a Look Up Table (LUT).
Related Links
28. PORT - I/O Pin Controller
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 955
37.5.2 Power Management
This peripheral can continue to operate in any sleep mode where its source clock is running. Events
connected to the event system can trigger other operations in the system without exiting sleep modes.
Related Links
19. PM – Power Manager
37.5.3 Clocks
The CCL bus clock (CLK_CCL_APB) can be enabled and disabled in the Main Clock module, MCLK (see
MCLK - Main Clock), and the default state of CLK_CCL_APB can be found in Peripheral Clock Masking.
A generic clock (GCLK_CCL) is optionally required to clock the CCL. This clock must be configured and
enabled in the Generic Clock Controller (GCLK) before using input events, filter, edge detection or
sequential logic. GCLK_CCL is required when input events, a filter, an edge detector, or a sequential sub-
module is enabled. Refer to GCLK - Generic Clock Controller for details.
This generic clock is asynchronous to the user interface clock (CLK_CCL_APB).
Related Links
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
37.5.4 DMA
Not applicable.
37.5.5 Interrupts
Not applicable.
37.5.6 Events
The CCL can use events from other peripherals and generate events that can be used by other
peripherals. For this feature to function, the events have to be configured properly. Refer to the Related
Links below for more information about the event users and event generators.
Related Links
29. EVSYS – Event System
37.5.7 Debug Operation
When the CPU is halted in Debug mode the CCL continues normal operation. However, the CCL cannot
be halted when the CPU is halted in Debug mode. If the CCL is configured in a way that requires it to be
periodically serviced by the CPU, improper operation or data loss may result during debugging.
37.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the peripheral access controller (PAC).
Refer to PAC - Peripheral Access Controller for details.
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 956
37.5.9 Analog Connections
Not applicable.
37.6 Functional Description
37.6.1 Principle of Operation
Configurable Custom Logic (CCL) is a programmable logic block that can use the device port pins,
internal peripherals, and the internal Event System as both input and output channels. The CCL can
serve as glue logic between the device and external devices. The CCL can eliminate the need for
external logic component and can also help the designer overcome challenging real-time constrains by
combining core independent peripherals in clever ways to handle the most time critical parts of the
application independent of the CPU.
37.6.2 Operation
37.6.2.1 Initialization
The following bits are enable-protected, meaning that they can only be written when the corresponding
even LUT is disabled (LUTCTRLx.ENABLE=0):
• Sequential Selection bits in the Sequential Control x (SEQCTRLx.SEQSEL) register
The following registers are enable-protected, meaning that they can only be written when the
corresponding LUT is disabled (LUTCTRLx.ENABLE=0):
• LUT Control x (LUTCTRLx) register, except the ENABLE bit
Enable-protected bits in the LUTCTRLx registers can be written at the same time as LUTCTRLx.ENABLE
is written to '1', but not at the same time as LUTCTRLx.ENABLE is written to '0'.
Enable-protection is denoted by the Enable-Protected property in the register description.
37.6.2.2 Enabling, Disabling, and Resetting
The CCL is enabled by writing a '1' to the Enable bit in the Control register (CTRL.ENABLE). The CCL is
disabled by writing a '0' to CTRL.ENABLE.
Each LUT is enabled by writing a '1' to the Enable bit in the LUT Control x register (LUTCTRLx.ENABLE).
Each LUT is disabled by writing a '0' to LUTCTRLx.ENABLE.
The CCL is reset by writing a '1' to the Software Reset bit in the Control register (CTRL.SWRST). All
registers in the CCL will be reset to their initial state, and the CCL will be disabled. Refer to 37.8.1 CTRL
for details.
37.6.2.3 Lookup Table Logic
The lookup table in each LUT unit can generate any logic expression OUT as a function of three inputs
(IN[2:0]), as shown in Figure 37-2. One or more inputs can be masked. The truth table for the expression
is defined by TRUTH bits in LUT Control x register (LUTCTRLx.TRUTH).
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 957
Figure 37-2. Truth Table Output Value Selection
TRUTH[0]
TRUTH[1]
TRUTH[2]
TRUTH[3]
TRUTH[4]
TRUTH[5]
TRUTH[6]
TRUTH[7]
OUT
IN[2:0]
LUTCTRL
(ENABLE)
LUT
Table 37-1. Truth Table of LUT
IN[2] IN[1] IN[0] OUT
0 0 0 TRUTH[0]
0 0 1 TRUTH[1]
0 1 0 TRUTH[2]
0 1 1 TRUTH[3]
1 0 0 TRUTH[4]
1 0 1 TRUTH[5]
1 1 0 TRUTH[6]
1 1 1 TRUTH[7]
37.6.2.4 Truth Table Inputs Selection
Input Overview
The inputs can be individually:
• Masked
• Driven by peripherals:
– Analog comparator output (AC)
– Timer/Counters waveform outputs (TC)
– Serial Communication output transmit interface (SERCOM)
• Driven by internal events from Event System
• Driven by other CCL sub-modules
The Input Selection for each input y of LUT x is configured by writing the Input y Source Selection bit in
the LUT x Control register (LUTCTRLx.INSELy).
Masked Inputs (MASK)
When a LUT input is masked (LUTCTRLx.INSELy=MASK), the corresponding TRUTH input (IN) is
internally tied to zero, as shown in this figure:
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 958
Figure 37-3. Masked Input Selection
Internal Feedback Inputs (FEEDBACK)
When selected (LUTCTRLx.INSELy=FEEDBACK), the Sequential (SEQ) output is used as input for the
corresponding LUT.
The output from an internal sequential sub-module can be used as input source for the LUT, see figure
below for an example for LUT0 and LUT1. The sequential selection for each LUT follows the formula:
IN 2N = SEQ
IN 2N+1 = SEQ
With N representing the sequencer number and i=0,1,2 representing the LUT input index.
For details, refer to 37.6.2.7 Sequential Logic.
Figure 37-4. Feedback Input Selection
Linked LUT (LINK)
When selected (LUTCTRLx.INSELy=LINK), the subsequent LUT output is used as the LUT input (e.g.,
LUT2 is the input for LUT1), as shown in this figure:
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 959
Figure 37-5. Linked LUT Input Selection
CTRL
(ENABLE)
LUT0 SEQ 0
LUT1
CTRL
(ENABLE)
LUT2 SEQ 1
LUT3
CTRL
(ENABLE)
LUT(2n – 2) SEQ n
LUT(2n-1)
Internal Events Inputs Selection (EVENT)
Asynchronous events from the Event System can be used as input selection, as shown in Figure 37-6.
For each LUT, one event input line is available and can be selected on each LUT input. Before enabling
the event selection by writing LUTCTRLx.INSELy=EVENT, the Event System must be configured first.
By default CCL includes an edge detector. When the event is received, an internal strobe is generated
when a rising edge is detected. The pulse duration is one GCLK_CCL clock cycle. Writing the
LUTCTRLx.INSELy=ASYNCEVENT will disable the edge detector. In this case, it is possible to combine
an asynchronous event input with any other input source. This is typically useful with event levels inputs
(external IO pin events, as example). The following steps ensure proper operation:
1. Enable the GCLK_CCL clock.
2. Configure the Event System to route the event asynchronously.
3. Select the event input type (LUTCTRLx.INSEL).
4. If a strobe must be generated on the event input falling edge, write a '1' to the Inverted Event Input
Enable bit in LUT Control register (LUTCTRLx.INVEI) .
5. Enable the event input by writing the Event Input Enable bit in LUT Control register
(LUTCTRLx.LUTEI) to '1'.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 960
Figure 37-6. Event Input Selection
I/O Pin Inputs (IO)
When the IO pin is selected as LUT input (LUTCTRLx.INSELy=IO), the corresponding LUT input will be
connected to the pin, as shown in the figure below.
Figure 37-7. I/O Pin Input Selection
Analog Comparator Inputs (AC)
The AC outputs can be used as input source for the LUT (LUTCTRLx.INSELy=AC).
The analog comparator outputs are distributed following the formula:
IN[N][i]=AC[N % ComparatorOutput_Number]
With N representing the LUT number and i=[0,1,2] representing the LUT input index.
Before selecting the comparator output, the AC must be configured first.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 961
Figure 37-8. AC Input Selection
COMP2
COMP3
COMP0
COMP1
CMP0
CMP1
CMP2
CMP3
LUT0
LUT1
LUT2
LUT3
OUT0
OUT1
OUT2
OUT3
TRUTH
TRUTH
TRUTH
TRUTH
Timer/Counter Inputs (TC)
The TC waveform output WO[0] can be used as input source for the LUT (LUTCTRLx.INSELy=TC). Only
consecutive instances of the TC, i.e. TCx and the subsequent TC(x+1), are available as default and
alternative TC selections (e.g., TC0 and TC1 are sources for LUT0, TC1 and TC2 are sources for LUT1,
etc). See the figure below for an example for LUT0. More general, the Timer/Counter selection for each
LUT follows the formula:
IN = % TC_Instance_Number
IN = + 1 % TC_Instance_Number
Where N represents the LUT number and i represents the LUT input index (i=0,1,2).
For devices with more than four TC instances, it is also possible to enable a second alternative option
(LUTCTRLx.INSEL=ALT2TC). This option is intended to relax the alternative pin function or PCB design
constraints when the default or the alternative TC instances are used for other purposes. When enabled,
the Timer/Counter selection for each LUT follows the formula:
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 962
IN = + 4 % TC_Instance_Number
Note that for not implemented TC_Instance_Number, the corresponding input is tied to ground.
Before selecting the waveform outputs, the TC must be configured first.
Figure 37-9. TC Input Selection
WO[0]
WO[0]
TC4
(second alternative) WO[0]
TC1
TC0
(alternative)
(default)
Timer/Counter for Control Application Inputs (TCC)
The TCC waveform outputs can be used as input source for the LUT. Only WO[2:0] outputs can be
selected and routed to the respective LUT input (i.e., IN0 is connected to WO0, IN1 to WO1, and IN2 to
WO2), as shown in the figure below.
Note: 
The TCC selection for each LUT follows the formula:
IN = %C_Instance_Number
Where N represents the LUT number.
Before selecting the waveform outputs, the TCC must be configured first.
Figure 37-10. TCC Input Selection
Serial Communication Output Transmit Inputs (SERCOM)
The serial engine transmitter output from Serial Communication Interface (SERCOM TX, TXd for USART,
MOSI for SPI) can be used as input source for the LUT. The figure below shows an example for LUT0
and LUT1. The SERCOM selection for each LUT follows the formula:
IN =[% SERCOM_Instance_Number
With N representing the LUT number and i=0,1,2 representing the LUT input index.
Before selecting the SERCOM as input source, the SERCOM must be configured first: the SERCOM TX
signal must be output on SERCOMn/pad[0], which serves as input pad to the CCL.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 963
Figure 37-11. SERCOM Input Selection
Related Links
6. I/O Multiplexing and Considerations
28. PORT - I/O Pin Controller
16. GCLK - Generic Clock Controller
40. AC – Analog Comparators
35. TC – Timer/Counter
36. TCC – Timer/Counter for Control Applications
30. SERCOM – Serial Communication Interface
6. I/O Multiplexing and Considerations
37.6.2.5 Filter
By default, the LUT output is a combinatorial function of the LUT inputs. This may cause some short
glitches when the inputs change value. These glitches can be removed by clocking through filters, if
demanded by application needs.
The Filter Selection bits in LUT Control register (LUTCTRLx.FILTSEL) define the synchronizer or digital
filter options. When a filter is enabled, the OUT output will be delayed by two to five GCLK cycles. One
APB clock after the corresponding LUT is disabled, all internal filter logic is cleared.
Note:  Events used as LUT input will also be filtered, if the filter is enabled.
Figure 37-12. Filter
DQ
R
DQ
R
DQ
R
DQ
R
FILTSEL
OUT
Input
GCLK_CCL
CLR
G
37.6.2.6 Edge Detector
The edge detector can be used to generate a pulse when detecting a rising edge on its input. To detect a
falling edge, the TRUTH table should be inverted.
The edge detector is enabled by writing '1' to the Edge Selection bit in LUT Control register
(LUTCTRLx.EDGESEL). In order to avoid unpredictable behavior, either the filter or synchronizer must be
enabled.
Edge detection is disabled by writing a '0' to LUTCTRLx.EDGESEL. After disabling a LUT, the
corresponding internal Edge Detector logic is cleared one APB clock cycle later.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 964
Figure 37-13. Edge Detector
37.6.2.7 Sequential Logic
Each LUT pair can be connected to the internal sequential logic which can be configured to work as D flip
flop, JK flip flop, gated D-latch or RS-latch by writing the Sequential Selection bits on the corresponding
Sequential Control x register (SEQCTRLx.SEQSEL). Before using sequential logic, the GCLK_CCL clock
and optionally each LUT filter or edge detector must be enabled.
Note:  While configuring the sequential logic, the even LUT must be disabled. When configured the even
LUT must be enabled.
Gated D Flip-Flop (DFF)
When the DFF is selected, the D-input is driven by the even LUT output (LUT0 and LUT2), and the G-
input is driven by the odd LUT output (LUT1 and LUT3), as shown in Figure 37-14.
Figure 37-14. D Flip Flop
When the even LUT is disabled (LUTCTRL0.ENABLE=0 / LUTCTRL2.ENABLE=0), the flip-flop is
asynchronously cleared. The reset command (R) is kept enabled for one APB clock cycle. In all other
cases, the flip-flop output (OUT) is refreshed on rising edge of the GCLK_CCL, as shown in Table 37-2.
Table 37-2. DFF Characteristics
R G D OUT
1 X X Clear
0 1 1 Set
0 Clear
0 X Hold state (no change)
JK Flip-Flop (JK)
When this configuration is selected, the J-input is driven by the even LUT output (LUT0 and LUT2), and
the K-input is driven by the odd LUT output (LUT1 and LUT3), as shown in Figure 37-15.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 965
Figure 37-15. JK Flip Flop
When the even LUT is disabled (LUTCTRL0.ENABLE=0 / LUTCTRL2.ENABLE=0), the flip-flop is
asynchronously cleared. The reset command (R) is kept enabled for one APB clock cycle. In all other
cases, the flip-flop output (OUT) is refreshed on rising edge of the GCLK_CCL, as shown in Table 37-3.
Table 37-3. JK Characteristics
R J K OUT
1 X X Clear
0 0 0 Hold state (no change)
0 0 1 Clear
0 1 0 Set
0 1 1 Toggle
Gated D-Latch (DLATCH)
When the DLATCH is selected, the D-input is driven by the even LUT output (LUT0 and LUT2), and the
G-input is driven by the odd LUT output (LUT1 and LUT3), as shown in Figure 37-14.
Figure 37-16. D-Latch
DQ
G
OUT
even LUT
odd LUT
When the even LUT is disabled (LUTCTRL0.ENABLE=0 /
LUTCTRL2.ENABLE=0), the latch output will be cleared. The G-input is forced enabled for one more APB
clock cycle, and the D-input to zero. In all other cases, the latch output (OUT) is refreshed as shown in
Table 37-4.
Table 37-4. D-Latch Characteristics
G D OUT
0 X Hold state (no change)
1 0 Clear
1 1 Set
RS Latch (RS)
When this configuration is selected, the S-input is driven by the even LUT output (LUT0 and LUT2), and
the R-input is driven by the odd LUT output (LUT1 and LUT3), as shown in Figure 37-17.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 966
Figure 37-17. RS-Latch
SQ
R
OUT
even LUT
odd LUT
When the even LUT is disabled LUTCTRL0.ENABLE=0 / LUTCTRL2.ENABLE=0), the latch output will be
cleared. The R-input is forced enabled for one more APB clock cycle and S-input to zero. In all other
cases, the latch output (OUT) is refreshed as shown in Table 37-5.
Table 37-5. RS-Latch Characteristics
S R OUT
0 0 Hold state (no change)
0 1 Clear
1 0 Set
1 1 Forbidden state
37.6.3 Events
The CCL can generate the following output events:
• OUTx: Lookup Table Output Value
Writing a '1' to the LUT Control Event Output Enable bit (LUTCTRL.LUTEO) enables the corresponding
output event. Writing a '0' to this bit disables the corresponding output event.
The CCL can take the following actions on an input event:
• INSELx: The event is used as input for the TRUTH table. For further details refer to 37.5.6 Events.
Writing a '1' to the LUT Control Event Input Enable bit (LUTCTRL.LUTEI) enables the corresponding
action on input event. Writing a '0' to this bit disables the corresponding action on input event.
Related Links
29. EVSYS – Event System
37.6.4 Sleep Mode Operation
When using the GCLK_CCL internal clocking, writing the Run In Standby bit in the Control register
(CTRL.RUNSTDBY) to '1' will allow GCLK_CCL to be enabled in Standby Sleep mode.
If CTRL.RUNSTDBY=0, the GCLK_CCL will be disabled in Standby Sleep mode. If the Filter, Edge
Detector or Sequential logic are enabled, the LUT output will be forced to zero in STANDBY mode. In all
other cases, the TRUTH table decoder will continue operation and the LUT output will be refreshed
accordingly.
Related Links
19. PM – Power Manager
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 967
37.7 Register Summary
Offset Name Bit Pos.
0x00 CTRL 7:0 RUNSTDBY ENABLE SWRST
0x01
...
0x03
Reserved
0x04 SEQCTRL0 7:0 SEQSEL[3:0]
0x05 SEQCTRL1 7:0 SEQSEL[3:0]
0x06
...
0x07
Reserved
0x08 LUTCTRLn0
7:0 EDGESEL FILTSEL[1:0] ENABLE
15:8 INSEL1[3:0] INSEL0[3:0]
23:16 LUTEO LUTEI INVEI INSEL2[3:0]
31:24 TRUTH[7:0]
0x0C LUTCTRLn1
7:0 EDGESEL FILTSEL[1:0] ENABLE
15:8 INSEL1[3:0] INSEL0[3:0]
23:16 LUTEO LUTEI INVEI INSEL2[3:0]
31:24 TRUTH[7:0]
0x10 LUTCTRLn2
7:0 EDGESEL FILTSEL[1:0] ENABLE
15:8 INSEL1[3:0] INSEL0[3:0]
23:16 LUTEO LUTEI INVEI INSEL2[3:0]
31:24 TRUTH[7:0]
0x14 LUTCTRLn3
7:0 EDGESEL FILTSEL[1:0] ENABLE
15:8 INSEL1[3:0] INSEL0[3:0]
23:16 LUTEO LUTEI INVEI INSEL2[3:0]
31:24 TRUTH[7:0]
37.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 37.5.8 Register Access Protection.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 968
37.8.1 Control
Name:  CTRL
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection
Note:  CTRL register (except the bits ENABLE & SWRST) is Enable Protected when
CCL.CTRL.ENABLE = 1.
Bit 7 6 5 4 3 2 1 0
RUNSTDBY ENABLE SWRST
Access R/W R/W W
Reset 0 0 0
Bit 6 – RUNSTDBY Run in Standby
This bit indicates if the GCLK_CCL clock must be kept running in standby mode. The setting is ignored
for configurations where the generic clock is not required. For details refer to 37.6.4 Sleep Mode
Operation.
Important:  This bit must be written before enabling the CCL.
Value Description
0Generic clock is not required in standby sleep mode.
1Generic clock is required in standby sleep mode.
Bit 1 – ENABLE Enable
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the CCL to their initial state.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 969
37.8.2 Sequential Control x
Name:  SEQCTRL
Offset:  0x04 + n*0x01 [n=0..1]
Reset:  0x00
Property:  PAC Write-Protection
Note:  SEQCTRL register is Enable Protected when CCL.CTRL.ENABLE = 1.
Bit 7 6 5 4 3 2 1 0
SEQSEL[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – SEQSEL[3:0] Sequential Selection
These bits select the sequential configuration:
Sequential Selection
Value Name Description
0x0 DISABLE Sequential logic is disabled
0x1 DFF D flip flop
0x2 JK JK flip flop
0x3 LATCH D latch
0x4 RS RS latch
0x5 -
0xF
Reserved
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 970
37.8.3 LUT Control x
Name:  LUTCTRLn
Offset:  0x08 + n*0x04 [n=0..3]
Reset:  0x00000000
Property:  PAC Write-Protection, Enable-protected
Note:  LUTCTRLn register is Enable Protected when CCL.LUTCTRLn.ENABLE = 1.
Bit 31 30 29 28 27 26 25 24
TRUTH[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
LUTEO LUTEI INVEI INSEL2[3:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
INSEL1[3:0] INSEL0[3:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
EDGESEL FILTSEL[1:0] ENABLE
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 31:24 – TRUTH[7:0] Truth Table
These bits define the value of truth logic as a function of inputs IN[2:0].
Bit 22 – LUTEO LUT Event Output Enable
Value Description
0LUT event output is disabled.
1LUT event output is enabled.
Bit 21 – LUTEI LUT Event Input Enable
Value Description
0LUT incoming event is disabled.
1LUT incoming event is enabled.
Bit 20 – INVEI Inverted Event Input Enable
Value Description
0Incoming event is not inverted.
1Incoming event is inverted.
Bits 8:11, 12:15, 16:19 – INSELx LUT Input x Source Selection
These bits select the LUT input x source:
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 971
Value Name Description
0x0 MASK Masked input
0x1 FEEDBACK Feedback input source
0x2 LINK Linked LUT input source
0x3 EVENT Event input source
0x4 IO I/O pin input source
0x5 AC AC input source: CMP[0] (LUT0) / CMP[1] (LUT1)
0x6 TC TC input source: TC0 (LUT0) / TC1 (LUT1)
0x7 ALTTC Alternative TC input source: TC1 (LUT0) / TC2 (LUT1)
0x8 Reserved Reserved
0x9 SERCOM SERCOM input source: SERCOM0 (LUT0) / SERCOM1 (LUT1)
0xA Reserved Reserved
0xC -
0xF
Reserved Reserved
Bit 7 – EDGESEL Edge Selection
Value Description
0Edge detector is disabled.
1Edge detector is enabled.
Bits 5:4 – FILTSEL[1:0] Filter Selection
These bits select the LUT output filter options:
Filter Selection
Value Name Description
0x0 DISABLE Filter disabled
0x1 SYNCH Synchronizer enabled
0x2 FILTER Filter enabled
0x3 - Reserved
Bit 1 – ENABLE LUT Enable
Value Description
0The LUT is disabled.
1The LUT is enabled.
SAM C20/C21 Family Data Sheet
CCL – Configurable Custom Logic
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 972
38. ADC – Analog-to-Digital Converter
38.1 Overview
The Analog-to-Digital Converter (ADC) converts analog signals to digital values. The ADC has up to 12-
bit resolution, and is capable of a sampling rate of up to 1MSPS. The input selection is flexible, and both
differential and single-ended measurements can be performed. In addition, several internal signal inputs
are available. The ADC can provide both signed and unsigned results.
ADC measurements can be started by either application software or an incoming event from another
peripheral in the device. ADC measurements can be started with predictable timing, and without software
intervention.
Both internal and external reference voltages can be used.
An integrated temperature sensor is available for use with the ADC. The INTREF voltage reference, as
well as the scaled I/O and core voltages, can also be measured by the ADC.
The ADC has a compare function for accurate monitoring of user-defined thresholds, with minimum
software intervention required.
The ADC can be configured for 8-, 10- or 12-bit results. ADC conversion results are provided left- or right-
adjusted, which eases calculation when the result is represented as a signed value. It is possible to use
DMA to move ADC results directly to memory or peripherals when conversions are done.
The SAM C20/C21 has two ADC instances, ADC0 and ADC1. The two inputs can be sampled
simultaneously, as each ADC includes sample and hold circuits.
38.2 Features
• Two Analog to Digital Converters (ADC) ADC0 and ADC1
• 8-, 10- or 12-bit resolution
• Up to 1,000,000 samples per second (1MSPS)
• Differential and single-ended inputs
– Up to 12 analog inputs per ADC (20 unique channels total)
16 positive and 7 negative, including internal and external
• Internal inputs:
– INTREF voltage reference
– Scaled core supply
– Scaled I/O supply
– DAC
• Single, continuous and sequencing options
• Windowing monitor with selectable channel
• Conversion range: Vref = [2.0V to VDDANA ]
• Built-in internal reference and external reference options
• Event-triggered conversion for accurate timing (one event input)
• Optional DMA transfer of conversion settings or result
• Hardware gain and offset compensation
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 973
• Averaging and oversampling with decimation to support up to 16-bit result
• Selectable sampling time
• Flexible Power / Throughput rate management
38.3 Block Diagram
Figure 38-1. ADC Block Diagram
ADC
AIN0
AINn
...
INT.SIG
AIN0
AINn
...
REFCTRL
INTREF
INTVCC1
OFFSETCORR
GAINCORRSWTRIG
EVCTRL
AVGCTRL
SEQCTRL
SAMPCTRL WINUT
POST
PROCESSING
PRESCALER
CTRLB
WINLT
VREFA
CTRLA
RESULT
INPUTCTRL
SEQSTATUS
INTVCC0
DAC
INTVCC2
38.4 Signal Description
Signal Description Type
VREFA Analog input External reference voltage
AIN[11..0] Analog input Analog input channels
Note:  One signal can be mapped on several pins.
Related Links
1. Configuration Summary
6. I/O Multiplexing and Considerations
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 974
38.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
38.5.1 I/O Lines
Using the ADC's I/O lines requires the I/O pins to be configured using the port configuration (PORT).
Related Links
28. PORT - I/O Pin Controller
38.5.2 Power Management
The ADC will continue to operate in any sleep mode where the selected source clock is running. The
ADC’s interrupts except the OVERRUN interrupt, can be used to wake up the device from sleep modes.
Events connected to the event system can trigger other operations in the system without exiting sleep
modes.
Related Links
19. PM – Power Manager
38.5.3 Clocks
The ADC bus clocks (CLK_APB_ADCx) can be enabled in the Main Clock, which also defines the default
state.
Each ADC requires a generic clock (GCLK_ADCx). This clock must be configured and enabled in the
Generic Clock Controller (GCLK) before using the ADC.
A generic clock is asynchronous to the bus clock. Due to this asynchronicity, writes to certain registers will
require synchronization between the clock domains. Refer to Synchronization for further details.
Related Links
38.6.8 Synchronization
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
38.5.4 DMA
The DMA request line is connected to the DMA Controller (DMAC). Using the ADC DMA requests
requires the DMA Controller to be configured first.
Related Links
25. DMAC – Direct Memory Access Controller
38.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the ADC interrupt requires the
interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
38.5.6 Events
The events are connected to the Event System.
Related Links
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 975
29. EVSYS – Event System
38.5.7 Debug Operation
When the CPU is halted in debug mode the ADC will halt normal operation. The ADC can be forced to
continue operation during debugging. Refer to DBGCTRL register for details.
38.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC),
except the following register:
• Interrupt Flag Status and Clear (INTFLAG) register
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
38.5.9 Analog Connections
I/O-pins (AINx), as well as the VREFA reference voltage pin are analog inputs to the ADC. Any internal
reference source, such as a bandgap voltage reference, or DAC must be configured and enabled prior to
its use with the ADC.
38.5.10 Calibration
The BIAS and LINEARITY calibration values from the production test must be loaded from the NVM
Software Calibration Area into the ADC Calibration register (CALIB) by software to achieve specified
accuracy.
Related Links
9.4 NVM Software Calibration Area Mapping
38.6 Functional Description
38.6.1 Principle of Operation
By default, the ADC provides results with 12-bit resolution. 8-bit or 10-bit results can be selected in order
to reduce the conversion time, see 38.6.2.8 Conversion Timing and Sampling Rate.
The ADC has an oversampling with decimation option that can extend the resolution to 16 bits. The input
values can be either internal or external (connected I/O pins). The user can also configure whether the
conversion should be single-ended or differential.
38.6.2 Basic Operation
38.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the ADC is
disabled (CTRLA.ENABLE=0):
• Control B register (CTRLB)
• Reference Control register (REFCTRL)
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 976
• Event Control register (EVCTRL)
• Calibration register (CALIB)
Enable-protection is denoted by the "Enable-Protected" property in the register description.
38.6.2.2 Enabling, Disabling and Resetting
The ADC is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The
ADC is disabled by writing CTRLA.ENABLE=0.
The ADC is reset by writing a '1' to the Software Reset bit in the Control A register (CTRLA.SWRST). All
registers in the ADC, except DBGCTRL, will be reset to their initial state, and the ADC will be disabled.
Refer to 38.8.1 CTRLA for details.
38.6.2.3 Operation
In the most basic configuration, the ADC samples values from the configured internal or external sources
(INPUTCTRL register). The rate of the conversion depends on the combination of the GCLK_ADCx
frequency and the clock prescaler.
To convert analog values to digital values, the ADC needs to be initialized first, as described in the
Initialization section. Data conversion can be started either manually by setting the Start bit in the
Software Trigger register (SWTRIG.START=1), or automatically by configuring an automatic trigger to
initiate the conversions. The ADC starts sampling the input only after the start of conversion is triggered.
This means that even after the MUX selection is made, sample and hold (S&H) operation starts only on
the conversion trigger. A free-running mode can be used to continuously convert an input channel. When
using free-running mode the first conversion must be started, while subsequent conversions will start
automatically at the end of previous conversions.
The ADC starts sampling the input only after the start of a conversion is triggered. This means that even
after the MUX selection is made, sample and hold operation starts only on the conversion trigger.
The result of the conversion is stored in the Result register (RESULT) overwriting the result from the
previous conversion.
To avoid data loss, if more than one channel is enabled, the conversion result must be read as soon as it
is available (INTFLAG.RESRDY). Failing to do so will result in an overrun error condition, indicated by the
OVERRUN bit in the Interrupt Flag Status and Clear register (INTFLAG.OVERRUN).
To enable one of the available interrupts sources, the corresponding bit in the Interrupt Enable Set
register (INTENSET) must be written to '1'.
38.6.2.4 Prescaler Selection
The ADC is clocked by GCLK_ADCx. There is also a prescaler in the ADC to enable conversion at lower
clock rates. Refer to CTRLB for details on prescaler settings. Refer to 38.6.2.8 Conversion Timing and
Sampling Rate for details on timing and sampling rate.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 977
Figure 38-2. ADC Prescaler
GCLK_ADCx 9-BIT PRESCALER
CTRLB.PRESCALER[2:0]
DIV256
DIV128
DIV64
DIV32
DIV16
DIV8
DIV4
DIV2
CLK_ADCx
Note:  The minimum prescaling factor is DIV2.
38.6.2.5 Reference Configuration
The ADC has various sources for its reference voltage VREF. The Reference Voltage Selection bit field in
the Reference Control register (REFCTRL.REFSEL) determines which reference is selected. By default,
the internal voltage reference INTREF is selected. Based on customer application requirements, the
external or internal reference can be selected. Refer to REFCTRL.REFSEL for further details on available
selections.
Related Links
38.8.3 REFCTRL
45.10.4 Analog-to-Digital Converter (ADC) Characteristics
38.6.2.6 ADC Resolution
The ADC supports 8-bit, 10-bit or 12-bit resolution. Resolution can be changed by writing the Resolution
bit group in the Control C register (CTRLC.RESSEL). By default, the ADC resolution is set to 12 bits. The
resolution affects the propagation delay, see also 38.6.2.8 Conversion Timing and Sampling Rate.
38.6.2.7 Differential and Single-Ended Conversions
The ADC has two conversion options: differential and single-ended:
If the positive input is always positive, the single-ended conversion should be used in order to have full
12-bit resolution in the conversion.
If the positive input may go below the negative input, the differential mode should be used in order to get
correct results.
The differential mode is enabled by setting DIFFMODE bit in the Control C register (CTRLC.DIFFMODE).
Both conversion types could be run in single mode or in free-running mode. When the free-running mode
is selected, an ADC input will continuously sample the input and performs a new conversion. The
INTFLAG.RESRDY bit will be set at the end of each conversion.
38.6.2.8 Conversion Timing and Sampling Rate
The following figure shows the ADC timing for one single conversion. A conversion starts after the
software or event start are synchronized with the GCLK_ADCx clock. The input channel is sampled in the
first half CLK_ADCx period.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 978
Figure 38-3. ADC Timing for One Conversion in 12-bit Resolution
CLK_ADC
STATE
START
SAMPLING MSB 10 9 8 7 6 5 4 3 2 1
LSB
INT
The sampling time can be increased by using the Sampling Time Length bit group in the Sampling Time
Control register (SAMPCTRL.SAMPLEN). As example, the next figure is showing the timing conversion
with sampling time increased to six CLK_ADC cycles.
Figure 38-4. ADC Timing for One Conversion with Increased Sampling Time, 12-bit
CLK_ADC
STATE
START
MSB 10 9 8 7 6 5 4 3 2 1
LSB
INT
SAMPLING
The ADC provides also offset compensation, see the following figure. The offset compensation is enabled
by the Offset Compensation bit in the Sampling Control register (SAMPCTRL.OFFCOMP).
Note:  ADC sampling time is fixed to 4 ADC Clock cycles when offset compensation (OFFCOMP=1) is
used.
In free running mode, the sampling rate RS is calculated by
RS = fCLK_ADC / ( nSAMPLING + nOFFCOMP + nDATA)
Here, nSAMPLING is the sampling duration in CLK_ADC cycles, nOFFCOMP is the offset compensation
duration in clock cycles, and nDATA is the bit resolution. fCLK_ADC is the ADC clock frequency from the
internal prescaler: fCLK_ADC = fGCLK_ADC / 2^(1 + CTRLB.PRESCALER)
Figure 38-5. ADC Timing for One Conversion with Offset Compensation, 12-bit
CLK_ADC
STATE
START
MSB 10 9 8 7 6 5 4 3 2 1
LSB
INT
Offset Compensation and Sampling
The impact of resolution on the sampling rate is seen in the next two figures, where free-running sampling
in 12-bit and 8-bit resolution are compared.
Figure 38-6. ADC Timing for Free Running in 12-bit Resolution
CLK_ADC
STATE
CONVERT
SAMPLING MSB 10 9 8 7 6 5 4 3 2 1
LSB
INT
SAMPLING MSB 9 810 7 6
LSB
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 979
Figure 38-7. ADC Timing for Free Running in 8-bit Resolution
CLK_ADC
STATE
CONVERT
SAMPLING 6 5 4 3 2 1
LSB
INT
LSB
MSB SAMPLING 6 5 4 3 2 1
LSB
MSB SAMPLING MSB
The propagation delay of an ADC measurement is given by:
PropagationDelay = 1 + Resolution
ADC
Example. In order to obtain 1MSPS in 12-bit resolution with a sampling time length of
four CLK_ADC cycles, fCLK_ADC must be 1MSPS * (4 + 12) = 16MHz. As the minimal
division factor of the prescaler is 2, GCLK_ADC must be 32MHz.
38.6.2.9 Accumulation
The result from multiple consecutive conversions can be accumulated. The number of samples to be
accumulated is specified by the Sample Number field in the Average Control register
(AVGCTRL.SAMPLENUM). When accumulating more than 16 samples, the result will be too large to
match the 16-bit RESULT register size. To avoid overflow, the result is right shifted automatically to fit
within the available register size. The number of automatic right shifts is specified in the table below.
Note:  To perform the accumulation of two or more samples, the Conversion Result Resolution field in
the Control C register (CTRLC.RESSEL) must be set.
Table 38-1. Accumulation
Number of
Accumulated
Samples
AVGCTRL.
SAMPLENUM
Number of
Automatic Right
Shifts
Final Result
Precision
Automatic
Division Factor
1 0x0 0 12 bits 0
2 0x1 0 13 bits 0
4 0x2 0 14 bits 0
8 0x3 0 15 bits 0
16 0x4 0 16 bits 0
32 0x5 1 16 bits 2
64 0x6 2 16 bits 4
128 0x7 3 16 bits 8
256 0x8 4 16 bits 16
512 0x9 5 16 bits 32
1024 0xA 6 16 bits 64
Reserved 0xB –0xF 12 bits 0
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 980
38.6.2.10 Averaging
Averaging is a feature that increases the sample accuracy, at the cost of a reduced sampling rate. This
feature is suitable when operating in noisy conditions.
Averaging is done by accumulating m samples, as described in 38.6.2.9 Accumulation, and dividing the
result by m. The averaged result is available in the RESULT register. The number of samples to be
accumulated is specified by writing to AVGCTRL.SAMPLENUM as shown in Table 38-2.
The division is obtained by a combination of the automatic right shift described above, and an additional
right shift that must be specified by writing to the Adjusting Result/Division Coefficient field in AVGCTRL
(AVGCTRL.ADJRES), as described in Table 38-2.
Note:  To perform the averaging of two or more samples, the Conversion Result Resolution field in the
Control C register (CTRLC.RESSEL) must be set.
Averaging AVGCTRL.SAMPLENUM samples will reduce the un-averaged sampling rate by a factor
1
AVGCTRL.SAMPLENUM.
When the averaged result is available, the INTFLAG.RESRDY bit will be set.
Table 38-2. Averaging
Number of
Accumulated
Samples
AVGCTRL.
SAMPLENUM
Intermediate
Result
Precision
Number of
Automatic
Right
Shifts
Division
Factor
AVGCTRL.ADJRES Total
Number
of Right
Shifts
Final
Result
Precision
Automatic
Division
Factor
1 0x0 12 bits 0 1 0x0 12 bits 0
2 0x1 13 0 2 0x1 1 12 bits 0
4 0x2 14 0 4 0x2 2 12 bits 0
8 0x3 15 0 8 0x3 3 12 bits 0
16 0x4 16 0 16 0x4 4 12 bits 0
32 0x5 17 1 16 0x4 5 12 bits 2
64 0x6 18 2 16 0x4 6 12 bits 4
128 0x7 19 3 16 0x4 7 12 bits 8
256 0x8 20 4 16 0x4 8 12 bits 16
512 0x9 21 5 16 0x4 9 12 bits 32
1024 0xA 22 6 16 0x4 10 12 bits 64
Reserved 0xB –0xF 0x0 12 bits 0
38.6.2.11 Oversampling and Decimation
By using oversampling and decimation, the ADC resolution can be increased from 12 bits up to 16 bits,
for the cost of reduced effective sampling rate.
To increase the resolution by n bits, 4n samples must be accumulated. The result must then be right-
shifted by n bits. This right-shift is a combination of the automatic right-shift and the value written to
AVGCTRL.ADJRES. To obtain the correct resolution, the ADJRES must be configured as described in the
table below. This method will result in n bit extra LSB resolution.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 981
Table 38-3. Configuration Required for Oversampling and Decimation
Result
Resolution
Number of
Samples to
Average
AVGCTRL.SAMPLENUM[3:0] Number of
Automatic
Right Shifts
AVGCTRL.ADJRES[2:0]
13 bits 41 = 4 0x2 0 0x1
14 bits 42 = 16 0x4 0 0x2
15 bits 43 = 64 0x6 2 0x1
16 bits 44 = 256 0x8 4 0x0
38.6.2.12 Automatic Sequences
The ADC has the ability to automatically sequence a series of conversions. This means that each time
the ADC receives a start-of-conversion request, it can perform multiple conversions automatically. All of
the 32 positive inputs can be included in a sequence by writing to corresponding bits in the Sequence
Control register (SEQCTRL). The order of the conversion in a sequence is the lower positive MUX
selection to upper positive MUX (AIN0, AIN1, AIN2 ...). In differential mode, the negative inputs selected
by MUXNEG field, will be used for the entire sequence.
When a sequence starts, the Sequence Busy status bit in Sequence Status register
(SEQSTATUS.SEQBUSY) will be set. When the sequence is complete, the Sequence Busy status bit will
be cleared.
Each time a conversion is completed, the Sequence State bit in Sequence Status register
(SEQSTATUS.SEQSTATE) will store the input number from which the conversion is done. The result will
be stored in the RESULT register, and the Result Ready Interrupt Flag (INTFLAG.RESRDY) is set.
If additional inputs must be scanned, the ADC will automatically start a new conversion on the next input
present in the sequence list.
Note that if SEQCTRL register has no bits set to '1', the conversion is done with the selected MUXPOS
input.
38.6.2.13 Window Monitor
The window monitor feature allows the conversion result in the RESULT register to be compared to
predefined threshold values. The window mode is selected by setting the Window Monitor Mode bits in
the Control C register (CTRLC.WINMODE). Threshold values must be written in the Window Monitor
Lower Threshold register (WINLT) and Window Monitor Upper Threshold register (WINUT).
If differential input is selected, the WINLT and WINUT are evaluated as signed values. Otherwise they are
evaluated as unsigned values. The significant WINLT and WINUT bits are given by the precision selected
in the Conversion Result Resolution bit group in the Control C register (CTRLC.RESSEL). This means
that for example in 8-bit mode, only the eight lower bits will be considered. In addition, in differential
mode, the eighth bit will be considered as the sign bit, even if the ninth bit is zero.
The INTFLAG.WINMON interrupt flag will be set if the conversion result matches the window monitor
condition.
38.6.2.14 Offset and Gain Correction
Inherent gain and offset errors affect the absolute accuracy of the ADC.
The offset error is defined as the deviation of the actual ADC transfer function from an ideal straight line
at zero input voltage. The offset error cancellation is handled by the Offset Correction register
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 982
(OFFSETCORR). The offset correction value is subtracted from the converted data before writing the
Result register (RESULT).
The gain error is defined as the deviation of the last output step’s midpoint from the ideal straight line,
after compensating for offset error. The gain error cancellation is handled by the Gain Correction register
(GAINCORR).
To correct these two errors, the Digital Correction Logic Enabled bit in the Control C register
(CTRLC.CORREN) must be set.
Offset and gain error compensation results are both calculated according to:
Result = Conversionvalue+ OFFSETCORR GAINCORR
The correction will introduce a latency of 13 CLK_ADC clock cycles. In free running mode this latency is
introduced on the first conversion only, since its duration is always less than the propagation delay. In
single conversion mode this latency is introduced for each conversion.
Figure 38-8.  ADC Timing Correction Enabled
START
CONV0 CONV1 CONV2 CONV3
CORR0 CORR1 CORR2 CORR3
38.6.2.15 Reference Buffer Compensation Offset
A hardware compensation using a reference buffer can be used. When the REFCTRL.REFCOMP bit is
set, the offset of the reference buffer is sensed during the ADC sampling phase. This offset will be then
canceled during the conversion phase. This feature allows for the decrease of the overall gain error of the
ADC.
There is a digital gain correction (refer to Offset and Gain Correction) but contrary to that digital gain
correction, the hardware compensation will not introduce any latency.
38.6.3 Additional Features
38.6.3.1 Master - Slave Operation
The master - slave operation is available only on devices with two ADC instances. The ADC1 will be
enabled as a slave of ADC0 instance when writing a one to the Slave Enable bit in Control A register of
the ADC1 instance (ADC1.CTRLA.SLAVEEN). When enabled, GCLK_ADC0 clock and ADC0 controls
are internally routed to the ADC1 instance.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 983
Figure 38-9. ADC Master - Slave Block Diagram
ADC 0
ADC0_AIN0
ADC0_AINn
...
INT.SIG
ADC0_AIN0
ADC0_AINn
...
ADC0.REFCTRL
INTREF
INTVCC1
DAC
ADC0.OFFSETCORR
ADC0.GAINCORRADC0.SWTRIG
ADC0.EVCTRL
ADC0.AVGCTRL
ADC0.SEQCTRL
ADC0.SAMPCTRL ADC0.WINUT
POST
PROCESSING
PRESCALER
ADC0.CTRLB
ADC0.WINLT
VREFA
ADC0.CTRLA
ADC0.RESULT
ADC0.INPUTCTRL
ADC0.SEQSTATUS
INTVCC0
ADC 1
ADC1_AIN0
ADC1_AINn
...
INT.SIG
ADC1_AIN0
ADC1_AINn
...
ADC1.REFCTRL
INTREF
INTVCC1
DAC ADC1.OFFSETCORR
ADC1.GAINCORR
ADC1.SEQCTRL
ADC1.WINUT
POST
PROCESSING
ADC1.WINLT
VREFA
ADC1.CTRLA
ADC1.RESULT
ADC1.INPUTCTRL
ADC1.SEQSTATUS
INTVCC0
SLAVEEN
ADC1.SWTRIG
ADC1.AVGCTRL
ADC1.SAMPCTRL
INTVCC2
INTVCC2
In this mode of operation, the slave ADC is enabled by accessing the CTRLA register of master ADC. In
the same way, the master ADC event inputs will be automatically routed to the slave ADC, meaning that
the input events configuration must be done in the master ADC (ADC0.EVCTRL).
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 984
ADC measurements can be started simultaneously on both ADC’s or interleaved. The trigger mode
selection is available in the master ADC Control C register (ADC0.CTRLC.DUALSEL).
To restart an interleaved sequence, the user can apply different options:
• Flush the master ADC (ADC0.SWTRIG.FLUSH = 1)
• Disable/re-enable the master ADC (ADC0.CTRLA.ENABLE)
• Reset and reconfigure master ADC (ADC0.CTRLA.SWRST = 1)
Figure 38-10. Interleaved Dual-Mode Trigger Selection
Start Trigger
(Software or Event)
ADC0 Start Conversion ADC0 Start Conversion ADC0 Start Conversion
ADC1 Start Conversion
ADC1 Start Conversion
38.6.3.2 Rail-to-Rail Operation
The accuracy of the ADC is highest when the input common mode voltage (VCMIN) is close to VREF/2. To
enable a full range of common mode voltages (rail-to-rail operation), the Rail-to-Rail bit in the Control C
register (CTRLC.R2R) should be written to one. Rail-to-rail operation requires a sampling period of four
cycles. This is achieved by enabling offset compensation (SAMPCTRL.OFFCOMP = 1). Rail-to-rail
operation should not be used when offset compensation is disabled.
38.6.3.3 Double Buffering
The following registers are double buffered:
• Input Control (INPUTCTRL)
• Control C (CTRLC)
• Average Control (AVGCTRL)
• Sampling Time Control (SAMPCTRL)
• Window Monitor Lower Threshold (WINLT)
• Window Monitor Upper Threshold (WINUT)
• Gain Correction (GAINCORR)
• Offset Correction (OFFSETCORR)
When one of these registers is written, the data is stored in the corresponding buffer as long as the
current conversion is not impacted, and the corresponding busy status will be set in the Synchronization
Busy register (SYNCBUSY). When a new RESULT is available, data stored in the buffer registers will be
transfered to the ADC and a new conversion can start.
38.6.3.4 Device Temperature Measurement
Principle
The device has an integrated temperature sensor which is part of the Supply Controller (SUPC). The
analog signal of that sensor can be converted into a digital value by the ADC. The digital value can be
converted into a temperature in °C by following the steps in this section.
Configuration and Conditions
In order to conduct temperature measurements, configure the device according to these steps.
1. Configure the clocks and device frequencies according to the Electrical Characteristics.
2. Configure the Voltage References System of the Supply Controller (SUPC):
2.1. Enable the temperature sensor by writing a '1' to the Temperature Sensor Enable bit in the
VREF Control register (SUPC.VREF.TSEN).
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 985
2.2. Select the required voltage for the internal voltage reference INTREF by writing to the
Voltage Reference Selection bits (SUPC.VREF.SEL). The required value can be found in
the Electrical Characteristics.
2.3. Enable routing INTREF to the ADC by writing a '1' to the Voltage Reference Output Enable
bit (SUPC.VREF.VREFOE).
3. Configure the ADC:
3.1. Select the internal voltage reference INTREF as ADC reference voltage by writing to the
Reference Control register (ADC.REFCTRL.REFSEL).
3.2. Select the temperature sensor vs. internal GND as input by writing TEMP and GND to the
positive and negative MUX Input Selection bit fields (ADC.INPUTCTRL.MUXNEG
and .MUXPOS, respectively).
3.3. Configure the remaining ADC parameters according to the Electrical Characteristics.
3.4. Enable the ADC and acquire a value, ADCm.
Calculation Parameter Values
The temperature sensor behavior is linear, but it is sensitive to several parameters such as the internal
voltage reference - which itself depends on the temperature. To take this into account, each device
contains a Temperature Log row with individual calibration data measured and written during the
production tests. These calibration values are read by software to infer the most accurate temperature
readings possible.
The Temperature Log Row basically contains the following parameter set for two different temperatures
("ROOM" and "HOT"):
• Calibration temperatures in °C. One at room temperature tempR, one at a higher temperature tempH:
– ROOM_TEMP_VAL_INT and ROOM_TEMP_VAL_DEC contain the measured temperature at
room insertion, tempR, in °C, separated in integer and decimal value.
Example: For ROOM_TEMP_VAL_INT=0x19=25 and ROOM_TEMP_VAL_DEC=2, the
measured temperature at room insertion is 25.2°C.
– HOT_TEMP_VAL_INT and HOT_TEMP_VAL_DEC contain the measured temperature at hot
insertion, tempH, in °C. The integer and decimal value are also separated.
• For each temperature, the corresponding sensor value at the ADC in 12-bit, ADCR and ADCH:
– ROOM_ADC_VAL contains the 12-bit ADC value, ADCR, corresponding to tempR. Its conversion
to Volt is denoted VADCR.
– HOT_ADC_VAL contains the 12-bit ADC value, ADCH, corresponding to tempH. Its conversion to
Volt is denoted VADCH.
• Actual reference voltages at each calibration temperature in Volt, INT1VR and INT1VH, respectively:
– ROOM_INT1V_VAL is the 2’s complement of the internal 1V reference value at tempR: INT1VR.
– HOT_INT1V_VAL is the 2’s complement of the internal 1V reference value at tempH: INT1VH.
– Both ROOM_INT1V_VAL and HOT_INT1V_VAL values are centered around 1V with a 0.001V
step. In other words, the range of values [0,127] corresponds to [1V, 0.873V] and the range of
values [-1, -127] corresponds to [1.001V, 1.127V]. INT1V == 1 - (VAL/1000) is valid for both
ranges.
Calculating the Temperature by Linear Interpolation
Using the data pairs (tempR, VADCR) and (tempH, VADCH) for a linear interpolation, we have the following
equation:
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 986
( 
 
) = (  
 
)
The voltages Vx are acquired as 12-bit ADC values ADCx, with respect to an internal reference voltage
INT1Vx:
[Equation 1]
 =INT1V
212 1
For the measured value of the temperature sensor, ADCm, the reference voltage is assumed to be
perfect, i.e., INT1Vm=INT1Vc=1V. These substitutions yield a coarse value of the measured temperature
tempC:
[Equation 2]
=+
INT1V
212 1
INT1V
212 1
 
INT1V
212 1
INT1V
212 1
Or, after eliminating the 12-bit scaling factor (212-1):
[Equation 3]
=+INT1V INT1V  
INT1V INT1V
Equations 3 is a coarse value, because we assumed that INT1Vc=1V. To achieve a more accurate result,
we replace INT1Vc with an interpolated value INT1Vm. We use the two data pairs (tempR, INT1VR) and
(tempH, INT1VH) and yield:
(INT1VINT1V
 
) = (INT1VINT1V
 
)
Using the coarse temperature value tempc, we can infer a more precise INT1Vm value during the ADC
conversion as:
[Equation 4]
INT1V= INT1V+ ((INT1VINT1V)( )
( ))
Back to Equation 3, we replace the simple INT1Vc=1V by the more precise INT1Vm of Equation 4, and
find a more accurate temperature value tempf:
[Equation 5]
=+INT1V INT1V  
INT1V INT1V
38.6.4 DMA Operation
The ADC generates the following DMA request:
• Result Conversion Ready (RESRDY): the request is set when a conversion result is available and
cleared when the RESULT register is read. When the averaging operation is enabled, the DMA
request is set when the averaging is completed and result is available.
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38.6.5 Interrupts
The ADC has the following interrupt sources:
• Result Conversion Ready: RESRDY
• Window Monitor: WINMON
• Overrun: OVERRUN
These interrupts, except the OVERRUN interrupt, are asynchronous wake-up sources. See Sleep Mode
Controller for details.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be
individually enabled by writing a one to the corresponding bit in the Interrupt Enable Set (INTENSET)
register, and disabled by writing a one to the corresponding bit in the Interrupt Enable Clear (INTENCLR)
register. An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is
enabled. The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or
the ADC is reset. See INTFLAG register for details on how to clear interrupt flags. All interrupt requests
from the peripheral are ORed together on system level to generate one combined interrupt request to the
NVIC. Refer to Nested Vector Interrupt Controller for details. The user must read the INTFLAG register to
determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated. Refer to Nested
Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
19.6.3.3 Sleep Mode Controller
38.8.5 INTENCLR
38.8.6 INTENSET
38.8.7 INTFLAG
38.6.6 Events
The ADC can generate the following output events:
• Result Ready (RESRDY): Generated when the conversion is complete and the result is available.
Refer to 38.8.4 EVCTRL for details.
• Window Monitor (WINMON): Generated when the window monitor condition match. Refer to 38.8.10
CTRLC for details.
Setting an Event Output bit in the Event Control Register (EVCTRL.xxEO=1) enables the corresponding
output event. Clearing this bit disables the corresponding output event. Refer to the Event System
chapter for details on configuring the event system.
The ADC can take the following actions on an input event:
• Start conversion (START): Start a conversion. Refer to 38.8.17 SWTRIG for details.
• Conversion flush (FLUSH): Flush the conversion. Refer to 38.8.17 SWTRIG for details.
Setting an Event Input bit in the Event Control register (EVCTRL.xxEI=1) enables the corresponding
action on input event. Clearing this bit disables the corresponding action on input event.
The ADC uses only asynchronous events, so the asynchronous Event System channel path must be
configured. By default, the ADC will detect a rising edge on the incoming event. If the ADC action must be
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performed on the falling edge of the incoming event, the event line must be inverted first. This is done by
setting the corresponding Event Invert Enable bit in Event Control register (EVCTRL.xINV=1).
Note:  If several events are connected to the ADC, the enabled action will be taken on any of the
incoming events. If FLUSH and START events are available at the same time, the FLUSH event has
priority.
Related Links
29. EVSYS – Event System
38.6.7 Sleep Mode Operation
The ONDEMAND and RUNSTDBY bits in the Control A register (CTRLA) control the behavior of the ADC
during standby sleep mode, in cases where the ADC is enabled (CTRLA.ENABLE = 1). For further details
on available options, refer to Table 38-4.
Note:  When CTRLA.ONDEMAND=1, the analog block is powered-off when the conversion is complete.
When a start request is detected, the system returns from sleep and starts a new conversion after the
start-up time delay.
Table 38-4. ADC Sleep Behavior
CTRLA.RUNSTDBY CTRLA.ONDEMAND CTRLA.ENABLE Description
x x 0 Disabled
0 0 1 Run in all sleep modes except
STANDBY.
0 1 1 Run in all sleep modes on request,
except STANDBY.
1 0 1 Run in all sleep modes.
1 1 1 Run in all sleep modes on request.
38.6.8 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in Control A register (CTRLA.SWRST)
• Enable bit in Control A register (CTRLA.ENABLE)
The following registers are synchronized when written:
• Input Control register (INPUTCTRL)
• Control C register (CTRLC)
• Average control register (AVGCTRL)
• Sampling time control register (SAMPCTRL)
• Window Monitor Lower Threshold register (WINLT)
• Window Monitor Upper Threshold register (WINUT)
• Gain correction register (GAINCORR)
• Offset Correction register (OFFSETCORR)
• Software Trigger register (SWTRIG)
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Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
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ADC – Analog-to-Digital Converter
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38.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 ONDEMAND RUNSTDBY SLAVEEN ENABLE SWRST
0x01 CTRLB 7:0 PRESCALER[2:0]
0x02 REFCTRL 7:0 REFCOMP REFSEL[3:0]
0x03 EVCTRL 7:0 WINMONEO RESRDYEO STARTINV FLUSHINV STARTEI FLUSHEI
0x04 INTENCLR 7:0 WINMON OVERRUN RESRDY
0x05 INTENSET 7:0 WINMON OVERRUN RESRDY
0x06 INTFLAG 7:0 WINMON OVERRUN RESRDY
0x07 SEQSTATUS 7:0 SEQBUSY SEQSTATE[4:0]
0x08 INPUTCTRL
7:0 MUXPOS[4:0]
15:8 MUXNEG[4:0]
0x0A CTRLC
7:0 R2R RESSEL[1:0] CORREN FREERUN LEFTADJ DIFFMODE
15:8 DUALSEL[1:0] WINMODE[2:0]
0x0C AVGCTRL 7:0 ADJRES[2:0] SAMPLENUM[3:0]
0x0D SAMPCTRL 7:0 OFFCOMP SAMPLEN[5:0]
0x0E WINLT
7:0 WINLT[7:0]
15:8 WINLT[15:8]
0x10 WINUT
7:0 WINUT[7:0]
15:8 WINUT[15:8]
0x12 GAINCORR
7:0 GAINCORR[7:0]
15:8 GAINCORR[11:8]
0x14 OFFSETCORR
7:0 OFFSETCORR[7:0]
15:8 OFFSETCORR[11:8]
0x16
...
0x17
Reserved
0x18 SWTRIG 7:0 START FLUSH
0x19
...
0x1B
Reserved
0x1C DBGCTRL 7:0 DBGRUN
0x1D
...
0x1F
Reserved
0x20 SYNCBUSY
7:0 WINUT WINLT SAMPCTRL AVGCTRL CTRLC INPUTCTRL ENABLE SWRST
15:8 SWTRIG OFFSETCOR
RGAINCORR
0x22
...
0x23
Reserved
0x24 RESULT
7:0 RESULT[7:0]
15:8 RESULT[15:8]
0x26
...
0x27
Reserved
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...........continued
Offset Name Bit Pos.
0x28 SEQCTRL
7:0 SEQENn[7:0]
15:8 SEQENn[15:8]
23:16 SEQENn[23:16]
31:24 SEQENn[31:24]
0x2C CALIB
7:0 BIASCOMP[2:0]
15:8 BIASREFBUF[2:0]
38.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to the section on Synchronization.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to Synchronization section.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
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38.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY SLAVEEN ENABLE SWRST
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 – ONDEMAND On Demand Control
The On Demand operation mode allows the ADC to be enabled or disabled, depending on other
peripheral requests.
In On Demand operation mode, i.e., if the ONDEMAND bit has been previously set, the ADC will only be
running when requested by a peripheral. If there is no peripheral requesting the ADC will be in a disable
state.
If On Demand is disabled the ADC will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the CTRLA.RUNSTDBY bit is '1'. If
CTRLA.RUNSTDBY is '0', the ADC is disabled.
This bit is not synchronized.
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
ONDEMAND bit from master ADC instance will control the On Demand operation mode.
Value Description
0The ADC is always on , if enabled.
1The ADC is enabled, when a peripheral is requesting the ADC conversion. The ADC is
disabled if no peripheral is requesting it.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the ADC behaves during standby sleep mode.
This bit is not synchronized.
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
RUNSTDBY bit from master ADC instance will control the slave ADC operation in standby sleep mode.
Value Description
0The ADC is halted during standby sleep mode.
1The ADC is not stopped in standby sleep mode. If CTRLA.ONDEMAND=1, the ADC will be
running when a peripheral is requesting it. If CTRLA.ONDEMAND=0, the ADC will always be
running in standby sleep mode.
Bit 5 – SLAVEEN Slave Enable
This bit enables the master/slave operation and it is available only in the slave ADC instance.
This bit is not synchronized.
This bit can be set only for the slave ADC. For the master ADC, this bit is always read zero.
Value Description
0The master-slave operation is disabled.
1The ADC1 is enabled as a slave of ADC0
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Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRL.ENABLE will read back immediately and the ENABLE bit in the
SYNCBUSY register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared when the
operation is complete.
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
Value Description
0The ADC is disabled.
1The ADC is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the ADC, except DBGCTRL, to their initial state, and the ADC
will be disabled.
Writing a '1' to CTRL.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
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38.8.2 Control B
Name:  CTRLB
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
PRESCALER[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – PRESCALER[2:0] Prescaler Configuration
This field defines the ADC clock relative to the peripheral clock.
This field is not synchronized. For the slave ADC, these bits have no effect when the SLAVEEN bit is set
(CTRLA.SLAVEEN= 1).
Value Name Description
0x0 DIV2 Peripheral clock divided by 2
0x1 DIV4 Peripheral clock divided by 4
0x2 DIV8 Peripheral clock divided by 8
0x3 DIV16 Peripheral clock divided by 16
0x4 DIV32 Peripheral clock divided by 32
0x5 DIV64 Peripheral clock divided by 64
0x6 DIV128 Peripheral clock divided by 128
0x7 DIV256 Peripheral clock divided by 256
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38.8.3 Reference Control
Name:  REFCTRL
Offset:  0x02
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
REFCOMP REFSEL[3:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 – REFCOMP Reference Buffer Offset Compensation Enable
The gain error can be reduced by enabling the reference buffer offset compensation. This will increase
the start-up time of the reference.
Value Description
0Reference buffer offset compensation is disabled.
1Reference buffer offset compensation is enabled.
Bits 3:0 – REFSEL[3:0] Reference Selection
These bits select the reference for the ADC.
Value Name Description
0x0 INTREF internal reference voltage
x01 INTVCC0 1/1.6 VDDANA
0x2 INTVCC1 1/2 VDDANA (only for VDDANA > 4.0V)
0x3 VREFA External reference
0x4 DAC DAC internal output
0x5 INTVCC2 VDDANA
0x6 -
0xF
Reserved
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38.8.4 Event Control
Name:  EVCTRL
Offset:  0x03
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
WINMONEO RESRDYEO STARTINV FLUSHINV STARTEI FLUSHEI
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 5 – WINMONEO Window Monitor Event Out
This bit indicates whether the Window Monitor event output is enabled or not and an output event will be
generated when the window monitor detects something.
Value Description
0Window Monitor event output is disabled and an event will not be generated.
1Window Monitor event output is enabled and an event will be generated.
Bit 4 – RESRDYEO Result Ready Event Out
This bit indicates whether the Result Ready event output is enabled or not and an output event will be
generated when the conversion result is available.
Value Description
0Result Ready event output is disabled and an event will not be generated.
1Result Ready event output is enabled and an event will be generated.
Bit 3 – STARTINV Start Conversion Event Invert Enable
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
Value Description
0Start event input source is not inverted.
1Start event input source is inverted.
Bit 2 – FLUSHINV Flush Event Invert Enable
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
Value Description
0Flush event input source is not inverted.
1Flush event input source is inverted.
Bit 1 – STARTEI Start Conversion Event Input Enable
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
Value Description
0A new conversion will not be triggered on any incoming event.
1A new conversion will be triggered on any incoming event.
Bit 0 – FLUSHEI Flush Event Input Enable
For the slave ADC, this bit has no effect when the SLAVEEN bit is set (CTRLA.SLAVEEN= 1).
Value Description
0A flush and new conversion will not be triggered on any incoming event.
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Value Description
1A flush and new conversion will be triggered on any incoming event.
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38.8.5 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 7 6 5 4 3 2 1 0
WINMON OVERRUN RESRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINMON Window Monitor Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Window Monitor Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The window monitor interrupt is disabled.
1The window monitor interrupt is enabled, and an interrupt request will be generated when the
Window Monitor interrupt flag is set.
Bit 1 – OVERRUN Overrun Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Overrun Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The Overrun interrupt is disabled.
1The Overrun interrupt is enabled, and an interrupt request will be generated when the
Overrun interrupt flag is set.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Result Ready Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The Result Ready interrupt is disabled.
1The Result Ready interrupt is enabled, and an interrupt request will be generated when the
Result Ready interrupt flag is set.
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38.8.6 Interrupt Enable Set
Name:  INTENSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 7 6 5 4 3 2 1 0
WINMON OVERRUN RESRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINMON Window Monitor Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Window Monitor Interrupt bit, which enables the Window Monitor
interrupt.
Value Description
0The Window Monitor interrupt is disabled.
1The Window Monitor interrupt is enabled.
Bit 1 – OVERRUN Overrun Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Overrun Interrupt bit, which enables the Overrun interrupt.
Value Description
0The Overrun interrupt is disabled.
1The Overrun interrupt is enabled.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Result Ready Interrupt bit, which enables the Result Ready interrupt.
Value Description
0The Result Ready interrupt is disabled.
1The Result Ready interrupt is enabled.
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38.8.7 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x06
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
WINMON OVERRUN RESRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINMON Window Monitor
This flag is cleared by writing a '1' to the flag or by reading the RESULT register.
This flag is set on the next GCLK_ADC cycle after a match with the window monitor condition, and an
interrupt request will be generated if INTENCLR/SET.WINMON is '1'.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Window Monitor interrupt flag.
Bit 1 – OVERRUN Overrun
This flag is cleared by writing a '1' to the flag.
This flag is set if RESULT is written before the previous value has been read by CPU, and an interrupt
request will be generated if INTENCLR/SET.OVERRUN=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Overrun interrupt flag.
Bit 0 – RESRDY Result Ready
This flag is cleared by writing a '1' to the flag or by reading the RESULT register.
This flag is set when the conversion result is available, and an interrupt will be generated if INTENCLR/
SET.RESRDY=1.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Result Ready interrupt flag.
SAM C20/C21 Family Data Sheet
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38.8.8 Sequence Status
Name:  SEQSTATUS
Offset:  0x07
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
SEQBUSY SEQSTATE[4:0]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 7 – SEQBUSY Sequence busy
This bit is set when the sequence start.
This bit is clear when the last conversion in a sequence is done.
Bits 4:0 – SEQSTATE[4:0] Sequence State
These bit fields are the pointer of sequence. This value identifies the last conversion done in the
sequence.
SAM C20/C21 Family Data Sheet
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38.8.9 Input Control
Name:  INPUTCTRL
Offset:  0x08
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
MUXNEG[4:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
MUXPOS[4:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bits 12:8 – MUXNEG[4:0] Negative MUX Input Selection
These bits define the MUX selection for the negative ADC input.
Value Name Description
0x00 AIN0 ADC AIN0 pin
0x01 AIN1 ADC AIN1 pin
0x02 AIN2 ADC AIN2 pin
0x03 AIN3 ADC AIN3 pin
0x04 AIN4 ADC AIN4 pin
0x05 AIN5 ADC AIN5 pin
0x06 -
0x17
- Reserved
0x18 GND Internal ground
0x19 -
0x1F
- Reserved
Bits 4:0 – MUXPOS[4:0] Positive MUX Input Selection
These bits define the MUX selection for the positive ADC input. If the internal bandgap voltage input
channel is selected, then the Sampling Time Length bit group in the Sampling Control register must be
written with a corresponding value.
Value Name Description
0x00 AIN0 ADC AIN0 pin
0x01 AIN1 ADC AIN1 pin
0x02 AIN2 ADC AIN2 pin
0x03 AIN3 ADC AIN3 pin
0x04 AIN4 ADC AIN4 pin
0x05 AIN5 ADC AIN5 pin
0x06 AIN6 ADC AIN6 pin
0x07 AIN7 ADC AIN7 pin
0x08 AIN8 ADC AIN8 pin
0x09 AIN9 ADC AIN9 pin
0x0A AIN10 ADC AIN10 pin
SAM C20/C21 Family Data Sheet
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Value Name Description
0x0B AIN11 ADC AIN11 pin
0xC -
0x17
- Reserved
0x18 - Reserved
0x19 BANDGAP INTREF Voltage Reference (Refer to SUPC.VREG.SEL for voltage
level information.)
0x1A SCALEDVDDCORE 1/4 Scaled VDDCORE Supply
0x1B SCALEDVDDANA 1/4 Scaled VDDANA Supply
0x1C DAC DAC Output
0x1D SCALEDVDDIO 1/4 Scaled VDDIO Supply
0x1E - Reserved
0x1F - Reserved
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1004
38.8.10 Control C
Name:  CTRLC
Offset:  0x0A
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
DUALSEL[1:0] WINMODE[2:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
R2R RESSEL[1:0] CORREN FREERUN LEFTADJ DIFFMODE
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 13:12 – DUALSEL[1:0] Dual Mode Trigger Selection
These bits define the trigger mode. These bits are available in the master ADC and have no effect if the
master-slave operation is disabled (ADC1.CTRLA.SLAVEEN=0).
Value Name Description
0x0 BOTH Start event or software trigger will start a conversion on both ADCs.
0x1 INTERLEAVE Start event or software trigger will alternatingly start a conversion on ADC0
and ADC1.
0x2 -
0x3
- Reserved
Bits 10:8 – WINMODE[2:0] Window Monitor Mode
These bits enable and define the window monitor mode.
Value Name Description
0x0 DISABLE No window mode (default)
0x1 MODE1 RESULT > WINLT
0x2 MODE2 RESULT < WINUT
0x3 MODE3 WINLT < RESULT < WINUT
0x4 MODE4 WINUT < RESULT < WINLT
0x5 -
0x7
Reserved
Bit 7 – R2R Rail-to-Rail Operation
Value Description
0Disable rail-to-rail operation.
1Enable rail-to-rail operation to increase the allowable range of the input common mode
voltage (VCMIN). When R2R is one, a sampling period of four cycles is required. Offset
compensation (SAMPCTRL.OFFCOMP) must be written to one when using this period.
Bits 5:4 – RESSEL[1:0] Conversion Result Resolution
These bits define whether the ADC completes the conversion 12-, 10- or 8-bit result resolution.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1005
Value Name Description
0x0 12BIT 12-bit result
0x1 16BIT For averaging mode output
0x2 10BIT 10-bit result
0x3 8BIT 8-bit result
Bit 3 – CORREN Digital Correction Logic Enabled
Value Description
0Disable the digital result correction.
1Enable the digital result correction. The ADC conversion result in the RESULT register is
then corrected for gain and offset based on the values in the GAINCORR and
OFFSETCORR registers. Conversion time will be increased by 13 cycles according to the
value in the Offset Correction Value bit group in the Offset Correction register.
Bit 2 – FREERUN Free Running Mode
Value Description
0The ADC run in single conversion mode.
1The ADC is in free running mode and a new conversion will be initiated when a previous
conversion completes.
Bit 1 – LEFTADJ Left-Adjusted Result
Value Description
0The ADC conversion result is right-adjusted in the RESULT register.
1The ADC conversion result is left-adjusted in the RESULT register. The high byte of the 12-
bit result will be present in the upper part of the result register. Writing this bit to zero
(default) will right-adjust the value in the RESULT register.
Bit 0 – DIFFMODE Differential Mode
Value Description
0The ADC is running in singled-ended mode.
1The ADC is running in differential mode. In this mode, the voltage difference between the
MUXPOS and MUXNEG inputs will be converted by the ADC.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1006
38.8.11 Average Control
Name:  AVGCTRL
Offset:  0x0C
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
ADJRES[2:0] SAMPLENUM[3:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 6:4 – ADJRES[2:0] Adjusting Result / Division Coefficient
These bits define the division coefficient in 2n steps.
Bits 3:0 – SAMPLENUM[3:0] Number of Samples to be Collected
These bits define how many samples are added together. The result will be available in the Result
register (RESULT). Note: if the result width increases, CTRLC.RESSEL must be changed.
Value Description
0x0 1 sample
0x1 2 samples
0x2 4 samples
0x3 8 samples
0x4 16 samples
0x5 32 samples
0x6 64 samples
0x7 128 samples
0x8 256 samples
0x9 512 samples
0xA 1024 samples
0xB -
0xF
Reserved
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1007
38.8.12 Sampling Time Control
Name:  SAMPCTRL
Offset:  0x0D
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
OFFCOMP SAMPLEN[5:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 – OFFCOMP Comparator Offset Compensation Enable
Setting this bit enables the offset compensation for each sampling period to ensure low offset and
immunity to temperature or voltage drift. This compensation increases the sampling time by three clock
cycles that results in a fixed sampling duration of 4 CLK_ADC cycles.
This bit must be set to zero to validate the SAMPLEN value. It’s not possible to use OFFCOMP=1 and
SAMPLEN>0.
Bits 5:0 – SAMPLEN[5:0] Sampling Time Length
These bits control the ADC sampling time in number of CLK_ADC cycles, depending of the prescaler
value, thus controlling the ADC input impedance. Sampling time is set according to the equation:
Samplingtime = SAMPLEN+1 CLKADC
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1008
38.8.13 Window Monitor Lower Threshold
Name:  WINLT
Offset:  0x0E
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
WINLT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINLT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – WINLT[15:0] Window Lower Threshold
If the window monitor is enabled, these bits define the lower threshold value.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1009
38.8.14 Window Monitor Upper Threshold
Name:  WINUT
Offset:  0x10
Reset:  0x0000
Property:  PAV Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
WINUT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINUT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – WINUT[15:0] Window Upper Threshold
If the window monitor is enabled, these bits define the upper threshold value.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1010
38.8.15 Gain Correction
Name:  GAINCORR
Offset:  0x12
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
GAINCORR[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
GAINCORR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 11:0 – GAINCORR[11:0] Gain Correction Value
If CTRLC.CORREN=1, these bits define how the ADC conversion result is compensated for gain error
before being written to the result register. The gain correction is a fractional value, a 1-bit integer plus an
11-bit fraction, and therefore ½ <= GAINCORR < 2. GAINCORR values range from 0.10000000000 to
1.11111111111.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1011
38.8.16 Offset Correction
Name:  OFFSETCORR
Offset:  0x14
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
OFFSETCORR[11:8]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OFFSETCORR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 11:0 – OFFSETCORR[11:0] Offset Correction Value
If CTRLC.CORREN=1, these bits define how the ADC conversion result is compensated for offset error
before being written to the Result register. This OFFSETCORR value is in two’s complement format.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1012
38.8.17 Software Trigger
Name:  SWTRIG
Offset:  0x18
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
START FLUSH
Access W W
Reset 0 0
Bit 1 – START ADC Start Conversion
Writing a '1' to this bit will start a conversion or sequence. The bit is cleared by hardware when the
conversion has started. Writing a '1' to this bit when it is already set has no effect.
Writing a '0' to this bit will have no effect.
Bit 0 – FLUSH ADC Conversion Flush
Writing a '1' to this bit will flush the ADC pipeline. A flush will restart the ADC clock on the next peripheral
clock edge, and all conversions in progress will be aborted and lost. This bit is cleared until the ADC has
been flushed.
After the flush, the ADC will resume where it left off; i.e., if a conversion was pending, the ADC will start a
new conversion.
Writing this bit to '0' will have no effect.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1013
38.8.18 Debug Control
Name:  DBGCTRL
Offset:  0x1C
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bit controls the functionality when the CPU is halted by an external debugger.
This bit should be written only while a conversion is not ongoing.
Value Description
0The ADC is halted when the CPU is halted by an external debugger.
1The ADC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1014
38.8.19 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x20
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
SWTRIG OFFSETCORR GAINCORR
Access R R R
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
WINUT WINLT SAMPCTRL AVGCTRL CTRLC INPUTCTRL ENABLE SWRST
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 10 – SWTRIG Software Trigger Synchronization Busy
This bit is cleared when the synchronization of SWTRIG register between the clock domains is complete.
This bit is set when the synchronization of SWTRIG register between clock domains is started.
Bit 9 – OFFSETCORR Offset Correction Synchronization Busy
This bit is cleared when the synchronization of OFFSETCORR register between the clock domains is
complete.
This bit is set when the synchronization of OFFSETCORR register between clock domains is started.
Bit 8 – GAINCORR Gain Correction Synchronization Busy
This bit is cleared when the synchronization of GAINCORR register between the clock domains is
complete.
This bit is set when the synchronization of GAINCORR register between clock domains is started.
Bit 7 – WINUT Window Monitor Lower Threshold Synchronization Busy
This bit is cleared when the synchronization of WINUT register between the clock domains is complete.
This bit is set when the synchronization of WINUT register between clock domains is started.
Bit 6 – WINLT Window Monitor Upper Threshold Synchronization Busy
This bit is cleared when the synchronization of WINLT register between the clock domains is complete.
This bit is set when the synchronization of WINLT register between clock domains is started.
Bit 5 – SAMPCTRL Sampling Time Control Synchronization Busy
This bit is cleared when the synchronization of SAMPCTRL register between the clock domains is
complete.
This bit is set when the synchronization of SAMPCTRL register between clock domains is started.
Bit 4 – AVGCTRL Average Control Synchronization Busy
This bit is cleared when the synchronization of AVGCTRL register between the clock domains is
complete.
This bit is set when the synchronization of AVGCTRL register between clock domains is started.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1015
Bit 3 – CTRLC Control C Synchronization Busy
This bit is cleared when the synchronization of CTRLC register between the clock domains is complete.
This bit is set when the synchronization of CTRLC register between clock domains is started.
Bit 2 – INPUTCTRL Input Control Synchronization Busy
This bit is cleared when the synchronization of INPUTCTRL register between the clock domains is
complete.
This bit is set when the synchronization of INPUTCTRL register between clock domains is started.
Bit 1 – ENABLE ENABLE Synchronization Busy
This bit is cleared when the synchronization of ENABLE register between the clock domains is complete.
This bit is set when the synchronization of ENABLE register between clock domains is started.
Bit 0 – SWRST SWRST Synchronization Busy
This bit is cleared when the synchronization of SWRST register between the clock domains is complete.
This bit is set when the synchronization of SWRST register between clock domains is started
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1016
38.8.20 Result
Name:  RESULT
Offset:  0x24
Reset:  0x0000
Property:  -
Bit 15 14 13 12 11 10 9 8
RESULT[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RESULT[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – RESULT[15:0] Result Conversion Value
These bits will hold up to a 16-bit ADC conversion result, depending on the configuration.
In single conversion mode without averaging, the ADC conversion will produce a 12-bit result, which can
be left- or right-shifted, depending on the setting of CTRLC.LEFTADJ.
If the result is left-adjusted (CTRLC.LEFTADJ), the high byte of the result will be in bit position [15:8],
while the remaining 4 bits of the result will be placed in bit locations [7:4]. This can be used only if an 8-bit
result is needed; i.e., one can read only the high byte of the entire 16-bit register.
If the result is not left-adjusted (CTRLC.LEFTADJ) and no oversampling is used, the result will be
available in bit locations [11:0], and the result is then 12 bits long. If oversampling is used, the result will
be located in bit locations [15:0], depending on the settings of the Average Control register.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1017
38.8.21 Sequence Control
Name:  SEQCTRL
Offset:  0x28
Reset:  0x00000000
Property:  PAC Write-Protection
Bit 31 30 29 28 27 26 25 24
SEQENn[31:24]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
SEQENn[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
SEQENn[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
SEQENn[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 31:0 – SEQENn[31:0] Enable Positive Input in the Sequence
For details on available positive mux selection, refer to INPUTCTRL.MUXENG.
The sequence start from the lowest input, and go to the next enabled input automatically when the
conversion is done. If no bits are set the sequence is disabled.
Value Description
0Disable the positive input mux n selection from the sequence.
1Enable the positive input mux n selection to the sequence.
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1018
38.8.22 Calibration
Name:  CALIB
Offset:  0x2C
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
BIASREFBUF[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bit 7 6 5 4 3 2 1 0
BIASCOMP[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 10:8 – BIASREFBUF[2:0] Bias Reference Buffer Scaling
This value from production test must be loaded from the NVM software calibration row into the CALIB
register by software to achieve the specified accuracy.
The value must be copied only, and must not be changed.
Bits 2:0 – BIASCOMP[2:0] Bias Comparator Scaling
This value from production test must be loaded from the NVM software calibration row into the CALIB
register by software to achieve the specified accuracy.
The value must be copied only, and must not be changed
Related Links
9.4 NVM Software Calibration Area Mapping
SAM C20/C21 Family Data Sheet
ADC – Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1019
39. SDADC – Sigma-Delta Analog-to-Digital Converter
39.1 Overview
The Sigma-Delta Analog-to-Digital Converter (SDADC) converts analog signals to digital values. The
SDADC has 16-bit resolution, and is capable of converting up to 1.5 Msps divided by the data over
sampling ratio (OSR). The input selection is up to three differential analog channels. The SDADC
provides signed results.
ADC measurements can be started by either application software or an incoming event from another
peripheral in the device. ADC measurements can be started with predictable timing, and without software
intervention.
The SDADC also integrates a sleep mode and a conversion sequencer. These features reduce power
consumption and processor intervention.
A set of reference voltages is generated internally.
39.2 Features
• 16-bit resolution
• Up to 1,500,000 divided by Over Sampling Ratio (OSR) samples per second
• Three analog differential inputs
– Up to 3 external analog differential pairs.
• Conversion Range:
– Differential mode: -VREF to +VREF
– Single-ended mode: 0V to +VREF
• Event-triggered conversion (one event input)
• Optional DMA transfer of conversion settings or result
• Single, continuous and sequencing options
• Hardware gain, offset and shift compensation
• Windowing monitor
• Chopper mode (offset reduction)
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1020
39.3 Block Diagram
Figure 39-1. SDADC Block Diagram.
SDADC
INN0
INNn
...
INP0
INPn
...
SWTRIG
EVCTRL
SEQCTRL
SAMPCTRL
WINUT
POST
PROCESSING
CTRLB
WINLT
CTRLA
INPUTCTRL
SEQSTATUS
CTRLC
RESULT
SHIFTCORR
OFFSETCORR
GAINCORR
ANACTRL
PRESCALER
INTREF
VDDANA
REFCTRL
VREFB
DAC
39.4 Signal Description
One signal can be mapped on several pins.
Signal Description Type
VREF Analog input External reference voltage
AINN0 Analog input Analog input channel
AINP0 Analog input Analog input channel
AINN1 Analog input Analog input channel
AINP1 Analog input Analog input channel
AINN2 Analog input Analog input channel
AINP2 Analog input Analog input channel
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1021
Related Links
6. I/O Multiplexing and Considerations
39.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
39.5.1 I/O Lines
Using the SDADC's I/O lines requires the I/O pins to be configured using the port configuration (PORT).
Related Links
28. PORT - I/O Pin Controller
45.10.5 Sigma-Delta Analog-to-Digital Converter (SDADC) Characteristics
39.5.2 Power Management
The SDADC will continue to operate in any sleep mode where the selected source clock is running. The
SDADC’s interrupts can be used to wake up the device from sleep modes. Events connected to the event
system can trigger other operations in the system without exiting sleep modes. Refer to the Power
Manager chapter for details on the different sleep modes.
39.5.3 Clocks
The SDADC bus clock (CLK_SDADC_APB) can be enabled and disabled in the Main Clock module, and
the default state of CLK_SDADC_APB can be found in the Peripheral Clock Masking section.
A generic clock (GCLK_SDADC) is required to generate the CLK_SDADC to the SDADC analog module.
This clock must be configured and enabled in the Generic Clock Controller (GCLK) before using the
SDADC. The CLK_SDADC is the SDADC clock connects to SDADC analog module and its range is
between GCLK_SDADC/2, if PRESCALER is 0, and GCLK_SDADC/512, if PRESCALER is set to 255
(0xFF). Please refers to CTRLB register for more detail.
The SDADC data sampling clock CLK_SDADC_FS in the SDADC analog module is the CLK_SDADC/4.
This GCLK_SDADC is asynchronous to the bus clock (CLK_SDADC_APB). Due to this asynchronicity,
writes to certain registers will require synchronization between the clock domains.
Related Links
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
39.5.4 DMA
The DMA request line is connected to the DMA Controller (DMAC). Using the SDADC DMA requests
requires the DMA
Controller to be configured first. .
Related Links
25. DMAC – Direct Memory Access Controller
39.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the SDADC interrupt requires the
interrupt controller to be configured first.
Related Links
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1022
10.2 Nested Vector Interrupt Controller
39.5.6 Events
The events are connected to the Event System. Refer to the Event System section for details on how to
configure the Event System.
Related Links
29. EVSYS – Event System
39.5.7 Debug Operation
When the CPU is halted in debug mode the SDADC will halt normal operation. The SDADC can be
forced to continue operation
during debugging. Refer to 39.8.22 DBGCTRL for details.
39.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the peripheral access controller (PAC),
except the following register:
• Interrupt Flag Status and Clear (INTFLAG) register
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Write-protection does not apply for accesses through an external debugger.
39.5.9 Analog Connections
I/O-pins (AINx), as well as the REF reference voltage pins are analog inputs to the SDADC.
39.6 Functional Description
39.6.1 Principle of Operation
The Sigma-Delta Analog-to-Digital Converter (SDADC) converts analog signals to digital values. The
SDADC has 16-bit resolution, and is capable of converting up to 1.5 Msps divided by the OSR data over
sampling ratio. The input selection is up to three input analog channels. The SDADC provides unsigned
results.
Related Links
39.8.3 CTRLB
39.6.2 Basic Operation
39.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the SDADC is
disabled (CTRLA.ENABLE is zero):
• CTRLA ONEDEMAND and RUNSTDBY bits
• CTRLB
• CTRLC
• EVCTRL
• ANACTRL
Enable-protection is denoted by the Enable-Protected property in the register description.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1023
39.6.2.2 Enabling, Disabling and Resetting
The SDADC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The
SDADC is disabled by writing a zero to CTRLA.ENABLE.
The SDADC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST).
All registers in the ADC will be reset to their initial state, and the SDADC will be disabled. Refer to 39.8.1
CTRLA for details.
39.6.2.3 Operation
In the most basic configuration, the SDADC sample values from the configured external sources (input
ctrl register). The rate of the conversion depends on the combination of the GCLK_SDADC frequency, the
clock prescaler from CTRLB.PRESCALER and the Over Sampling Ratio from CTRLB.OSR.
To convert analog values to digital values, the SDADC needs to be initialized first, as described in
39.6.2.1 Initialization . Data conversion can be started either manually, by writing a one to the Start bit in
the Software Trigger register (SWTRIG.START), or automatically, by configuring an automatic trigger to
initiate the conversions. A free-running mode could be used to continuously convert an input channel.
There is no need for a trigger to start the conversion. It will start automatically at the end of previous
conversion.
The first valid sample starts from the third sample onward. It can skip the first few samples by
programming the SKPCNT[3:0] in CTRLB register. The result of the conversion is stored in the Result
register (RESULT) overwriting the result from the previous conversion.
To avoid data loss the conversion result must be read as soon as it is available (INTFLAG.RESRDY).
Failing to do so will result in an overrun error condition, indicated by the OVERRUN bit in the Interrupt
Flag Status and Clear register (INTFLAG.OVERRUN).
To use an interrupt handler, the corresponding bit in the Interrupt Enable Set register (INTENSET) must
be written to one.
39.6.2.4 Conversion Reference
The conversion is performed on a full range between 0V and the reference voltage. Analog inputs
between these voltages convert to values based on a linear conversion.
39.6.2.5 Prescaler Selection
The SDADC is clocked by GCLK_SDADC. There is also a prescaler in the SDADC to enable conversion
at lower clock rates.
Refer to 39.8.3 CTRLB for details on prescaler settings.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1024
Figure 39-2. SDADC Prescaler Diagram.
GCLK_SDADC 7-BIT PRESCALER
CTRLB.PRESCALER[7:0]
DIV512
DIV510
. . .
DIV10
DIV8
DIV6
DIV4
DIV2
CLK_SDADC
39.6.2.6 SDADC Resolution
The SDADC provides 16-bit resolution.
39.6.2.7 Automatic Sequences
The SDADC has the ability to automatically sequence a series of conversion. This means that each time
the SDADC receives a start-of-conversion request, it can perform multiple conversions automatically. All
of the three inputs can be included in a sequence, by writing to the Sequence Control register
(SEQCTRL). The order of the conversion in a sequence is the lower positive input pair selection to upper
positive input pair (AINN0, AINP0, AINN1, AINP1 ...).
When a sequence starts, the Sequence Busy status bit in Sequence Status register
(SEQSTATUS.SEQBUSY) will be set to one. When the sequence is complete, the Sequence Busy status
bit will be cleared.
Each time a conversion is completed, the Sequence State status in Sequence Status register
(SEQSTATUS.SEQSTATE) will store the input number from which the conversion is done. The result will
be stored in RESULT register and the Result Ready Interrupt Flag (INTFLAG.RESRDY) is set.
If additional inputs must be scanned, the SDADC will automatically start a new conversion on the next
input present in the sequence list.
Note that if SEQCTRL register has no bits set to one, the conversion is done with the selected
INPUTCTRL input.
39.6.2.8 Window Monitor
The window monitor feature allows the conversion result in the RESULT register to be compared to
predefined threshold values. The window mode is selected by writing the Window Monitor Mode bits in
the Window Monitor Control register (WINCTRL.WINMODE). Threshold values must be written in the
Window Monitor Lower Threshold register (WINLT) and Window Monitor Upper Threshold register
(WINUT).
The INTFLAG.WINMON interrupt flag will be set if the conversion result matches the window monitor
condition.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1025
39.6.3 CIC (Cascaded Integrator-Comb) Decimation Filter
39.6.3.1 Description
The Analog-to-Digital Converter filters and decimates the sigma-delta ADC output bitstream. Its output is
defined on 16bits unsigned format with the following programmable output rates: CLK_SDADC_FS/64,
CLK_SDADC_FS/128, CLK_SDADC_FS/256, CLK_SDADC_FS/512 and CLK_SDADC_FS/1024, where
CLK_SDADC_FS is the sigma-delta ADC’s sampling frequency: CLK_SDADC_FS =
CLK_SDADC_PRESCALER/4, the reduction comes from the phase generator between the prescaler and
the SDADC.
The filtering and the decimation is performed by a SINC-based filter whose zeros are placed in order to
minimize aliasing effects of the decimation.
39.6.3.2 Decimation Filter
The sigma-delta architecture of the SDADC implies a filtering and a decimation of the bitstream at the
output of the SDADC. The decimation filter decimates the bitstream by 64, 128 or 256, 512, 1024. To
perform the decimation operation, a 3rd order SINC filter with programmable Over Sampling Ratio is
implemented with the following transfer function:
=1
OS3= 0
OSR+ 1 3
OSR is the Over Sampling Ratio which can be modified to change the output data rate (See CTRLC for
the setting of this parameter).
The DC gain of this filter is unity and does not depend on its OSR. However, as it generates a 3rd order
zero at (CLK_SDADC_FS / OSR) frequency multiples, its frequency response depends on the OSR
parameter. See next section for frequency plots.
Figure 39-3. Spectral Mask of an OSR = 64, CLK_SDADC_FS = 1 MHz, 3rd Order Sinc Filter Overall
Response (Continuous Line) and 0–1600Hz Bandwidth Response (Dashed Line)
0 Fs/16 2*Fs/16 3*Fs/16 4*Fs/16 5*Fs/16 6*Fs/16 7*Fs/16 8*Fs/16
-120
-96
-72
-48
-24
0
frequency (Hz), overall mask
gain (dB), overall mask
0 200 400 600 800 1000 1200 1400 1600
-0.5
-0.4
-0.3
-0.2
-0.1
0
frequency (Hz), base band
gain (dB), base band
The zeros of this filter are located at multiples of CLK_SDADC_FS/64.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1026
Figure 39-4. Spectral Mask of an OSR = 128, CLK_SDADC_FS = 1 MHz, 3rd Order Sinc Filter
Overall Response (Continuous Line) and 0–1600 Hz Bandwidth Response (Dashed Line)
0 Fs/16 2*Fs/16 3*Fs/16 4*Fs/16 5*Fs/16 6*Fs/16 7*Fs/16 8*Fs/16
-120
-96
-72
-48
-24
0
frequency (Hz), overall mask
gain (dB), overall mask
0 200 400 600 800 1000 1200 1400 1600
-2
-1.6
-1.2
-0.8
-0.4
0
frequency (Hz), base band
gain (dB), base band
The zeros of this filter are located at multiples of CLK_SDADC_FS/128.
Figure 39-5. Spectral Mask of an OSR = 256, CLK_SDADC_FS = 1 MHz, 3rd Order Sinc Filter
Overall Response (Continuous Line) and 0–1600 Hz Bandwidth Response (Dashed Line)
0 Fs/16 2*Fs/16 3*Fs/16 4*Fs/16 5*Fs/16 6*Fs/16 7*Fs/16 8*Fs/16
-120
-96
-72
-48
-24
0
frequency (Hz), overall mask
gain (dB), overall mask
0 200 400 600 800 1000 1200 1400 1600
-12
-9.6
-7.2
-4.8
-2.4
0
frequency (Hz), base band
gain (dB), base band
The zeros of this filter are located at multiples of CLK_SDADC_FS/256.
39.6.3.3 Conversion Time
The time needed to convert a value depends on the selected OSR, PRESCALER and on the frequency of
the SDADC.
For example, a sigma-delta converter running at CLK_GEN_SDADC = 1MHz with program the OSR of 64
and PRESCALER of 0. The output sampling rate equation is CLK_GEN_SDADC/(OSR * PRESCALER *
4) which means to converts data every (64*2*4)/1e6= 512μs. The output data rate is then 1.953ksps.
Note: The CLK_SDADC_PRESCAL clock range is CLK_GEN_SDADC/2, if PRESCAL is 0
The OSR and PRESCALER are described in 39.8.3 CTRLB register.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1027
39.6.3.4 Gain and Offset Compensation
A specific offset, gain and shift can be applied to each source of the SDADC by performing the following
operation:
Data = Dat0+ OFFSET × GAIN
2SHIFT
Where:
Data0 is an unsigned integer defined on 16 bits. It is the output of the decimation filter.
OFFSET is a signed integer defined on 24 bits (OFFSETCORR register).
GAIN is an unsigned integer defined on 14 bits (GAINCORR register).
SHIFT is an unsigned integer defined on 4 bits (SHIFTCORR register).
The result of the operation is then saturated to be within [0:216-1] and the 16 LSBs of this saturation
operation are sent to the controller as the result of the SDADC conversion.
Offset error can be compensated by setting the Chopper mode ON, refer to the 39.8.21
ANACTRL.ONCHOP bit.
39.6.4 DMA Operation
The SDADC generates the following DMA request:
Result Conversion Ready (RESRDY): the request is set when a conversion result is available and cleared
when
the RESULT register is read.
39.6.5 Interrupts
The SDADC has the following interrupt sources:
• Result Conversion Ready: RESRDY
• Window Monitor: WINMON
• Overrun: OVERRUN
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be
individually enabled by writing a one to the corresponding bit in the Interrupt Enable Set (INTENSET)
register, and disabled by writing a one to the corresponding bit in the Interrupt Enable Clear (INTENCLR)
register. An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is
enabled. The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or
the SDADC is reset. See 39.8.7 INTFLAG for details on how to clear interrupt flags. All interrupt requests
from the peripheral are ORed together on system level to generate one combined interrupt request to the
NVIC. The user must read the INTFLAG register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
39.6.6 Events
The SDADC can generate the following output events:
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1028
• Result Ready (RESRDY): Generated when the conversion is complete and the result is available.
Refer to 39.8.4 EVCTRL for details.
• Window Monitor (WINMON): Generated when the window monitor condition match. Refer to 39.8.11
WINCTRL register for details.
Writing a one to an Event Output bit in the Event Control Register (EVCTRL.xxEO) enables the
corresponding output event. Writing a zero to this bit disables the corresponding output event. Refer to
the Event System chapter for details on configuring the event system.
The SDADC can take the following actions on an input event:
• Start conversion (START): Start a conversion. Refer to 39.8.17 SWTRIG for details.
• Conversion flush (FLUSH): Flush the conversion. Refer to 39.8.17 SWTRIG for details.
Writing a one to an Event Input bit into the Event Control register (EVCTRL.xxEI) enables the
corresponding action on input event. Writing a zero to this bit disables the corresponding action on input
event.
The SDADC uses only asynchronous events and asynchronous Event System channel path must be
configured. By default, the SDADC will detect a rising edge on the incoming event. If the SDADC action
must be performed on the falling edge of the incoming event, the event line must be inverted first, by
writing to one the corresponding Event Invert Enable bit in Event Control register (EVCTRL.xINV).
Note that If FLUSH and START events are available at the same time, the FLUSH event has higher
priority.
Related Links
29. EVSYS – Event System
39.6.7 Sleep Mode Operation
The ONDEMAND and RUNSTDBY bits in the Control A register (CTRLA) control the behavior of the
SDADC during standby sleep mode, in cases where the SDADC is enabled (CTRLA.ENABLE = 1). Note
that when CTRLA.ONDEMAND is one, the analog
block is powered-off when the conversion is complete. When a start request is detected, the system
returns from sleep and starts a new conversion after the start-up time delay.
Table 39-1. SDADC Sleep Behavior
CTRLA.RUNSTDBY CTRLA.ONDEMAND CTRLA.ENABLE Description
x x 0 Disabled
0 0 1 Run in all sleep modes except
STANDBY.
0 1 1 Run in all sleep modes on request,
except STANDBY.
1 0 1 Run in all sleep modes.
1 1 1 Run in all sleep modes on request.
39.6.8 Synchronization
Due to the asynchronicity between CLK_SDADC_APB and CLK_GEN_SDADC some registers must be
synchronized when accessed. A register can require:
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1029
• Synchronization when written
• Synchronization when read
• Synchronization when written and read
• No synchronization
When executing an operation that requires synchronization, the corresponding synchronization bit is set
in Synchronization Busy register (SYNCBUSY) and cleared when synchronization is complete.
If an operation that require synchronization is executed while its busy bit is on, the operation is discarded
and a bus error is generated.
The following bits need synchronization when written:
• Software Reset bit in Control A register (CTRLA.SWRST)
• Enable bit in Control A register (CTRLA.ENABLE)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
The following registers need synchronization when written:
• Input Control register (INPUTCTRL)
• Reference Control register (REFCTRL)
• Control C register (CTRLC)
• Window Monitor Lower Threshold register (WINLT)
• Window Monitor Upper Threshold register (WINUT)
• Offset correction register (OFFSETCORR)
• Gain correction register (GAINCORR)
• Shift correction register (SHIFTCORR)
• Software Trigger register (SWTRIG)
• Analog Control Register (ANACTRL)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1030
39.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 ONDEMAND RUNSTDBY ENABLE SWRST
0x01 REFCTRL 7:0 ONREFBUF REFRANGE[1:0] REFSEL[1:0]
0x02 CTRLB
7:0 PRESCALER[7:0]
15:8 SKPCNT[3:0] OSR[2:0]
0x04 EVCTRL 7:0 WINMONEO RESRDYEO STARTINV FLUSHINV STARTEI FLUSHEI
0x05 INTENCLR 7:0 WINMON OVERRUN RESRDY
0x06 INTENSET 7:0 WINMON OVERRUN RESRDY
0x07 INTFLAG 7:0 WINMON OVERRUN RESRDY
0x08 SEQSTATUS 7:0 SEQBUSY SEQSTATE[3:0]
0x09 INPUTCTRL 7:0 MUXSEL[3:0]
0x0A CTRLC 7:0 FREERUN
0x0B WINCTRL 7:0 WINMODE[2:0]
0x0C WINLT
7:0 WINLT[7:0]
15:8 WINLT[15:8]
23:16 WINLT[23:16]
31:24
0x10 WINUT
7:0 WINUT[7:0]
15:8 WINUT[15:8]
23:16 WINUT[23:16]
31:24
0x14 OFFSETCORR
7:0 OFFSETCORR[7:0]
15:8 OFFSETCORR[15:8]
23:16 OFFSETCORR[23:16]
31:24
0x18 GAINCORR
7:0 GAINCORR[7:0]
15:8 GAINCORR[13:8]
0x1A SHIFTCORR 7:0 SHIFTCORR[3:0]
0x1B Reserved
0x1C SWTRIG 7:0 START FLUSH
0x1D
...
0x1F
Reserved
0x20 SYNCBUSY
7:0 OFFSETCOR
RWINUT WINLT WINCTRL MUXCTRL CTRLC ENABLE SWRST
15:8 ANACTRL SWTRIG SHIFTCORR GAINCORR
23:16
31:24
0x24 RESULT
7:0 RESULT[7:0]
15:8 RESULT[15:8]
23:16 RESULT[23:16]
31:24
0x28 SEQCTRL 7:0 SEQENn[2:0]
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1031
...........continued
Offset Name Bit Pos.
0x29
...
0x2B
Reserved
0x2C ANACTRL 7:0 BUFTEST ONCHOP CTLSDADC[4:0]
0x2D Reserved
0x2E DBGCTRL 7:0 DBGRUN
39.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1032
39.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized (ENABLE, SWRST)
Bit 7 6 5 4 3 2 1 0
ONDEMAND RUNSTDBY ENABLE SWRST
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 – ONDEMAND On Demand Control
The On Demand operation modes allows the SDADC to be enabled or disabled, depending on other
peripheral request.
In On Demand operation mode, i.e., if the ONDEMAND bit has been previously written to one, the
SDADC will only be running when requested by a peripheral. If there is no peripheral requesting the
SDADC will be in a disable state.
If On Demand is disable the SDADC will always be running when enabled.
In standby sleep mode, the On Demand operation is still active if the CTRLA.RUNSTDBY bit is one. If
CTRLA.RUNSTDBY is zero, the SDADC is disabled.
This bit is not synchronized.
Value Description
0The SDADC is always on , if enabled.
1The SDADC is enabled, when a peripheral is requesting the SDADC conversion. The
SDADC is disabled if no peripheral is requesting it.
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the SDADC behaves during standby sleep mode:
This bit is not synchronized.
Value Description
0The SDADC is halted during standby sleep mode.
1The SDADC is not stopped in standby sleep mode. If CTRLA.ONDEMAND is one, the
SDADC will be running when a peripheral is requesting it. If CTRLA.ONDEMAND is zero, the
SDADC will always be running in standby sleep mode.
Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRL.ENABLE will read back immediately and the ENABLE bit in the
SYNCBUSY register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared when the
operation is complete.
Value Description
0The SDADC is disabled.
1The SDADC is enabled.
Bit 0 – SWRST Software Reset
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the SDADC, except SYNCBUSY , to their initial state, and
the SDADC will be disabled.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1033
Writing a one to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1034
39.8.2 Reference Control
Name:  REFCTRL
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
ONREFBUF REFRANGE[1:0] REFSEL[1:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 7 – ONREFBUF Reference Buffer On
Turning on the buffer increases the impedance seen on the external reference, so that the current load
reduces from 5μA to 0.10μA. This needs to be matched with whatever type of reference circuit is used.
Value Description
0Reference Buffer Off
1Reference Buffer On
Bits 5:4 – REFRANGE[1:0] Reference Range
REFRANGE[1:0] Reference Voltage
0x0 Vref < 1.4V
0x1 1.4V < Vref < 2.4V
0x2 2.4 < Vref < 3.6V
0x3 Vref > 3.6V
Bits 1:0 – REFSEL[1:0] Reference Selection
These bits select the reference for the ADC.
Note:  The reference buffer should be enabled (ONREFBUF=1) when using the internal bandgap or DAC
output as reference.
Value Name Description
0x0 Internal bandgap Internal 1.024V, 2.048V, 4.096V
0x1 VREFB pin External 1-5.5V
0x2 DAC output Internal 1-5.5V
0x3 VDDANA Supply 2.7-5.5V
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1035
39.8.3 Control B
Name:  CTRLB
Offset:  0x02
Reset:  0x2000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
SKPCNT[3:0] OSR[2:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 1 0 0 0 0
Bit 7 6 5 4 3 2 1 0
PRESCALER[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 15:12 – SKPCNT[3:0] Skip Count
How many skip samples before retrieve the first valid sample.
The first valid sample starts from the third sample onward.
Bits 10:8 – OSR[2:0] Over Sampling Ratio
OSR is the Over Sampling Ratio which can be modified to change the output data rate.
The OSR must never be changed while the SDADC is running. One must first place the SDADC in reset
state, modify the OSR and then run the SDADC again.
Example: The sampling rate of the SDADC is 1.5Msps/OSR. The maximum sampling rate is then
1.5MSPS/OSR64 ≅ 23.4ksps and the minimum sampling rate is 1.5Msps/OSR1024 ≅ 1.5ksps
Value Name Description
0x0 OSR64 Over Sampling Ratio is 64
x01 OSR128 Over Sampling Ratio is 128
0x2 OSR256 Over Sampling Ratio is 256
0x3 OSR512 Over Sampling Ratio is 512
0x4 OSR1024 Over Sampling Ratio is 1024
0x4 -
0xF
- Reserved
Bits 7:0 – PRESCALER[7:0] Prescaler Configuration
The ADC uses the SDADC Clock to perform conversions.
The CLK_SDADC_PRESCAL clock range is between CLK_GEN_SDADC/2, if PRESCAL is 0, and
CLK_GEN_SDADC/512, if PRESCAL is set to 255 (0xFF). PRESCAL must be programmed in order to
provide an CLK_SDADC_PRESCAL clock frequency according to the parameters given in the product
Electrical Characteristics section.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1036
39.8.4 Event Control
Name:  EVCTRL
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
WINMONEO RESRDYEO STARTINV FLUSHINV STARTEI FLUSHEI
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 5 – WINMONEO Window Monitor Event Out
This bit indicates whether the Window Monitor event output is enabled or not and an output event will be
generated when the window monitor detects something.
Value Description
0Window Monitor event output is disabled and an event will not be generated.
1Window Monitor event output is enabled and an event will be generated.
Bit 4 – RESRDYEO Result Ready Event Out
This bit indicates whether the Result Ready event output is enabled or not and an output event will be
generated when the conversion result is available.
Value Description
0Result Ready event output is disabled and an event will not be generated.
1Result Ready event output is enabled and an event will be generated.
Bit 3 – STARTINV Start Conversion Event Invert Enable
Value Description
0start event input source is not inverted.
1start event input source is inverted.
Bit 2 – FLUSHINV Flush Event Invert Enable
Value Description
0flush event input source is not inverted.
1flush event input source is inverted.
Bit 1 – STARTEI Start Conversion Event Input Enable
Value Description
0A new conversion will not be triggered on any incoming event.
1A new conversion will be triggered on any incoming event.
Bit 0 – FLUSHEI Flush Event Input Enable
Value Description
0A flush and new conversion will not be triggered on any incoming event.
1A flush and new conversion will be triggered on any incoming event.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1037
39.8.5 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 7 6 5 4 3 2 1 0
WINMON OVERRUN RESRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINMON Window Monitor Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Window Monitor Interrupt Enable bit, which disables the
corresponding interrupt request.
Value Description
0The window monitor interrupt is disabled.
1The window monitor interrupt is enabled, and an interrupt request will be generated when the
Window Monitor interrupt flag is set.
Bit 1 – OVERRUN Overrun Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overrun Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The Overrun interrupt is disabled.
1The Overrun interrupt is enabled, and an interrupt request will be generated when the
Overrun interrupt flag is set.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Result Ready Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The Result Ready interrupt is disabled.
1The Result Ready interrupt is enabled, and an interrupt request will be generated when the
Result Ready interrupt flag is set.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1038
39.8.6 Interrupt Enable Set
Name:  INTENSET
Offset:  0x06
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 7 6 5 4 3 2 1 0
WINMON OVERRUN RESRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINMON Window Monitor Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Window Monitor Interrupt bit, which enables the Window Monitor
interrupt.
Value Description
0The Window Monitor interrupt is disabled.
1The Window Monitor interrupt is enabled.
Bit 1 – OVERRUN Overrun Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overrun Interrupt bit, which enables the Overrun interrupt.
Value Description
0The Overrun interrupt is disabled.
1The Overrun interrupt is enabled.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Result Ready Interrupt bit, which enables the Result Ready interrupt.
Value Description
0The Result Ready interrupt is disabled.
1The Result Ready interrupt is enabled.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1039
39.8.7 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x07
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
WINMON OVERRUN RESRDY
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINMON Window Monitor
This flag is cleared by writing a one to the flag or by reading the RESULT register.
This flag is set on the next CLK_GEN_SDADC cycle after a match with the window monitor condition,
and an interrupt request will be generated if INTENCLR/SET.WINMON is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Window Monitor interrupt flag.
Bit 1 – OVERRUN Overrun
This flag is cleared by writing a one to the flag.
This flag is set if RESULT is written before the previous value has been read by CPU, and an interrupt
request will be generated if INTENCLR/SET.OVERRUN is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overrun interrupt flag.
Bit 0 – RESRDY Result Ready
This flag is cleared by writing a one to the flag or by reading the RESULT register.
This flag is set when the conversion result is available, and an interrupt will be generated if INTENCLR/
SET.RESRDY is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Result Ready interrupt flag.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1040
39.8.8 Sequence Status
Name:  SEQSTATUS
Offset:  0x08
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
SEQBUSY SEQSTATE[3:0]
Access R R R R R
Reset 0 0 0 0 0
Bit 7 – SEQBUSY Sequence busy
This bit is set when the sequence start.
This bit is clear when the last conversion in a sequence is done.
Bits 3:0 – SEQSTATE[3:0] Sequence State
This bit field is the pointer of sequence. This value identifies the last conversion done in the sequence.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1041
39.8.9 Input Control
Name:  INPUTCTRL
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
MUXSEL[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – MUXSEL[3:0] ADC Analog Input Selection
These bits define the Mux selection for the SDADC input.
Value Name Description
0x00 AIN0 Select ADC AINN0 and AINP0 pins
0x01 AIN1 Select ADC AINN1 and AINP1 pins
0x02 AIN2 Select ADC AINN2 and AINP2 pins
0x03 -
0x0F
Reserved
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1042
39.8.10 Control C
Name:  CTRLC
Offset:  0x0A
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
FREERUN
Access R/W
Reset 0
Bit 0 – FREERUN Free Running Mode
Value Description
0The SDADC run in single conversion mode.
1The SDADC is in free running mode and a new conversion will be initiated when a previous
conversion completes.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1043
39.8.11 Window Monitor Control
Name:  WINCTRL
Offset:  0x0B
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
WINMODE[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – WINMODE[2:0] Window Monitor Mode
These bits enable and define the window monitor mode.
Value Name Description
0x0 DISABLE No window mode (default)
0x1 ABOVE RESULT > WINLT
0x2 BELOW RESULT < WINUT
0x3 INSIDE WINLT < RESULT < WINUT
0x4 OUTSIDE WINUT < RESULT or RESULT < WINLT
0x5 -
0x7
Reserved
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1044
39.8.12 Window Monitor Lower Threshold
Name:  WINLT
Offset:  0x0C
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
WINLT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
WINLT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINLT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – WINLT[23:0] Window Lower Threshold
If the window monitor is enabled, these bits define the lower threshold value.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1045
39.8.13 Window Monitor Upper Threshold
Name:  WINUT
Offset:  0x10
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
WINUT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
WINUT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINUT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – WINUT[23:0] Window Upper Threshold
If the window monitor is enabled, these bits define the upper threshold value.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1046
39.8.14 Offset Correction
Name:  OFFSETCORR
Offset:  0x14
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
OFFSETCORR[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OFFSETCORR[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OFFSETCORR[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – OFFSETCORR[23:0] Offset Correction
The OFFSETCORR is a signed integer value.
A specific offset, gain and shift can be applied to SDADC by performing the following operation:
(RESULT + OFFSETCORR)*GAINCORR/2^SHIFTCORR
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1047
39.8.15 Gain Correction
Name:  GAINCORR
Offset:  0x18
Reset:  0x0001
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
GAINCORR[13:8]
Access R R R R R R
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
GAINCORR[7:0]
Access R R R R R R R R
Reset 1 0 0 0 0 0 0 0
Bits 13:0 – GAINCORR[13:0] Gain Correction
A specific offset, gain and shift can be applied to SDADC by performing the following operation:
(RESULT + OFFSETCORR)*GAINCORR/2^SHIFTCORR
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1048
39.8.16 Shift Correction
Name:  SHIFTCORR
Offset:  0x1A
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
SHIFTCORR[3:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3:0 – SHIFTCORR[3:0] Shift Correction
A specific offset, gain and shift can be applied to SDADC by performing the following operation:
(RESULT + OFFSETCORR)*GAINCORR/2^SHIFTCORR
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1049
39.8.17 Software Trigger
Name:  SWTRIG
Offset:  0x1C
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
START FLUSH
Access W W
Reset 0 0
Bit 1 – START SDADC Start Conversion
Writing a one to this bit will start a conversion or sequence. The bit is cleared by hardware when the
conversion has started. Setting this bit when it is already set has no effect.
Writing this bit to zero will have no effect.
Bit 0 – FLUSH SDADC Conversion Flush
Writing a one to this bit will be flush the SDADC pipeline. A flush will restart the SDADC conversion and
all conversions in progress will be aborted and lost. This bit is cleared until the SDADC has been flushed.
After the flush, the ADC will resume where it left off; i.e., if a conversion was pending, the ADC will start a
new conversion.
Writing this bit to zero will have no effect.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1050
39.8.18 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x20
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
ANACTRL SWTRIG SHIFTCORR GAINCORR
Access R R R R
Reset 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OFFSETCORR WINUT WINLT WINCTRL MUXCTRL CTRLC ENABLE SWRST
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 11 – ANACTRL Analog Control Synchronization Busy
This bit is cleared when the synchronization of ANACTRL register between the clock domains is
complete.
This bit is set when the synchronization of ANACTRL register between clock domains is started.
Bit 10 – SWTRIG Software Trigger Synchronization Busy
This bit is cleared when the synchronization of SWTRIG register between the clock domains is complete.
This bit is set when the synchronization of SWTRIG register between clock domains is started.
Bit 9 – SHIFTCORR Shift Correction Synchronization Busy
This bit is cleared when the synchronization of SHIFTCORR register between the clock domains is
complete.
This bit is set when the synchronization of SHIFTCORR register between clock domains is started.
Bit 8 – GAINCORR Gain Correction Synchronization Busy
This bit is cleared when the synchronization of GAINCORR register between the clock domains is
complete.
This bit is set when the synchronization of GAINCORR register between clock domains is started.
Bit 7 – OFFSETCORR Offset Correction Synchronization Busy
This bit is cleared when the synchronization of OFFSETCORR register between the clock domains is
complete.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1051
This bit is set when the synchronization of OFFSETCORR register between clock domains is started.
Bit 6 – WINUT Window Monitor Lower Threshold Synchronization Busy
This bit is cleared when the synchronization of WINUT register between the clock domains is complete.
This bit is set when the synchronization of WINUT register between clock domains is started.
Bit 5 – WINLT Window Monitor Upper Threshold Synchronization Busy
This bit is cleared when the synchronization of WINLT register between the clock domains is complete.
This bit is set when the synchronization of WINLT register between clock domains is started.
Bit 4 – WINCTRL Window Monitor Control Synchronization Busy
This bit is cleared when the synchronization of WINCTRL register between the clock domains is
complete.
This bit is set when the synchronization of WINCTRL register between clock domains is started.
Bit 3 – MUXCTRL Mux Control Synchronization Busy
This bit is cleared when the synchronization of MUXCTRL register between the clock domains is
complete.
This bit is set when the synchronization of MUXCTRL register between clock domains is started.
Bit 2 – CTRLC Control C Synchronization Busy
This bit is cleared when the synchronization of CTRLC register between the clock domains is complete.
This bit is set when the synchronization of CTRLC register between clock domains is started.
Bit 1 – ENABLE ENABLE Synchronization Busy
This bit is cleared when the synchronization of ENABLE register between the clock domains is complete.
This bit is set when the synchronization of ENABLE register between clock domains is started.
Bit 0 – SWRST SWRST Synchronization Busy
This bit is cleared when the synchronization of SWRST register between the clock domains is complete.
This bit is set when the synchronization of SWRST register between clock domains is started
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1052
39.8.19 Result
Name:  RESULT
Offset:  0x24
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
RESULT[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
RESULT[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RESULT[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – RESULT[23:0] Result Conversion Value
The analog-to-digital conversion data is placed into this register at the end of a conversion and remains
until a new conversion is completed.
The RESULT is a signed integer value with 24-bit size. The SDADC conversion result is left-adjusted in
the RESULT register.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1053
39.8.20 Sequence Control
Name:  SEQCTRL
Offset:  0x28
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
SEQENn[2:0]
Access R/W R/W R/W
Reset 0 0 0
Bits 2:0 – SEQENn[2:0] Enable Positive Input in the Sequence
For details on available mux selections, refer to 39.8.9 INPUTCTRL.
The sequence start from the lowest input, and go to the next enabled input automatically when the
conversion is done. If no bits are set the sequence is disabled.
Value Description
0Disable the positive input mux n selection from the sequence.
1Enable the positive input mux n selection to the sequence.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1054
39.8.21 Analog Control
Name:  ANACTRL
Offset:  0x2C
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized.
Bit 7 6 5 4 3 2 1 0
BUFTEST ONCHOP CTLSDADC[4:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 – BUFTEST Buffer Test
Bit 6 – ONCHOP ONCHOP
Value Description
0No Chopper at SDADC input
1Chopper at SDADC input
Bits 4:0 – CTLSDADC[4:0] CTLSDADC
SDADC Bias Current Control and used for Debugg/Characterization
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1055
39.8.22 Debug Control
Name:  DBGCTRL
Offset:  0x2E
Reset:  0x00
Property:  PAC Write-Protectedion
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bit controls the functionality when the CPU is halted by an external debugger.
This bit should be written only while a conversion is not ongoing.
Value Description
0The SDADC is halted when the CPU is halted by an external debugger.
1The SDADC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
SDADC – Sigma-Delta Analog-to-Digital Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1056
40. AC – Analog Comparators
40.1 Overview
The Analog Comparator (AC) supports multiple individual comparators. Each comparator (COMP)
compares the voltage levels on two inputs, and provides a digital output based on this comparison. Each
comparator may be configured to generate interrupt requests and/or peripheral events upon several
different combinations of input change.
Hysteresis and propagation delay can be adjusted to achieve the optimal operation for each application.
The input selection includes four shared analog port pins and several internal signals. Each comparator
output state can also be output on a pin for use by external devices.
The comparators are grouped in pairs on each port. The AC peripheral implements one or two pairs of
comparators . These are called Comparator 0 (COMP0) and Comparator 1 (COMP1) for the first pair and
Comparator 2 (COMP2) and Comparator 3 (COMP3) for the second pair. They have identical behaviors,
but separate control registers. Each pair can be set in window mode to compare a signal to a voltage
range instead of a single voltage level.
40.2 Features
• Four individual comparators
• Selectable propagation delay versus current consumption
• Hysteresis: On or Off
• Analog comparator outputs available on pins
– Asynchronous or synchronous
• Flexible input selection:
– Four pins selectable for positive or negative inputs
– Ground (for zero crossing)
– Bandgap reference voltage
– 64-level programmable VDD scaler per comparator
– DAC (if available)
• Interrupt generation on:
– Rising or falling edge
– Toggle
– End of comparison
• Window function interrupt generation on:
– Signal above window
– Signal inside window
– Signal below window
– Signal outside window
• Event generation on:
– Comparator output
– Window function inside/outside window
• Optional digital filter on comparator output
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1057
• Low-power option
– Single-shot support
40.3 Block Diagram
Figure 40-1. Analog Comparator Block Diagram (First Pair)
INTERRUPT MODE
ENABLE
ENABLE
HYSTERESIS
HYSTERESIS
DAC
VDD
SCALER
BANDGAP
+
-
+
-
CMP0
CMP1
INTERRUPTS
EVENTS
GCLK_AC
AIN3
AIN2
AIN1
AIN0
COMP0
COMP1
COMPCTRLn WINCTRL
INTERRUPT
SENSITIVITY
CONTROL
&
WINDOW
FUNCTION
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1058
Figure 40-2. Analog Comparator Block Diagram (Second Pair)
INTERRUPT MODE
ENABLE
ENABLE
HYSTERESIS
HYSTERESIS
DAC
VDD
SCALER
BANDGAP
+
-
+
-
CMP2
CMP3
INTERRUPTS
EVENTS
GCLK_AC
AIN7
AIN6
AIN5
AIN4
COMP2
COMP3
COMPCTRLn WINCTRL
INTERRUPT
SENSITIVITY
CONTROL
&
WINDOW
FUNCTION
40.4 Signal Description
Signal Description Type
AIN[7..0] Analog input Comparator inputs
CMP[2..0] Digital output Comparator outputs
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
Related Links
6. I/O Multiplexing and Considerations
40.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
40.5.1 I/O Lines
Using the AC’s I/O lines requires the I/O pins to be configured. Refer to PORT - I/O Pin Controller for
details.
Related Links
28. PORT - I/O Pin Controller
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1059
40.5.2 Power Management
The AC will continue to operate in any sleep mode where the selected source clock is running. The AC’s
interrupts can be used to wake up the device from sleep modes. Events connected to the event system
can trigger other operations in the system without exiting sleep modes.
Related Links
19. PM – Power Manager
40.5.3 Clocks
The AC bus clock (CLK_AC_APB) can be enabled and disabled in the Main Clock module, MCLK (see
MCLK - Main Clock, and the default state of CLK_AC_APB can be found in Peripheral Clock Masking.
A generic clock (GCLK_AC) is required to clock the AC. This clock must be configured and enabled in the
generic clock controller before using the AC. Refer to the Generic Clock Controller chapter for details.
This generic clock is asynchronous to the bus clock (CLK_AC_APB). Due to this asynchronicity, writes to
certain registers will require synchronization between the clock domains. Refer to Synchronization for
further details.
Related Links
19. PM – Power Manager
40.5.4 DMA
Not applicable.
40.5.5 Interrupts
The interrupt request lines are connected to the interrupt controller. Using the AC interrupts requires the
interrupt controller to be configured first. Refer to Nested Vector Interrupt Controller for details.
Related Links
10.2 Nested Vector Interrupt Controller
40.5.6 Events
The events are connected to the Event System. Refer to EVSYS – Event System for details on how to
configure the Event System.
Related Links
29. EVSYS – Event System
40.5.7 Debug Operation
When the CPU is halted in debug mode, the AC will halt normal operation after any on-going comparison
is completed. The AC can be forced to continue normal operation during debugging. Refer to DBGCTRL
for details. If the AC is configured in a way that requires it to be periodically serviced by the CPU through
interrupts or similar, improper operation or data loss may result during debugging.
40.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except for the following registers:
• Control B register (CTRLB)
• Interrupt Flag register (INTFLAG)
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1060
PAC write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
40.5.9 Analog Connections
Each comparator has up to four I/O pins that can be used as analog inputs. Each pair of comparators
shares the same four pins. These pins must be configured for analog operation before using them as
comparator inputs.
Any internal reference source, such as a bandgap voltage reference, or DAC must be configured and
enabled prior to its use as a comparator input.
40.6 Functional Description
40.6.1 Principle of Operation
Each comparator has one positive input and one negative input. Each positive input may be chosen from
a selection of analog input pins. Each negative input may be chosen from a selection of both analog input
pins and internal inputs, such as a bandgap voltage reference.
The digital output from the comparator is '1' when the difference between the positive and the negative
input voltage is positive, and '0' otherwise.
The individual comparators can be used independently (normal mode) or paired to form a window
comparison (window mode).
40.6.2 Basic Operation
40.6.2.1 Initialization
Some registers are enable-protected, meaning they can only be written when the module is disabled.
The following register is enable-protected:
• Event Control register (EVCTRL)
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
40.6.2.2 Enabling, Disabling and Resetting
The AC is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The AC is
disabled writing a '0' to CTRLA.ENABLE.
The AC is reset by writing a '1' to the Software Reset bit in the Control A register (CTRLA.SWRST). All
registers in the AC will be reset to their initial state, and the AC will be disabled. Refer to CTRLA for
details.
40.6.2.3 Comparator Configuration
Each individual comparator must be configured by its respective Comparator Control register
(COMPCTRLx) before that comparator is enabled. These settings cannot be changed while the
comparator is enabled.
• Select the desired measurement mode with COMPCTRLx.SINGLE. See Starting a Comparison for
more details.
• Select the desired hysteresis with COMPCTRLx.HYSTEN. See Input Hysteresis for more details.
• Select the comparator speed versus power with COMPCTRLx.SPEED. See Propagation Delay vs.
Power Consumption for more details.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1061
• Select the interrupt source with COMPCTRLx.INTSEL.
• Select the positive and negative input sources with the COMPCTRLx.MUXPOS and
COMPCTRLx.MUXNEG bits. See Selecting Comparator Inputs for more details.
• Select the filtering option with COMPCTRLx.FLEN.
• Select standby operation with Run in Standby bit (COMPCTRLx.RUNSTDBY).
The individual comparators are enabled by writing a '1' to the Enable bit in the Comparator x Control
registers (COMPCTRLx.ENABLE). The individual comparators are disabled by writing a '0' to
COMPCTRLx.ENABLE. Writing a '0' to CTRLA.ENABLE will also disable all the comparators, but will not
clear their COMPCTRLx.ENABLE bits.
40.6.2.4 Starting a Comparison
Each comparator channel can be in one of two different measurement modes, determined by the Single
bit in the Comparator x Control register (COMPCTRLx.SINGLE):
• Continuous measurement
• Single-shot
After being enabled, a start-up delay is required before the result of the comparison is ready. This start-up
time is measured automatically to account for environmental changes, such as temperature or voltage
supply level, and is specified in Electrical Characteristics. During the start-up time, the COMP output is
not available.
The comparator can be configured to generate interrupts when the output toggles, when the output
changes from '0' to '1' (rising edge), when the output changes from '1' to '0' (falling edge) or at the end of
the comparison. An end-of-comparison interrupt can be used with the single-shot mode to chain further
events in the system, regardless of the state of the comparator outputs. The interrupt mode is set by the
Interrupt Selection bit group in the Comparator Control register (COMPCTRLx.INTSEL). Events are
generated using the comparator output state, regardless of whether the interrupt is enabled or not.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
40.6.2.4.1 Continuous Measurement
Continuous measurement is selected by writing COMPCTRLx.SINGLE to zero. In continuous mode, the
comparator is continuously enabled and performing comparisons. This ensures that the result of the
latest comparison is always available in the Current State bit in the Status A register (STATUSA.STATEx).
After the start-up time has passed, a comparison is done and STATUSA is updated. The Comparator x
Ready bit in the Status B register (STATUSB.READYx) is set, and the appropriate peripheral events and
interrupts are also generated. New comparisons are performed continuously until the
COMPCTRLx.ENABLE bit is written to zero. The start-up time applies only to the first comparison.
In continuous operation, edge detection of the comparator output for interrupts is done by comparing the
current and previous sample. The sampling rate is the GCLK_AC frequency. An example of continuous
measurement is shown in the Figure 40-3.
Figure 40-3. Continuous Measurement Example
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
COMPCTRLx.ENABLE
tSTARTUP
Write ‘1’
2-3 cycles
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1062
For low-power operation, comparisons can be performed during sleep modes without a clock. The
comparator is enabled continuously, and changes of the comparator state are detected asynchronously.
When a toggle occurs, the Power Manager will start GCLK_AC to register the appropriate peripheral
events and interrupts. The GCLK_AC clock is then disabled again automatically, unless configured to
wake up the system from sleep.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
40.6.2.4.2 Single-Shot
Single-shot operation is selected by writing COMPCTRLx.SINGLE to '1'. During single-shot operation, the
comparator is normally idle. The user starts a single comparison by writing '1' to the respective Start
Comparison bit in the write-only Control B register (CTRLB.STARTx). The comparator is enabled, and
after the start-up time has passed, a single comparison is done and STATUSA is updated. Appropriate
peripheral events and interrupts are also generated. No new comparisons will be performed.
Writing '1' to CTRLB.STARTx also clears the Comparator x Ready bit in the Status B register
(STATUSB.READYx). STATUSB.READYx is set automatically by hardware when the single comparison
has completed.
A single-shot measurement can also be triggered by the Event System. Setting the Comparator x Event
Input bit in the Event Control Register (EVCTRL.COMPEIx) enables triggering on incoming peripheral
events. Each comparator can be triggered independently by separate events. Event-triggered operation is
similar to user-triggered operation; the difference is that a peripheral event from another hardware module
causes the hardware to automatically start the comparison and clear STATUSB.READYx.
To detect an edge of the comparator output in single-shot operation for the purpose of interrupts, the
result of the current measurement is compared with the result of the previous measurement (one
sampling period earlier). An example of single-shot operation is shown in Figure 40-4.
Figure 40-4. Single-Shot Example
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
CTRLB.STARTx
tSTARTUP
Write ‘1’
tSTARTUP
Write ‘1’
2-3 cycles 2-3 cycles
For low-power operation, event-triggered measurements can be performed during sleep modes. When
the event occurs, the Power Manager will start GCLK_AC. The comparator is enabled, and after the
startup time has passed, a comparison is done and appropriate peripheral events and interrupts are also
generated. The comparator and GCLK_AC are then disabled again automatically, unless configured to
wake up the system from sleep.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
40.6.3 Selecting Comparator Inputs
Each comparator has one positive and one negative input. The positive input is one of the external input
pins (AINx). The negative input can be fed either from an external input pin (AINx) or from one of the
several internal reference voltage sources common to all comparators. The user selects the input source
as follows:
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1063
• The positive input is selected by the Positive Input MUX Select bit group in the Comparator Control
register (COMPCTRLx.MUXPOS)
• The negative input is selected by the Negative Input MUX Select bit group in the Comparator Control
register (COMPCTRLx.MUXNEG)
In the case of using an external I/O pin, the selected pin must be configured for analog use in the PORT
Controller by disabling the digital input and output. The switching of the analog input multiplexers is
controlled to minimize crosstalk between the channels. The input selection must be changed only while
the individual comparator is disabled.
Note:  For internal use of the comparison results by the CCL, this bit must be 0x1 or 0x2.
40.6.4 Window Operation
Each comparator pair can be configured to work together in window mode. In this mode, a voltage range
is defined, and the comparators give information about whether an input signal is within this range or not.
Window mode is enabled by the Window Enable x bit in the Window Control register (WINCTRL.WENx).
Both comparators in a pair must have the same measurement mode setting in their respective
Comparator Control Registers (COMPCTRLx.SINGLE).
To physically configure the pair of comparators for window mode, the same I/O pin must be chosen as
positive input for each comparator, providing a shared input signal. The negative inputs define the range
for the window. In Figure 40-5, COMP0 defines the upper limit and COMP1 defines the lower limit of the
window, as shown but the window will also work in the opposite configuration with COMP0 lower and
COMP1 higher. The current state of the window function is available in the Window x State bit group of
the Status register (STATUS.WSTATEx).
Window mode can be configured to generate interrupts when the input voltage changes to below the
window, when the input voltage changes to above the window, when the input voltage changes into the
window or when the input voltage changes outside the window. The interrupt selections are set by the
Window Interrupt Selection bit field in the Window Control register (WINCTRL.WINTSEL). Events are
generated using the inside/outside state of the window, regardless of whether the interrupt is enabled or
not. Note that the individual comparator outputs, interrupts and events continue to function normally
during window mode.
When the comparators are configured for window mode and single-shot mode, measurements are
performed simultaneously on both comparators. Writing '1' to either Start Comparison bit in the Control B
register (CTRLB.STARTx) will start a measurement. Likewise either peripheral event can start a
measurement.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1064
Figure 40-5. Comparators in Window Mode
+
-
+
-
STATE0
STATE1
WSTATE[1:0]
INTERRUPTS
EVENTS
INPUT SIGNAL
UPPER LIMIT OF WINDOW
COMP0
COMP1
INTERRUPT
SENSITIVITY
CONTROL
&
WINDOW
FUNCTION
LOWER LIMIT OF WINDOW
40.6.5 VDD Scaler
The VDD scaler generates a reference voltage that is a fraction of the device’s supply voltage, with 64
levels. One independent voltage channel is dedicated for each comparator. The scaler of a comparator is
enabled when the Negative Input Mux bit field or the Positive Input Mux in the respective Comparator
Control register (COMPCTRLx.MUXNEG, or COMPCTRLx.MUXPOS) is set to 0x5 for Negative Input or
0x04 for Positive Input and the comparator is enabled. The voltage of each channel is selected by the
Value bit field in the SCALERx registers (SCALERx.VALUE).
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1065
Figure 40-6. VDD Scaler
SCALERx.
VALUE
to
COMPx
6
COMPCTRLx.MUXPOS == 4
COMPCTRLx.MUXNEG == 5
OR
40.6.6 Input Hysteresis
Application software can selectively enable/disable hysteresis for the comparison. Applying hysteresis will
help prevent constant toggling of the output, which can be caused by noise when the input signals are
close to each other.
Hysteresis is enabled for each comparator individually by the Hysteresis Enable bit in the Comparator x
Control register (COMPCTRLx.HYSTEN). Hysteresis is available only in continuous mode
(COMPCTRLx.SINGLE=0).
40.6.7 Propagation Delay vs. Power Consumption
It is possible to trade off comparison speed for power efficiency to get the shortest possible propagation
delay or the lowest power consumption. The speed setting is configured for each comparator individually
by the Speed bit group in the Comparator x Control register (COMPCTRLx.SPEED). The Speed bits
select the amount of bias current provided to the comparator, and as such will also affect the start-up
time.
40.6.8 Filtering
The output of the comparators can be filtered digitally to reduce noise. The filtering is determined by the
Filter Length bits in the Comparator Control x register (COMPCTRLx.FLEN), and is independent for each
comparator. Filtering is selectable from none, 3-bit majority (N=3) or 5-bit majority (N=5) functions. Any
change in the comparator output is considered valid only if N/2+1 out of the last N samples agree. The
filter sampling rate is the GCLK_AC frequency.
Note that filtering creates an additional delay of N-1 sampling cycles from when a comparison is started
until the comparator output is validated. For continuous mode, the first valid output will occur when the
required number of filter samples is taken. Subsequent outputs will be generated every cycle based on
the current sample plus the previous N-1 samples, as shown in Figure 40-7. For single-shot mode, the
comparison completes after the Nth filter sample, as shown in Figure 40-8.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1066
Figure 40-7. Continuous Mode Filtering
Sampling Clock
Sampled
Comparator Output
3-bit Majority
Filter Output
5-bit Majority
Filter Output
Figure 40-8. Single-Shot Filtering
Sampling Clock
3-bit Sampled
Comparator Output
3-bit Majority
Filter Output
Start
5-bit Sampled
Comparator Output
5-bit Majority
Filter Output
tSTARTUP
During sleep modes, filtering is supported only for single-shot measurements. Filtering must be disabled if
continuous measurements will be done during sleep modes, or the resulting interrupt/event may be
generated incorrectly.
40.6.9 Comparator Output
The output of each comparator can be routed to an I/O pin by setting the Output bit group in the
Comparator Control x register (COMPCTRLx.OUT). This allows the comparator to be used by external
circuitry. Either the raw, non-synchronized output of the comparator or the CLK_AC-synchronized version,
including filtering, can be used as the I/O signal source. The output appears on the corresponding CMP[x]
pin.
40.6.10 Offset Compensation
The Swap bit in the Comparator Control registers (COMPCTRLx.SWAP) controls switching of the input
signals to a comparator's positive and negative terminals. When the comparator terminals are swapped,
the output signal from the comparator is also inverted, as shown in Figure 40-9. This allows the user to
measure or compensate for the comparator input offset voltage. As part of the input selection,
COMPCTRLx.SWAP can be changed only while the comparator is disabled.
Figure 40-9. Input Swapping for Offset Compensation
MUXPOS
MUXNEG
+
-
COMPx
SWAP
ENABLE
HYSTERESIS
SWAP
CMPx
COMPCTRLx
40.6.11 DMA Operation
Not applicable.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1067
40.6.12 Interrupts
The AC has the following interrupt sources:
• Comparator (COMP0, COMP1, COMP2, COMP3): Indicates a change in comparator status.
• Window (WIN0, WIN1): Indicates a change in the window status.
Comparator interrupts are generated based on the conditions selected by the Interrupt Selection bit group
in the Comparator Control registers (COMPCTRLx.INTSEL). Window interrupts are generated based on
the conditions selected by the Window Interrupt Selection bit group in the Window Control register
(WINCTRL.WINTSELx[1:0]).
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be
individually enabled by writing a one to the corresponding bit in the Interrupt Enable Set (INTENSET)
register, and disabled by writing a one to the corresponding bit in the Interrupt Enable Clear (INTENCLR)
register. An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is
enabled. The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or
the AC is reset. See INFLAG register for details on how to clear interrupt flags. All interrupt requests from
the peripheral are ORed together on system level to generate one combined interrupt request to the
NVIC. The user must read the INTFLAG register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
40.6.13 Events
The AC can generate the following output events:
• Comparator (COMP0, COMP1, COMP2, COMP3): Generated as a copy of the comparator status
• Window (WIN0, WIN1): Generated as a copy of the window inside/outside status
Writing a one to an Event Output bit in the Event Control Register (EVCTRL.xxEO) enables the
corresponding output event. Writing a zero to this bit disables the corresponding output event. Refer to
the Event System chapter for details on configuring the event system.
The AC can take the following action on an input event:
• Start comparison (START0, START1, START2, START3): Start a comparison.
Writing a one to an Event Input bit into the Event Control register (EVCTRL.COMPEIx) enables the
corresponding action on input event. Writing a zero to this bit disables the corresponding action on input
event. Note that if several events are connected to the AC, the enabled action will be taken on any of the
incoming events. Refer to the Event System chapter for details on configuring the event system.
When EVCTRL.COMPEIx is one, the event will start a comparison on COMPx after the start-up time
delay. In normal mode, each comparator responds to its corresponding input event independently. For a
pair of comparators in window mode, either comparator event will trigger a comparison on both
comparators simultaneously.
40.6.14 Sleep Mode Operation
The Run in Standby bits in the Comparator x Control registers (COMPCTRLx.RUNSTDBY) control the
behavior of the AC during standby sleep mode. Each RUNSTDBY bit controls one comparator. When the
bit is zero, the comparator is disabled during sleep, but maintains its current configuration. When the bit is
one, the comparator continues to operate during sleep. Note that when RUNSTDBY is zero, the analog
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1068
blocks are powered off for the lowest power consumption. This necessitates a start-up time delay when
the system returns from sleep.
For Window Mode operation, both comparators in a pair must have the same RUNSTDBY configuration.
When RUNSTDBY is one, any enabled AC interrupt source can wake up the CPU. The AC can also be
used during sleep modes where the clock used by the AC is disabled, provided that the AC is still
powered (not in shutdown). In this case, the behavior is slightly different and depends on the
measurement mode, as listed in Table 40-1.
Table 40-1. Sleep Mode Operation
COMPCTRLx.MODE RUNSTDBY=0 RUNSTDBY=1
0 (Continuous) COMPx disabled GCLK_AC stopped, COMPx enabled
1 (Single-shot) COMPx disabled GCLK_AC stopped, COMPx enabled only when triggered by
an input event
40.6.14.1 Continuous Measurement during Sleep
When a comparator is enabled in continuous measurement mode and GCLK_AC is disabled during
sleep, the comparator will remain continuously enabled and will function asynchronously. The current
state of the comparator is asynchronously monitored for changes. If an edge matching the interrupt
condition is found, GCLK_AC is started to register the interrupt condition and generate events. If the
interrupt is enabled in the Interrupt Enable registers (INTENCLR/SET), the AC can wake up the device;
otherwise GCLK_AC is disabled until the next edge detection. Filtering is not possible with this
configuration.
Figure 40-10. Continuous Mode SleepWalking
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
COMPCTRLx.ENABLE
tSTARTUP
Write ‘1’
2-3 cycles
40.6.14.2 Single-Shot Measurement during Sleep
For low-power operation, event-triggered measurements can be performed during sleep modes. When
the event occurs, the Power Manager will start GCLK_AC. The comparator is enabled, and after the start-
up time has passed, a comparison is done, with filtering if desired, and the appropriate peripheral events
and interrupts are also generated, as shown in Figure 40-11. The comparator and GCLK_AC are then
disabled again automatically, unless configured to wake the system from sleep. Filtering is allowed with
this configuration.
Figure 40-11. Single-Shot SleepWalking
GCLK_AC
Comparator
Output or Event
Input Event
tSTARTUP tSTARTUP
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1069
40.6.15 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits are synchronized when written:
• Software Reset bit in control register (CTRLA.SWRST)
• Enable bit in control register (CTRLA.ENABLE)
• Enable bit in Comparator Control register (COMPCTRLn.ENABLE)
The following registers are synchronized when written:
• Window Control register (WINCTRL)
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1070
40.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 ENABLE SWRST
0x01 CTRLB 7:0 STARTx STARTx STARTx STARTx
0x02 EVCTRL
7:0 WINEOx WINEOx COMPEOx COMPEOx COMPEOx COMPEOx
15:8 INVEIx INVEIx INVEIx INVEIx COMPEIx COMPEIx COMPEIx COMPEIx
0x04 INTENCLR 7:0 WINx WINx COMPx COMPx COMPx COMPx
0x05 INTENSET 7:0 WINx WINx COMPx COMPx COMPx COMPx
0x06 INTFLAG 7:0 WINx WINx COMPx COMPx COMPx COMPx
0x07 STATUSA 7:0 WSTATE1[1:0] WSTATE0[1:0] STATEx STATEx STATEx STATEx
0x08 STATUSB 7:0 READYx READYx READYx READYx
0x09 DBGCTRL 7:0 DBGRUN
0x0A WINCTRL 7:0 WINTSEL1[1:0] WEN1 WINTSEL0[1:0] WEN0
0x0B Reserved
0x0C SCALERn0 7:0 VALUE[5:0]
0x0D SCALERn1 7:0 VALUE[5:0]
0x0E SCALERn2 7:0 VALUE[5:0]
0x0F SCALERn3 7:0 VALUE[5:0]
0x10 COMPCTRL0
7:0 RUNSTDBY INTSEL[1:0] SINGLE ENABLE
15:8 SWAP MUXPOS[2:0] MUXNEG[2:0]
23:16 HYSTEN SPEED[1:0]
31:24 OUT[1:0] FLEN[2:0]
0x14 COMPCTRL1
7:0 RUNSTDBY INTSEL[1:0] SINGLE ENABLE
15:8 SWAP MUXPOS[2:0] MUXNEG[2:0]
23:16 HYSTEN SPEED[1:0]
31:24 OUT[1:0] FLEN[2:0]
0x18 COMPCTRL2
7:0 RUNSTDBY INTSEL[1:0] SINGLE ENABLE
15:8 SWAP MUXPOS[2:0] MUXNEG[2:0]
23:16 HYSTEN SPEED[1:0]
31:24 OUT[1:0] FLEN[2:0]
0x1C COMPCTRL3
7:0 RUNSTDBY INTSEL[1:0] SINGLE ENABLE
15:8 SWAP MUXPOS[2:0] MUXNEG[2:0]
23:16 HYSTEN SPEED[1:0]
31:24 OUT[1:0] FLEN[2:0]
0x20 SYNCBUSY
7:0 COMPCTRLx COMPCTRLx COMPCTRLx COMPCTRLx WINCTRL ENABLE SWRST
15:8
23:16
31:24
40.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1071
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to Register Access Protection.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to Synchronization.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1072
40.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
ENABLE SWRST
Access R/W W
Reset 0 0
Bit 1 – ENABLE Enable
Due to synchronization, there is delay from updating the register until the peripheral is enabled/disabled.
The value written to CTRL.ENABLE will read back immediately and the corresponding bit in the
Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE is cleared when
the peripheral is enabled/disabled.
Value Description
0The AC is disabled.
1The AC is enabled. Each comparator must also be enabled individually by the Enable bit in
the Comparator Control register (COMPCTRLn.ENABLE).
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the AC to their initial state, and the AC will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization, there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1073
40.8.2 Control B
Name:  CTRLB
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
STARTx STARTx STARTx STARTx
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bits 3,2,1,0 – STARTx Comparator x Start Comparison
Writing a '0' to this field has no effect.
Writing a '1' to STARTx starts a single-shot comparison on COMPx if both the Single-Shot and Enable
bits in the Comparator x Control Register are '1' (COMPCTRLx.SINGLE and COMPCTRLx.ENABLE). If
comparator x is not implemented, or if it is not enabled in single-shot mode, Writing a '1' has no effect.
This bit always reads as zero.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1074
40.8.3 Event Control
Name:  EVCTRL
Offset:  0x02
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 15 14 13 12 11 10 9 8
INVEIx INVEIx INVEIx INVEIx COMPEIx COMPEIx COMPEIx COMPEIx
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINEOx WINEOx COMPEOx COMPEOx COMPEOx COMPEOx
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 15,14,13,12 – INVEIx Inverted Event Input Enable x
Value Description
0Incoming event is not inverted for comparator x.
1Incoming event is inverted for comparator x.
Bits 11,10,9,8 – COMPEIx Comparator x Event Input
Note that several actions can be enabled for incoming events. If several events are connected to the
peripheral, the enabled action will be taken for any of the incoming events. There is no way to tell which
of the incoming events caused the action.
These bits indicate whether a comparison will start or not on any incoming event.
Value Description
0Comparison will not start on any incoming event.
1Comparison will start on any incoming event.
Bits 5,4 – WINEOx Window x Event Output Enable
These bits indicate whether the window x function can generate a peripheral event or not.
Value Description
0Window x Event is disabled.
1Window x Event is enabled.
Bits 3,2,1,0 – COMPEOx Comparator x Event Output Enable
These bits indicate whether the comparator x output can generate a peripheral event or not.
Value Description
0COMPx event generation is disabled.
1COMPx event generation is enabled.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1075
40.8.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
WINx WINx COMPx COMPx COMPx COMPx
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5,4 – WINx Window x Interrupt Enable
Reading this bit returns the state of the Window x interrupt enable.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit disables the Window x interrupt.
Value Description
0The Window x interrupt is disabled.
1The Window x interrupt is enabled.
Bits 3,2,1,0 – COMPx Comparator x Interrupt Enable
Reading this bit returns the state of the Comparator x interrupt enable.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit disables the Comparator x interrupt.
Value Description
0The Comparator x interrupt is disabled.
1The Comparator x interrupt is enabled.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1076
40.8.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
WINx WINx COMPx COMPx COMPx COMPx
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5,4 – WINx Window x Interrupt Enable
Reading this bit returns the state of the Window x interrupt enable.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit enables the Window x interrupt.
Value Description
0The Window x interrupt is disabled.
1The Window x interrupt is enabled.
Bits 3,2,1,0 – COMPx Comparator x Interrupt Enable
Reading this bit returns the state of the Comparator x interrupt enable.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Ready interrupt bit and enable the Ready interrupt.
Value Description
0The Comparator x interrupt is disabled.
1The Comparator x interrupt is enabled.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1077
40.8.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x06
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
WINx WINx COMPx COMPx COMPx COMPx
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5,4 – WINx  Window x
This flag is set according to the Window x Interrupt Selection bit group in the WINCTRL register
(WINCTRL.WINTSELx) and will generate an interrupt if INTENCLR/SET.WINx is also one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Window x interrupt flag.
Bits 3,2,1,0 – COMPx Comparator x
Reading this bit returns the status of the Comparator x interrupt flag. If comparator x is not implemented,
COMPx always reads as zero.
This flag is set according to the Interrupt Selection bit group in the Comparator x Control register
(COMPCTRLx.INTSEL) and will generate an interrupt if INTENCLR/SET.COMPx is also one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit clears the Comparator x interrupt flag.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1078
40.8.7 Status A
Name:  STATUSA
Offset:  0x07
Reset:  0x00
Property:  Read-Only
Bit 7 6 5 4 3 2 1 0
WSTATE1[1:0] WSTATE0[1:0] STATEx STATEx STATEx STATEx
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 7:6 – WSTATE1[1:0] Window 1 Current State
These bits show the current state of the signal if the window 1 mode is enabled.
Value Name Description
0x0 ABOVE Signal is above window
0x1 INSIDE Signal is inside window
0x2 BELOW Signal is below window
0x3 Reserved
Bits 5:4 – WSTATE0[1:0] Window 0 Current State
These bits show the current state of the signal if the window 0 mode is enabled.
Value Name Description
0x0 ABOVE Signal is above window
0x1 INSIDE Signal is inside window
0x2 BELOW Signal is below window
0x3 Reserved
Bits 3,2,1,0 – STATEx Comparator x Current State
This bit shows the current state of the output signal from COMPx. STATEx is valid only when
STATUSB.READYx is one.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1079
40.8.8 Status B
Name:  STATUSB
Offset:  0x08
Reset:  0x00
Property:  Read-Only
Bit 7 6 5 4 3 2 1 0
READYx READYx READYx READYx
Access R R R R
Reset 0 0 0 0
Bits 3,2,1,0 – READYx Comparator x Ready
This bit is cleared when the comparator x output is not ready.
This bit is set when the comparator x output is ready.
If comparator x is not implemented, READYx always reads as zero.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
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40.8.9 Debug Control
Name:  DBGCTRL
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bits controls the functionality when the CPU is halted by an external debugger.
Value Description
0The AC is halted when the CPU is halted by an external debugger. Any on-going comparison
will complete.
1The AC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1081
40.8.10 Window Control
Name:  WINCTRL
Offset:  0x0A
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
WINTSEL1[1:0] WEN1 WINTSEL0[1:0] WEN0
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 6:5 – WINTSEL1[1:0] Window 1 Interrupt Selection
These bits configure the interrupt mode for the comparator window 1 mode.
Value Name Description
0x0 ABOVE Interrupt on signal above window
0x1 INSIDE Interrupt on signal inside window
0x2 BELOW Interrupt on signal below window
0x3 OUTSIDE Interrupt on signal outside window
Bit 4 – WEN1 Window 1 Mode Enable
Value Description
0Window mode is disabled for comparators 2 and 3.
1Window mode is enabled for comparators 2 and 3.
Bits 2:1 – WINTSEL0[1:0] Window 0 Interrupt Selection
These bits configure the interrupt mode for the comparator window 0 mode.
Value Name Description
0x0 ABOVE Interrupt on signal above window
0x1 INSIDE Interrupt on signal inside window
0x2 BELOW Interrupt on signal below window
0x3 OUTSIDE Interrupt on signal outside window
Bit 0 – WEN0 Window 0 Mode Enable
Value Description
0Window mode is disabled for comparators 0 and 1.
1Window mode is enabled for comparators 0 and 1.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1082
40.8.11 Scaler n
Name:  SCALERn
Offset:  0x0C + n*0x01 [n=0..3]
Reset:  0x00
Property:  Write-Protected
Bit 7 6 5 4 3 2 1 0
VALUE[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 5:0 – VALUE[5:0] Scaler Value
These bits define the scaling factor for channel n of the VDD voltage scaler. The output voltage, VSCALE,
is:
SCALE =DD VALUE+1
64
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1083
40.8.12 Comparator Control n
Name:  COMPCTRL
Offset:  0x10 + n*0x04 [n=0..3]
Reset:  0x00000000
Property:  PAC Write-Protection, Write-Synchronized
Bit 31 30 29 28 27 26 25 24
OUT[1:0] FLEN[2:0]
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bit 23 22 21 20 19 18 17 16
HYSTEN SPEED[1:0]
Access R/W R/W R/W
Reset 0 0 0
Bit 15 14 13 12 11 10 9 8
SWAP MUXPOS[2:0] MUXNEG[2:0]
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
RUNSTDBY INTSEL[1:0] SINGLE ENABLE
Access R/W R/W R/W R/W R/W
Reset 0 0 0 0 0
Bits 29:28 – OUT[1:0] Output
These bits configure the output selection for comparator n. COMPCTRLn.OUT can be written only while
COMPCTRLn.ENABLE is zero.
Note:  For internal use of the comparison results by the CCL, this bit must be 0x1 or 0x2.
These bits are not synchronized.
Value Name Description
0x0 OFF The output of COMPn is not routed to the COMPn I/O port
0x1 ASYNC The asynchronous output of COMPn is routed to the COMPn I/O port
0x2 SYNC The synchronous output (including filtering) of COMPn is routed to the COMPn I/O
port
0x3 N/A Reserved
Bits 26:24 – FLEN[2:0] Filter Length
These bits configure the filtering for comparator n. COMPCTRLn.FLEN can only be written while
COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Name Description
0x0 OFF No filtering
0x1 MAJ3 3-bit majority function (2 of 3)
0x2 MAJ5 5-bit majority function (3 of 5)
0x3-0x7 N/A Reserved
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1084
Bit 19 – HYSTEN Hysteresis Enable
This bit indicates the hysteresis mode of comparator n. Hysteresis is available only for continuous mode
(COMPCTRLn.SINGLE=0).
This bit is not synchronized.
Value Description
0Hysteresis is disabled.
1Hysteresis is enabled.
Bits 17:16 – SPEED[1:0] Speed Selection
This bit indicates the speed/propagation delay mode of comparator n. COMPCTRLn.SPEED can be
written only while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Name Description
0x0 LOW Low speed
0x3 HIGH High speed
Bit 15 – SWAP Swap Inputs and Invert
This bit swaps the positive and negative inputs to COMPn and inverts the output. This function can be
used for offset cancellation. COMPCTRLn.SWAP can be written only while COMPCTRLn.ENABLE is
zero.
These bits are not synchronized.
Value Description
0The output of MUXPOS connects to the positive input, and the output of MUXNEG connects
to the negative input.
1The output of MUXNEG connects to the positive input, and the output of MUXPOS connects
to the negative input.
Bits 14:12 – MUXPOS[2:0] Positive Input Mux Selection
These bits select which input will be connected to the positive input of comparator n.
COMPCTRLn.MUXPOS can be written only while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Name Description
0x0 PIN0 I/O pin 0
0x1 PIN1 I/O pin 1
0x2 PIN2 I/O pin 2
0x3 PIN3 I/O pin 3
0x4 VSCALE VDD scaler
0x5–0x7 Reserved
Bits 10:8 – MUXNEG[2:0] Negative Input Mux Selection
These bits select which input will be connected to the negative input of comparator n.
COMPCTRLn.MUXNEG can only be written while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Name Description
0x0 PIN0 I/O pin 0
0x1 PIN1 I/O pin 1
0x2 PIN2 I/O pin 2
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1085
Value Name Description
0x3 PIN3 I/O pin 3
0x4 GND Ground
0x5 VSCALE VDD scaler
0x6 BANDGAP Internal bandgap voltage
0x7 DAC DAC output
Bit 6 – RUNSTDBY Run in Standby
This bit controls the behavior of the comparator during standby sleep mode.
This bit is not synchronized
Value Description
0The comparator is disabled during sleep.
1The comparator continues to operate during sleep.
Bits 4:3 – INTSEL[1:0] Interrupt Selection
These bits select the condition for comparator n to generate an interrupt or event. COMPCTRLn.INTSEL
can be written only while COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Name Description
0x0 TOGGLE Interrupt on comparator output toggle
0x1 RISING Interrupt on comparator output rising
0x2 FALLING Interrupt on comparator output falling
0x3 EOC Interrupt on end of comparison (single-shot mode only)
Bit 2 – SINGLE Single-Shot Mode
This bit determines the operation of comparator n. COMPCTRLn.SINGLE can be written only while
COMPCTRLn.ENABLE is zero.
These bits are not synchronized.
Value Description
0Comparator n operates in continuous measurement mode.
1Comparator n operates in single-shot mode.
Bit 1 – ENABLE Enable
Writing a zero to this bit disables comparator n.
Writing a one to this bit enables comparator n.
Due to synchronization, there is delay from updating the register until the comparator is enabled/disabled.
The value written to COMPCTRLn.ENABLE will read back immediately after being written.
SYNCBUSY.COMPCTRLn is set. SYNCBUSY.COMPCTRLn is cleared when the peripheral is enabled/
disabled.
Writing a one to COMPCTRLn.ENABLE will prevent further changes to the other bits in COMPCTRLn.
These bits remain protected until COMPCTRLn.ENABLE is written to zero and the write is synchronized.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1086
40.8.13 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x20
Reset:  0x00000000
Property:  Read-Only
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
COMPCTRLx COMPCTRLx COMPCTRLx COMPCTRLx WINCTRL ENABLE SWRST
Access R R R R R R R
Reset 0 0 0 0 0 0 0
Bits 6,5,4,3 – COMPCTRLx COMPCTRLx Synchronization Busy
This bit is cleared when the synchronization of the COMPCTRLx register between the clock domains is
complete.
This bit is set when the synchronization of the COMPCTRLx register between clock domains is started.
Bit 2 – WINCTRL WINCTRL Synchronization Busy
This bit is cleared when the synchronization of the WINCTRL register between the clock domains is
complete.
This bit is set when the synchronization of the WINCTRL register between clock domains is started.
Bit 1 – ENABLE Enable Synchronization Busy
This bit is cleared when the synchronization of the CTRLA.ENABLE bit between the clock domains is
complete.
This bit is set when the synchronization of the CTRLA.ENABLE bit between clock domains is started.
Bit 0 – SWRST Software Reset Synchronization Busy
This bit is cleared when the synchronization of the CTRLA.SWRST bit between the clock domains is
complete.
This bit is set when the synchronization of the CTRLA.SWRST bit between clock domains is started.
SAM C20/C21 Family Data Sheet
AC – Analog Comparators
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1087
41. DAC – Digital-to-Analog Converter
41.1 Overview
The Digital-to-Analog Converter (DAC) converts a digital value to a voltage. The DAC has one channel
with 10-bit resolution, and it is capable of converting up to 350,000 samples per second (350ksps).
41.2 Features
• DAC with 10-bit resolution
• Up to 350ksps conversion rate
• Hardware support for 14-bit using dithering
• Multiple trigger sources
• High-drive capabilities
• Output can be used as input to the Analog Comparator (AC), ADC or SDADC
• DMA support
41.3 Block Diagram
Figure 41-1. DAC Block Diagram
DATABUF
DATA
DAC Controller
DAC10 VOUT
VREFA
Internal input
VDDANA
Ref.voltage (VREF)
Output
Buffer
41.4 Signal Description
Signal Name Type Description
VOUT Analog output DAC output
VREFA Analog input External reference
Related Links
6. I/O Multiplexing and Considerations
41.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1088
41.5.1 I/O Lines
Using the DAC Controller’s I/O lines requires the I/O pins to be configured using the port configuration
(PORT).
Related Links
28. PORT - I/O Pin Controller
41.5.2 Power Management
The DAC will continue to operate in any Sleep mode where the selected source clock is running.
The DAC interrupts can be used to wake up the device from sleep modes.
Events connected to the event system can trigger other operations in the system without exiting sleep
modes.
Related Links
19. PM – Power Manager
41.5.3 Clocks
The DAC bus clock (CLK_DAC_APB) can be enabled and disabled by the Main Clock module, and the
default state of CLK_DAC_APB can be found in the Peripheral Clock Masking section.
A generic clock (GCLK_DAC) is required to clock the DAC Controller. This clock must be configured and
enabled in the Generic Clock Controller before using the DAC Controller. Refer to GCLK – Generic Clock
Controller for details.
This generic clock is asynchronous to the bus clock (CLK_DAC_APB). Due to this asynchronicity, writes
to certain registers will require synchronization between the clock domains. Refer to 41.6.7
Synchronization for further details.
Related Links
16. GCLK - Generic Clock Controller
41.5.4 DMA
The DMA request line is connected to the DMA Controller (DMAC). Using the DAC Controller DMA
requests requires to configure the DMAC first.
Related Links
25. DMAC – Direct Memory Access Controller
41.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the DAC Controller interrupt(s)
requires the interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
41.5.6 Events
The events are connected to the Event System.
Related Links
29. EVSYS – Event System
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1089
41.5.7 Debug Operation
When the CPU is halted in debug mode the DAC will halt normal operation. Any on-going conversions will
be completed. The DAC can be forced to continue normal operation during debugging. If the DAC is
configured in a way that requires it to be periodically serviced by the CPU through interrupts or similar,
improper operation or data loss may result during debugging.
41.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except the following registers:
• Interrupt Flag Status and Clear (INTFLAG) register
• Data Buffer (DATABUF) register
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
PAC write-protection does not apply to accesses through an external debugger
Related Links
11. PAC - Peripheral Access Controller
41.5.9 Analog Connections
The DAC has one output pin (VOUT) and one analog input pin (VREFA) that must be configured first.
When internal input is used, it must be enabled before DAC Controller is enabled.
41.6 Functional Description
41.6.1 Principle of Operation
The DAC converts the digital value located in the Data register (DATA) into an analog voltage on the DAC
output (VOUT).
A conversion is started when new data is written to the Data register. The resulting voltage is available on
the DAC output after the conversion time. A conversion can also be started by input events from the
Event System.
41.6.2 Basic Operation
41.6.2.1 Initialization
The following registers are enable-protected, meaning they can only be written when the DAC is disabled
(CTRLA.ENABLE is zero):
• Control B register (CTRLB)
• Event Control register (EVCTRL)
Enable-protection is denoted by the Enable-Protected property in the register description.
Before enabling the DAC, it must be configured by selecting the voltage reference using the Reference
Selection bits in the Control B register (CTRLB.REFSEL).
41.6.2.2 Enabling, Disabling and Resetting
The DAC Controller is enabled by writing a '1' to the Enable bit in the Control A register
(CTRLA.ENABLE). The DAC Controller is disabled by writing a '0' to CTRLA.ENABLE.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1090
The DAC Controller is reset by writing a '1' to the Software Reset bit in the Control A register
(CTRLA.SWRST). All registers in the DAC will be reset to their initial state, and the DAC Controller will be
disabled. Refer to the CTRLA register for details.
41.6.2.3 Enabling the Output Buffer
To enable the DAC output on the VOUT pin, the output driver must be enabled by writing a one to the
External Output Enable bit in the Control B register (CTRLB.EOEN).
The DAC output buffer provides a high-drive-strength output, and is capable of driving both resistive and
capacitive loads. To minimize power consumption, the output buffer should be enabled only when
external output is needed.
41.6.2.4 Digital to Analog Conversion
The DAC converts a digital value (stored in the DATA register) into an analog voltage. The conversion
range is between GND and the selected DAC voltage reference. The default voltage reference is the
internal reference voltage. Other voltage reference options are the analog supply voltage (VDDANA) and
the external voltage reference (VREFA). The voltage reference is selected by writing to the Reference
Selection bits in the Control B register (CTRLB.REFSEL).
The output voltage from the DAC can be calculated using the following formula:
OUT =DATA
03FF VREF
A new conversion starts as soon as a new value is loaded into DATA. DATA can either be loaded via the
APB bus during a CPU write operation, using DMA, or from the DATABUF register when a START event
occurs. Refer to 41.6.5 Events for details. As there is no automatic indication that a conversion is done,
the sampling period must be greater than or equal to the specified conversion time.
41.6.3 DMA Operation
The DAC generates the following DMA request:
• Data Buffer Empty (EMPTY): The request is set when data is transferred from DATABUF to the
internal data buffer of DAC. The request is cleared when DATABUF register is written, or by writing a
one to the EMPTY bit in the Interrupt Flag register (INTFLAG.EMPTY).
For each Start Conversion event, DATABUF is transferred into DATA and the conversion starts. When
DATABUF is empty, the DAC generates the DMA request for new data. As DATABUF is initially empty, a
DMA request is generated whenever the DAC is enabled.
If the CPU accesses the registers that are the source of a DMA request set/clear condition, the DMA
request can be lost or the DMA transfer can be corrupted, if enabled.
41.6.4 Interrupts
The DAC Controller has the following interrupt sources:
• Data Buffer Empty (EMPTY): Indicates that the internal data buffer of the DAC is empty.
• Underrun (UNDERRUN): Indicates that the internal data buffer of the DAC is empty and a DAC start
of conversion event occurred. Refer to 41.6.5 Events for details.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear register (INTFLAG) is set when the interrupt condition occurs. Each interrupt can be
individually enabled by writing a one to the corresponding bit in the Interrupt Enable Set register
(INTENSET), and disabled by writing a one to the corresponding bit in the Interrupt Enable Clear register
(INTENCLR).
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1091
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled or the DAC
is reset. See INTFLAG register for details on how to clear interrupt flags.
All interrupt requests from the peripheral are ORed together on system level to generate one combined
interrupt request to the NVIC. The user must read the INTFLAG register to determine which interrupt
condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated..
Related Links
10.2 Nested Vector Interrupt Controller
41.6.5 Events
The DAC Controller can generate the following output events:
• Data Buffer Empty (EMPTY): Generated when the internal data buffer of the DAC is empty. Refer to
DMA Operation for details.
Writing a '1' to an Event Output bit in the Event Control register (EVCTRL.EMPTYEO) enables the
corresponding output event. Writing a '0' to this bit disables the corresponding output event.
The DAC can take the following action on an input event:
• Start Conversion (START): DATABUF value is transferred into DATA as soon as the DAC is ready for
the next conversion, and then conversion is started. START is considered as asynchronous to
GCLK_DAC thus it is resynchronized in DAC Controller. Refer to 41.6.2.4 Digital to Analog
Conversion for details.
Writing a '1' to an Event Input bit in the Event Control register (EVCTRL.STARTEI) enables the
corresponding action on an input event. Writing a '0' to this bit disables the corresponding action on input
event.
Note: When several events are connected to the DAC Controller, the enabled action will be taken on any
of the incoming events.
By default, DAC Controller detects rising edge events. Falling edge detection can be enabled by writing a
'1' to EVCTRL.INVEIx.
Related Links
29. EVSYS – Event System
41.6.6 Sleep Mode Operation
The generic clock for the DAC is running in idle sleep mode. If the Run In Standby bit in the Control A
register (CTRLA.RUNSTDBY) is one, the DAC output buffer will keep its value in standby sleep mode. If
CTRLA.RUNSTDBY is zero, the DAC output buffer will be disabled in standby sleep mode.
41.6.7 Synchronization
Due to the asynchronicity between main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read. A register can require:
• Synchronization when written
• Synchronization when read
• Synchronization when written and read
• No synchronization
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1092
When executing an operation that requires synchronization, the corresponding status bit in the
Synchronization Busy register (SYNCBUSY) will be set immediately, and cleared when synchronization is
complete.
If an operation that requires synchronization is executed while its busy bit is one, the operation is
discarded and an error is generated.
The following bits need synchronization when written:
• Software Reset bit in the Control A register (CTRLA.SWRST)
• Enable bit in the Control A register (CTRLA.ENABLE)
• All bits in the Data register (DATA)
• All bits in the Data Buffer register (DATABUF)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
No bits need synchronization when read.
41.6.8 Additional Features
41.6.8.1 DAC as an Internal Reference
The DAC output can be internally enabled as input to the analog comparator. This is enabled by writing a
one to the Internal Output Enable bit in the Control B register (CTRLB.IOEN). It is possible to have the
internal and external output enabled simultaneously.
The DAC output can also be enabled as input to the Analog-to-Digital Converter. In this case, the output
buffer must be enabled.
41.6.8.2 Data Buffer
The Data Buffer register (DATABUF) and the Data register (DATA) are linked together to form a two-stage
FIFO. The DAC uses the Start Conversion event to load data from DATABUF into DATA and start a new
conversion. The Start Conversion event is enabled by writing a one to the Start Event Input bit in the
Event Control register (EVCTRL.STARTEI). If a Start Conversion event occurs when DATABUF is empty,
an Underrun interrupt request is generated if the Underrun interrupt is enabled.
The DAC can generate a Data Buffer Empty event when DATABUF becomes empty and new data can be
loaded to the buffer. The Data Buffer Empty event is enabled by writing a one to the Empty Event Output
bit in the Event Control register (EVCTRL.EMPTYEO). A Data Buffer Empty interrupt request is
generated if the Data Buffer Empty interrupt is enabled.
41.6.8.3 Voltage Pump
When the DAC is used at operating voltages lower than 2.5V, the voltage pump must be enabled. This
enabling is done automatically, depending on operating voltage.
The voltage pump can be disabled by writing a one to the Voltage Pump Disable bit in the Control B
register (CTRLB.VPD). This can be used to reduce power consumption when the operating voltage is
above 2.5V.
The voltage pump uses the asynchronous GCLK_DAC clock, and requires that the clock frequency be at
least four times higher than the sampling period.
41.6.8.4 Dithering mode
Dithering is enabled by setting CTRLB.DITHER to 1. In dithering mode, DATA is a 14-bit unsigned value
where DATA[13:4] is the 10-bit data converted by DAC and DATA[3:0] represents the dither bits, used for
minimizing the quantization error. The principle is to make 16 sub-conversions of the DATA[13:4] value or
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1093
the (DATA[13:4] + 1) value, so that by averaging those values, the conversion result of the 14-bit value
(DATA[13:0]) has improved accuracy due to minimized quantization error.
To use the dithering feature, EVSYS is used for generating a periodic STARTEI. And the STARTEI event
must be configured (EVCTRL.STARTEI = 1) to generate 16 events for each DATA[13:0] conversion, and
DATABUFx must be loaded every 16 DAC conversions. EMPTYx event and DMA request are therefore
generated every 16 DATABUF to DATA transfer. Using the DMA with dithering is optional. If the DMA is
not used, it is required to poll the INTFLAG.EMTPY flag, or use an interrupt on EMPTY to add a new
value in DATABUF.
Note that the input value for DAC is positioned in the DATA register based on CTRLB.LEFTADJ as shown
in the following figure. Refer to 41.8.8 DATA register description for further details. If LEFTADJ = 0: the
user writes DATA[13:4], and the dithering function will take care of bit DATA[3:0] during the 16 sub-
conversions.
If LEFTADJ = 1: the user writes DATA[15:6], and the dithering function will take care of bit DATA[5:2]
during the 16 sub-conversions.
Following timing diagram shows examples with DATA[15:0] = 0x1210 then DATA[15:0] = 0x12E0 and
CTRLB.LEFTADJ=1.
Figure 41-2. DAC Conversions in Dithering Mode (CTRLB.LEFTADJ=1)
DATA [15:0]
0x1300
0x12C0
0x1240
0x1200 0x1210
0x12E0
VOUT0
sub-conversion 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1094
41.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 RUNSTDBY ENABLE SWRST
0x01 CTRLB 7:0 REFSEL[1:0] DITHER VPD LEFTADJ IOEN EOEN
0x02 EVCTRL 7:0 INVEI EMPTYEO STARTEI
0x03 Reserved
0x04 INTENCLR 7:0 EMPTY UNDERRUN
0x05 INTENSET 7:0 EMPTY UNDERRUN
0x06 INTFLAG 7:0 EMPTY UNDERRUN
0x07 STATUS 7:0 READY
0x08 DATA
7:0 DATA[7:0]
15:8 DATA[15:8]
0x0A
...
0x0B
Reserved
0x0C DATABUF
7:0 DATABUF[7:0]
15:8 DATABUF[15:8]
0x0E
...
0x0F
Reserved
0x10 SYNCBUSY
7:0 DATABUF DATA ENABLE SWRST
15:8
23:16
31:24
0x14
...
0x17
Reserved
0x18 DBGCTRL 7:0 DBGRUN
41.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16- and 32-bit accesses are supported. In addition, the
8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
For details, refer to 41.5.8 Register Access Protection.
Some registers are synchronized when read and/or written. Synchronization is denoted by the "Write-
Synchronized" or the "Read-Synchronized" property in each individual register description. For details,
refer to 41.6.7 Synchronization.
Some registers are enable-protected, meaning they can only be written when the peripheral is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1095
41.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized
Bit 7 6 5 4 3 2 1 0
RUNSTDBY ENABLE SWRST
Access R/W R/W R/W
Reset 0 0 0
Bit 6 – RUNSTDBY Run in Standby
This bit is not synchronized
Value Description
0The DAC output buffer is disabled in standby sleep mode.
1The DAC output buffer can be enabled in standby sleep mode.
Bit 1 – ENABLE Enable DAC Controller
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the corresponding bit in
the Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be
cleared when the operation is complete.
Value Description
0The peripheral is disabled or being disabled.
1The peripheral is enabled or being enabled.
Bit 0 – SWRST Software Reset
Writing '0' to this bit has no effect.
Writing '1' to this bit resets all registers in the DAC to their initial state, and the DAC will be disabled.
Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1096
41.8.2 Control B
Name:  CTRLB
Offset:  0x01
Reset:  0x00
Property:  PAC Write-Protection, Enable-Protected
Bit 7 6 5 4 3 2 1 0
REFSEL[1:0] DITHER VPD LEFTADJ IOEN EOEN
Access R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 7:6 – REFSEL[1:0] Reference Selection
This bit field selects the Reference Voltage for the DAC.
Value Name Description
0x0 INTREF Internal voltage reference
0x1 VDDANA Analog voltage supply
0x2 VREFA External reference
0x3 Reserved
Bit 5 – DITHER Dithering Mode
This bit controls dithering operation according to 41.6.8.4 Dithering mode.
Value Description
0Dithering mode is disabled.
1Dithering mode is enabled.
Bit 3 – VPD Voltage Pump Disabled
This bit controls the behavior of the voltage pump.
Value Description
0Voltage pump is turned on/off automatically
1Voltage pump is disabled.
Bit 2 – LEFTADJ Left-Adjusted Data
This bit controls how the 10-bit conversion data is adjusted in the Data and Data Buffer registers.
Value Description
0DATA and DATABUF registers are right-adjusted.
1DATA and DATABUF registers are left-adjusted.
Bit 1 – IOEN Internal Output Enable
Value Description
0Internal DAC output not enabled.
1Internal DAC output enabled to be used by the AC or ADC.
Bit 0 – EOEN External Output Enable
Value Description
0The DAC output is turned off.
1The high-drive output buffer drives the DAC output to the VOUT pin.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1097
41.8.3 Event Control
Name:  EVCTRL
Offset:  0x02
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
INVEI EMPTYEO STARTEI
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – INVEI Enable Inversion Data Buffer Empty Event Output
This bit defines the edge detection of the input event for STARTEI.
Value Description
0Rising edge.
1Falling edge.
Bit 1 – EMPTYEO Data Buffer Empty Event Output
This bit indicates whether or not the Data Buffer Empty event is enabled and will be generated when the
Data Buffer register is empty.
Value Description
0Data Buffer Empty event is disabled and will not be generated.
1Data Buffer Empty event is enabled and will be generated.
Bit 0 – STARTEI Start Conversion Event Input
This bit indicates whether or not the Start Conversion event is enabled and data are loaded from the Data
Buffer register to the Data register upon event reception.
Value Description
0A new conversion will not be triggered on any incoming event.
1A new conversion will be triggered on any incoming event.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1098
41.8.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set register (INTENSET).
Bit 7 6 5 4 3 2 1 0
EMPTY UNDERRUN
Access R/W R/W
Reset 0 0
Bit 1 – EMPTY Data Buffer Empty Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Data Buffer Empty Interrupt Enable bit, which disables the Data Buffer
Empty interrupt.
Value Description
0The Data Buffer Empty interrupt is disabled.
1The Data Buffer Empty interrupt is enabled.
Bit 0 – UNDERRUN Underrun Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Data Buffer Underrun Interrupt Enable bit, which disables the Data
Buffer Underrun interrupt.
Value Description
0The Data Buffer Underrun interrupt is disabled.
1The Data Buffer Underrun interrupt is enabled.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1099
41.8.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear register (INTENCLR).
Bit 7 6 5 4 3 2 1 0
EMPTY UNDERRUN
Access R/W R/W
Reset 0 0
Bit 1 – EMPTY Data Buffer Empty Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Data Buffer Empty Interrupt Enable bit, which enables the Data Buffer
Empty interrupt.
Value Description
0The Data Buffer Empty interrupt is disabled.
1The Data Buffer Empty interrupt is enabled.
Bit 0 – UNDERRUN Underrun Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Data Buffer Underrun Interrupt Enable bit, which enables the Data Buffer
Underrun interrupt.
Value Description
0The Data Buffer Underrun interrupt is disabled.
1The Data Buffer Underrun interrupt is enabled.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1100
41.8.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x06
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
EMPTY UNDERRUN
Access R/W R/W
Reset 0 0
Bit 1 – EMPTY Data Buffer Empty
This flag is cleared by writing a '1' to it or by writing new data to DATABUF.
This flag is set when data is transferred from DATABUF to DATA, and the DAC is ready to receive new
data in DATABUF, and will generate an interrupt request if INTENCLR/SET.EMPTY is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Data Buffer Empty interrupt flag.
Bit 0 – UNDERRUN Underrun
This flag is cleared by writing a '1' to it.
This flag is set when a start conversion event occurs when DATABUF is empty, and will generate an
interrupt request if INTENCLR/SET.UNDERRUN is one.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Underrun interrupt flag.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1101
41.8.7 Status
Name:  STATUS
Offset:  0x07
Reset:  0x00
Property:  -
Bit 7 6 5 4 3 2 1 0
READY
Access R
Reset 0
Bit 0 – READY DAC Ready
Value Description
0DAC is not ready for conversion.
1Startup time has elapsed, DAC is ready for conversion.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1102
41.8.8 Data DAC
Name:  DATA
Offset:  0x08
Reset:  0x0000
Property:  PAC Write-Protection, Write-Synchronized
Bit 15 14 13 12 11 10 9 8
DATA[15:8]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DATA[7:0]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – DATA[15:0] Data value to be converted
DATA register contains the 10-bit value that is converted to a voltage by the DAC. The adjustment of
these 10 bits within the 16-bit register is controlled by CTRLB.LEFTADJ.
Four additional bits are also used for the dithering feature according to 41.6.8.4 Dithering mode.
Table 41-1. Valid Data Bits
CTRLB.DITHER CTRLB.LEFTADJ DATA Description
0 0 DATA[9:0] Right adjusted, 10-bits
0 1 DATA[15:6] Left adjusted, 10-bits
1 0 DATA[13:4], DATA[3:0] Right adjusted, 14-bits
1 1 DATA[15:6], DATA[5:2] Left adjusted, 14-bits
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1103
41.8.9 Data Buffer
Name:  DATABUF
Offset:  0x0C
Reset:  0x0000
Property:  Write-Synchronized
Bit 15 14 13 12 11 10 9 8
DATABUF[15:8]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DATABUF[7:0]
Access W W W W W W W W
Reset 0 0 0 0 0 0 0 0
Bits 15:0 – DATABUF[15:0] Data Buffer
DATABUF contains the value to be transferred into DATA register.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1104
41.8.10 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x10
Reset:  0x00000000
Property:  -
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
DATABUF DATA ENABLE SWRST
Access R R R R
Reset 0 0 0 0
Bit 3 – DATABUF Data Buffer DAC0
This bit is set when DATABUF register is written.
This bit is cleared when DATABUF synchronization is completed.
Value Description
0No ongoing synchronized access.
1Synchronized access is ongoing.
Bit 2 – DATA Data
This bit is set when DATA register is written.
This bit is cleared when DATA synchronization is completed.
Value Description
0No ongoing synchronized access.
1Synchronized access is ongoing.
Bit 1 – ENABLE DAC Enable Status
This bit is set when CTRLA.ENABLE bit is written.
This bit is cleared when CTRLA.ENABLE synchronization is completed.
Value Description
0No ongoing synchronization.
1Synchronization is ongoing.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1105
Bit 0 – SWRST Software Reset
This bit is set when CTRLA.SWRST bit is written.
This bit is cleared when CTRLA.SWRST synchronization is completed.
Value Description
0No ongoing synchronization.
1Synchronization is ongoing.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1106
41.8.11 Debug Control
Name:  DBGCTRL
Offset:  0x18
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bits controls the functionality when the CPU is halted by an external debugger.
Value Description
0The DAC is halted when the CPU is halted by an external debugger. Any ongoing conversion
will complete.
1The DAC continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1107
42. Peripheral Touch Controller (PTC)
42.1 Overview
The Peripheral Touch Controller (PTC) acquires signals in order to detect a touch on the capacitive
sensors. The external capacitive touch sensor is typically formed on a PCB, and the sensor electrodes
are connected to the analog front end of the PTC through the I/O pins in the device. The PTC supports
both self and mutual capacitance sensors.
In the Mutual Capacitance mode, sensing is done using capacitive touch matrices in various X-Y
configurations, including indium tin oxide (ITO) sensor grids. The PTC requires one pin per X-line and one
pin per Y-line.
In the Self Capacitance mode, the PTC requires only one pin (Y-line) for each touch sensor.
The number of available pins and the assignment of X- and Y-lines is depending on both package type
and device configuration. Refer to the Configuration Summary and I/O Multiplexing table for details.
Related Links
1. Configuration Summary
6. I/O Multiplexing and Considerations
42.2 Features
• Low-Power, High-Sensitivity, Environmentally Robust Capacitive Touch Buttons, Sliders, and Wheels
• Supports Wake-up on Touch from standby Sleep mode
• Supports Mutual Capacitance and Self Capacitance Sensing
– Mix-and-Match Mutual and Self Capacitance Sensors
• One Pin per Electrode – No External Components
• Load Compensating Charge Sensing
– Parasitic capacitance compensation and adjustable gain for superior sensitivity
• Zero Drift Over the Temperature and VDD Range
– Auto calibration and recalibration of sensors
• Single-shot Charge Measurement
• Hardware Noise Filtering and Noise Signal Desynchronization for High Conducted Immunity
• Selectable channel change delay allows choosing the settling time on a new channel, as required
• Acquisition-start triggered by command or through auto-triggering feature
• Low CPU utilization through interrupt on acquisition-complete
Related Links
1. Configuration Summary
6. I/O Multiplexing and Considerations
42.3 Block Diagram
Figure 42-1. PTC Block Diagram Mutual Capacitance
Note:  For SAM C20/C21 the RS = 0, 20, 50, 100 KΩ.
SAM C20/C21 Family Data Sheet
Peripheral Touch Controller (PTC)
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1108
Figure 42-2. PTC Block Diagram Self Capacitance
Note:  For SAM C20/C21 the RS = 0, 20, 50, 100 KΩ.
42.4 Signal Description
Table 42-1. Signal Description for PTC
Name Type Description
Y[m:0] Analog Y-line (Input/Output)
X[n:0] Digital X-line (Output)
Note:  The number of X- and Y-lines are device dependent. Refer to Configuration Summary for details.
Refer to I/O Multiplexing and Considerations for details on the pin mapping for this peripheral. One signal
can be mapped on several pins.
Related Links
1. Configuration Summary
6. I/O Multiplexing and Considerations
42.5 System Dependencies
In order to use this peripheral, configure the other components of the system as described in the following
sections.
42.5.1 I/O Lines
The I/O lines used for analog X-lines and Y-lines must be connected to external capacitive touch sensor
electrodes. External components are not required for normal operation. However, to improve the EMC
performance, a series resistor of 1 kΩ or more can be used on X-lines and Y-lines.
42.5.1.1 Mutual Capacitance Sensor Arrangement
A mutual capacitance sensor is formed between two I/O lines - an X electrode for transmitting and Y
electrode for sensing. The mutual capacitance between the X and Y electrode is measured by the
peripheral touch controller.
SAM C20/C21 Family Data Sheet
Peripheral Touch Controller (PTC)
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1109
Figure 42-3. Mutual Capacitance Sensor Arrangement
PTC
Module
MCU
X0
Xn
Y0
Ym
X1
Y1
Sensor Capacitance Cx,y
Cx0,y0 Cx0,y1 Cx0,ym
Cx1,y0 Cx1,y1 Cx1,ym
Cxn,y0 Cxn,y1 Cxn,ym
PTC
Module
42.5.1.2 Self Capacitance Sensor Arrangement
A self capacitance sensor is connected to a single pin on the peripheral touch controller through the Y
electrode for sensing the signal. The sense electrode capacitance is measured by the peripheral touch
controller.
Figure 42-4. Self-Capacitance Sensor Arrangement
MCU
PTC
Module
Y0
Y1
Ym
Cy0
Cy1
Cym
Sensor Capacitance Cy
For more information about designing the touch sensor, refer to Buttons, Sliders and Wheels Touch
Sensor Design Guide.
SAM C20/C21 Family Data Sheet
Peripheral Touch Controller (PTC)
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1110
42.6 Functional Description
In order to access the PTC, the user must use the Atmel Start QTouch® Configurator to configure and link
the QTouch Library firmware with the application software. QTouch Library can be used to implement
buttons, sliders, and wheels in a variety of combinations on a single interface.
Figure 42-5. QTouch Library Usage
Custom Code Compiler
Link Application
QTouch
Library
For more information about QTouch Library, refer to the QTouch Library Peripheral Touch Controller User
Guide.
SAM C20/C21 Family Data Sheet
Peripheral Touch Controller (PTC)
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1111
43. TSENS – Temperature Sensor
43.1 Overview
The Temperature Sensor (TSENS) can be used to accurately measure the operating temperature of the
device.
Related Links
45.10.9 Temperature Sensor Characteristics
43.2 Features
• Accurately measures a temperature
• A selectable reference clock source
43.3 Block Diagram
Figure 43-1. Temperature Sensor Block Diagram.
TOSC
FCAL
GCLK_TSENS
GAIN
EN
ENABLE
EN
START
VALUE
INTFLAG
RESRDY
COUNTER
OFFSET
TIME AMPLIFIER
43.4 Signal Description
Not applicable.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1112
43.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
43.5.1 I/O Lines
Not applicable.
43.5.2 Power Management
The TSENS will continue to operate in any sleep mode where the selected source clock is running. The
TSENS’s interrupts can be used to wake up the device from sleep modes. Events connected to the event
system can trigger other operations in the system without exiting sleep modes. Refer to the Power
Manager chapter for details on the different sleep modes.
43.5.3 Clocks
The TSENS bus clock (CLK_TSENS_APB) can be enabled and disabled in the Main Clock module, and
the default state of CLK_TSENS_APB can be found in the Peripheral Clock Masking section.
A generic clock (GCLK_TSENS) is required to clock the TSENS. This clock must be configured and
enabled in the generic clock controller before using the TSENS.
This generic clock is asynchronous to the bus clock (CLK_TSENS_APB). Due to this asynchronicity,
writes to certain registers will require synchronization between the clock domains. Refer to 43.6.7
Synchronization for details.
Related Links
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
43.5.4 DMA
The DMA request line is connected to the DMA Controller (DMAC). Using the TSENS Controller DMA
request requires the DMA Controller to be configured first.
Related Links
25. DMAC – Direct Memory Access Controller
43.5.5 Interrupts
The interrupt request lines are connected to the interrupt controller. Using the TSENS interrupts requires
the interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
43.5.6 Events
The events are connected to the Event System. Refer to the Event System section for details on how to
configure the Event System.
Related Links
29. EVSYS – Event System
43.5.7 Debug Operation
When the CPU is halted in debug mode the TSENS will halt normal operation. Any on-going
measurements will be completed. The TSENS can be forced to continue operation during debugging.
Refer to 43.8.16 DBGCTRL for details.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1113
43.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC),
except the following registers:
• Control B (43.8.2 CTRLB) register
• Interrupt Flag Status and Clear (43.8.7 INTFLAG) register
Write-protection is denoted by the PAC Write-Protection property in the register description.
Write-protection does not apply to accesses through an external debugger. Refer to the Peripheral
Access Controller chapter for details.
43.5.9 Calibration
The GAIN, OFFSET, FCAL, and TCAL calibration values from the production test must be loaded from
the NVM Temperature Calibration Area into the TSENS Gain register (GAIN), Offset register (OFFSET)
and Calibration register (CAL) by software to achieve specified accuracy.
Related Links
9.4 NVM Software Calibration Area Mapping
45.10.9 Temperature Sensor Characteristics
43.6 Functional Description
43.6.1 Principle of Operation
The TSENS accurately measures the operating temperature of the device by comparing the difference in
two temperature dependent frequencies to a known frequency. The frequency of the temperature
dependent oscillator (TOSC) is measured twice: first with the min configuration and next with the max
configuration. The number of periods of GCLK_TSENS used for the measurement is defined by the GAIN
register. The width of the resulting pulse is measured using a counter clocked by GCLK_TSENS in the up
direction for the 1st phase and in the down 2nd phase.
The resulting signed value is proportional to the temperature and is corrected for offset by the contents of
the OFFSET register.
VALUE = OFFSET+GAIN × TOSCMIN
GCLK
+TOSCMAX
GCLK
Note: 
• The values of GAIN and OFFSET are factory programmed to give a specific temperature slope when
using the undivided internal 48MHz oscillator (OSC48M) as the GCLK_TSENS source. Other
frequencies/sources may be used, but the GAIN setting and/or expected slope will need to be scaled
accordingly.
• The calibration value should be copied and written into the GAIN and OFFSET registers to get the
specified accuracy.
Related Links
43.8.10 VALUE
43.6.2 Basic Operation
43.6.2.1 Initialization
The generic clocks (GCLK_TSENS) should be configured and enabled. Refer to the Generic Clock
Controller chapter for details.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1114
The following bits are enable-protected, meaning that they can only be written when the TSENS is
disabled (43.8.1 CTRLA.ENABLE is zero):
• Run in Standby bit in Control A register (43.8.1 CTRLA.RUNSTDBY)
The following registers are enable-protected:
• Control C (43.8.3 CTRLC)
• Event Control (43.8.4 EVCTRL)
• Window Monitor Lower Threhold (43.8.11 WINLT)
• Window Monitor Upper Threshold (43.8.12 WINUT)
• Gain Correction (43.8.13 GAIN)
• Offset Correction (43.8.14 OFFSET)
• Calibration (43.8.15 CAL)
Enable-protection is denoted by the Enable-Protected property in the register description.
43.6.2.2 Enabling, Disabling and Resetting
The TSENS is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The
TSENS is disabled by writing a zero to CTRLA.ENABLE.
The TSENS is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST).
All registers in the TSENS will be reset to their initial state, and the TSENS will be disabled. Refer to
43.8.1 CTRLA for details.
43.6.2.3 Measurement
After the TSENS is enabled, a measurement can be started either manually, by writing a one to the
START bit in Control B register (CTRLB.START), or automatically by configuring an event input. A free-
running mode can be used to continuously measure the temperature. When the Free running bit in the
Control C register (CTRLC.FREERUN) is written to one, there is no need for a trigger to start the
measurement. It will start automatically at the end of previous measurement.
The result of the measurement is stored in the Value register (VALUE), overwriting the result from the
previous measurement and setting the Result Ready flag in the Interrupt Flag Status and Clear register
(INTFLAG.RESRDY). To avoid data loss, the conversion result must be read as soon as it is available.
Failing to do so will result in an overrun error condition, indicated by the OVERRUN bit in the Interrupt
Flag Status and Clear register (INTFLAG.OVERRUN).
To use an interrupt handler, the corresponding bit in the Interrupt Enable Set register (INTENSET) must
be written to one.
To prevent any discrepancies in the temperature measurement, an average on 10 measurements is
recommended.
Related Links
43.8.10 VALUE
43.6.2.4 Window Monitor
The window monitor feature allows the measurement result in the VALUE register to be compared to
predefined threshold values. The window mode is selected by writing the Window Monitor Mode bits in
the Control C register (CTRLC.WINMODE). Threshold values must be written in the Window Monitor
Lower Threshold register (WINLT) and Window Monitor Upper Threshold register (WINUT).
43.6.3 DMA Operation
The TSENS generates the following DMA request:
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1115
• Result Ready (RESRDY): the request is set when a measurement result is available, and cleared
when the VALUE register is read. The request is generated independent of any Window Monitor
condition.
Related Links
25. DMAC – Direct Memory Access Controller
43.6.4 Interrupts
The TSENS has the following interrupt sources:
• Result Ready (RESRDY): Indicates when a measurement result is available.
• Window Monitor (WINMON): Generated when the measurement result matches the window monitor
condition. Refer to 43.8.3 CTRLC for details.
• Overrun (OVERRUN): Indicates that a new result is ready before the previous result has been read.
• Overflow (OVF): Indicates that the result is invalid because the result required more than 16 bits and
overflowed the VALUE register.
Each interrupt source has an interrupt flag associated with it. The interrupt flag in the Interrupt Flag Status
and Clear (INTFLAG) register is set when the interrupt condition occurs. Each interrupt can be
individually enabled by writing a one to the corresponding bit in the Interrupt Enable Set (INTENSET)
register, and disabled by writing a one to the corresponding bit in the Interrupt Enable Clear (INTENCLR)
register. An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is
enabled. The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or
the TSENS is reset. See 43.8.7 INTFLAG for details on how to clear interrupt flags. All interrupt requests
from the peripheral are ORed together on system level to generate one combined interrupt request to the
NVIC. The user must read the INTFLAG register to determine which interrupt condition is present.
Note that interrupts must be globally enabled for interrupt requests to be generated.
Related Links
10.2 Nested Vector Interrupt Controller
43.6.5 Events
The TSENS can generate the following output event:
• Window Monitor (WINMON): Generated when the measurement results matches the window monitor
condition. Refer to 43.8.3 CTRLC for details.
Writing a one to an Event Output bit in the Event Control Register (EVCTRL.WINEO) enables the
corresponding output event. Writing a zero to this bit disables the corresponding output event. Refer to
the Event System chapter for details on configuring the event system.
The TSENS can take the following action on an input event:
• Start measurement (START): Start a measurement. Refer to 43.8.2 CTRLB for details.
Writing a one to an Event Input bit into the Event Control register (EVCTRL.STARTEI) enables the
corresponding action on input event. Writing a zero to this bit disables the corresponding action on input
event. Refer to the Event System chapter for details. By default, the TSENS will detect a rising edge on
the incoming event. If the TSENS action must be performed on the falling edge of the incoming event, the
event line must be inverted first, by writing to one the corresponding Event Invert Enable bit in Event
Control register (EVCTRL.STARTINV).
Related Links
29. EVSYS – Event System
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1116
43.6.6 Sleep Mode Operation
The Run in Standby bit in the Control A register (43.8.1 CTRLA.RUNSTDBY) controls the behavior of the
TSENS during standby sleep mode, in cases where the TSENS is enabled (CTRLA.ENABLE = 1).
Table 43-1. TSENS Sleep Behavior
CTRLA.RUNSTDBY CTRLC.FREERUN CTRLA.ENABLE Description
x x 0 Disabled
0 0 1 Run in all sleep modes on request, except
STANDBY.
0 1 1 Run in all sleep modes, except
STANDBY.
1 0 1 Run in all sleep modes on request.
1 1 1 Run in all sleep modes.
43.6.7 Synchronization
Due to the asynchronicity between the main clock domain (CLK_TSENS_APB) and the peripheral clock
domain (GCLK_TSENS) some registers are synchronized when written. When a write-synchronized
register is written, the corresponding bit in the Synchronization Busy register (SYNCBUSY) is set
immediately. When the write-synchronization is complete, this bit is cleared. Reading a write-
synchronized register while the synchronization is ongoing will return the value written, and not the
current value in the peripheral clock domain. To read the current value in the peripheral clock domain
after writing a register, the user must wait for the corresponding SYNCBUSY bit to be cleared before
reading the value.
If an operation that require synchronization is executed while its busy bit is on, the operation is discarded
and a bus error is generated.
The following bits need synchronization when written:
• Software Reset bit in Control A register (43.8.1 CTRLA.SWRST)
• Enable bit in Control A register (43.8.1 CTRLA.ENABLE)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1117
43.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 RUNSTDBY ENABLE SWRST
0x01 CTRLB 7:0 START
0x02 CTRLC 7:0 FREERUN WINMODE[2:0]
0x03 EVCTRL 7:0 WINEO STARTINV STARTEI
0x04 INTENCLR 7:0 OVF WINMON OVERRUN RESRDY
0x05 INTENSET 7:0 OVF WINMON OVERRUN RESRDY
0x06 INTFLAG 7:0 OVF WINMON OVERRUN RESRDY
0x07 STATUS 7:0 OVF
0x08 SYNCBUSY
7:0 ENABLE SWRST
15:8
23:16
31:24
0x0C VALUE
7:0 VALUE[7:0]
15:8 VALUE[15:8]
23:16 VALUE[23:16]
31:24
0x10 WINLT
7:0 WINLT[7:0]
15:8 WINLT[15:8]
23:16 WINLT[23:16]
31:24
0x14 WINUT
7:0 WINUT[7:0]
15:8 WINUT[15:8]
23:16 WINUT[23:16]
31:24
0x18 GAIN
7:0 GAIN[7:0]
15:8 GAIN[15:8]
23:16 GAIN[23:16]
31:24
0x1C OFFSET
7:0 OFFSETC[7:0]
15:8 OFFSETC[15:8]
23:16 OFFSETC[23:16]
31:24
0x20 CAL
7:0 FCAL[5:0]
15:8 TCAL[5:0]
23:16
31:24
0x24 DBGCTRL 7:0 DBGRUN
43.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1118
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1119
43.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection, Write-Synchronized (ENABLE, SWRST)
Bit 7 6 5 4 3 2 1 0
RUNSTDBY ENABLE SWRST
Access R/W R/W R/W
Reset 0 0 0
Bit 6 – RUNSTDBY Run in Standby
This bit controls how the TSENS behaves during standby sleep mode:
This bit is not synchronized.
Value Description
0The TSENS is halted during standby sleep mode.
1The TSENS is not stopped in standby sleep mode. If CTRLC.FREERUN is zero, the TSENS
will be running when a peripheral is requesting it. If CTRLC.FREERUN is one, the TSENS
will always be running in standby sleep mode.
Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the ENABLE bit in the
Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared
when the operation is complete.
This bit is not enable-protected.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a zero to this bit has no effect.
Writing a one to this bit resets all registers in the TSENS, except GAIN, OFFSET, CAL and DBGCTRL, to
their initial state, and the TSENS will be disabled.
Writing a one to CTRLA.SWRST will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.
This bit is not enable-protected.
Value Description
0There is no reset operation ongoing.
1The reset operation is ongoing.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1120
43.8.2 Control B
Name:  CTRLB
Offset:  0x01
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
START
Access W
Reset 0
Bit 0 – START Start Measurement
Value Description
0Writing a zero to this bit has no effect.
1Writing a one to this bit starts a measurement
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1121
43.8.3 Control C
Name:  CTRLC
Offset:  0x02
Reset:  0x00
Property:  PAC Write-Protection, Enable-protected
Bit 7 6 5 4 3 2 1 0
FREERUN WINMODE[2:0]
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 4 – FREERUN Free Running Measurement
Value Description
0TSENS operates in single measurement mode.
1TSENS is in free running mode and a new measurement will be initiated when the previous
measurement completes.
Bits 2:0 – WINMODE[2:0] Window Monitor Mode
These bits enable and define the window monitor mode.
Value Name Description
0x0 DISABLE No window mode (default)
0x1 ABOVE VALUE > WINLT
0x2 BELOW VALUE < WINUT
0x3 INSIDE WINLT < VALUE < WINUT
0x4 OUTSIDE WINUT < VALUE < WINLT
0x5 HYST_ABOVE VALUE > WINUT with hysteresis to WINLT
0x6 HYST_BELOW VALUE < WINLT with hysteresis to WINUT
0x07 Reserved
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1122
43.8.4 Event Control
Name:  EVCTRL
Offset:  0x03
Reset:  0x00
Property:  PAC Write-Protection, Enable-protected
Bit 7 6 5 4 3 2 1 0
WINEO STARTINV STARTEI
Access R/W R/W R/W
Reset 0 0 0
Bit 2 – WINEO Window Monitor Event Out
This bit indicates whether the Window Monitor event output is enabled or not and an output event will be
generated when the window monitor detects something.
Value Description
0Window Monitor event output is disabled and an event will not be generated.
1Window Monitor event output is enabled and an event will be generated.
Bit 1 – STARTINV Start Conversion Event Invert Enable
Value Description
0start event input source is not inverted.
1start event input source is inverted.
Bit 0 – STARTEI Start Conversion Event Input Enable
Value Description
0A new conversion will not be triggered on any incoming event.
1A new conversion will be triggered on any incoming event.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1123
43.8.5 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x04
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to disable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Set (INTENSET) register.
Bit 7 6 5 4 3 2 1 0
OVF WINMON OVERRUN RESRDY
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 3 – OVF Overflow Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overflow Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The overflow interrupt is disabled.
1The overflow interrupt is enabled, and an interrupt request will be generated when the
Overflow interrupt flag is set.
Bit 2 – WINMON Window Monitor Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Window Monitor Interrupt Enable bit, which disables the
corresponding interrupt request.
Value Description
0The window monitor interrupt is disabled.
1The window monitor interrupt is enabled, and an interrupt request will be generated when the
Window Monitor interrupt flag is set.
Bit 1 – OVERRUN Overrun Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Overrun Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The Overrun interrupt is disabled.
1The Overrun interrupt is enabled, and an interrupt request will be generated when the
Overrun interrupt flag is set.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will clear the Result Ready Interrupt Enable bit, which disables the corresponding
interrupt request.
Value Description
0The Result Ready interrupt is disabled.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1124
Value Description
1The Result Ready interrupt is enabled, and an interrupt request will be generated when the
Result Ready interrupt flag is set.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1125
43.8.6 Interrupt Enable Set
Name:  INTENSET
Offset:  0x05
Reset:  0x00
Property:  PAC Write-Protection
This register allows the user to enable an interrupt without doing a read-modify-write operation. Changes
in this register will also be reflected in the Interrupt Enable Clear (INTENCLR) register.
Bit 7 6 5 4 3 2 1 0
OVF WINMON OVERRUN RESRDY
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 3 – OVF Overflow Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overflow Interrupt bit, which enables the Overflow interrupt.
Value Description
0The Overflow interrupt is disabled.
1The Overflow interrupt is enabled.
Bit 2 – WINMON Window Monitor Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Window Monitor Interrupt bit, which enables the Window Monitor
interrupt.
Value Description
0The Window Monitor interrupt is disabled.
1The Window Monitor interrupt is enabled.
Bit 1 – OVERRUN Overrun Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Overrun Interrupt Enable bit, which enables the corresponding
interrupt request.
Value Description
0The Overrun interrupt is disabled.
1The Overrun interrupt is enabled.
Bit 0 – RESRDY Result Ready Interrupt Enable
Writing a zero to this bit has no effect.
Writing a one to this bit will set the Result Ready Interrupt bit, which enables the Result Ready interrupt.
Value Description
0The Result Ready interrupt is disabled.
1The Result Ready interrupt is enabled.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1126
43.8.7 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x06
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
OVF WINMON OVERRUN RESRDY
Access R/W R/W R/W R/W
Reset 0 0 0 0
Bit 3 – OVF Overflow
This flag is cleared by writing a one to the flag.
This flag is set when the conversion result requires more than 24 bits and overflows the VALUE register,
and an interrupt request will be generated if INTENCLR/SET.OVF is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overflow interrupt flag.
Bit 2 – WINMON Window Monitor
This flag is cleared by writing a one to the flag or by reading the VALUE register.
This flag is set on the next cycle after a match with the window monitor condition, and an interrupt request
will be generated if INTENCLR/SET.WINMON is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Window Monitor interrupt flag.
Bit 1 – OVERRUN Overrun
This flag is cleared by writing a one to the flag.
This flag is set if a valid VALUE is updated before the previous valid value has been read by the CPU,
and an interrupt will be generated if INTENCLR/SET.OVERRUN is one.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Overrun interrupt flag.
Bit 0 – RESRDY Result Ready
This flag is cleared by writing a one to the flag or by reading the VALUE register.
This flag is set when the conversion result is available, and an interrupt will be generated if INTENCLR/
SET.RESRDY is one.
This flag will not set if an overflow occurs during the conversion.
Writing a zero to this bit has no effect.
Writing a one to this bit clears the Result Ready interrupt flag.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1127
43.8.8 Status
Name:  STATUS
Offset:  0x07
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
OVF
Access R
Reset 0
Bit 0 – OVF Result Overflow
Writing a zero to this bit has no effect.
Writing a one to this bit has no effect.
Value Description
0No overflow in the VALUE register has occurred. The result is valid.
1An overflow occurred in the VALUE register. The result is not valid.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1128
43.8.9 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x08
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ENABLE SWRST
Access R R
Reset 0 0
Bit 1 – ENABLE Enable Busy
This bit is cleared when the synchronization of CTRLA.ENABLE is complete.
This bit is set when the synchronization of CTRLA.ENABLE is started.
Bit 0 – SWRST Software Reset Busy
This bit is cleared when the synchronization of CTRLA.SWRST is complete.
This bit is set when the synchronization of CTRLA.SWRST is started.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1129
43.8.10 Value
Name:  VALUE
Offset:  0x0C
Reset:  0x0000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
VALUE[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
VALUE[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
VALUE[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – VALUE[23:0] Measurement Value
Result from measurement. This VALUE is in two’s complement format.
Example: If the TSENS GAIN and OFFSET registers are setup with values stored in the NVM
Temperature Calibration Area (Refer to Table 9-6), the TSENS resolution is set at 100 which will result in
the following values
Temperature VALUE
T = 25°C 2500 = 0x09C4
T = -25°C -2500 = 0xFFF63C
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1130
43.8.11 Window Monitor Lower Threshold
Name:  WINLT
Offset:  0x10
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
WINLT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
WINLT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINLT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – WINLT[23:0] Window Lower Threshold
If the window monitor is enabled, these bits define the lower threshold value. This WINLT value is in two’s
complement format.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1131
43.8.12 Window Monitor Upper Threshold
Name:  WINUT
Offset:  0x14
Reset:  0x0000
Property:  PAC Write-Protection, Enable-Protected
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
WINUT[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
WINUT[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
WINUT[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – WINUT[23:0] Window Upper Threshold
If the window monitor is enabled, these bits define the upper threshold value. This WINUT value is in
two’s complement format.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1132
43.8.13 Gain
Name:  GAIN
Offset:  0x18
Reset:  0x0000
Property:  Enable-Protected, PAC Write-Protection, not reset by a software reset
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
GAIN[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
GAIN[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
GAIN[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – GAIN[23:0] Time Amplifier Gain
This value from production test must be loaded from the NVM temperature calibration row into the
register by software to achieve the specified accuracy.
The bitfield can also be written by CPU.
The GAIN value defines the number of GCLK_TSENS periods that will be used for a measurement cycle.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1133
43.8.14 Offset
Name:  OFFSET
Offset:  0x1C
Reset:  0x0000
Property:  Enable-Protected, PAC Write-Protection, not reset by a software reset
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
OFFSETC[23:16]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
OFFSETC[15:8]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
OFFSETC[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – OFFSETC[23:0] Offset Correction
This value from production test must be loaded from the NVM temperature calibration row into the
register by software to achieve the specified accuracy.
The bitfield can also be written by CPU.
These bits define how the TSENS measurement result is compensated for offset error before being
written to the VALUE register. This OFFSET value is in two’s complement format.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1134
43.8.15 Calibration
Name:  CAL
Offset:  0x20
Reset:  0x00000000
Property:  Enable-Protected, PAC Write-Protection, not reset by a software reset
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
TCAL[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
FCAL[5:0]
Access R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0
Bits 13:8 – TCAL[5:0] Temperature Calibration
This value from production test must be loaded from the NVM software calibration row into the CAL
register by software to achieve the specified accuracy. The value must be copied only, and must not be
changed.
Bits 5:0 – FCAL[5:0] Frequency Calibration
This value from production test must be loaded from the NVM software calibration row into the CAL
register by software to achieve the specified accuracy. The value must be copied only, and must not be
changed.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1135
43.8.16 Debug Control
Name:  DBGCTRL
Offset:  0x24
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
DBGRUN
Access R/W
Reset 0
Bit 0 – DBGRUN Debug Run
This bit is not reset by a software reset.
This bits controls the functionality when the CPU is halted by an external debugger.
Value Description
0The TSENS is halted when the CPU is halted by an external debugger. Any on-going
measurement will complete.
1The TSENS continues normal operation when the CPU is halted by an external debugger.
SAM C20/C21 Family Data Sheet
TSENS – Temperature Sensor
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1136
44. FREQM – Frequency Meter
44.1 Overview
The Frequency Meter (FREQM) can be used to accurately measure the frequency of a clock by
comparing it to a known reference clock.
44.2 Features
• Ratio can be measured with 24-bit accuracy
• Accurately measures the frequency of an input clock with respect to a reference clock
• Reference clock can be selected from the available GCLK_FREQM_REF sources
• Measured clock can be selected from the available GCLK_FREQM_MSR sources
44.3 Block Diagram
Figure 44-1. FREQM Block Diagram
ENABLE
VALUE
REFNUM INTFLAG
GCLK_FREQM_REF
GCLK_FREQM_MSR
DONE
START
COUNTER
TIMER
CLK_MSR
CLK_REF_MUX
EN
EN
DIVREF
DIV8
44.4 Signal Description
Not applicable.
44.5 Product Dependencies
In order to use this peripheral, other parts of the system must be configured correctly, as described below.
44.5.1 I/O Lines
The GCLK I/O lines (GCLK_IO[7:0]) can be used as measurement or reference clock sources. This
requires the I/O pins to be configured.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1137
44.5.2 Power Management
The FREQM will continue to operate in idle sleep mode where the selected source clock is running. The
FREQM’s interrupts can be used to wake up the device from idle sleep mode. Refer to the Power
Manager chapter for details on the different sleep modes.
Related Links
19. PM – Power Manager
44.5.3 Clocks
The clock for the FREQM bus interface (CLK_APB_FREQM) is enabled and disabled by the Main Clock
Controller, the default state of CLK_APB_FREQM can be found in Peripheral Clock Masking.
Two generic clocks are used by the FREQM: Reference Clock (GCLK_FREQM_REF) and Measurement
Clock (GCLK_FREQM_MSR).
GCLK_FREQM_REF is required to clock the internal reference timer, which acts as the frequency
reference.
GCLK_FREQM_MSR is required to clock a ripple counter for frequency measurement. These clocks
must be configured and enabled in the generic clock controller before using the FREQM.
Related Links
17. MCLK – Main Clock
17.6.2.6 Peripheral Clock Masking
16. GCLK - Generic Clock Controller
44.5.4 DMA
Not applicable.
44.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using FREQM interrupt requires the
interrupt controller to be configured first.
Related Links
10.2 Nested Vector Interrupt Controller
44.5.6 Events
Not applicable
44.5.7 Debug Operation
When the CPU is halted in debug mode the FREQM continues its normal operation. The FREQM cannot
be halted when the CPU is halted in debug mode. If the FREQM is configured in a way that requires it to
be periodically serviced by the CPU, improper operation or data loss may result during debugging.
44.5.8 Register Access Protection
All registers with write-access can be write-protected optionally by the Peripheral Access Controller
(PAC), except the following registers:
• Control B register (CTRLB)
• Interrupt Flag Status and Clear register (INTFLAG)
• Status register (STATUS)
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1138
Optional write-protection by the Peripheral Access Controller (PAC) is denoted by the "PAC Write-
Protection" property in each individual register description.
Write-protection does not apply to accesses through an external debugger.
Related Links
11. PAC - Peripheral Access Controller
44.6 Functional Description
44.6.1 Principle of Operation
FREQM counts the number of periods of the measured clock (GCLK_FREQM_MSR) with respect to the
reference clock (GCLK_FREQM_REF). The measurement is done for a period of REFNUM/fCLK_REF and
stored in the Value register (VALUE.VALUE). REFNUM is the number of Reference clock cycles selected
in the Configuration A register (CFGA.REFNUM).
The frequency of the measured clock, CLK_MSR, is calculated by
CLK_MSR =VALUE
REFNUM CLK_REF
44.6.2 Basic Operation
44.6.2.1 Initialization
Before enabling FREQM, the device and peripheral must be configured:
• Each of the generic clocks (GCLK_FREQM_REF and GCLK_FREQM_MSR) must be configured and
enabled.
•
Important:  The reference clock must be slower than the measurement clock.
• Write the number of Reference clock cycles for which the measurement is to be done in the
Configuration A register (CFGA.REFNUM). This must be a non-zero number.
The following register is enable-protected, meaning that it can only be written when the FREQM is
disabled (CTRLA.ENABLE=0):
• Configuration A register (CFGA)
Enable-protection is denoted by the "Enable-Protected" property in the register description.
Related Links
16. GCLK - Generic Clock Controller
44.6.2.2 Enabling, Disabling and Resetting
The FREQM is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The
peripheral is disabled by writing CTRLA.ENABLE=0.
The FREQM is reset by writing a '1' to the Software Reset bit in the Control A register (CTRLA.SWRST).
On software reset, all registers in the FREQM will be reset to their initial state, and the FREQM will be
disabled.
Then ENABLE and SWRST bits are write-synchronized.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1139
Related Links
44.6.7 Synchronization
44.6.2.3 Measurement
In the Configuration A register, the Number of Reference Clock Cycles field (CFGA.REFNUM) selects the
duration of the measurement. The measurement is given in number of GCLK_FREQM_REF periods.
Note:  The REFNUM field must be written before the FREQM is enabled.
After the FREQM is enabled, writing a '1' to the START bit in the Control B register (CTRLB.START)
starts the measurement. The BUSY bit in Status register (STATUS.BUSY) is set when the measurement
starts, and cleared when the measurement is complete.
There is also an interrupt request for Measurement Done: When the Measurement Done bit in Interrupt
Enable Set register (INTENSET.DONE) is '1' and a measurement is finished, the Measurement Done bit
in the Interrupt Flag Status and Clear register (INTFLAG.DONE) will be set and an interrupt request is
generated.
The result of the measurement can be read from the Value register (VALUE.VALUE). The frequency of
the measured clock GCLK_FREQM_MSR is then:
CLK_MSR =VALUE
REFNUM CLK_REF
Note:  In order to make sure the measurement result (VALUE.VALUE[23:0]) is valid, the overflow status
(STATUS.OVF) should be checked.
In case an overflow condition occurred, indicated by the Overflow bit in the STATUS register
(STATUS.OVF), either the number of reference clock cycles must be reduced (CFGA.REFNUM), or a
faster reference clock must be configured. Once the configuration is adjusted, clear the overflow status by
writing a '1' to STATUS.OVF. Then another measurement can be started by writing a '1' to CTRLB.START.
44.6.3 DMA Operation
Not applicable.
44.6.4 Interrupts
The FREQM has one interrupt source:
• DONE: A frequency measurement is done.
The interrupt flag in the Interrupt Flag Status and Clear (44.8.6 INTFLAG) register is set when the
interrupt condition occurs. The interrupt can be enabled by writing a '1' to the corresponding bit in the
Interrupt Enable Set (44.8.5 INTENSET) register, and disabled by writing a '1' to the corresponding bit in
the Interrupt Enable Clear (44.8.4 INTENCLR) register.
An interrupt request is generated when the interrupt flag is set and the corresponding interrupt is enabled.
The interrupt request remains active until the interrupt flag is cleared, the interrupt is disabled, or the
FREQM is reset. See 44.8.6 INTFLAG for details on how to clear interrupt flags. All interrupt requests
from the peripheral are ORed together on system level to generate one combined interrupt request to the
NVIC. The user must read the 44.8.6 INTFLAG register to determine which interrupt condition is present.
This interrupt is a synchronous wake-up source.
Note that interrupts must be globally enabled for interrupt requests to be generated.
44.6.5 Events
Not applicable.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1140
44.6.6 Sleep Mode Operation
The FREQM will continue to operate in Idle Sleep mode where the selected source clock is running. The
FREQM’s interrupts can be used to wake up the device from Idle Sleep mode.
For lowest chip power consumption in sleep modes, FREQM should be disabled before entering a Sleep
mode.
Related Links
19. PM – Power Manager
44.6.7 Synchronization
Due to asynchronicity between the main clock domain and the peripheral clock domains, some registers
need to be synchronized when written or read.
The following bits and registers are write-synchronized:
• Software Reset bit in Control A register (CTRLA.SWRST)
• Enable bit in Control A register (CTRLA.ENABLE)
Required write-synchronization is denoted by the "Write-Synchronized" property in the register
description.
Related Links
15.3 Register Synchronization
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1141
44.7 Register Summary
Offset Name Bit Pos.
0x00 CTRLA 7:0 ENABLE SWRST
0x01 CTRLB 7:0 START
0x02 CFGA
7:0 REFNUM[7:0]
15:8 DIVREF
0x04
...
0x07
Reserved
0x08 INTENCLR 7:0 DONE
0x09 INTENSET 7:0 DONE
0x0A INTFLAG 7:0 DONE
0x0B STATUS 7:0 OVF BUSY
0x0C SYNCBUSY
7:0 ENABLE SWRST
15:8
23:16
31:24
0x10 VALUE
7:0 VALUE[7:0]
15:8 VALUE[15:8]
23:16 VALUE[23:16]
31:24
44.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition,
the 8-bit quarters and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be
accessed directly.
Some registers require synchronization when read and/or written. Synchronization is denoted by the
"Read-Synchronized" and/or "Write-Synchronized" property in each individual register description.
Some registers are enable-protected, meaning they can only be written when the module is disabled.
Enable-protection is denoted by the "Enable-Protected" property in each individual register description.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Optional PAC
write-protection is denoted by the "PAC Write-Protection" property in each individual register description.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1142
44.8.1 Control A
Name:  CTRLA
Offset:  0x00
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
ENABLE SWRST
Access R/W R/W
Reset 0 0
Bit 1 – ENABLE Enable
Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/
disabled. The value written to CTRLA.ENABLE will read back immediately and the ENABLE bit in the
Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared
when the operation is complete.
This bit is not enable-protected.
Value Description
0The peripheral is disabled.
1The peripheral is enabled.
Bit 0 – SWRST Software Reset
Writing a '0' to this bit has no effect.
Writing a '1' to this bit resets all registers in the FREQM to their initial state, and the FREQM will be
disabled. Writing a '1' to this bit will always take precedence, meaning that all other writes in the same
write-operation will be discarded.
Due to synchronization there is a delay from writing CTRLA.SWRST until the Reset is complete.
CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the Reset is complete.
This bit is not enable-protected.
Value Description
0There is no ongoing Reset operation.
1The Reset operation is ongoing.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1143
44.8.2 Control B
Name:  CTRLB
Offset:  0x01
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
START
Access W
Reset 0
Bit 0 – START Start Measurement
Value Description
0Writing a '0' has no effect.
1Writing a '1' starts a measurement.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1144
44.8.3 Configuration A
Name:  CFGA
Offset:  0x02
Reset:  0x0000
Property:  PAC Write-Protection, Enable-protected
Bit 15 14 13 12 11 10 9 8
DIVREF
Access R/W
Reset 0
Bit 7 6 5 4 3 2 1 0
REFNUM[7:0]
Access R/W R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0 0
Bit 15 – DIVREF Divide Reference Clock
Divides the reference clock by 8
Value Description
0The reference clock is divided by 1.
1The reference clock is divided by 8.
Bits 7:0 – REFNUM[7:0] Number of Reference Clock Cycles
Selects the duration of a measurement in number of CLK_FREQM_REF cycles. This must be a non-zero
value, i.e. 0x01 (one cycle) to 0xFF (255 cycles).
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1145
44.8.4 Interrupt Enable Clear
Name:  INTENCLR
Offset:  0x08
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DONE
Access R/W
Reset 0
Bit 0 – DONE Measurement Done Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the Measurement Done Interrupt Enable bit, which disables the
Measurement Done interrupt.
Value Description
0The Measurement Done interrupt is disabled.
1The Measurement Done interrupt is enabled.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1146
44.8.5 Interrupt Enable Set
Name:  INTENSET
Offset:  0x09
Reset:  0x00
Property:  PAC Write-Protection
Bit 7 6 5 4 3 2 1 0
DONE
Access R/W
Reset 0
Bit 0 – DONE Measurement Done Interrupt Enable
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will set the Measurement Done Interrupt Enable bit, which enables the
Measurement Done interrupt.
Value Description
0The Measurement Done interrupt is disabled.
1The Measurement Done interrupt is enabled.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1147
44.8.6 Interrupt Flag Status and Clear
Name:  INTFLAG
Offset:  0x0A
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
DONE
Access R/W
Reset 0
Bit 0 – DONE Mesurement Done
This flag is cleared by writing a '1' to it.
This flag is set when the STATUS.BUSY bit has a one-to-zero transition.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the DONE interrupt flag.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1148
44.8.7 Status
Name:  STATUS
Offset:  0x0B
Reset:  0x00
Property:  –
Bit 7 6 5 4 3 2 1 0
OVF BUSY
Access R/W R
Reset 0 0
Bit 1 – OVF Sticky Count Value Overflow
This bit is cleared by writing a '1' to it.
This bit is set when an overflow condition occurs to the value counter.
Writing a '0' to this bit has no effect.
Writing a '1' to this bit will clear the OVF status.
Bit 0 – BUSY FREQM Status
Value Description
0No ongoing frequency measurement.
1Frequency measurement is ongoing.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1149
44.8.8 Synchronization Busy
Name:  SYNCBUSY
Offset:  0x0C
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
Access
Reset
Bit 15 14 13 12 11 10 9 8
Access
Reset
Bit 7 6 5 4 3 2 1 0
ENABLE SWRST
Access R R
Reset 0 0
Bit 1 – ENABLE Enable
This bit is cleared when the synchronization of CTRLA.ENABLE is complete.
This bit is set when the synchronization of CTRLA.ENABLE is started.
Bit 0 – SWRST Synchronization Busy
This bit is cleared when the synchronization of CTRLA.SWRST is complete.
This bit is set when the synchronization of CTRLA.SWRST is started.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1150
44.8.9 Value
Name:  VALUE
Offset:  0x10
Reset:  0x00000000
Property:  –
Bit 31 30 29 28 27 26 25 24
Access
Reset
Bit 23 22 21 20 19 18 17 16
VALUE[23:16]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 15 14 13 12 11 10 9 8
VALUE[15:8]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
VALUE[7:0]
Access R R R R R R R R
Reset 0 0 0 0 0 0 0 0
Bits 23:0 – VALUE[23:0] Measurement Value
Result from measurement.
SAM C20/C21 Family Data Sheet
FREQM – Frequency Meter
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1151
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
Related Links
46. Electrical Characteristics 105°C (SAM C20/C21 E/G/J)
45.1 Disclaimer
All typical values are measured at Ta = 25°C unless otherwise specified. All minimum and maximum
values are valid across operating temperature and voltage unless otherwise specified.
This chapter only contains characteristics specific for SAM C20/C21 E/G/J.
45.2 Absolute Maximum Ratings
Stresses beyond those listed in the below table may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at these or other conditions beyond those
indicated in the operational sections of this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.
Table 45-1. Absolute maximum ratings
Symbol Parameter Min. Max. Units
VDD Power supply voltage 0 6.1 V
IVDD Current into a VDD pin - 92 mA
IGND Current out of a GND pin - 130 mA
VPIN Pin voltage with respect to GND and VDD GND-0.6V VDD +0.6V V
TSTORAGE Storage temperature -60 150 °C
CAUTION
This device is sensitive to electrostatic discharges (ESD). Improper handling may lead to
permanent performance degradation or malfunctioning.
Handle the device following best practice ESD protection rules: Be aware that the human body
can accumulate charges large enough to impair functionality or destroy the device.
CAUTION
In debugger cold-plugging mode, NVM erase operations are not protected by the BODVDD and
BODCORE. NVM erase operation at supply voltages below specified minimum can cause
corruption of NVM areas that are mandatory for correct device behavior.
Related Links
6.2.4 GPIO Clusters
45.3 General Operating Ratings
The device must operate within the ratings listed in the table below in order for all other electrical
characteristics and typical characteristics of the device to be valid.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1152
NVM erase operations are not protected by the BODVDD and BODCORE in debugger cold-plugging
mode. NVM erase operation at supply voltages below product specification minimum can cause
corruption of the calibration and other areas mandatory for a correct product behavior.
Table 45-2. General operating conditions
Symbol Parameter Min. Typ. Max. Units
VDDIN Power supply voltage 2.7(1) 5.0 5.5 V
VDDANA Analog supply voltage 2.7(1) 5.0 5.5 V
VDDIO IO supply voltage 2.7(1) 5.0 5.5 V
TATemperature range -40 25 85 °C
TJJunction temperature - - 100 °C
Note: 
1. With BODVDD disabled. If the BODVDD is enabled, refer to Table 45-15.
Note:  The same voltage must be applied to VDDIN and VDDANA. VDDIO should be lower or equal to
VDDIN/ VDDANA. The common voltage is referred to as VDD in the data sheet. Some I/O are in the
VDDIO cluster, but can be multiplexed as analog outputs (e.g. PTC.X[n] pads). In such a case, VDDANA
is used to power the I/O. Using this configuration may result in an electrical conflict if the VDDIO voltage
is lower than the VDDIN/VDDANA.
Related Links
45.10.2 Brown Out Detectors Characteristics
45.4 Injection Current
Stresses beyond those listed in the table below may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at these or other conditions beyond those
indicated in the operational sections of this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.
Table 45-3. Injection Current(1)
Symbol Description min max Unit
IINJ1(2) IO pin injection current -1 +1 mA
IINJ2(3) IO pin injection current -15 +15 mA
IINJtotal Sum of IO pins injection current -45 +45 mA
Note: 
1. Injecting current may have an effect on the accuracy of the analog blocks.
2. Conditions for VPIN: VPIN<GND-0.6V or 5.5V<VPIN<=6.1V.
Conditions for VDD 4.9V<VDD<=5.5V.
If Vpin is lower than GND-0.6V, then a current limiting resistor is required. The negative DC
injection current limiting resistor is calculated as R = |(GND-0.6V – VPIN)/IINJ1|. If Vpin is greater
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1153
than VDD+0.6V, then a current limiting resistor is required. The positive DC injection current limiting
resistor is calculated as R = (VPIN-(VDD+0.6))/IINJ1.
3. Conditions for VPIN: VPIN<GND-0.6V or VPIN<=5.5V.
Conditions for VDD: VDD<=4.9V.
If Vpin is lower than GND-0.6V, then a current limiting resistor is required. The negative DC
injection current limiting resistor is calculated as R = |(GND-0.6V - VPIN)/IINJ2|. If Vpin is greater than
VDD+0.6V, then a current limiting resistor is required. The positive DC injection current limiting
resistor is calculated as R = (VPIN-(VDD+0.6))/IINJ2.
45.5 Supply Characteristics
Table 45-4. Supply Characteristics
Symbol Conditions Voltage
Min. Max. Units
VDDIO
VDDIN
VDDANA
Full Voltage Range 2.7 5.5 V
Table 45-5. Supply Rise Rates
Symbol Parameter Fall Rate Rise Rate Units
Max Max.
VDDIO DC supply peripheral I/Os, internal regulator and analog supply 0.05 0.1 V/μs
VDDIN 0.05 0.1
VDDANA 0.05 0.1
Table 45-6. Power Supply Current Requirement
Symbol Conditions Current Units
Max
IINPUT(1) Power up Maximum current 1.9 mA
Note: 
1. IINPUT is the minimum requirement for the power supply connected to the device.
Related Links
7. Power Supply and Start-Up Considerations
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1154
45.6 Maximum Clock Frequencies
Table 45-7. Maximum GCLK Generator Output Frequencies
Symbol Condition Max. Units
fGCLKGEN0 / fGCLK_MAIN Undivided 96 MHz
fGCLKGEN1
fGCLKGEN2
fGCLKGEN3 Divided 66 MHz
fGCLKGEN4
fGCLKGEN5
fGCLKGEN6
fGCLKGEN7
fGCLKGEN8
Table 45-8. Maximum Peripheral Clock Frequencies
Symbol Description Max. Units
fCPU CPU clock frequency 48 MHz
fAHB AHB clock frequency 48 MHz
fAPBA APBA clock frequency 48 MHz
fAPBB APBB clock frequency 48 MHz
fAPBC APBC clock frequency 48 MHz
fAPBD APBD clock frequency 48 MHz
fGCLK_DPLL FDPLL96M Reference clock frequency 2 MHz
fGCLK_DPLL_32K FDPLL96M 32k Reference clock frequency 32 kHz
fGCLK_EIC EIC input clock frequency 48 MHz
fGCLK_FREQM_MSR FREQM Measure 96 MHz
fGCLK_FREQM_REF FREQM Reference 48 MHz
fGCLK_TSENS TSENS input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_0 EVSYS channel 0 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_1 EVSYS channel 1 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_2 EVSYS channel 2 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_3 EVSYS channel 3 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_4 EVSYS channel 4 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_5 EVSYS channel 5 input clock frequency 48 MHz
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1155
...........continued
Symbol Description Max. Units
fGCLK_EVSYS_CHANNEL_6 EVSYS channel 6 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_7 EVSYS channel 7 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_8 EVSYS channel 8 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_9 EVSYS channel 9 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_10 EVSYS channel 10 input clock frequency 48 MHz
fGCLK_EVSYS_CHANNEL_11 EVSYS channel 11 input clock frequency 48 MHz
fGCLK_SERCOMn_SLOW Common SERCOM slow input clock frequency 5 MHz
fGCLK_SERCOMn_CORE SERCOM input clock frequency 48 MHz
fGCLK_CANn CAN input clock frequency 48 MHz
fGCLK_TCC0, 1 TCCn input clock frequency 92 MHz
fGCLK_TCC2 TCC2 input clock frequency 48 MHz
fGCLK_TCn TCn input clock frequency 48 MHz
fGCLK_ADCn0 ADCn0 input clock frequency 48 MHz
fGCLK_SDADC SDADC input clock frequency 48 MHz
fGCLK_DAC DAC input clock frequency 48 MHz
fGCLK_PTC PTC input clock frequency 48 MHz
fGCLK_CCL CCL input clock frequency 48 MHz
fGCLK_AC AC digital input clock frequency 48 MHz
45.7 Power Consumption
The values in the Power Consumption table below are measured values of power consumption under the
following conditions, except where noted:
• Operating conditions
– VDDIN = 3.0 V, 5.0V
• Oscillators
– XOSC (crystal oscillator) stopped
– XOSC32K (32 kHz crystal oscillator) running with external 32kHz crystal
– FDPLL using XOSC32K as reference and running at 48 MHz
• Clocks
– FDPLL used as main clock source, except otherwise specified
– CPU, AHB clocks undivided
– All peripheral clocks stopped
• I/Os are inactive with input trigger disable
• CPU is running on Flash with Wait states specified in NVM Max Speed Characteristics
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1156
• NVMCTRL cache enabled
• BODVDD disabled
Table 45-9. Current Consumption (1)
Mode conditions Ta Vcc Typ. Max. Units
ACTIVE CPU running a While 1
algorithm
25°C 5.0V 3.8 4.2 mA
85°C 5.0V 3.9 4.3
CPU running a While 1
algorithm
25°C 3.0V 3.7 4.1 mA
85°C 3.0V 3.9 4.3
CPU running a While 1
algorithm, with GCLKIN as
reference
25°C 5.0V 71*Freq+160 78*Freq+162 µA (with freq
in MHz)
85°C 5.0V 71*Freq+253 74*Freq+447
CPU running a Fibonacci
algorithm
25°C 5.0V 4.7 5.2 mA
85°C 5.0V 4.8 5.3
CPU running a Fibonacci
algorithm
25°C 3.0V 4.7 5.1 mA
85°C 3.0V 4.8 5.3
CPU running a Fibonacci
algorithm, with GCLKIN as
reference
25°C 5.0V 90*Freq+163 99*Freq+168 µA (with freq
in MHz)
85°C 5.0V 90*Freq+258 95*Freq+450
CPU running a CoreMark
algorithm
25°C 5.0V 5.9 6.4 mA
85°C 5.0V 6.1 6.6
CPU running a CoreMark
algorithm
25°C 3.0V 5.2 5.7 mA
85°C 3.0V 5.4 5.8
CPU running a CoreMark
algorithm, with GCLKIN as
reference
25°C 5.0V 115*Freq+167 126*Freq+167 µA (with freq
in MHz)
85°C 5.0V 117*Freq+261 122*Freq+454
IDLE 25°C 5.0V 1.2 1.3 mA
85°C 5.0V 1.3 2.3
STANDBY XOSC32K running RTC running
at 1kHz
25°C 5.0V 15.9 37.0 µA
85°C 5.0V 89.8 302.0
XOSC32K and RTC stopped 25°C 5.0V 14.6 35.0
85°C 5.0V 87.8 300.0
Note: 
1. These values are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1157
45.8 Wake-Up Time
Conditions:
• VDD = 5.0V
• CPU clock = OSC48M @8Mhz
• 0 Wait-state
• Cache enabled
• Flash in WAKEUPINSTANT mode (NVMCTRL.CTRLB.SLEEPPRM=1)
CPU sets an IO by writing PORT->IOBUS without jumping in an interrupt handler (Cortex M0+ register
PRIMASK=1). The wakeup time is measured between the edge of the wakeup input signal and the edge
of the GPIO pin.
Table 45-10. Wake-up Timings
Sleep Mode Typ. Unit
Idle 15.2 µs
Standby 48 µs
45.9 I/O Pin Characteristics
There are two different pin types with two different speeds: Normal and High Sink(2). The Drive Strengh
bit is located in the Pin Configuration register PORT (PORT.PINCFG.DRVSTR).
The pins with I2C alternative mode available are compliant with I2C specifications. All I2C pins support
Standard (Sm), Fast (Fm), Fast plus (Fm+) and High speed (Hs) modes. The available I2C pins are listed
in the I/O Multiplexing section.
Table 45-11. I/O Pins Common Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
VIL Input low-level voltage VDD=2.7-4.5V - - 0.3*VDD V
VDD=4.5-5.5V - - 0.3*VDD
VIH Input high-level voltage VDD=2.7-4.5V 0.7*VDD - -
VDD=4.5-5.5V 0.7*VDD - -
VOL Output low-level voltage VDD>2.7V, IOL max - 0.1*VDD 0.2*VDD
VOH Output high-level voltage VDD>2.7V, IOH max 0.8*VDD 0.9*VDD -
RPULL Pull-up - Pull-down resistance All pins 20 40 60 kΩ
ILEAK Input leakage current Pull-up resistors disabled -1 - 1 µA
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1158
Table 45-12. I/O Pins Maximum Output Current
Symbol Parameter Conditions Normal
pins
High
Sink
pins
Normal
pins
High
Sink
pins
Units
DRVSTR=0 DRVSTR=1
IOL Maximum output
low-level current
VDD=2.7V-4.5V 2.5 5 5 10 mA
VDD=4.5V-5.5V 5 10 10 20
IOH Maximum output
high-level current
VDD=2.7V-4.5V 1.5 3 3 6
VDD=4.5V-5.5V 3 6 6 12
Table 45-13.  I/O Pins Dynamic Characteristics (1)
Symbol Parameter Conditions Normal
pins
High
Sink
pins
Normal
pins
High
Sink
pins
Units
DRVSTR=0 DRVSTR=1
tRISE Maximum rise
time
VDD = 5.0V, load =
20pF
15 12 8 7 ns
tFALL Maximum fall
time
VDD = 5.0V, load =
20pF
14 11 7 7
Note: 
1. These values are based on simulation. These values are not covered by test limits in production or
characterization.
2. The following pins are High Sink pins and have different properties than normal pins: PA10, PA11,
PB10, PB11.
Related Links
6. I/O Multiplexing and Considerations
28.8.14 PINCFG
45.10 Analog Characteristics
45.10.1 POR - Power On Reset Characteristics
Table 45-14. POR Characteristics
Symbol Parameters Min Typ Max Unit
VPOT+ Voltage threshold Level on Vddin rising - 2.55 - V
VPOT- Voltage threshold Level on Vddin falling 1.53 1.75 1.97
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1159
Figure 45-1. POR Operating Principle
Reset VDDCORE
VPOT+
V
Time
POT-
45.10.2 Brown Out Detectors Characteristics
Refer to NVM User Row Mapping for the BODVDD default value settings. These values are based on
simulation and are not covered by test limits in production or characterization.
Figure 45-2. BODVDD Hysteresis OFF
Figure 45-3. BODVDD Hysteresis ON
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1160
Table 45-15. BODVDD Characteristics(2)
Symbol Parameters Conditions Min. Typ. Max. Unit
VBOD+(1) BODVDD high threshold Level VDD level, BOD setting = 8
(default)
- 2.86 2.97 V
VDD level, BOD setting = 9 - 2.92 3.0
VDD level, Bod setting = 44 - 4.57 4.81
VBOD- /
VBOD(1)
BODVDD low threshold Level VDD level, BOD setting = 8
(default)
2.71 2.8 2.89
VDD level, BOD setting = 9 2.75 2.85 2.95
VDD level, BOD setting = 44 4.37 4.51 4.66
Step size - 60 - mV
VHys(1) Hysteresis (VBOD+ - VBOD-)
BODVDD.LEVEL = 8 to 48
VDD 40 - 75 mV
TSTART(3) Startup time Time from enable to RDY - 3.1 - µs
Note: 
1. These values are based on characterization.
2. BODVDD in continuous mode.
3. These values are based on simulation and not covered by test or characterization.
Table 45-16. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max. Units
IDD IDLE, Mode CONT VDD = 2.7V Max 85°C
Typ 25°C
22.5 26.3 µA
VDD = 5.0V 41.0 47.1
IDLE, Mode SAMPL VDD = 2.7V 0.1 1.2
VDD = 5.0V 0.1 1.2
STANDBY, Mode SAMPL VDD = 2.7V 0.8 1.6
VDD = 5.0V 3.5 4.6
Note: 
1. These values are based on characterization.
Related Links
9.3 NVM User Row Mapping
45.10.3 Voltage Regulator Characteristics
Table 45-17. Voltage Regulator Characteristics
Symbol Parameter Min. Typ. Max. Units
VDDIN Input voltage range 2.7 - 5.5 V
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1161
...........continued
Symbol Parameter Min. Typ. Max. Units
VDDCORE DC calibrated output voltage - 1.23 - V
Table 45-18. Decoupling Requirements
Symbol Parameter Conditions Min. Typ. Max. Units
Cin(1) Input regulator capacitor ceramic dielectric X7R - 10 - uF
- 100 - nF
Cout(2) Output regulator capacitor 0.8 1 - uF
ceramic dielectric X7R - 100 - nF
ESR Cout External Series Resistance of Cout - - 0.5 Ω
Note: 
1. It is recommended to use ceramic X7R capacitor with low-series resistance. Refer to Power Supply
Connections for a typical circuit connections.
2. It is recommended to use ceramic or solid tantalum capacitor with low ESR.
45.10.4 Analog-to-Digital Converter (ADC) Characteristics
Table 45-19. Operating Conditions(1)
Symbol Parameters Conditions Min. Typ. Max. Unit
Res Resolution - - 12 bits
Rs Sampling rate(2) SAMPLEN = 3 and resolution 12
bit (CTRLC.RESSEL= 0)
10 - 1000 ksps
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1162
...........continued
Symbol Parameters Conditions Min. Typ. Max. Unit
Nb_cycles Differential mode Number of ADC clock
cycles SAMPCTRL.OFFCOMP=1
resolution 12 bit
(CTRLC.RESSEL= 0)
- 16 - cycles
resolution 10 bit
(CTRLC.RESSEL= 2)
14
resolution 8 bit
(CTRLC.RESSEL= 3)
12
Differential mode Number of ADC clock
cycles SAMPCTRL.OFFCOMP=0 SAMPLEN
corresponds to the decimal value of
SAMPCTRL.SAMPLEN[5:0] register
resolution 12 bit
(CTRLC.RESSEL= 0)
- SAMPLEN+13 - cycles
resolution 10 bit
(CTRLC.RESSEL= 2)
SAMPLEN+11
resolution 8 bit
(CTRLC.RESSEL= 3)
SAMPLEN+9
Single-ended mode Number of ADC clock
cycles SAMPCTRL.OFFCOMP=1
resolution 12 bit
(CTRLC.RESSEL= 0)
- 16 - cycles
resolution 10 bit
(CTRLC.RESSEL= 2)
15
resolution 8 bit
(CTRLC.RESSEL= 3)
13
Single-ended mode Number of ADC clock
cycles SAMPCTRL.OFFCOMP=0 SAMPLEN
corresponds to the decimal value of
SAMPCTRL.SAMPLEN[5:0] register
resolution 12 bit
(CTRLC.RESSEL= 0)
- SAMPLEN+13 - cycles
resolution 10 bit
(CTRLC.RESSEL= 2)
SAMPLEN+12
resolution 8 bit
(CTRLC.RESSEL= 3)
SAMPLEN+10
fadc ADC Clock frequency - 160 - 16000 kHz
Ts Sampling time SAMPCTRL.OFFCOMP = 1 250 - 25000 ns
SAMPCTRL.OFFCOMP = 0 (SAMPLEN
+1)/fadc
- - s
Sampling time with DAC as input 3000 - - ns
Sampling time with Bandgap as input 10 - - us
VCNV Conversion range Differential mode -VREF - +VREF V
Conversion range Single-ended mode 0 - VREF
Vref Reference input - 2 - VDDANA-0.6 V
Vin Input channel range - 0 - VDDANA V
Vcmin Input common mode voltage CTRLC.R2R = 1 0.2 - VREF-0.2 V
CTRLC.R2R = 0 VREF/2-0.2 - VREF/2+0.2 V
CSAMPLE Input sampling capacitance - 1.6 4.5 pF
RSAMPLE Input sampling on-resistance For a sampling rate at 1 Msps - 1000 1715 Ω
Rref Reference input source resistance 0 - 1000 kΩ
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1163
Note: 
1. These values are based on simulation and not covered by test limits in production or
characterization.
2. Sampling rate (in samples per second) is equal to (fadc/Nb_cycles).
Figure 45-4. ADC Analog Input AINx
The minimum sampling time tsamplehold for a given Rsource can be calculated using this formula:
samplehold sample +source ×sample ×+ 2 × ln 2
For 12-bit accuracy:
samplehold sample +source ×sample × 9.7
where, samplehold 1
2 × ADC
.
Table 45-20. Differential Mode (1)
Symbol Parameter Conditions
Measurement
Unit
Min. Typ Max.
ENOB Effective
Number of bits
Vddana = 5.0V Vref = Vddana 10.5 10.8 11.3 bits
Vddana = 2.7V Vref = 2.0V 9.9 10.0 11.2
TUE Total
Unadjusted
Error
Vddana = 5.0V Vref = Vddana - 4.2 6.7 LSB
Vddana = 2.7V Vref = 2.0V - 4.8 7.9
INL Integral Non
Linearity
Vddana = 5.0V Vref = Vddana - +/-1.5 +/-3 LSB
Vddana = 2.7V Vref = 2.0V - +/-3.2 +/-3.9
DNL Differential Non
Linearity
Vddana = 5.0V Vref = Vddana - -0.8/+1.1 -1/+1.9 LSB
Vddana = 2.7V Vref = 2.0V - -0.9/+1.3 -1/+2.1
Gain Gain Error Vddana = 2.7V Vref = 2.0V - +/-18 +/-57 mV
Vddana = 5.0V Vref = 4.096V - +/-41 +/-100
Vddana = 3.0V Vref = Vddana - +/-17 +/-66
Vddana = 5.0V Vref = Vddana - +/-39 +/-81
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1164
...........continued
Symbol Parameter Conditions
Measurement
Unit
Min. Typ Max.
TCg Gain Drift Vddana = 5.0V Vref = Vddana -250 -210 -170 uV/°C
Offset Offset Error Vddana = 2.7V Vref = 2.0V - +/-1.4 +/-11 mV
Vddana = 5.0V Vref = 4.096V - +/-6 +/-18
Vddana = 3.0V Vref=Vddana - +/-2 +/-9
Vddana = 5.0V Vre f= Vddana - +/-0.2 +/-23
Tco Offset Drift Vddana = 5.0V Vref = Vddana 20 80 120 uV/°C
SFDR Spurious
Free
Dynamic
Range
Fs = 1Msps / Fin = 14 kHz /
Full range Input signal
Vddana = 5.0V Vref = Vddana
71 75 81 dB
SINAD Signal to
Noise and
Distortion
ratio
65 67 68
SNR Signal to
Noise ratio
67 68 69
THD -77 -74 -70
Noise RMS External Reference voltage - 0.5 2.0 mV
Note: 
1. These values are based on characterization and not covered by test limits in production.
Table 45-21. Single-Ended Mode (1)
Symbol Parameter Conditions
Measurement
Unit
Min. Typ Max.
ENOB Effective Number
of bits
Vddana = 5.0V Vref=Vddana 9.1 9.7 10
bits
Vddana = 2.7V Vref=2.0V 9.0 9.2 10
TUE Total Unadjusted
Error
Vddana = 5.0V Vref = Vddana - 18.4 26.5
LSB
Vddana = 2.7V Vref = 2.0V - 30.4 53.8
INL Integral Non
Linearity
Vddana = 5.0V Vref = Vddana - +/-2.2 +/-4
LSB
Vddana = 2.7V Vref = 2.0V - +/-4.1 +/-6
DNL Differential Non
Linearity
Vddana = 5.0V Vref=Vddana - -0.8/+1 -1/+1.9
LSB
Vddana = 2.7V Vref = 2.0V - -1/+1.1 -1/+2.4
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1165
...........continued
Symbol Parameter Conditions
Measurement
Unit
Min. Typ Max.
Gain Gain Error
Vddana = 2.7V Vref = 2.0V - +/-13 +/-28
mV
Vddana = 5.0V Vref = 4.096V - +/-26 +/-52
Vddana = 3.0V Vref = Vddana - +/-14 +/-24
Vddana = 5.0V Vref = Vddana - +/-22 +/-42
TCg Gain Drift Vddana = 5.0V Vref = Vddana -170 -140 -80 uV/°C
Offset Offset Error
Vddana = 2.7V Vref = 2.0V - +/-2.2 +/-21
mV
Vddana = 5.0V Vref = 4.096V - +/-2.3 +/-61
Vddana = 3.0V Vref=Vddana - +/-15 +/-42
Vddana = 5.0V Vref = Vddana - +/-31 +/-80
Tco Offset Drift Vddana = 5.0V Vref = Vddana 160 180 210 uV/°C
SFDR
Spurious
Free
Dynamic
Range
Fs = 1Msps / Fin = 14 kHz /
Full range Input signal Vddana
= 5.0V Vref = Vddana
69 71 73
dB
SINAD
Signal to
Noise and
Distortion
ratio
57 60 61
SNR Signal to
Noise ratio 57 61 61
THD -72 -70 -66
Noise RMS External Reference voltage - 0.7 2.0 mV
Note: 
1. These values are based on characterization and not covered by test limits in production.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1166
Table 45-22. Power Consumption (1)
Symbol Parameters Conditions Ta Typ. Max. Units
IDD
VDDANA
Differential
mode
fs = 1Msps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
Max 85°C
Typ 25°C
905 1021
uA
fs = 1Msps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111' VDDANA =
Vref = 5.5V
1144 1403
fs = 10 ksps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
381 460
fs = 10 ksps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111' VDDANA =
Vref = 5.5V
609 857
Single Ended
mode
fs = 1Msps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111' VDDANA =
Vref = 5.5V
Max 85°C
Typ 25°C
984 1077
uA
fs = 1Msps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111' VDDANA =
Vref=5.5V
1178 1444
fs = 10 ksps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111' VDDANA =
Vref = 5.5V
437 528
fs = 10 ksps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111' VDDANA =
Vref = 5.5V
635 888
Note: 
1. These values are based on characterization.
45.10.5 Sigma-Delta Analog-to-Digital Converter (SDADC) Characteristics
Table 45-23. Operating Conditions(1)
Symbol Parameters Conditions Min. Typ. Max. Unit
Res Resolution
Differential mode - 16 -
bits
Single-Ended mode - 15 -
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1167
...........continued
Symbol Parameters Conditions Min. Typ. Max. Unit
CLK_SDADC Sampling Clock
Speed - 1 - 6
MHz
CLK_SDADC_FS Conversion rate - CLK_SDADC/4
fs Output Data
Rate
Free Running mode CLK_SDADC_FS / OSR
Single Conversion mode
SKPCNT = N
(CLK_SDADC_FS / OSR) x
(N+1)
OSR Oversampling
ratio Differential mode 64 256 1024 Cycles
Vin
Input
Conversion
range
VREF<AVDD-0.3V
Differential
mode
Gaincorr =
0x1
- VREF - VREF
V
Single-
Ended
mode
Gaincorr =
0x1
0 - VREF
VREF> =
AVDD-0.3V
Differential
mode
Gaincorr =
0x1
-0.7xVREF - 0.7xVREF
V
Single-
Ended
mode
Gaincorr =
0x1
0 - 0.7xVREF
Vref Reference
Voltage range 1 - AVDD V
Vcom Common mode
voltage Differential mode 0 - AVDD V
Cin Input
capacitance 0.425 0.5 0.575 pF
Zin Input impedance
Differential mode 1/(Cin x CLK_SDADC_FS)
kΩ
Single-Ended mode 1/(Cin x CLK_SDADC_FS x
2)
Input anti-alias
filter
recommendation
(2)
Rext - 1.0 - kΩ
Cext 3.3 - 10 nF
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1168
Note: 
1. These values are based on simulation and not covered by test or characterization.
2. External anti-alias filter must be placed in front of each SDADC input to ensure high-frequency
signals to not alias into measurement bandwidth. Use capacitors of X5R type for DC measurement,
or capacitors of COG or NPO type for AC measurement.
Table 45-24. SDADC DC Performance: Differential Input Mode (1)(2)
Symbol Parameters Conditions (2) Min. Typ. Max. Unit
INL Integral Non Linearity CLK_SDADC = 6MHz; VREF =
1.2V
- +/-1.3 +/-2 LSB
CLK_SDADC = 6MHz; INT
VREF = 5.5V
- +/-5.3 +/-11
DNL Differential Non
Linearity
CLK_SDADC = 6MHz; VREF =
1.2V
- +1.4/-1 +1.3/-1 LSB
CLK_SDADC = 6MHz; INT
VREF = 5.5V
- +2.1/-1 +1.7/-1
Off Offset Error CLK_SDADC = 6MHz; VREF =
1.2V
- +/-0.6 +/-3 mV
CLK_SDADC = 6MHz; INT
VREF = 5.5V
- +/-3.9 +/-6
Tco Offset Error Drift CLK_SDADC = 6MHz; VREF =
1.2V
2.3 3.6 5.0 uV/°C
Eg Gain Errors CLK_SDADC = 6MHz; VREF =
1.2V
- +/-1.1 +/-3.7 %
CLK_SDADC = 6MHz; INT
VREF = 5.5V
- +/-1.1 +/-3.4
TCg Gain Drift CLK_SDADC = 6MHz; VREF =
1.2V
-10.9 1.2 7.6 ppm/°C
Input noise
rms
AC Input noise rms OSR = 256 - 0.08 0.12 mVrms
Note: 
1. These values are based on characterization.
2. OSR = 256, Chopper ON.
Table 45-25. SDADC AC Performance: : Differential Input Mode(1)
Symbol Parameters Conditions (2) Min. Typ. Max. Unit
ENOB Effective Number Of Bits Ext ref = 1.2V 13.5 14.2 14.4 bits
Int Ref = 5.5V 11 11.2 11.4
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1169
...........continued
Symbol Parameters Conditions (2) Min. Typ. Max. Unit
DR Dynamic Range Ext ref = 1.2V 89 91 92 dB
Int Ref = 5.5V 83 92 96
SNR Signal to Noise Ratio Ext ref = 1.2V 84 88 89 dB
Int Ref = 5.5V 77 79 80
SINAD Signal to Noise + Distortion Ratio Ext ref = 1.2V 83 87 89 dB
Int Ref = 5.5V 68 69 71
THD Total Harmonic Distortion Ext ref = 1.2V -105 -100 -92 dB
Int Ref = 5.5V -70 -69 -69
Note: 
1. These values are based on characterization.
2. OSR = 256, Fs = 6 MHz, Fin = 13 kHz.
Table 45-26.  Power consumption (1)
Symbol Parameters Conditions Ta Typ. Max. Units
IDD
VDDANA
Power
consumption
CTLSDADC = 0x0 External Ref -
VDDANA = 5.5V Vref = 2V Ref buf on
SCLK_SDADC = 6 MHz
Max 85°C
Typ 25°C
644 695 μA
CTLSDADC = 0x0 Internal Ref -
VDDANA = Vref = 5.5V Ref buf off
SCLK_SDADC = 6 MHz
605 636
Note: 
1. These are based on characterization.
45.10.6 Digital to Analog Converter (DAC) Characteristics
Table 45-27. Operating Conditions(1)
Symbol Parameters Conditions Min. Typ. Max. Unit
RES Input resolution - - 10 Bits
VDDANA Analog supply voltage 2.7 - 5.5 V
AVREF External reference voltage 1 - VDDANA - 0.6 V
Internal reference voltage 1 VREF.SEL = 0x0 - 1.024 - V
VREF.SEL = 0x2 - 2.048 -
VREF.SEL = 0x3 - 4.096 (2) -
Internal reference voltage 2 - VDDANA - V
Linear output voltage range 0.05 - VDDANA - 0.05 V
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1170
...........continued
Symbol Parameters Conditions Min. Typ. Max. Unit
Minimum resistive load 5 - - kΩ
Maximum capacitance load - - 100 pF
Note: 
1. These values are based on simulation and not covered by test or characterization.
2. For VDDANA > 4.5V.
Table 45-28. Clock and Timing(1)
Symbol Parameter Conditions Max. Units
Conversion rate Cload = 100pF
Rload > 5kΩ
Normal mode 350 ksps
For DDATA = ±1 1000
Startup time 3 μs
Note: 
1. These values are based on simulation and not covered by test limits in production or characterization.
Table 45-29. Accuracy Characteristics(1)
Symbol Parameter Conditions Typ. Max. Units
INL Integral non-linearity VREF = Ext 2.0V VDD = 2.7V +/-0.7 +/-1.3 LSB
VDD = 5.5V +/-0.5 +/-0.6
VREF = VDDANA VDD = 2.7V +/-0.6 +/-0.9
VDD = 5.5V +/-0.4 +/-0.6
VREF = 1.024V INT REF VDD = 2.7V +/-1 +/-2.5
VDD = 5.5V +/-1.5 +/-3.5
DNL Differential non-linearity VREF = Ext 2.0V VDD = 2.7V +/-0.3 +/-0.4 LSB
VDD = 5.5V +/-0.4 +/-0.5
VREF = VDDANA VDD = 2.7V +/-0.2 +/-0.3
VDD = 5.5V +/-0.2 +/-0.3
VREF = 1.024V INT REF VDD = 2.7V +/-1.0 +/-2.5
VDD = 5.5V +/-1.4 +/-3.5
Gain error Ext. VREF +/-8 +/-20 mV
Offset error Ext. VREF +/-4 +/-20 mV
Note: 
1. These values are based on characterization and not covered by test limits in production.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1171
Table 45-30. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max. Units
IDD
VDDANA
DC supply current Output buffer On
VREF = VDDANA = 5.0V
Max 85°C
Typ 25°C
318 404 µA
Output buffer Off
VREF = VDDANA=5.0V
74 81
Note: 
1. These values are based on characterization.
45.10.7 Analog Comparator Characteristics
Table 45-31. Analog Comparator Characteristics
Symbol Parameters Conditions Min. Typ. Max. Unit
PNIVR Positive and Negative input
range voltage
0 - VDDANA V
ICMR Input common mode range 0 - VDDANA V
Off (1)(2) Offset Low power
COMPCTRLn.SPEED = 0x0
-36 +0.4/+2 +48 mV
High speed
COMPCTRLn.SPEED = 0x3
-12 -0.1/+1 +20
VHYS (1)(3) Hysteresis Low Power
COMPCTRLn.SPEED = 0x0
25 100 248 mV
High speed
COMPCTRLn.SPEED = 0x3
29 100 190
TPD (1, 4) Propagation Delay
Vcm=Vddana/2
Vin = ±100mV overdrive from
Vcm
Low power
COMPCTRLn.SPEED = 0x0
- 133 237 ns
High speed
COMPCTRLn.SPEED = 0x3
- 38 73
TSTART (1) Startup time Low power
COMPCTRLn.SPEED = 0x0
- 6.5 8.5 μs
High speed
COMPCTRLn.SPEED = 0x3
- 2 3
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1172
...........continued
Symbol Parameters Conditions Min. Typ. Max. Unit
VSCALE (1) INL - 0.2 - LSB
DNL - 0.023 -
Offset Error - 0.049 -
Gain Error - 0.064 -
Note: 
1. These are based on characterization.
2. Hysteresis disabled.
3. Hysteresis enabled.
4. Tpd is measured from Vin transition to ACOUT (AC direct output) toggle.
Table 45-32. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max. Units
IDDANA Current consumption - VCM=
VDDANA/2
±100 mV overdrive from Vcm
Voltage scaler disabled
COMPCTRLn.SPEED = 0x0
VDDANA = 5.0V
Max 85°C
Typ 25°C
10 16 μA
COMPCTRLn.SPEED = 0x3
VDDANA = 5.0V
39 58
Current consumption Voltage
scaler only
VDDANA = 5.0V 43 60
Note: 
1. These values are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1173
45.10.8 Voltage Reference Characteristics
Table 45-33. Voltage Reference Characteristics(1)
Symbol Parameter Conditions Min. Typ. Max. Units
ADC / SDADC / DAC
Ref
ADC, SDADC, DAC
Internal reference
nom. 1.024V
VDDANA = 5.0V
Ta = 25°C
1.003 1.024 1.045 V
nom. 2.048V
VDDANA = 5.0V
Ta = 25°C
2.007 2.048 2.089
nom. 4.096V
VDDANA = 5.0V
Ta = 25°C
4.014 4.096 4.178
Reference
temperature
coefficient
Drift over [-40, +25]°C - -0.025/0.04 - %/°C
Drift over [+25, +85]°C - -0.015/0.03 -
Drift over [+25,
+105]°C
- -0.015/0.03 -
Reference supply
coefficient
Drift over [2.7, 5.5]V - -0.2/0.3 - %/V
Note: 
1. These values are based on characterization.
45.10.9 Temperature Sensor Characteristics
Table 45-34. Temperature Sensor Characteristics(1)
Parameter Condition Min. Max. Unit
Accuracy [0,60]°C -11.3 6.2 °C
[-40,85]°C -14.6 10.5
Note: 
1. These values are based on characterization. Data has been obtained by averaging 10 TSENS
acquisitions per measurement.
45.10.10 PTC Characteristics
Table 45-35. Sensor Load Capacitance (1)
Symbol Mode PTC channel Max. Units
Cload Self-capacitance Y0 18 pF
Cload Self-capacitance Y1 25 pF
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1174
...........continued
Symbol Mode PTC channel Max. Units
Y2
Y3
Y4
Y5
Y6
Y7
Y8
Y9
Y10
Y11
Y12
Y13
Y14
Y15
Y16
Y17
Y18
Y19
Y20
Y21
Y22
Y23
Y24
Y25
Cload Self-capacitance
Y26
22 pF
Y27
Cload Self-capacitance
Y28
25 pF
Y29
Y30
Y31
Cload Mutual-capacitance All 31 pF
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1175
Note: 
1. Capacitance load that the PTC circuitry can compensate for each channel.
Table 45-36. Analog Gain Settings (1) (2)
Symbol Setting Average
Gain
GAIN_1 1
GAIN_2 2.1
GAIN_4 4.3
GAIN_8 9.9
GAIN_16 -
GAIN_32 -
Note: 
1. Analog Gain is a parameter of the QTouch Library. Refer to the QTouch Library Peripheral Touch
Controller User Guide for more information.
2. GAIN_16 and GAIN_32 settings are not recommended; otherwise, the PTC measurements might
become unstable.
45.10.10.1 PTC Power Consumption
The values given in the table below are measured values of power consumption under the following
conditions:
Operating conditions
VDD = 5.0V
Clocks
OSC48M used as main clock source, running undivided at 48 MHz
CPU is running on flash with 2 wait states, at 48 MHz
PTC running at 4 MHz
PTC configuration
Mutual-capacitance mode
One-touch channel
System configuration
Standby Sleep mode enabled
RTC running on ULP32K: used to define the PTC scan rate, through the event system
Drift Calibration disabled: no interrupts, PTC scans are performed in standby mode
Drift Calibration enabled: RTC interrupts (wakeup) the CPU to perform PTC scans. PTC drift calibration is
performed every 1.5 sec.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1176
Table 45-37. Power Consumption (1)
Symbol Parameters Drift
Calibration
PTC
scan
rate
Oversamples Ta Typ. Max. Units
IDD Current
Consumption
Disabled
10
4
Max 85°C
Typ 25°C
24 308
µA
16 43 330
50
4 17 301
16 22 307
100
4 16 301
16 19 304
200
4 16 301
16 17 303
Enabled
10
4 30 319
16 50 342
50
4 20 306
16 24 311
100
4 18 305
16 21 308
200
4 17 304
16 19 305
Note: 
1. These values are based on characterization.
45.11 NVM Characteristics
Table 45-38. NVM Max Speed Characteristics
CPU FMAX (MHz) 0WS 1WS 2WS
VDD>2.7V 19 38 48
VDD>4.5V 20 38 48
Table 45-39. NVM Timing Characteristics
Symbol Parameter Max. Units
tFPP Page Write (1) 2.5 ms
tFRE Row erase (1) 6 ms
tFSE Chip erase (1) 260 ms
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1177
Note: 
1. These are based on simulation. These values are not covered by test or characterization. For this
Flash technology, a maximum number of 8 consecutive writes is allowed per row. Once this number
is reached, a row erase is mandatory.
Table 45-40. Flash Endurance and Data Retention
Symbol Parameter Conditions Min. Typ. Units
RetNVM25k Retention after up to 25k Average ambient 55°C 10 50 Years
RetNVM2.5k Retention after up to 2.5k Average ambient 55°C 20 100 Years
RetNVM100 Retention after up to 100 Average ambient 55°C 25 >100 Years
CycNVM Cycling Endurance(1) -40°C < TA < 85°C 25k - Cycles
Note: 
1. An endurance cycle is a write and an erase operation.
Table 45-41. EEPROM Emulation(1) Endurance and Data Retention
Symbol Parameter Conditions Min. Typ. Units
RetEEPROM100k Retention after up to 100k Average ambient 55°C 10 50 Years
RetEEPROM10k Retention after up to 10k Average ambient 55°C 20 100 Years
CycEEPROM Cycling Endurance(2) -40°C < Ta < 85°C 100k - Cycles
Note: 
1. The EEPROM emulation is a software emulation described in the Application Note AT03265.
2. An endurance cycle is a write and an erase operation.
Table 45-42. Flash erase and programming current
Symbol Parameter Typ. Units
IDDIN Maximum Current (peak) during whole programming or erase operation 10 mA
45.12 Oscillator Characteristics
45.12.1 Crystal Oscillator (XOSC) Characteristics
45.12.1.1 Digital Clock Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN.
Table 45-43. Digital Clock Characteristics
Symbol Parameter Condition Min Typ Max Units
fCPXIN XIN clock frequency Digital mode - - 48 MHz
DCXIN(1) XIN clock duty cycle Digital mode 40 50 60 %
1. These are based on simulation. These values are not covered by test or characterization
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1178
45.12.1.2 Crystal Oscillator Characteristics
The following table describes the characteristics for the oscillator when a crystal is connected between
XIN and XOUT as shown in Figure 45-5. The user must choose a crystal oscillator where the crystal load
capacitance CL is within the range given in the table. The exact value of CL can be found in the crystal
datasheet. The capacitance of the external capacitors (CLEXT) can then be computed as follows:
CLEXT = 2 CL+CSTRAY CSHUNT
where CSTRAY is the capacitance of the pins and PCB, CSHUNT is the shunt capacitance of the crystal.
Figure 45-5. Oscillator Connection
CSHUNT
LM
RM
CM
CSTRAY
CLE XT
CLE XT
Xin
Crystal
Xout
Table 45-44. Multi Crystal Oscillator Electrical Characteristics (1)
Symbol Parameter Conditions Min. Typ. Max Units
Fout Crystal oscillator frequency 0.4 - 32 MHz
CL Crystal Load F = 0.455 MHz - - 100 pF
F = 2 MHz - - 20
F = 4 MHz - - 20
F = 8 MHz - - 20
F = 16 MHz - - 20
F = 32 MHz - - 18
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1179
...........continued
Symbol Parameter Conditions Min. Typ. Max Units
ESR Crystal Equivalent Series
Resistance - SF = 3
F = 0.455 MHz
CL = 100pF
XOSC.GAIN = 0
- - 443 Ω
F = 2MHz
CL=20pF
XOSC.GAIN=0
- - 383
F = 4MHz
CL=20pF
XOSC.GAIN=1
- - 218
F = 8MHz
CL=20pF
XOSC.GAIN=2
- - 114
F = 16MHz
CL=20pF
XOSC.GAIN=3
- - 61
F = 32MHz
CL=18pF
XOSC.GAIN=4
- - 41
Cxin Parasitic load capacitor - 5.9 - pF
Cxout - 3.1 -
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1180
...........continued
Symbol Parameter Conditions Min. Typ. Max Units
Tstart Startup time F = 2MHz
CL=20pF
XOSC.GAIN=0
- 12.3 35.3 KCycles
F = 4MHz
CL=20pF
XOSC.GAIN=1
- 8.2 21.4
F = 8MHz
CL=20pF
XOSC.GAIN=2
- 6.2 14.3
F = 16MHz
CL=20pF
XOSC.GAIN=3
- 10.8 18.1
F = 32MHz
CL=18pF
XOSC.GAIN=4
- 8.7 15.4
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1181
Table 45-45. Power Consumption (1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption F = 2MHz
CL=20pF
XOSC.GAIN=0
VDD = 5.0V
AGC=OFF
Max 85°C
Typ 25°C
150 202 µA
AGC=ON 138 192
F = 4MHz
CL=20pF
XOSC.GAIN=1
VDD = 5.0V
AGC=OFF
220 288
AGC=ON 175 260
F = 8MHz
CL=20pF
XOSC.GAIN=2
VDD = 5.0V
AGC=OFF
350 416
AGC=ON 247 321
F = 16MHz
CL=20pF
XOSC.GAIN=3
VDD = 5.0V
AGC=OFF
663 843
AGC=ON 429 699
F = 32MHz
CL=18pF
XOSC.GAIN=4
VDD = 5.0V
AGC=OFF
1975 2329
AGC=ON 874 1181
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1182
45.12.2 External 32 kHz Crystal Oscillator (XOSC32K) Characteristics
45.12.2.1 Digital Clock Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN32
pin.
Table 45-46. Digital Clock Characteristics
Symbol Parameter Condition Typ Units
fCPXIN32 XIN32 clock frequency Digital mode 32.768 kHz
DCXIN32 XIN32 clock duty cycle Digital mode 50 %
45.12.2.2 Crystal Oscillator Characteristics
The following table describes the characteristics for the oscillator when a crystal is connected between
XIN32 and XOUT32.
Figure 45-6. Oscillator Connection
XIN32
CSTRAY
CLEXT
CLEXT
CM
RM
LM
CSHUNT
XOUT32
DEVICE
Crystal
The user must choose a crystal oscillator where the crystal load capacitance CL is within the range given
in the table. The exact value of CL can be found in the crystal datasheet. The capacitance of the external
capacitors (CLEXT) can then be computed as follows:
CLEXT=2(CL-CSTRAY-CSHUNT)
where CSTRAY is the capacitance of the pins and PCB and CSHUNT is the shunt capacitance of the crystal.
Table 45-47. 32kHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
fOUT (1) Crystal oscillator frequency - 32768 - Hz
CL (1) Crystal load capacitance - - 12.5 pF
CSHUNT (1) Crystal shunt capacitance - - 1.75 pF
Cm (1) Motional capacitance - 1.25 - fF
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1183
...........continued
Symbol Parameter Conditions Min. Typ. Max Units
ESR Crystal Equivalent Series Resistance
- SF = 3
F = 32.768kHz,
CL=12.5 pF
- - 79 kΩ
Cxin32k Parasitic capacitor load - 2.9 - pF
Cxout32k - 3.2 - pF
Tstart Startup time F = 32.768kHz,
CL=12.5 pF
- 16 24 Kcycles
1. These are based on simulation. These values are not covered by test or characterization
Table 45-48. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V Max 85°C
Typ 25°C
1528 1720 nA
1. These are based on characterization.
45.12.3 Digital Phase Locked Loop (DPLL) Characteristics
Table 45-49. Fractional Digital Phase Locked Loop Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
fIN(1) Input frequency 32 2000 KHz
fOUT(1) Output frequency 48 96 MHz
Jp(2) Period jitter
(Peak-Peak value)
fIN= 32 kHz, fOUT= 48 MHz - 1.5 3.0 %
fIN= 32 kHz, fOUT= 96 MHz - 2.7 8.0
fIN= 2 MHz, fOUT= 48 MHz - 1.8 4.0
fIN= 2 MHz, fOUT= 96 MHz - 2.5 6.0
tLOCK(2) Lock Time After startup, time to get lock signal.
fIN= 32 kHz,
fOUT= 96 MHz
- 1.1 1.5 ms
After startup, time to get lock signal.
fIN= 2 MHz,
fOUT= 96 MHz
- 25 35 μs
Duty(1) Duty cycle - 50 - %
1. These values are based on simulation. These values are not covered by test limits in production or
characterization.
2. These values are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1184
Table 45-50. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current Consumption Ck=48MHz, VDD=5.0V Max 85°C
Typ 25°C
536 612 µA
Ck=96MHz, VDD=5.0V 865 970
1. These values are based on characterization.
45.12.4 32.768kHz Internal oscillator (OSC32K) Characteristics
Table 45-51. 32 kHz RC Oscillator Characteristics
Symbol Parameter Condition Min Typ Max Units
fOUT Output frequency T =25°C, VDDANA = 5.0V 32.112 32.768 33.423 kHz
T =25°C, over [2.7, 5.5]V 29.491 32.768 36.044
over [-40, 85]°C, over [2.7, 5.5]V 25.559 32.768 37.355
tSTARTUP Startup time 1 2 cycle
Duty(1) Duty Cycle 50 %
1. These are based on simulation. These values are not covered by test or characterization.
Table 45-52. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V Max 85°C
Typ 25°C
0.864 1.080 μA
1. These are based on characterization.
45.12.5 Ultra Low Power Internal 32kHz RC Oscillator (OSCULP32K) Characteristics
Table 45-53. Ultra Low Power Internal 32 kHz RC Oscillator Electrical Characteristics
Symbol Parameter Condition Min Typ Max Units
fOUT Output frequency T =25°C, VDDANA = 5.0V 30.965 32.768 34.57 kHz
T =25°C, over [2.7, 5.5]V 30.801 32.768 34.73
Over [-40, 85]°C, over [2.7, 5.5]V 22.937 32.768 38.99
Duty Duty Cycle 50 %
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1185
45.12.6 48 MHz RC Oscillator (OSC48M) Characteristics
Table 45-54. RC 48 MHz Oscillator Electrical Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
FOUT(1) Output frequency 0 to 40 °C 47.52 48 48.48 MHz
-20 to 85 °C 47.28 48 48.72
-40 to 85 °C 47.04 48 48.96
TSTART (2) Startup time - 3.9 15 μs
Duty (3) Duty Cycle - 50 - %
1. Applicable for all package types except the WLCSP, on which accuracy is degraded by ±1% from
the current values.
2. OSC48MSTUP.STARTUP field must be set accordingly.
3. These are based on simulation. These values are not covered by test or characterization.
Table 45-55. Power Consumption
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption Fout = 48 MHz, VDD =5.0V Max 85°C
Typ 25°C
87 174 µA
45.13 Timing Characteristics
45.13.1 SERCOM in SPI Mode Timing
Table 45-56. SPI Timing Characteristics and Requirements (1)
Symbol Parameter Conditions Min. Typ. Max. Units
tSCK(10) SCK period Master Reception 2*(tMIS+tSLAVE_OUT) (3) - - ns
Master Transmission 2*(tMOV+tSLAVE_IN) (4) - -
tSCKW SCK high/low width Master - 0.5*tSCK - ns
tSCKR SCK rise time (2) Master - 0.25*tSCK - ns
tSCKF SCK fall time (2) Master - 0.25*tSCK - ns
tMIS MISO setup to SCK Master, VDD>4.5V 50.7 - - ns
Master, VDD>2.7V 60.6 - -
tMIH MISO hold after SCK Master, VDD>4.5V 0 - - ns
Master, VDD>2.7V 0 - -
tMOV MOSI output valid SCK Master, VDD>4.5V - - 17.1 ns
Master, VDD>2.7V - - 23.6
tMOH MOSI hold after SCK Master, VDD>4.5V 2.5 - - ns
Master, VDD>2.7V 2.5 - -
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1186
...........continued
Symbol Parameter Conditions Min. Typ. Max. Units
tSSCK Slave SCK Period Slave Reception 2*(tSIS+tMASTER_OUT) (5) - - ns
Slave Transmission 2*(tSOV+tMASTER_IN) (6) - -
tSSCKW SCK high/low width Slave - 0.5*tSSCK - ns
tSSCKR SCK rise time (2) Slave - 0.25*tSSCK - ns
tSSCKF SCK fall time (2) Slave - 0.25*tSSCK - ns
tSIS MOSI setup to SCK Slave, VDD>4.5V 13.6 - - ns
Slave, VDD>2.7V 14.1 - -
tSIH MOSI hold after SCK Slave, VDD>4.5V 0 - - ns
Slave, VDD>2.7V 0 - -
tSSS SS setup to SCK Slave PRELOADEN=1 tSOSS+tEXT_MIS+2*tAPBC (8) (9) - - ns
PRELOADEN=0 tSOSS+tEXT_MIS (8) - -
tSSH SS hold after SCK Slave 0.5*tSSCK - - ns
tSOV MISO output valid SCK Slave, VDD>4.5V - - 45 ns
Slave, VDD>2.7V - - 55.1
tSOH MISO hold after SCK Slave, VDD>4.5V 11.9 - - ns
Slave, VDD>2.7V 11.9 - -
tSOSS MISO setup after SS low Slave, VDD>4.5V - - 41 ns
Slave, VDD>2.7V - - 50.7
tSOSH MISO hold after SS high Slave, VDD>4.5V 11.1 - - ns
Slave, VDD>2.7V 11.1 - -
1. These values are based on simulation. These values are not covered by test limits in production.
2. See I/O pin characteristics.
3. Where tSLAVE_OUT is the slave external device output response time, generally tEXT_SOV+tLINE_DELAY
(7).
4. Where tSLAVE_IN is the slave external device input constraint, generally tEXT_SIS+tLINE_DELAY (7).
5. Where tMASTER_OUT is the master external device output response time, generally tEXT_MOV
+tLINE_DELAY (7).
6. Where tMASTER_IN is the master external device input constraint, generally tEXT_MIS+tLINE_DELAY (7).
7. tLINE_DELAY is the transmission line time delay.
8. tEXT_MIS is the input constraint for the master external device.
9. tAPBC is the APB period for SERCOM.
10. When the integrity of communication is required to maintain both transmission and reception, the
maximum SPI clock frequency should be the lower value of the reception or transmission mode
maximum frequency as shown in the following equations.
– Reception: tSCK = 2*(tMIS+tSLAVE_OUT)
– Transmission: tSCK = 2*(tMOV+tSLAVE_IN)
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1187
Figure 45-7. SPI Timing Requirements in Master Mode
MSB LSB
BSLBSM
tMOH
tMIS tMIH
tSCKW
tSCK
tMOV
tMOH
tSCKF
tSCKR
tSCKW
MOSI
(Data Output)
MISO
(Data Input)
SCK
(CPOL = 1)
SCK
(CPOL = 0)
SS
Figure 45-8. SPI Timing Requirements in Slave Mode
MSB LSB
BSLBSM
tSIS tSIH
tSSCKW
tSSCKW
tSSCK
tSSH
tSCKR tSCKF
tSOV
tSSS
tSOSS
MISO
(Data Output)
MOSI
(Data Input)
SCK
(CPOL = 1)
SCK
(CPOL = 0)
SS
tSOH
tSOSH
45.13.2 External Reset
Table 45-57. External Reset Characteristics(1)
Symbol Parameter Min. Units
tEXT Minimum reset pulse width 1 μs
1. These are based on simulation. These values are not covered by test or characterization
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1188
45.13.3 CAN Timing
Table 45-58. CAN Physical Layer Timing(1)
Parameter Conditions Max. Units
TXCAN output delay VDD = 2.7V
Load = 20pF
VOL/VOH = VDD/2
13.9 ns
VDD = 4.5V
Load = 20pF
VOL/VOH = VDD/2
12.55
RXCAN input delay VDD = 2.7V
VOL/VOH = VDD/2
27.4
VDD = 4.5V
VOL/VOH = VDD/2
18.9
1. These values are based on simulation. These values are not covered by test limits in production.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 85°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1189
46. Electrical Characteristics 105°C (SAM C20/C21 E/G/J)
46.1 Disclaimer
All typical values are measured at Ta = 25°C unless otherwise specified. All minimum and maximum
values are valid across operating temperature and voltage unless otherwise specified.
This chapter contains only characteristics specific for the SAM C20/C21 E/G/J (Ta = 105°C). For all other
values or missing characteristics, refer to the 85°C chapter.
46.2 General Operating Ratings
The device must operate within the ratings listed in the table below in order for all other electrical
characteristics and typical characteristics of the device to be valid.
Table 46-1. General operating conditions
Symbol Parameter Min. Typ. Max. Units
TATemperature range -40 25 105 °C
TJJunction temperature - - 125 °C
46.3 Power Consumption
The values in the Power Consumption table below are measured values of power consumption under the
following conditions, except where noted:
• Operating conditions
– VDDIN = 3.0 V, 5.0V
• Oscillators
– XOSC (crystal oscillator) stopped
– XOSC32K (32 kHz crystal oscillator) running with external 32kHz crystal
– FDPLL using XOSC32K as reference and running at 48 MHz
• Clocks
– FDPLL used as main clock source, except otherwise specified
– CPU, AHB clocks undivided
– All peripheral clocks stopped
• I/Os are inactive with input trigger disable
• CPU is running on Flash with Wait states specified in NVM Max Speed Characteristics
• NVMCTRL cache enabled
• BODVDD disabled
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1190
Table 46-2. Current Consumption(1)
Mode Conditions Ta Vcc Typ. Max. Units
ACTIVE CPU running a While 1
algorithm
25°C 5.0V 3.8 4.2 mA
105°C 5.0V 4.0 4.5
CPU running a While 1
algorithm
25°C 3.0V 3.7 4.1 mA
105°C 3.0V 4.0 4.5
CPU running a While 1
algorithm. with GCLKIN as
reference
25°C 5.0V 71*Freq+160 78*Freq+162 µA (with freq
in MHz)
105°C 5.0V 71*Freq+374 72*Freq+819
CPU running a Fibonacci
algorithm
25°C 5.0V 4.7 5.2 mA
105°C 5.0V 5.0 5.5
CPU running a Fibonacci
algorithm
25°C 3.0V 4.7 5.1 mA
105°C 3.0V 5.0 5.5
CPU running a Fibonacci
algorithm. with GCLKIN as
reference
25°C 5.0V 90*Freq+163 99*Freq+168 µA (with freq
in MHz)
105°C 5.0V 90*Freq+379 92*Freq+820
CPU running a CoreMark
algorithm
25°C 5.0V 5.9 6.4 mA
105°C 5.0V 6.3 6.9
CPU running a CoreMark
algorithm
25°C 3.0V 5.2 5.7 mA
105°C 3.0V 5.5 6.1
CPU running a CoreMark
algorithm. with GCLKIN as
reference
25°C 5.0V 115*Freq+167 126*Freq+167 µA (with freq
in MHz)
105°C 5.0V 118*Freq+383 121*Freq+823
IDLE 25°C 5.0V 1.2 1.3 mA
105°C 5.0V 1.5 2.6
STANDBY XOSC32K running RTC
running at 1kHz
25°C 5.0V 15.9 37.0 µA
105°C 5.0V 187.0 512.0
XOSC32K and RTC stopped 25°C 5.0V 14.6 35.0
105°C 5.0V 185.0 510.0
1. These are based on characterization.
46.4 Analog Characteristics
46.4.1 Brown-out Detector Characteristics - BODVDD
See NVM User Row Mapping for the BODVDD default value settings. These values are based on
simulation and are not covered by test limits in production or characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1191
Figure 46-1. BODVDD Hysteresis OFF
Figure 46-2. BODVDD Hysteresis ON
Table 46-3. Power Consumption (see Note 1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD IDLE, Mode CONT VDD = 2.7V Max 105°C
Typ 25°C
22.5 26.7 µA
VDD = 5.0V 41.0 47.9
IDLE, Mode SAMPL VDD = 2.7V 0.1 1.5
VDD = 5.0V 0.1 1.9
STANDBY, Mode SAMPL VDD = 2.7V 0.8 2.1
VDD = 5.0V 3.5 4.9
Note: 
1. These values are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1192
Table 46-4. BODVDD Characteristics (see Note 2)
Symbol Parameters Conditions Min Typ Max Unit
VBOD+ (see Note 1) BODVDD high threshold
Level
VDD level, BOD setting =
8 (default)
- 2.86 2.98 V
VDD level, BOD setting =
9
- 2.92 3.01
VDD level, BOD setting =
44
- 4.57 4.82
VBOD- / VBOD (see
Note 1)
BODVDD low threshold Level VDD level, BOD setting =
8 (default)
2.71 2.8 2.90
VDD level, BOD setting =
9
2.75 2.85 2.96
VDD level, Bod setting =
44
4.37 4.51 4.66
Step size - 60 - mV
VHys (see Note 1) Hysteresis (VBOD+ - VBOD-)
BODVDD.LEVEL = 8 to 48
VDD 40 - 75 mV
Tstart (see Note 3) Startup time Time from enable to RDY - 3.1 - μs
Note: 
1. These values are based on characterization.
2. BODVDD in Continuous mode.
3. These values are based on simulation, and are not covered by test or characterization.
Related Links
9.3 NVM User Row Mapping
9.3 NVM User Row Mapping
SAM C20/C21 Family Data Sheet
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46.4.2 Analog-to-Digital Converter (ADC) Characteristics
Table 46-5. Power Consumption (1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD
VDDANA
Differential
mode
fs = 1 Msps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
Max 105°C
Typ 25°C
905 1084
uA
fs = 1 Msps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
1144 1425
fs = 10 ksps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
381 518
fs = 10 ksps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
609 877
Single Ended
mode
fs = 1 Msps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref=5.5V
Max 105°C
Typ 25°C
984 1154
uA
fs = 1 Msps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref=5.5V
1178 1467
fs = 10 ksps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
437 588
fs = 10 ksps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
635 908
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1194
46.4.3 Sigma-Delta-Analog-to-Digital Converter (SDADC) Characteristics
Table 46-6. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD
VDDANA
Power
consumption
CTLSDADC=0x0 External Ref -
VDDANA = 5.5V Vref = 2V Ref buf on
SCLK_SDADC = 6 MHz
Max 105°C
Typ 25°C
644 710 uA
CTLSDADC=0x0 Internal Ref -
VDDANA=Vref= 5.5V Ref buf off
SCLK_SDADC = 6 MHz
605 649
1. These are based on characterization.
46.4.4 Digital-to-Analog Converter (DAC) Characteristics
Table 46-7. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD VDDANA DC supply current Output buffer On, VREF =
VDDANA=5.0V
Max 105°C
Typ 25°C
318 414 µA
Output buffer Off, VREF =
VDDANA=5.0V
74 82
1. These values are based on characterization.
46.4.5 Analog Comparator (AC) Characteristics
Table 46-8. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDDANA Current consumption -
Vcm=Vddana/2,
+-100 mV overdrive from Vcm,
Voltage scaler disabled
COMPCTRLn.SPEED = 0x0,
VDDANA =5.0V
Max 105°C
Typ 25°C
10 18 µA
COMPCTRLn.SPEED = 0x3,
VDDANA =5.0V
39 60
Current consumption Voltage
scaler only
VDDANA =5.0V 43 63
1. These values are based on characterization.
46.4.6 Temperature Sensor Characteristics
Table 46-9. Temperature Sensor Characteristics(1)
Parameter Condition Min. Max. Unit
Accuracy [-40,105]°C -14.6 10.5 °C
1. These are based on characterization. Data has been obtained by averaging 10 TSENS acquisitions
per measurement.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1195
46.5 NVM Characteristics
Table 46-10. Flash Endurance
Symbol Parameter Conditions Min. Typ. Units
CycNVM Cycling Endurance(1) -40°C < TA < 105°C 5k - Cycles
1. An endurance cycle is a write and an erase operation.
Table 46-11. EEPROM Emulation(1) Endurance
Symbol Parameter Conditions Min. Typ. Units
CycEEPROM Cycling Endurance(2) -40°C < TA < 105°C 100k - Cycles
1. The EEPROM emulation is a software emulation described in the application note AT03265.
2. An endurance cycle is a write and an erase operation.
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1196
46.6 Oscillator Characteristics
46.6.1 Crystal Oscillator (XOSC) Characteristics
Table 46-12. Power Consumption(1)
Symbol Parameters Conditions TATyp. Max Units
IDD Current consumption F = 2MHz
CL=20pF
XOSC.GAIN=0
VDD = 5.0V
AGC=OFF Max 105°C
Typ 25°C
150 206 µA
AGC=ON 138 198
F = 4MHz
CL=20pF
XOSC.GAIN=1
VDD = 5.0V
AGC=OFF 220 293
AGC=ON 175 267
F = 8MHz
CL=20pF
XOSC.GAIN=2
VDD = 5.0V
AGC=OFF 350 425
AGC=ON 247 331
F = 16MHz
CL=20pF
XOSC.GAIN=3
VDD = 5.0V
AGC=OFF 663 861
AGC=ON 429 725
F = 32MHz
CL=18pF
XOSC.GAIN=4
VDD = 5.0V
AGC=OFF 1975 2397
AGC=ON 874 1252
1. These are based on characterization
46.6.2 External 32kHz Crystal Oscillator (XOSC32K) Characteristics
Table 46-13. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V Max 105°C
Typ 25°C
1528 1740 nA
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1197
46.6.3 Digital Phase Locked Loop (DPLL) Characteristics
Table 46-14. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current Consumption Ck=48MHz
VDD=5.0V
Max 105°C
Typ 25°C
536 629 µA
Ck=96MHz
VDD=5.0V
865 986
1. These are based on characterization.
46.6.4 32.768kHz Internal Oscillator (OSC32K) Characteristics
Table 46-15. 32 kHz RC Oscillator Electrical Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
FOUT Output frequency T=25°C
VDDANA = 5.0V
32.112 32.768 33.423 kHz
T=25°C
Over [2.7, 5.5]V
29.491 32.768 36.044 kHz
Over [-40,105]°C
Over [2.7, 5.5]V
25.559 32.768 37.683 kHz
Tstartup Startup time - 1 2 cycles
Duty (1) Duty cycle - 50 - %
1. These are based on simulation. These values are not covered by test or characterization.
Table 46-16. Power Consumption
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V Max 105°C
Typ 25°C
0.864 1.116 μA
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1198
46.6.5 Ultra Low Power Internal 32kHz RC Oscillator (OSCULP32K) Characteristics
Table 46-17. Ultra Low Power Internal 32 kHz RC Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
Fout Output frequency T=25°C
VDDANA = 5.0V
30.965 32.768 34.57 kHz
T=25°C
Over [2.7, 5.5]V
30.801 32.768 34.734 kHz
Over [-40, 105]°C
Over [2.7, 5.5]V
22.937 32.768 40.632 kHz
Duty Duty Cycle - 50 - %
46.6.6 48 MHz RC Oscillator (OSC48M) Characteristics
Table 46-18. RC 48 MHz Oscillator Electrical Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
FOUT Output frequency 0 to 40°C 47.52 48 48.48 MHz
-20 to 85°C 47.28 48 48.72
-40 to 105°C 46.8 48 49.2
TSTART (1) Startup time - 3.9 15 μs
Duty (2) Duty Cycle - 50 - %
1. OSC48MSTUP.STARTUP field must be set accordingly.
2. These are based on simulation. These values are not covered by test or characterization.
Table 46-19. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption FOUT = 48 MHz
VDD =5.0V
Max 105°C
Typ 25°C
87 267 µA
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1199
47. Electrical Characteristics 105°C (SAM C20/C21 N)
47.1 Disclaimer
All typical values are measured at Ta = 25°C unless otherwise specified. All minimum and maximum
values are valid across operating temperature and voltage unless otherwise specified.
This chapter contains only characteristics specific for the SAM C20/C21N devices (Ta = 105°C). For all
other values or missing characteristics, refer to the SAM C20/C21E/G/J 85°C and 105°C chapters.
Related Links
45. Electrical Characteristics 85°C (SAM C20/C21 E/G/J)
47.2 General Operating Ratings
The device must operate within the ratings listed in the table below in order for all other electrical
characteristics and typical characteristics of the device to be valid.
Table 47-1. General operating conditions
Symbol Parameter Min. Typ. Max. Units
TATemperature range -40 25 105 °C
TJJunction temperature - - 125 °C
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1200
47.3 Power Consumption
Table 47-2. Power Consumption(1)
Mode Conditions Ta Vcc Typ. Max. Units
ACTIVE CPU running a While 1 algorithm 25°C 5.0V 3.8 4.2 mA
105°C 5.0V 4.0 5.0
CPU running a While 1 algorithm 25°C 3.0V 3.7 4.1 mA
105°C 3.0V 4.0 5.0
CPU running a While 1 algorithm. with
GCLKIN as reference
25°C 5.0V 71*Freq+160 78*Freq+162 µA (with freq in
MHz)
105°C 5.0V 71*Freq+374 68*Freq+1564
CPU running a Fibonacci algorithm 25°C 5.0V 4.7 5.2 mA
105°C 5.0V 5.0 6.1
CPU running a Fibonacci algorithm 25°C 3.0V 4.7 5.1 mA
105°C 3.0V 5.0 6.0
CPU running a Fibonacci algorithm. with
GCLKIN as reference
25°C 5.0V 90*Freq+163 99*Freq+168 µA (with freq in
MHz)
105°C 5.0V 90*Freq+379 90*Freq+1568
CPU running a CoreMark algorithm 25°C 5.0V 5.9 6.4 mA
105°C 5.0V 6.3 7.1
CPU running a CoreMark algorithm 25°C 3.0V 5.2 5.7 mA
105°C 3.0V 5.5 6.6
CPU running a CoreMark algorithm. with
GCLKIN as reference
25°C 5.0V 115*Freq+167 126*Freq+167 µA (with freq in
MHz)
105°C 5.0V 118*Freq+383 110*Freq+1583
IDLE 25°C 5.0V 1.2 1.7 mA
105°C 5.0V 1.5 2.6
STANDBY XOSC32K running RTC running at 1kHz 25°C 5.0V 15.9 37.0 µA
105°C 5.0V 187.0 602.0
XOSC32K and RTC stopped 25°C 5.0V 14.6 35.0
105°C 5.0V 185.0 600.0
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1201
47.4 Analog Characteristics
47.4.1 Power On Reset (POR) Characteristics
Table 47-3. POR Characteristics
Symbol Parameters Min Typ Max Unit
VPOT+ Voltage threshold Level on VDDIN rising - 2.55 - V
VPOT- Voltage threshold Level on VDDIN falling 1.77 1.92 2.04
Figure 47-1. POR Operating Principle
Reset VDDCORE
VPOT+
V
Time
POT-
47.4.2 Brown Out Detectors (BOD) Characteristics
See NVM User Row Mapping for the BODVDD default value settings. These values are based on
simulation and are not covered by test limits in production or characterization.
Figure 47-2. BODVDD Hysteresis OFF
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
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Figure 47-3. BODVDD Hysteresis ON
Table 47-4. BODVDD Characteristics(2)
Symbol Parameters Conditions Min Typ Max Unit
VBOD+(1) BODVDD high threshold Level VDD level, Bod setting = 8 (default) - 2.86 2.98 V
VDD level, Bod setting = 9 - 2.92 3.01
VDD level, Bod setting = 44 - 4.57 4.82
VBOD- / VBOD(1) BODVDD low threshold Level VDD level, Bod setting = 8 (default) 2.71 2.80 2.90
VDD level, Bod setting = 9 2.75 2.85 2.96
VDD level, Bod setting = 44 4.37 4.51 4.66
Step size - 60 - mV
VHys(1) Hysteresis (VBOD+ - VBOD-)
BODVDD.LEVEL = 8 to 48
VDD 40 - 75 mV
TSTART(3) Startup time Time from enable to RDY - 3.1 - µs
1. These are based on characterization.
2. BODVDD in continuous mode.
3. These are based on simulation. These values are not covered by test or characterization.
47.4.3 Analog-to-Digital Converter (ADC) Characteristics
Table 47-5. Operating Conditions(1)
Symbol Parameters Conditions Min Typ Max Unit
Res Resolution - - 12 bits
Rs Sampling rate 10 - 1000 ksps
fs Sampling clock 10 - 1000 kHz
Differential mode Number of ADC clock cycles
SAMPCTRL.OFFCOMP=1
resolution 12 bit
(CTRLC.RESSEL=0)
- 16 - cycles
resolution 10 bit
(CTRLC.RESSEL=2)
14
resolution 8 bit
(CTRLC.RESSEL=3)
12
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Electrical Characteristics 105°C (SAM ...
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...........continued
Symbol Parameters Conditions Min Typ Max Unit
Differential mode Number of ADC clock cycles
SAMPCTRL.OFFCOMP=0 SAMPLEN
corresponds to the decimal value of
SAMPCTRL.SAMPLEN[5:0] register
resolution 12 bit
(CTRLC.RESSEL=0)
- SAMPLEN+13 - cycles
resolution 10 bit
(CTRLC.RESSEL=2)
SAMPLEN+11
resolution 8 bit
(CTRLC.RESSEL=3)
SAMPLEN+9
Single-ended mode Number of ADC clock
cycles SAMPCTRL.OFFCOMP=1
resolution 12 bit
(CTRLC.RESSEL=0)
- 16 - cycles
resolution 10 bit
(CTRLC.RESSEL=2)
15
resolution 8 bit
(CTRLC.RESSEL=3)
13
Single-ended mode Number of ADC clock
cycles SAMPCTRL.OFFCOMP=0 SAMPLEN
corresponds to the decimal value of
SAMPCTRL.SAMPLEN[5:0] register
resolution 12 bit
(CTRLC.RESSEL=0)
- SAMPLEN+13 - cycles
resolution 10 bit
(CTRLC.RESSEL=2)
SAMPLEN+12
resolution 8 bit
(CTRLC.RESSEL=3)
SAMPLEN+10
fadc ADC Clock frequency SAMPCTRL.OFFCOMP=1 or
CTRLC.R2R=1
- fs*16 - Hz
SAMPCTRL.OFFCOMP=0 - fs*13 -
Ts Sampling time SAMPCTRL.OFFCOMP=1 or
CTRLC.R2R=1
250 - 25000 ns
SAMPCTRL.OFFCOMP=0 76 - 7692
Sampling time with DAC as input SAMPCTRL.OFFCOMP=1 or
CTRLC.R2R=1
3000 - 25000
SAMPCTRL.OFFCOMP=0 3000 - 7692
Conversion range Differential mode -VREF - +VREF V
Conversion range Single-ended mode 0 - VREF
Vref Reference input REFCTRL.REFCOMP=1 2 - VDDANA-0.6 V
REFCTRL.REFCOMP=0 VDDANA - VDDANA
Vin Input channel range - 0 - VDDANA V
Vcmin Input common mode voltage CTRLC.R2R=1 0.2 - VREF-0.2 V
CTRLC.R2R=0 VREF/2-0.2 - VREF/2+0.2 V
CSAMPLE Input sampling capacitance - 1.6 4.5 pF
RSAMPLE Input sampling on-resistance For a sampling rate at 1 Msps - 1000 1715 Ω
Rref Reference input source resistance 0 - 1000 kΩ
1. These values are based on simulation. These values are not covered by test limits in production or
characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1204
Figure 47-4. ADC Analog Input AINx
The minimum sampling time tsamplehold for a given Rsource can be found using this formula:
samplehold sample +source ×sample ×+ 2 × ln 2
For 12-bit accuracy:
samplehold sample +source ×sample × 9.7
where samplehold 1
2 × ADC
.
Table 47-6. Differential Mode
Symbol Parameter Conditions Measurement Unit
Min Typ Max
ENOB(1) Effective Number of
bits
Fadc = 500 ksps - R2R disabled Vddana=5.0V Vref=Vddana 9.9 10.7 11.4 bits
Vddana=2.7V Vref=2.0V 10.0 10.8 11.3
Fadc = 1 Msps - R2R disabled Vddana=5.0V Vref=Vddana 9.7 10.6 11.3
Vddana=2.7V Vref=2.0V 9.8 10.6 11.2
Fadc = 500 ksps - R2R Enabled(2) Vddana=5.0V Vref=Vddana 9.8 11.3 11.9
Fadc = 1 Msps - R2R Enabled(2) Vddana=5.0V Vref=Vddana 9.7 11.1 11.8
TUE Total Unadjusted
Error
Fadc = 500 ksps - R2R disabled with offset
and gain compensation
Vddana=5.0V Vref=Vddana - +/-3.4 +/-5 LSB
Vddana=2.7V Vref=2.0V - +/-3 +/-5.6
Fadc = 1 Msps - R2R disabled with offset
and gain compensation
Vddana=5.0V Vref=Vddana - +/-4.2 +/-6.3
Vddana=2.7V Vref=2.0V - +/-3.6 +/-7.7
INL Integral Non Linearity Fadc = 500 ksps - R2R disabled Vddana=5.0V Vref=Vddana - +/-1.9 +/-3.5 LSB
Vddana=2.7V Vref=2.0V - +/-1.6 +/-3.5
Fadc = 1 Msps - R2R disabled Vddana=5.0V Vref=Vddana - +/-2 +/-3.3
Vddana=2.7V Vref=2.0V - +/-1.9 +/-3.6
DNL Differential Non
Linearity
Fadc = 500 ksps - R2R disabled Vddana=5.0V Vref=Vddana - -0.9/+1 -1/+1.2 LSB
Vddana=2.7V Vref=2.0V - -0.9/+1.1 -1/+2.1
Fadc = 1 Msps - R2R disabled Vddana=5.0V Vref=Vddana - -0.9/+1 -1/+1
Vddana=2.7V Vref=2.0V - -1/+1.6 -1/+3.6
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1205
...........continued
Symbol Parameter Conditions Measurement Unit
Min Typ Max
Gain Gain Error Fadc = 1 Msps - R2R disabled w/o gain
compensation
Vddana=5.0V Vref=Vddana - +/-0.06 +/-0.3 %
Vddana=2.7V Vref=2.0V - +/-0.06 +/-1.2
Vddana=5.0V 1V internal
Ref
- +/-1.9 +/-6.5
Vddana=5.0V
Vref=Vddana/2
- +/-0.11 +/-0.82
Fadc = 1 Msps - R2R disabled with gain
compensation
Vddana=2.7V Vref=2.0V - +/-0.03 +/-0.46
Vddana=5.0V
Vref=Vddana/2
- +/-0.13 +/-0.58
Offset Offset Error Fadc = 1 Msps - R2R disabled without offset
compensation
Vddana=5.0V
Vref=Vddana/2
- +/-0.8 +/-13 mV
Vddana=2.7V Vref=2.0V - +/-0.7 +/-9.7
Fadc = 1 Msps - R2R disabled with offset
compensation
Vddana=5.0V
Vref=Vddana/2
- +/-0.01 +/-5.6
Vddana=2.7V Vref=2.0V - +/-0.4 +/-4.2
SFDR Spurious Free Dynamic Range Fs = 1Msps / Fin = 14 kHz /
Full range Input signal
Vddana=5.0V Vref=Vddana
63 71 81 dB
SINAD(1) Signal to Noise and Distortion ratio 60 65 70
SNR at -3 db
FS
Signal to Noise ratio 64 67 70
THD Total Harmonic Distortion 63 -70 81
Noise RMS External Reference voltage - 0.4 3.2 mV
1. Referred to Full Scale.
2. Dynamical input range is +/-6% of Full scale.
Table 47-7. Single-Ended Mode
Symbol Parameter Conditions Measurement Unit
Min Typ Max
ENOB(1) Effective Number of
bits
Fadc = 500 ksps - R2R disabled Vddana=3.0V Vref=Vddana 9.0 9.7 10.2 bits
Vddana=3.0V Vref=2.0V 9.0 9.6 10.1
Fadc = 1 Msps - R2R disabled Vddana=3.0V Vref=Vddana 8.9 9.6 10.0
Vddana=3.0V Vref=2.0V 8.9 9.4 9.7
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1206
...........continued
Symbol Parameter Conditions Measurement Unit
Min Typ Max
TUE Total Unadjusted
Error
Fadc = 500 ksps - R2R disabled with offset
and gain compensation
Vddana=5.0V Vref=Vddana - +/-12.9 +/-25.2 LSB
Vddana=2.7V Vref=2.0V - +/-25 +/-49.6
Fadc = 1 Msps - R2R disabled with offset
and gain compensation
Vddana=5.0V Vref=Vddana - +/-13.5 +/-26.4
Vddana=2.7V Vref=2.0V - +/-27 +/-52
INL Integral Non Linearity Fadc = 500 ksps - R2R disabled Vddana=5.0V Vref=Vddana - +/-3.7 +/-6.5
Vddana=2.7V Vref=2.0V - +/-3.4 +/-5.9
Fadc = 1 Msps - R2R disabled Vddana=5.0V Vref=Vddana - +/-4.2 +/-7.4 LSB
Vddana=2.7V Vref=2.0V - +/-3.5 +/-6.2
DNL Differential Non
Linearity
Fadc = 500 ksps - R2R disabled Vddana=5.0V Vref=Vddana - -0.9/+1.2 -1/+1.6
Vddana=2.7V Vref=2.0V - -0.9/+1.3 -1/+2.3
Fadc = 1 Msps - R2R disabled Vddana=5.0V Vref=Vddana - -1/+1.1 -1/+1.3
Vddana=2.7V Vref=2.0V - -1/+1.4 -1/+3.1
Gain Gain Error Fadc = 1 Msps - R2R disabled w/o gain
compensation
Vddana=5.0V Vref=Vddana - +/-0.2 +/-0.7 %
Vddana=2.7V Vref=2.0V - +/-0.3 +/-1.4
Vddana=5.0V 1V internal Ref - +/-1.6 +/-6.6
Vddana=5.0V Vref=Vddana/2 - +/-0.2 +/-1.1
Fadc = 1 Msps - R2R disabled with gain
compensation
Vddana=2.7V Vref=2.0V - +/-0.3 +/-0.8
Vddana=5.0V Vref=Vddana/2 - +/-0.1 +/-0.5
Offset Offset Error Fadc = 1 Msps - R2R disabled Vddana=5.0V Vref=Vddana - +/-7 +/-63 mV
Vddana=2.7V Vref=2.0V - +/-7 +/-64
SFDR Spurious Free Dynamic Range Fs = 1Msps / Fin = 14 kHz /
Full range Input signal
Vddana=5.0V Vref=Vddana
57 66 73 dB
SINAD(1) Signal to Noise and Distortion ratio 54 59 62
SNR at -3 db
FS
Signal to Noise ratio 57 60 62
THD Total Harmonic Distortion -71 -64 -56
Noise RMS External Reference voltage - 0.6 1.9 mV
1. Referred to Full Scale.
47.4.4 Sigma-Delta Analog-to-Digital Converter (SDADC) Characteristics
Table 47-8. Operating Conditions(1)
Symbol Parameters Conditions Min Typ Max Unit
Res Resolution Differential mode - 16 - bits
Single-Ended mode - 15 -
SAM C20/C21 Family Data Sheet
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...........continued
Symbol Parameters Conditions Min Typ Max Unit
CLK_SDADC Sampling Clock Speed Chopper OFF (ANACTRL.ONCHOP = 0) 1 - 6 MHz
Chopper ON (ANACTRL.ONCHOP = 1) 1 - 3
CLK_SDADC_FS Conversion rate CLK_SDADC/4
fs Output Data Rate Free running mode CLK_SDADC_FS / OSR
Single conversion mode SKPCNT = N (CLK_SDADC_FS / OSR) x (N+1)
OSR Oversampling ratio Differential mode 64 256 1024 Cycles
Input Conversion range Differential mode
Gaincorr = 0x1
- VREF - VREF V
Single-Ended mode
Gaincorr = 0x1
0 - VREF
Vref Reference Voltage range 1 - 5.5 V
Vcom Common mode voltage Differential mode 0 - AVDD V
Cin Input capacitance 0.425 0.5 0.575 pF
Zin Input impedance Differential mode 1/(Cin x CLK_SDADC_FS) kΩ
Single-Ended mode 1/(Cin x CLK_SDADC_FS x 2)
Input anti-alias filter recommendation(2) Rext - 1.0 - kΩ
Cext 3.3 - 10 nF
1. These are based on simulation. These values are not covered by test or characterization.
2. External Anti-alias filter must be placed in front of each SDADC input to ensure high-frequency
signals to not alias into measurement bandwidth. Use capacitors of X5R type for DC measurement.
or capacitors of COG or NPO type for AC measurement.
Table 47-9. SDADC DC Performance: Differential Input Mode. Chopper ON(1)
Symbol Parameters Conditions (2) Min Typ Max Unit
INL Integral Non Linearity CLK_SDADC = 3MHz VREF = 1.2V - +/-2.9 +/-3.9 LSB
CLK_SDADC = 3MHz INT VREF = 5.5V - +/-8.4 +/-9.3
DNL Differential Non Linearity CLK_SDADC = 3MHz VREF = 1.2V - +/-1.5 +/-2.1 LSB
CLK_SDADC = 3MHz INT VREF = 5.5V - +/-1.7 +/-2.3
Eg Gain Errors CLK_SDADC = 3MHz VREF = 1.2V - +/-0.3 +/-1.9 %
CLK_SDADC = 3MHz INT VREF = 5.5V - +/-0.3 +/-1.7
TCg Gain Drift CLK_SDADC = 3MHz VREF = 1.2V -0.9 3.9 17.5 ppm/°C
Off Offset Error CLK_SDADC = 3MHz VREF = 1.2V - +/-2.3 +/-3.7 mV
CLK_SDADC = 3MHz INT VREF = 5.5V - +/-0.3 +/-2.4
Tco Offset Error Drift CLK_SDADC = 3MHz VREF = 1.2V -1.4 0.01 0.6 uV/°C
1. OSR=256
SAM C20/C21 Family Data Sheet
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© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1208
Table 47-10. SDADC DC Performance: Differential Input Mode. Chopper OFF(1)
Symbol Parameters Conditions (2) Min Typ Max Unit
INL Integral Non Linearity CLK_SDADC = 6MHz VREF = 1.2V - +/-5.5 +/-9.3 LSB
CLK_SDADC = 6MHz INT VREF = 5.5V - +/-8.9 +/-10.1
DNL Differential Non Linearity CLK_SDADC = 6MHz VREF = 1.2V - +/-2.8 +/-4.1 LSB
CLK_SDADC = 6MHz INT VREF = 5.5V - +/-1.8 +/-3
Eg Gain Errors CLK_SDADC = 6MHz VREF = 1.2V - +/-0.6 +/-2.1 %
CLK_SDADC = 6MHz INT VREF = 5.5V - +/-0.3 +/-1.7
TCg Gain Drift CLK_SDADC = 6MHz VREF = 1.2V -19.7 2.2 20.9 ppm/°C
Off Offset Error CLK_SDADC = 6MHz VREF = 1.2V - +/-1.7 +/-14.3 mV
CLK_SDADC = 6MHz INT VREF = 5.5V - +/-4.9 +/-13.2
Tco Offset Error Drift CLK_SDADC = 6MHz VREF = 1.2V -14 12.4 60 μV/°C
Input noise rms AC Input noise rms OSR = 256 VREF = 1.2V - 19 20
OSR = 256 VREF = 5.5V - 59 76 mVrms
1. OSR=256
Table 47-11. SDADC AC Performance: : Differential Input Mode(1)
Symbol Parameters Conditions (2) Min Typ Max Unit
ENOB Effective Number Of Bits Ext ref = 1.2V 12 15.3 15.4 bits
Int Ref = 5.5V 12.9 13.1 14
DR Dynamic Range Ext ref = 1.2V 90.5 92.4 93.2 dB
Int Ref = 5.5V 83.0 95.6 97.0
SNR Signal to Noise Ratio Ext ref = 1.2V 68.7 88.7 89 dB
Int Ref = 5.5V 83 95.6 97
SINAD Signal to Noise + Distortion Ratio Ext ref = 1.2V 71.1 90.7 91.7 dB
Int Ref = 5.5V 77.1 78.6 83.2
THD Total Harmonic Distortion Ext ref = 1.2V -102.3 -94.6 -75.3 dB
Int Ref = 5.5V -99.9 -94.7 -85.4
1. Values based on characterization.
2. OSR=256, Chopper OFF, Sampling Clock Speed at 6MHz.
47.4.5 Digital to Analog Converter (DAC) Characteristics
Table 47-12. Operating Conditions(1)
Symbol Parameters Conditions Min Typ Max Unit
RES Input resolution - - 10 Bits
VDDANA Analog supply voltage 2.7 - 5.5 V
AVREF External reference voltage 1 - VDDANA - 0.6 V
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1209
...........continued
Symbol Parameters Conditions Min Typ Max Unit
Internal reference voltage 1 VREF.SEL = 0x0 - 1.024 - V
VREF.SEL = 0x2 - 2.048 -
VREF.SEL = 0x3 - 4.096 (2) -
Internal reference voltage 2 - VDDANA - V
Linear output voltage range 0.05 - VDDANA - 0.05 V
Minimum resistive load 5 - - kΩ
Maximum capacitance load - - 100 pF
1. These are based on simulation. These values are not covered by test or characterization.
2. For VDDANA > 4.5V.
Table 47-13. Clock and Timing(1)
Symbol Parameter Conditions Max. Units
Conversion rate Cload=100pF
Rload > 5kΩ
Normal mode 350 ksps
For DDATA=±1 1000
Startup time 3 μs
1. These values are based on simulation. These values are not covered by test limits in production or
characterization.
Table 47-14. Accuracy Characteristics(1)
Symbol Parameter Conditions Typ. Max. Units
INL Integral non-linearity VREF= Ext 2.0V VDD = 2.7V +/-0.7 +/-2.4 LSB
VDD = 5.5V +/-0.5 +/-1.6
VREF = VDDANA VDD = 2.7V +/-0.6 +/-2.0
VDD = 5.5V +/-0.4 +/-1.6
VREF= 1.024V INT REF VDD = 2.7V +/-1.0 +/-2.5
VDD = 5.5V +/-1.5 +/-3.5
DNL Differential non-linearity VREF= Ext 2.0V VDD = 2.7V +/-0.3 +/-2.3 LSB
VDD = 5.5V +/-0.4 +/-2.2
VREF = VDDANA VDD = 2.7V +/-0.2 +/-2.1
VDD = 5.5V +/-0.2 +/-2.1
VREF= 1.024V INT REF VDD = 2.7V +/-1.0 +/-2.5
VDD = 5.5V +/-1.4 +/-3.5
Gain error Ext. VREF +/-8 +/-28 mV
Offset error Ext. VREF +/-4 +/-26 mV
1. These values are based on characterization. These values are not covered by test limits in
production.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1210
47.4.6 Analog Comparator Characteristics
Table 47-15. Analog Comparator Characteristics
Symbol Parameters Conditions Min Typ Max Unit
PNIVR Positive and Negative input
range voltage
0 - VDDANA V
ICMR Input common mode range 0 - VDDANA V
Off (1)(2) Offset Low power
COMPCTRLn.SPEED = 0x0
-55 -4/+2 51 mV
High speed
COMPCTRLn.SPEED = 0x3
-22 -2/+1 20
VHYS (1)(3) Hysteresis High speed
COMPCTRLn.SPEED = 0x3
39 106 156 mV
TPD (1) Propagation Delay
Vcm=Vddana/2
Vin = ±100mV overdrive from
Vcm
Low power
COMPCTRLn.SPEED = 0x0
- 149 268 ns
High speed
COMPCTRLn.SPEED =0x3
- 41 73
TSTART (1) Startup time Low power
COMPCTRLn.SPEED = 0x0
- 6.8 10.4 μs
High speed
COMPCTRLn.SPEED = 0x3
- 2.2 3.7
VSCALE (1) INL - 0.569 - LSB
DNL - 0.053 -
Offset Error - 0.042 -
Gain Error - 0.041 -
1. These are based on characterization.
2. Hysteresis disabled.
3. Hysteresis enabled.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1211
47.4.7 Voltage Reference Characteristics
Table 47-16. Voltage Reference Characteristics(1)
Symbol Parameter Conditions Min. Typ. Max. Units
ADC / SDADC / DAC
Ref
ADC, SDADC,
DAC Internal
reference
nom. 1.024V
VDDANA=5.0V
Ta= 25°C
1.003 1.024 1.045 V
nom. 2.048V
VDDANA=5.0V
Ta= 25°C
2.007 2.048 2.089
nom. 4.096V
VDDANA=5.0V
Ta= 25°C
4.014 4.096 4.178
Reference
temperature
coefficient
Drift over [-40, +25]°C - -0.016/0.028 - %/°C
Drift over [+25, +85]°C - -0.022/0.029 -
Drift over [+25,
+105]°C
- -0.031/0.03 -
Reference supply
coefficient
Drift over [2.7, 5.5]V - -0.2/0.3 - %/V
1. These are based on characterization.
47.5 NVM Characteristics
Table 47-17. NVM Max Speed caracteristics
CPU FMAX (MHz) 0WS 1WS 2WS
VDD>2.7V 19 38 48
VDD>4.5V 19 38 48
47.6 Oscillator Characteristics
47.6.1 Crystal Oscillator (XOSC) Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN.
Table 47-18. Digital Clock Characteristics
Symbol Parameter Condition Min Typ Max Units
fCPXIN XIN clock frequency Digital mode - - 48 MHz
DCXIN(1) XIN clock duty cycle Digital mode 40 50 60 %
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1212
1. These are based on simulation. These values are not covered by test or characterization
The following table describes the characteristics for the oscillator when a crystal is connected between
XIN and XOUT as shown in the figure belwo. The user must choose a crystal oscillator where the crystal
load capacitance CL is within the range given in the table. The exact value of CL can be found in the
crystal datasheet. The capacitance of the external capacitors (CLEXT) can then be computed as follows:
CLEXT = 2 CL+CSTRAY CSHUNT
where CSTRAY is the capacitance of the pins and PCB, CSHUNT is the shunt capacitance of the crystal.
Figure 47-5. Oscillator Connection
CSHUNT
LM
RM
CM
CSTRAY
CLE XT
CLE XT
Xin
Crystal
Xout
Table 47-19. Multi Crystal Oscillator Electrical Characteristics (1)
Symbol Parameter Conditions Min. Typ. Max Units
Fout Crystal oscillator frequency 0.4 - 32 MHz
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1213
...........continued
Symbol Parameter Conditions Min. Typ. Max Units
ESR Crystal Equivalent Series
Resistance - SF = 3
F = 0.455 MHz
CL = 100pF
XOSC.GAIN = 0
- - 443 Ω
F = 2MHz
CL=20pF
XOSC.GAIN=0
- - 383
F = 4MHz
CL=20pF
XOSC.GAIN=1
- - 218
F = 8MHz
CL=20pF
XOSC.GAIN=2
- - 114
F = 16MHz
CL=20pF
XOSC.GAIN=3
- - 58
F = 32MHz
CL=12pF
XOSC.GAIN=4
- - 62
Cxin Parasitic load capacitor - 6.7 - pF
Cxout - 4.1 -
Tstart Startup time F = 2MHz
CL=20pF
XOSC.GAIN=0
- 12.3 48.7 KCycles
F = 4MHz
CL=20pF
XOSC.GAIN=1
- 8.2 30.1
F = 8MHz
CL=20pF
XOSC.GAIN=2
- 6.2 19.9
F = 16MHz
CL=20pF
XOSC.GAIN=3
- 10.8 30.1
F = 32MHz
CL=12pF
XOSC.GAIN=4
- 8.7 23.6
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1214
47.6.2 External 32kHz Crystal Oscillator (XOSC32K) Characteristics
The following table describes the characteristics for the oscillator when a digital clock is applied on XIN32
pin.
Table 47-20. Digital Clock Characteristics(1)
Symbol Parameter Condition Typ Units
fCPXIN32 XIN32 clock frequency Digital mode 32.768 kHz
DCXIN32 XIN32 clock duty cycle Digital mode 50 %
1. These are based on simulation. These values are not covered by test or characterization
The following table describes the characteristics for the oscillator when a crystal is connected between
XIN32 and XOUT32.
Figure 47-6. Oscillator Connection
XIN32
CSTRAY
CLEXT
CLEXT
CM
RM
LM
CSHUNT
XOUT32
DEVICE
Crystal
The user must choose a crystal oscillator where the crystal load capacitance CL is within the range given
in the table. The exact value of CL can be found in the crystal datasheet. The capacitance of the external
capacitors (CLEXT) can then be computed as follows:
CLEXT=2(CL-CSTRAY-CSHUNT)
where CSTRAY is the capacitance of the pins and PCB and CSHUNT is the shunt capacitance of the crystal.
Table 47-21. 32kHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
fOUT (1) Crystal oscillator frequency - 32768 - Hz
CL (1) Crystal load capacitance - - 12.5 pF
CSHUNT (1) Crystal shunt capacitance - - 1.75 pF
CM (1) Motional capacitance - 1.25 - fF
ESR Crystal Equivalent Series Resistance - SF = 3 F = 32.768kHz, CL=12.5 pF - - 70 kΩ
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1215
...........continued
Symbol Parameter Conditions Min. Typ. Max Units
CXIN32K Parasitic capacitor load - 3.8 - pF
CXOUT32K - 4.1 - pF
TSTART Startup time F = 32.768kHz, CL=12.5 pF - 16 24 Kcycles
1. These are based on simulation. These values are not covered by test or characterization
47.6.3 32.768kHz Internal Oscillator (OSC32K) Characteristics
Table 47-22. 32 kHz RC Oscillator Electrical Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
FOUT Output frequency Ta=25°C
VDDANA = 5.0V
30.965 32.768 34.570 kHz
Ta=25°C
Over [2.7, 5.5]V
29.164 32.768 36.044 kHz
Over [-40,105]°C
Over [2.7, 5.5]V
25.559 32.768 37.683 kHz
TSTARTUP Startup time - 1 2 cycles
Duty (1) Duty cycle - 50 - %
1. These are based on simulation. These values are not covered by test or characterization.
47.6.4 48MHz RC Oscillator (OSC48M) Characteristics
Table 47-23. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption FOUT = 48 MHz
VDD =5.0V
Max 105°C
Typ 25°C
87 341 µA
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
Electrical Characteristics 105°C (SAM ...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1216
48. AEC Q-100 Grade 1, 125°C Electrical Characteristics (SAM C20/C21
E/G/J)
This section provides electrical characteristics for SAM C20/21 devices running up to 125ºC with AEC
Q-100 Grade 1. Additional information will be provided in future revisions of this document as it becomes
available.
The specifications provided in this chapter for AEC Q-100 Grade 1 125°C are identical to those shown in
45. Electrical Characteristics at 85°C, with the exception of the parameters listed in this chapter.
48.1 Electrical Characteristics at 125°C Disclaimer
All typical values are measured at Ta = 25°C unless otherwise specified. All minimum and maximum
values are valid across operating temperature and voltage unless otherwise specified.
48.2 General Operating Ratings
The device must operate within the ratings listed in the table below in order for all other electrical
characteristics and typical characteristics of the device to be valid.
NVM erase operations are not protected by the BODVDD and BODCORE in debugger cold-plugging
mode. NVM erase operation at supply voltages below product specification minimum can cause
corruption of the calibration and other areas mandatory for a correct product behavior.
Table 48-1. General operating conditions
Symbol Parameter Min. Typ. Max. Units
TATemperature range -40 25 125 °C
TJJunction temperature - - 145 °C
48.3 Supply Characteristics
Table 48-2. Power Supply Current Requirement
Symbol Conditions
Current
Units
Max
IINPUT(1) Power up Maximum
current 2.5 mA
1. IINPUT is the minimum requirement for the power supply connected to the device, until the device
comes out of POR.
48.4 Power Consumption
The values in the Power Consumption table below are measured values of power consumption under the
following conditions, except where noted:
• Operating conditions
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1217
– VDDIN = 3.0 V, 5.0V
• Oscillators
– XOSC (crystal oscillator) stopped
– XOSC32K (32 kHz crystal oscillator) running with external 32kHz crystal
– FDPLL using XOSC32K as reference and running at 48 MHz
• Clocks
– FDPLL used as main clock source, except otherwise specified
– CPU, AHB clocks undivided
– All peripheral clocks stopped
• I/Os are inactive with input trigger disable
• CPU is running on Flash with Wait states specified in NVM Max Speed Characteristics
• NVMCTRL cache enabled
• BODVDD disabled
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1218
Table 48-3. Current Consumption (1)
Mode conditions Ta Vcc Typ. Max. Units
ACTIVE
CPU running a While 1 algorithm
25°C 5.0V 3.8 4.2
mA
125°C 5.0V 4.4 5.4
CPU running a While 1 algorithm
25°C 3.0V 3.7 4.2
mA
125°C 3.0V 4.4 5.4
CPU running a While 1 algorithm,
with GCLKIN as reference
25°C 5.0V 71*Freq
+160
79*Freq
+166 µA (with
freq in
MHz)
125°C 5.0V 72*Freq
+659
68*Freq
+1866
CPU running a Fibonacci algorithm
25°C 5.0V 4.7 5.2
mA
125°C 5.0V 5.3 6.4
CPU running a Fibonacci algorithm
25°C 3.0V 4.7 5.2
mA
125°C 3.0V 5.3 6.3
CPU running a Fibonacci algorithm,
with GCLKIN as reference
25°C 5.0V 90*Freq
+163
100*Freq
+173 µA (with
freq in
MHz)
125°C 5.0V 91*Freq
+664
88*Freq
+1863
CPU running a CoreMark algorithm
25°C 5.0V 5.9 6.5
mA
125°C 5.0V 6.7 8.0
CPU running a CoreMark algorithm
25°C 3.0V 5.2 5.7
mA
125°C 3.0V 5.9 6.9
CPU running a CoreMark algorithm,
with GCLKIN as reference
25°C 5.0V 115*Freq
+167
127*Freq
+169 µA (with
freq in
MHz)
125°C 5.0V 119*Freq
+668
122*Freq
+1849
IDLE
25°C 5.0V 1.2 1.3
mA
125°C 5.0V 1.8 3.1
STANDBY
XOSC32K running RTC running at
1kHz
25°C 5.0V 15.9 37
µA
125°C 5.0V 363.4 1100
XOSC32K and RTC stopped
25°C 5.0V 14.6 35
125°C 5.0V 361.4 1103
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1219
48.5 I/O Pin Characteristics
There are two different pin types with two different speeds: Normal and High Sink(2). The Drive Strength
bit is located in the Pin Configuration register PORT (PORT.PINCFG.DRVSTR).
The pins with I2C alternative mode available are compliant with I2C specifications. All I2C pins support
Standard (Sm), Fast (Fm), Fast plus (Fm+) and High speed (Hs) modes. The available I2C pins are listed
in the I/O Multiplexing section.
Table 48-4.  I/O Pins Dynamic Characteristics (1)
Symbol Parameter Conditions Normal
pins
High
Sink
pins
Normal
pins
High
Sink
pins
Units
DRVSTR=0 DRVSTR=1
tRISE Maximum rise
time
VDD = 5.0V, load =
20pF
15 12 8 11 ns
tFALL Maximum fall
time
VDD = 5.0V, load =
20pF
15 11 7 10
1. These values are based on simulation. These values are not covered by test limits in production or
characterization.
2. The following pins are High Sink pins and have different properties than normal pins: PA10, PA11,
PB10, PB11.
48.6 Analog Characteristics
48.6.1 Analog Brown Out Detectors Characteristics
See NVM User Row Mapping for the BODVDD default value settings. These values are based on
simulation and are not covered by test limits in production or characterization.
Table 48-5. BODVDD Characteristics(1) (2)
Symbol Parameters Conditions Min Typ Max Unit
VBOD+ BODVDD high threshold Level VDD level, Bod setting = 8
(default)
- 2.86 3.00 V
VDD level, Bod setting = 44 - 4.57 4.85
VBOD- /
VBOD
BODVDD low threshold Level VDD level, Bod setting = 8
(default)
2.60 2.8 2.95
VDD level, Bod setting = 44 4.10 4.51 4.80
Step size - 60 - mV
VHys Hysteresis (VBOD+ - VBOD-)
BODVDD.LEVEL = 8 to 48
VDD 40 - 75 mV
Tstart Startup time time from enable to RDY - 8 - us
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1220
Note: 
1. These are based on characterization.
2. BODVDD in continuous mode.
Table 48-6. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD IDLE, Mode CONT VDD = 2.7V Max 125°C
Typ 25°C
22.5 32.1 µA
VDD = 5.0V 41.0 51.4
IDLE, Mode SAMPL VDD = 2.7V 0.1 4.4
VDD = 5.0V 0.1 3.3
STANDBY, Mode SAMPL VDD = 2.7V 0.8 4.0
VDD = 5.0V 3.5 6.3
1. These are based on characterization.
48.6.2 Analog-to-Digital (ADC) Characteristics
Table 48-7. Differential Mode (1)
Symbol Parameter Conditions
Measurement
Unit
Min Typ Max
ENOB Effective
Number of bits
R2R Disabled
Vddana=5.0V
Vref=Vddana 9.7 10.6 11.3
bits
Vddana=2.7V
Vref=2.0V 9.8 10.6 11.2
R2R Enabled Vddana=5.0V
Vref=Vddana 9.7 11.1 11.8
TUE
Total
Unadjusted
Error
R2R disabled with
offset and gain
compensation
Vddana=5.0V
Vref=Vddana - +/-4.2 +/-7.1
LSB
Vddana=2.7V
Vref=2.0V - +/-4.8 +/-8.3
INL Integral Non
Linearity R2R disabled
Vddana=5.0V
Vref=Vddana - +/-1.5 +/-4
LSB
Vddana=2.7V
Vref=2.0V - +/-3.2 +/-4.1
DNL Differential Non
Linearity R2R disabled
Vddana=5.0V
Vref=Vddana - -0.8/+1.1 -1/+2.0
LSB
Vddana=2.7V
Vref=2.0V - -0.9/+1.3 -1/+2.2
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1221
...........continued
Symbol Parameter Conditions
Measurement
Unit
Min Typ Max
Gain Gain Error
R2R disabled w/o gain
compensation
Vddana=5.0V
Vref=Vddana - +/-0.8 +/-1.8
%
Vddana=2.7V
Vref=2.0V - +/-0.9 +/-3.2
Vddana=5.0V 1V
internal Ref - +/-1.9 +/-7.3
Vddana=5.0V
Vref=Vddana/2 - +/-0.1 +/-1.3
R2R disabled with
gain compensation
Vddana=2.7V
Vref=2.0V - +/-0.1 +/-0.5
Vddana=5.0V
Vref=Vddana/2 - +/-0.2 +/-0.7
Offset Offset Error
R2R disabled without
offset compensation
Vddana=5.0V
Vref=Vddana/2 - +/-0.2 +/-25
mV
Vddana=2.7V
Vref=2.0V - +/-1.4 +/-17
R2R disabled with
offset compensation
Vddana=5.0V
Vref=Vddana/2 - +/-2 +/-10
Vddana=2.7V
Vref=2.0V - +/-0.2 +/-11
SFDR Spurious Free
Dynamic Range
Fs = 1Msps / Fin = 14
kHz / Full range Input
signal Vddana=5.0V
Vref=Vddana
63 75 81
dB
SINAD Signal to Noise and
Distortion ratio 60 67 70
SNR Signal to Noise ratio 64 68 70
THD Total Harmonic
Distortion -81 -74 -63
Noise RMS External Reference
voltage - 0.5 3.3 mV
Note: 
1. These values are based on characterization. These values are not covered by test limits in
production.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1222
Table 48-8. Single Ended Mode (1)
Symbol Parameter Conditions
Measurement
Unit
Min Typ Max
ENOB Effective
Number of bits R2R disabled
Vddana=3.0V
Vref=Vddana 8.9 9.7 10.0
bits
Vddana=3.0V
Vref=2.0V 8.9 9.2 9.7
TUE
Total
Unadjusted
Error
R2R disabled with
offset and gain
compensation
Vddana=5.0V
Vref=Vddana - 18 +/-28
LSB
Vddana=2.7V
Vref=2.0V - 30 +/-57
INL Integral Non
Linearity R2R disabled
Vddana=5.0V
Vref=Vddana - +/-2.2 +/-7.5
LSB
Vddana=2.7V
Vref=2.0V - +/-4.1 +/-7.1
DNL Differential Non
Linearity R2R disabled
Vddana=5.0V
Vref=Vddana - -0.8/+1 -1/+1.9
Vddana=2.7V
Vref=2.0V - -1/+1.1 -1/+2.5
Gain Gain Error
R2R disabled w/o gain
compensation
Vddana=5.0V
Vref=Vddana - +/-0.4 +/-1.1
%
Vddana=2.7V
Vref=2.0V - +/-0.7 +/-1.9
Vddana=5.0V 1V
internal Ref - +/-1.6 +/-7.4
Vddana=5.0V
Vref=Vddana/2 - +/-0.2 +/-1.4
R2R disabled with
gain compensation
Vddana=2.7V
Vref=2.0V - +/-0.3 +/-0.9
Vddana=5.0V
Vref=Vddana/2 - +/-0.1 +/-1.4
Offset Offset Error R2R disabled
Vddana=5.0V
Vref=Vddana - +/-31 +/-76
mV
Vddana=2.7V
Vref=2.0V - +/-2.2 +/-64
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1223
...........continued
Symbol Parameter Conditions
Measurement
Unit
Min Typ Max
SFDR Spurious Free
Dynamic Range
Fs = 1Msps / Fin = 14
kHz / Full range Input
signal Vddana=5.0V
Vref=Vddana
57 71 73
dB
SINAD Signal to Noise and
Distortion ratio 54 60 62
SNR Signal to Noise ratio 57 61 62
THD Total Harmonic
Distortion -71 -70 -56
Noise RMS External Reference
voltage - 0.7 2 mV
Note: 
1. These values are based on characterization. These values are not covered by test limits in
production.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1224
Table 48-9. Power Consumption (1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD
VDDANA
Differential
mode
fs = 1Msps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
Max 125°C
Typ 25°C
905 1162
uA
fs = 1Msps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
1144 1507
fs = 10 ksps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
381 555
fs = 10 ksps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
609 952
Single Ended
mode
fs = 1Msps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref=5.5V
Max 125°C
Typ 25°C
984 1183
uA
fs = 1Msps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref=5.5V
1178 1548
fs = 10 ksps / Reference buffer
disabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
437 629
fs = 10 ksps / Reference buffer
enabled / BIASREFBUF = '110',
BIASREFCOMP = '111'
VDDANA=Vref= 5.5V
635 983
Note: 
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
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48.6.3 Sigma-Delta ADC Characteristics
Table 48-10. SDADC DC Performance: Differential Input Mode, Chopper ON (1)
Symbol Parameters Conditions Min Typ Max Unit
INL Integral Non Linearity
CLK_SDADC = 3MHz, VREF = 1.2V,
VDDANA = 2.7V - +/-2.9 +/-4.1
LSB
CLK_SDADC = 3MHz INT VREF =
5.5V - +/-8.4 +/-9.3
DNL Differential Non
Linearity
CLK_SDADC = 3MHz, VREF = 1.2V,
VDDANA = 2.7V - +1.5/-1 +2.2/-1
LSB
CLK_SDADC = 3MHz INT VREF =
5.5V - +2.1/-1 +2.9/-1
Eg Gain Errors
CLK_SDADC = 3MHz, VREF = 1.2V,
VDDANA = 2.7V - +/-0.7 +/-2.4
%
CLK_SDADC = 3MHz INT VREF =
5.5V - +/-0.9 +/-2.2
TCg Gain Drift CLK_SDADC = 3MHz, VREF = 1.2V,
VDDANA = 2.7V -6.9 4.4 17.5 ppm/°C
Off Offset Error
CLK_SDADC = 3MHz, VREF = 1.2V,
VDDANA = 2.7V - +/-3.1 +/-10.7
mV
CLK_SDADC = 3MHz INT VREF =
5.5V - +/-0.5 +/-3.3
Tco Offset Error Drift CLK_SDADC = 3MHz, VREF = 1.2V,
VDDANA = 2.7V -1.5 -0.1 1.2 µV/°C
Note: 
1. OSR=256
Table 48-11. SDADC DC Performance: Differential Input Mode, Chopper OFF (1)
Symbol Parameters Conditions Min Typ Max Unit
INL Integral Non
Linearity
CLK_SDADC = 6MHz, VREF =
1.2V, VDDANA = 2.7V - +/-5.5 +/-10.2
LSB
CLK_SDADC = 6MHz INT VREF =
5.5V - +/-8.9 +/-10.8
DNL Differential Non
Linearity
CLK_SDADC = 6MHz, VREF =
1.2V, VDDANA = 2.7V - +2.8/-1 +4.1/-1
LSB
CLK_SDADC = 6MHz INT VREF =
5.5V - +2.5/-1 +4.8/-1
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
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...........continued
Symbol Parameters Conditions Min Typ Max Unit
Eg Gain Errors
CLK_SDADC = 6MHz, VREF =
1.2V, VDDANA = 2.7V - +/-0.7 +/-3.1
%
CLK_SDADC = 6MHz INT VREF =
5.5V - +/-0.9 +/-2.2
TCg Gain Drift CLK_SDADC = 6MHz, VREF =
1.2V, VDDANA = 2.7V -19.7 5.2 20.9 ppm/°C
Off Offset Error
CLK_SDADC = 6MHz, VREF =
1.2V, VDDANA = 2.7V - +/-2.2 +/-21.2
mV
CLK_SDADC = 6MHz INT VREF =
5.5V - +/-4.9 +/-25.7
Tco Offset Error Drift CLK_SDADC = 6MHz, VREF =
1.2V, VDDANA = 2.7V -14.2 12.4 60 µV/°C
Input noise
rms AC Input noise rms
OSR = 256 VREF = 1.2V,
VDDANA = 2.7V - 19 20
µVrms
OSR = 256 VREF = 5.5V - 59 76
Note: 
1. OSR=256
Table 48-12. SDADC AC Performance: Differential Input Mode (1)
Symbol Parameters Conditions (2) Min Typ Max Unit
ENOB Effective Number Of Bits Ext ref = 1.2V, VDDANA = 2.7V 12 14.2 - bit
Int Ref = 5.5V 11 11.2 -
DR Dynamic Range Ext ref = 1.2V, VDDANA = 2.7V 89.0 91.0 - dB
Int Ref = 5.5V 83.0 92.0 -
SNR Signal to Noise Ratio Ext ref = 1.2V, VDDANA = 2.7V 68.7 88 - dB
Int Ref = 5.5V 77 79 -
SINAD Signal to Noise + Distortion Ratio Ext ref = 1.2V, VDDANA = 2.7V 73.9 87 - dB
Int Ref = 5.5V 68 69 -
THD Total Harmonic Distortion Ext ref = 1.2V, VDDANA = 2.7V - -94.6 -74.4 dB
Int Ref = 5.5V - -69 -68
Note: 
1. values based on characterization.
2. OSR=256, Chopper OFF, Sampling Clock Speed at 6Mhz, Fin = 13kHz.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1227
Table 48-13. Power Consumption (1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD
VDDANA
Power
consumption
CTLSDADC=0x0 External Ref -
VDDANA = 5.5V Vref = 2V Ref buf
on SCLK_SDADC = 6 MHz Max 125°C
Typ 25°C
644 764 uA
CTLSDADC=0x0 Internal Ref -
VDDANA=Vref= 5.5V Ref buf off
SCLK_SDADC = 6 MHz
605 696 uA
Note: 
1. These are based on characterization.
48.6.4 Digital to Analog Converter Characteristics
Table 48-14. Accuracy Characteristics (1)
Symbol Parameter Conditions Typ. Max. Units
INL Integral non-linearity
VREF= Ext 2.0V
VDD = 2.7V +/-0.7 +/-2.4
LSB
VDD = 5.5V +/-0.6 +/-1.7
VREF = VDDANA
VDD = 2.7V +/-0.6 +/-2
VDD = 5.5V +/-0.5 +/-1.7
VREF= 1.024V INT REF
VDD = 2.7V +/-1 +/-2.5
VDD = 5.5V +/-1.5 +/-3.5
DNL Differential non-linearity
VREF= Ext 2.0V
VDD = 2.7V +/-0.5 +/-2.3
LSB
VDD = 5.5V +/-0.5 +/-2.2
VREF = VDDANA
VDD = 2.7V +/-0.4 +/-2.1
VDD = 5.5V +/-0.4 +/-2.1
VREF= 1.024V INT REF
VDD = 2.7V +/-1 +/-2.5
VDD = 5.5V +/-1.4 +/-3.5
Gain error Ext. VREF +/-10 +/-28 mV
Offset error Ext. VREF +/-4 +/-26 mV
Note: 
1. These values are based on characterization. These values are not covered by test limits in
production.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1228
Table 48-15. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD
VDDANA
DC supply current Output buffer On
VREF = VDDANA=5.0V
Max 125°C
Typ 25°C
318 481 µA
Output buffer Off
VREF = VDDANA=5.0V
74 100
1. These values are based on characterization.
48.6.5 Analog Comparator (AC) Characteristics
Table 48-16. Analog Comparator Characteristics
Symbol Parameters Conditions Min Typ Max Unit
Off (1)(2) Offset
Low power COMPCTRLn.SPEED = 0x0 -62 +/-3 62
mV
High speed COMPCTRLn.SPEED = 0x3 -25 +/-2 25
Vhys (1)(3) Hysteresis
Low power COMPCTRLn.SPEED = 0x0 25 100 276
mV
High speed COMPCTRLn.SPEED = 0x3 29 100 211
Tstart (1) Startup time
Low power COMPCTRLn.SPEED = 0x0 - 7.4 13.6
us
High speed COMPCTRLn.SPEED = 0x3 - 2.1 4
Vscale (1)
INL - 0.51 - LSB
DNL - 0.04 - LSB
Offset Error - 0.05 - LSB
Gain Error - 0.03 - LSB
Note: 
1. These are based on characterization.
2. Hysteresis disabled.
3. Hysteresis enabled.
Table 48-17. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDDANA Current consumption -
VCM=VDDANA/2
±100 mV overdrive from Vcm
Voltage scaler disabled
COMPCTRLn.SPEED = 0x0
VDDANA =5.0V
Max 125°C
Typ 25°C
10 20 μA
COMPCTRLn.SPEED = 0x3
VDDANA =5.0V
39 66
Current consumption Voltage
scaler only
VDDANA =5.0V 43 68
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
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1. These are based on characterization.
48.6.6 Analog Voltage Reference Characteristics
Table 48-18. Voltage Reference Characteristics(1)
Symbol Parameter Conditions Min. Typ. Max. Units
ADC / SDADC / DAC Ref
Reference
temperature
coefficient
Drift over [+25,
+125]°C - -0.015/0.03 - %/°C
1. These are based on characterization.
48.6.7 PTC Characteristics
48.6.7.1 PTC Power Consumption
The values given in the table below are measured values of power consumption under the following
conditions:
Operating conditions
VDD = 5.0V
Clocks
OSC48M used as main clock source, running undivided at 48MHz
CPU is running on flash with 2 wait states, at 48MHz
PTC running at 4MHz
PTC configuration
Mutual-capacitance mode
One touch channel
System configuration
Standby sleep mode enabled
RTC running on ULP32K: used to define the PTC scan rate, through the event system.
Drift Calibration disabled: no interrupts, PTC scans are performed in standby mode.
Drift Calibration enabled: RTC interrupts (wakeup) the CPU to perform PTC scans. PTC drift calibration is
performed every 1.5 sec.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1230
Table 48-19. Power Consumption (1)
Symbol Parameters Drift
Calibration
PTC
scan
rate
Oversamples Ta Typ. Max Units
IDD Current
Consumption
Disabled
10
4
Max 125°C
Typ 25°C
24 1112
µA
16 43 1136
50
4 17 1105
16 22 1111
100
4 16 1104
16 19 1108
200
4 16 1104
16 17 1106
Enabled
10
4 30 1123
16 50 1147
50
4 20 1110
16 24 1115
100
4 18 1109
16 21 1111
200
4 17 1108
16 19 1110
Note: 
1. These are based on characterization.
48.7 NVM Characteristics
Table 48-20. NVM Max Speed Characteristics
CPU FMAX (MHz) 0WS 1WS 2WS 3WS
VDD>2.7V 14 35 47 48
VDD>4.5V 17 35 48 48
Table 48-21. Flash Endurance and Data Retention
Symbol Parameter Conditions Min. Typ. Units
CycNVM Cycling Endurance(1) -40°C < TA < 125°C 5k - Cycles
1. An endurance cycle is a write and an erase operation.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
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Table 48-22. EEPROM Emulation(1) Endurance and Data Retention
Symbol Parameter Conditions Min. Typ. Units
CycEEPROM Cycling Endurance(2) -40°C < Ta < 125°C 20k - Cycles
1. The EEPROM emulation is a software emulation described in the App note AT03265.
2. An endurance cycle is a write and an erase operation.
48.8 Oscillator Characteristics
48.8.1 Crystal Oscillator (XOSC) Characteristics
48.8.1.1 XOSC Crystal Oscillator Characteristics
Table 48-23. Multi Crystal Oscillator Electrical Characteristics (1)
Symbol Parameter Conditions Min. Typ. Max Units
CL Crystal Load F = 32MHz - - 12 pF
ESR Crystal Equivalent Series
Resistance - SF = 3
F = 16MHz - CL=20 pF XOSC,GAIN=3 - - 58
Ω
F = 32MHz - CL=12 pF XOSC,GAIN=4 - - 62
Tstart Startup time
F = 2MHz - CL=20 pF XOSC,GAIN=0 - 12.3 54.7
K cycles
F = 4MHz - CL=20 pF XOSC,GAIN=1 - 8.2 33.9
F = 8MHz - CL=20 pF XOSC,GAIN=2 - 6.2 22.2
F = 16MHz - CL=20 pF XOSC,GAIN=3 - 10.8 33.8
F = 32MHz - CL=12 pF XOSC,GAIN=4 - 8.7 25.6
Note: 
1. These are based on characterization.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1232
Table 48-24. Power Consumption (1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current
consumption
F = 2MHz - CL=20 pF
XOSC,GAIN=0,VDD = 5.0V
AGC=OFF
Max 125°C Typ
25°C
150 224
µA
AGC=ON 138 218
F = 4MHz - CL=20 pF
XOSC,GAIN=1,VDD = 5.0V
AGC=OFF
220 315
AGC=ON 175 296
F = 8MHz - CL=20 pF
XOSC,GAIN=2,VDD = 5.0V
AGC=OFF
350 463
AGC=ON 247 361
F = 16MHz - CL=20 pF
XOSC,GAIN=3,VDD = 5.0V
AGC=OFF
663 924
AGC=ON 429 840
F = 32MHz - CL=12 pF
XOSC,GAIN=4,VDD = 5.0V
AGC=OFF
1975 2806
AGC=ON 874 1436
Note: 
1. These are based on characterization.
48.8.2 External 32kHz Crystal Oscillator (XOSC32K) Characteristics
48.8.2.1 XOSC32K Crystal Oscillator Characteristics
The following table describes the characteristics for the oscillator when a crystal is connected between
XIN32 and XOUT32.
Table 48-25. 32kHz Crystal Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
ESR Crystal Equivalent Series Resistance -
SF = 3
F = 32.768kHz, CL=12.5 pF - - 70 kΩ
Tstart Startup time F = 32.768kHz, CL=12.5 pF - 16 26 Kcycles
1. These are based on simulation. These values are not covered by test or characterization
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1233
Table 48-26. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V Max 125°C
Typ 25°C
1528 1900 nA
1. These are based on characterization.
48.8.3 Digital Phase Locked Loop (DPLL) Characteristics
Table 48-27. Digital Phase Locked Loop Characteristics
Symbol Parameter Conditions Min. Typ. Max. Units
fIN (1) Input frequency 32 - 2000 KHz
fOUT (1) Output frequency 48 - 96 MHz
Jp (2) Period jitter (Peak-Peak
value)
fIN= 32 kHz, fOUT= 48 MHz - 1.5 4.0 %
fIN= 32 kHz, fOUT= 96 MHz - 2.7 10.0
fIN= 2 MHz, fOUT= 48 MHz - 1.8 5.0
fIN= 2 MHz, fOUT= 96 MHz - 2.5 8.0
tLOCK (2) Lock Time After startup, time to get lock signal.
fIN= 32 kHz, fOUT= 96 MHz
- 1.1 1.6 ms
After startup, time to get lock signal.
fIN= 2 MHz, fOUT= 96 MHz
- 25 40 µs
Duty (1) Duty cycle - 50 - %
1. These values are based on simulation. These values are not covered by test limits in production or
characterization.
2. These values are based on characterization.
Table 48-28. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current Consumption Ck=48MHz, VDD=5.0V Max 125°C
Typ 25°C
536 693 µA
Ck=96MHz, VDD=5.0V 865 1048
1. These values are based on characterization.
48.8.4 32.768kHz Internal Oscillator (OSC32K) Characteristics
Table 48-29. 32 kHz RC Oscillator Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
Fout Output frequency at 25 degC , at Vddana = 5.0V 31.948 32.768 33.587 kHz
at 25 degC , over [2.7, 5.5]V 28.835 32.768 36.700 kHz
over[-40,125]C, over [2.7, 5.5]V 24.282 32.768 38.010 kHz
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
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...........continued
Symbol Parameter Conditions Min. Typ. Max Units
Tstartup Startup time - 1 2 cycles
Duty (1) Duty Cycle - 50 - %
1. These are based on simulation. These values are not covered by test or characterization.
Table 48-30. Power Consumption(1)
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption VDD = 5.0V Max 125°C
Typ 25°C
0.864 1.4 μA
1. These are based on characterization.
48.8.5 OSC Ultra Low Power Internal 32kHz RC Oscillator (OSCULP32) Characteristics
Table 48-31. Ultra Low Power Internal 32 kHz RC Oscillator Electrical Characteristics
Symbol Parameter Condition Min Typ Max Units
fOUT Output frequency Over [-40, 125]°C, over [2.7, 5.5]V 22.937 32.768 40.960 kHz
Duty Duty Cycle 50 %
48.8.6 48MHz RC Oscillator (OSC48M) Characteristics
Table 48-32. RC 48 MHz Oscillator Electrical Characteristics
Symbol Parameter Conditions Min. Typ. Max Units
FOUT Output frequency -40 to 125 °C 45.6 48 50.4 MHz
TSTART (1) Startup time - 3.9 15 μs
Duty (2) Duty Cycle - 50 - %
1. OSC48MSTUP.STARTUP field must be set accordingly.
2. These are based on simulation. These values are not covered by test or characterization.
Table 48-33. Power Consumption
Symbol Parameters Conditions Ta Typ. Max Units
IDD Current consumption Fout = 48 MHz, VDD =5.0V Max 125°C
Typ 25°C
87 787 µA
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1235
48.9 Timing Characteristics
48.9.1 SERCOM in SPI Mode Timing
Table 48-34. SPI Timing Characteristics and Requirements (1)
Symbol Parameter Conditions Min. Typ. Max. Units
tSCK(10) SCK period Master Reception 2*(tMIS+tSLAVE_OUT) (3) - - ns
Master Transmission 2*(tMOV+tSLAVE_IN) (4) - -
tSCKW SCK high/low width Master - 0.5*tSCK - ns
tSCKR SCK rise time (2) Master - 0.25*tSCK - ns
tSCKF SCK fall time (2) Master - 0.25*tSCK - ns
tMIS MISO setup to SCK Master, VDD>4.5V 51.7 - - ns
Master, VDD>2.7V 61.6 - -
tMIH MISO hold after SCK Master, VDD>4.5V 0 - - ns
Master, VDD>2.7V 0 - -
tMOV MOSI output valid SCK Master, VDD>4.5V - - 18.1 ns
Master, VDD>2.7V - - 24.6
tMOH MOSI hold after SCK Master, VDD>4.5V 2.5 - - ns
Master, VDD>2.7V 2.5 - -
tSSCK Slave SCK Period Slave Reception 2*(tSIS+tMASTER_OUT) (5) - - ns
Slave Transmission 2*(tSOV+tMASTER_IN) (6) - -
tSSCKW SCK high/low width Slave - 0.5*tSSCK - ns
tSSCKR SCK rise time (2) Slave - 0.25*tSSCK - ns
tSSCKF SCK fall time (2) Slave - 0.25*tSSCK - ns
tSIS MOSI setup to SCK Slave, VDD>4.5V 14.6 - - ns
Slave, VDD>2.7V 15.1 - -
tSIH MOSI hold after SCK Slave, VDD>4.5V 0 - - ns
Slave, VDD>2.7V 0 - -
tSSS SS setup to SCK Slave PRELOADEN=1 tSOSS+tEXT_MIS+2*tAPBC (8) (9) - - ns
PRELOADEN=0 tSOSS+tEXT_MIS (8) - -
tSSH SS hold after SCK Slave 0.5*tSSCK - - ns
tSOV MISO output valid SCK Slave, VDD>4.5V - - 46 ns
Slave, VDD>2.7V - - 56.1
tSOH MISO hold after SCK Slave, VDD>4.5V 11.9 - - ns
Slave, VDD>2.7V 11.9 - -
tSOSS MISO setup after SS low Slave, VDD>4.5V - - 42 ns
Slave, VDD>2.7V - - 51.7
tSOSH MISO hold after SS high Slave, VDD>4.5V 11.1 - - ns
Slave, VDD>2.7V 11.1 - -
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1236
1. These values are based on simulation. These values are not covered by test limits in production.
2. See I/O pin characteristics.
3. Where tSLAVE_OUT is the slave external device output response time, generally tEXT_SOV+tLINE_DELAY
(7).
4. Where tSLAVE_IN is the slave external device input constraint, generally tEXT_SIS+tLINE_DELAY (7).
5. Where tMASTER_OUT is the master external device output response time, generally tEXT_MOV
+tLINE_DELAY (7).
6. Where tMASTER_IN is the master external device input constraint, generally tEXT_MIS+tLINE_DELAY (7).
7. tLINE_DELAY is the transmission line time delay.
8. tEXT_MIS is the input constraint for the master external device.
9. tAPBC is the APB period for SERCOM.
10. When the integrity of communication is required to maintain both transmission and reception, the
maximum SPI clock frequency should be the lower value of the reception or transmission mode
maximum frequency as shown in the following equations.
– Reception: tSCK = 2*(tMIS+tSLAVE_OUT)
– Transmission: tSCK = 2*(tMOV+tSLAVE_IN)
48.9.2 External Reset
Table 48-35. External Reset Characteristics(1)
Symbol Parameter Min. Units
tEXT Minimum reset pulse width 1.1 μs
1. These are based on simulation. These values are not covered by test or characterization.
48.9.3 CAN Timing
Table 48-36. CAN Physical Layer Timing(1)(2)
Parameter Conditions Max. Units
TxCAN output delay
VDD = 2.7V
Load = 20pF
VOL/VOH = VDD/2
29.4
ns
VDD = 4.5V
Load = 20pF
VOL/VOH = VDD/2
20.6
1. These values are based on simulation. These values are not covered by test limits in production.
2. These values are obtained with Output Driver Strength Selection as DRVSTR = 1.
SAM C20/C21 Family Data Sheet
AEC Q-100 Grade 1, 125°C Electrical Characteri...
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49. Packaging Information
49.1 Package Marking Information
All devices are marked with the Atmel logo and the ordering code.
Where:
• "YY": Manufacturing year
• "WW": Manufacturing week
• "R": Internal Code
• "XXXXXXX": Lot number
Figure 49-1. C21 32-Pin TQFP
Figure 49-2. C20 32-pin TQFP
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1238
Figure 49-3. C21 48-Pin TQFP
Figure 49-4. C20 48-Pin TQFP
Figure 49-5. C21 64-Pin TQFP
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1239
Figure 49-6. C20 64-Pin TQFP
Figure 49-7. C21 100-Pin TQFP
Figure 49-8. C20 100-Pin TQFP
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1240
Figure 49-9. C21 64-Pin VQFN
Figure 49-10. C20 64-Pin VQFN
Figure 49-11. C21 48-Pin VQFN
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1241
Figure 49-12. C20 48-Pin VQFN
Figure 49-13. C21 32-Pin VQFN
Figure 49-14. C20 32-Pin VQFN
49.2 Thermal Considerations
49.2.1 Thermal Resistance Data
The following table summarizes the thermal resistance data depending on the package.
Table 49-1. Thermal Resistance Data
Package Type θJA θJC
32-pin TQFP 63.1°C/W 14.3°C/W
48-pin TQFP 62.7°C/W 11.6°C/W
64-pin TQFP 56.3°C/W 11.1°C/W
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1242
...........continued
Package Type θJA θJC
100-pin TQFP 55.0°C/W 11.1°C/W
32-pin VQFN 40.5°C/W 16.0°C/W
48-pin VQFN 30.9°C/W 10.4°C/W
64-pin VQFN 31.4°C/W 10.2°C/W
56-ball WLCSP 37.5°C/W 5.48°C/W
49.2.2 Junction Temperature
The average chip-junction temperature, TJ, in °C can be obtained from the following:
1. TJ = TA + (PD x θJA)
2. TJ = TA + (PD x (θHEATSINK + θJC))
where:
• θJA = Package thermal resistance, Junction-to-ambient (°C/W), see Thermal Resistance Data
• θJC = Package thermal resistance, Junction-to-case thermal resistance (°C/W), see Thermal
Resistance Data
• θHEATSINK = Thermal resistance (°C/W) specification of the external cooling device
• PD = Device power consumption (W)
• TA = Ambient temperature (°C)
From the first equation, the user can derive the estimated lifetime of the chip and decide if a cooling
device is necessary or not. If a cooling device has to be fitted on the chip, the second equation should be
used to compute the resulting average chip-junction temperature TJ in °C.
49.3 Package Drawings
Note:  For current package drawings, refer to the Microchip Packaging Specification, which is available
at http://www.microchip.com/packaging.
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1243
49.3.1 100-Pin TQFP
Table 49-2. Device and Package Maximum Weight
500 mg
Table 49-3. Package Characteristics
Moisture Sensitivity Level MSL3
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1244
Table 49-4. Package Reference
JEDEC Drawing Reference MS-026
JESD97 Classification e3
49.3.2 64-Pin TQFP
Table 49-5. Device and Package Maximum Weight
300 mg
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1245
Table 49-6. Package Characteristics
Moisture Sensitivity Level MSL3
Table 49-7. Package Reference
JEDEC Drawing Reference MS-026
JESD97 Classification E3
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1246
49.3.3 64-Pin VQFN
Note:  The exposed die attach pad is not connected electrically inside the device.
Table 49-8. Device and Package Maximum Weight
200 mg
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1247
Table 49-9. Package Charateristics
Moisture Sensitivity Level MSL3
Table 49-10. Package Reference
JEDEC Drawing Reference MO-220
JESD97 Classification E3
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1248
49.3.4 64-Pin VQFN AEC-Q100
B
A
0.10 C
0.10 C
0.10 C A B
0.05 C
(DATUM B)
(DATUM A)
C
SEATING
PLANE
2X TOP VIEW
SIDE VIEW
BOTTOM VIEW
NOTE 1
1
2
N
0.10 C A B
0.10 C A B
0.10 C
0.08 C
Microchip Technology Drawing C04-21497 Rev A Sheet 1 of 2
2X
64X
http://www.microchip.com/packaging
Note: For the most current package drawings, please see the Microchip Packaging Specification lo cate d a t
64-Lead Very Thin Plastic Quad Flat, No Lead Package (U6B) - 9x9 mm Body [VQFN]
With 4.7 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZRB
© 2018 Microchip Technology Inc.
SECTION A-A
D3
A4
STEPPED
WETTABLE
FLANK
AA
D
E
D2
E2
64X b
(K)
L
e
e
2
1
2
N
0.05
0.20
0.90
DETAIL A
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1249
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
© 2018 Microchip Technology Inc.
REF: Reference Dimension, usually without tolerance, for information purposes only.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
1.
2.
3.
Pin 1 visual index feature may vary, but must be located within the hatched area.
Package is saw singulated
Dimensioning and tolerancing per ASME Y14.5M
Number of Ter minals
Overall He ig h t
Terminal Width
Overall Width
Terminal Length
Exposed Pad Width
Terminal Thickness
Pitch
Standoff
Units
Dimension Limit s
A1
A
b
E2
A3
e
L
E
N0.50 BSC
0.203 REF
0.35
0.15
0.80
0.00
0.20
0.40
0.85
0.035
MILLIMETERS
MIN NOM
64
0.45
0.25
0.90
0.05
MAX
K 1.75 REFTerminal-to-Exposed-Pad
Overall Length
Expos ed Pad Length D
D2 4.60 9.00 BSC
4.70 4.80
Wettable Flank Step Length D3 - - 0.085
A4 -0.10 0.19Wettable Flank Step Height
4.60 9.00 BSC
4.70 4.80
Microchip Technology Drawing C04-21497 Rev A Sheet 1 of 2
64-Lead Very Thin Plastic Quad Flat, No Lead Package (U6B) - 9x9 mm Body [VQFN]
With 4.7 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZRB
DETAIL 1
ALTERNATE TERMINAL
CONFIGURATIONS
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1250
RECOMMENDED LAND PATTERN
Dimension Limit s
Units
C2
Optional Center Pad Width
Contact Pad Spacing
Optional Center Pad Length
Contact Pitch
Y2
X2 4.80
4.80
MILLIMETERS
0.50 BSC
MIN
EMAX
8.90
Cont act Pad Length (X64)
Contact Pa d Width (X64) Y1
X1 0.85
0.30
NOM
1
2
64
C1Contact Pad Spacing 8.90
Contact Pad to Contact Pad (X60) G2 0.20
Thermal Via Diamete r V
Thermal Via Pitch EV 0.33
1.20
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
Dimensioning and tolerancing per ASME Y14.5M
For best soldering results, thermal vias, if used, should be fille d o r t e nted to avoid solde r lo ss during
reflow process
1.
2.
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
© 2018 Microchip Technology Inc.
Cont act Pad to Center Pad (X64) G1 1 .63
EV
EV
C2
C1
X2
Y2
E
X1
Y1
G1
G2
ØV
SILK SCREEN
Microchip Technolo gy Drawing C04-23497 Rev A
64-Lead Very Thin Plastic Quad Flat, No Lead Package (U6B) - 9x9 mm Body [VQFN]
With 4.7 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZRB
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1251
49.3.5 56-Ball WLCSP
Table 49-11. Device and Package Maximum Weight
9.63 mg
Table 49-12. Package Characteristics
Moisture Sensitivity Level MSL1
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1252
Table 49-13. Package Reference
JEDEC Drawing Reference N/A
JESD97 Classification e1
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1253
49.3.6 48-Pin VQFN AEC-Q100
B
A
0.10 C
0.10 C
0.10 C A B
0.05 C
(DATUM B)
(DATUM A)
C
SEATING
PLANE
2X TOP VIEW
SIDE VIEW
BOTTOM VIEW
NOTE 1
0.10 C
0.08 C
Microchip Technology Drawing C04-21493 Rev A Sheet 1 of 2
2X
48X
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
48-Lead Very Thin Plastic Quad Flat, No Lead Package (U5B) - 7x7 mm Body [VQFN]
With 5.15 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZLH
© 2018 Microchip Technology Inc.
A1
(A3)
A
D
D
4
E
4
E
2
1
N
2
1
N
D2
E2
(K)
e
e
2
L48X b
0.10 C A B
0.10 C A B
A4
D3
AA
SECTION A-A
DETAIL A
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1254
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
© 2018 Microchip Technology Inc.
REF: Reference Dimension, usually without tolerance, for information purposes only.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
1.
2.
3.
Pin 1 visual index feature may vary, but must be located within the hatched area.
Package is saw singulated
Dimensioning and tolerancing per ASME Y14.5M
Microchip Technology Drawing C04-21493 Rev A Sheet 2 of 2
48-Lead Very Thin Plastic Quad Flat, No Lead Package (U5B) - 7x7 mm Body [VQFN]
With 5.15 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZLH
Number of Ter minals
Overall He ig h t
Terminal Width
Overall Width
Terminal Length
Exposed Pad Width
Terminal Thickness
Pitch
Standoff
Units
Dimension Limit s
A1
A
b
E2
A3
e
L
E
N0.50 BSC
0.203 REF
0.35
0.20
0,80
0.00
0.25
0.40
0.85
0.02
MILLIMETERS
MIN NOM
48
0.45
0.30
0.90
0.05
MAX
K 0.53 REFTerminal-to-Exposed-Pad
Overall Length
Expos ed Pad Length D
D2 5.05 7.00 BSC
5.15 5.25
5.05 7.00 BSC
5.15 5.25
Wettable Flank Step Length D3 - - 0.085
A4 -0.10 0.19Wettable Flank Step Height
DETAIL 1
ALTERNATE TERMINAL
CONFIGURATIONS
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1255
RECOMMENDED LAND PATTERN
Dimension Limit s
Units
C2
Optional Center Pad Width
Contact Pad Spacing
Optional Center Pad Length
Contact Pitch
Y2
X2 5.25
5.25
MILLIMETERS
0.50 BSC
MIN
EMAX
6.90
Contact Pad Length (X48)
Contact Pa d Width (X48) Y1
X1 0.85
0.30
NOM
C1Contact Pad Spacing 6.90
Contact Pad to Center Pad (X48) G1 0.20
Thermal Via Diamete r V
Thermal Via Pitch EV 0.30
1.00
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
Dimensioning and tolerancing pe r ASME Y14.5M
For best soldering results, thermal vias, if used, should be fille d o r t ented to a void solde r lo ss during
reflow process
1.
2.
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
© 2018 Microchip Technology Inc.
Microchip Technolo gy Drawing C04-23493 Rev A
48-Lead Very Thin Plastic Quad Flat, No Lead Package (U5B) - 7x7 mm Body [VQFN]
With 5.15 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZLH
C1
C2 EV
EV
X2
Y2
X1
Y1
G1
G2
ØV
E
SILK SCREEN
1
2
48
Contact Pad to Center Pad (X44) G2 0.40
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1256
49.3.7 48-Pin TQFP
Table 49-14. Device and Package Maximum Weight
140 mg
Table 49-15. Package Characteristics
Moisture Sensitivity Level MSL3
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1257
Table 49-16. Package Reference
JEDEC Drawing Reference MS-026
JESD97 Classification E3
49.3.8 48-Pin VQFN
Note:  The exposed die attach pad is not connected electrically inside the device.
Table 49-17. Device and Package Maximum Weight
140 mg
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1258
Table 49-18. Package Characteristics
Moisture Sensitivity Level MSL3
Table 49-19. Package Reference
JEDEC Drawing Reference MO-220
JESD97 Classification E3
49.3.9 32-Pin TQFP
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1259
Table 49-20. Device and Package Maximum Weight
100 mg
Table 49-21. Package Charateristics
Moisture Sensitivity Level MSL3
Table 49-22. Package Reference
JEDEC Drawing Reference MS-026
JESD97 Classification E3
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1260
49.3.10 32-Pin VQFN AEC-Q100
B
A
0.10 C
0.10 C
0.10 C A B
0.05 C
(DATUM B)
(DATUM A)
C
SEATING
PLANE
NOTE 1
1
2
N
2X TOP VIEW
SIDE VIEW
BOTTOM VIEW
NOTE 1
1
2
N
0.10 C A B
0.10 C A B
0.10 C
0.08 C
Microchip Technology Drawing C04-21391 Rev C Sheet 1 of 2
2X
32X
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
32-Lead Very Thin Plastic Quad Flat, No Lead Package (RTB) - 5x5 mm Body [VQFN]
© 2017 Microchip Technology Inc.
D
E
e
32X b
E2
D2
e
2K
L
A
A1
With 3.6x3.6 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZBS
(A3)
AA
DETAIL A
A4
E3
SECTION A–A
PARTIALLY
PLATED
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1261
Microchip Technology Drawing C04-21391 Rev C Sheet 2 of 2
REF: Reference Dimension, usually without tolerance, for information purposes only.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
1.
2.
3.
Notes:
Pin 1 visual index feature may vary, but must be located within the hatched area.
Package is saw singulated
Dimensioning and tolerancing per ASME Y14.5M
32-Lead Very Thin Plastic Quad Flat, No Lead Package (RTB) - 5x5 mm Body [VQFN]
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
© 2017 Microchip Technology Inc.
With 3.6x3.6 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZBS
Number of Ter minals
Overall He ig h t
Terminal Width
Overall Width
Terminal Length
Exposed Pad Width
Terminal Thickness
Pitch
Standoff
Units
Dimension Limit s
A1
A
b
E2
A3
e
L
E
N0.50 BSC
0.203 REF
3.50
0.35
0.20
0.80
0.00
0.25
0.40
3.60
0.85
0.035
5.00 BSC
MILLIMETERS
MIN NOM
32
3.70
0.45
0.30
0.90
0.05
MAX
K-0.20 -Terminal-to-Exposed-Pad
Overall Length
Expos ed Pad Length D
D2 3.50 5.00 BSC
3.60 3.70
Wettable Flank Step Cut Depth A4 0.10 - 0.19
E3 --0.085Wettable Flank Step Cut Width
Wettable Flank Step Length D3 0.035 0.06 0.085
A4 -0.10 0.19Wettable Flank Step Height
Dimensions D3 and A4 above apply to all new products released after
November 1, and all products shipped after January 1, 2019, and supersede
dimensions D3 and A4 below.
No physical changes are being made to any package; this update is to align
cosmetic and toler ance variations from existing suppliers.
DETAIL 1
ALTERNATE TERMINAL
CONFIGURATIONS
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1262
RECOMMENDED LAND PATTERN
Dimension Limit s
Units
C2
Optional Center Pad Width
Contact Pad Spacing
Optional Center Pad Length
Contact Pitch
Y2
X2 3.70
3.70
MILLIMETERS
0.50 BSC
MIN
EMAX
5.00
Cont act Pad Length (X32)
Contact Pa d Width (X32) Y1
X1 0.80
0.30
NOM
1
2
32
C1Contact Pad Spacing 5.00
Cont act Pad to Center Pad (X32) G1 0.25
Thermal Via Diamete r V
Thermal Via Pitch EV 0.30
1.00
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Notes:
Dimensioning and tolerancing per ASME Y14.5M
For best soldering results, thermal vias, if used, should be fille d o r t e n ted to av o i d s o ld er loss du rin g
reflow process
1.
2.
For the most current package drawings, please see the Microchip Packaging Specification locate d a t
http://www.microchip.com/packaging
Note:
© 2017 Microchip Technology Inc.
Microchip Technolo gy Drawing C04-23391 Rev. C
32-Lead Very Thin Plastic Quad Flat, No Lead Package (RTB) - 5x5 mm Body [VQFN]
With 3.6x3.6 mm Exposed Pad and Stepped Wettable Flanks; Atmel Legacy ZBS
C1
C2
EV
EV
X2
CH
Y2
G2
X1
X1
E
SILK SCREEN
ØV
CHExposed Pa d 45 ° Co rn er Chamf e r 0.25
Contact Pad to Contact Pad (X28) G2 0.20
G1
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1263
49.3.11 32-Pin VQFN
Note:  The exposed die attach pad is connected inside the device to GND and GNDANA.
Table 49-23. Device and Package Maximum Weight
90 mg
Table 49-24. Package Characteristics
Moisture Sensitivity Level MSL3
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1264
Table 49-25. Package Reference
JEDEC Drawing Reference MO-220
JESD97 Classification E3
49.4 Soldering Profile
The following table gives the recommended soldering profile from J-STD-20.
Table 49-26. Recommended Soldering Profile
Profile Feature Green Package
Average Ramp-up Rate (217°C to peak) 3°C/s max.
Preheat Temperature 175°C ±25°C 150-200°C
Time Maintained Above 217°C 60-150s
Time within 5°C of Actual Peak Temperature 30s
Peak Temperature Range 260°C
Ramp-down Rate 6°C/s max.
Time 25°C to Peak Temperature 8 minutes max.
A maximum of three reflow passes is allowed per component.
SAM C20/C21 Family Data Sheet
Packaging Information
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1265
50. Schematic Checklist
50.1 Introduction
This chapter describes a common checklist which should be used when starting and reviewing the
schematics for a SAM C20/C21 design. This chapter illustrates the recommended power supply
connections, how to connect external analog references, programmer, debugger, oscillator and crystal.
50.2 Operation in Noisy Environment
If the device is operating in an environment with much electromagnetic noise it must be protected from
this noise to ensure reliable operation. In addition to following best practice EMC design guidelines, the
recommendations listed in the schematic checklist sections must be followed. In particular placing
decoupling capacitors very close to the power pins, a RC-filter on the RESET pin, and a pull-up resistor
on the SWCLK pin is critical for reliable operations. It is also relevant to eliminate or attenuate noise in
order to avoid that it reaches supply pins, I/O pins and crystals.
50.3 Power Supply
The SAM C20/C21 supports a single power supply or dual power supplies from 2.7 to 5.5V.
50.3.1 Power Supply Connections
Figure 50-1. Single Power Supply Schematic
10μF
100nF
2.7V - 5.5V Close to device
(for every pin)
VDDANA
VDDIO
VDDIN
VDDCORE
GND
10μF
100nF
100nF
1μF
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1266
Figure 50-2. Dual Power Supply Schematic
10μF
100nF
(2.7V - 5.5V) Close to device
(for every pin)
VDDANA
VDDIO
VDDIN
VDDCORE
GND
10μF
100nF
100nF
1μF
10μF
(2.7V - 5.5V)
IO Supply
Main Supply
Table 50-1. Power Supply Connections, VDDCORE From Internal Regulator
Signal Name Recommended Pin Connection Description
VDDIO 2.7V to 5.5V
Decoupling/filtering capacitors 100nF(1)(2) and 10µF(1)
Decoupling/filtering inductor 10µH(1)(3)
I/O supply voltage
VDDANA 2.7V to 5.5V
Decoupling/filtering capacitors 100nF(1)(2) and 10µF(1)
Ferrite bead(4) prevents the VDD noise interfering with
VDDANA
Analog supply voltage
VDDIN 2.7V to 5.5V
Decoupling/filtering capacitors 100nF(1)(2) and 10µF(1)
Decoupling/filtering inductor 10µH(1)(3)
Digital supply voltage
VDDCORE 1.1V to 1.3V typical
Decoupling/filtering capacitors 100nF(1)(2)and 1µF(1)
Core supply voltage /
external decoupling pin
GND Ground
GNDANA Ground for the analog
power domain
1. These values are only given as a typical example.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1267
2. Decoupling capacitors should be placed close to the device for each supply pin pair in the signal group,
low ESR capacitors should be used for better decoupling.
3. An inductor should be added between the external power and the VDD for power filtering.
4. A ferrite bead has better filtering performance compared to standard inductor at high frequencies. A
ferrite bead can be added between the main power supply (VDD) and VDDANA to prevent digital noise from
entering the analog power domain. The bead should provide enough impedance (e.g. 50Ω at 20MHz and
220Ω at 100MHz) to separate the digital and analog power domains. Make sure to select a ferrite bead
designed for filtering applications with a low DC resistance to avoid a large voltage drop across the ferrite
bead.
50.4 External Analog Reference Connections
The following schematic checklist is only necessary if the application is using one or more of the external
analog references. If the internal references are used instead, the following circuits are not necessary.
Figure 50-3. External Analog Reference Schematic With Two References
GND
VREFA
EXTERNAL
REFERENCE 1 4.7μF 100nF
GND
VREFB
EXTERNAL
REFERENCE 2 4.7μF 100nF
Close to device
(for every pin)
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1268
Figure 50-4. External Analog Reference Schematic With One Reference
GND
VREFA
EXTERNAL
REFERENCE 4.7μF 100nF
GND
VREFB
100nF
Close to device
(for every pin)
GND
VREFB
EXTERNAL
REFERENCE 4.7μF 100nF
Close to device
(for every pin)
Table 50-2. External Analog Reference Connections
Signal Name Recommended Pin Connection Description
VREFA 2.0V to VDDANA - 0.6V for ADC
1.0V to VDDANA - 0.6V for DAC
Decoupling/filtering capacitors: 100nF(1)(2) and 4.7µF(1)
External reference from VREFA
pin on the analog port.
VREFB 1.0V to 5.5V for SDADC
Decoupling/filtering capacitors: 100nF(1)(2) and 4.7µF(1)
External reference from VREFB
pin on the analog port.
GND Ground
Note: 
1. These values are given as a typical example.
2. Decoupling capacitor should be placed close to the device for each supply pin pair in the signal
group.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1269
50.5 External Reset Circuit
The external Reset circuit is connected to the RESET pin when the external Reset function is used. The
circuit is not necessary when the RESET pin is not driven LOW externally by the application circuitry.
The reset switch can also be removed, if a manual reset is not desired. The RESET pin itself has an
internal pull-up resistor, hence it is optional to add any external pull-up resistor.
Figure 50-5. External Reset Circuit Schematic
GND
RESET
Ω
VDD
330Ω
2.2k 100pF
A pull-up resistor makes sure that the reset does not go low and unintentionally causing a device reset.
An additional resistor has been added in series with the switch to safely discharge the filtering capacitor,
i.e. preventing a current surge when shorting the filtering capacitor which again can cause a noise spike
that can have a negative effect on the system.
Table 50-3. Reset Circuit Connections
Signal Name Recommended Pin Connection Description
RESET Reset low level threshold voltage
VDDIO = 2.7V - 5.5V: Below 0.3 * VDDIO
Decoupling/filter capacitor 100 pF(1)
Pull-up resistor 2.2 kΩ(1)(2)
Resistor in series with the switch 330Ω(1)
Reset pin
1. These values are only given as a typical example.
2. The SAM C20/C21 features an internal pull-up resistor on the RESET pin; therefore, an external
pull-up is optional.
50.6 Unused or Unconnected Pins
Unused or unconnected pins (unless marked as NC where applicable) should not be left unconnected
and floating. Floating pins will add to the overall power consumption of the device. To prevent this one
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1270
should always draw the pin voltage towards a given level, either VDD or GND, through a pull up/down
resistor. External or internal pull up/down resistors can be used, e.g. the pins can be configured in pull-up
or pull-down mode eliminating the need for external components. There are no obvious benefit in
choosing external vs. internal pull resistors.
Related Links
28. PORT - I/O Pin Controller
50.7 Clocks and Crystal Oscillators
The SAM C20/C21 can be run from internal or external clock sources, or a mix of internal and external
sources. An example of usage will be to use the internal 48MHz oscillator as source for the system clock,
and an external 32.768kHz watch crystal as clock source for the Real-Time counter (RTC).
50.7.1 External Clock Source
Figure 50-6. External Clock Source Schematic
XOUT/GPIO
XIN
NC/GPIO
External
Clock
Table 50-4. External Clock Source Connections
Signal Name Recommended Pin Connection Description
XIN XIN is used as input for an external clock signal Input for inverting oscillator pin
XOUT/GPIO Can be left unconnected or used as normal GPIO NC/GPIO
50.7.2 Crystal Oscillator
Figure 50-7. Crystal Oscillator Schematic
XOUT
XIN
15pF
15pF
The crystal should be located as close to the device as possible. Long signal lines may cause too high
load to operate the crystal, and cause crosstalk to other parts of the system.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1271
Table 50-5. Crystal Oscillator Checklist
Signal Name Recommended Pin Connection Description
XIN Load capacitor 15pF(1)(2) External crystal between 0.4 to 32MHz
XOUT Load capacitor 15pF(1)(2)
1. These values are only given as a typical example.
2. The capacitors should be placed close to the device for each supply pin pair in the signal group.
50.7.3 External Real Time Oscillator
The low frequency crystal oscillator is optimized for use with a 32.768kHz watch crystal. When selecting
crystals, load capacitance and the crystal’s Equivalent Series Resistance (ESR) must be taken into
consideration. Both values are specified by the crystal vendor.
SAM C20/C21 oscillator is optimized for very low power consumption, hence close attention should be
made when selecting crystals.
The typical parasitic load capacitance values are available in the Electrical Characteristics section. This
capacitance and PCB capacitance can allow using a crystal inferior to 12.5pF load capacitance without
external capacitors as shown in Figure 50-8.
Figure 50-8. External Real Time Oscillator without Load Capacitor
XOUT32
XIN32
32.768kHz
To improve accuracy and Safety Factor, the crystal datasheet can recommend adding external capacitors
as shown in Figure 50-9.
To find suitable load capacitance for a 32.768kHz crystal, consult the crystal datasheet.
Figure 50-9. External Real Time Oscillator with Load Capacitor
XOUT32
XIN32
32.768kHz
22pF
22pF
Table 50-6. External Real Time Oscillator Checklist
Signal Name Recommended Pin Connection Description
XIN32 Load capacitor 22pF(1)(2) Timer oscillator input
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1272
...........continued
Signal Name Recommended Pin Connection Description
XOUT32 Load capacitor 22pF(1)(2) Timer oscillator output
1. These values are only given as typical examples.
2. The capacitors should be placed close to the device for each supply pin pair in the signal group.
Note:  In order to minimize the cycle-to-cycle jitter of the external oscillator, keep the neighboring pins as
steady as possible. For neighboring pin details, refer to the Oscillator Pinout section.
50.7.4 Calculating the Correct Crystal Decoupling Capacitor
The model shown in Figure 50-10 can be used to calculate correct load capacitor for a given crystal. This
model includes internal capacitors CLn, external parasitic capacitance CELn and external load capacitance
CPn.
Figure 50-10. Crystal Circuit With Internal, External and Parasitic Capacitance
XOUT
Internal
CEL1
CL1 CL2
CP1 CP2 CEL2
External
XIN
Using this model the total capacitive load for the crystal can be calculated as shown in the equation
below:
tot =1+1+EL1 2+2+EL2
1+1+EL1 +2+2+EL2
where Ctot is the total load capacitance seen by the crystal. This value should be equal to the load
capacitance value found in the crystal manufacturer datasheet.
The parasitic capacitance CELn can in most applications be disregarded as these are usually very small. If
accounted for, these values are dependent on the PCB material and PCB layout.
For some crystal the internal capacitive load provided by the device itself can be enough. To calculate the
total load capacitance in this case. CELn and CPn are both zero, CL1 = CL2 = CL, and the equation reduces
to the following:
tot =
2
See the related links for equivalent internal pin capacitance values.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1273
Related Links
45.12.2.2 Crystal Oscillator Characteristics
50.8 Programming and Debug Ports
For programming and/or debugging the SAM C20/C21 the device should be connected using the Serial
Wire Debug (SWD) interface. Currently the SWD interface is supported by several Microchip and third
party programmers and debuggers, like the SAM-ICE, JTAGICE3.
Refer to the SAM-ICE, JTAGICE3 user guides for details on debugging and programming connections
and options. For connecting to any other programming or debugging tool, refer to that specific
programmer or debugger’s user guide.
Note that a pull-up resistor on the SWCLK pin is critical for reliable operations. Refer to related link for
more information.
Figure 50-11. SWCLK Circuit Connections
SWCLK
1kΩ
VDD
Table 50-7. SWCLK Circuit Connections
Pin Name Description Recommended Pin Connection
SWCLK Serial wire clock pin Pull-up resistor 1kΩ
Related Links
50.2 Operation in Noisy Environment
50.8.1 Cortex Debug Connector (10-pin)
For debuggers and/or programmers that support the Cortex Debug Connector (10-pin) interface the
signals should be connected as shown in Figure 50-12 with details described in Table 50-8.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1274
Figure 50-12. Cortex Debug Connector (10-pin)
1
Cortex Debug Connector
(10-pin)
VDD
VTref
GND
GND
NC
NC
NC
NC
SWDCLK
SWDIO
RESET
RESET
SWDIO
SWCLK
GND
Table 50-8. Cortex Debug Connector (10-pin)
Header Signal Name Description
SWDCLK Serial wire clock pin
SWDIO Serial wire bidirectional data pin
RESET Target device reset pin, active low
VTref Target voltage sense, should be connected to the device VDD
GND Ground
50.8.2 10-pin JTAGICE3 Compatible Serial Wire Debug Interface
The JTAGICE3 debugger and programmer does not support the Cortex Debug Connector (10-pin)
directly, hence a special pinout is needed to directly connect the SAM C20/C21 to the JTAGICE3,
alternatively one can use the JTAGICE3 squid cable and manually match the signals between the
JTAGICE3 and SAM C20/C21. Figure 50-13 describes how to connect a 10-pin header that support
connecting the JTAGICE3 directly to the SAM C20/C21 without the need for a squid cable. This can also
be used for the Atmel-ICE AVR connector port.
The JTAGICE3 squid cable or the JTACICE3 50mil cable can be used to connect the JTAGICE3
programmer and debugger to the SAM C20/C21. Figure 50-13 illustrates the correct pinout for the
JTAGICE3 50 mil, and details are given in Table 50-9.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1275
Figure 50-13. 10-pin JTAGICE3 Compatible Serial Wire Debug Interface
1
10-pin JTAGICE3 Compatible
Serial Wire Debug Header
VDD
SWDCLK
NC
SWDIO
NC
NC
GND
VTG
RESET
NC
NC
SWCLK
RESET
SWDIO
GND
Table 50-9. 10-pin JTAGICE3 Compatible Serial Wire Debug Interface
Header Signal Name Description
SWDCLK Serial wire clock pin
SWDIO Serial wire bidirectional data pin
RESET Target device reset pin, active low
VTG Target voltage sense, should be connected to the device VDD
GND Ground
50.8.3 20-pin IDC JTAG Connector
For debuggers and/or programmers that support the 20-pin IDC JTAG Connector, e.g. the SAM-ICE, the
signals should be connected as shown in Figure 50-14 with details described in Table 50-10.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1276
Figure 50-14. 20-pin IDC JTAG Connector
1
20-pin IDC JTAG Connector
VDD
VCC
NC
NC
SWDIO
SWDCLK
NC
NC
RESET
NC
NC
NC
GND
GND
GND
GND
GND
GND*
GND*
GND*
GND*
RESET
SWCLK
SWDIO
GND
Table 50-10. 20-pin IDC JTAG Connector
Header Signal Name Description
SWDCLK Serial wire clock pin
SWDIO Serial wire bidirectional data pin
RESET Target device reset pin, active low
VCC Target voltage sense, should be connected to the device VDD
GND Ground
GND* These pins are reserved for firmware extension purposes. They can be left
unconnected or connected to GND in normal debug environment. They are not
essential for SWD in general.
SAM C20/C21 Family Data Sheet
Schematic Checklist
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1277
51. Revision History
51.1 Revision C - 01/2019
Ordering Information • Added a note to clarify SAM C2xN availability
in 105°C
• Introduced AEC Q-100 Grade 1 qualified
silicon revision F
• Clarified availability of factory programmed
Bootloader for WLCSP
PAC • Added missing CAN1 bit field to INTFLAGC
register
• Corrected a typographical error for PTC bit
field in INTFLAGC & STATUSC register
• Corrected a typographical error for RSTC bit
field in STATUSA register
OSC32KCTRL •RTCCTRL register was missing, and same
has been added in this version
I/O Multiplexing and Considerations • Corrected a typographical error for SERCOM4
and SERCOM5 in Table 6-2
RTC • Register (EVCTRL, INTENCLR, INTENSET,
INTFLAG, SYNCBUSY) summary
typographical error was addressed
•FREQCORR, DBGCTRL registers were
missing in register summary, added in this
version
SUPC • Clarified the ENABLE bit in section 22.8.6
Voltage Regulator System (VREG) Control
• Corrected typo for Reset value of the Voltage
Regulator System (VREG) Control register in
the section 22.8.6
SERCOM-USART • Clarified Auto baud detection mode for LIN
Slave in CTRLA register
TCC • Corrected a typo in the Register summary -
32-bit mode for the PER & PERBUF registers
has been removed
ADC • Updated section 38.6.2.3 Operation
• Updated section 38.6.5 Interrupts
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1278
Electrical Characteristics at 85°C • Typographical errors in the Electrical
specification chapter addressed
–Table 45-32. Power Consumption
• Clarified SPI maximum speed information in
Table 45-56
•ADC , SD ADC, and AC Electrical
Characteristics for silicon revision F added
Electrical Characteristics at 105°C Updated AC Table 46-8. Power Consumption
AEC-Q100 Grade 1, 125°C Electrical
Characteristics
New chapter of electrical specifications for AEC
Q-100 Grade qualified device.
Packaging • Top marking legend information added for all
packages
51.2 Revision B - 06/2017
General • The SAM C20 Family Data Sheet
(DS60001480A) was combined with this data
sheet to create this version
• The Errata chapter was removed. This content
is now provided in a separate document.
51.3 Revision A - 03/2017
General Updates • Updated the document from Atmel to Microchip style and
template
• The literature number changed from the Atmel 42365 to
the Microchip DS60001479A
• The Data Sheet revision letter was restarted to A
• An ISBN number was added
2. Ordering Information • Removed space form the ordering codes.
Introducing SAM C20/C21N • 100-pin TQFP package option.
• More features: Eight TCs, eight SERCOMs
26. EIC – External Interrupt Controller • Added interrupt pin debouncing for SAM C20/C21N.
37. CCL – Configurable Custom Logic •37.8.3 LUTCTRLn.INSELx: Added ALT2TC at
INSELx=0xA. For the ALT2TC options the LUT 0 to 3
mapping will be TC4,TC5,TC6,TC7. The ALT2TC is only
applicable for SAM C20/C21N.
21. OSC32KCTRL – 32KHz Oscillators
Controller
•21.8.6 XOSC32K.STARTUP[2:0]: Table for start-up
times updated.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1279
34. CAN - Control Area Network • Updated block diagram.
• The CAN cannot operate in Standby sleep mode:
– Merged content from "Power Down (Sleep Mode)"
section into 34.6.9 Sleep Mode Operation.
– Updated description of 34.5.2 Power Management .
–34.8.3 MRCFG.RUNSTDBY bit removed.
45. Electrical Characteristics 85°C (SAM
C20/C21 E/G/J)
•45.10.6 Digital to Analog Converter (DAC)
Characteristics: Updated conditions and typical numbers
for power consumption.
•45.12.3 Digital Phase Locked Loop (DPLL)
Characteristics: Added typical characterization numbers.
•45.12.6 48 MHz RC Oscillator (OSC48M)
Characteristics: Updated TSTART values, updated note 4
and removed the condition.
46. Electrical Characteristics 105°C
(SAM C20/C21 E/G/J)
•46.4.4 Digital-to-Analog Converter (DAC)
Characteristics: Updated conditions and typical numbers
for power consumption.
•46.6.3 Digital Phase Locked Loop (DPLL)
Characteristics: Added typical characterization numbers.
•46.6.6 48 MHz RC Oscillator (OSC48M) Characteristics:
Updated TSTART values, updated note 4 and removed the
condition.
47. Electrical Characteristics 105°C
(SAM C20/C21 N)
• Electrical characterization data added for SAM C20/C21.
50. Schematic Checklist •50.5 External Reset Circuit: Updated schematic diagram
and recommended pin connections.
51.4 Rev KJ - 11/2016
Errata SAM C20 and Errata SAM C21 • Added DMAC errata (reference 15670).
51.5 Rev J - 10/2016
11. PAC - Peripheral Access Controller •11.7.6 INTFLAGA.TSENS moved to bit position 12.
•11.7.10 STATUSA.TSENS moved to bit position 12.
51.6 Rev I - 09/2016
General • Removed preliminary status from the datasheet.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1280
2. Ordering Information • SAM C20J/SAM C21J: Added -UUT ordering codes for
SAM C20/C21J17 and SAM C20/C21J18
4. Pinout • Added pinout for the 4.3.2 WLCSP56 package.
6. I/O Multiplexing and Considerations •6.1 Multiplexed Signals: VREFB removed from the
reference (REF) column. This is not an option.
20. OSCCTRL – Oscillators Controller •20.6.4 48MHz Internal Oscillator (OSC48M) Operation:
Removed the sentence "Frequency selection must be
done when OSC48M is disabled."
22. SUPC – Supply Controller • Removed references to backup domain.
23. WDT – Watchdog Timer • Removed references to backup domain.
24. RTC – Real-Time Counter •24.6.2.5 Clock/Calendar (Mode 2): Updated description.
25. DMAC – Direct Memory Access
Controller
•25.6.7 Sleep Mode Operation: Added information on
behaviour of DMA channels with
CHCTRLA.RUNSTDBY=0.
26. EIC – External Interrupt Controller • Added interrupt pin debouncing.
31. SERCOM USART - SERCOM
Synchronous and Asynchronous
Receiver and Transmitter
•31.6.3.5 LIN Master section added.
•31.8.1 CTRLA.TXPO: Row heading updated from RTS
to RTS/TE.
•31.8.1 CTRLA.FORM: Added LIN Master to
FORM[3:0]=0x2. Added LIN Slave to FORM[3:0]=0x4.
•31.8.2 CTRLB.LINCMD[3:0] bit group added
•31.8.3 CTRLC.GTIME: Bitfield values removed.
35. TC – Timer/Counter •35.7.1.1 CTRLA.ENABLE and SWRST bit description
updated: Added "This bit is not enable protected."
38. ADC – Analog-to-Digital Converter •38.6.2.5 Reference Configuration: Removed information
on number of external and internal voltage references
and supported voltage supply range. This information is
replaced with references to the REFCTRL.REFSEL
register bits and ADC characteristics for reference
selection details and voltage ranges respectively.
41. DAC – Digital-to-Analog Converter •41.8.2 CTRLB.ION bit description updated: For bit value
'1' the internal DAC can be used as input to the AC or
ADC.
43. TSENS – Temperature Sensor • Added example to the 43.8.10 VALUE register.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1281
45. Electrical Characteristics 85°C (SAM
C20/C21 E/G/J)
•45.2 Absolute Maximum Ratings: VDD max updated
from 5.5V to 6.1V.
•45.3 General Operating Ratings: Updated note.
•45.4 Injection Current: New section added.
•45.7 Power Consumption: Standby typical values
updated and maximum values added.
•45.10.4 Analog-to-Digital Converter (ADC)
Characteristics:
– Added Ts, sampling tile with DAC as input.
–45.10.4 Analog-to-Digital Converter (ADC)
Characteristics: In the condition column
REFCTRL.REFSEL is corrected to
CTRLC.RESSEL.
–45.10.7 Analog Comparator Characteristics:
Removed Hysteresis for COMPCTRLn.SPEED =
0x0 (low power), Updated IDDANS units from nA to
μA and updated condition for IDDANA with voltage
scaler disabled (COMPCTRLn.SPEED = 0x1
changed to 0x3).
•45.12.3 Digital Phase Locked Loop (DPLL)
Characteristics: Updated values.
•45.12.6 48 MHz RC Oscillator (OSC48M)
Characteristics: Added note on the output frequency
regarding accuracy for the WLCSP package.
46. Electrical Characteristics 105°C
(SAM C20/C21 E/G/J)
•46.3 Power Consumption: Standby typical values
updated and maximum values added.
•46.5 NVM Characteristics: New section added.
•46.4.5 Analog Comparator (AC) Characteristics:
Updated IDDANA units from nA to μA and updated
condition for IDD with voltage scaler disabled
(COMPCTRLn.SPEED = 0x1 changed to 0x3).
•46.6.3 Digital Phase Locked Loop (DPLL)
Characteristics: Characterization data added.
49. Packaging Information • Added package outline drawing (POD) for 49.3.5 56-Ball
WLCSP.
50. Schematic Checklist •50.4 External Analog Reference Connections:
Recommended pin connections column updated.
• External Reset Circuit: Updated description.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1282
51.7 Rev H - 05/2016
8. Product Mapping AHB-APB Bridge B:
• DMAC base address corrected from 0x41004400 to
0x4106000.
• MTB base address corrected from 0x41004800 to
0x41008000.
• Reserved space corrected from 0x41005000 to
0x41009000.
10.3 Micro Trace Buffer MTB base address corrected from 0x41006000 to
0x41008000.
22. SUPC – Supply Controller 22.6.3.3 VDD Brown-Out Detector (BODVDD): Removed
references to battery backup (VBAT) and voltage monitored
bit (BODVDD.VMON).
38. ADC – Analog-to-Digital Converter Updated formula to increase the resolution by n bits in
38.6.2.11 Oversampling and Decimation.
39. SDADC – Sigma-Delta Analog-to-
Digital Converter
39.6.3.2 Decimation Filter: Removed figure of spectral mask
of an OSR=32. This option is not available.
43. TSENS – Temperature Sensor • INTFLAG.OVF bit description updated.
• GAIN and OFFSET register bit description updated.
45. Electrical Characteristics 85°C (SAM
C20/C21 E/G/J)
•45.10.6 Digital to Analog Converter (DAC)
Characteristics: Clock and timing conversion rate
conditions updated: Rload > 5kW corrected to Rload >
5kΩ.
• Added 45.10.9 Temperature Sensor Characteristics.
46. Electrical Characteristics 105°C
(SAM C20/C21 E/G/J)
Added 46.4 Analog Characteristics.
51.8 Rev G - 04/2015
2. Ordering Information Added Device Identification.
6. I/O Multiplexing and
Considerations
New sections added:
•6.2.3 SERCOM I2C Pins: Information moved from the "Type"
column in Table 6-2 into separate table.
• Updated CCL column.
•6.2.4 GPIO Clusters: Moved from 45.2 Absolute Maximum
Ratings.
•6.2.5 TCC Configurations: Moved from 36. TCC – Timer/Counter
for Control Applications.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1283
9. Memories • Updated Table 9-4.
• Updated Table 9-1.
11. PAC - Peripheral Access
Controller
Register bit correction: INTFLAGAHB, INTFLAGA, INTFLAGB,
INTFLAGC, STATUSA, STATUSB and STATUSC
13. DSU - Device Service Unit Table 13-6 updated: MBIST is not available when the device is
protected from the external address space.
16. GCLK - Generic Clock
Controller
•16.3 Block Diagram: GCLK_MAIN goes into the MCLK, not the
PM.
•16.4 Signal Description: Available signals are GCLK_IO[7:0].
17. MCLK – Main Clock • Updated block diagram in 17.6.2.4 Selecting the Synchronous
Clock Division Ratio.
20. OSCCTRL – Oscillators
Controller
Added OSC48M Calibration (CAL48M) register added (only available
for Rev D silicon).
22. SUPC – Supply Controller • Updated VREF.SEL bit selection table.
• Removed references to BODCORE register and bit descriptions
and updated description in 22.6.3.4 VDDCORE Brown-Out
Detector (BODCORE).
19. PM – Power Manager • Sleep modes: Removed references to IDLE0 and IDLE1.
Renamed IDLE2 to IDLE.
25. DMAC – Direct Memory
Access Controller
CTRL.CRCENABLE bit added in bit position 2.
27. NVMCTRL – Nonvolatile
Memory Controller
27.8.2 CTRLB.CACHEDIS: Updated from one bit in postion 18 to two
bits in position 19:18. Updated bit description and bit value settings.
32. SERCOM SPI – SERCOM
Serial Peripheral Interface
32.2 Features: Updated references to serial clock speed in master and
slave operation.
34. CAN - Control Area
Network
34.8.1 CREL: Updated reset value from 0x31000000 (device rev B) to
0x32100000 (device rev C and newer).
35. TC – Timer/Counter Added register property "Write-Synchronized" to the CCBUFx and
PERBUF registers.
36. TCC – Timer/Counter for
Control Applications
• Updated number of TCC instances from one to three.
•36.6.2.4 Counter Operation: 'Stop Command and Event Action'
split into 'Stop Command' and 'Pause Event Action'
•36.6.2.7 Capture Operations: Value 0 in CAPTMIN mode is
captured only in down-counting mode.
•36.6.3.4 Ramp Operations: RAMP2C Operation added.
•36.6.2.5 Compare Operations: Reorganization of section.
• Corrected bit names in the WAVE register: CIRCCENx ->
CICCENx and CIRPEREN -> CIPEREN.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1284
37. CCL – Configurable
Custom Logic
• Number of LUTCTRL registers changed from eight to four.
• Number of SEQCTRL registers changed from four to two.
•37.6.2.4 Truth Table Inputs Selection: Updated description and
figure in Analog Comparator Inputs (AC).
39. SDADC – Sigma-Delta
Analog-to-Digital Converter
• Resolution corrected from 24-bit to 16-bit.
• Conversion range updated from "0V to Vref "to "0V to 0.7xVref"
• Test Mode section removed.
• Updated operation formula in the following registers:
–39.8.14 OFFSETCORR
–39.8.15 GAINCORR
–39.8.16 SHIFTCORR
• Updated RESULT bit description in 39.8.19 RESULT.
40. AC – Analog Comparators 40.8.12 COMPCTRL: SPEED bit description updated. Values 0x1 and
0x2 is reserved.
41. DAC – Digital-to-Analog
Converter
Updated DATA register: DATA bits access corrected from read/write
(R/W) to write (W).TPUBSAMD-354
43. TSENS – Temperature
Sensor
43.6.2.3 Measurement: Added temperature measurement
recommendation to avoid discrepancies.
45. Electrical Characteristics
85°C (SAM C20/C21 E/G/J)
• Added electrical characteristics for 85°C.
•6.2.4 GPIO Clusters moved to 6. I/O Multiplexing and
Considerations.
46. Electrical Characteristics
105°C (SAM C20/C21 E/G/J)
• Added electrical characteristics for 105°C.
49. Packaging Information Updated package drawings to include GPC, drawing no. and revision
letter.
Errata SAM C20 and Errata
SAM C21
• Updated revision B errata: Added Errata reference 14497, 14633
and 15342.
• Added revision C errata.
• Added revision D errata.
51.9 Rev F - 02/2015
1. Configuration Summary Number of PTC X and Y lines updated for SAM
C20/C21G and SAM C20/C21E.
13. DSU - Device Service Unit 13.13.4 ADDR: Added AMOD bits.
22. SUPC – Supply Controller 22.5.7 Debug Operation: Updated description.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1285
References to oscillator OSC16M removed and
replaced with OSC48M:
•15.1 Clock Distribution: Block diagram
updated.
•16.3 Block Diagram: OSCM16M replaced by
OSC48M. DFLL48M removed.
• GENCTRLn.SRC[4:0]: Value 0x6 description
updated.
•20.6.4 48MHz Internal Oscillator (OSC48M)
Operation.
29. EVSYS – Event System 29.8.1 CTRLA: Note added to CTRLA.SWRST bit
description.
25. DMAC – Direct Memory Access Controller Updated description of the PRICTRL0.LVLPRIn
bits.
35. TC – Timer/Counter Updated section 35.5.3 Clocks: The TC bus clocks
(CLK_TCx_APB) can be enabled and disabled in
the Main Clock Module (MCLK) (not the Power
Manager).
39. SDADC – Sigma-Delta Analog-to-Digital
Converter
•39.3 Block Diagram: Reference selection
updated.
•39.8.2 REFCTRL: Added note to REFSEL bit
description.
40. AC – Analog Comparators Removed references to multiple level hystereseis.
Levels are not available, only on or off:
•40.2 Features: Selectable hysteresis updated
from "4-levels" or off to "on or off".
•40.6.2.3 Comparator Configuration: Removed
references to COMPCTRLx.HYST bits.
•40.6.6 Input Hysteresis: Removed references
to COMPCTRLx.HYST bits.
• Register Summary: Removed the
COMPCTRLx.HYST bits.
•40.8.12 COMPCTRL: Removed the HYST
bits.
51.10 Rev E - 12/2015
1. Configuration Summary • Corrected memory sizes.
• Number of ADC channels corrected.
• Number of TCC instances corrected from
three to one.
2. Ordering Information • Introduced 105°C ordering codes.
• Corrected package type from QFN48 to
TQFP48 for ATSAM C20/C21G16A-AUT.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1286
13. DSU - Device Service Unit Bit CTRL.CRC is write-only.
27. NVMCTRL – Nonvolatile Memory Controller Updated description in 27.6.4.3 NVM Write:
Removed reference to default MANW value. This
is covered in the CTRLB.MANW bit description.
25. DMAC – Direct Memory Access Controller Added note in 25.6.7 Sleep Mode Operation.
37. CCL – Configurable Custom Logic Removed oscillator related sub sections from
37.6.2.7 Sequential Logic.
31. SERCOM USART - SERCOM Synchronous
and Asynchronous Receiver and Transmitter
• Added RS485 to the TXPO bit description in
the 31.8.1 CTRLAregister.
51.11 Rev D - 09/2015
31. SERCOM USART - SERCOM Synchronous
and Asynchronous Receiver and Transmitter
• Updated formula in the 31.8.5 RXPLregister.
Errata SAMC20 and Errata SAMC21 • Reinserted errata section which was missing
from datasheet rev C.
51.12 Rev C - 09/2015
General Editorial updates.
25. DMAC – Direct Memory Access Controller • Updated number of bits in the SWTRIGCTRL,
INTSTATUS, BUSYCH and PENDCH registers
(Related to number of DMA channels
available).
28. PORT - I/O Pin Controller • Functional Description: Overview diagram
updated.
38. ADC – Analog-to-Digital Converter • Block Diagram: Renamed ADC input signals
from ADC to AIN.
• Signal Description: Renamed ADC signal to
AIN
42. Peripheral Touch Controller (PTC) • Block Diagram updated.
• Section Self-capacitance Sensor Arrangement
updated.
51.13 Rev B - 06/2015
2. Ordering Information • Remove carrier type Tray option.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1287
51.14 Rev A - 04/2015
Initial revision.
SAM C20/C21 Family Data Sheet
Revision History
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1288
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SAM C20/C21 Family Data Sheet
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1289
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ATSAMC 21 N 18 A - M U T
Product Family
E = 32 Pins
G = 48 Pins
J = 64 Pins
N = 100 Pins
No character = Tray (Default)
T = Tape and Reel
U = -40 - 85°C Matte Sn Plating
N = -40 - 105°C Matte Sn Plating
Z = -40°C - 125°C Matte Sn
Plating (AEC-Q100 Qualified)
A = TQFP
M = VQFN
U = WLCSP
21 = Cortex M0+ CPU, DMA, CAN,
16-bit SDADC
SAMC = 5V Microcontroller
Product Series
Flash Memory Density
Device Variant
A = Default Variant
Pin Count
Package Carrier
Package Grade
Package Type
18 = 256KB
17 = 128KB
16 = 64KB
15 = 32KB
20 = Cortex M0+ CPU, DMA
(3)
(4)(5)
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SAM C20/C21 Family Data Sheet
© 2019 Microchip Technology Inc. Datasheet DS60001479C-page 1290
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ISBN: 978-1-5224-4042-0
SAM C20/C21 Family Data Sheet
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