8/16 kB ISP Flash MCU Family
C8051F310/1/2/3/4/5/6/7
Rev. 1.7 8/06 Copyright © 2006 by Silicon Laboratorie s C8051F31x
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
Analog Peripherals
-10-Bit ADC (C8051F310/1/2/3/6 only)
•Up to 200 ksps
•Up to 21, 17, or 13 external single-ended or differen-
tial inputs
•VREF from external pin or VDD
•Built-in temperature sensor
•External conversion start input
-Comparators
•Programmable hysteresis and response time
•Configurable as interrupt or reset source
(Comparator0)
•Low current ( 0.5 µA)
On-Chip Debug
-On-chip debug circuitry facilitates full speed,
non-intrusive in-system debug
(no emulator required)
-Provides breakpoints, single stepping,
inspect/modify memory and registers
-Superior performance to emulation systems using
ICE-Chips, target pods, and sockets
-Complete development kit
Supply Voltage 2.7 to 3.6 V
-Typical operating current: 5 mA at 25 MHz;
11 µA at 32 kHz
-Typical stop mode current: 0.1 µA
-Temperature range: –40 to +85 °C
High Speed 8051 µC Core
-Pipelined instruction architecture; executes 70% of
instructions in 1 or 2 system clocks
-Up to 25 MIPS throughput with 25 MHz clock
-Expanded interrupt handler
Memory
-1280 bytes internal data RAM (1024 + 256)
-
16 kB (C8051F310/1/6/7) or 8 kB (C8051F312/3/4/5)
Flash; In-system programmable in 512-byte sectors
Digital Peripherals
-29/25/21 Port I/O;
All 5 V tolerant with high sink current
-Hardware enhanced UART, SMBus™, and SPI™
serial ports
-Four general purpose 16-bit counter/timers
-16-bit programmable counter array (PCA) with five
capture/compare modules
-Real time clock capability using PCA or timer and
external clock source
Clock Sources
-Internal oscillator: 24.5 MHz with ±2% accuracy
supports crystal-less UART operation
-External oscillator: Crystal, RC, C, or clock (1 or 2
pin modes)
-Can switch between clock sources on-the-fly; useful
in power saving modes
Packages
-32-pin LQFP (C8051F310/2/4)
-28-pin QFN (C8051F3 11/3/5)
-24-pin QFN (C8051F3 16/7)
ANALOG
PERIPHERALS
10-bit
200ksps
ADC
16 k B /8 k B
ISP FLASH 1280 B
SRAM
POR
DEBUG
CIRCUITRY
14
INTERRUPTS
8051 CPU
(25MIPS)
TEMP
SENSOR
DIGITAL I/O
P R OGRAMM A BL E PRECISION INT ERNA L
OSCILLATOR
HIGH-SPEED CONTROLLER CORE
A
M
U
X
CROSSBAR
VOLTAGE
COMPARATORS
+
-
WDT
Port 0
+
-
UART
SMBus
PCA
Timer 0
Timer 1
Timer 2
Timer 3
Port 1
Port 2
Port 3
SPI
C8051F310/1/2/3/6 only
C8051F310/1/2/3/4/5/6/7
2 Rev. 1.7
NOTES:
Rev. 1.7 3
C8051F310/1/2/3/4/5/6/7
Table Of Contents
1. System Overview.................................................................................................... 17
1.1. CIP-51™ Microcontroller Core.......................................................................... 27
1.1.1. Fully 8051 Compatible.............................................................................. 27
1.1.2. Improved Throughput............................................................................... 27
1.1.3. Additional Features .................................................................................. 28
1.2. On-Chip Memory............................................................................................... 29
1.3. On-Chip Debug Circuitry................................................................................... 30
1.4. Programmable Digital I/O and Crossbar........................................................... 31
1.5. Serial Ports ....................................................................................................... 32
1.6. Programmable Counter Array........................................................................... 32
1.7. 10-Bit Analog to Digital Converter..................................................................... 33
1.8. Comparators..................................................................................................... 34
2. Absolute Maximum Ratings .................................................................................. 35
3. Global DC Electrical Characteristics.................................................................... 36
4. Pinout and Package Definitions............................................................................ 39
5. 10-Bit ADC (ADC0, C8051F310/1/2/3/6 only) ........................................................ 51
5.1. Analog Multiplexer ............................................................................................ 51
5.2. Temperature Sensor......................................................................................... 52
5.3. Modes of Operation .......................................................................................... 54
5.3.1. Starting a Conversion............................................................................... 54
5.3.2. Tracking Modes........................................................................................ 55
5.3.3. Settling Time Requirements..................................................................... 56
5.4. Programmable Window Detector...................................................................... 61
5.4.1. Window Detector In Single-Ended Mode ................................................. 63
5.4.2. Window Detector In Differential Mode...................................................... 64
6. Voltage Reference (C8051F310/1/2/3/6 only)........................................................ 67
7. Comparators........................................................................................................... 69
8. CIP-51 Microcontroller .......................................................................................... 79
8.1. Instruction Set................................................................................................... 80
8.1.1. Instruction and CPU Timing ..................................................................... 80
8.1.2. MOVX Instruction and Program Memory ................................................. 81
8.2. Memory Organization........................................................................................ 85
8.2.1. Program Memory...................................................................................... 85
8.2.2. Data Memory............................................................................................ 86
8.2.3. General Purpose Registers...................................................................... 86
8.2.4. Bit Addressable Locations........................................................................ 86
8.2.5. Stack ....................................................................................................... 86
8.2.6. Special Function Registers....................................................................... 87
8.2.7. Register Descriptions............................................................................... 90
8.3. Interrupt Handler............................................................................................... 93
8.3.1. MCU Interrupt Sources and Vectors ........................................................ 94
8.3.2. External Interrupts.................................................................................... 95
8.3.3. Interrupt Priorities..................................................................................... 95
C8051F310/1/2/3/4/5/6/7
4 Rev. 1.7
8.3.4. Interrupt Latency ...................................................................................... 95
8.3.5. Interrupt Register Descriptions................................................................. 97
8.4. Power Management Modes............................................................................ 102
8.4.1. Idle Mode................................................................................................ 102
8.4.2. Stop Mode.............................................................................................. 103
9. Reset Sources....................................................................................................... 105
9.1. Power-On Reset ............................................................................................. 106
9.2. Power-Fail Reset / VDD Monitor...................................................................... 106
9.3. External Reset ................................................................................................ 107
9.4. Missing Clock Detector Reset......................................................................... 108
9.5. Comparator0 Reset ......................................................................................... 108
9.6. PCA Watchdog Timer Reset........................................................................... 108
9.7. Flash Error Reset............................................................................................ 108
9.8. Software Reset ............................................................................................... 108
10.Flash Memory ..................................................................................................... 111
10.1.Programming The Flash Memory................................................................... 111
10.1.1.Flash Lock and Key Functions............................................................... 111
10.1.2.Flash Erase Procedure .......................................................................... 111
10.1.3.Flash Write Procedure ........................................................................... 112
10.2.Non-volatile Data Storage .............................................................................. 112
10.3.Security Options............................................................................................. 113
10.4.Flash Write and Erase Guidelines.................................................................. 115
10.4.1.VDD Maintenance and the VDD Monitor ................................................. 115
10.4.2.PSWE Maintenance............................................................................... 115
10.4.3.System Clock......................................................................................... 116
11.External RAM........................................................................................................ 119
12.Oscillators............................................................................................................. 121
12.1.Programmable Internal Oscillator................................................................... 121
12.2.External Oscillator Drive Circuit...................................................................... 124
12.3.System Clock Selection.................................................................................. 124
12.4.External Crystal Example............................................................................... 126
12.5.External RC Example..................................................................................... 127
12.6.External Capacitor Example........................................................................... 127
13.Port Input/Output ................................................................................................ 129
13.1.Priority Crossbar Decoder.............................................................................. 131
13.2.Port I/O Initializati on ....................................................................................... 133
13.3.General Purpose Port I/O............................................................................... 135
14.SMBus ................................................................................................................... 145
14.1.Supporting Documents................................................................................... 146
14.2.SMBus Configuration...................................................................................... 146
14.3.SMBus Operation........................................................................................... 146
14.3.1.Arbitration............................................................................................... 147
14.3.2.Clock Low Extension.............................................................................. 148
14.3.3.SCL Low Timeout................................................................................... 148
14.3.4.SCL High (SMBus Free) Timeout .......................................................... 148
Rev. 1.7 5
C8051F310/1/2/3/4/5/6/7
14.4.Using the SMBus............................................................................................ 149
14.4.1.SMBus Configuration Register............................................................... 150
14.4.2.SMB0CN Control Register..................................................................... 153
14.4.3.Data Register......................................................................................... 156
14.5.SMBus Transfer Modes.................................................................................. 157
14.5.1.Master Transmitter Mode....................................................................... 157
14.5.2.Master Receiver Mode........................................................................... 158
14.5.3.Slave Receiver Mode............................................................................. 159
14.5.4.Slave Transmitter Mode......................................................................... 160
14.6.SMBus Status Decoding................................................................................. 161
15.UART0.................................................................................................................... 163
15.1.Enhanced Baud Rate Generation................................................................... 164
15.2.Operational Modes......................................................................................... 165
15.2.1.8-Bit UART............................................................................................. 165
15.2.2.9-Bit UART............................................................................................. 166
15.3.Multiprocessor Communications .................................................................... 167
16.Enhanced Serial Peripheral Interface (SPI0)...................................................... 173
16.1.Signal Descriptions......................................................................................... 174
16.1.1.Master Out, Slave In (MOSI).................................................................. 174
16.1.2.Master In, Slave Out (MISO).................................................................. 174
16.1.3.Serial Clock (SCK)................................................................................. 174
16.1.4.Slave Select (NSS) ................................................................................ 174
16.2.SPI0 Master Mode Operation......................................................................... 175
16.3.SPI0 Slave Mode Operation........................................................................... 177
16.4.SPI0 Interrupt Sources................................................................................... 177
16.5.Serial Clock Timing......................................................................................... 178
16.6.SPI Special Function Registers...................................................................... 180
17.Timers ................................................................................................................... 187
17.1.Timer 0 and Timer 1....................................................................................... 187
17.1.1.Mode 0: 13-bit Counter/Timer................................................................ 187
17.1.2.Mode 1: 16-bit Counter/Timer................................................................ 189
17.1.3.Mode 2: 8-bit Counter/Timer with Auto-Reload...................................... 189
17.1.4.Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)................................. 190
17.2.Timer 2 .......................................................................................................... 195
17.2.1.16-bit Timer with Auto-Reload................................................................ 195
17.2.2.8-bit Timers with Auto-Reload................................................................ 196
17.3.Timer 3 .......................................................................................................... 199
17.3.1.16-bit Timer with Auto-Reload................................................................ 199
17.3.2.8-bit Timers with Auto-Reload................................................................ 200
18.Programmable Counter Array ............................................................................ 203
18.1.PCA Counter/Timer........................................................................................ 204
18.2.Capture/Compare Modules ............................................................................ 205
18.2.1.Edge-triggered Capture Mode................................................................ 206
18.2.2.Software Timer (Compare) Mode........................................................... 207
C8051F310/1/2/3/4/5/6/7
6 Rev. 1.7
18.2.3.High-Speed Output Mode ...................................................................... 208
18.2.4.Frequency Output Mode ........................................................................ 209
18.2.5.8-Bit Pulse Width Modulator Mode......................................................... 210
18.2.6.16-Bit Pulse Width Modulator Mode....................................................... 211
18.3.Watchdog Timer Mode................................................................................... 212
18.3.1.Watchdog Timer Operation.................................................................... 212
18.3.2.Watchdog Timer Usage ......................................................................... 213
18.4.Register Descriptions for PCA........................................................................ 215
19.Revision Specific Behavior ................................................................................. 221
19.1.Revision Identification..................................................................................... 221
19.2.Reset Behavior............................................................................................... 221
19.2.1.Weak Pullups on GPIO Pins.................................................................. 221
19.2.2.VDD Monitor and the RST Pin................................................................ 221
19.3.PCA Counter .................................................................................................. 222
20.C2 Interface........................................................................................................... 223
20.1.C2 Interface Registers.................................................................................... 223
20.2.C2 Pin Sharing ............................................................................................... 225
Document Change List............................................................................................. 226
Contact Information.................................................................................................. 228
Rev. 1.7 7
C8051F310/1/2/3/4/5/6/7
List of Figures
1. System Overview
Figure 1.1. C8051F310 Block Diagram.................................................................... 19
Figure 1.2. C8051F311 Block Diagram.................................................................... 20
Figure 1.3. C8051F312 Block Diagram.................................................................... 21
Figure 1.4. C8051F313 Block Diagram.................................................................... 22
Figure 1.5. C8051F314 Block Diagram.................................................................... 23
Figure 1.6. C8051F315 Block Diagram.................................................................... 24
Figure 1.7. C8051F316 Block Diagram.................................................................... 25
Figure 1.8. C8051F317 Block Diagram.................................................................... 26
Figure 1.9. Comparison of Peak MCU Execution Speeds ....................................... 27
Figure 1.10. On-Chip Clock and Reset..................................................................... 28
Figure 1.11. On-Board Memory Map........................................................................ 29
Figure 1.12. Development/In-System Debug Diagram............................................. 30
Figure 1.13. Digital Crossbar Diagram..................................................................... 31
Figure 1.14. PCA Block Diagram.............................................................................. 32
Figure 1.15. 10-Bit ADC Block Diagram................................................................... 33
Figure 1.16. Comparator0 Block Diagram................................................................ 34
2. Absolute Maximum Ratings
3. Global DC Electrical Characteristics
4. Pinout and Package Definitions
Figure 4.1. LQFP-32 Pinout Diagram (Top View) .................................................... 41
Figure 4.2. LQFP-32 Package Diagram................................................................... 42
Figure 4.3. QFN-28 Pinout Diagram (Top View)...................................................... 43
Figure 4.4. QFN-28 Package Drawing..................................................................... 44
Figure 4.5. Typical QFN-28 Landing Diagram.......................................................... 45
Figure 4.6. QFN-28 Solder Paste Recommendation................................................ 46
Figure 4.7. QFN-24 Pinout Diagram (Top View)...................................................... 47
Figure 4.8. QFN-24 Package Drawing..................................................................... 48
Figure 4.9. Typical QFN-24 Landing Diagram.......................................................... 49
Figure 4.10. QFN-24 Solder Paste Recommendation.............................................. 50
5. 10-Bit ADC (ADC0, C8051F310/1/2/3/6 only)
Figure 5.1. ADC0 Functional Block Diagram............................................................ 51
Figure 5.2. Typical Temperature Sensor Transfer Function..................................... 52
Figure 5.3. Temperature Sensor Error with 1-Point Calibration............................... 53
Figure 5.4. 10-Bit ADC Track and Conversion Example Timing.............................. 55
Figure 5.5. ADC0 Equivalent Input Circuits.............................................................. 56
Figure 5.6. ADC Window Compare Example: Right-Justified Single-Ended Data... 63
Figure 5.7. ADC Window Compare Example: Left-Justified Single-Ended Data ..... 63
Figure 5.8. ADC Window Compare Example: Right-Justified Differential Data ....... 64
Figure 5.9. ADC Window Compare Example: Left-Justified Differential Data.......... 64
6. Voltage Reference (C8051F310/1/2/3/6 only)
Figure 6.1. Voltage Reference Functional Block Diagram ....................................... 67
C8051F310/1/2/3/4/5/6/7
8 Rev. 1.7
7. Comparators
Figure 7.1. Comparator0 Functional Block Diagram................................................ 69
Figure 7.2. Comparator1 Functional Block Diagram................................................ 70
Figure 7.3. Comparator Hysteresis Plot................................................................... 71
8. CIP-51 Microcontroller
Figure 8.1. CIP-51 Block Diagram............................................................................ 79
Figure 8.2. Memory Map.......................................................................................... 85
9. Reset Sources
Figure 9.1. Reset Sources...................................................................................... 105
Figure 9.2. Power-On and VDD Monitor Reset Timing ........................................... 106
10.Flash Memory
Figure 10.1. Flash Program Memory Map.............................................................. 113
11.External RAM
12.Oscillators
Figure 12.1. Oscillator Diagram.............................................................................. 121
Figure 12.2. 32.768 kHz External Crystal Example................................................ 126
13.Port Input/Output
Figure 13.1. Port I/O Functional Block Diagram..................................................... 129
Figure 13.2. Port I/O Cell Block Diagram ............................................................... 130
Figure 13.3. Crossbar Priority Decoder with No Pins Skipped............................... 131
Figure 13.4. Crossbar Priority Decoder with Crystal Pins Skipped ........................ 132
14.SMBus
Figure 14.1. SMBus Block Diagram ....................................................................... 145
Figure 14.2. Typical SMBus Configuration............................................................. 146
Figure 14.3. SMBus Transaction............................................................................ 147
Figure 14.4. Typical SMBus SCL Generation......................................................... 151
Figure 14.5. Typical Master Transmitter Sequence................................................ 157
Figure 14.6. Typical Master Receiver Sequence.................................................... 158
Figure 14.7. Typical Slave Receiver Sequence...................................................... 159
Figure 14.8. Typical Slave Transmitter Sequence.................................................. 160
15.UART0
Figure 15.1. UART0 Block Diagram....................................................................... 163
Figure 15.2. UART0 Baud Rate Logic.................................................................... 164
Figure 15.3. UART Interconnect Diagram.............................................................. 165
Figure 15.4. 8-Bit UART Timing Diagram............................................................... 165
Figure 15.5. 9-Bit UART Timing Diagram............................................................... 166
Figure 15.6. UART Multi-Processor Mode Interconnect Diagram.......................... 167
16.Enhanced Serial Peripheral Interface (SPI0)
Figure 16.1. SPI Block Diagram............................................................................. 173
Figure 16.2. Multiple-Master Mode Connection Diagram....................................... 176
Figure 16.3. 3-Wire Single Master and Slave Mode Connection Diagram............. 176
Figure 16.4. 4-Wire Single Master and Slave Mode Connection Diagram............. 176
Figure 16.5. Master Mode Data/Clock Timing........................................................ 178
Figure 16.6. Slave Mode Data/Clock Timing (CKPHA = 0).................................... 179
Figure 16.7. Slave Mode Data/Clock Timing (CKPHA = 1).................................... 179
Rev. 1.7 9
C8051F310/1/2/3/4/5/6/7
Figure 16.8. SPI Master Timing (CKPHA = 0)........................................................ 183
Figure 16.9. SPI Master Timing (CKPHA = 1)........................................................ 183
Figure 16.10. SPI Slave Timing (CKPHA = 0)........................................................ 184
Figure 16.11. SPI Slave Timing (CKPHA = 1)........................................................ 184
17.Timers
Figure 17.1. T0 Mode 0 Block Diagram.................................................................. 188
Figure 17.2. T0 Mode 2 Block Diagram.................................................................. 189
Figure 17.3. T0 Mode 3 Block Diagram.................................................................. 190
Figure 17.4. Timer 2 16-Bit Mode Block Diag ram .................................................. 195
Figure 17.5. Timer 2 8-Bit Mode Block Diagram .................................................... 196
Figure 17.6. Timer 3 16-Bit Mode Block Diag ram .................................................. 199
Figure 17.7. Timer 3 8-Bit Mode Block Diagram .................................................... 200
18.Programmable Counter Array
Figure 18.1. PCA Block Diagram............................................................................ 203
Figure 18.2. PCA Counter/Timer Block Diagram.................................................... 204
Figure 18.3. PCA Interrupt Block Diagram............................................................. 205
Figure 18.4. PCA Capture Mode Diagram.............................................................. 206
Figure 18.5. PCA Software Timer Mode Diagram.................................................. 207
Figure 18.6. PCA High Speed Output Mode Diagram............................................ 208
Figure 18.7. PCA Frequency Output Mode............................................................ 209
Figure 18.8. PCA 8-Bit PWM Mode Diagram......................................................... 210
Figure 18.9. PCA 16-Bit PWM Mode...................................................................... 211
Figure 18.10. PCA Module 4 with Watchdog Timer Enabled................................. 212
19.Revision Specific Behavior
Figure 19.1. Reading Package Marking................................................................. 221
20.C2 Interface
Figure 20.1. Typical C2 Pin Sharing....................................................................... 225
C8051F310/1/2/3/4/5/6/7
10 Rev. 1.7
NOTES:
Rev. 1.7 11
C8051F310/1/2/3/4/5/6/7
List of Tables
1. System Overview
Table 1.1. Product Selection Guide ......................................................................... 18
2. Absolute Maximum Ratings
Table 2.1. Absolute Maximum Ratings .................................................................... 35
3. Global DC Electrical Characteristics
Table 3.1. Global DC Electrical Characteristics ....................................................... 36
Table 3.2. Electrical Characteristics Quick Reference ............................................ 38
4. Pinout and Package Definitions
Table 4.1. Pin Definitions for the C8051F31x .......................................................... 39
Table 4.2. LQFP-32 Package Dimensions .............................................................. 42
Table 4.3. QFN-28 Package Dimensions ................................................................ 44
Table 4.4. QFN-24 Package Dimensions ................................................................ 48
5. 10-Bit ADC (ADC0, C8051F310/1/2/3/6 only)
Table 5.1. ADC0 Electrical Characteristics .............................................................. 65
6. Voltage Reference (C8051F310/1/2/3/6 only)
Table 6.1. External Voltage Reference Circuit Electrical Characteristics ................ 68
7. Comparators
Table 7.1. Comparator Electrical Characteristics .................................................... 78
8. CIP-51 Microcontroller
Table 8.1. CIP-51 Instruction Set Summary ............................................................ 81
Table 8.2. Special Function Register (SFR) Memory Map ...................................... 87
Table 8.3. Special Function Registers ..................................................................... 88
Table 8.4. Interrupt Summary .................................................................................. 96
9. Reset Sources
Table 9.1. Reset Electrical Characteristics ............................................................ 110
10.Flash Memory
Table 10.1. Flash Electrical Characteristics .......................................................... 112
Table 10.2. Flash Security Summary .................................................................... 114
11.External RAM
12.Oscillators
Table 12.1. Internal Oscillator Electrical Characteristics ....................................... 123
13.Port Input/Output
Table 13.1. Port I/O DC Electrical Characteristics ................................................ 143
14.SMBus
Table 14.1. SMBus Clock Source Selection .......................................................... 150
Table 14.2. Minimum SDA Setup and Hold Times ................................................ 151
Table 14.3. Sources for Hardware Changes to SMB0CN ..................................... 155
Table 14.4. SMBus Status Decoding ..................................................................... 161
C8051F310/1/2/3/4/5/6/7
12 Rev. 1.7
15.UART0
Table 15.1. Timer Settings for Standard Baud Rates
Using the Internal Oscillator ............................................................... 170
Table 15.2. Timer Settings for Standard Baud Rates
Using an External 25 MHz Oscillator .................................................. 170
Table 15.3. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator ......................................... 171
Table 15.4. Timer Settings for Standard Baud Rates
Using an External 18.432 MHz Oscillator ........................................... 171
Table 15.5. Timer Settings for Standard Baud Rates
Using an External 11.0592 MHz Oscillator ......................................... 172
Table 15.6. Timer Settings for Standard Baud Rates
Using an External 3.6864 MHz Oscillator ........................................... 172
16.Enhanced Serial Peripheral Interface (SPI0)
Table 16.1. SPI Slave Timing Parameters ............................................................ 185
17.Timers
18.Programmable Counter Array
Table 18.1. PCA Timebase Input Options ............................................................. 204
Table 18.2. PCA0CPM Register Settings for PCA Capture/Compare Modules .... 205
Table 18.3. Watchdog Timer Timeout Intervals ..................................................... 214
19.Revision Specific Behavior
20.C2 Interface
Rev. 1.7 13
C8051F310/1/2/3/4/5/6/7
List of Registers
SFR Definition 5.1. AMX0P: AMUX0 Positive Channel Select . . . . . . . . . . . . . . . . . . . 57
SFR Definition 5.2. AMX0N: AMUX0 Negative Channel Select . . . . . . . . . . . . . . . . . . 58
SFR Definition 5.3. ADC0CF: ADC0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
SFR Definition 5.4. ADC0H: ADC0 Data Word MSB . . . . . . . . . . . . . . . . . . . . . . . . . . 59
SFR Definition 5.5. ADC0L: ADC0 Data Word LSB . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
SFR Definition 5.6. ADC0CN: ADC0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
SFR Definition 5.7. ADC0GTH: ADC0 Greater-Than Data High Byte . . . . . . . . . . . . . 61
SFR Definition 5.8. ADC0GTL: ADC0 Greater-Than Data Low Byte . . . . . . . . . . . . . . 61
SFR Definition 5.9. ADC0LTH: ADC0 Less-Than Data High Byte . . . . . . . . . . . . . . . . 62
SFR Definition 5.10. ADC0LTL: ADC0 Less-Than Data Low Byte . . . . . . . . . . . . . . . . 62
SFR Definition 6.1. REF0CN: Reference Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
SFR Definition 7.1. CPT0CN: Comparator0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
SFR Definition 7.2. CPT0MX: Comparator0 MUX Selection . . . . . . . . . . . . . . . . . . . . 73
SFR Definition 7.3. CPT0MD: Comparator0 Mode Selection . . . . . . . . . . . . . . . . . . . . 74
SFR Definition 7.4. CPT1CN: Comparator1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
SFR Definition 7.5. CPT1MX: Comparator1 MUX Selection . . . . . . . . . . . . . . . . . . . . 76
SFR Definition 7.6. CPT1MD: Comparator1 Mode Selection . . . . . . . . . . . . . . . . . . . . 77
SFR Definition 8.1. DPL: Data Pointer Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
SFR Definition 8.2. DPH: Data Pointer High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
SFR Definition 8.3. SP: Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
SFR Definition 8.4. PSW: Program Status Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
SFR Definition 8.5. ACC: Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
SFR Definition 8.6. B: B Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
SFR Definition 8.7. IE: Interrupt Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
SFR Definition 8.8. IP: Interrupt Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
SFR Definition 8.9. EIE1: Extended Interrupt Enable 1 . . . . . . . . . . . . . . . . . . . . . . . . 99
SFR Definition 8.10. EIP1: Extended Interrupt Priority 1 . . . . . . . . . . . . . . . . . . . . . . 100
SFR Definition 8.11. IT01CF: INT0/INT1 Configuration . . . . . . . . . . . . . . . . . . . . . . . 101
SFR Definition 8.12. PCON: Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
SFR Definition 9.1. VDM0CN: VDD Monitor Control . . . . . . . . . . . . . . . . . . . . . . . . . . 107
SFR Definition 9.2. RSTSRC: Reset Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
SFR Definition 10.1. PSCTL: Program Store R/W Cont rol . . . . . . . . . . . . . . . . . . . . . 116
SFR Definition 10.2. FLKEY: Flash Lock and Key . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
SFR Definition 10.3. FLSCL: Flash Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
SFR Definition 11.1. EMI0CN: External Memory Interface Control . . . . . . . . . . . . . . 119
SFR Definition 12.1. OSCICL: Internal Oscillator Calibration . . . . . . . . . . . . . . . . . . . 122
SFR Definition 12.2. OSCICN: Internal Oscillator Control . . . . . . . . . . . . . . . . . . . . . 122
SFR Definition 12.3. CLKSEL: Clock Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
SFR Definition 12.4. OSCXCN: External Oscillator Control . . . . . . . . . . . . . . . . . . . . 125
SFR Definition 13.1. XBR0: Port I/O Crossbar Register 0 . . . . . . . . . . . . . . . . . . . . . 134
SFR Definition 13.2. XBR1: Port I/O Crossbar Register 1 . . . . . . . . . . . . . . . . . . . . . 135
SFR Definition 13.3. P0: Port0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
SFR Definition 13.4. P0MDIN: Port0 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
C8051F310/1/2/3/4/5/6/7
14 Rev. 1.7
SFR Definition 13.5. P0MDOUT: Port0 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . . 137
SFR Definition 13.6. P0SKIP: Port0 Skip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
SFR Definition 13.7. P1: Port1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
SFR Definition 13.8. P1MDIN: Port1 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
SFR Definition 13.9. P1MDOUT: Port1 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . . 139
SFR Definition 13.10. P1SKIP: Port1 Skip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
SFR Definition 13.11. P2: Port2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
SFR Definition 13.12. P2MDIN: Port2 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
SFR Definition 13.13. P2MDOUT: Port2 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 141
SFR Definition 13.14. P2SKIP: Port2 Skip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
SFR Definition 13.15. P3: Port3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
SFR Definition 13.16. P3MDIN: Port3 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
SFR Definition 13.17. P3MDOUT: Port3 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 143
SFR Definition 14.1. SMB0CF: SMBus Clock/Configuration . . . . . . . . . . . . . . . . . . . 152
SFR Definition 14.2. SMB0CN: SMBus Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
SFR Definition 14.3. SMB0DAT: SMBus Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
SFR Definition 15.1. SCON0: Serial Port 0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . 168
SFR Definition 15.2. SBUF0: Serial (UART0) Port Data Buffer . . . . . . . . . . . . . . . . . 169
SFR Definition 16.1. SPI0CFG: SPI0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 180
SFR Definition 16.2. SPI0CN: SPI0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
SFR Definition 16.3. SPI0CKR: SPI0 Clock Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
SFR Definition 16.4. SPI0DAT: SPI0 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
SFR Definition 17.1. TCON: Timer Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
SFR Definition 17.2. TMOD: Timer Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
SFR Definition 17.3. CKCON: Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
SFR Definition 17.4. TL0: Timer 0 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
SFR Definition 17.5. TL1: Timer 1 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
SFR Definition 17.6. TH0: Timer 0 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
SFR Definition 17.7. TH1: Timer 1 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
SFR Definition 17.8. TMR2CN: Timer 2 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
SFR Definition 17.9. TMR2RLL: Timer 2 Reload Register Low Byte . . . . . . . . . . . . . 198
SFR Definition 17.10. TMR2RLH: Timer 2 Reload Register High Byte . . . . . . . . . . . 198
SFR Definition 17.11. TMR2L: Timer 2 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
SFR Definition 17.12. TMR2H Timer 2 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
SFR Definition 17.13. TMR3CN: Timer 3 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
SFR Definition 17.14. TMR3RLL: Timer 3 Reload Register Low Byte . . . . . . . . . . . . 202
SFR Definition 17.15. TMR3RLH: Timer 3 Reload Register High Byte . . . . . . . . . . . 202
SFR Definition 17.16. TMR3L: Timer 3 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
SFR Definition 17.17. TMR3H Timer 3 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
SFR Definition 18.1. PCA0CN: PCA Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
SFR Definition 18.2. PCA0MD: PCA Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
SFR Definition 18.3. PCA0CPMn: PCA Capture/Compare Mode Registers . . . . . . . 217
SFR Definition 18.4. PCA0L: PCA Counter/Timer Low Byte . . . . . . . . . . . . . . . . . . . 218
SFR Definition 18.5. PCA0H: PCA Counter/Timer High Byte . . . . . . . . . . . . . . . . . . . 218
SFR Definition 18.6. PCA0CPLn: PCA Capture Module Low Byte . . . . . . . . . . . . . . . 218
Rev. 1.7 15
C8051F310/1/2/3/4/5/6/7
SFR Definition 18.7. PCA0CPHn: PCA Capture Module High Byte . . . . . . . . . . . . . . 219
C2 Register Definition 20.1. C2ADD: C2 Address . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
C2 Register Definition 20.2. DEVICEID: C2 Device ID . . . . . . . . . . . . . . . . . . . . . . . . 223
C2 Register Definition 20.3. REVID: C2 Revision ID . . . . . . . . . . . . . . . . . . . . . . . . . 224
C2 Register Definition 20.4. FPCTL: C2 Flash Programming Control . . . . . . . . . . . . 224
C2 Register Definition 20.5. FPDAT: C2 Flash Programming Data . . . . . . . . . . . . . . 224
C8051F310/1/2/3/4/5/6/7
16 Rev. 1.7
NOTES:
Rev. 1.7 17
C8051F310/1/2/3/4/5/6/7
1. System Overview
C8051F31x devices are fully integrated mixed-signal System-on-a-Chip MCUs. Highlighted features are
listed below. Refer to Table 1.1 for specific product feature selection.
• High-speed pipelined 8051-compatible microcontroller core (up to 25 MIPS)
• In-system, full-speed, non-intrusive debug interface (on-chip)
• True 10-bit 200 ksps 25-channel single-ended/differential ADC with analog multiplexer
(C8051F310/1/2/3/6)
• Precision programmable 25 MHz internal oscillator
• 16 kB (C8051F310/1/6/7) or 8 kB (C8051F312/3/4/5) of on-chip Flash memory
• 1280 bytes of on-chip RAM
• SMBus/I2C, Enhanced UART, and Enhanced SPI serial interfaces implemented in hardware
• Four gener al- pu rp o se 16 - bit tim er s
• Programmable Counter/Timer Array (PCA) with five capture/compare modules and Watchdog Timer
function
• On-chip Power-On Reset, VDD Monitor, and Temperature Sensor
• On-chip Voltage Comparators (2)
• 29/25/21 Port I/O (5 V tolerant)
With on-chip Power-On Reset, VDD monitor, Watchdog Timer, and clock oscillator, the C8051F31x devices
are truly stand-alone System-on-a-Chip solutions. The Flash memory can be reprogrammed even in-cir-
cuit, providing non-volatile data storage, and also allowing field upgrades of the 8051 firmware. User soft-
ware has complete control of all peripherals, and may individually shut down any or all peripherals for
power savings.
The on-chip Silicon Labs 2-Wire (C2) Development Interface allows non-intrusive (uses no on-chip
resources), full speed, in-circuit debugging using the production MCU installed in th e final app lication. This
debug logic supports inspection and modification of memory and registers, setting breakpoints, single
stepping, run and halt commands. All analog and digital peripherals are fully functional while debugging
using C2. The two C2 interface pins can be shared with user functions, allowing in-system programming
and debugging without occupying package pins.
Each device is specified for 2.7-to-3.6 V operation over the industrial temperature range (–45 to +85 °C).
The Port I/O and RST pins are tolerant of input signals up to 5 V. The C8051F31x are available in 32-pin
LQFP, 28-pin QFN, and 24-pin QFN packages. See Table 1.1 for ordering part numbers. Note: QFN pack-
ages are also referred to as MLP or MLF packages.
Table 1.1. Product Selection Guide
Ordering Part Number
MIPS (Peak)
Flash Mem or y
RAM
Calibrated Internal 24.5 MHz Oscillator
SMBus/I2C
Enhanced SPI
UART
Timers (16-bit)
Programmab l e Co unte r A rr ay
Digital Port I/Os
10-bit 200 ksps ADC
Temperature Sensor
Analog Comparators
Lead-free (RoHS Compliant)
Package
C8051F310 25 16 1280 29 2 - LQFP-32
C8051F310-GQ 25 16 1280 29 2LQFP-32
C8051F311 25 16 1280 25 2 - QFN-28
C8051F311-GM 25 16 1280 25 2QFN-28
C8051F312 25 81280 29 2 - LQFP-32
C8051F312-GQ 25 81280 29 2LQFP-32
C8051F313 25 81280 25 2 - QFN-28
C8051F313-GM 25 81280 25 2QFN-28
C8051F314 25 81280 29 - - 2 - LQFP-32
C8051F314-GQ 25 81280 29 - - 2 LQFP-32
C8051F315 25 81280 25 - - 2 - QFN-28
C8051F315-GM 25 81280 25 - - 2 QFN-28
C8051F316-GM 25 16 1280 21 2QFN-24
C8051F317-GM 25 16 1280 21 - - 2 QFN-24
C8051F310/1/2/3/4/5/6/7
18 Rev. 1.7
UART
16kbyte
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
External
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power
P
0
D
r
v
1K byte
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Internal
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0/C2D
P3.1
P3.2
P3.3
P3.4
10-bit
200ksps
ADC
A
M
U
X
AIN0-AIN20
VREF
VDD
CP1
+
-
Temp
VDD
CP0
+
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
Rev. 1.7 19
C8051F310/1/2/3/4/5/6/7
Figure 1.1. C8051F310 Block Diagram
UART
16kbyte
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
External
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power
P
0
D
r
v
1K byte
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Internal
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0/C2D
10-bit
200ksps
ADC
A
M
U
X
AIN0-AIN20
VREF
VDD
CP1
+
-
Temp
VDD
CP0
+
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
C8051F310/1/2/3/4/5/6/7
20 Rev. 1.7
Figure 1.2. C8051F311 Block Diagram
Rev. 1.7 21
C8051F310/1/2/3/4/5/6/7
Figure 1.3. C8051F312 Block Diagram
UART
8 kB
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
External
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power P
0
D
r
v
1K byte
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Internal
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0/C2D
P3.1
P3.2
P3.3
P3.4
10-bit
200ksps
ADC
A
M
U
X
AIN0-AIN20
VREF
VDD
CP1 +
-
Temp
VDD
CP0 +
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
C8051F310/1/2/3/4/5/6/7
22 Rev. 1.7
Figure 1.4. C8051F313 Block Diagram
UART
8 kB
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
External
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power P
0
D
r
v
1K byte
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Interna l
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0/C2D
10-b it
200ks p s
ADC
A
M
U
X
AIN0-AIN20
VREF
VDD
CP1 +
-
Temp
VDD
CP0 +
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
Rev. 1.7 23
C8051F310/1/2/3/4/5/6/7
Figure 1.5. C8051F314 Block Diagram
UART
8 kB
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
External
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power P
0
D
r
v
1K byte
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Internal
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0/C2D
P3.1
P3.2
P3.3
P3.4
CP1 +
-
CP0 +
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
C8051F310/1/2/3/4/5/6/7
24 Rev. 1.7
Figure 1.6. C8051F315 Block Diagram
UART
8 kB
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
Extern al
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power P
0
D
r
v
1K byte
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Internal
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0/C2D
CP1 +
-
CP0 +
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
Rev. 1.7 25
C8051F310/1/2/3/4/5/6/7
Figure 1.7. C8051F316 Block Diagram
UART
16 kB
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
External
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power P
0
D
r
v
1 kB
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Intern al
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P3.0/C2D
10-bit
200 ksps
ADC
A
M
U
X
AIN0–AIN20
VREF
VDD
CP1 +
-
Temp
VDD
CP0 +
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
C8051F310/1/2/3/4/5/6/7
26 Rev. 1.7
Figure 1.8. C8051F317 Block Diagram
UART
16 kB
FLASH
256 byte
SRAM
POR
SFR Bus
8
0
5
1
C
o
r
e
Reset
/RST/C2CK
Extern al
Oscillator
Circuit
Debug HW
Brown-
Out
Analog/Digital
Power P
0
D
r
v
1 kB
SRAM
XTAL1
XTAL2
P0.0/VREF
P0.1
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVST
P0.7
SPI
VDD
GND
C
R
O
S
S
B
A
R
P
1
D
r
v
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
Port 0
Latch
SMBus
Timer
0,1,2,3 /
RTC
Port 1
Latch
2%
Internal
Oscillator
System Clock
P
2
D
r
v
P
3
D
r
v
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P3.0/C2D
CP1 +
-
CP0 +
-
C2D
Port 2
Latch
Port 3
Latch
PCA/
WDT
Rev. 1.7 27
C8051F310/1/2/3/4/5/6/7
1.1. CIP-51™ Microcontroller Core
1.1.1. Fully 8051 Compatible
The C8051F31x family utilizes Silicon Laboratories' proprietary CIP-51 microcontroller core. The CIP-51 is
fully compatible with the MCS- 51™ instructio n set; standard 803x/8 05x assemblers a nd compilers can be
used to develop sof tware. The CIP-51 core offers all the peripherals included with a standard 8052, includ-
ing four 16-bit counter/timers, a full-duplex UART with extended baud rate configuration, an enhanced SPI
port, 1280 bytes of internal RAM, 128 byte Special Function Register (SFR) address space, and 29/25/21
I/O pins.
1.1.2. Improved Throughput
The CIP-51 employ s a p ipelined architectu re that grea tly increases it s instr uction throughpu t over the st an-
dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system
clock cycles to execute with a maximum system clock of 12-to-24 MHz. By contrast, the CIP-51 core exe-
cutes 70% of its instr uctions in one or two syste m cloc k cycles, with only four instructions taking more than
four system clock cycles.
The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that
require each execution time.
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. Figure 1.9
shows a comparison of peak throughputs for various 8-bit microcontroller cores with their maximum sys-
tem clocks.
Figure 1.9. Comparison of Peak MCU Execution Speeds
Clocks to Execute 1 2 2/3 33/4 44/5 5 8
Number of Instructions 26 50 514 73121
5
10
15
20
ADuC812
8051
(16 MHz clk)
Philips
80C51
(33 MHz clk)
Microchip
PIC17C75x
(33 MHz clk)
Silico n L a b s
CIP-51
(25 MHz clk)
MIPS
25
C8051F310/1/2/3/4/5/6/7
28 Rev. 1.7
1.1.3. Additional Features
The C8051F31x SoC family includes several key enhancements to the CIP-51 core and peripherals to
improve performance and ease of use in end applications.
The extended interrup t handler provides 14 interr upt sources into the CIP- 51 (as opposed to 7 for the st an-
dard 8051), allowing numerous analog and digital peripherals to interrupt the controller. An interrupt driven
system requires less intervention by the MCU, giving it more effective throughput. The extra interrupt
sources are very useful when building multi-tasking, real-time systems.
Eight reset sources are available: power-on reset circuitry (POR), an on-chip VDD monitor (forces reset
when power supply voltage drops below VRST as given in Table 9.1 on page 110), a Watchdog Timer, a
Missing Clock Detector, a voltage level detection from Comparator0, a forced software reset, an external
reset pin, and an errant Flash read/write protection circuit. Each reset source except for the POR, Reset
Input Pin, or Flash error may be disabled by the user in software. The WDT may be permanently enabled
in software after a power-on reset during MCU initialization.
The internal oscillator is factory calibrated to 24.5 MHz ±2%. An external oscillator drive circuit is also
included, allowing an ex ternal cryst al, ceramic resonator, capacitor, RC, or CMOS clock source to generate
the system clock. If desired, the system clock source may be switched on-the-fly between the internal and
external oscillator circuits. An external oscillator can be ex tremely useful in low power applications, allow-
ing the MCU to run from a slow (power saving) external crystal source, while periodically sw itching to the
fast internal oscillator as needed.
Figure 1.10. On-Chip Clock and Reset
PCA
WDT
Missing
Clock
Detector
(one-
shot) (Software Rese t)
System Reset
Reset
Funnel
Px.x
Px.x
EN
SWRSF
Internal
Oscillator System
Clock
CIP-51
Microcontroller
Core
Extended Interrupt
Handler
Clock Select
EN
WDT
Enable
MCD
Enable
XTAL1
XTAL2
External
Oscillator
Drive
Errant
FLASH
Operation
/RST
(wired-OR)
Power On
Reset
'0'
+
-
Comparator 0
C0RSEF
VDD
+
-
Supply
Monitor
Enable
Rev. 1.7 29
C8051F310/1/2/3/4/5/6/7
1.2. On-Chip Memory
The CIP-51 has a standard 8051 program and data address configuration. It includes 256 bytes of data
RAM, with the upper 128 bytes dual-map ped. Indi rect addressing accesses the upper 128 bytes of general
purpose RAM, and direct addressing accesses the 128 byte SFR address space. The lower 128 bytes of
RAM are accessible via direct and indirect addressing. The first 32 bytes are addressable as four banks of
general purpose registers, and the next 16 bytes can be byte addressable or bit addressable.
Program memory consists of 8 or 16 kB of Flash. This memory may be reprogrammed in-system in 512
byte sectors, and requires no special off-chip programming voltage. See Figure 1.11 for the MCU syst em
memory map.
Figure 1.11. On-Board Memory Map
PROGRAM/DATA MEMORY
(Flash)
(Direct and Indirect
Addressing)
0x00
0x7F
Upper 128 RAM
(Indirect Addressing
Only)
0x80
0xFF Special Function
Register's
(Direct Add ressing Only)
DATA MEMORY (RAM)
General Purpose
Registers
0x1F
0x20
0x2F Bit Addressable
Lower 128 RAM
(Direct and Indirect
Addressing)
0x30
INTERN AL DATA ADDRESS SPACE
EXTERNAL DATA ADDRESS SPACE
XRA M - 1024 B ytes
(accessable using M O VX
instruction)
0x0000
0x03FF
Same 1024 bytes as from
0x0000 to 0x03FF, wrapped
on 1 kB boundaries
0x0400
0xFFFF
16 kB Flash
(In-System
Programmable in 512
B y te S ec to r s )
0x0000
RESERVED
0x3E00
0x3DFF
8 kB Flash
(In-System
Programmable in 512
B y te S ec to r s )
0x0000
RESERVED
0x2000
0x1FFF
C8051F310/1/6/7
C8051F312/3/4/5
C8051F310/1/2/3/4/5/6/7
30 Rev. 1.7
1.3. On-Chip Debug Circuitry
The C8051F31x devices include on-chip Silicon Labs 2-Wire (C2) debug circuitry that provides non-intru -
sive, full speed, in-circuit debugging of the production part installed in the end application.
Silicon Labs' debugging system supports inspection and modification of memory and registers, break-
points, and single stepping. No additional target RAM, program memory, timers, or communications chan-
nels are required. All the digital and analog peripherals are functional and work correctly while debugging.
All the peripherals (except for the ADC and SMBus) are stalled when the MCU is halted, during single
stepping, or at a brea kp o int in or de r to kee p them synchronized.
The C8051F310DK development kit provides all the hardware and software necessary to develop applica-
tion code and perform in-circuit debugging with the C8051F31x MCUs. The kit includes software with a
developer's studio and debugger, an integrated 8051 assembler, a debug adapter, a target application
board with the associated MCU installed, and the required cables and wall-mount power supply.
The Silicon Labs IDE interface is a vastly superior developing and debugging configuration, compared to
standard MCU emulators that use on-board "ICE Chips" and require the MCU in the application board to
be socketed. Silicon Labs' debug paradigm increases ease of use and preserves the performance of the
precision analog peripherals.
Figure 1.12. Development/In-System Debug Diagram
TARGET PCB
Debug
Adapter
VDD GND
C2 (x 2 ), VD D, GND
Window s 98SE o r later
Silicon Laboratories Integrated
Development Environment
C8051F31x
Rev. 1.7 31
C8051F310/1/2/3/4/5/6/7
1.4. Programmable Digital I/O and Crossbar
C8051F310/2/4 devices include 29 I/O pins (three byte-wide Ports and one 5-bit-wide Port);
C8051F311/3/5 devices include 25 I/O pins (three byte-wide Ports and one 1-bit-wide Port); C8051F316/7
devices include 21 I/O pins (one byte-wide Port, two 6-bit-wide Ports and one 1-bit-wide Port). The
C8051F31x Ports behave like typical 8051 Ports with a few enhancements. Each Port pin may be config-
ured as an analog input or a digital I/O pin. Pins selected as digital I/Os may additionally be configured for
push-pull or op en-drain outpu t. The “weak pullups” tha t are fixed on typical 8051 devices may be globally
disabled, providing power savings capabilities.
The Digita l Crossbar allows mapp ing of internal d igital system re sources to Port I/O pins ( See Figure 1.13).
On-chip counter/timers, serial buses, HW interrupts, comparator output, and other digital signals in the
controller can be configu red to app ear on the Port I/O pins specified in the Crossbar Control r egisters. This
allows the user to select the exact mix of general purpose Port I/O and digital resources needed for the
particular application.
Figure 1.13. Digit a l Crossbar Diagram
XBR0, XBR1,
PnSKIP Registers
Digital
Crossbar
Priority
Decoder
2
P0.0
P0.7
PnMDOUT,
PnMDIN Registers
UART
(Intern al Di gital Signals)
Highest
Priority
Lowest
Priority
SYSCLK
2
SMBus
T0, T1 2
6
PCA
CP1
Outputs 2
4
SPI
CP0
Outputs 2P1.0
P1.7
P2.0
P2.7
P3.0
P3.4
(Port Latches)
P0 (P0.0-P0.7)
(P1.0-P1.7)
(P2.0-P2.3)
(P2.4-P2.7)
8
8
4
4
P1
P2
Notes:
1. P3.1–P3.4 only available on the
C8051F310/2/4.
2. P1.6, P1.7 , P 2. 6, P 2 .7 only
available on the C8051F310/1/2/3/4/5
(P3.0-P3.4)
5
P3
5
P2
I/O
Cells
P3
I/O
Cells
P1
I/O
Cells
P0
I/O
Cells
8
8
84
4
C8051F310/1/2/3/4/5/6/7
32 Rev. 1.7
1.5. Serial Ports
The C8051F31x Family includes an SMBus/I2C interface, a full-duplex UART with enhanced baud rate
configuration, and an Enhanced SPI interface. Each of the serial buses is fully implemented in hardware
and makes extensive use of the CIP-51's interrupts, thus requiring very little CPU intervention.
1.6. Programmable Counter Array
An on-chip Programm able Cou nter/Timer Array (PCA) is includ ed in addition to the four 1 6- bit gene ra l pu r-
pose counter/timers. The PCA co nsists of a dedicated 16-bit counter/time r time ba se with five pr ogra mma-
ble capture/compare modules. The PCA clock is derived from one of six sources: the system clock divided
by 12, the system clock divided by 4, T imer 0 overflows, an External Clock Input (ECI), the system clock, or
the external oscillator clock source divided by 8. The external clock source selection is useful for real-time
clock functionality, where the PCA is clocked by an external source while the internal oscillator drives the
system clock.
Each capture/compare module can be configured to operate in one of six modes: Edge-Triggered Capture,
Software Timer, High Speed Output, 8- or 16- bit Pulse Width Modulator, or Frequency Output. Additionally,
Capture/Compare Module 4 offers watchdog timer (WDT) capabilities. Following a system reset, Module 4
is configured and enabled in WDT mode. The PCA Capture/Comp are Mod ule I/O and External Clock Input
may be routed to Port I/O v ia th e Digital Crossb ar.
Figure 1.14. PCA Block Diagram
Capture/Compare
Module 1
Capture/Compare
Module 0 Capture/Compare
Module 2 Capture/Compare
Module 3 Capture/Compare
Module 4 / WDT
CEX1
ECI
Crossbar
CEX2
CEX3
CEX4
CEX0
Port I/O
16-Bit Counter/Timer
PCA
CLOCK
MUX
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
Rev. 1.7 33
C8051F310/1/2/3/4/5/6/7
1.7. 10-Bit Analog to Digital Converter
The C8051F310/1/2/3/6 devices include an on-chip 10-bit SAR ADC with a 25-channel differential input
multiplexer. With a maximum throughput of 200 ksps, the ADC offers true 10-bit accuracy with an INL of
±1LSB. The ADC system includes a configurable analog multiplexer that selects both positive and nega-
tive ADC inputs. Ports1-3 are available as an ADC inputs; additionally, the on-chip Temperature Sensor
output and the power supply voltage (VDD) are available as ADC inputs. User firmware may shut down the
ADC to save power.
Conversions can be started in six ways: a software command, an overflow of Timer 0, 1, 2, or 3, or an
external convert start signal. This flexibility allows the start of conversion to be triggered by software
events, a periodic signal (timer overflows), or external HW signals. Conversion completions are indicated
by a status bit and an interrupt (if enabled). The resulting 10-bit data word is latched into the ADC data
SFRs upon completion of a conversion.
Window comp are registers for the ADC dat a can be conf igured to interr upt the co ntroller when ADC data is
either within or outside of a specified range. The ADC can monitor a key voltage continuously in back-
ground mode, but not interrupt the controller unless the converted data is within/outside the specified
range.
Figure 1.15. 10-Bit ADC Block Diagram
10-Bit
SAR
ADC
Timer 1 Overflow
CNVSTR Input
Timer 3 Overflow
(+)
(-)
Configuration, C ontrol, and Data Registers
23-to-1
AMUX
Temp
Sensor
23-to-1
AMUX
VDD
P1.0
P1.7
P2.0
P2.7
GND
P1.0
P1.7
P2.0
P2.7
P3.0
P3.4
P3.0
P3.4
P3.1-3.4
available on
C8051F310/2
P3.1-3.4
available on
C8051F310/2
An a log Mult ip l e xer
Timer 0 Overflow
Timer 2 Overflow
Start
Conversion
000 AD0BUSY (W)
001
010
011
100
101
16
Window Compare
Logic
Window
Compare
Interrupt
ADC Data
Registers
End of
Conversion
Interrupt
P1.6, P1.7 available on
C8051F31 0/1/2/3/4/5
P2.6, P2.7 available on
C8051F31 0/1/2/3/4/5
P1.6, P1.7 available on
C8051F31 0/1/2/3/4/5
P2.6, P2.7 available on
C8051F31 0/1/2/3/4/5
VREF
C8051F310/1/2/3/4/5/6/7
34 Rev. 1.7
1.8. Comparators
C8051F31x devices include two on- chip vo ltage comparators that are en ab led/disabl ed an d con figur ed vi a
user software. Port I/O pins may be configured as comparator inputs via a selection mux. Two comparator
outputs may be routed to a Port pin if desired: a latched output and/or an unlatched (asynchr onous) output.
Comparator response time is programmable, allowing the user to select between high-speed and low-
power modes. Positive and negative hysteresis are also configurable.
Comparator interrupts may be generated on rising, falling, or both edges. When in IDLE mode, these inter-
rupts may be used as a “wake-up” source. Comparator0 may also be configured as a reset source.
Figure 1.16 shows he Comparator0 block diag ra m.
Figure 1.16. Comparator0 Block Diagram
VDD
CPT0CN
Reset
Decision
Tree
+
-
Crossbar
Interrupt
Logic
Q
Q
SET
CLR
D
Q
Q
SET
CLR
D
(SYNCHRONIZER)
GND
CP0 +
P1.0
P1.4
P2.0
P2.4
CP0 -
P1.1
P1.5
P2.1
P2.5
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP1
CP0HYP0
CP0HYN1
CP0HYN0
CPT0MX
CMX0N1
CMX0N0
CMX0P1
CMX0P0
CPT0MD
CP0RIE
CP0FIE
CP0MD1
CP0MD0
CP0
CP0A
CP0
Rising-edge CP0
Falling-edge
CP0
Interrupt
Rev. 1.7 35
C8051F310/1/2/3/4/5/6/7
2. Absolute Maximum Ratings
Table 2.1. Absolute Maximum Ratings*
Parameter Conditions Min Typ Max Units
Ambient temperature under bias –55 — 125 °C
Storage Temperature –65 — 150 °C
Voltage on any Port I/O Pin or RST with
respect to GND –0.3 — 5.8 V
Voltage on VDD with respect to GND –0.3 — 4.2 V
Maximum Total current through VDD and
GND ——500mA
Maximum output current sunk by RST or any
Port pin ——100mA
*Note: S tresses above th ose listed under “Absolute Maximum Ratings” may cause permanent dam age to
the device. This is a str ess rating only a nd functiona l oper ation of the de vices at those or any other condi-
tions above those ind i ca te d in th e op er at ion listing s of this specification is not implied. Exposure to maxi-
mum rating conditions for extended periods may affect device reliability.
C8051F310/1/2/3/4/5/6/7
36 Rev. 1.7
3. Global DC Electrical Characteristics
Table 3.1. Global DC Electrical Characteristics
–40°C to +85°C, 25 MHz System Clock unless otherwise specified.
Parameter Conditions Min Typ Max Units
Digital Supply Voltage VRST13.0 3.6 V
Digital Supply RAM Data Retention
Voltage —1.5— V
Specifie d Op er a ting Tem p er ature
Range –40 — +85 °C
SYSCLK (system clock frequency) 02—25MHz
Ts ysl (SYSCLK low time) 18 — — ns
Tsysh (SYSCLK high time) 18 — — ns
Digital Supply Current—CPU Active (Normal Mode, fetching instructions from Flash)
IDD (Note 3) VDD = 3.0 V, F = 25 MHz — 7.8 8.6 mA
VDD = 3.0 V, F = 1 MHz — 0.38 — mA
VDD = 3.0 V, F = 80 kHz — 31 — µA
VDD = 3.6 V, F = 25 MHz — 10.7 12.1 mA
IDD Supply Sensitivity (Note 3,
Note 4) F = 25 MHz — 67 — %/V
F = 1 MHz — 62 — %/V
IDD Frequency Sensitivity (Note 3,
Note 5) VDD = 3.0 V, F < 15 MHz, T = 25 ºC — 0.39 — mA/MHz
VDD = 3.0 V, F > 15 MHz, T = 25 ºC — 0.21 — mA/MHz
VDD = 3.6 V, F < 15 MHz, T = 25 ºC — 0.55 — mA/MHz
VDD = 3.6 V, F > 15 MHz, T = 25 ºC — 0.27 — mA/MHz
Notes:
1. Given in Table 9.1 on page 110.
2. SYSCLK must be at least 32 kHz to enable debugging.
3. Based on device characterization data, not production tested.
4. Active and Inactive IDD at voltages and frequencies other than those specified can be calculated
using the IDD Supply Sensitivity. For example, if the VDD is 3.3 V instead of 3.0 V at 25 MHz: I DD =
7.8 mA typical at 3.0 V and f = 25 MHz. From this, IDD = 7.8 mA + 0.67 x (3.3 V – 3.0 V) = 8 mA at
3.3 V and f = 25 MHz.
5. IDD can be estimated for frequencies < 15 MHz by multiplying the frequency of interest by the fre-
quency sensitivity number for th at range. When u sing these nu mbers to estimate IDD for > 15 MHz,
the estimate should be the current at 25 MHz minus the difference in current indicated by the fre-
quency sensitivity number. For example:
VDD = 3.0 V; F = 20 MHz, IDD = 7.8 mA – (25 MHz – 20 MHz) x 0.21 mA/MHz = 6.75 mA.
6. Idle IDD can be estimated for frequencies < 1 MHz by multiplying the frequency of interest by the
frequency sensitivity number for that range. When using the se numbers to estimate Idle IDD for > 1
MHz, the estimate should be the current at 25 MHz minus the difference in current indicated by the
frequency sensitivity number. For example:
VDD = 3.0 V; F = 5 MHz, Idle IDD = 4.8 mA – (25 MHz – 5 MHz) x 0.15 mA/MHz = 1.8 mA.
Rev. 1.7 37
C8051F310/1/2/3/4/5/6/7
Digital Supply Current—CPU Inactive (Idle Mode, not fetching instructions from Flash)
IDD (Note 3) VDD = 3.0 V, F = 25 MHz —3.84.3mA
VDD = 3.0 V, F = 1 MHz —0.20— mA
VDD = 3.0 V, F = 80 kHz —16— µA
VDD = 3.6 V, F = 25 MHz —4.85.3mA
IDD Supply Sensitivity (Note 3,
Note 4) F = 25 MHz —44—%/V
F = 1 MHz —56—%/V
IDD Frequency Sensitivity (Note 3,
Note 6) VDD = 3.0 V, F < 1 MHz, T = 25 °C— 0.21 — mA/MHz
VDD = 3.0 V, F > 1 MHz, T = 25 °C— 0.15 — mA/MHz
VDD = 3.6 V, F < 1 MHz, T = 25 °C— 0.28 — mA/MHz
VDD = 3.6 V, F > 1 MHz, T = 25 °C— 0.19 — mA/MHz
Digital Supply Current
(Stop Mode, shutdown) Oscillator not running,
VDD Monitor Disabled —< 0.1— µA
Table 3.1. Global DC Electrical Characteristics (Continued)
–40°C to +85°C, 25 MHz System Clock unless otherwise specified.
Parameter Conditions Min Typ Max Units
Notes:
1. Given in Table 9.1 on page 110.
2. SYSCLK must be at least 32 kHz to enable debugging.
3. Based on device characterization data, not production tested.
4. Active and Inactive IDD at voltages and frequencies other than those specified can be calculated
using the IDD Supply Sensitivity. For example, if the VDD is 3.3 V instead of 3.0 V at 25 MHz: I DD =
7.8 mA typical at 3.0 V and f = 25 MHz. From this, IDD = 7.8 mA + 0.67 x (3.3 V – 3.0 V) = 8 mA at
3.3 V and f = 25 MHz.
5. IDD can be estimated for frequencies < 15 MHz by multiplying the frequency of interest by the fre-
quency sensitivity number for th at range. When u sing these nu mbers to estimate IDD for > 15 MHz,
the estimate should be the current at 25 MHz minus the difference in current indicated by the fre-
quency sensitivity number. For example:
VDD = 3.0 V; F = 20 MHz, IDD = 7.8 mA – (25 MHz – 20 MHz) x 0.21 mA/MHz = 6.75 mA.
6. Idle IDD can be estimated for frequencies < 1 MHz by multiplying the frequency of interest by the
frequency sensitivity number for that range. When using the se numbers to estimate Idle IDD for > 1
MHz, the estimate should be the current at 25 MHz minus the difference in current indicated by the
frequency sensitivity number. For example:
VDD = 3.0 V; F = 5 MHz, Idle IDD = 4.8 mA – (25 MHz – 5 MHz) x 0.15 mA/MHz = 1.8 mA.
C8051F310/1/2/3/4/5/6/7
38 Rev. 1.7
Other electric al characteristics tables ar e found in the data sheet section corresponding to the associated
peripherals. For more information on electrical characteristics for a specific peripheral, refer to the page
indicated in Table 3.2.
Table 3.2. Electrical Characteristics Quick Reference
Peripheral Electrical Characteristics Page No.
ADC0 Electric al Ch ar ac te rist ics 65
External Voltage Reference Circuit Electrical Characteristics 68
Comparator Electrical Characteristics 78
Reset Electrical Characteristics 110
Flash Electrical Ch ar ac te rist ics 112
Internal Oscillator Electrical Characteristics 123
Port I/O DC Electrical Characteristics 143
Rev. 1.7 39
C8051F310/1/2/3/4/5/6/7
4. Pinout and Package Definitions
Table 4.1. Pin Definitions for the C8051F31x
Name Pin Numbers Type Description
‘F310/2/4 ‘F311/3/5 ‘F316/7
VDD 4 4 4 Power Supply Voltage.
GND 3 3 3 Ground.
RST/
C2CK
5 5 5
D I/O
D I/O
Device Reset. Open-drain outpu t of internal POR. An
external source can initiate a system reset by driving
this pin low for at least 10 µs.
Clock signal for the C2 Debug Interface.
P3.0/
C2D 6 6 6 D I/O
D I/O
Port 3.0. See Section 13 for a complete description.
Bi-directional data signal for the C2 Debug Interface.
P0.0/
VREF 2 2 2 D I/O
A In
Port 0.0. See Section 13 for a complete description.
External VREF input. (‘F310/1/2/3 only)
P0.1 1 1 1 D I/O Port 0.1. See Section 13 for a complete description.
P0.2/
XTAL1
32 28 24
D I/O
A In
Port 0.2. See Section 13 for a complete description.
External Clock Inpu t. This pin is the external oscillator
return for a crystal or resonator.
P0.3/
XTAL2
31 27 23
D I/O
A Out or
D In
Port 0.3. See Section 13 for a complete description.
External Clock Output. For an external cryst al or reso-
nator, this pin is the excitation driver. This pin is the
external clock input for CMOS, capacitor, or RC oscil-
lator configurations.
P0.4 30 26 22 D I/O Port 0.4. See Section 13 for a complete description.
P0.5 29 25 21 D I/O Port 0.5. See Section 13 for a complete description.
P0.6/
CNVSTR 28 24 20 Port 0.6. See Section 13 for a complete description.
ADC0 External Convert Start Input. (‘F310/1/2/3 only)
P0.7 27 23 19 D I/O Port 0.7. See Section 13 for a complete description.
P1.0 26 22 18 D I/O or
A In Port 1.0. See Section 13 for a complete description.
P1.1 25 21 17 D I/O or
A In Port 1.1. See Section 13 for a complete description.
P1.2 24 20 16 D I/O or
A In Port 1.2. See Section 13 for a complete description.
P1.3 23 19 15 D I/O or
A In Port 1.3. See Section 13 for a complete description.
P1.4 22 18 14 D I/O or
A In Port 1.4. See Section 13 for a complete description.
C8051F310/1/2/3/4/5/6/7
40 Rev. 1.7
P1.5 21 17 13 D I/O or
A In Port 1.5. See Section 13 for a complete description.
P1.6 20 16 D I/O or
A In Port 1.6. See Section 13 for a complete description.
P1.7 19 15 D I/O or
A In Port 1.7. See Section 13 for a complete description.
P2.0 18 14 12 D I/O or
A In Port 2.0. See Section 13 for a complete description.
P2.1 17 13 11 D I/O or
A In Port 2.1. See Section 13 for a complete description.
P2.2 16 12 10 D I/O or
A In Port 2.2. See Section 13 for a complete description.
P2.3 15 11 9D I/O or
A In Port 2.3. See Section 13 for a complete description.
P2.4 14 10 8D I/O or
A In Port 2.4. See Section 13 for a complete description.
P2.5 13 9 7 D I/O or
A In Port 2.5. See Section 13 for a complete description.
P2.6 12 8D I/O or
A In Port 2.6. See Section 13 for a complete description.
P2.7 11 7D I/O or
A In Port 2.7. See Section 13 for a complete description.
P3.1 7D I/O or
A In Port 3.1. See Section 13 for a complete description.
P3.2 8D I/O or
A In Port 3.2. See Section 13 for a complete description.
P3.3 9D I/O or
A In Port 3.3. See Section 13 for a complete description.
P3.4 10 D I/O or
A In Port 3.4. See Section 13 for a complete description.
Table 4.1. Pin Definitions for the C8051F31x (Continued)
Name Pin Numbers Type Description
‘F310/2/4 ‘F311/3/5 ‘F316/7
Rev. 1.7 41
C8051F310/1/2/3/4/5/6/7
Figure 4.1. LQFP-32 Pinout Diagram (Top View)
1
P3.2
P1.2
P1.7
P1.4
P1.3
P1.5VDD
/RST/C2CK
GND
P0.1
P0.0
P2.0
P2.1
2
3
4
5
6
7
8
24
23
22
21
20
19
18
17
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
P1.6
C8051F310/2/4
Top View
P3.0/C2D
P3.1
P3.3
P3.4
P2.7
P2.6
P2.5
P2.4
P2.3
P2.2 P1.1
P1.0
P0.7
P0.6
P0.5
P0.4
P0.3
P0.2
C8051F310/1/2/3/4/5/6/7
42 Rev. 1.7
Figure 4.2. LQFP-32 Package Diagram
Ta ble 4.2. LQFP-32
Package Dimensions
MM
MIN TYP MAX
A--1.60
A1 0.05 - 0.15
A2 1.35 1.40 1.45
b 0.30 0.37 0.45
D-9.00-
D1 - 7.00 -
e-0.80-
E-9.00-
E1 - 7.00 -
L 0.45 0.60 0.75
PIN 1
IDENTIFIER
A1
eb
1
32
E1
D1
D
E
A2 A
L
Rev. 1.7 43
C8051F310/1/2/3/4/5/6/7
Figure 4.3. QFN-28 Pinout Diagram (Top View)
4
5
6
7
2
1
3
11
12
13
14
9
8
10
18
17
16
15
20
21
19
25
26
27
28
23
22
24
C8051F311/3/5
Top View
P0.1
P0.0
GND
VDD
/RST/C2CK
P3.0/C2D
P2.7
P2.6
P2.5
P2.4
P2.3
P2.2
P2.1
P2.0
P1.7
P1.6
P1.5
P1.4
P1.3
P1.2
P1.1
P1.0
P0.7
P0.6
P0.5
P0.4
P0.3
P0.2
GND
GND
C8051F310/1/2/3/4/5/6/7
44 Rev. 1.7
Figure 4.4. QFN-28 Package Drawing
Table 4.3. QFN-28
Package Dimensions
MM
MIN TYP MAX
A 0.80 0.90 1.00
A1 0 0.02 0.05
A2 0 0.65 1.00
A3 - 0.25 -
b 0.18 0.23 0.30
D-5.00-
D2 2.90 3.15 3.35
E-5.00-
E2 2.90 3.15 3.35
e-0.5-
L 0.45 0.55 0.65
N-28-
ND - 7 -
NE - 7 -
R0.09- -
AA - 0.435 -
BB - 0.435 -
CC - 0.18 -
DD - 0.18 -
1
E
D
A2
A
A1
e
A3
E2
R
e
L
Bottom View
Side View
2
3
4
5
6
7
8
9
10
12
13
14
21
20
19
17
16
15
28
27
26
24
23
22
E2
25
2
D2
11
18
D2
2
6 x e
6 x e
DETAIL 1
DETAIL 1 AA
BB
CC
DD
b
Rev. 1.7 45
C8051F310/1/2/3/4/5/6/7
Figure 4.5. Typical QFN-28 Landing Diagram
Optional
GND
Connection
b
L
0.50 mm
0.30 mm
0.10 mm
0.20 mm
0.85 mm
0.35 mm
e
E
D
0.50 mm
0.30 mm
0.10 mm
0.20 mm
0.85 mm
0.35 mm
Top View
E2
D2
0.20 mm
0.20 mm
0.50 mm
0.50 mm
C8051F310/1/2/3/4/5/6/7
46 Rev. 1.7
Figure 4.6. QFN-28 Solder Paste Recommendation
b
L
0.50 mm
0.30 mm
0.10 mm
0.20 mm
0.85 mm
0.35 mm
e
E
D
0.50 mm
0.30 mm
0.10 mm
0.20 mm
0.85 mm
0.35 mm
Top View
E2
D2
0.20 mm
0.20 mm
0.50 mm
0.50 mm
0.30 mm
0.20 mm
0.60 mm
0.40 mm
0.70 mm
0.60 mm
Rev. 1.7 47
C8051F310/1/2/3/4/5/6/7
Figure 4.7. QFN-24 Pinout Diagram (Top View)
GND P1.5
P1.4
P1.3
P1.2
P1.1
P1.0
15
14
13
17
18
16
P2.5
P2.4
P2.3
P2.2
P2.1
P2.0
10
11
12
8
7
9
P0.1
P0.0
GND
VDD
/R ST / C2 CK
P 3 .0 / C2 D
4
5
6
2
1
3
P0.7
P0.6
P0.5
P0.4
P0.3
P0.2
22
23
24
20
19
21
C8051F316/7
Top View
C8051F310/1/2/3/4/5/6/7
48 Rev. 1.7
Figure 4.8. QFN-24 Package Drawing
Table 4.4. QFN-24
Package Dimensions
MM
MIN TYP MAX
A 0.70 0.75 0.80
A1 0.00 0.02 0.05
A2 — 0.50 —
A3 — 0.25 —
b 0.18 0.25 0.30
D — 4.00 —
D2 2.50 2.60 2.70
E — 4.00 —
E2 2.50 2.60 2.70
e — 0.50 —
L 0.35 0.40 0.45
N—24—
ND — 6 —
NE — 6 —
R0.09— —
5 x e
5 x e
Bottom View
e
E
D
6
5
4
3
2
1
24
23
22
21
20
19
13
14
15
16
17
18
12
11
10
9
8
7
D2
E2
L
D2 / 2
E 2 / 2
R
Pin #1 ID
A2
A
A1
e
A3
Side View
b
D / 2
E / 2
Rev. 1.7 49
C8051F310/1/2/3/4/5/6/7
Figure 4.9. Typical QFN-24 Landing Diagram
Top View
E2
D2
b e
0.35 mm
0.30 mm
0.10 mm
0.20 mm
0.45 mm
0.75 mm
0.35 mm
0.10 mm
0.45 mm
E
D
Optional
GND
Connection
0.75 mm
Pin #1
C8051F310/1/2/3/4/5/6/7
50 Rev. 1.7
Figure 4.10. QFN-24 Solder Paste Recommendation
Top View
E2
D2
b e
0.35 mm
0.30 mm
0.10 mm
0.20 mm
0.45 mm
0.75 mm
0.35 mm
0.10 mm
0.45 mm
E
D
0.75 mm
0.80 mm
0.60 m m
0.35 mm 0.35 mm
0.45 mm
0.30 mm
0.20 mm
Pin #1
Rev. 1.7 51
C8051F310/1/2/3/4/5/6/7
5. 10-Bit ADC (ADC0, C8051F310/1/2/3/6 only)
The ADC0 subsystem for the C8051F310/1/2/3/6 consists of two analog multiplexers (referred to collec-
tively as AMUX0) with 25 total input selections, and a 200 ksps, 10-bit successive-approximation-register
ADC with integrated track-and-hold and programmable window detector. The AMUX0, data conversion
modes, and win dow detector ar e a ll con figur able un de r software control via the Special Function Registers
shown in Figure 5.1. ADC0 oper ates in both Single -ended and Differentia l modes, and may be configured
to measure P1.0–P3.4, the Temperature Sensor output, or VDD with respect to P1.0–P3.4, VREF, or GND.
The ADC0 subsystem is enabled only when the AD0EN bit in the ADC 0 Control register (ADC0CN) is set
to logic 1. The ADC0 subsystem is in low power shutdown when this bit is logic 0.
ADC0CF
AD0LJST
AD0SC0
AD0SC1
AD0SC2
AD0SC3
AD0SC4
10-Bit
SAR
ADC
REF
SYSCLK
ADC0H
32
ADC0CN
AD0CM0
AD0CM1
AD0CM2
AD0WINT
AD0BUSY
AD0INT
AD0TM
AD0EN
Timer 0 Overflow
Timer 2 Overflow
Timer 1 Overflow
Start
Conversion
000 AD0BUSY (W )
VDD
ADC0LTH
23-to-1
AMUX
AD0WINT
Temp
Sensor
23-to-1
AMUX
VDD
P1.0
P1.7
001
010
011
100 CNVSTR Input
Window
Compare
Logic
P2.0
P2.7
GND
P1.0
P1.7
P2.0
P2.7
P3.0
P3.4
101 Timer 3 Overflow
ADC0LTL
ADC0GTH ADC0GTL
ADC0L
AMX0P
AMX0P4
AMX0P3
AMX0P2
AMX0P1
AMX0P0
AMX0N
AMX0N4
AMX0N3
AMX0N2
AMX0N1
AMX0N0
P3.0
P3.4
P3.1-3.4
available on
C8051F31 0/2
P3.1-3 .4
available on
C8051F31 0/2
(+)
(-)
VREF
P2.6-2.7 available on
C8051F310/1/2/3/4/5
P1.6-1.7 available on
C8051F31 0/1/2/3/4/5
P2.6-2.7 available on
C8051F31 0/1/2/3/4/5
P1.6-1.7 availa ble on
C8051F310/1/2/3/4/5
Figure 5.1. ADC0 Functional Block Diagram
5.1. Analog Multiplexer
AMUX0 selects the positive and negative inputs to the ADC. Any of the following may be selected as the
positive input: P1.0-P3.4, the on-chip temperature sensor, or the positive power supply (VDD). Any of the
following may be selected as the negative input: P1.0-P3.4, VREF, or GND. When GND is selected as
the negative input, ADC0 operates in Single-ended Mode; all other times, ADC0 operates in Differ-
ential Mode. The ADC0 input channels are selected in the AMX0P and AMX0N registers as described in
SFR Definition 5.1 and SFR Definition 5.2.
The conversion code format differs between Single-ended and Differential modes. The registers ADC0H
and ADC0L contain the high and low bytes of the output conversion code fro m the ADC at th e comple tion
of each conversion. Data can be righ t-justifie d or left-justified, depending on the setting of the AD0LJST bit
(ADC0CN.0). When in Single-ende d Mode, conversion codes ar e repre sented as 10-bit u nsigned integ ers.
C8051F310/1/2/3/4/5/6/7
52 Rev. 1.7
Inputs ar e measured from ‘0’ to VREF * 1023/10 24. Example codes are shown below for both right-j ustified
and left-justified data. Unused bits in the ADC0H and ADC0L registers are set to ‘0’.
When in Differential Mode, conversion codes are represented as 10-bit signed 2’s complement numbers.
Inputs are measured from -VREF to VREF * 511/512. Example codes are shown below for both right-justi-
fied and left -justified data. For right-justified data, the unused MSBs of ADC0H are a sign-extension of the
data word. For left-justified data, the unused LSBs in the ADC0L register are set to ‘0’.
Important Note About ADC0 Input Configuration: Port pins selected as ADC0 inputs should be config-
ured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog
input, set to ‘0’ the corresponding bit in register PnMDIN (for n = 0,1,2,3). To force the Crossbar to skip a
Port pin, set to ‘1’ the corresponding bit in register PnSKIP (for n = 0,1,2). See Section “13. Port Input/
Output” on page 129 for more Port I/O configuration de tails.
5.2. Temperature Sensor
The typical t emperat ure se nsor tr ansfer functio n is show n in Figure 5.2. The output voltage (VTEMP) is the
positive ADC input when the temperature sensor is selected by bits AMX0P4-0 in register AMX0P.
0-50 50 100
(Celsius)
V
TEMP
= 3.35*(TEMP
C
) + 897 mV
700
800
900
1000
1100
(mV)
1200
Figure 5.2. Typical Temperature Sensor Transfer Function
Input Voltage Right-Justified ADC0H:ADC0L
(AD0LJST = 0) Left-Justified ADC0H:ADC0L
(AD0LJST = 1)
VREF x 1023/1024 0x03FF 0xFFC0
VREF x 512/1024 0x0200 0x8000
VREF x 256/1024 0x0100 0x4000
0 0x0000 0x0000
Input Voltage Right-Justified ADC0H:ADC0L
(AD0LJST = 0) Left-Justified ADC0H:ADC0L
(AD0LJST = 1)
VREF x 511/512 0x01FF 0x7FC0
VREF x 256/512 0x0100 0x4000
0 0x0000 0x0000
–VREF x 256/512 0xFF00 0xC000
–VREF 0xFE00 0x8000
Rev. 1.7 53
C8051F310/1/2/3/4/5/6/7
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature mea-
surements (see Table 5.1 for linearity specifications). For absolute temperature measurements, gain and/
or offset calibration is recommended. Typically a 1-point calibration includes the following steps:
Step 1. Control/measure the ambient temperature (this temperature must be known).
Step 2. Power the device, and delay for a few seconds to allow for self-heating.
Step 3. Perform an ADC conversion with the temperature sensor selected as the positive input
and GND selected as the negative input.
Step 4. Calculate the offset and/or gain characteristics, and store these values in non-volatile
memory for use with subsequent temperature sensor measurements.
Figure 5.3 shows the typical temperature sensor error assuming a 1-point calibration at 25 °C. Note that
parameters which affect ADC measurement, in particular the voltage reference value, will also
affect temperature measurement.
-40.00 -20.00 0.00 20.00 40.00 60.00 80.00
Temperatur e (degrees C)
Error (degrees C)
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
Figure 5.3. Temperature Sensor Error with 1-Point Calibration
C8051F310/1/2/3/4/5/6/7
54 Rev. 1.7
5.3. Modes of Operation
ADC0 has a maximum conversion speed of 200 ksps. The ADC0 conversion clock is a divided version of
the system clock, determined by the AD0SC bits in the ADC0CF register (system clock divided by
(AD0SC + 1) for 0 AD0SC 31).
5.3.1. Starting a Conversion
A conversion ca n be in itiated in one of five w ays, de pending on the programmed states of the ADC0 Start
of Conversion Mode bits (AD0CM2-0) in register ADC0CN. Conversions may be initiated by one o f the fol-
lowing:
1. Writing a ‘1’ to the AD0BUSY bit of register ADC0CN
2. A Timer 0 overflow (i.e., timed continuous conversions)
3. A Timer 2 overflow
4. A Timer 1 overflow
5. A rising edge on the CNVSTR input signal (pin P0.6)
6. A Timer 3 overflow
Writing a ‘1’ to AD0BUSY provides software control of ADC0 whereby conversions are performed "on-
demand". During conversion, the AD0BUSY bit is set to logic 1 and reset to logic 0 when the conversion is
complete. The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the ADC0 interrupt
flag (AD0INT). Note: When polling for ADC conversion completions, the ADC0 interrupt flag (AD0INT)
should be used. Converted dat a is availa ble in the ADC0 data registers, ADC0H:ADC0L, when bi t AD0INT
is logic 1. Note that when Timer 2 or Timer 3 overflows are used as the conversion source, Low Byte over-
flows are used if Timer 2/3 is in 8-bit mode ; High byte overflows a re used if T imer 2/3 is in 16-bit mode . See
Section “17. Timers” on page 187 for timer configuration.
Import ant Note Ab out Using CNVSTR: The CNVSTR input pin also functions as Port pin P0.6. When the
CNVSTR input is used as the ADC0 conversion source, Port pin P0.6 should be skipped by the Digital
Crossbar. To configure the Crossbar to skip P0.6, set to ‘1’ Bit6 in register P0SKIP. See Section “13. Port
Input/Output” on page 129 for details on Port I/O configuration.
Rev. 1.7 55
C8051F310/1/2/3/4/5/6/7
5.3.2. Tracking Modes
According to Table 5.1, each ADC0 conversion must be preceded by a minimum tracking time for the con-
verted result to be accurate. The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode.
In its default state, the ADC0 input is continuously tracked, except when a conversion is in progress. When
the AD0TM bit is logic 1, ADC0 operates in low- power track-and-h old mode. In this mod e, each conversion
is preceded by a tracking period of 3 SAR clocks (after the start-of-conversion signal). When the CNVSTR
signal is used to initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR is low;
conversion begins on the rising edge of CNVSTR (see Figure 5.4). Tracking can also be disabled (shut-
down) when the device is in low power standby or sleep modes. Low-power track-and-hold mode is also
useful when AMUX settings are frequently changed, due to the settling time requirements described in
Section “5.3.3. Settling Time Requirements” on page 56.
Write '1' to AD0BUSY,
Timer 0, T imer 2,
Timer 1, Timer 3 Overflow
(AD0CM[2:0]=000, 001,010
011, 101)
AD0TM=1 Track Convert Low Power Mode
AD0TM=0 Track or
Convert Convert Track
Low P ower
or Convert
SAR Clocks
123456789101112
123456789
SAR Clocks
B. ADC0 Timing for Internal Trigger Source
123456789
CNVSTR
(AD0CM[2:0]=100)
AD0TM=1
A. ADC0 Timing for External Trigger Source
SAR Clocks
Track or Convert Convert TrackAD0TM=0
Track Convert Low Power
Mode
Low Power
or Convert
10 11
13 14
10 11
Figure 5.4. 10-Bit ADC Track and Conversion Example Timing
C8051F310/1/2/3/4/5/6/7
56 Rev. 1.7
5.3.3. Settling Time Requirements
When the ADC0 input configuration is changed (i.e., a different AMUX0 selection is made), a minimum
tracking time is required before an accurate conversion can be performed. This tracking time is determined
by the AMUX0 resistance, the ADC0 sampling capacitance, any external source resistance, and the accu-
racy required for the conversion. In low-power tracking mode, th ree SAR clocks are used for tra cking at the
start of every conversion. For most applications, these three SAR clocks will meet the minimum tracking
time requireme nts.
Figure 5.5 shows the equiv alent ADC0 input c ircuits for both Differential and Single-ended modes. Notice
that the equivalent time constant for both input circuits is the same. The required ADC0 settling time for a
given settling accuracy (SA) may be approximated by Equation 5.1. When measuring the Temperature
Sensor output or VDD with respect to GND, RTOTAL reduces to RMUX. See Table 5.1 for ADC0 minimum
settling time requirements.
Equation 5.1. ADC0 Settling Time Requirements
t2n
SA
-------
RTOTALCSAMPLE
ln=
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
RTOTAL is the sum of the AMUX0 resistance and any external source resistance.
n is the ADC resolution in bits (10).
R
MUX
= 5k
RC
Input
= R
MUX
* C
SAMPLE
R
MUX
= 5k
C
SAMPLE
= 5pF
C
SAMPLE
= 5pF
MUX Select
MUX Select
Differential Mode
Px.x
Px.x
R
MUX
= 5k
C
SAMPLE
= 5pF
RC
Input
= R
MUX
* C
SAMPLE
MUX Select
Single-Ended Mode
Px.x
Figure 5.5. ADC0 Equivalent Input Circuits
Rev. 1.7 57
C8051F310/1/2/3/4/5/6/7
SFR Definition 5.1. AMX0P: AMUX0 Positive Channel Select
Bits7–5: UNUSED. Read = 000b; Write = don’t care.
Bits4–0: AMX0P4–0: AMUX0 Positive Input Selection
R R R R/W R/W R/W R/W R/W Reset Value
- - - AMX0P4 AMX0P3 AMX0P2 AMX0P1 AMX0P0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xBB
AMX0P4–0 ADC0 Positive Input
00000 P1.0
00001 P1.1
00010 P1.2
00011 P1.3
00100 P1.4
00101 P1.5
00110 P1.6(1)
00111 P1.7(1)
01000 P2.0
01001 P2.1
01010 P2.2
01011 P2.3
01100 P2.4
01101 P2.5
01110 P2.6(1)
01111 P2.7(1)
10000 P3.0
10001(2) P3.1(2)
10010(2) P3.2(2)
10011(2) P3.3(2)
10100(2) P3.4(2)
10101–11101 RESERVED
11110 Temp Sensor
11111 VDD
Notes:
1. Only applies to C8051F310/1/2/3/4/5; selection
RESERVED on C8051F316/7 devices.
2. Only applies to C8051F310/2; selection RESERVED on
C8051F311/3/6/7 devices.
C8051F310/1/2/3/4/5/6/7
58 Rev. 1.7
SFR Definition 5.2. AMX0N: AMUX0 Negative Channel Select
Bits7–5: UNUSED. Read = 000b; Write = don’t care.
Bits4–0: AMX0N4–0: AMUX0 Negative Input Selection.
Note that when GND is selected as the Negative Input, ADC0 operates in Single-ended
mode. For all other Negative Input selections, ADC0 operates in Differential mode.
R R R R/W R/W R/W R/W R/W Reset Value
- - - AMX0N4 AMX0N3 AMX0N2 AMX0N1 AMX0N0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xBA
AMX0N4–0 ADC0 Negative Input
00000 P1.0
00001 P1.1
00010 P1.2
00011 P1.3
00100 P1.4
00101 P1.5
00110 P1.6(1)
00111 P1.7(1)
01000 P2.0
01001 P2.1
01010 P2.2
01011 P2.3
01100 P2.4
01101 P2.5
01110 P2.6(1)
01111 P2.7(1)
10000 P3.0
10001(2) P3.1(2)
10010(2) P3.2(2)
10011(2) P3.3(2)
10100(2) P3.4(2)
10101–11101 RESERVED
11110 VREF
11111 GND (ADC in Single-Ended Mode)
Notes:
1. Only applies to C8051F310/1/2/3/4/5; selection
RESERVED on C8051F316/7 devices.
2. Only applies to C8051F310/2; selection RESERVED on
C8051F311/3/6/7 devices.
Rev. 1.7 59
C8051F310/1/2/3/4/5/6/7
SFR Definition 5.3. ADC0CF: ADC0 Configuration
Bits7–3: AD0SC4–0: ADC0 SAR Conversion Clock Period Bits.
SAR Conversion clock is derived from system clock by the following equation, where
AD0SC refers to the 5-bit value held in bits AD0SC4–0. SAR Conversion clock require-
ments are given in Table 5.1.
Bit2: AD0LJST: ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
Bits1–0: UNUSED. Read = 00b; Write = don’t care.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD0SC4 AD0SC3 AD0SC2 AD0SC1 AD0SC0 AD0LJST - - 11111000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xBC
AD0SC SYSCLK
CLKSAR
----------------------1–=
SFR Definition 5.4. ADC0H: ADC0 Data Word MSB
Bits7–0: ADC0 Data Word High-Order Bits.
For AD0LJST = 0: Bit s 7–2 are th e sign extension of Bit1. Bits 1–0 are the upper 2 bit s of the
10-bit ADC0 Data Word.
For AD0LJST = 1: Bits 7–0 are the most-significant bits of the 10-bit ADC0 Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W R eset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xBE
SFR Definition 5.5. ADC0L: ADC0 Data Word LSB
Bits7–0: ADC0 Data Word Low-Order Bits.
For AD0LJST = 0: Bits 7–0 are the lower 8 bits of the 10-bit Data Word.
For AD0LJST = 1: Bits 7–6 are the lower 2 bits of the 10-bit Dat a W ord. Bit s 5–0 will always
read ‘0’.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xBD
C8051F310/1/2/3/4/5/6/7
60 Rev. 1.7
SFR Definition 5.6. ADC0CN: ADC0 Control
Bit7: AD0EN: ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data con versions.
Bit6: AD0TM: ADC0 Track Mode Bit.
0: Normal Track Mode: When ADC0 is enabled, tracking is continuo us unles s a conve rs ion is
in progress.
1: Low-power Track Mode: Tracking Defined by AD0C M2-0 bits (see below).
Bit5: AD0INT: ADC0 Conversion Complete Interrupt Flag.
0: ADC0 has not completed a data conversion since the last time AD0INT was cleared.
1: ADC0 has completed a data conversion.
Bit4: AD0BUSY: ADC0 Busy Bit.
Read:
0: ADC0 conversion is co mplete or a c onversion is not curre ntly in progress. AD0INT is set to
logic 1 on the falling edge of AD0BUSY.
1: ADC0 conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC0 Conversion if AD0CM2-0 = 000b
Bit3: AD0WINT: ADC0 Window Compare Interrupt Flag.
0: ADC0 Window Comparison Data match has not occurred since this flag was last cleared.
1: ADC0 Window Comparison Data match has occurred.
Bits2–0: AD0CM2–0: ADC0 Start of Conversion Mode Select.
When AD0TM = 0:
000: ADC0 conversion initiated on ev ery write of ‘1’ to AD0BUSY.
001: ADC0 conversion initiated on overflow of Timer 0.
010: ADC0 conversion initiated on overflow of Timer 2.
011: ADC0 conversion initiated on overflow of Timer 1.
100: ADC0 conversion initiated on rising edge of external CNVSTR.
101: ADC0 conversion initiated on overflow of Timer 3.
11x: Reserved.
When AD0TM = 1:
000: Tracking initiated on write of ‘1’ to AD0BUSY and lasts 3 SAR clocks, followed by con-
version.
001: Tracking initiated on overflow of Timer 0 and lasts 3 SAR clocks, followed by conversion.
010: Tracking initiated on overflow of Timer 2 and lasts 3 SAR clocks, followed by conversion.
011: Tracking initiated on overflow of Timer 1 and lasts 3 SAR clocks, followed by conversion.
100: ADC0 tracks only when CNVSTR input is lo gic low; con version st art s on rising CNVSTR
edge.
101: Tracking initiated on overflow of Timer 3 and lasts 3 SAR clocks, followed by conversion.
11x: Reserved.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD0EN AD0TM AD0INT AD0BUSY AD0WINT AD0CM2 AD0CM1 AD0CM0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xE8
Rev. 1.7 61
C8051F310/1/2/3/4/5/6/7
5.4. Programmable Window Detector
The ADC Programmable Window Detector continuously compares the ADC0 output registers to user-pro-
grammed limit s, and notifies the system whe n a desired condition is detected. This is especially ef fective i n
an interrupt-driven system, saving code space and CPU bandwidth while delivering faster system
response times. The window detector interrupt flag (AD0WINT in register ADC0CN) can also be used in
polled mode. The ADC0 Greater-Than (ADC0GTH, ADC0GTL) and Less-Than (ADC0LTH, ADC0LTL)
registers hold the comp arison values. The window detector flag can be programmed to in dicate when mea-
sured data is inside or outside of the user-programmed limits, depending on the contents of the ADC0
Less-Than and ADC0 Greater-Than registers.
SFR Definition 5.7. ADC0GTH: ADC0 Greater-Than Data High Byte
Bits7–0: High byte of ADC0 Greater-Than Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xC4
SFR Definition 5.8. ADC0GTL: ADC0 Greater-Than Data Low Byte
Bits7–0: Low byte of ADC0 Greater-Than Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xC3
C8051F310/1/2/3/4/5/6/7
62 Rev. 1.7
SFR Definition 5.9. ADC0LTH: ADC0 Less-Than Data High Byte
Bits7–0: High byte of ADC0 Less-Than Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xC6
SFR Definition 5.10. ADC0LTL: ADC0 Less-Than Data Low Byte
Bits7–0: Low byte of ADC0 Less-Than Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xC5
0xFFC0
0x2040
0x2000
0x1FC0
0x1040
0x1000
0x0FC0
0x0000
0
Input Voltage
(Px.x - G N D)
VREF x (1023/1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
0xFFC0
0x2040
0x2000
0x1FC0
0x1040
0x1000
0x0FC0
0x0000
0
Input Voltage
(Px.x - GN D)
VREF x (1023/1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT
not affected
AD0WINT=1
AD0WINT=1
ADC0H:ADC0L ADC0H:ADC0L
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
Rev. 1.7 63
C8051F310/1/2/3/4/5/6/7
5.4.1. Window Detector In Single-Ended Mode
Figure 5.6 shows two example window comparisons for right-justified, single-ended data, with
ADC0LTH:ADC0LTL = 0x0080 (128d) and ADC0GTH:ADC0GTL = 0x0040 (64d). In single-ended mode,
the input voltage can range from ‘0’ to VREF x (1023/1024) with respect to GND, and is represented by a
10-bit unsigned integer value. In the left example, an AD0WINT interrupt will be generated if the ADC0
conversion word (ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL and
ADC0LTH:ADC0LTL (if 0x0040 < ADC0H:ADC0L < 0x0080). In the right example, and AD0WINT interrupt
will be generated if the ADC0 conversion word is outside of the range defined by the ADC0GT and
ADC0LT registers (if ADC0H:ADC0L < 0x0040 or ADC0H:ADC0L > 0x0080). Figure 5.7 shows an exam-
ple using left-justified data with the same comparison values.
0x03FF
0x0081
0x0080
0x007F
0x0041
0x0040
0x003F
0x0000
0
Input Voltage
(Px.x - GND)
VREF x (1023/1024)
VREF x (128/ 1024)
VREF x (64/1024)
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
0x03FF
0x0081
0x0080
0x007F
0x0041
0x0040
0x003F
0x0000
0
Input Voltage
(Px.x - GND)
VREF x (1023/1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT
not affe cted
AD0WINT=1
AD0WINT=1
ADC0H:ADC0L ADC0H:ADC0L
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
Figure 5.6. ADC Window Compare Example: Right-Justified Single-Ended Data
Figure 5.7. ADC Window Compare Example: Left-Justified Single-Ended Data
C8051F310/1/2/3/4/5/6/7
64 Rev. 1.7
5.4.2. Window Detector In Differential Mode
Figure 5.8 shows two example window comparisons for right-justified, differential data, with
ADC0LTH:ADC0LTL = 0x0040 (+64d) and ADC0GTH:ADC0GTH = 0xFFFF (-1d). In differential mode, the
measurable volt age between the input pins is between - VREF and VREF*(511/512). Output codes are rep-
resented as 10-bit 2’s complement signed integers . In the left example, an AD0WINT interrupt will be gen-
erated if the ADC0 conversion word (ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL
and ADC0LTH:ADC0LTL (if 0xFFFF (-1d) < ADC0H:ADC0L < 0x0040 (64d)). In the right example, an
AD0WINT interrupt will be generated if the ADC0 conversion word is outside of the range defined by the
ADC0GT and ADC0LT registers (if ADC0H:ADC0L < 0xFFFF (-1d) or ADC0H:ADC0L > 0x0040 (+64d)).
Figure 5.9 shows an example using lef t-justified data with the same comparison values.
Figure 5.8. ADC Window Compare Example: Right-Justified Differential Data
Figure 5.9. ADC Window Compare Example: Left-Justified Differential Data
0x01FF
0x0041
0x0040
0x003F
0x0000
0xFFFF
0xFFFE
0x0200
-VREF
Input Voltage
(Px.x - Px.x)
VREF x (511/512)
VREF x (64/512)
VREF x (-1/512)
0x01FF
0x0041
0x0040
0x003F
0x0000
0xFFFF
0xFFFE
0x0200
-VREF
Input Voltage
(Px.x - Px.x)
VREF x (511/512 )
VREF x (64/512)
VREF x (-1/512)
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
AD0WINT
not affected
AD0WINT=1
AD0WINT=1
ADC0H:ADC0LADC0H:ADC0L
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0x7FC0
0x1040
0x1000
0x0FC0
0x0000
0xFFC0
0xFF80
0x8000
-VREF
Input Voltage
(Px.x - Px.y)
VREF x (511/512)
VREF x (64/512)
VREF x (-1/512)
0x7FC0
0x1040
0x1000
0x0FC0
0x0000
0xFFC0
0xFF80
0x8000
-VREF
Input Voltage
(Px.x - Px.x)
VREF x (511/512 )
VREF x (64/512)
VREF x (-1/512)
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
AD0WINT
not affected
ADC0GTH:ADC0GTL
AD0WINT=1
AD0WINT=1
ADC0H:ADC0LADC0H:ADC0L
ADC0LTH:ADC0LTL
Rev. 1.7 65
C8051F310/1/2/3/4/5/6/7
Table 5.1. ADC0 Electrical Characteristics
VDD = 3.0 V, VREF = 2.40 V (REFSL=0), –40 to +85 °C unless otherwise specified
Parameter Conditions Min Typ Max Units
DC Accuracy
Resolution 10 bits
Integral Nonlinearity —±0.5±1LSB
Differential Nonlinearity Guaranteed Monotonic — ±0.5 ±1 LSB
Offset Error –12 1 +12 LSB
Full Scale Error Differential mode –15 –5 +5 LSB
Offset Temperature Coefficient — 3.6 — ppm/°C
Dynamic Performance (10 kHz sine-wave Single-ended input, 0 t o 1 dB be lo w Full Scale , 200 ksps)
Signal-to-Noise Plus Distortion 53 55.5 — dB
Total Harmonic Distortion Up to the 5th harmonic —–67—dB
Spurious-Free Dynamic Range —78—dB
Conversion Rate
SAR Conversion Clock —— 3MHz
Conversion Time in SAR Clocks 10 — — clocks
Track/Hold Acquisition Time 300 — — ns
Throughput Rate — — 200 ksps
Analog Inputs
Input Voltage Range 0—VREFV
Input Capacitance —5—pF
Temperature Sensor ———
Linearity* —±0.5—°C
Gain* — 3350 ± 10 — µV / °C
Offset* (Temp = 0 °C) — 897 ± 31 — mV
Power Specifications
Power Supply Current
(VDD supplied to ADC0) Operating Mode, 200 ksps — 400 900 µA
Power Supply Rejection —±0.3—mV/V
*Note: Represents one standard deviation from the mean. Includes ADC offset, gain, and linearity variations.
C8051F310/1/2/3/4/5/6/7
66 Rev. 1.7
NOTES:
Rev. 1.7 67
C8051F310/1/2/3/4/5/6/7
6. Voltage Reference (C8051F310/1/2/3/6 only)
The voltage reference MUX on C8051F310/1/2/3/6 devices is configurable to use an externally connected
voltage reference, or the power supply voltage (see Figure 6.1). The REFSL bit in the Reference Control
register (REF0CN) selects the reference source. For an external source, REFSL should be set to ‘0’; For
VDD as the reference source, REFSL should be set to ‘1’.
The BIASE bit enables the internal voltage bi as generator, which is used by the ADC, Temperature Sensor,
and Internal Oscillator. This bit is forced to logic 1 when any of the aforementioned peripherals is enabled.
The bias generator may be enabled manually by writing a ‘1’ to the BIASE bit in register REF0CN; see
SFR Definition 6.1 for REF0CN register details. The electrical specifications for the voltage reference cir-
cuit are given in Table 6.1.
Important Note About the VREF Input: Port pin P0 .0 is used as the external VREF in put. Whe n using a n
external volt age r eference, P0.0 should be co nfigured as a nalog in put and skipped by the Digit al Cr ossbar.
To configure P0.0 as analog input, set to ‘0’ Bit0 in register P0MDIN. To configure the Crossbar to skip
P0.0, set to ‘1’ Bit0 in register P0SKIP. Refer to Section “13. Port Input/Output” on page 129 for com-
plete Port I/O configuration details.
The temperature sensor connects to the highest order input of the ADC0 positive input multiplexer (see
Section “5.1. Analog Multiplexer” on page 51 for details). The TEMPE bit in register REF0CN
enables/disables the tem perature sensor. While disa bled, th e temperature sensor defaults to a high imped-
ance state and any ADC0 measurements performed on the sensor result in meaningless data.
Internal
VREF
(to ADC)
To Analog Mux
VDD
VREF
R1
VDD External
Voltage
Reference
Circuit
GND
REF0CN
REFSL
TEMPE
BIASE
Temp Sensor
EN
Bias Generator To ADC, Internal
Oscillator
EN
IOSCEN
0
1
Figure 6.1. Voltage Reference Functional Block Diagra m
C8051F310/1/2/3/4/5/6/7
68 Rev. 1.7
SFR Definition 6.1. REF0CN: Reference Control
Bits7–4: UNUSED. Read = 0000b; Write = don’t care.
Bit3: REFSL: Voltage Reference Select.
This bit selects the source for the internal voltage reference.
0: VREF input pin used as voltage reference.
1: VDD used as voltage reference.
Bit2: T EMP E : Tem p er at ur e Sen so r Ena bl e Bit.
0: Internal Temperature Sensor off.
1: Internal Temperature Sensor on.
Bit1: BIASE: Internal Analog Bias Generator Enable Bit. (Must be ‘1’ if using ADC).
0: Internal Bias Generator off.
1: Internal Bias Generator on.
Bit0: UNUSED. Read = 0b. Write = don’t care.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
REFSL TEMPE BIASE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xD1
Table 6.1. External Voltage Reference Circuit Electrical Characteristics
VDD = 3.0 V; –40 to +85 °C unless otherwise specified
Parameter Conditions Min Typ Max Units
Input Voltage Range
Input Current
0V
DD V
Sample Rate = 200 ksps;
VREF = 3.0 V 12 µA
Rev. 1.7 69
C8051F310/1/2/3/4/5/6/7
7. Comparators
C8051F31x devices include two on-chip programmable voltage comparators: Comparator0 is shown in
Figure 7.1; Comparator1 is shown in Figure 7.2. The two comparators operate identically with the following
exceptions: (1) Their input selections differ as shown in Figure 7.1 and Figure 7.2; (2) Comparator0 can be
used as a reset source.
The Comparator offers programmable response time and hysteresis, an analog input multiplexer, and two
outputs that are optionally available at the Port pins: a synchronous “latched” output (CP0, CP1), or an
asynchronous “raw” output (CP0A, CP1A). The asynchronous CP0A signal is available even when the
system clock is not active. This allows the Comparator to operate and generate an output with the device
in STOP mode. When assigned to a Port pin, the Comparator output may be configured as open drain or
push-pull (s ee Secti on “13. 2. Port I/O Initialization” on page 133). Comparator0 may also be used as a
reset source (see Section “9.5. Comparator0 Reset” on page 108).
The Compa rator0 input s ar e selected in the CPT0MX register (SFR Definition 7.2). The CMX0P1-CMX0P0
bits select the Comparator0 positive input; the CMX0N1-CMX0N0 bits select the Comparator0 negative
input. The Comparator1 inputs are selected in the CPT1MX register (SFR Definition 7.5). The CMX1P1-
CMX1P0 bits select the Comparator1 positive input; the CMX1N1-CMX1N0 bits select the Comparator1
negative input.
Important Note About Comparator Inputs: The Port pins selected as comparator inputs should be con-
figured as analog inputs in their associated Port configuration register, and configured to be skipped by th e
Crossbar (for details on Port configuration, see Section “13.3. General Purpose Port I/O” on page 135).
VDD
CPT0CN
Reset
Decision
Tree
+
-
Crossbar
Interrupt
Logic
Q
Q
SET
CLR
D
Q
Q
SET
CLR
D
(SYNCHRONIZER)
GND
CP0 +
P1.0
P1.4
P2.0
P2.4
CP0 -
P1.1
P1.5
P2.1
P2.5
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP1
CP0HYP0
CP0HYN1
CP0HYN0
CPT0MX
CMX0N1
CMX0N0
CMX0P1
CMX0P0
CPT0MD
CP0RIE
CP0FIE
CP0MD1
CP0MD0
CP0
CP0A
CP0
Rising-edge CP0
Falling-edge
CP0
Interrupt
Figure 7.1. Comparator0 Functional Block Diagram
C8051F310/1/2/3/4/5/6/7
70 Rev. 1.7
The Comparator output can be polled in software, used as an interrupt source, and/or routed to a Port pin.
When routed to a Port pin, the Comparator output is available asynchronous or synchronous to the system
clock; the asynchronous output is available even in STOP mode (with no system clock active). When dis-
abled, the Compar ator outpu t (i f assigned to a Port I/O pin via the Cr ossbar ) defaults to the logic low state,
and its supply current falls to less than 100 nA. See Section “13.1. Priority Crossbar Decoder” on
page 131 for det ails on configurin g Comparator outputs via the digit al Crossbar. Comparator inputs can be
externally driven from –0.25 V to (VDD) + 0.25 V without damage or up set. The co mplete Comparator elec-
trical specifications are given in Table 7.1.
The Comparator response time may be configured in software via the CPTnMD registers (see SFR Defini-
tion 7.3 and SFR Definition 7.6). Selecting a longer response time reduces the Compar ator supp ly cu rr ent.
See Table 7.1 for complete timing and current consumption specifications.
VDD
CPT1CN
Reset
Decision
Tree
+
-
Crossbar
Interrupt
Logic
Q
Q
SET
CLR
D
Q
Q
SET
CLR
D
(SYNCHRONIZER)
GND
CP1 +
P1.2
P1.6
P2.2
P2.6
CP1 -
P1.3
P1.7
P2.3
P2.7
CP1EN
CP1OUT
CP1RIF
CP1FIF
CP1HYP1
CP1HYP0
CP1HYN1
CP1HYN0
CPT1MX
CMX1N1
CMX1N0
CMX1P1
CMX1P0
CPT1MD
CP1RIE
CP1FIE
CP1MD1
CP1MD0
CP1
CP1A
CP1
Rising-edge CP1
Falling-edge
CP1
Interrupt
Figure 7.2. Comparator1 Functional Block Diagram
Positive Hysteresis Voltage
(Programmed wi t h CP0HYP Bi ts)
Negative Hysteresis Voltage
(Programmed by CP0HYN Bits)
VIN-
VIN+
INPUTS
CIRCUIT CONFIGURATION
+
_
CP0+
CP0- CP0
VIN+
VIN- OUT
V
OH
Positive Hysteresis
Disabled Maximum
Positive Hysteresis
Negative Hysteresis
Disabled Maximum
Negative Hysteresis
OUTPUT
V
OL
The Comparator hysteresis is software-programmable via its Comparator Control register CPTnCN (for
n = 0 or 1). The us er ca n p rog ra m bo th the a mount of h yster esis vo ltage (referred to the input volt ag e) an d
the positive and negat i ve -g oin g symm et ry of th is hysteresis around the threshold voltage.
The Comparator hysteresis is programmed using Bits3-0 in the Comparator Control Register CPTnCN
(shown in SFR Definition 7.1 and SFR Definition 7.4). The amount of negative hysteresis voltage is
determined by the settings of the CPnHYN bits. As shown in Table 7.1, settings of 20, 10 or 5 mV of
negative hysteresis can be programmed, or negative hysteresis can be disabled. In a similar way, the
amount of positive hysteresis is determined by the setting the CPnHYP bits.
Comparator interrupts can be generated on both rising-edge and falling-edge output transitions. (For Inter-
rupt enable and prior ity control, see Section “8.3. Int errupt Handler” on p a ge 93). The CPnFIF flag is set
to logic 1 upon a Comparator falling-edge interrupt, and the CPnRIF flag is set to logic 1 upon the Compar-
ator rising-edg e inte r ru pt . On ce se t, th es e bits remain set until cleared by software. The outpu t state of the
Comparator can be obtained at any time by rea ding the CPnOUT bit. The Co mparator is en abled by set-
ting the CPnEN bit to logic 1, and is disabled by clearing this bit to logic 0.
The output state of the Comparator can be obtained at any time by reading the CPnOUT bit. The Compar-
ator is enabled by setting the CPnEN bit to logic 1, and is disabled by clearing this bit to logic 0.
Note that false rising edges and falling edges can be detected when the c omparator is first powered-on or
if changes are made to the hysteresis or response time control bits. Therefore, it is recommended that the
rising-edge and falling-edge flags be explicitly cleared to logic 0 a short time after the comparator is
enabled or its mode bits have been changed. This Power Up Time is specified in Table 7.1 on page 78.
Rev. 1.7 71
C8051F310/1/2/3/4/5/6/7
Figure 7.3. Comparator Hysteresis Plot
C8051F310/1/2/3/4/5/6/7
72 Rev. 1.7
SFR Definition 7.1. CPT0CN: Comparator0 Control
Bit7: CP0 EN: Comparat or 0 En able Bit.
0: Comparator0 Disabled.
1: Comparator0 Enabled.
Bit6: CP0 OUT: Comparator0 Ou tp ut State Flag .
0: Voltage on CP0+ < CP0–.
1: Voltage on CP0+ > CP0–.
Bit5: CP0 RIF : Co mparator 0 Risin g -Ed ge Int er rupt Flag .
0: No Comparator0 Rising Edge Interrupt has occurred since this flag was last cleared.
1: Comparator0 Rising Edge Interrupt has occurred.
Bit4: CP0FIF: Comparator0 Falling-Edge Interrupt Flag.
0: No Comparator0 Falling-Edge Interrupt has occurred since this flag was last cleared.
1: Comparator0 Falling-Edge Interrupt has occurred.
Bits3–2: CP0H YP1 -0 : Comparat or 0 Pos i tive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
Bits1–0: CP0HYN1-0: Comparator0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hyste r esis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
R/W R R/W R/W R/W R/W R/W R/W Reset Value
CP0EN CP0OUT CP0RIF CP0FIF CP0HYP1 CP0HYP0 CP0HYN1 CP0HYN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x9B
Rev. 1.7 73
C8051F310/1/2/3/4/5/6/7
SFR Definition 7.2. CPT0MX: Comparator0 MUX Selection
Bits7–6: UNUSED. Read = 00b, Write = don’t care.
Bits5–4: CMX0N1–CMX0N0: Comparator0 Negative Input MUX Select.
These bits select which Port pin is used as the Comparator0 negative input.
Bits3–2: UNUSED. Read = 00b, Write = don’t care.
Bits1–0: CMX0P1–CMX0P0: Comparator0 Positive Input MUX Select.
These bits select which Port pin is used as the Comparator0 positive input.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - CMX0N1 CMX0N0 - - CMX0P1 CMX0P0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x9F
CMX0N1 CMX0N0 Negative Input
00 P1.1
01 P1.5
10 P2.1
11 P2.5
CMX0P1 CMX0P0 Positive Input
00 P1.0
01 P1.4
10 P2.0
11 P2.4
C8051F310/1/2/3/4/5/6/7
74 Rev. 1.7
SFR Definition 7.3. CPT0MD: Comparator0 Mode Selection
Bits7–6: UNUSED. Read = 00b. Write = don’t care.
Bit5: CP0RIE: Comparator Rising-Edge Interrupt Enable.
0: Comparator rising-edge interrupt disabled.
1: Comparator rising-edge interrupt enabled.
Bit4: CP0FIE: Comparator Falling-Edge Interrupt Enable.
0: Comparator falling-edge interrupt disabled.
1: Comparator falling-edge interrupt enabled.
Bits1–0: CP0MD1–CP0MD0: Comparator0 Mode Select
These bits select the response time for Comparator0.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - CP0RIE CP0FIE - - CP0MD1 CP0MD0 00000010
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x9D
Mode CP0MD1 CP0MD0 CP0 Response Time (TYP)
0 0 0 Fastest Response Time
101 —
210 —
3 1 1 Lowest Power Consumption
Rev. 1.7 75
C8051F310/1/2/3/4/5/6/7
SFR Definition 7.4. CPT1CN: Comparator1 Control
Bit7: CP1 EN: Comparat or 1 En able Bit.
0: Comparator1 Disabled.
1: Comparator1 Enabled.
Bit6: CP1 OUT: Comparator1 Ou tp ut State Flag .
0: Voltage on CP1+ < CP1–.
1: Voltage on CP1+ > CP1–.
Bit5: CP1 RIF : Co mparator 1 Risin g -Ed ge Int er rupt Flag .
0: No Comparator1 Rising Edge Interrupt has occurred since this flag was last cleared.
1: Comparator1 Rising Edge Interrupt has occurred.
Bit4: CP1FIF: Comparator1 Falling-Edge Interrupt Flag.
0: No Comparator1 Falling-Edge Interrupt has occurred since this flag was last cleared.
1: Comparator1 Falling-Edge Interrupt has occurred.
Bits3–2: CP1HYP1–0: Comparator1 Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
Bits1–0: CP1HYN1–0: Comparator1 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hyste r esis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
R/W R R/W R/W R/W R/W R/W R/W Reset Value
CP1EN CP1OUT CP1RIF CP1FIF CP1HYP1 CP1HYP0 CP1HYN1 CP1HYN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x9A
C8051F310/1/2/3/4/5/6/7
76 Rev. 1.7
SFR Definition 7.5. CPT1MX: Comparator1 MUX Selection
Bits7–6: UNUSED. Read = 00b, Write = don’t care.
Bits5–4: CMX1N1–CMX1N0: Comparator1 Negative Input MUX Select.
These bits select which Port pin is used as the Comparator1 negative input.
Bits3–2: UNUSED. Read = 00b, Write = don’t care.
Bits1–0: CMX1P1–CMX1P0: Comparator1 Positive Input MUX Select.
These bits select which Port pin is used as the Comparator1 positive input.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - CMX1N1 CMX1N0 - - CMX1P1 CMX1P0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x9E
CMX1N1 CMX1N0 Negative Input
00 P1.3
01 P1.7
10 P2.3
11 P2.7
CMX1P1 CMX1P0 Positive Input
00 P1.2
01 P1.6
10 P2.2
11 P2.6
Rev. 1.7 77
C8051F310/1/2/3/4/5/6/7
SFR Definition 7.6. CPT1MD: Comparator1 Mode Selection
Bits7–6: UNUSED. Read = 00b, Write = don’t care.
Bit5: CP1RIE: Comparator Rising-Edge Interrupt Enable.
0: Comparator rising-edge interrupt disabled
1: Comparator rising-edge interrupt enabled.
Bit4: CP1FIE: Comparator Falling-Edge Interrupt Enable.
0: Comparator falling-edge interrupt disabled.
1: Comparator falling-edge interrupt enabled.
Bits1–0: CP1MD1–CP1MD0: Comparator1 Mode Select.
These bits select the response time for Comparator1.
R/W R/W R/W R/W R/W R/W R/W R/W R eset Value
- - CP1RIE CP1FIE - - CP1MD1 CP1MD0 00000010
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x9C
Mode CP1MD1 CP1MD0 CP1 Response Time (TYP)
0 0 0 Fastest Response Time
101 —
210 —
3 1 1 Lowest Power Consumption
C8051F310/1/2/3/4/5/6/7
78 Rev. 1.7
Table 7.1. Comparator Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C unless otherwise noted.
All specifications apply to both Comparator0 and Comparator1 unless otherwise noted.
Parameter Conditions Min Typ Max Units
Response Time:
Mode 0, Vcm1 = 1.5 V CP0+ – CP0– = 100 mV — 100 — ns
CP0+ – CP0– = –100 mV — 250 — ns
Response Time:
Mode 1, Vcm1 = 1.5 V CP0+ – CP0– = 100 mV — 175 — ns
CP0+ – CP0– = –100 mV — 500 — ns
Response Time:
Mode 2, Vcm1 = 1.5 V CP0+ – CP0– = 100 mV — 320 — ns
CP0+ – CP0– = –100 mV — 1100 — ns
Response Time:
Mode 3, Vcm1 = 1.5 V CP0+ – CP0– = 100 mV — 1050 — ns
CP0+ – CP0– = –100 mV — 5200 — ns
Common-Mode Rejection Ratio —1.5 4 mV/V
Positive Hysteresis 1 CP0HYP1-0 = 00 — 0 1 mV
Positive Hysteresis 2 CP0HYP1-0 = 01 2 5 7 mV
Positive Hysteresis 3 CP0HYP1-0 = 10 5 10 13 mV
Positive Hysteresis 4 CP0HYP1-0 = 11 12 20 25 mV
Negative Hysteresis 1 CP0HYN1-0 = 00 0 1 mV
Negative Hysteresis 2 CP0HYN1-0 = 01 2 5 7 mV
Negative Hysteresis 3 CP0HYN1-0 = 10 5 10 13 mV
Negative Hysteresis 4 CP0HYN1-0 = 11 12 20 25 mV
Inverting or Non-Inverting Input
Voltage Range –0.25 — VDD +
0.25 V
Input Capacitance —7— pF
Input Bias Current —1— nA
Input Offset Voltage –5 — +5 mV
Power Supply
Power Supply Rejection2 —0.1 1 mV/V
Power-up Time —10— µs
Supply Current at DC
Mode 0 — 7.6 20 µA
Mode 1 — 3.2 10 µA
Mode 2 — 1.3 5 µA
Mode 3 — 0.4 2.5 µA
Notes:
1. Vcm is the common-mode voltage on CP0+ and CP0–.
2. Guaranteed by design and/or chara c terization.
Rev. 1.7 79
C8051F310/1/2/3/4/5/6/7
8. CIP-51 Microcontroller
The MCU system controller core is the CIP-51 microcontroller. The CIP-51 is fully compatible with the
MCS-51™ instruction set; standard 803x/805x assemblers and compilers can be used to develop soft-
ware. The MCU family has a superset of all the peripherals included with a standard 8051. Included are
four 16-bit counter/timers (see description in Section 17), an enhanced full-duplex UART (see description
in Section 15), an Enhanced SPI (see description in Section 16), 256 bytes of internal RAM, 128 byte
Special Fun ction Register (SFR) ad dress space (Section 8.2.6), and 29 Port I/O (see description in Sec-
tion 13). The CIP-51 also includes on-chip debug ha rdware (see d escription in Sect ion 20), and interf aces
directly with the analog and digital subsystems providing a complete data acquisition or control-system
solution in a single integrated circuit.
The CIP-51 Microcontroller core implements the standard 8051 organization and peripherals as well as
additional custom peripherals and functions to extend its capability (see Figure 8.1 for a block diagram).
The CIP-51 includes the following features:
- Fully Compatible with MCS-51 Instructio n
Set
- 25 MIPS Peak Throughput with 25 MHz
Clock
- 0 to 25 MHz Clock Frequency
- 256 Bytes of Internal RAM
-29 Port I/O
- Extended Interrupt Handler
- Reset Input
- Power Management Modes
- On-chip Debug Logic
- Program and Data Memory Security
DATA BUS
TMP1 TMP2
PRGM. ADDRESS REG.
PC INCREMENTER
ALU
PSW
DATA BUS
DATA BUS
MEMORY
INTERFACE
MEM_ADDRESS
D8
PIPELINE
BUFFER
DATA POINTER
INTERRUPT
INTERFACE
SYSTEM_IRQs
EMULATION_IRQ
MEM_CONTROL
CONTROL
LOGIC
A16
PROGRAM COUNTER (PC)
STOP
CLOCK
RESET
IDLE POWER CONTROL
REGISTER
DATA B US
SFR
BUS
INTERFACE
SFR_ADDRESS
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
D8
D8
B REGISTER
D8
D8
ACCUMULATOR
D8
D8
D8
D8
D8
D8
D8
D8
MEM_WRITE_DATA
MEM_READ_DATA
D8
SRAM
ADDRESS
REGISTER
SRAM
(256 X 8)
D8
STACK POINTER
D8
Figure 8.1. CIP-51 Block Diagram
C8051F310/1/2/3/4/5/6/7
80 Rev. 1.7
Performance
The CIP-51 employ s a p ipelined architectu re that grea tly increases it s instr uction throughpu t over the st an-
dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system
clock cycles to execute, and usually have a maximum system clock of 12 MHz. By contrast, the CIP-51
core executes 70% of its instructions in one or two system clock cycles, with no instructions taking more
than eight system clock cycles.
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. The CIP-51 has
a total of 109 instr uctions. The table below shows the total number of instructions that require each execu-
tion time.
Clocks to Execute 1 2 2/3 33/4 44/5 5 8
Number of Instructions 26 50 514 73121
Programming and Debugging Support
In-system programming of the Flash program memory and communication with on-chip debug support
logic is accomplished via the Silicon Labs 2-Wire Development Interface (C2). The re-programmable Flash
can also be read and changed a single byte at a time by the application software using the MOVC and
MOVX instructions. This feature allows program memory to be used for non-volatile data storage as well
as updating program code under software control.
The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware
breakpoints, starting, stopping and single stepping through prog ram execution (including interrupt service
routines), examination of the program's call stack, and reading/writing the contents of registers and mem-
ory. This method of on-chip debugging is completely non-intrusive, requiring no RAM, Stack, timers, or
other on-chip resources. C2 details can be found in Section “20. C2 Interfac e” on page 223.
The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs pro-
vides an integrated development environment (IDE) including an editor, evaluation compiler, assembler,
debugger and programmer. The IDE's debugger and programmer interface to the CIP-51 via the C2 inter-
face to provide fast and efficient in-system device programming and debugging. Third party macro assem-
blers and C compilers are also available.
8.1. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51™ instruc-
tion set. Standard 8051 development tools can be used to develop software for the CIP-51. All CIP-51
instructions are the binary and functional equivalent of their MCS-51™ counterparts, including opcodes,
addressing modes and effect on PSW flags. However, instruction timing is different than that of the stan-
dard 8051.
8.1.1. Instruction and CPU Timing
In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with
machine cycles varying from 2 to 12 clock cycles in length. However, the CIP-51 implementation is based
solely on clock cycle timing. All instruction timings are specified in terms of clock cycles.
Due to the pipelined architecture of the CIP-51, most instructions execute in the same number of clock
cycles as there are program bytes in the instruction. Conditional branch instructions take one less clock
cycle to com plete when the branch is not taken a s opposed to when the branch is taken. Table 8.1 is the
Rev. 1.7 81
C8051F310/1/2/3/4/5/6/7
CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock
cycles for each instruction.
8.1.2. MOVX Instruction and Program Memory
The MOVX instruction is typically used to access external data memory (Note: the C8051F31x does not
support exte rnal data or program memory) . In the CIP-5 1, the MOVX write instructio n is used to ac cesses
external RAM and the on-chip program memory space implemented as re-programmable Flash memory.
The Flash access feature provides a mechanism for the CIP-51 to update program code and use the pro-
gram memory space fo r n on -v ola tile data storag e. Ref er to Section “10. Flash Memory” on page 111 for
further details.
Table 8.1. CIP-51 Instruction Set Summary
Mnemonic Description Bytes Clock
Cycles
Arithmetic Operations
ADD A, Rn Add register to A 1 1
ADD A, direct Add direct byte to A 2 2
ADD A, @Ri Add indirect RAM to A 1 2
ADD A, #data Add immediate to A 2 2
ADDC A, Rn Add register to A with carry 1 1
ADDC A, direct Add direct byte to A with carry 2 2
ADDC A, @Ri Add indirect RAM to A with carry 1 2
ADDC A, #data Add immediate to A with carry 2 2
SUBB A, Rn Subtra ct re gis ter fro m A with borr ow 1 1
SUBB A, direct Subtract direct byte from A with borrow 2 2
SUBB A, @Ri Subtra ct ind ire ct RAM fro m A with borr ow 1 2
SUBB A, #data Subtract imme dia te from A with bo rr ow 2 2
INC A Increment A 1 1
INC Rn Increment register 1 1
INC direct Increment direct byte 2 2
INC @Ri Increment indirect RAM 1 2
DEC A Decrement A 1 1
DEC Rn Decrement register 1 1
DEC direct Decrement direc t byt e 2 2
DEC @Ri Decrement indirect RAM 1 2
INC DPTR Increment Data Pointer 1 1
MUL AB Multiply A and B 1 4
DIV AB Divide A by B 1 8
DA A Decimal adjust A 1 1
Logical Operations
ANL A, Rn AND Register to A 1 1
ANL A, direct AND direct byte to A 2 2
ANL A, @Ri AND indirect RAM to A 1 2
ANL A, #data AND immediate to A 2 2
ANL direct, A AND A to direct byte 2 2
ANL direct, #data AND immediate to direct byte 3 3
ORL A, Rn OR Register to A 1 1
C8051F310/1/2/3/4/5/6/7
82 Rev. 1.7
ORL A, direct OR direct byte to A 2 2
ORL A, @Ri OR indirect RAM to A 1 2
ORL A, #data OR immediate to A 2 2
ORL direct, A OR A to direct byte 2 2
ORL direct, #data OR immediate to direct byte 3 3
XRL A, Rn Exclusive-OR Register to A 1 1
XRL A, direct Exclusive-OR direct byte to A 2 2
XRL A, @Ri Exclusive-OR indirect RAM to A 1 2
XRL A, #data Exclusive-OR immediate to A 2 2
XRL direct, A Exclusive-OR A to direct byte 2 2
XRL direct, #data Exclusive-OR immediate to direct byte 3 3
CLR A Clear A 1 1
CPL A Complement A 1 1
RL A Rotate A left 1 1
RLC A Rotate A left through Carry 1 1
RR A Rotate A right 1 1
RRC A Rotate A right through Carry 1 1
SWAP A Swap nibbles of A 1 1
Data Transfer
MOV A, Rn Move Register to A 1 1
MOV A, direct Move direct byte to A 2 2
MOV A, @Ri Move indirect RAM to A 1 2
MOV A, #data Move immediate to A 2 2
MOV Rn, A Move A to Register 1 1
MOV Rn, direct Move direct byte to Register 2 2
MOV Rn, #data Move immediate to Register 2 2
MOV direct, A Move A to direct byte 2 2
MOV direct, Rn Move Register to direct byte 2 2
MOV direct, direct Move direct byte to direct byte 3 3
MOV direct, @Ri Move indirect RAM to direct byte 2 2
MOV direct, #data Move immediate to direct byte 3 3
MOV @Ri, A Move A to indirect RAM 1 2
MOV @Ri, direct Move direct byte to indirect RAM 2 2
MOV @Ri, #data Move immediate to indirect RAM 2 2
MOV DPTR, #data16 Load DPTR with 16-bit constant 3 3
MOVC A, @A+DPTR Move code byte relative DPTR to A 1 3
MOVC A, @A+PC Move code byte relative PC to A 1 3
MOVX A, @Ri Move external data (8-bit address) to A 1 3
MOVX @Ri, A Move A to external data (8-bit address) 1 3
MOVX A, @DPTR Move external data (16-bit address) to A 1 3
MOVX @DPTR, A Move A to external data (16-bit address) 1 3
PUSH direct Push direct byte onto stack 2 2
POP direct Pop direct byte from stack 2 2
XCH A, Rn Exchange Register with A 1 1
XCH A, direct Exchange direct byte with A 2 2
Table 8.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
Rev. 1.7 83
C8051F310/1/2/3/4/5/6/7
XCH A, @Ri Exchange indirect RAM with A 1 2
XCHD A, @Ri Exchange low nibble of indirect RAM with A 1 2
Boolean Manipulation
CLR C Clear Carry 1 1
CLR bit Clear direct bit 2 2
SETB C Set Carry 1 1
SETB bit Set direct bit 2 2
CPL C Complement Carry 1 1
CPL bit Complement direct bit 2 2
ANL C, bit AND direct bit to Carry 2 2
ANL C, /bit AND complement of direct bit to Carry 2 2
ORL C, bit OR direct bit to carry 2 2
ORL C, /bit OR complement of direct bit to Carry 2 2
MOV C, bit Move direct bit to Carry 2 2
MOV bit, C Move Carry to direct bit 2 2
JC rel Jump if Carry is set 22/3
JNC rel Jump if Carry is not set 22/3
JB bit, rel Jump if direct bit is set 33/4
JNB bit, rel Jump if direct bit is not set 33/4
JBC bit, rel Jump if direct bit is set and clear bit 33/4
Program Branch in g
ACALL addr11 Absolute subroutine call 2 3
LCALL addr16 Long subroutine call 3 4
RET Return from subroutine 1 5
RETI Return from interrupt 1 5
AJMP addr11 Absolute jump 2 3
LJMP addr16 Long jump 3 4
SJMP rel Short jump (relative address) 2 3
JMP @A+DPTR Jump indirect relative to DPTR 1 3
JZ rel Jump if A equals zero 22/3
JNZ rel Jump if A does not equal zero 22/3
CJNE A, direct, rel Compare direct byte to A and jump if not equal 33/4
CJNE A, #data, rel Compare immediate to A and jump if not equal 33/4
CJNE Rn, #data, rel Compare immediate to Register and jump if not
equal 33/4
CJNE @Ri, #data, rel Compare immediate to indirect and jump if not
equal 34/5
DJNZ Rn, rel Decrement Register and jump if not zero 22/3
DJNZ direct, rel Decrement direc t byte and jump if not zero 33/4
NOP No operation 1 1
Table 8.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
Notes on Registers, Operands and Addressing Modes:
Rn - Register R0–R7 of the currently selected register bank.
@Ri - Data RAM location addressed indirectly through R0 or R1.
rel - 8-bit, signed (two’s complement) offset relative to the first byte of the following instruction. Used by
SJMP and all conditional jumps.
direct - 8-bit internal data location’s address. This could be a direct-access Data RAM location (0x00–
0x7F) or an SFR (0x80–0xFF).
#data - 8-bit constant
#data16 - 16-bit constant
bit - Direct-accessed bit in Data RAM or SFR
addr11 - 1 1-b it destination address used by ACALL and AJMP. The destination must be within the same
2 kB page of program memory as the first byte of the following instruction.
addr16 - 16-bit destination address used by L CALL and LJMP. The destination ma y be anywhere within
the 8 kB program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
C8051F310/1/2/3/4/5/6/7
84 Rev. 1.7
Rev. 1.7 85
C8051F310/1/2/3/4/5/6/7
8.2. Memory Organization
The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are
two separate memory spaces: program memory and data memory. Program and data memory share the
same address s pace but are acces sed via different instruction types. The CIP-51 memory organization is
shown in Figure 8.2.
PROGRAM/DATA MEMORY
(Flash)
(Direct and Indirect
Addressing)
0x00
0x7F
Upper 128 RAM
(Indirect Addressing
Only)
0x80
0xFF Special Function
Register's
(Direct Addressing Only)
DATA MEMORY (RAM)
General Purpose
Registers
0x1F
0x20
0x2F Bit A ddressable
Lower 128 RAM
(Direct and Indirect
Addressing)
0x30
INTERNAL DATA AD DRES S SP ACE
EXTERNAL DATA ADDRESS SPACE
XRAM - 1024 Bytes
(accessable using MO VX
instruction)
0x0000
0x03FF
Same 1024 bytes as from
0x0000 to 0x03FF, wrapped
on 1 kB boundaries
0x0400
0xFFFF
16 kB Flash
(In-System
Programmable in 512
Byte Sectors)
0x0000
RESERVED
0x3E00
0x3DFF
8 kB Flash
(In-System
Programmable in 512
Byte Sectors)
0x0000
RESERVED
0x2000
0x1FFF
C8051F310/1
C8051F312/3/4/5
Figure 8.2. Memory Map
8.2.1. Program Memory
The CIP-51 core has a 64k-byte program memo ry space. The C8051F310/1 and C8051F312/3/4/5 imple-
ment 16 and 8 kB, respectively, of this program memory space as in-system, re-programmable Flash
memory, organized in a contiguous block from addresses 0x0000 to 0x3FFF or 0x0000 to 0x1FFF.
Addresses above 0x3E00 are reserved on the 16 kB devices.
Program memory is nor mally assumed to be re ad-on ly. However, the CIP-51 can write to p rogr am memo ry
by setting the Program S tore Write Enable bit (PSCTL.0) and using the MOVX instruction. This feature pro-
vides a mechanism for the CIP-51 to update program code and use the program memory space for non-
volatile data storage. Refer to Section “10. Flash Memory” on page 111 for further details.
C8051F310/1/2/3/4/5/6/7
86 Rev. 1.7
8.2.2. Data Memory
The CIP-51 includes 256 bytes of internal RAM mapped into the data memory space from 0x00 through
0xFF. The lower 128 bytes of data memory are used for general purpose re gisters and scratch pad mem-
ory. Either direct or indirect addressing may be used to access the lower 128 bytes of data memory. Loca-
tions 0x00 through 0x1F are addr essable as four banks of general pur pose regi sters, each bank consisting
of eight byte-wide registers. The next 16 bytes, locations 0x20 through 0x2F, may either be addressed as
bytes or as 128 bit locations accessible with the direct addressing mode.
The upper 128 bytes of data memory are accessib le only b y indirect addressing. This region occupies the
same address space as the Special Function Registers (SFR) but is physically separate from the SFR
space. The addressing mode used by an instruction when accessing locations above 0x7F determines
whether the CPU accesses the upper 128 bytes of data memory space or the SFRs. Instructions that use
direct addressing will access the SFR space. Instructions using indirect addressing above 0x7F access the
upper 128 bytes of data memory. Figure 8.2 illustrates the data memory organization of the CIP-51.
8.2.3. General Purpose Registers
The lower 32 bytes of dat a memory, locations 0x00 through 0x1F, may be addressed as four banks of gen -
eral-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only
one of these banks may be ena bled at a time. Two bits in th e progr am st atus wo rd , RS0 (PSW.3) and RS1
(PSW.4), select the active register bank (see description of the PSW in SFR Definition 8.4). This allows
fast context switching when entering su brou tines and interrupt se rvice routines. Indir ect addressin g modes
use registers R0 and R1 as index registers.
8.2.4. Bit Addressable Locations
In addition to dir ect access to data memory organized as bytes, the sixteen d ata memory locations at 0x20
through 0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from
0x00 to 0x7F. Bit 0 of the byte at 0x2 0 has bit address 0x 00 while bit7 o f the byte at 0x20 ha s bit address
0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bit access is distinguished fro m a full byte access by
the type of instruction used (bit source or destination operands as opposed to a byte source or destina-
tion).
The MCS-51™ assembly language allows an alternate notation for bit addressing of the form XX.B where
XX is the byte address and B is the bit position within the byte. For example, the instruction:
MOV C, 22.3h
moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the Carry flag.
8.2.5. Stack
A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is desig-
nated using the Stack Pointer (SP, 0x81) SFR. The SP will point to the last location used. The next value
pushed on the stack is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to
location 0x07. Therefor e, the first value pushed on the stack is placed at location 0x08, which is also the
first register (R0) of re gister bank 1. Thus, if m ore than one register bank is to be used, the SP should be
initialized to a location in the data memory not being used for dat a storage. Th e stack depth can extend up
to 256 bytes.
Rev. 1.7 87
C8051F310/1/2/3/4/5/6/7
8.2.6. Special Function Registers
The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers
(SFRs). The SFRs provide control and data exchange with the CIP-51's resources and peripherals. The
CIP-51 duplicates the SFRs found in a typical 8051 implementation as well as implementing additional
SFRs used to configure and access the sub-systems unique to the MCU. This allows the addition of new
functionality while retaining compatibility with the MCS-51™ instruction set. Table 8.2 lists the SFRs imple-
mented in the CIP-51 System Controller.
The SFR regist ers are access ed anytime the direct a ddressing mode is used to access memory locations
from 0x80 to 0xFF. SFRs with a ddresses ending in 0x0 or 0x8 (e.g. P0, TCON, SCON0, IE, etc.) are bit-
addressable as well as byte-addressable. All other SFRs are byte-addressable only. Unoccupied
addresses in the SFR space are reserved for future use. Accessing these areas will have an indeterminate
effect an d should be avoided . Refer to the cor respond ing p ages of the dat asheet, a s indicated in Table 8.3,
for a detailed description of ea ch reg ist er.
Table 8.2. Special Function Register (SFR) Memory Map
F8 SPI0CN PCA0L PCA0H PCA0CPL0 PCA0CPH0 PCA0CPL4 PCA0CPH4 VDM0CN
F0 BP0MDIN P1MDIN P2MDIN P3MDIN EIP1
E8 ADC0CN PCA0CPL1 PCA0CPH1 PCA0CPL2 PCA0CPH2 PCA0CPL3 PCA0CPH3 RSTSRC
E0 ACC XBR0 XBR1 IT01CF EIE1
D8 PCA0CN PCA0MD PCA0CPM0 PCA0CPM1 PCA0CPM2
D0 PSW REF0CN
C8 TMR2CN TMR2RLL TMR2RLH TMR2L TMR2H
C0 SMB0CN SMB0CF SMB0DAT ADC0GTL ADC0GTH ADC0LTL ADC0LTH
B8 IP AMX0N AMX0P ADC0CF ADC0L
B0 P3 OSCXCN OSCICN OSCICL FLSCL FLKEY
A8 IE
A0 P2 SPI0CFG SPI0CKR SPI0DAT P0MDOUT P1MDOUT P2MDOUT P3MDOUT
98 SCON0 SBUF0 CPT1CN CPT0CN CPT1MD CPT0MD CPT1MX CPT0MX
90 P1 TMR3CN TMR3RLL TMR3RLH TMR3L TMR3H
88 TCON TMOD TL0 TL1 TH0 TH1 CKCON PSCTL
80 P0 SP DPL DPH PCON
0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F)
(bit addressable)
PCA0CPM3 PCA0CPM4
P0SKIP P1SKIP P2SKIP
ADC0H
CLKSEL EMI0CN
C8051F310/1/2/3/4/5/6/7
88 Rev. 1.7
Table 8.3. Special Function Registers
Register Address Description Page
SFRs are listed in alphab et ica l or d er. All undefin ed SFR locat ion s ar e re se rve d
ACC 0xE0 Accumulator 92
ADC0CF 0xBC ADC0 Configuration 59
ADC0CN 0xE8 ADC0 Control 60
ADC0GTH 0xC4 ADC0 Greate r- Th a n Compare High 61
ADC0GTL 0xC3 ADC0 Greate r- Th a n Compare Lo w 61
ADC0H 0xBE ADC0 High 59
ADC0L 0xBD ADC0 Low 59
ADC0LTH 0xC6 ADC 0 Less-Than Compare Word High 62
ADC0LTL 0xC5 ADC0 Less-Than Compare Word Low 62
AMX0N 0xBA AMUX0 Negative Channel Select 58
AMX0P 0xBB AMUX0 Positive Channel Select 57
B0xF0 B Register 93
CKCON 0x8E Clock Control 193
CLKSEL 0xA9 Clock Select 123
CPT0CN 0x9B Comparator0 Control 72
CPT0MD 0x9D Comparator0 Mode Selection 74
CPT0MX 0x9F Comparator0 MUX Selection 73
CPT1CN 0x9A Comparator1 Control 75
CPT1MD 0x9C Comparator1 Mode Selection 77
CPT1MX 0x9E Comparator1 MUX Selection 76
DPH 0x83 Data Pointer High 91
DPL 0x82 Data Pointer Low 90
EIE1 0xE6 Extended Interrupt Enable 1 99
EIP1 0xF6 Extended Interrupt Priority 1 100
EMI0CN 0xAA External Memory Interface Control 119
FLKEY 0xB7 Flash Lock and Key 117
FLSCL 0xB6 Flash Scale 117
IE 0xA8 Interrupt Enable 97
IP 0xB8 Interrupt Priority 98
IT01CF 0xE4 INT0/INT1 Configuration 101
OSCICL 0xB3 Internal Oscillator Calibration 122
OSCICN 0xB2 Internal Oscillator Control 122
OSCXCN 0xB1 External Oscillator Control 125
P0 0x80 Port 0 Latch 136
P0MDIN 0xF1 Port 0 Inpu t Mode C onfig ur at ion 136
P0MDOUT 0xA4 Port 0 Output Mode Configuration 137
P0SKIP 0xD4 Port 0 Skip 137
P1 0x90 Port 1 Latch 138
P1MDIN 0xF2 Port 1 Input Mo de Con fig ur at ion 138
P1MDOUT 0xA5 Port 1 Output Mode Configuration 139
P1SKIP 0xD5 Port 1 Skip 139
P2 0xA0 Port 2 Latch 140
P2MDIN 0xF3 Port 2 Input Mo de Con fig ur at ion 140
P2MDOUT 0xA6 Port 2 Output Mode Configuration 141
Rev. 1.7 89
C8051F310/1/2/3/4/5/6/7
P2SKIP 0xD6 Port 2 Skip 141
P3 0xB0 Port 3 Latch 142
P3MDIN 0xF4 Port 3 Input Mo de Con fig ur at ion 142
P3MDOUT 0xA7 Port 3 Output Mode Configuration 143
PCA0CN 0xD8 PCA Control 215
PCA0CPH0 0xFC PCA Capture 0 High 219
PCA0CPH1 0xEA PCA Captur e 1 High 219
PCA0CPH2 0xEC PCA Capture 2 High 219
PCA0CPH3 0xEE PCA Capture 3Hig h 219
PCA0CPH4 0xFE PCA Capture 4 High 219
PCA0CPL0 0xFB PCA Capture 0 Low 218
PCA0CPL1 0xE9 PCA Capture 1 Low 218
PCA0CPL2 0xEB PCA Capture 2 Lo w 218
PCA0CPL3 0xED PCA Capture 3Low 218
PCA0CPL4 0xFD PCA Capture 4 Low 218
PCA0CPM0 0xDA PCA Module 0 Mode 217
PCA0CPM1 0xDB PCA Module 1 Mode 217
PCA0CPM2 0xDC PCA Module 2 Mode 217
PCA0CPM3 0xDD PCA Module 3 Mode 217
PCA0CPM4 0xDE PCA Module 4 Mode 217
PCA0H 0xFAPCA Counter High 218
PCA0L 0xF9 PCA Counter Low 218
PCA0MD 0xD9 PCA Mode 216
PCON 0x87 Power Control 103
PSCTL 0x8F Program Store R/W Control 116
PSW 0xD0 Program Status Word 92
REF0CN 0xD1 Voltage Reference Control 68
RSTSRC 0xEF Reset Source Configuration/Status 109
SBUF0 0x99 UART0 Data Buffer 169
SCON0 0x98 UART0 Control 168
SMB0CF 0xC1 SMBus Configuration 152
SMB0CN 0xC0 SMBus Control 154
SMB0DAT 0xC2 SMBus Data 156
SP 0x81 Stack Pointer 91
SPI0CFG 0xA1 SPI Configuration 180
SPI0CKR 0xA2 SPI Clock Rate Control 182
SPI0CN 0xF8 SPI Control 181
SPI0DAT 0xA3 SPI Data 182
TCON 0x88 Timer/Counter Control 191
TH0 0x8C Timer/Counter 0 High 194
TH1 0x8D Timer/Counter 1 High 194
TL0 0x8A Timer/Counter 0 Low 194
TL1 0x8B Timer/Counter 1 Low 194
TMOD 0x89 Timer/Counter Mode 192
TMR2CN 0xC8 Timer/Counter 2 Control 197
TMR2H 0xCD Timer/Counter 2 High 198
Table 8.3. S pecial Function Registers (Continued)
Register Address Description Page
C8051F310/1/2/3/4/5/6/7
90 Rev. 1.7
8.2.7. Register Descriptions
Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits
should not be set to logic 1. Future product versions may use these bits to implement new features in
which case the reset value of the bit will be logic 0, selecting the feature's default state. Detailed descrip-
tions of the remaining SFRs are included in the sections of the data sheet associated with their corre-
sponding system function.
SFR Definition 8.1. DPL: Data Pointer Low Byte
Bits7–0: DPL: Data Pointer Low.
The DPL register is the low byte of the 16-bit DPTR. DPTR is used to access indirectly
addressed Flash memory.
R/W R/W R/W R/W R/W R/W R/W R/W R eset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x82
TMR2L 0xCC Timer/Counter 2 Low 198
TMR2RLH 0xCB Timer/Counter 2 Reload High 198
TMR2RLL 0xCA Timer/Counter 2 Reload Low 198
TMR3CN 0x91 Timer/Counter 3Control 201
TMR3H 0x95 Timer/Counter 3 High 202
TMR3L 0x94 Timer/Counter 3Low 202
TMR3RLH 0x93 Timer/Counter 3 Reload High 202
TMR3RLL 0x92 Timer/Counter 3 Reload Low 202
VDM0CN 0xFF VDD Monitor Control 107
XBR1 0xE2 Port I/O Crossbar Control 1 135
XBR0 0xE1 Port I/O Crossbar Control 0 134
0x84-0x86, 0x96-0x97,
0xAB-0xAF, 0xB4, 0xB9,
0xBF, 0xC7, 0xC9, 0xCE,
0xCF, 0xD2, 0xD3, 0xD7,
0xDF, 0xE3, 0xE5, 0xF5
Reserved
Table 8.3. S pecial Function Registers (Continued)
Register Address Description Page
Rev. 1.7 91
C8051F310/1/2/3/4/5/6/7
SFR Definition 8.2. DPH: Data Pointer High Byte
Bits7–0: DPH: Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR. DPTR is used to access indirectly
addressed Flash memory.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x83
SFR Definition 8.3. SP: Stack Pointer
Bits7–0: SP: Stack Pointer.
The S tack Pointer holds the location of the top of the stack. The stack pointer is incremented
before every PUSH operation. The SP register defaults to 0x07 after reset.
R/W R/W R/W R/W R/W R/W R/W R/W R eset Value
00000111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x81
C8051F310/1/2/3/4/5/6/7
92 Rev. 1.7
SFR Definition 8.4. PSW: Program Status Word
Bit7: CY: Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow
(subtraction). It is cleared to logic 0 by all other arithmetic operations.
Bit6: AC: Auxiliary Carry Flag
This bit is set when the last a rithmetic operation resulte d in a carry into (addition) or a borrow
from (subtraction) the high order nibble. It is cleared to logic 0 by all other arithmetic opera-
tions.
Bit5: F 0: Use r Flag 0.
This is a bit-addressable, general purpose flag for use under software control.
Bits4–3: RS1–RS0: Register Bank Select.
These bits select which register bank is used during register accesses.
Bit2: OV: Overflow Flag.
This bit is set to 1 under the following circumstances: an ADD, ADDC, or SUBB instruction
causes a sign-change overflow, a MUL instruction results in an overflow (result is greater
than 255), or a DIV instruction causes a divide-by-zero condition. The OV bit is cleared to 0
by the ADD, ADDC, SUBB, MUL, and DIV instructions in all other cases.
Bit1: F 1: Use r Flag 1.
This is a bit-addressable, general purpose flag for use under software control.
Bit0: PARITY: Parity Flag.
This bit is set to logic 1 if the sum of the eight bi ts in the accumulator is odd and cleared if the
sum is even.
R/WR/WR/WR/WR/WR/WR/W RReset Value
CY AC F0 RS1 RS0 OV F1 PARITY 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xD0
RS1 RS0 Register Bank Address
0 0 0 0x00–0x07
0 1 1 0x08–0x0F
1 0 2 0x10–0x17
1 1 3 0x18–0x1F
SFR Definition 8.5. ACC: Accumulator
Bits7–0: ACC: Accumulator.
This register is the accumulator for arithmetic operations.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
ACC.7 ACC.6 ACC.5 ACC.4 ACC.3 ACC.2 ACC.1 ACC.0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xE0
Rev. 1.7 93
C8051F310/1/2/3/4/5/6/7
SFR Definition 8.6.
Bits7–0: B: B Register.
This register serves as a second accumulator for certain arithme tic operations.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
B.7 B.6 B.5 B.4 B.3 B.2 B.1 B.0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xF0
B: B Register
8.3. Interrupt Handler
The CIP-51 includes an extended interrup t system supp or ting a total of 14 interrupt sources with two prior-
ity levels. The allocation of interrupt sources between on-chip peripherals and external inputs pins varies
according to the specific version of th e device. Each in terrupt sou rce has one or mor e associated interrup t-
pending flag(s) located in an SFR. When a peripheral or external source meets a valid interrupt condition,
the associat ed inte rrup t- pe n ding flag is set to logic 1.
If interrupt s are ena bled for the sour ce, an interrupt req uest is generated when the inter rupt-pend ing flag is
set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a prede-
termined address to begin execu tion of an interrupt service ro utine (ISR). Each ISR must end with an RETI
instruction, which returns program execution to the next instruction that would have been executed if the
interrupt request h ad not occurred. If inter rupt s are not enabled, the inter rupt-pen ding flag is ignored by the
hardware and program execution continues as normal. (The interrupt-pending flag is set to logic 1 regard-
less of the interrupt's enable/disable state.)
Each interrupt source can be individually enabled or disabled through the use of an associated interrupt
enable bit in an SFR (IE-EIE1). However, interrupts must first be globally enabled by setting the EA bit
(IE.7) to logic 1 before the individual interr upt enables a re re cognized. Setting the EA bit to logic 0 disabl es
all interrupt sources regardless of the individual interrupt-enable settings.
Note: Any instruction that clears the EA bit should be immediately followed by an instruction that
has two or more opcode bytes. For example:
// in 'C':
EA = 0; // clear EA bit
EA = 0; // ... followed by another 2-byte opcode
; in assembly:
CLR EA ; clear EA bit
CLR EA ; ... followed by another 2-byte opcode
If an interrupt is posted during the execution phase of a "CLR EA" opcode (or any instruction which clears
the EA bit), and the instruction is followed by a single-cycle instruction, the interrupt may be taken. How-
ever, a read of the EA bit will return a '0' inside the interrupt service routine. When the "CLR EA" opcode is
followed by a multi-cycle instruction, the interrupt will not be taken.
Some interrupt-pending flags ar e au tomatically cleare d by the hardware when the CPU vector s to the ISR.
However, most are not cleared by the hardware and must be cleared by sof tware befo re returning from the
ISR. If an interrupt-pending flag remains set after the CPU completes the return-from-interrupt (RETI)
C8051F310/1/2/3/4/5/6/7
94 Rev. 1.7
instruction, a new interrupt request will be generated immediately and the CPU will re-enter the ISR after
the completion of the next instruction.
8.3.1. MCU Interrupt Sources and Vectors
The MCUs support 14 interrupt sources. Soft ware can simulate an interrupt by setting any interrupt-pend-
ing flag to logic 1. If interrupts are enabled for the flag, an interrupt request will be generated and the C PU
will vector to the ISR address associated with the interrupt-pending flag. MCU interrupt sources, associ-
ated vector addresses, priority order and control bits are summarized in Table 8.4 on page 96. Refer to the
datasheet section associated with a particular on-chip peripheral for information regarding valid interrupt
conditions for th e pe riph er al an d th e be ha vio r of its interrupt-p end ing flag (s) .
Rev. 1.7 95
C8051F310/1/2/3/4/5/6/7
8.3.2. External Interrupts
The /INT0 and /INT1 external interrupt sources are configurable as active high or low, edge or level sensi-
tive. The IN0PL (/INT0 Polarity) and IN1PL (/INT1 Polarity) bits in the IT01CF register select active high or
active low; the IT0 and IT 1 bits in TCON (Section “17.1. Timer 0 and Timer 1” on page 187) select lev el
or edge sensitive. The table below lists the possible configurations.
Active low, edge sensitive Active low, edge sensitive
Active high, edge sensitive Active high, edge sensitive
Active low, level sensitive Active low, level sensitive
Active high, level sensitive Active high, level sensitive
/INT0 and /INT1 are assigned to Port pins as defined in the IT01CF register (see SFR Definition 8.11).
Note that /INT0 and /INT0 Port pin assignments are independent of any Crossbar assignments. /INT0 and
/INT1 will monitor their assigned Port pins without disturbing the peripheral that was assigned the Port pin
via the Crossbar. To assign a Port pin only to /INT0 and/or /INT1, configure the Crossbar to skip the
selected pin(s). This is accomplished by setting the associated bit in register XBR0 (see Section
“13.1. Priority Crossbar Decoder” on page 131 for complete details on configuring the Crossbar).
IE0 (TCON.1) and IE1 (TCON.3) serve as the interrupt-pending flags for the /INT0 and /INT1 external
interrupts, respectively. If an /INT0 or /INT1 external interrupt is configured as edge-sensitive, the corre-
sponding interrup t-pendin g flag is automatica lly cleared by th e hardware whe n the CPU vectors to the ISR.
When configured as level sensitive, the interrupt-pending flag remains logic 1 while the input is active as
defined by the corresponding polarity bit (IN0PL or IN1PL); the flag remains logic 0 while the input is inac-
tive. The external interrupt source must hold the input active until the interrupt request is recognized. It
must then deactivate the interrupt request before execution of the ISR completes or another interrupt
request will be generated.
8.3.3. Interrupt Priorities
Each interrupt source can be in dividually pr og rammed to one of two priority levels: low or high. A low prior-
ity interrupt service routine can be pree mpted by a high priority interrupt. A high priority interrupt cannot b e
preempted. Each interrupt has an associated interrupt priority bit in an SFR (IP or EIP1) used to configure
its priority level. Low priority is the defa ult. If two interrupt s are recogn ized simulta neously, the interrupt with
the higher priority is serviced first. If both interrupts have the same priority level, a fixed priority order is
used to arbitrate, given in Table 8.4.
8.3.4. Interrupt Latency
Interrupt response time dep en ds on the state of the CPU when the interrupt occurs. Pending inter rupts are
sampled and priority decoded each system clock cycle. Therefore, the fastest possible response time is 5
system clock cycles: 1 clock cycle to detect the interrupt and 4 clock cycles to complete the LCALL to the
ISR. If an interrupt is pending when a RETI is executed, a single instruction is executed before an LCALL
is made to service t he pe ndin g inte rrupt. T her efor e, the maxim um res pons e time for an interru pt (wh en no
other interrupt is currently being serviced or the ne w interrupt is of greater priority) occurs when the CPU is
performing an RETI instruction followed by a DIV as the next instruction. In this case, the response time is
18 system clock cycles: 1 clock cycle to detect the interrupt, 5 clock cycles to execute the RETI, 8 clock
cycles to complete the DIV instruction and 4 clock cycles to execute the LCALL to the ISR. If the CPU is
executing an ISR for an interrupt with equal or higher priority, the new interrupt will not be serviced until the
current ISR completes, including the RETI and following instruction.
IT0 IN0PL /INT0 Interrupt IT1 IN1PL /INT1 Interrupt
10 10
11 11
00 00
01 01
Table 8.4. Interrupt Summary
Reset 0x0000 Top None N/A N/A Always
Enabled Always
Highest
External Interrupt 0 (/INT0) 0x0003 0IE0 (TCON.1) Y Y EX0 (IE.0) PX0 (IP.0)
Timer 0 Overflow 0x000B 1TF0 (TCON.5) Y Y ET0 (IE.1) PT0 (IP.1)
External Interrupt 1 (/INT1) 0x0013 2IE1 (TCON.3) Y Y EX1 (IE.2) PX1 (IP.2)
Timer 1 Overflow 0x001B 3TF1 (TCON.7) Y Y ET1 (IE.3) PT1 (IP.3)
UART0 0x0023 4RI0 (SCON0.0)
TI0 (SCON0.1) Y N ES0 (IE.4) PS0 (IP.4)
Timer 2 Overflow 0x002B 5TF2H (TMR2CN.7)
TF2L (TMR2CN.6) Y N ET2 (IE.5) PT2 (IP.5)
SPI0 0x0033 6
SPIF (SPI0CN.7)
WCOL (SPI0CN.6)
MODF (SPI0CN.5)
RXOVRN
(SPI0CN.4)
Y N ESPI0
(IE.6)PSPI0
(IP.6)
SMB0 0x003B 7SI (SMB0CN.0) Y N ESMB0
(EIE1.0) PSMB0
(EIP1.0)
RESERVED 0x0043 8 N/A N/A N/A N/A N/A
ADC0 Window Compare 0x004B 9AD0WINT
(ADC0CN.3) Y N EWADC0
(EIE1.2) PWADC0
(EIP1.2)
ADC0 Conversion
Complete 0x0053 10 AD0INT
(ADC0CN.5) Y N EADC0
(EIE1.3) PADC0
(EIP1.3)
Programmab l e Co unte r
Array 0x005B 11 CF (PCA0CN.7)
CCFn (PCA0CN.n) Y N EPCA0
(EIE1.4) PPCA0
(EIP1.4)
Comparator0 0x0063 12
CP0FIF
(CPT0CN.4)
CP0RIF
(CPT0CN.5)
N N ECP0
(EIE1.5) PCP0
(EIP1.5)
Comparator1 0x006B 13
CP1FIF
(CPT1CN.4)
CP1RIF
(CPT1CN.5)
N N ECP1
(EIE1.6) PCP1
(EIP1.6)
Timer 3 Overflow 0x0073 14 TF3H (TMR3CN.7)
TF3L (TMR3CN.6) N N ET3
(EIE1.7) PT3
(EIP1.7)
C8051F310/1/2/3/4/5/6/7
96 Rev. 1.7
Interrupt Source Interrupt
Vector Priority
Order Pending Flag
Bit addressable?
Cleared by HW?
Enable
Flag Priority
Control
Rev. 1.7 97
C8051F310/1/2/3/4/5/6/7
8.3.5. Interrupt Register Descriptions
The SFRs used to enable th e inte rrupt sources an d set their priori ty level ar e descr ibed be low. Refer to the
data sheet section associated with a particular on-chip peripheral for information regarding valid interrupt
conditions for th e pe rip her al an d th e be ha vio r of its interrupt-p end ing flag (s) .
SFR Definition 8.7. IE: Interrupt Enable
Bit7: EA: Enable All Interrupts.
This bit globally enables/disables all interrupts. It overrides the individual interrupt mask set-
tings.
0: Disable all interrupt sources.
1: Enable each interrupt according to its individual mask setting.
Bit6: ESPI0: Enable Serial Peripheral Interface (SPI0) Interrupt.
This bit sets the masking of the SPI0 interrupts.
0: Disable all SPI0 interrupts.
1: Enable interrupt requests generated by SPI0.
Bit5: ET2: Enable Timer 2 Interrupt.
This bit sets the masking of the Timer 2 interrupt.
0: Disable Timer 2 interrupt.
1: Enable interrupt requests generated by the TF2L or TF2H flags.
Bit4: ES0: Enable UART0 Interrupt.
This bit sets the masking of the UART0 interrupt.
0: Disable UART0 interrupt.
1: Enable UART0 interrupt.
Bit3: ET1: Enable Timer 1 Interrupt.
This bit sets the masking of the Timer 1 interrupt.
0: Disable all Timer 1 interrupt.
1: Enable interrupt requests generated by the TF1 flag.
Bit2: EX1: Enable External Interrupt 1.
This bit sets the masking of External Interrupt 1.
0: Disable extern al inte r ru pt 1.
1: Enable interrupt requests generated by the /INT1 input.
Bit1: ET0: Enable Timer 0 Interrupt.
This bit sets the masking of the Timer 0 interrupt.
0: Disable all Timer 0 interrupt.
1: Enable interrupt requests generated by the TF0 flag.
Bit0: EX0: Enable External Interrupt 0.
This bit sets the masking of External Interrupt 0.
0: Disable extern al inte r ru pt 0.
1: Enable interrupt requests generated by the /INT0 input.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
EA ESPI0 ET2 ES0 ET1 EX1 ET0 EX0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xA8
C8051F310/1/2/3/4/5/6/7
98 Rev. 1.7
SFR Definition 8.8. IP: Interrupt Priority
Bit7: UNUSED. Read = 1, Write = don't care.
Bit6: PSPI0: Serial Peripheral Interface (SPI0) Interrupt Priority Control.
This bit sets the priority of the SPI0 interrupt.
0: SPI0 interrupt set to low priority level.
1: SPI0 interrupt set to high priority level.
Bit5: PT2: Timer 2 Interrupt Priority Control.
This bit sets the priority of the Timer 2 interrupt.
0: Ti me r 2 int erru pts set to low priority level.
1: Timer 2 int errupts set to high priority level.
Bit4: PS0: UART0 Interrupt Priority Control.
This bit sets the priority of the UART0 interrupt.
0: UART0 interrupts set to low priority level.
1: UART0 interrupts set to high priority level.
Bit3: PT1: Timer 1 Interrupt Priority Control.
This bit sets the priority of the Timer 1 interrupt.
0: Ti me r 1 int erru pts set to low priority level.
1: Timer 1 int errupts set to high priority level.
Bit2: PX1: External Interrupt 1 Priority Control.
This bit sets the priority of the External Interrupt 1 interrupt.
0: External Interrupt 1 set to low priority level.
1: External Interrupt 1 set to high priority level.
Bit1: PT0: Timer 0 Interrupt Priority Control.
This bit sets the priority of the Timer 0 interrupt.
0: Ti me r 0 int erru pt set to low priority level.
1: Ti me r 0 int erru pt set to high priority level.
Bit0: PX0: External Interrupt 0 Priority Control.
This bit sets the priority of the External Interrupt 0 interrupt.
0: External Interrupt 0 set to low priority level.
1: External Interrupt 0 set to high priority level.
R/W R/W R/W R/W R/W R/W R/W R/W R eset Value
- PSPI0 PT2 PS0 PT1 PX1 PT0 PX0 10000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xB8
Rev. 1.7 99
C8051F310/1/2/3/4/5/6/7
SFR Definition 8.9. EIE1: Extended Interrupt Enable 1
Bit7: ET3: Enable Timer 3 Interrupt.
This bit sets the masking of the Timer 3 interrupt.
0: Disable Timer 3 interrupts.
1: Enable interrupt requests generated by the TF3L or TF3H flags.
Bit6: ECP1: Enable Comparator1 (CP1) Interrupt.
This bit sets the masking of the CP1 interrupt.
0: Disable CP1 interrupts.
1: Enable interrupt requests generated by the CP1RIF or CP1FIF flags.
Bit5: ECP0: Enable Comparator0 (CP0) Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 interrupts.
1: Enable interrupt requests generated by the CP0RIF or CP0FIF flags.
Bit4: EPCA0: Enable Programmable Counter Array (PCA0) Interrupt.
This bit sets the masking of the PCA0 interrupts.
0: Disable all PCA0 interrupts.
1: Enable interrupt requests generated by PCA0.
Bit3: EADC0: Enable ADC0 Conversion Complete Interrupt.
This bit sets the masking of the ADC0 Conversion Complete interrupt.
0: Disable ADC0 Conversion Complete interrupt.
1: Enable interrupt requests generated by the AD0INT flag.
Bit2: EWADC0: Enable Window Comparison ADC0 Interrupt.
This bit sets the masking of ADC0 Window Comparison interrupt.
0: Disable ADC0 Window Comparison interrupt.
1: Enable interrupt requests generated by ADC0 Window Compare flag (AD0WINT).
Bit1: RESERVED. Read = 0. Must Write 0.
Bit0: ESMB0: Enable SMBus (SMB0) Interrupt.
This bit sets the masking of the SMB0 interrupt.
0: Disable all SMB0 interrupts.
1: Enable interrupt requests generated by SMB0.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
ET3 ECP1 ECP0 EPCA0 EADC0 EWADC0 Reserved ESMB0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xE6
C8051F310/1/2/3/4/5/6/7
100 Rev. 1.7
SFR Definition 8.10. EIP1: Extended Interrupt Priority 1
Bit7: PT3: Timer 3 Interrupt Priority Control.
This bit sets the priority of the Timer 3 interrupt.
0: Timer 3 interrupts set to low priority level.
1: Timer 3 interrupts set to high priority level.
Bit6: PCP1: Comparator1 (CP1) Interrupt Priority Control.
This bit sets the priority of the CP1 interrupt.
0: CP1 interrupt set to low priority level.
1: CP1 interrupt set to high priority level.
Bit5: PCP0: Comparator0 (CP0) Interrupt Priority Control.
This bit sets the priority of the CP0 interrupt.
0: CP0 interrupt set to low priority level.
1: CP0 interrupt set to high priority level.
Bit4: PPCA0: Programmable Counter Array (PCA0) Interrupt Priority Control.
This bit sets the priority of the PCA0 interrupt.
0: PCA0 interrupt set to low priority lev el.
1: PCA0 interrupt set to high priority level.
Bit3: PADC0 ADC0 Conversion Complete Interrupt Priority Control.
This bit sets the priority of the ADC0 Conversion Complete interrupt.
0: ADC0 Conversion Complete interrupt set to low priority level.
1: ADC0 Conversion Complete interrupt set to high priority level.
Bit2: PWADC0: ADC0 Window Comparator Interrupt Priority Control.
This bit sets the priority of the ADC0 Window interrupt.
0: ADC0 Window interrupt set to low priority level.
1: ADC0 Window interrupt set to high priority level.
Bit1: RESERVED. Read = 0. Must Write 0.
Bit0: PSMB0: SMBus (SMB0) Interrupt Priority Control.
This bit sets the priority of the SMB0 interrupt.
0: SMB0 interrupt set to low priority level.
1: SMB0 interrupt set to high priority level.
R/W R/W R/W R/W R/W R/W R/W R/W R eset Value
PT3 PCP1 PCP0 PCP0 PADC0 PWADC0 Reserved PSMB0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xF6
Rev. 1.7 101
C8051F310/1/2/3/4/5/6/7
SFR Definition 8.11. IT01CF: INT0/INT1 Configuration
Bit7: IN1PL: /INT1 Polarity
0: /INT1 input is active low.
1: /INT1 input is active high.
Bits6–4: IN1SL2–0: /INT1 Port Pin Selection Bits
These bits select which Port pin is assigned to /INT1. Note that this pin assignment is inde-
pendent of the Crossbar; /INT1 will monitor the assigned Port pin without disturbing the
peripheral that has been assigned the Port pin via the Crossbar. The Crossbar will not
assign the Port pin to a pe ripheral if it is configu red to skip the selected pin (accomplished by
setting to ‘1’ the corresponding bit in register P0SKIP).
Bit3: IN0PL: /INT0 Polarity
0: /INT0 interrupt is active low.
1: /INT0 interrupt is active high.
Bits2–0: INT0SL2–0: /INT0 Port Pin Selection Bits
These bits select which Port pin is assigned to /INT0. Note that this pin assignment is inde-
pendent of the Crossbar. /INT0 will monitor the assigned Port pin without disturbing the
peripheral that has been assigned the Port pin via the Crossbar. The Crossbar will not
assign the Port pin to a pe ripheral if it is configu red to skip the selected pin (accomplished by
setting to ‘1’ the corresponding bit in register P0SKIP).
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
IN1PL IN1SL2 IN1SL1 IN1SL0 IN0PL IN0SL2 IN0SL1 IN0SL0 00000001
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xE4
Note: Refer to SFR Definition 17.1 for INT0/1 edge- or level-sensitive interrupt selection.
IN1SL2–0 /INT1 Port Pin
000 P0.0
001 P0.1
010 P0.2
011 P0.3
100 P0.4
101 P0.5
110 P0.6
111 P0.7
IN0SL2–0 /INT0 Port Pin
000 P0.0
001 P0.1
010 P0.2
011 P0.3
100 P0.4
101 P0.5
110 P0.6
111 P0.7
C8051F310/1/2/3/4/5/6/7
102 Rev. 1.7
8.4. Power Management Modes
The CIP-51 core has two software programmable power management modes: Idle and Stop. Idle mode
halts the CPU while leaving the peripherals and clocks active. In Stop mode, the CPU is halted, all inter-
rupts and timers (except the Missing Clock Detector) are inactive, and the internal oscillator is stopped
(analog peripherals remain in their selected states; the external oscillator is not effected). Since clocks are
running in Idle mode, power consumption is dependent upon the system clock frequency and the number
of peripherals left in active mode before entering Idle. Stop mode consumes the least power. SFR Defini-
tion 8.12 describes the Power Control Register (PCON) used to control the CIP-51's power management
modes.
Although the CIP-51 has Idle and Stop modes built in (as with any standard 8051 architecture), power
management of the entire MCU is better accomplished by enabling/disabling individual peripherals as
needed. Each analog peripheral can be disabled when not in use and placed in low power mode. Digital
peripherals, such as timers or serial buses, d raw little power wh en they are not in use. T urning of f the oscil -
lators lowers power consumption considerably; however, a reset is required to restart the MCU.
8.4.1. Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the CIP-51 to halt the CPU and enter Idle mode as soon
as the instruction that sets the bit completes execution. All internal registers and memory maintain their
original data. All analog and digital peripherals can remain active during Idle mode.
Idle mode is terminated when an enabled interrupt is asserted or a reset occurs. The assertion of an
enabled interrupt will cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume
operation. The pending interrupt will be serviced and the next instruction to be executed after the return
from interrupt (RETI) will be the instruction immediately following the one that set the Idle Mode Select bit.
If Idle mode is terminated by an internal or external reset, the CIP-51 performs a normal reset sequence
and begins program execution at address 0x0000.
If enabled, the Watchdog Timer (WDT) will eventually cause an internal watchdog reset and thereby termi-
nate the Idle mode. This featur e protect s the system from an unintended per manent sh ut down in the event
of an inadvertent write to the PCON register. If this behavior is not desired, the WDT may be disabled by
softwar e prior to en tering the Idle mo de if the WDT was initially configured to allow this operat ion. This pro-
vides the opportunity for additional power savings, allowing the system to remain in the Idle mode indefi-
nitely, waiting for an external stimulus to wake up the system. Refer to Section “9.6. PCA Watchdog
Timer Res et ” o n page 108 for more information on the use and configuration of the WDT.
Note: Any instruction that sets the IDLE bit should be immediately followed by an instruction that
has 2 or more opcode bytes. For exam ple:
// in 'C':
PCON |= 0x01; // set IDLE bit
PCON = PCON; // ... followed by a 3-cycle dummy instruction
; in assembly:
ORL PCON, #01h ; set IDLE bit
MOV PCON, PCON; ... followed by a 3-cycle dummy instruction
If the instruction following the write of the IDLE bit is a single -byte instruction and an interrupt occurs du ring
the execution phase of the instruction that sets the IDLE bit, the CPU may not wake from IDLE mode whe n
a future interrupt occurs.
Rev. 1.7 103
C8051F310/1/2/3/4/5/6/7
8.4.2. Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the CIP-51 to e nter Stop mode as so on as the in struc-
tion that sets the bit completes execution. In Stop mode the internal oscillator , CPU, and all digita l peripher-
als are stopped; the state of the external oscillator circuit is not affected. Each analog peripheral (including
the external oscillator circuit) may be shut down individually prior to entering Stop Mode. Stop mode can
only be terminated by an internal or external reset. On reset, the CIP-51 performs the normal reset
sequence and be gin s pr og ra m execution at address 0x0000.
If enabled, the Missing Clock Detector will cause an internal reset and thereby terminate the Stop mode.
The Missing Clock De tector sho uld be d isabled if the CPU is to be put to in ST OP mode fo r long er than th e
MCD timeout of 100 µsec.
SFR Definition 8.12.
Bits7–2: GF5–GF0: General Purpose Flags 5–0.
These are general purpose flags for use under software control.
Bit1: STOP: Stop Mode Select.
Setting this bit will place the CIP-51 in Stop mode. This bit will always be read as 0.
1: CPU goes into Stop mode (internal oscillator stopped).
Bit0: IDLE: Idle Mode Select.
Setting this bit will place the CIP-51 in Idle mode. This bit will always be read as 0.
1: CPU goes into Idle mode. (Shuts off clock to CPU, but clock to Timers, Interrupts, Serial
Ports, and Analog Peripherals are still active.)
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
GF5 GF4 GF3 GF2 GF1 GF0 STOP IDLE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x87
PCON: Power Control
C8051F310/1/2/3/4/5/6/7
104 Rev. 1.7
NOTES:
Rev. 1.7 105
C8051F310/1/2/3/4/5/6/7
9. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this
reset state, the following occur:
• CIP-51 halts program execution
• Special Function Registers (SFRs) are initialized to their defined reset values
• External Port pins are forced to a known state
• Interrupts and timers are disabled.
All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal
data memory are unaffected during a reset; any previously stored data is preserved. However, since the
stack pointer SFR is reset, the stack is effectively lost, even though th e data on the stack is not altered.
The Port I/O latc hes are reset to 0xFF (all lo gic ones ) in open -drain m ode. Weak pullups are en abled d ur-
ing and after the reset. For VDD Monitor and power-on resets, the RST pin is driven low until the device
exits the reset state.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the inter-
nal oscillator. Refer to Section “12. Oscillators” on page 121 for information on selecting an d configuring
the system clock source. The Watchdog Timer is enabled with the system clock divided by 12 as its clock
source (Section “18.3. Watchdog Timer Mode” on page 212 details the use of the Watchdog Timer).
Program execution begins at location 0x0000.
PCA
WDT
Missing
Clock
Detector
(one-
shot) (Software Reset)
System Reset
Reset
Funnel
Px.x
Px.x
EN
SWRSF
System
Clock
CIP-51
Microcontroller
Core
Extended Interrupt
Handler
EN
WDT
Enable
MCD
Enable
Errant
FLASH
Operation
/RST
(wired-OR)
Power On
Reset
'0'
+
-
Comparator 0
C0RSEF
VDD
+
-
Supply
Monitor
Enable
Figure 9.1. Reset Sources
C8051F310/1/2/3/4/5/6/7
106 Rev. 1.7
9.1. Power-On Reset
During power-up, the device is held in a reset state and the RST pin is driven low until VDD settles above
VRST. An additional delay occurs before the device is released fr om reset; the delay decreases as the VDD
ramp time increases (VDD ramp time is defined as how fast VDD ramps from 0 V to VRST). Figure 9.2. plots
the power-on and VDD monitor reset timing. For valid ramp times (less than 1 ms), the power-on reset
delay (TPORDelay) is typically less than 0.3 ms.
Note: The maximum VDD ramp time is 1 ms; slower ramp times may cause the device to be released from
reset before VDD reaches the VRST level.
On exit from a power-on reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1. When PORSF is
set, all of the other reset flags in the RSTSRC Register are indeterminate (PORSF is cleared by all other
resets). Since all resets cause program execution to begin at the same location (0x0000) software can
read the PORSF flag to deter mine if a powe r- up was the cause of reset. The co nten t of inter nal da ta mem-
ory should be assumed to be undefined after a power-on reset. The VDD monitor is disabled following a
power-on reset.
Power-On
Reset
VDD
Monitor
Reset
/RST
t
volts
1.0
2.0
Logic HIGH
Logic LOW T
PORDelay
VDD
2.70
2.55
V
RST
VDD
Figure 9.2. Power-On and VDD Monitor Reset Timing
9.2. Power-Fail Reset / VDD Monitor
When a power-down transition or power irregularity causes VDD to drop below VRST, the power supply
monitor will drive the RST pin low and hold the CIP-51 in a reset state (see Figure 9.2). When VDD returns
to a level above VRST, the CIP-51 will be released from the reset state. Note that even though internal data
memory content s a re no t altered by the power -fail reset, it is impossible to determine if VDD dropped below
the level required for data retention. If the PORSF flag reads ‘1’, the data may no longer be valid. The VDD
monitor is disabled after power-on resets; however its defined state (enabled/disabled) is not altered by
Rev. 1.7 107
C8051F310/1/2/3/4/5/6/7
any other re set source. F or examp le, if th e VDD monitor is enabled and a software reset is performed, the
VDD monitor will still be enabled after the reset.
Important Note: The VDD monitor must be enabled before it is selected as a reset source. Selecting the
VDD monitor as a reset source before it is enabled and stabilized may cause a system reset. The proce-
dure for configuring the VDD monitor as a reset source is shown below:
Step 1. Enable the VDD monitor (VDMEN bit in VDM0CN = ‘1’).
Step 2. Wait for the VDD monitor to stabilize (see Table 9.1 for the VDD Monitor turn-on time).
Note: This delay should be omitted if software contains routines that erase or write Flash
memory.
Step 3. Select the VDD monitor as a reset source (PORSF bit in RSTSRC = ‘1’).
See Figure 9.2 for VDD monitor tim ing; note that the r eset delay is not incur red after a VDD monitor reset.
See Table 9.1 for complete electrical characteristics of the VDD monitor.
SFR Definition 9.1. VDM0CN: VDD Monitor Control
Bit7: VDMEN: VDD Monitor Enable.
This bit is turns the VDD monitor circuit on/off. The VDD Monitor cannot generate system
resets until it is also selected as a reset source in register RSTSRC (Figure 9.2). The VDD
Monitor must be allowed to stabilize before it is selected as a reset source. Selecting the
VDD monitor as a reset source bef ore it has stabilized may generate a system reset.
See Table 9.1 for the minimum VDD Monitor turn-on time.
0: VDD Monitor Disabled.
1: VDD Monitor Enabled.
Bit6: VDD STAT: VDD Status.
This bit indicates the current power supply status (VDD Monitor output).
0: VDD is at or below the VDD monitor threshold.
1: VDD is above the VDD monitor threshold.
Bits5–0: Reserved. Read = Variable. Write = don’t care.
R/W R R R R R R R Reset Value
VDMEN VDDSTAT Reserved Reserved Reserved Reserved Reserved Reserved Variable
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xFF
9.3. External Reset
The extern al RST pin provides a means for external circuitry to force the device into a reset state. Assert-
ing an active-low signal on the RST pin g enera tes a reset; a n externa l pullu p and/or decoup ling of the RST
pin may be necessary to avoid erroneous noise-induced resets. See Table 9.1 for complete RST pin spec-
ifications. The PINRSF flag (RSTSRC.0) is set on exit from an external reset.
C8051F310/1/2/3/4/5/6/7
108 Rev. 1.7
9.4. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is t riggered by the s yst em clock . If the syst em
clock remains high or low for more than 100 µs, the one-shot will time out and generate a reset. After a
MCD reset, the MCDRSF flag (RSTSRC.2) will read ‘1’, signifying the MCD as the reset source; otherwise,
this bit reads ‘0’. Writing a ‘1’ to the MCDRSF bit enables the Missing Clock Detector; writing a ‘0’ disables
it. The state of the RST pin is unaffected by this reset.
9.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a ‘1’ to the C0RSEF flag (RSTSRC.5).
Comparator0 should be enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on
chatter on the output from generating an unwanted reset. The Comparator 0 reset is active- low: if t he non-
inverting input voltage (on CP0+) is less than the inverting input voltage (on CP0-), the device is put into
the reset state. After a Comparator0 reset, the C0RSEF flag (RSTSRC.5) will read ‘1’ signifying
Comparator0 as the reset source; otherwise, this bit reads ‘0’. The state of the RST pin is unaffected by
this reset.
9.6. PCA Watchdog Timer Reset
The programmable Watchdog Timer (WDT) function of the Programmable Counter Array (PCA) can be
used to prevent software from running out of control during a system malfunction. The PCA WDT function
can be enabled or disabled by software as described in Section “18.3. Watchdog Timer Mode” on
page 212; the WDT is enabled and clocked by SYSCLK / 12 following any reset. If a system malfunction
prevents user software from updating the WDT, a reset is generated and the WDTRSF bit (RSTSRC.5) is
set to ‘1’. The state of the RST pin is unaf fected by this reset.
9.7. Flash Error Reset
If a Flash read/write/erase or program read targets an illegal address, a system reset is generated. This
may occur due to any of the fo llowing:
• A Flash write or erase is attempted a bove user code sp ace. This occurs when PSWE is set to ‘1’ and a
MOVX write operation targets an ad dress above address 0x3DFF for C8051F310/1 or 0x1FFF for
C8051F312/3/4/5.
• A Flash read is attempted above user code space. This occurs when a MOVC operation targets an
address above address 0x3DFF for C8051F310/1 or 0x1FFF for C8051F312/3/4/5.
• A Program read is attemp ted ab ove user code sp ac e. This occurs wh en user code attemp t s to branch
to an address above 0x3DFF for C8051F310/1 or 0x1FFF for C8051F312/3/4/5.
• A Flash read, write or erase attempt is restricted due to a Flash security setting (see Section
“10.3. Security Options” on page 113).
The FERROR bit (RSTSRC.6) is set following a Flash error reset. The st ate of the RST p in is unaf fected by
this reset.
9.8. Software Reset
Software may force a reset by writing a ‘1’ to the SWRSF bit (RSTSRC.4). The SWRSF bit will read ‘1’ fol-
lowing a software forced reset. The state of the RST pin is unaffected by this reset.
Rev. 1.7 109
C8051F310/1/2/3/4/5/6/7
SFR Definition 9.2. RSTSRC: Reset Source
Bit7: UNUSED. Read = 0. Write = don’t care.
Bit6: FERROR: Flash Error Indicator.
0: Source of last reset was not a Flash read/write/erase error.
1: Source of last reset was a Flash read/write/erase error.
Bit5: C0RSEF: Comparator0 Reset Enable and Flag.
0: Read: Source of last reset was not Comparator0. Write: Comparator0 is not a reset
source.
1: Read: Source of last reset was Comparator0. Write: Comparator0 is a reset source
(active-low).
Bit4: SWRSF: Software Reset Force and Flag.
0: Read: Source of last reset was not a write to the SWRSF bit. Write: No Effect.
1: Read: Source of last was a write to the SWRSF bit. Write: Forces a system reset.
Bit3: WDTRSF: Watchdog Timer Reset Flag.
0: Source of last reset was not a WDT timeout.
1: Source of last reset was a WDT timeout.
Bit2: MCDRSF: Missing Clock Detector Flag.
0: Read: Source of last reset was not a Missing Clock Detector timeout. Write: Missing
Clock Detector disabled.
1: Read: Source of last reset was a Missing Clock Detector timeout. Write: Missing Clock
Detector enable d; trigg e rs a re se t if a missing clock condition is detected.
Bit1: PORSF: Power-On Reset Force and Flag.
This bit is set anytime a power-on reset occurs. Writing this bit enables/disables the VDD
monitor as a rese t sour ce. Note: writing ‘1’ to this bit before the VDD monitor is e nabled
and stabilized may cause a system reset. See register VDM0CN (Figure 9.1)
0: Read: Last reset was not a power-on or VDD monitor reset. Write: VDD monitor is not a
reset source.
1: Read: Last reset was a power-on or VDD monitor reset; all other reset flags indeterminate.
Write: VDD monitor is a reset source.
Bit0: PINRSF: HW Pin Reset Flag.
0: Source of last reset was not RST pin.
1: Source of last reset was RST pin.
Note: For bits that act as both reset source enables (on a write) and reset indicato r flags (on a read),
read-modify-write instructions read and modify the source enable only. This applies to bits:
C0RSEF, SWRSF, MCDRSF, PORSF.
R R R/W R/W R R/W R/W R Reset Value
- FERROR C0RSEF SWRSF WDTRSF MCDRSF PORSF PINRSF Variable
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xEF
Table 9.1. Reset Electrical Characteristics
–40 to +85 °C unless otherwise specified.
C8051F310/1/2/3/4/5/6/7
110 Rev. 1.7
Parameter Conditions Min Typ Max Units
RST Output Low Voltage IOL = 8.5 mA, VDD = 2.7 to 3.6 V ——0.6 V
RST Input High Voltage 0.7 x
VDD —— V
RST Input Low Voltage — — 0.3 x
VDD
RST Input Pullup Current RST = 0.0 V — 25 40 µA
VDD Monitor Threshold (VRST)2.40 2.55 2.70 V
Missing Clock Detector Timeout T ime from last system clock rising
edge to reset initiation 100 220 600 µs
Reset Time Delay Delay between release of any
reset source and code execution
at location 0x0000 5.0 — — µs
Minimum RST Low Time to
Generate a System Reset 15 — — µs
VDD Monitor Turn-on Tim e 100 — — µs
VDD Monitor Supply Current —2050 µA
VDD Ramp Time VDD = 0 V to VDD = 2.7 V —— 1 ms
Rev. 1.7 111
C8051F310/1/2/3/4/5/6/7
10. Flash Memory
On-chip, re-programmable Flash memory is included for program code and non-vola tile data storage. The
Flash memory can be programmed in-system, a single byte at a time, through the C2 interface or by soft-
ware using the MOVX instru ction . On ce clear ed to lo gic 0, a Flash bit must be erased to set it back to logic
1. Flash bytes would typically be erased (set to 0xFF) before being reprogrammed. The write and erase
operations are automatically timed by hardware for pr oper execution; data polling to determine the end of
the write/erase operation is not required. Code execution is stalled during a Flash write/erase operation.
Refer to Table 10.1 for complete Flash memory electrical characteristics.
10.1. Programming The Flash Memory
The simplest means of programming the Flash memory is through the C2 interface using programming
tools provided by Silicon Labs or a third party vendor. This is the only means for programming a non-initial-
ized device. For details on the C2 commands to program Flash memory, see Section “20. C2 Interface”
on page 223.
To ensure the integrity of Flash contents, it is strongly recommended that the on-chip VDD Monitor
be enabled in any system that includes code that writes and/or erases Flash memory from soft-
ware.
10.1.1. Flash Lock and Key Functions
Flash writes and erases by user software are protected with a lock and key function. The Flash Lock and
Key Register (FLKEY) must be written with the correct key codes, in sequence, before Flash operations
may be performed. The key codes are: 0xA5, 0xF1. The timing does not matter, but the codes must be
written in order. If the key codes are written out of order, or the wrong codes are written, Flash writes and
erases will be disabled until the next system reset. Flash writes and erases will also be disabled if a Flash
write or erase is attempted before the key codes have been written properly. The Flash lock resets after
each write or erase; the key codes must be written again before a following Flash operation can be per-
formed. The FLKEY register is detailed in SFR Definition 10.2.
10.1.2. Flash Erase Procedure
The Flash memory can be programmed from software using the MOVX write instruction with the address
and data byte to be programmed provided as normal operands. Before writing to Flash memory using
MOVX, Flash write operations must be enabled by: (1) setting the PSWE Program Store Write Enable bit
(PSCTL.0) to logic 1 (this directs the MOVX writes to target Flash memory ); and (2) Writing the Flash ke y
codes in sequence to the Flash Lock register (FLKEY). The PSWE bit remains set until cleared by soft-
ware.
A write to Flash memory can clear bits to logic 0 but cannot set them; only an erase operation can set bits
to logic 1 in Flash. A byte loc ation to be programmed should be erased b efore a ne w value is written.
The Flash memory is organized in 512-byte pages. The erase operation applies to an entire page (setting
all bytes in the page to 0xFF). To erase an entire 512-byte page, perform the following steps:
Step 1. Disable interrupts (recommended).
Step 2. Set the PSEE bit (register PSCTL).
Step 3. Set the PSWE bit (register PSCTL).
Step 4. Write the first key code to FLKEY: 0xA5.
Step 5. Write th e second key code to FLKEY: 0xF1.
Step 6. Using the MOVX instruction, write a data byte to any location within the 512-byte page to
be erased.
C8051F310/1/2/3/4/5/6/7
112 Rev. 1.7
10.1.3. Flash Write Procedure
Flash bytes are programmed by software with the following sequence:
Step 1. Disable interrupts (recommended).
Step 2. Erase the 512-byte Flash page containing the target location, as described in Section
10.1.2.
Step 3. Set the PSWE bit (register PSCTL).
Step 4. Clear the PSEE bit (register PSCTL).
Step 5. Write the first key code to FLKEY: 0xA5.
Step 6. Write th e second key code to FLKEY: 0xF1.
Step 7. Using the MOVX instruction, write a single data byte to the desired location within the
512 byte sector.
Steps 5–7 must b e re pe at ed f or each b yt e t o be wr itte n . After F las h w rit es ar e co mp le te, PSWE should be
cleared so that MOVX instructions do not target program memory.
Table 10.1. Flash Electrical Characteristics
VDD = 2.7 to 3.6 V; –40 to +85 °C unless otherwise specified.
*Note: 5 12 bytes at locations 0x3E00 (C8051F310/1) are reserved.
10.2. Non-volatile Data Storage
The Flash memory can be used for non-volatile data storage as well as program code. This allows data
such as calibration coefficients to be calculated and stored at run time. Data is written using the MOVX
write instruction and read using the MOVC instruction. Note: MOVX read instru ctions always t a rget XRAM.
Parameter Conditions Min Typ Max Units
Flash Size C8051F310/1/6/7 16384* — — bytes
C8051F312/3/4/5 8192 — —
Endurance 20 k 100 k — Erase/Write
Erase Cycle Time 25 MHz System Clock 10 15 20 ms
Write Cycle Time 25 MHz System Clock 40 55 70 µs
Rev. 1.7 113
C8051F310/1/2/3/4/5/6/7
10.3. Security Options
The CIP-51 provides security options to protect the Flash memory from inadvertent modification by soft-
ware as well as to prevent the viewing of proprietary program code and constants. The Program Store
Write Enable (bit PSWE in register PSCTL) and the Program Store Erase Enable (bit PSEE in register
PSCTL) bits protect the Flash memory from accidental modification by software. PSWE must be explicitly
set to ‘1’ before software can modify the Flash memory; both PSWE and PSEE must be set to ‘1’ before
software can erase Flash memory. Additional security features prevent proprietary program code and data
constants from being read or altered across the C2 interface.
A Security Lock Byte located at the last byte of Flash user space offers protection of the Flash program
memory from access (read s, writes, or er ases) by unprotected code or the C2 interface. The Flash security
mechanism allows the user to lock n 512-byte Flash pages, starting at page 0 (addresses 0x0000 to
0x01FF), where n is the 1’s complement number represented by the Security Lock Byte. Note that the
page containing the Flash Security Lock Byte is unlocked when no other Flash pages are locked
(all bits of the Lock Byte are ‘1’) and locked when any other Flash pages are locked (any bit of the
Lock Byte is ‘0’). See the example below.
Access limit set
according to the
FLASH security lock
byte
C8051F310/1/6/7
0x0000
0x3DFF
Lock Byte
Reserved
0x3DFE
0x3E00
FLASH memory
organized in 512-byte
pages
0x3C00
Unlocked FLASH Pages
Locked when any
other FLA SH pa ge s
are locked
C8051F312/3/4/5
0x0000
0x1FFF
Lock Byte
Reserved
0x1FFE
0x2000
0x1E00
Unlocked FLASH Pages
Figure 10.1. Flash Program Memory Map
Security Lock Byte: 11111101b
1’s Complement: 00000010b
Flash pages locked: 3 (First two Flash pages + Lock Byte Page)
Addresses locked: 0x0000 to 0x03FF (first two Flash pages)
and 0x3C00 to 0x3DFF or 0x1E00 to 0x1FFF (Lock Byte Page)
C8051F310/1/2/3/4/5/6/7
114 Rev. 1.7
The level of Flash security depends on the Flash access method. The three Flash access methods that
can be restricted are reads, writes, and erases from the C2 debug interface, user firmware executing on
unlocked pages, and user firmware executin g on locked pages. Table 10.2 summarizes the Flash security
features of the C8051F31x devices.
Table 10.2. Flash Security Summary
Action C2 Debug
Interface User Firmware executing fro m:
an unlocked page a locked page
Read, Write or Erase unlocked pages
(except page with Lock Byte) Permitted Permitted Permitted
Read, Write or Erase locked pages
(except page with Lock Byte) Not Permitted Flash Error Reset Permitted
Read or Write page containing Lock Byte
(if no pages are locked) Permitted Permitted Permitted
Read or Write page containing Lock Byte
(if any page is locked) Not Permitted Flash Error Reset Permitted
Read contents of Lock Byte
(if no pages are locked) Permitted Permitted Permitted
Read contents of Lock Byte
(if any page is locked) Not Permitted Flash Error Reset Permitted
Erase page containing Lock Byte
(if no pages are locked) Permitted Flash Error Reset Flash Error Reset
Erase page containing Lock Byte - Unlock all
pages (if any page is locked) C2 Device
Erase Only Flash Error Reset Flash Error Reset
Lock additional pages
(change '1's to '0's in the Lock Byte) Not Permitted Flash Error Reset Flash Error Reset
Unlock individual pages
(change '0's to '1's in the Lock Byte) Not Permitted Flash Error Reset Flash Error Reset
Read, Write or Erase Reserved Area Not Permitted Flash Error Reset Flash Error Reset
C2 Device Erase - Erases all Flash pages including the page containing the Lock Byte.
Flash Error Reset - Not permitted; Causes Flash Error Device Reset (FERROR bit in RSTSRC is '1' after
reset).
- All prohibited operations that are performed via the C2 interface are ignored (do not cause device reset).
- Locking any Flash page also locks the page cont aining the Lock Byte.
- Once written to, the Lock Byte cannot be modified except by performing a C2 Device Erase.
- If user code writes to the Lock Byte, the Lock does not take effect until the next device reset.
Rev. 1.7 115
C8051F310/1/2/3/4/5/6/7
10.4. Flash Write and Erase Guidelines
Any system which contains routines which write or erase Flash memory from software involves some risk
that the write or erase routines will execute unintentionally if the CPU is operating outside its specified
operating ra nge of VDD, system clock frequency, or temperature. This accidental execution of Flash modi-
fying code can result in alteration of Flash memory contents causing a system failure that is only recover-
able by re-Flashing the code in the device.
The following guidelines are recommended for any system that contains routines which write or erase
Flash from code.
10.4.1. VDD Maintenance and the VDD Monitor
1. If the system power supply is subject to voltage or current "spikes," add sufficient transient
protection devices to the p ower supply to ensure that the supply voltages listed in the Absolute
Maximum Ratings table are not exceeded.
2. Make cert ain that th e minimum VDD rise time specification of 1 ms is met. If the system cannot
meet this rise time specification, then add an external VDD brownout circuit to the RST pin of
the device that holds the device in reset until VDD reaches 2.7 V and re-asserts RST if VDD
drops below 2.7 V.
3. Enable the on-chip VDD monitor and enable the VDD moni tor as a reset source as e arly in code
as possible. This should be the first set of instructions execute d af ter the Reset Vector. For 'C'-
based systems, this will involve modifying the startup code added by the 'C' compiler. See your
compiler documentation for more details. Make certain that there are no delays in software
between enabling the VDD monitor and enabling the VDD monitor as a reset source. Code
examples showing this can be found in "AN201: Writing to Flash from Firmware", available
from the Silicon Laboratories web site.
4. As an added precaution, explicitly enable the VDD monitor and enable the VDD monitor as a
reset source ins ide th e functions that w rite and er ase Flas h memo ry. The V DD monitor enable
instructions should be placed just after the instruction to set PSWE to a '1', but before the
Flash write or erase operation instruction.
5. Make certain that all writes to the RSTSRC (Reset Sources) register use direct assignment
operators and explicitly DO NOT use the bit-wise operators (such as AND or OR). For exam-
ple, "RSTSRC = 0x02" is correct. "RSTSRC |= 0x02" is incorrect.
6. Make certain that all writes to the RSTSRC register explicitly set the PORSF bit to a '1'. Areas
to check are initialization code which enables other reset sources, such as the Missing Clock
Detector or Comparator, for example, and instructions which force a Software Reset. A global
search on "RSTSRC" can quickly verify this.
10.4.2. PSWE Maintenance
7. Reduce the number of places in code where the PSWE bit (b0 in PSCTL) is set to a '1'. There
should be exactly one routine in code that set s PSWE to a '1' to write Flash bytes and one r ou-
tine in code that sets PSWE and PSEE both to a '1' to erase Flash pages.
8. Minimize the number of variable accesses while PSWE is set to a '1'. Handle pointer address
updates and loop variable maintenance outside the "PSWE = 1; ... PSWE = 0;" area. Code
examples showing this can be found in AN201, "Writing to Flash from Firmware", available
from the Silicon Laboratories web site.
9. Disable inte rr up ts prior to se tti ng PSWE to a '1' and leave them disabled until after PSWE has
been reset to '0'. Any interrupts posted during the Flash write or erase operation will be ser-
viced in priority order after the Flash operation has been completed and interrupts have been
re-enabled by software.
C8051F310/1/2/3/4/5/6/7
116 Rev. 1.7
10. Make certain that the Flash write and erase pointer variables are not located in XRAM. See
your compiler documentation for instructions regarding how to explicitly locate variables in dif-
ferent memory areas.
11. Add address bounds checking to the routines that write or erase Flash memory to ensure that
a routine called with an illegal address does not result in modification of the Flash.
10.4.3. System Clock
12. If operating from an external crystal, be advised that crystal performance is susceptible to
electrical interferen ce and is sensitive to layout and to changes in tem perature. If the syste m is
operating in an electrically noisy environment, use the internal oscillator or use an external
CMOS clock.
13. If operating from the external oscillator, switch to the internal oscillator during Flash write or
erase operations. The external oscillator can continue to run, and the CPU can switch back to
the external oscillator after the Flash operation has completed.
Additional Flash recomme nd ations a nd examp le co de ca n be fou nd in AN20 1, "Writing to Flash from Firm-
ware", available from the Silicon Laboratories web site.
SFR Definition 10.1. PSCTL: Program Store R/W Control
Bits7–2: UNUSED: Read = 000000b, Write = don’t care.
Bit1: PSEE: Program Store Erase Enable
Setting this bit (in combination with PSWE) allows an entire page of Flash program me mory
to be erased. If this bit is logic 1 and Flash writes are enabled (PSWE is logic 1), a write to
Flash memory using the MOVX instruction will erase the entire page that contains the loca-
tion addressed by the MOVX instruction. The value of the data byte written does not matter.
0: Flash program memory erasure disabled.
1: Flash program memory erasure enabled.
Bit0: PSWE: Program Store Write Enable
Setting this bit allows writing a byte of data to the Flash program memory using the MOVX
write instruction. The Flash location should be erased before writing data.
0: Writes to Flash program mem o ry disab le d.
1: Writes to Flash program mem o ry enable d ; the MOVX write instruction targets Flash
memory.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - - - - PSEE PSWE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x8F
Rev. 1.7 117
C8051F310/1/2/3/4/5/6/7
SFR Definition 10.2. FLKEY: Flash Lock and Key
Bits7–0: FLKEY: Flash Lock and Key Register
Write:
This register must be written to before Flash writes or erases can be performed. Flash
remains locked until this register is written to with the following key codes: 0xA5, 0xF1. The
timing of the writes does not matter , as long as the codes are written in order. The key codes
must be written for each Flash write or erase operation. Flash will be locked until the next
system reset if the wrong codes are written or if a Flash operation is attempted before the
codes have been written correctly.
Read:
When read, bits 1-0 indicate the current Flash lock state.
00: Flash is write/erase locked.
01: The first key code has been written (0xA5).
10: Flash is unlocked (writes/erases allowed).
11: Flash writes/erases disabled until the next rese t.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xB7
SFR Definition 10.3. FLSCL: Flash Scale
Bits7: FOSE: Flash One-shot Enable
This bit enables the Flash read one-shot. When the Flash one-shot disabled, the Flash
sense amps are enabled for a full clock cycle during Flash reads. At system clock frequen-
cies below 10 MHz, disabling the Flash one-shot will increase system power consumption.
0: Flash one-shot disabled.
1: Flash one-shot enabled.
Bits6–0: RESERVED. Read = 0. Must Write 0.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
FOSE Reserved Reserved Reserved Reserved Reserved Reserved Reserved 10000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xB6
C8051F310/1/2/3/4/5/6/7
118 Rev. 1.7
NOTES:
Rev. 1.7 119
C8051F310/1/2/3/4/5/6/7
11. External RAM
The C8051F31x devices include 1024 bytes of RAM mapped into the external data memory s pac e. All of
these address locations may be accessed using the external move instruction (MOVX) and the data
pointer (DPTR), or using MOVX indirect addressing mode. If the MOVX instruction is used with an 8-bit
address operand (such as @R1), then the high byte of the 16-bit address is provided by the External Mem-
ory Interface Control Register (EMI0CN as shown in SFR Definition 11.1). Note: the MOVX instruction is
also used for writes to the Flash memory. See Section “10. Flash Memory” on page 111 for details. The
MOVX instruction accesses XRAM by default.
For a 16-bit MOVX operation (@DPTR), the upper 6-bits of the 16-bit external data memory address word
are "don't cares.” As a result, the 1024 byte RAM is mapped modulo style over the entire 64 k external
data memory address range. For example, the XRAM byte at address 0x0000 is shadowed at addresses
0x0400, 0x0800, 0x0C00, 0x1000, etc. This is a useful feature when performing a linear memory fill, as the
address pointer doesn't have to be reset when reaching the RAM block boundary.
SFR Definition 11.1. EMI0CN: External Memory Interface Control
Bits 7–2: UNUSED. Read = 000000b. Write = don’t care.
Bits 1–0: PGSEL: XRAM Page Select.
The EMI0CN register provides the high byte of the 16-bit external data memory address
when using an 8-bit MOVX command, effectively selecting a 256-byte page of RAM. Since
the upper (unused) bits of the register are always zero, the PGSEL determines which page
of XRAM is accessed.
For Example: If EMI0CN = 0x01, addresses 0x0100 through 0x01FF will be accessed.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
PGSEL 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xAA
C8051F310/1/2/3/4/5/6/7
120 Rev. 1.7
NOTES:
Rev. 1.7 121
C8051F310/1/2/3/4/5/6/7
12. Oscillators
C8051F31x devices include a programmable internal oscillator and an external oscillator drive circuit. The
internal oscillator can be enabled/disabled and calibrated using the OSCICN and OSCICL registers, as
shown in Figure 12.1. The system c lock can be sourced by the ex ternal oscillator circuit, the internal oscil-
lator, or a scaled version of the internal oscillator. The internal oscillator's electrical specifications are given
in Table 12.1 on page 123.
OSC
Programmable
Internal Clock
Generator
Input
Circuit
EN
SYSCLK
n
OSCICL OSCICN
IOSCEN
IFRDY
IFCN1
IFCN0
XTAL1
XTAL2
Option 2
VDD
XTAL2
Option 1
10M
Option 3
XTAL2
Option 4
XTAL2
OSCXCN
XTLVLD
XOSCMD2
XOSCMD1
XOSCMD0
XFCN2
XFCN1
XFCN0
CLKSEL
CLKSL0
Figure 12.1. Oscillator Diagram
12.1. Programmable Internal Oscillator
All C8051F31x devices include a programmable internal oscillator that defaults as the system clock after a
system reset. The internal oscillator period can be programmed via the OSCICL register as defined by
SFR Definition 12.1 OSCICL is factor calibrated to obtain a 24.5 MHz frequency.
Electrical specifications for the precision internal oscillator are given in Table 12.1 on page 123. Note that
the system clock may be derived from the programmed internal oscillator divided by 1, 2, 4, or 8, as
defined by the IFCN bits in register OSCICN. The divide value defaults to 8 following a reset.
C8051F310/1/2/3/4/5/6/7
122 Rev. 1.7
SFR Definition 12.1. OSCICL: Internal Oscillator Calibration
Bit7: UNUSED. Read = 0. Write = don’t care.
Bits 6–0: OSCICL: Internal Oscillator Calibration Register.
This register determines the internal oscillator period. This reset value for OSCICL deter-
mines the oscillator base frequency. The reset value is factory calibrated to generate an
internal oscillator frequency of 24.5 MHz.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
Variable
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xB3
SFR Definition 12.2. OSCICN: Internal Oscillator Control
Bit7: IOSCEN: Internal Oscillator Enable Bit.
0: Internal Oscillator Disabled.
1: Internal Oscillator Enabled.
Bit6: IFRDY: Internal Oscillator Frequency Ready Flag.
0: Internal Oscillator is not running at programmed frequency.
1: Internal Oscillator is running at programmed frequency.
Bits5–2: UNUSED. Read = 0000b, Write = don't care.
Bits1–0: IFCN1-0: Internal Oscillator Frequency Control Bits.
00: SYSCLK derived from Internal Oscillator divided by 8.
01: SYSCLK derived from Internal Oscillator divided by 4.
10: SYSCLK derived from Internal Oscillator divided by 2.
11: SYSCLK derived from Internal Oscillator divided by 1.
R/W R R/W R/W R/W R/W R/W R/W R eset Value
IOSCEN IFRDY IFCN1 IFCN0 11000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xB2
Rev. 1.7 123
C8051F310/1/2/3/4/5/6/7
SFR Definition 12.3. CLKSEL: Clock Select
Bits7–1: Reserved. Read = 0000000b, Must Write = 0000000.
Bit0: CLKSL0: System Clock Source Select Bit.
0: SYSCLK derived from the Internal Oscillator, and scales per the IFCN bits in register
OSCICN.
1: SYSCLK derived from the External Oscillator circuit.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
Reserved Reserved Reserved Reserved Reserved Reserved Reserved CLKSL0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xA9
Table 12.1. Internal Oscillator Electrical Characteristics
VDD = 2.7 to 3.6 V; –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Internal Oscillator Frequency 24 24.5 25 MHz
Internal Oscillator Supply
Current (from VDD)OSCICN.7 = 1 — 450 1000 µA
C8051F310/1/2/3/4/5/6/7
124 Rev. 1.7
12.2. External Oscillator Drive Circuit
The external oscillator circuit may drive an external crystal, ceramic resonator, capacitor, or RC network. A
CMOS clock may also provide a clock input. For a crystal or ceramic resonator configuration, the crys-
tal/resonator must be wired across the XTAL1 and XTAL2 pins as shown in Option 1 of Figure 12.1. A
10 Mresistor also must be wired across the XTAL2 and XTAL1 pins for the crystal/resonator configura-
tion. In RC, capacitor, or CMOS c lock configuration, the clock source should be wired to the XTAL2 pin as
shown in Option 2, 3, or 4 of Figure 12.1. The type of external oscillator must be selected in the OSCX CN
register, and the frequency control bits (XFCN) must be selected appropriately (see SFR Definition 12.4).
Important Note on External Oscillator Usage: Port pins must be configured when using the external
oscillator circuit. When the external oscillator drive circuit is enabled in crystal/resonator mode, Port pins
P0.2 and P0.3 are used as XTAL1 and XTAL2 respectively. When the external oscillator drive circuit is
enabled in capacitor, RC, or CMOS clock mode, Port pin P0.3 is used as XTAL2. The Port I/O Crossbar
should be configured to skip the Port pins used by the oscillator circuit; see Section “13.1. Priority Cross-
bar Decoder” on page 131 for Crossbar configuration. Additionally, when using the external osc illator cir-
cuit in crystal/resonator, capacitor, or RC mode, the associated Port pins should be configured as anal og
inputs. In CMOS clock mode, the associated pin should be configured as a digital input. See Section
“13.2. Port I/O Initialization” on page 133 for details on Port input mode selection.
12.3. System Clock Selection
The CLKSL0 bit in register CLKSEL selects which oscillator is used as the system clock. CLKSL0 must be
set to ‘1’ for the system clock to run from the external oscillator; however the external oscillator may still
clock certain peripherals (timers, PCA) when the internal oscillator is selected as the system clock. The
system clock may be switched on-the-fly between the internal and external oscillator, so long as the
selected oscillator is enabled and has settled. The internal oscillator requires little st art-up time and may be
selected as the system clock immediately following the OSCICN write that enables the internal oscillator.
External crystals and ceramic resonators typically require a start-up time before they are settled an d ready
for use as the system clock. The Crystal Valid Flag (XTLVLD in register OSCXCN) is set to ‘1’ by hardware
when the external oscillator is settled. To avoid reading a false XTLVLD, in crystal mode software
should delay at least 1 ms between e nabling the external osci llator and c hecking XT LVLD. RC and
C modes typically require no startup time.
Rev. 1.7 125
C8051F310/1/2/3/4/5/6/7
SFR Definition 12.4. OSCXCN: External Oscillator Control
Bit7: XTLVLD: Crystal Oscillator Valid Flag.
(Read only when XOSCMD = 11x.)
0: Crystal Oscillator is unused or not yet stable.
1: Crystal Oscillator is running and stable.
Bits6–4: XOSCMD2-0: External Oscillator Mode Bits.
00x: External Oscillator circuit off.
010: External CMOS Clock Mode.
011: External CMOS Clock Mode with divide by 2 stage.
100: RC Oscillator Mode.
101: Capacitor Oscillator Mode.
110: Crystal Oscillator Mode.
111: Crystal Oscillator Mode with divide by 2 stage.
Bit3: RESERVED. Read = 0, Write = don't care.
Bits2–0: XFCN2-0: External Oscillator Frequency Control Bits.
000-111: See table below:
CRYSTAL MODE (Circuit from Figure 12.1, Option 1; XOSCMD = 11x)
Choose XFCN value to match crystal frequency.
RC MODE (Circuit from Figure 12.1, Option 2; XOSCMD = 10x)
Choose XFCN value to match frequency range:
f = 1.23(103) / (R x C), where
f = frequency of clock in MHz
C = capacitor value in pF
R = Pullup resistor value in k
C MODE (Circuit from Figure 12.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF / (C x VDD), where
f = frequency of clock in MHz
C = capacitor value the XTAL2 pin in pF
VDD = Power Supply on MCU in volts
R R/W R/W R/W R R/W R/W R/W Reset Value
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0 XFCN2 XFCN1 XFCN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xB1
XFCN Crystal (XOSCMD = 11x) RC (XOSCMD = 10x) C (XOSCMD = 10x)
000 f 32 kHz f 25 kHz K Factor = 0.87
001 32 kH z f 84 kHz 25 kHz f 50 kHz K Factor = 2.6
010 84 kHz f 225 kHz 50 kHz f 100 kHz K Factor = 7.7
011 225 kHz f 590 kHz 100 kHz f 200 kHz K Factor = 22
100 590 kHz f 1.5 MHz 200 kHz f 400 kHz K Factor = 65
101 1.5 MHz f 4 MHz 400 kHz f 800 kHz K Factor = 180
110 4 MHz f 10 MHz 800 kHz f 1.6 MHz K Factor = 664
111 10 MHz f 30 MHz 1.6 MHz f 3.2 MHz K Factor = 1590
C8051F310/1/2/3/4/5/6/7
126 Rev. 1.7
12.4. External Cryst al Example
If a crystal or ceramic resonator is used as an external oscillator source for the MCU, the circuit should be
configured as shown in Figure 12.1, Option 1. The External Oscillator Frequency Control value (XFCN)
should be chosen from the Crystal column of the table in SFR Definition 12.4. For example, an
11.0592 MHz crystal requires an XFCN setting of 111b.
When the crystal oscillator is first enabled, the oscillator amplitude detection circuit requires a s ettling time
to achieve proper bias. Introducing a delay of 1 ms between enabling the oscillator and checking the
XTLVLD bit will prevent a premature switch to the external oscillator as the system clock. Switc hing to the
external oscillator before the crystal oscillator has stabilized can result in unpredicta ble behavior. The rec-
ommended procedure is:
Step 1. Force the XTAL1 and XTAL2 pins low by writing 0s to the port latch.
Step 2. Configure XTAL1 and XTAL2 as analog inputs.
Step 3. Enable the external oscillator.
Step 4. Wait at least 1 ms.
Step 5. Poll for XTLVLD => '1'.
Step 6. Switch the system clock to the external oscillator.
Note: Tuning-fork crystals may require additional settling time before XTLVLD returns a valid result.
The capacitors shown in the external crystal configuration provide the load capacitance required by the
crystal for correct oscillation. These capacitors are "in series" as seen by the crystal and "in parallel" with
the stray capacitance of the XTAL1 an d XTAL2 pins.
Note: The load capacitance depends upon the crystal and the manufacturer. Please refer to the crystal
data sheet when completing these calculations.
For examp le, a tun ing-fo rk crystal of 32.7 68 kHz with a recommended load capacitance of 12.5 pF should
use the configuration shown in Figure 12.1, Option 1. The to tal val ue of the cap acitors and the stray capac-
itance of the XTAL pins shou ld equal 25 pF. Wit h a stray capacitance of 3 pF per pin, the 22 pF capacitors
yield an equivalent capacitance of 12.5 pF across the crystal, as shown in Figure 12.2.
22 pF
22 pF
32.768 kHz 10 M
XTAL1
XTAL2
Figure 12.2. 32.768 kHz External Crystal Example
Important Note on External Crystals: Crystal oscillator circuits are quite sensitive to PCB layout. The
crystal should be placed as close as possible to the XTAL pins on the device. The traces should be as
short as possible and shielded with ground plane from any other traces which could introduce noise or
interference.
Rev. 1.7 127
C8051F310/1/2/3/4/5/6/7
12.5. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circ uit should be configured as
shown in Figure 12.1, Option 2. The capacitor should be no greater than 100 pF; however, for very small
capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To deter-
mine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first
select the RC network value to produce the desired frequency of oscillation. If the frequency desired is
100 kHz, let R = 246 k and C = 50 pF:
f = 1.23( 103 ) / RC = 1.23 ( 103 ) / [ 246 x 50 ] = 0.1 MHz = 100 kHz
Referring to the table in SFR Definition 12.4, the required XFCN setting is 010b.
12.6. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 12.1, Option 3. The capacitor should be no greater than 100 pF; however for ve ry small capacitors,
the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the
required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, select the capaci-
tor to be used and find the frequency of oscillation from the equations below. Assume VDD = 3.0 V and
C = 50 pF:
f = KF / ( C x VDD ) = KF / ( 50 x 3 ) MHz
f = KF / 150 MHz
If a frequency of roughly 150 kHz is desired, select the K Factor from the table in SFR Definition 12.4 as
KF = 22:
f = 22 / 150 = 0.146 MHz, or 146 kHz
Therefore, the XFCN value to use in this example is 011b.
C8051F310/1/2/3/4/5/6/7
128 Rev. 1.7
NOTES:
Rev. 1.7 129
C8051F310/1/2/3/4/5/6/7
13. Port Input/Output
Digital and analog resources are available through 29 I/O pins (C8051F310/2/4), or 25 I/O pins
(C8051F311/3/5), or 21 I/O pins (C8051F316/7). Port pins are organized as three byte-wide Ports and one
5-bit-wide (C8051F310/2/4) or 1-bit-wide (C8051F311/3/5) Port. In the C8051F316/7, the port pins are
organized as one byte-wide Port, two 6-bit-wide Ports and one 1-bit-wide Port. Each of the Port pins can
be defined as general-purpose I/O (GPIO) or analog input; Port pins P0.0-P2.3 can be assigned to one of
the internal digital resources as shown in Figure 13.3. The designer has complete control over which func-
tions are assigned, limited on ly by the number of physical I/O pins. This resource assignment flexibility is
achieved through the use of a Priority Crossbar Decoder. The state of a Port I/O pin can always be read in
the corresponding Port latch, regardless of the Crossbar settings.
The Crossbar assigns the selected internal digital resources to the I/O pins based on the Priority Decoder
(Figure 13.3 and Figure 13.4). The registers XBR0 and XBR1, defined in SFR Definition 13.1 and SFR
Definition 13.2, are used to select internal digital functions.
All Port I/Os are 5 V tolerant (refer to Figure 13.2 for the Port cell circuit). The Por t I/O cells are c on fig ur ed
as either push-pull or open-drain in the Port Output Mode registers (PnMDOUT, where n = 0,1,2,3). Com-
plete Electrical Specifications for Port I/O are given in Table 13.1 on page 143.
XBR0, XBR1,
PnSKIP Registers
Digital
Crossbar
Priority
Decoder
2
P0.0
P0.7
PnMDOUT,
PnMDIN Registers
UART
(Internal Digital Signals)
Highest
Priority
Lowest
Priority
SYSCLK
2
SMBus
T0, T1 2
6
PCA
CP1
Outputs 2
4
SPI
CP0
Outputs 2P1.0
P1.7
P2.0
P2.7
P3.0
P3.4
(Port Latches)
P0 (P0.0-P0.7)
(P1.0-P1.7)
(P2.0-P2.3)
(P2.4-P2.7)
8
8
4
4
P1
P2
Notes:
1. P3.1-P3.4 only available on the
C8051F310/2/4
2. P1.6,P1.7,P2.6,P2.7 only available
on the C8051F310/1/2/3/4/5
(P3.0-P3.4)
5
P3
5
P2
I/O
Cells
P3
I/O
Cells
P1
I/O
Cells
P0
I/O
Cells
8
8
84
4
Figure 13.1. Port I/O Functional Block Diagram
GND
/PORT-OUTENABLE
PORT-OUTPUT
PUSH-PULL VDD VDD
/WEAK-PULLUP
(WEAK)
PORT
PAD
ANALOG INPUT
Analog Select
PORT-INPUT
C8051F310/1/2/3/4/5/6/7
130 Rev. 1.7
Figure 13.2. Port I/O Cell Block Diagram
Rev. 1.7 131
C8051F310/1/2/3/4/5/6/7
13.1. Priority Crossbar Decoder
The Priority Crossbar Decoder (Figure 13.3) assigns a priority to each I/O function, starting at the top with
UART0. When a digital resource is selected, the least-significant unassigned Port pin is assigned to that
resource (excluding UART0, which is always at pins 4 and 5). If a Port pin is assigned, the Crossbar skips
that pin when assigning the next selected resource. Additionally, the Crossbar will skip Port pins whose
associated bits in the PnSKIP registers are set. The PnSKIP registers allow software to skip Port pins that
are to be used for analog input, dedicated functions, or GPIO.
Important Note on Crossbar Configuration: If a Port pin is claimed by a peripheral without use of the
Crossbar, its corresponding PnSKIP bit should be set. This applies to P0.0 if VREF is used, P0.3 and/or
P0.2 if the external oscillator circuit is enabled, P0.6 if the ADC is configured to use the external conversion
start signal (CNVSTR), and any selected ADC or Comparator inputs. The Crossbar skips selected pins as
if they were already assigned, and moves to the next unassigned pin. Figure 13.3 shows the Crossbar
Decoder priority with no Port pins skipped (P0SKIP, P1SKIP, P2SKIP = 0x00); Figure 13.4 shows the
Crossbar Decoder priority with the XTAL1 (P0.2) and XTAL2 (P0.3) pins skipped (P0SKIP = 0x0C to skip
P0.2 and P0.3 for XTAL use).
Figure 13.3. Crossbar Priority Decoder with No Pins Skipped
VREF
XTAL1
XTAL2
CNVSTR
012345670123456701234567
SCK
MISO
MOSI
NSS*
CP0
CP0A
CP1
00000000000000000000
S pec i al F unction S i gnal s are not assigned by the Cros sbar. When t hese signals are enabled, the Crossbar mus t
be manual l y configured t o sk ip t hei r correspondi ng port pi ns.
P ort pi n pot entiall y avail abl e to peripheral
SF Signals
ECI
T0
T1
P0SKIP[0:7] P2SKIP[0:3]
Signals Unavailable
SF Signals
PIN I/O
TX0
RX0
SDA
SCL
P0 P2
CEX3
CEX4
P1SKIP[0:7]
P1
CP1A
CEX2
CEX0
CEX1
SYSCLK
*Note: NSS is only pinned out in 4-wire SPI mode.
Note: P1.6,P1.7,P2.6,P2.7 only available on the C8051F310/1/2/3/4/5; P1SKIP[7:6] should always be
set to 11b for the C8051F316/7 devices.
C8051F310/1/2/3/4/5/6/7
132 Rev. 1.7
Figure 13.4. Crossbar Priority Decoder with Crystal Pins Skipped
Registers XBR0 and XBR1 are used to assign the digital I/O resources to the physical I/O Port pins. Note
that when the SMBus is selected, the Crossbar assigns both pins associated with the SMBus (SDA and
SCL); when the UART is selected, the Crossbar assign s both pins associated with the UART (TX and RX).
UART0 pin assignments are fixed for bootloading purposes: UART TX0 is always assigned to P0.4; UART
RX0 is always assigned to P0.5. Standard Port I/Os appear contiguously after the prioritized functions
have been assigned.
Important Note: The SPI can be operated in either 3-wire or 4-wire modes, pending the state of the
NSSMD1-NSSMD0 bits in register SPI0CN. Accor ding to the SPI mode, the NSS signal may or may not be
routed to a Port pin.
VREF
XTAL1
XTAL2
CNVSTR
012345670123456701234567
SCK
MISO
MOSI
NSS*
CP0
CP0A
CP1
00110000000000000000
Si gnals Unavailable
CEX2
CEX0
CEX1
SYSCLK
P2
CP1A
CEX3
CEX4
SF Signa l s
PIN I/O
TX0
RX0
SDA
SCL
P0 P1
S pecial Fu nction S i gna ls are not assign ed by the Cros s b ar. When t hese s i gnal s are enable d, t h e Cros sbar must
be manuall y configured to s ki p t heir corres ponding port pi ns .
Port pi n potent i al ly avail able t o peripheral
SF Signa l s
ECI
T0
T1
P0SKIP[0:7] P2SKIP[0:3]P1SKIP[0:7]
*Note: NSS is only pin ned out in 4-wire SPI mode.
Note: P1.6,P1.7,P2.6,P2.7 only available on the C8051F310/1/2/3/4/5; P1SKIP[7:6] should always be set to
11b for the C8051F316/7 devices.
Rev. 1.7 133
C8051F310/1/2/3/4/5/6/7
13.2. Port I/O Initialization
Port I/O initialization consists of the following steps:
Step 1. Select the input mode (analog or digital) for all Port pins, using the Port Input Mode
register (PnMDIN).
Step 2. Select the output mode (open-drain or push-pull) for all Port pins, using the Port Output
Mode register (PnMDOUT).
Step 3. Select any pins to be skipped by the I/O Crossbar using the Por t Skip re gisters (PnSKIP).
Step 4. Assign Port pins to desired peripherals.
Step 5. Enable the Crossbar (XBARE = ‘1’).
All Port pins must be configured as either analog or digital inputs. Any pins to be us ed as Comparator or
ADC inputs should be configured as an analog inputs. When a pin is configured as an analog input, its
weak pullup, digita l driver, and digital receiver are disabled. This process saves power and reduces noise
on the analog input. Pins configured as digital inputs may still be used by analog peripherals; however this
practice is not recommended.
Additionally, all analog input pins should be configured to be skipped by the Crossbar (accomplished by
setting the associated bits in PnSKIP). Port input mode is set in the PnMDIN register, where a ‘1’ indicates
a digital inpu t, and a ‘0’ indicates an analog in put. All pins default to digital inputs on reset. See SFR Defini-
tion 13.4 for the PnMDIN register details.
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMD-
OUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is
required even for the digital resources selected in the XBRn registers, and is not automatic. The only
exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the
PnMDOUT settings. When the WEAKPUD bit in XBR1 is ‘0’, a weak pullup is enabled for all Port I/O con-
figured as open-drain. WEAKPUD does not affect the push-pull Port I/O. Furthermore, the weak pullup is
turned off on an output that is driving a ‘0’ to avoid unnecessary power dissipation.
Registers XBR0 and XBR1 must be loaded with the appropriate values to select the digital I/O functions
required by the design. Setting the XBARE bit in XBR1 to ‘1’ enables the Crossbar. Until the Crossbar is
enabled, the external pins remain as standard Port I/O (in input mode), regardless of the XBRn Register
settings. For given XBRn Register settings, one can determine the I/O pin-out using the Priority Decode
Table; as an alternative, the Configuration Wizard utility of the Silicon Labs IDE software will determine the
Port I/O pin-assignments based on the XBRn Register settings.
The Crossbar must be enabled to use Port pins as standard Port I/O in output mode. Port output
drivers are disabled while the Crossbar is disabled.
C8051F310/1/2/3/4/5/6/7
134 Rev. 1.7
SFR Definition 13.1. XBR0: Port I/O Crossbar Register 0
Bit7: CP1AE: Comparator1 Asynchronous Output Enable
0: Asynchronou s CP 1 unavailable at Port pin .
1: Asynchronous CP1 routed to Port pin.
Bit6: CP1E: Comparator1 Output Enable
0: CP1 unavailable at Port pin.
1: CP1 routed to Port pin.
Bit5: CP0AE: Comparator0 Asynchronous Output Enable
0: Asynchronou s CP 0 unavailable at Port pin .
1: Asynchronous CP0 routed to Port pin.
Bit4: CP0E: Comparator0 Output Enable
0: CP0 unavailable at Port pin.
1: CP0 routed to Port pin.
Bit3: SYSCKE: /SYSCLK Output Enable
0: /SYSCLK unavailable at Port pin.
1: /SYSCLK output routed to Port pin.
Bit2: SMB0E: SMBus I/O Enable
0: SMBus I/O unavailable at Port pins.
1: SMBus I/O routed to Port pins.
Bit1: SPI0E: SPI I/O Enable
0: SPI I/O unavailable at Port pins.
1: SPI I/O routed to Port pins.
Bit0: URT0E: UART I/O Output Enable
0: UART I/O unavailable at Port pin.
1: UART TX0, RX0 routed to Port pins P0.4 and P0.5.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CP1AE CP1E CP0AE CP0E SYSCKE SMB0E SPI0E URT0E 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xE1
Rev. 1.7 135
C8051F310/1/2/3/4/5/6/7
SFR Definition 13.2. XBR1: Port I/O Crossbar Register 1
13.3. General Purpose P ort I/O
Port pins that remain unassigned by the Crossbar and are not used by analog peripherals can be used for
general purpose I/O. Ports3-0 are accessed through corresponding special function registers (SFRs) that
are both byte addressable and bit addressable. When writing to a Port, the value written to the SFR is
latched to maint ain the ou tput dat a value at each pin. When reading, the logic levels of the Port's input pins
are returned regardless of the XBRn settings (i.e., even when the pin is assigned to another signal by the
Crossbar, the Port register can always read its corresponding Port I/O pin). The exception to this is the
execution of the read-modify-write instructions. The read-modify-write instructions when operating on a
Port SFR are the following: ANL, ORL, XRL, JBC, CPL, INC, DEC, DJNZ and MOV, CLR or SET, when the
destination is an individual bit in a Port SFR. For these instructions, the value of the register (not the pin) is
read, modified, and written back to the SFR.
Bit7: WEAKPUD: Port I/O Weak Pullup Disable.
0: Weak Pullups enabled (except for Ports whose I/O are configured as analog input).
1: Weak Pullups disabled.
Bit6: XBARE: Crossbar Enable.
0: Crossbar disabled.
1: Crossbar enabled.
Bit5: T1E: T1 Enable
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
Bit4: T0E: T0 Enable
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
Bit3: ECIE: PCA0 External Counter Input Enable
0: ECI unavailable at Port pin.
1: ECI routed to Port pin.
Bits2–0: PCA0ME: PCA Module I/O Enable Bits.
000: All PCA I/O unavailable at Port pins.
001: CEX0 routed to Port pin.
010: CEX0, CEX1 routed to Port pins.
011: CEX0, CEX1, CEX2 routed to Port pins.
100: CEX0, CEX1, CEX2, CEX3 routed to Port pins.
101: CEX0, CEX1, CEX2, CEX3, CEX4 routed to Port pins.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
WEAKPUD XBARE T1E T0E ECIE PCA0ME 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xE2
C8051F310/1/2/3/4/5/6/7
136 Rev. 1.7
SFR Definition 13.3. P0: Port0
SFR Definition 13.4. P0MDIN: Port0 Input Mode
Bits7–0: P0.[7:0]
Write - Output appears on I/O pins per Crossbar Registers.
0: Logic Low Output.
1: Logic High Outp u t (high im pe da n ce if corresponding P0MDOUT.n bit = 0).
Read - Always reads ‘1’ if selected as analog input in register P0MDIN. Directly reads Port
pin when configured as digital input.
0: P0.n pin is logic low.
1: P0.n pin is logic high.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P0.7 P0.6 P0.5 P0.4 P0.3 P0.2 P0.1 P0.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0x80
Bits7–0: Analog Input Configuration Bits for P0.7–P0.0 (respectively).
Port pins configured as analog inputs have their weak pullup, digital driver, and digital
receiver disabled.
0: Corresponding P0.n pin is configured as an analog input.
1: Corresponding P0.n pin is not configured as an analog input.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xF1
Rev. 1.7 137
C8051F310/1/2/3/4/5/6/7
SFR Definition 13.5. P0MDOUT: Port0 Output Mode
SFR Definition 13.6. P0SKIP: Port0 Skip
Bits7–0: Output Configuration Bits for P0.7–P0.0 (respe ctively): ignored if corresponding bit in regis-
ter P0MDIN is logic 0.
0: Corresponding P0.n Output is open-drain.
1: Corresponding P0.n Output is push-pull.
Note: When SDA and SCL appe ar on any of the Port I/O, each are open-drain regardless of the value of
P0MDOUT.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xA4
Bits7–0: P0SKIP[7:0]: Port0 Crossbar Skip Enable Bits.
These bits select Port pins to be skipped by the Crossbar Decoder. Port pins used as ana-
log inputs (for ADC or Compa rator) or use d as special functions (VREF input, external oscil-
lator circuit, CNVSTR input) should be skipped by the Crossbar.
0: Corresponding P0.n pin is not skipped by the Crossbar.
1: Corresponding P0.n pin is skipped by the Crossbar.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xD4
C8051F310/1/2/3/4/5/6/7
138 Rev. 1.7
SFR Definition 13.7. P1: Port1
SFR Definition 13.8. P1MDIN: Port1 Input Mode
Bits7–0: P1.[7:0]
Write - Output appears on I/O pins per Crossbar Registers.
0: Logic Low Output.
1: Logic High Outp u t (high im pe da n ce if corresponding P1MDOUT.n bit = 0).
Read - Always reads ‘1’ if selected as analog input in register P1MDIN. Directly reads Port
pin when configured as digital input.
0: P1.n pin is logic low.
1: P1.n pin is logic high.
Note: Only P1.0–P1.5 are associate d with Port pins on the C8051F316/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0x90
Bits7–0: Analog Input Configuration Bits for P1.7-P1.0 (respectively).
Port pins configured as analog inputs have their weak pullup, digital driver, and digital
receiver disabled.
0: Corresponding P1.n pin is configured as an analog input.
1: Corresponding P1.n pin is not configured as an analog input.
Note: Only P1.0–P1.5 are associated with Port pins on the C8051F316/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xF2
Rev. 1.7 139
C8051F310/1/2/3/4/5/6/7
SFR Definition 13.9. P1MDOUT: Port1 Output Mode
SFR Definition 13.10. P1SKIP: Port1 Skip
Bits7–0: Output Configuration Bits for P1.7-P1.0 (respe ctively): ignored if corresponding bit in regis-
ter P1MDIN is logic 0.
0: Corresponding P1.n Output is open-drain.
1: Corresponding P1.n Output is push-pull.
Note: Only P1.0–P1.5 are associated with Port pins on the C8051F316/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xA5
Bits7–0: P1SKIP[7:0]: Port1 Crossbar Skip Enable Bits.
These bits select Port pins to be skipped by the Crossbar Decoder. Port pins used as ana-
log inputs (for ADC or Compa rator) or use d as special functions (VREF input, external oscil-
lator circuit, CNVSTR input) should be skipped by the Crossbar.
0: Corresponding P1.n pin is not skipped by the Crossbar.
1: Corresponding P1.n pin is skipped by the Crossbar.
Note: Only P1.0–P1.5 are associate d with Port pins on the C8051F316/7 devices. Hence, in C8 051F316/7
devices, user code writing to this SFR should always set P1SKIP[7:6] = 11b so that those two pins are
skipped by the crossbar decoder.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
‘F310/1/2/3/4/5:
00000000
‘F316/7:
11000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
0xD5
C8051F310/1/2/3/4/5/6/7
140 Rev. 1.7
SFR Definition 13.11. P2: Port2
SFR Definition 13.12. P2MDIN: Port2 Input Mode
Bits7–0: P2.[7:0]
Write - Output appears on I/O pins per Crossbar Registers.
0: Logic Low Output.
1: Logic High Outp u t (high im pe da n ce if corresponding P2MDOUT.n bit = 0).
Read - Always reads ‘1’ if selected as analog input in register P2MDIN. Directly reads Port
pin when configured as digital input.
0: P2.n pin is logic low.
1: P2.n pin is logic high.
Note: Only P2.0–P2.5 are associate d with Port pins on the C8051F316/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xA0
Bits7–0: Analog Input Configuration Bits for P2.7–P2.0 (respectively).
Port pins configured as analog inputs have their weak pullup, digital driver, and digital
receiver disabled.
0: Corresponding P2.n pin is configured as an analog input.
1: Corresponding P2.n pin is not configured as an analog input.
Note: Only P2.0–P2.5 are associated with Port pins on the C8051F316/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xF3
Rev. 1.7 141
C8051F310/1/2/3/4/5/6/7
SFR Definition 13.13. P2MDOUT: Port2 Output Mode
SFR Definition 13.14. P2SKIP: Port2 Skip
Bits7–0: Output Configuration Bits for P2.7–P2.0 (respe ctively): ignored if corresponding bit in regis-
ter P2MDIN is logic 0.
0: Corresponding P2.n Output is open-drain.
1: Corresponding P2.n Output is push-pull.
Note: Only P2.0–P2.5 are associate d with Port pins on the C8051F316/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xA6
Bits7–0: P2SKIP[7:0]: Port2 Crossbar Skip Enable Bits.
These bits select Port pins to be skipped by the Crossbar Decoder. Port pins used as ana-
log inputs (for ADC or Compa rator) or use d as special functions (VREF input, external oscil-
lator circuit, CNVSTR input) should be skipped by the Crossbar.
0: Corresponding P2.n pin is not skipped by the Crossbar.
1: Corresponding P2.n pin is skipped by the Crossbar.
Note: Only P2.0–P2.3 are associate d with the Crossbar.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - - 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xD6
C8051F310/1/2/3/4/5/6/7
142 Rev. 1.7
SFR Definition 13.15. P3: Port3
SFR Definition 13.16. P3MDIN: Port3 Input Mode
Bits7–0: P3.[7:0]
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Outp u t (high im pe da n ce if corresponding P3MDOUT.n bit = 0).
Read - Always reads ‘1’ if selected as analog input in register P3MDIN. Directly reads Port
pin when configured as digital input.
0: P3.n pin is logic low.
1: P3.n pin is logic high.
Note: Only P3.0–P3.4 are associated with Port pins on C8051F310/2/4 devices; Only P3.0 is associated with a
Port pin on C8051F311/3/5/6/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P3.7 P3.6 P3.5 P3.4 P3.3 P3.2 P3.1 P3.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xB0
Bits7–5: UNUSED. Read = 000b; Write = don’t care.
Bits4–0: Input Configuration Bits for P3.4–P3.0 (respectively).
Port pins configured as analog inputs have their weak pullup, digital driver, and digital
receiver disabled.
0: Corresponding P3.n pin is configured as an analog input.
1: Corresponding P3.n pin is not configured as an analog input.
Note: Only P3.0–P3.4 are associated with Port pins on C8051F310/2/4 devices; Only P3.0 is associated with a
Port pin on C8051F311/3/5/6/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xF4
Rev. 1.7 143
C8051F310/1/2/3/4/5/6/7
SFR Definition 13.17. P3MDOUT: Port3 Output Mode
Table 13.1. Port I/O DC Electrical Characteristics
VDD = 2.7 to 3.6 V, –40 to +85 °C unless otherwise specified
Parameters Conditions Min Typ Max Units
Output High Voltage
IOH = –3 mA, Port I/O push-pull
IOH = –10 µA, Port I/O push-pull
IOH = –10 mA, Port I/O push-pull
VDD – 0.7
VDD – 0.1
—
—
—
VDD – 0.8
—
—
—V
Output Low Voltage
IOL = 8.5 mA
IOL = 10 µA
IOL = 25 mA
—
—
—
—
—
1.0
0.6
0.1
—V
Input High Voltage 2.0 — — V
Input Low Voltage — — 0.8 V
Input Leakag e Curr en t Weak Pullup Off
Weak Pullup On, VIN = 0 V —
——
25 ±1
40 µA
Bits7–5: UNUSED. Read = 000b; Write - don’t care.
Bits4–0: Output Configuration Bits for P3.4–P3.0 (respe ctively): ignored if corresponding bit in regis-
ter P3MDIN is logic 0.
0: Corresponding P3.n Output is open-drain.
1: Corresponding P3.n Output is push-pull.
Note: Only P3.0–P3.4 are associated with Port pins on C8051F310/2/4 devices; Only P3.0 is associated with a
Port pin on C8051F311/3/5/6/7 devices.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xA7
C8051F310/1/2/3/4/5/6/7
144 Rev. 1.7
NOTES:
Rev. 1.7 145
C8051F310/1/2/3/4/5/6/7
14. SMBus
The SMBus I/O interface is a two-wire, bi-directional serial bus. The SMBus is compliant with the System
Management Bus Specification, version 1.1, and compatible with the I2C serial bus. Reads and writes to
the interface by the system controller are byte oriented with the SMBus interface autonomously controlling
the serial transfer of the data. Data can be transferred at up to 1/10th of the system clock as a master or
slave (this can be faster than allowed by the SM Bus specification, dependin g on the system clock used). A
method of extending the clock-low duration is available to accommodate devices with different speed
capabilities on the same bus.
The SMBus interface may ope ra te as a maste r an d/or slave, and may function on a bus with multiple mas-
ters. The SMBus provides control of SDA (serial da ta), SCL (serial clock) generation and synchronization,
arbitration logic, and START/STOP control and generation. Three SFRs are associated with the SMBus:
SMB0CF configures the SMBus; SMB0CN controls the status of the SMBus; and SMB0DAT is the data
register, used for both transmitting and receiving SMBus data and slave addresses.
Data Path
Control
SMBUS CONTROL LOGIC
C
R
O
S
S
B
A
R
SCL
FILTER
N
SDA
Control
SCL
Control
Arbitration
SCL Synchroni zation
IRQ Generation
SCL Generation (Master Mode)
SDA Control
Interrupt
Request
Port I/O
SMB0CN
S
T
A
A
C
K
R
Q
A
R
B
L
O
S
T
A
C
K
S
I
T
X
M
O
D
E
M
A
S
T
E
R
S
T
O
01
00
10
11
T0 Overflow
T1 Overflow
TMR2H Overflo w
TMR2L Overflow
SMB0CF
E
N
S
M
B
I
N
H
B
U
S
Y
E
X
T
H
O
L
D
S
M
B
T
O
E
S
M
B
F
T
E
S
M
B
C
S
1
S
M
B
C
S
0
01234567 SMB0DAT SDA
FILTER
N
Figure 14.1. SMBus Block Diagram
C8051F310/1/2/3/4/5/6/7
146 Rev. 1.7
14.1. Supporting Document s
It is assumed the reader is familiar with or has access to the following supporting documents:
• The I2C-Bus and How to Use It (including specifications), Philips Semiconductor.
• The I2C-Bus Specification—Version 2.0, Philips Semiconductor.
• System Management Bus Specification—Version 1.1, SBS Implementers Forum.
14.2. SMBus Configuration
Figure 14.2 shows a typical SMBus configuration. The SMBus specification allows any recessive voltage
between 3.0 V and 5.0 V; different devices on the bus may operate at dif fe rent volt age levels. The bi-d irec-
tional SCL (serial clock) and SDA (serial data) lines must be connected to a positive power supply voltage
through a pullup resistor or similar circuit. Every device connected to the bus must have an open-drain or
open-collector output for both the SCL and SDA lines, so that both are pulled high (recessive state) when
the bus is free. The maximum number of devices on th e bus is limited only by the requ irement that the r ise
and fall times on the bus not exceed 300 ns and 1000 ns, respectively.
VDD = 5 V
Master
Device Slave
Device 1 Slave
Device 2
VDD = 3 V VDD = 5 V VDD = 3 V
SDA
SCL
Figure 14.2. Typical SMBus Configuration
14.3. SMBus Operation
Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave
receiver (WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ).
The master device initiates both types of data transfers and provides the serial clock pulses on SCL. The
SMBus interface may operate as a master or a slave, and multiple master devices on the same bus are
supported. If two or more masters attempt to initiate a data transfer simultaneously, an arbitration scheme
is employed with a single master always winnin g the arbitration. Note that it is not n ecessary to specify one
device as the Master in a system; any device who transmits a START and a slave address becomes the
master for the duration of that transfer.
A typical SMBus transaction consists of a START condition followed by an address byte (Bits7–1: 7-bit
slave address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Each byte that is
received (by a master or slave) must be acknowledged (ACK) with a low SDA during a high SCL (see
Figure 14.3). If the receiving device does not ACK, the transmitting device will read a NACK (not acknowl-
edge), which is a high SDA during a high SCL.
Rev. 1.7 147
C8051F310/1/2/3/4/5/6/7
The direction bi t (R/W) occupie s the least-sign ificant bit position of th e address byte. The di rection bit is set
to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation.
All transactions are initiated by a master, with one or more addressed slave devices as the target. The
master generates the START condition and then transmits the slave address and direction bit. If the trans-
action is a WRITE operation from the master to the slave, the master transmits the da ta a byte at a time
waiting for an ACK from the slave at the end of each byte. For READ operations, the slave transmits the
data waiting for an ACK from the master at the end of each byte. At the end of the data transfer, the master
generates a STOP condition to terminate the transaction and free the bus. Figure 14.3 illustrates a typical
SMBus transaction.
SLA6
SDA SLA5-0 R/W D7 D6-0
SCL
Slave Address + R/W Data ByteSTART ACK NACK STOP
Figure 14.3. SMBus Transaction
14.3.1. Arbitration
A master may star t a transfer on ly if the bus is free. The b us is free af ter a STOP condition or after the SCL
and SDA lines remain high for a specified time (see Section “14.3.4. SCL High (SMBus Free) Timeout”
on page 148). In the event that two or more devices attempt to begin a transfer at the same time, an arbi-
tration scheme is employed to force one master to give up the bus. The master devices continue transmit-
ting until one attempts a HIGH while the other transmits a LOW. Since the bus is open-drain, the bus will
be pulled LOW. The master attempting the HIGH will detect a LOW SDA and lose the arbitration. The win-
ning master continues its transmission without interruption; the losing master becomes a slave and
receives the rest of the transfer if addressed. This arbitration scheme is non-destructive: one device
always wins, and no data is lost.
C8051F310/1/2/3/4/5/6/7
148 Rev. 1.7
14.3.2. Clock Low Extension
SMBus provides a clock synchronization mechanism, similar to I2C, which allows devices with different
speed capabilities to coexist on the bus. A clock-low extension is used during a transfer in order to allow
slower slave devices to communicate with faster masters. The slave may temporarily hold the SCL line
LOW to extend the clock low period, effectively decreasing the serial clock frequency.
14.3.3. SCL Low Timeout
If the SCL line is held low b y a slave device on the bus, no fur ther communication i s possible. Fur thermore,
the master cann ot force the SCL lin e high to corr ect th e error condition. To solve this problem, the SMBus
protocol specifies that devices participating in a transfer must detect any clock cycle held low longer than
25 ms as a “timeout” condition. Devices that have detected the timeout condition must reset the communi-
cation no later than 10 ms after detecting the timeout condition.
When the SMBTOE bit in SMB0CF is set, Timer 3 is used to detect SCL low timeou ts. Timer 3 is forced to
reload when SCL is high, and allowed to count when SCL is low. With Timer 3 enabled and configured to
overflow after 25 ms (and SMBTOE set), the T imer 3 interrupt ser vice routine can be used to reset (disabl e
and re-enable) the SMBus in the event of an SCL low timeout.
14.3.4. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50 µs, the bus
is designated as free. When the SMBFTE bit in SMB0CF is set, the bus will be considered free if SCL and
SDA remain high for more than 10 SMBus clock source periods. If the SMBus is waiting to generate a
Master START, the START will be generated following this timeout. Note that a clock source is required for
free timeout dete ctio n , eve n in a slav e- on ly imp le me n tation.
Rev. 1.7 149
C8051F310/1/2/3/4/5/6/7
14.4. Using the SMBus
The SMBus can operate in both Master and Slave modes. The interface provides timing and shifting con-
trol for serial transfers; higher level protocol is determined by user software. The SMBus interface provides
the following application-independent features:
• Byte-wise serial data transfers
• Clock signal generation on SCL (Master Mode only) and SDA data synchronization
• Timeout/bus error recognition, as defined by the SMB0CF configuration regis te r
• START/STOP timing, detection, and generation
• Bus arbitration
• Interrupt generation
• Status information
SMBus interrupt s are gene rated fo r each dat a byte or slave address that is transferred. When transmitting,
this interrupt is generated after the ACK cycle so that software may read the received ACK value; when
receiving data, this interrupt is generated before the ACK cycle so that software may define the outgoing
ACK value. See Section “14.5. SMBus Transfer Modes” on page 157 for more details on transmission
sequences.
Interrupts are also generated to indicate the beginning of a transfer when a master (START generated), or
the end of a transfer when a slave (STOP detected). Software should read the SMB0CN (SMBus Control
register) to find the cause of the SMBus interrupt. The SMB0CN register is described in Section
“14.4.2. SMB0CN Control Register” on page 153; Table 14.4 provides a quick SMB0CN decoding refer-
ence.
SMBus configuration options include:
• Timeout detection (SCL Low Timeout and/or Bus Free Timeout)
• SDA setup and hold time extensions
• Slave event en ab le /d isab le
• Clock source selection
These options are selected in the SMB0CF register, as described in Section “14.4.1. SMBus Configura-
tion Register” on page 150.
C8051F310/1/2/3/4/5/6/7
150 Rev. 1.7
14.4.1. SMBus Configuration Register
The SMBus Configuration register (SMB0CF) is used to enable the SMBus Master and/or Slave modes,
select the SMBus clock source, and select the SMBus timing and timeout options. When the ENSMB bit is
set, the SMBus is enabled for all master and slave events. Slave events may be disabled by setting the
INH bit. With slave events inhibited, the SMBus interface will still monitor the SCL and SDA pins; however,
the interface will NACK all received addresses and will not generate any slave interrupts. When the INH bit
is set, all slave events will be inhibited following the next START (interrupts will continue for the duration of
the current trans fe r) .
Table 14.1. SMBus Clock Source Selection
The SMBCS1-0 bits select the SMBus clock source, which is used only when operating as a master or
when the Free Timeout detection is enabled. When operating as a master, overflows from the selected
source determine the a bsolute minimum SCL low a nd high times as defined in Equation 14.1. Note that the
selected clock source may be shared by other peripherals so long as the timer is left running at all times.
For example, Timer 1 overflows may generate the SMBus and UART baud rates simultaneously. Timer
configuration is covered in Section “17. Timers” on page 187.
Equation 14.1. Minimum SCL High and Low Times
THighMin TLowMin 1
fClockSourceOverflow
----------------------------------------------
==
The selected clock source should be configured to establish the minimum SCL High and Low times as per
Equation 14.1. When the interface is operating as a master (and SCL is not driven or extended by any
other devices on the bus ), the typ i ca l SMBus bit rate is approximated by Equation 14.2.
Equation 14.2. Typical SMBus Bit Rate
BitRate fClockSourceOverflow
3
----------------------------------------------
=
SMBCS1 SMBCS0 SMBus Clock Source
0 0 Timer 0 Overflow
0 1 Timer 1 Overflow
1 0 Timer 2 High Byte Overflow
1 1 Timer 2 Low Byte Overflow
Rev. 1.7 151
C8051F310/1/2/3/4/5/6/7
Figure 14.4 shows the typical SCL generation described by Equation 14.2. Notice that THIGH is typically
twice as large as TLOW. The actual SCL output may vary due to other devices on the bus (SCL may be
extended low by slower slave devices, or driven low by contending master devices). The bit rate when
operating as a master will never exceed the limits defined by equation Equation 14.1.
SCL
Timer Source
Overflows
SCL High Ti meoutT
Low
T
High
Figure 14.4. Typical SMBus SCL Generation
Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA
setup time defines the absolute minimum time that SDA is stable before SCL tran sitions from low- to-high.
The minimum SDA hold time defin es the absolute mini mum time that the cur rent SDA value remains stabl e
after SCL transitions from high-to-low. EXTHOLD should be set so that the minimum setup and hold times
meet the SMBus Specification requirement s o f 250 n s and 300 ns, re spective ly. Table 14.2 shows the min-
imum setup and hold times for the two EXTHOLD settings. Setup and hold time extensions are typically
necessary when SYSCLK is above 10 MHz.
Table 14.2. Minimum SDA Setup and Hold Times
*Note: Setup Time for ACK bit transmissions and the MSB of all data transfers. The s/w
delay occurs between the time SMB0DAT or ACK is written and when SI is cleared.
Note that if SI is cleared in the same write that defines the outgoing ACK value, s/w
delay is zero.
With the SMBTOE bit set, Timer 3 should be configured to overflow after 25 ms in order to detect SCL low
timeouts (see Section “14.3.3. SCL Low Timeout” on page 148). The SMBus interface will force Ti mer 3
to reload while SCL is high, and allow Timer 3 to coun t when SCL is low. The T im er 3 interrup t servic e rou-
tine should be used to reset SMBus communication by disabling and re-enabling the SMBus.
SMBus Free T imeout detection can be enabled by setting the SMBFTE bit. When this bit is set, the bus will
be considered free if SDA and SCL remain high for more than 10 SMBus clock source periods (see
Figure 14.4). When a Free Timeout is detected, the interface will respond as if a STOP was detected (an
interrupt will be generated, and STO will be set).
EXTHOLD Minimum SDA Setup Time Minimum SDA Hold Time
0
Tlow – 4 system clocks
OR
1 system clock + s/w delay*
3 system clocks
1 11 system clocks 12 system clocks
C8051F310/1/2/3/4/5/6/7
152 Rev. 1.7
SFR Definition 14.1. SMB0CF: SMBus Clock/Configuration
Bit7: ENSMB: SMBus Enable.
This bit enables/disables the SMBus interface. When enabled, the inter face constantly mon-
itors the SDA and SCL pins.
0: SMBus interface disabled.
1: SMBus interface enabled.
Bit6: INH: SMBus Slave Inhibit.
When this bit is set to logic 1, the SMBus does not generate an interrupt when slave events
occur. This effectively removes the SMBus slave from the bus. Master Mode interrupts are
not affected.
0: SMBus Slave Mode enabled.
1: SMBus Slave Mode inhibited.
Bit5: BUSY: SMBus Busy Indicator.
This bit is set to logic 1 by hardware when a transfer is in progress. It is cleared to logic 0
when a STOP or free-timeout is sensed.
Bit4: EXTHOLD: SMBus Setup and Hold Time Extension Enable.
This bit controls the SDA setup and hold times according to Table 14.2.
0: SDA Extended Setup and Hold Times disabled.
1: SDA Extended Setup and Hold Times enabled.
Bit3: SMBTOE: SMBus SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the SMBus forces Timer 3 to
reload while SCL is high and allows Timer 3 to count when SCL goes low. If Timer 3 is con-
figured in split mode (T3SPLIT is set), only the high byte of Timer 3 is held in reload while
SCL is high. Timer 3 should be programmed to generate interr upts at 25 ms, and the
Timer 3 interrupt service routine should reset SMBus communication.
Bit2: SMBFTE: SMBus Free Timeout Detection Enable.
When this bit is set to logic 1, the bus will be considered free if SCL and SDA remain high for
more than 10 SMBus clock source periods.
Bits1–0: SMBCS1-SMBCS0: SMBus Clock Source Selection.
These two bits select the SMBus clock source, which is used to generate the SMBus bit
rate. The selected device should be configured according to Equation 14.1.
R/W R/W R R/W R/W R/W R/W R/W Reset Value
ENSMB INH BUSY EXTHOLD SMBTOE SMBFTE SMBCS1 SMBCS0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xC1
SMBCS1 SMBCS0 SMBus Clock Source
0 0 Timer 0 Overflow
0 1 Timer 1 Overflow
1 0 Timer 2 High Byte Overflow
1 1 Timer 2 Low Byte Overflow
Rev. 1.7 153
C8051F310/1/2/3/4/5/6/7
14.4.2. SMB0CN Control Register
SMB0CN is used to control the interface and to provide status information (see SFR Definition 14.2). The
higher four bits of SMB0CN (MASTER, TXMODE, STA, and STO) form a status vector that can be used to
jump to service routines. MASTER and TXMODE indicate the master/slave state and transmit/receive
modes, respectively.
STA and STO indicate that a START and/or STOP has been detected or generated since the last SMBus
interrupt. STA and STO are also used to gene ra te START and STOP conditions when operating as a mas-
ter. Writing a ‘1’ to STA will cause the SMBus interface to enter Master Mode and generate a START when
the bus becomes free (STA is not cleared by hardware after the START is generated). Writing a ‘1’ to STO
while in Master Mode will cause the interface to generate a STOP and end the current transfer after the
next ACK cycle. If STO and STA are both set (while in Master Mode), a STOP followed by a START will be
generated.
As a receiver, writing the ACK bit defines the outgoing ACK value; as a transmitter, reading the ACK bit
indicates the value received on the last ACK cycle. A CKRQ is set each time a byte is received, indicating
that an outgoing ACK value is needed. When ACKRQ is set, software should write the desired outgoing
value to the ACK bit before clearing SI. A NACK will be generated if software does not write the ACK bit
before clearing SI. SDA will reflect the defined ACK value immediately following a write to the ACK bit;
however SCL will remain low until SI is cleared. If a received slave address is not acknowledged, further
slave events will be ignored until the next START is detected.
The ARBLOST bit indicates that the interface has lost an arbitration. This may occur anytime the interface
is transmitting (master or slave). A lost arbitration while operating as a slave indicates a bus error condi-
tion. ARBLOST is cleared by hardware each time SI is cleared.
The SI bit (SMBus Interrupt Flag) is set at the be ginning and end of each tran sfer, after each byte frame, or
when an arbitration is lost; see Table 14.3 for more details.
Import ant Note About t he SI Bit : The SMBus interface is stalled while SI is set; thus SCL is held low, and
the bus is stalled until software clears SI.
Table 14.3 lists all sources for hardware changes to the SMB0CN bits. Refer to Table 14.4 for SMBus sta-
tus decoding using the SMB0CN register.
C8051F310/1/2/3/4/5/6/7
154 Rev. 1.7
SFR Definition 14.2. SMB0CN: SMBus Control
Bit7: MASTER: SMBus Mast er/Slave Indicator.
This read-only bit indicates when the SMBus is operating as a master.
0: SMBus operating in Slave Mode.
1: SMBus operating in Master Mode.
Bit6: TXMODE: SMBus Transmit Mode Indicator.
This read-only bit indicates when the SMBus is operating as a transmitter.
0: SMBus in Receiver Mode.
1: SMBus in Transmitter Mode.
Bit5: STA: SMBus Start Flag.
Write:
0: No Start generated.
1: When operating as a master , a START condition is transmitted if the bus is free (I f the bus
is not free, the START is transmitted after a STOP is received or a timeout is detected). If
STA is set by software as an active Master, a repeated START will be generated after the
next ACK cycle.
Read:
0: No Start or repeated Start detected.
1: Start or repeated Start detected.
Bit4: STO: SMBus Stop Flag.
Write:
0: No STOP condition is transmitted.
1: Setting STO to logic 1 causes a STOP condition to be transmitted after the next ACK
cycle. When the STOP condition is generated, hardware clears STO to logic 0. If both STA
and STO are set, a STOP condition is transmitted followed by a START condition.
Read:
0: No Stop condition detected.
1: Stop condition detected (if in Slave Mode) or pending (if in Master Mode).
Bit3: ACKRQ: SMBus Acknowledge Request
This read-only bit is set to logic 1 when the SMBus has received a byte and needs the ACK
bit to be written with the correct ACK response value.
Bit2: ARBLOS T: SMB us Arbitration Lost Indicator.
This read-only bit is set to logic 1 when the SMBus loses arbitration while operating as a
transmitter. A lost arbitration while a slave indicates a bus error condition.
Bit1: ACK: SMBus Acknowledge Flag.
This bit defines the out-going ACK level and records incoming ACK levels. It should be writ-
ten each time a byte is received (when ACKRQ=1), or read after each byte is transmitted.
0: A "not acknowledge" has been received (if in Transmitter Mode) OR will be transmitted (if
in Receiver Mode).
1: An "acknowledge" has been received (if in Transmitter Mode) OR will be transmitted (if in
Receiver Mode).
Bit0: SI: SMBus Interrupt Flag.
This bit is set by hardware under the conditions listed in Table 14.3. SI must be cleared by
software. While SI is set, SCL is held low and the SMBus is stalled.
R R R/W R/W R R R/W R/W Reset Value
MASTER TXMODE STA STO ACKRQ ARBLOST ACK SI 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit Addressable
SFR Address: 0xC0
Table 14.3. Sources for Hardware Changes to SMB0CN
• A START i s generated. • A STOP is generated.
• Arbitration is lost.
• START is generated.
• SMB0DAT is written before the start of an
SMBus frame.
• A START is detected.
• Arbitration is lost.
• SMB0DAT is not written before the
start of an SMBus frame.
• A START followed by an address byte is
received. • Must be cleared by software.
• A STOP is detected while addressed as a
slave.
• Arbitration is lost due to a detected STOP.
• A pending STOP is generated.
• A byte has been received and an ACK
response value is needed. • After each ACK cycle.
• A repeated START is detected as a MASTER
when STA is low (unwanted repeated START).
• SCL is sensed low while attempting to gener-
ate a STOP or repeated START condition.
• SDA is sensed low while transmitting a ‘1’
(excluding ACK bits).
• Each time SI is cleared.
• The incoming ACK value is low (ACKNOWL-
EDGE). • The incoming ACK value is high (NOT
ACKNOWLEDGE).
• A START has been generated.
• Lost arbit ra tio n.
• A byte has been transmitted and an
ACK/NACK received.
• A byte has been received.
• A START or repeated START followed by a
slave address + R/W has been received.
• A STOP has been received.
• Must be cleared by software.
Rev. 1.7 155
C8051F310/1/2/3/4/5/6/7
Bit Set by Hardware When... Cleared by Hardware When...
MASTER
TXMODE
STA
STO
ACKRQ
ARBLOST
ACK
SI
C8051F310/1/2/3/4/5/6/7
156 Rev. 1.7
14.4.3. Data Re gister
The SMBus Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just been
received. Software may safely read or write to the data r egister when th e SI flag is set. Sof twar e should not
attempt to acce ss the SMB0DAT register when the SMBu s is enabled a nd the SI flag is cleared to logic 0,
as the interface may be in th e process of shifting a byte of data into or out of the register.
Data in SMB0DAT is always s hifted out MSB first. After a byte has been received, the first bit of received
data is located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously
being shifted in. SMB0DAT always contains the last data byte prese nt on the bu s. In th e even t of lost arb i-
tration, the transition from master transmitter to slave receiver is made with the correct data or address in
SMB0DAT.
SFR Definition 14.3. SMB0DAT: SMBus Data
Bits7–0: SMB0DAT: SMBus Data.
The SMB0DAT register contains a byte of data to be transmitted on the SMBus serial inter-
face or a byte that has just been received on the SMBus serial interface. The CPU can read
from or write to this register whenever the SI serial interrupt flag (SMB0CN.0) is set to
logic 1. The serial data in the register remains stable as long as the SI flag is set. When the
SI flag is not set, the system may be in the process of shifting data in/out and the CPU
should not attempt to access this register.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xC2
Rev. 1.7 157
C8051F310/1/2/3/4/5/6/7
14.5. SMBus Transfer Modes
The SMBus interface may be configured to operate as master and/or slave. At any particular time, it will be
operating in one of the following four modes: Master Transmitter, Master Receiver, Slave Transmitter, or
Slave Receiver. The SMBus interface enters Master Mod e any time a START is generate d, and rem ains i n
Master Mode until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end
of all SMBus byte frames; however, note that the interrupt is generated before th e ACK cycle when opera t-
ing as a receiver, and after the ACK cycle when operating as a transmitter.
14.5.1. Master Transmitter Mode
Serial data is transmitted on SDA while the serial clock is output on SCL. The SMBus interface generates
the START condition and transmits the first byte containing the address of the target slave and the data
direction bit. In this case the data direction bit (R/W) will be logic 0 (WRITE). The master then transmits
one or more bytes of serial data. After each byte is transmitted, an acknowledge bit is generated by the
slave. The transfer is ended when the STO bit is set and a STOP is generated. Note that the interface will
switch to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt.
Figure 14.5 shows a typical Master Transmitter sequence. Two transmit data bytes are shown, though any
number of by tes may be transmitt ed. Notice t hat the ‘data byte transferred ’ interrup ts occur after the ACK
cycle in this mode.
A AAS W PData Byte Data ByteSLA
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmi tted by
SMBus Interface
Interrupt Interrupt InterruptInterrupt
Figure 14.5. Typical Master Transmitter Sequence
C8051F310/1/2/3/4/5/6/7
158 Rev. 1.7
14.5.2. Master Receiver Mode
Serial data is received on SDA while the serial clock is output on SCL. The SMBus interface generates the
START condition and transmits the first byte containing the address of the target slave and the data direc-
tion bit. In this case the data direction bit (R/W) will be logic 1 (READ). Serial dat a is th en received from the
slave on SDA while the SMBus outputs the serial clock. The slave transmits one or more bytes of serial
data. After each byte is received, ACKRQ is set to ‘1’ and an interrupt is generated. Software must write
the ACK bit (SMB0CN.1) to define the outgoing acknowledge value (Note: writing a ‘1’ to the ACK bit gen-
erates an ACK; writing a ‘0’ generates a NACK). Software should write a ‘0’ to the ACK bit after the last
byte is received, to transmit a NACK. The interface exit s Master Re ceiver Mode af ter the STO bit is set and
a STOP is generated. Note that the interface will switch to Master Transmitter Mode if SMB0DAT is written
while an active Master Receiver. Figure 14.6 shows a typical Master Receiver sequence. Two received
data bytes are sh own, tho ugh a ny numbe r of bytes m ay be r eceived. Notice that the ‘data byte transferred’
interrupts occur before the ACK cycle in this mode.
Data ByteData Byte A NAS R PSLA
S = START
P = STOP
A = ACK
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Interrupt Interrupt InterruptInterrupt
Figure 14.6. Typical Master Receiver Sequence
Rev. 1.7 159
C8051F310/1/2/3/4/5/6/7
14.5.3. Slave Receiver Mode
Serial data is received on SDA and the clock is received on SCL. When slave events are enabled (INH =
0), the interfa ce en ters Slav e Rece iver Mo de wh en a START followed by a s lav e addr ess an d dir ectio n bit
(WRITE in this case) is received. Upon entering Slave Receiver Mode, an interrupt is generated and the
ACKRQ bit is set. Software responds to the received slave address with an ACK, or ignores the received
slave address with a NACK. If the receiv ed slave address is ignored, slave interrupts will be inhibited until
the next START is detected. If the received slave address is acknowledged, zero or more data bytes are
received. Sof tware must write the ACK bit af ter each r eceived byte to ACK or NACK the received byte. Th e
interface exits Slave Receiver Mode after receiving a STOP. Note that the interface will switch to Slave
Transmitter Mode if SMB0DAT is written while an active Slave Receiver. Figure 14.7 shows a typical Slave
Receiver sequence. Two received data bytes are shown, though any number of bytes may be received.
Notice that the ‘data byte transferred’ interrupts occur before the ACK cycle in this mode.
PWSLASData ByteData Byte A AA
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Interrupt Interrupt Interrupt
Interrupt
Figure 14.7. Typical Slave Receiver Sequence
C8051F310/1/2/3/4/5/6/7
160 Rev. 1.7
14.5.4. Slave Transmitter Mode
Serial data is transmitted on SDA and the clock is received on SCL. When slave events are enabled (INH
= 0), the interface ente rs Slave Receiver M ode (to r eceive the sla ve address) when a START followed by a
slave address and direction bit (READ in this case) is received. Upo n ente ring Sla ve Transmitter Mode, an
interrupt is generated and the ACKRQ bit is set. Software responds to the received slave address with an
ACK, or ignores the received slave address with a NACK. If the received slave address is ignored, slave
interrupts will be inhibited until a START is detected. If the received slave address is acknowledged, data
should be written to SMB0DAT to be transmitted. The interface enters Slave Transmitter Mode, and trans-
mits one or more bytes of data. After each byte is transmitted, the master sends an acknowledge bit; if the
acknowledge bit is an ACK, SMB0DAT should be written with the next data byte. If the acknowledge bit is
a NACK, SMB0DAT should not be written to before SI is cleared (Note: an erro r condition may be gener-
ated if SMB0DAT is written following a received NACK while in Slave Transmitter Mode). The interface
exits Slave Transmitter Mode after receiving a STOP. Note that the interface will switch to Slave Receiver
Mode if SMB0DAT is not written following a Slave Transmitter interrupt. Figure 14.8 shows a typical Slave
Transmitter sequence. Two transmitted data bytes are shown, though any number of bytes may be trans-
mitted. Notice that the ‘data byte tran sfe rre d’ inte rr u pts occur after the ACK cycle in this mode.
PRSLASData ByteData Byte A NA
S = START
P = STOP
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Interrupt Interrupt Interrupt
Interrupt
Figure 14.8. Typical Slave Transmitter Sequence
Rev. 1.7 161
C8051F310/1/2/3/4/5/6/7
14.6. SMBus Status Decoding
The current SMBus status can be easily decoded using the SMB0CN register. In the table below, STATUS
VECTOR refers to the four upper bits of SMB0CN: MASTER, TXMODE, STA, and STO. Note that the
shown response options are only the typical responses; application-specific procedures are allowed as
long as they conform to the SMBus specification. Highlighted re sp onses ar e allowed but do no t confor m to
the SMBus specification.
Table 14.4. SMBus Status Decoding
Mode
Values Read
Current SMbus State Typical Response Options
Values
Written
Status
Vector
ACKRQ
ARBLOST
ACK
STA
STO
ACK
Master Transmitter
1110 0 0 X A master START was
generated. Load slave address + R/W into
SMB0DAT. 0 0 X
1100
000
A master dat a or address byte
was transmitted; NACK
received.
Set STA to restart transfer. 1 0 X
Abort transfer. 0 1 X
001
A master dat a or address byte
was transmitted; ACK
received.
Load next data byte into
SMB0DAT. 0 0 X
End transfer with STOP. 0 1 X
End transfer with STOP and start
another tra n sfe r. 1 1 X
Send repeated START. 1 0 X
Switch to Master Receiver Mode
(clear SI without writing new data
to SMB0DAT). 0 0 X
Master Receiver
1000 1 0 X A master data byte was
received; ACK requested.
Acknowledge received byte; Read
SMB0DAT. 001
Send NACK to indicate last byte,
and send STOP. 010
Send NACK to indicate last byte,
and send STOP followed by
START. 110
Send ACK followed by repeated
START. 101
Send NACK to indicate last byte,
and send repeated STAR T. 1 0 0
Send ACK and switch to Master
Transmitter Mode (write to
SMB0DAT before clearing SI). 0 0 1
Send NACK and switch to Master
Transmitter Mode (write to
SMB0DAT before clearing SI). 0 0 0
C8051F310/1/2/3/4/5/6/7
162 Rev. 1.7
Slave Transmitter
0100
000
A slave byte was transmitte d;
NACK received. No action required (expecting
STOP condition). 0 0 X
001
A slave byte was transmitte d;
ACK received. Load SMB0DAT with next data
byte to transmit. 0 0 X
01X
A Slave byte was transmitted ;
error detected. No action required (e xp ec tin g
Master to end transfer). 0 0 X
0101 0 X X A STOP was detected while
an addressed Slave Transmit-
ter.
No action required (t ra nsfer com-
plete). 0 0 X
Slave Receiver
0010
10X
A slave address was
received; ACK requested.
Acknowledge received address. 001
Do not acknowledge received
address. 000
11X
Lost arbitration as master;
slave address received; ACK
requested.
Acknowledge received address. 001
Do not acknowledge received
address. 000
Reschedule failed transfer; do not
acknowledge received address. 100
0010 0 1 X Lost arbitration while attempt-
ing a repeated START. Abort failed transfer. 0 0 X
Reschedule failed transfer. 1 0 X
0001
11X
Lost arbitration while attempt-
ing a STOP. No action required (tra ns fer com-
plete/aborted). 000
00X
A STOP was detected while
an addressed slave receiver. No action required (t ra nsfer com-
plete). 0 0 X
01X
Lost arbitration due to a
detected STOP. Abort transfer. 0 0 X
Reschedule failed transfer. 1 0 X
0000 10X
A slave byte was received;
ACK requested.
Acknowledge received byte; Read
SMB0DAT. 001
Do not acknowledge received
byte. 000
11X
Lost arbitration while transmit-
ting a data byte as master. Abort failed transfer. 000
Reschedule failed transfer. 100
Table 14.4. SMBus Status Decoding (Continued)
Mode
Values Read
Current SMbus State Typical Response Options
Values
Written
Status
Vector
ACKRQ
ARBLOST
ACK
STA
STO
ACK
Rev. 1.7 163
C8051F310/1/2/3/4/5/6/7
15. UART0
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART.
Enhanced baud rate su pport allows a wide r ange o f clock sources to ge nera te st an dard ba ud r ates (det ails
in Section “15.1. Enhanced Baud Rate Generation” on page 164). Received data buffering allows
UART0 to st art rece ption of a second incoming dat a byte before sof tware has finished reading the previous
data byte.
UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0).
The single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0
always access the Transmit register. Reads of SBUF0 always access the buf fe red Receive regist er;
it is not possible to read data from the Transmit register.
With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in
SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not
cleared by hardwa re when the CPU vectors to th e interrupt ser vice routine. They must be cle ared manually
by software, allowing software to determine the cause of the UART0 interrupt ( transmit complete or receive
complete).
UART Baud
Rate Generator
RI
SCON
RI
TI
RB8
TB8
REN
MCE
SMODE
Tx Control
Tx Clock Send
SBUF
(TX Shift)
Start
Data
Write to
SBUF
Crossbar
TX
Shift
Zero Detector
Tx IRQ
SET
QD
CLR
Stop Bit
TB8
SFR Bus
Serial
Port
Interrupt
TI
Port I/O
Rx Control
Start
Rx Clock
Load
SBUF
Shift 0x1FF RB8
Rx IRQ
Input Shift Register
(9 bits)
Load SBUF
Read
SBUF
SFR Bus
Crossbar
RX
SBUF
(RX Latch)
Figure 15.1. UART0 Block Diagram
C8051F310/1/2/3/4/5/6/7
164 Rev. 1.7
15.1. Enhanced Baud Rate Generation
The UART0 baud rate is generated by Timer 1 in 8-bit auto-reload mode. The TX clock is generated by
TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure 15.2), which is not user-
accessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates.
The RX Timer runs when Timer 1 is enabled, and uses the same reload value (TH1). However, an
RX Timer reload is forced when a START condition is detected on the RX pin. This allows a receive to
begin any time a START is detected, independent of the TX Timer state.
RX Timer
Start
Detected
Overflow
Overflow
TH1
TL1
TX Clock
2
RX Cl ock
2
Timer 1 UART
Figure 15.2. UART0 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see Section “17.1.3. Mode 2: 8-bit Coun-
ter/Timer with Auto-Reload” on page 189). The Timer 1 reload value should be set so that overflows will
occur at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by one of six
sources: SYSCLK, SYSCLK / 4, SYSCLK / 12, SYSCLK / 48, the external oscillator clock / 8, or an exter-
nal input T1. For any given Timer 1 clock source, the UART0 baud rate is determined by Equation 15.1.
Equation 15.1. UART0 Baud Rate
UartBaudRate T1CLK
256 T1H–
-------------------------------1
2
---
=
Where T1CLK is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (reload
value). Timer 1 clock frequency is selected as described in Section “17. Timers” on page 187. A quick
reference for typical baud rates and system clock frequencies is given in Table 15.1 through Table 15.6.
Note that the internal oscillator may still generate the system clock when the external oscillator is driving
Timer 1.
Rev. 1.7 165
C8051F310/1/2/3/4/5/6/7
15.2. Operational Modes
UART0 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is
selected by the S0MODE bit (SCON0.7). Typical UART connection options are shown in Figure 15.3.
OR
RS-232
C8051Fxxx
RS-232
LEVEL
XLTR
TX
RX
C8051Fxxx
RX
TX
MCU RX
TX
Figure 15.3. UART Interconnect Diagram
15.2.1. 8-Bit UART
8-Bit UART mode uses a total of 10 bits per data byte : one st art bit, eight dat a bi ts (LSB first), and on e stop
bit. Data are transmitted LSB first from the TX0 pin and received at the RX0 pin. On receive, the eight data
bits are stored in SBUF0 and the stop bit goes into RB80 (SCON0.2).
Data transmission begins when software writes a data byte to the SBUF0 register. The TI0 Transmit Inter-
rupt Flag ( SCON0.1) is set at th e end of the transm ission (the beginning of the stop-bit time). Data recep-
tion can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop bit is
received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met:
RI0 must be logic 0, and if MCE0 is logic 1, the stop bit must be logic 1. In the event of a receive data over-
run, the first received 8 bits are latched into the SBUF0 receive register and the following overrun data bits
are lost.
If these condition s ar e me t, the eig h t bits of data is stored in SBUF0, the stop bit is stored in RB80 and the
RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not
be set. An interrupt will occur if enabled when either TI0 or RI0 is set.
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE
Figure 15.4. 8-Bit UART Timing Diagram
C8051F310/1/2/3/4/5/6/7
166 Rev. 1.7
15.2.2. 9-Bit UART
9-bit UART mode uses a total of eleven bits pe r data byte: a start bit, 8 data bits (LSB first), a programma-
ble ninth data bit, and a stop bit. The sta te of the ninth transmit data bit is determined by the value in TB80
(SCON0.3), which is assigned by user so f twa re. It ca n be assigned the value of the parity flag (bit P in reg-
ister PSW) for error detection, or used in multiprocessor communications. On receive, the ninth data bit
goes into RB80 (SCON0.2) and the stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit
Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data
reception ca n begin any time after the REN0 Receive Enable bit (SC ON0.4) is set to ‘1’. After the stop bit
is received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met:
(1) RI0 must be logic 0, and (2) if MCE0 is logic 1, the 9th bit must be logic 1 (when MCE0 is logic 0, the
state of the ninth data bit is unimportant). If these conditions are met, the eight bits of data are stored in
SBUF0, the ninth bit is stored in RB80, and the RI0 flag is set to ‘1’. If the above conditions are not met,
SBUF0 and RB80 will not be loaded and the RI0 flag will not be set to ‘1’. A UART0 interrupt will occur if
enabled when either TI0 or RI0 is set to ‘1’.
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE D8
Figure 15.5. 9-Bit UART Timing Diagram
Rev. 1.7 167
C8051F310/1/2/3/4/5/6/7
15.3. Multiprocessor Communications
9-Bit UART mode supports multiprocessor communication between a master processor and one or more
slave processors by special use of the ninth dat a bit. When a master proce ssor wa nts to transmit to one or
more slaves, it first sends an address byte to select the target(s). An address byte diff ers from a data byte
in that its ninth bit is logic 1; in a data by te , the nint h bit is alwa ys se t to logic 0.
Setting the MCE0 bit (SCON0.5) of a slave processor configures its UART such that when a stop bit is
received, the UART will generate an interrupt only if the ninth bit is logic 1 (RB8 0 = 1) signifying an address
byte has been received. In the UART interrupt handler, software will compare the received address with
the slave's own assigned 8-bit address. If the addresses match, the slave will clear its MCE0 bit to enable
interrupts on the reception of the following data byte(s). Slaves that weren't addressed leave their MCE0
bits set and do not generate interrupts on the reception of the following data bytes, thereby ignoring the
data. Once the entire message is received, the addressed slave resets its MCE0 bit to ignore all transmis-
sions until it receives the next address byte.
Multiple address es can be assigned to a sin gle slave and/or a single address can be assigned to multiple
slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master
processor can be configured to receive all transmissions or a protocol can be implemented such that the
master/slave role is temporarily reversed to enable half-duplex transmission between the original master
and slave(s).
Master
Device Slave
Device
TXRX RX TX
Slave
Device
RX TX
Slave
Device
RX TX
V+
Figure 15.6. UART Multi-Processor Mode Interconnect Diagram
C8051F310/1/2/3/4/5/6/7
168 Rev. 1.7
SFR Definition 15.1. SCON0: Serial Port 0 Control
Bit7: S0MODE: Serial Port 0 Operation Mode.
This bit selects the UART0 Operation Mode.
0: 8-bit UART with Variable Baud Rate.
1: 9-bit UART with Variable Baud Rate.
Bit6: UNUSED. Read = 1b. Write = don’t care.
Bit5: MCE0: Multiprocessor Communication Enable.
The function of this bit is dependent on the Serial Port 0 Operation Mode.
S0MODE = 0: Checks for valid stop bit.
0: Logic level of stop bit is ignored.
1: RI0 will only be activated if stop bit is logic level 1.
S0MODE = 1: Multiprocessor Communications Enable.
0: Logic level of ninth bit is ignored.
1: RI0 is set and an interrupt is generated only when the ninth bit is logic 1.
Bit4: REN0: Receive Enable.
This bit enables/disables the UART receiver.
0: UART0 reception disabled.
1: UART0 reception enabled.
Bit3: TB80: Ninth Transmission Bit.
The logic level of this bit will be assigned to the ninth transmission bit in 9-bit UART Mode. It
is not used in 8-bit UART Mode. Set or cleared by software as required.
Bit2: RB80: Ninth Receive Bit.
RB80 is assigned the value of the STOP bit in Mode 0; it is assigned the valu e of the 9th
data bit in Mode 1.
Bit1: TI0: Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit in 8-
bit UAR T Mode, or at the beginni ng of th e ST OP bit in 9-bit UART Mode). When the UART0
interrupt is enable d, setting this bit causes the CPU to vector to the UAR T0 interrupt servi ce
routine. This bit must be cleared manually by software.
Bit0: RI0: Receive Interrupt Flag.
Set to ‘1’ by hardware wh en a byte of data ha s been received by UAR T0 (set at the STOP bit
sampling time). When the UART0 interrupt is enabled, setting this bit to ‘1’ causes the CPU
to vector to the UART0 interrupt se rvic e ro ut ine . This bit must be cleared manually by soft-
ware.
R/W R R/W R/W R/W R/W R/W R/W Reset Value
S0MODE MCE0 REN0 TB80 RB80 TI0 RI0 01000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit Addressable
SFR Address: 0x98
Rev. 1.7 169
C8051F310/1/2/3/4/5/6/7
SFR Definition 15.2. SBUF0: Serial (UART0) Port Data Buffer
Bits7–0: SBUF0[7:0]: Serial Data Buffer Bits 7–0 (MSB–LSB)
This SFR accesses two registers; a transmit shift register and a receive latch register. When
data is written to SBUF0, it goes to the transmit shift register and is held for serial transmis-
sion. Writing a byte to SBUF0 initiates the transmission. A read of SBUF0 returns the con-
tents of the receive latch.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0x99
Table 15.1. Timer Settings for Standard Baud Rates
Using the Internal Oscillator
SYSCLK from
Internal Osc.
*Note: SCA1–SCA0 and T1M bit definitions can be found in Section 17.1.
C8051F310/1/2/3/4/5/6/7
170 Rev. 1.7
Table 15.2. Timer Settings for Standard Baud Rates
Using an External 25 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
*Note: SCA1–SCA0 and T1M bit definitions can be found in Section 17.1.
Frequency: 24.5 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscilla-
tor Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M* Timer 1
Reload Value
(hex)
230400 –0.32% 106 SYSCLK XX 1 0xCB
115200 –0.32% 212 SYSCLK XX 1 0x96
57600 0.15% 426 SYSCLK XX 1 0x2B
28800 –0.32% 848 SYSCLK / 4 01 0 0x96
14400 0.15% 1704 SYSCLK / 12 00 0 0xB9
9600 –0.32% 2544 SYSCLK / 12 00 0 0x96
2400 –0.32% 10176 SYSCLK / 48 10 0 0x96
1200 0.15% 20448 SYSCLK / 48 10 0 0x2B
X = Don’t care
Frequency: 25.0 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscilla-
tor Divide
Factor
Ti mer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M* Timer 1
Reload Value
(hex)
230400 –0.47% 108 SYSCLK XX 1 0xCA
115200 0.45% 218 SYSCLK XX 1 0x93
57600 –0.01% 434 SYSCLK XX 1 0x27
28800 0.45% 872 SYSCLK / 4 01 0 0x93
14400 –0.01% 1736 SYSCLK / 4 01 0 0x27
9600 0.15% 2608 EXTCLK / 8 11 0 0x5D
2400 0.45% 10464 SYSCLK / 48 10 0 0x93
1200 –0.01% 20832 SYSCLK / 48 10 0 0x27
57600 –0.47% 432 EXTCLK / 8 11 0 0xE5
28800 –0.47% 864 EXTCLK / 8 11 0 0xCA
14400 0.45% 1744 EXTCLK / 8 11 0 0x93
9600 0.15% 2608 EXTCLK / 8 11 0 0x5D
X = Don’t care
Table 15.3. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
*Note: SCA1–SCA0 and T1M bit definitions can be found in Section 17.1.
Rev. 1.7 171
C8051F310/1/2/3/4/5/6/7
Table 15.4. Timer Settings for Standard Baud Rates
Using an External 18.432 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
*Note: SCA1–SCA0 and T1M bit definitions can be found in Section 17.1.
Frequency: 22.1184 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscilla-
tor Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M* Timer 1
Reload V alue
(hex)
230400 0.00% 96 SYSCLK XX 1 0xD0
115200 0.00% 192 SYSCLK XX 1 0xA0
57600 0.00% 384 SYSCLK XX 1 0x40
28800 0.00% 768 SYSCLK / 12 00 0 0 xE0
14400 0.00% 1536 SYSCLK / 12 00 0 0xC0
9600 0.00% 2304 SYSCLK / 12 00 0 0xA0
2400 0.00% 9216 SYSCLK / 48 10 0 0xA0
1200 0.00% 18432 SYSCLK / 48 10 0 0x40
230400 0.00% 96 EXTCLK / 8 11 0 0xFA
115200 0.00% 192 EXTCLK / 8 11 0 0xF4
57600 0.00% 384 EXTCLK / 8 11 0 0xE8
28800 0.00% 768 EXTCLK / 8 11 0 0xD0
14400 0.00% 1536 EXTCLK / 8 11 0 0xA0
9600 0.00% 2304 EXTCLK / 8 11 0 0x70
X = Don’t care
Frequency: 18.432 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscilla-
tor Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M* Timer 1
Reload
Value (hex )
230400 0.00% 80 SYSCLK XX 1 0xD8
115200 0.00% 160 SYSCLK XX 1 0xB0
57600 0.00% 320 SYSCLK XX 1 0x60
28800 0.00% 640 SYSCLK / 4 01 0 0xB0
14400 0.00% 1280 SYSCLK / 4 01 0 0x60
9600 0.00% 1920 SYSCLK / 12 00 0 0xB0
2400 0.00% 7680 SYSCLK / 48 10 0 0xB0
1200 0.00% 15360 SYSCLK / 48 10 0 0x60
230400 0.00% 80 EXTCLK / 8 11 0 0xFB
115200 0.00% 16 0 EXTCLK / 8 11 0 0xF6
57600 0.00% 320 EXTCLK / 8 11 0 0xEC
28800 0.00% 640 EXTCLK / 8 11 0 0xD8
14400 0.00% 1280 EXTCLK / 8 11 0 0xB0
9600 0.00% 1920 EXTCLK / 8 11 0 0x88
X = Don’t care
Table 15.5. Timer Settings for Standard Baud Rates
Using an External 11.0592 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
*Note: SCA1–SCA0 and T1M bit definitions can be found in Section 17.1 .
C8051F310/1/2/3/4/5/6/7
172 Rev. 1.7
Table 15.6. Timer Settings for Standard Baud Rates
Using an External 3.6864 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
*Note: SCA1–SCA0 and T1M bit definitions can be found in Section 17.1.
Frequency: 11.0592 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscilla-
tor Divide
Factor
Timer Clo ck
Source SCA1-SCA0
(pre-scale
select)*
T1M* Timer 1
Reload Value
(hex)
230400 0.00% 48 SYSCLK XX 1 0xE8
115200 0.00% 96 SYSCLK XX 1 0xD0
57600 0.00% 192 SYSCLK XX 1 0xA0
28800 0.00% 384 SYSCLK XX 1 0x40
14400 0.00% 768 SYSCLK / 12 00 0 0xE0
9600 0.00% 1152 SYSCLK / 12 00 0 0xD0
2400 0.00% 4608 SYSCLK / 12 00 0 0x40
1200 0.00% 9216 SYSCLK / 48 10 0 0xA0
230400 0.00% 48 EXTCLK / 8 11 0 0xFD
115200 0.00% 96 EXTCLK / 8 11 0 0xFA
57600 0.00% 192 EXTCLK / 8 11 0 0x F 4
28800 0.00% 384 EX TCLK / 8 11 0 0xE8
14400 0.00% 768 EXTCLK / 8 11 0 0xD0
9600 0.00% 1152 EXTCLK / 8 11 0 0xB8
X = Don’t care
Frequency: 3.6864 MHz
Target
Baud Rate
(bps)
Baud
Rate%
Error
Oscilla-
tor Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M* Timer 1
Reload
Value (hex)
230400 0.00% 16 SYSCLK XX 1 0xF8
115200 0.00% 32 SYSCLK XX 1 0xF0
57600 0.00% 64 SYSCLK XX 1 0xE0
28800 0.00% 128 SYSCLK XX 1 0xC0
14400 0.00% 256 SYSCLK XX 1 0x80
9600 0.00% 384 SYSCLK XX 1 0x40
2400 0.00% 1536 SYSCLK / 12 00 0 0xC0
1200 0.00% 3072 SYSCLK / 12 00 0 0x80
230400 0.00% 16 EXTCLK / 8 11 0 0xFF
115200 0.00% 32 EXTCLK / 8 11 0 0xFE
57600 0.00% 64 EXTCLK / 8 11 0 0xFC
28800 0.00% 128 EXTCLK / 8 11 0 0xF8
14400 0.00% 256 EXTCLK / 8 11 0 0xF0
9600 0.00% 384 EXTCLK / 8 11 0 0xE8
X = Don’t care
Rev. 1.7 173
C8051F310/1/2/3/4/5/6/7
16. Enhanced Serial Peripheral Interface (SPI0)
The Enhanced Serial Peripheral Interface (SPI0) provides access to a flexible, full-duplex synchronous
serial bus. SPI0 can operate as a master or slave device in both 3-wire or 4-wire modes, and supports mul-
tiple masters and slaves on a single SPI bus. The slave-select (NSS) signal can be configured as an input
to select SPI0 in slave mode, or to disable Master Mode operation in a multi-master environment, avoiding
contention on the SPI bus when more than one master attempts simultaneous data transfers. NSS can
also be configur ed as a ch ip-select ou tput in master mode, or disabled fo r 3-wire operation. Add itional gen-
eral purpose port I/O pins can be used to select multiple slave devices in master mode.
SFR Bus
Data Path
Control
SFR Bus
Write
SPI0DAT
Receive Data Buffer
SPI0DAT
01234567
Shift Register
SPI CONTROL LOGIC
SPI0CKR
SCR7
SCR6
SCR5
SCR4
SCR3
SCR2
SCR1
SCR0
SPI0CFG SPI0CN
Pin Interface
Control
Pin
Control
Logic
C
R
O
S
S
B
A
R
Port I/O
Read
SPI0DAT
SPI IRQ
Tx Data
Rx Data
SCK
MOSI
MISO
NSS
Transmit Data Buffer
Clock Divide
Logic
SYSCLK
CKPHA
CKPOL
SLVSEL
NSSMD1
NSSMD0
SPIBSY
MSTEN
NSSIN
SRMT
RXBMT
SPIF
WCOL
MODF
RXOVRN
TXBMT
SPIEN
Figure 16.1. SPI Block Diagram
C8051F310/1/2/3/4/5/6/7
174 Rev. 1.7
16.1. Signal Descriptions
The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below.
16.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master dev ice and an inpu t to slav e device s. It
is used to serially trans fer data from the ma ster to th e slave. This signal is an output when SPI0 is operat-
ing as a master and an input when SPI0 is operating as a slave. Data is transferred most-significant bit
first. When configured as a master, MOSI is driven by the MSB of the shift register in both 3- and 4-wire
mode.
16.1.2. Master In, Slave Out (MISO)
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device.
It is used to serially transfer data from the slave to the master. This signal is an input when SPI0 is operat-
ing as a master and an output when SPI0 is operating as a slave. Data is transferred most-signific ant bit
first. The MISO pin is placed in a high-impeda nce sta te when the SPI module is di sabled and when the SPI
operates in 4-wire mode as a slave that is not selected. When acting as a slave in 3-wire mode, MISO is
always driven by the MSB of the shift register.
16.1.3. Serial Clock (SCK)
The serial c lock (SCK) signal is an ou tput from the m aster device and an input to slave devices. It is used
to synchronize the transfer of data between the master and slave on the MOSI and MISO lines. SPI0 gen-
erates this signal when operating as a master. The SCK signal is ignored by a SPI slave when the slave is
not selected (NSS = 1) in 4-wire slave mode.
16.1.4. Slave Select (NSS)
The function of the slave-select (NSS) signal is dependent on the setting of the NSSMD1 and NSSMD0
bits in the SPI0CN register. There are three possible modes that can be selected with these bits:
• NSSMD[1:0] = 00: 3-Wire Master or 3-Wire Slave Mode: SPI0 operates in 3-wire mode, and NSS is
disabled. When operating as a slave device, SPI0 is always selected in 3-wire mode. Since no select
signal is present, SPI0 must be the only slave on the bus in 3-wire mode. This is intended for point-to-
point communication between a master and one slave.
• NSSMD[1:0] = 01: 4-Wire Slave or Multi-Master Mode: SPI0 operates in 4-wire mode, and NSS is
enabled as an input. When operating as a slave, NSS selects the SPI0 device. When operating as a
master, a 1-to-0 transition of the NSS signal disables the master fu nction of SPI0 so that multiple mas-
ter devices can be used on the same SPI bus.
• NSSMD[1:0] = 1x: 4-Wire Master Mode: SPI0 operates in 4-wir e mode, and NSS is enabled as an out-
put. The setting of NSSMD0 determines what logic level the NSS pin will output. This configuration
should only be used when operating SPI0 as a master device.
See Figure 16.2, Figure 16.3, and Figure 16.4 for typical connection diagrams of the various operational
modes. Note that the sett ing of NSSMD bits affect s t he pinout of the device. Wh en in 3- wire ma ster or
3-wire slave mode, the NSS pin will not be mapped by the crossbar. In all other modes, the NSS signal will
be mapped to a pin on the device. See Section “13. Port Input/Output” on page 129 for general purpose
port I/O and crossbar information.
Rev. 1.7 175
C8051F310/1/2/3/4/5/6/7
16.2. SPI0 Master Mode Operation
A SPI master device initiates all data transfe r s on a SPI bu s. SPI0 is p laced in master m ode by se tting the
Master Enable flag (MSTEN, SPI0CN.6). Writing a byte of data to the SPI0 data register (SPI0DAT) when
in master mode writes to the transmit buffer. If the SPI shift register is empty, the byte in the transmit buff er
is moved to the shift registe r, and a da ta transfer begins. The SPI0 master immediately shifts out the data
serially on the MOSI line while providing the serial clock on SCK. The SPIF (SPI0CN.7) flag is set to logic
1 at the end of the transfer. If interrupts are enabled, an interrupt request is generated when the SPIF flag
is set. While the SPI0 master transfers data to a slave on the MOSI line, the addressed SPI slave device
simultaneously transfers the contents of its shift register to the SPI master on the MISO line in a full-duplex
operation. Therefore, the SPIF flag serves as both a transmit-complete and receive-data-ready flag. The
data byte received from the slave is transferred MSB-first into the master's shift register. When a byte is
fully shifted into the register, it is moved to the receive buffer where it can be read by the processor by
reading SPI0DAT.
When configured as a master, SPI0 can operate in one of three dif ferent mo des: multi-master mode, 3-wir e
single-master mode, and 4-wire single-master mode. The default, multi-master mode is active when
NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In this mode, NSS is an input to the device, and
is used to disable the master SPI0 when another master is accessing the bus. When NSS is pulled low in
this mode, MSTEN (SPI0CN.6) and SPIEN (SPI0CN.0) are set to 0 to disable the SPI master device, and
a Mode Fault is generated (MODF, SPI0C N.5 = 1). Mode Fault will generate an interrupt if enabled. SPI0
must be manually re-enabled in software under these circumstances. In multi-master systems, devices will
typically default to being sla ve devices wh ile they are not a cting as the system master device. In multi-mas -
ter mode, slave devices can be addressed individually (if needed) using general-purpose I/O pins.
Figure 16.2 shows a connection diagram between two master devices in multiple-master mode.
3-wire single-m aster m ode is active wh en NSSMD1 (S PI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. In this
mode, NSS is not used, and is not mapped to an external por t pin through the crossbar. Any slave devices
that must be addressed in this mode should be selected using general-purpose I/O pins. Figure 16.3
shows a connection diagram between a master device in 3-wire master mode and a slave device.
4-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 1. In this mode, NSS is configured as an
output pin, and can be used as a slave-select signal for a single SPI device. In this mode, the output value
of NSS is controlled (in software) with the bit NSSMD0 (SPI0CN.2). Additional slave devices can be
addressed using gene ral-p urpose I/O pins. Figure 16.4 shows a connection diagra m for a master device i n
4-wire master mode and two slave devices.
Slave
Device
Master
Device
MOSI
MISO
SCK
MISO
MOSI
SCK
Slave
Device
Master
Device
MOSI
MISO
SCK
MISO
MOSI
SCK
NSS NSS
GPIO
Slave
Device
MOSI
MISO
SCK
NSS
Master
Device 2
Master
Device 1
MOSI
MISO
SCK
MISO
MOSI
SCK
NSS
GPIO NSS
GPIO
C8051F310/1/2/3/4/5/6/7
176 Rev. 1.7
Figure 16.2. Multiple-Master Mode Connection Diagram
Figure 16.3. 3-Wire Single Master and Slave Mode Connection Diagram
Figure 16.4. 4-Wire Single Master and Slave Mode Connection Diagram
Rev. 1.7 177
C8051F310/1/2/3/4/5/6/7
16.3. SPI0 Slave Mode Operation
When SPI0 is enabled and not configured as a master, it will operate as a SPI slave. As a slave, bytes are
shifted in through the MOSI pin and out through the MISO pin by a master device controlling the SCK sig-
nal. A bit coun te r in the SPI0 lo gic cou nts SCK edges. When 8 bits have be en shifted through the shif t r eg-
ister, the SPIF flag is set to logic 1, and the byte is copied into the receive buffer. Data is read from the
receive buffer by reading SPI0DAT. A slave device cannot initiate transfers. Data to be transferred to the
master device is pre-loaded into the shift register by writing to SPI0DAT. Writes to SPI0DAT are double-
buf fered, and a re placed in the tra nsmit buf fer first. If the shif t re gister is e mpty, the contents of the transmit
buffer will immediately be transferred into the shift register. When the shift register already contains data,
the SPI will load the shift register with the transmit buffer’s contents after the last SCK edge of the next (or
current) SPI transfer.
When configured as a slave, SPI0 can be configured for 4-wire or 3-wire operation. The default, 4-wire
slave mode, is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In 4- wire mode, the
NSS signal is routed to a port pin and configured as a digital input. SPI0 is enabled when NSS is logic 0,
and disabled when NSS is logic 1. The bit counter is reset on a falling edge of NSS. Note that the NSS sig-
nal must be driven low at least 2 system clocks before the first active edge of SCK for each byte transfer.
Figure 16.4 shows a connection diagram between two slave devices in 4-wire slave mode and a master
device.
3-wire slave mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. NSS is not
used in this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of
uniquely addressing the device in 3-wire slave mode, SPI0 must be the only slave device present on the
bus. It is important to note that in 3-wire slave mode there is no external means of resetting the bit counter
that determines when a full byte has been received. The bit counter can only be reset by disabling and re-
enabling SPI0 with the SPI EN bit. Figure 16.3 shows a connection diagram between a slave device in 3-
wire slave mode an d a ma st er dev ice.
16.4. SPI0 Interrupt Sources
When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to
logic 1:
Note that all of the following bits must be cleared by software.
1. The SPI Interrupt Flag, SPIF (SPI0CN.7) is set to logic 1 at the end of each byte transfer. This
flag can occur in all SPI0 modes.
2. The Write Collision Flag, WCOL (SPI0CN.6) is set to logic 1 if a write to SPI0DAT is attempted
when the transmit buffer has not been emptied to the SPI shift register. When this occurs, the
write to SPI0DAT will be ignored, and the transmit buffer will not be written.This flag can occur
in all SPI0 modes.
3. The Mode Fault Flag MODF (SPI0CN.5) is set to logic 1 when SPI0 is configured as a master,
and for multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the
MSTEN and SPIEN bits in SPI0CN are set to logi c 0 to di sable SPI0 and allow another master
device to access the bus.
4. The Receive Overrun Flag RXOVRN (SPI0CN.4) is set to logic 1 when configured as a slave,
and a transfer is completed and the receive buffer still holds an unread byte from a previous
transfer. The n ew byt e is no t tr an sf er re d to th e r eceive bu ffer, allowin g th e p rev io us ly re ce ived
data byte to be read. The data byte which caused the overrun is lost.
C8051F310/1/2/3/4/5/6/7
178 Rev. 1.7
16.5. Serial Clock Timing
Four combinations of serial clock phase and polarity can be selected using the clock control bits in the
SPI0 Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.5) selects one of two clock phases
(edge used to latch the data). The CKPOL bit (SPI0CFG.4) selects between an active-high or active-low
clock. Both master and slave devices must be configured to use the same clock ph ase and polarity. SPI0
should be disabled (by clearing the SPIEN bit, SPI0CN.0) when changing the clock phase or polarity. The
clock and data line relationships for master mode are shown in Figure 16.5. For slave mode, the clock and
data relationships are shown in Figure 16.6 and Figure 16.7. CKPHA must be set to ‘0’ on both the master
and slave SPI when communicating between two of the following devices: C8051F04x, C8051F06x,
C8051F12x, C8051F31x, C8051F32x, and C8051F33x
The SPI0 Clock Rate Register (SPI0CKR) as shown in SFR Definition 16.3 controls the master mode
serial clock frequency. This register is ignored when operating in slave mode. When the SPI is configured
as a master, the maximum data transfe r rate (bit s/sec) is one-half the system clock frequency or 12.5 MHz,
whichever is slower. When the SPI is configured as a slave, the maximum da ta transfer rate (bits/sec) for
full-duplex operation is 1/10 the system clock frequency, provided that the master issues SCK, NSS (in 4-
wire slave mode), and the serial input data synchronously with the slave’s system clock. If the master
issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer rate (bits/sec)
must be less than 1/10 the system clock frequency. In the special case where the master only wants to
transmit data to the sla ve and does not n eed to receive data from the slave (i.e. half-duplex operation), the
SPI slave can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency.
This is provided that the master issues SCK, NSS, and the seri al input data synchronously with the slave’s
system clock.
Figure 16.5. Master Mode Data/Clock Timing
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=1, CKPHA=1)
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0MISO/MOSI
NSS (Must Remain High
in Multi-Master Mode)
Rev. 1.7 179
C8051F310/1/2/3/4/5/6/7
Figure 16.6. Slave Mode Data/Clock Timing (CKPHA = 0)
Figure 16.7. Slave Mode Data/Clock Timing (CKPHA = 1)
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0MISO
NSS (4-Wire Mode)
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0MOSI
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=1)
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0MISO
NSS (4-Wi re Mode)
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0MOSI
C8051F310/1/2/3/4/5/6/7
180 Rev. 1.7
16.6. SPI Special Function Registers
SPI0 is accessed and controlled through four special function registers in the system controller: SPI0CN
Control Register, SPI0DAT Data Register, SPI0CFG Configuration Register, and SPI0CKR Clock Rate
Register. The four special function registers related to the operation of the SPI0 Bus are described in the
following register definitions.
SFR Definition 16.1. SPI0CFG: SPI0 Configuration
Bit 7: SPIBSY: SPI Busy (read only).
This bit is set to logic 1 when a SPI transfer is in progress (Master or slave Mode).
Bit 6: MSTEN: Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
Bit 5: CKPHA: SPI0 Clock Phase.
This bit controls the SPI0 clock phase.
0: Data centered on first edge of SCK period.*
1: Data centered on second edge of SCK period.*
Bit 4: CKPOL: SPI0 Clock Polarity.
This bit controls the SPI0 clock polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
Bit 3: SLVSEL: Slave Selected Flag (read only).
This bit is set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected slave. It
is cleared to logic 0 when NSS is high (slave not selected). This bit does not indicate the
instantaneous value at the NSS pin, but rather a de-glitched version of the pin input.
Bit 2: NSSIN: NSS Instantaneous Pin Input (read only).
This bit mimics the instantaneous value that is present on the NSS port pin at the tim e that
the register is read. This input is not de-glitched.
Bit 1: SRMT: Shift Register Empty (Valid in Slave Mode, read only).
This bit will be set to logic 1 when all data has been transferred in/out of the shift register,
and there is no new information available to read from the transmit buffer or write to the
receive buffer. It returns to logic 0 when a data byte is transferred to the shift register from
the transmit buffer or by a transition on SCK.
NOTE: SRMT = 1 when in Master Mode.
Bit 0: RXBMT: Receive Buffer Empty (Valid in Slave Mode, read only).
This bit will be set to logic 1 when the receive buffer has been read and contains no new
information. If there is new information availa ble in the receive buf fer that ha s not been read,
this bit will return to logic 0.
NOTE: RXBMT = 1 when in Master Mode.
*Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is
sampled one SYSCLK before the end of each data bit, to provide maximum settling time for the slave
device. See Table 16.1 for timing parameters.
R R/W R/W R/W R R R R Reset Value
SPIBSY MSTEN CKPHA CKPOL SLVSEL NSSIN SRMT RXBMT 00000111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xA1
Rev. 1.7 181
C8051F310/1/2/3/4/5/6/7
SFR Definition 16.2. SPI0CN: SPI0 Control
Bit 7: SPIF: SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If interrupts are enabled,
setting this bit causes the CPU to vector to the SPI0 interrupt service routine. This bit is not
automatically cleared by hardware. It must be cleared by software.
Bit 6: WCOL: Write Collision Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) to indicate a write to
the SPI0 data register was attempted while a data transfer was in progress. It must be
cleared by software.
Bit 5: MODF: Mode Fault Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) when a master mode
collision is detected (NSS is low, MSTEN = 1, and NSSMD[1:0] = 01). This bit is not auto-
matically cleared by hardware. It must be cleared by software.
Bit 4: RXOVRN: Receive Overrun Flag (Slave Mode only).
This bit is set to logic 1 by hardware (and ge nerates a SPI0 interrupt) when the receive buf-
fer still holds unread data from a previous transfer and the last bit of the current transfer is
shifted into the SPI0 shift register. This bit is not automatically cleared by hardware . It mu st
be cleared by software.
Bits 3–2: NSSMD1–NSSMD0: Slave Select Mode.
Selects between the following NSS operation modes:
(See Section “16.2. SPI0 Master Mode Operation” on p age 175 and Section “16.3. SPI0
Slave Mode Operation” on page 177).
00: 3-Wire Slave or 3-wire Master Mode. NSS signal is not routed to a port pin.
01: 4-Wire Slave or Multi-Master Mode (Default). NSS is always an input to the device.
1x: 4-Wire Single-Master Mode. NSS signal is mapped as an output from the device and will
assume the value of NSSMD0.
Bit 1: TXBMT: Transmit Buf fer Empty.
This bit will be set to logic 0 when new data has been written to the transmit buffer. When
data in the transmit buffer is transferred to the SPI shift register, this bit will be set to logic 1,
indicating that it is safe to write a new byte to the transmit buffer.
Bit 0: SPIEN: SPI0 Enable.
This bit enables/disables the SPI.
0: SPI disabled.
1: SPI enabled.
R/W R/W R/W R/W R/W R/W R R/W Reset Value
SPIF WCOL MODF RXOVRN NSSMD1 NSSMD0 TXBMT SPIEN 00000110
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address: 0xF8
C8051F310/1/2/3/4/5/6/7
182 Rev. 1.7
SFR Definition 16.3. SPI0CKR: SPI0 Clock Rate
SFR Definition 16.4. SPI0DAT: SPI0 Data
Bits 7–0: SCR7–SCR0: SPI0 Clock Rate.
These bits determine the frequency of the SCK output when the SPI0 modu le is co nfigur ed
for master mode operation. The SCK clock frequency is a divided ver sion of the system
clock, and is given in the following equation, where SYSCLK is the system clock frequency
and SPI0CKR is the 8-bit value held in the SPI0CKR register.
for 0 <= SPI0CKR <= 255
Example: If SYSCLK = 2 MHz and SPI0CKR = 0x04,
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
SCR7 SCR6 SCR5 SCR4 SCR3 SCR2 SCR1 SCR0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xA2
fSCK 2000000
241+
--------------------------
=
fSCK 200kHz=
fSCK SYSCLK
2SPI0CKR 1+
-------------------------------------------------
=
Bits 7–0: SPI0DAT: SPI0 Transmit and Receive Data.
The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to SPI0DAT
places the data into the transmit buffer and initiates a transfer when in Master Mode. A read
of SPI0DAT returns the contents of the receive buffer.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: 0xA3
Rev. 1.7 183
C8051F310/1/2/3/4/5/6/7
Figure 16.8. SPI Master Timing (CKPHA = 0)
Figure 16.9. SPI Master Timing (CKPHA = 1)
SCK*
T
MCKH
T
MCKL
MOSI
T
MIS
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
T
MIH
SCK*
T
MCKH
T
MCKL
MISO
T
MIH
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
T
MIS
C8051F310/1/2/3/4/5/6/7
184 Rev. 1.7
Figure 16.10. SPI Slave Timing (CKPHA = 0)
Figure 16.11. SPI Slave Timing (CKPHA = 1)
SCK*
T
SE
NSS
T
CKH
T
CKL
MOSI
T
SIS
T
SIH
MISO
T
SD
T
SOH
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
T
SEZ
T
SDZ
SCK*
T
SE
NSS
T
CKH
T
CKL
MOSI
T
SIS
T
SIH
MISO
T
SD
T
SOH
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
T
SLH
T
SEZ
T
SDZ
Rev. 1.7 185
C8051F310/1/2/3/4/5/6/7
Table 16.1. SPI Slave Timing Parameters
Parameter Description Min Max Units
Master Mode Timing* (See Figure 16.8 and Figure 16.9)
TMCKH SCK High Time 1 x TSYSCLK —ns
TMCKL SCK Low Time 1 x TSYSCLK —ns
TMIS MISO Valid to SCK Shift Edge 1 x TSYSCLK + 20 — ns
TMIH SCK Shift Edge to MISO Change 0—ns
Slave Mode Timing* (See Figure 16.10 and Figure 16.11)
TSE NSS Falling to First SCK Edge 2 x TSYSCLK —ns
TSD Last SCK Edge to NSS Rising 2 x TSYSCLK —ns
TSEZ NSS Falling to MISO Valid — 4 x TSYSCLK ns
TSDZ NSS Rising to MISO High-Z — 4 x TSYSCLK ns
TCKH SCK High Time 5 x TSYSCLK —ns
TCKL SCK Low Time 5 x TSYSCLK —ns
TSIS MOSI Valid to SCK Sample Edge 2 x TSYSCLK —ns
TSIH SCK Sample Edge to MOSI Change 2 x TSYSCLK —ns
TSOH SCK Shift Edge to MISO Change — 4 x TSYSCLK ns
TSLH Last SCK Edge to MISO Change
(CKPHA = 1 ONLY) 6 x TSYSCLK 8 x TSYSCLK ns
*Note: TSYSCLK is equal to one period of the device system clock (SYSCLK).
C8051F310/1/2/3/4/5/6/7
186 Rev. 1.7
NOTES:
Rev. 1.7 187
C8051F310/1/2/3/4/5/6/7
17. Timers
Each MCU includes four counter/timers: two are 16-bit counter/timers compatible with those found in the
standard 8051, and two are 16-bit auto-reload timer for use with the ADC, SMBus, or for general purpose
use. These timers can be used to measure time intervals, count external events and generate periodic
interrupt requests. Timer 0 and Timer 1 are nearly identical and have four primary modes of operation.
Timer 2 and Timer 3 offer 16-bit and split 8-bit timer functionality with auto-reload.
Timers 0 and 1 may be clocked by one of five sources, determined by the Timer Mode Select bits (T1M-
T0M) and the Clock Scale bits (SCA1-SCA0). The Clock Scale bits define a pre-scaled clock from which
Timer 0 and/or Timer 1 may be clocked (S e e SFR Definition 17.3 for pre-scale d cl ock selection).
Timer 0/1 may then be configured to use this pre-scaled clock signal or the system clock. Timer 2 and
Timer 3 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
clock source divided by 8.
Timer 0 and Timer 1 may also be operated as counters. When functioning as a counter, a counter/timer
register is incr emented on each hi gh-to-low transition at the sele cted input pin (T0 o r T1). Event s with a fre-
quency of up to one-fourth the system clock's freq uency can be counte d. The input signal need n ot be peri-
odic, but it should be held at a given level for at least two full system clock cycles to ensure the level is
properly sampled.
17.1. Timer 0 and Timer 1
Each timer is implemented as 16-bit register accessed as two sepa rate bytes: a low byte (TL0 or TL1) and
a high byte (TH0 or TH1 ). The Counte r/Timer Control register (TCON) is used to enable Timer 0 and Timer
1 as well as ind icate st atus. Timer 0 interrupt s can be enabled by setting the ET0 bit in the IE r egister (SFR
Definition 8.7. “IE: Interrupt Enable” on page 97); Timer 1 interrupts can be enabled by setting the ET1 bit
in the IE register. Both counter/timers operate in one of four primary modes selected by setting the Mode
Select bits T1M1-T0M0 in the Counter/Timer Mode register (TMOD). Each timer can be configured inde-
pendently. Each operating mode is described below.
17.1.1. Mode 0: 13-bit Counter/Timer
Timer 0 and Timer 1 operate as 13-bit counter/timers in Mode 0. The following describes the configuration
and operation of Timer 0. However, both timers operate identically, and Timer 1 is configured in the same
manner as described for Timer 0.
The TH0 register holds the eight MSBs of the 13-bit counter/timer. TL0 holds the five LSBs in bit positions
TL0.4–TL0.0. The three upper bits of TL0 (TL0.7–TL0.5) are indeterminate and should be masked out or
ignored when reading. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to
0x0000, the timer overflow flag TF0 (TCON.5) is set and an interrupt will occur if Timer 0 interrupts are
enabled.
Timer 0 and Timer 1 Modes: Ti mer 2 Modes: Timer 3 Modes:
13-bit counter/timer 16-bit tim er with au to-r elo a d 16-bit timer with au to -r elo ad
16-bit counter/timer
8-bit counter/timer
with auto-reload Two 8-bit timers with auto-reload Two 8-bit timers with auto-reload
Two 8-bit counter/timers
(Timer 0 only)
C8051F310/1/2/3/4/5/6/7
188 Rev. 1.7
The C/T0 bit (TMOD.2) selects the counter/timer's clock source. When C/T0 is set to logic 1, high-to-low
transitions at the selected Timer 0 input pin (T0) increment the timer register (Refer to Section
“13.1. Priority Crossbar Decoder” on page 131 for information on selecting and configuring external I/O
pins). Clearing C/T selects the clock defined by the T0M bit (CKCON.3). When T0M is set, Timer 0 is
clocked by the system clock. When T0M is cleared, Timer 0 is clocked by the sour ce selecte d by the Clock
Scale bits in CKCON (see SFR Definition 17.3).
Setting the TR0 bit (TCON.4) enables the timer when either GATE0 (TMOD.3) is logic 0 or the input signal
/INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 8.11. “IT01CF: INT0/INT1
Configuration” on page 101). Setting GATE0 to ‘1’ allows the timer to be controlled by the external input
signal /INT0 (see Section “8.3.5. Interrupt Register Descriptions” on page 97), facilitating pulse width
measurements.
Setting TR0 does not force the timer to reset. The timer registers should be loaded with the desired initial
value before the timer is enabled.
TL1 and TH1 form the 13-bit re gister for Timer 1 in the same manner as describe d above for TL0 a nd TH0.
Timer 1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0. The
input signal /INT1 is used with Timer 1; the /INT1 polarity is defined by bit IN1PL in register IT01CF (see
SFR Definition 8.11. “IT01CF : INT 0/I NT 1 Co nf igu ra tio n” on page 101).
TCLK
TL0
(5 bits) TH0
(8 bits)
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
TR0
0
1
0
1
SYSCLK
Pre-scaled Clock
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
TMOD
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
GATE0
/INT0
T0
Crossbar
INT01CF
I
N
1
S
L
1
I
N
1
S
L
0
I
N
1
S
L
2
I
N
1
P
L
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
IN0PL
XOR
Figure 17.1. T0 Mode 0 Block Diagram
TR0 GATE0 /INT0 Counter/Timer
0 X X Disabled
1 0 X Enabled
110Disabled
111Enabled
X = Don't Care
Rev. 1.7 189
C8051F310/1/2/3/4/5/6/7
17.1.2. Mode 1: 16-bit Counter/Timer
Mode 1 operation is the same as Mode 0, except that the counter/timer re gisters use all 16 bits. The coun-
ter/timers are enabled and configured in Mode 1 in the same manner as for Mode 0.
17.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit cou nter/timers with automa tic reload of the st art
value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all
ones to 0x00, the timer overflow flag TF0 (TCON.5) is set and the counter in TL0 is reloaded from TH0. If
Timer 0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload value in TH0 is
not changed. TL0 must be initialized to the desired value before enabling the timer for the first count to be
correct. When in Mode 2, Timer 1 operates identically to Timer 0.
Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the
TR0 bit (TCON.4) enab les the timer wh en either GATE0 (TMOD.3) is logic 0 or when the input signal /INT0
is active as defined by bit IN0PL in register IT01CF (see Sect ion “ 8 .3 .2. Ext ernal Int errupts” on p age 95
for details on the external input signals /INT0 and /INT1).
TCLK
TMOD
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
TL0
(8 bits)
Reload
TH0
(8 bits)
0
1
0
1
SYSCLK
Pre-scaled Clock
INT01CF
I
N
1
S
L
1
I
N
1
S
L
0
I
N
1
S
L
2
I
N
1
P
L
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
TR0
GATE0
IN0PL
XOR
/INT0
T0
Crossbar
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
Figure 17.2. T0 Mode 2 Block Diagram
C8051F310/1/2/3/4/5/6/7
190 Rev. 1.7
17.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The coun-
ter/timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0
and TF0. TL0 can use either the system clock or an ex ternal inp ut signal as it s tim ebase. The TH0 r egister
is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the
Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the
Time r 1 inte rr u pt .
Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0,
1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However,
the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate A DC
conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode set-
tings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1,
configure it for Mode 3.
TL0
(8 bits)
TMOD
0
1
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
Interrupt
0
1
SYSCLK
Pre-scaled Clock TR1 TH0
(8 bits)
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
TR0
GATE0
IN0PL
XOR
/INT0
T0
Crossbar
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
Figure 17.3. T0 Mode 3 Block Diagram
Rev. 1.7 191
C8051F310/1/2/3/4/5/6/7
SFR Definition 17.1. TCON: Timer Control
Bit7: TF1: Timer 1 Overflow Flag.
Set by hardware when Timer 1 overflows. This flag can be cleared by software but is auto-
matically cleared when the CPU vectors to the Time r 1 inte rr u pt service routine.
0: No Time r 1 overflow detec te d.
1: Timer 1 has overflowed.
Bit6: TR1: Timer 1 Run Control.
0: Tim e r 1 disa b l ed .
1: Timer 1 enabled.
Bit5: TF0: Timer 0 Overflow Flag.
Set by hardware when Timer 0 overflows. This flag can be cleared by software but is auto-
matically cleared when the CPU vectors to the Time r 0 inte rr u pt service routine.
0: No Time r 0 overflow detec te d.
1: Timer 0 has overflowed.
Bit4: TR0: Timer 0 Run Control.
0: Tim e r 0 disa b l ed .
1: Timer 0 enabled.
Bit3: IE1: External Interrupt 1.
This flag is set by hardware when an edge/le vel of type defined by IT1 is de tected. It can be
cleared by soft ware but is automatica lly cleared when the CPU vectors to the Exter nal Inter-
rupt 1 service routine if IT1 = 1. When IT1 = 0, this flag is set to ‘1’ when /INT1 is active as
defined by bit IN1PL in register IT01CF (see SFR Definition 8.11).
Bit2: IT1: Interrupt 1 Type Select.
This bit selects whether the configured /INT1 interrupt will be edge or level sensitive. /INT1
is configured active low or high by the IN1PL bit in the IT01CF register (see SFR Definition
8.11).
0: /INT1 is level triggered.
1: /INT1 is edge triggered.
Bit1: IE0: External Interrupt 0.
This flag is set by hardware when an edge/le vel of type defined by IT0 is de tected. It can be
cleared by soft ware but is automatica lly cleared when the CPU vectors to the Exter nal Inter-
rupt 0 service routine if IT0 = 1. When IT0 = 0, this flag is set to ‘1’ when /INT0 is active as
defined by bit IN0PL in register IT01CF (see SFR Definition 8.11).
Bit0: IT0: Interrupt 0 Type Select.
This bit selects whether the configured /INT0 interrupt will be edge or level sensitive. /INT0
is configured active low or high by the IN0PL bit in register IT01CF (see SFR Definition
8.11).
0: /INT0 is level triggered.
1: /INT0 is edge triggered.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0x88
C8051F310/1/2/3/4/5/6/7
192 Rev. 1.7
SFR Definition 17.2. TMOD: Timer Mode
Bit7: GATE1: Timer 1 Gate Control.
0: Time r 1 en a ble d wh en TR1 = 1 irres pe ctive of /INT1 logic level.
1: Time r 1 en a ble d on ly whe n TR1 = 1 AND /INT1 is active as defined by bit IN1PL in regis-
ter IT01CF (see SFR Definition 8.11).
Bit6: C/T1: Counter/Timer 1 Select.
0: Timer Function: Timer 1 incremented by clock defined by T1M bit (CKCON.4).
1: Counter Function: Timer 1 incremented by high-to-low transitions on external input pin
(T1).
Bits5–4: T1M1–T1M0: Timer 1 Mode Select.
These bits select the Timer 1 operation mode.
Bit3: GATE0: Timer 0 Gate Control.
0: Time r 0 en a ble d wh en TR0 = 1 irres pe ctive of /INT0 logic level.
1: Time r 0 en a ble d on ly whe n TR0 = 1 AND /INT0 is active as defined by bit IN0PL in regis-
ter IT01CF (see SFR Definition 8.11).
Bit2: C/T0: Counter/Timer Select.
0: Timer Function: Timer 0 incremented by clock defined by T0M bit (CKCON.3).
1: Counter Function: Timer 0 incremented by high-to-low transitions on external input pin
(T0).
Bits1–0: T0M1–T0M0: Timer 0 Mode Select.
These bits select the Timer 0 operation mode.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
GATE1 C/T1 T1M1 T1M0 GATE0 C/T0 T0M1 T0M0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x89
T1M1 T1M0 Mode
0 0 Mode 0: 13-bit counter/timer
0 1 Mode 1: 16-bit counter/timer
1 0 Mode 2: 8-bit counter/timer with auto-reload
1 1 Mode 3: Ti mer 1 inactive
T0M1 T0M0 Mode
0 0 Mode 0: 13-bit counter/timer
0 1 Mode 1: 16-bit counter/timer
1 0 Mode 2: 8-bit counter/timer with auto-reload
1 1 Mode 3: Two 8-bit counter/timers
Rev. 1.7 193
C8051F310/1/2/3/4/5/6/7
SFR Definition 17.3. CKCON: Clock Control
Bit7: T3MH: Timer 3 High Byte Clock Select.
This bit selects the clock supplied to the Timer 3 high byte if Timer 3 is configured in split 8-
bit timer mode. T3MH is ignored if Timer 3 is in any other mode.
0: Timer 3 high byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 high byte uses the system clock.
Bit6: T3ML: Timer 3 Low Byte Clock Select.
This bit selects the clock supplied to Timer 3. If Timer 3 is configured in split 8-bit timer
mode, this bit selects the clock supplied to the lower 8-bit timer.
0: Timer 3 low byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 low byte uses the system clock.
Bit5: T2MH: Timer 2 High Byte Clock Select.
This bit selects the clock supplied to the Timer 2 high byte if Timer 2 is configured in split 8-
bit timer mode. T2MH is ignored if Timer 2 is in any other mode.
0: Timer 2 high byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 high byte uses the system clock.
Bit4: T2ML: Timer 2 Low Byte Clock Select.
This bit selects the clock supplied to Timer 2. If Timer 2 is configured in split 8-bit timer
mode, this bit selects the clock supplied to the lower 8-bit timer.
0: Timer 2 low byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 low byte uses the system clock.
Bit3: T1M: Timer 1 Clock Select.
This select the clock source supplied to Timer 1. T1M is ignored when C/T1 is set to logic 1.
0: Timer 1 uses the clock defined by the prescale bits, SCA1-SCA0.
1: Timer 1 uses the system cloc k.
Bit2: T0M: Timer 0 Clock Select.
This bit selects the clock source supplied to Timer 0. T0M is ignored when C/T0 is set to
logic 1.
0: Counter/Timer 0 uses the clock defined by the prescale bits, SCA1-SCA0.
1: Counter/Timer 0 uses the system clock.
Bits1–0: SCA1-SCA0: Timer 0/1 Prescale Bits.
These bits control the division of the clock supplied to Timer 0 and/or Timer 1 if configured
to use prescaled clock inputs.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
T3MH T3ML T2MH T2ML T1M T0M SCA1 SCA0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x8E
SCA1 SCA0 Prescaled Clock
0 0 System clock divided by 12
0 1 System clock divided by 4
1 0 System clock divided by 48
1 1 External clock divided by 8
Note: External clock divided by 8 is synchronized with the system clock, and the external
clock must be less than or equal to the system clock to operate in this mode.
C8051F310/1/2/3/4/5/6/7
194 Rev. 1.7
SFR Definition 17.4. TL0: Timer 0 Low Byte
Bits 7–0: TL0: Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x8A
SFR Definition 17.5. TL1: Timer 1 Low Byte
Bits 7–0: TL1: Timer 1 Low Byte.
The TL1 register is the low byte of the 16-bit Timer 1.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x8B
SFR Definition 17.6. TH0: Timer 0 High Byte
Bits 7–0: TH0: Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x8C
SFR Definition 17.7. TH1: Timer 1 High Byte
Bits 7–0: TH1: Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x8D
Rev. 1.7 195
C8051F310/1/2/3/4/5/6/7
17.2. Timer 2
T imer 2 is a 16-bit time r formed by two 8-bi t SFRs: TMR2L (low byte) and TMR2H (high byte ). Timer 2 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T2SPLIT bit (TMR2CN.3) defines
the Timer 2 operation mode.
Timer 2 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
source divided by 8. The external clock mode is ideal for real-time clock (RTC) functionality, where the
internal oscillator drives the system c lock while Timer 2 (and/or the PCA) is clocked by an external preci-
sion oscillator. Note that the external oscillator source divided by 8 is synchronized with the system clock.
17.2.1. 16-bit Timer with Auto-Reload
When T2SPLIT (TMR2CN.3) is zero, Timer 2 operates as a 16-bit timer with auto-reload. Timer 2 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 2
reload registers (TMR2RLH and TMR2RLL) is loaded into the Timer 2 register as shown in Figure 17.4,
and the Timer 2 High Byte Overflow Flag (TMR2CN.7) is set. If Timer 2 interrupts are enabled (if IE.5 is
set), an interrupt will be generated on each Timer 2 overflow. Additionally, if Timer 2 interrupts are enabled
and the TF2LEN bit is set (TMR2CN.5), an interrupt will be generated each time the lower 8 bits (TMR2L)
overflow fro m 0xFF to 0x00.
Ex te rn a l C lo c k / 8
SYSCLK / 12
SYSCLK
TMR2L TMR2H
TMR2RLL TMR2RLH Reload
TCLK
0
1
TR2
TMR2CN
T2SPLIT
TF2L
TF2H
T2XCLK
TR2
0
1
T2XCLK
Interrupt
TF2LEN
To ADC,
SMBus
To SMBus
TMR2L
Overflow
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
Figure 17.4. Timer 2 16-Bit Mode Block Diagram
C8051F310/1/2/3/4/5/6/7
196 Rev. 1.7
17.2.2. 8-bit Timers with Auto-Reload
When T2SPLIT is s et, Time r 2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers oper-
ate in auto-reload mode as shown in Figure 17.5. TMR2RLL holds the reload value for TMR2L; TMR2RLH
holds the reload value for TMR2H. The TR2 bit in TMR2CN handles the run control TMR2H. TMR2L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Timer 2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or
the clock defined by the Timer 2 External Clock Select bit (T2XCLK in TMR2CN), as follows:
Note: External clock divided by 8 is synchronized with the system clock, and the external clock must be
less than or equal to the system clock to operate in this mode.
The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows
from 0xFF to 0x00. When Timer 2 interrupts are enabled (IE.5), an interrupt is generated each time
TMR2H overflo ws. If Timer 2 interrupts ar e e nab led and TF2LEN (TMR2CN.5) is set, an interrup t is g ener -
ated each time either TMR2L or TMR2H overflows. When TF2LEN is enabled, software must check the
TF2H and TF2L flags to determine the source of the Timer 2 interrupt. The TF2H and TF2L interrupt flags
are not cleared by hardware and must be manually cleared by software.
SYSCLK
TCLK
0
1TR2
External Clock / 8
SYSCLK / 12 0
1
T2XCLK
1
0
TMR2H
TMR2RLH Reload
Reload
TCLK TMR2L
TMR2RLL
Interrupt
TMR2CN
T2SPLIT
TF2LEN
TF2L
TF2H
T2XCLK
TR2
To ADC,
SMBus
To SMB us
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
Figure 17.5. Timer 2 8-Bit Mode Block Diagram
T2MH T2XCLK TMR2H Clock
Source T2ML T2XCLK TMR2L Clock
Source
0 0 SYSCLK/12 0 0 SYSCLK/12
0 1 External Clock/8 0 1 External Clock/8
1 X SYSCLK 1 X SYSCLK
Rev. 1.7 197
C8051F310/1/2/3/4/5/6/7
SFR Definition 17.8. TMR2CN: Timer 2 Control
Bit7: TF2H: Timer 2 High Byte Overflow Flag.
Set by hardware when the Timer 2 high byte overflows from 0xFF to 0x00. In 16 bit mode,
this will occur when T imer 2 overflows from 0xFFFF to 0x0000. When the T imer 2 interrupt is
enabled, setting this bit causes the CPU to vector to the Timer 2 interrupt service routine.
TF2H is not automatically cleared by hardware and must be cleared by software.
Bit6: TF2L: Timer 2 Low Byte Overflow Flag.
Set by hardware when the Timer 2 low byte overflows from 0xFF to 0x00. When this bit is
set, an interrupt will be generated if TF2LEN is set and Timer 2 interrupts are enabled. TF2L
will set when the low byte overflows regardless of the Timer 2 mode. This bit is not automat-
ically cleared by hardware.
Bit5: TF2LEN: Timer 2 Low Byte Interrupt Enable.
This bit enables/dis ab les Timer 2 Low Byte interrupts. If TF2LEN is set and Timer 2 inter-
rupts are enabled, an interrupt will be generated when the low byte of Timer 2 overflows.
This bit should be cleared when operating Timer 2 in 16-bit mode.
0: Time r 2 Lo w Byte inte rr up ts disabled .
1: Time r 2 Lo w Byte inte rr up ts enable d.
Bit4: UNUSED. Read = 0b. Write = don’t care.
Bit3: T2SPLIT: Timer 2 Split Mode Enable.
When this bit is set, Timer 2 operates as two 8-bit timers with auto-reload.
0: Timer 2 operates in 16-bit auto-reload mode.
1: Timer 2 operates as two 8-bit auto-reload timers.
Bit2: TR2: Timer 2 Run Control.
This bit enables/disables Timer 2. In 8-bit mode, this bit enables/disables TMR2H only;
TMR2L is always enabled in this mode.
0: Ti me r 2 dis ab l ed .
1: Ti me r 2 en a bled.
Bit1: UNUSED. Read = 0b. Write = don’t care.
Bit0: T2XCLK: Timer 2 External Clock Select.
This bit selects the external clock source for Timer 2. If Timer 2 is in 8-bit mode, this bit
selects the external oscillator clock source for both timer bytes. However, the Timer 2 Clock
Select bits (T2MH and T2ML in register CKCON) may still be used to select between the
external clock and the system clock for either timer.
0: Timer 2 external clock selection is the system clock divided by 12.
1: Timer 2 external clock selection is the external clock divided by 8. Note that the external
oscillator source divided by 8 is synchronized with the system clock.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
TF2H TF2L TF2LEN - T2SPLIT TR2 - T2XCLK 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xC8
C8051F310/1/2/3/4/5/6/7
198 Rev. 1.7
SFR Definition 17.9. TMR2RLL: Timer 2 Reload Register Low Byte
Bits 7–0: TMR2RLL: Timer 2 Reload Register Low Byte.
TMR2RLL holds the low byte of the reload value for Timer 2.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xCA
SFR Definition 17.10. TMR2RLH: Timer 2 Reload Register High Byte
Bits 7–0: TMR2RLH: Timer 2 Reload Register High Byte.
The TMR2RLH holds the high byte of the reload value for Timer 2.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xCB
SFR Definition 17.11. TMR2L: Timer 2 Low Byte
Bits 7–0: TMR2L: Timer 2 Low Byte.
In 16-bit mode, the TMR2L register cont ains the low byte of the 16-bit T imer 2. In 8-bit mode ,
TMR2L contains the 8-bit low byte timer value.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xCC
SFR Definition 17.12. TMR2H Timer 2 High Byte
Bits 7–0: TMR2H: Timer 2 High Byte.
In 16-bit mode, the TMR2H register contains the high byte of the 16-bit Timer 2. In 8-bit
mode, TMR2H contains the 8-bit high byte timer value.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xCD
Rev. 1.7 199
C8051F310/1/2/3/4/5/6/7
17.3. Timer 3
T imer 3 is a 16-bit time r formed by two 8-bi t SFRs: TMR3L (low byte) and TMR3H (high byte ). Timer 3 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T3SPLIT bit (TMR3CN.3) defines
the Timer 3 operation mode.
Timer 3 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
source divided by 8. The external clock mode is ideal for real-time clock (RTC) functionality, where the
internal oscillator drives the system c lock while Timer 3 (and/or the PCA) is clocked by an external preci-
sion oscillator. Note that the external oscillator source divided by 8 is synchronized with the system clock.
17.3.1. 16-bit Timer with Auto-Reload
When T3SPLIT (TMR3CN.3) is zero, Timer 3 operates as a 16-bit timer with auto-reload. Timer 3 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 3
reload registers (TMR3RLH and TM32RLL) is loaded into the Timer 3 register as shown in Figure 17.4,
and the Timer 3 High Byte Overflow Flag (TMR3CN.7) is set. If Timer 3 interrupts are en able d, an interru pt
will be generated on each Timer 3 overflow. Additionally, if Timer 3 interrupts are enabled and the TF3LEN
bit is set (TMR3CN.5), an interrupt will be generated each time the lower 8 bits (TMR3L) overflow from
0xFF to 0x00 .
Ex te rn a l C loc k / 8
SYSCLK / 12
SYSCLK
TMR3L TMR3H
TMR3RLL TMR3RLH Reload
TCLK
0
1
TR3
TMR3CN
T3SPLIT
TF3L
TF3H
T3XCLK
TR3
0
1
T3XCLK
Interrupt
TF3LEN
To ADC
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
Figure 17.6. Timer 3 16-Bit Mode Block Diagram
C8051F310/1/2/3/4/5/6/7
200 Rev. 1.7
17.3.2. 8-bit Timers with Auto-Reload
When T3SPLIT is s et, Time r 3 operates as two 8-bit timers (TMR3H and TMR3L). Both 8-bit timers oper-
ate in auto-reload mode as shown in Figure 17.5. TMR3RLL holds the reload value for TMR3L; TMR3RLH
holds the reload value for TMR3H. The TR3 bit in TMR3CN handles the run control TMR3H. TMR3L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Timer 3 Clock Select bits (T3MH and T3ML in CKCON) select either SYSCLK or
the clock defined by the Timer 3 External Clock Select bit (T3XCLK in TMR3CN), as follows:
Note: External clock divided by 8 is synchronized with the system clock, and the external clock must be
less than or equal to the system clock to operate in this mode.
The TF3H bit is set when TMR3H overflows from 0xFF to 0x00; the TF3L bit is set when TMR3L overflows
from 0xFF to 0x00. When Timer 3 interrupt s are ena bled, an interrupt is gene rated each time TMR3H over -
flows. If Timer 3 interrupts are enabled and TF3LEN (TMR3CN.5) is set, an interrupt is generated each
time either TMR3L or TMR3H overflows. When TF3LEN is enabled, software must check the TF3H and
TF3L flags to determine the source of the Timer 3 interrupt. The TF3H and TF3L interrupt flags are not
cleared by hardware and must be manually cleared by software.
SYSCLK
TCLK
0
1TR3
Ex te rna l C lo c k / 8
SYSCLK / 12 0
1
T3XCLK
1
0
TMR3H
TMR3RLH Reload
Reload
TCLK TMR3L
TMR3RLL
Interrupt
TMR3CN
T3SPLIT
TF3LEN
TF3L
TF3H
T3XCLK
TR3
To ADC
CKCON
T
3
M
H
T
3
M
L
S
C
A
0
S
C
A
1
T
0
M
T
2
M
H
T
2
M
L
T
1
M
Figure 17.7. Timer 3 8-Bit Mode Block Diagram
T3MH T3XCLK TMR3H Clock
Source T3ML T3XCLK TMR3L Clock
Source
0 0 SYSCLK/12 0 0 SYSCLK/12
0 1 External Clock/8 0 1 External Clock/8
1 X SYSCLK 1 X SYSCLK
Rev. 1.7 201
C8051F310/1/2/3/4/5/6/7
SFR Definition 17.13. TMR3CN: Timer 3 Control
Bit7: TF3H: Timer 3 High Byte Overflow Flag.
Set by hardware when the Timer 3 high byte overflows from 0xFF to 0x00. In 16 bit mode,
this will occur when T imer 3 overflows from 0xFFFF to 0x0000. When the T imer 3 interrupt is
enabled, setting this bit causes the CPU to vector to the Timer 3 interrupt service routine.
TF3H is not automatically cleared by hardware and must be cleared by software.
Bit6: TF3L: Timer 3 Low Byte Overflow Flag.
Set by hardware when the Timer 3 low byte overflows from 0xFF to 0x00. When this bit is
set, an interrupt will be generated if TF3LEN is set and Timer 3 interrupts are enabled. TF3L
will set when the low byte overflows regardless of the Timer 3 mode. This bit is not automat-
ically cleared by hardware.
Bit5: TF3LEN: Timer 3 Low Byte Interrupt Enable.
This bit enables/dis ab les Timer 3 Low Byte interrupts. If TF3LEN is set and Timer 3 inter-
rupts are enabled, an interrupt will be generated when the low byte of Timer 3 overflows.
This bit should be cleared when operating Timer 3 in 16-bit mode.
0: Time r 3 Lo w Byte inte rr up ts disabled .
1: Time r 3 Lo w Byte inte rr up ts enable d.
Bit4: UNUSED. Read = 0b. Write = don’t care.
Bit3: T3SPLIT: Timer 3 Split Mode Enable.
When this bit is set, Timer 3 operates as two 8-bit timers with auto-reload.
0: Timer 3 operates in 16-bit auto-reload mode.
1: Timer 3 operates as two 8-bit auto-reload timers.
Bit2: TR3: Timer 3 Run Control.
This bit enables/disables Timer 3. In 8-bit mode, this bit enables/disables TMR3H only;
TMR3L is always enabled in this mode.
0: Ti me r 3 dis ab l ed .
1: Ti me r 3 en a bled.
Bit1: UNUSED. Read = 0b. Write = don’t care.
Bit0: T3XCLK: Timer 3 External Clock Select.
This bit selects the external clock source for Timer 3. If Timer 3 is in 8-bit mode, this bit
selects the external oscillator clock source for both timer bytes. However, the Timer 3 Clock
Select bits (T3MH and T3ML in register CKCON) may still be used to select between the
external clock and the system clock for either timer.
0: Timer 3 external clock selection is the system clock divided by 12.
1: Timer 3 external clock selection is the external clock divided by 8. Note that the external
oscillator source divided by 8 is synchronized with the system clock.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
TF3H TF3L TF3LEN - T3SPLIT TR3 - T3XCLK 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x91
C8051F310/1/2/3/4/5/6/7
202 Rev. 1.7
SFR Definition 17.14. TMR3RLL: Timer 3 Reload Register Low Byte
Bits 7–0: TMR3RLL: Timer 3 Reload Register Low Byte.
TMR3RLL holds the low byte of the reload value for Timer 3.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x92
SFR Definition 17.15. TMR3RLH: Timer 3 Reload Register High Byte
Bits 7–0: TMR3RLH: Timer 3 Reload Register High Byte.
The TMR3RLH holds the high byte of the reload value for Timer 3.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x93
SFR Definition 17.16. TMR3L: Timer 3 Low Byte
Bits 7–0: TMR3L: Timer 3 Low Byte.
In 16-bit mode, the TMR3L register cont ains the low byte of the 16-bit T imer 3. In 8-bit mode ,
TMR3L contains the 8-bit low byte timer value.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x94
SFR Definition 17.17. TMR3H Timer 3 High Byte
Bits 7–0: TMR3H: Timer 3 High Byte.
In 16-bit mode, the TMR3H register contains the high byte of the 16-bit Timer 3. In 8-bit
mode, TMR3H contains the 8-bit high byte timer value.
R/W R/W R/W R/W R /W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0x95
Rev. 1.7 203
C8051F310/1/2/3/4/5/6/7
18. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU
intervention than the standard 8051 counter/timers. The PCA consists of a dedicated 16-bit counter/timer
and five 16-bit capture/compare modules. Each capture/compare module has its own associated I/O line
(CEXn) which is routed through the Crossbar to Port I/O when enabled (See Section “13.1. Priority
Crossbar Decoder” on page 131 for details on configuring the Crossbar). The counter/timer is driven by
a programmable time base that can select betwe en six sources: system clock, system clock divided by four,
system clock divided by twelve, the external oscillator clock source divided by 8, Timer 0 overflow, or an
external clock signal on the ECI input pin. Each capture/compare module may be configured to operate
independently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Fre-
quency Output, 8-Bit PWM, or 16-Bit PWM (each mode is described in Section “18.2. Capture/Compare
Modules” on page 205). The external oscillator clock option is ideal for real-time clock (R TC) functionality,
allowing the PCA to be clocked by a precision external oscillator while the internal oscillator drives the sys-
tem clock. The PCA is configured and controlled through the system controller's Special Function Regis-
ters. The PCA block diagram is shown in Figure 18.1
Import ant Note: The PCA Module 4 may be used as a watchdog timer (WDT), and is enabled in this mod e
following a system reset. Access to certain PCA registers is restricted while WDT mode is enabled. See
Section 18.3 for details.
Capture/Compare
Module 1
Capture/Compare
Module 0 Capture/Compare
Module 2 Capture/Compare
Module 3 Capture/Compare
Module 4 / WDT
CEX1
ECI
Crossbar
CEX2
CEX3
CEX4
CEX0
Port I/O
16-Bit Counter/Timer
PCA
CLOCK
MUX
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
Figure 18.1. PCA Block Diagram
C8051F310/1/2/3/4/5/6/7
204 Rev. 1.7
18.1. PCA Counter/Timer
The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte
(MSB) of the 16-bit counter/tim er and PCA0L is the low byte (LSB). Reading PCA0L automatically latches
the value of PCA0H into a “snapshot” register; the following PCA0H read accesses this “snapshot” register.
Reading the PCA0L Register first guarantees an accurate reading of the entire 16-bit PCA0 counter .
Reading PCA0H or PCA0L does not disturb the counter operation. The CPS2-CPS0 bits in the PCA0MD
register select the timebase for the counter/timer as shown in Table 18.1. Note that in ‘External oscilla tor
source divided by 8’ mode, the external oscillator source is synchronized with the system clock,
and must have a frequency less than or equal to the system clock.
When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is
set to logic 1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in
PCA0MD to logic 1 enables the CF flag to generate an interrupt request. The CF bit is not automatically
cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by soft-
ware (Note: PCA0 interrupts must be globally enabled before CF interrupts are recognized. PCA0 inter-
rupts are globally enabled by setting the EA bit (IE.7) and the EPCA0 bit in EIE1 to logic 1). Clearing the
CIDL bit in the PCA0MD register allows the PCA to continue normal operation while the CPU is in Idle
mode.
Table 18.1. PCA Timebase Input Options
*Note: External oscillator source divided by 8 is synchronized with the system clock.
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
4
C
C
F
3
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
IDLE
0
1
PCA0H PCA0L
Snapshot
Register
To SFR Bus
Overflow To PCA Interrupt System
CF
PCA0L
read
To PCA Modules
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
000
001
010
011
100
101
SYSCLK
External Clock/8
Figure 18.2. PCA Counter/Timer Block Diagram
CPS2 CPS1 CPS0 Timebase
0 0 0 System clock divided by 12
0 0 1 System clock divided by 4
0 1 0 Timer 0 overflow
0 1 1 High-to-low transitions on ECI (max rate = system clock divided by 4)
1 0 0 System clock
1 0 1 External oscillator source divided by 8*
Rev. 1.7 205
C8051F310/1/2/3/4/5/6/7
18.2. Capture/Compare Modules
Each module can be configured to operate independently in one of six operation modes: Edge-triggered
Capture, Software Timer, High Speed Output, Frequency Output, 8-Bit Pulse Width Modulator, or 16-Bit
Pulse Width Modulator. Each module has Special Function Registers (SFRs) associated with it in the CIP-
51 system controller. These registers are used to exchange dat a with a module and configu re the modu le's
mode of operation.
Table 18.2 summarizes the bit settings in the PCA0CPMn registers used to select the PCA capture/com-
pare module’s operating modes. Setting the ECCFn bit in a PCA0CPMn register enables the module's
CCFn interrupt. Note: PCA0 interr upts must be globally enabled before individual CCFn interrupts are rec-
ognized. PCA0 interrupts are globally enabled by setting the EA bit and the EPCA0 bit to logic 1. See
Figure 18.3 for details on the PCA interrupt configuration.
Table 18.2. PCA0CPM Register Settings for PCA Capture/Compare Modules
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
4
C
C
F
3
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
0
1
PCA Module 0
(CCF0)
PCA Module 1
(CCF1)
ECCF1
0
1
ECCF0
0
1
PCA Module 2
(CCF2)
ECCF2
0
1
PCA Module 3
(CCF3)
ECCF3
0
1
PCA Module 4
(CCF4)
ECCF4
PCA Counter/
Timer Overflow
0
1
Interrupt
Priority
Decoder
EPCA0
0
1
EA
0
1
PCA0CPMn
(for n = 0 to 4)
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
Figure 18.3. PCA Interrupt Block Diagram
PWM16 ECOM CAPP CAPN MAT TOG PWM ECCF Operation Mode
X X 10000X
Capture triggered by positive edge
on CEXn
X X 01000X
Capture triggered by negative edge
on CEXn
X X 11000X
Capture triggered by transition on
CEXn
X 1 00100XSoftware Timer
X 1 00110XHigh Speed Output
X 1 0 0 X 1 1 X Frequency Outp ut
0 1 0 0 X 0 1 X 8-Bit Pulse Width Modu lator
1 1 0 0 X 0 1 X 16 -Bit Puls e Width Modula tor
X = Don’t Care
C8051F310/1/2/3/4/5/6/7
206 Rev. 1.7
18.2.1. Edge-triggered Capture Mode
In this mode, a valid tra nsition on the CEXn pin ca uses the PCA to capture the value of the PCA counter/
timer and load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and
PCA0CPHn). The CAPPn and CAPNn bits in the PCA0CPMn re gister ar e u sed to sele ct th e type o f tr an si-
tion that triggers the capture: low-to-high transition (positive edge), high-to-low transition (negative edge),
or either transition (positive or negative edge). When a capture occurs, the Capture/Compare Flag (CCFn)
in PCA0CN is set to logic 1 and an interrup t requ est is generated if CCF interrup ts are enabled. The CCFn
bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and
must be cleared by software. If both CAPPn and CAPNn bits are set to logic 1, then the state of the Port
pin associated with CEXn can be read directly to determine whether a rising-edge or falling-edge caused
the capture.
PCA0L
PCA0CPLn
PCA
Timebase
CEXn
CrossbarPort I/O
PCA0H
Capture
PCA0CPHn
0
1
0
1
(to CCFn)
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
4
C
C
F
3
PCA Interrupt
0x00xx
Figure 18.4. PCA Capture Mode Diagram
Note: The CEXn input signal mu st remain high or low for at least 2 system clock cycles in order to be valid.
Rev. 1.7 207
C8051F310/1/2/3/4/5/6/7
18.2.2. Software Timer (Compare) Mode
In Softwa re Timer mode, the PCA counter/timer value is compared to the module's 16- bit capture / compare
register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in
PCA0CN is set to logic 1 and an interr upt requ est is ge nerated if CCF inte rrupt s ar e enabled. Th e CCFn bit
is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must
be cleared by software. Setting the ECOMn and MATn bits in the PCA0CPMn register enables Software
Tim e r mo d e.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to ‘0’; writing to PCA0CPHn sets ECOMn to ‘1’.
Match
16-bit Comparator
PCA0H
PCA0CPHn
Enable
PCA0L
PCA
Timebase
PCA0CPLn
00 00
0
1
x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
4
C
C
F
3
PCA Interrupt
Figure 18.5. PCA Software Timer Mode Diagram
C8051F310/1/2/3/4/5/6/7
208 Rev. 1.7
18.2.3. High-Speed Output Mode
In High Speed Output mode, a module’s associated CEXn pin is toggled each time a match occurs
between the PCA Counter and the module's 16-bit capture/compare register (PCA0CPHn and
PCA0CPLn) Setting the TOGn, MATn, and ECOMn bits in the PCA0CPMn register enables the High-
Speed Outp ut mode.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to ‘0’; writing to PCA0CPHn sets ECOMn to ‘1’.
Match
16-bit Comparator
PCA0H
PCA0CPHn
Enable
PCA0L
PCA
Timebase
PCA0CPLn
0
1
00 0x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
CEXn
Crossbar Port I/O
Toggle
0
1
TOGn
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
4
C
C
F
3
PCA Interrupt
Figure 18.6. PCA High Speed Output Mode Diagram
Rev. 1.7 209
C8051F310/1/2/3/4/5/6/7
18.2.4. Frequency Output Mode
Frequency Output Mode produces a programmable-frequency square wave on the module’s associated
CEXn pin. The capture/compare module high byte holds the number of PCA clocks to count before the out-
put is toggled. The frequency of the square wave is then defined by Equation 18.1, where FPCA is the fre-
quency of the clock selected by the CPS2-0 bits in the PCA mo de register, PCA0MD.
Equation 18.1. Square Wave Frequency Output
FCEXn FPCA
2PCA0CPHn
-----------------------------------------
=
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
The lower byte of the capture/compare module is compared to the PCA counter low byte; on a match,
CEXn is toggled and the offset held in the high byte is added to the matched value in PCA0CPLn. Fre-
quency Output Mode is enable d by setting the ECOMn, TOGn, and PWMn bits in the PCA0 CPMn r eg iste r.
8-bit
Comparator
PCA0L
Enable
PCA Timebase
match
PCA0CPHn8-bit AdderPCA0CPLn
Adder
Enable
CEXn
Crossbar Port I/O
Toggle
0
1
TOGn
000 x
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
ENB
ENB
0
1
Writ e to
PCA0CPLn
Write to
PCA0CPHn
Reset
Figure 18.7. PCA Frequency Output Mode
C8051F310/1/2/3/4/5/6/7
210 Rev. 1.7
18.2.5. 8-Bit Pulse Width Modulator Mode
Each module can be u sed inde pe ndently to gen er ate a pulse width modulated (PWM) output on its associ-
ated CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer. The
duty cycle of the PWM output signal is varied using the module's PCA0CPLn capture/compare register.
When the value in the low byte of the PCA counter/timer (PCA0L) is equal to the value in PCA0CPLn, the
output on the CEXn pin will be set. When the count value in PCA0L overflows, the CEXn output will be
reset (see Figure 18.8). Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00,
PCA0CPLn is reloaded automatically with the value stored in the module’s capture/compare high byte
(PCA0CPHn) without software intervention. Setting the ECOMn and PWMn b it s in the PCA0CPM n register
enables 8-Bit Pulse Wid th Modulator mod e. The duty cycle for 8-Bit PWM Mode is given by Equation 18.2.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to ‘0’; writing to PCA0CPHn sets ECOMn to ‘1’.
DutyCycle 256 PCA0CPHn–
256
---------------------------------------------------
=
Equation 18.2. 8-Bit PWM Duty Cycle
Using Equation 18.2, the largest duty cycle is 100% (PCA0CPHn = 0), and the smallest duty cycle is
0.39% (PCA0CPHn = 0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to ‘0’.
8-bit
Comparator
PCA0L
PCA0CPLn
PCA0CPHn
CEXn
Crossbar Port I/O
Enable
Overflow
PCA Timebase
00x0 x
Q
Q
SET
CLR
S
R
match
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
0
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
Figure 18.8. PCA 8-Bit PWM Mode Diagram
Rev. 1.7 211
C8051F310/1/2/3/4/5/6/7
18.2.6. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-Bit PWM mode. In this mode, the 16-bit captu re/compare mod-
ule defines the nu mber o f PCA clocks for the low tim e of the PWM signal. When the PCA cou nter match es
the module contents, the output on CEXn is asserted high; when the counter overflows , CEXn is asserted
low. To output a varying duty cycle, new value writes should be synchronized with PCA CCFn match inter-
rupts. 16-Bit PWM Mo de is enabled by setting the ECOMn, PWMn, and PWM16n bits in the PCA0CPMn
register. For a varying duty cycle, match interrupts should be enabled (ECCFn = 1 AND MATn = 1) to help
synchronize the capture/compare register writes. The duty cycle for 16-Bit PWM Mode is given by
Equation 18.3.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to ‘0’; writing to PCA0CPHn sets ECOMn to ‘1’.
Equation 18.3. 16-Bit PWM Duty Cycle
DutyCycle 65536 PCA0CPn–
65536
-----------------------------------------------------
=
Using Equation 18.3, the largest duty cycle is 100% (PCA0CPn = 0), and the smallest duty cycle is
0.0015% (PCA0CP n = 0xFF FF) . A 0% duty cycle ma y be generated by clearing the ECOMn bit to ‘0’.
PCA0CPLnPCA0CPHn
Enable
PCA Timebase
00x0 x
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
1
16-bit Comparator
CEXn
Crossbar Port I/O
Overflow
Q
Q
SET
CLR
S
R
match
PCA0H PCA0L
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
Figure 18.9. PCA 16-Bit PWM Mode
C8051F310/1/2/3/4/5/6/7
212 Rev. 1.7
18.3. Watchdog Timer Mode
A programmable wa tchdog timer (WDT) function is avail able throu gh the PCA Module 4. The WDT is used
to generate a reset if the time between writes to the WDT up date register (P CA0CPH4 ) exceed a specified
limit. The WDT can be configured and enabled/disabled as needed by software.
With the WDTE bit set in the PCA0MD register, Module 4 operates as a watchdog timer (WDT). The Mod-
ule 4 high byte is compared to the PCA counter high byte; the Module 4 low byte holds the offset to be
used when WDT updates are performed. The Watchdog Timer is enabled on reset. Writes to some
PCA registers are restricted while the Watchdog Timer is enabled.
18.3.1. Watchdog Timer Operation
While the WDT is enabled:
• PCA counter is forced on.
• Writes to PCA0L and PCA0H are not allowed.
• PCA clock source bits (CPS2-CPS0) are fr oze n .
• PCA Idle control bit (CIDL) is frozen.
• Module 4 is forced into software timer mode.
• Writes to the Module 4 mode register (PCA0CPM4) are disabled.
While the WDT is enabled, writes to the CR bit will not change the PCA counter state; the counter will run
until the WDT is disabled. The PCA counter run control (CR) will read zero if the WDT is enabled but user
software has not enabled the PCA counter. If a match occurs between PCA0CPH4 and PCA0H while the
WDT is enabled, a reset will be generated. To prevent a WDT reset, the WDT may be updated with a write
of any value to PCA0CPH4. Upon a PCA0CPH4 write, PCA0H plus the offset held in PCA0CPL4 is loaded
into PCA0CPH4 (See Figure 18.10).
PCA0H
Enable
PCA0L Overflow
Reset
PCA0CPL4 8-bit Adder
PCA0CPH4
Adder
Enable
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
Match
Write to
PCA0CPH4
8-bit
Comparator
Figure 18.10. PCA Module 4 with Watchdog Timer Enabled
Rev. 1.7 213
C8051F310/1/2/3/4/5/6/7
Note that the 8-bit offset held in PCA0CPH4 is compared to the upper byte of the 16-bit PCA counter. This
offset value is the number of PCA0L overflows before a reset. Up to 256 PCA clocks may pass before the
first PCA0L overflow occurs, depending on the value of the PCA0L when the update is performed. The
total offset is then given (in PCA clocks) by Equation 18.4, where PCA0L is the value of the PCA0L register
at the time of the update.
Equation 18.4. Watchdog Timer Offset in PCA Clocks
Offset 256 PCA0CPL4256 PCA0L–+=
The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH4 and
PCA0H. Software may force a WDT reset by writing a ‘1’ to the CCF4 flag (PCA0CN.4) while the WDT is
enabled.
18.3.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:
• Disable the WDT by writing a ‘0’ to the WDTE bit.
• Select the desired PCA clock source (with the CPS2-CPS0 bits).
• Load PCA0CPL4 with the desired WDT update offset value.
• Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle
mode).
• Enable the WDT by setting the WDTE bit to ‘1’.
• Write a value to PCA0CPH4 to reload the WDT.
The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog
timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the
WDT cannot be disabled until the next system reset. If WDLC K is not set, the WDT is disabled by clearing
the WDTE bit.
The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by
12, PCA0L defaults to 0x00, and PCA0CPL4 defaults to 0x00. Using Equation 18.4, this results in a WDT
timeout interval of 256 syste m clock cycles. Table 18.3 lists some example timeout intervals for typical sys-
tem clocks.
Table 18.3. Watchdog Timer Timeout Intervals1
Notes:
1. Assumes SYSCLK / 12 as the PCA clock source, and a PCA0L
value of 0x00 at the update time.
2. Internal oscillator reset frequency.
C8051F310/1/2/3/4/5/6/7
214 Rev. 1.7
System Clock (Hz) PCA0CPL4 Timeout Interval (ms)
24,500,000 255 32.1
24,500,000 128 16.2
24,500,000 32 4.1
18,432,000 255 42.7
18,432,000 128 21.5
18,432,000 32 5.5
11,059,200 255 71.1
11,059,200 128 35.8
11,059,200 32 9.2
3,062,5002 255 257
3,062,5002128 129.5
3,062,500232 33.1
32,000 255 24576
32,000 128 12384
32,000 32 3168
Rev. 1.7 215
C8051F310/1/2/3/4/5/6/7
18.4. Register Descriptions for PCA
Following are detailed descriptions of the special function registers related to the operation of the PCA.
SFR Definition 18.1. PCA0CN: PCA Control
Bit7: CF: PCA Counter/Timer Overflow Flag.
Set by hardware when the PCA Counter/Timer overflows from 0xFFFF to 0x0000. When the
Counter/Timer Overflow (CF) interrupt is enabled, setting this bit causes the CPU to vector
to the PCA interrupt service routine. This bit is not automatically cleared by hardware and
must be cleared by software.
Bit6: CR: PCA Counter/Timer Run Control.
This bit enables/disables the PCA Counter/Timer.
0: PCA Counter/Timer disabled.
1: PCA Counter/Timer enabled.
Bit5: UNUSED. Read = 0b, Write = don't care.
Bit4: CCF4: PCA Module 4 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF4 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit3: CCF3: PCA Module 3 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF3 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit2: CCF2: PCA Module 2 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF2 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit1: CCF1: PCA Module 1 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF1 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit0: CCF0: PCA Module 0 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF0 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CF CR CCF4 CCF3 CCF2 CCF1 CCF0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
(bit addressable) 0xD8
C8051F310/1/2/3/4/5/6/7
216 Rev. 1.7
SFR Definition 18.2. PCA0MD: PCA Mode
Bit7: CIDL: PCA Counter/Timer Idle Control.
Specifies PCA behavior when CPU is in Idle Mode.
0: PCA continues to function normally while the system controller is in Idle Mode.
1: PCA operation is suspended while the system controller is in Idle Mode.
Bit6: WDTE: Watchdog Timer Enable
If this bit is set, PCA Module 4 is used as the watchdog timer.
0: Watchdog Timer disabled .
1: PCA Module 4 enabled as Watchdog Timer.
Bit5: WDLCK: Watchdog Timer Lock
This bit locks/unlocks the Wat chdog Timer Enable. When WDLCK is set, the Watchdog
Timer may not be disabled until the next system reset.
0: Watchdog Timer Enable unlocked.
1: Watchdog Ti mer Enable locked.
Bit4: UNUSED. Read = 0b, Write = don't care.
Bits3–1: CPS2–CPS0: PCA Counter/Timer Pulse Select.
These bits select the timebase source for the PCA counter.
Bit0: ECF: PCA Counter/Timer Overflow Interrupt Enable.
This bit sets the masking of the PCA Counter/Timer Overflow (CF) interrupt.
0: Disable the CF interrupt.
1: Enable a PCA Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is set.
Note: When the WDTE bit is set to ‘1’, the PCA0MD register cannot be modified. To change the contents
of the PCA0MD register, the Watchdog Timer must first be disabled.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
CIDL WDTE WDLCK CPS2 CPS1 CPS0 ECF 01000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xD9
CPS2 CPS1 CPS0 Timebase
0 0 0 System clock divided by 12
0 0 1 System clock divided by 4
0 1 0 Timer 0 overflow
011
High-to-low transitions on ECI (max rate = system clock
divided by 4)
1 0 0 System clock
1 0 1 External clock divided by 8*
1 1 0 Reserved
1 1 1 Reserved
*Note: External oscillator source divided by 8 is synchronized with the system clock.
Rev. 1.7 217
C8051F310/1/2/3/4/5/6/7
SFR Definition 18.3. PCA0CPMn: PCA Capture/Compare Mode Registers
PCA0CPMn Address: PCA0CPM0 = 0xDA (n = 0), PCA0CPM1 = 0xDB (n = 1),
PCA0CPM2 = 0xDC (n = 2), PCA0CPM3 = 0xDD (n = 3),
PCA0CPM4 = 0xDE (n = 4)
Bit7: PWM16n: 16-bit Pulse Width Modulation Enable .
This bit selects 16-bit mode when Pulse Width Modulation mode is enabled (PWMn = 1).
0: 8-bit PWM selected.
1: 16-bit PWM selected.
Bit6: ECOMn: Comparator Function Enable.
This bit enables/disables the comparator function for PCA module n.
0: Disabled.
1: Enabled.
Bit5: CAPPn: Capture Positive Function Enable.
This bit enables/disables the positive edge capture for PCA module n.
0: Disabled.
1: Enabled.
Bit4: CAPNn: Capture Negative Function Enable.
This bit enables/disables the negative edge capture for PCA module n.
0: Disabled.
1: Enabled.
Bit3: MATn: Match Function Enable.
This bit enables/di sables the match function for PCA module n. When enabled, matches of
the PCA counter with a module's capture/compare register cause the CCFn bit in PCA0MD
register to be set to logic 1.
0: Disabled.
1: Enabled.
Bit2: TOGn: Toggle Function Enable.
This bit enables/disables the toggle function for PCA module n. When enabled, matches of
the PCA counter with a module's capture/comp are register cause the logic level on the CEXn
pin to toggle. If the PWMn b it is also set to logi c 1, the mo dule op erates in Fre quency Outp ut
Mode.
0: Disabled.
1: Enabled.
Bit1: PWMn: Pulse Width Modulation Mode Enable.
This bit enables/disables the PWM function for PCA module n. When enabled, a pulse width
modulated signal is output on the CEXn pin. 8-bit PWM is used if PWM16n is cleared; 16-bit
mode is used if PWM16n is set to logic 1. If the TOGn bit is also set, the module operates in
Frequency Output Mode.
0: Disabled.
1: Enabled.
Bit0: ECCFn: Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCFn) interrupt.
0: Disable CCFn interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCFn is set.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
PWM16n ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xDA, 0xDB, 0xDC,
0xDD, 0xDE
C8051F310/1/2/3/4/5/6/7
218 Rev. 1.7
SFR Definition 18.4. PCA0L: PCA Counter/Timer Low Byte
Bits 7–0: PCA0L: PCA Counter/Timer Low By te.
The PCA0L register holds the low byte (LSB) of the 16-bit PCA Counter/Timer.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xF9
SFR Definition 18.5. PCA0H: PCA Counter/Timer High Byte
Bits 7–0: PCA0H: PCA Counter/Timer High Byte.
The PCA0H register holds the high byte (MSB) of the 16-bit PCA Counter/Timer.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Valu e
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xFA
SFR Definition 18.6. PCA0CPLn: PCA Capture Module Low Byte
PCA0CPLn Address: PCA0CPL0 = 0xFB (n = 0), PCA0CPL1 = 0xE9 (n = 1),
PCA0CPL2 = 0xEB (n = 2), PCA0CPL3 = 0xED (n = 3),
PCA0CPL4 = 0xFD (n = 4)
Bits7–0: PCA0CPLn: PCA Capture Module Low Byte.
The PCA0CPLn register holds the low byte (LSB) of the 16-bit capture module n.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xFB, 0xE9, 0xEB,
0xED, 0xFD
Rev. 1.7 219
C8051F310/1/2/3/4/5/6/7
SFR Definition 18.7. PCA0CPHn: PCA Capture Module High Byte
PCA0CPHn Address: PCA0CPH0 = 0xFC (n = 0), PCA0CPH1 = 0xEA (n = 1),
PCA0CPH2 = 0xEC (n = 2), PCA0CPH3 = 0xEE (n = 3),
PCA0CPH4 = 0xFE (n = 4)
Bits7–0: PCA0CPHn: PCA Capture Module High Byte.
The PCA0CPHn register holds the high byte (M SB) of the 16-bit capture module n.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xFC, 0xEA,
0xEC,0xEE, 0xFE
C8051F310/1/2/3/4/5/6/7
220 Rev. 1.7
NOTES:
Rev. 1.7 221
C8051F310/1/2/3/4/5/6/7
19. Revision Specific Behavior
This chapter contains behavioral dif fere nces between C8051 F310/1 “REV A” and “REV B” or later devices.
These differences do not affect the functionality or performance o f most systems and are described below.
19.1. Revision Identification
The Lot ID Code on the top side of the device package can be used for decoding device revision informa-
tion. On C8051F310 devices, the revision letter is the second-to-last letter of the Lot ID Code. On
C8051F311 devices, the revision letter is the last letter of the Lot ID Code. Figure 19.1 shows how to find
the Lot ID Code on the top side of the device package.
C8051F310
T2ABGFAC
^ indicates REV A
0227 EP
CYG
F311
ABGFA
^ indicates REV A
C8051F311 Package MarkingC8051F310 Package Marking
Figure 19.1. Reading Package Marking
19.2. Reset Behavior
The reset behavior of C8051F310/1 “REV A” devices is different than “REV B” and late r devices. The dif-
ferences affect the st ate of the RST pin during a VDD Monitor reset and GPIO pins during any device reset.
19.2.1. Weak Pullups on GPIO Pins
On “REV A” devices, GPIO pins are tri-stated with weak pullups disabled during the assertion phase of
any reset. The pullu ps are enab le d imme dia te l y followin g re se t de -a sse rt ion .
On “REV B” and later devices, GPIO pins are tri-stated with weak pullups enabled during and after the
assertion phase of any reset.
19.2.2. VDD Monitor and the RST Pin
On “REV A” devices, a VDD Monitor reset does not affect the state of the RST pin.
On “REV B” and later devices, a VDD Monitor reset will pull the RST pin low for the duration of the brown-
out condition.
C8051F310/1/2/3/4/5/6/7
222 Rev. 1.7
19.3. PCA Counter
On “REV A” devices, if the main PCA counter (PCA0H : PCA0L) overflows during the exe cution ph ase of a
read-modify-write instruction (bit-wise SETB or CLR, ANL, ORL, XRL) that targets the PCA0CN register,
the CF (Counter Overflow) bit will not be set. An example software work-around is as follows:
Step 1. Disable global interrupts (EA = 0).
Step 2. Read PCA0L. This will latch the value of PCA0H.
Step 3. Read PCA0H, saving the value.
Step 4. Execute the bit-wise operation on CCFn (for example, CLR CCF0, or CCF0 = 0;).
Step 5. Read PCA0L.
Step 6. Read PCA0H, saving the value.
Step 7. If the value of PCA0H read in Step 3 is 0xFF and the value for PCA0H read in Step 6 is
0x00, then manually set the CF bit in software (for example, SETB CF, or CF = 1;).
Step 8. Re-enable interrupts (EA = 1).
This behavior is not present on “REV B” and later devices. Software written for “REV A” devices will run on
“REV B” and later devices without modification.
Rev. 1.7 223
C8051F310/1/2/3/4/5/6/7
20. C2 Interface
C8051F31x devices include an on-chip Silic on Labs 2-Wire (C2) debug interface to allow Flash program-
ming and in-system debugging with the production part installed in the end application. The C2 interface
uses a clock signal (C2CK) and a bi-directional C2 data signal (C2D) to transfer info rmation between the
device and a host sys te m. See th e C2 In te rfa ce Specification for de tails on the C2 prot oco l .
20.1. C2 Interface Registers
The following describes the C2 registers necessary to perform Flash programming through the C2 inter-
face. All C2 registers are accessed throug h the C2 interface as de scribed in the C2 Interfa ce Specification.
C2 Register Definition 20.1. C2ADD: C2 Address
Bits7–0: The C2ADD register is accessed via the C2 interface to select the target Data register for
C2 Data Read and Data Write commands.
Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Address Description
0x00 Selects the Device ID register for Data Read instructions
0x01 Selects the Revision ID register for Data Read instructions
0x02 Selects the C2 Flash Programming Control register for Data
Read/Write instructions
0xB4 Selects the C2 Flash Programming Data register for Data
Read/Write instructions
C2 Register Definition 20.2. DEVICEID: C2 Device ID
This read-only reg ist er retu r ns th e 8- bit device ID: 0x08 (C8051F310/1/2/3/4/5/6/7).
Reset Value
00001000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
C8051F310/1/2/3/4/5/6/7
224 Rev. 1.7
C2 Register Definition 20.3. REVID: C2 Revision ID
This read-only register returns the 8-bit revision ID.
Reset Value
Variable
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
C2 Register Definition 20.4. FPCTL: C2 Flash Programming Control
Bits7–0 FPCTL: Flash Programming Control Register.
This register is used to enable Flash programming via the C2 interface. To enable C2 Flash
programming , th e follo win g co de s mu st be writt e n in order: 0x02, 0x01. Note that once C2
Flash programming is enabled, a system reset must be issued to resume normal operation.
Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
C2 Register Definition 20.5. FPDAT: C2 Flash Programming Data
Bits7–0: FPDAT: C2 Flash Programming Data Register.
This register is used to pass Flash commands, addresses, and data during C2 Flash
accesses. Valid commands are listed below.
Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Code Command
0x06 Flash Block Read
0x07 Flash Block Write
0x08 Flash Page Erase
0x03 Device Erase
Rev. 1.7 225
C8051F310/1/2/3/4/5/6/7
20.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and
Flash programming functions may be performed. This is possible because C2 communication is typically
performed when the device is in the halt state, where all on-chip peripherals and user software are stalled.
In this halted state, the C2 interface can safely ‘borrow’ the C2CK (/RST) and C2D (P3.0) pins. In most
applications, external resistors are required to isolate C2 interface traffic from the user application. A typi-
cal isolation configuration is shown in Figure 20.1.
C2D
C2CK
/Reset (a)
Input (b)
Output (c)
C2 Interface Master
C8051Fxxx
Figure 20.1. Typical C2 Pin Sharing
The configuration in Figure 20.1 assumes the following:
1. The user input (b) cannot change state while the target device is halted.
2. The /RST pin on the target device is used as an input only.
Additional resistors may be necessary depending on the specific application.
DOCUMENT CHANGE LIST
Revision 1.5 to Revision 1.6
• Added two part numbers: C8051F316 and C8051F317
• Changed package nomenclature from MLP to QFN.
• Chapter 1.“System Overview”: Updated Table 1.1, “Product Selection Guide,” on page 18, with new
ordering part numbers; added block diagrams for the new parts, and updated Figure 1.13.
• Added Table 3.2, “Electrical Characteristics Quick Reference,” on page 38.
• Chapter 4.“Pinout and Package D efinitio n s ”: Updated Table 4.1 and added package diagrams for the
new parts.
• Chapter 5.“10-Bit ADC (ADC0, C8051F310/1/2/3/6 only)”: Updated Figure 5.1, SFR Definition 5.1, and
SFR Definition 5.2 to show behavior of new pa rts.
• Chapter 9.“Reset Sources” : Added note to SFR Definition 9.2 describing the behavior of read-modify-
write instructions on this register; Corrected Max VDD Ramp Time to 1 mS.
• Chapter 10.“Flash Memory”: Updated Table 10.1 to accommodate the new parts; Added Table 10.2,
“Flash Security Summary,” on page 114 for clarity, replacing the Flash security summaries text.
• Chapter 13.“Port Input/Output”: Updated text, Figure 13.1, Figure 13.3, Figure 13.4, and SFR Defini-
tion 13.7 through SFR Definition 13.17 to accommodate the new part numbers.
• Chapter 18.“Programmable Counter Array”: In Table 18.3, corrected internal oscillator reset frequency
from 3,060,000 Hz to 3,062,500 Hz.
• Chapter 20.“C2 Interface”: Updated C2 Register Definition 20.2 to accommodate the new part num-
bers. Corrected Device ID that is common to all 'F31x devices from 0x09 to 0x08; Removed references
to "boundary scan" because this feature is not supported by the 'F31x devices.
Revision 1.6 to Revision 1.7
• Fixed various minor errors.
• Updated values in Table 3.1, “Global DC Electrical Characteristics,” on page 36.
• Added Section “10.4. Flash Wr ite and Erase Guidelines” on page 115.
C8051F310/1/2/3/4/5/6/7
226 Rev. 1.7
Rev. 1.7 227
C8051F310/1/2/3/4/5/6/7
NOTES:
C8051F310/1/2/3/4/5/6/7
228 Rev. 1.7
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