© 2009 Microchip Technology Inc. DS39689F
PIC18F2221/2321/4221/4321
Family Data Sheet
Enhanced Flash Microcontrollers with
10-Bit A/D and nanoWatt Technology
DS39689F-page 2 © 2009 Microchip Technology Inc.
Information contained in this publication regarding device
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rfPIC and UNI/O are registered trademarks of Microchip
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© 2009, Microchip Technology Incorporated, Printed in the
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Printed on recycled paper.
Note the following details of the code protection feature on Microchip devices:
Microchip products meet the specification contained in their particular Microchip Data Sheet.
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
Microchip is willing to work with the customer who is concerned about the integrity of their code.
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
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and India. The Company’s quality system processes and procedures
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and manufacture of development systems is ISO 9001:2000 certified.
© 2009 Microchip Technology Inc. DS39689F-page 3
PIC18F2221/2321/4221/4321 FAMILY
Power-Managed Modes:
Run: CPU On, Peripherals On
Idle: CPU Off, Peripherals On
Sleep: CPU Off, Peripherals Off
Idle mode Currents Down to 2.5 μA Typical
Sleep mode Currents Down to 500 nA Typical
Timer1 Oscillator: 1.8 μA, 32 kHz, 2V Typical
Watchdog Timer: 1.6 μA, 2V Typical
Two-Speed Oscillator Start-up
Flexible Oscillator Structure:
Four Crystal modes, up to 40 MHz
4x Phase Lock Loop (PLL) – Available for Crystal
and Internal Oscillators
Two External RC modes, up to 4 MHz
Two External Clock modes, up to 40 MHz
Internal Oscillator Block:
- 8 user-selectable frequencies, from 31 kHz to
8MHz
- Provides a complete range of clock speeds
from 31 kHz to 32 MHz when used with PLL
- User-tunable to compensate for frequency drift
Secondary Oscillator using Timer1 @ 32 kHz
Fail-Safe Clock Monitor
- Allows for safe shutdown if peripheral clock stops
Peripheral Highlights:
High-Current Sink/Source 25 mA/25 mA
Three Programmable External Interrupts
Four Input Change Interrupts
Up to 2 Capture/Compare/PWM (CCP) modules,
one with Auto-Shutdown (28-pin devices)
Enhanced Capture/Compare/PWM (ECCP)
module (40/44-pin devices only):
- One, two or four PWM outputs
- Selectable polarity
- Programmable dead time
- Auto-shutdown and auto-restart
Peripheral Highlights (Continued):
Master Synchronous Serial Port (MSSP) module
Supporting 3-Wire SPI (all 4 modes) and I2C™
Master and Slave modes
Enhanced Addressable USART module:
- Supports RS-485, RS-232 and LIN/J2602
- Auto-wake-up on Start bit
- Auto-Baud Detect
10-Bit, up to 13-Channel Analog-to-Digital
Converter module (A/D):
- Auto-acquisition capability
- Conversion available during Sleep
Dual Analog Comparators with Input Multiplexing
Programmable 16-Level High/Low-Voltage
Detection (HLVD) module:
- Supports interrupt on High/Low-Voltage Detection
Special Microcontroller Features:
C Compiler Optimized Architecture:
- Optional extended instruction set designed to
optimize re-entrant code
100,000 Erase/Write Cycle Enhanced Flash
Program Memory Typical
1,000,000 Erase/Write Cycle Data EEPROM
Memory Typical
Flash/Data EEPROM Retention: 100 Years Typical
Self-Programmable under Software Control
Priority Levels for Interrupts
8 x 8 Single-Cycle Hardware Multiplier
Extended Watchdog Timer (WDT):
- Programmable period from 4 ms to 131s
Single-Supply 5V In-Circuit Serial
Programming™ (ICSP™) via Two Pins
In-Circuit Debug (ICD) via Two Pins
Wide Operating Voltage Range: 2.0V to 5.5V
Programmable Brown-out Reset (BOR) with
Software Enable Option)
-
Device
Program Memory Data Memory
I/O 10-Bit
A/D (ch)
CCP/
ECCP
(PWM)
MSSP
EUSART
Comp. Timers
8/16-Bit
Flash
(bytes)
# Single-Word
Instructions
SRAM
(bytes)
EEPROM
(bytes) SPI Master
I2C™
PIC18F2221 4K 2048 512 256 25 10 2/0 Y Y 1 2 1/3
PIC18F2321 8K 4096 512 256 25 10 2/0 Y Y 1 2 1/3
PIC18F4221 4K 2048 512 256 36 13 1/1 Y Y 1 2 1/3
PIC18F4321 8K 4096 512 256 36 13 1/1 Y Y 1 2 1/3
28/40/44-Pin Enhanced Flash Microcontrollers with
10-Bit A/D and nanoWatt Technology
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 4 © 2009 Microchip Technology Inc.
Pin Diagrams
PIC18F2321
10
11
2
3
4
5
6
1
8
7
9
12
13
14 15
16
17
18
19
20
23
24
25
26
27
28
22
21
MCLR/VPP/RE3
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/HLVDIN/C2OUT
VSS
OSC1/CLKI/RA7
OSC2/CLKO/RA6
RC0/T1OSO/T13CKI
RC1/T1OSI/CCP2
RC2/CCP1
RC3/SCK/SCL
RB7/KBI3/PGD
RB6//KBI2/PGC
RB5/KBI1/PGM
RB4/KBI0/AN11
RB3/AN9/CCP2
RB2/INT2/AN8
RB1/INT1/AN10
RB0/INT0/FLT0/AN12
VDD
VSS
RC7/RX/DT
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
28-Pin SPDIP, SOIC, SSOP
PIC18F2221
28-Pin QFN
10 11
2
3
6
1
18
19
20
21
22
12 13 14 15
8
7
16
17
232425262728
9
PIC18F2221
RC0/T1OSO/T13CKI
5
4
RB7/KBI3/PGD
RB6/KBI2/PGC
RB5/KBI1/PGM
RB4/KBI0/AN11
RB3/AN9/CCP2(1)
RB2/INT2/AN8
RB1/INT1/AN10
RB0/INT0/FLT0/AN12
VDD
VSS
RC7/RX/DT
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
MCLR/VPP/RE3
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/HLVDIN/C2OUT
VSS
OSC1/CLKI/RA7
OSC2/CLKO/RA6
RC1/T1OSI/CCP2(1)
RC2/CCP1
RC3/SCK/SCL
Note 1: RB3 is the alternate pin for CCP2 multiplexing.
PIC18F2321
© 2009 Microchip Technology Inc. DS39689F-page 5
PIC18F2221/2321/4221/4321 FAMILY
Pin Diagrams (Continued)
10
11
2
3
4
5
6
1
18
19
20
21
22
12
13
14
15
38
8
7
44
43
42
41
40
39
16
17
29
30
31
32
33
23
24
25
26
27
28
36
34
35
9
PIC18F4221
37
RA3/AN3/VREF+
RA2/AN2/VREF-/CVREF
RA1/AN1
RA0/AN0
MCLR/VPP/RE3
RB3/AN9/CCP2(1)
RB7/KBI3/PGD
RB6/KBI2/PGC
RB5/KBI1/PGM
RB4/KBI0/AN11
NC
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
RD3/PSP3
RD2/PSP2
RD1/PSP1
RD0/PSP0
RC3/SCK/SCL
RC2/CCP1/P1A
RC1/T1OSI/CCP2(1)
RC0/T1OSO/T13CKI
OSC2/CLKO/RA6
OSC1/CLKI/RA7
VSS
VSS
VDD
VDD
RE2/CS/AN7
RE1/WR/AN6
RE0/RD/AN5
RA5/AN4/SS/HLVDIN/C2OUT
RA4/T0CKI/C1OUT
RC7/RX/DT
RD4/PSP4
RD5/PSP5/P1B
RD6/PSP6/P1C
RD7/PSP7/P1D
VSS
VDD
VDD
RB0/INT0/FLT0/AN12
RB1/INT1/AN10
RB2/INT2/AN8
44-Pin QFN(2)
PIC18F4321
Note 1: RB3 is the alternate pin for CCP2 multiplexing.
2: For the QFN package, it is recommended that the bottom pad be connected to VSS.
RB7/KBI3/PGD
RB6/KBI2/PGC
RB5/KBI1/PGM
RB4/KBI0/AN11
RB3/AN9/CCP2
RB2/INT2/AN8
RB1/INT1/AN10
RB0/INT0/FLT0/AN12
VDD
VSS
RD7/PSP7/P1D
RD6/PSP6/P1C
RD5/PSP5/P1B
RD4/PSP4
RC7/RX/DT
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
RD3/PSP3
RD2/PSP2
MCLR/VPP/RE3
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/HLVDIN/C2OUT
RE0/RD/AN5
RE1/WR/AN6
RE2/CS/AN7
VDD
VSS
OSC1/CLKI/RA7
OSC2/CLKO/RA6
RC0/T1OSO/T13CKI
RC1/T1OSI/CCP2
RC2/CCP1/P1A
RC3/SCK/SCL
RD0/PSP0
RD1/PSP1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
PIC18F4321
40-Pin PDIP
PIC18F4221
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 6 © 2009 Microchip Technology Inc.
Pin Diagrams (Continued)
10
11
2
3
4
5
6
1
18
19
20
21
22
12
13
14
15
38
8
7
44
43
42
41
40
39
16
17
29
30
31
32
33
23
24
25
26
27
28
36
34
35
9
PIC18F4221
37
RA3/AN3/VREF+
RA2/AN2/VREF-/CVREF
RA1/AN1
RA0/AN0
MCLR/VPP/RE3
NC
RB7/KBI3/PGD
RB6/KBI2/PGC
RB5/KBI1/PGM
RB4/KBI0/AN11
NC
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
RD3/PSP3
RD2/PSP2
RD1/PSP1
RD0/PSP0
RC3/SCK/SCL
RC2/CCP1/P1A
RC1/T1OSI/CCP2(1)
NC
NC
RC0/T1OSO/T13CKI
OSC2/CLKO/RA6
OSC1/CLKI/RA7
VSS
VDD
RE2/CS/AN7
RE1/WR/AN6
RE0/RD/AN5
RA5/AN4/SS/HLVDIN/C2OUT
RA4/T0CKI/C1OUT
RC7/RX/DT
RD4/PSP4
RD5/PSP5/P1B
RD6/PSP6/P1C
RD7/PSP7/P1D
VSS
VDD
RB0/INT0/FLT0/AN12
RB1/INT1/AN10
RB2/INT2/AN8
RB3/AN9/CCP2(1)
44-Pin TQFP
PIC18F4321
Note 1: RB3 is the alternate pin for CCP2 multiplexing.
© 2009 Microchip Technology Inc. DS39689F-page 7
PIC18F2221/2321/4221/4321 FAMILY
Table of Contents
1.0 Device Overview .......................................................................................................................................................................... 9
2.0 Guidelines for Getting Started with PIC18F Microcontrollers ..................................................................................................... 25
3.0 Oscillator Configurations ............................................................................................................................................................ 29
4.0 Power-Managed Modes ............................................................................................................................................................. 39
5.0 Reset .......................................................................................................................................................................................... 47
6.0 Memory Organization ................................................................................................................................................................. 59
7.0 Flash Program Memory.............................................................................................................................................................. 79
8.0 Data EEPROM Memory ............................................................................................................................................................. 89
9.0 8 x 8 Hardware Multiplier............................................................................................................................................................ 95
10.0 Interrupts .................................................................................................................................................................................... 97
11.0 I/O Ports ................................................................................................................................................................................... 111
12.0 Timer0 Module ......................................................................................................................................................................... 129
13.0 Timer1 Module ......................................................................................................................................................................... 133
14.0 Timer2 Module ......................................................................................................................................................................... 139
15.0 Timer3 Module ......................................................................................................................................................................... 141
16.0 Capture/Compare/PWM (CCP) Modules ................................................................................................................................. 145
17.0 Enhanced Capture/Compare/PWM (ECCP) Module................................................................................................................ 153
18.0 Master Synchronous Serial Port (MSSP) Module .................................................................................................................... 167
19.0 Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) ............................................................... 211
20.0 10-Bit Analog-to-Digital Converter (A/D) Module ..................................................................................................................... 233
21.0 Comparator Module.................................................................................................................................................................. 243
22.0 Comparator Voltage Reference Module................................................................................................................................... 249
23.0 High/Low-Voltage Detect (HLVD)............................................................................................................................................. 253
24.0 Special Features of the CPU.................................................................................................................................................... 259
25.0 Instruction Set Summary .......................................................................................................................................................... 279
26.0 Development Support............................................................................................................................................................... 329
27.0 Electrical Characteristics.......................................................................................................................................................... 333
28.0 Packaging Information.............................................................................................................................................................. 373
Appendix A: Revision History............................................................................................................................................................. 385
Appendix B: Device Differences ........................................................................................................................................................ 386
Appendix C: Conversion Considerations ........................................................................................................................................... 387
Appendix D: Migration from Baseline to Enhanced Devices.............................................................................................................. 387
Appendix E: Migration From Mid-Range to Enhanced Devices ......................................................................................................... 388
Appendix F: Migration From High-End to Enhanced Devices............................................................................................................ 388
Index ................................................................................................................................................................................................. 389
The Microchip Web Site..................................................................................................................................................................... 399
Customer Change Notification Service .............................................................................................................................................. 399
Customer Support .............................................................................................................................................................................. 399
Reader Response .............................................................................................................................................................................. 400
PIC18F2221/2321/4221/4321 Product Identification System ............................................................................................................ 401
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 8 © 2009 Microchip Technology Inc.
TO OUR VALUED CUSTOMERS
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© 2009 Microchip Technology Inc. DS39689F-page 9
PIC18F2221/2321/4221/4321 FAMILY
1.0 DEVICE OVERVIEW
This document contains device specific information for
the following devices:
This family offers the advantages of all PIC18 micro-
controllers – namely, high computational performance at
an economical price – with the addition of high-
endurance, Enhanced Flash program memory. On top of
these features, the PIC18F2221/2321/4221/4321 family
introduces design enhancements that make these micro-
controllers a logical choice for many high-performance,
power sensitive applications.
1.1 New Core Features
1.1.1 nanoWatt TECHNOLOGY
All of the devices in the PIC18F2221/2321/4221/4321
family incorporate a range of features that can signifi-
cantly reduce power consumption during operation.
Key items include:
Alternate Run Modes: By clocking the controller
from the Timer1 source or the internal oscillator
block, power consumption during code execution
can be reduced by as much as 90%.
Multiple Idle Modes: The controller can also run
with its CPU core disabled but the peripherals still
active. In these states, power consumption can be
reduced even further, to as little as 4% of normal
operation requirements.
On-the-Fly Mode Switching: The
power-managed modes are invoked by user code
during operation, allowing the user to incorporate
power-saving ideas into their application’s
software design.
Low Consumption in Key Modules: The
power requirements for both Timer1 and the
Watchdog Timer are minimized. See
Section 27.0 “Electrical Characteristics” for
values.
1.1.2 MULTIPLE OSCILLATOR OPTIONS
AND FEATURES
All of the devices in the PIC18F2221/2321/4221/4321
family offer ten different oscillator options, allowing
users a wide range of choices in developing application
hardware. These include:
Four Crystal modes, using crystals or ceramic
resonators.
Two External Clock modes, offering the option of
using two pins (oscillator input and a divide-by-4
clock output) or one pin (oscillator input, with the
second pin reassigned as general I/O).
Two External RC Oscillator modes with the same
pin options as the External Clock modes.
Two Internal Oscillator modes which provide
an 8 MHz clock and an INTRC source
(approximately 31 kHz), as well as a range of
6 user-selectable clock frequencies, between
125 kHz to 4 MHz, for a total of 8 clock frequencies.
One or both of the oscillator pins can be used for
general purpose I/O.
A Phase Lock Loop (PLL) frequency multiplier,
available to both the high-speed crystal and
internal oscillator modes, which allows clock
speeds of up to 40 MHz. Used with the internal
oscillator, the PLL gives users a complete selection
of clock speeds, from 31 kHz to 32 MHz – all
without using an external crystal or clock circuit.
Besides its availability as a clock source, the internal
oscillator block provides a stable reference source that
gives the family additional features for robust
operation:
Fail-Safe Clock Monitor: This option constantly
monitors the main clock source against a reference
signal provided by the internal oscillator. If a clock
failure occurs, the controller is switched to the
internal oscillator block, allowing for continued
low-speed operation or a safe application
shutdown.
Two-Speed Start-up: This option allows the
internal oscillator to serve as the clock source
from Power-on Reset, or wake-up from Sleep
mode, until the primary clock source is available.
PIC18F2221 PIC18LF2221
PIC18F2321 PIC18LF2321
PIC18F4221 PIC18LF4221
PIC18F4321 PIC18LF4321
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 10 © 2009 Microchip Technology Inc.
1.2 Other Special Features
Memory Endurance: The Enhanced Flash cells
for both program memory and data EEPROM are
rated to last for many thousands of erase/write
cycles – up to 100,000 for program memory and
1,000,000 for EEPROM. Data retention without
refresh is conservatively estimated to be greater
than 40 years.
Self-Programmability: These devices can write to
their own program memory spaces under internal
software control. By using a bootloader routine,
located in the protected Boot Block at the top of
program memory, it becomes possible to create an
application that can update itself in the field.
Extended Instruction Set: The PIC18F2221/
2321/4221/4321 family introduces an optional
extension to the PIC18 instruction set, which adds
8 new instructions and an Indexed Addressing
mode. This extension, enabled as a device con-
figuration option, has been specifically designed
to optimize re-entrant application code originally
developed in high-level languages, such as C.
Enhanced CCP Module: In PWM mode, this
module provides 1, 2 or 4 modulated outputs for
controlling half-bridge and full-bridge drivers.
Other features include auto-shutdown, for
disabling PWM outputs on interrupt or other select
conditions and auto-restart, to reactivate outputs
once the condition has cleared.
Enhanced Addressable USART: This serial
communication module is capable of standard
RS-232 operation and provides support for the
LIN/J2602 bus protocol. Other enhancements
include automatic baud rate detection and a 16-bit
Baud Rate Generator for improved resolution.
When the microcontroller is using the internal
oscillator block, the EUSART provides stable
operation for applications that talk to the outside
world without using an external crystal (or its
accompanying power requirement).
10-Bit A/D Converter: This module incorporates
programmable acquisition time, allowing for a
channel to be selected and a conversion to be
initiated without waiting for a sampling period and
thus, reducing code overhead.
Extended Watchdog Timer (WDT): This
Enhanced version incorporates a 16-bit prescaler,
allowing an extended time-out range that is stable
across operating voltage and temperature. See
Section 27.0 “Electrical Characteristics” for
time-out periods.
1.3 Details on Individual Family
Members
Devices in the PIC18F2221/2321/4221/4321 family are
available in 28-pin and 40/44-pin packages. Block
diagrams for the two groups are shown in Figure 1-1 and
Figure 1-2.
The devices are differentiated from each other in five
ways:
1. Flash program memory (4 Kbytes for
PIC18F2221/4221 devices, 8 Kbytes for
PIC18F2321/4321).
2. A/D channels (10 for 28-pin devices, 13 for
40/44-pin devices).
3. I/O ports (3 bidirectional ports on 28-pin devices,
5 bidirectional ports on 40/44-pin devices).
4. CCP and Enhanced CCP implementation
(28-pin devices have 2 standard CCP
modules, 40/44-pin devices have one standard
CCP module and one ECCP module).
5. Parallel Slave Port (present only on 40/44-pin
devices).
All other features for devices in this family are identical.
These are summarized in Table 1-1.
The pinouts for all devices are listed in Table 1-2 and
Table 1-3.
Like all Microchip PIC18 devices, members of the
PIC18F2221/2321/4221/4321 family are available as
both standard and low-voltage devices. Standard
devices with Enhanced Flash memory, designated with
an “F” in the part number (such as PIC18F2321),
accommodate an operating VDD range of 4.2V to 5.5V.
Low-voltage parts, designated by “LF” (such as
PIC18LF2321), function over an extended VDD range
of 2.0V to 5.5V.
© 2009 Microchip Technology Inc. DS39689F-page 11
PIC18F2221/2321/4221/4321 FAMILY
TABLE 1-1: DEVICE FEATURES
Features PIC18F2221 PIC18F2321 PIC18F4221 PIC18F4321
Operating Frequency DC – 40 MHz DC – 40 MHz DC – 40 MHz DC – 40 MHz
Program Memory (Bytes) 4096 8192 4096 8192
Program Memory (Instructions) 2048 4096 2048 4096
Data Memory (Bytes) 512 512 512 512
Data EEPROM Memory (Bytes) 256 256 256 256
Interrupt Sources 19 19 20 20
I/O Ports Ports A, B, C, (E) Ports A, B, C, (E) Ports A, B, C, D, E Ports A, B, C, D, E
Timers 4 4 4 4
Capture/Compare/PWM Modules 2 2 1 1
Enhanced Capture/Compare/
PWM Modules
0011
Serial Communications MSSP,
Enhanced USART
MSSP,
Enhanced USART
MSSP,
Enhanced USART
MSSP,
Enhanced USART
Parallel Communications (PSP) No No Yes Yes
10-bit Analog-to-Digital Module 10 Input Channels 10 Input Channels 13 Input Channels 13 Input Channels
Resets (and Delays) POR, BOR,
RESET Instruction,
Stack Full,
Stack Underflow
(PWRT, OST),
MCLR (optional),
WDT
POR, BOR,
RESET Instruction,
Stack Full,
Stack Underflow
(PWRT, OST),
MCLR (optional),
WDT
POR, BOR,
RESET Instruction,
Stack Full,
Stack Underflow
(PWRT, OST),
MCLR (optional),
WDT
POR, BOR,
RESET Instruction,
Stack Full,
Stack Underflow
(PWRT, OST),
MCLR (optional),
WDT
Programmable Low-Voltage
Detect
Yes Yes Yes Yes
Programmable Brown-out Reset Yes Yes Yes Yes
Instruction Set 75 Instructions;
83 with Extended
Instruction Set
enabled
75 Instructions;
83 with Extended
Instruction Set
enabled
75 Instructions;
83 with Extended
Instruction Set
enabled
75 Instructions;
83 with Extended
Instruction Set
enabled
Packages 28-pin SPDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
28-pin SPDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
40-pin PDIP
44-pin QFN
44-pin TQFP
40-pin PDIP
44-pin QFN
44-pin TQFP
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 12 © 2009 Microchip Technology Inc.
FIGURE 1-1: PIC18F2221/2321 (28-PIN) BLOCK DIAGRAM
Instruction
Decode &
Control
PORTA
PORTB
PORTC
RA4/T0CKI/C1OUT
RA5/AN4/SS/HLVDIN/C2OUT
RB0/INT0/FLT0/AN12
RC0/T1OSO/T13CKI
RC1/T1OSI/CCP2(1)
RC2/CCP1
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RC6/TX/CK
RC7/RX/DT
RA3/AN3/VREF+
RA2/AN2/VREF-/CVREF
RA1/AN1
RA0/AN0
RB1/INT1/AN10
Data Latch
Data Memory
(3.9 Kbytes)
Address Latch
Data Address<12>
12
Access
BSR FSR0
FSR1
FSR2
inc/dec
logic
Address
412 4
PCH PCL
PCLATH
8
31 Level Stack
Program Counter
PRODLPRODH
8 x 8 Multiply
8
BITOP
8
8
ALU<8>
Address Latch
Program Memory
(4 Kbytes)
Data Latch
20
8
8
Table Pointer<21>
inc/dec logic
21
8
Data Bus<8>
Table Latch
8
IR
12
3
ROM Latch
RB2/INT2/AN8
RB3/AN9/CCP2(1)
PCLATU
PCU
OSC2/CLKO(3)/RA6
Note 1: CCP2 is multiplexed with RC1 when Configuration bit, CCP2MX, is set, or RB3 when CCP2MX is not set.
2: RE3 is only available when MCLR functionality is disabled.
3: OSC1/CLKI and OSC2/CLKO are only available in select oscillator modes and when these pins are not being used as digital I/O.
Refer to Section 3.0 “Oscillator Configurations” for additional information.
RB4/KBI0/AN11
RB5/KBI1/PGM
RB6/KBI2/PGC
RB7/KBI3/PGD
EUSARTComparator MSSP 10-Bit
ADC
Timer2Timer1 Timer3Timer0
CCP2
LVD
CCP1
BOR Data
EEPROM
W
Instruction Bus <16>
STKPTR Bank
8
State Machine
Control Signals
Decode
8
8
Power-up
Timer
Oscillator
Start-up Timer
Power-on
Reset
Watchdog
Timer
OSC1(3)
OSC2(3)
VDD,
Brown-out
Reset
Internal
Oscillator
Fail-Safe
Clock Monitor
Precision
Reference
Band Gap
VSS
MCLR(2)
Block
INTRC
Oscillator
8 MHz
Oscillator
Single-Supply
Programming
In-Circuit
Debugger
T1OSO
OSC1/CLKI(3)/RA7
T1OSI
PORTE
MCLR/VPP/RE3(2)
© 2009 Microchip Technology Inc. DS39689F-page 13
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 1-2: PIC18F4221/4321 (40/44-PIN) BLOCK DIAGRAM
Instruction
Decode &
Control
Data Latch
Data Memory
(3.9 Kbytes)
Address Latch
Data Address<12>
12
Access
BSR FSR0
FSR1
FSR2
inc/dec
logic
Address
412 4
PCH PCL
PCLATH
8
31 Level Stack
Program Counter
PRODLPRODH
8 x 8 Multiply
8
BITOP
8
8
ALU<8>
Address Latch
Program Memory
(8 Kbytes)
Data Latch
20
8
8
Table Pointer<21>
inc/dec logic
21
8
Data Bus<8>
Table Latch
8
IR
12
3
ROM Latch
PORTD
RD0/PSP0
PCLATU
PCU
PORTE
MCLR/VPP/RE3(2)
RE2/CS/AN7
RE0/RD/AN5
RE1/WR/AN6
Note 1: CCP2 is multiplexed with RC1 when Configuration bit, CCP2MX, is set, or RB3 when CCP2MX is not set.
2: RE3 is only available when MCLR functionality is disabled.
3: OSC1/CLKI and OSC2/CLKO are only available in select oscillator modes and when these pins are not being used as digital I/O.
Refer to Section 3.0 “Oscillator Configurations” for additional information.
:RD4/PSP4
EUSARTComparator MSSP 10-Bit
ADC
Timer2Timer1 Timer3Timer0
CCP2
LVD
ECCP1
BOR Data
EEPROM
W
Instruction Bus <16>
STKPTR Bank
8
State Machine
Control Signals
Decode
8
8
Power-up
Timer
Oscillator
Start-up Timer
Power-on
Reset
Watchdog
Timer
OSC1(3)
OSC2(3)
VDD,
Brown-out
Reset
Internal
Oscillator
Fail-Safe
Clock Monitor
Precision
Reference
Band Gap
VSS
MCLR(2)
Block
INTRC
Oscillator
8 MHz
Oscillator
Single-Supply
Programming
In-Circuit
Debugger
T1OSI
T1OSO
RD5/PSP5/P1B
RD6/PSP6/P1C
RD7/PSP7/P1D
PORTA
PORTB
PORTC
RA4/T0CKI/C1OUT
RA5/AN4/SS/HLVDIN/C2OUT
RB0/INT0/FLT0/AN12
RC0/T1OSO/T13CKI
RC1/T1OSI/CCP2(1)
RC2/CCP1/P1A
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RC6/TX/CK
RC7/RX/DT
RA3/AN3/VREF+
RA2/AN2/VREF-/CVREF
RA1/AN1
RA0/AN0
RB1/INT1/AN10
RB2/INT2/AN8
RB3/AN9/CCP2(1)
OSC2/CLKO(3)/RA6
RB4/KBI0/AN11
RB5/KBI1/PGM
RB6/KBI2/PGC
RB7/KBI3/PGD
OSC1/CLKI(3)/RA7
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 14 © 2009 Microchip Technology Inc.
TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS
Pin Name
Pin Number
Pin
Type
Buffer
Type Description
SPDIP,
SOIC,
SSOP
QFN
MCLR/VPP/RE3
MCLR
VPP
RE3
126
I
P
I
ST
ST
Master Clear (input) or programming voltage (input).
Master Clear (Reset) input. This pin is an active-low
Reset to the device.
Programming voltage input.
Digital input.
OSC1/CLKI/RA7
OSC1
CLKI
RA7
96
I
I
I/O
Analog
CMOS
TTL
Oscillator crystal or external clock input.
Oscillator crystal input or external clock source input.
ST buffer when configured in RC mode; CMOS otherwise.
External clock source input. Always associated with
pin function OSC1. (See related OSC1/CLKI,
OSC2/CLKO pins.)
General purpose I/O pin.
OSC2/CLKO/RA6
OSC2
CLKO
RA6
10 7
O
O
I/O
TTL
Oscillator crystal or clock output.
Oscillator crystal output. Connects to crystal or resonator
in Crystal Oscillator mode.
In RC, EC and INTIO modes, OSC2 pin outputs CLKO
which has one-fourth the frequency of OSC1 and denotes
the instruction cycle rate.
General purpose I/O pin.
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
© 2009 Microchip Technology Inc. DS39689F-page 15
PIC18F2221/2321/4221/4321 FAMILY
PORTA is a bidirectional I/O port.
RA0/AN0
RA0
AN0
227
I/O
I
TTL
Analog
Digital I/O.
Analog Input 0.
RA1/AN1
RA1
AN1
328
I/O
I
TTL
Analog
Digital I/O.
Analog Input 1.
RA2/AN2/VREF-/CVREF
RA2
AN2
VREF-
CVREF
41
I/O
I
I
O
TTL
Analog
Analog
Analog
Digital I/O.
Analog Input 2.
A/D reference voltage (low) input.
Comparator reference voltage output.
RA3/AN3/VREF+
RA3
AN3
VREF+
52
I/O
I
I
TTL
Analog
Analog
Digital I/O.
Analog Input 3.
A/D reference voltage (high) input.
RA4/T0CKI/C1OUT
RA4
T0CKI
C1OUT
63
I/O
I
O
ST
ST
Digital I/O. Open-collector output.
Timer0 external clock input.
Comparator 1 output.
RA5/AN4/SS/HLVDIN/
C2OUT
RA5
AN4
SS
HLVDIN
C2OUT
74
I/O
I
I
I
O
TTL
Analog
TTL
Analog
Digital I/O.
Analog Input 4.
SPI slave select input.
High/Low-Voltage Detect input.
Comparator 2 output.
RA6 See the OSC2/CLKO/RA6 pin.
RA7 See the OSC1/CLKI/RA7 pin.
TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number
Pin
Type
Buffer
Type Description
SPDIP,
SOIC,
SSOP
QFN
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 16 © 2009 Microchip Technology Inc.
PORTB is a bidirectional I/O port. PORTB can be software
programmed for internal weak pull-ups on all inputs.
RB0/INT0/FLT0/AN12
RB0
INT0
FLT0
AN12
21 18
I/O
I
I
I
TTL
ST
ST
Analog
Digital I/O.
External Interrupt 0.
PWM Fault input for CCP1.
Analog Input 12.
RB1/INT1/AN10
RB1
INT1
AN10
22 19
I/O
I
I
TTL
ST
Analog
Digital I/O.
External Interrupt 1.
Analog Input 10.
RB2/INT2/AN8
RB2
INT2
AN8
23 20
I/O
I
I
TTL
ST
Analog
Digital I/O.
External Interrupt 2.
Analog Input 8.
RB3/AN9/CCP2
RB3
AN9
CCP2(2)
24 21
I/O
I
I/O
TTL
Analog
ST
Digital I/O.
Analog Input 9.
Capture 2 input/Compare 2 output/PWM2 output.
RB4/KBI0/AN11
RB4
KBI0
AN11
25 22
I/O
I
I
TTL
TTL
Analog
Digital I/O.
Interrupt-on-change pin.
Analog Input 11.
RB5/KBI1/PGM
RB5
KBI1
PGM
26 23
I/O
I
I/O
TTL
TTL
ST
Digital I/O.
Interrupt-on-change pin.
Low-Voltage ICSP™ programming enable pin.
RB6/KBI2/PGC
RB6
KBI2
PGC
27 24
I/O
I
I/O
TTL
TTL
ST
Digital I/O.
Interrupt-on-change pin.
In-circuit debugger and ICSP programming clock pin.
RB7/KBI3/PGD
RB7
KBI3
PGD
28 25
I/O
I
I/O
TTL
TTL
ST
Digital I/O.
Interrupt-on-change pin.
In-circuit debugger and ICSP programming data pin.
TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number
Pin
Type
Buffer
Type Description
SPDIP,
SOIC,
SSOP
QFN
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
© 2009 Microchip Technology Inc. DS39689F-page 17
PIC18F2221/2321/4221/4321 FAMILY
PORTC is a bidirectional I/O port.
RC0/T1OSO/T13CKI
RC0
T1OSO
T13CKI
11 8
I/O
O
I
ST
ST
Digital I/O.
Timer1 oscillator analog output.
Timer1/Timer3 external clock input.
RC1/T1OSI/CCP2
RC1
T1OSI
CCP2(1)
12 9
I/O
I
I/O
ST
Analog
ST
Digital I/O.
Timer1 oscillator analog input.
Capture 2 input/Compare 2 output/PWM2 output.
RC2/CCP1
RC2
CCP1
13 10
I/O
I/O
ST
ST
Digital I/O.
Capture 1 input/Compare 1 output/PWM1 output.
RC3/SCK/SCL
RC3
SCK
SCL
14 11
I/O
I/O
I/O
ST
ST
I2C
Digital I/O.
Synchronous serial clock input/output for SPI mode.
Synchronous serial clock input/output for I2C™ mode.
RC4/SDI/SDA
RC4
SDI
SDA
15 12
I/O
I
I/O
ST
ST
I2C
Digital I/O.
SPI data in.
I2C data I/O.
RC5/SDO
RC5
SDO
16 13
I/O
O
ST
Digital I/O.
SPI data out.
RC6/TX/CK
RC6
TX
CK
17 14
I/O
O
I/O
ST
ST
Digital I/O.
EUSART asynchronous transmit.
EUSART synchronous clock (see related RX/DT).
RC7/RX/DT
RC7
RX
DT
18 15
I/O
I
I/O
ST
ST
ST
Digital I/O.
EUSART asynchronous receive.
EUSART synchronous data (see related TX/CK).
RE3 See MCLR/VPP/RE3 pin.
VSS 8, 19 5, 16 P Ground reference for logic and I/O pins.
VDD 20 17 P Positive supply for logic and I/O pins.
TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number
Pin
Type
Buffer
Type Description
SPDIP,
SOIC,
SSOP
QFN
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 18 © 2009 Microchip Technology Inc.
TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS
Pin Name
Pin Number Pin
Type
Buffer
Type Description
PDIP QFN TQFP
MCLR/VPP/RE3
MCLR
VPP
RE3
11818
I
P
I
ST
ST
Master Clear (input) or programming voltage (input).
Master Clear (Reset) input. This pin is an active-low
Reset to the device.
Programming voltage input.
Digital input.
OSC1/CLKI/RA7
OSC1
CLKI
RA7
13 32 30
I
I
I/O
Analog
Analog
TTL
Oscillator crystal or external clock input.
Oscillator crystal input or external clock source input.
ST buffer when configured in RC mode;
analog otherwise.
External clock source input. Always associated with
pin function OSC1. (See related OSC1/CLKI,
OSC2/CLKO pins.)
General purpose I/O pin.
OSC2/CLKO/RA6
OSC2
CLKO
RA6
14 33 31
O
O
I/O
TTL
Oscillator crystal or clock output.
Oscillator crystal output. Connects to crystal
or resonator in Crystal Oscillator mode.
In RC, EC and INTIO modes, OSC2 pin outputs
CLKO which has one-fourth the frequency of OSC1
and denotes the instruction cycle rate.
General purpose I/O pin.
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
© 2009 Microchip Technology Inc. DS39689F-page 19
PIC18F2221/2321/4221/4321 FAMILY
PORTA is a bidirectional I/O port.
RA0/AN0
RA0
AN0
21919
I/O
I
TTL
Analog
Digital I/O.
Analog Input 0.
RA1/AN1
RA1
AN1
32020
I/O
I
TTL
Analog
Digital I/O.
Analog Input 1.
RA2/AN2/VREF-/CVREF
RA2
AN2
VREF-
CVREF
42121
I/O
I
I
O
TTL
Analog
Analog
Analog
Digital I/O.
Analog Input 2.
A/D reference voltage (low) input.
Comparator reference voltage output.
RA3/AN3/VREF+
RA3
AN3
VREF+
52222
I/O
I
I
TTL
Analog
Analog
Digital I/O.
Analog Input 3.
A/D reference voltage (high) input.
RA4/T0CKI/C1OUT
RA4
T0CKI
C1OUT
62323
I/O
I
O
ST
ST
Digital I/O.
Timer0 external clock input.
Comparator 1 output.
RA5/AN4/SS/HLVDIN/
C2OUT
RA5
AN4
SS
HLVDIN
C2OUT
72424
I/O
I
I
I
O
TTL
Analog
TTL
Analog
Digital I/O.
Analog Input 4.
SPI slave select input.
High/Low-Voltage Detect input.
Comparator 2 output.
RA6 See the OSC2/CLKO/RA6 pin.
RA7 See the OSC1/CLKI/RA7 pin.
TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number Pin
Type
Buffer
Type Description
PDIP QFN TQFP
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 20 © 2009 Microchip Technology Inc.
PORTB is a bidirectional I/O port. PORTB can be
software programmed for internal weak pull-ups on all
inputs.
RB0/INT0/FLT0/AN12
RB0
INT0
FLT0
AN12
33 9 8
I/O
I
I
I
TTL
ST
ST
Analog
Digital I/O.
External Interrupt 0.
PWM Fault input for Enhanced CCP1.
Analog input 12.
RB1/INT1/AN10
RB1
INT1
AN10
34 10 9
I/O
I
I
TTL
ST
Analog
Digital I/O.
External Interrupt 1.
Analog Input 10.
RB2/INT2/AN8
RB2
INT2
AN8
35 11 10
I/O
I
I
TTL
ST
Analog
Digital I/O.
External Interrupt 2.
Analog Input 8.
RB3/AN9/CCP2
RB3
AN9
CCP2(2)
36 12 11
I/O
I
I/O
TTL
Analog
ST
Digital I/O.
Analog Input 9.
Capture 2 input/Compare 2 output/PWM2 output.
RB4/KBI0/AN11
RB4
KBI0
AN11
37 14 14
I/O
I
I
TTL
TTL
Analog
Digital I/O.
Interrupt-on-change pin.
Analog input 11.
RB5/KBI1/PGM
RB5
KBI1
PGM
38 15 15
I/O
I
I/O
TTL
TTL
ST
Digital I/O.
Interrupt-on-change pin.
Low-Voltage ICSP™ Programming enable pin.
RB6/KBI2/PGC
RB6
KBI2
PGC
39 16 16
I/O
I
I/O
TTL
TTL
ST
Digital I/O.
Interrupt-on-change pin.
In-circuit debugger and ICSP programming
clock pin.
RB7/KBI3/PGD
RB7
KBI3
PGD
40 17 17
I/O
I
I/O
TTL
TTL
ST
Digital I/O.
Interrupt-on-change pin.
In-circuit debugger and ICSP programming
data pin.
TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number Pin
Type
Buffer
Type Description
PDIP QFN TQFP
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
© 2009 Microchip Technology Inc. DS39689F-page 21
PIC18F2221/2321/4221/4321 FAMILY
PORTC is a bidirectional I/O port.
RC0/T1OSO/T13CKI
RC0
T1OSO
T13CKI
15 34 32
I/O
O
I
ST
ST
Digital I/O.
Timer1 oscillator analog output.
Timer1/Timer3 external clock input.
RC1/T1OSI/CCP2
RC1
T1OSI
CCP2(1)
16 35 35
I/O
I
I/O
ST
CMOS
ST
Digital I/O.
Timer1 oscillator analog input.
Capture 2 input/Compare 2 output/PWM2 output.
RC2/CCP1/P1A
RC2
CCP1
P1A
17 36 36
I/O
I/O
O
ST
ST
Digital I/O.
Capture 1 input/Compare 1 output/PWM1 output.
Enhanced CCP1 output.
RC3/SCK/SCL
RC3
SCK
SCL
18 37 37
I/O
I/O
I/O
ST
ST
I2C
Digital I/O.
Synchronous serial clock input/output for
SPI mode.
Synchronous serial clock input/output for I2C™
mode.
RC4/SDI/SDA
RC4
SDI
SDA
23 42 42
I/O
I
I/O
ST
ST
I2C
Digital I/O.
SPI data in.
I2C data I/O.
RC5/SDO
RC5
SDO
24 43 43
I/O
O
ST
Digital I/O.
SPI data out.
RC6/TX/CK
RC6
TX
CK
25 44 44
I/O
O
I/O
ST
ST
Digital I/O.
EUSART asynchronous transmit.
EUSART synchronous clock (see related RX/DT).
RC7/RX/DT
RC7
RX
DT
26 1 1
I/O
I
I/O
ST
ST
ST
Digital I/O.
EUSART asynchronous receive.
EUSART synchronous data (see related TX/CK).
TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number Pin
Type
Buffer
Type Description
PDIP QFN TQFP
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 22 © 2009 Microchip Technology Inc.
PORTD is a bidirectional I/O port or a Parallel Slave
Port (PSP) for interfacing to a microprocessor port.
These pins have TTL input buffers when the PSP
module is enabled.
RD0/PSP0
RD0
PSP0
19 38 38
I/O
I/O
ST
TTL
Digital I/O.
Parallel Slave Port data.
RD1/PSP1
RD1
PSP1
20 39 39
I/O
I/O
ST
TTL
Digital I/O.
Parallel Slave Port data.
RD2/PSP2
RD2
PSP2
21 40 40
I/O
I/O
ST
TTL
Digital I/O.
Parallel Slave Port data.
RD3/PSP3
RD3
PSP3
22 41 41
I/O
I/O
ST
TTL
Digital I/O.
Parallel Slave Port data.
RD4/PSP4
RD4
PSP4
27 2 2
I/O
I/O
ST
TTL
Digital I/O.
Parallel Slave Port data.
RD5/PSP5/P1B
RD5
PSP5
P1B
28 3 3
I/O
I/O
O
ST
TTL
Digital I/O.
Parallel Slave Port data.
Enhanced CCP1 output.
RD6/PSP6/P1C
RD6
PSP6
P1C
29 4 4
I/O
I/O
O
ST
TTL
Digital I/O.
Parallel Slave Port data.
Enhanced CCP1 output.
RD7/PSP7/P1D
RD7
PSP7
P1D
30 5 5
I/O
I/O
O
ST
TTL
Digital I/O.
Parallel Slave Port data.
Enhanced CCP1 output.
TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number Pin
Type
Buffer
Type Description
PDIP QFN TQFP
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
© 2009 Microchip Technology Inc. DS39689F-page 23
PIC18F2221/2321/4221/4321 FAMILY
PORTE is a bidirectional I/O port.
RE0/RD/AN5
RE0
RD
AN5
82525
I/O
I
I
ST
TTL
Analog
Digital I/O.
Read control for Parallel Slave Port
(see also WR and CS pins).
Analog Input 5.
RE1/WR/AN6
RE1
WR
AN6
92626
I/O
I
I
ST
TTL
Analog
Digital I/O.
Write control for Parallel Slave Port
(see CS and RD pins).
Analog Input 6.
RE2/CS/AN7
RE2
CS
AN7
10 27 27
I/O
I
I
ST
TTL
Analog
Digital I/O.
Chip Select control for Parallel Slave Port
(see related RD and WR).
Analog Input 7.
RE3 See MCLR/VPP/RE3 pin.
VSS 12, 31 6, 30,
31
6, 29 P Ground reference for logic and I/O pins.
VDD 11, 32 7, 8,
28, 29
7, 28 P Positive supply for logic and I/O pins.
NC 13 12, 13,
33, 34
No Connect.
TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Name
Pin Number Pin
Type
Buffer
Type Description
PDIP QFN TQFP
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input P = Power
I2C = ST with I2C™ or SMB levels O = Output
Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.
2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 24 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 25
PIC18F2221/2321/4221/4321 FAMILY
2.0 GUIDELINES FOR GETTING
STARTED WITH PIC18F
MICROCONTROLLERS
2.1 Basic Connection Requirements
Getting started with the PIC18F2221/2321/4221/4321
family family of 8-bit microcontrollers requires attention
to a minimal set of device pin connections before
proceeding with development.
The following pins must always be connected:
•All V
DD and VSS pins
(see Section 2.2 “Power Supply Pins”)
•All AV
DD and AVSS pins, regardless of whether or
not the analog device features are used
(see Section 2.2 “Power Supply Pins”)
•M
CLR pin
(see Section 2.3 “Master Clear (MCLR) Pin”)
These pins must also be connected if they are being
used in the end application:
PGC/PGD pins used for In-Circuit Serial
Programming™ (ICSP™) and debugging purposes
(see Section 2.4 “ICSP Pins”)
OSCI and OSCO pins when an external oscillator
source is used
(see Section 2.5 “External Oscillator Pins”)
Additionally, the following pins may be required:
•V
REF+/VREF- pins used when external voltage
reference for analog modules is implemented
The minimum mandatory connections are shown in
Figure 2-1.
FIGURE 2-1: RECOMMENDED
MINIMUM CONNECTIONS
Note: The AVDD and AVSS pins must always be
connected, regardless of whether any of
the analog modules are being used.
PIC18FXXXX
VDD
VSS
VDD
VSS
VSS
VDD
AVDD
AVSS
VDD
VSS
C1
R1
VDD
MCLR
R2
C2(1)
C3(1)
C4(1)
C5(1)
C6(1)
Key (all values are recommendations):
C1 through C6: 0.1 μF, 20V ceramic
C7: 10 μF, 16V tantalum or ceramic
R1: 10 k
R2: 100 to 470
Note 1: The example shown is for a PIC18F device
with five VDD/VSS and AVDD/AVSS pairs.
Other devices may have more or less pairs;
adjust the number of decoupling capacitors
appropriately.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 26 © 2009 Microchip Technology Inc.
2.2 Power Supply Pins
2.2.1 DECOUPLING CAPACITORS
The use of decoupling capacitors on every pair of
power supply pins, such as VDD, VSS, AVDD and
AVSS, is required.
Consider the following criteria when using decoupling
capacitors:
Value and type of capacitor: A 0.1 μF (100 nF),
10-20V capacitor is recommended. The capacitor
should be a low-ESR device with a resonance
frequency in the range of 200 MHz and higher.
Ceramic capacitors are recommended.
Placement on the printed circuit board: The
decoupling capacitors should be placed as close
to the pins as possible. It is recommended to
place the capacitors on the same side of the
board as the device. If space is constricted, the
capacitor can be placed on another layer on the
PCB using a via; however, ensure that the trace
length from the pin to the capacitor is no greater
than 0.25 inch (6 mm).
Handling high-frequency noise: If the board is
experiencing high-frequency noise (upward of
tens of MHz), add a second ceramic type capaci-
tor in parallel to the above described decoupling
capacitor. The value of the second capacitor can
be in the range of 0.01 μF to 0.001 μF. Place this
second capacitor next to each primary decoupling
capacitor. In high-speed circuit designs, consider
implementing a decade pair of capacitances as
close to the power and ground pins as possible
(e.g., 0.1 μF in parallel with 0.001 μF).
Maximizing performance: On the board layout
from the power supply circuit, run the power and
return traces to the decoupling capacitors first,
and then to the device pins. This ensures that the
decoupling capacitors are first in the power chain.
Equally important is to keep the trace length
between the capacitor and the power pins to
a minimum, thereby reducing PCB trace
inductance.
2.2.2 TANK CAPACITORS
On boards with power traces running longer than six
inches in length, it is suggested to use a tank capacitor
for integrated circuits including microcontrollers to
supply a local power source. The value of the tank
capacitor should be determined based on the trace
resistance that connects the power supply source to
the device and the maximum current drawn by the
device in the application. In other words, select the tank
capacitor so that it meets the acceptable voltage sag at
the device. Typical values range from 4.7 μF to 47 μF.
2.3 Master Clear (MCLR) Pin
The MCLR pin provides two specific device
functions: device Reset, and device programming
and debugging. If programming and debugging are
not required in the end application, a direct
connection to VDD may be all that is required. The
addition of other components, to help increase the
application’s resistance to spurious Resets from
voltage sags, may be beneficial. A typical
configuration is shown in Figure 2-1. Other circuit
designs may be implemented depending on the
application’s requirements.
During programming and debugging, the resistance
and capacitance that can be added to the pin must
be considered. Device programmers and debuggers
drive the MCLR pin. Consequently, specific voltage
levels (VIH and VIL) and fast signal transitions must
not be adversely affected. Therefore, specific values
of R1 and C1 will need to be adjusted based on the
application and PCB requirements. For example, it is
recommended that the capacitor, C1, be isolated
from the MCLR pin during programming and
debugging operations by using a jumper (Figure 2-2).
The jumper is replaced for normal run-time
operations.
Any components associated with the MCLR pin
should be placed within 0.25 inch (6 mm) of the pin.
FIGURE 2-2: EXAMPLE OF MCLR PIN
CONNECTIONS
Note 1: R1 10 kΩ is recommended. A suggested
starting value is 10 kΩ. Ensure that the
MCLR pin VIH and VIL specifications are met.
2: R2 470Ω will limit any current flowing into
MCLR from the external capacitor, C, in the
event of MCLR pin breakdown, due to
Electrostatic Discharge (ESD) or Electrical
Overstress (EOS). Ensure that the MCLR pin
VIH and VIL specifications are met.
C1
R2
R1
VDD
MCLR
PIC18FXXXX
JP
© 2009 Microchip Technology Inc. DS39689F-page 27
PIC18F2221/2321/4221/4321 FAMILY
2.4 ICSP Pins
The PGC and PGD pins are used for In-Circuit Serial
Programming (ICSP) and debugging purposes. It is
recommended to keep the trace length between the
ICSP connector and the ICSP pins on the device as
short as possible. If the ICSP connector is expected to
experience an ESD event, a series resistor is recom-
mended, with the value in the range of a few tens of
ohms, not to exceed 100.
Pull-up resistors, series diodes and capacitors on the
PGC and PGD pins are not recommended as they will
interfere with the programmer/debugger com-
munications to the device. If such discrete components
are an application requirement, they should be removed
from the circuit during programming and debugging.
Alternatively, refer to the AC/DC characteristics and
timing requirements information in the respective device
Flash programming specification for information on
capacitive loading limits and pin input voltage high (VIH)
and input low (VIL) requirements.
For device emulation, ensure that the “Communication
Channel Select” (i.e., PGC/PGD pins) programmed
into the device matches the physical connections for
the ICSP to the MPLAB® ICD 2, MPLAB ICD 3 or REAL
ICE™ emulator.
For more information on the ICD 2, ICD 3 and REAL
ICE emulator connection requirements, refer to the
following documents that are available on the
Microchip web site.
“MPLAB® ICD 2 In-Circuit Debugger User’s
Guide” (DS51331)
“Using MPLAB® ICD 2” (poster) (DS51265)
“MPLAB® ICD 2 Design Advisory” (DS51566)
“Using MPLAB® ICD 3” (poster) (DS51765)
“MPLAB® ICD 3 Design Advisory” (DS51764)
“MPLAB® REAL ICE™ In-Circuit Emulator User’s
Guide” (DS51616)
“Using MPLAB® REAL ICE™ In-Circuit Emulator”
(poster) (DS51749)
2.5 External Oscillator Pins
Many microcontrollers have options for at least two
oscillators: a high-frequency primary oscillator and a
low-frequency secondary oscillator (refer to
Section 3.0 “Oscillator Configurations” for details).
The oscillator circuit should be placed on the same
side of the board as the device. Place the oscillator
circuit close to the respective oscillator pins with no
more than 0.5 inch (12 mm) between the circuit
components and the pins. The load capacitors should
be placed next to the oscillator itself, on the same side
of the board.
Use a grounded copper pour around the oscillator
circuit to isolate it from surrounding circuits. The
grounded copper pour should be routed directly to the
MCU ground. Do not run any signal traces or power
traces inside the ground pour. Also, if using a
two-sided board, avoid any traces on the other side of
the board where the crystal is placed. A suggested
layout is shown in Figure 2-3.
For additional information and design guidance on
oscillator circuits, please refer to these Microchip
Application Notes, available at the corporate web site
(www.microchip.com):
AN826, Crystal Oscillator Basics and Crystal
Selection for rfPIC™ and PICmicro® Devices”
AN849, “Basic PICmicro® Oscillator Design”
AN943, “Practical PICmicro® Oscillator Analysis
and Design”
AN949, “Making Your Oscillator Work”
FIGURE 2-3: SUGGESTED PLACEMENT
OF THE OSCILLATOR
CIRCUIT
2.6 Unused I/Os
Unused I/O pins should be configured as outputs and
driven to a logic low state. Alternatively, connect a 1 k
to 10 k resistor to VSS on unused pins and drive the
output to logic low.
13
Main Oscillator
Guard Ring
Guard Trace
Secondary
Oscillator
14
15
16
17
18
19
20
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 28 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 29
PIC18F2221/2321/4221/4321 FAMILY
3.0 OSCILLATOR
CONFIGURATIONS
3.1 Oscillator Types
The PIC18F2221/2321/4221/4321 family of devices
can be operated in ten different oscillator modes. The
user can program the Configuration bits, FOSC<3:0>,
in Configuration Register 1H to select one of these ten
modes:
1. LP Low-Power Crystal
2. XT Crystal/Resonator
3. HS High-Speed Crystal/Resonator
4. HSPLL High-Speed Crystal/Resonator
with PLL enabled
5. RC External Resistor/Capacitor with
FOSC/4 output on RA6
6. RCIO External Resistor/Capacitor with I/O
on RA6
7. INTIO1 Internal Oscillator with FOSC/4 output
on RA6 and I/O on RA7
8. INTIO2 Internal Oscillator with I/O on RA6
and RA7
9. EC External Clock with FOSC/4 output
10. ECIO External Clock with I/O on RA6
3.2 Crystal Oscillator/Ceramic
Resonators
In XT, LP, HS or HSPLL Oscillator modes, a crystal or
ceramic resonator is connected to the OSC1 and
OSC2 pins to establish oscillation. Figure 3-1 shows
the pin connections.
The oscillator design requires the use of a parallel cut
crystal.
FIGURE 3-1: CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
TABLE 3-1: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Note: Use of a series cut crystal may give a
frequency out of the crystal manufacturer’s
specifications.
Typical Capacitor Values Used:
Mode Freq OSC1 OSC2
XT 3.58 MHz 22 pF 22 pF
Capacitor values are for design guidance only.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application. Refer
to the following application notes for oscillator specific
information:
AN588, “PIC® Microcontroller Oscillator Design
Guide”
AN826, “Crystal Oscillator Basics and Crystal
Selection for rfPIC® and PIC® Devices”
AN849, “Basic PIC® Oscillator Design”
AN943, “Practical PIC® Oscillator Analysis and
Design”
AN949, “Making Your Oscillator Work”
See the notes following Table 3-2 for additional
information.
Note: When using resonators with frequencies
above 3.5 MHz, the use of HS mode,
rather than XT mode, is recommended.
HS mode may be used at any VDD for
which the controller is rated. If HS is
selected, it is possible that the gain of the
oscillator will overdrive the resonator.
Therefore, a series resistor may be placed
between the OSC2 pin and the resonator.
As a good starting point, the
recommended value of RS is 330Ω.
Note 1: See Table 3-1 and Table 3-2 for initial values of
C1 and C2.
2: A series resistor (RS) may be required for AT
strip cut crystals.
3: RF varies with the oscillator mode chosen.
C1(1)
C2(1)
XTAL
OSC2
OSC1
RF(3)
Sleep
To
Logic
PIC18FXXXX
RS(2)
Internal
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 30 © 2009 Microchip Technology Inc.
TABLE 3-2: CAPACITOR SELECTION FOR
QUARTZ CRYSTALS
An external clock source may also be connected to the
OSC1 pin in the HS mode, as shown in Figure 3-2.
When operated in this mode, parameters D033 and
D043 apply.
FIGURE 3-2: EXTERNAL CLOCK INPUT
OPERATION (HS OSC
CONFIGURATION)
3.3 External Clock Input
The EC and ECIO Oscillator modes require an external
clock source to be connected to the OSC1 pin. There is
no oscillator start-up time required after a Power-on
Reset or after an exit from Sleep mode.
In the EC Oscillator mode, the oscillator frequency
divided by 4 is available on the OSC2 pin. This signal
may be used for test purposes or to synchronize other
logic. Figure 3-3 shows the pin connections for the EC
Oscillator mode.
FIGURE 3-3: EXTERNAL CLOCK
INPUT OPERATION
(EC CONFIGURATION)
The ECIO Oscillator mode functions like the EC mode,
except that the OSC2 pin becomes an additional
general purpose I/O pin. The I/O pin becomes bit 6 of
PORTA (RA6). Figure 3-4 shows the pin connections
for the ECIO Oscillator mode. When operated in this
mode, parameters D033A and D043A apply.
FIGURE 3-4: EXTERNAL CLOCK
INPUT OPERATION
(ECIO CONFIGURATION)
Osc Type Crystal
Freq
Typical Capacitor Values
Tested:
C1 C2
LP 32 kHz 22 pF 22 pF
XT 1 MHz
4 MHz
22 pF
22 pF
22 pF
22 pF
HS 4 MHz
10 MHz
20 MHz
25 MHz
22 pF
22 pF
22 pF
22 pF
22 pF
22 pF
22 pF
22 pF
Capacitor values are for design guidance only.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application. Refer
to the following application notes for oscillator specific
information:
AN588, “PIC® Microcontroller Oscillator Design
Guide”
AN826, “Crystal Oscillator Basics and Crystal
Selection for rfPIC® and PIC® Devices”
AN849, “Basic PIC® Oscillator Design”
AN943, “Practical PIC® Oscillator Analysis and
Design”
AN949, “Making Your Oscillator Work”
See the notes following this table for additional
information.
Note 1: Higher capacitance increases the stability
of the oscillator but also increases the
start-up time.
2: When operating below 3V VDD, or when
using certain ceramic resonators at any
voltage, it may be necessary to use the
HS mode or switch to a crystal oscillator.
3: Since each resonator/crystal has its own
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate values of external
components.
4: Rs may be required to avoid overdriving
crystals with low drive level specification.
5: Always verify oscillator performance over
the VDD and temperature range that is
expected for the application.
OSC1
OSC2
Open
Clock from
Ext. System PIC18FXXXX
(HS Mode)
OSC1/CLKI
OSC2/CLKO
FOSC/4
Clock from
Ext. System PIC18FXXXX
OSC1/CLKI
I/O (OSC2)
RA6
Clock from
Ext. System PIC18FXXXX
© 2009 Microchip Technology Inc. DS39689F-page 31
PIC18F2221/2321/4221/4321 FAMILY
3.4 RC Oscillator
For timing insensitive applications, the RC and RCIO
Oscillator modes offer additional cost savings. The
actual oscillator frequency is a function of several
factors:
supply voltage
values of the external resistor (REXT) and
capacitor (CEXT)
operating temperature
Given the same device, operating voltage, temperature
and component values, there will also be unit-to-unit
frequency variations. These are due to factors such as:
normal manufacturing variation
difference in lead frame capacitance between
package types (especially for low CEXT values)
variations within the tolerance of limits of REXT
and CEXT
In the RC Oscillator mode, the oscillator frequency
divided by 4 is available on the OSC2 pin. This signal
may be used for test purposes or to synchronize other
logic. Figure 3-5 shows how the R/C combination is
connected.
FIGURE 3-5: RC OSCILLATOR MODE
The RCIO Oscillator mode (Figure 3-6) functions like
the RC mode, except that the OSC2 pin becomes an
additional general purpose I/O pin. The I/O pin
becomes bit 6 of PORTA (RA6).
FIGURE 3-6: RCIO OSCILLATOR MODE
3.5 PLL Frequency Multiplier
A Phase Locked Loop (PLL) circuit is provided as an
option for users who wish to use a lower frequency
oscillator circuit or to clock the device up to its highest
rated frequency from a crystal oscillator. This may be
useful for customers who are concerned with EMI due
to high-frequency crystals or users who require higher
clock speeds from an internal oscillator.
3.5.1 HSPLL OSCILLATOR MODE
The HSPLL mode makes use of the HS mode oscillator
for frequencies up to 10 MHz. A PLL then multiplies the
oscillator output frequency by 4 to produce an internal
clock frequency up to 40 MHz. The PLLEN bit is not
available when this mode is configured as the primary
clock source.
The PLL is only available to the crystal oscillator when
the FOSC<3:0> Configuration bits are programmed for
HSPLL mode (= 0110).
FIGURE 3-7: HSPLL BLOCK DIAGRAM
3.5.2 PLL AND INTOSC
The PLL is also available to the internal oscillator block
when the internal oscillator block is configured as the
primary clock source. In this configuration, the PLL is
enabled in software and generates a clock output of up
to 32 MHz. The operation of INTOSC with the PLL is
described in Section 3.6.4 “PLL in INTOSC Modes”.
OSC2/CLKO
CEXT
REXT
PIC18FXXXX
OSC1
FOSC/4
Internal
Clock
VDD
VSS
Recommended values: 3 kΩ REXT 100 kΩ
20 pF CEXT 300 pF
CEXT
REXT
PIC18FXXXX
OSC1 Internal
Clock
VDD
VSS
Recommended values: 3 kΩ REXT 100 kΩ
20 pF CEXT 300 pF
I/O (OSC2)
RA6
MUX
VCO
Loop
Filter
Crystal
Osc
OSC2
OSC1
PLL Enable
FIN
FOUT
SYSCLK
Phase
Comparator
HS Oscillator Enable
÷4
(from Configuration Register 1H)
HS Mode
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 32 © 2009 Microchip Technology Inc.
3.6 Internal Oscillator Block
The PIC18F2221/2321/4221/4321 family of devices
includes an internal oscillator block which generates
two different clock signals; either can be used as the
microcontroller’s clock source. This may eliminate the
need for external oscillator circuits on the OSC1 and/or
OSC2 pins.
The main output (INTOSC) is an 8 MHz clock source,
which can be used to directly drive the device clock. It
also drives a postscaler, which can provide a range of
clock frequencies from 31 kHz to 4 MHz. The INTOSC
output is enabled when a clock frequency from 125 kHz
to 8 MHz is selected. The INTOSC output can also be
enabled when 31 kHz is selected, depending on the
INTSRC bit (OSCTUNE<7>).
The other clock source is the internal RC oscillator
(INTRC), which provides a nominal 31 kHz output.
INTRC is enabled if it is selected as the device clock
source; it is also enabled automatically when any of the
following are enabled:
Power-up Timer
Fail-Safe Clock Monitor
Watchdog Timer
Two-Speed Start-up
These features are discussed in greater detail in
Section 24.0 “Special Features of the CPU”.
The clock source frequency (INTOSC direct, INTRC
direct or INTOSC postscaler) is selected by configuring
the IRCF bits of the OSCCON register (page 37).
3.6.1 INTIO MODES
Using the internal oscillator as the clock source elimi-
nates the need for up to two external oscillator pins,
which can then be used for digital I/O. Two distinct
configurations are available:
In INTIO1 mode, the OSC2 pin outputs FOSC/4,
while OSC1 functions as RA7 (see Figure 3-8) for
digital input and output.
In INTIO2 mode, OSC1 functions as RA7 and
OSC2 functions as RA6 (see Figure 3-9), both for
digital input and output.
FIGURE 3-8: INTIO1 OSCILLATOR MODE
FIGURE 3-9: INTIO2 OSCILLATOR MODE
3.6.2 INTOSC OUTPUT FREQUENCY
The internal oscillator block is calibrated at the factory
to produce an INTOSC output frequency of 8 MHz.
The INTRC oscillator operates independently of the
INTOSC source. Any changes in INTOSC across
voltage and temperature are not necessarily reflected
by changes in INTRC or vice versa.
3.6.3 OSCTUNE REGISTER
The INTOSC output has been calibrated at the
factory but can be adjusted in the user’s application.
This is done by writing to TUN<4:0>
(OSCTUNE<4:0>) in the OSCTUNE register
(Register 3-1).
When the OSCTUNE register is modified, the INTOSC
frequency will begin shifting to the new frequency.
Code execution continues during this shift. There is no
indication that the shift has occurred. The INTRC is not
affected by OSCTUNE.
The OSCTUNE register also implements the INTSRC
(OSCTUNE<7>) and PLLEN (OSCTUNE<6>) bits,
which control certain features of the internal oscillator
block. The INTSRC bit allows users to select which
internal oscillator provides the clock source when the
31 kHz frequency option is selected. This is covered in
greater detail in Section 3.7.1 “Oscillator Control
Register”.
The PLLEN bit controls the operation of the Phase
Locked Loop (PLL) in Internal Oscillator modes (see
Figure 3-10).
FIGURE 3-10: INTOSC AND PLL BLOCK
DIAGRAM
PIC18FXXXX
OSC2
FOSC/4
I/O (OSC1)
RA7
PIC18FXXXX
I/O (OSC2)
RA6
I/O (OSC1)
RA7
MUX
VCO
Loop
Filter
OSC2
PLLEN
FIN
FOUT
SYSCLK
Phase
Comparator
8 or 4 MHz
÷4
(OSCTUNE<6>)
MUX
RA6
CLKO
INTOSC
© 2009 Microchip Technology Inc. DS39689F-page 33
PIC18F2221/2321/4221/4321 FAMILY
3.6.4 PLL IN INTOSC MODES
The 4x Phase Locked Loop (PLL) can be used with the
internal oscillator block to produce faster device clock
speeds than are normally possible with the internal
oscillator sources. When enabled, the PLL produces a
clock speed of 16 MHz or 32 MHz.
Unlike HSPLL mode, the PLL is controlled through
software. The control bit, PLLEN (OSCTUNE<6>), is
used to enable or disable its operation. If PLL is
enabled and a Two-Speed Start-up from wake is
performed, execution is delayed until the PLL starts.
The PLL is available when the device is configured to
use the internal oscillator block as its primary clock
source (FOSC<3:0> = 1001 or 1000). Additionally, the
PLL will only function when the selected output fre-
quency is either 4 MHz or 8 MHz (OSCCON<6:4> = 111
or 110). If both of these conditions are not met, the PLL
is disabled and the PLLEN bit remains clear (writes are
ignored).
3.6.5 INTOSC FREQUENCY DRIFT
The factory calibrates the internal oscillator block
output (INTOSC) for 8 MHz. However, this frequency
may drift as VDD or temperature changes and can
affect the controller operation in a variety of ways. It is
possible to adjust the INTOSC frequency by modifying
the value in the OSCTUNE register. This has no effect
on the INTRC clock source frequency.
Tuning the INTOSC source requires knowing when to
make the adjustment, in which direction it should be
made and in some cases, how large a change is
needed. Three compensation techniques are discussed
in Section 3.6.5.1 “Compensating with the
EUSART”, Section 3.6.5.2 “Compensating with the
Timers and Section 3.6.5.3 “Compensating with the
CCP Module in Capture Mode” but other techniques
may be used.
REGISTER 3-1: OSCTUNE: OSCILLATOR TUNING REGISTER
R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
INTSRC PLLEN(1) TUN4 TUN3 TUN2 TUN1 TUN0
bit 7 bit 0
bit 7 INTSRC: Internal Oscillator Low-Frequency Source Select bit
1 = 31.25 kHz device clock derived from 8 MHz INTOSC source (divide-by-256 enabled)
0 = 31 kHz device clock derived directly from INTRC internal oscillator
bit 6 PLLEN: Frequency Multiplier PLL for INTOSC Enable bit(1)
1 = PLL enabled for INTOSC (4 MHz and 8 MHz only)
0 = PLL disabled
Note 1: Available only in certain oscillator configurations; otherwise, this bit is unavailable
and reads as ‘0’. See Section 3.6.4 “PLL in INTOSC Modes” for details.
bit 5 Unimplemented: Read as ‘0
bit 4-0 TUN<4:0>: Frequency Tuning bits
01111 = Maximum frequency
00001
00000 = Center frequency. Oscillator module is running at the calibrated frequency.
11111
10000 = Minimum frequency
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 34 © 2009 Microchip Technology Inc.
3.6.5.1 Compensating with the EUSART
An adjustment may be required when the EUSART
begins to generate framing errors or receives data with
errors while in Asynchronous mode. Framing errors
indicate that the device clock frequency is too high. To
adjust for this, decrement the value in OSCTUNE to
reduce the clock frequency. On the other hand, errors
in data may suggest that the clock speed is too low. To
compensate, increment OSCTUNE to increase the
clock frequency.
3.6.5.2 Compensating with the Timers
This technique compares device clock speed to some
reference clock. Two timers may be used; one timer is
clocked by the peripheral clock, while the other is
clocked by a fixed reference source, such as the
Timer1 oscillator.
Both timers are cleared, but the timer clocked by the
reference generates interrupts. When an interrupt
occurs, the internally clocked timer is read and both
timers are cleared. If the internally clocked timer value
is much greater than expected, then the internal
oscillator block is running too fast. To adjust for this,
decrement the OSCTUNE register.
3.6.5.3 Compensating with the CCP Module
in Capture Mode
A CCP module can use free running Timer1 (or
Timer3), clocked by the internal oscillator block and an
external event with a known period (i.e., AC power
frequency). The time of the first event is captured in the
CCPRxH:CCPRxL registers and is recorded for use
later. When the second event causes a capture, the
time of the first event is subtracted from the time of the
second event. Since the period of the external event is
known, the time difference between events can be
calculated.
If the measured time is much greater than the
calculated time, the internal oscillator block is running
too fast. To compensate, decrement the OSCTUNE
register. If the measured time is much less than the
calculated time, the internal oscillator block is running
too slow. To compensate, increment the OSCTUNE
register.
© 2009 Microchip Technology Inc. DS39689F-page 35
PIC18F2221/2321/4221/4321 FAMILY
3.7 Clock Sources and Oscillator
Switching
The PIC18F2221/2321/4221/4321 family of devices
includes a feature that allows the device clock source
to be switched from the main oscillator to an alternate
clock source. These devices also offer two alternate
clock sources. When an alternate clock source is
enabled, the various power-managed operating modes
are available.
Essentially, there are three clock sources for these
devices:
Primary oscillators
Secondary oscillators
Internal oscillator block
The primary oscillators include the External Crystal
and Resonator modes, the External RC modes, the
External Clock modes and the internal oscillator block.
The particular mode is defined by the FOSC<3:0> Con-
figuration bits. The details of these modes are covered
earlier in this chapter.
The secondary oscillators are those external sources
not connected to the OSC1 or OSC2 pins. These
sources may continue to operate even after the
controller is placed in a power-managed mode.
The PIC18F2221/2321/4221/4321 family of devices
offers the Timer1 oscillator as a secondary oscillator.
This oscillator, in all power-managed modes, is often
the time base for functions such as a Real-Time Clock.
Most often, a 32.768 kHz watch crystal is connected
between the RC0/T1OSO/T13CKI and RC1/T1OSI
pins. Like the LP mode oscillator circuit, loading
capacitors are also connected from each pin to ground.
The Timer1 oscillator is discussed in greater detail in
Section 13.3 “Timer1 Oscillator”.
In addition to being a primary clock source, the internal
oscillator block is available as a power-managed
mode clock source. The INTRC source is also used as
the clock source for several special features, such as
the WDT and Fail-Safe Clock Monitor.
The clock sources for the PIC18F2221/2321/4221/4321
family of devices are shown in Figure 3-11. See
Section 24.0 “Special Features of the CPU” for
Configuration register details.
FIGURE 3-11: PIC18F2221/2321/4221/4321 FAMILY CLOCK DIAGRAM
4 x PLL
FOSC<3:0>
Secondary Oscillator
T1OSCEN
Enable
Oscillator
T1OSO
T1OSI
Clock Source Option
for Other Modules
OSC1
OSC2
Sleep HSPLL, INTOSC/PLL
LP, XT, HS, RC, EC
T1OSC
CPU
Peripherals
IDLEN
Postscaler
MUX
MUX
8 MHz
4 MHz
2 MHz
1 MHz
500 kHz
125 kHz
250 kHz
OSCCON<6:4>
111
110
101
100
011
010
001
000
31 kHz
INTRC
Source
Internal
Oscillator
Block
WDT, PWRT, FSCM
8 MHz
Internal Oscillator
(INTOSC)
OSCCON<6:4>
Clock
Control
OSCCON<1:0>
Source
8 MHz
31 kHz (INTRC)
OSCTUNE<6>
0
1
OSCTUNE<7>
and Two-Speed Start-up
Primary Oscillator
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 36 © 2009 Microchip Technology Inc.
3.7.1 OSCILLATOR CONTROL REGISTER
The OSCCON register (Register 3-2) controls several
aspects of the device clock’s operation, both in full
power operation and in power-managed modes.
The System Clock Select bits, SCS<1:0>, select the
clock source. The available clock sources are the
primary clock (defined by the FOSC<3:0> Configura-
tion bits), the secondary clock (Timer1 oscillator) and
the internal oscillator block. The clock source changes
immediately after either of the SCS<1:0> bits are
changed, following a brief clock transition interval. The
SCS bits are reset on all forms of Reset.
The Internal Oscillator Frequency Select bits
(IRCF<2:0>) select the frequency output of the internal
oscillator block to drive the device clock. The choices
are the INTRC source (31 kHz), the INTOSC source
(8 MHz) or one of the frequencies derived from the
INTOSC postscaler (31.25 kHz to 4 MHz). If the
internal oscillator block is supplying the device clock,
changing the states of these bits will have an immedi-
ate change on the internal oscillator’s output. On
device Resets, the default output frequency of the
internal oscillator block is set at 1 MHz.
When a nominal output frequency of 31 kHz is selected
(IRCF<2:0> = 000), users may choose which internal
oscillator acts as the source. This is done with the
INTSRC bit in the OSCTUNE register (OSCTUNE<7>).
Setting this bit selects INTOSC as a 31.25 kHz clock
source derived from the INTOSC postscaler. Clearing
INTSRC selects INTRC (nominally 31 kHz) as the
clock source and disables the INTOSC to reduce
current consumption.
This option allows users to select the tunable and more
precise INTOSC as a clock source, while maintaining
power savings with a very low clock speed. Addition-
ally, the INTOSC source will already be stable should a
switch to a higher frequency be needed quickly.
Regardless of the setting of INTSRC, INTRC always
remains the clock source for features such as the
Watchdog Timer and the Fail-Safe Clock Monitor.
The OSTS, IOFS and T1RUN bits indicate which clock
source is currently providing the device clock. The
OSTS bit indicates that the Oscillator Start-up Timer
and PLL Start-up Timer (if enabled) have timed out and
the primary clock is providing the device clock in
primary clock modes. The IOFS bit indicates when the
internal oscillator block has stabilized and is providing
the device clock in RC Clock modes. The T1RUN bit
(T1CON<6>) indicates when the Timer1 oscillator is
providing the device clock in secondary clock modes.
In power-managed modes, only one of these three bits
will be set at any time. If none of these bits are set, the
INTRC is providing the clock or the internal oscillator
block has just started and is not yet stable.
The IDLEN bit controls whether the device goes into
Sleep mode or one of the Idle modes when the SLEEP
instruction is executed.
The use of the flag and control bits in the OSCCON
register is discussed in more detail in Section 4.0
“Power-Managed Modes”.
3.7.2 OSCILLATOR TRANSITIONS
The PIC18F2221/2321/4221/4321 family of devices con-
tains circuitry to prevent clock “glitches” when switching
between clock sources. A short pause in the device clock
occurs during the clock switch. The length of this pause
is the sum of two cycles of the old clock source and three
to four cycles of the new clock source. This formula
assumes that the new clock source is stable.
Clock transitions are discussed in greater detail in
Section 4.1.2 “Entering Power-Managed Modes”.
Note 1: The Timer1 oscillator must be enabled to
select the secondary clock source. The
Timer1 oscillator is enabled by setting the
T1OSCEN bit in the Timer1 Control regis-
ter (T1CON<3>). If the Timer1 oscillator
is not enabled, then any attempt to select
a secondary clock source will be ignored.
2: It is recommended that the Timer1
oscillator be operating and stable before
selecting the secondary clock source or a
very long delay may occur while the
Timer1 oscillator starts.
© 2009 Microchip Technology Inc. DS39689F-page 37
PIC18F2221/2321/4221/4321 FAMILY
REGISTER 3-2: OSCCON: OSCILLATOR CONTROL REGISTER
R/W-0 R/W-1 R/W-0 R/W-0 R(1) R-0 R/W-0 R/W-0
IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0
bit 7 bit 0
bit 7 IDLEN: Idle Enable bit
1 = Device enters an Idle mode when a SLEEP instruction is executed
0 = Device enters Sleep mode when a SLEEP instruction is executed
bit 6-4 IRCF<2:0>: Internal Oscillator Frequency Select bits
111 = 8 MHz (INTOSC drives clock directly)
110 = 4MHz
101 = 2MHz
100 = 1MHz
(3)
011 = 500 kHz
010 = 250 kHz
001 = 125 kHz
000 = 31 kHz (from either INTOSC/256 or INTRC directly)(2)
bit 3 OSTS: Oscillator Start-up Time-out Status bit(1)
1 = Oscillator Start-up Timer (OST) time-out has expired; primary oscillator is running
0 = Oscillator Start-up Timer (OST) time-out is running; primary oscillator is not ready
bit 2 IOFS: INTOSC Frequency Stable bit
1 = INTOSC frequency is stable
0 = INTOSC frequency is not stable
bit 1-0 SCS<1:0>: System Clock Select bits
1x = Internal oscillator block
01 = Secondary (Timer1) oscillator
00 = Primary oscillator
Note 1: Reset state depends on state of the IESO Configuration bit.
2: Source selected by the INTSRC bit (OSCTUNE<7>), see text.
3: Default output frequency of INTOSC on Reset.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 38 © 2009 Microchip Technology Inc.
3.8 Effects of Power-Managed Modes
on the Various Clock Sources
When PRI_IDLE mode is selected, the designated pri-
mary oscillator continues to run without interruption.
For all other power-managed modes, the oscillator
using the OSC1 pin is disabled. The OSC1 pin (and
OSC2 pin in Crystal Oscillator modes) will stop
oscillating.
In secondary clock modes (SEC_RUN and
SEC_IDLE), the Timer1 oscillator is operating and
providing the device clock. The Timer1 oscillator may
also run in all power-managed modes if required to
clock Timer1 or Timer3.
In internal oscillator modes (RC_RUN and RC_IDLE),
the internal oscillator block provides the device clock
source. The 31 kHz INTRC output can be used directly
to provide the clock and may be enabled to support
various special features, regardless of the power-
managed mode (see Section 24.2 “Watchdog Timer
(WDT)”, Section 24.3 “Two-Speed Start-up” and
Section 24.4 “Fail-Safe Clock Monitor” for more
information). The INTOSC output at 8 MHz may be
used directly to clock the device or may be divided
down by the postscaler. The INTOSC output is disabled
if the clock is provided directly from the INTRC output.
The INTOSC output is also enabled for Two-Speed
Start-up at 1 MHz after a Reset.
If the Sleep mode is selected, all clock sources are
stopped. Since all the transistor switching currents
have been stopped, Sleep mode achieves the lowest
current consumption of the device (only leakage
currents).
Enabling any on-chip feature that will operate during
Sleep will increase the current consumed during Sleep.
The INTRC is required to support WDT operation. The
Timer1 oscillator may be operating to support a Real-
Time Clock. Other features may be operating that do
not require a device clock source (i.e., MSSP slave,
PSP, INTx pins and others). Peripherals that may add
significant current consumption are listed in
Section 27.2 “DC Characteristics”.
3.9 Power-up Delays
Power-up delays are controlled by two or three timers,
so that no external Reset circuitry is required for most
applications. The delays ensure that the device is kept
in Reset until the device power supply is stable under
normal circumstances and the primary clock is operat-
ing and stable. For additional information on power-up
delays, see Section 5.5 “Device Reset Timers”.
The first timer is the Power-up Timer (PWRT) which
provides a fixed delay on power-up (parameter 33,
Table 27-10). It is enabled by clearing (= 0) the
PWRTEN Configuration bit (CONFIG2L<0>).
3.9.1 DELAYS FOR POWER-UP AND
RETURN TO PRIMARY CLOCK
The second timer is the Oscillator Start-up Timer
(OST), intended to delay execution until the crystal
oscillator is stable (LP, XT and HS modes). The OST
does this by counting 1024 oscillator cycles before
allowing the oscillator to clock the device.
When the HSPLL Oscillator mode is selected, a third
timer delays execution for an additional 2 ms following
the HS mode OST delay, so the PLL can lock to the
incoming clock frequency. At the end of these delays,
the OSTS bit (OSCCON<3>) is set.
There is a delay of interval T
CSD (parameter 38,
Table 27-10), once execution is allowed to start, when
the controller becomes ready to execute instructions.
This delay runs concurrently with any other delays.
This may be the only delay that occurs when any of the
EC, RC or INTIO modes are used as the primary clock
source.
TABLE 3-3: OSC1 AND OSC2 PIN STATES IN SLEEP MODE
OSC Mode OSC1 Pin OSC2 Pin
RC, INTIO1 Floating, external resistor pulls high At logic low (clock/4 output)
RCIO Floating, external resistor pulls high Configured as PORTA, bit 6
INTIO2 Configured as PORTA, bit 7 Configured as PORTA, bit 6
ECIO Floating, driven by external clock Configured as PORTA, bit 6
EC Floating, driven by external clock At logic low (clock/4 output)
LP, XT and HS Feedback inverter disabled at quiescent
voltage level
Feedback inverter disabled at quiescent
voltage level
Note: See Table 5-2 in Section 5.0 “Reset” for time-outs due to Sleep and MCLR Reset.
© 2009 Microchip Technology Inc. DS39689F-page 39
PIC18F2221/2321/4221/4321 FAMILY
4.0 POWER-MANAGED MODES
PIC18F2221/2321/4221/4321 family devices offer a
total of seven operating modes for more efficient
power-management. These modes provide a variety of
options for selective power conservation in applications
where resources may be limited (i.e., battery-powered
devices).
There are three categories of power-managed modes:
Run modes
Idle modes
Sleep mode
These categories define which portions of the device
are clocked and sometimes, what speed. The Run and
Idle modes may use any of the three available clock
sources (primary, secondary or internal oscillator
block); the Sleep mode does not use a clock source.
The power-managed modes include several power-
saving features offered on previous PIC® devices. One
is the clock switching feature, offered in other PIC18
devices, allowing the controller to use the Timer1 oscil-
lator in place of the primary oscillator. Also included is
the Sleep mode, offered by all PIC devices, where all
device clocks are stopped.
4.1 Selecting Power-Managed Modes
Selecting a power-managed mode requires two
decisions: if the CPU is to be clocked or not and the
selection of a clock source. The IDLEN bit
(OSCCON<7>) controls CPU clocking, while the
SCS<1:0 bits (OSCCON<1:0>) select the clock source.
The individual modes, bit settings, clock sources and
affected modules are summarized in Table 4-1.
4.1.1 CLOCK SOURCES
The SCS<1:0 bits allow the selection of one of three
clock sources for power-managed modes. They are:
the primary clock, as defined by the FOSC<3:0>
Configuration bits
the secondary clock (the Timer1 oscillator)
the internal oscillator block (for RC modes)
4.1.2 ENTERING POWER-MANAGED
MODES
Switching from one power-managed mode to another
begins by loading the OSCCON register. The
SCS1:SCS0 bits select the clock source and determine
which Run or Idle mode is to be used. Changing these
bits causes an immediate switch to the new clock
source, assuming that it is running. The switch may
also be subject to clock transition delays. These are
discussed in Section 4.1.3 “Clock Transitions and
Status Indicators” and subsequent sections.
Entry to the power-managed Idle or Sleep modes is
triggered by the execution of a SLEEP instruction. The
actual mode that results depends on the status of the
IDLEN bit.
Depending on the current mode and the mode being
switched to, a change to a power-managed mode does
not always require setting all of these bits. Many
transitions may be done by changing the oscillator select
bits, or changing the IDLEN bit, prior to issuing a SLEEP
instruction. If the IDLEN bit is already configured
correctly, it may only be necessary to perform a SLEEP
instruction to switch to the desired mode.
TABLE 4-1: POWER-MANAGED MODES
Mode
OSCCON Bits Module Clocking
Available Clock and Oscillator Source
IDLEN<7>(1) SCS<1:0> CPU Peripherals
Sleep 0N/A Off Off None – All clocks are disabled
PRI_RUN N/A 00 Clocked Clocked Primary – LP, XT, HS, HSPLL, RC, EC and
Internal Oscillator Block.(2)
This is the normal full power execution mode.
SEC_RUN N/A 01 Clocked Clocked Secondary – Timer1 Oscillator
RC_RUN N/A 1x Clocked Clocked Internal Oscillator Block(2)
PRI_IDLE 100Off Clocked Primary – LP, XT, HS, HSPLL, RC, EC
SEC_IDLE 101Off Clocked Secondary – Timer1 Oscillator
RC_IDLE 11xOff Clocked Internal Oscillator Block(2)
Note 1: IDLEN reflects its value when the SLEEP instruction is executed.
2: Includes INTOSC and INTOSC postscaler, as well as the INTRC source.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 40 © 2009 Microchip Technology Inc.
4.1.3 CLOCK TRANSITIONS AND STATUS
INDICATORS
The length of the transition between clock sources is
the sum of two cycles of the old clock source and three
to four cycles of the new clock source. This formula
assumes that the new clock source is stable.
Three bits indicate the current clock source and its
status. They are:
OSTS (OSCCON<3>)
IOFS (OSCCON<2>)
T1RUN (T1CON<6>)
In general, only one of these bits will be set while in a
given power-managed mode. When the OSTS bit is
set, the primary clock is providing the device clock.
When the IOFS bit is set, the INTOSC output is
providing a stable 8 MHz clock source to a divider that
actually drives the device clock. When the T1RUN bit is
set, the Timer1 oscillator is providing the clock. If none
of these bits are set, then either the INTRC clock
source is clocking the device, or the INTOSC source is
not yet stable.
If the internal oscillator block is configured as the primary
clock source by the FOSC<3:0> Configuration bits, then
both the OSTS and IOFS bits may be set when in
PRI_RUN or PRI_IDLE modes. This indicates that the
primary clock (INTOSC) is generating a stable 8 MHz
output. Switching the clock source to the Timer1
oscillator would clear the OSTS bit.
4.1.4 MULTIPLE SLEEP COMMANDS
The power-managed mode that is invoked with the
SLEEP instruction is determined by the setting of the
IDLEN bit at the time the instruction is executed. If
another SLEEP instruction is executed, the device will
enter the power-managed mode specified by IDLEN at
that time. If IDLEN has changed, the device will enter
the new power-managed mode specified by the new
setting.
4.2 Run Modes
In the Run modes, clocks to both the core and
peripherals are active. The difference between these
modes is the clock source.
4.2.1 PRI_RUN MODE
The PRI_RUN mode is the normal, full power execution
mode of the microcontroller. This is also the default
mode upon a device Reset unless Two-Speed Start-up
is enabled (see Section 24.3 “Two-Speed Start-up”
or Section 24.4 “Fail-Safe Clock Monitor for
details). In this mode, the OSTS bit is set. The IOFS bit
may be set if the internal oscillator block is the primary
clock source (see Section 3.7.1 “Oscillator Control
Register”).
4.2.2 SEC_RUN MODE
The SEC_RUN mode is the compatible mode to the
“clock switching” feature offered in other PIC18
devices. In this mode, the CPU and peripherals are
clocked from the Timer1 oscillator. This gives users the
option of lower power consumption while still using a
high-accuracy clock source.
SEC_RUN mode is entered by setting the SCS<1:0>
bits to ‘01’. The device clock source is switched to the
Timer1 oscillator (see Figure 4-1), the primary oscillator
is shut down, the T1RUN bit (T1CON<6>) is set and the
OSTS bit is cleared.
On transitions from SEC_RUN mode to PRI_RUN, the
peripherals and CPU continue to be clocked from the
Timer1 oscillator while the primary clock is started.
When the primary clock becomes ready, a clock switch
back to the primary clock occurs (see Figure 4-2).
When the clock switch is complete, the T1RUN bit is
cleared, the OSTS bit is set and the primary clock is
providing the clock. The IDLEN and SCS bits are not
affected by the wake-up; the Timer1 oscillator
continues to run.
Note 1: Caution should be used when modifying a
single IRCF bit. If VDD is less than 3V, it is
possible to select a higher clock speed
than is supported by the low VDD.
Improper device operation may result if
the VDD/FOSC specifications are violated.
2: Executing a SLEEP instruction does not
necessarily place the device into Sleep
mode. It acts as the trigger to place the
controller into either the Sleep mode or
one of the Idle modes, depending on the
setting of the IDLEN bit.
Note: The Timer1 oscillator should already be
running prior to entering SEC_RUN mode.
If the T1OSCEN bit is not set when the
SCS<1:0> bits are set to ‘01’, entry to
SEC_RUN mode will not occur. If the
Timer1 oscillator is enabled, but not yet
running, device clocks will be delayed until
the oscillator has started. In such situa-
tions, initial oscillator operation is far from
stable and unpredictable operation may
result.
© 2009 Microchip Technology Inc. DS39689F-page 41
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 4-1: TRANSITION TIMING FOR ENTRY TO SEC_RUN MODE
FIGURE 4-2: TRANSITION TIMING FROM SEC_RUN MODE TO PRI_RUN MODE (HSPLL)
4.2.3 RC_RUN MODE
In RC_RUN mode, the CPU and peripherals are
clocked from the internal oscillator block using the
INTOSC multiplexer. In this mode, the primary clock is
shut down. When using the INTRC source, this mode
provides the best power conservation of all the Run
modes, while still executing code. It works well for user
applications which are not highly timing sensitive or do
not require high-speed clocks at all times.
If the primary clock source is the internal oscillator block
(either INTRC or INTOSC), there are no distinguishable
differences between PRI_RUN and RC_RUN modes
during execution. However, a clock switch delay will
occur during entry to and exit from RC_RUN mode.
Therefore, if the primary clock source is the internal
oscillator block, the use of RC_RUN mode is not
recommended.
This mode is entered by setting the SCS1 bit to ‘1’.
Although it is ignored, it is recommended that the SCS0
bit also be cleared; this is to maintain software compat-
ibility with future devices. When the clock source is
switched to the INTOSC multiplexer (see Figure 4-3),
the primary oscillator is shut down and the OSTS bit is
cleared. The IRCF bits may be modified at any time to
immediately change the clock speed.
Q4Q3Q2
OSC1
Peripheral
Program
Q1
T1OSI
Q1
Counter
Clock
CPU
Clock
PC + 2PC
123
n-1
n
Clock Transition(1)
Q4Q3Q2 Q1 Q3Q2
PC + 4
Note 1: Clock transition typically occurs within 2-4 TOSC.
Q1 Q3 Q4
OSC1
Peripheral
Program PC
T1OSI
PLL Clock
Q1
PC + 4
Q2
Output
Q3 Q4 Q1
CPU Clock
PC + 2
Clock
Counter
Q2 Q2 Q3
Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.
2: Clock transition typically occurs within 2-4 TOSC.
SCS<1:0> bits Changed
TPLL(1)
12 n-1n
Clock
OSTS bit Set
Transition(2)
TOST(1)
Note: Caution should be used when modifying a
single IRCF bit. If VDD is less than 3V, it is
possible to select a higher clock speed
than is supported by the low VDD.
Improper device operation may result if
the VDD/FOSC specifications are violated.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 42 © 2009 Microchip Technology Inc.
If the IRCF bits and the INTSRC bit are all clear, the
INTOSC output is not enabled and the IOFS bit will
remain clear; there will be no indication of the current
clock source. The INTRC source is providing the
device clocks.
If the IRCF bits are changed from all clear (thus,
enabling the INTOSC output) or if INTSRC is set, the
IOFS bit becomes set after the INTOSC output
becomes stable. Clocks to the device continue while
the INTOSC source stabilizes after an interval of
TIOBST (parameter 39, Table 27-10).
If the IRCF bits were previously at a non-zero value, or
if INTSRC was set before setting SCS1 and the
INTOSC source was already stable, the IOFS bit will
remain set.
On transitions from RC_RUN mode to PRI_RUN mode,
the device continues to be clocked from the INTOSC
multiplexer while the primary clock is started. When the
primary clock becomes ready, a clock switch to the
primary clock occurs (see Figure 4-4). When the clock
switch is complete, the IOFS bit is cleared, the OSTS
bit is set and the primary clock is providing the device
clock. The IDLEN and SCS bits are not affected by the
switch. The INTRC source will continue to run if either
the WDT or the Fail-Safe Clock Monitor is enabled.
FIGURE 4-3: TRANSITION TIMING TO RC_RUN MODE
FIGURE 4-4: TRANSITION TIMING FROM RC_RUN MODE TO PRI_RUN MODE
Q4Q3Q2
OSC1
Peripheral
Program
Q1
INTRC
Q1
Counter
Clock
CPU
Clock
PC + 2PC
123 n-1n
Clock Transition(1)
Q4Q3Q2 Q1 Q3Q2
PC + 4
Note 1: Clock transition typically occurs within 2-4 TOSC.
Q1 Q3 Q4
OSC1
Peripheral
Program PC
INTOSC
PLL Clock
Q1
PC + 4
Q2
Output
Q3 Q4 Q1
CPU Clock
PC + 2
Clock
Counter
Q2 Q2 Q3
Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.
2: Clock transition typically occurs within 2-4 TOSC.
SCS<1:0> bits Changed
TPLL(1)
12 n-1n
Clock
OSTS bit Set
Transition(2)
Multiplexer
TOST(1)
© 2009 Microchip Technology Inc. DS39689F-page 43
PIC18F2221/2321/4221/4321 FAMILY
4.3 Sleep Mode
The power-managed Sleep mode in the PIC18F2221/
2321/4221/4321 family devices is identical to the leg-
acy Sleep mode offered in all other PIC devices. It is
entered by clearing the IDLEN bit (the default state on
device Reset) and executing the SLEEP instruction.
This shuts down the selected oscillator (Figure 4-5). All
clock source status bits are cleared.
Entering the Sleep mode from any other mode does not
require a clock switch. This is because no clocks are
needed once the controller has entered Sleep. If the
WDT is selected, the INTRC source will continue to
operate. If the Timer1 oscillator is enabled, it will also
continue to run.
When a wake event occurs in Sleep mode (by interrupt,
Reset or WDT time-out), the device will not be clocked
until the clock source selected by the SCS<1:0> bits
becomes ready (see Figure 4-6), or it will be clocked
from the internal oscillator block if either the Two-Speed
Start-up or the Fail-Safe Clock Monitor are enabled
(see Section 24.0 “Special Features of the CPU”). In
either case, the OSTS bit is set when the primary clock
is providing the device clocks. The IDLEN and SCS bits
are not affected by the wake-up.
4.4 Idle Modes
The Idle modes allow the controller’s CPU to be
selectively shut down while the peripherals continue to
operate. Selecting a particular Idle mode allows users
to further manage power consumption.
If the IDLEN bit is set to a ‘1’ when a SLEEP instruction is
executed, the peripherals will be clocked from the clock
source selected using the SCS<1:0> bits; however, the
CPU will not be clocked. The clock source status bits are
not affected. Setting IDLEN and executing a SLEEP
instruction provides a quick method of switching from a
given Run mode to its corresponding Idle mode.
If the WDT is selected, the INTRC source will continue
to operate. If the Timer1 oscillator is enabled, it will also
continue to run.
Since the CPU is not executing instructions, the only
exits from any of the Idle modes are by interrupt, WDT
time-out or a Reset. When a wake event occurs, CPU
execution is delayed by an interval of TCSD
(parameter 38, Table 27-10) while it becomes ready to
execute code. When the CPU begins executing code,
it resumes with the same clock source for the current
Idle mode. For example, when waking from RC_IDLE
mode, the internal oscillator block will clock the CPU
and peripherals (in other words, RC_RUN mode). The
IDLEN and SCS bits are not affected by the wake-up.
While in any Idle mode or the Sleep mode, a WDT
time-out will result in a WDT wake-up to the Run mode
currently specified by the SCS<1:0> bits.
FIGURE 4-5: TRANSITION TIMING FOR ENTRY TO SLEEP MODE
FIGURE 4-6: TRANSITION TIMING FOR WAKE FROM SLEEP (HSPLL)
Q4Q3Q2
OSC1
Peripheral
Sleep
Program
Q1Q1
Counter
Clock
CPU
Clock
PC + 2PC
Q3 Q4 Q1 Q2
OSC1
Peripheral
Program PC
PLL Clock
Q3 Q4
Output
CPU Clock
Q1 Q2 Q3 Q4 Q1 Q2
Clock
Counter PC + 6
PC + 4
Q1 Q2 Q3 Q4
Wake Event
Note1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.
TOST(1) TPLL(1)
OSTS bit Set
PC + 2
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 44 © 2009 Microchip Technology Inc.
4.4.1 PRI_IDLE MODE
This mode is unique among the three low-power Idle
modes, in that it does not disable the primary device
clock. For timing sensitive applications, this allows for
the fastest resumption of device operation with its more
accurate primary clock source, since the clock source
does not have to “warm-up” or transition from another
oscillator.
PRI_IDLE mode is entered from PRI_RUN mode by
setting the IDLEN bit and executing a SLEEP instruc-
tion. If the device is in another Run mode, set IDLEN
first, then clear the SCS bits and execute SLEEP.
Although the CPU is disabled, the peripherals continue
to be clocked from the primary clock source specified
by the FOSC<3:0> Configuration bits. The OSTS bit
remains set (see Figure 4-7).
When a wake event occurs, the CPU is clocked from the
primary clock source. A delay of interval TCSD (parame-
ter 38, Table 27-10) is required between the wake event
and when code execution starts. This is required to
allow the CPU to become ready to execute instructions.
After the wake-up, the OSTS bit remains set. The
IDLEN and SCS bits are not affected by the wake-up
(see Figure 4-8).
4.4.2 SEC_IDLE MODE
In SEC_IDLE mode, the CPU is disabled but the
peripherals continue to be clocked from the Timer1
oscillator. This mode is entered from SEC_RUN by
setting the IDLEN bit and executing a SLEEP
instruction. If the device is in another Run mode, set the
IDLEN bit first, then set the SCS<1:0> bits to ‘01’ and
execute SLEEP. When the clock source is switched to
the Timer1 oscillator, the primary oscillator is shut down,
the OSTS bit is cleared and the T1RUN bit is set.
When a wake event occurs, the peripherals continue to
be clocked from the Timer1 oscillator. After an interval
of TCSD following the wake event, the CPU begins exe-
cuting code being clocked by the Timer1 oscillator. The
IDLEN and SCS bits are not affected by the wake-up;
the Timer1 oscillator continues to run (see Figure 4-8).
FIGURE 4-7: TRANSITION TIMING FOR ENTRY TO IDLE MODE
FIGURE 4-8: TRANSITION TIMING FOR WAKE FROM IDLE TO RUN MODE
Note: The Timer1 oscillator should already be
running prior to entering SEC_IDLE mode.
If the T1OSCEN bit is not set when writing
the SCS<1:0> bits, entry to SEC_IDLE
mode will not occur. If the Timer1 oscillator
is enabled but not yet running, peripheral
clocks will be delayed until the oscillator
has started. In such situations, initial oscil-
lator operation is far from stable and
unpredictable operation may result.
Q1
Peripheral
Program PC PC + 2
OSC1
Q3 Q4 Q1
CPU Clock
Clock
Counter
Q2
OSC1
Peripheral
Program PC
CPU Clock
Q1 Q3 Q4
Clock
Counter
Q2
Wake Event
TCSD
© 2009 Microchip Technology Inc. DS39689F-page 45
PIC18F2221/2321/4221/4321 FAMILY
4.4.3 RC_IDLE MODE
In RC_IDLE mode, the CPU is disabled but the periph-
erals continue to be clocked from the internal oscillator
block using the INTOSC multiplexer. This mode allows
for controllable power conservation during Idle periods.
From RC_RUN, this mode is entered by setting the
IDLEN bit and executing a SLEEP instruction. If the
device is in another Run mode, first set IDLEN, then set
the SCS1 bit and execute SLEEP. Although its value is
ignored, it is recommended that SCS0 also be cleared;
this is to maintain software compatibility with future
devices. The INTOSC multiplexer may be used to
select a higher clock frequency by modifying the IRCF
bits before executing the SLEEP instruction. When the
clock source is switched to the INTOSC multiplexer, the
primary oscillator is shut down and the OSTS bit is
cleared.
If the IRCF bits are set to any non-zero value, or the
INTSRC bit is set, the INTOSC output is enabled. The
IOFS bit becomes set, after the INTOSC output
becomes stable, after an interval of TIOBST
(parameter 39, Table 27-10). Clocks to the peripherals
continue while the INTOSC source stabilizes. If the
IRCF bits were previously at a non-zero value, or
INTSRC was set before the SLEEP instruction was
executed and the INTOSC source was already stable,
the IOFS bit will remain set. If the IRCF bits and
INTSRC are all clear, the INTOSC output will not be
enabled, the IOFS bit will remain clear and there will be
no indication of the current clock source.
When a wake event occurs, the peripherals continue to
be clocked from the INTOSC multiplexer. After a delay of
T
CSD following the wake event, the CPU begins execut-
ing code being clocked by the INTOSC multiplexer. The
IDLEN and SCS bits are not affected by the wake-up.
The INTRC source will continue to run if either the WDT
or the Fail-Safe Clock Monitor is enabled.
4.5 Exiting Idle and Sleep Modes
An exit from Sleep mode or any of the Idle modes is
triggered by an interrupt, a Reset or a WDT time-out.
This section discusses the triggers that cause exits
from power-managed modes. The clocking subsystem
actions are discussed in each of the power-managed
modes (see Section 4.2 “Run Modes”, Section 4.3
“Sleep Modeand Section 4.4 “Idle Modes).
4.5.1 EXIT BY INTERRUPT
Any of the available interrupt sources can cause the
device to exit from an Idle mode, or the Sleep mode to
a Run mode. To enable this functionality, an interrupt
source must be enabled by setting its enable bit in one
of the INTCON or PIE registers. The exit sequence is
initiated when the corresponding interrupt flag bit is set.
On all exits from Idle or Sleep modes by interrupt, code
execution branches to the interrupt vector if the GIE/
GIEH bit (INTCON<7>) is set. Otherwise, code execution
continues or resumes without branching (see
Section 10.0 “Interrupts”).
A fixed delay of interval TCSD following the wake event
is required when leaving Sleep and Idle modes. This
delay is required for the CPU to prepare for execution.
Instruction execution resumes on the first clock cycle
following this delay.
4.5.2 EXIT BY WDT TIME-OUT
A WDT time-out will cause different actions depending
on which power-managed mode the device is in when
the time-out occurs.
If the device is not executing code (all Idle modes and
Sleep mode), the time-out will result in an exit from the
power-managed mode (see Section 4.2 “Run
Modes” and Section 4.3 “Sleep Mode”). If the device
is executing code (all Run modes), the time-out will
result in a WDT Reset (see Section 24.2 “Watchdog
Timer (WDT)”).
The WDT timer and postscaler are cleared by
executing a SLEEP or CLRWDT instruction, the loss of a
currently selected clock source (if the Fail-Safe Clock
Monitor is enabled) and modifying the IRCF bits in the
OSCCON register if the internal oscillator block is the
device clock source.
4.5.3 EXIT BY RESET
Normally, the device is held in Reset by the Oscillator
Start-up Timer (OST) until the primary clock becomes
ready. At that time, the OSTS bit is set and the device
begins executing code. If the internal oscillator block is
the new clock source, the IOFS bit is set instead.
The exit delay time from Reset to the start of code
execution depends on both the clock sources before
and after the wake-up and the type of oscillator if the
new clock source is the primary clock. Exit delays are
summarized in Table 4-2.
Code execution can begin before the primary clock
becomes ready. If either the Two-Speed Start-up (see
Section 24.3 “Two-Speed Start-up”) or Fail-Safe
Clock Monitor (see Section 24.4 “Fail-Safe Clock
Monitor”) is enabled, the device may begin execution
as soon as the Reset source has cleared. Execution is
clocked by the INTOSC multiplexer driven by the
internal oscillator block. Execution is clocked by the
internal oscillator block until either the primary clock
becomes ready or a power-managed mode is entered
before the primary clock becomes ready; the primary
clock is then shut down.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 46 © 2009 Microchip Technology Inc.
4.5.4 EXIT WITHOUT AN OSCILLATOR
START-UP DELAY
Certain exits from power-managed modes do not
invoke the OST at all. There are two cases:
PRI_IDLE mode, where the primary clock source
is not stopped; and
the primary clock source is not any of the LP, XT,
HS or HSPLL modes.
In these instances, the primary clock source either
does not require an oscillator start-up delay since it is
already running (PRI_IDLE), or normally does not
require an oscillator start-up delay (RC, EC and INTIO
Oscillator modes). However, a fixed delay of interval
T
CSD following the wake event is still required when
leaving Sleep and Idle modes to allow the CPU to
prepare for execution. Instruction execution resumes
on the first clock cycle following this delay.
TABLE 4-2: EXIT DELAY ON WAKE-UP BY RESET FROM SLEEP MODE OR ANY IDLE MODE
(BY CLOCK SOURCES)
Clock Source
before Wake-up
Clock Source
after Wake-up Exit Delay Clock Ready Status
Bit (OSCCON)
Primary Device Clock
(PRI_IDLE mode)
LP, XT, HS
T
CSD(1) OSTSHSPLL
EC, RC
INTOSC(2) IOFS
T1OSC
LP, XT, HS TOST(3)
OSTSHSPLL TOST + trc(3)
EC, RC TCSD(1)
INTOSC(2) TIOBST(4) IOFS
INTOSC(3)
LP, XT, HS TOST(3)
OSTSHSPLL TOST + trc(3)
EC, RC TCSD(1)
INTOSC(2) None IOFS
None
(Sleep mode)
LP, XT, HS TOST(3)
OSTSHSPLL TOST + trc(3)
EC, RC TCSD(1)
INTOSC(2) TIOBST(4) IOFS
Note 1: TCSD (parameter 38) is a required delay when waking from Sleep and all Idle modes and runs concurrently
with any other required delays (see Section 4.4 “Idle Modes”). On Reset, INTOSC defaults to 1 MHz.
2: Includes both the INTOSC 8 MHz source and postscaler derived frequencies.
3: T
OST is the Oscillator Start-up Timer (parameter 32). trc is the PLL Lock-out Timer (parameter F12); it is
also designated as TPLL.
4: Execution continues during TIOBST (parameter 39), the INTOSC stabilization period.
© 2009 Microchip Technology Inc. DS39689F-page 47
PIC18F2221/2321/4221/4321 FAMILY
5.0 RESET
The PIC18F2221/2321/4221/4321 family devices
differentiate between various kinds of Reset:
a) Power-on Reset (POR)
b) MCLR Reset during normal operation
c) MCLR Reset during power-managed modes
d) Watchdog Timer (WDT) Reset (during
execution)
e) Programmable Brown-out Reset (BOR)
f) RESET Instruction
g) Stack Full Reset
h) Stack Underflow Reset
This section discusses Resets generated by MCLR,
POR and BOR and covers the operation of the various
start-up timers. Stack Reset events are covered in
Section 6.1.2.4 “Stack Full and Underflow Resets”.
WDT Resets are covered in Section 24.2 “Watchdog
Timer (WDT)”.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 5-1.
5.1 RCON Register
Device Reset events are tracked through the RCON
register (Register 5-1). The lower five bits of the regis-
ter indicate that a specific Reset event has occurred. In
most cases, these bits can only be cleared by the event
and must be set by the application after the event. The
state of these flag bits, taken together, can be read to
indicate the type of Reset that just occurred. This is
described in more detail in Section 5.6 “Reset State
of Registers”.
The RCON register also has control bits for setting
interrupt priority (IPEN) and software control of the
BOR (SBOREN). Interrupt priority is discussed in
Section 10.0 “Interrupts”. BOR is covered in
Section 5.4 “Brown-out Reset (BOR)”.
FIGURE 5-1: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
External Reset
MCLR
VDD
OSC1
WDT
Time-out
VDD Rise
Detect
OST/PWRT
INTRC
(1)
POR Pulse
OST
10-bit Ripple Counter
PWRT
11-Bit Ripple Counter
Enable OST(2)
Enable PWRT
Note 1: This is the INTRC source from the internal oscillator block and is separate from the RC oscillator of the CLKI pin.
2: See Table 5-2 for time-out situations.
Brown-out
Reset
BOREN
RESET
Instruction
Stack
Pointer
Stack Full/Underflow Reset
Sleep
( )_IDLE
1024 Cycles
65.5 ms
32 μs
MCLRE
S
RQ
Chip_Reset
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 48 © 2009 Microchip Technology Inc.
REGISTER 5-1: RCON: RESET CONTROL REGISTER
R/W-0 R/W-1(1) U-0 R/W-1 R-1 R-1 R/W-0(2) R/W-0
IPEN SBOREN —RITO PD POR BOR
bit 7 bit 0
bit 7 IPEN: Interrupt Priority Enable bit
1 = Enable priority levels on interrupts
0 = Disable priority levels on interrupts (PIC16CXXX Compatibility mode)
bit 6 SBOREN: BOR Software Enable bit(1)
If BOREN<1:0> = 01:
1 = BOR is enabled
0 = BOR is disabled
If BOREN<1:0> = 00, 10 or 11:
Bit is disabled and read as ‘0’.
bit 5 Unimplemented: Read as ‘0
bit 4 RI: RESET Instruction Flag bit
1 = The RESET instruction was not executed (set by firmware only)
0 = The RESET instruction was executed causing a device Reset (must be set in software after
a Brown-out Reset occurs)
bit 3 TO: Watchdog Time-out Flag bit
1 = Set by power-up, CLRWDT instruction or SLEEP instruction
0 = A WDT time-out occurred
bit 2 PD: Power-Down Detection Flag bit
1 = Set by power-up or by the CLRWDT instruction
0 = Set by execution of the SLEEP instruction
bit 1 POR: Power-on Reset Status bit(2)
1 = A Power-on Reset has not occurred (set by firmware only)
0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)
bit 0 BOR: Brown-out Reset Status bit
1 = A Brown-out Reset has not occurred (set by firmware only)
0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset occurs)
Note 1: If SBOREN is enabled, its Reset state is ‘1’; otherwise, it is ‘0’.
2: The actual Reset value of POR is determined by the type of device Reset. See the
notes following this register and Section 5.6 “Reset State of Registers” for
additional information.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
Note 1: It is recommended that the POR bit be set after a Power-on Reset has been
detected so that subsequent Power-on Resets may be detected.
2: Brown-out Reset is said to have occurred when BOR is ‘0’ and POR is1’ (assuming
that POR was set to1’ by software immediately after Power-on Reset).
© 2009 Microchip Technology Inc. DS39689F-page 49
PIC18F2221/2321/4221/4321 FAMILY
5.2 Master Clear (MCLR)
The MCLR pin provides a method for triggering an
external Reset of the device. A Reset is generated by
holding the pin low. These devices have a noise filter in
the MCLR Reset path which detects and ignores small
pulses.
The MCLR pin is not driven low by any internal Resets,
including the WDT.
In PIC18F2221/2321/4221/4321 family devices, the
MCLR input can be disabled with the MCLRE Configu-
ration bit. When MCLR is disabled, the pin becomes a
digital input. See Section 11.5 “PORTE, TRISE and
LATE Registers” for more information.
5.3 Power-on Reset (POR)
A Power-on Reset pulse is generated on-chip
whenever VDD rises above a certain threshold. This
allows the device to start in the initialized state when
VDD is adequate for operation.
To take advantage of the POR circuitry, tie the MCLR
pin through a resistor (1 kΩ to 10 kΩ) to VDD. This will
eliminate external RC components usually needed to
create a Power-on Reset delay. A minimum rise rate for
VDD is specified (parameter D004). For a slow rise
time, see Figure 5-2.
When the device starts normal operation (i.e., exits the
Reset condition), device operating parameters
(voltage, frequency, temperature, etc.) must be met to
ensure operation. If these conditions are not met, the
device must be held in Reset until the operating
conditions are met.
Power-on Reset events are captured by the POR bit
(RCON<1>). The state of the bit is set to ‘0’ whenever
a POR occurs; it does not change for any other Reset
event. POR is not reset to ‘1’ by any hardware event.
To capture multiple events, the user manually resets
the bit to ‘1’ in software following any POR.
FIGURE 5-2: EXTERNAL POWER-ON
RESET CIRCUIT (FOR
SLOW VDD POWER-UP)
Note 1: External Power-on Reset circuit is required
only if the VDD power-up slope is too slow.
The diode D helps discharge the capacitor
quickly when VDD powers down.
2: R < 40 kΩ is recommended to make sure that
the voltage drop across R does not violate
the device’s electrical specification.
3: R1 1 kΩ will limit any current flowing into
MCLR from external capacitor C, in the event
of MCLR/VPP pin breakdown, due to
Electrostatic Discharge (ESD) or Electrical
Overstress (EOS).
C
R1
R
D
VDD
MCLR
PIC18FXXXX
VDD
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DS39689F-page 50 © 2009 Microchip Technology Inc.
5.4 Brown-out Reset (BOR)
PIC18F2221/2321/4221/4321 family devices implement
a BOR circuit that provides the user with a number of
configuration and power-saving options. The BOR is
controlled by the BORV<1:0> and BOREN<1:0>
Configuration bits. There are a total of four BOR
configurations which are summarized in Table 5-1.
The BOR threshold is set by the BORV<1:0> bits. If BOR
is enabled (any values of BOREN<1:0>, except ‘00’),
any drop of VDD below VBOR (parameter D005) for
greater than TBOR (parameter 35) will reset the device.
A Reset may or may not occur if VDD falls below VBOR
for less than TBOR. The chip will remain in Brown-out
Reset until VDD rises above VBOR.
If the Power-up Timer is enabled, it will be invoked after
VDD rises above VBOR; it then will keep the chip in
Reset for an additional time delay, TPWRT
(parameter 33). If VDD drops below VBOR while the
Power-up Timer is running, the chip will go back into a
Brown-out Reset and the Power-up Timer will be
initialized. Once VDD rises above VBOR, the Power-up
Timer will execute the additional time delay.
BOR and the Power-on Timer (PWRT) are
independently configured. Enabling BOR Reset does
not automatically enable the PWRT.
5.4.1 SOFTWARE ENABLED BOR
When BOREN<1:0> = 01, the BOR can be enabled or
disabled by the user in software. This is done with the
control bit, SBOREN (RCON<6>). Setting SBOREN
enables the BOR to function as previously described.
Clearing SBOREN disables the BOR entirely. The
SBOREN bit operates only in this mode; otherwise it is
read as ‘0’.
Placing the BOR under software control gives the user
the additional flexibility of tailoring the application to its
environment without having to reprogram the device to
change BOR configuration. It also allows the user to
tailor device power consumption in software by elimi-
nating the incremental current that the BOR consumes.
While the BOR current is typically very small, it may
have some impact in low-power applications.
5.4.2 DETECTING BOR
When Brown-out Reset is enabled, the BOR bit always
resets to ‘0’ on any Brown-out Reset or Power-on
Reset event. This makes it difficult to determine if a
Brown-out Reset event has occurred just by reading
the state of BOR alone. A more reliable method is to
simultaneously check the state of both POR and BOR.
This assumes that the POR bit is reset to ‘1’ in software
immediately after any Power-on Reset event. If BOR is
0’ while POR is ‘1’, it can be reliably assumed that a
Brown-out Reset event has occurred.
5.4.3 DISABLING BOR IN SLEEP MODE
When BOREN<1:0> = 10, the BOR remains under
hardware control and operates as previously
described. Whenever the device enters Sleep mode,
however, the BOR is automatically disabled. When the
device returns to any other operating mode, BOR is
automatically re-enabled.
This mode allows for applications to recover from
brown-out situations, while actively executing code,
when the device requires BOR protection the most. At
the same time, it saves additional power in Sleep mode
by eliminating the small incremental BOR current.
TABLE 5-1: BOR CONFIGURATIONS
Note: Even when BOR is under software control,
the Brown-out Reset voltage level is still
set by the BORV<1:0> Configuration bits.
It cannot be changed in software.
BOR Configuration Status of
SBOREN
(RCON<6>)
BOR Operation
BOREN1 BOREN0
00Unavailable BOR disabled; must be enabled by reprogramming the Configuration bits.
01Available BOR enabled in software; operation controlled by SBOREN.
10Unavailable BOR enabled in hardware in Run and Idle modes, disabled during
Sleep mode.
11Unavailable BOR enabled in hardware; must be disabled by reprogramming the
Configuration bits.
© 2009 Microchip Technology Inc. DS39689F-page 51
PIC18F2221/2321/4221/4321 FAMILY
5.5 Device Reset Timers
PIC18F2221/2321/4221/4321 family devices incorpo-
rate three separate on-chip timers that help regulate the
Power-on Reset process. Their main function is to
ensure that the device clock is stable before code is
executed. These timers are:
Power-up Timer (PWRT)
Oscillator Start-up Timer (OST)
PLL Lock Time-out
5.5.1 POWER-UP TIMER (PWRT)
The Power-up Timer (PWRT) of the PIC18F2221/
2321/4221/4321 family devices is an 11-bit counter
which uses the INTRC source as the clock input.
This yields an approximate time interval of
2048 x 32 μs = 65.6 ms. While the PWRT is counting,
the device is held in Reset.
The power-up time delay depends on the INTRC clock
and will vary from chip to chip due to temperature and
process variation. See DC parameter 33 for details.
The PWRT is enabled by clearing the PWRTEN
Configuration bit.
5.5.2 OSCILLATOR START-UP TIMER
(OST)
The Oscillator Start-up Timer (OST) provides a 1024
oscillator cycle (from OSC1 input) delay after the
PWRT delay is over (parameter 33). This ensures that
the crystal oscillator or resonator has started and
stabilized.
The OST time-out is invoked only for XT, LP, HS and
HSPLL modes and only on Power-on Reset, or on exit
from most power-managed modes.
5.5.3 PLL LOCK TIME-OUT
With the PLL enabled in HSPLL mode, the time-out
sequence following a Power-on Reset is slightly differ-
ent from other oscillator modes. A separate timer is
used to provide a fixed time-out that is sufficient for the
PLL to lock to the main oscillator frequency. This PLL
lock time-out (TPLL) is typically 2 ms and follows the
oscillator start-up time-out.
5.5.4 TIME-OUT SEQUENCE
On power-up, the time-out sequence is as follows:
1. After the POR pulse has cleared, PWRT time-out
is invoked (if enabled).
2. Then, the OST is activated.
The total time-out will vary based on oscillator configu-
ration and the status of the PWRT. Figure 5-3,
Figure 5-4, Figure 5-5, Figure 5-6 and Figure 5-7 all
depict time-out sequences on power-up, with the
Power-up Timer enabled and the device operating in
HS Oscillator mode. Figures 5-3 through 5-6 also
apply to devices operating in XT or LP modes. For
devices in RC mode and with the PWRT disabled, there
will be no time-out at all.
Since the time-outs occur from the POR pulse, if MCLR
is kept low long enough, all time-outs will expire. Bring-
ing MCLR high will begin execution immediately
(Figure 5-5). This is useful for testing purposes or to
synchronize more than one PIC18FXXXX device
operating in parallel.
TABLE 5-2: TIME-OUT IN VARIOUS SITUATIONS
Oscillator
Configuration
Power-up(2) and Brown-out Reset Exit from
Power-Managed Mode
PWRTEN = 0PWRTEN = 1
HSPLL 66 ms(1) + 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2)
HS, XT, LP 66 ms(1) + 1024 TOSC 1024 TOSC 1024 TOSC
EC, ECIO 66 ms(1) ——
RC, RCIO 66 ms(1) ——
INTIO1, INTIO2 66 ms(1) ——
Note 1: 66 ms (65.5 ms) is the nominal Power-up Timer (PWRT) delay.
2: 2 ms is the nominal time required for the PLL to lock.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 52 © 2009 Microchip Technology Inc.
FIGURE 5-3: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD, VDD RISE < TPWRT)
FIGURE 5-4: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1
FIGURE 5-5: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 2
TPWRT
TOST
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
TPWRT
TOST
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
TPWRT
TOST
© 2009 Microchip Technology Inc. DS39689F-page 53
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 5-6: SLOW RISE TIME (MCLR TIED TO VDD, VDD RISE > TPWRT)
FIGURE 5-7: TIME-OUT SEQUENCE ON POR w/PLL ENABLED (MCLR TIED TO VDD)
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
0V
5V
TPWRT
TOST
TPWRT
TOST
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
OST TIME-OUT
INTERNAL RESET
PLL TIME-OUT
TPLL
Note: TOST = 1024 clock cycles.
TPLL 2 ms max. First three stages of the PWRT timer.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 54 © 2009 Microchip Technology Inc.
5.6 Reset State of Registers
Most registers are unaffected by a Reset. Their status
is unknown on POR and unchanged by all other
Resets. The other registers are forced to a “Reset
state” depending on the type of Reset that occurred.
Most registers are not affected by a WDT wake-up,
since this is viewed as the resumption of normal oper-
ation. Status bits from the RCON register, RI, TO, PD,
POR and BOR, are set or cleared differently in different
Reset situations, as indicated in Table 5-3. These bits
are used in software to determine the nature of the
Reset.
Table 5-4 describes the Reset states for all of the
Special Function Registers. These are categorized by
Power-on and Brown-out Resets, Master Clear and
WDT Resets and WDT wake-ups.
TABLE 5-3: STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION
FOR RCON REGISTER
Condition Program
Counter
RCON Register STKPTR Register
RI TO PD POR BOR STKFUL STKUNF
Power-on Reset 0000h 11100 0 0
RESET Instruction 0000h 0uuuu u u
Brown-out 0000h 111u0 u u
MCLR during power-managed Run modes 0000h u1uuu u u
MCLR during power-managed Idle modes
and Sleep mode
0000h u10uu u u
WDT Time-out during full power or
power-managed Run mode
0000h u0uuu u u
MCLR during full power execution 0000h uuuuu u u
Stack Full Reset (STVREN = 1) 0000h uuuuu 1 u
Stack Underflow Reset (STVREN = 1) 0000h uuuuu u 1
Stack Underflow Error (not an actual Reset,
STVREN = 0)
0000h uuuuu u 1
WDT time-out during power-managed Idle or
Sleep modes
PC + 2 u00uu u u
Interrupt exit from power-managed modes PC + 2(1) uu0uu u u
Legend: u = unchanged
Note 1: When the wake-up is due to an interrupt and the GIEH or GIEL bits are set, the PC is loaded with the
interrupt vector (008h or 0018h).
2: Reset state is ‘1’ for POR and unchanged for all other Resets when software BOR is enabled
(BOREN<1:0> Configuration bits = 01 and SBOREN = 1); otherwise, the Reset state is ‘0’.
© 2009 Microchip Technology Inc. DS39689F-page 55
PIC18F2221/2321/4221/4321 FAMILY
TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS
Register Applicable Devices Power-on Reset,
Brown-out Reset
MCLR Resets,
WDT Reset,
RESET Instruction,
Stack Resets
Wake-up via WDT
or Interrupt
TOSU 2221 2321 4221 4321 ---0 0000 ---0 0000 ---0 uuuu(3)
TOSH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu(3)
TOSL 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu(3)
STKPTR 2221 2321 4221 4321 00-0 0000 uu-0 0000 uu-u uuuu(3)
PCLATU 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu
PCLATH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
PCL 2221 2321 4221 4321 0000 0000 0000 0000 PC + 2(2)
TBLPTRU 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu
TBLPTRH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
TBLPTRL 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
TABLAT 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
PRODH 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
PRODL 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
INTCON 2221 2321 4221 4321 0000 000x 0000 000u uuuu uuuu(1)
INTCON2 2221 2321 4221 4321 1111 -1-1 1111 -1-1 uuuu -u-u(1)
INTCON3 2221 2321 4221 4321 11-0 0-00 11-0 0-00 uu-u u-uu(1)
INDF0 2221 2321 4221 4321 N/A N/A N/A
POSTINC0 2221 2321 4221 4321 N/A N/A N/A
POSTDEC0 2221 2321 4221 4321 N/A N/A N/A
PREINC0 2221 2321 4221 4321 N/A N/A N/A
PLUSW0 2221 2321 4221 4321 N/A N/A N/A
FSR0H 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu
FSR0L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
WREG 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
INDF1 2221 2321 4221 4321 N/A N/A N/A
POSTINC1 2221 2321 4221 4321 N/A N/A N/A
POSTDEC1 2221 2321 4221 4321 N/A N/A N/A
PREINC1 2221 2321 4221 4321 N/A N/A N/A
PLUSW1 2221 2321 4221 4321 N/A N/A N/A
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt
vector (0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are
updated with the current value of the PC. The STKPTR is modified to point to the next location in the
hardware stack.
4: See Table 5-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When
not enabled as PORTA pins, they are disabled and read ‘0’.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 56 © 2009 Microchip Technology Inc.
FSR1H 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu
FSR1L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
BSR 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu
INDF2 2221 2321 4221 4321 N/A N/A N/A
POSTINC2 2221 2321 4221 4321 N/A N/A N/A
POSTDEC2 2221 2321 4221 4321 N/A N/A N/A
PREINC2 2221 2321 4221 4321 N/A N/A N/A
PLUSW2 2221 2321 4221 4321 N/A N/A N/A
FSR2H 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu
FSR2L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
STATUS 2221 2321 4221 4321 ---x xxxx ---u uuuu ---u uuuu
TMR0H 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
TMR0L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
T0CON 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu
OSCCON 2221 2321 4221 4321 0100 q000 0100 q000 uuuu uuqu
HLVDCON 2221 2321 4221 4321 0-00 0101 0-00 0101 u-uu uuuu
WDTCON 2221 2321 4221 4321 ---- ---0 ---- ---0 ---- ---u
RCON(4) 2221 2321 4221 4321 0q-1 11q0 0q-q qquu uq-u qquu
TMR1H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
TMR1L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
T1CON 2221 2321 4221 4321 0000 0000 u0uu uuuu uuuu uuuu
TMR2 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
PR2 2221 2321 4221 4321 1111 1111 1111 1111 1111 1111
T2CON 2221 2321 4221 4321 -000 0000 -000 0000 -uuu uuuu
SSPBUF 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
SSPADD 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
SSPSTAT 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
SSPCON1 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
SSPCON2 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
Register Applicable Devices Power-on Reset,
Brown-out Reset
MCLR Resets,
WDT Reset,
RESET Instruction,
Stack Resets
Wake-up via WDT
or Interrupt
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt
vector (0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are
updated with the current value of the PC. The STKPTR is modified to point to the next location in the
hardware stack.
4: See Table 5-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When
not enabled as PORTA pins, they are disabled and read ‘0’.
© 2009 Microchip Technology Inc. DS39689F-page 57
PIC18F2221/2321/4221/4321 FAMILY
ADRESH 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
ADRESL 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
ADCON0 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu
ADCON1 2221 2321 4221 4321 --00 0qqq --00 0qqq --uu uuuu
ADCON2 2221 2321 4221 4321 0-00 0000 0-00 0000 u-uu uuuu
CCPR1H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
CCPR1L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
CCP1CON 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu
CCPR2H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
CCPR2L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
CCP2CON 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu
BAUDCON 2221 2321 4221 4321 0100 0-00 0100 0-00 --uu uuuu
ECCP1DEL 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
ECCP1AS 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
2221 2321 4221 4321 0000 00-- 0000 00-- uuuu uu--
CVRCON 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
CMCON 2221 2321 4221 4321 0000 0111 0000 0111 uuuu uuuu
TMR3H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
TMR3L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
T3CON 2221 2321 4221 4321 0000 0000 uuuu uuuu uuuu uuuu
SPBRGH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
SPBRG 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
RCREG 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
TXREG 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
TXSTA 2221 2321 4221 4321 0000 0010 0000 0010 uuuu uuuu
RCSTA 2221 2321 4221 4321 0000 000x 0000 000x uuuu uuuu
EEADR 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
EEDATA 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
EECON2 2221 2321 4221 4321 0000 0000 0000 0000 0000 0000
EECON1 2221 2321 4221 4321 xx-0 x000 uu-0 u000 uu-0 u000
TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
Register Applicable Devices Power-on Reset,
Brown-out Reset
MCLR Resets,
WDT Reset,
RESET Instruction,
Stack Resets
Wake-up via WDT
or Interrupt
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt
vector (0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are
updated with the current value of the PC. The STKPTR is modified to point to the next location in the
hardware stack.
4: See Table 5-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When
not enabled as PORTA pins, they are disabled and read ‘0’.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 58 © 2009 Microchip Technology Inc.
IPR2 2221 2321 4221 4321 11-1 1111 11-1 1111 uu-u uuuu
PIR2 2221 2321 4221 4321 00-0 0000 00-0 0000 uu-u uuuu(1)
PIE2 2221 2321 4221 4321 00-0 0000 00-0 0000 uu-u uuuu
IPR1 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu
2221 2321 4221 4321 -111 1111 -111 1111 -uuu uuuu
PIR1 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu(1)
2221 2321 4221 4321 -000 0000 -000 0000 -uuu uuuu(1)
PIE1 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu
2221 2321 4221 4321 -000 0000 -000 0000 -uuu uuuu
OSCTUNE 2221 2321 4221 4321 00-0 0000 00-0 0000 uu-u uuuu
TRISE 2221 2321 4221 4321 0000 -111 0000 -111 uuuu -uuu
TRISD 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu
TRISC 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu
TRISB 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu
TRISA(5) 2221 2321 4221 4321 1111 1111(5) 1111 1111(5) uuuu uuuu(5)
LATE 2221 2321 4221 4321 ---- -xxx ---- -uuu ---- -uuu
LATD 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
LATC 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
LATB 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
LATA(5) 2221 2321 4221 4321 xxxx xxxx(5) uuuu uuuu(5) uuuu uuuu(5)
PORTE 2221 2321 4221 4321 ---- xxxx ---- uuuu ---- uuuu
2221 2321 4221 4321 ---- x--- ---- u--- ---- u---
PORTD 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
PORTC 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
PORTB 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu
PORTA(5) 2221 2321 4221 4321 xx0x 0000(5) uu0u 0000(5) uuuu uuuu(5)
TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
Register Applicable Devices Power-on Reset,
Brown-out Reset
MCLR Resets,
WDT Reset,
RESET Instruction,
Stack Resets
Wake-up via WDT
or Interrupt
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt
vector (0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are
updated with the current value of the PC. The STKPTR is modified to point to the next location in the
hardware stack.
4: See Table 5-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When
not enabled as PORTA pins, they are disabled and read ‘0’.
© 2009 Microchip Technology Inc. DS39689F-page 59
PIC18F2221/2321/4221/4321 FAMILY
6.0 MEMORY ORGANIZATION
There are three types of memory in PIC18 Enhanced
microcontroller devices:
Program Memory
Data RAM
Data EEPROM
As Harvard architecture devices, the data and program
memories use separate busses; this allows for con-
current access of the two memory spaces. The data
EEPROM, for practical purposes, can be regarded as
a peripheral device, since it is addressed and accessed
through a set of control registers.
Additional detailed information on the operation of the
Flash program memory is provided in Section 7.0
“Flash Program Memory”. Data EEPROM is
discussed separately in Section 8.0 “Data EEPROM
Memory.
6.1 Program Memory Organization
PIC18 microcontrollers implement a 21-bit program
counter, which is capable of addressing a 2-Mbyte
program memory space. Accessing a location between
the upper boundary of the physically implemented
memory and the 2-Mbyte address will return all ‘0’s (a
NOP instruction).
The PIC18F2221 and PIC18F4221 each have 4 Kbytes
of Flash memory and can store up to 2048 single-word
instructions. The PIC18F2321 and PIC18F4321 each
have 8 Kbytes of Flash memory and can store up to
4096 single-word instructions.
PIC18 devices have two interrupt vectors. The Reset
vector address is at 0000h and the interrupt vector
addresses are at 0008h and 0018h.
The program memory maps for PIC18F2221/4221 and
PIC18F2321/4321 devices are shown in Figure 6-1.
FIGURE 6-1: PROGRAM MEMORY MAP AND STACK FOR PIC18F2221/2321/4221/4321 FAMILY
DEVICES
PC<20:0>
Stack Level 1
Stack Level 31
Reset Vector
Low-Priority Interrupt Vector
CALL,RCALL,RETURN
RETFIE,RETLW
21
0000h
0018h
On-Chip
Program Memory
High-Priority Interrupt Vector 0008h
User Memory Space
1FFFFFh
1000h
0FFFh
Read ‘0
200000h
PC<20:0>
Stack Level 1
Stack Level 31
Reset Vector
Low-Priority Interrupt Vector
CALL,RCALL,RETURN
RETFIE,RETLW
21
0000h
0018h
2000h
1FFFh
On-Chip
Program Memory
High-Priority Interrupt Vector 0008h
User Memory Space
Read ‘0
1FFFFFh
200000h
PIC18FX221 PIC18FX321
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 60 © 2009 Microchip Technology Inc.
6.1.1 PROGRAM COUNTER
The Program Counter (PC) specifies the address of the
instruction to fetch for execution. The PC is 21 bits wide
and is contained in three separate 8-bit registers. The
low byte, known as the PCL register, is both readable
and writable. The high byte, or PCH register, contains
the PC<15:8> bits; it is not directly readable or writable.
Updates to the PCH register are performed through the
PCLATH register. The upper byte is called PCU. This
register contains the PC<20:16> bits; it is also not
directly readable or writable. Updates to the PCU
register are performed through the PCLATU register.
The contents of PCLATH and PCLATU are transferred
to the program counter by any operation that writes
PCL. Similarly, the upper two bytes of the program
counter are transferred to PCLATH and PCLATU by an
operation that reads PCL. This is useful for computed
offsets to the PC (see Section 6.1.4.1 “Computed
GOTO”).
The PC addresses bytes in the program memory. To
prevent the PC from becoming misaligned with word
instructions, the Least Significant bit of PCL is fixed to
a value of0’. The PC increments by 2 to address
sequential instructions in the program memory.
The CALL, RCALL, GOTO and program branch
instructions write to the program counter directly. For
these instructions, the contents of PCLATH and
PCLATU are not transferred to the program counter.
6.1.2 RETURN ADDRESS STACK
The return address stack allows any combination of up
to 31 program calls and interrupts to occur. The PC is
pushed onto the stack when a CALL or RCALL instruc-
tion is executed or an interrupt is Acknowledged. The
PC value is pulled off the stack on a RETURN, RETLW
or a RETFIE instruction. PCLATU and PCLATH are not
affected by any of the RETURN or CALL instructions.
The stack operates as a 31-word by 21-bit RAM and a
5-bit Stack Pointer, STKPTR. The stack space is not
part of either program or data space. The Stack Pointer
is readable and writable and the address on the top of
the stack is readable and writable through the Top-of-
Stack Special Function Registers. Data can also be
pushed to, or popped from the stack, using these
registers.
A CALL type instruction causes a push onto the stack;
the Stack Pointer is first incremented and the location
pointed to by the Stack Pointer is written with the
contents of the PC (already pointing to the instruction
following the CALL). A RETURN type instruction causes
a pop from the stack; the contents of the location
pointed to by the STKPTR are transferred to the PC
and then the Stack Pointer is decremented.
The Stack Pointer is initialized to ‘00000’ after all
Resets. There is no RAM associated with the location
corresponding to a Stack Pointer value of00000’; this
is only a Reset value. Status bits indicate if the stack is
full or has overflowed or has underflowed.
6.1.2.1 Top-of-Stack Access
Only the top of the return address stack (TOS) is
readable and writable. A set of three registers,
TOSU:TOSH:TOSL, hold the contents of the stack
location pointed to by the STKPTR register (Figure 6-2).
This allows users to implement a software stack if
necessary. After a CALL, RCALL or interrupt, the
software can read the pushed value by reading the
TOSU:TOSH:TOSL registers. These values can be
placed on a user-defined software stack. At return time,
the software can return these values to
TOSU:TOSH:TOSL and do a return.
The user must disable the global interrupt enable bits
while accessing the stack to prevent inadvertent stack
corruption.
FIGURE 6-2: RETURN ADDRESS STACK AND ASSOCIATED REGISTERS
00011
001A34h
11111
11110
11101
00010
00001
00000
00010
Return Address Stack <20:0>
To p - o f - St a c k
000D58h
TOSLTOSHTOSU
34h1Ah00h
STKPTR<4:0>
Top-of-Stack Registers Stack Pointer
© 2009 Microchip Technology Inc. DS39689F-page 61
PIC18F2221/2321/4221/4321 FAMILY
6.1.2.2 Return Stack Pointer (STKPTR)
The STKPTR register (Register 6-1) contains the Stack
Pointer value, the STKFUL (Stack Full) status bit and
the STKUNF (Stack Underflow) status bits. The value
of the Stack Pointer can be 0 through 31. The Stack
Pointer increments before values are pushed onto the
stack and decrements after values are popped off the
stack. On Reset, the Stack Pointer value will be zero.
The user may read and write the Stack Pointer value.
This feature can be used by a Real-Time Operating
System (RTOS) for return stack maintenance.
After the PC is pushed onto the stack 31 times (without
popping any values off the stack), the STKFUL bit is
set. The STKFUL bit is cleared by software or by a
POR.
The action that takes place when the stack becomes
full depends on the state of the STVREN (Stack
Overflow Reset Enable) Configuration bit. (Refer to
Section 24.1 “Configuration Bits” for a description of
the device Configuration bits.) If STVREN is set
(default), the 31st push will push the (PC + 2) value
onto the stack, set the STKFUL bit and reset the
device. The STKFUL bit will remain set and the Stack
Pointer will be set to zero.
If STVREN is cleared, the STKFUL bit will be set on the
31st push and the Stack Pointer will increment to 31.
Any additional pushes will not overwrite the 31st push
and STKPTR will remain at 31.
When the stack has been popped enough times to
unload the stack, the next pop will return a value of zero
to the PC and sets the STKUNF bit, while the Stack
Pointer remains at zero. The STKUNF bit will remain
set until cleared by software or until a POR occurs.
6.1.2.3 PUSH and POP Instructions
Since the Top-of-Stack is readable and writable, the
ability to push values onto the stack and pull values off
the stack without disturbing normal program execution
is a desirable feature. The PIC18 instruction set
includes two instructions, PUSH and POP, that permit
the TOS to be manipulated under software control.
TOSU, TOSH and TOSL can be modified to place data
or a return address on the stack.
The PUSH instruction places the current PC value onto
the stack. This increments the Stack Pointer and loads
the current PC value onto the stack.
The POP instruction discards the current TOS by decre-
menting the Stack Pointer. The previous value pushed
onto the stack then becomes the TOS value.
REGISTER 6-1: STKPTR: STACK POINTER REGISTER
Note: Returning a value of zero to the PC on an
underflow has the effect of vectoring the
program to the Reset vector, where the
stack conditions can be verified and
appropriate actions can be taken. This is
not the same as a Reset, as the contents
of the SFRs are not affected.
R/C-0 R/C-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
STKFUL(1) STKUNF(1) SP4 SP3 SP2 SP1 SP0
bit 7 bit 0
bit 7 STKFUL: Stack Full Flag bit(1)
1 = Stack became full or overflowed
0 = Stack has not become full or overflowed
bit 6 STKUNF: Stack Underflow Flag bit(1)
1 = Stack underflow occurred
0 = Stack underflow did not occur
bit 5 Unimplemented: Read as ‘0
bit 4-0 SP<4:0>: Stack Pointer Location bits
Note 1: Bit 7 and bit 6 are cleared by user software or by a POR.
Legend:
R = Readable bit W = Writable bit U = Unimplemented C = Clearable only bit
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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6.1.2.4 Stack Full and Underflow Resets
Device Resets on stack overflow and stack underflow
conditions are enabled by setting the STVREN bit in
Configuration Register 4L. When STVREN is set, a full
or underflow will set the appropriate STKFUL or
STKUNF bit and then cause a device Reset. When
STVREN is cleared, a full or underflow condition will set
the appropriate STKFUL or STKUNF bit but not cause
a device Reset. The STKFUL or STKUNF bits are
cleared by the user software or a Power-on Reset.
6.1.3 FAST REGISTER STACK
A Fast Register Stack is provided for the STATUS,
WREG and BSR registers, to provide a “fast return”
option for interrupts. The stack for each register is only
one level deep and is neither readable nor writable. It is
loaded with the current value of the corresponding
register when the processor vectors for an interrupt. All
interrupt sources will push values into the stack regis-
ters. The values in the registers are then loaded back
into their associated registers if the RETFIE, FAST
instruction is used to return from the interrupt.
If both low and high-priority interrupts are enabled, the
stack registers cannot be used reliably to return from
low-priority interrupts. If a high-priority interrupt occurs
while servicing a low-priority interrupt, the Stack regis-
ter values stored by the low-priority interrupt will be
overwritten. In these cases, users must save the key
registers in software during a low-priority interrupt.
If interrupt priority is not used, all interrupts may use the
Fast Register Stack for returns from interrupt. If no
interrupts are used, the Fast Register Stack can be
used to restore the STATUS, WREG and BSR registers
at the end of a subroutine call. To use the Fast Register
Stack for a subroutine call, a CALL label,FAST
instruction must be executed to save the STATUS,
WREG and BSR registers to the Fast Register Stack. A
RETURN, FAST instruction is then executed to restore
these registers from the Fast Register Stack.
Example 6-1 shows a source code example that uses
the Fast Register Stack during a subroutine call and
return.
EXAMPLE 6-1: FAST REGISTER STACK
CODE EXAMPLE
6.1.4 LOOK-UP TABLES IN PROGRAM
MEMORY
There may be programming situations that require the
creation of data structures, or look-up tables, in
program memory. For PIC18 devices, look-up tables
can be implemented in two ways:
Computed GOTO
Table Reads
6.1.4.1 Computed GOTO
A computed GOTO is accomplished by adding an offset
to the program counter. An example is shown in
Example 6-2.
A look-up table can be formed with an ADDWF PCL
instruction and a group of RETLW nn instructions. The
W register is loaded with an offset into the table before
executing a call to that table. The first instruction of the
called routine is the ADDWF PCL instruction. The next
instruction executed will be one of the RETLW nn
instructions that returns the value ‘nn’ to the calling
function.
The offset value (in WREG) specifies the number of
bytes that the program counter should advance and
should be multiples of 2 (LSb = 0).
In this method, only one data byte may be stored in
each instruction location and room on the return
address stack is required.
EXAMPLE 6-2: COMPUTED GOTO USING
AN OFFSET VALUE
6.1.4.2 Table Reads and Table Writes
A better method of storing data in program memory
allows two bytes of data to be stored in each instruction
location.
Look-up table data may be stored two bytes per
program word by using table reads and writes. The
Table Pointer (TBLPTR) register specifies the byte
address and the Table Latch (TABLAT) register
contains the data that is read from or written to program
memory. Data is transferred to or from program
memory one byte at a time.
Table read and table write operations are discussed
further in Section 7.1 “Table Reads and Table
Writes”.
CALL SUB1, FAST ;STATUS, WREG, BSR
;SAVED IN FAST REGISTER
;STACK
SUB1
RETURN, FAST ;RESTORE VALUES SAVED
;IN FAST REGISTER STACK
MOVF OFFSET, W
CALL TABLE
ORG nn00h
TABLE ADDWF PCL
RETLW nnh
RETLW nnh
RETLW nnh
.
.
.
© 2009 Microchip Technology Inc. DS39689F-page 63
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6.2 PIC18 Instruction Cycle
6.2.1 CLOCKING SCHEME
The microcontroller clock input, whether from an
internal or external source, is internally divided by four
to generate four non-overlapping quadrature clocks
(Q1, Q2, Q3 and Q4). Internally, the program counter is
incremented on every Q1; the instruction is fetched
from the program memory and latched into the
Instruction Register (IR) during Q4. The instruction is
decoded and executed during the following Q1 through
Q4. The clocks and instruction execution flow are
shown in Figure 6-3.
6.2.2 INSTRUCTION FLOW/PIPELINING
An “Instruction Cycle” consists of four Q cycles: Q1
through Q4. The instruction fetch and execute are
pipelined in such a manner that a fetch takes one
instruction cycle, while the decode and execute take
another instruction cycle. However, due to the pipe-
lining, each instruction effectively executes in one
cycle. If an instruction causes the program counter to
change (e.g., GOTO), then two cycles are required to
complete the instruction (Example 6-3).
A fetch cycle begins with the Program Counter (PC)
incrementing in Q1.
In the execution cycle, the fetched instruction is latched
into the Instruction Register (IR) in cycle Q1. This
instruction is then decoded and executed during the
Q2, Q3 and Q4 cycles. Data memory is read during Q2
(operand read) and written during Q4 (destination
write).
FIGURE 6-3: CLOCK/INSTRUCTION CYCLE
EXAMPLE 6-3: INSTRUCTION PIPELINE FLOW
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
Q1
Q2
Q3
Q4
PC
OSC2/CLKO
(RC mode)
PC PC + 2 PC + 4
Fetch INST (PC)
Execute INST (PC – 2)
Fetch INST (PC + 2)
Execute INST (PC)
Fetch INST (PC + 4)
Execute INST (PC + 2)
Internal
Phase
Clock
All instructions are single cycle, except for any program branches. These take two cycles since the fetch instruction
is “flushed” from the pipeline while the new instruction is being fetched and then executed.
TCY0TCY1TCY2TCY3TCY4TCY5
1. MOVLW 55h Fetch 1 Execute 1
2. MOVWF PORTB Fetch 2 Execute 2
3. BRA SUB_1 Fetch 3 Execute 3
4. BSF PORTA, BIT3 (Forced NOP) Fetch 4 Flush (NOP)
5. Instruction @ address SUB_1 Fetch SUB_1 Execute SUB_1
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DS39689F-page 64 © 2009 Microchip Technology Inc.
6.2.3 INSTRUCTIONS IN PROGRAM
MEMORY
The program memory is addressed in bytes. Instruc-
tions are stored as two bytes or four bytes in program
memory. The Least Significant Byte of an instruction
word is always stored in a program memory location
with an even address (LSb = 0). To maintain alignment
with instruction boundaries, the PC increments in steps
of 2 and the LSb will always read ‘0’ (see Section 6.1.1
“Program Counter”).
Figure 6-4 shows an example of how instruction words
are stored in the program memory.
The CALL and GOTO instructions have the absolute
program memory address embedded into the instruc-
tion. Since instructions are always stored on word
boundaries, the data contained in the instruction is a
word address. The word address is written to PC<20:1>,
which accesses the desired byte address in program
memory. Instruction #2 in Figure 6-4 shows how the
instruction GOTO 0006h is encoded in the program
memory. Program branch instructions, which encode a
relative address offset, operate in the same manner. The
offset value stored in a branch instruction represents the
number of single-word instructions that the PC will be
offset by. Section 24.0 “Instruction Set Summary”
provides further details of the instruction set.
FIGURE 6-4: INSTRUCTIONS IN PROGRAM MEMORY
6.2.4 TWO-WORD INSTRUCTIONS
The standard PIC18 instruction set has four two-word
instructions: CALL, MOVFF, GOTO and LSFR. In all
cases, the second word of the instructions always has
1111’ as its four Most Significant bits; the other 12 bits
are literal data, usually a data memory address.
The use of ‘1111’ in the 4 MSbs of an instruction spec-
ifies a special form of NOP. If the instruction is executed
in proper sequence – immediately after the first word –
the data in the second word is accessed and used by
the instruction sequence. If the first word is skipped for
some reason and the second word is executed by itself,
a NOP is executed instead. This is necessary for cases
when the two-word instruction is preceded by a condi-
tional instruction that changes the PC. Example 6-4
shows how this works.
EXAMPLE 6-4: TWO-WORD INSTRUCTIONS
Word Address
LSB = 1LSB = 0
Program Memory
Byte Locations
000000h
000002h
000004h
000006h
Instruction 1: MOVLW 055h 0Fh 55h 000008h
Instruction 2: GOTO 0006h EFh 03h 00000Ah
F0h 00h 00000Ch
Instruction 3: MOVFF 123h, 456h C1h 23h 00000Eh
F4h 56h 000010h
000012h
000014h
Note: See Section 6.6 “PIC18 Instruction
Execution and the Extended Instruc-
tion Set” for information on two-word
instructions in the extended instruction set.
CASE 1:
Object Code Source Code
0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0?
1100 0001 0010 0011 MOVFF REG1, REG2 ; No, skip this word
1111 0100 0101 0110 ; Execute this word as a NOP
0010 0100 0000 0000 ADDWF REG3 ; continue code
CASE 2:
Object Code Source Code
0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0?
1100 0001 0010 0011 MOVFF REG1, REG2 ; Yes, execute this word
1111 0100 0101 0110 ; 2nd word of instruction
0010 0100 0000 0000 ADDWF REG3 ; continue code
© 2009 Microchip Technology Inc. DS39689F-page 65
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6.3 Data Memory Organization
The data memory in PIC18 devices is implemented as
static RAM. Each register in the data memory has a
12-bit address, allowing up to 4096 bytes of data
memory. The memory space is divided into as many as
16 banks that contain 256 bytes each; PIC18F2221/
2321/4221/4321 family devices implement 2 banks.
Figure 6-5 shows the data memory organization for the
PIC18F2221/2321/4221/4321 family devices.
The data memory contains Special Function Registers
(SFRs) and General Purpose Registers (GPRs). The
SFRs are used for control and status of the controller
and peripheral functions, while GPRs are used for data
storage and scratchpad operations in the user’s
application. Any read of an unimplemented location will
read as ‘0’s.
The instruction set and architecture allow operations
across all banks. The entire data memory may be
accessed by Direct, Indirect or Indexed Addressing
modes. Addressing modes are discussed later in this
subsection.
To ensure that commonly used registers (SFRs and
select GPRs) can be accessed in a single cycle, PIC18
devices implement an Access Bank. This is a 256-byte
memory space that provides fast access to SFRs and
the lower portion of GPR Bank 0 without using the
BSR. Section 6.3.2 “Access Bank” provides a
detailed description of the Access RAM.
6.3.1 BANK SELECT REGISTER (BSR)
Large areas of data memory require an efficient
addressing scheme to make rapid access to any
address possible. Ideally, this means that an entire
address does not need to be provided for each read or
write operation. For PIC18 devices, this is accomplished
with a RAM banking scheme. This divides the memory
space into 16 contiguous banks of 256 bytes. Depend-
ing on the instruction, each location can be addressed
directly by its full 12-bit address, or an 8-bit low-order
address and a 4-bit Bank Pointer.
Most instructions in the PIC18 instruction set make use
of the Bank Pointer, known as the Bank Select Register
(BSR). This SFR holds the four Most Significant bits of
a location’s address; the instruction itself includes the
8 Least Significant bits. Only the four lower bits of the
BSR are implemented (BSR3:BSR0). The upper four
bits are unused; they will always read ‘0’ and cannot be
written to. The BSR can be loaded directly by using the
MOVLB instruction.
The value of the BSR indicates the bank in data
memory; the 8 bits in the instruction show the location
in the bank and can be thought of as an offset from the
bank’s lower boundary. The relationship between the
BSR’s value and the bank division in data memory is
shown in Figure 6-6.
Since up to 16 registers may share the same low-order
address, the user must always be careful to ensure that
the proper bank is selected before performing a data
read or write. For example, writing what should be
program data to an 8-bit address of F9h, while the BSR
is 0Fh, will end up resetting the program counter.
While any bank can be selected, only those banks that
are actually implemented can be read or written to.
Writes to unimplemented banks are ignored, while
reads from unimplemented banks will return0’s. Even
so, the STATUS register will still be affected as if the
operation was successful. The data memory map in
Figure 6-5 indicates which banks are implemented.
In the core PIC18 instruction set, only the MOVFF
instruction fully specifies the 12-bit address of the
source and target registers. This instruction ignores the
BSR completely when it executes. All other instructions
include only the low-order address as an operand and
must use either the BSR or the Access Bank to locate
their target registers.
Note: The operation of some aspects of data
memory are changed when the PIC18
extended instruction set is enabled. See
Section 6.5 “Data Memory and the
Extended Instruction Set” for more
information.
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FIGURE 6-5: DATA MEMORY MAP FOR PIC18F2221/2321/4221/4321 FAMILY DEVICES
Bank 0
Bank 14
Bank 15
Data Memory Map
BSR<3:0>
= 0000
= 1111
080h
07Fh
F80h
FFFh
00h
7Fh
80h
FFh
Access Bank
When a = 0,
The BSR is ignored and the
Access Bank is used.
The first 128 bytes are
General Purpose RAM
(from Bank 0).
The second 128 bytes are
Special Function Registers
(from Bank 15).
When a = 1,
The BSR specifies the Bank
used by the instruction.
F7Fh
F00h
EFFh
0FFh
000h
Access RAM
FFh
00h
FFh
00h
GPR
SFR
Unused
Access RAM High
Access RAM Low
Bank 2
to Unused
Read ‘00h’
= 1110
= 0010
(SFRs)
Bank 1
= 0001 100h
1FFh
GPR
© 2009 Microchip Technology Inc. DS39689F-page 67
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FIGURE 6-6: USE OF THE BANK SELECT REGISTER (DIRECT ADDRESSING)
6.3.2 ACCESS BANK
While the use of the BSR with an embedded 8-bit
address allows users to address the entire range of
data memory, it also means that the user must always
ensure that the correct bank is selected. Otherwise,
data may be read from or written to the wrong location.
This can be disastrous if a GPR is the intended target
of an operation, but an SFR is written to instead.
Verifying and/or changing the BSR for each read or
write to data memory can become very inefficient.
To streamline access for the most commonly used data
memory locations, the data memory is configured with
an Access Bank, which allows users to access a
mapped block of memory without specifying a BSR.
The Access Bank consists of the first 128 bytes of
memory (00h-7Fh) in Bank 0 and the last 128 bytes of
memory (80h-FFh) in Block 15. The lower half is known
as the “Access RAM” and is composed of GPRs. This
upper half is also where the device’s SFRs are
mapped. These two areas are mapped contiguously in
the Access Bank and can be addressed in a linear
fashion by an 8-bit address (Figure 6-5).
The Access Bank is used by core PIC18 instructions
that include the Access RAM bit (the ‘a’ parameter in
the instruction). When ‘a’ is equal to ‘1’, the instruction
uses the BSR and the 8-bit address included in the
opcode for the data memory address. When ‘a’ is ‘0’,
however, the instruction is forced to use the Access
Bank address map; the current value of the BSR is
ignored entirely.
Using this “forced” addressing allows the instruction to
operate on a data address in a single cycle, without
updating the BSR first. For 8-bit addresses of 80h and
above, this means that users can evaluate and operate
on SFRs more efficiently. The Access RAM below 80h
is a good place for data values that the user might need
to access rapidly, such as immediate computational
results or common program variables. Access RAM
also allows for faster and more code efficient context
saving and switching of variables.
The mapping of the Access Bank is slightly different
when the extended instruction set is enabled (XINST
Configuration bit = 1). This is discussed in more detail
in Section 6.5.3 “Mapping the Access Bank in
Indexed Literal Offset Addressing Mode”.
6.3.3 GENERAL PURPOSE
REGISTER FILE
PIC18 devices may have banked memory in the GPR
area. This is data RAM which is available for use by all
instructions. GPRs start at the bottom of Bank 0
(address 000h) and grow upwards towards the bottom of
the SFR area. GPRs are not initialized by a Power-on
Reset and are unchanged on all other Resets.
Note 1: The Access RAM bit of the instruction can be used to force an override of the selected bank (BSR<3:0>) to
the registers of the Access Bank.
2: The MOVFF instruction embeds the entire 12-bit address in the instruction.
Data Memory
Bank Select(2)
70
From Opcode(2)
0000 000h
100h
200h
F00h
FFFh
Bank 0
Bank 1
Bank 15
00h
FFh
00h
FFh
00h
00h
FFh
Bank 2
through
Bank 14
0001 11111111
70
BSR(1)
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6.3.4 SPECIAL FUNCTION REGISTERS
The Special Function Registers (SFRs) are registers
used by the CPU and peripheral modules for controlling
the desired operation of the device. These registers are
implemented as static RAM. SFRs start at the top of
data memory (FFFh) and extend downward to occupy
the top half of Bank 15 (F80h to FFFh). A list of these
registers is given in Table 6-1 and Table 6-2.
The SFRs can be classified into two sets: those associ-
ated with the “core” device functionality (ALU, Resets
and interrupts) and those related to the peripheral
functions. The reset and interrupt registers are
described in their respective chapters, while the ALU’s
STATUS register is described later in this section.
Registers related to the operation of a peripheral feature
are described in the chapter for that peripheral.
The SFRs are typically distributed among the
peripherals whose functions they control. Unused SFR
locations are unimplemented and read as ‘0’s.
TABLE 6-1: SPECIAL FUNCTION REGISTER MAP FOR PIC18F2221/2321/4221/4321 FAMILY
DEVICES
Address Name Address Name Address Name Address Name
FFFh TOSU FDFh INDF2(1) FBFh CCPR1H F9Fh IPR1
FFEh TOSH FDEh POSTINC2(1) FBEh CCPR1L F9Eh PIR1
FFDh TOSL FDDh POSTDEC2(1) FBDh CCP1CON F9Dh PIE1
FFCh STKPTR FDCh PREINC2(1) FBCh CCPR2H F9Ch (2)
FFBh PCLATU FDBh PLUSW2(1) FBBh CCPR2L F9Bh OSCTUNE
FFAh PCLATH FDAh FSR2H FBAh CCP2CON F9Ah (2)
FF9h PCL FD9h FSR2L FB9h (2) F99h (2)
FF8h TBLPTRU FD8h STATUS FB8h BAUDCON F98h (2)
FF7h TBLPTRH FD7h TMR0H FB7h ECCP1DEL(3) F97h (2)
FF6h TBLPTRL FD6h TMR0L FB6h ECCP1AS(3) F96h TRISE(3)
FF5h TABLAT FD5h T0CON FB5h CVRCON F95h TRISD(3)
FF4h PRODH FD4h (2) FB4h CMCON F94h TRISC
FF3h PRODL FD3h OSCCON FB3h TMR3H F93h TRISB
FF2h INTCON FD2h HLVDCON FB2h TMR3L F92h TRISA
FF1h INTCON2 FD1h WDTCON FB1h T3CON F91h (2)
FF0h INTCON3 FD0h RCON FB0h SPBRGH F90h (2)
FEFh INDF0(1) FCFh TMR1H FAFh SPBRG F8Fh (2)
FEEh POSTINC0(1) FCEh TMR1L FAEh RCREG F8Eh (2)
FEDh POSTDEC0(1) FCDh T1CON FADh TXREG F8Dh LATE(3)
FECh PREINC0(1) FCCh TMR2 FACh TXSTA F8Ch LATD(3)
FEBh PLUSW0(1) FCBh PR2 FABh RCSTA F8Bh LATC
FEAh FSR0H FCAh T2CON FAAh (2) F8Ah LATB
FE9h FSR0L FC9h SSPBUF FA9h EEADR F89h LATA
FE8h WREG FC8h SSPADD FA8h EEDATA F88h (2)
FE7h INDF1(1) FC7h SSPSTAT FA7h EECON2(1) F87h (2)
FE6h POSTINC1(1) FC6h SSPCON1 FA6h EECON1 F86h (2)
FE5h POSTDEC1(1) FC5h SSPCON2 FA5h (2) F85h (2)
FE4h PREINC1(1) FC4h ADRESH FA4h (2) F84h PORTE
FE3h PLUSW1(1) FC3h ADRESL FA3h (2) F83h PORTD(3)
FE2h FSR1H FC2h ADCON0 FA2h IPR2 F82h PORTC
FE1h FSR1L FC1h ADCON1 FA1h PIR2 F81h PORTB
FE0h BSR FC0h ADCON2 FA0h PIE2 F80h PORTA
Note 1: This is not a physical register.
2: Unimplemented registers are read as ‘0’.
3: This register is not available on 28-pin devices.
© 2009 Microchip Technology Inc. DS39689F-page 69
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TABLE 6-2: REGISTER FILE SUMMARY (PIC18F2221/2321/4221/4321)
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR, BOR
Details on
page:
TOSU Top-of-Stack Upper Byte (TOS<20:16>) ---0 0000 55, 60
TOSH Top-of-Stack High Byte (TOS<15:8>) 0000 0000 55, 60
TOSL Top-of-Stack Low Byte (TOS<7:0>) 0000 0000 55, 60
STKPTR STKFUL(6) STKUNF(6) SP4 SP3 SP2 SP1 SP0 00-0 0000 55, 61
PCLATU Holding Register for PC<21:16> --00 0000 55, 60
PCLATH Holding Register for PC<15:8> 0000 0000 55, 60
PCL PC Low Byte (PC<7:0>) 0000 0000 55, 60
TBLPTRU bit 21 Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) --00 0000 55, 82
TBLPTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 0000 0000 55, 82
TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 0000 0000 55, 82
TABLAT Program Memory Table Latch 0000 0000 55, 82
PRODH Product Register High Byte xxxx xxxx 55, 95
PRODL Product Register Low Byte xxxx xxxx 55, 95
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 55, 99
INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 —TMR0IP —RBIP1111 -1-1 55, 100
INTCON3 INT2IP INT1IP INT2IE INT1IE INT2IF INT1IF 11-0 0-00 55, 101
INDF0 Uses contents of FSR0 to address data memory – value of FSR0 not changed (not a physical register) N/A 55, 74
POSTINC0 Uses contents of FSR0 to address data memory – value of FSR0 post-incremented (not a physical register) N/A 55, 74
POSTDEC0 Uses contents of FSR0 to address data memory – value of FSR0 post-decremented (not a physical register) N/A 55, 74
PREINC0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) N/A 55, 74
PLUSW0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) –
value of FSR0 offset by W
N/A 55, 74
FSR0H Indirect Data Memory Address Pointer 0 High Byte ---- 0000 55, 74
FSR0L Indirect Data Memory Address Pointer 0 Low Byte xxxx xxxx 55, 74
WREG Working Register xxxx xxxx 55
INDF1 Uses contents of FSR1 to address data memory – value of FSR1 not changed (not a physical register) N/A 55, 74
POSTINC1 Uses contents of FSR1 to address data memory – value of FSR1 post-incremented (not a physical register) N/A 55, 74
POSTDEC1 Uses contents of FSR1 to address data memory – value of FSR1 post-decremented (not a physical register) N/A 55, 74
PREINC1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) N/A 55, 74
PLUSW1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) –
value of FSR1 offset by W
N/A 55, 74
FSR1H Indirect Data Memory Address Pointer 1 High Byte ---- 0000 56, 74
FSR1L Indirect Data Memory Address Pointer 1 Low Byte xxxx xxxx 56, 74
BSR Bank Select Register ---- 0000 56, 65
INDF2 Uses contents of FSR2 to address data memory – value of FSR2 not changed (not a physical register) N/A 56, 74
POSTINC2 Uses contents of FSR2 to address data memory – value of FSR2 post-incremented (not a physical register) N/A 56, 74
POSTDEC2 Uses contents of FSR2 to address data memory – value of FSR2 post-decremented (not a physical register) N/A 56, 74
PREINC2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) N/A 56, 74
PLUSW2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) –
value of FSR2 offset by W
N/A 56, 74
FSR2H Indirect Data Memory Address Pointer 2 High Byte ---- 0000 56, 74
FSR2L Indirect Data Memory Address Pointer 2 Low Byte xxxx xxxx 56, 74
STATUS —NOVZ DC C---x xxxx 56, 72
Legend: x = unknown, u = unchanged, = unimplemented, q = value depends on condition
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and reads as ‘0’. See
Section 5.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are not implemented on 28-pin devices and are read as 0’. Reset values are shown for 40/44-pin devices;
individual unimplemented bits should be interpreted as-’.
3: The PLLEN bit is only available in specific oscillator configurations; otherwise, it is disabled and reads as ‘0’. See Section 3.6.4 “PLL in
INTOSC Modes.
4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0); otherwise, RE3 reads as0’. This bit is
read-only.
5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.
When disabled, these bits read as ‘0’.
6: Bit 7 and bit 6 are cleared by user software or by a POR.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 70 © 2009 Microchip Technology Inc.
TMR0H Timer0 Register High Byte 0000 0000 56, 131
TMR0L Timer0 Register Low Byte xxxx xxxx 56, 131
T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 1111 1111 56, 129
OSCCON IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0 0100 q000 37, 56
HLVDCON VDIRMAG IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 0-00 0101 56, 253
WDTCON —SWDTEN--- ---0 56, 270
RCON IPEN SBOREN(1) —RITO PD POR BOR 0q-1 11q0 48, 54, 108
TMR1H Timer1 Register High Byte xxxx xxxx 56, 137
TMR1L Timer1 Register Low Byte xxxx xxxx 56, 137
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 0000 0000 56, 133
TMR2 Timer2 Register 0000 0000 56, 140
PR2 Timer2 Period Register 1111 1111 56, 140
T2CON T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 56, 139
SSPBUF MSSP Receive Buffer/Transmit Register xxxx xxxx 56, 175,
176
SSPADD MSSP Address Register in I2C™ Slave mode. MSSP Baud Rate Reload Register in I2C Master mode. 0000 0000 56, 176
SSPSTAT SMP CKE D/A PSR/WUA BF 0000 0000 56, 168,
177
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 56, 169,
178
SSPCON2 GCEN ACKSTAT ACKDT/
ADMSK5
ACKEN/
ADMSK4
RCEN/
ADMSK3
PEN/
ADMSK2
RSEN/
ADMSK1
SEN 0000 0000 56, 179
ADRESH A/D Result Register High Byte xxxx xxxx 57, 242
ADRESL A/D Result Register Low Byte xxxx xxxx 57, 242
ADCON0 CHS3 CHS2 CHS1 CHS0 GO/DONE ADON --00 0000 57, 233
ADCON1 VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 --00 0qqq 57, 234
ADCON2 ADFM ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 0-00 0000 57, 235
CCPR1H Capture/Compare/PWM Register 1 High Byte xxxx xxxx 57, 146
CCPR1L Capture/Compare/PWM Register 1 Low Byte xxxx xxxx 57, 146
CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 0000 0000 57, 145,
153
CCPR2H Capture/Compare/PWM Register 2 High Byte xxxx xxxx 57, 146
CCPR2L Capture/Compare/PWM Register 2 Low Byte xxxx xxxx 57, 146
CCP2CON DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 57, 145
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 0100 0-00 57, 214
ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 0000 0000 57, 162
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 0000 0000 57, 163
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 0000 0000 57, 249
CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 0000 0111 57, 243
TMR3H Timer3 Register High Byte xxxx xxxx 57, 143
TMR3L Timer3 Register Low Byte xxxx xxxx 57, 143
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 0000 0000 57, 141
TABLE 6-2: REGISTER FILE SUMMARY (PIC18F2221/2321/4221/4321) (CONTINUED)
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR, BOR
Details on
page:
Legend: x = unknown, u = unchanged, = unimplemented, q = value depends on condition
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and reads as ‘0’. See
Section 5.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are not implemented on 28-pin devices and are read as 0’. Reset values are shown for 40/44-pin devices;
individual unimplemented bits should be interpreted as-’.
3: The PLLEN bit is only available in specific oscillator configurations; otherwise, it is disabled and reads as ‘0’. See Section 3.6.4 “PLL in
INTOSC Modes.
4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0); otherwise, RE3 reads as0’. This bit is
read-only.
5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.
When disabled, these bits read as ‘0’.
6: Bit 7 and bit 6 are cleared by user software or by a POR.
© 2009 Microchip Technology Inc. DS39689F-page 71
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SPBRGH EUSART Baud Rate Generator Register High Byte 0000 0000 57, 216
SPBRG EUSART Baud Rate Generator Register Low Byte 0000 0000 57, 216
RCREG EUSART Receive Register 0000 0000 57, 224
TXREG EUSART Transmit Register 0000 0000 57, 221
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 0000 0010 57, 212
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 57, 213
EEADR EEPROM Address Register 0000 0000 57, 80, 89
EEDATA EEPROM Data Register 0000 0000 57, 80, 89
EECON2 EEPROM Control Register 2 (not a physical register) 0000 0000 57, 80, 89
EECON1 EEPGD CFGS FREE WRERR WREN WR RD xx-0 x000 57, 81, 90
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 11-1 1111 58, 107
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 00-0 0000 58, 103
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 00-0 0000 58, 105
IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 58, 106
PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 58, 102
PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 58, 104
OSCTUNE INTSRC PLLEN(3) TUN4 TUN3 TUN2 TUN1 TUN0 00-0 0000 33, 58
TRISE(2) IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0 0000 -111 58, 124
TRISD(2) PORTD Data Direction Control Register 1111 1111 58, 120
TRISC PORTC Data Direction Control Register 1111 1111 58, 117
TRISB PORTB Data Direction Control Register 1111 1111 58, 114
TRISA TRISA7(5) TRISA6(5) PORTA Data Direction Control Register 1111 1111 58, 111
LATE(2) PORTE Data Latch Register
(Read and Write to Data Latch)
---- -xxx 58, 123
LATD(2) PORTD Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 120
LATC PORTC Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 117
LATB PORTB Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 114
LATA LATA7(5) LATA6(5) PORTA Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 111
PORTE —RE3
(4) RE2(2) RE1(2) RE0(2) ---- xxxx 58, 123
PORTD(2) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 xxxx xxxx 58, 120
PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 xxxx xxxx 58, 117
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 xxxx xxxx 58, 114
PORTA RA7(5) RA6(5) RA5 RA4 RA3 RA2 RA1 RA0 xx0x 0000 58, 111
TABLE 6-2: REGISTER FILE SUMMARY (PIC18F2221/2321/4221/4321) (CONTINUED)
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on
POR, BOR
Details on
page:
Legend: x = unknown, u = unchanged, = unimplemented, q = value depends on condition
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and reads as ‘0’. See
Section 5.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are not implemented on 28-pin devices and are read as 0’. Reset values are shown for 40/44-pin devices;
individual unimplemented bits should be interpreted as-’.
3: The PLLEN bit is only available in specific oscillator configurations; otherwise, it is disabled and reads as ‘0’. See Section 3.6.4 “PLL in
INTOSC Modes.
4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0); otherwise, RE3 reads as0’. This bit is
read-only.
5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.
When disabled, these bits read as ‘0’.
6: Bit 7 and bit 6 are cleared by user software or by a POR.
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DS39689F-page 72 © 2009 Microchip Technology Inc.
6.3.5 STATUS REGISTER
The STATUS register, shown in Register 6-2, contains
the arithmetic status of the ALU. As with any other SFR,
it can be the operand for any instruction.
If the STATUS register is the destination for an instruc-
tion that affects the Z, DC, C, OV or N bits, the results
of the instruction are not written; instead, the STATUS
register is updated according to the instruction
performed. Therefore, the result of an instruction with
the STATUS register as its destination may be different
than intended. As an example, CLRF STATUS will set
the Z bit and leave the remaining Status bits
unchanged (‘000u u1uu’).
It is recommended that only BCF, BSF, SWAPF, MOVFF
and MOVWF instructions are used to alter the STATUS
register, because these instructions do not affect the Z,
C, DC, OV or N bits in the STATUS register.
For other instructions that do not affect Status bits, see
the instruction set summaries in Table 24-2 and
Table 24-3.
REGISTER 6-2: STATUS REGISTER
Note: The C and DC bits operate as the borrow
and digit borrow bits, respectively, in
subtraction.
U-0 U-0 U-0 R/W-x R/W-x R/W-x R/W-x R/W-x
—NOVZDCC
bit 7 bit 0
bit 7-5 Unimplemented: Read as ‘0
bit 4 N: Negative bit
This bit is used for signed arithmetic (2’s complement). It indicates whether the result was
negative (ALU MSB = 1).
1 = Result was negative
0 = Result was positive
bit 3 OV: Overflow bit
This bit is used for signed arithmetic (2’s complement). It indicates an overflow of the 7-bit
magnitude which causes the sign bit (bit 7 of the result) to change state.
1 = Overflow occurred for signed arithmetic (in this arithmetic operation)
0 = No overflow occurred
bit 2 Z: Zero bit
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
bit 1 DC: Digit Carry/borrow bit
For ADDWF, ADDLW, SUBLW and SUBWF instructions:
1 = A carry-out from the 4th low-order bit of the result occurred
0 = No carry-out from the 4th low-order bit of the result
Note: For borrow, the polarity is reversed. A subtraction is executed by adding the 2’s
complement of the second operand. For rotate (RRF, RLF) instructions, this bit is
loaded with either bit 4 or bit 3 of the source register.
bit 0 C: Carry/borrow bit
For ADDWF, ADDLW, SUBLW and SUBWF instructions:
1 = A carry-out from the Most Significant bit of the result occurred
0 = No carry-out from the Most Significant bit of the result occurred
Note: For borrow, the polarity is reversed. A subtraction is executed by adding the 2’s
complement of the second operand. For rotate (RRF, RLF) instructions, this bit is
loaded with either the high or low-order bit of the source register.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 73
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6.4 Data Addressing Modes
The data memory space can be addressed in several
ways. For most instructions, the addressing mode is
fixed. Other instructions may use up to three modes,
depending on which operands are used and whether or
not the extended instruction set is enabled.
The addressing modes are:
Inherent
Literal
•Direct
•Indirect
An additional addressing mode, Indexed Literal Offset,
is available when the extended instruction set is
enabled (XINST Configuration bit = 1). Its operation is
discussed in greater detail in Section 6.5.1 “Indexed
Addressing with Literal Offset”.
6.4.1 INHERENT AND LITERAL
ADDRESSING
Many PIC18 control instructions do not need any
argument at all; they either perform an operation that
globally affects the device or they operate implicitly on
one register. This addressing mode is known as Inherent
Addressing. Examples include SLEEP, RESET and DAW.
Other instructions work in a similar way but require an
additional explicit argument in the opcode. This is
known as Literal Addressing mode because they
require some literal value as an argument. Examples
include ADDLW and MOVLW, which respectively, add or
move a literal value to the W register. Other examples
include CALL and GOTO, which include a 20-bit
program memory address.
6.4.2 DIRECT ADDRESSING
Direct addressing specifies all or part of the source
and/or destination address of the operation within the
opcode itself. The options are specified by the
arguments accompanying the instruction.
In the core PIC18 instruction set, bit-oriented and byte-
oriented instructions use some version of direct
addressing by default. All of these instructions include
some 8-bit literal address as their Least Significant
Byte. This address specifies either a register address in
one of the banks of data RAM (Section 6.3.3 “General
Purpose Register File”) or a location in the Access
Bank (Section 6.3.2 “Access Bank”) as the data
source for the instruction.
The Access RAM bit ‘a’ determines how the address is
interpreted. When ‘a’ is1’, the contents of the BSR
(Section 6.3.1 “Bank Select Register (BSR)”) are
used with the address to determine the complete 12-bit
address of the register. When ‘a’ is ‘0’, the address is
interpreted as being a register in the Access Bank.
Addressing that uses the Access RAM is sometimes
also known as Direct Forced Addressing mode.
A few instructions, such as MOVFF, include the entire
12-bit address (either source or destination) in their
opcodes. In these cases, the BSR is ignored entirely.
The destination of the operation’s results is determined
by the destination bit ‘d’. When ‘d’ is1’, the results are
stored back in the source register, overwriting its origi-
nal contents. When ‘d’ is ‘0, the results are stored in
the W register. Instructions without the ‘d’ argument
have a destination that is implicit in the instruction; their
destination is either the target register being operated
on or the W register.
6.4.3 INDIRECT ADDRESSING
Indirect addressing allows the user to access a location
in data memory without giving a fixed address in the
instruction. This is done by using File Select Registers
(FSRs) as pointers to the locations to be read or written
to. Since the FSRs are themselves located in RAM as
Special Function Registers, they can also be directly
manipulated under program control. This makes FSRs
very useful in implementing data structures, such as
tables and arrays in data memory.
The registers for indirect addressing are also
implemented with Indirect File Operands (INDFs) that
permit automatic manipulation of the pointer value with
auto-incrementing, auto-decrementing or offsetting
with another value. This allows for efficient code, using
loops, such as the example of clearing an entire RAM
bank in Example 6-5.
EXAMPLE 6-5: HOW TO CLEAR RAM
(BANK 1) USING
INDIRECT ADDRESSING
Note: The execution of some instructions in the
core PIC18 instruction set are changed
when the PIC18 extended instruction set is
enabled. See Section 6.5 “Data Memory
and the Extended Instruction Set” for
more information.
LFSR FSR0, 100h ;
NEXT CLRF POSTINC0 ; Clear INDF
; register then
; inc pointer
BTFSS FSR0H, 1 ; All done with
; Bank1?
BRA NEXT ; NO, clear next
CONTINUE ; YES, continue
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DS39689F-page 74 © 2009 Microchip Technology Inc.
6.4.3.1 FSR Registers and the
INDF Operand
At the core of indirect addressing are three sets of
registers: FSR0, FSR1 and FSR2. Each represents a
pair of 8-bit registers, FSRnH and FSRnL. The four
upper bits of the FSRnH register are not used so each
FSR pair holds a 12-bit value. This represents a value
that can address the entire range of the data memory
in a linear fashion. The FSR register pairs, then, serve
as pointers to data memory locations.
Indirect addressing is accomplished with a set of
Indirect File Operands, INDF0 through INDF2. These
can be thought of as “virtual” registers: they are
mapped in the SFR space but are not physically imple-
mented. Reading or writing to a particular INDF register
actually accesses its corresponding FSR register pair.
A read from INDF1, for example, reads the data at the
address indicated by FSR1H:FSR1L. Instructions that
use the INDF registers as operands actually use the
contents of their corresponding FSR as a pointer to the
instruction’s target. The INDF operand is just a
convenient way of using the pointer.
Because indirect addressing uses a full 12-bit address,
data RAM banking is not necessary. Thus, the current
contents of the BSR and the Access RAM bit have no
effect on determining the target address.
6.4.3.2 FSR Registers and POSTINC,
POSTDEC, PREINC and PLUSW
In addition to the INDF operand, each FSR register pair
also has four additional indirect operands. Like INDF,
these are “virtual” registers that cannot be indirectly
read or written to. Accessing these registers actually
accesses the associated FSR register pair, but also
performs a specific action on its stored value. They are:
POSTDEC: accesses the FSR value, then
automatically decrements it by 1 afterwards
POSTINC: accesses the FSR value, then
automatically increments it by 1 afterwards
PREINC: increments the FSR value by 1, then
uses it in the operation
PLUSW: adds the signed value of the W register
(range of -127 to 128) to that of the FSR and uses
the new value in the operation.
In this context, accessing an INDF register uses the
value in the FSR registers without changing them. Sim-
ilarly, accessing a PLUSW register gives the FSR value
offset by that in the W register; neither value is actually
changed in the operation. Accessing the other virtual
registers changes the value of the FSR registers.
Operations on the FSRs with POSTDEC, POSTINC
and PREINC affect the entire register pair; that is, roll-
overs of the FSRnL register from FFh to 00h carry over
to the FSRnH register. On the other hand, results of
these operations do not change the value of any flags
in the STATUS register (e.g., Z, N, OV, etc.).
FIGURE 6-7: INDIRECT ADDRESSING
FSR1H:FSR1L
0
7
Data Memory
000h
100h
200h
300h
F00h
E00h
FFFh
Bank 0
Bank 1
Bank 2
Bank 14
Bank 15
Bank 3
through
Bank 13
ADDWF, INDF1, 1
07
Using an instruction with one of the
indirect addressing registers as the
operand....
...uses the 12-bit address stored in
the FSR pair associated with that
register....
...to determine the data memory
location to be used in that operation.
In this case, the FSR1 pair contains
ECCh. This means the contents of
location ECCh will be added to that
of the W register and stored back in
ECCh.
xxxx1110 11001100
© 2009 Microchip Technology Inc. DS39689F-page 75
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The PLUSW register can be used to implement a form
of indexed addressing in the data memory space. By
manipulating the value in the W register, users can
reach addresses that are fixed offsets from pointer
addresses. In some applications, this can be used to
implement some powerful program control structure,
such as software stacks, inside of data memory.
6.4.3.3 Operations by FSRs on FSRs
Indirect addressing operations that target other FSRs or
virtual registers represent special cases. For example,
using an FSR to point to one of the virtual registers will
not result in successful operations. As a specific case,
assume that FSR0H:FSR0L contains FE7h, the address
of INDF1. Attempts to read the value of the INDF1 using
INDF0 as an operand will return 00h. Attempts to write
to INDF1 using INDF0 as the operand will result in a NOP.
On the other hand, using the virtual registers to write to
an FSR pair may not occur as planned. In these cases,
the value will be written to the FSR pair but without any
incrementing or decrementing. Thus, writing to INDF2
or POSTDEC2 will write the same value to the
FSR2H:FSR2L.
Since the FSRs are physical registers mapped in the
SFR space, they can be manipulated through all direct
operations. Users should proceed cautiously when
working on these registers, particularly if their code
uses indirect addressing.
Similarly, operations by indirect addressing are generally
permitted on all other SFRs. Users should exercise the
appropriate caution that they do not inadvertently
change settings that might affect the operation of the
device.
6.5 Data Memory and the Extended
Instruction Set
Enabling the PIC18 extended instruction set (XINST
Configuration bit = 1) significantly changes certain
aspects of data memory and its addressing. Specifically,
the use of the Access Bank for many of the core PIC18
instructions is different. This is due to the introduction of
a new addressing mode for the data memory space.
What does not change is just as important. The size of
the data memory space is unchanged, as well as its
linear addressing. The SFR map remains the same.
Core PIC18 instructions can still operate in both Direct
and Indirect Addressing mode; inherent and literal
instructions do not change at all. Indirect addressing
with FSR0 and FSR1 also remain unchanged.
6.5.1 INDEXED ADDRESSING WITH
LITERAL OFFSET
Enabling the PIC18 extended instruction set changes
the behavior of indirect addressing using the FSR2
register pair within Access RAM. Under the proper
conditions, instructions that use the Access Bank – that
is, most bit-oriented and byte-oriented instructions – can
invoke a form of indexed addressing using an offset
specified in the instruction. This special addressing
mode is known as Indexed Addressing with Literal
Offset, or Indexed Literal Offset mode.
When using the extended instruction set, this
addressing mode requires the following:
The use of the Access Bank is forced (‘a’ = 0);
and
The file address argument is less than or equal to
5Fh.
Under these conditions, the file address of the instruc-
tion is not interpreted as the lower byte of an address
(used with the BSR in direct addressing), or as an 8-bit
address in the Access Bank. Instead, the value is
interpreted as an offset value to an Address Pointer,
specified by FSR2. The offset and the contents of
FSR2 are added to obtain the target address of the
operation.
6.5.2 INSTRUCTIONS AFFECTED BY
INDEXED LITERAL OFFSET MODE
Any of the core PIC18 instructions that can use direct
addressing are potentially affected by the Indexed
Literal Offset Addressing mode. This includes all
byte-oriented and bit-oriented instructions, or almost
one-half of the standard PIC18 instruction set.
Instructions that only use Inherent or Literal Addressing
modes are unaffected.
Additionally, byte-oriented and bit-oriented instructions
are not affected if they do not use the Access Bank
(Access RAM bit is ‘1’), or include a file address of 60h
or above. Instructions meeting these criteria will
continue to execute as before. A comparison of the dif-
ferent possible addressing modes when the extended
instruction set is enabled is shown in Figure 6-8.
Those who desire to use bit-oriented or byte-oriented
instructions in the Indexed Literal Offset mode should
note the changes to assembler syntax for this mode.
This is described in more detail in Section 24.2.1
“Extended Instruction Syntax”.
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FIGURE 6-8: COMPARING ADDRESSING OPTIONS FOR BIT-ORIENTED AND
BYTE-ORIENTED INSTRUCTIONS (EXTENDED INSTRUCTION SET ENABLED)
EXAMPLE INSTRUCTION: ADDWF, f, d, a (Opcode: 0010 01da ffff ffff)
When ‘a’ = 0 and ‘f’ 60h:
The instruction executes in
Direct Forced mode. ‘f’ is inter-
preted as a location in the
Access RAM between 060h
and 0FFh. This is the same as
locations 060h to 07Fh
(Bank 0) and F80h to FFFh
(Bank 15) of data memory.
Locations below 60h are not
available in this addressing
mode.
When ‘a’ = 0 and ‘f’5Fh:
The instruction executes in
Indexed Literal Offset mode. ‘f’
is interpreted as an offset to the
address value in FSR2. The
two are added together to
obtain the address of the target
register for the instruction. The
address can be anywhere in
the data memory space.
Note that in this mode, the
correct syntax is now:
ADDWF [k], d
where ‘k’ is the same as ‘f’.
When ‘a’ = 1 (all values of ‘f’):
The instruction executes in
Direct mode (also known as
Direct Long mode). ‘f’ is inter-
preted as a location in one of
the 16 banks of the data
memory space. The bank is
designated by the Bank Select
Register (BSR). The address
can be in any implemented
bank in the data memory
space.
000h
060h
100h
F00h
F80h
FFFh
Valid range
00h
60h
80h
FFh
Data Memory
Access RAM
Bank 0
Bank 1
through
Bank 14
Bank 15
SFRs
000h
080h
100h
F00h
F80h
FFFh
Data Memory
Bank 0
Bank 1
through
Bank 14
Bank 15
SFRs
FSR2H FSR2L
ffffffff001001da
ffffffff001001da
000h
080h
100h
F00h
F80h
FFFh
Data Memory
Bank 0
Bank 1
through
Bank 14
Bank 15
SFRs
for ‘f’
BSR
00000000
080h
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6.5.3 MAPPING THE ACCESS BANK IN
INDEXED LITERAL OFFSET
ADDRESSING MODE
The use of Indexed Literal Offset Addressing mode
effectively changes how the first 96 locations of Access
RAM (00h to 5Fh) are mapped. Rather than containing
just the contents of the bottom half of Bank 0, this mode
maps the contents from Bank 0 and a user-defined
“window” that can be located anywhere in the data
memory space. The value of FSR2 establishes the
lower boundary of the addresses mapped into the
window, while the upper boundary is defined by FSR2
plus 95 (5Fh). Addresses in the Access RAM above
5Fh are mapped as previously described (see
Section 6.3.2 “Access Bank”). An example of Access
Bank remapping in this addressing mode is shown in
Figure 6-9.
Remapping of the Access Bank applies only to opera-
tions using the Indexed Literal Offset Addressing
mode. Operations that use the BSR (Access RAM bit is
1’) will continue to use direct addressing as before.
6.6 PIC18 Instruction Execution and
the Extended Instruction Set
Enabling the extended instruction set adds eight
additional commands to the existing PIC18 instruction
set. These instructions are executed as described in
Section 24.2 “Extended Instruction Set”.
FIGURE 6-9: REMAPPING THE ACCESS BANK WITH INDEXED LITERAL OFFSET
ADDRESSING MODE
Data Memory
000h
100h
200h
F80h
F00h
FFFh
Bank 1
Bank 15
Bank 2
through
Bank 14
SFRs
05Fh
ADDWF f, d, a
FSR2H:FSR2L = 120h
Locations in the region
from the FSR2 Pointer
(120h) to the pointer plus
05Fh (17Fh) are mapped
to the bottom of the
Access RAM (000h-05Fh).
Locations in Bank 0, from
060h to 07Fh, are mapped
as usual to the middle of
the Access Bank.
Special Function Regis-
ters at F80h through FFFh
are mapped to 80h
through FFh, as usual.
Bank 0 addresses below
5Fh can still be addressed
by using the BSR.
Access Bank
00h
80h
FFh
7Fh
Bank 0
SFRs
Bank 1 “Window”
Bank 0
Bank 0
Window
Example Situation:
07Fh
120h
17Fh
5Fh
Bank 1
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NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 79
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7.0 FLASH PROGRAM MEMORY
The Flash program memory is readable, writable and
erasable during normal operation over the entire VDD
range.
A read from program memory is executed on one byte
at a time. A write to program memory is executed on
blocks of 8 bytes at a time. Program memory is erased
in blocks of 64 bytes at a time. A bulk erase operation
may not be issued from user code.
Writing or erasing program memory will cease
instruction fetches until the operation is complete. The
program memory cannot be accessed during the write
or erase, therefore, code cannot execute. An internal
programming timer terminates program memory writes
and erases.
A value written to program memory does not need to be
a valid instruction. Executing a program memory
location that forms an invalid instruction results in a
NOP.
7.1 Table Reads and Table Writes
In order to read and write program memory, there are
two operations that allow the processor to move bytes
between the program memory space and the data RAM:
Table Read (TBLRD)
Table Write (TBLWT)
The program memory space is 16 bits wide, while the
data RAM space is 8 bits wide. Table reads and table
writes move data between these two memory spaces
through an 8-bit register (TABLAT).
Table read operations retrieve data from program
memory and place it into the data RAM space.
Figure 7-1 shows the operation of a table read with
program memory and data RAM.
Table write operations store data from the data memory
space into holding registers in program memory. The
procedure to write the contents of the holding registers
into program memory is detailed in Section 7.5 “Writing
to Flash Program Memory”. Figure 7-2 shows the
operation of a table write with program memory and data
RAM.
Table operations work with byte entities. A table block
containing data, rather than program instructions, is not
required to be word-aligned. Therefore, a table block can
start and end at any byte address. If a table write is being
used to write executable code into program memory,
program instructions will need to be word-aligned.
FIGURE 7-1: TABLE READ OPERATION
Table Pointer(1)
Table Latch (8-bit)
Program Memory
TBLPTRH TBLPTRL
TABLAT
TBLPTRU
Instruction: TBLRD*
Note 1: Table Pointer register points to a byte in program memory.
Program Memory
(TBLPTR)
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FIGURE 7-2: TABLE WRITE OPERATION
7.2 Control Registers
Several control registers are used in conjunction with
the TBLRD and TBLWT instructions. These include the:
EECON1 register
EECON2 register
TABLAT register
TBLPTR registers
7.2.1 EECON1 AND EECON2 REGISTERS
The EECON1 register (Register 7-1) is the control
register for memory accesses. The EECON2 register is
not a physical register; it is used exclusively in the
memory write and erase sequences. Reading
EECON2 will read all ‘0’s.
The EEPGD control bit determines if the access will be
a program or data EEPROM memory access. When
clear, any subsequent operations will operate on the
data EEPROM memory. When set, any subsequent
operations will operate on the program memory.
The CFGS control bit determines if the access will be
to the Configuration/Calibration registers or to program
memory/data EEPROM memory. When set,
subsequent operations will operate on Configuration
registers regardless of EEPGD (see Section 24.0
“Special Features of the CPU). When clear, memory
selection access is determined by EEPGD.
The FREE bit, when set, will allow a program memory
erase operation. When FREE is set, the erase
operation is initiated on the next WR command. When
FREE is clear, only writes are enabled.
The WREN bit, when set, will allow a write operation.
On power-up, the WREN bit is clear. The WRERR bit is
set in hardware when the WR bit is set and cleared
when the internal programming timer expires and the
write operation is complete.
The WR control bit initiates write operations. The bit
cannot be cleared, only set, in software; it is cleared in
hardware at the completion of the write operation.
Tab l e P oi n te r (1) Table Latch (8-bit)
TBLPTRH TBLPTRL TABLAT
Program Memory
(TBLPTR)
TBLPTRU
Instruction: TBLWT*
Note 1: Table Pointer actually points to one of 64 holding registers, the address of which is determined by
TBLPTRL<5:0>. The process for physically writing data to the program memory array is discussed in
Section 7.5 “Writing to Flash Program Memory”.
Holding Registers
Program Memory
Note: During normal operation, the WRERR bit
may read as ‘1’. This can indicate that a
write operation was prematurely termi-
nated by a Reset, or a write operation was
attempted improperly.
Note: The EEIF interrupt flag bit (PIR2<4>) is set
when the write is complete. It must be
cleared in software.
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REGISTER 7-1: EECON1: DATA EEPROM CONTROL REGISTER 1
R/W-x R/W-x U-0 R/W-0 R/W-x R/W-0 R/S-0 R/S-0
EEPGD CFGS FREE WRERR WREN WR RD
bit 7 bit 0
bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit
1 = Access Flash program memory
0 = Access data EEPROM memory
bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit
1 = Access Configuration registers
0 = Access Flash program or data EEPROM memory
bit 5 Unimplemented: Read as ‘0
bit 4 FREE: Flash Row Erase Enable bit
1 = Erase the program memory row addressed by TBLPTR on the next WR command
(cleared by completion of erase operation)
0 = Perform write-only
bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit
1 = A write operation is prematurely terminated (any Reset during self-timed programming in
normal operation, or an improper write attempt)
0 = The write operation completed
Note: When a WRERR occurs, the EEPGD and CFGS bits are not cleared.
This allows tracing of the error condition.
bit 2 WREN: Flash Program/Data EEPROM Write Enable bit
1 = Allows write cycles to Flash program/data EEPROM
0 = Inhibits write cycles to Flash program/data EEPROM
bit 1 WR: Write Control bit
1 = Initiates a data EEPROM erase/write cycle or a program memory erase/write cycle.
(The operation is self-timed and the bit is cleared by hardware once write is complete.
The WR bit can only be set (not cleared) in software.)
0 = Write cycle to the EEPROM is complete
bit 0 RD: Read Control bit
1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared in hardware. The RD bit can
only be set (not cleared) in software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.)
0 = Does not initiate an EEPROM read
Legend:
R = Readable bit W = Writable bit
S = Bit can be set by software, but not cleared U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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7.2.2 TABLAT – TABLE LATCH REGISTER
The Table Latch (TABLAT) is an 8-bit register mapped
into the SFR space. The Table Latch register is used to
hold 8-bit data during data transfers between program
memory and data RAM.
7.2.3 TBLPTR – TABLE POINTER
REGISTER
The Table Pointer (TBLPTR) register addresses a byte
within the program memory. The TBLPTR is comprised
of three SFR registers: Table Pointer Upper Byte, Table
Pointer High Byte and Table Pointer Low Byte
(TBLPTRU:TBLPTRH:TBLPTRL). These three regis-
ters join to form a 22-bit wide pointer. The low-order
21 bits allow the device to address up to 2 Mbytes of
program memory space. The 22nd bit allows access to
the device ID, the user ID and the Configuration bits.
The Table Pointer register, TBLPTR, is used by the
TBLRD and TBLWT instructions. These instructions can
update the TBLPTR in one of four ways based on the
table operation. These operations are shown in
Table 7-1. These operations on the TBLPTR only affect
the low-order 21 bits.
7.2.4 TABLE POINTER BOUNDARIES
TBLPTR is used in reads, writes and erases of the
Flash program memory.
When a TBLRD is executed, all 22 bits of the TBLPTR
determine which byte is read from program memory
into TABLAT.
When the timed write to program memory begins (via
the WR bit), the 19 MSbs of the TBLPTR
(TBLPTR<21:3>) determine which program memory
block of 8 bytes is written to. The Table Pointer regis-
ter’s three LSBs (TBLPTR<2:0>) are ignored. For more
detail, see Section 7.5 “Writing to Flash Program
Memory.
When an erase of program memory is executed, the
16 MSbs of the Table Pointer register (TBLPTR<21:6>)
point to the 64-byte block that will be erased. The Least
Significant bits (TBLPTR<5:0>) are ignored.
Figure 7-3 describes the relevant boundaries of
TBLPTR based on Flash program memory operations.
TABLE 7-1: TABLE POINTER OPERATIONS WITH TBLRD AND TBLWT INSTRUCTIONS
FIGURE 7-3: TABLE POINTER BOUNDARIES BASED ON OPERATION
Example Operation on Table Pointer
TBLRD*
TBLWT* TBLPTR is not modified
TBLRD*+
TBLWT*+ TBLPTR is incremented after the read/write
TBLRD*-
TBLWT*- TBLPTR is decremented after the read/write
TBLRD+*
TBLWT+* TBLPTR is incremented before the read/write
21 16 15 87 0
TABLE ERASE
TABLE WRITE
TABLE READ – TBLPTR<21:0>
TBLPTRL
TBLPTRH
TBLPTRU
TBLPTR<21:3>
TBLPTR<21:6>
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7.3 Reading the Flash Program
Memory
The TBLRD instruction is used to retrieve data from
program memory and place it into data RAM. Table
reads from program memory are performed one byte at
a time.
TBLPTR points to a byte address in program space.
Executing TBLRD places the byte pointed to into
TABLAT. In addition, TBLPTR can be modified
automatically for the next table read operation.
The internal program memory is typically organized by
words. The Least Significant bit of the address selects
between the high and low bytes of the word. Figure 7-4
shows the interface between the internal program
memory and the TABLAT.
FIGURE 7-4: READS FROM FLASH PROGRAM MEMORY
EXAMPLE 7-1: READING A FLASH PROGRAM MEMORY WORD
(Even Byte Address)
Program Memory
(Odd Byte Address)
TBLRD TABLAT
TBLPTR = xxxxx1
FETCH
Instruction Register
(IR) Read Register
TBLPTR = xxxxx0
MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base
MOVWF TBLPTRU ; address of the word
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
READ_WORD
TBLRD*+ ; read into TABLAT and increment
MOVF TABLAT, W ; get data
MOVWF WORD_EVEN
TBLRD*+ ; read into TABLAT and increment
MOVF TABLAT, W ; get data
MOVWF WORD_ODD
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7.4 Erasing Flash Program Memory
The minimum erase block is 32 words or 64 bytes. Only
through the use of an external programmer, or through
ICSP control, can larger blocks of program memory be
bulk erased. Word erase in the Flash array is not
supported.
When initiating an erase sequence from the micro-
controller itself, a block of 64 bytes of program memory
is erased. The Most Significant 16 bits of the
TBLPTR<21:6> point to the block being erased.
TBLPTR<5:0> are ignored.
The EECON1 register commands the erase operation.
The EEPGD bit must be set to point to the Flash
program memory. The WREN bit must be set to enable
write operations. The FREE bit is set to select an erase
operation.
For protection, the write initiate sequence for EECON2
must be used.
A long write is necessary for erasing the internal Flash.
Instruction execution is halted while in a long write
cycle. The long write will be terminated by the internal
programming timer.
7.4.1 FLASH PROGRAM MEMORY
ERASE SEQUENCE
The sequence of events for erasing a block of internal
program memory location is:
1. Load Table Pointer register with address of row
being erased.
2. Set the EECON1 register for the erase operation:
set EEPGD bit to point to program memory;
clear the CFGS bit to access program memory;
set WREN bit to enable writes;
set FREE bit to enable the erase.
3. Disable interrupts.
4. Write 55h to EECON2.
5. Write 0AAh to EECON2.
6. Set the WR bit. This will begin the row erase
cycle.
7. The CPU will stall for duration of the erase
(about 2 ms using internal timer).
8. Re-enable interrupts.
EXAMPLE 7-2: ERASING A FLASH PROGRAM MEMORY ROW
MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
ERASE_ROW
BSF EECON1, EEPGD ; point to Flash program memory
BCF EECON1, CFGS ; access Flash program memory
BSF EECON1, WREN ; enable write to memory
BSF EECON1, FREE ; enable Row Erase operation
BCF INTCON, GIE ; disable interrupts
Required MOVLW 55h
Sequence MOVWF EECON2 ; write 55h
MOVLW 0AAh
MOVWF EECON2 ; write 0AAh
BSF EECON1, WR ; start erase (CPU stall)
BSF INTCON, GIE ; re-enable interrupts
© 2009 Microchip Technology Inc. DS39689F-page 85
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7.5 Writing to Flash Program Memory
The minimum programming block is 4 words or 8 bytes.
Word or byte programming is not supported.
Table writes are used internally to load the holding
registers needed to program the Flash memory. There
are 8 holding registers used by the table writes for
programming.
Since the Table Latch (TABLAT) is only a single byte,
the TBLWT instruction may need to be executed 8 times
for each programming operation. All of the table write
operations will essentially be short writes because only
the holding registers are written. At the end of updating
the 8 holding registers, the EECON1 register must be
written to in order to start the programming operation with
a long write.
The long write is necessary for programming the
internal Flash. Instruction execution is halted while in a
long write cycle. The long write will be terminated by
the internal programming timer.
The EEPROM on-chip timer controls the write time.
The write/erase voltages are generated by an on-chip
charge pump, rated to operate over the voltage range
of the device.
FIGURE 7-5: TABLE WRITES TO FLASH PROGRAM MEMORY
7.5.1 FLASH PROGRAM MEMORY
WRITE SEQUENCE
The sequence of events for programming an internal
program memory location should be:
1. Read 64 bytes into RAM.
2. Update data values in RAM as necessary.
3. Load Table Pointer register with address being
erased.
4. Execute the row erase procedure.
5. Load Table Pointer register with address of first
byte being written.
6. Write the 8 bytes into the holding registers.
7. Set the EECON1 register for the write operation:
set EEPGD bit to point to program memory;
clear the CFGS bit to access program memory;
set WREN to enable byte writes.
8. Disable interrupts.
9. Write 55h to EECON2.
10. Write 0AAh to EECON2.
11. Set the WR bit. This will begin the write cycle.
12. The CPU will stall for duration of the write (about
2 ms using internal timer).
13. Repeat from step 5 seven more times.
14. Re-enable interrupts.
15. Verify the memory (table read).
This procedure will require about 18 ms to update one
row of 64 bytes of memory. An example of the required
code is given in Example 7-3.
Note: The default value of the holding registers on
device Resets and after write operations is
FFh. A write of FFh to a holding register
does not modify that byte. This means that
individual bytes of program memory may be
modified, provided that the modification
does not attempt to change any bit from a
0’ to a ‘1’. When modifying individual bytes,
it is not necessary to load all 8 holding
registers before executing a write operation.
TABLAT
TBLPTR = xxxxx7TBLPTR = xxxxx1TBLPTR = xxxxx0
Write Register
TBLPTR = xxxxx2
Program Memory
Holding Register Holding Register Holding Register Holding Register
88 8 8
Note: Before setting the WR bit, the Table
Pointer address needs to be within the
intended address range of the 8 bytes in
the holding register.
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EXAMPLE 7-3: WRITING TO FLASH PROGRAM MEMORY
MOVLW D'64' ; number of bytes in erase block
MOVWF COUNTER
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW ; 6 LSB = 0
MOVWF TBLPTRL
READ_BLOCK
TBLRD*+ ; read into TABLAT, and inc
MOVF TABLAT, W ; get data
MOVWF POSTINC0 ; store data and increment FSR0
DECFSZ COUNTER ; done?
BRA READ_BLOCK ; repeat
MODIFY_WORD
MOVLW DATA_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW DATA_ADDR_LOW
MOVWF FSR0L
MOVLW NEW_DATA_LOW ; update buffer word and increment FSR0
MOVWF POSTINC0
MOVLW NEW_DATA_HIGH ; update buffer word
MOVWF INDF0
ERASE_BLOCK
MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW ; 6 LSB = 0
MOVWF TBLPTRL
BCF EECON1, CFGS ; point to PROG/EEPROM memory
BSF EECON1, EEPGD ; point to Flash program memory
BSF EECON1, WREN ; enable write to memory
BSF EECON1, FREE ; enable Row Erase operation
BCF INTCON, GIE ; disable interrupts
MOVLW 55h ; Required sequence
MOVWF EECON2 ; write 55h
MOVLW 0AAh
MOVWF EECON2 ; write AAh
BSF EECON1, WR ; start erase (CPU stall)
NOP
BSF INTCON, GIE ; re-enable interrupts
WRITE_BUFFER_BACK
MOVLW 8 ; number of write buffer groups of 8 bytes
MOVWF COUNTER_HI
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
PROGRAM_LOOP
MOVLW 8 ; number of bytes in holding register
MOVWF COUNTER
WRITE_WORD_TO_HREGS
MOVF POSTINC0, W ; get low byte of buffer data and increment FSR0
MOVWF TABLAT ; present data to table latch
TBLWT+* ; short write
; to internal TBLWT holding register, increment
; TBLPTR
DECFSZ COUNTER ; loop until buffers are full
GOTO WRITE_WORD_TO_HREGS
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EXAMPLE 7-3: WRITING TO FLASH PROGRAM MEMORY (CONTINUED)
7.5.2 WRITE VERIFY
Depending on the application, good programming
practice may dictate that the value written to the
memory should be verified against the original value.
This should be used in applications where excessive
writes can stress bits near the specification limit.
7.5.3 UNEXPECTED TERMINATION OF
WRITE OPERATION
If a write is terminated by an unplanned event, such as
loss of power or an unexpected Reset, the memory
location just programmed should be verified and repro-
grammed if needed. If the write operation is interrupted
by a MCLR Reset or a WDT Time-out Reset during
normal operation, the user can check the WRERR bit
and rewrite the location(s) as needed.
7.5.4 PROTECTION AGAINST
SPURIOUS WRITES
To protect against spurious writes to Flash program
memory, the write initiate sequence must also be
followed. See Section 24.0 “Special Features of the
CPU” for more detail.
7.6 Flash Program Operation During
Code Protection
See Section 24.5 “Program Verification and Code
Protection” for details on code protection of Flash
program memory.
TABLE 7-2: REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY
PROGRAM_MEMORY
BCF INTCON, GIE ; disable interrupts
MOVLW 55h ; required sequence
MOVWF EECON2 ; write 55h
MOVLW 0AAh
MOVWF EECON2 ; write AAh
BSF EECON1, WR ; start program (CPU stall)
NOP
BSF INTCON, GIE ; re-enable interrupts
DECFSZ COUNTER_HI ; loop until done
GOTO PROGRAM_LOOP
BCF EECON1, WREN ; disable write to memory
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values on
page
TBLPTRU bit 21 Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) 55
TBPLTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 55
TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 55
TABLAT Program Memory Table Latch 55
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
EECON2 EEPROM Control Register 2 (not a physical register) 57
EECON1 EEPGD CFGS FREE WRERR WREN WR RD 57
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 88 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 89
PIC18F2221/2321/4221/4321 FAMILY
8.0 DATA EEPROM MEMORY
The data EEPROM is a nonvolatile memory array,
separate from the data RAM and program memory, that
is used for long-term storage of program data. It is not
directly mapped in either the register file or program
memory space but is indirectly addressed through the
Special Function Registers (SFRs). The EEPROM is
readable and writable during normal operation over the
entire VDD range.
Four SFRs are used to read and write to the data
EEPROM as well as the program memory. They are:
EECON1
EECON2
EEDATA
EEADR
The data EEPROM allows byte read and write. When
interfacing to the data memory block, EEDATA holds
the 8-bit data for read/write and the EEADR register
holds the address of the EEPROM location being
accessed.
The EEPROM data memory is rated for high erase/write
cycle endurance. A byte write automatically erases the
location and writes the new data (erase-before-write).
The write time is controlled by an on-chip timer. It will
vary with voltage and temperature as well as from chip
to chip. Please refer to parameter D122 (Table 27-1 in
Section 27.0 “Electrical Characteristics”) for exact
limits.
8.1 EECON1 and EECON2 Registers
Access to the data EEPROM is controlled by two
registers: EECON1 and EECON2. These are the same
registers which control access to the program memory
and are used in a similar manner for the data
EEPROM.
The EECON1 register (Register 8-1) is the control
register for data and program memory access. Control
bit EEPGD determines if the access will be to program
or data EEPROM memory. When clear, operations will
access the data EEPROM memory. When set, program
memory is accessed.
Control bit CFGS determines if the access will be to the
Configuration registers or to program memory/data
EEPROM memory. When set, subsequent operations
access Configuration registers. When CFGS is clear,
the EEPGD bit selects either program Flash or data
EEPROM memory.
The WREN bit, when set, will allow a write operation.
On power-up, the WREN bit is clear. The WRERR bit is
set in hardware when the WREN bit is set and cleared
when the internal programming timer expires and the
write operation is complete.
The WR control bit initiates write operations. The bit
cannot be cleared, only set, in software; it is cleared in
hardware at the completion of the write operation.
Control bits, RD and WR, start read and erase/write
operations, respectively. These bits are set by firmware
and cleared by hardware at the completion of the
operation.
The RD bit cannot be set when accessing program
memory (EEPGD = 1). Program memory is read using
table read instructions. See Section 7.1 “Table Reads
and Table Writes” regarding table reads.
The EECON2 register is not a physical register. It is
used exclusively in the memory write and erase
sequences. Reading EECON2 will read all ‘0’s.
Note: During normal operation, the WRERR bit
is read as ‘1’. This can indicate that a write
operation was prematurely terminated by
a Reset, or a write operation was
attempted improperly.
Note: The EEIF interrupt flag bit (PIR2<4>) is set
when the write is complete. It must be
cleared in software.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 90 © 2009 Microchip Technology Inc.
REGISTER 8-1: EECON1: DATA EEPROM CONTROL REGISTER 1
R/W-x R/W-x U-0 R/W-0 R/W-x R/W-0 R/S-0 R/S-0
EEPGD CFGS FREE WRERR WREN WR RD
bit 7 bit 0
bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit
1 = Access Flash program memory
0 = Access data EEPROM memory
bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit
1 = Access Configuration registers
0 = Access Flash program or data EEPROM memory
bit 5 Unimplemented: Read as ‘0
bit 4 FREE: Flash Row Erase Enable bit
1 = Erase the program memory row addressed by TBLPTR on the next WR command (cleared
by completion of erase operation)
0 = Perform write only
bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit
1 = A write operation is prematurely terminated (any Reset during self-timed programming in
normal operation, or an improper write attempt)
0 = The write operation completed
Note: When a WRERR occurs, the EEPGD and CFGS bits are not cleared.
This allows tracing of the error condition.
bit 2 WREN: Flash Program/Data EEPROM Write Enable bit
1 = Allows write cycles to Flash program/data EEPROM
0 = Inhibits write cycles to Flash program/data EEPROM
bit 1 WR: Write Control bit
1 = Initiates a data EEPROM erase/write cycle or a program memory erase cycle or write cycle
(The operation is self-timed and the bit is cleared by hardware once write is complete.
The WR bit can only be set (not cleared) in software.)
0 = Write cycle to the EEPROM is complete
bit 0 RD: Read Control bit
1 = Initiates an EEPROM read
(Read takes one cycle. RD is cleared in hardware. The RD bit can only be set (not cleared)
in software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.)
0 = Does not initiate an EEPROM read
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 91
PIC18F2221/2321/4221/4321 FAMILY
8.2 Reading the Data EEPROM
Memory
To read a data memory location, the user must write the
address to the EEADR register, clear the EEPGD
control bit (EECON1<7>) and then set control bit, RD
(EECON1<0>). The data is available on the very next
instruction cycle; therefore, the EEDATA register can
be read by the next instruction. EEDATA will hold this
value until another read operation, or until it is written to
by the user (during a write operation).
The basic process is shown in Example 8-1.
8.3 Writing to the Data EEPROM
Memory
To write an EEPROM data location, the address must
first be written to the EEADR register and the data
written to the EEDATA register. The sequence in
Example 8-2 must be followed to initiate the write cycle.
The write will not begin if this sequence is not exactly
followed (write 55h to EECON2, write 0AAh to
EECON2, then set WR bit) for each byte. It is strongly
recommended that interrupts be disabled during this
code segment.
Additionally, the WREN bit in EECON1 must be set to
enable writes. This mechanism prevents accidental
writes to data EEPROM due to unexpected code
execution (i.e., runaway programs). The WREN bit
should be kept clear at all times, except when updating
the EEPROM. The WREN bit is not cleared by
hardware.
After a write sequence has been initiated, EECON1,
EEADR and EEDATA cannot be modified. The WR bit
will be inhibited from being set unless the WREN bit is
set. The WREN bit must be set on a previous instruc-
tion. Both WR and WREN cannot be set with the same
instruction.
At the completion of the write cycle, the WR bit is
cleared in hardware and the EEPROM Interrupt Flag
bit, EEIF, is set. The user may either enable this
interrupt, or poll this bit. EEIF must be cleared by
software.
8.4 Write Verify
Depending on the application, good programming
practice may dictate that the value written to the mem-
ory should be verified against the original value. This
should be used in applications where excessive writes
can stress bits near the specification limit.
EXAMPLE 8-1: DATA EEPROM READ
EXAMPLE 8-2: DATA EEPROM WRITE
MOVLW DATA_EE_ADDR ;
MOVWF EEADR ; Data Memory Address to read
BCF EECON1, EEPGD ; Point to DATA memory
BCF EECON1, CFGS ; Access EEPROM
BSF EECON1, RD ; EEPROM Read
MOVF EEDATA, W ; W = EEDATA
MOVLW DATA_EE_ADDR ;
MOVWF EEADR ; Data Memory Address to write
MOVLW DATA_EE_DATA ;
MOVWF EEDATA ; Data Memory Value to write
BCF EECON1, EEPGD ; Point to DATA memory
BCF EECON1, CFGS ; Access EEPROM
BSF EECON1, WREN ; Enable writes
BCF INTCON, GIE ; Disable Interrupts
MOVLW 55h ;
Required MOVWF EECON2 ; Write 55h
Sequence MOVLW 0AAh ;
MOVWF EECON2 ; Write 0AAh
BSF EECON1, WR ; Set WR bit to begin write
BTFSC EECON1, WR ; Wait for write to complete
GOTO $-2
BSF INTCON, GIE ; Enable Interrupts
; User code execution
BCF EECON1, WREN ; Disable writes on write complete (EEIF set)
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 92 © 2009 Microchip Technology Inc.
8.5 Operation During Code-Protect
Data EEPROM memory has its own code-protect bits in
Configuration Words. External read and write
operations are disabled if code protection is enabled.
The microcontroller itself can both read and write to the
internal data EEPROM, regardless of the state of the
code-protect Configuration bit. Refer to Section 24.0
“Special Features of the CPU for additional
information.
8.6 Protection Against Spurious Write
To protect against spurious EEPROM writes, various
mechanisms have been implemented. On power-up,
the WREN bit is cleared. In addition, writes to the
EEPROM are blocked during the Power-up Timer
period (TPWRT, parameter 33).
The write initiate sequence and the WREN bit together
help prevent an accidental write during Brown-out
Reset, power glitch or software malfunction.
8.7 Using the Data EEPROM
The data EEPROM is a high-endurance, byte
addressable array that has been optimized for the
storage of frequently changing data. Such data is
typically updated at least one time within the number of
writes defined by specification, D124. If any location
storing data is not written at least this often, the data
EEPROM array must be refreshed. For this reason,
values that change infrequently, or not at all, should be
stored in Flash program memory.
A simple data EEPROM refresh routine is shown in
Example 8-3.
EXAMPLE 8-3: DATA EEPROM REFRESH ROUTINE
Note: If data EEPROM is only used to store con-
stants and/or data that changes often, an
array refresh is likely not required. See
specification, D124.
CLRF EEADR ; Start at address 0
BCF EECON1, CFGS ; Set for memory
BCF EECON1, EEPGD ; Set for Data EEPROM
BCF INTCON, GIE ; Disable interrupts
BSF EECON1, WREN ; Enable writes
LOOP ; Loop to refresh array
BSF EECON1, RD ; Read current address
MOVLW 55h ;
MOVWF EECON2 ; Write 55h
MOVLW 0AAh ;
MOVWF EECON2 ; Write 0AAh
BSF EECON1, WR ; Set WR bit to begin write
BTFSC EECON1, WR ; Wait for write to complete
BRA $-2
INCFSZ EEADR, F ; Increment address
BRA LOOP ; Not zero, do it again
BCF EECON1, WREN ; Disable writes
BSF INTCON, GIE ; Enable interrupts
© 2009 Microchip Technology Inc. DS39689F-page 93
PIC18F2221/2321/4221/4321 FAMILY
TABLE 8-1: REGISTERS ASSOCIATED WITH DATA EEPROM MEMORY
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
EEADR EEPROM Address Register 57
EEDATA EEPROM Data Register 57
EECON2 EEPROM Control Register 2 (not a physical register) 57
EECON1 EEPGD CFGS FREE WRERR WREN WR RD 57
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 94 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 95
PIC18F2221/2321/4221/4321 FAMILY
9.0 8 x 8 HARDWARE MULTIPLIER
9.1 Introduction
All PIC18 devices include an 8 x 8 hardware multiplier
as part of the ALU. The multiplier performs an unsigned
operation and yields a 16-bit result that is stored in the
product register pair, PRODH:PRODL. The multiplier’s
operation does not affect any flags in the STATUS
register.
Making multiplication a hardware operation allows it to
be completed in a single instruction cycle. This has the
advantages of higher computational throughput and
reduced code size for multiplication algorithms and
allows the PIC18 devices to be used in many applica-
tions previously reserved for digital signal processors.
A comparison of various hardware and software
multiply operations, along with the savings in memory
and execution time, is shown in Table 9-1.
9.2 Operation
Example 9-1 shows the instruction sequence for an 8 x 8
unsigned multiplication. Only one instruction is required
when one of the arguments is already loaded in the
WREG register.
Example 9-2 shows the sequence to do an 8 x 8 signed
multiplication. To account for the sign bits of the
arguments, each argument’s Most Significant bit (MSb)
is tested and the appropriate subtractions are done.
EXAMPLE 9-1: 8 x 8 UNSIGNED
MULTIPLY ROUTINE
EXAMPLE 9-2: 8 x 8 SIGNED MULTIPLY
ROUTINE
TABLE 9-1: PERFORMANCE COMPARISON FOR VARIOUS MULTIPLY OPERATIONS
MOVF ARG1, W ;
MULWF ARG2 ; ARG1 * ARG2 ->
; PRODH:PRODL
MOVF ARG1, W
MULWF ARG2 ; ARG1 * ARG2 ->
; PRODH:PRODL
BTFSC ARG2, SB ; Test Sign Bit
SUBWF PRODH, F ; PRODH = PRODH
; - ARG1
MOVF ARG2, W
BTFSC ARG1, SB ; Test Sign Bit
SUBWF PRODH, F ; PRODH = PRODH
; - ARG2
Routine Multiply Method
Program
Memory
(Words)
Cycles
(Max)
Time
@ 40 MHz @ 10 MHz @ 4 MHz
8 x 8 unsigned Without hardware multiply 13 69 6.9 μs27.6 μs69 μs
Hardware multiply 1 1 100 ns 400 ns 1 μs
8 x 8 signed Without hardware multiply 33 91 9.1 μs36.4 μs91 μs
Hardware multiply 6 6 600 ns 2.4 μs6 μs
16 x 16 unsigned Without hardware multiply 21 242 24.2 μs96.8 μs242 μs
Hardware multiply 28 28 2.8 μs 11.2 μs28 μs
16 x 16 signed Without hardware multiply 52 254 25.4 μs 102.6 μs254 μs
Hardware multiply 35 40 4.0 μs16.0 μs40 μs
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 96 © 2009 Microchip Technology Inc.
Example 9-3 shows the sequence to do a 16 x 16
unsigned multiplication. Equation 9-1 shows the
algorithm that is used. The 32-bit result is stored in four
registers (RES3:RES0).
EQUATION 9-1: 16 x 16 UNSIGNED
MULTIPLICATION
ALGORITHM
EXAMPLE 9-3: 16 x 16 UNSIGNED
MULTIPLY ROUTINE
Example 9-4 shows the sequence to do a 16 x 16
signed multiply. Equation 9-2 shows the algorithm
used. The 32-bit result is stored in four registers
(RES3:RES0). To account for the sign bits of the
arguments, the MSb for each argument pair is tested
and the appropriate subtractions are done.
EQUATION 9-2: 16 x 16 SIGNED
MULTIPLICATION
ALGORITHM
EXAMPLE 9-4: 16 x 16 SIGNED
MULTIPLY ROUTINE
RES3:RES0 = ARG1H:ARG1L ARG2H:ARG2L
= (ARG1H ARG2H 216) +
(ARG1H ARG2L 28) +
(ARG1L ARG2H 28) +
(ARG1L ARG2L)
MOVF ARG1L, W
MULWF ARG2L ; ARG1L * ARG2L->
; PRODH:PRODL
MOVFF PRODH, RES1 ;
MOVFF PRODL, RES0 ;
;
MOVF ARG1H, W
MULWF ARG2H ; ARG1H * ARG2H->
; PRODH:PRODL
MOVFF PRODH, RES3 ;
MOVFF PRODL, RES2 ;
;
MOVF ARG1L, W
MULWF ARG2H ; ARG1L * ARG2H->
; PRODH:PRODL
MOVF PRODL, W ;
ADDWF RES1, F ; Add cross
MOVF PRODH, W ; products
ADDWFC RES2, F ;
CLRF WREG ;
ADDWFC RES3, F ;
;
MOVF ARG1H, W ;
MULWF ARG2L ; ARG1H * ARG2L->
; PRODH:PRODL
MOVF PRODL, W ;
ADDWF RES1, F ; Add cross
MOVF PRODH, W ; products
ADDWFC RES2, F ;
CLRF WREG ;
ADDWFC RES3, F ;
RES3:RES0 = ARG1H:ARG1L ARG2H:ARG2L
= (ARG1H ARG2H 216) +
(ARG1H ARG2L 28) +
(ARG1L ARG2H 28) +
(ARG1L ARG2L) +
(-1 ARG2H<7> ARG1H:ARG1L 216) +
(-1 ARG1H<7> ARG2H:ARG2L 216)
MOVF ARG1L, W
MULWF ARG2L ; ARG1L * ARG2L ->
; PRODH:PRODL
MOVFF PRODH, RES1 ;
MOVFF PRODL, RES0 ;
;
MOVF ARG1H, W
MULWF ARG2H ; ARG1H * ARG2H ->
; PRODH:PRODL
MOVFF PRODH, RES3 ;
MOVFF PRODL, RES2 ;
;
MOVF ARG1L, W
MULWF ARG2H ; ARG1L * ARG2H ->
; PRODH:PRODL
MOVF PRODL, W ;
ADDWF RES1, F ; Add cross
MOVF PRODH, W ; products
ADDWFC RES2, F ;
CLRF WREG ;
ADDWFC RES3, F ;
;
MOVF ARG1H, W ;
MULWF ARG2L ; ARG1H * ARG2L ->
; PRODH:PRODL
MOVF PRODL, W ;
ADDWF RES1, F ; Add cross
MOVF PRODH, W ; products
ADDWFC RES2, F ;
CLRF WREG ;
ADDWFC RES3, F ;
;
BTFSS ARG2H, 7 ; ARG2H:ARG2L neg?
BRA SIGN_ARG1 ; no, check ARG1
MOVF ARG1L, W ;
SUBWF RES2 ;
MOVF ARG1H, W ;
SUBWFB RES3
;
SIGN_ARG1
BTFSS ARG1H, 7 ; ARG1H:ARG1L neg?
BRA CONT_CODE ; no, done
MOVF ARG2L, W ;
SUBWF RES2 ;
MOVF ARG2H, W ;
SUBWFB RES3
;
CONT_CODE
:
© 2009 Microchip Technology Inc. DS39689F-page 97
PIC18F2221/2321/4221/4321 FAMILY
10.0 INTERRUPTS
The PIC18F2221/2321/4221/4321 family devices have
multiple interrupt sources and an interrupt priority
feature that allows most interrupt sources to be
assigned a high-priority level or a low-priority level. The
high-priority interrupt vector is at 0008h and the low-
priority interrupt vector is at 0018h. High-priority
interrupt events will interrupt any low-priority interrupts
that may be in progress.
There are ten registers which are used to control
interrupt operation. These registers are:
RCON
•INTCON
INTCON2
INTCON3
PIR1, PIR2
PIE1, PIE2
IPR1, IPR2
It is recommended that the Microchip header files
supplied with MPLAB® IDE be used for the symbolic bit
names in these registers. This allows the assembler/
compiler to automatically take care of the placement of
these bits within the specified register.
In general, interrupt sources have three bits to control
their operation. They are:
Flag bit to indicate that an interrupt event
occurred
Enable bit that allows program execution to
branch to the interrupt vector address when the
flag bit is set
Priority bit to select high priority or low priority
The interrupt priority feature is enabled by setting the
IPEN bit (RCON<7>). When interrupt priority is
enabled, there are two bits which enable interrupts
globally. Setting the GIEH bit (INTCON<7>) enables all
interrupts that have the priority bit set (high priority).
Setting the GIEL bit (INTCON<6>) enables all
interrupts that have the priority bit cleared (low priority).
When the interrupt flag, enable bit and appropriate
global interrupt enable bit are set, the interrupt will vec-
tor immediately to address 0008h or 0018h, depending
on the priority bit setting. Individual interrupts can be
disabled through their corresponding enable bits.
When the IPEN bit is cleared (default state), the
interrupt priority feature is disabled and interrupts are
compatible with PIC® mid-range devices. In
Compatibility mode, the interrupt priority bits for each
source have no effect. INTCON<6> is the PEIE bit,
which enables/disables all peripheral interrupt sources.
INTCON<7> is the GIE bit, which enables/disables all
interrupt sources. All interrupts branch to address
0008h in Compatibility mode.
When an interrupt is responded to, the global interrupt
enable bit is cleared to disable further interrupts. If the
IPEN bit is cleared, this is the GIE bit. If interrupt priority
levels are used, this will be either the GIEH or GIEL bit.
High-priority interrupt sources can interrupt a low-
priority interrupt. Low-priority interrupts are not
processed while high-priority interrupts are in progress.
The return address is pushed onto the stack and the
PC is loaded with the interrupt vector address (0008h
or 0018h). Once in the Interrupt Service Routine, the
source(s) of the interrupt can be determined by polling
the interrupt flag bits. The interrupt flag bits must be
cleared in software before re-enabling interrupts to
avoid recursive interrupts.
The “return from interrupt” instruction, RETFIE, exits
the interrupt routine and sets the GIE bit (GIEH or GIEL
if priority levels are used), which re-enables interrupts.
For external interrupt events, such as the INTx pins or
the PORTB input change interrupt, the interrupt latency
will be three to four instruction cycles. The exact
latency is the same for one or two-cycle instructions.
Individual interrupt flag bits are set, regardless of the
status of their corresponding enable bit or the GIE bit.
Note: Do not use the MOVFF instruction to modify
any of the interrupt control registers while
any interrupt is enabled. Doing so may
cause erratic microcontroller behavior.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 98 © 2009 Microchip Technology Inc.
FIGURE 10-1: PIC18 INTERRUPT LOGIC
TMR0IE
GIE/GIEH
PEIE/GIEL
Wake-up if in
Interrupt to CPU
Vector to Location
0008h
INT2IF
INT2IE
INT2IP
INT1IF
INT1IE
INT1IP
TMR0IF
TMR0IE
TMR0IP
RBIF
RBIE
RBIP
IPEN
TMR0IF
TMR0IP
INT1IF
INT1IE
INT1IP
INT2IF
INT2IE
INT2IP
RBIF
RBIE
RBIP
INT0IF
INT0IE
PEIE/GIEL
Interrupt to CPU
Vector to Location
IPEN
IPEN
0018h
SSPIF
SSPIE
SSPIP
SSPIF
SSPIE
SSPIP
ADIF
ADIE
ADIP
RCIF
RCIE
RCIP
Additional Peripheral Interrupts
ADIF
ADIE
ADIP
High-Priority Interrupt Generation
Low-Priority Interrupt Generation
RCIF
RCIE
RCIP
Additional Peripheral Interrupts
Idle or Sleep modes
GIE/GIEH
© 2009 Microchip Technology Inc. DS39689F-page 99
PIC18F2221/2321/4221/4321 FAMILY
10.1 INTCON Registers
The INTCON registers are readable and writable
registers, which contain various enable, priority and
flag bits.
REGISTER 10-1: INTCON: INTERRUPT CONTROL REGISTER
Note: Interrupt flag bits are set when an interrupt
condition occurs, regardless of the state of
its corresponding enable bit or the global
interrupt enable bit. User software should
ensure the appropriate interrupt flag bits
are clear prior to enabling an interrupt.
This feature allows for software polling.
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x
GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF
bit 7 bit 0
bit 7 GIE/GIEH: Global Interrupt Enable bit
When IPEN = 0:
1 = Enables all unmasked interrupts
0 = Disables all interrupts
When IPEN = 1:
1 = Enables all high-priority interrupts
0 = Disables all interrupts
bit 6 PEIE/GIEL: Peripheral Interrupt Enable bit
When IPEN = 0:
1 = Enables all unmasked peripheral interrupts
0 = Disables all peripheral interrupts
When IPEN = 1:
1 = Enables all low-priority peripheral interrupts
0 = Disables all low-priority peripheral interrupts
bit 5 TMR0IE: TMR0 Overflow Interrupt Enable bit
1 = Enables the TMR0 overflow interrupt
0 = Disables the TMR0 overflow interrupt
bit 4 INT0IE: INT0 External Interrupt Enable bit
1 = Enables the INT0 external interrupt
0 = Disables the INT0 external interrupt
bit 3 RBIE: RB Port Change Interrupt Enable bit
1 = Enables the RB port change interrupt
0 = Disables the RB port change interrupt
bit 2 TMR0IF: TMR0 Overflow Interrupt Flag bit
1 = TMR0 register has overflowed (must be cleared in software)
0 = TMR0 register did not overflow
bit 1 INT0IF: INT0 External Interrupt Flag bit
1 = The INT0 external interrupt occurred (must be cleared in software)
0 = The INT0 external interrupt did not occur
bit 0 RBIF: RB Port Change Interrupt Flag bit
1 = At least one of the RB<7:4> pins changed state (must be cleared in software)
0 = None of the RB<7:4> pins have changed state
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 100 © 2009 Microchip Technology Inc.
REGISTER 10-2: INTCON2: INTERRUPT CONTROL REGISTER 2
R/W-1 R/W-1 R/W-1 R/W-1 U-0 R/W-1 U-0 R/W-1
RBPU INTEDG0 INTEDG1 INTEDG2 —TMR0IP—RBIP
bit 7 bit 0
bit 7 RBPU: PORTB Pull-up Enable bit
1 = All PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
bit 6 INTEDG0: External Interrupt 0 Edge Select bit
1 = Interrupt on rising edge
0 = Interrupt on falling edge
bit 5 INTEDG1: External Interrupt 1 Edge Select bit
1 = Interrupt on rising edge
0 = Interrupt on falling edge
bit 4 INTEDG2: External Interrupt 2 Edge Select bit
1 = Interrupt on rising edge
0 = Interrupt on falling edge
bit 3 Unimplemented: Read as ‘0
bit 2 TMR0IP: TMR0 Overflow Interrupt Priority bit
1 = High priority
0 = Low priority
bit 1 Unimplemented: Read as ‘0
bit 0 RBIP: RB Port Change Interrupt Priority bit
1 = High priority
0 = Low priority
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
Note: Interrupt flag bits are set when an interrupt condition occurs, regardless of the state
of its corresponding enable bit or the global interrupt enable bit. User software
should ensure the appropriate interrupt flag bits are clear prior to enabling an
interrupt. This feature allows for software polling.
© 2009 Microchip Technology Inc. DS39689F-page 101
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REGISTER 10-3: INTCON3: INTERRUPT CONTROL REGISTER 3
R/W-1 R/W-1 U-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0
INT2IP INT1IP —INT2IEINT1IE INT2IF INT1IF
bit 7 bit 0
bit 7 INT2IP: INT2 External Interrupt Priority bit
1 = High priority
0 = Low priority
bit 6 INT1IP: INT1 External Interrupt Priority bit
1 = High priority
0 = Low priority
bit 5 Unimplemented: Read as ‘0
bit 4 INT2IE: INT2 External Interrupt Enable bit
1 = Enables the INT2 external interrupt
0 = Disables the INT2 external interrupt
bit 3 INT1IE: INT1 External Interrupt Enable bit
1 = Enables the INT1 external interrupt
0 = Disables the INT1 external interrupt
bit 2 Unimplemented: Read as ‘0
bit 1 INT2IF: INT2 External Interrupt Flag bit
1 = The INT2 external interrupt occurred (must be cleared in software)
0 = The INT2 external interrupt did not occur
bit 0 INT1IF: INT1 External Interrupt Flag bit
1 = The INT1 external interrupt occurred (must be cleared in software)
0 = The INT1 external interrupt did not occur
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
Note: Interrupt flag bits are set when an interrupt condition occurs, regardless of the state
of its corresponding enable bit or the global interrupt enable bit. User software
should ensure the appropriate interrupt flag bits are clear prior to enabling an
interrupt. This feature allows for software polling.
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DS39689F-page 102 © 2009 Microchip Technology Inc.
10.2 PIR Registers
The PIR registers contain the individual flag bits for the
peripheral interrupts. Due to the number of peripheral
interrupt sources, there are two Peripheral Interrupt
Request (Flag) registers (PIR1 and PIR2).
REGISTER 10-4: PIR1: PERIPHERAL INTERRUPT REQUEST (FLAG) REGISTER 1
Note 1: Interrupt flag bits are set when an interrupt
condition occurs, regardless of the state of
its corresponding enable bit or the Global
Interrupt Enable bit, GIE (INTCON<7>).
2: User software should ensure the appropri-
ate interrupt flag bits are cleared prior to
enabling an interrupt and after servicing
that interrupt.
R/W-0 R/W-0 R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0
PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF
bit 7 bit 0
bit 7 PSPIF: Parallel Slave Port Read/Write Interrupt Flag bit(1)
1 = A read or a write operation has taken place (must be cleared in software)
0 = No read or write has occurred
Note 1: This bit is unimplemented on 28-pin devices and will read as ‘0’.
bit 6 ADIF: A/D Converter Interrupt Flag bit
1 = An A/D conversion completed (must be cleared in software)
0 = The A/D conversion is not complete
bit 5 RCIF: EUSART Receive Interrupt Flag bit
1 = The EUSART receive buffer, RCREG, is full (cleared when RCREG is read)
0 = The EUSART receive buffer is empty
bit 4 TXIF: EUSART Transmit Interrupt Flag bit
1 = The EUSART transmit buffer, TXREG, is empty (cleared when TXREG is written)
0 = The EUSART transmit buffer is full
bit 3 SSPIF: Master Synchronous Serial Port Interrupt Flag bit
1 = The transmission/reception is complete (must be cleared in software)
0 = Waiting to transmit/receive
bit 2 CCP1IF: CCP1 Interrupt Flag bit
Capture mode:
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare mode:
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM mode:
Unused in this mode.
bit 1 TMR2IF: TMR2 to PR2 Match Interrupt Flag bit
1 = TMR2 to PR2 match occurred (must be cleared in software)
0 = No TMR2 to PR2 match occurred
bit 0 TMR1IF: TMR1 Overflow Interrupt Flag bit
1 = TMR1 register overflowed (must be cleared in software)
0 = TMR1 register did not overflow
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set 0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 103
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REGISTER 10-5: PIR2: PERIPHERAL INTERRUPT REQUEST (FLAG) REGISTER 2
R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF
bit 7 bit 0
bit 7 OSCFIF: Oscillator Fail Interrupt Flag bit
1 = Device oscillator failed, clock input has changed to INTOSC (must be cleared in software)
0 = Device clock operating
bit 6 CMIF: Comparator Interrupt Flag bit
1 = Comparator input has changed (must be cleared in software)
0 = Comparator input has not changed
bit 5 Unimplemented: Read as ‘0
bit 4 EEIF: Data EEPROM/Flash Write Operation Interrupt Flag bit
1 = The write operation is complete (must be cleared in software)
0 = The write operation is not complete or has not been started
bit 3 BCLIF: Bus Collision Interrupt Flag bit
1 = A bus collision occurred (must be cleared in software)
0 = No bus collision occurred
bit 2 HLVDIF: High/Low-Voltage Detect Interrupt Flag bit
1 = A high/low-voltage condition occurred; direction determined by VDIRMAG bit
(HLVDCON<7>)
0 = A high/low-voltage condition has not occurred
bit 1 TMR3IF: TMR3 Overflow Interrupt Flag bit
1 = TMR3 register overflowed (must be cleared in software)
0 = TMR3 register did not overflow
bit 0 CCP2IF: CCP2 Interrupt Flag bit
Capture mode:
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare mode:
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM mode:
Unused in this mode.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 104 © 2009 Microchip Technology Inc.
10.3 PIE Registers
The PIE registers contain the individual enable bits for
the peripheral interrupts. Due to the number of periph-
eral interrupt sources, there are two Peripheral Interrupt
Enable registers (PIE1 and PIE2). When IPEN = 0, the
PEIE bit must be set to enable any of these peripheral
interrupts.
REGISTER 10-6: PIE1: PERIPHERAL INTERRUPT ENABLE REGISTER 1
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE
bit 7 bit 0
bit 7 PSPIE: Parallel Slave Port Read/Write Interrupt Enable bit(1)
1 = Enables the PSP read/write interrupt
0 = Disables the PSP read/write interrupt
Note 1: This bit is unimplemented on 28-pin devices and will read as ‘0’.
bit 6 ADIE: A/D Converter Interrupt Enable bit
1 = Enables the A/D interrupt
0 = Disables the A/D interrupt
bit 5 RCIE: EUSART Receive Interrupt Enable bit
1 = Enables the EUSART receive interrupt
0 = Disables the EUSART receive interrupt
bit 4 TXIE: EUSART Transmit Interrupt Enable bit
1 = Enables the EUSART transmit interrupt
0 = Disables the EUSART transmit interrupt
bit 3 SSPIE: Master Synchronous Serial Port Interrupt Enable bit
1 = Enables the MSSP interrupt
0 = Disables the MSSP interrupt
bit 2 CCP1IE: CCP1 Interrupt Enable bit
1 = Enables the CCP1 interrupt
0 = Disables the CCP1 interrupt
bit 1 TMR2IE: TMR2 to PR2 Match Interrupt Enable bit
1 = Enables the TMR2 to PR2 match interrupt
0 = Disables the TMR2 to PR2 match interrupt
bit 0 TMR1IE: TMR1 Overflow Interrupt Enable bit
1 = Enables the TMR1 overflow interrupt
0 = Disables the TMR1 overflow interrupt
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set 0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 105
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REGISTER 10-7: PIE2: PERIPHERAL INTERRUPT ENABLE REGISTER 2
R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE
bit 7 bit 0
bit 7 OSCFIE: Oscillator Fail Interrupt Enable bit
1 = Enabled
0 =Disabled
bit 6 CMIE: Comparator Interrupt Enable bit
1 = Enabled
0 =Disabled
bit 5 Unimplemented: Read as ‘0
bit 4 EEIE: Data EEPROM/Flash Write Operation Interrupt Enable bit
1 = Enabled
0 =Disabled
bit 3 BCLIE: Bus Collision Interrupt Enable bit
1 = Enabled
0 =Disabled
bit 2 HLVDIE: High/Low-Voltage Detect Interrupt Enable bit
1 = Enabled
0 =Disabled
bit 1 TMR3IE: TMR3 Overflow Interrupt Enable bit
1 = Enabled
0 =Disabled
bit 0 CCP2IE: CCP2 Interrupt Enable bit
1 = Enabled
0 =Disabled
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 106 © 2009 Microchip Technology Inc.
10.4 IPR Registers
The IPR registers contain the individual priority bits for
the peripheral interrupts. Due to the number of periph-
eral interrupt sources, there are two Peripheral Interrupt
Priority registers (IPR1 and IPR2). Using the priority bits
requires that the Interrupt Priority Enable (IPEN) bit be
set.
REGISTER 10-8: IPR1: PERIPHERAL INTERRUPT PRIORITY REGISTER 1
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP
bit 7 bit 0
bit 7 PSPIP: Parallel Slave Port Read/Write Interrupt Priority bit(1)
1 =High priority
0 = Low priority
Note 1: This bit is unimplemented on 28-pin devices and will read as ‘0’.
bit 6 ADIP: A/D Converter Interrupt Priority bit
1 =High priority
0 = Low priority
bit 5 RCIP: EUSART Receive Interrupt Priority bit
1 =High priority
0 = Low priority
bit 4 TXIP: EUSART Transmit Interrupt Priority bit
1 =High priority
0 = Low priority
bit 3 SSPIP: Master Synchronous Serial Port Interrupt Priority bit
1 =High priority
0 = Low priority
bit 2 CCP1IP: CCP1 Interrupt Priority bit
1 =High priority
0 = Low priority
bit 1 TMR2IP: TMR2 to PR2 Match Interrupt Priority bit
1 =High priority
0 = Low priority
bit 0 TMR1IP: TMR1 Overflow Interrupt Priority bit
1 =High priority
0 = Low priority
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set 0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 107
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REGISTER 10-9: IPR2: PERIPHERAL INTERRUPT PRIORITY REGISTER 2
R/W-1 R/W-1 U-0 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP
bit 7 bit 0
bit 7 OSCFIP: Oscillator Fail Interrupt Priority bit
1 =High priority
0 = Low priority
bit 6 CMIP: Comparator Interrupt Priority bit
1 =High priority
0 = Low priority
bit 5 Unimplemented: Read as ‘0
bit 4 EEIP: Data EEPROM/Flash Write Operation Interrupt Priority bit
1 =High priority
0 = Low priority
bit 3 BCLIP: Bus Collision Interrupt Priority bit
1 =High priority
0 = Low priority
bit 2 HLVDIP: High/Low-Voltage Detect Interrupt Priority bit
1 =High priority
0 = Low priority
bit 1 TMR3IP: TMR3 Overflow Interrupt Priority bit
1 =High priority
0 = Low priority
bit 0 CCP2IP: CCP2 Interrupt Priority bit
1 =High priority
0 = Low priority
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 108 © 2009 Microchip Technology Inc.
10.5 RCON Register
The RCON register contains flag bits which are used to
determine the cause of the last Reset or wake-up from
Idle or Sleep modes. RCON also contains the IPEN bit
which enables interrupt priorities.
The operation of the SBOREN bit and the Reset flag
bits is discussed in more detail in Section 5.1 “RCON
Register”.
REGISTER 10-10: RCON: RESET CONTROL REGISTER
R/W-0 R/W-1(1) U-0 R/W-1 R-1 R-1 R/W-0(2) R/W-0
IPEN SBOREN —RITO PD POR BOR
bit 7 bit 0
bit 7 IPEN: Interrupt Priority Enable bit
1 = Enable priority levels on interrupts
0 = Disable priority levels on interrupts (PIC16XXX Compatibility mode)
bit 6 SBOREN: Software BOR Enable bit(1)
For details of bit operation, see Register 5-1.
bit 5 Unimplemented: Read as ‘0
bit 4 RI: RESET Instruction Flag bit
For details of bit operation, see Register 5-1.
bit 3 TO: Watchdog Time-out Flag bit
For details of bit operation, see Register 5-1.
bit 2 PD: Power-down Detection Flag bit
For details of bit operation, see Register 5-1.
bit 1 POR: Power-on Reset Status bit(2)
For details of bit operation, see Register 5-1.
bit 0 BOR: Brown-out Reset Status bit
For details of bit operation, see Register 5-1.
Note 1: If SBOREN is enabled, its Reset state is ‘1’; otherwise, it is ‘0’.
2: Actual Reset values are determined by device configuration and the nature of the
device Reset. See Register 5-1 for additional information.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set 0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 109
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10.6 INTx Pin Interrupts
External interrupts on the RB0/INT0, RB1/INT1 and
RB2/INT2 pins are edge-triggered. If the corresponding
INTEDGx bit in the INTCON2 register is set (= 1), the
interrupt is triggered by a rising edge; if the bit is clear,
the trigger is on the falling edge. When a valid edge
appears on the RBx/INTx pin, the corresponding flag
bit, INTxF, is set. This interrupt can be disabled by
clearing the corresponding enable bit, INTxE. Flag bit,
INTxF, must be cleared in software in the Interrupt
Service Routine before re-enabling the interrupt.
All external interrupts (INT0, INT1 and INT2) can wake-
up the processor from Idle or Sleep modes if bit INTxE
was set prior to going into those modes. If the Global
Interrupt Enable bit, GIE, is set, the processor will
branch to the interrupt vector following wake-up.
Interrupt priority for INT1 and INT2 is determined by
the value contained in the interrupt priority bits,
INT1IP (INTCON3<6>) and INT2IP (INTCON3<7>).
There is no priority bit associated with INT0. It is
always a high-priority interrupt source.
10.7 TMR0 Interrupt
In 8-bit mode (which is the default), an overflow in the
TMR0 register (FFh 00h) will set flag bit, TMR0IF. In
16-bit mode, an overflow in the TMR0H:TMR0L
register pair (FFFFh 0000h) will set TMR0IF. The
interrupt can be enabled/disabled by setting/clearing
enable bit, TMR0IE (INTCON<5>). Interrupt priority for
Timer0 is determined by the value contained in the
interrupt priority bit, TMR0IP (INTCON2<2>). See
Section 12.0 “Timer0 Module” for further details on
the Timer0 module.
10.8 PORTB Interrupt-on-Change
An input change on PORTB<7:4> sets flag bit, RBIF
(INTCON<0>). The interrupt can be enabled/disabled
by setting/clearing enable bit, RBIE (INTCON<3>).
Interrupt priority for PORTB interrupt-on-change is
determined by the value contained in the interrupt
priority bit, RBIP (INTCON2<0>).
10.9 Context Saving During Interrupts
During interrupts, the return PC address is saved on
the stack. Additionally, the WREG, STATUS and BSR
registers are saved on the fast return stack. If a fast
return from interrupt is not used (see Section 6.3
“Data Memory Organization”), the user may need to
save the WREG, STATUS and BSR registers on entry
to the Interrupt Service Routine. Depending on the
user’s application, other registers may also need to be
saved. Example 10-1 saves and restores the WREG,
STATUS and BSR registers during an Interrupt Service
Routine.
EXAMPLE 10-1: SAVING STATUS, WREG AND BSR REGISTERS IN RAM
MOVWF W_TEMP ; W_TEMP is in virtual bank
MOVFF STATUS, STATUS_TEMP ; STATUS_TEMP located anywhere
MOVFF BSR, BSR_TEMP ; BSR_TMEP located anywhere
;
; USER ISR CODE
;
MOVFF BSR_TEMP, BSR ; Restore BSR
MOVF W_TEMP, W ; Restore WREG
MOVFF STATUS_TEMP, STATUS ; Restore STATUS
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DS39689F-page 110 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 111
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11.0 I/O PORTS
Depending on the device selected and features
enabled, there are up to five ports available. Some pins
of the I/O ports are multiplexed with an alternate
function from the peripheral features on the device. In
general, when a peripheral is enabled, that pin may not
be used as a general purpose I/O pin.
Each port has three registers for its operation. These
registers are:
TRIS register (Data Direction register)
PORT register (reads the levels on the pins of the
device)
LAT register (Data Latch register)
The Data Latch (LAT register) is useful for read-modify-
write operations on the value that the I/O pins are
driving.
A simplified model of a generic I/O port, without the
interfaces to other peripherals, is shown in Figure 11-1.
FIGURE 11-1: GENERIC I/O PORT
OPERATION
11.1 PORTA, TRISA and LATA Registers
PORTA is an 8-bit wide, bidirectional port. The corre-
sponding Data Direction register is TRISA. Setting a
TRISA bit (= 1) will make the corresponding PORTA pin
an input (i.e., put the corresponding output driver in a
High-Impedance mode). Clearing a TRISA bit (= 0) will
make the corresponding PORTA pin an output (i.e., put
the contents of the output latch on the selected pin).
Reading the PORTA register reads the status of the
pins, whereas writing to it, will write to the port latch.
The Data Latch (LATA) register is also memory mapped.
Read-modify-write operations on the LATA register read
and write the latched output value for PORTA.
The RA4 pin is multiplexed with the Timer0 module
clock input and one of the comparator outputs to
become the RA4/T0CKI/C1OUT pin. Pins RA6 and
RA7 are multiplexed with the main oscillator pins. They
are enabled as oscillator or I/O pins by the selection of
the main oscillator in the Configuration register (see
Section 24.1 “Configuration Bits” for details). When
they are not used as port pins, RA6 and RA7 and their
associated TRIS and LAT bits are read as ‘0’.
The other PORTA pins are multiplexed with analog
inputs, the analog VREF+ and VREF- inputs and the
comparator voltage reference output. The operation of
pins RA<3:0> and RA5 as A/D converter inputs is
selected by clearing or setting the control bits in the
ADCON1 register (A/D Control Register 1).
Pins RA0 through RA5 may also be used as comparator
inputs or outputs by setting the appropriate bits in the
CMCON register. To use RA<3:0> as digital inputs, it is
also necessary to turn off the comparators.
The RA4/T0CKI/C1OUT pin is a Schmitt Trigger input.
All other PORTA pins have TTL input levels and full
CMOS output drivers.
The TRISA register controls the direction of the PORTA
pins, even when they are being used as analog inputs.
The user must ensure the bits in the TRISA register are
maintained set when using them as analog inputs.
EXAMPLE 11-1: INITIALIZING PORTA
Data
Bus
WR LAT
WR TRIS
RD PORT
Data Latch
TRIS Latch
RD TRIS
Input
Buffer
I/O pin(1)
QD
CK
QD
CK
EN
QD
EN
RD LAT
or PORT
Note 1: I/O pins have diode protection to VDD and VSS.
Note: On a Power-on Reset, RA5 and RA<3:0>
are configured as analog inputs and read
as ‘0’. RA4 is configured as a digital input.
CLRF PORTA ; Initialize PORTA by
; clearing output
; data latches
CLRF LATA ; Alternate method
; to clear output
; data latches
MOVLW 0Fh ; Configure all A/D
MOVWF ADCON1 ; for digital inputs
MOVWF 07h ; Configure comparators
MOVWF CMCON ; for digital input
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISA ; Set RA<7:6,3:0> as inputs
; RA<5:4> as outputs
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DS39689F-page 112 © 2009 Microchip Technology Inc.
TABLE 11-1: PORTA I/O SUMMARY
Pin Function TRIS
Setting I/O I/O
Type Description
RA0/AN0 RA0 0O DIG LATA<0> data output; not affected by analog input.
1I TTL PORTA<0> data input; disabled when analog input enabled.
AN0 1I ANA A/D Input Channel 0 and Comparator C1- input. Default input
configuration on POR; does not affect digital output.
RA1/AN1 RA1 0O DIG LATA<1> data output; not affected by analog input.
1I TTL PORTA<1> data input; disabled when analog input enabled.
AN1 1I ANA A/D Input Channel 1 and Comparator C2- input. Default input
configuration on POR; does not affect digital output.
RA2/AN2/
VREF-/CVREF
RA2 0O DIG LATA<2> data output; not affected by analog input. Disabled when
CVREF output enabled.
1I TTL PORTA<2> data input. Disabled when analog functions enabled;
disabled when CVREF output enabled.
AN2 1I ANA A/D Input Channel 2 and Comparator C2+ input. Default input
configuration on POR; not affected by analog output.
VREF-1I ANA A/D and comparator voltage reference low input.
CVREF xO ANA Comparator voltage reference output. Enabling this feature disables
digital I/O.
RA3/AN3/VREF+RA30O DIG LATA<3> data output; not affected by analog input.
1I TTL PORTA<3> data input; disabled when analog input enabled.
AN3 1I ANA A/D Input Channel 3 and Comparator C1+ input. Default input
configuration on POR.
VREF+1I ANA A/D and comparator voltage reference high input.
RA4/T0CKI/C1OUT RA4 0O DIG LATA<4> data output.
1I ST PORTA<4> data input; default configuration on POR.
T0CKI 1I ST Timer0 clock input.
C1OUT 0O DIG Comparator 1 output; takes priority over port data.
RA5/AN4/SS/
HLVDIN/C2OUT
RA5 0O DIG LATA<5> data output; not affected by analog input.
1I TTL PORTA<5> data input; disabled when analog input enabled.
AN4 1I ANA A/D Input Channel 4. Default configuration on POR.
SS 1I TTL Slave Select input for MSSP (MSSP module).
HLVDIN 1I ANA High/Low-Voltage Detect external trip point input.
C2OUT 0O DIG Comparator 2 output; takes priority over port data.
OSC2/CLKO/RA6 RA6 0O DIG LATA<6> data output. Enabled in RCIO, INTIO2 and ECIO modes only.
1I TTL PORTA<6> data input. Enabled in RCIO, INTIO2 and ECIO modes only.
OSC2 xO ANA Main oscillator feedback output connection (XT, HS and LP modes).
CLKO xO DIG System cycle clock output (FOSC/4) in RC, INTIO1 and EC Oscillator
modes.
OSC1/CLKI/RA7 RA7 0O DIG LATA<7> data output. Disabled in external oscillator modes.
1I TTL PORTA<7> data input. Disabled in external oscillator modes.
OSC1 xI ANA Main oscillator input connection.
CLKI xI ANA Main clock input connection.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
© 2009 Microchip Technology Inc. DS39689F-page 113
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TABLE 11-2: SUMMARY OF REGISTERS ASSOCIATED WITH PORTA
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
PORTA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 58
LATA LATA7(1) LATA6(1) PORTA Data Latch Register (Read and Write to Data Latch) 58
TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Register 58
ADCON1 VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57
CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 57
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTA.
Note 1: RA<7:6> and their associated latch and data direction bits are enabled as I/O pins based on oscillator
configuration; otherwise, they are read as0’.
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DS39689F-page 114 © 2009 Microchip Technology Inc.
11.2 PORTB, TRISB and LATB
Registers
PORTB is an 8-bit wide, bidirectional port. The
corresponding Data Direction register is TRISB. Setting
a TRISB bit (= 1) will make the corresponding PORTB
pin an input (i.e., put the corresponding output driver in
a High-Impedance mode). Clearing a TRISB bit (= 0)
will make the corresponding PORTB pin an output (i.e.,
put the contents of the output latch on the selected pin).
The Data Latch register (LATB) is also memory
mapped. Read-modify-write operations on the LATB
register read and write the latched output value for
PORTB.
EXAMPLE 11-2: INITIALIZING PORTB
Each of the PORTB pins has a weak internal pull-up. A
single control bit can turn on all the pull-ups. This is
performed by clearing bit, RBPU (INTCON2<7>). The
weak pull-up is automatically turned off when the port
pin is configured as an output. The pull-ups are
disabled on a Power-on Reset.
Four of the PORTB pins (RB<7:4>) have an interrupt-
on-change feature. Only pins configured as inputs can
cause this interrupt to occur (i.e., any RB<7:4> pin
configured as an output is excluded from the interrupt-
on-change comparison). The input pins (of RB<7:4>)
are compared with the old value latched on the last
read of PORTB. The “mismatch” outputs of RB<7:4>
are ORed together to generate the RB Port Change
Interrupt with Flag bit, RBIF (INTCON<0>).
This interrupt can wake the device from Sleep mode or
any of the Idle modes. The user, in the Interrupt Service
Routine, can clear the interrupt in the following manner:
a) Any read or write of PORTB (except with the
MOVFF (ANY), PORTB instruction).
b) 1 TCY.
c) Clear flag bit, RBIF.
A mismatch condition will continue to set flag bit, RBIF.
Reading PORTB and waiting 1 TCY will end the
mismatch condition and allow flag bit, RBIF, to be
cleared. Also, if the port pin returns to its original state,
the mismatch condition will be cleared.
The interrupt-on-change feature is recommended for
wake-up on key depression operation and operations
where PORTB is only used for the interrupt-on-change
feature. Polling of PORTB is not recommended while
using the interrupt-on-change feature.
RB3 can be configured by the Configuration bit,
CCP2MX, as the alternate peripheral pin for the CCP2
module (CCP2MX = 0).
Note: On a Power-on Reset, RB<4:0> are
configured as analog inputs by default and
read as ‘0’; RB<7:5> are configured as
digital inputs.
By clearing the Configuration bit,
PBADEN, RB<4:0> will alternatively be
configured as digital inputs on POR.
CLRF PORTB ; Initialize PORTB by
; clearing output
; data latches
CLRF LATB ; Alternate method
; to clear output
; data latches
MOVLW 0Fh ; Set RB<4:0> as
MOVWF ADCON1 ; digital I/O pins
; (required if config bit
; PBADEN is set)
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISB ; Set RB<3:0> as inputs
; RB<5:4> as outputs
; RB<7:6> as inputs
© 2009 Microchip Technology Inc. DS39689F-page 115
PIC18F2221/2321/4221/4321 FAMILY
TABLE 11-3: PORTB I/O SUMMARY
Pin Function TRIS
Setting I/O I/O
Type Description
RB0/INT0/FLT0/
AN12
RB0 0O DIG LATB<0> data output; not affected by analog input.
1I TTL PORTB<0> data input; weak pull-up when RBPU bit is cleared.
Disabled when analog input enabled.(1)
INT0 1I ST External Interrupt 0 input.
FLT0 1I ST Enhanced PWM Fault input (ECCP1 module); enabled in software.
AN12 1I ANA A/D Input Channel 12.(1)
RB1/INT1/AN10 RB1 0O DIG LATB<1> data output; not affected by analog input.
1I TTL PORTB<1> data input; weak pull-up when RBPU bit is cleared.
Disabled when analog input enabled.(1)
INT1 1I ST External Interrupt 1 input.
AN10 1I ANA A/D Input Channel 10.(1)
RB2/INT2/AN8 RB2 0O DIG LATB<2> data output; not affected by analog input.
1I TTL PORTB<2> data input; weak pull-up when RBPU bit is cleared.
Disabled when analog input enabled.(1)
INT2 1I ST External Interrupt 2 input.
AN8 1I ANA A/D Input Channel 8.(1)
RB3/AN9/CCP2 RB3 0O DIG LATB<3> data output; not affected by analog input.
1I TTL PORTB<3> data input; weak pull-up when RBPU bit is cleared.
Disabled when analog input enabled.(1)
AN9 1I ANA A/D Input Channel 9.(1)
CCP2(2) 0O DIG CCP2 compare and PWM output.
1I ST CCP2 capture input.
RB4/KBI0/AN11 RB4 0O DIG LATB<4> data output; not affected by analog input.
1I TTL PORTB<4> data input; weak pull-up when RBPU bit is cleared.
Disabled when analog input enabled.(1)
KBI0 1I TTL Interrupt-on-change pin.
AN11 1I ANA A/D Input Channel 11.(1)
RB5/KBI1/PGM RB5 0O DIG LATB<5> data output.
1I TTL PORTB<5> data input; weak pull-up when RBPU bit is cleared.
KBI1 1I TTL Interrupt-on-change pin.
PGM xI ST Single-Supply Programming mode entry (ICSP™). Enabled by LVP
Configuration bit; all other pin functions disabled.
RB6/KBI2/PGC RB6 0O DIG LATB<6> data output.
1I TTL PORTB<6> data input; weak pull-up when RBPU bit is cleared.
KBI2 1I TTL Interrupt-on-change pin.
PGC xI ST Serial execution (ICSP™) clock input for ICSP and ICD operation.(3)
RB7/KBI3/PGD RB7 0O DIG LATB<7> data output.
1I TTL PORTB<7> data input; weak pull-up when RBPU bit is cleared.
KBI3 1I TTL Interrupt-on-change pin.
PGD xO DIG Serial execution data output for ICSP and ICD operation.(3)
xI ST Serial execution data input for ICSP and ICD operation.(3)
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: Configuration on POR is determined by the PBADEN Configuration bit. Pins are configured as analog inputs by default
when PBADEN is set and digital inputs when PBADEN is cleared.
2: Alternate assignment for CCP2 when the CCP2MX Configuration bit is ‘0’. Default assignment is RC1.
3: All other pin functions are disabled when ICSP or ICD are enabled.
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DS39689F-page 116 © 2009 Microchip Technology Inc.
TABLE 11-4: SUMMARY OF REGISTERS ASSOCIATED WITH PORTB
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 58
LATB PORTB Data Latch Register (Read and Write to Data Latch) 58
TRISB PORTB Data Direction Register 58
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 TMR0IP —RBIP55
INTCON3 INT2IP INT1IP —INT2IEINT1IE INT2IF INT1IF 55
ADCON1 VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57
Legend: = unimplemented, read as ‘0’. Shaded cells are not used by PORTB.
© 2009 Microchip Technology Inc. DS39689F-page 117
PIC18F2221/2321/4221/4321 FAMILY
11.3 PORTC, TRISC and LATC
Registers
PORTC is an 8-bit wide, bidirectional port. The
corresponding Data Direction register is TRISC. Set-
ting a TRISC bit (= 1) will make the corresponding
PORTC pin an input (i.e., put the corresponding output
driver in a High-Impedance mode). Clearing a TRISC
bit (= 0) will make the corresponding PORTC pin an
output (i.e., put the contents of the output latch on the
selected pin).
The Data Latch register (LATC) is also memory
mapped. Read-modify-write operations on the LATC
register read and write the latched output value for
PORTC.
PORTC is multiplexed with several peripheral functions
(Table 11-5). The pins have Schmitt Trigger input
buffers. RC1 is normally configured by Configuration
bit, CCP2MX, as the default peripheral pin of the CCP2
module (default/erased state, CCP2MX = 1).
When enabling peripheral functions, care should be
taken in defining TRIS bits for each PORTC pin. Some
peripherals override the TRIS bit to make a pin an output,
while other peripherals override the TRIS bit to make a
pin an input. The user should refer to the corresponding
peripheral section for additional information.
The contents of the TRISC register are affected by
peripheral overrides. Reading TRISC always returns
the current contents, even though a peripheral device
may be overriding one or more of the pins.
EXAMPLE 11-3: INITIALIZING PORTC
Note: On a Power-on Reset, these pins are
configured as digital inputs.
CLRF PORTC ; Initialize PORTC by
; clearing output
; data latches
CLRF LATC ; Alternate method
; to clear output
; data latches
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISC ; Set RC<3:0> as inputs
; RC<5:4> as outputs
; RC<7:6> as inputs
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DS39689F-page 118 © 2009 Microchip Technology Inc.
TABLE 11-5: PORTC I/O SUMMARY
Pin Function TRIS
Setting I/O I/O
Type Description
RC0/T1OSO/
T13CKI
RC0 0O DIG LATC<0> data output.
1I ST PORTC<0> data input.
T1OSO xO ANA Timer1 oscillator output; enabled when Timer1 oscillator enabled.
Disables digital I/O.
T13CKI 1I ST Timer1/Timer3 counter input.
RC1/T1OSI/CCP2 RC1 0O DIG LATC<1> data output.
1I ST PORTC<1> data input.
T1OSI xI ANA Timer1 oscillator input; enabled when Timer1 oscillator enabled.
Disables digital I/O.
CCP2(1) 0O DIG CCP2 compare and PWM output; takes priority over port data.
1I ST CCP2 capture input.
RC2/CCP1/P1A RC2 0O DIG LATC<2> data output.
1I ST PORTC<2> data input.
CCP1 0O DIG CCP1 compare or PWM output; takes priority over port data.
1I ST CCP1 capture input.
P1A(2) 0O DIG ECCP1 Enhanced PWM output, Channel A. May be configured for
tri-state during Enhanced PWM shutdown events. Takes priority over
port data.
RC3/SCK/SCL RC3 0O DIG LATC<3> data output.
1I ST PORTC<3> data input.
SCK 0O DIG SPI clock output (MSSP module); takes priority over port data.
1I ST SPI clock input (MSSP module).
SCL 0ODIGI
2C™ clock output (MSSP module); takes priority over port data.
1II
2C/SMB I2C clock input (MSSP module); input type depends on module setting.
RC4/SDI/SDA RC4 0O DIG LATC<4> data output.
1I ST PORTC<4> data input.
SDI 1I ST SPI data input (MSSP module).
SDA 1ODIGI
2C data output (MSSP module); takes priority over port data.
1II
2C/SMB I2C data input (MSSP module); input type depends on module setting.
RC5/SDO RC5 0O DIG LATC<5> data output.
1I ST PORTC<5> data input.
SDO 0O DIG SPI data output (MSSP module); takes priority over port data.
RC6/TX/CK RC6 0O DIG LATC<6> data output.
1I ST PORTC<6> data input.
TX 1O DIG Asynchronous serial transmit data output (EUSART module);
takes priority over port data. User must configure as output.
CK 1O DIG Synchronous serial clock output (EUSART module); takes priority
over port data.
1I ST Synchronous serial clock input (EUSART module).
RC7/RX/DT RC7 0O DIG LATC<7> data output.
1I ST PORTC<7> data input.
RX 1I ST Asynchronous serial receive data input (EUSART module).
DT 1O DIG Synchronous serial data output (EUSART module); takes priority over
port data.
1I ST Synchronous serial data input (EUSART module). User must
configure as an input.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
I2C/SMB = I2C/SMBus input buffer; x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: Default assignment for CCP2 when the CCP2MX Configuration bit is set. Alternate assignment is RB3.
2: Enhanced PWM output is available only on PIC18F4221/4321 devices.
© 2009 Microchip Technology Inc. DS39689F-page 119
PIC18F2221/2321/4221/4321 FAMILY
TABLE 11-6: SUMMARY OF REGISTERS ASSOCIATED WITH PORTC
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 58
LATC PORTC Data Latch Register (Read and Write to Data Latch) 58
TRISC PORTC Data Direction Register 58
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DS39689F-page 120 © 2009 Microchip Technology Inc.
11.4 PORTD, TRISD and LATD
Registers
PORTD is an 8-bit wide, bidirectional port. The
corresponding Data Direction register is TRISD. Set-
ting a TRISD bit (= 1) will make the corresponding
PORTD pin an input (i.e., put the corresponding output
driver in a High-Impedance mode). Clearing a TRISD
bit (= 0) will make the corresponding PORTD pin an
output (i.e., put the contents of the output latch on the
selected pin).
The Data Latch register (LATD) is also memory
mapped. Read-modify-write operations on the LATD
register read and write the latched output value for
PORTD.
All pins on PORTD are implemented with Schmitt Trigger
input buffers. Each pin is individually configurable as an
input or output.
Three of the PORTD pins are multiplexed with outputs
P1B, P1C and P1D of the Enhanced CCP module. The
operation of these additional PWM output pins is
covered in greater detail in Section 17.0 “Enhanced
Capture/Compare/PWM (ECCP) Module”.
PORTD can also be configured as an 8-bit wide micro-
processor port (Parallel Slave Port) by setting control
bit, PSPMODE (TRISE<4>). In this mode, the input
buffers are TTL. See Section 11.6 “Parallel Slave
Port” for additional information on the Parallel Slave
Port (PSP).
EXAMPLE 11-4: INITIALIZING PORTD
Note: PORTD is only available on 40/44-pin
devices.
Note: On a Power-on Reset, these pins are
configured as digital inputs.
Note: When the Enhanced PWM mode is used
with either dual or quad outputs, the PSP
functions of PORTD are automatically
disabled.
CLRF PORTD ; Initialize PORTD by
; clearing output
; data latches
CLRF LATD ; Alternate method
; to clear output
; data latches
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISD ; Set RD<3:0> as inputs
; RD<5:4> as outputs
; RD<7:6> as inputs
© 2009 Microchip Technology Inc. DS39689F-page 121
PIC18F2221/2321/4221/4321 FAMILY
TABLE 11-7: PORTD I/O SUMMARY
Pin Function TRIS
Setting I/O I/O
Type Description
RD0/PSP0 RD0 0O DIG LATD<0> data output.
1I ST PORTD<0> data input.
PSP0 xO DIG PSP read data output (LATD<0>); takes priority over port data.
xI TTL PSP write data input.
RD1/PSP1 RD1 0O DIG LATD<1> data output.
1I ST PORTD<1> data input.
PSP1 xO DIG PSP read data output (LATD<1>); takes priority over port data.
xI TTL PSP write data input.
RD2/PSP2 RD2 0O DIG LATD<2> data output.
1I ST PORTD<2> data input.
PSP2 xO DIG PSP read data output (LATD<2>); takes priority over port data.
xI TTL PSP write data input.
RD3/PSP3 RD3 0O DIG LATD<3> data output.
1I ST PORTD<3> data input.
PSP3 xO DIG PSP read data output (LATD<3>); takes priority over port data.
xI TTL PSP write data input.
RD4/PSP4 RD4 0O DIG LATD<4> data output.
1I ST PORTD<4> data input.
PSP4 xO DIG PSP read data output (LATD<4>); takes priority over port data.
xI TTL PSP write data input.
RD5/PSP5/P1B RD5 0O DIG LATD<5> data output.
1I ST PORTD<5> data input.
PSP5 xO DIG PSP read data output (LATD<5>); takes priority over port data.
xI TTL PSP write data input.
P1B 0O DIG ECCP1 Enhanced PWM output, Channel B; takes priority over port and
PSP data. May be configured for tri-state during Enhanced PWM
shutdown events.
RD6/PSP6/P1C RD6 0O DIG LATD<6> data output.
1I ST PORTD<6> data input.
PSP6 xO DIG PSP read data output (LATD<6>); takes priority over port data.
xI TTL PSP write data input.
P1C 0O DIG ECCP1 Enhanced PWM output, channel C; takes priority over port and
PSP data. May be configured for tri-state during Enhanced PWM
shutdown events.
RD7/PSP7/P1D RD7 0O DIG LATD<7> data output.
1I ST PORTD<7> data input.
PSP7 xO DIG PSP read data output (LATD<7>); takes priority over port data.
xI TTL PSP write data input.
P1D 0O DIG ECCP1 Enhanced PWM output, Channel D; takes priority over port
and PSP data. May be configured for tri-state during Enhanced PWM
shutdown events.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; x = Don’t care
(TRIS bit does not affect port direction or is overridden for this option).
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DS39689F-page 122 © 2009 Microchip Technology Inc.
TABLE 11-8: SUMMARY OF REGISTERS ASSOCIATED WITH PORTD
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
PORTD RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 58
LATD PORTD Data Latch Register (Read and Write to Data Latch) 58
TRISD PORTD Data Direction Register 58
TRISE IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0 58
CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57
Legend: = unimplemented, read as ‘0’. Shaded cells are not used by PORTD.
© 2009 Microchip Technology Inc. DS39689F-page 123
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11.5 PORTE, TRISE and LATE
Registers
Depending on the particular PIC18F2221/2321/4221/
4321 family device selected, PORTE is implemented in
two different ways.
For 40/44-pin devices, PORTE is a 4-bit wide port.
Three pins (RE0/RD/AN5, RE1/WR/AN6 and RE2/CS/
AN7) are individually configurable as inputs or outputs.
These pins have Schmitt Trigger input buffers. When
selected as analog inputs, these pins will read as ‘0’.
The corresponding Data Direction register is TRISE.
Setting a TRISE bit (= 1) will make the corresponding
PORTE pin an input (i.e., put the corresponding output
driver in a High-Impedance mode). Clearing a TRISE
bit (= 0) will make the corresponding PORTE pin an
output (i.e., put the contents of the output latch on the
selected pin).
TRISE controls the direction of the RE pins, even when
they are being used as analog inputs. The user must
make sure to keep the pins configured as inputs when
using them as analog inputs.
The upper four bits of the TRISE register also control
the operation of the Parallel Slave Port. Their operation
is explained in Register 11-1.
The Data Latch register (LATE) is also memory
mapped. Read-modify-write operations on the LATE
register, read and write the latched output value for
PORTE.
The fourth pin of PORTE (MCLR/VPP/RE3) is an input
only pin. Its operation is controlled by the MCLRE Con-
figuration bit. When selected as a port pin (MCLRE = 0),
it functions as a digital input only pin; as such, it does not
have TRIS or LAT bits associated with its operation.
Otherwise, it functions as the device’s Master Clear
input. In either configuration, RE3 also functions as the
programming voltage input during programming.
EXAMPLE 11-5: INITIALIZING PORTE
11.5.1 PORTE IN 28-PIN DEVICES
For 28-pin devices, PORTE is only available when
Master Clear functionality is disabled (MCLRE = 0). In
these cases, PORTE is a single bit, input only port
comprised of RE3 only. The pin operates as previously
described.
Note: On a Power-on Reset, RE<2:0> are
configured as analog inputs.
Note: On a Power-on Reset, RE3 is enabled as
a digital input only if Master Clear
functionality is disabled.
CLRF PORTE ; Initialize PORTE by
; clearing output
; data latches
CLRF LATE ; Alternate method
; to clear output
; data latches
MOVLW 0Fh ; Configure A/D
MOVWF ADCON1 ; for digital inputs
MOVLW 03h ; Value used to
; initialize data
; direction
MOVWF TRISE ; Set RE<0> as inputs
; RE<1> as outputs
; RE<2> as inputs
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DS39689F-page 124 © 2009 Microchip Technology Inc.
REGISTER 11-1: TRISE REGISTER (40/44-PIN DEVICES ONLY)
R-0 R-0 R/W-0 R/W-0 U-0 R/W-1 R/W-1 R/W-1
IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0
bit 7 bit 0
bit 7 IBF: Input Buffer Full Status bit
1 = A word has been received and waiting to be read by the CPU
0 = No word has been received
bit 6 OBF: Output Buffer Full Status bit
1 = The output buffer still holds a previously written word
0 = The output buffer has been read
bit 5 IBOV: Input Buffer Overflow Detect bit (in Microprocessor mode)
1 = A write occurred when a previously input word has not been read (must be cleared in software)
0 = No overflow occurred
bit 4 PSPMODE: Parallel Slave Port Mode Select bit
1 = Parallel Slave Port mode
0 = General Purpose I/O mode
bit 3 Unimplemented: Read as0
bit 2 TRISE2: RE2 Direction Control bit
1 = Input
0 = Output
bit 1 TRISE1: RE1 Direction Control bit
1 = Input
0 = Output
bit 0 TRISE0: RE0 Direction Control bit
1 = Input
0 = Output
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 125
PIC18F2221/2321/4221/4321 FAMILY
TABLE 11-9: PORTE I/O SUMMARY
TABLE 11-10: SUMMARY OF REGISTERS ASSOCIATED WITH PORTE
Pin Function TRIS
Setting I/O I/O
Type Description
RE0/RD/AN5 RE0 0O DIG LATE<0> data output; not affected by analog input.
1I ST PORTE<0> data input; disabled when analog input enabled.
RD 1I TTL PSP read enable input (PSP enabled).
AN5 1I ANA A/D Input Channel 5; default input configuration on POR.
RE1/WR/AN6 RE1 0O DIG LATE<1> data output; not affected by analog input.
1I ST PORTE<1> data input; disabled when analog input enabled.
WR 1I TTL PSP write enable input (PSP enabled).
AN6 1I ANA A/D Input Channel 6; default input configuration on POR.
RE2/CS/AN7 RE2 0O DIG LATE<2> data output; not affected by analog input.
1I ST PORTE<2> data input; disabled when analog input enabled.
CS 1I TTL PSP write enable input (PSP enabled).
AN7 1I ANA A/D Input Channel 7; default input configuration on POR.
MCLR/VPP/RE3(1) MCLR I ST External Master Clear input; enabled when MCLRE Configuration bit
is set.
VPP I ANA High-voltage detection; used for ICSP™ mode entry detection. Always
available, regardless of pin mode.
RE3 (2) I ST PORTE<3> data input; enabled when MCLRE Configuration bit is
clear.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: RE3 is available on both 28-pin and 40/44-pin devices. All other PORTE pins are only implemented on 40/44-pin devices.
2: RE3 does not have a corresponding TRIS bit to control data direction.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
PORTE —RE3
(1,2) RE2 RE1 RE0 58
LATE(2) PORTE Data Latch Register
(Read and Write to Data Latch)
58
TRISE IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0 58
ADCON1 VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTE.
Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0).
2: RE3 is the only PORTE bit implemented on both 28-pin and 40/44-pin devices. All other bits are
implemented only when PORTE is implemented (i.e., 40/44-pin devices).
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DS39689F-page 126 © 2009 Microchip Technology Inc.
11.6 Parallel Slave Port
In addition to its function as a general I/O port, PORTD
can also operate as an 8-bit wide Parallel Slave Port
(PSP) or microprocessor port. PSP operation is
controlled by the 4 upper bits of the TRISE register
(Register 11-1). Setting control bit, PSPMODE
(TRISE<4>), enables PSP operation as long as the
Enhanced CCP module is not operating in Dual Output
or Quad Output PWM mode. In Slave mode, the port is
asynchronously readable and writable by the external
world.
The PSP can directly interface to an 8-bit micro-
processor data bus. The external microprocessor can
read or write the PORTD latch as an 8-bit latch. Setting
the control bit, PSPMODE, enables the PORTE I/O
pins to become control inputs for the microprocessor
port. When set, port pin RE0 is the RD input, RE1 is the
WR input and RE2 is the CS (Chip Select) input. For
this functionality, the corresponding data direction bits
of the TRISE register (TRISE<2:0>) must be config-
ured as inputs (set). The A/D port configuration bits,
PFCG<3:0> (ADCON1<3:0>), must also be set to a
value in the range of1010’ through ‘1111’.
A write to the PSP occurs when both the CS and WR
lines are first detected low and ends when either are
detected high. The PSPIF and IBF flag bits are both set
when the write ends.
A read from the PSP occurs when both the CS and RD
lines are first detected low. The data in PORTD is read
out and the OBF bit is clear. If the user writes new data
to PORTD to set OBF, the data is immediately read out;
however, the OBF bit is not set.
When either the CS or RD lines are detected high, the
PORTD pins return to the input state and the PSPIF bit
is set. User applications should wait for PSPIF to be set
before servicing the PSP. When this happens, the IBF
and OBF bits can be polled and the appropriate action
taken.
The timing for the control signals in Write and Read
modes is shown in Figure 11-3 and Figure 11-4,
respectively.
FIGURE 11-2: PORTD AND PORTE
BLOCK DIAGRAM
(PARALLEL SLAVE PORT)
Note: The Parallel Slave Port is only available on
40/44-pin devices.
Data Bus
WR LATD RDx pin
QD
CK
EN
QD
EN
RD PORTD
One bit of PORTD
Set Interrupt Flag
PSPIF (PIR1<7>)
Read
Chip Select
Write
RD
CS
WR
TTL
TTL
TTL
TTL
or
WR PORTD
RD LATD
Data Latch
Note: I/O pins have diode protection to VDD and VSS.
PORTE Pins
© 2009 Microchip Technology Inc. DS39689F-page 127
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 11-3: PARALLEL SLAVE PORT WRITE WAVEFORMS
FIGURE 11-4: PARALLEL SLAVE PORT READ WAVEFORMS
TABLE 11-11: REGISTERS ASSOCIATED WITH PARALLEL SLAVE PORT
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values on
page
PORTD RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 58
LATD PORTD Data Latch Register (Read and Write to Data Latch) 58
TRISD PORTD Data Direction Register 58
PORTE RE3 RE2 RE1 RE0 58
LATE PORTE Data Latch Register
(Read and Write to Data Latch)
58
TRISE IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0 58
INTCON GIE/GIEH PEIE/GIEL TMR0IF INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
ADCON1 VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Parallel Slave Port.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
Q1 Q2 Q3 Q4
CS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
WR
RD
IBF
OBF
PSPIF
PORTD<7:0>
Q1 Q2 Q3 Q4
CS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
WR
IBF
PSPIF
RD
OBF
PORTD<7:0>
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DS39689F-page 128 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 129
PIC18F2221/2321/4221/4321 FAMILY
12.0 TIMER0 MODULE
The Timer0 module incorporates the following features:
Software selectable operation as a timer or coun-
ter in both 8-bit or 16-bit modes
Readable and writable registers
Dedicated 8-bit, software programmable
prescaler
Selectable clock source (internal or external)
Edge select for external clock
Interrupt-on-overflow
The T0CON register (Register 12-1) controls all
aspects of the module’s operation, including the
prescale selection. It is both readable and writable.
A simplified block diagram of the Timer0 module in 8-bit
mode is shown in Figure 12-1. Figure 12-2 shows a
simplified block diagram of the Timer0 module in 16-bit
mode.
REGISTER 12-1: T0CON: TIMER0 CONTROL REGISTER
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0
bit 7 bit 0
bit 7 TMR0ON: Timer0 On/Off Control bit
1 = Enables Timer0
0 = Stops Timer0
bit 6 T08BIT: Timer0 8-Bit/16-Bit Control bit
1 = Timer0 is configured as an 8-bit timer/counter
0 = Timer0 is configured as a 16-bit timer/counter
bit 5 T0CS: Timer0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKO)
bit 4 T0SE: Timer0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
bit 3 PSA: Timer0 Prescaler Assignment bit
1 = TImer0 prescaler is NOT assigned. Timer0 clock input bypasses prescaler.
0 = Timer0 prescaler is assigned. Timer0 clock input comes from prescaler output.
bit 2-0 T0PS<2:0>: Timer0 Prescaler Select bits
111 = 1:256 Prescale value
110 = 1:128 Prescale value
101 = 1:64 Prescale value
100 = 1:32 Prescale value
011 = 1:16 Prescale value
010 = 1:8 Prescale value
001 = 1:4 Prescale value
000 = 1:2 Prescale value
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 130 © 2009 Microchip Technology Inc.
12.1 Timer0 Operation
Timer0 can operate as either a timer or a counter; the
mode is selected with the T0CS bit (T0CON<5>). In
Timer mode (T0CS = 0), the module increments on
every clock by default unless a different prescaler value
is selected (see Section 12.3 “Prescaler”). If the
TMR0 register is written to, the increment is inhibited
for the following two instruction cycles. The user can
work around this by writing an adjusted value to the
TMR0 register.
The Counter mode is selected by setting the T0CS bit
(= 1). In this mode, Timer0 increments either on every
rising or falling edge of pin RA4/T0CKI. The increment-
ing edge is determined by the Timer0 Source Edge
Select bit, T0SE (T0CON<4>); clearing this bit selects
the rising edge. Restrictions on the external clock input
are discussed below.
An external clock source can be used to drive Timer0;
however, it must meet certain requirements to ensure
that the external clock can be synchronized with the
internal phase clock (T
OSC). There is a delay between
synchronization and the onset of incrementing the
timer/counter.
12.2 Timer0 Reads and Writes in
16-Bit Mode
TMR0H is not the actual high byte of Timer0 in 16-bit
mode; it is actually a buffered version of the real high
byte of Timer0 which is not directly readable nor
writable (refer to Figure 12-2). TMR0H is updated with
the contents of the high byte of Timer0 during a read of
TMR0L. This provides the ability to read all 16 bits of
Timer0 without having to verify that the read of the high
and low byte were valid, due to a rollover between
successive reads of the high and low byte.
Similarly, a write to the high byte of Timer0 must also
take place through the TMR0H Buffer register. The high
byte is updated with the contents of TMR0H when a
write occurs to TMR0L. This allows all 16 bits of Timer0
to be updated at once.
FIGURE 12-1: TIMER0 BLOCK DIAGRAM (8-BIT MODE)
FIGURE 12-2: TIMER0 BLOCK DIAGRAM (16-BIT MODE)
Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI max. prescale.
T0CKI pin
T0SE
0
1
1
0
T0CS
FOSC/4
Programmable
Prescaler
Sync with
Internal
Clocks
TMR0L
(2 TOSC Delay)
Internal Data Bus
PSA
T0PS<2:0>
Set
TMR0IF
on Overflow
38
8
Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI max. prescale.
T0CKI pin
T0SE
0
1
1
0
T0CS
FOSC/4
Programmable
Prescaler
Sync with
Internal
Clocks TMR0L
(2 TOSC Delay)
Internal Data Bus
8
PSA
T0PS<2:0>
Set
TMR0IF
on Overflow
3
TMR0
TMR0H
High Byte
88
8
Read TMR0L
Write TMR0L
8
© 2009 Microchip Technology Inc. DS39689F-page 131
PIC18F2221/2321/4221/4321 FAMILY
12.3 Prescaler
An 8-bit counter is available as a prescaler for the Timer0
module. The prescaler is not directly readable or writable;
its value is set by the PSA and T0PS<2:0> bits
(T0CON<3:0>) which determine the prescaler
assignment and prescale ratio.
Clearing the PSA bit assigns the prescaler to the
Timer0 module. When it is assigned, prescale values
from 1:2 through 1:256 in power-of-2 increments are
selectable.
When assigned to the Timer0 module, all instructions
writing to the TMR0 register (e.g., CLRF TMR0, MOVWF
TMR0, BSF TMR0, etc.) clear the prescaler count.
12.3.1 SWITCHING PRESCALER
ASSIGNMENT
The prescaler assignment is fully under software
control and can be changed “on-the-fly” during program
execution.
12.4 Timer0 Interrupt
The TMR0 interrupt is generated when the TMR0
register overflows from FFh to 00h in 8-bit mode, or
from FFFFh to 0000h in 16-bit mode. This overflow sets
the TMR0IF flag bit. The interrupt can be masked by
clearing the TMR0IE bit (INTCON<5>). Before re-
enabling the interrupt, the TMR0IF bit must be cleared
in software by the Interrupt Service Routine.
Since Timer0 is shut down in Sleep mode, the TMR0
interrupt cannot awaken the processor from Sleep.
TABLE 12-1: REGISTERS ASSOCIATED WITH TIMER0
Note: Writing to TMR0 when the prescaler is
assigned to Timer0 will clear the prescaler
count but will not change the prescaler
assignment.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
TMR0L Timer0 Register Low Byte 56
TMR0H Timer0 Register High Byte 56
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 56
TRISA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 58
Legend: Shaded cells are not used by Timer0.
Note 1: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.
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DS39689F-page 132 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 133
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13.0 TIMER1 MODULE
The Timer1 timer/counter module incorporates these
features:
Software selectable operation as a 16-bit timer or
counter
Readable and writable 8-bit registers (TMR1H
and TMR1L)
Selectable clock source (internal or external) with
device clock or Timer1 oscillator internal options
Interrupt-on-overflow
Reset on CCP Special Event Trigger
Device clock status flag (T1RUN)
A simplified block diagram of the Timer1 module is
shown in Figure 13-1. A block diagram of the module’s
operation in Read/Write mode is shown in Figure 13-2.
The module incorporates its own low-power oscillator
to provide an additional clocking option. The Timer1
oscillator can also be used as a low-power clock source
for the microcontroller in power-managed operation.
Timer1 can also be used to provide Real-Time Clock
(RTC) functionality to applications with only a minimal
addition of external components and code overhead.
Timer1 is controlled through the T1CON Control
register (Register 13-1). It also contains the Timer1
Oscillator Enable bit (T1OSCEN). Timer1 can be
enabled or disabled by setting or clearing control bit,
TMR1ON (T1CON<0>).
REGISTER 13-1: T1CON: TIMER1 CONTROL REGISTER
R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit 7 bit 0
bit 7 RD16: 16-Bit Read/Write Mode Enable bit
1 = Enables register read/write of TImer1 in one 16-bit operation
0 = Enables register read/write of Timer1 in two 8-bit operations
bit 6 T1RUN: Timer1 System Clock Status bit
1 = Device clock is derived from Timer1 oscillator
0 = Device clock is derived from another source
bit 5-4 T1CKPS<1:0>: Timer1 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value
bit 3 T1OSCEN: Timer1 Oscillator Enable bit
1 = Timer1 oscillator is enabled
0 = Timer1 oscillator is shut off
The oscillator inverter and feedback resistor are turned off to eliminate power drain.
bit 2 T1SYNC: Timer1 External Clock Input Synchronization Select bit
When TMR1CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
bit 1 TMR1CS: Timer1 Clock Source Select bit
1 = External clock from pin RC0/T1OSO/T13CKI (on the rising edge)
0 = Internal clock (FOSC/4)
bit 0 TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 134 © 2009 Microchip Technology Inc.
13.1 Timer1 Operation
Timer1 can operate in one of these modes:
•Timer
Synchronous Counter
Asynchronous Counter
The operating mode is determined by the clock select
bit, TMR1CS (T1CON<1>). When TMR1CS is cleared
(= 0), Timer1 increments on every internal instruction
cycle (Fosc/4). When the bit is set, Timer1 increments
on every rising edge of the Timer1 external clock input
or the Timer1 oscillator, if enabled.
When Timer1 is enabled, the RC1/T1OSI and RC0/
T1OSO/T13CKI pins become inputs. This means the
values of TRISC<1:0> are ignored and the pins are
read as 0’.
FIGURE 13-1: TIMER1 BLOCK DIAGRAM
FIGURE 13-2: TIMER1 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)
T1SYNC
TMR1CS
T1CKPS<1:0>
Peripheral Clock
T1OSCEN(1)
FOSC/4
Internal
Clock
On/Off
Prescaler
1, 2, 4, 8
Synchronize
Detect
1
0
2
T1OSO/T13CKI
T1OSI
1
0
TMR1ON
TMR1L Set
TMR1IF
on Overflow
TMR1
High Byte
Clear TMR1
(CCP Special Event Trigger)
Timer1 Oscillator
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
On/Off
Timer1
Timer1 Clock Input
T1SYNC
TMR1CS
T1CKPS<1:0>
Peripheral Clock
T1OSCEN(1)
FOSC/4
Internal
Clock
Prescaler
1, 2, 4, 8
Synchronize
Detect
1
0
2
T1OSO/T13CKI
T1OSI
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
1
0
TMR1L
Internal Data Bus
8
Set
TMR1IF
on Overflow
TMR1
TMR1H
High Byte
88
8
Read TMR1L
Write TMR1L
8
TMR1ON
Clear TMR1
(CCP Special Event Trigger)
Timer1 Oscillator
On/Off
Timer1
Timer1 Clock Input
© 2009 Microchip Technology Inc. DS39689F-page 135
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13.2 Timer1 16-Bit Read/Write Mode
Timer1 can be configured for 16-bit reads and writes
(see Figure 13-2). When the RD16 control bit
(T1CON<7>) is set, the address for TMR1H is mapped
to a buffer register for the high byte of Timer1. A read
from TMR1L will load the contents of the high byte of
Timer1 into the Timer1 high byte buffer. This provides
the user with the ability to accurately read all 16 bits of
Timer1 without having to determine whether a read of
the high byte, followed by a read of the low byte, has
become invalid due to a rollover between reads.
A write to the high byte of Timer1 must also take place
through the TMR1H Buffer register. The Timer1 high
byte is updated with the contents of TMR1H when a
write occurs to TMR1L. This allows a user to write all
16 bits to both the high and low bytes of Timer1 at once.
The high byte of Timer1 is not directly readable or
writable in this mode. All reads and writes must take
place through the Timer1 High Byte Buffer register.
Writes to TMR1H do not clear the Timer1 prescaler.
The prescaler is only cleared on writes to TMR1L.
13.3 Timer1 Oscillator
An on-chip crystal oscillator circuit is incorporated
between pins T1OSI (input) and T1OSO (amplifier
output). It is enabled by setting the Timer1 Oscillator
Enable bit, T1OSCEN (T1CON<3>). The oscillator is a
low-power circuit rated for 32 kHz crystals. It will
continue to run during all power-managed modes. The
circuit for a typical LP oscillator is shown in Figure 13-3.
Table 13-1 shows the capacitor selection for the Timer1
oscillator.
The user must provide a software time delay to ensure
proper start-up of the Timer1 oscillator.
FIGURE 13-3: EXTERNAL COMPONENTS
FOR THE TIMER1
LP OSCILLATOR
TABLE 13-1: CAPACITOR SELECTION FOR
THE TIMER OSCILLATOR
13.3.1 USING TIMER1 AS A
CLOCK SOURCE
The Timer1 oscillator is also available as a clock source
in power-managed modes. By setting the clock select
bits, SCS<1:0> (OSCCON<1:0>), to ‘01’, the device
switches to SEC_RUN mode; both the CPU and
peripherals are clocked from the Timer1 oscillator. If the
IDLEN bit (OSCCON<7>) is cleared and a SLEEP
instruction is executed, the device enters SEC_IDLE
mode. Additional details are available in Section 4.0
“Power-Managed Modes”.
Whenever the Timer1 oscillator is providing the clock
source, the Timer1 system clock status flag, T1RUN
(T1CON<6>), is set. This can be used to determine the
controller’s current clocking mode. It can also indicate
the clock source being currently used by the Fail-Safe
Clock Monitor. If the Clock Monitor is enabled and the
Timer1 oscillator fails while providing the clock, polling
the T1RUN bit will indicate whether the clock is being
provided by the Timer1 oscillator or another source.
13.3.2 LOW-POWER TIMER1 OPTION
The Timer1 oscillator can operate at two distinct levels
of power consumption based on device configuration.
When the LPT1OSC Configuration bit is set, the Timer1
oscillator operates in a low-power mode. When
LPT1OSC is not set, Timer1 operates at a higher power
level. Power consumption for a particular mode is
relatively constant, regardless of the device’s operating
mode. The default Timer1 configuration is the higher
power mode.
As the low-power Timer1 mode tends to be more
sensitive to interference, high noise environments may
cause some oscillator instability. The low-power option is,
therefore, best suited for low noise applications where
power conservation is an important design consideration.
Note: See the Notes with Table 13-1 for additional
information about capacitor selection.
C1
C2
XTAL
PIC18FXXXX
T1OSI
T1OSO
32.768 kHz
27 pF
27 pF
Osc Type Freq C1 C2
LP 32 kHz 27 pF(1) 27 pF(1)
Note 1: Microchip suggests these values as a
starting point in validating the oscillator
circuit.
2: Higher capacitance increases the stability
of the oscillator but also increases the
start-up time.
3: Since each resonator/crystal has its own
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate values of external
components.
4: Capacitor values are for design guidance
only.
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DS39689F-page 136 © 2009 Microchip Technology Inc.
13.3.3 TIMER1 OSCILLATOR LAYOUT
CONSIDERATIONS
The Timer1 oscillator circuit draws very little power
during operation. Due to the low-power nature of the
oscillator, it may also be sensitive to rapidly changing
signals in close proximity.
The oscillator circuit, shown in Figure 13-3, should be
located as close as possible to the microcontroller.
There should be no circuits passing within the oscillator
circuit boundaries other than VSS or VDD.
If a high-speed circuit must be located near the
oscillator (such as the CCP1 pin in Output Compare or
PWM mode, or the primary oscillator using the OSC2
pin), a grounded guard ring around the oscillator circuit,
as shown in Figure 13-4, may be helpful when used on
a single-sided PCB or in addition to a ground plane.
FIGURE 13-4: OSCILLATOR CIRCUIT
WITH GROUNDED
GUARD RING
13.4 Timer1 Interrupt
The TMR1 register pair (TMR1H:TMR1L) increments
from 0000h to FFFFh and rolls over to 0000h. The
Timer1 interrupt, if enabled, is generated on overflow
which is latched in interrupt flag bit, TMR1IF
(PIR1<0>). This interrupt can be enabled or disabled
by setting or clearing the Timer1 Interrupt Enable bit,
TMR1IE (PIE1<0>).
13.5 Resetting Timer1 Using the CCP
Special Event Trigger
If either of the CCP modules is configured to use
Timer1 and generate a Special Event Trigger in Com-
pare mode (CCP1M<3:0> or CCP2M<3:0> = 1011),
this signal will reset Timer1. The trigger from CCP2 will
also start an A/D conversion if the A/D module is
enabled (see Section 16.3.4 “Special Event Trigger”
for more information).
The module must be configured as either a timer or a
synchronous counter to take advantage of this feature.
When used this way, the CCPRH:CCPRL register pair
effectively becomes a period register for Timer1.
If Timer1 is running in Asynchronous Counter mode,
this Reset operation may not work.
In the event that a write to Timer1 coincides with a
Special Event Trigger, the write operation will take
precedence.
13.6 Using Timer1 as a Real-Time Clock
Adding an external LP oscillator to Timer1 (such as the
one described in Section 13.3 “Timer1 Oscillator”)
gives users the option to include RTC functionality to
their applications. This is accomplished with an
inexpensive watch crystal to provide an accurate time
base and several lines of application code to calculate
the time. When operating in Sleep mode and using a
battery or supercapacitor as a power source, it can
completely eliminate the need for a separate RTC
device and battery backup.
The application code routine, RTCisr, shown in
Example 13-1, demonstrates a simple method to
increment a counter at one-second intervals using an
Interrupt Service Routine. Incrementing the TMR1
register pair to overflow, triggers the interrupt and calls
the routine, which increments the seconds counter by
one. Additional counters for minutes and hours are
incremented as the previous counter overflow.
Since the register pair is 16 bits wide, counting up to
overflow the register directly from a 32.768 kHz clock
would take 2 seconds. To force the overflow at the
required one-second intervals, it is necessary to
preload it. The simplest method is to set the MSb of
TMR1H with a BSF instruction. Note that the TMR1L
register is never preloaded or altered. Doing so may
introduce cumulative errors over many cycles.
For this method to be accurate, Timer1 must operate in
Asynchronous mode and the Timer1 overflow interrupt
must be enabled (PIE1<0> = 1), as shown in the
routine, RTCinit. The Timer1 oscillator must also be
enabled and running at all times.
VDD
OSC1
VSS
OSC2
RC0
RC1
RC2
Note: Not drawn to scale.
Note: The Special Event Triggers from the
CCP2 module will not set the TMR1IF
interrupt flag bit (PIR1<0>).
© 2009 Microchip Technology Inc. DS39689F-page 137
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EXAMPLE 13-1: IMPLEMENTING A REAL-TIME CLOCK USING A TIMER1 INTERRUPT SERVICE
TABLE 13-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER
RTCinit
MOVLW 80h ; Preload TMR1 register pair
MOVWF TMR1H ; for 1 second overflow
CLRF TMR1L
MOVLW b'00001111' ; Configure for external clock,
MOVWF T1CON ; Asynchronous operation, external oscillator
CLRF secs ; Initialize timekeeping registers
CLRF mins ;
MOVLW .12
MOVWF hours
BSF PIE1, TMR1IE ; Enable Timer1 interrupt
RETURN
RTCisr
BSF TMR1H, 7 ; Preload for 1 sec overflow
BCF PIR1, TMR1IF ; Clear interrupt flag
INCF secs, F ; Increment seconds
MOVLW .59 ; 60 seconds elapsed?
CPFSGT secs
RETURN ; No, done
CLRF secs ; Clear seconds
INCF mins, F ; Increment minutes
MOVLW .59 ; 60 minutes elapsed?
CPFSGT mins
RETURN ; No, done
CLRF mins ; clear minutes
INCF hours, F ; Increment hours
MOVLW .23 ; 24 hours elapsed?
CPFSGT hours
RETURN ; No, done
CLRF hours ; Reset hours
RETURN ; Done
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
TMR1L Timer1 Register Low Byte 56
TMR1H Timer1 Register High Byte 56
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56
Legend: Shaded cells are not used by the Timer1 module.
Note 1: These bits are unimplemented on 28-pin devices and read as0’.
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DS39689F-page 138 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 139
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14.0 TIMER2 MODULE
The Timer2 timer module incorporates the following
features:
8-bit timer and period registers (TMR2 and PR2,
respectively)
Readable and writable (both registers)
Software programmable prescaler (1:1, 1:4 and
1:16)
Software programmable postscaler (1:1 through
1:16)
Interrupt on TMR2 to PR2 match
Optional use as the shift clock for the MSSP
module
The module is controlled through the T2CON register
(Register 14-1), which enables or disables the timer
and configures the prescaler and postscaler. Timer2
can be shut off by clearing control bit, TMR2ON
(T2CON<2>), to minimize power consumption.
A simplified block diagram of the module is shown in
Figure 14-1.
14.1 Timer2 Operation
In normal operation, TMR2 is incremented from 00h on
each clock (FOSC/4). A 4-bit counter/prescaler on the
clock input gives direct input, divide-by-4 and divide-by-
16 prescale options. These are selected by the prescaler
control bits, T2CKPS<1:0> (T2CON<1:0>). The value of
TMR2 is compared to that of the Period register, PR2, on
each clock cycle. When the two values match, the com-
parator generates a match signal as the timer output.
This signal also resets the value of TMR2 to 00h on the
next cycle and drives the output counter/postscaler (see
Section 14.2 “Timer2 Interrupt”).
The TMR2 and PR2 registers are both directly readable
and writable. The TMR2 register is cleared on any
device Reset, while the PR2 register initializes at FFh.
Both the prescaler and postscaler counters are cleared
on the following events:
a write to the TMR2 register
a write to the T2CON register
any device Reset (Power-on Reset, MCLR Reset,
Watchdog Timer Reset or Brown-out Reset)
TMR2 is not cleared when T2CON is written.
REGISTER 14-1: T2CON: TIMER2 CONTROL REGISTER
U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit 7 bit 0
bit 7 Unimplemented: Read as ‘0
bit 6-3 T2OUTPS<3:0>: Timer2 Output Postscale Select bits
0000 = 1:1 Postscale
0001 = 1:2 Postscale
1111 = 1:16 Postscale
bit 2 TMR2ON: Timer2 On bit
1 = Timer2 is on
0 = Timer2 is off
bit 1-0 T2CKPS<1:0>: Timer2 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 140 © 2009 Microchip Technology Inc.
14.2 Timer2 Interrupt
Timer2 can also generate an optional device interrupt.
The Timer2 output signal (TMR2 to PR2 match)
provides the input for the 4-bit output counter/post-
scaler. This counter generates the TMR2 match inter-
rupt flag which is latched in TMR2IF (PIR1<1>). The
interrupt is enabled by setting the TMR2 Match Inter-
rupt Enable bit, TMR2IE (PIE1<1>).
A range of 16 postscale options (from 1:1 through 1:16
inclusive) can be selected with the postscaler control
bits, T2OUTPS<3:0> (T2CON<6:3>).
14.3 Timer2 Output
The unscaled output of TMR2 is available primarily to
the CCP modules, where it is used as a time base for
operations in PWM mode.
Timer2 can be optionally used as the shift clock source
for the MSSP module operating in SPI mode.
Additional information is provided in Section 18.0
“Master Synchronous Serial Port (MSSP) Module”.
FIGURE 14-1: TIMER2 BLOCK DIAGRAM
TABLE 14-1: REGISTERS ASSOCIATED WITH TIMER2 AS A TIMER/COUNTER
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
TMR2 Timer2 Register 56
T2CON T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 56
PR2 Timer2 Period Register 56
Legend: = unimplemented, read as ‘0’. Shaded cells are not used by the Timer2 module.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
Comparator
TMR2 Output
TMR2
Postscaler
Prescaler PR2
2
FOSC/4
1:1 to 1:16
1:1, 1:4, 1:16
4
T2OUTPS<3:0>
T2CKPS<1:0>
Set TMR2IF
Internal Data Bus
8
Reset
TMR2/PR2
8
8
(to PWM or MSSP)
Match
© 2009 Microchip Technology Inc. DS39689F-page 141
PIC18F2221/2321/4221/4321 FAMILY
15.0 TIMER3 MODULE
The Timer3 timer/counter module incorporates these
features:
Software selectable operation as a 16-bit timer or
counter
Readable and writable 8-bit registers (TMR3H
and TMR3L)
Selectable clock source (internal or external) with
device clock or Timer1 oscillator internal options
Interrupt-on-overflow
Module Reset on CCP Special Event Trigger
A simplified block diagram of the Timer3 module is
shown in Figure 15-1. A block diagram of the module’s
operation in Read/Write mode is shown in Figure 15-2.
The Timer3 module is controlled through the T3CON
register (Register 15-1). It also selects the clock source
options for the CCP modules (see Section 16.1.1
“CCP Modules and Timer Resources” for more
information).
REGISTER 15-1: T3CON: TIMER3 CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON
bit 7 bit 0
bit 7 RD16: 16-Bit Read/Write Mode Enable bit
1 = Enables register read/write of Timer3 in one 16-bit operation
0 = Enables register read/write of Timer3 in two 8-bit operations
bit 6,3 T3CCP<2:1>: Timer3 and Timer1 to CCPx Enable bits
1x = Timer3 is the capture/compare clock source for the CCP modules
01 = Timer3 is the capture/compare clock source for CCP2; Timer1 is the capture/compare
clock source for CCP1
00 = Timer1 is the capture/compare clock source for the CCP modules
bit 5-4 T3CKPS<1:0>: Timer3 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value
bit 2 T3SYNC: Timer3 External Clock Input Synchronization Control bit
(Not usable if the device clock comes from Timer1/Timer3.)
When TMR3CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR3CS = 0:
This bit is ignored. Timer3 uses the internal clock when TMR3CS = 0.
bit 1 TMR3CS: Timer3 Clock Source Select bit
1 = External clock input from Timer1 oscillator or T13CKI (on the rising edge after the first
falling edge)
0 = Internal clock (FOSC/4)
bit 0 TMR3ON: Timer3 On bit
1 = Enables Timer3
0 = Stops Timer3
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 142 © 2009 Microchip Technology Inc.
15.1 Timer3 Operation
Timer3 can operate in one of three modes:
•Timer
Synchronous Counter
Asynchronous Counter
The operating mode is determined by the clock select
bit, TMR3CS (T3CON<1>). When TMR3CS is cleared
(= 0), Timer3 increments on every internal instruction
cycle (FOSC/4). When the bit is set, Timer3 increments
on every rising edge of the Timer1 external clock input
or the Timer1 oscillator, if enabled.
As with Timer1, the RC1/T1OSI and RC0/T1OSO/
T13CKI pins become inputs when the Timer1 oscillator
is enabled. This means the values of TRISC<1:0> are
ignored and the pins are read as ‘0’.
FIGURE 15-1: TIMER3 BLOCK DIAGRAM (8-BIT READ/WRITE MODE)
FIGURE 15-2: TIMER3 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)
T3SYNC
TMR3CS
T3CKPS<1:0>
Sleep Input
T1OSCEN(1)
FOSC/4
Internal
Clock
Prescaler
1, 2, 4, 8
Synchronize
Detect
1
0
2
T1OSO/T13CKI
T1OSI
1
0
TMR3ON
TMR3L Set
TMR3IF
on Overflow
TMR3
High Byte
Timer1 Oscillator
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
On/Off
Timer3
CCP1/CCP2 Special Event Trigger
CCP1/CCP2 Select from T3CON<6,3>
Clear TMR3
Timer1 Clock Input
T3SYNC
TMR3CS
T3CKPS<1:0>
Sleep Input
T1OSCEN(1)
FOSC/4
Internal
Clock
Prescaler
1, 2, 4, 8
Synchronize
Detect
1
0
2
T13CKI/T1OSO
T1OSI
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
1
0
TMR3L
Internal Data Bus
8
Set
TMR3IF
on Overflow
TMR3
TMR3H
High Byte
88
8
Read TMR1L
Write TMR1L
8
TMR3ON
CCP1/CCP2 Special Event Trigger
Timer1 Oscillator
On/Off
Timer3
Timer1 Clock Input
CCP1/CCP2 Select from T3CON<6,3>
Clear TMR3
© 2009 Microchip Technology Inc. DS39689F-page 143
PIC18F2221/2321/4221/4321 FAMILY
15.2 Timer3 16-Bit Read/Write Mode
Timer3 can be configured for 16-bit reads and writes
(see Figure 15-2). When the RD16 control bit
(T3CON<7>) is set, the address for TMR3H is mapped
to a buffer register for the high byte of Timer3. A read
from TMR3L will load the contents of the high byte of
Timer3 into the Timer3 High Byte Buffer register. This
provides the user with the ability to accurately read all
16 bits of Timer1 without having to determine whether
a read of the high byte, followed by a read of the low
byte, has become invalid due to a rollover between
reads.
A write to the high byte of Timer3 must also take place
through the TMR3H Buffer register. The Timer3 high
byte is updated with the contents of TMR3H when a
write occurs to TMR3L. This allows a user to write all
16 bits to both the high and low bytes of Timer3 at once.
The high byte of Timer3 is not directly readable or
writable in this mode. All reads and writes must take
place through the Timer3 High Byte Buffer register.
Writes to TMR3H do not clear the Timer3 prescaler.
The prescaler is only cleared on writes to TMR3L.
15.3 Using the Timer1 Oscillator as the
Timer3 Clock Source
The Timer1 internal oscillator may be used as the clock
source for Timer3. The Timer1 oscillator is enabled by
setting the T1OSCEN (T1CON<3>) bit. To use it as the
Timer3 clock source, the TMR3CS bit must also be set.
As previously noted, this also configures Timer3 to
increment on every rising edge of the oscillator source.
The Timer1 oscillator is described in Section 13.0
“Timer1 Module”.
15.4 Timer3 Interrupt
The TMR3 register pair (TMR3H:TMR3L) increments
from 0000h to FFFFh and overflows to 0000h. The
Timer3 interrupt, if enabled, is generated on overflow
and is latched in interrupt flag bit, TMR3IF (PIR2<1>).
This interrupt can be enabled or disabled by setting or
clearing the Timer3 Interrupt Enable bit, TMR3IE
(PIE2<1>).
15.5 Resetting Timer3 Using the CCP
Special Event Trigger
If either of the CCP modules is configured to use Timer3
and to generate a Special Event Trigger in Compare
mode (CCP1M<3:0> or CCP2M<3:0> = 1011), this
signal will reset Timer3. It will also start an A/D conver-
sion if the A/D module is enabled (see Section 16.3.4
“Special Event Trigger” for more information).
The module must be configured as either a timer or
synchronous counter to take advantage of this feature.
When used this way, the CCPR2H:CCPR2L register
pair effectively becomes a period register for Timer3.
If Timer3 is running in Asynchronous Counter mode,
the Reset operation may not work.
In the event that a write to Timer3 coincides with a
Special Event Trigger from a CCP module, the write will
take precedence.
TABLE 15-1: REGISTERS ASSOCIATED WITH TIMER3 AS A TIMER/COUNTER
Note: The Special Event Triggers from the
CCP2 module will not set the TMR3IF
interrupt flag bit (PIR2<1>).
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
TMR3L Timer3 Register Low Byte 57
TMR3H Timer3 Register High Byte 57
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer3 module.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 144 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 145
PIC18F2221/2321/4221/4321 FAMILY
16.0 CAPTURE/COMPARE/PWM
(CCP) MODULES
PIC18F2221/2321/4221/4321 family devices all have
two CCP (Capture/Compare/PWM) modules. Each
module contains a 16-bit register which can operate as
a 16-bit Capture register, a 16-bit Compare register or
a PWM Master/Slave Duty Cycle register.
In 28-pin devices, the two standard CCP modules
(CCP1 and CCP2) operate as described in this
chapter. In 40/44-pin devices, CCP1 is implemented
as an Enhanced CCP module with standard Capture
and Compare modes and Enhanced PWM modes.
The ECCP implementation is discussed in
Section 17.0 “Enhanced Capture/Compare/PWM
(ECCP) Module.
The Capture and Compare operations described in this
chapter apply to all standard and Enhanced CCP
modules.
REGISTER 16-1: CCPxCON REGISTER (CCP2 MODULE, CCP1 MODULE IN 28-PIN DEVICES)
Note: Throughout this section and Section 17.0
“Enhanced Capture/Compare/PWM (ECCP)
Module”, references to the register and bit
names for CCP modules are referred to
generically by the use of ‘x’ or ‘y’ in place
of the specific module number. Thus,
“CCPxCON” might refer to the control regis-
ter for CCP1, CCP2 or ECCP1. “CCPxCON”
is used throughout these sections to refer to
the module control register, regardless of
whether the CCP module is a standard or
Enhanced implementation.
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
DCxB1 DCxB0 CCPxM3 CCPxM2 CCPxM1 CCPxM0
bit 7 bit 0
bit 7-6 Unimplemented: Read as ‘0
bit 5-4 DCxB<1:0>: PWM Duty Cycle bit 1 and bit 0 for CCP Module x
Capture mode:
Unused.
Compare mode:
Unused.
PWM mode:
These bits are the two LSbs (bit 1 and bit 0) of the 10-bit PWM duty cycle. The eight MSbs
(DCxB<9:2>) of the duty cycle are found in CCPRxL.
bit 3-0 CCPxM<3:0>: CCPx Module Mode Select bits
0000 = Capture/Compare/PWM disabled (resets CCP module)
0001 = Reserved
0010 = Compare mode, toggle output on match (CCPxIF bit is set)
0011 = Reserved
0100 = Capture mode, every falling edge
0101 = Capture mode, every rising edge
0110 = Capture mode, every 4th rising edge
0111 = Capture mode, every 16th rising edge
1000 = Compare mode: initialize CCP pin low; on compare match, force CCP pin high
(CCPxIF bit is set)
1001 = Compare mode: initialize CCP pin high; on compare match, force CCP pin low
(CCPxIF bit is set)
1010 = Compare mode: generate software interrupt on compare match (CCPxIF bit is set,
CCP pin reflects I/O state)
1011 = Compare mode: trigger special event, reset timer, start A/D conversion on
CCPx match (CCPxIF bit is set)
11xx = PWM mode
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 146 © 2009 Microchip Technology Inc.
16.1 CCP Module Configuration
Each Capture/Compare/PWM module is associated
with a control register (generically, CCPxCON) and a
data register (CCPRx). The data register, in turn, is
comprised of two 8-bit registers: CCPRxL (low byte)
and CCPRxH (high byte). All registers are both
readable and writable.
16.1.1 CCP MODULES AND TIMER
RESOURCES
The CCP modules utilize Timers 1, 2 or 3, depending
on the mode selected. Timer1 and Timer3 are available
to modules in Capture or Compare modes, while
Timer2 is available for modules in PWM mode.
TABLE 16-1: CCP MODE – TIMER
RESOURCES
The assignment of a particular timer to a module is
determined by the Timer to CCP enable bits in the
T3CON register (Register 15-1). Both modules may be
active at any given time and may share the same timer
resource if they are configured to operate in the same
mode (Capture/Compare or PWM) at the same time. The
interactions between the two modules are summarized in
Figure 16-1 and Figure 16-2. In Timer1 in Asynchronous
Counter mode, the capture operation will not work.
16.1.2 CCP2 PIN ASSIGNMENT
The pin assignment for CCP2 (Capture input, Compare
and PWM output) can change, based on device config-
uration. The CCP2MX Configuration bit determines
which pin CCP2 is multiplexed to. By default, it is
assigned to RC1 (CCP2MX = 1). If the Configuration bit
is cleared, CCP2 is multiplexed with RB3.
Changing the pin assignment of CCP2 does not
automatically change any requirements for configuring
the port pin. Users must always verify that the appropri-
ate TRIS register is configured correctly for CCP2
operation, regardless of where it is located.
TABLE 16-2: INTERACTIONS BETWEEN CCP1 AND CCP2 FOR TIMER RESOURCES
CCP/ECCP Mode Timer Resource
Capture
Compare
PWM
Timer1 or Timer3
Timer1 or Timer3
Timer2
CCP1 Mode CCP2 Mode Interaction
Capture Capture Each module can use TMR1 or TMR3 as the time base. The time base can be different
for each CCP.
Capture Compare CCP2 can be configured for the Special Event Trigger to reset TMR1 or TMR3
(depending upon which time base is used). Automatic A/D conversions on trigger event
can also be done. Operation of CCP1 could be affected if it is using the same timer as a
time base.
Compare Capture CCP1 can be configured for the Special Event Trigger to reset TMR1 or TMR3
(depending upon which time base is used). Operation of CCP2 could be affected if it is
using the same timer as a time base.
Compare Compare Either module can be configured for the Special Event Trigger to reset the time base.
Automatic A/D conversions on CCP2 trigger event can be done. Conflicts may occur if
both modules are using the same time base.
Capture PWM(1) None
Compare PWM(1) None
PWM(1) Capture None
PWM(1) Compare None
PWM(1) PWM Both PWMs will have the same frequency and update rate (TMR2 interrupt).
Note 1: Includes standard and Enhanced PWM operation.
© 2009 Microchip Technology Inc. DS39689F-page 147
PIC18F2221/2321/4221/4321 FAMILY
16.2 Capture Mode
In Capture mode, the CCPRxH:CCPRxL register pair
captures the 16-bit value of the TMR1 or TMR3
registers when an event occurs on the corresponding
CCPx pin. An event is defined as one of the following:
every falling edge
every rising edge
every 4th rising edge
every 16th rising edge
The event is selected by the mode select bits,
CCPxM<3:0> (CCPxCON<3:0>). When a capture is
made, the interrupt request flag bit, CCPxIF, is set; it
must be cleared in software. If another capture occurs
before the value in register CCPRx is read, the old
captured value is overwritten by the new captured value.
16.2.1 CCP PIN CONFIGURATION
In Capture mode, the appropriate CCPx pin should be
configured as an input by setting the corresponding
TRIS direction bit.
16.2.2 TIMER1/TIMER3 MODE SELECTION
The timers that are to be used with the capture feature
(Timer1 and/or Timer3) must be running in Timer mode or
Synchronized Counter mode. In Asynchronous Counter
mode, the capture operation will not work. The timer to be
used with each CCP module is selected in the T3CON
register (see Section 16.1.1 “CCP Modules and Timer
Resources”).
16.2.3 SOFTWARE INTERRUPT
When the Capture mode is changed, a false capture
interrupt may be generated. The user should keep the
CCPxIE interrupt enable bit clear to avoid false
interrupts. The interrupt flag bit, CCPxIF, should also be
cleared following any such change in operating mode.
16.2.4 CCP PRESCALER
There are four prescaler settings in Capture mode.
They are specified as part of the operating mode
selected by the mode select bits (CCPxM<3:0>).
Whenever the CCP module is turned off or Capture
mode is disabled, the prescaler counter is cleared. This
means that any Reset will clear the prescaler counter.
Switching from one capture prescaler to another may
generate an interrupt. Also, the prescaler counter will
not be cleared; therefore, the first capture may be from
a non-zero prescaler. Example 16-1 shows the
recommended method for switching between capture
prescalers. This example also clears the prescaler
counter and will not generate the “false” interrupt.
EXAMPLE 16-1: CHANGING BETWEEN
CAPTURE PRESCALERS
(CCP2 SHOWN)
FIGURE 16-1: CAPTURE MODE OPERATION BLOCK DIAGRAM
Note: If RB3/CCP2 or RC1/CCP2 is configured
as an output, a write to the port can cause
a capture condition.
CLRF CCP2CON ; Turn CCP module off
MOVLW NEW_CAPT_PS ; Load WREG with the
; new prescaler mode
; value and CCP ON
MOVWF CCP2CON ; Load CCP2CON with
; this value
CCPR1H CCPR1L
TMR1H TMR1L
Set CCP1IF
TMR3
Enable
Q1:Q4
CCP1CON<3:0>
CCP1 pin
Prescaler
÷ 1, 4, 16
and
Edge Detect
TMR1
Enable
T3CCP2
T3CCP2
CCPR2H CCPR2L
TMR1H TMR1L
Set CCP2IF
TMR3
Enable
CCP2CON<3:0>
CCP2 pin
Prescaler
÷ 1, 4, 16
TMR3H TMR3L
TMR1
Enable
T3CCP2
T3CCP1
T3CCP2
T3CCP1
TMR3H TMR3L
and
Edge Detect
4
4
4
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DS39689F-page 148 © 2009 Microchip Technology Inc.
16.3 Compare Mode
In Compare mode, the 16-bit CCPRx register value is
constantly compared against either the TMR1 or TMR3
register pair value. When a match occurs, the CCPx pin
can be:
driven high
driven low
toggled (high-to-low or low-to-high)
remain unchanged (that is, reflects the state of the
I/O latch)
The action on the pin is based on the value of the mode
select bits (CCPxM<3:0>). At the same time, the
interrupt flag bit, CCPxIF, is set.
16.3.1 CCP PIN CONFIGURATION
The user must configure the CCPx pin as an output by
clearing the appropriate TRIS bit.
16.3.2 TIMER1/TIMER3 MODE SELECTION
Timer1 and/or Timer3 must be running in Timer mode
or Synchronized Counter mode if the CCP module is
using the compare feature. In Asynchronous Counter
mode, the compare operation may not work.
16.3.3 SOFTWARE INTERRUPT MODE
When the Generate Software Interrupt mode is chosen
(CCPxM<3:0> = 1010), the corresponding CCPx pin is
not affected. Only a CCP interrupt is generated, if
enabled and the CCPxIE bit is set.
16.3.4 SPECIAL EVENT TRIGGER
Both CCP modules are equipped with a Special Event
Trigger. This is an internal hardware signal generated
in Compare mode to trigger actions by other modules.
The Special Event Trigger is enabled by selecting
the Compare Special Event Trigger mode
(CCPxM<3:0> = 1011).
For either CCP module, the Special Event Trigger resets
the Timer register pair for whichever timer resource is
currently assigned as the module’s time base. This
allows the CCPRx registers to serve as a programmable
period register for either timer.
The Special Event Trigger for CCP2 can also start an
A/D conversion. In order to do this, the A/D converter
must already be enabled.
FIGURE 16-2: COMPARE MODE OPERATION BLOCK DIAGRAM
Note: Clearing the CCP2CON register will force
the RB3 or RC1 compare output latch
(depending on device configuration) to the
default low level. This is not the PORTB or
PORTC I/O data latch.
CCPR1H CCPR1L
TMR1H TMR1L
Comparator Q
S
R
Output
Logic
Special Event Trigger
Set CCP1IF
CCP1 pin
TRIS
CCP1CON<3:0>
Output Enable
TMR3H TMR3L
CCPR2H CCPR2L
Comparator
1
0
T3CCP2
T3CCP1
Set CCP2IF
1
0
Compare
4
(Timer1/Timer3 Reset)
QS
R
Output
Logic
Special Event Trigger
CCP2 pin
TRIS
CCP2CON<3:0>
Output Enable
4
(Timer1/Timer3 Reset, A/D Trigger)
Match
Compare
Match
© 2009 Microchip Technology Inc. DS39689F-page 149
PIC18F2221/2321/4221/4321 FAMILY
TABLE 16-3: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE, TIMER1 AND TIMER3
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
RCON IPEN
SBOREN
(1)
RI TO PD POR BOR 54
PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
TRISB PORTB Data Direction Register 58
TRISC PORTC Data Direction Register 58
TMR1L Timer1 Register Low Byte 56
TMR1H Timer1 Register High Byte 56
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56
TMR3H Timer3 Register High Byte 57
TMR3L Timer3 Register Low Byte 57
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 57
CCPR1L Capture/Compare/PWM Register 1 Low Byte 57
CCPR1H Capture/Compare/PWM Register 1 High Byte 57
CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57
CCPR2L Capture/Compare/PWM Register 2 Low Byte 57
CCPR2H Capture/Compare/PWM Register 2 High Byte 57
CCP2CON DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by Capture/Compare, Timer1 or Timer3.
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled
and reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.
2: These bits are unimplemented on 28-pin devices and read as ‘0’.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 150 © 2009 Microchip Technology Inc.
16.4 PWM Mode
In Pulse-Width Modulation (PWM) mode, the CCPx pin
produces up to a 10-bit resolution PWM output. Since
the CCP2 pin is multiplexed with a PORTB or PORTC
data latch, the appropriate TRIS bit must be cleared to
make the CCP2 pin an output.
Figure 16-3 shows a simplified block diagram of the
CCP module in PWM mode.
For a step-by-step procedure on how to set up the CCP
module for PWM operation, see Section 16.4.4
“Setup for PWM Operation”.
FIGURE 16-3: SIMPLIFIED PWM BLOCK
DIAGRAM
A PWM output (Figure 16-4) has a time base (period)
and a time that the output stays high (duty cycle).
The frequency of the PWM is the inverse of the
period (1/period).
FIGURE 16-4: PWM OUTPUT
16.4.1 PWM PERIOD
The PWM period is specified by writing to the PR2
register. The PWM period can be calculated using the
following formula:
EQUATION 16-1:
PWM frequency is defined as 1/[PWM period].
When TMR2 is equal to PR2, the following three events
occur on the next increment cycle:
•TMR2 is cleared
The CCPx pin is set (exception: if PWM duty
cycle = 0%, the CCPx pin will not be set)
The PWM duty cycle is latched from CCPRxL into
CCPRxH
16.4.2 PWM DUTY CYCLE
The PWM duty cycle is specified by writing to the
CCPRxL register and to the CCPxCON<5:4> bits. Up
to 10-bit resolution is available. The CCPRxL contains
the eight MSbs and the CCPxCON<5:4> contains the
two LSbs. This 10-bit value is represented by
CCPRxL:CCPxCON<5:4>. The following equation is
used to calculate the PWM duty cycle in time:
EQUATION 16-2:
CCPRxL and CCPxCON<5:4> can be written to at any
time, but the duty cycle value is not latched into
CCPRxH until after a match between PR2 and TMR2
occurs (i.e., the period is complete). In PWM mode,
CCPRxH is a read-only register.
Note: Clearing the CCP2CON register will force
the RB3 or RC1 output latch (depending on
device configuration) to the default low
level. This is not the PORTB or PORTC I/O
data latch.
CCPRxL
CCPRxH (Slave)
Comparator
TMR2
Comparator
PR2
(Note 1)
RQ
S
Duty Cycle Registers CCPxCON<5:4>
Clear Timer,
CCPx pin and
latch D.C.
Note 1: The 8-bit TMR2 value is concatenated with the 2-bit
internal Q clock, or 2 bits of the prescaler, to create the
10-bit time base.
CCPx Output
Corresponding
TRIS bit
Period
Duty Cycle
TMR2 = PR2
TMR2 = Duty Cycle
TMR2 = PR2
Note: The Timer2 postscalers (see Section 14.0
“Timer2 Module”) are not used in the
determination of the PWM frequency. The
postscaler could be used to have a servo
update rate at a different frequency than
the PWM output.
PWM Period = [(PR2) + 1] • 4 • TOSC
(TMR2 Prescale Value)
PWM Duty Cycle = (CCPRXL:CCPXCON<5:4>) •
TOSC • (TMR2 Prescale Value)
© 2009 Microchip Technology Inc. DS39689F-page 151
PIC18F2221/2321/4221/4321 FAMILY
The CCPRxH register and a 2-bit internal latch are
used to double-buffer the PWM duty cycle. This
double-buffering is essential for glitchless PWM
operation.
When the CCPRxH and 2-bit latch match TMR2,
concatenated with an internal 2-bit Q clock or 2 bits of
the TMR2 prescaler, the CCPx pin is cleared.
The maximum PWM resolution (bits) for a given PWM
frequency is given by the equation:
EQUATION 16-3:
TABLE 16-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz
16.4.3 PWM AUTO-SHUTDOWN
(CCP1 ONLY)
The PWM auto-shutdown features of the Enhanced CCP
module are also available to CCP1 in 28-pin devices. The
operation of this feature is discussed in detail in
Section 17.4.7 “Enhanced PWM Auto-Shutdown”.
Auto-shutdown features are not available for CCP2.
16.4.4 SETUP FOR PWM OPERATION
The following steps should be taken when configuring
the CCP module for PWM operation:
1. Set the PWM period by writing to the PR2
register.
2. Set the PWM duty cycle by writing to the
CCPRxL register and CCPxCON<5:4> bits.
3. Make the CCPx pin an output by clearing the
appropriate TRIS bit.
4. Set the TMR2 prescale value, then enable
Timer2 by writing to T2CON.
5. Configure the CCPx module for PWM operation.
Note: If the PWM duty cycle value is longer than
the PWM period, the CCPx pin will not be
cleared.
FOSC
FPWM
---------------
⎝⎠
⎛⎞
log
2()log
----------------------------- b i t s=
PWM Resolution (max)
PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz
Timer Prescaler (1, 4, 16)1641111
PR2 Value FFh FFh FFh 3Fh 1Fh 17h
Maximum Resolution (bits) 10 10 10 8 7 6.58
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 152 © 2009 Microchip Technology Inc.
TABLE 16-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
RCON IPEN SBOREN(1) RI TO PD POR BOR 54
PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
TRISB PORTB Data Direction Register 58
TRISC PORTC Data Direction Register 58
TMR2 Timer2 Register 56
PR2 Timer2 Period Register 56
T2CON T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 56
CCPR1L Capture/Compare/PWM Register 1 Low Byte 57
CCPR1H Capture/Compare/PWM Register 1 High Byte 57
CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57
CCPR2L Capture/Compare/PWM Register 2 Low Byte 57
CCPR2H Capture/Compare/PWM Register 2 High Byte 57
CCP2CON DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 57
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 57
ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PWM or Timer2.
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled
and reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.
2: These bits are unimplemented on 28-pin devices and read as ‘0’.
© 2009 Microchip Technology Inc. DS39689F-page 153
PIC18F2221/2321/4221/4321 FAMILY
17.0 ENHANCED CAPTURE/
COMPARE/PWM (ECCP)
MODULE
In PIC18F4221/4321 devices, CCP1 is implemented
as a standard CCP module with Enhanced PWM
capabilities. These include the provision for 2 or
4 output channels, user-selectable polarity, dead-band
control and automatic shutdown and restart. The
Enhanced features are discussed in detail in
Section 17.4 “Enhanced PWM Mode”. Capture,
Compare and single-output PWM functions of the
ECCP module are the same as described for the
standard CCP module.
The control register for the Enhanced CCP module is
shown in Register 17-1. It differs from the CCPxCON
registers in PIC18F2221/2321 devices in that the two
Most Significant bits are implemented to control PWM
functionality.
REGISTER 17-1: CCP1CON REGISTER (ECCP1 MODULE, 40/44-PIN DEVICES)
Note: The ECCP module is implemented only in
40/44-pin devices.
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0
bit 7 bit 0
bit 7-6 P1M<1:0>: Enhanced PWM Output Configuration bits
If CCP1M<3:2> = 00, 01, 10:
xx = P1A assigned as Capture/Compare input/output; P1B, P1C, P1D assigned as port pins
If CCP1M<3:2> = 11:
00 = Single output: P1A modulated; P1B, P1C, P1D assigned as port pins
01 = Full-bridge output forward: P1D modulated; P1A active; P1B, P1C inactive
10 = Half-bridge output: P1A, P1B modulated with dead-band control; P1C, P1D assigned
as port pins
11 = Full-bridge output reverse: P1B modulated; P1C active; P1A, P1D inactive
bit 5-4 DC1B<1:0>: PWM Duty Cycle bit 1 and bit 0
Capture mode:
Unused.
Compare mode:
Unused.
PWM mode:
These bits are the two LSbs of the 10-bit PWM duty cycle. The eight MSbs of the duty cycle are
found in CCPR1L.
bit 3-0 CCP1M<3:0>: Enhanced CCP Mode Select bits
0000 = Capture/Compare/PWM off (resets ECCP module)
0001 = Reserved
0010 = Compare mode, toggle output on match
0011 = Capture mode
0100 = Capture mode, every falling edge
0101 = Capture mode, every rising edge
0110 = Capture mode, every 4th rising edge
0111 = Capture mode, every 16th rising edge
1000 = Compare mode, initialize CCP1 pin low, set output on compare match (set CCP1IF)
1001 = Compare mode, initialize CCP1 pin high, clear output on compare match (set CCP1IF)
1010 = Compare mode, generate software interrupt only, CCP1 pin reverts to I/O state
1011 = Compare mode, trigger special event (ECCP resets TMR1 or TMR3, sets CC1IF bit)
1100 = PWM mode; P1A, P1C active-high; P1B, P1D active-high
1101 = PWM mode; P1A, P1C active-high; P1B, P1D active-low
1110 = PWM mode; P1A, P1C active-low; P1B, P1D active-high
1111 = PWM mode; P1A, P1C active-low; P1B, P1D active-low
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 154 © 2009 Microchip Technology Inc.
In addition to the expanded range of modes available
through the CCP1CON and ECCP1AS registers, the
ECCP module has an additional register associated
with Enhanced PWM operation and auto-shutdown
features; it is:
ECCP1DEL (PWM Dead-Band Delay)
17.1 ECCP Outputs and Configuration
The Enhanced CCP module may have up to four PWM
outputs, depending on the selected operating mode.
These outputs, designated P1A through P1D, are
multiplexed with I/O pins on PORTC and PORTD. The
outputs that are active depend on the CCP operating
mode selected. The pin assignments are summarized
in Table 17-1.
To configure the I/O pins as PWM outputs, the proper
PWM mode must be selected by setting the P1M<1:0>
and CCP1M<3:0> bits. The appropriate TRISC and
TRISD direction bits for the port pins must also be set
as outputs.
17.1.1 ECCP MODULES AND TIMER
RESOURCES
Like the standard CCP modules, the ECCP module can
utilize Timers 1, 2 or 3, depending on the mode
selected. Timer1 and Timer3 are available for modules
in Capture or Compare modes, while Timer2 is avail-
able for modules in PWM mode. Interactions between
the standard and Enhanced CCP modules are identical
to those described for standard CCP modules.
Additional details on timer resources are provided in
Section 16.1.1 “CCP Modules and Timer
Resources”.
17.2 Capture and Compare Modes
Except for the operation of the Special Event Trigger
discussed below, the Capture and Compare modes of
the ECCP module are identical in operation to that of
CCP2. These are discussed in detail in Section 16.2
“Capture Mode” and Section 16.3 “Compare
Mode”. No changes are required when moving
between 28-pin and 40/44-pin devices.
17.2.1 SPECIAL EVENT TRIGGER
The Special Event Trigger output of ECCP1 resets the
TMR1 or TMR3 register pair, depending on which timer
resource is currently selected. This allows the CCPR1
register to effectively be a 16-bit programmable period
register for Timer1 or Timer3.
17.3 Standard PWM Mode
When configured in Single Output mode, the ECCP
module functions identically to the standard CCP
module in PWM mode, as described in Section 16.4
“PWM Mode”. This is also sometimes referred to as
“Compatible CCP” mode, as in Table 17-1.
TABLE 17-1: PIN ASSIGNMENTS FOR VARIOUS ECCP1 MODES
Note: When setting up single output PWM
operations, users are free to use either
of the processes described in
Section 16.4.4 “Setup for PWM
Operation” or Section 17.4.9 “Setup
for PWM Operation”. The latter is more
generic and will work for either single or
multi-output PWM.
ECCP Mode CCP1CON
Configuration RC2 RD5 RD6 RD7
All 40/44-pin devices:
Compatible CCP 00xx 11xx CCP1 RD5/PSP5 RD6/PSP6 RD7/PSP7
Dual PWM 10xx 11xx P1A P1B RD6/PSP6 RD7/PSP7
Quad PWM x1xx 11xx P1A P1B P1C P1D
Legend: x = Don’t care. Shaded cells indicate pin assignments not used by ECCP1 in a given mode.
© 2009 Microchip Technology Inc. DS39689F-page 155
PIC18F2221/2321/4221/4321 FAMILY
17.4 Enhanced PWM Mode
The Enhanced PWM mode provides additional PWM
output options for a broader range of control applica-
tions. The module is a backward compatible version of
the standard CCP module and offers up to four outputs,
designated P1A through P1D. Users are also able to
select the polarity of the signal (either active-high or
active-low). The module’s output mode and polarity are
configured by setting the P1M<1:0> and CCP1M<3:0>
bits of the CCP1CON register.
Figure 17-1 shows a simplified block diagram of PWM
operation. All control registers are double-buffered and
are loaded at the beginning of a new PWM cycle (the
period boundary when Timer2 resets) in order to
prevent glitches on any of the outputs. The exception is
the PWM Dead-Band Delay register, ECCP1DEL,
which is loaded at either the duty cycle boundary or the
period boundary (whichever comes first). Because of
the buffering, the module waits until the assigned timer
resets, instead of starting immediately. This means that
Enhanced PWM waveforms do not exactly match the
standard PWM waveforms, but are instead offset by
one full instruction cycle (4 TOSC).
As before, the user must manually configure the
appropriate TRIS bits for output.
17.4.1 PWM PERIOD
The PWM period is specified by writing to the PR2
register. The PWM period can be calculated using the
following equation.
EQUATION 17-1:
PWM frequency is defined as 1/[PWM period]. When
TMR2 is equal to PR2, the following three events occur
on the next increment cycle:
•TMR2 is cleared
The CCP1 pin is set (if PWM duty cycle = 0%, the
CCP1 pin will not be set)
The PWM duty cycle is copied from CCPR1L into
CCPR1H
FIGURE 17-1: SIMPLIFIED BLOCK DIAGRAM OF THE ENHANCED PWM MODULE
Note: The Timer2 postscaler (see Section 14.0
“Timer2 Module”) is not used in the
determination of the PWM frequency. The
postscaler could be used to have a servo
update rate at a different frequency than
the PWM output.
PWM Period = [(PR2) + 1] • 4 • TOSC
(TMR2 Prescale Value)
CCPR1L
CCPR1H (Slave)
Comparator
TMR2
Comparator
PR2
(Note 1)
RQ
S
Duty Cycle Registers
CCP1CON<5:4>
Clear Timer,
set CCP1 pin and
latch D.C.
Note: The 8-bit TMR2 register is concatenated with the 2-bit internal Q clock, or 2 bits of the prescaler, to create the 10-bit
time base.
TRISx<x>
CCP1/P1A
TRISx<x>
P1B
TRISx<x>
TRISx<x>
P1D
Output
Controller
P1M1<1:0>
2
CCP1M<3:0>
4
ECCP1DEL
CCP1/P1A
P1B
P1C
P1D
P1C
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 156 © 2009 Microchip Technology Inc.
17.4.2 PWM DUTY CYCLE
The PWM duty cycle is specified by writing to the
CCPR1L register and to the CCP1CON<5:4> bits. Up
to 10-bit resolution is available. The CCPR1L contains
the eight MSbs and the CCP1CON<5:4> contains the
two LSbs. This 10-bit value is represented by
CCPR1L:CCP1CON<5:4>. The PWM duty cycle is
calculated by the following equation.
EQUATION 17-2:
CCPR1L and CCP1CON<5:4> can be written to at any
time, but the duty cycle value is not copied into
CCPR1H until a match between PR2 and TMR2 occurs
(i.e., the period is complete). In PWM mode, CCPR1H
is a read-only register.
The CCPR1H register and a 2-bit internal latch are
used to double-buffer the PWM duty cycle. This
double-buffering is essential for glitchless PWM
operation. When the CCPR1H and 2-bit latch match
TMR2, concatenated with an internal 2-bit Q clock or
two bits of the TMR2 prescaler, the CCP1 pin is
cleared. The maximum PWM resolution (bits) for a
given PWM frequency is given by the following
equation.
EQUATION 17-3:
17.4.3 PWM OUTPUT CONFIGURATIONS
The P1M<1:0> bits in the CCP1CON register allow one
of four configurations:
Single Output
Half-Bridge Output
Full-Bridge Output, Forward mode
Full-Bridge Output, Reverse mode
The Single Output mode is the standard PWM mode
discussed in Section 17.4 “Enhanced PWM Mode”.
The Half-Bridge and Full-Bridge Output modes are
covered in detail in the sections that follow.
The general relationship of the outputs in all
configurations is summarized in Figure 17-2.
TABLE 17-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz
PWM Duty Cycle = (CCPR1L:CCP1CON<5:4>) •
TOSC • (TMR2 Prescale Value)
Note: If the PWM duty cycle value is longer than
the PWM period, the CCP1 pin will not be
cleared.
()
PWM Resolution (max) =
FOSC
FPWM
log
log(2) bits
PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz
Timer Prescaler (1, 4, 16)1641111
PR2 Value FFh FFh FFh 3Fh 1Fh 17h
Maximum Resolution (bits) 10 10 10 8 7 6.58
© 2009 Microchip Technology Inc. DS39689F-page 157
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 17-2: PWM OUTPUT RELATIONSHIPS (ACTIVE-HIGH STATE)
FIGURE 17-3: PWM OUTPUT RELATIONSHIPS (ACTIVE-LOW STATE)
0
Period
00
10
01
11
SIGNAL PR2 + 1
CCP1CON
<7:6>
P1A Modulated
P1A Modulated
P1B Modulated
P1A Active
P1B Inactive
P1C Inactive
P1D Modulated
P1A Inactive
P1B Modulated
P1C Active
P1D Inactive
Duty
Cycle
(Single Output)
(Half-Bridge)
(Full-Bridge,
Forward)
(Full-Bridge,
Reverse)
Delay(1) Delay(1)
0
Period
00
10
01
11
SIGNAL PR2 + 1
CCP1CON
<7:6>
P1A Modulated
P1A Modulated
P1B Modulated
P1A Active
P1B Inactive
P1C Inactive
P1D Modulated
P1A Inactive
P1B Modulated
P1C Active
P1D Inactive
Duty
Cycle
(Single Output)
(Half-Bridge)
(Full-Bridge,
Forward)
(Full-Bridge,
Reverse)
Delay(1) Delay(1)
Relationships:
Period = 4 * T
OSC * (PR2 + 1) * (TMR2 Prescale Value)
Duty Cycle = TOSC * (CCPR1L<7:0>:CCP1CON<5:4>) * (TMR2 Prescale Value)
Delay = 4 * TOSC * (ECCP1DEL<6:0>)
Note 1: Dead-band delay is programmed using the ECCP1DEL register (see Section 17.4.6 “Programmable
Dead-Band Delay”).
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 158 © 2009 Microchip Technology Inc.
17.4.4 HALF-BRIDGE MODE
In the Half-Bridge Output mode, two pins are used as
outputs to drive push-pull loads. The PWM output signal
is output on the P1A pin, while the complementary PWM
output signal is output on the P1B pin (Figure 17-4). This
mode can be used for half-bridge applications, as shown
in Figure 17-5, or for full-bridge applications where four
power switches are being modulated with two PWM
signals.
In Half-Bridge Output mode, the programmable dead-
band delay can be used to prevent shoot-through
current in half-bridge power devices. The value of bits,
PDC<6:0>, sets the number of instruction cycles before
the output is driven active. If the value is greater than
the duty cycle, the corresponding output remains
inactive during the entire cycle. See Section 17.4.6
“Programmable Dead-Band Delay” for more details
of the dead-band delay operations.
Since the P1A and P1B outputs are multiplexed with
the PORTC<2> and PORTD<5> data latches, the
TRISC<2> and TRISD<5> bits must be cleared to
configure P1A and P1B as outputs.
FIGURE 17-4: HALF-BRIDGE PWM
OUTPUT
FIGURE 17-5: EXAMPLES OF HALF-BRIDGE OUTPUT MODE APPLICATIONS
Period
Duty Cycle
td
td
(1)
P1A(2)
P1B(2)
td = Dead-Band Delay
Period
(1) (1)
Note 1: At this time, the TMR2 register is equal to the
PR2 register.
2: Output signals are shown as active-high.
PIC18F4X21
P1A
P1B
FET
Driver
FET
Driver
V+
V-
Load
+
V
-
+
V
-
FET
Driver
FET
Driver
V+
V-
Load
FET
Driver
FET
Driver
PIC18F4X21
P1A
P1B
Standard Half-Bridge Circuit (“Push-Pull”)
Half-Bridge Output Driving a Full-Bridge Circuit
© 2009 Microchip Technology Inc. DS39689F-page 159
PIC18F2221/2321/4221/4321 FAMILY
17.4.5 FULL-BRIDGE MODE
In Full-Bridge Output mode, four pins are used as
outputs; however, only two outputs are active at a time.
In the Forward mode, pin P1A is continuously active
and pin P1D is modulated. In the Reverse mode, pin
P1C is continuously active and pin P1B is modulated.
These are illustrated in Figure 17-6.
P1A, P1B, P1C and P1D outputs are multiplexed with
the PORTC<2> and PORTD<7:5> data latches. The
TRISC<2> and TRISD<7:5> bits must be cleared to
make the P1A, P1B, P1C and P1D pins outputs.
FIGURE 17-6: FULL-BRIDGE PWM OUTPUT
Period
Duty Cycle
P1A(2)
P1B(2)
P1C(2)
P1D(2)
Forward Mode
(1)
Period
Duty Cycle
P1A(2)
P1C(2)
P1D(2)
P1B(2)
Reverse Mode
(1)
(1)
(1)
Note 1: At this time, the TMR2 register is equal to the PR2 register.
Note 2: Output signal is shown as active-high.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 160 © 2009 Microchip Technology Inc.
FIGURE 17-7: EXAMPLE OF FULL-BRIDGE APPLICATION
17.4.5.1 Direction Change in Full-Bridge Mode
In the Full-Bridge Output mode, the P1M1 bit in the
CCP1CON register allows user to control the forward/
reverse direction. When the application firmware
changes this direction control bit, the module will
assume the new direction on the next PWM cycle.
Just before the end of the current PWM period, the
modulated outputs (P1B and P1D) are placed in their
inactive state, while the unmodulated outputs (P1A and
P1C) are switched to drive in the opposite direction.
This occurs in a time interval of 4 TOSC * (Timer2
Prescale Value) before the next PWM period begins.
The Timer2 prescaler will be either 1, 4 or 16, depend-
ing on the value of the T2CKPS<1:0> bits
(T2CON<1:0>). During the interval from the switch of
the unmodulated outputs to the beginning of the next
period, the modulated outputs (P1B and P1D) remain
inactive. This relationship is shown in Figure 17-8.
Note that in the Full-Bridge Output mode, the ECCP1
module does not provide any dead-band delay. In
general, since only one output is modulated at all times,
dead-band delay is not required. However, there is a
situation where a dead-band delay might be required.
This situation occurs when both of the following
conditions are true:
1. The direction of the PWM output changes when
the duty cycle of the output is at or near 100%.
2. The turn-off time of the power switch, including
the power device and driver circuit, is greater
than the turn-on time.
Figure 17-9 shows an example where the PWM
direction changes from forward to reverse at a near
100% duty cycle. At time t1, the outputs P1A and P1D
become inactive, while output P1C becomes active. In
this example, since the turn-off time of the power
devices is longer than the turn-on time, a shoot-through
current may flow through power devices, QC and QD
(see Figure 17-7), for the duration of ‘t’. The same
phenomenon will occur to power devices, QA and QB,
for PWM direction change from reverse to forward.
If changing PWM direction at high duty cycle is required
for an application, one of the following requirements
must be met:
1. Reduce PWM for a PWM period before
changing directions.
2. Use switch drivers that can drive the switches off
faster than they can drive them on.
Other options to prevent shoot-through current may
exist.
P1A
P1C
FET
Driver
FET
Driver
V+
V-
Load
FET
Driver
FET
Driver
P1B
P1D
QA
QB QD
QC
PIC18F4X21
© 2009 Microchip Technology Inc. DS39689F-page 161
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 17-8: PWM DIRECTION CHANGE
FIGURE 17-9: PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE
DC
Period(1)
SIGNAL
Note 1: The direction bit in the CCP1 Control register (CCP1CON<7>) is written any time during the PWM cycle.
2: When changing directions, the P1A and P1C signals switch before the end of the current PWM cycle at intervals
of 4 TOSC, 16 TOSC or 64 TOSC, depending on the Timer2 prescaler value. The modulated P1B and P1D signals
are inactive at this time.
Period
(Note 2)
P1A (Active-High)
P1B (Active-High)
P1C (Active-High)
P1D (Active-High)
DC
Forward Period Reverse Period
P1A(1)
tON(2)
tOFF(3)
t = tOFF – tON(2,3)
P1B(1)
P1C(1)
P1D(1)
External Switch D(1)
Potential
Shoot-Through
Current(1)
Note 1: All signals are shown as active-high.
2: tON is the turn-on delay of power switch QC and its driver.
3: tOFF is the turn-off delay of power switch QD and its driver.
External Switch C(1)
t1
DC
DC
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DS39689F-page 162 © 2009 Microchip Technology Inc.
17.4.6 PROGRAMMABLE DEAD-BAND
DELAY
In half-bridge applications, where all power switches
are modulated at the PWM frequency at all times, the
power switches normally require more time to turn off
than to turn on. If both the upper and lower power
switches are switched at the same time (one turned on
and the other turned off), both switches may be on for
a short period of time until one switch completely turns
off. During this brief interval, a very high current (shoot-
through current) may flow through both power
switches, shorting the bridge supply. To avoid this
potentially destructive shoot-through current from
flowing during switching, turning on either of the power
switches is normally delayed to allow the other switch
to completely turn off.
In the Half-Bridge Output mode, a digitally programmable
dead-band delay is available to avoid shoot-through
current from destroying the bridge power switches. The
delay occurs at the signal transition from the nonactive
state to the active state (see Figure 17-4 for illustra-
tion). Bits PDC<6:0> of the ECCP1DEL register
(Register 17-2) set the delay period in terms of micro-
controller instruction cycles (TCY or 4 TOSC). These bits
are not available on 28-pin devices as the standard
CCP module does not support half-bridge operation.
17.4.7 ENHANCED PWM AUTO-SHUTDOWN
When the ECCP1 is programmed for any of the
Enhanced PWM modes, the active output pins may be
configured for auto-shutdown. Auto-shutdown immedi-
ately places the Enhanced PWM output pins into a
defined shutdown state when a shutdown event occurs.
A shutdown event can be caused by either of the
comparator modules, a low level on the Fault input pin
(FLT0) or any combination of these three sources. The
comparators may be used to monitor a voltage input
proportional to a current being monitored in the bridge
circuit. If the voltage exceeds a threshold, the
comparator switches state and triggers a shutdown.
Alternatively, a low digital signal on FLT0 can also trigger
a shutdown. The auto-shutdown feature can be disabled
by not selecting any auto-shutdown sources. The auto-
shutdown sources to be used are selected using the
ECCPAS<2:0> bits (ECCP1AS<6:4>).
When a shutdown occurs, the output pins are asyn-
chronously placed in their shutdown states, specified
by the PSSAC<1:0> and PSSBD<1:0> bits
(ECCP1AS<3:0>). Each pin pair (P1A/P1C and P1B/
P1D) may be set to drive high, drive low or be tri-stated
(not driving). The ECCPASE bit (ECCP1AS<7>) is also
set to hold the Enhanced PWM outputs in their
shutdown states.
The ECCPASE bit is set by hardware when a shutdown
event occurs. If automatic restarts are not enabled, the
ECCPASE bit is cleared by firmware when the cause of
the shutdown clears. If automatic restarts are enabled,
the ECCPASE bit is automatically cleared when the
cause of the auto-shutdown has cleared.
If the ECCPASE bit is set when a PWM period begins,
the PWM outputs remain in their shutdown state for that
entire PWM period. When the ECCPASE bit is cleared,
the PWM outputs will return to normal operation at the
beginning of the next PWM period.
REGISTER 17-2: ECCP1DEL: PWM DEAD-BAND DELAY REGISTER
Note: Programmable dead-band delay is not
implemented in 28-pin devices with
standard CCP modules.
Note: Writing to the ECCPASE bit is disabled
while a shutdown condition is active.
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
PRSEN PDC6(1) PDC5(1) PDC4(1) PDC3(1) PDC2(1) PDC1(1) PDC0(1)
bit 7 bit 0
bit 7 PRSEN: PWM Restart Enable bit
1 = Upon auto-shutdown, the ECCPASE bit clears automatically once the shutdown event
goes away; the PWM restarts automatically
0 = Upon auto-shutdown, ECCPASE must be cleared in software to restart the PWM
bit 6-0 PDC<6:0>: PWM Delay Count bits(1)
Delay time, in number of FOSC/4 (4 * TOSC) cycles, between the scheduled and actual time for
a PWM signal to transition to active.
Note 1: Unimplemented on 28-pin devices; bits read ‘0’.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 163
PIC18F2221/2321/4221/4321 FAMILY
REGISTER 17-3: ECCP1AS: ENHANCED CAPTURE/COMPARE/PWM AUTO-SHUTDOWN
CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(1) PSSBD0(1)
bit 7 bit 0
bit 7 ECCPASE: ECCP Auto-Shutdown Event Status bit
1 = A shutdown event has occurred; ECCP outputs are in shutdown state
0 = ECCP outputs are operating
bit 6-4 ECCPAS<2:0>: ECCP Auto-Shutdown Source Select bits
111 = FLT0 or Comparator 1 or Comparator 2
110 = FLT0 or Comparator 2
101 = FLT0 or Comparator 1
100 =FLT0
011 = Either Comparator 1 or 2
010 = Comparator 2 output
001 = Comparator 1 output
000 = Auto-shutdown is disabled
bit 3-2 PSSAC<1:0>: Pins A and C Shutdown State Control bits
1x = Pins A and C are tri-state (40/44-pin devices);
PWM output is tri-state (28-pin devices)
01 = Drive Pins A and C to ‘1
00 = Drive Pins A and C to ‘0
bit 1-0 PSSBD<1:0>: Pins B and D Shutdown State Control bits(1)
1x = Pins B and D tri-state
01 = Drive Pins B and D to ‘1
00 = Drive Pins B and D to ‘0
Note 1: Unimplemented on 28-pin devices; bits read as ‘0’.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 164 © 2009 Microchip Technology Inc.
17.4.7.1 Auto-Shutdown and
Automatic Restart
The auto-shutdown feature can be configured to allow
automatic restarts of the module following a shutdown
event. This is enabled by setting the PRSEN bit of the
ECCP1DEL register (ECCP1DEL<7>).
In Shutdown mode with PRSEN = 1 (Figure 17-10), the
ECCPASE bit will remain set for as long as the cause
of the shutdown continues. When the shutdown condi-
tion clears, the ECCP1ASE bit is cleared. If PRSEN = 0
(Figure 17-11), once a shutdown condition occurs, the
ECCPASE bit will remain set until it is cleared by
firmware. Once ECCPASE is cleared, the Enhanced
PWM will resume at the beginning of the next PWM
period.
Independent of the PRSEN bit setting, if the auto-
shutdown source is one of the comparators, the
shutdown condition is a level. The ECCPASE bit
cannot be cleared as long as the cause of the shutdown
persists.
The Auto-Shutdown mode can be forced by writing a ‘1
to the ECCPASE bit.
17.4.8 START-UP CONSIDERATIONS
When the ECCP module is used in the PWM mode, the
application hardware must use the proper external pull-
up and/or pull-down resistors on the PWM output pins.
When the microcontroller is released from Reset, all of
the I/O pins are in the high-impedance state. The
external circuits must keep the power switch devices in
the OFF state until the microcontroller drives the I/O
pins with the proper signal levels, or activates the PWM
output(s).
The CCP1M<1:0> bits (CCP1CON<1:0>) allow the
user to choose whether the PWM output signals are
active-high or active-low for each pair of PWM output
pins (P1A/P1C and P1B/P1D). The PWM output
polarities must be selected before the PWM pins are
configured as outputs. Changing the polarity configura-
tion while the PWM pins are configured as outputs is
not recommended, since it may result in damage to the
application circuits.
The P1A, P1B, P1C and P1D output latches may not be
in the proper states when the PWM module is initialized.
Enabling the PWM pins for output at the same time as
the ECCP module may cause damage to the applica-
tion circuit. The ECCP module must be enabled in the
proper output mode and complete a full PWM cycle
before configuring the PWM pins as outputs. The com-
pletion of a full PWM cycle is indicated by the TMR2IF
bit being set as the second PWM period begins.
FIGURE 17-10: PWM AUTO-SHUTDOWN (PRSEN = 1, AUTO-RESTART ENABLED)
FIGURE 17-11: PWM AUTO-SHUTDOWN (PRSEN = 0, AUTO-RESTART DISABLED)
Note: Writing to the ECCPASE bit is disabled
while a shutdown condition is active.
Shutdown
PWM
ECCPASE bit
Activity
Event
PWM Period PWM Period PWM Period
Duty Cycle
Dead Time
Duty Cycle
Dead TimeDead Time
Duty Cycle
Shutdown
PWM
ECCPASE bit
Activity
Event
PWM Period PWM Period PWM Period
ECCPASE
Cleared by Firmware
Duty Cycle
Dead Time
Duty Cycle Duty Cycle
Dead TimeDead Time
© 2009 Microchip Technology Inc. DS39689F-page 165
PIC18F2221/2321/4221/4321 FAMILY
17.4.9 SETUP FOR PWM OPERATION
The following steps should be taken when configuring
the ECCP module for PWM operation:
1. Configure the PWM pins, P1A and P1B (and
P1C and P1D, if used), as inputs by setting the
corresponding TRIS bits.
2. Set the PWM period by loading the PR2 register.
3. If auto-shutdown is required, do the following:
Disable auto-shutdown (ECCPASE = 0)
Configure source (FLT0, Comparator 1 or
Comparator 2)
Wait for non-shutdown condition
4. Configure the ECCP module for the desired
PWM mode and configuration by loading the
CCP1CON register with the appropriate values:
Select one of the available output
configurations and direction with the P1M<1:0
bits.
Select the polarities of the PWM output
signals with the CCP1M<3:0> bits.
5. Set the PWM duty cycle by loading the CCPR1L
register and CCP1CON<5:4> bits.
6. For Half-Bridge Output mode, set the dead-
band delay by loading ECCP1DEL<6:0> with
the appropriate value.
7. If auto-shutdown operation is required, load the
ECCP1AS register:
Select the auto-shutdown sources using the
ECCPAS<2:0> bits.
Select the shutdown states of the PWM
output pins using the PSSAC<1:0> and
PSSBD<1:0> bits.
Set the ECCPASE bit (ECCP1AS<7>).
Configure the comparators using the CMCON
register.
Configure the comparator inputs as analog
inputs.
8. If auto-restart operation is required, set the
PRSEN bit (ECCP1DEL<7>).
9. Configure and start TMR2:
Clear the TMR2 interrupt flag bit by clearing
the TMR2IF bit (PIR1<1>).
Set the TMR2 prescale value by loading the
T2CKPS bits (T2CON<1:0>).
Enable Timer2 by setting the TMR2ON bit
(T2CON<2>).
10. Enable PWM outputs after a new PWM cycle
has started:
Wait until TMRx overflows (TMRxIF bit is set).
Enable the CCP1/P1A, P1B, P1C and/or P1D
pin outputs by clearing the respective TRIS
bits.
Clear the ECCPASE bit (ECCP1AS<7>).
17.4.10 OPERATION IN POWER-MANAGED
MODES
In Sleep mode, all clock sources are disabled. Timer2
will not increment and the state of the module will not
change. If the ECCP pin is driving a value, it will continue
to drive that value. When the device wakes up, it will
continue from this state. If Two-Speed Start-ups are
enabled, the initial start-up frequency from INTOSC and
the postscaler may not be stable immediately.
In PRI_IDLE mode, the primary clock will continue to
clock the ECCP module without change. In all other
power-managed modes, the selected power-managed
mode clock will clock Timer2. Other power-managed
mode clocks will most likely be different than the
primary clock frequency.
17.4.10.1 Operation with Fail-Safe
Clock Monitor
If the Fail-Safe Clock Monitor is enabled, a clock failure
will force the device into the power-managed RC_RUN
mode and the OSCFIF bit (PIR2<7>) will be set. The
ECCP will then be clocked from the internal oscillator
clock source, which may have a different clock
frequency than the primary clock.
See the previous section for additional details.
17.4.11 EFFECTS OF A RESET
Both Power-on Reset and subsequent Resets will force
all ports to Input mode and the CCP registers to their
Reset states.
This forces the Enhanced CCP module to reset to a
state compatible with the standard CCP module.
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DS39689F-page 166 © 2009 Microchip Technology Inc.
TABLE 17-3: REGISTERS ASSOCIATED WITH ECCP1 MODULE AND TIMER1 TO TIMER3
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
RCON IPEN SBOREN(1) RI TO PD POR BOR 54
PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
TRISB PORTB Data Direction Register 58
TRISC PORTC Data Direction Register 58
TRISD(2) PORTD Data Direction Register 58
TMR1L Timer1 Register Low Byte 56
TMR1H Timer1 Register High Byte 56
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56
TMR2 Timer2 Register 56
T2CON T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 56
PR2 Timer2 Period Register 56
TMR3L Timer3 Register Low Byte 57
TMR3H Timer3 Register High Byte 57
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 57
CCPR1L Capture/Compare/PWM Register 1 Low Byte 57
CCPR1H Capture/Compare/PWM Register 1 High Byte 57
CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 57
ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 57
Legend: = unimplemented, read as0. Shaded cells are not used during ECCP operation.
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and
reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are unimplemented on 28-pin devices; always maintain these bits clear.
© 2009 Microchip Technology Inc. DS39689F-page 167
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18.0 MASTER SYNCHRONOUS
SERIAL PORT (MSSP)
MODULE
18.1 Master SSP (MSSP) Module
Overview
The Master Synchronous Serial Port (MSSP) module is
a serial interface, useful for communicating with other
peripheral or microcontroller devices. These peripheral
devices may be serial EEPROMs, shift registers,
display drivers, A/D converters, etc. The MSSP module
can operate in one of two modes:
Serial Peripheral Interface (SPI)
Inter-Integrated Circuit (I2C™)
- Full Master mode
- Slave mode (with address masking for both
10-bit and 7-bit addressing)
The I2C interface supports the following modes in
hardware:
•Master mode
Multi-Master mode
Slave mode
18.2 Control Registers
The MSSP module has three associated registers.
These include a status register (SSPSTAT) and two
control registers (SSPCON1 and SSPCON2). The use
of these registers and their individual Configuration bits
differ significantly depending on whether the MSSP
module is operated in SPI or I2C mode.
Additional details are provided under the individual
sections.
18.3 SPI Mode
The SPI mode allows 8 bits of data to be synchronously
transmitted and received simultaneously. All four SPI
modes are supported. To accomplish communication,
typically three pins are used:
Serial Data Out (SDO) – SDO
Serial Data In (SDI) – SDI/SDA
Serial Clock (SCK) – SCK/SCL
Additionally, a fourth pin may be used when in a Slave
mode of operation:
Slave Select (SS)
Figure 18-1 shows the block diagram of the MSSP
module when operating in SPI mode.
FIGURE 18-1: MSSP BLOCK DIAGRAM
(SPI MODE)
( )
Read Write
Internal
Data Bus
SSPSR reg
SSPM<3:0>
bit 0 Shift
Clock
SS Control
Enable
Edge
Select
Clock Select
TMR2 Output
TOSC
Prescaler
4, 16, 64
2
Edge
Select
2
4
Data to TX/RX in SSPSR
TRIS bit
2
SMP:CKE
SDO
SSPBUF reg
SDI/SDA
SS
SCK/SCL
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DS39689F-page 168 © 2009 Microchip Technology Inc.
18.3.1 REGISTERS
The MSSP module has four registers for SPI mode
operation. These are:
MSSP Control Register 1 (SSPCON1)
MSSP Status Register (SSPSTAT)
Serial Receive/Transmit Buffer Register
(SSPBUF)
MSSP Shift Register (SSPSR) – Not directly
accessible
SSPCON1 and SSPSTAT are the control and status
registers in SPI mode operation. The SSPCON1 register
is readable and writable. The lower 6 bits of the
SSPSTAT are read-only. The upper two bits of the
SSPSTAT are read/write.
SSPSR is the shift register used for shifting data in or
out. SSPBUF is the buffer register to which data bytes
are written to or read from.
In receive operations, SSPSR and SSPBUF together
create a double-buffered receiver. When SSPSR
receives a complete byte, it is transferred to SSPBUF
and the SSPIF interrupt is set.
During transmission, the SSPBUF is not double-
buffered. A write to SSPBUF will write to both SSPBUF
and SSPSR.
REGISTER 18-1: SSPSTAT: MSSP STATUS REGISTER (SPI MODE)
R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A PSR/WUA BF
bit 7 bit 0
bit 7 SMP: Sample bit
SPI Master mode:
1 = Input data sampled at end of data output time
0 = Input data sampled at middle of data output time
SPI Slave mode:
SMP must be cleared when SPI is used in Slave mode.
bit 6 CKE: SPI Clock Select bit
1 = Transmit occurs on transition from active to Idle clock state
0 = Transmit occurs on transition from Idle to active clock state
Note: Polarity of clock state is set by the CKP bit (SSPCON1<4>).
bit 5 D/A: Data/Address bit
Used in I2C™ mode only.
bit 4 P: Stop bit
Used in I2C mode only. This bit is cleared when the MSSP module is disabled, SSPEN is
cleared.
bit 3 S: Start bit
Used in I2C mode only.
bit 2 R/W: Read/Write Information bit
Used in I2C mode only.
bit 1 UA: Update Address bit
Used in I2C mode only.
bit 0 BF: Buffer Full Status bit (Receive mode only)
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 169
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REGISTER 18-2: SSPCON1: MSSP CONTROL REGISTER 1 (SPI MODE)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit (Transmit mode only)
1 = The SSPBUF register is written while it is still transmitting the previous word
(must be cleared in software)
0 = No collision
bit 6 SSPOV: Receive Overflow Indicator bit
SPI Slave mode:
1 = A new byte is received while the SSPBUF register is still holding the previous data. In case
of overflow, the data in SSPSR is lost. Overflow can only occur in Slave mode. The user
must read the SSPBUF, even if only transmitting data, to avoid setting overflow (must be
cleared in software).
0 = No overflow
Note: In Master mode, the overflow bit is not set since each new reception (and
transmission) is initiated by writing to the SSPBUF register.
bit 5 SSPEN: Synchronous Serial Port Enable bit
1 = Enables serial port and configures SCK, SDO, SDI and SS as serial port pins
0 = Disables serial port and configures these pins as I/O port pins
Note: When enabled, these pins must be properly configured as input or output.
bit 4 CKP: Clock Polarity Select bit
1 = Idle state for clock is a high level
0 = Idle state for clock is a low level
bit 3-0 SSPM<3:0>: Synchronous Serial Port Mode Select bits
0101 = SPI Slave mode, clock = SCK pin, SS pin control disabled, SS can be used as I/O pin
0100 = SPI Slave mode, clock = SCK pin, SS pin control enabled
0011 = SPI Master mode, clock = TMR2 output/2
0010 = SPI Master mode, clock = FOSC/64
0001 = SPI Master mode, clock = FOSC/16
0000 = SPI Master mode, clock = FOSC/4
Note: Bit combinations not specifically listed here are either reserved or implemented in
I2C™ mode only.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set 0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 170 © 2009 Microchip Technology Inc.
18.3.2 OPERATION
When initializing the SPI, several options need to be
specified. This is done by programming the appropriate
control bits (SSPCON1<5:0> and SSPSTAT<7:6>).
These control bits allow the following to be specified:
Master mode (SCK is the clock output)
Slave mode (SCK is the clock input)
Clock Polarity (Idle state of SCK)
Data Input Sample Phase (middle or end of data
output time)
Clock Edge (output data on rising/falling edge
of SCK)
Clock Rate (Master mode only)
Slave Select mode (Slave mode only)
The MSSP consists of a transmit/receive shift register
(SSPSR) and a buffer register (SSPBUF). The SSPSR
shifts the data in and out of the device, MSb first. The
SSPBUF holds the data that was written to the SSPSR
until the received data is ready. Once the 8 bits of data
have been received, that byte is moved to the SSPBUF
register. Then, the Buffer Full detect bit, BF
(SSPSTAT<0>), and the interrupt flag bit, SSPIF, are
set. This double-buffering of the received data
(SSPBUF) allows the next byte to start reception before
reading the data that was just received. Any write to the
SSPBUF register during transmission/reception of data
will be ignored and the write collision detect bit, WCOL
(SSPCON1<7>), will be set. User software must clear
the WCOL bit so that it can be determined if the following
write(s) to the SSPBUF register completed successfully.
When the application software is expecting to receive
valid data, the SSPBUF should be read before the next
byte of data to transfer is written to the SSPBUF. The
Buffer Full bit, BF (SSPSTAT<0>), indicates when
SSPBUF has been loaded with the received data
(transmission is complete). When the SSPBUF is read,
the BF bit is cleared. This data may be irrelevant if the
SPI is only a transmitter. Generally, the MSSP interrupt
is used to determine when the transmission/reception
has completed. The SSPBUF must be read and/or
written. If the interrupt method is not going to be used,
then software polling can be done to ensure that a write
collision does not occur. Example 18-1 shows the
loading of the SSPBUF (SSPSR) for data transmission.
The SSPSR is not directly readable or writable and can
only be accessed by addressing the SSPBUF register.
Additionally, the MSSP Status register (SSPSTAT)
indicates the various status conditions.
EXAMPLE 18-1: LOADING THE SSPBUF (SSPSR) REGISTER
Note: To avoid lost data in Master mode, a read of
the SSPBUF must be performed to clear the
Buffer Full (BF) detect bit (SSPSTAT<0>)
between each transmission.
Note: The SSPBUF register cannot be used with
read-modify-write instructions, such as
BCF, BTFSC and COMF, etc.
LOOP BTFSS SSPSTAT, BF ;Has data been received (transmit complete)?
BRA LOOP ;No
MOVF SSPBUF, W ;WREG reg = contents of SSPBUF
MOVWF RXDATA ;Save in user RAM, if data is meaningful
MOVF TXDATA, W ;W reg = contents of TXDATA
MOVWF SSPBUF ;New data to xmit
© 2009 Microchip Technology Inc. DS39689F-page 171
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18.3.3 ENABLING SPI I/O
To enable the serial port, MSSP Enable bit, SSPEN
(SSPCON1<5>), must be set. To reset or reconfigure
SPI mode, clear the SSPEN bit, reinitialize the
SSPCON registers and then set the SSPEN bit. This
configures the SDI, SDO, SCK and SS pins as serial
port pins. For the pins to behave as the serial port
function, some must have their data direction bits (in
the TRIS register) appropriately programmed as
follows:
SDI is automatically controlled by the SPI module
SDO must have TRISC<5> bit cleared
SCK (Master mode) must have TRISC<3> bit
cleared
SCK (Slave mode) must have TRISC<3> bit set
•SS
must have TRISA<5> bit set
Any serial port function that is not desired may be
overridden by programming the corresponding data
direction (TRIS) register to the opposite value.
18.3.4 TYPICAL CONNECTION
Figure 18-2 shows a typical connection between two
microcontrollers. The master controller (Processor 1)
initiates the data transfer by sending the SCK signal.
Data is shifted out of both shift registers on their pro-
grammed clock edge and latched on the opposite edge
of the clock. Both processors should be programmed to
the same Clock Polarity (CKP), then both controllers
would send and receive data at the same time.
Whether the data is meaningful (or dummy data)
depends on the application software. This leads to
three scenarios for data transmission:
Master sends data Slave sends dummy data
Master sends data Slave sends data
Master sends dummy data Slave sends data
FIGURE 18-2: SPI MASTER/SLAVE CONNECTION
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb LSb
SDO
SDI
PROCESSOR 1
SCK
SPI Master SSPM<3:0> = 00xxb
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
LSb
MSb
SDI
SDO
PROCESSOR 2
SCK
SPI Slave SSPM<3:0> = 010xb
Serial Clock
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18.3.5 MASTER MODE
The master can initiate the data transfer at any time
because it controls the SCK. The master determines
when the slave (Processor 2, Figure 18-2) is to
broadcast data by the software protocol.
In Master mode, the data is transmitted/received as
soon as the SSPBUF register is written to. If the SPI
operation is only going to receive, the SDO output
could be disabled (programmed as an input). The
SSPSR register will continue to shift in the signal pres-
ent on the SDI pin at the programmed clock rate. As
each byte is received, it will be loaded into the SSPBUF
register as if a normal received byte (interrupts and sta-
tus bits appropriately set). This could be useful in
receiver applications as a “Line Activity Monitor” mode.
The clock polarity is selected by appropriately
programming the CKP bit (SSPCON1<4>). This then,
would give waveforms for SPI communication as
shown in Figure 18-3, Figure 18-5 and Figure 18-6,
where the MSB is transmitted first. In Master mode, the
SPI clock rate (bit rate) is user-programmable to be one
of the following:
•F
OSC/4 (or TCY)
•FOSC/16 (or 4 • TCY)
•F
OSC/64 (or 16 • TCY)
Timer2 output/2
This allows a maximum data rate (at 40 MHz) of
10.00 Mbps.
Figure 18-3 shows the waveforms for Master mode.
When the CKE bit is set, the SDO data is valid before
there is a clock edge on SCK. The change of the input
sample is shown based on the state of the SMP bit. The
time when the SSPBUF is loaded with the received
data is shown.
FIGURE 18-3: SPI MODE WAVEFORM (MASTER MODE)
SCK
(CKP = 0
SCK
(CKP = 1
SCK
(CKP = 0
SCK
(CKP = 1
4 Clock
Modes
Input
Sample
Input
Sample
SDI
bit 7 bit 0
SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
bit 7
SDI
SSPIF
(SMP = 1)
(SMP = 0)
(SMP = 1)
CKE = 1)
CKE = 0)
CKE = 1)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
(CKE = 0)
(CKE = 1)
Next Q4 Cycle
after Q2
bit 0
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18.3.6 SLAVE MODE
In Slave mode, the data is transmitted and received as
the external clock pulses appear on SCK. When the
last bit is latched, the SSPIF interrupt flag bit is set.
Before enabling the module in SPI Slave mode, the
clock line must match the proper Idle state. The clock
line can be observed by reading the SCK pin. The Idle
state is determined by the CKP bit (SSPCON1<4>).
While in Slave mode, the external clock is supplied by
the external clock source on the SCK pin. This external
clock must meet the minimum high and low times as
specified in the electrical specifications.
While in Sleep mode, the slave can transmit/receive
data. When a byte is received, the device will wake-up
from Sleep.
18.3.7 SLAVE SELECT
SYNCHRONIZATION
The SS pin allows a Synchronous Slave mode. The SPI
operation must be in Slave mode with the SS pin control
enabled (SSPCON1<3:0> = 04h). When the SS pin is
low, transmission and reception are enabled and the
SDO pin is driven. When the SS pin goes high, the SDO
pin is no longer driven, even if in the middle of a
transmitted byte and becomes a floating output. External
pull-up/pull-down resistors may be desirable depending
on the application.
When the SPI module resets, the bit counter is forced
to ‘0’. This can be done by either forcing the SS pin to
a high level or clearing the SSPEN bit.
To emulate two-wire communication, the SDO pin can
be connected to the SDI pin. When the SPI needs to
operate as a receiver, the SDO pin can be configured
as an input. This disables transmissions from the SDO.
The SDI can always be left as an input (SDI function)
since it cannot create a bus conflict.
FIGURE 18-4: SLAVE SYNCHRONIZATION WAVEFORM
Note 1: When the SPI interface is in Slave mode
with SS pin control enabled
(SSPCON1<3:0> = 0100), the SPI module
will reset if the SS pin is set to VDD.
2: If the SPI interface is used in Slave mode
with CKE set, then the SS pin control
must be enabled.
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI
bit 7
SDO bit 7 bit 6 bit 7
SSPIF
Interrupt
(SMP = 0)
CKE = 0)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
bit 0
bit 7
bit 0
Next Q4 Cycle
after Q2
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FIGURE 18-5: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 0)
FIGURE 18-6: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 1)
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI
bit 7
SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
SSPIF
Interrupt
(SMP = 0)
CKE = 0)
CKE = 0)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
Optional
Next Q4 Cycle
after Q2
bit 0
SCK
(CKP = 1
SCK
(CKP = 0
Input
Sample
SDI
bit 7 bit 0
SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
SSPIF
Interrupt
(SMP = 0)
CKE = 1)
CKE = 1)
(SMP = 0)
Write to
SSPBUF
SSPSR to
SSPBUF
SS
Flag
Not Optional
Next Q4 Cycle
after Q2
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18.3.8 OPERATION IN POWER-MANAGED
MODES
In SPI Master mode, module clocks may be operating
at a different speed than when in full power mode. In
the case of Sleep mode, all clocks are halted.
In Idle modes, a clock is provided to the peripherals.
That clock should be from the primary clock source, the
secondary clock (Timer1 oscillator at 32.768 kHz) or
the INTOSC source. See Section 3.7 “Clock Sources
and Oscillator Switching” for additional information.
In most cases, the speed that the master clocks SPI
data is not important; however, this should be
evaluated for each system.
If MSSP interrupts are enabled, they can wake the
controller from Sleep mode, or one of the Idle modes,
when the master completes sending data. If an exit
from Sleep or Idle mode is not desired, MSSP
interrupts should be disabled.
If the Sleep mode is selected, all module clocks are
halted and the transmission/reception will remain in
that state until the devices wakes. After the device
returns to Run mode, the module will resume
transmitting and receiving data.
In SPI Slave mode, the SPI Transmit/Receive Shift
register operates asynchronously to the device. This
allows the device to be placed in any power-managed
mode and data to be shifted into the SPI Transmit/
Receive Shift register. When all 8 bits have been
received, the MSSP interrupt flag bit will be set and if
enabled, will wake the device.
18.3.9 EFFECTS OF A RESET
A Reset disables the MSSP module and terminates the
current transfer.
18.3.10 BUS MODE COMPATIBILITY
Table 18-1 shows the compatibility between the
standard SPI modes and the states of the CKP and
CKE control bits.
TABLE 18-1: SPI BUS MODES
There is also an SMP bit which controls when the data
is sampled.
TABLE 18-2: REGISTERS ASSOCIATED WITH SPI OPERATION
Standard SPI Mode
Terminology
Control Bits State
CKP CKE
0, 0 0 1
0, 1 0 0
1, 0 1 1
1, 1 1 0
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
TRISA TRISA7(2) TRISA6(2) PORTA Data Direction Control Register 58
TRISC PORTC Data Direction Control Register 58
SSPBUF MSSP Receive Buffer/Transmit Register 56
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 56
SSPSTAT SMP CKE D/A P S R/W UA BF 56
Legend: Shaded cells are not used by the MSSP in SPI mode.
Note 1: These bits are unimplemented on 28-pin devices and read as0’.
2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.
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18.4 I2C Mode
The MSSP module in I2C mode fully implements all
master and slave functions (including general call
support) and provides interrupts on Start and Stop bits
in hardware to determine a free bus (multi-master
function). The MSSP module implements the standard
mode specifications, as well as 7-bit and 10-bit
addressing.
Two pins are used for data transfer:
Serial clock (SCL) – RC3/SCK/SCL
Serial data (SDA) – RC4/SDI/SDA
The user must configure these pins as inputs or outputs
through the TRISC<4:3> bits.
FIGURE 18-7: MSSP BLOCK DIAGRAM
(I2C™ MODE)
18.4.1 REGISTERS
The MSSP module has six registers for I2C operation.
These are:
MSSP Control Register 1 (SSPCON1)
MSSP Control Register 2 (SSPCON2)
MSSP Status Register (SSPSTAT)
Serial Receive/Transmit Buffer Register
(SSPBUF)
MSSP Shift Register (SSPSR) – Not directly
accessible
MSSP Address Register (SSPADD)
SSPCON1, SSPCON2 and SSPSTAT are the control
and status registers in I2C mode operation. The
SSPCON1 and SSPCON2 registers are readable and
writable. The lower 6 bits of the SSPSTAT are read-only.
The upper two bits of the SSPSTAT are read/write.
SSPSR is the shift register used for shifting data in or
out. SSPBUF is the buffer register to which data bytes
are written to or read from.
SSPADD register holds the slave device address when
the MSSP is configured in I2C Slave mode. When the
MSSP is configured in Master mode, the lower seven
bits of SSPADD act as the Baud Rate Generator reload
value.
In receive operations, SSPSR and SSPBUF together
create a double-buffered receiver. When SSPSR
receives a complete byte, it is transferred to SSPBUF
and the SSPIF interrupt is set.
During transmission, the SSPBUF is not double-
buffered. A write to SSPBUF will write to both SSPBUF
and SSPSR.
Read Write
SSPSR reg
Match Detect
SSPADD reg
Start and
Stop bit Detect
SSPBUF reg
Internal
Data Bus
Addr Match
Set, Reset
S, P bits
(SSPSTAT reg)
RC3/SCK/SCL
RC4/SDI/
Shift
Clock
MSb
SDA LSb
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REGISTER 18-3: SSPSTAT: MSSP STATUS REGISTER (I2C™ MODE)
R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A PSR/WUA BF
bit 7 bit 0
bit 7 SMP: Slew Rate Control bit
In Master or Slave mode:
1 = Slew rate control disabled for Standard Speed mode (100 kHz and 1 MHz)
0 = Slew rate control enabled for High-Speed mode (400 kHz)
bit 6 CKE: SMBus Select bit
In Master or Slave mode:
1 = Enable SMBus specific inputs
0 = Disable SMBus specific inputs
bit 5 D/A: Data/Address bit
In Master mode:
Reserved.
In Slave mode:
1 = Indicates that the last byte received or transmitted was data
0 = Indicates that the last byte received or transmitted was address
bit 4 P: Stop bit
1 = Indicates that a Stop bit has been detected last
0 = Stop bit was not detected last
Note: This bit is cleared on Reset and when SSPEN is cleared.
bit 3 S: Start bit
1 = Indicates that a Start bit has been detected last
0 = Start bit was not detected last
Note: This bit is cleared on Reset and when SSPEN is cleared.
bit 2 R/W: Read/Write Information bit (I2C™ mode only)
In Slave mode:
1 = Read
0 = Write
Note: This bit holds the R/W bit information following the last address match. This bit is
only valid from the address match to the next Start bit, Stop bit or not ACK bit.
In Master mode:
1 = Transmit is in progress
0 = Transmit is not in progress
Note: ORing this bit with SEN, RSEN, PEN, RCEN or ACKEN will indicate if the MSSP is
in Active mode.
bit 1 UA: Update Address bit (10-bit Slave mode only)
1 = Indicates that the user needs to update the address in the SSPADD register
0 = Address does not need to be updated
bit 0 BF: Buffer Full Status bit
In Transmit mode:
1 = SSPBUF is full
0 = SSPBUF is empty
In Receive mode:
1 = SSPBUF is full (does not include the ACK and Stop bits)
0 = SSPBUF is empty (does not include the ACK and Stop bits)
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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REGISTER 18-4: SSPCON1: MSSP CONTROL REGISTER 1 (I2C™ MODE)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit
In Master Transmit mode:
1 = A write to the SSPBUF register was attempted while the I2C™ conditions were not valid for
a transmission to be started (must be cleared in software)
0 = No collision
In Slave Transmit mode:
1 = The SSPBUF register is written while it is still transmitting the previous word (must be
cleared in software)
0 = No collision
In Receive mode (Master or Slave modes):
This is a “don’t care” bit.
bit 6 SSPOV: Receive Overflow Indicator bit
In Receive mode:
1 = A byte is received while the SSPBUF register is still holding the previous byte (must be
cleared in software)
0 = No overflow
In Transmit mode:
This is a “don’t care” bit in Transmit mode.
bit 5 SSPEN: Master Synchronous Serial Port Enable bit
1 = Enables the serial port and configures the SDA and SCL pins as the serial port pins
0 = Disables serial port and configures these pins as I/O port pins
Note: When enabled, the SDA and SCL pins must be properly configured as inputs.
bit 4 CKP: SCK Release Control bit
In Slave mode:
1 = Release clock
0 = Holds clock low (clock stretch), used to ensure data setup time
In Master mode:
Unused in this mode.
bit 3-0 SSPM<3:0>: Master Synchronous Serial Port Mode Select bits
1111 = I2C Slave mode, 10-bit address with Start and Stop bit interrupts enabled
1110 = I2C Slave mode, 7-bit address with Start and Stop bit interrupts enabled
1011 = I2C Firmware Controlled Master mode (slave Idle)
1000 = I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))
0111 = I2C Slave mode, 10-bit address
0110 = I2C Slave mode, 7-bit address
Bit combinations not specifically listed here are either reserved or implemented in SPI mode only.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set 0’ = Bit is cleared x = Bit is unknown
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REGISTER 18-5: SSPCON2: MSSP CONTROL REGISTER 2 (I2C™ MODE)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
GCEN ACKSTAT ACKDT/
ADMSK5
ACKEN(1)/
ADMSK4
RCEN(1)/
ADMSK3
PEN(1)/
ADMSK2
RSEN(1)/
ADMSK1
SEN(1)
bit 7 bit 0
bit 7 GCEN: General Call Enable bit (Slave mode only)
1 = Enable interrupt when a general call address (0000h) is received in the SSPSR
0 = General call address disabled
bit 6 ACKSTAT: Acknowledge Status bit (Master Transmit mode only)
1 = Acknowledge was not received from slave
0 = Acknowledge was received from slave
bit 5 ACKDT/ADMSK5: Acknowledge Data bit
In Master Receive mode:
1 = Not Acknowledge
0 = Acknowledge
Note: Value that will be transmitted when the user initiates an Acknowledge sequence at
the end of a receive.
In Slave mode:
1 = Address masking of ADD5 enabled
0 = Address masking of ADD5 disabled
bit 4 ACKEN/ADMSK4: Acknowledge Sequence Enable bit
In Master Receive mode:(1)
1 = Initiate Acknowledge sequence on SDA and SCL pins and transmit ACKDT data bit.
Automatically cleared by hardware.
0 = Acknowledge sequence Idle
In Slave mode:
1 = Address masking of ADD4 enabled
0 = Address masking of ADD4 disabled
bit 3 RCEN/ADMSK3: Receive Enable bit
In Master Receive mode:(1)
1 = Enables Receive mode for I2C
0 = Receive Idle
In Slave mode:
1 = Address masking of ADD3 enabled
0 = Address masking of ADD3 disabled
bit 2 PEN/ADMSK2: Stop Condition Enable bit
In Master mode:(1)
1 = Initiate Stop condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Stop condition Idle
In Slave mode:
1 = Address masking of ADD2 enabled
0 = Address masking of ADD2 disabled
bit 1 RSEN/ADMSK1: Repeated Start Condition Enable bit
In Master mode:(1)
1 = Initiate Repeated Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Repeated Start condition Idle
In Slave mode (7-Bit Addressing mode):
1 = Address masking of ADD1 enabled
0 = Address masking of ADD1 disabled
In Slave mode (10-Bit Addressing mode):
1 = Address masking of ADD1 and ADD0 enabled
0 = Address masking of ADD1 and ADD0 disabled
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REGISTER 18-5: SSPCON2: MSSP CONTROL REGISTER 2 (I2C™ MODE) – CONTINUED
REGISTER 18-6: SSPADD: MSSP ADDRESS REGISTER(1)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
GCEN ACKSTAT ACKDT/
ADMSK5
ACKEN(1)/
ADMSK4
RCEN(1)/
ADMSK3
PEN(1)/
ADMSK2
RSEN(1)/
ADMSK1
SEN(1)
bit 7 bit 0
bit 0 SEN: Start Condition Enable/Stretch Enable bit(1)
In Master mode:
1 = Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Start condition Idle
In Slave mode:
1 = Clock stretching is enabled for both slave transmit and slave receive (stretch enabled)
0 = Clock stretching is disabled
Note 1: For bits ACKEN, RCEN, PEN, RSEN, SEN: If the I2C module is active, these bits
may not be set (no spooling) and the SSPBUF may not be written (or writes to the
SSPBUF are disabled).
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 ADD0
bit 7 bit 0
bit 7-0 ADD<7:0>: MSSP Address bits
Note 1: MSSP Address register in I2C Slave mode. MSSP Baud Rate register in I2C Master
mode.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 181
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18.4.2 OPERATION
The MSSP module functions are enabled by setting
MSSP Enable bit, SSPEN (SSPCON1<5>).
The SSPCON1 register allows control of the I2C
operation. Four mode selection bits (SSPCON1<3:0>)
allow one of the following I2C modes to be selected:
•I
2C Master mode clock
•I
2C Slave mode (7-bit address)
•I
2C Slave mode (10-bit address)
•I
2C Slave mode (7-bit address) with Start and
Stop bit interrupts enabled
•I
2C Slave mode (10-bit address) with Start and
Stop bit interrupts enabled
•I
2C Firmware Controlled Master mode, slave is Idle
Selection of any I2C mode with the SSPEN bit set,
forces the SCL and SDA pins to be open-drain,
provided these pins are programmed to inputs by
setting the appropriate TRISC bits. To ensure proper
operation of the module, pull-up resistors must be
provided externally to the SCL and SDA pins.
18.4.3 SLAVE MODE
In Slave mode, the SCL and SDA pins must be config-
ured as inputs (TRISC<4:3> set). The MSSP module
will override the input state with the output data when
required (slave-transmitter).
The I2C Slave mode hardware will always generate an
interrupt on an address match. Address masking will
allow the hardware to generate an interrupt for more
than one address (up to 31 in 7-Bit Addressing mode
and up to 63 in 10-Bit Addressing mode). Through the
mode select bits, the user can also choose to interrupt
on Start and Stop bits
When an address is matched, or the data transfer after
an address match is received, the hardware auto-
matically will generate the Acknowledge (ACK) pulse
and load the SSPBUF register with the received value
currently in the SSPSR register.
Any combination of the following conditions will cause
the MSSP module not to give this ACK pulse:
The Buffer Full bit, BF (SSPSTAT<0>), was set
before the transfer was received.
The overflow bit, SSPOV (SSPCON1<6>), was
set before the transfer was received.
In this case, the SSPSR register value is not loaded
into the SSPBUF, but bit SSPIF (PIR1<3>) is set. The
BF bit is cleared by reading the SSPBUF register, while
bit SSPOV is cleared through software.
The SCL clock input must have a minimum high and
low for proper operation. The high and low times of the
I2C specification, as well as the requirement of the
MSSP module, are shown in timing parameter 100 and
parameter 101.
18.4.3.1 Addressing
Once the MSSP module has been enabled, it waits for
a Start condition to occur. Following the Start condition,
the 8 bits are shifted into the SSPSR register. All incom-
ing bits are sampled with the rising edge of the clock
(SCL) line. The value of register SSPSR<7:1> is
compared to the value of the SSPADD register. The
address is compared on the falling edge of the eighth
clock (SCL) pulse. If the addresses match and the BF
and SSPOV bits are clear, the following events occur:
1. The SSPSR register value is loaded into the
SSPBUF register.
2. The Buffer Full bit, BF, is set.
3. An ACK pulse is generated.
4. MSSP Interrupt Flag bit, SSPIF (PIR1<3>), is
set (interrupt is generated, if enabled) on the
falling edge of the ninth SCL pulse.
In 10-Bit Addressing mode, two address bytes need to
be received by the slave. The five Most Significant bits
(MSbs) of the first address byte specify if this is a 10-bit
address. Bit R/W (SSPSTAT<2>) must specify a write so
the slave device will receive the second address byte.
For a 10-bit address, the first byte would equal ‘11110
A9 A8 0’, where ‘A9’ and ‘A8’ are the two MSbs of the
address. The sequence of events for 10-bit address is as
follows, with steps 7 through 9 for the slave-transmitter:
1. Receive first (high) byte of address (bits SSPIF,
BF and UA (SSPSTAT<1>) are set).
2. Update the SSPADD register with second (low)
byte of address (clears bit UA and releases the
SCL line).
3. Read the SSPBUF register (clears bit BF) and
clear flag bit, SSPIF.
4. Receive second (low) byte of address (bits
SSPIF, BF and UA are set).
5. Update the SSPADD register with the first (high)
byte of address. If match releases SCL line, this
will clear bit UA.
6. Read the SSPBUF register (clears bit BF) and
clear flag bit, SSPIF.
7. Receive Repeated Start condition.
8. Receive first (high) byte of address (bits SSPIF
and BF are set).
9. Read the SSPBUF register (clears bit BF) and
clear flag bit, SSPIF.
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18.4.3.2 Address Masking
Masking an address bit causes that bit to become a
“don’t care”. When one address bit is masked, two
addresses will be Acknowledged and cause an inter-
rupt. It is possible to mask more than one address bit at
a time, which makes it possible to Acknowledge up to
31 addresses in 7-Bit Addressing mode and up to
63 addresses in 10-Bit Addressing mode (see
Example 18-2).
The I2C slave behaves the same way whether address
masking is used or not. However, when address mask-
ing is used, the I2C slave can Acknowledge multiple
addresses and cause interrupts. When this occurs, it is
necessary to determine which address caused the
interrupt by checking the SSPBUF register.
7-Bit Addressing mode
Address mask bits, ADMSK<5:1>, mask the corre-
sponding address bits in the SSPADD register. For any
ADMSK bits that are active (ADMSK<n> = 1), the
corresponding address bit is ignored (ADD<n> = x). For
the module to issue an address Acknowledge, it is
sufficient to match only on addresses that do not have an
active address mask.
10-Bit Addressing mode
Address mask bits, ADMSK<5:2>, mask the
corresponding address bits in the SSPADD register. In
addition, ADMSK<1> simultaneously masks the two
LSBs of the address, ADD<1:0>. For any ADMSK bits
that are active (ADMSK<n> = 1), the corresponding
address bit is ignored (ADD<n> = x). Also note that
although in 10-Bit Addressing mode, the upper address
bits reuse part of the SSPADD register bits, the address
mask bits do not interact with those bits. They only
affect the lower address bits.
EXAMPLE 18-2: ADDRESS MASKING
Note 1: ADMSK<1> masks the two Least
Significant bits of the address.
2: The two Most Significant bits of the
address are not affected by address
masking.
7-Bit Addressing mode:
SSPADD<7:1> = 1010 0000
ADMSK<5:1> = 00 111
Addresses Acknowledged = 0xA0, 0xA2, 0xA4, 0xA6, 0xA8, 0xAA, 0xAC, 0xAE
10-Bit Addressing mode:
SSPADD<7:0> = 1010 0000 (The two MSbs are ignored in this example since they are not affected)
ADMSK<5:1> = 00 111
Addresses Acknowledged = 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB,
0xAC, 0xAD, 0xAE, 0xAF
The upper two bits are not affected by the address masking.
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18.4.3.3 Reception
When the R/W bit of the address byte is clear and an
address match occurs, the R/W bit of the SSPSTAT
register is cleared. The received address is loaded into
the SSPBUF register and the SDA line is held low
(ACK).
When the address byte overflow condition exists, then
the no Acknowledge (ACK) pulse is given. An overflow
condition is defined as either bit BF (SSPSTAT<0>) is
set, or bit SSPOV (SSPCON1<6>) is set.
An MSSP interrupt is generated for each data transfer
byte. Flag bit, SSPIF (PIR1<3>), must be cleared in
software. The SSPSTAT register is used to determine
the status of the byte.
If SEN is enabled (SSPCON2<0> = 1), RC3/SCK/SCL
will be held low (clock stretch) following each data
transfer. The clock must be released by setting bit,
CKP (SSPCON1<4>). See Section 18.4.4 “Clock
Stretching” for more detail.
18.4.3.4 Transmission
When the R/W bit of the incoming address byte is set
and an address match occurs, the R/W bit of the
SSPSTAT register is set. The received address is
loaded into the SSPBUF register. The ACK pulse will
be sent on the ninth bit and pin RC3/SCK/SCL is held
low regardless of SEN (see Section 18.4.4 “Clock
Stretching” for more detail). By stretching the clock,
the master will be unable to assert another clock pulse
until the slave is done preparing the transmit data. The
transmit data must be loaded into the SSPBUF register
which also loads the SSPSR register. Then pin RC3/
SCK/SCL should be enabled by setting bit, CKP
(SSPCON1<4>). The eight data bits are shifted out on
the falling edge of the SCL input. This ensures that the
SDA signal is valid during the SCL high time
(Figure 18-10).
The ACK pulse from the master-receiver is latched on
the rising edge of the ninth SCL input pulse. If the SDA
line is high (not ACK), then the data transfer is
complete. In this case, when the ACK is latched by the
slave, the slave logic is reset and the slave monitors for
another occurrence of the Start bit. If the SDA line was
low (ACK), the next transmit data must be loaded into
the SSPBUF register. Again, pin RC3/SCK/SCL must
be enabled by setting bit CKP.
An MSSP interrupt is generated for each data transfer
byte. The SSPIF bit must be cleared in software and
the SSPSTAT register is used to determine the status
of the byte. The SSPIF bit is set on the falling edge of
the ninth clock pulse.
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DS39689F-page 184 © 2009 Microchip Technology Inc.
FIGURE 18-8: I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 7-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
S1 234 56 7 89 1 2 34 5 67 89 1 2345 7 89 P
A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0
ACK
Receiving Data
ACK
Receiving Data
R/W = 0
ACK
Receiving Address
Cleared in software
SSPBUF is read
Bus master
terminates
transfer
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
D2
6
CKP (CKP does not reset to ‘0’ when SEN = 0)
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FIGURE 18-9: I2C™ SLAVE MODE TIMING WITH SEN = 0 AND ADMSK<5:1> = 01011
(RECEPTION, 7-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
S12345678912345678912345 789 P
A7 A6 A5 X A3 X X D7D6D5D4D3D2D1 D0 D7D6D5D4D3 D1D0
ACK
Receiving Data
ACK
Receiving Data
R/W = 0
ACK
Receiving Address
Cleared in software
SSPBUF is read
Bus master
terminates
transfer
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
D2
6
CKP
(CKP does not reset to ‘0’ when SEN = 0)
Note 1: x = Don’t care (i.e., address bit can be either a ‘1’ or a ‘0’).
2: In this example, an address equal to A7.A6.A5.X.A3.X.X will be Acknowledged and cause an interrupt.
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DS39689F-page 186 © 2009 Microchip Technology Inc.
FIGURE 18-10: I2C™ SLAVE MODE TIMING (TRANSMISSION, 7-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
A6 A5 A4 A3 A2 A1 D6 D5 D4 D3 D2 D1 D0
1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 9
SSPBUF is written in software
Cleared in software
Data in
sampled
S
ACK
Transmitting Data
R/W =
1
ACK
Receiving Address
A7 D7
9 1
D6 D5 D4 D3 D2 D1 D0
2 3 4 5 6 7 8 9
SSPBUF is written in software
Cleared in software
From SSPIF ISR
Transmitting Data
D7
1
CKP
P
ACK
CKP is set in software CKP is set in software
SCL held low
while CPU
responds to SSPIF
Clear by reading
From SSPIF ISR
© 2009 Microchip Technology Inc. DS39689F-page 187
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FIGURE 18-11: I2C™ SLAVE MODE TIMING WITH SEN = 0 AND ADMSK = 01001
(RECEPTION, 10-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
S123456789 123456789 12345 789 P
1 1 1 1 0 A9 A8 A7 A6 A5 X A3 A2 X X D7 D6 D5 D4 D3 D1 D0
Receive Data Byte
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
D2
6
Cleared in software
Receive Second Byte of Address
Cleared by hardware
when SSPADD is updated
with low byte of address
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated with high
byte of address
SSPBUF is written with
contents of SSPSR
Dummy read of SSPBUF
to clear BF flag
ACK
CKP
12345 789
D7 D6 D5 D4 D3 D1 D0
Receive Data Byte
Bus master
terminates
transfer
D2
6
ACK
Cleared in software Cleared in software
SSPOV (SSPCON1<6>)
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
(CKP does not reset to ‘0’ when SEN = 0)
Clock is held low until
update of SSPADD has
taken place
Note 1: x = Don’t care (i.e., address bit can be either a ‘1’ or a ‘0’).
2: In this example, an address equal to A9.A8.A7.A6.A5.X.A3.A2.X.X will be Acknowledged and cause an interrupt.
3: Note that the Most Significant bits of the address are not affected by the bit masking.
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DS39689F-page 188 © 2009 Microchip Technology Inc.
FIGURE 18-12: I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 10-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
S123456789 123456789 12345 789 P
1 1 1 1 0 A9 A8 A7 A6A5 A4A3A2A1 A0 D7 D6D5D4D3 D1D0
Receive Data Byte
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
D2
6
Cleared in software
Receive Second Byte of Address
Cleared by hardware
when SSPADD is updated
with low byte of address
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated with high
byte of address
SSPBUF is written with
contents of SSPSR
Dummy read of SSPBUF
to clear BF flag
ACK
CKP
12345 789
D7 D6 D5 D4 D3 D1 D0
Receive Data Byte
Bus master
terminates
transfer
D2
6
ACK
Cleared in software Cleared in software
SSPOV (SSPCON1<6>)
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
(CKP does not reset to ‘0’ when SEN = 0)
Clock is held low until
update of SSPADD has
taken place
© 2009 Microchip Technology Inc. DS39689F-page 189
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FIGURE 18-13: I2C™ SLAVE MODE TIMING (TRANSMISSION, 10-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
S1234 5 6789 1 2345 678 9 12345 7 89 P
1 1 1 1 0 A9A8 A7 A6A5A4A3A2A1 A0 1 1 1 1 0 A8
R/W=1
ACK
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
Bus master
terminates
transfer
A9
6
Receive Second Byte of Address
Cleared by hardware when
SSPADD is updated with low
byte of address
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated with high
byte of address.
SSPBUF is written with
contents of SSPSR
Dummy read of SSPBUF
to clear BF flag
Receive First Byte of Address
12345 789
D7 D6 D5 D4 D3 D1
ACK
D2
6
Transmitting Data Byte
D0
Dummy read of SSPBUF
to clear BF flag
Sr
Cleared in software
Write of SSPBUF
initiates transmit
Cleared in software
Completion of
clears BF flag
CKP (SSPCON1<4>)
CKP is set in software
CKP is automatically cleared in hardware, holding SCL low
Clock is held low until
update of SSPADD has
taken place
data transmission
Clock is held low until
CKP is set to ‘1
third address sequence
BF flag is clear
at the end of the
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DS39689F-page 190 © 2009 Microchip Technology Inc.
18.4.4 CLOCK STRETCHING
Both 7-Bit and 10-Bit Slave modes implement
automatic clock stretching during a transmit sequence.
The SEN bit (SSPCON2<0>) allows clock stretching to
be enabled during receives. Setting SEN will cause
the SCL pin to be held low at the end of each data
receive sequence.
18.4.4.1 Clock Stretching for 7-Bit Slave
Receive Mode (SEN = 1)
In 7-Bit Slave Receive mode, on the falling edge of the
ninth clock at the end of the ACK sequence if the BF
bit is set, the CKP bit in the SSPCON1 register is
automatically cleared, forcing the SCL output to be
held low. The CKP bit being cleared to ‘0’ will assert
the SCL line low. The CKP bit must be set in the user’s
ISR before reception is allowed to continue. By holding
the SCL line low, the user has time to service the ISR
and read the contents of the SSPBUF before the
master device can initiate another receive sequence.
This will prevent buffer overruns from occurring (see
Figure 18-15).
18.4.4.2 Clock Stretching for 10-Bit Slave
Receive Mode (SEN = 1)
In 10-Bit Slave Receive mode during the address
sequence, clock stretching automatically takes place
but CKP is not cleared. During this time, if the UA bit is
set after the ninth clock, clock stretching is initiated.
The UA bit is set after receiving the upper byte of the
10-bit address and following the receive of the second
byte of the 10-bit address with the R/W bit cleared to
0’. The release of the clock line occurs upon updating
SSPADD. Clock stretching will occur on each data
receive sequence as described in 7-bit mode.
18.4.4.3 Clock Stretching for 7-Bit Slave
Transmit Mode
7-Bit Slave Transmit mode implements clock stretch-
ing by clearing the CKP bit after the falling edge of the
ninth clock if the BF bit is clear. This occurs regardless
of the state of the SEN bit.
The user’s ISR must set the CKP bit before transmis-
sion is allowed to continue. By holding the SCL line
low, the user has time to service the ISR and load the
contents of the SSPBUF before the master device can
initiate another transmit sequence (see Figure 18-10).
18.4.4.4 Clock Stretching for 10-Bit Slave
Transmit Mode
In 10-Bit Slave Transmit mode, clock stretching is
controlled during the first two address sequences by
the state of the UA bit, just as it is in 10-Bit Slave
Receive mode. The first two addresses are followed
by a third address sequence which contains the high-
order bits of the 10-bit address and the R/W bit set to
1’. After the third address sequence is performed, the
UA bit is not set, the module is now configured in
Transmit mode and clock stretching is controlled by
the BF flag as in 7-Bit Slave Transmit mode (see
Figure 18-13).
Note 1: If the user reads the contents of the
SSPBUF before the falling edge of the
ninth clock, thus clearing the BF bit, the
CKP bit will not be cleared and clock
stretching will not occur.
2: The CKP bit can be set in software
regardless of the state of the BF bit. The
user should be careful to clear the BF bit
in the ISR before the next receive
sequence in order to prevent an overflow
condition.
Note: If the user polls the UA bit and clears it by
updating the SSPADD register before the
falling edge of the ninth clock occurs and if
the user hasn’t cleared the BF bit by read-
ing the SSPBUF register before that time,
then the CKP bit will still NOT be asserted
low. Clock stretching on the basis of the
state of the BF bit only occurs during a
data sequence, not an address sequence.
Note 1: If the user loads the contents of SSPBUF,
setting the BF bit before the falling edge of
the ninth clock, the CKP bit will not be
cleared and clock stretching will not occur.
2: The CKP bit can be set in software
regardless of the state of the BF bit.
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18.4.4.5 Clock Synchronization and
the CKP bit
When the CKP bit is cleared, the SCL output is forced
to ‘0’. However, clearing the CKP bit will not assert the
SCL output low until the SCL output is already
sampled low. Therefore, the CKP bit will not assert the
SCL line until an external I2C master device has
already asserted the SCL line. The SCL output will
remain low until the CKP bit is set and all other
devices on the I2C bus have deasserted SCL. This
ensures that a write to the CKP bit will not violate the
minimum high time requirement for SCL (see
Figure 18-14).
FIGURE 18-14: CLOCK SYNCHRONIZATION TIMING
SDA
SCL
DX – 1DX
WR
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
SSPCON
CKP
Master device
deasserts clock
Master device
asserts clock
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DS39689F-page 192 © 2009 Microchip Technology Inc.
FIGURE 18-15: I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 7-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
S1 234 56 7 89 1 2345 67 89 1 23 45 7 89 P
A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0
ACK
Receiving Data
ACK
Receiving Data
R/W = 0
ACK
Receiving Address
Cleared in software
SSPBUF is read
Bus master
terminates
transfer
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
D2
6
CKP
CKP
written
to ‘1’ in
If BF is cleared
prior to the falling
edge of the 9th clock,
CKP will not be reset
to ‘0’ and no clock
stretching will occur
software
Clock is held low until
CKP is set to ‘1
Clock is not held low
because buffer full bit is
clear prior to falling edge
of 9th clock
Clock is not held low
because ACK =
1
BF is set after falling
edge of the 9th clock,
CKP is reset to ‘0’ and
clock stretching occurs
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FIGURE 18-16: I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 10-BIT ADDRESSING)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
S123456789 123456789 12345 789 P
1 1 1 1 0 A9A8 A7 A6 A5A4A3A2A1 A0 D7D6D5D4D3 D1D0
Receive Data Byte
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
D2
6
Cleared in software
Receive Second Byte of Address
Cleared by hardware when
SSPADD is updated with low
byte of address after falling edge
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
UA is set indicating that
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated with high
byte of address after falling edge
SSPBUF is written with
contents of SSPSR
Dummy read of SSPBUF
to clear BF flag
ACK
CKP
12345 789
D7 D6 D5 D4 D3 D1 D0
Receive Data Byte
Bus master
terminates
transfer
D2
6
ACK
Cleared in software Cleared in software
SSPOV (SSPCON1<6>)
CKP written to
1
Note: An update of the SSPADD register before
the falling edge of the ninth clock will have
no effect on UA and UA will remain set.
Note: An update of the SSPADD
register before the falling
edge of the ninth clock will
have no effect on UA and
UA will remain set.
in software
Clock is held low until
update of SSPADD has
taken place
of ninth clock
of ninth clock
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
Dummy read of SSPBUF
to clear BF flag
Clock is held low until
CKP is set to
1
Clock is not held low
because ACK =
1
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DS39689F-page 194 © 2009 Microchip Technology Inc.
18.4.5 GENERAL CALL ADDRESS
SUPPORT
The addressing procedure for the I2C bus is such that
the first byte after the Start condition usually
determines which device will be the slave addressed by
the master. The exception is the general call address
which can address all devices. When this address is
used, all devices should, in theory, respond with an
Acknowledge.
The general call address is one of eight addresses
reserved for specific purposes by the I2C protocol. It
consists of all0’s with R/W = 0.
The general call address is recognized when the
General Call Enable bit, GCEN, is enabled
(SSPCON2<7> is set). Following a Start bit detect,
8 bits are shifted into the SSPSR and the address is
compared against the SSPADD. It is also compared to
the general call address and fixed in hardware.
If the general call address matches, the SSPSR is
transferred to the SSPBUF, the BF flag bit is set (eighth
bit) and on the falling edge of the ninth bit (ACK bit), the
SSPIF interrupt flag bit is set.
When the interrupt is serviced, the source for the
interrupt can be checked by reading the contents of the
SSPBUF. The value can be used to determine if the
address was device specific or a general call address.
In 10-bit mode, the SSPADD is required to be updated
for the second half of the address to match and the UA
bit (SSPSTAT<1>) is set. If the general call address is
sampled when the GCEN bit is set, while the slave is
configured in 10-Bit Addressing mode, then the second
half of the address is not necessary, the UA bit will not
be set and the slave will begin receiving data after the
Acknowledge (Figure 18-17).
FIGURE 18-17: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7 OR 10-BIT ADDRESSING MODE)
SDA
SCL
S
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
Cleared in software
SSPBUF is read
R/W = 0
ACK
General Call Address
Address is compared to General Call Address
GCEN (SSPCON2<7>)
Receiving Data ACK
123456789123456789
D7 D6 D5 D4 D3 D2 D1 D0
after ACK, set interrupt
0
1
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18.4.6 MASTER MODE
Master mode is enabled by setting and clearing the
appropriate SSPM bits in SSPCON1 and by setting the
SSPEN bit. In Master mode, the SCL and SDA lines
are manipulated by the MSSP hardware.
Master mode of operation is supported by interrupt
generation on the detection of the Start and Stop
conditions. The Stop (P) and Start (S) bits are cleared
from a Reset or when the MSSP module is disabled.
Control of the I2C bus may be taken when the P bit is
set, or the bus is Idle, with both the S and P bits clear.
In Firmware Controlled Master mode, user code
conducts all I2C bus operations based on Start and
Stop bit conditions.
Once Master mode is enabled, the user has six
options.
1. Assert a Start condition on SDA and SCL.
2. Assert a Repeated Start condition on SDA and
SCL.
3. Write to the SSPBUF register initiating
transmission of data/address.
4. Configure the I2C port to receive data.
5. Generate an Acknowledge condition at the end
of a received byte of data.
6. Generate a Stop condition on SDA and SCL.
The following events will cause the MSSP Interrupt
Flag bit, SSPIF, to be set (MSSP interrupt, if enabled):
Start condition
Stop condition
Data transfer byte transmitted/received
Acknowledge transmit
Repeated Start
FIGURE 18-18: MSSP BLOCK DIAGRAM (I2C™ MASTER MODE)
Note: The MSSP module, when configured in
I2C Master mode, does not allow queueing
of events. For instance, the user is not
allowed to initiate a Start condition and
immediately write the SSPBUF register to
initiate transmission before the Start
condition is complete. In this case, the
SSPBUF will not be written to and the
WCOL bit will be set, indicating that a write
to the SSPBUF did not occur.
Read Write
SSPSR
Start bit, Stop bit,
SSPBUF
Internal
Data Bus
Set/Reset, S, P, WCOL (SSPSTAT);
Shift
Clock
MSb LSb
SDA
Acknowledge
Generate
Stop bit Detect
Write Collision Detect
Clock Arbitration
State Counter for
end of XMIT/RCV
SCL
SCL In
Bus Collision
SDA In
Receive Enable
Clock Cntl
Clock Arbitrate/WCOL Detect
(hold off clock source)
SSPADD<6:0>
Baud
Set SSPIF, BCLIF;
Reset ACKSTAT, PEN (SSPCON2)
Rate
Generator
SSPM<3:0>
Start bit Detect
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18.4.6.1 I2C Master Mode Operation
The master device generates all of the serial clock
pulses and the Start and Stop conditions. A transfer is
ended with a Stop condition or with a Repeated Start
condition. Since the Repeated Start condition is also
the beginning of the next serial transfer, the I2C bus will
not be released.
In Master Transmitter mode, serial data is output
through SDA, while SCL outputs the serial clock. The
first byte transmitted contains the slave address of the
receiving device (7 bits) and the Read/Write (R/W) bit.
In this case, the R/W bit will be logic ‘0’. Serial data is
transmitted 8 bits at a time. After each byte is transmit-
ted, an Acknowledge bit is received. Start and Stop
conditions are output to indicate the beginning and the
end of a serial transfer.
In Master Receive mode, the first byte transmitted
contains the slave address of the transmitting device
(7 bits) and the R/W bit. In this case, the R/W bit will be
logic ‘1’. Thus, the first byte transmitted is a 7-bit slave
address followed by a ‘1to indicate the receive bit.
Serial data is received via SDA, while SCL outputs the
serial clock. Serial data is received 8 bits at a time. After
each byte is received, an Acknowledge bit is transmit-
ted. Start and Stop conditions indicate the beginning
and end of transmission.
The Baud Rate Generator used for the SPI mode
operation is used to set the SCL clock frequency for
either 100 kHz, 400 kHz or 1 MHz I2C operation. See
Section 18.4.7 “Baud Rate for more detail.
A typical transmit sequence would go as follows:
1. The user generates a Start condition by setting
the Start Enable bit, SEN (SSPCON2<0>).
2. SSPIF is set. The MSSP module will wait the
required start time before any other operation
takes place.
3. The user loads the SSPBUF with the slave
address to transmit.
4. Address is shifted out the SDA pin until all 8 bits
are transmitted.
5. The MSSP module shifts in the ACK bit from the
slave device and writes its value into the
SSPCON2 register.
6. The MSSP module generates an interrupt at the
end of the ninth clock cycle by setting the SSPIF
bit.
7. The user loads the SSPBUF with eight bits of
data.
8. Data is shifted out the SDA pin until all 8 bits are
transmitted.
9. The MSSP module shifts in the ACK bit from the
slave device and writes its value into the
SSPCON2 register.
10. The MSSP module generates an interrupt at the
end of the ninth clock cycle by setting the SSPIF
bit.
11. The user generates a Stop condition by setting
the Stop Enable bit, PEN (SSPCON2<2>).
12. Interrupt is generated once the Stop condition is
complete.
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18.4.7 BAUD RATE
In I2C Master mode, the Baud Rate Generator (BRG)
reload value is placed in the lower 7 bits of the
SSPADD register (Figure 18-19). When a write occurs
to SSPBUF, the Baud Rate Generator will automatically
begin counting. The BRG counts down to 0 and stops
until another reload has taken place. The BRG count is
decremented twice per instruction cycle (T
CY) on the
Q2 and Q4 clocks. In I2C Master mode, the BRG is
reloaded automatically.
Once the given operation is complete (i.e., transmis-
sion of the last data bit is followed by ACK), the internal
clock will automatically stop counting and the SCL pin
will remain in its last state.
Table 18-3 demonstrates clock rates based on
instruction cycles and the BRG value loaded into
SSPADD.
FIGURE 18-19: BAUD RATE GENERATOR BLOCK DIAGRAM
TABLE 18-3: I2C™ CLOCK RATE W/BRG
Fosc FCY FCY * 2 BRG Value FSCL
(2 Rollovers of BRG)
40 MHz 10 MHz 20 MHz 18h 400 kHz
40 MHz 10 MHz 20 MHz 1Fh 312.5 kHz
40 MHz 10 MHz 20 MHz 63h 100 kHz
16 MHz 4 MHz 8 MHz 09h 400 kHz
16 MHz 4 MHz 8 MHz 0Ch 308 kHz
16 MHz 4 MHz 8 MHz 27h 100 kHz
4 MHz 1 MHz 2 MHz 02h 333 kHz
4 MHz 1 MHz 2 MHz 09h 100 kHz
4 MHz 1 MHz 2 MHz 00h 1 MHz
SSPM<3:0>
BRG Down Counter
CLKO FOSC/4
SSPADD<6:0>
SSPM<3:0>
SCL
Reload
Control
Reload
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DS39689F-page 198 © 2009 Microchip Technology Inc.
18.4.7.1 Clock Arbitration
Clock arbitration occurs when the master, during any
receive, transmit or Repeated Start/Stop condition,
deasserts the SCL pin (SCL allowed to float high).
When the SCL pin is allowed to float high, the Baud
Rate Generator (BRG) is suspended from counting
until the SCL pin is actually sampled high. When the
SCL pin is sampled high, the Baud Rate Generator is
reloaded with the contents of SSPADD<6:0> and
begins counting. This ensures that the SCL high time
will always be at least one BRG rollover count in the
event that the clock is held low by an external device
(Figure 18-20).
FIGURE 18-20: BAUD RATE GENERATOR TIMING WITH CLOCK ARBITRATION
SDA
SCL
SCL deasserted but slave holds
DX – 1DX
BRG
SCL is sampled high, reload takes
place and BRG starts its count
03h 02h 01h 00h (hold off) 03h 02h
Reload
BRG
Value
SCL low (clock arbitration)
SCL allowed to transition high
BRG decrements on
Q2 and Q4 cycles
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18.4.8 I2C MASTER MODE START
CONDITION TIMING
To initiate a Start condition, the user sets the Start
Enable bit, SEN (SSPCON2<0>). If the SDA and SCL
pins are sampled high, the Baud Rate Generator is
reloaded with the contents of SSPADD<6:0> and starts
its count. If SCL and SDA are both sampled high when
the Baud Rate Generator times out (TBRG), the SDA
pin is driven low. The action of the SDA being driven
low while SCL is high is the Start condition and causes
the S bit (SSPSTAT<3>) to be set. Following this, the
Baud Rate Generator is reloaded with the contents of
SSPADD<6:0> and resumes its count. When the Baud
Rate Generator times out (TBRG), the SEN bit
(SSPCON2<0>) will be automatically cleared by
hardware; the Baud Rate Generator is suspended,
leaving the SDA line held low and the Start condition is
complete.
18.4.8.1 WCOL Status Flag
If the user writes the SSPBUF when a Start sequence
is in progress, the WCOL is set and the contents of the
buffer are unchanged (the write doesn’t occur).
FIGURE 18-21: FIRST START BIT TIMING
Note: If at the beginning of the Start condition,
the SDA and SCL pins are already sam-
pled low, or if during the Start condition, the
SCL line is sampled low before the SDA
line is driven low, a bus collision occurs,
the Bus Collision Interrupt Flag, BCLIF, is
set, the Start condition is aborted and the
I2C module is reset into its Idle state.
Note: Because queueing of events is not
allowed, writing to the lower 5 bits of
SSPCON2 is disabled until the Start
condition is complete.
SDA
SCL
S
TBRG
1st bit 2nd bit
TBRG
SDA = 1, At completion of Start bit,
SCL = 1
Write to SSPBUF occurs here
TBRG
hardware clears SEN bit
TBRG
Write to SEN bit occurs here Set S bit (SSPSTAT<3>)
and sets SSPIF bit
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DS39689F-page 200 © 2009 Microchip Technology Inc.
18.4.9 I2C MASTER MODE REPEATED
START CONDITION TIMING
A Repeated Start condition occurs when the RSEN bit
(SSPCON2<1>) is programmed high and the I2C logic
module is in the Idle state. When the RSEN bit is set,
the SCL pin is asserted low. When the SCL pin is
sampled low, the Baud Rate Generator is loaded with
the contents of SSPADD<5:0> and begins counting.
The SDA pin is released (brought high) for one Baud
Rate Generator count (TBRG). When the Baud Rate
Generator times out, if SDA is sampled high, the SCL
pin will be deasserted (brought high). When SCL is
sampled high, the Baud Rate Generator is reloaded
with the contents of SSPADD<6:0> and begins count-
ing. SDA and SCL must be sampled high for one TBRG.
This action is then followed by assertion of the SDA pin
(SDA = 0) for one TBRG while SCL is high. Following
this, the RSEN bit (SSPCON2<1>) will be automatically
cleared and the Baud Rate Generator will not be
reloaded, leaving the SDA pin held low. As soon as a
Start condition is detected on the SDA and SCL pins,
the S bit (SSPSTAT<3>) will be set. The SSPIF bit will
not be set until the Baud Rate Generator has timed out.
Immediately following the SSPIF bit getting set, the user
may write the SSPBUF with the 7-bit address in 7-bit
mode, or the default first address in 10-bit mode. After
the first eight bits are transmitted and an ACK is
received, the user may then transmit an additional eight
bits of address (10-bit mode) or eight bits of data (7-bit
mode).
18.4.9.1 WCOL Status Flag
If the user writes the SSPBUF when a Repeated Start
sequence is in progress, the WCOL is set and the
contents of the buffer are unchanged (the write doesn’t
occur).
FIGURE 18-22: REPEATED START CONDITION WAVEFORM
Note 1: If RSEN is programmed while any other
event is in progress, it will not take effect.
2: A bus collision during the Repeated Start
condition occurs if:
SDA is sampled low when SCL goes
from low-to-high.
SCL goes low before SDA is
asserted low. This may indicate that
another master is attempting to
transmit a data ‘1’.
Note: Because queueing of events is not
allowed, writing of the lower 5 bits of
SSPCON2 is disabled until the Repeated
Start condition is complete.
SDA
SCL
Sr = Repeated Start
Write to SSPCON2
Write to SSPBUF occurs here
on falling edge of ninth clock,
end of Xmit
At completion of Start bit,
hardware clears RSEN bit
1st bit
S bit set by hardware
TBRG
TBRG
SDA = 1,
SDA = 1,
SCL (no change).
SCL = 1
occurs here.
and sets SSPIF
RSEN bit set by hardware
TBRG TBRG TBRG
© 2009 Microchip Technology Inc. DS39689F-page 201
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18.4.10 I2C MASTER MODE TRANSMISSION
Transmission of a data byte, a 7-bit address or the
other half of a 10-bit address is accomplished by simply
writing a value to the SSPBUF register. This action will
set the Buffer Full flag bit, BF and allow the Baud Rate
Generator to begin counting and start the next
transmission. Each bit of address/data will be shifted
out onto the SDA pin after the falling edge of SCL is
asserted (see data hold time specification
parameter 106). SCL is held low for one Baud Rate
Generator rollover count (TBRG). Data should be valid
before SCL is released high (see data setup time
specification parameter 107). When the SCL pin is
released high, it is held that way for TBRG. The data on
the SDA pin must remain stable for that duration and
some hold time after the next falling edge of SCL. After
the eighth bit is shifted out (the falling edge of the eighth
clock), the BF flag is cleared and the master releases
SDA. This allows the slave device being addressed to
respond with an ACK bit during the ninth bit time if an
address match occurred, or if data was received
properly. The status of ACK is written into the ACKDT
bit on the falling edge of the ninth clock. If the master
receives an Acknowledge, the Acknowledge Status bit,
ACKSTAT, is cleared. If not, the bit is set. After the ninth
clock, the SSPIF bit is set and the master clock (Baud
Rate Generator) is suspended until the next data byte
is loaded into the SSPBUF, leaving SCL low and SDA
unchanged (Figure 18-23).
After the write to the SSPBUF, each bit of the address
will be shifted out on the falling edge of SCL until all
seven address bits and the R/W bit are completed. On
the falling edge of the eighth clock, the master will
deassert the SDA pin, allowing the slave to respond
with an Acknowledge. On the falling edge of the ninth
clock, the master will sample the SDA pin to see if the
address was recognized by a slave. The status of the
ACK bit is loaded into the ACKSTAT status bit
(SSPCON2<6>). Following the falling edge of the ninth
clock transmission of the address, the SSPIF is set, the
BF flag is cleared and the Baud Rate Generator is
turned off until another write to the SSPBUF takes
place, holding SCL low and allowing SDA to float.
18.4.10.1 BF Status Flag
In Transmit mode, the BF bit (SSPSTAT<0>) is set
when the CPU writes to SSPBUF and is cleared when
all 8 bits are shifted out.
18.4.10.2 WCOL Status Flag
If the user writes the SSPBUF when a transmit is
already in progress (i.e., SSPSR is still shifting out a
data byte), the WCOL flag is set and the contents of the
buffer are unchanged (the write doesn’t occur) after
2TCY after the SSPBUF write. If SSPBUF is rewritten
within 2 TCY, the WCOL bit is set and SSPBUF is
updated. This may result in a corrupted transfer. The
user should verify that the WCOL flag is clear after
each write to SSPBUF to ensure the transfer is correct.
18.4.10.3 ACKSTAT Status Flag
In Transmit mode, the ACKSTAT bit (SSPCON2<6>) is
cleared when the slave has sent an Acknowledge
(ACK =0) and is set when the slave does not Acknowl-
edge (ACK = 1). A slave sends an Acknowledge when
it has recognized its address (including a general call),
or when the slave has properly received its data.
18.4.11 I2C MASTER MODE RECEPTION
Master mode reception is enabled by programming the
Receive Enable bit, RCEN (SSPCON2<3>).
The Baud Rate Generator begins counting and on each
rollover, the state of the SCL pin changes (high-to-low/
low-to-high) and data is shifted into the SSPSR. After
the falling edge of the eighth clock, the receive enable
flag is automatically cleared, the contents of the
SSPSR are loaded into the SSPBUF, the BF flag bit is
set, the SSPIF flag bit is set and the Baud Rate Gener-
ator is suspended from counting, holding SCL low. The
MSSP is now in Idle state awaiting the next command.
When the buffer is read by the CPU, the BF flag bit is
automatically cleared. The user can then send an
Acknowledge bit at the end of reception by setting the
Acknowledge Sequence Enable bit, ACKEN
(SSPCON2<4>).
18.4.11.1 BF Status Flag
In receive operation, the BF bit is set when an address
or data byte is loaded into SSPBUF from SSPSR. It is
cleared when the SSPBUF register is read.
18.4.11.2 SSPOV Status Flag
In receive operation, the SSPOV bit is set when 8 bits
are received into the SSPSR and the BF flag bit is
already set from a previous reception.
18.4.11.3 WCOL Status Flag
If the user writes the SSPBUF when a receive is
already in progress (i.e., SSPSR is still shifting in a data
byte), the WCOL bit is set and the contents of the buffer
are unchanged (the write doesn’t occur).
Note: The MSSP module must be in an Idle state
before the RCEN bit is set or the RCEN bit
will be disregarded.
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DS39689F-page 202 © 2009 Microchip Technology Inc.
FIGURE 18-23: I2C™ MASTER MODE WAVEFORM (TRANSMISSION, 7 OR 10-BIT ADDRESSING)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
SEN
A7 A6 A5 A4 A3 A2 A1 ACK = ‘0 D7D6D5D4D3D2D1D0
ACK
Transmitting Data or Second Half
R/W = 0Transmit Address to Slave
123456789 123456789 P
Cleared in software service routine
SSPBUF is written in software
from MSSP interrupt
After Start condition, SEN cleared by hardware
S
SSPBUF written with 7-bit address and R/W,
start transmit
SCL held low
while CPU
responds to SSPIF
SEN = 0
of 10-bit Address
Write SSPCON2<0> SEN = 1
Start condition begins From slave, clear ACKSTAT bit SSPCON2<6>
ACKSTAT in
SSPCON2 = 1
Cleared in software
SSPBUF written
PEN
R/W
Cleared in software
© 2009 Microchip Technology Inc. DS39689F-page 203
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FIGURE 18-24: I2C™ MASTER MODE WAVEFORM (RECEPTION, 7-BIT ADDRESSING)
P
9
87
6
5
D0
D1
D2
D3D4
D5
D6D7
S
A7 A6 A5 A4 A3 A2 A1
SDA
SCL 12
345678912345678 9 1234
Bus master
terminates
transfer
ACK
Receiving Data from Slave
Receiving Data from Slave
D0
D1
D2
D3D4
D5
D6D7
ACK
R/W = 1
Transmit Address to Slave
SSPIF
BF
ACK is not sent
Write to SSPCON2<0> (SEN = 1),
Write to SSPBUF occurs here, ACK from Slave
Master configured as a receiver
by programming SSPCON2<3> (RCEN = 1)
PEN bit = 1
written here
Data shifted in on falling edge of CLK
Cleared in software
start XMIT
SEN = 0
SSPOV
SDA = 0, SCL = 1
while CPU
(SSPSTAT<0>)
ACK
Cleared in software
Cleared in software
Set SSPIF interrupt
at end of receive
Set P bit
(SSPSTAT<4>)
and SSPIF
Cleared in
software
ACK from Master
Set SSPIF at end
Set SSPIF interrupt
at end of Acknowledge
sequence
Set SSPIF interrupt
at end of Acknow-
ledge sequence
of receive
Set ACKEN, start Acknowledge sequence
SSPOV is set because
SSPBUF is still full
SDA = ACKDT = 1
RCEN cleared
automatically
RCEN = 1, start
next receive
Write to SSPCON2<4>
to start Acknowledge sequence
SDA = ACKDT (SSPCON2<5>) = 0
RCEN cleared
automatically
responds to SSPIF
ACKEN
begin Start condition
Cleared in software
SDA = ACKDT = 0
Last bit is shifted into SSPSR and
contents are unloaded into SSPBUF
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DS39689F-page 204 © 2009 Microchip Technology Inc.
18.4.12 ACKNOWLEDGE SEQUENCE
TIMING
An Acknowledge sequence is enabled by setting the
Acknowledge Sequence Enable bit, ACKEN
(SSPCON2<4>). When this bit is set, the SCL pin is
pulled low and the contents of the Acknowledge data bit
are presented on the SDA pin. If the user wishes to gen-
erate an Acknowledge, then the ACKDT bit should be
cleared. If not, the user should set the ACKDT bit before
starting an Acknowledge sequence. The Baud Rate
Generator then counts for one rollover period (TBRG)
and the SCL pin is deasserted (pulled high). When the
SCL pin is sampled high (clock arbitration), the Baud
Rate Generator counts for TBRG. The SCL pin is then
pulled low. Following this, the ACKEN bit is automatically
cleared, the Baud Rate Generator is turned off and the
MSSP module then goes into Idle mode (Figure 18-25).
18.4.12.1 WCOL Status Flag
If the user writes the SSPBUF when an Acknowledge
sequence is in progress, then WCOL is set and the
contents of the buffer are unchanged (the write doesn’t
occur).
18.4.13 STOP CONDITION TIMING
A Stop bit is asserted on the SDA pin at the end of a
receive/transmit by setting the Stop Sequence Enable
bit, PEN (SSPCON2<2>). At the end of a receive/
transmit, the SCL line is held low after the falling edge
of the ninth clock. When the PEN bit is set, the master
will assert the SDA line low. When the SDA line is
sampled low, the Baud Rate Generator is reloaded and
counts down to 0. When the Baud Rate Generator
times out, the SCL pin will be brought high and one
TBRG (Baud Rate Generator rollover count) later, the
SDA pin will be deasserted. When the SDA pin is
sampled high while SCL is high, the P bit
(SSPSTAT<4>) is set. A TBRG later, the PEN bit is
cleared and the SSPIF bit is set (Figure 18-26).
18.4.13.1 WCOL Status Flag
If the user writes the SSPBUF when a Stop sequence
is in progress, then the WCOL bit is set and the
contents of the buffer are unchanged (the write doesn’t
occur).
FIGURE 18-25: ACKNOWLEDGE SEQUENCE WAVEFORM
FIGURE 18-26: STOP CONDITION RECEIVE OR TRANSMIT MODE
Note: TBRG = one Baud Rate Generator period.
SDA
SCL
SSPIF set at
Acknowledge sequence starts here,
write to SSPCON2 ACKEN automatically cleared
Cleared in
TBRG TBRG
the end of receive
8
ACKEN = 1, ACKDT = 0
D0
9
SSPIF
software SSPIF set at the end
of Acknowledge sequence
Cleared in
software
ACK
SCL
SDA
SDA asserted low before rising edge of clock
Write to SSPCON2,
set PEN
Falling edge of
SCL = 1 for TBRG, followed by SDA = 1 for TBRG
9th clock
SCL brought high after TBRG
Note: TBRG = one Baud Rate Generator period.
TBRG TBRG
after SDA sampled high. P bit (SSPSTAT<4>) is set.
TBRG
to setup Stop condition
ACK
P
TBRG
PEN bit (SSPCON2<2>) is cleared by
hardware and the SSPIF bit is set
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18.4.14 SLEEP OPERATION
While in Sleep mode, the I2C module can receive
addresses or data and when an address match or
complete byte transfer occurs, wake the processor
from Sleep (if the MSSP interrupt is enabled).
18.4.15 EFFECTS OF A RESET
A Reset disables the MSSP module and terminates the
current transfer.
18.4.16 MULTI-MASTER MODE
In Multi-Master mode, the interrupt generation on the
detection of the Start and Stop conditions allows the
determination of when the bus is free. The Stop (P) and
Start (S) bits are cleared from a Reset or when the
MSSP module is disabled. Control of the I2C bus may
be taken when the P bit (SSPSTAT<4>) is set, or the
bus is Idle, with both the S and P bits clear. When the
bus is busy, enabling the MSSP interrupt will generate
the interrupt when the Stop condition occurs.
In multi-master operation, the SDA line must be
monitored for arbitration to see if the signal level is the
expected output level. This check is performed in
hardware with the result placed in the BCLIF bit.
The states where arbitration can be lost are:
Address Transfer
Data Transfer
A Start Condition
A Repeated Start Condition
An Acknowledge Condition
18.4.17 MULTI -MASTER COMMUNICATION,
BUS COLLISION AND BUS
ARBITRATION
Multi-Master mode support is achieved by bus arbitra-
tion. When the master outputs address/data bits onto
the SDA pin, arbitration takes place when the master
outputs a ‘1on SDA, by letting SDA float high and
another master asserts a ‘0’. When the SCL pin floats
high, data should be stable. If the expected data on
SDA is a1’ and the data sampled on the SDA pin = 0,
then a bus collision has taken place. The master will set
the Bus Collision Interrupt Flag, BCLIF and reset the
I2C port to its Idle state (Figure 18-27).
If a transmit was in progress when the bus collision
occurred, the transmission is halted, the BF flag is
cleared, the SDA and SCL lines are deasserted and the
SSPBUF can be written to. When the user services the
bus collision Interrupt Service Routine and if the I2C
bus is free, the user can resume communication by
asserting a Start condition.
If a Start, Repeated Start, Stop or Acknowledge
condition was in progress when the bus collision
occurred, the condition is aborted, the SDA and SCL
lines are deasserted and the respective control bits in
the SSPCON2 register are cleared. When the user ser-
vices the bus collision Interrupt Service Routine and if
the I2C bus is free, the user can resume communication
by asserting a Start condition.
The master will continue to monitor the SDA and SCL
pins. If a Stop condition occurs, the SSPIF bit will be set.
A write to the SSPBUF will start the transmission of
data at the first data bit, regardless of where the
transmitter left off when the bus collision occurred.
In Multi-Master mode, the interrupt generation on the
detection of Start and Stop conditions allows the
determination of when the bus is free. Control of the I2C
bus can be taken when the P bit is set in the SSPSTAT
register, or the bus is Idle and the S and P bits are
cleared.
FIGURE 18-27: BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE
SDA
SCL
BCLIF
SDA released
SDA line pulled low
by another source
Sample SDA. While SCL is high,
data doesn’t match what is driven
Bus collision has occurred.
Set bus collision
interrupt (BCLIF)
by the master.
by master
Data changes
while SCL = 0
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DS39689F-page 206 © 2009 Microchip Technology Inc.
18.4.17.1 Bus Collision During a
Start Condition
During a Start condition, a bus collision occurs if:
a) SDA or SCL are sampled low at the beginning of
the Start condition (Figure 18-28).
b) SCL is sampled low before SDA is asserted low
(Figure 18-29).
During a Start condition, both the SDA and the SCL
pins are monitored.
If the SDA pin is already low, or the SCL pin is already
low, then all of the following occur:
the Start condition is aborted,
the BCLIF flag is set and
the MSSP module is reset to its Idle state
(Figure 18-28).
The Start condition begins with the SDA and SCL pins
deasserted. When the SDA pin is sampled high, the
Baud Rate Generator is loaded from SSPADD<6:0>
and counts down to 0. If the SCL pin is sampled low
while SDA is high, a bus collision occurs because it is
assumed that another master is attempting to drive a
data ‘1’ during the Start condition.
If the SDA pin is sampled low during this count, the
BRG is reset and the SDA line is asserted early
(Figure 18-30). If, however, a ‘1’ is sampled on the SDA
pin, the SDA pin is asserted low at the end of the BRG
count. The Baud Rate Generator is then reloaded and
counts down to 0; if the SCL pin is sampled as ‘0
during this time, a bus collision does not occur. At the
end of the BRG count, the SCL pin is asserted low.
FIGURE 18-28: BUS COLLISION DURING START CONDITION (SDA ONLY)
Note: The reason that bus collision is not a factor
during a Start condition is that no two bus
masters can assert a Start condition at the
exact same time. Therefore, one master
will always assert SDA before the other.
This condition does not cause a bus
collision because the two masters must be
allowed to arbitrate the first address
following the Start condition. If the address
is the same, arbitration must be allowed to
continue into the data portion, Repeated
Start or Stop conditions.
SDA
SCL
SEN
SDA sampled low before
SDA goes low before the SEN bit is set.
S bit and SSPIF set because
MSSP module reset into Idle state.
SEN cleared automatically because of bus collision.
S bit and SSPIF set because
Set SEN, enable Start
condition if SDA = 1, SCL = 1
SDA = 0, SCL = 1.
BCLIF
S
SSPIF
SDA = 0, SCL = 1.
SSPIF and BCLIF are
cleared in software
SSPIF and BCLIF are
cleared in software
Set BCLIF,
Start condition. Set BCLIF.
© 2009 Microchip Technology Inc. DS39689F-page 207
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 18-29: BUS COLLISION DURING START CONDITION (SCL = 0)
FIGURE 18-30: BRG RESET DUE TO SDA ARBITRATION DURING START CONDITION
SDA
SCL
SEN bus collision occurs. Set BCLIF.
SCL = 0 before SDA = 0,
Set SEN, enable Start
sequence if SDA = 1, SCL = 1
TBRG TBRG
SDA = 0, SCL = 1
BCLIF
S
SSPIF
Interrupt cleared
in software
bus collision occurs. Set BCLIF.
SCL = 0 before BRG time-out,
0’‘0
00
SDA
SCL
SEN
Set S
Less than TBRG TBRG
SDA = 0, SCL = 1
BCLIF
S
SSPIF
S
Interrupts cleared
in software
set SSPIF
SDA = 0, SCL = 1,
SCL pulled low after BRG
time-out
Set SSPIF
0
SDA pulled low by other master.
Reset BRG and assert SDA.
Set SEN, enable Start
sequence if SDA = 1, SCL = 1
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 208 © 2009 Microchip Technology Inc.
18.4.17.2 Bus Collision During a Repeated
Start Condition
During a Repeated Start condition, a bus collision
occurs if:
a) A low level is sampled on SDA when SCL goes
from low level to high level.
b) SCL goes low before SDA is asserted low,
indicating that another master is attempting to
transmit a data ‘1’.
When the user deasserts SDA and the pin is allowed to
float high, the BRG is loaded with SSPADD<6:0> and
counts down to 0. The SCL pin is then deasserted and
when sampled high, the SDA pin is sampled.
If SDA is low, a bus collision has occurred (i.e., another
master is attempting to transmit a data ‘0’, Figure 18-31).
If SDA is sampled high, the BRG is reloaded and begins
counting. If SDA goes from high-to-low before the BRG
times out, no bus collision occurs because no two
masters can assert SDA at exactly the same time.
If SCL goes from high-to-low before the BRG times out
and SDA has not already been asserted, a bus collision
occurs. In this case, another master is attempting to
transmit a data ‘1’ during the Repeated Start condition,
see Figure 18-32.
If, at the end of the BRG time-out, both SCL and SDA
are still high, the SDA pin is driven low and the BRG is
reloaded and begins counting. At the end of the count,
regardless of the status of the SCL pin, the SCL pin is
driven low and the Repeated Start condition is
complete.
FIGURE 18-31: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)
FIGURE 18-32: BUS COLLISION DURING REPEATED START CONDITION (CASE 2)
SDA
SCL
RSEN
BCLIF
S
SSPIF
Sample SDA when SCL goes high.
If SDA = 0, set BCLIF and release SDA and SCL.
Cleared in software
0
0
SDA
SCL
BCLIF
RSEN
S
SSPIF
Interrupt cleared
in software
SCL goes low before SDA,
set BCLIF. Release SDA and SCL.
TBRG TBRG
0
© 2009 Microchip Technology Inc. DS39689F-page 209
PIC18F2221/2321/4221/4321 FAMILY
18.4.17.3 Bus Collision During a Stop
Condition
Bus collision occurs during a Stop condition if:
a) After the SDA pin has been deasserted and
allowed to float high, SDA is sampled low after
the BRG has timed out.
b) After the SCL pin is deasserted, SCL is sampled
low before SDA goes high.
The Stop condition begins with SDA asserted low.
When SDA is sampled low, the SCL pin is allowed to
float. When the pin is sampled high (clock arbitration),
the Baud Rate Generator is loaded with SSPADD<6:0>
and counts down to 0. After the BRG times out, SDA is
sampled. If SDA is sampled low, a bus collision has
occurred. This is due to another master attempting to
drive a data ‘0’ (Figure 18-33). If the SCL pin is
sampled low before SDA is allowed to float high, a bus
collision occurs. This is another case of another master
attempting to drive a data ‘0’ (Figure 18-34).
FIGURE 18-33: BUS COLLISION DURING A STOP CONDITION (CASE 1)
FIGURE 18-34: BUS COLLISION DURING A STOP CONDITION (CASE 2)
SDA
SCL
BCLIF
PEN
P
SSPIF
TBRG TBRG TBRG
SDA asserted low
SDA sampled
low after TBRG,
set BCLIF
0
0
SDA
SCL
BCLIF
PEN
P
SSPIF
TBRG TBRG TBRG
Assert SDA SCL goes low before SDA goes high,
set BCLIF
0
0
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 210 © 2009 Microchip Technology Inc.
TABLE 18-4: REGISTERS ASSOCIATED WITH I2C™ OPERATION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 58
TRISD TRISD7 TRISD6 TRISD5 TRISD4 TRISD3 TRISD2 TRISD1 TRISD0 58
SSPBUF MSSP Receive Buffer/Transmit Register 56
SSPADD ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 ADD0 56
TMR2 Timer2 Register 56
PR2 Timer2 Period Register 56
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 56
SSPCON2 GCEN ACKSTAT ACKDT/
ADMSK5
ACKEN/
ADMSK5
RCEN/
ADMSK5
PEN/
ADMSK5
RSEN/
ADMSK5
SEN 56
SSPSTAT SMP CKE D/A PSR/WUA BF 56
Legend: = unimplemented, read as ‘0’. Shaded cells are not used by the MSSP module in I2C mode.
© 2009 Microchip Technology Inc. DS39689F-page 211
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19.0 ENHANCED UNIVERSAL
SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (EUSART)
The Enhanced Universal Synchronous Asynchronous
Receiver Transmitter (EUSART) module is one of the
two serial I/O modules. (Generically, the USART is also
known as a Serial Communications Interface or SCI.)
The EUSART can be configured as a full-duplex
asynchronous system that can communicate with
peripheral devices, such as CRT terminals and
personal computers. It can also be configured as a half-
duplex synchronous system that can communicate
with peripheral devices, such as A/D or D/A integrated
circuits, serial EEPROMs, etc.
The Enhanced USART module implements additional
features, including automatic baud rate detection and
calibration, automatic wake-up on Sync Break recep-
tion and 12-bit Break character transmit. These make it
ideally suited for use in Local Interconnect Network bus
(LIN/J2602 bus) systems.
The EUSART can be configured in the following
modes:
Asynchronous (full duplex) with:
- Auto-wake-up on Break signal
- Auto-baud calibration
- 12-bit Break character transmission
Synchronous – Master (half duplex) with
selectable clock polarity
Synchronous – Slave (half duplex) with selectable
clock polarity
The pins of the Enhanced USART are multiplexed
with PORTC. In order to configure RC6/TX/CK and
RC7/RX/DT as an EUSART:
bit SPEN (RCSTA<7>) must be set (= 1)
bit TRISC<7> must be set (= 1)
bit TRISC<6> must be set (= 1)
The operation of the Enhanced USART module is
controlled through three registers:
Transmit Status and Control (TXSTA)
Receive Status and Control (RCSTA)
Baud Rate Control (BAUDCON)
These are detailed on the following pages in
Register 19-1, Register 19-2 and Register 19-3,
respectively.
Note: The EUSART control will automatically
reconfigure the pin from input to output as
needed.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 212 © 2009 Microchip Technology Inc.
REGISTER 19-1: TXSTA: TRANSMIT STATUS AND CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-1 R/W-0
CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D
bit 7 bit 0
bit 7 CSRC: Clock Source Select bit
Asynchronous mode:
Don’t care.
Synchronous mode:
1 = Master mode (clock generated internally from BRG)
0 = Slave mode (clock from external source)
bit 6 TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
bit 5 TXEN: Transmit Enable bit
1 = Transmit enabled
0 = Transmit disabled
Note: SREN/CREN overrides TXEN in Sync mode.
bit 4 SYNC: EUSART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode
bit 3 SENDB: Send Break Character bit
Asynchronous mode:
1 = Send Sync Break on next transmission (cleared by hardware upon completion)
0 = Sync Break transmission completed
Synchronous mode:
Don’t care.
bit 2 BRGH: High Baud Rate Select bit
Asynchronous mode:
1 = High speed
0 = Low speed
Synchronous mode:
Unused in this mode.
bit 1 TRMT: Transmit Shift Register Status bit
1 = TSR empty
0 = TSR full
bit 0 TX9D: 9th bit of Transmit Data
Can be address/data bit or a parity bit.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 213
PIC18F2221/2321/4221/4321 FAMILY
REGISTER 19-2: RCSTA: RECEIVE STATUS AND CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-0 R-0 R-x
SPEN RX9 SREN CREN ADDEN FERR OERR RX9D
bit 7 bit 0
bit 7 SPEN: Serial Port Enable bit
1 = Serial port enabled (configures RX/DT and TX/CK pins as serial port pins)
0 = Serial port disabled (held in Reset)
bit 6 RX9: 9-bit Receive Enable bit
1 = Selects 9-bit reception
0 = Selects 8-bit reception
bit 5 SREN: Single Receive Enable bit
Asynchronous mode:
Don’t care.
Synchronous mode – Master:
1 = Enables single receive
0 = Disables single receive
This bit is cleared after reception is complete.
Synchronous mode – Slave:
Don’t care.
bit 4 CREN: Continuous Receive Enable bit
Asynchronous mode:
1 = Enables receiver
0 = Disables receiver
Synchronous mode:
1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides SREN)
0 = Disables continuous receive
bit 3 ADDEN: Address Detect Enable bit
Asynchronous mode 9-bit (RX9 = 1):
1 = Enables address detection, enables interrupt and loads the receive buffer when RSR<8>
is set
0 = Disables address detection, all bytes are received and ninth bit can be used as parity bit
Asynchronous mode 9-bit (RX9 = 0):
Don’t care.
bit 2 FERR: Framing Error bit
1 = Framing error (can be updated by reading RCREG register and receiving next valid byte)
0 = No framing error
bit 1 OERR: Overrun Error bit
1 = Overrun error (can be cleared by clearing bit CREN)
0 = No overrun error
bit 0 RX9D: 9th bit of Received Data
This can be address/data bit or a parity bit and must be calculated by user firmware.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 214 © 2009 Microchip Technology Inc.
REGISTER 19-3: BAUDCON: BAUD RATE CONTROL REGISTER
R/W-0 R-1 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0
ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN
bit 7 bit 0
bit 7 ABDOVF: Auto-Baud Acquisition Rollover Status bit
1 = A BRG rollover has occurred during Auto-Baud Rate Detect mode
(must be cleared in software)
0 = No BRG rollover has occurred
bit 6 RCIDL: Receive Operation Idle Status bit
1 = Receive operation is Idle
0 = Receive operation is active
bit 5 RXDTP: Received Data Polarity Select bit
Asynchronous mode:
1 = Receive data (RX) is inverted (active-low)
0 = Receive data (RX) is not inverted (active-high)
Synchronous mode:
No affect.
bit 4 TXCKP: Clock and Data Polarity Select bit
Asynchronous mode:
1 = Idle state for transmit (TX) is a low level
0 = Idle state for transmit (TX) is a high level
Synchronous mode:
1 = Idle state for clock (CK) is a high level
0 = Idle state for clock (CK) is a low level
bit 3 BRG16: 16-bit Baud Rate Register Enable bit
1 = 16-bit Baud Rate Generator – SPBRGH and SPBRG
0 = 8-bit Baud Rate Generator – SPBRG only (Compatible mode), SPBRGH value ignored
bit 2 Unimplemented: Read as0
bit 1 WUE: Wake-up Enable bit
Asynchronous mode:
1 = EUSART will continue to sample the RX pin – interrupt generated on falling edge; bit
cleared in hardware on following rising edge
0 = RX pin not monitored or rising edge detected
Synchronous mode:
Unused in this mode.
bit 0 ABDEN: Auto-Baud Detect Enable bit
Asynchronous mode:
1 = Enable baud rate measurement on the next character. Requires reception of a Sync field
(55h); cleared in hardware upon completion
0 = Baud rate measurement disabled or completed
Synchronous mode:
Unused in this mode.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
© 2009 Microchip Technology Inc. DS39689F-page 215
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19.1 Baud Rate Generator (BRG)
The BRG is a dedicated 8-bit or 16-bit generator that
supports both the Asynchronous and Synchronous
modes of the EUSART. By default, the BRG operates
in 8-bit mode; setting the BRG16 bit (BAUDCON<3>)
selects 16-bit mode.
The SPBRGH:SPBRG register pair controls the period
of a free running timer. In Asynchronous mode, bits
BRGH (TXSTA<2>) and BRG16 (BAUDCON<3>) also
control the baud rate. In Synchronous mode, BRGH is
ignored. Table 19-1 shows the formula for computation
of the baud rate for different EUSART modes which
only apply in Master mode (internally generated clock).
Given the desired baud rate and FOSC, the nearest
integer value for the SPBRGH:SPBRG registers can be
calculated using the formulas in Table 19-1. From this,
the error in baud rate can be determined. An example
calculation is shown in Example 19-1. Typical baud
rates and error values for the various Asynchronous
modes are shown in Table 19-2. It may be advantageous
to use the high baud rate (BRGH = 1) or the 16-bit BRG
to reduce the baud rate error, or achieve a slow baud
rate for a fast oscillator frequency.
Writing a new value to the SPBRGH:SPBRG registers
causes the BRG timer to be reset (or cleared). This
ensures the BRG does not wait for a timer overflow
before outputting the new baud rate.
19.1.1 OPERATION IN POWER-MANAGED
MODES
The device clock is used to generate the desired baud
rate. When one of the power-managed modes is
entered, the new clock source may be operating at a
different frequency. This may require an adjustment to
the value in the SPBRG register pair.
19.1.2 SAMPLING
The data on the RX pin is sampled three times by a
majority detect circuit to determine if a high or a low
level is present at the RX pin when SYNC is clear or
when BRG16 and BRGH are both not set. The data on
the RX pin is sampled once when SYNC is set or when
BRGH16 and BRGH are both set.
TABLE 19-1: BAUD RATE FORMULAS
Note: A BRG value of 0 is not supported.
Configuration Bits BRG/EUSART Mode Baud Rate Formula
SYNC BRG16 BRGH
000 8-bit/Asynchronous FOSC/[64 (n + 1)]
001 8-bit/Asynchronous FOSC/[16 (n + 1)]
010 16-bit/Asynchronous
011 16-bit/Asynchronous
FOSC/[4 (n + 1)]10x 8-bit/Synchronous
11x 16-bit/Synchronous
Legend: x = Don’t care, n = value of SPBRGH:SPBRG register pair
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 216 © 2009 Microchip Technology Inc.
EXAMPLE 19-1: CALCULATING BAUD RATE ERROR
TABLE 19-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR
For a device with FOSC of 16 MHz, desired baud rate of 9600, Asynchronous mode, 8-bit BRG:
Desired Baud Rate = FOSC/(64 ([SPBRGH:SPBRG] + 1))
Solving for SPBRGH:SPBRG:
X=((FOSC/Desired Baud Rate)/64) – 1
= ((16000000/9600)/64) – 1
= [25.042] = 25
Calculated Baud Rate = 16000000/(64 (25 + 1))
= 9615
Error = (Calculated Baud Rate – Desired Baud Rate)/Desired Baud Rate
= (9615 – 9600)/9600 = 0.16%
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values
on page
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the BRG.
© 2009 Microchip Technology Inc. DS39689F-page 217
PIC18F2221/2321/4221/4321 FAMILY
TABLE 19-3: BAUD RATES FOR ASYNCHRONOUS MODES
BAUD
RATE
(K)
SYNC = 0, BRGH = 0, BRG16 = 0
FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3———————————
1.2 1.221 1.73 255 1.202 0.16 129 1.201 -0.16 103
2.4 2.441 1.73 255 2.404 0.16 129 2.404 0.16 64 2.403 -0.16 51
9.6 9.615 0.16 64 9.766 1.73 31 9.766 1.73 15 9.615 -0.16 12
19.2 19.531 1.73 31 19.531 1.73 15 19.531 1.73 7
57.6 56.818 -1.36 10 62.500 8.51 4 52.083 -9.58 2
115.2 125.000 8.51 4 104.167 -9.58 2 78.125 -32.18 1
BAUD
RATE
(K)
SYNC = 0, BRGH = 0, BRG16 = 0
FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3 0.300 0.16 207 0.300 -0.16 103 0.300 -0.16 51
1.2 1.202 0.16 51 1.201 -0.16 25 1.201 -0.16 12
2.4 2.404 0.16 25 2.403 -0.16 12
9.6 8.929 -6.99 6
19.2 20.833 8.51 2
57.6 62.500 8.51 0
115.2 62.500 -45.75 0
BAUD
RATE
(K)
SYNC = 0, BRGH = 1, BRG16 = 0
FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3———————————
1.2———————————
2.4 2.441 1.73 255 2.403 -0.16 207
9.6 9.766 1.73 255 9.615 0.16 129 9.615 0.16 64 9.615 -0.16 51
19.2 19.231 0.16 129 19.231 0.16 64 19.531 1.73 31 19.230 -0.16 25
57.6 58.140 0.94 42 56.818 -1.36 21 56.818 -1.36 10 55.555 3.55 8
115.2 113.636 -1.36 21 113.636 -1.36 10 125.000 8.51 4
BAUD
RATE
(K)
SYNC = 0, BRGH = 1, BRG16 = 0
FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3 0.300 -0.16 207
1.2 1.202 0.16 207 1.201 -0.16 103 1.201 -0.16 51
2.4 2.404 0.16 103 2.403 -0.16 51 2.403 -0.16 25
9.6 9.615 0.16 25 9.615 -0.16 12
19.2 19.231 0.16 12
57.6 62.500 8.51 3
115.2 125.000 8.51 1
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 218 © 2009 Microchip Technology Inc.
BAUD
RATE
(K)
SYNC = 0, BRGH = 0, BRG16 = 1
FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3 0.300 0.00 8332 0.300 0.02 4165 0.300 0.02 2082 0.300 -0.04 1665
1.2 1.200 0.02 2082 1.200 -0.03 1041 1.200 -0.03 520 1.201 -0.16 415
2.4 2.402 0.06 1040 2.399 -0.03 520 2.404 0.16 259 2.403 -0.16 207
9.6 9.615 0.16 259 9.615 0.16 129 9.615 0.16 64 9.615 -0.16 51
19.2 19.231 0.16 129 19.231 0.16 64 19.531 1.73 31 19.230 -0.16 25
57.6 58.140 0.94 42 56.818 -1.36 21 56.818 -1.36 10 55.555 3.55 8
115.2 113.636 -1.36 21 113.636 -1.36 10 125.000 8.51 4
BAUD
RATE
(K)
SYNC = 0, BRGH = 0, BRG16 = 1
FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3 0.300 0.04 832 0.300 -0.16 415 0.300 -0.16 207
1.2 1.202 0.16 207 1.201 -0.16 103 1.201 -0.16 51
2.4 2.404 0.16 103 2.403 -0.16 51 2.403 -0.16 25
9.6 9.615 0.16 25 9.615 -0.16 12
19.2 19.231 0.16 12
57.6 62.500 8.51 3
115.2 125.000 8.51 1
BAUD
RATE
(K)
SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1
FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3 0.300 0.00 33332 0.300 0.00 16665 0.300 0.00 8332 0.300 -0.01 6665
1.2 1.200 0.00 8332 1.200 0.02 4165 1.200 0.02 2082 1.200 -0.04 1665
2.4 2.400 0.02 4165 2.400 0.02 2082 2.402 0.06 1040 2.400 -0.04 832
9.6 9.606 0.06 1040 9.596 -0.03 520 9.615 0.16 259 9.615 -0.16 207
19.2 19.193 -0.03 520 19.231 0.16 259 19.231 0.16 129 19.230 -0.16 103
57.6 57.803 0.35 172 57.471 -0.22 86 58.140 0.94 42 57.142 0.79 34
115.2 114.943 -0.22 86 116.279 0.94 42 113.636 -1.36 21 117.647 -2.12 16
BAUD
RATE
(K)
SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1
FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
Actual
Rate
(K)
%
Error
SPBRG
value
(decimal)
0.3 0.300 0.01 3332 0.300 -0.04 1665 0.300 -0.04 832
1.2 1.200 0.04 832 1.201 -0.16 415 1.201 -0.16 207
2.4 2.404 0.16 415 2.403 -0.16 207 2.403 -0.16 103
9.6 9.615 0.16 103 9.615 -0.16 51 9.615 -0.16 25
19.2 19.231 0.16 51 19.230 -0.16 25 19.230 -0.16 12
57.6 58.824 2.12 16 55.555 3.55 8
115.2 111.111 -3.55 8
TABLE 19-3: BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED)
© 2009 Microchip Technology Inc. DS39689F-page 219
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19.1.3 AUTO-BAUD RATE DETECT
The Enhanced USART module supports the automatic
detection and calibration of baud rate. This feature is
active only in Asynchronous mode and while the WUE
bit is clear.
The automatic baud rate measurement sequence
(Figure 19-1) begins whenever a Start bit is received
and the ABDEN bit is set. The calculation is
self-averaging.
In the Auto-Baud Rate Detect (ABD) mode, the clock to
the BRG is reversed. Rather than the BRG clocking the
incoming RX signal, the RX signal is timing the BRG. In
ABD mode, the internal Baud Rate Generator is used
as a counter to time the bit period of the incoming serial
byte stream.
Once the ABDEN bit is set, the state machine will clear
the BRG and look for a Start bit. The Auto-Baud Rate
Detect must receive a byte with the value 55h (ASCII
“U”, which is also the LIN/J2602 bus Sync character) in
order to calculate the proper bit rate. The measurement
is taken over both a low and a high bit time in order to
minimize any effects caused by asymmetry of the incom-
ing signal. After a Start bit, the SPBRG begins counting
up, using the preselected clock source on the first rising
edge of RX. After eight bits on the RX pin, or the fifth ris-
ing edge, an accumulated value totalling the proper BRG
period is left in the SPBRGH:SPBRG register pair. Once
the 5th edge is seen (this should correspond to the Stop
bit), the ABDEN bit is automatically cleared.
If a rollover of the BRG occurs (an overflow from FFFFh
to 0000h), the event is trapped by the ABDOVF status
bit (BAUDCON<7>). It is set in hardware by BRG
rollovers and can be set or cleared by the user in
software. ABD mode remains active after rollover
events and the ABDEN bit remains set (Figure 19-2).
While calibrating the baud rate period, the BRG
registers are clocked at 1/8th the preconfigured clock
rate. Note that the BRG clock can be configured by the
BRG16 and BRGH bits. The BRG16 bit must be set to
use both SPBRG1 and SPBRGH1 as a 16-bit counter
This allows the user to verify that no carry occurred for
8-bit modes by checking for 00h in the SPBRGH
register. Refer to Table 19-4 for counter clock rates to
the BRG.
While the ABD sequence takes place, the EUSART
state machine is held in Idle. The RCIF interrupt is set
once the fifth rising edge on RX is detected. The value
in the RCREG needs to be read to clear the RCIF
interrupt. The contents of RCREG should be discarded.
TABLE 19-4: BRG COUNTER
CLOCK RATES
19.1.3.1 ABD and EUSART Transmission
Since the BRG clock is reversed during ABD acquisi-
tion, the EUSART transmitter cannot be used during
ABD. This means that whenever the ABDEN bit is set,
TXREG cannot be written to. Users should also ensure
that ABDEN does not become set during a transmit
sequence. Failing to do this may result in unpredictable
EUSART operation.
Note 1: If the WUE bit is set with the ABDEN bit,
Auto-Baud Rate Detection will occur on
the byte following the Break character.
2: It is up to the user to determine that the
incoming character baud rate is within the
range of the selected BRG clock source.
Some combinations of oscillator frequency
and EUSART baud rates are not possible
due to bit error rates. Overall system
timing and communication baud rates
must be taken into consideration when
using the Auto-Baud Rate Detection
feature.
3: To maximize the baud rate range, it is
recommended to set the BRG16 bit if the
auto-baud feature is used.
BRG16 BRGH BRG Counter Clock
00 FOSC/512
01 FOSC/128
10 FOSC/128
11 FOSC/32
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DS39689F-page 220 © 2009 Microchip Technology Inc.
FIGURE 19-1: AUTOMATIC BAUD RATE CALCULATION
FIGURE 19-2: BRG OVERFLOW SEQUENCE
BRG Value
RX pin
ABDEN bit
RCIF bit
Bit 0 Bit 1
(Interrupt)
Read
RCREG
BRG Clock
Start
Auto-Cleared
Set by User
XXXXh 0000h
Edge #1
Bit 2 Bit 3
Edge #2
Bit 4 Bit 5
Edge #3
Bit 6 Bit 7
Edge #4
Stop Bit
Edge #5
001Ch
Note: The ABD sequence requires the EUSART module to be configured in Asynchronous mode and WUE = 0.
SPBRG XXXXh 1Ch
SPBRGH XXXXh 00h
Start Bit 0
XXXXh 0000h 0000h
FFFFh
BRG Clock
ABDEN bit
RX pin
ABDOVF bit
BRG Value
© 2009 Microchip Technology Inc. DS39689F-page 221
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19.2 EUSART Asynchronous Mode
The Asynchronous mode of operation is selected by
clearing the SYNC bit (TXSTA<4>). In this mode, the
EUSART uses standard Non-Return-to-Zero (NRZ)
format (one Start bit, eight or nine data bits and one
Stop bit). The most common data format is 8 bits. An
on-chip dedicated 8-bit/16-bit Baud Rate Generator
can be used to derive standard baud rate frequencies
from the oscillator.
The EUSART transmits and receives the LSb first. The
EUSART’s transmitter and receiver are functionally
independent but use the same data format and baud
rate. The Baud Rate Generator produces a clock, either
x16 or x64 of the bit shift rate depending on the BRGH
and BRG16 bits (TXSTA<2> and BAUDCON<3>). Parity
is not supported by the hardware but can be
implemented in software and stored as the 9th data bit.
The TXCKP (BAUDCON<4>) and RXDTP
(BAUDCON<5>) bits allow the TX and RX signals to be
inverted (polarity reversed). Devices that buffer signals
between TTL and RS-232 levels also invert the signal.
Setting the TXCKP and RXDTP bits allows for the use of
circuits that provide buffering without inverting the signal.
In Asynchronous mode, clock polarity is selected with
the TXCKP bit (BAUDCON<4>). Setting TXCKP sets
the Idle state on CK as high, while clearing the bit sets
the Idle state as low. Data polarity is selected with the
RXDTP bit (BAUDCON<5>). Setting RXDTP inverts
data on RX, while clearing the bit has no affect on
received data.
When operating in Asynchronous mode, the EUSART
module consists of the following important elements:
Baud Rate Generator
Sampling Circuit
Asynchronous Transmitter
Asynchronous Receiver
Auto-Wake-up on Break signal
12-bit Break Character Transmit
Auto-Baud Rate Detection
Pin State Polarity
19.2.1 EUSART ASYNCHRONOUS
TRANSMITTER
The EUSART transmitter block diagram is shown in
Figure 19-3. The heart of the transmitter is the Transmit
(Serial) Shift Register (TSR). The Shift register obtains
its data from the Read/Write Transmit Buffer register,
TXREG. The TXREG register is loaded with data in
software. The TSR register is not loaded until the Stop
bit has been transmitted from the previous load. As
soon as the Stop bit is transmitted, the TSR is loaded
with new data from the TXREG register (if available).
Once the TXREG register transfers the data to the TSR
register (occurs in one T
CY), the TXREG register is empty
and the TXIF flag bit (PIR1<4>) is set. This interrupt can
be enabled or disabled by setting or clearing the interrupt
enable bit, TXIE (PIE1<4>). TXIF will be set regardless of
the state of TXIE; it cannot be cleared in software. TXIF
is also not cleared immediately upon loading TXREG, but
becomes valid in the second instruction cycle following
the load instruction. Polling TXIF immediately following a
load of TXREG will return invalid results.
While TXIF indicates the status of the TXREG register,
another bit, TRMT (TXSTA<1>), shows the status of
the TSR register. TRMT is a read-only bit which is set
when the TSR register is empty. No interrupt logic is
tied to this bit so the user has to poll this bit in order to
determine if the TSR register is empty.
The TXCKP bit (BAUDCON<4>) allows the TX signal to
be inverted (polarity reversed). Devices that buffer
signals from TTL to RS-232 levels also invert the signal
(when TTL = 1, RS-232 = negative). Inverting the
polarity of the TX pin data by setting the TXCKP bit
allows for use of circuits that provide buffering without
inverting the signal.
To set up an Asynchronous Transmission:
1. Initialize the SPBRGH:SPBRG registers for the
appropriate baud rate. Set or clear the BRGH
and BRG16 bits, as required, to achieve the
desired baud rate.
2. Enable the asynchronous serial port by clearing
bit, SYNC, and setting bit, SPEN.
3. If the signal from the TX pin is to be inverted, set
the TXCKP bit.
4. If interrupts are desired, set enable bit, TXIE.
5. If 9-bit transmission is desired, set transmit bit,
TX9; can be used as address/data bit.
6. Enable the transmission by setting bit, TXEN,
which will also set bit, TXIF.
7. If 9-bit transmission is selected, the ninth bit
should be loaded in bit, TX9D.
8. Load data to the TXREG register (starts
transmission).
9. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
Note 1: The TSR register is not mapped in data
memory so it is not available to the user.
2: Flag bit TXIF is set when enable bit TXEN
is set.
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DS39689F-page 222 © 2009 Microchip Technology Inc.
FIGURE 19-3: EUSART TRANSMIT BLOCK DIAGRAM
FIGURE 19-4: ASYNCHRONOUS TRANSMISSION, TXCKP = 0 (TX NOT INVERTED)
FIGURE 19-5: ASYNCHRONOUS TRANSMISSION (BACK TO BACK),
TXCKP = 0 (TX NOT INVERTED)
TXIF
TXIE
Interrupt
TXEN Baud Rate CLK
SPBRG
Baud Rate Generator TX9D
MSb LSb
Data Bus
TXREG Register
TSR Register
(8) 0
TX9
TRMT SPEN
TX pin
Pin Buffer
and Control
8
• •
SPBRGH
BRG16
TXCKP
Word 1
Word 1
Transmit Shift Reg
Start bit bit 0 bit 1 bit 7/8
Write to TXREG
BRG Output
(Shift Clock)
TX (pin)
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
1 TCY
Stop bit
Word 1
Transmit Shift Reg.
Write to TXREG
BRG Output
(Shift Clock)
TX (pin)
TXIF bit
(Interrupt Reg. Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Word 1 Word 2
Word 1 Word 2
Stop bit Start bit
Transmit Shift Reg.
Word 1 Word 2
bit 0 bit 1 bit 7/8 bit 0
Note: This timing diagram shows two consecutive transmissions.
1 TCY
1 TCY
Start bit
© 2009 Microchip Technology Inc. DS39689F-page 223
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TABLE 19-5: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
TXREG EUSART Transmit Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous transmission.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
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DS39689F-page 224 © 2009 Microchip Technology Inc.
19.2.2 EUSART ASYNCHRONOUS
RECEIVER
The receiver block diagram is shown in Figure 19-6.
The data is received on the RX pin and drives the data
recovery block. The data recovery block is actually a
high-speed shifter operating at x16 times the baud rate,
whereas the main receive serial shifter operates at the
bit rate or at FOSC. This mode would typically be used
in RS-232 systems.
The RXDTP bit (BAUDCON<5>) allows the RX signal to
be inverted (polarity reversed). Devices that buffer
signals from RS-232 to TTL levels also perform an inver-
sion of the signal (when RS-232 = positive, TTL = 0).
Inverting the polarity of the RX pin data by setting the
RXDTP bit allows for the use of circuits that provide
buffering without inverting the signal.
To set up an Asynchronous Reception:
1. Initialize the SPBRGH:SPBRG registers for the
appropriate baud rate. Set or clear the BRGH
and BRG16 bits, as required, to achieve the
desired baud rate.
2. Enable the asynchronous serial port by clearing
bit, SYNC, and setting bit, SPEN.
3. If the signal at the RX pin is to be inverted, set
the RXDTP bit.
4. If interrupts are desired, set enable bit, RCIE.
5. If 9-bit reception is desired, set bit, RX9.
6. Enable the reception by setting bit, CREN.
7. Flag bit, RCIF, will be set when reception is
complete and an interrupt will be generated if
enable bit, RCIE, was set.
8. Read the RCSTA register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
9. Read the 8-bit received data by reading the
RCREG register.
10. If any error occurred, clear the error by clearing
enable bit, CREN.
11. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
19.2.3 SETTING UP 9-BIT MODE WITH
ADDRESS DETECT
This mode would typically be used in RS-485 systems.
To set up an Asynchronous Reception with Address
Detect Enable:
1. Initialize the SPBRGH:SPBRG registers for the
appropriate baud rate. Set or clear the BRGH
and BRG16 bits, as required, to achieve the
desired baud rate.
2. Enable the asynchronous serial port by clearing
the SYNC bit and setting the SPEN bit.
3. If the signal at the RX pin is to be inverted, set
the RXDTP bit. If the signal from the TX pin is to
be inverted, set the TXCKP bit.
4. If interrupts are required, set the RCEN bit and
select the desired priority level with the RCIP bit.
5. Set the RX9 bit to enable 9-bit reception.
6. Set the ADDEN bit to enable address detect.
7. Enable reception by setting the CREN bit.
8. The RCIF bit will be set when reception is
complete. The interrupt will be Acknowledged if
the RCIE and GIE bits are set.
9. Read the RCSTA register to determine if any
error occurred during reception, as well as read
bit 9 of data (if applicable).
10. Read RCREG to determine if the device is being
addressed.
11. If any error occurred, clear the CREN bit.
12. If the device has been addressed, clear the
ADDEN bit to allow all received data into the
receive buffer and interrupt the CPU.
© 2009 Microchip Technology Inc. DS39689F-page 225
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FIGURE 19-6: EUSART RECEIVE BLOCK DIAGRAM
FIGURE 19-7: ASYNCHRONOUS RECEPTION, TXCKP = 0 (TX NOT INVERTED)
TABLE 19-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
RCREG EUSART Receive Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
x64 Baud Rate CLK
Baud Rate Generator
RX
Pin Buffer
and Control
SPEN
Data
Recovery
CREN OERR FERR
RSR Register
MSb LSb
RX9D RCREG Register
FIFO
Interrupt RCIF
RCIE
Data Bus
8
÷ 64
÷ 16
or
Stop Start
(8) 7 1 0
RX9
• • •
SPBRGSPBRGH
BRG16
or
÷ 4
RXDTP
Start
bit bit 7/8
bit 1bit 0 bit 7/8 bit 0
Stop
bit
Start
bit
Start
bitbit 7/8 Stop
bit
RX (pin)
Rcv Buffer Reg
Rcv Shift Reg
Read Rcv
Buffer Reg
RCREG
RCIF
(Interrupt Flag)
OERR bit
CREN
Word 1
RCREG
Word 2
RCREG
Stop
bit
Note: This timing diagram shows three words appearing on the RX input. The RCREG (receive buffer) is read after the third word causing
the OERR (overrun) bit to be set.
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DS39689F-page 226 © 2009 Microchip Technology Inc.
19.2.4 AUTO-WAKE-UP ON SYNC
BREAK CHARACTER
During Sleep mode, all clocks to the EUSART are
suspended. Because of this, the Baud Rate Generator
is inactive and a proper byte reception cannot be per-
formed. The auto-wake-up feature allows the controller
to wake-up due to activity on the RX/DT line while the
EUSART is operating in Asynchronous mode.
The auto-wake-up feature is enabled by setting the
WUE bit (BAUDCON<1>). Once set, the typical receive
sequence on RX/DT is disabled and the EUSART
remains in an Idle state, monitoring for a wake-up event
independent of the CPU mode. A wake-up event
consists of a high-to-low transition on the RX/DT line.
(This coincides with the start of a Sync Break or a
Wake-up Signal character for the LIN/J2602 protocol.)
Following a wake-up event, the module generates an
RCIF interrupt. The interrupt is generated synchro-
nously to the Q clocks in normal operating modes
(Figure 19-8) and asynchronously, if the device is in
Sleep mode (Figure 19-9). The interrupt condition is
cleared by reading the RCREG register.
The WUE bit is automatically cleared once a low-to-
high transition is observed on the RX line following the
wake-up event. At this point, the EUSART module is in
Idle mode and returns to normal operation. This signals
to the user that the Sync Break event is over.
19.2.4.1 Special Considerations Using
Auto-Wake-up
Since auto-wake-up functions by sensing rising edge
transitions on RX/DT, information with any state changes
before the Stop bit may signal a false end-of-character
and cause data or framing errors. To work properly,
therefore, the initial character in the transmission must
be all ‘0’s. This can be 00h (8 bytes) for standard RS-232
devices or 000h (12 bits) for the LIN/J2602 bus.
Oscillator start-up time must also be considered,
especially in applications using oscillators with longer
start-up intervals (i.e., XT or HS mode). The Sync
Break (or Wake-up Signal) character must be of
sufficient length and be followed by a sufficient interval
to allow enough time for the selected oscillator to start
and provide proper initialization of the EUSART.
19.2.4.2 Special Considerations Using
the WUE Bit
The timing of WUE and RCIF events may cause some
confusion when it comes to determining the validity of
received data. As noted, setting the WUE bit places the
EUSART in an Idle mode. The wake-up event causes a
receive interrupt by setting the RCIF bit. The WUE bit is
cleared after this when a rising edge is seen on RX/DT.
The interrupt condition is then cleared by reading the
RCREG register. Ordinarily, the data in RCREG will be
dummy data and should be discarded.
The fact that the WUE bit has been cleared (or is still
set) and the RCIF flag is set should not be used as an
indicator of the integrity of the data in RCREG. Users
should consider implementing a parallel method in
firmware to verify received data integrity.
To assure that no actual data is lost, check the RCIDL
bit to verify that a receive operation is not in process. If
a receive operation is not occurring, the WUE bit may
then be set just prior to entering the Sleep mode.
FIGURE 19-8: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING NORMAL OPERATION
FIGURE 19-9: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
WUE bit(1)
RX/DT Line
RCIF
Note 1: The EUSART remains in Idle while the WUE bit is set.
Bit set by user
Cleared due to user read of RCREG
Auto-Cleared
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
WUE bit(2)
RX/DT Line
RCIF
Bit set by user
Cleared due to user read of RCREG
Sleep Command Executed
Note 1: If the wake-up event requires long oscillator warm-up time, the auto-clear of the WUE bit can occur before the oscillator is ready. This
sequence should not depend on the presence of Q clocks.
2: The EUSART remains in Idle while the WUE bit is set.
Sleep Ends
Note 1
Auto-Cleared
© 2009 Microchip Technology Inc. DS39689F-page 227
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19.2.5 BREAK CHARACTER SEQUENCE
The EUSART module has the capability of sending the
special Break character sequences that are required by
the LIN/J2602 bus standard. The Break character
transmit consists of a Start bit, followed by twelve0
bits and a Stop bit. The Frame Break character is sent
whenever the SENDB and TXEN bits (TXSTA<3> and
TXSTA<5>) are set while the Transmit Shift register is
loaded with data. Note that the value of data written to
TXREG will be ignored and all ‘0’s will be transmitted.
The SENDB bit is automatically reset by hardware after
the corresponding Stop bit is sent. This allows the user
to preload the transmit FIFO with the next transmit byte
following the Break character (typically, the Sync
character in the LIN/J2602 specification).
Note that the data value written to the TXREG for the
Break character is ignored. The write simply serves the
purpose of initiating the proper sequence.
The TRMT bit indicates when the transmit operation is
active or Idle, just as it does during normal transmis-
sion. See Figure 19-10 for the timing of the Break
character sequence.
19.2.5.1 Break and Sync Transmit Sequence
The following sequence will send a message frame
header made up of a Break, followed by an Auto-Baud
Sync byte. This sequence is typical of a LIN/J2602 bus
master.
1. Configure the EUSART for the desired mode.
2. Set the TXEN and SENDB bits to set up the
Break character.
3. Load the TXREG with a dummy character to
initiate transmission (the value is ignored).
4. Write ‘55h’ to TXREG to load the Sync character
into the transmit FIFO buffer.
5. After the Break has been sent, the SENDB bit is
reset by hardware. The Sync character now
transmits in the preconfigured mode.
When the TXREG becomes empty, as indicated by the
TXIF, the next data byte can be written to TXREG.
19.2.6 RECEIVING A BREAK CHARACTER
The Enhanced USART module can receive a Break
character in two ways.
The first method forces configuration of the baud rate
at a frequency of 9/13 the typical speed. This allows for
the Stop bit transition to be at the correct sampling loca-
tion (13 bits for Break versus Start bit and 8 data bits for
typical data).
The second method uses the auto-wake-up feature
described in Section 19.2.4 “Auto-Wake-up on Sync
Break Character”. By enabling this feature, the
EUSART will sample the next two transitions on RX/DT,
cause an RCIF interrupt and receive the next data byte
followed by another interrupt.
Note that following a Break character, the user will
typically want to enable the Auto-Baud Rate Detect
feature. For both methods, the user can set the ABD bit
once the TXIF interrupt is observed.
FIGURE 19-10: SEND BREAK CHARACTER SEQUENCE
Write to TXREG
BRG Output
(Shift Clock)
Start Bit Bit 0 Bit 1 Bit 11 Stop Bit
Break
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
TX (pin)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
SENDB
(Transmit Shift
Reg. Empty Flag)
SENDB sampled here Auto-Cleared
Dummy Write
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DS39689F-page 228 © 2009 Microchip Technology Inc.
19.3 EUSART Synchronous
Master Mode
The Master mode indicates that the processor trans-
mits the master clock on the CK line. The Synchronous
Master mode is entered by setting the CSRC bit
(TXSTA<7>). In this mode, the data is transmitted in a
half-duplex manner (i.e., transmission and reception do
not occur at the same time). When transmitting data,
the reception is inhibited and vice versa. Synchronous
mode is entered by setting bit SYNC (TXSTA<4>). In
addition, enable bit SPEN (RCSTA<7>) is set in order
to configure the TX and RX pins to CK (clock) and DT
(data) lines, respectively.
The Master mode indicates that the processor
transmits the master clock on the CK line.
Clock polarity (CK) is selected with the TXCKP bit
(BAUDCON<4>). Setting TXCKP sets the Idle state on
CK as high, while clearing the bit sets the Idle state as
low.
19.3.1 EUSART SYNCHRONOUS MASTER
TRANSMISSION
The EUSART transmitter block diagram is shown in
Figure 19-3. The heart of the transmitter is the Transmit
(Serial) Shift Register (TSR). The Shift register obtains
its data from the Read/Write Transmit Buffer register,
TXREG. The TXREG register is loaded with data in
software. The TSR register is not loaded until the last
bit has been transmitted from the previous load. As
soon as the last bit is transmitted, the TSR is loaded
with new data from the TXREG (if available).
Once the TXREG register transfers the data to the TSR
register (occurs in one TCY), the TXREG is empty and
the TXIF flag bit (PIR1<4>) is set. The interrupt can be
enabled or disabled by setting or clearing the interrupt
enable bit, TXIE (PIE1<4>). TXIF is set regardless of
the state of enable bit TXIE; it cannot be cleared in
software. It will reset only when new data is loaded into
the TXREG register.
While flag bit TXIF indicates the status of the TXREG
register, another bit, TRMT (TXSTA<1>), shows the
status of the TSR register. TRMT is a read-only bit which
is set when the TSR is empty. No interrupt logic is tied to
this bit so the user has to poll this bit in order to deter-
mine if the TSR register is empty. The TSR is not
mapped in data memory so it is not available to the user.
To set up a Synchronous Master Transmission:
1. Initialize the SPBRGH:SPBRG registers for the
appropriate baud rate. Set or clear the BRG16
bit, as required, to achieve the desired baud rate.
2. Enable the synchronous master serial port by
setting bits, SYNC, SPEN and CSRC.
3. If the signal from the CK pin is to be inverted, set
the TXCKP bit.
4. If interrupts are desired, set enable bit, TXIE.
5. If 9-bit transmission is desired, set bit, TX9.
6. Enable the transmission by setting bit, TXEN.
7. If 9-bit transmission is selected, the ninth bit
should be loaded in bit, TX9D.
8. Start transmission by loading data to the TXREG
register.
9. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
FIGURE 19-11: SYNCHRONOUS TRANSMISSION
bit 0 bit 1 bit 7
Word 1
Q1 Q2 Q3Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
bit 2 bit 0 bit 1 bit 7RC7/RX/DT
RC6/TX/CK pin
Write to
TXREG Reg
TXIF bit
(Interrupt Flag)
TXEN bit 1 1
Word 2
TRMT bit
Write Word 1 Write Word 2
Note: Sync Master mode, SPBRG = 0, continuous transmission of two 8-bit words.
RC6/TX/CK pin
(TXCKP = 0)
(TXCKP = 1)
© 2009 Microchip Technology Inc. DS39689F-page 229
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FIGURE 19-12: SYNCHRONOUS TRANSMISSION (THROUGH TXEN)
TABLE 19-7: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER TRANSMISSION
RC7/RX/DT pin
RC6/TX/CK pin
Write to
TXREG reg
TXIF bit
TRMT bit
bit 0 bit 1 bit 2 bit 6 bit 7
TXEN bit
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
TXREG EUSART Transmit Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master transmission.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
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DS39689F-page 230 © 2009 Microchip Technology Inc.
19.3.2 EUSART SYNCHRONOUS
MASTER RECEPTION
Once Synchronous mode is selected, reception is
enabled by setting either the Single Receive Enable bit,
SREN (RCSTA<5>), or the Continuous Receive
Enable bit, CREN (RCSTA<4>). Data is sampled on the
RX pin on the falling edge of the clock.
If enable bit SREN is set, only a single word is received.
If enable bit CREN is set, the reception is continuous
until CREN is cleared. If both bits are set, then CREN
takes precedence.
To set up a Synchronous Master Reception:
1. Initialize the SPBRGH:SPBRG registers for the
appropriate baud rate. Set or clear the BRG16
bit, as required, to achieve the desired baud rate.
2. Enable the synchronous master serial port by
setting bits, SYNC, SPEN and CSRC.
3. Ensure bits, CREN and SREN, are clear.
4. If the signal from the CK pin is to be inverted, set
the TXCKP bit.
5. If interrupts are desired, set enable bit, RCIE.
6. If 9-bit reception is desired, set bit, RX9.
7. If a single reception is required, set bit, SREN.
For continuous reception, set bit, CREN.
8. Interrupt flag bit, RCIF, will be set when reception
is complete and an interrupt will be generated if
the enable bit, RCIE, was set.
9. Read the RCSTA register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
10. Read the 8-bit received data by reading the
RCREG register.
11. If any error occurred, clear the error by clearing
bit, CREN.
12. If using interrupts, ensure that the GIE and PEIE bits
in the INTCON register (INTCON<7:6>) are set.
FIGURE 19-13: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
TABLE 19-8: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER RECEPTION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
RCREG EUSART Receive Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
CREN bit
RC7/RX/DT
RC6/TX/CK pin
Write to
bit SREN
SREN bit
RCIF bit
(Interrupt)
Read
RXREG
Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4Q2 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
0
bit 0 bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7
0
Q1 Q2 Q3 Q4
Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0.
RC6/TX/CK pin
pin
(TXCKP = 0)
(TXCKP = 1)
© 2009 Microchip Technology Inc. DS39689F-page 231
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19.4 EUSART Synchronous
Slave Mode
Synchronous Slave mode is entered by clearing bit,
CSRC (TXSTA<7>). This mode differs from the
Synchronous Master mode in that the shift clock is sup-
plied externally at the CK pin (instead of being supplied
internally in Master mode). This allows the device to
transfer or receive data while in any power-managed
mode.
19.4.1 EUSART SYNCHRONOUS
SLAVE TRANSMISSION
The operation of the Synchronous Master and Slave
modes are identical, except in the case of the Sleep
mode.
If two words are written to the TXREG and then the
SLEEP instruction is executed, the following will occur:
a) The first word will immediately transfer to the
TSR register and transmit.
b) The second word will remain in the TXREG
register.
c) Flag bit, TXIF, will not be set.
d) When the first word has been shifted out of TSR,
the TXREG register will transfer the second word
to the TSR and flag bit, TXIF, will now be set.
e) If enable bit, TXIE, is set, the interrupt will wake
the chip from Sleep. If the global interrupt is
enabled, the program will branch to the interrupt
vector.
To set up a Synchronous Slave Transmission:
1. Enable the synchronous slave serial port by
setting bits, SYNC and SPEN, and clearing bit,
CSRC.
2. Clear bits, CREN and SREN.
3. If interrupts are desired, set enable bit, TXIE.
4. If the signal from the CK pin is to be inverted, set
the TXCKP bit.
5. If 9-bit transmission is desired, set bit, TX9.
6. Enable the transmission by setting enable bit,
TXEN.
7. If 9-bit transmission is selected, the ninth bit
should be loaded in bit TX9D.
8. Start transmission by loading data to the
TXREGx register.
9. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
TABLE 19-9: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
TXREG EUSART Transmit Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave transmission.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
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DS39689F-page 232 © 2009 Microchip Technology Inc.
19.4.2 EUSART SYNCHRONOUS SLAVE
RECEPTION
The operation of the Synchronous Master and Slave
modes is identical, except in the case of Sleep, or any
Idle mode and bit SREN, which is a “don’t care” in
Slave mode.
If receive is enabled by setting the CREN bit prior to
entering Sleep or any Idle mode, then a word may be
received while in this low-power mode. Once the word
is received, the RSR register will transfer the data to the
RCREG register; if the RCIE enable bit is set, the
interrupt generated will wake the chip from the low-
power mode. If the global interrupt is enabled, the
program will branch to the interrupt vector.
To set up a Synchronous Slave Reception:
1. Enable the synchronous master serial port by
setting bits, SYNC and SPEN, and clearing bit,
CSRC.
2. If interrupts are desired, set enable bit RCIE.
3. If the signal from the CK pin is to be inverted, set
the TXCKP bit.
4. If 9-bit reception is desired, set bit, RX9.
5. To enable reception, set enable bit, CREN.
6. Flag bit, RCIF, will be set when reception is
complete. An interrupt will be generated if
enable bit, RCIE, was set.
7. Read the RCSTA register to get the 9th bit (if
enabled) and determine if any error occurred
during reception.
8. Read the 8-bit received data by reading the
RCREG register.
9. If any error occurred, clear the error by clearing
bit, CREN.
10. If using interrupts, ensure that the GIE and PEIE
bits in the INTCON register (INTCON<7:6>) are
set.
TABLE 19-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57
RCREG EUSART Receive Register 57
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57
BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 WUE ABDEN 57
SPBRGH EUSART Baud Rate Generator Register High Byte 57
SPBRG EUSART Baud Rate Generator Register Low Byte 57
Legend: = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave reception.
Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.
© 2009 Microchip Technology Inc. DS39689F-page 233
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20.0 10-BIT ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The Analog-to-Digital (A/D) converter module has
10 inputs for the 28-pin devices and 13 for the 40/44-pin
devices. This module allows conversion of an analog
input signal to a corresponding 10-bit digital number.
The module has five registers:
A/D Result High Register (ADRESH)
A/D Result Low Register (ADRESL)
A/D Control Register 0 (ADCON0)
A/D Control Register 1 (ADCON1)
A/D Control Register 2 (ADCON2)
The ADCON0 register, shown in Register 20-1,
controls the operation of the A/D module. The
ADCON1 register, shown in Register 20-2, configures
the functions of the port pins. The ADCON2 register,
shown in Register 20-3, configures the A/D clock
source, programmed acquisition time and justification.
REGISTER 20-1: ADCON0: A/D CONTROL REGISTER 0
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
CHS3 CHS2 CHS1 CHS0 GO/DONE ADON
bit 7 bit 0
bit 7-6 Unimplemented: Read as ‘0
bit 5-2 CHS<3:0>: Analog Channel Select bits
0000 = Channel 0 (AN0)
0001 = Channel 1 (AN1)
0010 = Channel 2 (AN2)
0011 = Channel 3 (AN3)
0100 = Channel 4 (AN4)
0101 = Channel 5 (AN5)(1,2)
0110 = Channel 6 (AN6)(1,2)
0111 = Channel 7 (AN7)(1,2)
1000 = Channel 8 (AN8)
1001 = Channel 9 (AN9)
1010 = Channel 10 (AN10)
1011 = Channel 11 (AN11)
1100 = Channel 12 (AN12
1101 = Unimplemented(2)
1110 = Unimplemented(2)
1111 = Unimplemented(2)
Note 1: These channels are not implemented on 28-pin devices.
2: Performing a conversion on unimplemented channels will return a floating input
measurement.
bit 1 GO/DONE: A/D Conversion Status bit
When ADON = 1:
1 = A/D conversion in progress
0 = A/D Idle
bit 0 ADON: A/D On bit
1 = A/D converter module is enabled
0 = A/D converter module is disabled
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 234 © 2009 Microchip Technology Inc.
REGISTER 20-2: ADCON1: A/D CONTROL REGISTER 1
U-0 U-0 R/W-0 R/W-0 R/W-0(1) R/W(1) R/W(1) R/W(1)
VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0
bit 7 bit 0
bit 7-6 Unimplemented: Read as ‘0
bit 5 VCFG1: Voltage Reference Configuration bit (VREF- source)
1 = VREF- (AN2)
0 = VSS
bit 4 VCFG0: Voltage Reference Configuration bit (VREF+ source)
1 = VREF+ (AN3)
0 = VDD
bit 3-0 PCFG<3:0>: A/D Port Configuration Control bits
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
A = Analog input D = Digital I/O
Note 1: The POR value of the PCFG bits depends on the value of the PBADEN Con-
figuration bit. When PBADEN = 1, PCFG<3:0> = 0000; when PBADEN = 0,
PCFG<3:0> = 0111.
2: AN5 through AN7 are available only on 40/44-pin devices.
PCFG<3:0>
AN12
AN11
AN10
AN9
AN8
AN7(2)
AN6(2)
AN5(2)
AN4
AN3
AN2
AN1
AN0
0000(1) AAAAAAAAAAAAA
0001 AAAAAAAAAAAAA
0010 AAAAAAAAAAAAA
0011 DAAAAAAAAAAAA
0100 DDAAAAAAAAAAA
0101 DDDAAAAAAAAAA
0110 DDDDAAAAAAAAA
0111(1) DDDDDAAAAAAAA
1000 DDDDDDAAAAAAA
1001 DDDDDDDAAAAAA
1010 DDDDDDDDAAAAA
1011 DDDDDDDDDAAAA
1100 DDDDDDDDDDAAA
1101 DDDDDDDDDDDAA
1110 DDDDDDDDDDDDA
1111 DDDDDDDDDDDDD
© 2009 Microchip Technology Inc. DS39689F-page 235
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REGISTER 20-3: ADCON2: A/D CONTROL REGISTER 2
R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADFM ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0
bit 7 bit 0
bit 7 ADFM: A/D Result Format Select bit
1 = Right justified
0 = Left justified
bit 6 Unimplemented: Read as0
bit 5-3 ACQT<2:0>: A/D Acquisition Time Select bits
111 = 20 T
AD
110 = 16 TAD
101 = 12 TAD
100 = 8 TAD
011 = 6 TAD
010 = 4 TAD
001 = 2 TAD
000 = 0 TAD(1)
bit 2-0 ADCS<2:0>: A/D Conversion Clock Select bits
111 = FRC (clock derived from A/D RC oscillator)(1)
110 = FOSC/64
101 = FOSC/16
100 = FOSC/4
011 = FRC (clock derived from A/D RC oscillator)(1)
010 = FOSC/32
001 = FOSC/8
000 = FOSC/2
Note 1: If the A/D FRC clock source is selected, a delay of one TCY (instruction cycle) is
added before the A/D clock starts. This allows the SLEEP instruction to be executed
before starting a conversion.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR 1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 236 © 2009 Microchip Technology Inc.
The analog reference voltage is software selectable to
either the device’s positive and negative supply voltage
(VDD and VSS), or the voltage level on the RA3/AN3/
VREF+ and RA2/AN2/VREF-/CVREF pins.
The A/D converter has a unique feature of being able
to operate while the device is in Sleep mode. To
operate in Sleep, the A/D conversion clock must be
derived from the A/D’s internal RC oscillator.
The output of the sample and hold is the input into the
converter, which generates the result via successive
approximation.
A device Reset forces all registers to their Reset state.
This forces the A/D module to be turned off and any
conversion in progress is aborted.
Each port pin associated with the A/D converter can be
configured as an analog input, or as a digital I/O. The
ADRESH and ADRESL registers contain the result of
the A/D conversion. When the A/D conversion is
complete, the result is loaded into the
ADRESH:ADRESL register pair, the GO/DONE bit
(ADCON0 register) is cleared and A/D Interrupt Flag bit,
ADIF, is set. The block diagram of the A/D module is
shown in Figure 20-1.
FIGURE 20-1: A/D BLOCK DIAGRAM
(Input Voltage)
VAIN
VREF+
Reference
Voltage
VDD
VCFG<1:0>
CHS<3:0>
AN7(1)
AN6(1)
AN5(1)
AN4
AN3
AN2
AN1
AN0
0111
0110
0101
0100
0011
0010
0001
0000
10-Bit
A/D
VREF-
VSS
Converter
AN12
AN11
AN10
AN9
AN8
1100
1011
1010
1001
1000
Note 1: Channels AN5 through AN7 are not available on 28-pin devices.
2: I/O pins have diode protection to VDD and VSS.
0X
1X
X1
X0
© 2009 Microchip Technology Inc. DS39689F-page 237
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The value in the ADRESH:ADRESL registers is not
modified for a Power-on Reset. The ADRESH:ADRESL
registers will contain unknown data after a Power-on
Reset.
After the A/D module has been configured as desired,
the selected channel must be acquired before the
conversion is started. The analog input channels must
have their corresponding TRIS bits selected as an
input. To determine acquisition time, see Section 20.1
“A/D Acquisition Requirements”. After this acquisi-
tion time has elapsed, the A/D conversion can be
started. An acquisition time can be programmed to
occur between setting the GO/DONE bit and the actual
start of the conversion.
The following steps should be followed to perform an A/D
conversion:
1. Configure the A/D module:
Configure analog pins, voltage reference and
digital I/O (ADCON1)
Select A/D input channel (ADCON0)
Select A/D acquisition time (ADCON2)
Select A/D conversion clock (ADCON2)
Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
Clear ADIF bit
Set ADIE bit
Set GIE bit
3. Wait the required acquisition time (if required).
4. Start conversion:
Set GO/DONE bit (ADCON0 register)
5. Wait for A/D conversion to complete, by either:
Polling for the GO/DONE bit to be cleared
OR
Waiting for the A/D interrupt
6. Read A/D Result registers (ADRESH:ADRESL);
clear bit ADIF, if required.
7. For next conversion, go to step 1 or step 2, as
required. The A/D conversion time per bit is
defined as T
AD. A minimum wait of 2 TAD is
required before the next acquisition starts.
FIGURE 20-2: A/D TRANSFER FUNCTION
FIGURE 20-3: ANALOG INPUT MODEL
Digital Code Output
3FEh
003h
002h
001h
000h
0.5 LSB
1 LSB
1.5 LSB
2 LSB
2.5 LSB
1022 LSB
1022.5 LSB
3 LSB
Analog Input Voltage
3FFh
1023 LSB
1023.5 LSB
VAIN CPIN
Rs ANx
5 pF
VT = 0.6V
VT = 0.6V ILEAKAGE
RIC 1k
Sampling
Switch
SS RSS
CHOLD = 25 pF
VSS
VDD
±100 nA
Legend: CPIN
VT
ILEAKAGE
RIC
SS
CHOLD
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to
= Interconnect Resistance
= Sampling Switch
= Sample/Hold Capacitance (from DAC)
various junctions
= Sampling Switch ResistanceRSS
VDD
6V
Sampling Switch
5V
4V
3V
2V
1234
(kΩ)
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DS39689F-page 238 © 2009 Microchip Technology Inc.
20.1 A/D Acquisition Requirements
For the A/D converter to meet its specified accuracy,
the charge holding capacitor (CHOLD) must be allowed
to fully charge to the input channel voltage level. The
analog input model is shown in Figure 20-3. The
source impedance (RS) and the internal sampling
switch (RSS) impedance directly affect the time
required to charge the capacitor CHOLD. The sampling
switch (RSS) impedance varies over the device voltage
(VDD). The source impedance affects the offset voltage
at the analog input (due to pin leakage current). The
maximum recommended impedance for analog
sources is 2.5 kΩ. After the analog input channel is
selected (changed), the channel must be sampled for
at least the minimum acquisition time before starting a
conversion.
To calculate the minimum acquisition time,
Equation 20-1 may be used. This equation assumes
that 1/2 LSb error is used (1024 steps for the A/D). The
1/2 LSb error is the maximum error allowed for the A/D
to meet its specified resolution.
Example 20-3 shows the calculation of the minimum
required acquisition time TACQ. This calculation is
based on the following application system
assumptions:
CHOLD = 25 pF
Rs = 2.5 kΩ
Conversion Error 1/2 LSb
VDD =5V Rss = 2 kΩ
Temperature = 85°C (system max.)
EQUATION 20-1: ACQUISITION TIME
EQUATION 20-2: A/D MINIMUM CHARGING TIME
EQUATION 20-3: CALCULATING THE MINIMUM REQUIRED ACQUISITION TIME
Note: When the conversion is started, the
holding capacitor is disconnected from the
input pin.
TACQ = Amplifier Settling Time + Holding Capacitor Charging Time + Temperature Coefficient
=T
AMP + TC + TCOFF
VHOLD = (VREF – (VREF/2048)) • (1 – e(-TC/CHOLD(RIC + RSS + RS)))
or
TC = -(CHOLD)(RIC + RSS + RS) ln(1/2048)
TACQ =TAMP + TC + TCOFF
TAMP =0.2 μs
TCOFF = (Temp – 25°C)(0.02 μs/°C)
(85°C – 25°C)(0.02 μs/°C)
1.2 μs
Temperature coefficient is only required for temperatures > 25°C. Below 25°C, TCOFF = 0 ms.
TC = -(CHOLD)(RIC + RSS + RS) ln(1/2047)
-(25 pF) (1 kΩ + 2 kΩ + 2.5 kΩ) ln(0.0004883)
1.05 μs
TACQ =0.2 μs + 1 μs + 1.2 μs
2.4 μs
© 2009 Microchip Technology Inc. DS39689F-page 239
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20.2 Selecting and Configuring
Acquisition Time
The ADCON2 register allows the user to select an
acquisition time that occurs each time the GO/DONE
bit is set. It also gives users the option to use an
automatically determined acquisition time.
Acquisition time may be set with the ACQT<2:0> bits
(ADCON2<5:3>), which provides a range of 2 to
20 TAD. When the GO/DONE bit is set, the A/D module
continues to sample the input for the selected acquisi-
tion time, then automatically begins a conversion.
Since the acquisition time is programmed, there may
be no need to wait for an acquisition time between
selecting a channel and setting the GO/DONE bit.
Manual acquisition is selected when
ACQT<2:0> = 000. When the GO/DONE bit is set,
sampling is stopped and a conversion begins. The user
is responsible for ensuring the required acquisition time
has passed between selecting the desired input
channel and setting the GO/DONE bit. This option is
also the default Reset state of the ACQT<2:0> bits and
is compatible with devices that do not offer
programmable acquisition times.
In either case, when the conversion is completed, the
GO/DONE bit is cleared, the ADIF flag is set and the
A/D begins sampling the currently selected channel
again. If an acquisition time is programmed, there is
nothing to indicate if the acquisition time has ended or
if the conversion has begun.
20.3 Selecting the A/D Conversion
Clock
The A/D conversion time per bit is defined as TAD. The
A/D conversion requires 11 TAD per 10-bit conversion.
The source of the A/D conversion clock is software
selectable. There are seven possible options for T
AD:
•2 T
OSC
•4 TOSC
•8 TOSC
•16 TOSC
•32 TOSC
•64 TOSC
Internal RC Oscillator
For correct A/D conversions, the A/D conversion clock
(T
AD) must be as short as possible, but greater than the
minimum TAD (see parameter 130 for more
information).
Table 20-1 shows the resultant T
AD times derived from
the device operating frequencies and the A/D clock
source selected.
TABLE 20-1: TAD vs. DEVICE OPERATING FREQUENCIES
AD Clock Source (TAD) Maximum Device Frequency
Operation ADCS<2:0> PIC18F2X21/4X21 PIC18LF2X21/4X21(4)
2 T
OSC 000 2.86 MHz 1.43 kHz
4 TOSC 100 5.71 MHz 2.86 MHz
8 T
OSC 001 11.43 MHz 5.72 MHz
16 TOSC 101 22.86 MHz 11.43 MHz
32 T
OSC 010 40.0 MHz 22.86 MHz
64 T
OSC 110 40.0 MHz 22.86 MHz
RC(3) x11 1.00 MHz(1) 1.00 MHz(2)
Note 1: The RC source has a typical TAD time of 1.2 μs.
2: The RC source has a typical TAD time of 2.5 μs.
3: For device frequencies above 1 MHz, the device must be in Sleep for the entire conversion or the A/D
accuracy may be out of specification.
4: Low-power (PIC18LFXXXX) devices only.
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DS39689F-page 240 © 2009 Microchip Technology Inc.
20.4 Operation in Power-Managed
Modes
The selection of the automatic acquisition time and A/D
conversion clock is determined in part by the clock
source and frequency while in a power-managed mode.
If the A/D is expected to operate while the device is in
a power-managed mode, the ACQT<2:0> and
ADCS<2:0> bits in ADCON2 should be updated in
accordance with the clock source to be used in that
mode. After entering the mode, an A/D acquisition or
conversion may be started. Once started, the device
should continue to be clocked by the same clock
source until the conversion has been completed.
If desired, the device may be placed into the
corresponding Idle mode during the conversion. If the
device clock frequency is less than 1 MHz, the A/D RC
clock source should be selected.
Operation in Sleep mode requires the A/D FRC clock to
be selected. If bits ACQT<2:0> are set to ‘000’ and a
conversion is started, the conversion will be delayed
one instruction cycle to allow execution of the SLEEP
instruction and entry to Sleep mode. The IDLEN bit
(OSCCON<7>) must have already been cleared prior
to starting the conversion.
20.5 Configuring Analog Port Pins
The ADCON1, TRISA, TRISB and TRISE registers all
configure the A/D port pins. The port pins needed as
analog inputs must have their corresponding TRIS bits
set (input). If the TRIS bit is cleared (output), the digital
output level (VOH or VOL) will be converted.
The A/D operation is independent of the state of the
CHS<3:0> bits and the TRIS bits.
Note 1: When reading the Port register, all pins
configured as analog input channels will
read as cleared (a low level). Pins
configured as digital inputs will convert as
analog inputs. Analog levels on a digitally
configured input will be accurately
converted.
2: Analog levels on any pin defined as a
digital input may cause the digital input
buffer to consume current out of the
device’s specification limits.
3: The PBADEN bit in Configuration
Register 3H configures PORTB pins to
reset as analog or digital pins by control-
ling how the PCFG<3:0> bits in ADCON1
are reset.
© 2009 Microchip Technology Inc. DS39689F-page 241
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20.6 A/D Conversions
Figure 20-4 shows the operation of the A/D converter
after the GO/DONE bit has been set and the
ACQT<2:0> bits are cleared. A conversion is started
after the following instruction to allow entry into Sleep
mode before the conversion begins.
Figure 20-5 shows the operation of the A/D converter
after the GO/DONE bit has been set and the
ACQT<2:0> bits are set to ‘010’ and selecting a 4 TAD
acquisition time before the conversion starts.
Clearing the GO/DONE bit during a conversion will abort
the current conversion. The A/D Result register pair will
NOT be updated with the partially completed A/D
conversion sample. This means the ADRESH:ADRESL
registers will continue to contain the value of the last
completed conversion (or the last value written to the
ADRESH:ADRESL registers).
After the A/D conversion is completed or aborted, a
2T
AD wait is required before the next acquisition can be
started. After this wait, acquisition on the selected
channel is automatically started.
20.7 Discharge
The discharge phase is used to initialize the value of
the capacitor array. The array is discharged before
every sample. This feature helps to optimize the unity-
gain amplifier, as the circuit always needs to charge the
capacitor array, rather than charge/discharge based on
previous measure values.
FIGURE 20-4: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 000, TACQ = 0)
FIGURE 20-5: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 010, TACQ = 4 TAD)
Note: The GO/DONE bit should NOT be set in
the same instruction that turns on the A/D.
TAD1TAD2TAD3TAD4 TAD5TAD6 TAD7TAD8 TAD11
Set GO/DONE bit
Holding capacitor is disconnected from analog input (typically 100 ns)
TAD9 TAD10
TCY - TAD
ADRESH:ADRESL is loaded, GO/DONE bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.
Conversion starts
b0
b9 b6 b5 b4 b3 b2 b1
b8 b7
On the following cycle:
TAD1
Discharge
123 4 5 67811
Set GO/DONE bit
(Holding capacitor is disconnected)
910
Conversion starts
123 4
(Holding capacitor continues
acquiring input)
TACQT Cycles TAD Cycles
Automatic
Acquisition
Time
b0b9 b6 b5 b4 b3 b2 b1
b8 b7
ADRESH:ADRESL is loaded, GO/DONE bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.
On the following cycle:
TAD1
Discharge
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DS39689F-page 242 © 2009 Microchip Technology Inc.
20.8 Use of the CCP2 Trigger
An A/D conversion can be started by the Special Event
Trigger of the CCP2 module. This requires that the
CCP2M<3:0> bits (CCP2CON<3:0>) be programmed
as ‘1011’ and that the A/D module is enabled (ADON
bit is set). When the trigger occurs, the GO/DONE bit
will be set, starting the A/D acquisition and conversion
and the Timer1 (or Timer3) counter will be reset to zero.
Timer1 (or Timer3) is reset to automatically repeat the
A/D acquisition period with minimal software overhead
(moving ADRESH:ADRESL to the desired location).
The appropriate analog input channel must be selected
and the minimum acquisition period is either timed by
the user, or an appropriate TACQ time selected before
the Special Event Trigger sets the GO/DONE bit (starts
a conversion).
If the A/D module is not enabled (ADON is cleared), the
Special Event Trigger will be ignored by the A/D module
but will still reset the Timer1 (or Timer3) counter.
TABLE 20-2: REGISTERS ASSOCIATED WITH A/D OPERATION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
ADRESH A/D Result Register High Byte 57
ADRESL A/D Result Register Low Byte 57
ADCON0 CHS3 CHS2 CHS1 CHS0 GO/DONE ADON 57
ADCON1 VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57
ADCON2 ADFM ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 57
PORTA RA7(2) RA6(2) RA5 RA4 RA3 RA2 RA1 RA0 58
TRISA TRISA7(2) TRISA6(2) PORTA Data Direction Control Register 58
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 58
TRISB PORTB Data Direction Control Register 58
LATB PORTB Data Latch Register (Read and Write to Data Latch) 58
PORTE —RE3
(3) RE2(1) RE1(1) RE0(1) 58
TRISE(1) IBF OBF IBOV PSPMODE TRISE2 TRISE1 TRISE0 58
LATE(1) PORTE Data Latch Register 58
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.
Note 1: These registers and/or bits are unimplemented on 28-pin devices and are read as ‘0’.
2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.
3: RE3 port bit is available only as an input pin when the MCLRE Configuration bit is ‘0’.
© 2009 Microchip Technology Inc. DS39689F-page 243
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21.0 COMPARATOR MODULE
The analog comparator module contains two
comparators that can be configured in a variety of
ways. The inputs can be selected from the analog
inputs multiplexed with pins RA0 through RA5, as well
as the on-chip voltage reference (see Section 22.0
“Comparator Voltage Reference Module”). The digi-
tal outputs (normal or inverted) are available at the pin
level and can also be read through the control register.
The CMCON register (Register 21-1) selects the
comparator input and output configuration. Block
diagrams of the various comparator configurations are
shown in Figure 21-1.
REGISTER 21-1: CMCON: COMPARATOR CONTROL REGISTER
R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1
C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0
bit 7 bit 0
bit 7 C2OUT: Comparator 2 Output bit
When C2INV = 0:
1 = C2 VIN+ > C2 VIN-
0 = C2 VIN+ < C2 VIN-
When C2INV = 1:
1 = C2 VIN+ < C2 VIN-
0 = C2 VIN+ > C2 VIN-
bit 6 C1OUT: Comparator 1 Output bit
When C1INV = 0:
1 = C1 VIN+ > C1 VIN-
0 = C1 VIN+ < C1 VIN-
When C1INV = 1:
1 = C1 VIN+ < C1 VIN-
0 = C1 VIN+ > C1 VIN-
bit 5 C2INV: Comparator 2 Output Inversion bit
1 = C2 output inverted
0 = C2 output not inverted
bit 4 C1INV: Comparator 1 Output Inversion bit
1 = C1 output inverted
0 = C1 output not inverted
bit 3 CIS: Comparator Input Switch bit
When CM<2:0> = 110:
1 =C1 VIN- connects to RA3/AN3/VREF+
C2 VIN- connects to RA2/AN2/VREF-/CVREF
0 =C1 VIN- connects to RA0/AN0
C2 VIN- connects to RA1/AN1
bit 2-0 CM<2:0>: Comparator Mode bits
Figure 21-1 shows the Comparator modes and the CM<2:0> bit settings.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
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DS39689F-page 244 © 2009 Microchip Technology Inc.
21.1 Comparator Configuration
There are eight modes of operation for the comparators,
shown in Figure 21-1. Bits CM<2:0> of the CMCON
register are used to select these modes. The TRISA reg-
ister controls the data direction of the comparator pins
for each mode. If the Comparator mode is changed, the
comparator output level may not be valid for the
specified mode change delay shown in Section 27.0
“Electrical Characteristics”.
FIGURE 21-1: COMPARATOR I/O OPERATING MODES
Note: Comparator interrupts should be disabled
during a Comparator mode change;
otherwise, a false interrupt may occur.
C1
RA0/AN0 VIN-
VIN+
RA3/AN3/ Off (Read as ‘0’)
Comparators Reset
A
A
CM<2:0> = 000
C2
RA1/AN1 VIN-
VIN+
RA2/AN2/ Off (Read as ‘0’)
A
A
C1
VIN-
VIN+C1OUT
Two Independent Comparators
A
A
CM<2:0> = 010
C2
VIN-
VIN+C2OUT
A
A
C1
VIN-
VIN+C1OUT
Two Common Reference Comparators
A
A
CM<2:0> = 100
C2
VIN-
VIN+C2OUT
A
D
C2
VIN-
VIN+Off (Read as ‘0’)
One Independent Comparator with Output
D
D
CM<2:0> = 001
C1
VIN-
VIN+C1OUT
A
A
C1
VIN-
VIN+Off (Read as0’)
Comparators Off (POR Default Value)
D
D
CM<2:0> = 111
C2
VIN-
VIN+Off (Read as0’)
D
D
C1
VIN-
VIN+C1OUT
Four Inputs Multiplexed to Two Comparators
A
A
CM<2:0> = 110
C2
VIN-
VIN+C2OUT
A
A
From VREF Module
CIS = 0
CIS = 1
CIS = 0
CIS = 1
C1
VIN-
VIN+C1OUT
Two Common Reference Comparators with Outputs
A
A
CM<2:0> = 101
C2
VIN-
VIN+C2OUT
A
D
A = Analog Input, port reads zeros always D = Digital Input CIS (CMCON<3>) is the Comparator Input Switch
CVREF
C1
VIN-
VIN+C1OUT
Two Independent Comparators with Outputs
A
A
CM<2:0> = 011
C2
VIN-
VIN+C2OUT
A
A
RA5/AN4/SS/HLVDIN/C2OUT*
RA4/T0CKI/C1OUT*
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
VREF+
RA1/AN1
RA2/AN2/
VREF-/CVREF
RA4/T0CKI/C1OUT*
RA5/AN4/SS/HLVDIN/C2OUT*
RA0/AN0
RA3/AN3/
VREF+
RA1/AN1
RA2/AN2/
VREF-/CVREF
RA4/T0CKI/C1OUT*
* Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs.
© 2009 Microchip Technology Inc. DS39689F-page 245
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21.2 Comparator Operation
A single comparator is shown in Figure 21-2, along with
the relationship between the analog input levels and
the digital output. When the analog input at VIN+ is less
than the analog input VIN-, the output of the comparator
is a digital low level. When the analog input at VIN+ is
greater than the analog input VIN-, the output of the
comparator is a digital high level. The shaded areas of
the output of the comparator in Figure 21-2 represent
the uncertainty, due to input offsets and response time.
21.3 Comparator Reference
Depending on the comparator operating mode, either
an external or internal voltage reference may be used.
The analog signal present at VIN- is compared to the
signal at VIN+ and the digital output of the comparator
is adjusted accordingly (Figure 21-2).
FIGURE 21-2: SINGLE COMPARATOR
21.3.1 EXTERNAL REFERENCE SIGNAL
When external voltage references are used, the
comparator module can be configured to have the
comparators operate from the same or different
reference sources. However, threshold detector
applications may require the same reference. The
reference signal must be between VSS and VDD and
can be applied to either pin of the comparator(s).
21.3.2 INTERNAL REFERENCE SIGNAL
The comparator module also allows the selection of an
internally generated voltage reference from the
comparator voltage reference module. This module is
described in more detail in Section 22.0 “Comparator
Voltage Reference Module”.
The internal reference is only available in the mode
where four inputs are multiplexed to two comparators
(CM<2:0> = 110). In this mode, the internal voltage ref-
erence is applied to the VIN+ pin of both comparators.
21.4 Comparator Response Time
Response time is the minimum time, after selecting a
new reference voltage or input source, before the
comparator output has a valid level. If the internal ref-
erence is changed, the maximum delay of the internal
voltage reference must be considered when using the
comparator outputs. Otherwise, the maximum delay of
the comparators should be used (see Section 27.0
“Electrical Characteristics”).
21.5 Comparator Outputs
The comparator outputs are read through the CMCON
register. These bits are read-only. The comparator
outputs may also be directly output to the RA4 and RA5
I/O pins. When enabled, multiplexors in the output path
of the RA4 and RA5 pins will switch and the output of
each pin will be the unsynchronized output of the
comparator. The uncertainty of each of the
comparators is related to the input offset voltage and
the response time given in the specifications.
Figure 21-3 shows the comparator output block
diagram.
The TRISA bits will still function as an output enable/
disable for the RA4 and RA5 pins while in this mode.
The polarity of the comparator outputs can be changed
using the C2INV and C1INV bits (CMCON<5:4>).
+
VIN+
VIN-
Output
Output
VIN-
VIN+
Note 1: When reading the Port register, all pins
configured as analog inputs will read as a
0’. Pins configured as digital inputs will
convert an analog input according to the
Schmitt Trigger input specification.
2: Analog levels on any pin defined as a
digital input may cause the input buffer to
consume more current than is specified.
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DS39689F-page 246 © 2009 Microchip Technology Inc.
FIGURE 21-3: COMPARATOR OUTPUT BLOCK DIAGRAM
21.6 Comparator Interrupts
The comparator interrupt flag is set whenever there is
a change in the output value of either comparator.
Software will need to maintain information about the
status of the output bits, as read from CMCON<7:6>, to
determine the actual change that occurred. The CMIF
bit (PIR2<6>) is the Comparator Interrupt Flag. The
CMIF bit must be reset by clearing it. Since it is also
possible to write a ‘1’ to this register, a simulated
interrupt may be initiated.
Both the CMIE bit (PIE2<6>) and the PEIE bit
(INTCON<6>) must be set to enable the interrupt. In
addition, the GIE bit (INTCON<7>) must also be set. If
any of these bits are clear, the interrupt is not enabled,
though the CMIF bit will still be set if an interrupt
condition occurs.
The user, in the Interrupt Service Routine, can clear the
interrupt in the following manner:
a) Any read or write of CMCON will end the
mismatch condition.
b) Clear flag bit CMIF.
A mismatch condition will continue to set flag bit CMIF.
Reading CMCON will end the mismatch condition and
allow flag bit CMIF to be cleared.
21.7 Comparator Operation
During Sleep
When a comparator is active and the device is placed
in Sleep mode, the comparator remains active and the
interrupt is functional if enabled. This interrupt will
wake-up the device from Sleep mode, when enabled.
Each operational comparator will consume additional
current, as shown in the comparator specifications. To
minimize power consumption while in Sleep mode, turn
off the comparators (CM<2:0> = 111) before entering
Sleep. If the device wakes up from Sleep, the contents
of the CMCON register are not affected.
21.8 Effects of a Reset
A device Reset forces the CMCON register to its Reset
state, causing the comparator modules to be turned off
(CM<2:0> = 111). However, the input pins (RA0
through RA3) are configured as analog inputs by
default on device Reset. The I/O configuration for these
pins is determined by the setting of the PCFG<3:0> bits
(ADCON1<3:0>). Therefore, device current is
minimized when analog inputs are present at Reset
time.
DQ
EN
To RA4 or
RA5 pin
Bus
Data
Set
MULTIPLEX
CMIF
bit
-+
Port Pins
Read CMCON
Reset
From
Other
Comparator
CxINV
DQ
EN CL
Note: If a change in the CMCON register
(C1OUT or C2OUT) should occur when a
read operation is being executed (start of
the Q2 cycle), then the CMIF (PIR2
register) interrupt flag may not get set.
© 2009 Microchip Technology Inc. DS39689F-page 247
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21.9 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 21-4. Since the analog pins are connected to a
digital output, they have reverse biased diodes to VDD
and VSS. The analog input, therefore, must be between
VSS and VDD. If the input voltage deviates from this
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latch-up condition may
occur. A maximum source impedance of 10 kΩ is
recommended for the analog sources. Any external
component connected to an analog input pin, such as
a capacitor or a Zener diode, should have very little
leakage current.
FIGURE 21-4: COMPARATOR ANALOG INPUT MODEL
TABLE 21-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 57
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 57
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 58
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
PORTA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 58
LATA LATA7(1) LATA6(1) PORTA Data Latch Register (Read and Write to Data Latch) 58
TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 58
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.
Note 1: PORTA<7:6> and their direction and latch bits are individually configured as port pins based on various
primary oscillator modes. When disabled, these bits read as ‘0’.
VA
RS < 10k
AIN
CPIN
5 pF
VDD
VT = 0.6V
VT = 0.6V
RIC
ILEAKAGE
±100 nA
VSS
Legend: CPIN = Input Capacitance
VT= Threshold Voltage
ILEAKAGE = Leakage Current at the pin due to various junctions
RIC = Interconnect Resistance
RS= Source Impedance
VA = Analog Voltage
Comparator
Input
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 248 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 249
PIC18F2221/2321/4221/4321 FAMILY
22.0 COMPARATOR VOLTAGE
REFERENCE MODULE
The comparator voltage reference is a 16-tap resistor
ladder network that provides a selectable reference
voltage. Although its primary purpose is to provide a
reference for the analog comparators, it may also be
used independently of them.
A block diagram of the module is shown in Figure 22-1.
The resistor ladder is segmented to provide two ranges
of CVREF values and has a power-down function to
conserve power when the reference is not being used.
The module’s supply reference can be provided from
either device VDD/VSS or an external voltage reference.
22.1 Configuring the Comparator
Voltage Reference
The voltage reference module is controlled through the
CVRCON register (Register 22-1). The comparator
voltage reference provides two ranges of output
voltage, each with 16 distinct levels. The range to be
used is selected by the CVRR bit (CVRCON<5>). The
primary difference between the ranges is the size of the
steps selected by the CVREF selection bits
(CVR<3:0>), with one range offering finer resolution.
The equations used to calculate the output of the
comparator voltage reference are as follows:
If CVRR = 1:
CVREF = ((CVR<3:0>)/24) x CVRSRC
If CVRR = 0:
CVREF = (CVRSRC x 1/4) + (((CVR<3:0>)/32) x
CVRSRC)
The comparator reference supply voltage can come
from either VDD and VSS, or the external VREF+ and
VREF- that are multiplexed with RA2 and RA3. The
voltage source is selected by the CVRSS bit
(CVRCON<4>).
The settling time of the comparator voltage reference
must be considered when changing the CVREF
output (see Table 27-3 in Section 27.0 “Electrical
Characteristics”).
REGISTER 22-1: CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
CVREN CVROE(1) CVRR CVRSS CVR3 CVR2 CVR1 CVR0
bit 7 bit 0
bit 7 CVREN: Comparator Voltage Reference Enable bit
1 =CV
REF circuit powered on
0 =CV
REF circuit powered down
bit 6 CVROE: Comparator VREF Output Enable bit(1)
1 =CVREF voltage level is also output on the RA2/AN2/VREF-/CVREF pin
0 =CV
REF voltage is disconnected from the RA2/AN2/VREF-/CVREF pin
Note 1: CVROE overrides the TRISA<2> bit setting.
bit 5 CVRR: Comparator VREF Range Selection bit
1 = 0.00 CVRSRC to 0.667 CVRSRC, with CVRSRC/24 step size (low range)
0 = 0.25 CVRSRC to 0.75 CVRSRC, with CVRSRC/32 step size (high range)
bit 4 CVRSS: Comparator VREF Source Selection bit
1 = Comparator reference source, CVRSRC = (VREF+) – (VREF-)
0 = Comparator reference source, CVRSRC = VDD – VSS
bit 3-0 CVR<3:0>: Comparator VREF Value Selection bits (0 (CVR<3:0>) 15)
When CVRR = 1:
CVREF = ((CVR<3:0>)/24) (CVRSRC)
When CVRR = 0:
CVREF = (CVRSRC/4) + ((CVR<3:0>)/32) (CVRSRC)
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 250 © 2009 Microchip Technology Inc.
FIGURE 22-1: COMPARATOR VOLTAGE REFERENCE BLOCK DIAGRAM
22.2 Voltage Reference Accuracy/Error
The full range of voltage reference cannot be realized
due to the construction of the module. The transistors
on the top and bottom of the resistor ladder network
(Figure 22-1) keep CVREF from approaching the
reference source rails. The voltage reference is derived
from the reference source; therefore, the CVREF output
changes with fluctuations in that source. The tested
absolute accuracy of the voltage reference can be
found in Section 27.0 “Electrical Characteristics”.
22.3 Operation During Sleep
When the device wakes up from Sleep through an
interrupt or a Watchdog Timer time-out, the contents of
the CVRCON register are not affected. To minimize
current consumption in Sleep mode, the voltage
reference should be disabled.
22.4 Effects of a Reset
A device Reset disables the voltage reference by
clearing bit, CVREN (CVRCON<7>). This Reset also
disconnects the reference from the RA2 pin by clearing
bit, CVROE (CVRCON<6>) and selects the high-voltage
range by clearing bit, CVRR (CVRCON<5>). The CVR
value select bits are also cleared.
22.5 Connection Considerations
The voltage reference module operates independently
of the comparator module. The output of the reference
generator may be connected to the RA2 pin if the
CVROE bit is set. Enabling the voltage reference
output onto RA2 when it is configured as a digital input
will increase current consumption. Connecting RA2 as
a digital output with CVRSS enabled will also increase
current consumption.
The RA2 pin can be used as a simple D/A output with
limited drive capability. Due to the limited current drive
capability, a buffer must be used on the voltage
reference output for external connections to VREF.
Figure 22-2 shows an example buffering technique.
16-to-1 MUX
CVR<3:0>
8R
R
CVREN
CVRSS = 0
VDD
VREF+CVRSS = 1
8R
CVRSS = 0
VREF-CVRSS = 1
R
R
R
R
R
R
16 Steps
CVRR
CVREF
© 2009 Microchip Technology Inc. DS39689F-page 251
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 22-2: COMPARATOR VOLTAGE REFERENCE OUTPUT BUFFER EXAMPLE
TABLE 22-1: REGISTERS ASSOCIATED WITH COMPARATOR VOLTAGE REFERENCE
CVREF Output
+
CVREF
Module
Voltage
Reference
Output
Impedance
R(1)
RA2
Note 1: R is dependent upon the voltage reference configuration bits, CVRCON<3:0> and CVRCON<5>.
PIC18FXXXX
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 57
CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 57
TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 58
Legend: Shaded cells are not used with the comparator voltage reference.
Note 1: PORTA pins are enabled based on oscillator configuration.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 252 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 253
PIC18F2221/2321/4221/4321 FAMILY
23.0 HIGH/LOW-VOLTAGE DETECT
(HLVD)
PIC18F2221/2321/4221/4321 family devices have a
High/Low-Voltage Detect module (HLVD). This is a
programmable circuit that allows the user to specify both
a device voltage trip point and the direction of change
from that point. If the device experiences an excursion
past the trip point in that direction, an interrupt flag is set.
If the interrupt is enabled, the program execution will
branch to the interrupt vector address and the software
can then respond to the interrupt.
The High/Low-Voltage Detect Control register
(Register 23-1) completely controls the operation of the
HLVD module. This allows the circuitry to be “turned
off” by the user under software control, which
minimizes the current consumption for the device.
The block diagram for the HLVD module is shown in
Figure 23-1.
REGISTER 23-1: HLVDCON: HIGH/LOW-VOLTAGE DETECT CONTROL REGISTER
The module is enabled by setting the HLVDEN bit.
Each time that the HLVD module is enabled, the
circuitry requires some time to stabilize. The IRVST bit
is a read-only bit and is used to indicate when the circuit
is stable. The module can only generate an interrupt
after the circuit is stable and IRVST is set.
The VDIRMAG bit determines the overall operation of
the module. When VDIRMAG is cleared, the module
monitors for drops in VDD below a predetermined set
point. When the bit is set, the module monitors for rises
in VDD above the set point.
R/W-0 U-0 R-0 R/W-0 R/W-0 R/W-1 R/W-0 R/W-1
VDIRMAG IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0
bit 7 bit 0
bit 7 VDIRMAG: Voltage Direction Magnitude Select bit
1 = Event occurs when voltage equals or exceeds trip point (HLVDL<3:0>)
0 = Event occurs when voltage equals or falls below trip point (HLVDL<3:0>)
bit 6 Unimplemented: Read as ‘0
bit 5 IRVST: Internal Reference Voltage Stable Flag bit
1 = Indicates that the voltage detect logic will generate the interrupt flag at the specified voltage
range
0 = Indicates that the voltage detect logic will not generate the interrupt flag at the specified
voltage range and the HLVD interrupt should not be enabled
bit 4 HLVDEN: High/Low-Voltage Detect Power Enable bit
1 = HLVD enabled
0 = HLVD disabled
bit 3-0 HLVDL<3:0>: Voltage Detection Limit bits
1111 = External analog input is used (input comes from the HLVDIN pin)
1110 = Maximum setting
.
.
.
0000 = Minimum setting
Note: See Table 27-4 in Section 27.0 “Electrical Characteristics” for the specifications.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 254 © 2009 Microchip Technology Inc.
23.1 Operation
When the HLVD module is enabled, a comparator uses
an internally generated reference voltage as the set
point. The set point is compared with the trip point,
where each node in the resistor divider represents a
trip point voltage. The “trip point” voltage is the voltage
level at which the device detects a high or low-voltage
event, depending on the configuration of the module.
When the supply voltage is equal to the trip point, the
voltage tapped off of the resistor array is equal to the
internal reference voltage generated by the voltage
reference module. The comparator then generates an
interrupt signal by setting the HLVDIF bit.
The trip point voltage is software programmable to
any one of 16 values. The trip point is selected by
programming the HLVDL<3:0> bits (HLVDCON<3:0>).
The HLVD module has an additional feature that allows
the user to supply the trip voltage to the module from an
external source. This mode is enabled when bits
HLVDL<3:0> are set to ‘1111’. In this state, the
comparator input is multiplexed from the external input
pin, HLVDIN. This gives users flexibility because it
allows them to configure the High/Low-Voltage Detect
interrupt to occur at any voltage in the valid operating
range.
FIGURE 23-1: HLVD MODULE BLOCK DIAGRAM (WITH EXTERNAL INPUT)
Set
VDD
16-to-1 MUX
HLVDEN
HLVDCON
HLVDIN
HLVDL<3:0>
Register
HLVDIN
VDD
Externally Generated
Trip Point
HLVDIF
HLVDEN
BOREN
Internal Voltage
Reference
VDIRMAG
© 2009 Microchip Technology Inc. DS39689F-page 255
PIC18F2221/2321/4221/4321 FAMILY
23.2 HLVD Setup
The following steps are needed to set up the HLVD
module:
1. Disable the module by clearing the HLVDEN bit
(HLVDCON<4>).
2. Write the value to the HLVDL<3:0> bits that
selects the desired HLVD trip point.
3. Set the VDIRMAG bit to detect high voltage
(VDIRMAG = 1) or low voltage (VDIRMAG = 0).
4. Enable the HLVD module by setting the
HLVDEN bit.
5. Clear the HLVD interrupt flag (PIR2<2>), which
may have been set from a previous interrupt.
6. Enable the HLVD interrupt if interrupts are
desired by setting the HLVDIE and GIE bits
(PIE<2> and INTCON<7>). An interrupt will not
be generated until the IRVST bit is set.
23.3 Current Consumption
When the module is enabled, the HLVD comparator
and voltage divider are enabled and will consume static
current. The total current consumption, when enabled,
is specified in electrical specification parameter D022B.
Depending on the application, the HLVD module does
not need to be operating constantly. To decrease the
current requirements, the HLVD circuitry may only
need to be enabled for short periods where the voltage
is checked. After doing the check, the HLVD module
may be disabled.
23.4 HLVD Start-up Time
The internal reference voltage of the HLVD module,
specified in electrical specification parameter D420,
may be used by other internal circuitry, such as the
Programmable Brown-out Reset. If the HLVD or other
circuits using the voltage reference are disabled to
lower the device’s current consumption, the reference
voltage circuit will require time to become stable before
a low or high-voltage condition can be reliably
detected. This start-up time, TIRVST, is an interval that
is independent of device clock speed. It is specified in
electrical specification parameter 36.
The HLVD interrupt flag is not enabled until TIRVST has
expired and a stable reference voltage is reached. For
this reason, brief excursions beyond the set point may
not be detected during this interval. Refer to
Figure 23-2 or Figure 23-3.
FIGURE 23-2: LOW-VOLTAGE DETECT OPERATION (VDIRMAG = 0)
VLVD
VDD
HLVDIF
VLVD
VDD
Enable HLVD
TIRVST
HLVDIF may not be set
Enable HLVD
HLVDIF
HLVDIF cleared in software
HLVDIF cleared in software
HLVDIF cleared in software,
CASE 1:
CASE 2:
HLVDIF remains set since HLVD condition still exists
TIRVST
Internal Reference is stable
Internal Reference is stable
IRVST
IRVST
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 256 © 2009 Microchip Technology Inc.
FIGURE 23-3: HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1)
23.5 Applications
In many applications, the ability to detect a drop below
or rise above a particular threshold is desirable. For
example, the HLVD module could be periodically
enabled to detect a Universal Serial Bus (USB) attach
or detach. This assumes the device is powered by a
lower voltage source than the USB when detached. An
attach would indicate a high-voltage detect from, for
example, 3.3V to 5V (the voltage on USB) and vice
versa for a detach. This feature could save a design a
few extra components and an attach signal (input pin).
For general battery applications, Figure 23-4 shows a
possible voltage curve. Over time, the device voltage
decreases. When the device voltage reaches voltage
VA, the HLVD logic generates an interrupt at time TA.
The interrupt could cause the execution of an ISR,
which would allow the application to perform “house-
keeping tasks” and perform a controlled shutdown
before the device voltage exits the valid operating
range at TB. The HLVD, thus, would give the applica-
tion a time window, represented by the difference
between T
A and TB, to safely exit.
FIGURE 23-4: TYPICAL LOW-VOLTAGE
DETECT APPLICATION
VLVD
VDD
HLVDIF
VLVD
VDD
Enable HLVD
TIRVST
HLVDIF may not be set
Enable HLVD
HLVDIF
HLVDIF cleared in software
HLVDIF cleared in software
HLVDIF cleared in software,
CASE 1:
CASE 2:
HLVDIF remains set since HLVD condition still exists
TIRVST
IRVST
Internal Reference is stable
Internal Reference is stable
IRVST
Time
Voltage
VA
VB
TATB
VA = HLVD trip point
VB = Minimum valid device
operating voltage
Legend:
© 2009 Microchip Technology Inc. DS39689F-page 257
PIC18F2221/2321/4221/4321 FAMILY
23.6 Operation During Sleep
When enabled, the HLVD circuitry continues to operate
during Sleep. If the device voltage crosses the trip
point, the HLVDIF bit will be set and the device will
wake-up from Sleep. Device execution will continue
from the interrupt vector address if interrupts have
been globally enabled.
23.7 Effects of a Reset
A device Reset forces all registers to their Reset state.
This forces the HLVD module to be turned off.
TABLE 23-1: REGISTERS ASSOCIATED WITH HIGH/LOW-VOLTAGE DETECT MODULE
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on Page
HLVDCON VDIRMAG IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 56
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55
PIR2 OSCFIF CMIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 58
PIE2 OSCFIE CMIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 58
IPR2 OSCFIP CMIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 58
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the HLVD module.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 258 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 259
PIC18F2221/2321/4221/4321 FAMILY
24.0 SPECIAL FEATURES OF THE
CPU
PIC18F2221/2321/4221/4321 family devices include
several features intended to maximize reliability and
minimize cost through elimination of external
components. These are:
Oscillator Selection
Resets:
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
Interrupts
Watchdog Timer (WDT)
Fail-Safe Clock Monitor
Two-Speed Start-up
Code Protection
ID Locations
In-Circuit Serial Programming
The oscillator can be configured for the application
depending on frequency, power, accuracy and cost. All
of the options are discussed in detail in Section 3.0
“Oscillator Configurations”.
A complete discussion of device Resets and interrupts
is available in previous sections of this data sheet.
In addition to their Power-up and Oscillator Start-up
Timers provided for Resets, PIC18F2221/2321/4221/
4321 family devices have a Watchdog Timer, which is
either permanently enabled via the Configuration bits
or software controlled (if configured as disabled).
The inclusion of an internal RC oscillator also provides
the additional benefits of a Fail-Safe Clock Monitor
(FSCM) and Two-Speed Start-up. FSCM provides for
background monitoring of the peripheral clock and
automatic switchover in the event of its failure. Two-
Speed Start-up enables code to be executed almost
immediately on start-up, while the primary clock source
completes its start-up delays.
All of these features are enabled and configured by
setting the appropriate Configuration register bits.
24.1 Configuration Bits
The Configuration bits can be programmed (read as
0’) or left unprogrammed (read as ‘1’) to select various
device configurations. These bits are mapped starting
at program memory location 300000h.
The user will note that address 300000h is beyond the
user program memory space. In fact, it belongs to the
configuration memory space (300000h-3FFFFFh), which
can only be accessed using table reads and table writes.
Programming the Configuration registers is done in a
manner similar to programming the Flash memory. The
WR bit in the EECON1 register starts a self-timed write
to the Configuration register. In normal operation mode,
a TBLWT instruction with the TBLPTR pointing to the
Configuration register sets up the address and the data
for the Configuration register write. Setting the WR bit
starts a long write to the Configuration register. The
Configuration registers are written a byte at a time. To
write or erase a configuration cell, a TBLWT instruction
can write a ‘1’ or a ‘0’ into the cell. For additional details
on Flash programming, refer to Section 7.5 “Writing
to Flash Program Memory”.
TABLE 24-1: CONFIGURATION BITS AND DEVICE IDs
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Default/
Unprogrammed
Value
300001h CONFIG1H IESO FCMEN FOSC3 FOSC2 FOSC1 FOSC0 00-- 0111
300002h CONFIG2L —— BORV1 BORV0 BOREN1 BOREN0 PWRTEN ---1 1111
300003h CONFIG2H —— WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN ---1 1111
300005h CONFIG3H MCLRE LPT1OSC PBADEN CCP2MX 1--- -011
300006h CONFIG4L DEBUG XINST BBSIZ1 BBSIZ0 rLVP—STVREN1000 01-1
300008h CONFIG5L —CP1CP0---- --11
300009h CONFIG5H CPD CPB 11-- ----
30000Ah CONFIG6L —WRT1WRT0---- --11
30000Bh CONFIG6H WRTD WRTB WRTC —————111- ----
30000Ch CONFIG7L EBTR1 EBTR0 ---- --11
30000Dh CONFIG7H —EBTRB -1-- ----
3FFFFEh DEVID1(1) DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0 xxxx xxxx(2)
3FFFFFh DEVID2(1) DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3 0000 1100
Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition, r = reserved, maintain as ‘0’.
Shaded cells are unimplemented, read as ‘0’.
Note 1: Unimplemented in PIC18F2221/4221 devices; maintain these bits set.
2: See Register 24-14 for DEVID1 values. DEVID registers are read-only and cannot be programmed by the user.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 260 © 2009 Microchip Technology Inc.
REGISTER 24-1: CONFIG1H: CONFIGURATION REGISTER 1 HIGH (BYTE ADDRESS 300001h)
R/P-0 R/P-0 U-0 U-0 R/P-0 R/P-1 R/P-1 R/P-1
IESO FCMEN FOSC3 FOSC2 FOSC1 FOSC0
bit 7 bit 0
bit 7 IESO: Internal/External Oscillator Switchover bit
1 = Oscillator Switchover mode enabled
0 = Oscillator Switchover mode disabled
bit 6 FCMEN: Fail-Safe Clock Monitor Enable bit
1 = Fail-Safe Clock Monitor enabled
0 = Fail-Safe Clock Monitor disabled
bit 5-4 Unimplemented: Read as ‘0
bit 3-0 FOSC<3:0>: Oscillator Selection bits
11xx = External RC oscillator, CLKO function on RA6
101x = External RC oscillator, CLKO function on RA6
1001 = Internal oscillator block, CLKO function on RA6, port function on RA7
1000 = Internal oscillator block, port function on RA6 and RA7
0111 = External RC oscillator, port function on RA6
0110 = HS oscillator, PLL enabled (Clock Frequency = 4 x FOSC1)
0101 = EC oscillator, port function on RA6
0100 = EC oscillator, CLKO function on RA6
0011 = External RC oscillator, CLKO function on RA6
0010 = HS oscillator
0001 = XT oscillator
0000 = LP oscillator
Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0
-n = Value when device is unprogrammed u = Unchanged from programmed state
© 2009 Microchip Technology Inc. DS39689F-page 261
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REGISTER 24-2: CONFIG2L: CONFIGURATION REGISTER 2 LOW (BYTE ADDRESS 300002h)
U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1
———BORV1
(1) BORV0(1) BOREN1(2) BOREN0(2) PWRTEN(2)
bit 7 bit 0
bit 7-5 Unimplemented: Read as ‘0
bit 4-3 BORV<1:0>: Brown-out Reset Voltage bits(1)
11 = Minimum setting
.
.
.
00 = Maximum setting
bit 2-1 BOREN<1:0>: Brown-out Reset Enable bits(2)
11 = Brown-out Reset enabled in hardware only (SBOREN is disabled)
10 = Brown-out Reset enabled in hardware only and disabled in Sleep mode
(SBOREN is disabled)
01 = Brown-out Reset enabled and controlled by software (SBOREN is enabled)
00 = Brown-out Reset disabled in hardware and software
bit 0 PWRTEN: Power-up Timer Enable bit(2)
1 = PWRT disabled
0 = PWRT enabled
Note 1: See Section 27.1 “DC Characteristics for the specifications.
2: The Power-up Timer is decoupled from Brown-out Reset, allowing these features to
be independently controlled.
Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
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DS39689F-page 262 © 2009 Microchip Technology Inc.
REGISTER 24-3: CONFIG2H: CONFIGURATION REGISTER 2 HIGH (BYTE ADDRESS 300003h)
U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1
WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN
bit 7 bit 0
bit 7-5 Unimplemented: Read as ‘0
bit 4-1 WDTPS<3:0>: Watchdog Timer Postscale Select bits
1111 = 1:32,768
1110 = 1:16,384
1101 = 1:8,192
1100 = 1:4,096
1011 = 1:2,048
1010 = 1:1,024
1001 = 1:512
1000 = 1:256
0111 = 1:128
0110 = 1:64
0101 = 1:32
0100 = 1:16
0011 = 1:8
0010 = 1:4
0001 = 1:2
0000 = 1:1
bit 0 WDTEN: Watchdog Timer Enable bit
1 = WDT enabled
0 = WDT disabled (control is placed on the SWDTEN bit)
Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0
-n = Value when device is unprogrammed u = Unchanged from programmed state
© 2009 Microchip Technology Inc. DS39689F-page 263
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REGISTER 24-4: CONFIG3H: CONFIGURATION REGISTER 3 HIGH (BYTE ADDRESS 300005h)
R/P-1 U-0 U-0 U-0 U-0 R/P-0 R/P-1 R/P-1
MCLRE LPT1OSC PBADEN CCP2MX
bit 7 bit 0
bit 7 MCLRE: MCLR Pin Enable bit
1 = MCLR pin enabled; RE3 input pin disabled
0 = RE3 input pin enabled; MCLR disabled
bit 6-3 Unimplemented: Read as ‘0
bit 2 LPT1OSC: Low-Power Timer1 Oscillator Enable bit
1 = Timer1 configured for low-power operation
0 = Timer1 configured for higher power operation
bit 1 PBADEN: PORTB A/D Enable bit
(Affects ADCON1 Reset state. ADCON1 controls PORTB<4:0> pin configuration.)
1 = PORTB<4:0> pins are configured as analog input channels on Reset
0 = PORTB<4:0> pins are configured as digital I/O on Reset
bit 0 CCP2MX: CCP2 MUX bit
1 = CCP2 input/output is multiplexed with RC1
0 = CCP2 input/output is multiplexed with RB3
Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0
-n = Value when device is unprogrammed u = Unchanged from programmed state
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DS39689F-page 264 © 2009 Microchip Technology Inc.
REGISTER 24-5: CONFIG4L: CONFIGURATION REGISTER 4 LOW (BYTE ADDRESS 300006h)
R/P-1 R/P-0 U-0 U-0 r-0 R/P-1 U-0 R/P-1
DEBUG XINST BBSIZ1 BBSIZ0 —LVP—STVREN
bit 7 bit 0
bit 7 DEBUG: Background Debugger Enable bit
1 = Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins
0 = Background debugger enabled, RB6 and RB7 are dedicated to in-circuit debug
bit 6 XINST: Extended Instruction Set Enable bit
1 = Instruction set extension and Indexed Addressing mode enabled
0 = Instruction set extension and Indexed Addressing mode disabled (Legacy mode)
bit 5-4 BBSIZ<1:0>: Boot Block Size Select bits
PIC18F4221/4321 Devices:
1x = 1024 Words
01 = 512 Words
00 = 256 Words
PIC18F2221/2321 Devices:
1x = 512 Words
x1 = 512 Words
00 = 256 Words
bit 3 Reserved: Maintain as ‘0
bit 2 LVP: Single-Supply ICSP™ Enable bit
1 = Single-Supply ICSP enabled
0 = Single-Supply ICSP disabled
bit 1 Unimplemented: Read as ‘0
bit 0 STVREN: Stack Full/Underflow Reset Enable bit
1 = Stack full/underflow will cause Reset
0 = Stack full/underflow will not cause Reset
Legend: r = Reserved bit, program as ‘0’
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
© 2009 Microchip Technology Inc. DS39689F-page 265
PIC18F2221/2321/4221/4321 FAMILY
REGISTER 24-6: CONFIG5L: CONFIGURATION REGISTER 5 LOW (BYTE ADDRESS 300008h)
REGISTER 24-7: CONFIG5H: CONFIGURATION REGISTER 5 HIGH (BYTE ADDRESS 300009h)
U-0 U-0 U-0 U-0 U-0 U-0 R/C-1 R/C-1
——————CP1CP0
bit 7 bit 0
bit 7-2 Unimplemented: Read as ‘0
bit 1 CP1: Code Protection bit
1 = Block 1 not code-protected(1)
0 = Block 1 code-protected(1)
bit 0 CP0: Code Protection bit
1 = Block 0 not code-protected(1)
0 = Block 0 code-protected(1)
Note 1: See Figure 24-5 for variable block boundaries.
Legend:
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
R/C-1 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0
CPD CPB
bit 7 bit 0
bit 7 CPD: Data EEPROM Code Protection bit
1 = Data EEPROM not code-protected
0 = Data EEPROM code-protected
bit 6 CPB: Boot Block Code Protection bit
1 = Boot block not code-protected(1)
0 = Boot block code-protected(1)
bit 5-0 Unimplemented: Read as ‘0
Note 1: See Figure 24-5 for variable block boundaries.
Legend:
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
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DS39689F-page 266 © 2009 Microchip Technology Inc.
REGISTER 24-8: CONFIG6L: CONFIGURATION REGISTER 6 LOW (BYTE ADDRESS 30000Ah)
REGISTER 24-9: CONFIG6H: CONFIGURATION REGISTER 6 HIGH (BYTE ADDRESS 30000Bh)
U-0 U-0 U-0 U-0 U-0 U-0 R/C-1 R/C-1
WRT1 WRT0
bit 7 bit 0
bit 7-2 Unimplemented: Read as ‘0
bit 1 WRT1: Write Protection bit
1 = Block 1 not write-protected(1)
0 = Block 1 write-protected(1)
bit 0 WRT0: Write Protection bit
1 = Block 0 not write-protected(1)
0 = Block 0 write-protected(1)
Note 1: See Figure 24-5 for variable block boundaries.
Legend:
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
R/C-1 R/C-1 R-1 U-0 U-0 U-0 U-0 U-0
WRTD WRTB WRTC(1)
bit 7 bit 0
bit 7 WRTD: Data EEPROM Write Protection bit
1 = Data EEPROM not write-protected
0 = Data EEPROM write-protected
bit 6 WRTB: Boot Block Write Protection bit
1 = Boot block not write-protected(2)
0 = Boot block write-protected(2)
bit 5 WRTC: Configuration Register Write Protection bit(1)
1 = Configuration registers (300000-3000FFh) not write-protected
0 = Configuration registers (300000-3000FFh) write-protected
bit 4-0 Unimplemented: Read as ‘0
Note 1: This bit is read-only in normal execution mode; it can be written only in Program mode.
2: See Figure 24-5 for block boundaries.
Legend:
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
© 2009 Microchip Technology Inc. DS39689F-page 267
PIC18F2221/2321/4221/4321 FAMILY
REGISTER 24-10: CONFIG7L: CONFIGURATION REGISTER 7 LOW (BYTE ADDRESS 30000Ch)
REGISTER 24-11: CONFIG7H: CONFIGURATION REGISTER 7 HIGH (BYTE ADDRESS 30000Dh)
U-0 U-0 U-0 U-0 U-0 U-0 R/C-1 R/C-1
EBTR1 EBTR0
bit 7 bit 0
bit 7-2 Unimplemented: Read as 0
bit 1 EBTR1: Table Read Protection bit
1 = Block 1 not protected from table reads executed in other blocks(1)
0 = Block 1 protected from table reads executed in other blocks(1)
bit 0 EBTR0: Table Read Protection bit
1 = Block 0 not protected from table reads executed in other blocks(1)
0 = Block 0 protected from table reads executed in other blocks(1)
Note 1: See Figure 24-5 for variable block boundaries.
Legend:
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
U-0 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0
EBTRB
bit 7 bit 0
bit 7 Unimplemented: Read as ‘0
bit 6 EBTRB: Boot Block Table Read Protection bit
1 = Boot block not protected from table reads executed in other blocks(1)
0 = Boot block protected from table reads executed in other blocks(1)
bit 5-0 Unimplemented: Read as ‘0
Note 1: See Figure 24-5 for variable block boundaries.
Legend:
R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
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DS39689F-page 268 © 2009 Microchip Technology Inc.
REGISTER 24-12: DEVID1: DEVICE ID REGISTER 1 FOR PIC18F2221/2321/4221/4321 DEVICES
REGISTER 24-13: DEVID2: DEVICE ID REGISTER 2 FOR PIC18F2221/2321/4221/4321 DEVICES
RRRRRRRR
DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0
bit 7 bit 0
bit 7-5 DEV<2:0>: Device ID bits
000 = PIC18F4321
010 = PIC18F4221
001 = PIC18F2321
011 = PIC18F2221
bit 4-0 REV<4:0>: Revision ID bits
These bits are used to indicate the device revision.
Legend:
R = Read-only bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
RRRRRRRR
DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3
bit 7 bit 0
bit 7-0 DEV<10:3>: Device ID bits
These bits are used with the DEV<2:0> bits in the Device ID Register 1 to identify the
part number.
0010 0001 = PIC18F2221/2321/4221/4321 devices
Note: These values for DEV<10:3> may be shared with other devices. The specific
device is always identified by using the entire DEV<10:0> bit sequence.
Legend:
R = Read-only bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed u = Unchanged from programmed state
© 2009 Microchip Technology Inc. DS39689F-page 269
PIC18F2221/2321/4221/4321 FAMILY
24.2 Watchdog Timer (WDT)
For PIC18F2221/2321/4221/4321 family devices, the
WDT is driven by the INTRC source. When the WDT is
enabled, the clock source is also enabled. The nominal
WDT period is 4 ms and has the same stability as the
INTRC oscillator.
The 4 ms period of the WDT is multiplied by a 16-bit
postscaler. Any output of the WDT postscaler is
selected by a multiplexer, controlled by bits in Configu-
ration Register 2H. Available periods range from 4 ms
to 131.072 seconds (2.18 minutes). The WDT and
postscaler are cleared when any of the following events
occur: a SLEEP or CLRWDT instruction is executed, the
IRCF bits (OSCCON<6:4>) are changed or a clock
failure has occurred.
24.2.1 CONTROL REGISTER
Register 24-14 shows the WDTCON register. This is a
readable and writable register which contains a control
bit that allows software to override the WDT enable
Configuration bit, but only if the Configuration bit has
disabled the WDT.
FIGURE 24-1: WDT BLOCK DIAGRAM
Note 1: The CLRWDT and SLEEP instructions
clear the WDT and postscaler counts
when executed.
2: Changing the setting of the IRCF bits
(OSCCON<6:4>) clears the WDT and
postscaler counts.
3: When a CLRWDT instruction is executed,
the postscaler count will be cleared.
INTRC Source
WDT
Wake-up from
Reset
WDT Counter
Programmable Postscaler
1:1 to 1:32,768
Enable WDT
WDTPS<3:0>
SWDTEN
WDTEN
CLRWDT
4
Power-Managed
Reset
All Device Resets
Sleep
÷128
Change on IRCF bits
Modes
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DS39689F-page 270 © 2009 Microchip Technology Inc.
REGISTER 24-14: WDTCON: WATCHDOG TIMER CONTROL REGISTER
TABLE 24-2: SUMMARY OF WATCHDOG TIMER REGISTERS
U-0 U-0 U-0 U-0 U-0 U-0 U-0 R/W-0
—SWDTEN
(1)
bit 7 bit 0
bit 7-1 Unimplemented: Read as0
bit 0 SWDTEN: Software Controlled Watchdog Timer Enable bit(1)
1 = Watchdog Timer is on
0 = Watchdog Timer is off
Note 1: This bit has no effect if the Configuration bit, WDTEN, is enabled.
Legend:
R = Readable bit W = Writable bit
U = Unimplemented bit, read as ‘0’ -n = Value at POR
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Reset
Values
on page
RCON IPEN SBOREN(1) RI TO PD POR BOR 56
WDTCON —SWDTEN56
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Watchdog Timer.
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled
and reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.
© 2009 Microchip Technology Inc. DS39689F-page 271
PIC18F2221/2321/4221/4321 FAMILY
24.3 Two-Speed Start-up
The Two-Speed Start-up feature helps to minimize the
latency period from oscillator start-up to code execution
by allowing the microcontroller to use the INTOSC
oscillator as a clock source until the primary clock
source is available. It is enabled by setting the IESO
Configuration bit.
Two-Speed Start-up should be enabled only if the
primary oscillator mode is LP, XT, HS or HSPLL
(crystal-based modes). Other sources do not require
an OST start-up delay; for these, Two-Speed Start-up
should be disabled.
When enabled, Resets and wake-ups from Sleep mode
cause the device to configure itself to run from the
internal oscillator block as the clock source, following
the time-out of the Power-up Timer after a Power-on
Reset is enabled. This allows almost immediate code
execution while the primary oscillator starts and the
OST is running. Once the OST times out, the device
automatically switches to PRI_RUN mode.
To use a higher clock speed on wake-up, the INTOSC
or postscaler clock sources can be selected to provide
a higher clock speed by setting bits, IRCF<2:0>,
immediately after Reset. For wake-ups from Sleep, the
INTOSC or postscaler clock sources can be selected
by setting the IRCF<2:0> bits prior to entering Sleep
mode.
In all other power-managed modes, Two-Speed Start-
up is not used. The device will be clocked by the
currently selected clock source until the primary clock
source becomes available. The setting of the IESO bit
is ignored.
24.3.1 SPECIAL CONSIDERATIONS FOR
USING TWO-SPEED START-UP
While using the INTOSC oscillator in Two-Speed Start-
up, the device still obeys the normal command
sequences for entering power-managed modes,
including multiple SLEEP instructions (refer to
Section 4.1.4 “Multiple Sleep Commands”). In
practice, this means that user code can change the
SCS<1:0> bit settings or issue SLEEP instructions
before the OST times out. This would allow an applica-
tion to briefly wake-up, perform routine “housekeeping”
tasks and return to Sleep before the device starts to
operate from the primary oscillator.
User code can also check if the primary clock source is
currently providing the device clocking by checking the
status of the OSTS bit (OSCCON<3>). If the bit is set,
the primary oscillator is providing the clock. Otherwise,
the internal oscillator block is providing the clock during
wake-up from Reset or Sleep mode.
FIGURE 24-2: TIMING TRANSITION FOR TWO-SPEED START-UP (INTOSC TO HSPLL)
Q1 Q3 Q4
OSC1
Peripheral
Program PC PC + 2
INTOSC
PLL Clock
Q1
PC + 6
Q2
Output
Q3 Q4 Q1
CPU Clock
PC + 4
Clock
Counter
Q2 Q2 Q3
Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.
2: Clock transition typically occurs within 2-4 TOSC.
Wake from Interrupt Event
TPLL(1)
12 n-1n
Clock
OSTS bit Set
Transition(2)
Multiplexer
TOST(1)
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DS39689F-page 272 © 2009 Microchip Technology Inc.
24.4 Fail-Safe Clock Monitor
The Fail-Safe Clock Monitor (FSCM) allows the
microcontroller to continue operation in the event of an
external oscillator failure by automatically switching the
device clock to the internal oscillator block. The FSCM
function is enabled by setting the FCMEN Configuration
bit.
When FSCM is enabled, the INTRC oscillator runs at
all times to monitor clocks to peripherals and provide a
backup clock in the event of a clock failure. Clock
monitoring (shown in Figure 24-3) is accomplished by
creating a sample clock signal, which is the INTRC
output divided by 64. This allows ample time between
FSCM sample clocks for a peripheral clock edge to
occur. The peripheral device clock and the sample
clock are presented as inputs to the Clock Monitor latch
(CM). The CM is set on the falling edge of the device
clock source, but cleared on the rising edge of the
sample clock.
FIGURE 24-3: FSCM BLOCK DIAGRAM
Clock failure is tested for on the falling edge of the
sample clock. If a sample clock falling edge occurs
while CM is still set, a clock failure has been detected
(Figure 24-4). This causes the following:
the FSCM generates an oscillator fail interrupt by
setting bit, OSCFIF (PIR2<7>);
the device clock source is switched to the internal
oscillator block (OSCCON is not updated to show
the current clock source – this is the fail-safe
condition); and
•the WDT is reset.
During switchover, the postscaler frequency from the
internal oscillator block may not be sufficiently stable
for timing sensitive applications. In these cases, it may
be desirable to select another clock configuration and
enter an alternate power-managed mode. This can be
done to attempt a partial recovery or execute a
controlled shutdown. See Section 4.1.4 “Multiple
Sleep Commands” and Section 24.3.1 “Special
Considerations for Using Two-Speed Start-up” for
more details.
To use a higher clock speed on wake-up, the INTOSC
or postscaler clock sources can be selected to provide
a higher clock speed by setting bits, IRCF<2:0>,
immediately after Reset. For wake-ups from Sleep, the
INTOSC or postscaler clock sources can be selected
by setting the IRCF<2:0> bits prior to entering Sleep
mode.
The FSCM will detect failures of the primary or second-
ary clock sources only. If the internal oscillator block
fails, no failure would be detected, nor would any action
be possible.
24.4.1 FSCM AND THE WATCHDOG TIMER
Both the FSCM and the WDT are clocked by the
INTRC oscillator. Since the WDT operates with a
separate divider and counter, disabling the WDT has
no effect on the operation of the INTRC oscillator when
the FSCM is enabled.
As already noted, the clock source is switched to the
INTOSC clock when a clock failure is detected.
Depending on the frequency selected by the
IRCF<2:0> bits, this may mean a substantial change in
the speed of code execution. If the WDT is enabled
with a small prescale value, a decrease in clock speed
allows a WDT time-out to occur and a subsequent
device Reset. For this reason, fail-safe clock events
also reset the WDT and postscaler, allowing it to start
timing from when execution speed was changed and
decreasing the likelihood of an erroneous time-out.
24.4.2 EXITING FAIL-SAFE OPERATION
The fail-safe condition is terminated by either a device
Reset or by entering a power-managed mode. On
Reset, the controller starts the primary clock source
specified in Configuration Register 1H (with any
required start-up delays that are required for the
oscillator mode, such as OST or PLL timer). The
INTOSC multiplexer provides the device clock until the
primary clock source becomes ready (similar to a Two-
Speed Start-up). The clock source is then switched to
the primary clock (indicated by the OSTS bit in the
OSCCON register becoming set). The Fail-Safe Clock
Monitor then resumes monitoring the peripheral clock.
The primary clock source may never become ready
during start-up. In this case, operation is clocked by the
INTOSC multiplexer. The OSCCON register will remain
in its Reset state until a power-managed mode is
entered.
Peripheral
INTRC ÷ 64
S
C
Q
(32 μs) 488 Hz
(2.048 ms)
Clock Monitor
Latch (CM)
(edge-triggered)
Clock
Failure
Detected
Source
Clock
Q
© 2009 Microchip Technology Inc. DS39689F-page 273
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 24-4: FSCM TIMING DIAGRAM
24.4.3 FSCM INTERRUPTS IN
POWER-MANAGED MODES
By entering a power-managed mode, the clock
multiplexer selects the clock source selected by the
OSCCON register. Fail-Safe Monitoring of the power-
managed clock source resumes in the power-managed
mode.
If an oscillator failure occurs during power-managed
operation, the subsequent events depend on whether
or not the oscillator failure interrupt is enabled. If
enabled (OSCFIF = 1), code execution will be clocked
by the INTOSC multiplexer. An automatic transition
back to the failed clock source will not occur.
If the interrupt is disabled, subsequent interrupts while
in Idle mode will cause the CPU to begin executing
instructions while being clocked by the INTOSC
source.
24.4.4 POR OR WAKE FROM SLEEP
The FSCM is designed to detect oscillator failure at any
point after the device has exited Power-on Reset
(POR) or low-power Sleep mode. When the primary
device clock is EC, RC or INTRC modes, monitoring
can begin immediately following these events.
For oscillator modes involving a crystal or resonator
(HS, HSPLL, LP or XT), the situation is somewhat
different. Since the oscillator may require a start-up
time considerably longer than the FCSM sample clock
time, a false clock failure may be detected. To prevent
this, the internal oscillator block is automatically config-
ured as the device clock and functions until the primary
clock is stable (the OST and PLL timers have timed
out). This is identical to Two-Speed Start-up mode.
Once the primary clock is stable, the INTRC returns to
its role as the FSCM source.
As noted in Section 24.3.1 “Special Considerations
for Using Two-Speed Start-up”, it is also possible to
select another clock configuration and enter an
alternate power-managed mode while waiting for the
primary clock to become stable. When the new power-
managed mode is selected, the primary clock is
disabled.
OSCFIF
CM Output
Device
Clock
Output
Sample Clock
Failure
Detected
Oscillator
Failure
Note: The device clock is normally at a much higher frequency than the sample clock. The relative frequencies in this
example have been chosen for clarity.
(Q)
CM Test CM Test CM Test
Note: The same logic that prevents false oscilla-
tor failure interrupts on POR, or wake from
Sleep, will also prevent the detection of
the oscillator’s failure to start at all follow-
ing these events. This can be avoided by
monitoring the OSTS bit and using a
timing routine to determine if the oscillator
is taking too long to start. Even so, no
oscillator failure interrupt will be flagged.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 274 © 2009 Microchip Technology Inc.
24.5 Program Verification and
Code Protection
The overall structure of the code protection on the
PIC18 Flash devices differs significantly from other
PIC® devices.
The user program memory is divided into three blocks.
One of these is a boot block of variable size. The
remainder of the memory is divided into two blocks on
binary boundaries.
Each of the three blocks has three code protection bits
associated with them. They are:
Code-Protect bit (CPn)
Write-Protect bit (WRTn)
External Block Table Read bit (EBTRn)
Figure 24-5 shows the program memory organization
for 4 and 8-Kbyte devices and the specific code
protection bit associated with each block. The actual
locations of the bits are summarized in Table 24-3.
FIGURE 24-5: CODE-PROTECTED PROGRAM MEMORY FOR PIC18F2221/2321/4221/4321
FAMILY DEVICES
MEMORY SIZE/DEVICE Address
Range
Block Code Protection
Controlled By:
8Kbytes
(PIC18FX321)
4Kbytes
(PIC18FX221)
BBSIZ<1:0>
11/10 01 00 11/10/01 00
Boot Block
1K word
Boot Block
512 words
Boot Block
256 words Boot Block
512 words
Boot Block
256 words
000000h
0001FFh
CPB, WRTB, EBTRB
Block 0
1.75K words
Block 0
0.75K words
000200h
0003FFh
Block 0
1.5K words
Block 0
0.5K words
000400h
0007FFh CP0, WRT0, EBTR0
Block 0
1K word
Block 1
1K word
Block 1
1K word
000800h
000FFFh
Block 1
2K words
Block 1
2K words
Block 1
2K words Unimplemented
Reads all ‘0’s
001000h
001FFFh
CP1, WRT1, EBTR1
Unimplemented
Reads all ‘0’s
002000h
1FFFFFh
(Unimplemented Memory
Space)
© 2009 Microchip Technology Inc. DS39689F-page 275
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TABLE 24-3: SUMMARY OF CODE PROTECTION REGISTERS
24.5.1 PROGRAM MEMORY
CODE PROTECTION
The program memory may be read to or written from
any location using the table read and table write
instructions. The device ID may be read with table
reads. The Configuration registers may be read and
written with the table read and table write instructions.
In normal execution mode, the CPn bits have no direct
effect. CPn bits inhibit external reads and writes. A
block of user memory may be protected from table
writes if the WRTn Configuration bit is ‘0. The EBTRn
bits control table reads. For a block of user memory
with the EBTRn bit set to ‘0’, a table read instruction
that executes from within that block is allowed to read.
A table read instruction that executes from a location
outside of that block is not allowed to read and will result
in reading ‘0s. Figures 24-6 through 24-8 illustrate table
write and table read protection.
FIGURE 24-6: TABLE WRITE (WRTn) DISALLOWED
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
300008h CONFIG5L ——————CP1CP0
300009h CONFIG5H CPD CPB
30000Ah CONFIG6L ——————WRT1WRT0
30000Bh CONFIG6H WRTD WRTB WRTC
30000Ch CONFIG7L ————— EBTR1 EBTR0
30000Dh CONFIG7H EBTRB
Legend: Shaded cells are unimplemented.
Note: Code protection bits may only be written to
a ‘0’ from a ‘1’ state. It is not possible to
write a ‘1 to a bit in the ‘0’ state. Code
protection bits are only set to ‘1’ by a full
chip erase or block erase function. The full
chip erase and block erase functions can
only be initiated via ICSP operation or an
external programmer.
WRTB, EBTRB = 11
WRT0, EBTR0 = 01
WRT1, EBTR1 = 11
TBLWT*
TBLPTR = 0008FFh
PC = 003FFEh
PC = 00BFFEh
Register Values Program Memory(1) Configuration Bit Settings
TBLWT*
Boot Block
Block 0
Block 1
Results: All table writes disabled to Blockn whenever WRTn = 0.
Note 1: See Figure 24-5 for block boundaries.
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DS39689F-page 276 © 2009 Microchip Technology Inc.
FIGURE 24-7: EXTERNAL BLOCK TABLE READ (EBTRn) DISALLOWED
FIGURE 24-8: EXTERNAL BLOCK TABLE READ (EBTRn) ALLOWED
WRTB, EBTRB = 11
WRT0, EBTR0 = 10
WRT1, EBTR1 = 11
TBLRD*
TBLPTR = 0008FFh
PC = 007FFEh
Register Values Program Memory(1) Configuration Bit Settings
Boot Block
Block 0
Block 1
Results: All table reads from external blocks to Blockn are disabled whenever EBTRn = 0.
TABLAT register returns a value of ‘0’.
Note 1: See Figure 24-5 for block boundaries.
WRTB, EBTRB = 11
WRT0, EBTR0 = 10
WRT1, EBTR1 = 11
TBLRD*
TBLPTR = 0008FFh
PC = 003FFEh
Register Values Program Memory(1) Configuration Bit Settings
Boot Block
Block 0
Block 1
Results: Table reads permitted within Blockn, even when EBTRBn = 0.
TABLAT register returns the value of the data at the location TBLPTR.
Note 1: See Figure 24-5 for block boundaries.
© 2009 Microchip Technology Inc. DS39689F-page 277
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24.5.2 DATA EEPROM
CODE PROTECTION
The entire data EEPROM is protected from external
reads and writes by two bits: CPD and WRTD. CPD
inhibits external reads and writes of data EEPROM.
WRTD inhibits internal and external writes to data
EEPROM. The CPU can always read data EEPROM
under normal operation, regardless of the protection bit
settings.
24.5.3 CONFIGURATION REGISTER
PROTECTION
The Configuration registers can be write-protected.
The WRTC bit controls protection of the Configuration
registers. In normal execution mode, the WRTC bit is
readable only. WRTC can only be written via ICSP
operation or an external programmer.
24.6 ID Locations
Eight memory locations (200000h-200007h) are
designated as ID locations, where the user can store
checksum or other code identification numbers. These
locations are both readable and writable during normal
execution through the TBLRD and TBLWT instructions
or during program/verify. The ID locations can be read
when the device is code-protected.
24.7 In-Circuit Serial Programming
PIC18F2221/2321/4221/4321 family microcontrollers
can be serially programmed while in the end applica-
tion circuit. This is simply done with two lines for clock
and data and three other lines for power, ground and
the programming voltage. This allows customers to
manufacture boards with unprogrammed devices and
then program the microcontroller just before shipping
the product. This also allows the most recent firmware
or a custom firmware to be programmed.
24.8 In-Circuit Debugger
When the DEBUG Configuration bit is programmed to
a ‘0’, the In-Circuit Debugger functionality is enabled.
This function allows simple debugging functions when
used with MPLAB® IDE. When the microcontroller has
this feature enabled, some resources are not available
for general use. Table 24-4 shows which resources are
required by the background debugger.
TABLE 24-4: DEBUGGER RESOURCES
To use the In-Circuit Debugger function of the micro-
controller, the design must implement In-Circuit Serial
Programming connections to MCLR/VPP/RE3, VDD,
VSS, RB7 and RB6. This will interface to the In-Circuit
Debugger module available from Microchip or one of
the third party development tool companies.
24.9 Single-Supply ICSP Programming
The LVP Configuration bit enables Single-Supply ICSP
Programming (formerly known as Low-Voltage ICSP
Programming or LVP). When Single-Supply Program-
ming is enabled, the microcontroller can be programmed
without requiring high voltage being applied to the
MCLR/VPP/RE3 pin, but the RB5/KBI1/PGM pin is then
dedicated to controlling Program mode entry and is not
available as a general purpose I/O pin.
While programming, using Single-Supply Program-
ming, VDD is applied to the MCLR/VPP/RE3 pin as in
normal execution mode. To enter Programming mode,
VDD is applied to the PGM pin.
If Single-Supply ICSP Programming mode will not be
used, the LVP bit can be cleared. RB5/KBI1/PGM then
becomes available as the digital I/O pin, RB5. The LVP
bit may be set or cleared only when using standard
high-voltage programming (VIHH applied to the MCLR/
VPP/RE3 pin). Once LVP has been disabled, only the
standard high-voltage programming is available and
must be used to program the device.
Memory that is not code-protected can be erased using
either a block erase, or erased row by row, then written
at any specified VDD. If code-protected memory is to be
erased, a block erase is required. If a block erase is to
be performed when using Low-Voltage ICSP
Programming, the device must be supplied with VDD of
4.5V to 5.5V.
I/O Pins: RB6, RB7
Stack: 2 levels
Program Memory: 512 bytes
Data Memory: 10 bytes
Note 1: High-voltage programming is always
available, regardless of the state of the
LVP bit or the PGM pin, by applying VIHH
to the MCLR pin.
2: By default, Single-Supply ICSP Program-
ming is enabled in unprogrammed
devices (as supplied from Microchip) and
erased devices.
3: When Single-Supply ICSP Programming
is enabled, the RB5 pin can no longer be
used as a general purpose I/O pin.
4: When LVP is enabled, externally pull the
PGM pin to VSS to allow normal program
execution.
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NOTES:
PIC18F2221/2321/4221/4321 FAMILY
© 2009 Microchip Technology Inc. DS39689F-page 279
25.0 INSTRUCTION SET SUMMARY
PIC18F2221/2321/4221/4321 family devices incorpo-
rate the standard set of 75 PIC18 core instructions, as
well as an extended set of 8 new instructions for the
optimization of code that is recursive or that utilizes a
software stack. The extended set is discussed later in
this section.
25.1 Standard Instruction Set
The standard PIC18 instruction set adds many
enhancements to the previous PIC® MCU instruction
sets, while maintaining an easy migration from these
PIC MCU instruction sets. Most instructions are a
single program memory word (16 bits), but there are
four instructions that require two program memory
locations.
Each single-word instruction is a 16-bit word divided
into an opcode, which specifies the instruction type and
one or more operands, which further specify the
operation of the instruction.
The instruction set is highly orthogonal and is grouped
into four basic categories:
Byte-oriented operations
Bit-oriented operations
Literal operations
Control operations
The PIC18 instruction set summary in Table 25-2 lists
byte-oriented, bit-oriented, literal and control
operations. Table 25-1 shows the opcode field
descriptions.
Most byte-oriented instructions have three operands:
1. The file register (specified by ‘f’)
2. The destination of the result (specified by ‘d’)
3. The accessed memory (specified by ‘a’)
The file register designator ‘f’ specifies which file
register is to be used by the instruction. The destination
designator ‘d’ specifies where the result of the
operation is to be placed. If ‘d’ is zero, the result is
placed in the WREG register. If ‘d’ is one, the result is
placed in the file register specified in the instruction.
All bit-oriented instructions have three operands:
1. The file register (specified by ‘f’)
2. The bit in the file register (specified by ‘b’)
3. The accessed memory (specified by ‘a’)
The bit field designator ‘b’ selects the number of the bit
affected by the operation, while the file register
designator ‘f’ represents the number of the file in which
the bit is located.
The literal instructions may use some of the following
operands:
A literal value to be loaded into a file register
(specified by ‘k’)
The desired FSR register to load the literal value
into (specified by ‘f’)
No operand required
(specified by ‘—’)
The control instructions may use some of the following
operands:
A program memory address (specified by ‘n’)
The mode of the CALL or RETURN instructions
(specified by ‘s’)
The mode of the table read and table write
instructions (specified by ‘m’)
No operand required
(specified by ‘—’)
All instructions are a single word, except for four
double-word instructions. These instructions were
made double-word to contain the required information
in 32 bits. In the second word, the 4 MSbs are 1’s. If
this second word is executed as an instruction (by
itself), it will execute as a NOP.
All single-word instructions are executed in a single
instruction cycle, unless a conditional test is true or the
program counter is changed as a result of the
instruction. In these cases, the execution takes two
instruction cycles, with the additional instruction
cycle(s) executed as a NOP.
The double-word instructions execute in two instruction
cycles.
One instruction cycle consists of four oscillator periods.
Thus, for an oscillator frequency of 4 MHz, the normal
instruction execution time is 1 μs. If a conditional test is
true, or the program counter is changed as a result of
an instruction, the instruction execution time is 2 μs.
Two-word branch instructions (if true) would take 3 μs.
Figure 25-1 shows the general formats that the
instructions can have. All examples use the convention
‘nnh’ to represent a hexadecimal number.
The Instruction Set Summary, shown in Table 25-2,
lists the standard instructions recognized by the
Microchip MPASM™ Assembler.
Section 25.1.1 “Standard Instruction Set” provides
a description of each instruction.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 280 © 2009 Microchip Technology Inc.
TABLE 25-1: OPCODE FIELD DESCRIPTIONS
Field Description
aRAM access bit
a = 0: RAM location in Access RAM (BSR register is ignored)
a = 1: RAM bank is specified by BSR register
bbb Bit address within an 8-bit file register (0 to 7).
BSR Bank Select Register. Used to select the current RAM bank.
C, DC, Z, OV, N ALU Status bits: Carry, Digit Carry, Zero, Overflow, Negative.
dDestination select bit
d = 0: store result in WREG
d = 1: store result in file register f
dest Destination: either the WREG register or the specified register file location.
f8-bit Register file address (00h to FFh) or 2-bit FSR designator (0h to 3h).
fs12-bit Register file address (000h to FFFh). This is the source address.
fd12-bit Register file address (000h to FFFh). This is the destination address.
GIE Global Interrupt Enable bit.
kLiteral field, constant data or label (may be either an 8-bit, 12-bit or a 20-bit value).
label Label name.
mm The mode of the TBLPTR register for the table read and table write instructions.
Only used with table read and table write instructions:
*No change to register (such as TBLPTR with table reads and writes)
*+ Post-Increment register (such as TBLPTR with table reads and writes)
*- Post-Decrement register (such as TBLPTR with table reads and writes)
+* Pre-Increment register (such as TBLPTR with table reads and writes)
nThe relative address (2’s complement number) for relative branch instructions or the direct address for
Call/Branch and Return instructions.
PC Program Counter.
PCL Program Counter Low Byte.
PCH Program Counter High Byte.
PCLATH Program Counter High Byte Latch.
PCLATU Program Counter Upper Byte Latch.
PD Power-Down bit.
PRODH Product of Multiply High Byte.
PRODL Product of Multiply Low Byte.
sFast Call/Return mode select bit
s = 0: do not update into/from shadow registers
s = 1: certain registers loaded into/from shadow registers (Fast mode)
TBLPTR 21-bit Table Pointer (points to a program memory location).
TABLAT 8-bit Table Latch.
TO Time-out bit.
TOS Top-of-Stack.
uUnused or unchanged.
WDT Watchdog Timer.
WREG Working register (accumulator).
xDon’t care (‘0’ or ‘1’). The assembler will generate code with x = 0. It is the recommended form of use for
compatibility with all Microchip software tools.
zs7-bit offset value for indirect addressing of register files (source).
zd7-bit offset value for indirect addressing of register files (destination).
{ } Optional argument.
[text] Indicates an indexed address.
(text) The contents of text.
[expr]<n> Specifies bit n of the register indicated by the pointer expr.
Assigned to.
< > Register bit field.
In the set of.
italics User-defined term (font is Courier New).
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© 2009 Microchip Technology Inc. DS39689F-page 281
FIGURE 25-1: GENERAL FORMAT FOR INSTRUCTIONS
Byte-oriented file register operations
15 10 9 8 7 0
d = 0 for result destination to be WREG register
OPCODE d a f (FILE #)
d = 1 for result destination to be file register (f)
a = 0 to force Access Bank
Bit-oriented file register operations
15 12 11 9 8 7 0
OPCODE b (BIT #) a f (FILE #)
b = 3-bit position of bit in file register (f)
Literal operations
15 8 7 0
OPCODE k (literal)
k = 8-bit immediate value
Byte to Byte move operations (2-word)
15 12 11 0
OPCODE f (Source FILE #)
CALL, GOTO and Branch operations
15 8 7 0
OPCODE n<7:0> (literal)
n = 20-bit immediate value
a = 1 for BSR to select bank
f = 8-bit file register address
a = 0 to force Access Bank
a = 1 for BSR to select bank
f = 8-bit file register address
15 12 11 0
1111 n<19:8> (literal)
15 12 11 0
1111 f (Destination FILE #)
f = 12-bit file register address
Control operations
Example Instruction
ADDWF MYREG, W, B
MOVFF MYREG1, MYREG2
BSF MYREG, bit, B
MOVLW 7Fh
GOTO Label
15 8 7 0
OPCODE n<7:0> (literal)
15 12 11 0
1111 n<19:8> (literal)
CALL MYFUNC
15 11 10 0
OPCODE n<10:0> (literal)
S = Fast bit
BRA MYFUNC
15 8 7 0
OPCODE n<7:0> (literal) BC MYFUNC
S
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DS39689F-page 282 © 2009 Microchip Technology Inc.
TABLE 25-2: PIC18FXXXX INSTRUCTION SET
Mnemonic,
Operands Description Cycles
16-Bit Instruction Word Status
Affected Notes
MSb LSb
BYTE-ORIENTED OPERATIONS
ADDWF
ADDWFC
ANDWF
CLRF
COMF
CPFSEQ
CPFSGT
CPFSLT
DECF
DECFSZ
DCFSNZ
INCF
INCFSZ
INFSNZ
IORWF
MOVF
MOVFF
MOVWF
MULWF
NEGF
RLCF
RLNCF
RRCF
RRNCF
SETF
SUBFWB
SUBWF
SUBWFB
SWAPF
TSTFSZ
XORWF
f, d, a
f, d, a
f, d, a
f, a
f, d, a
f, a
f, a
f, a
f, d, a
f, d, a
f, d, a
f, d, a
f, d, a
f, d, a
f, d, a
f, d, a
fs, fd
f, a
f, a
f, a
f, d, a
f, d, a
f, d, a
f, d, a
f, a
f, d, a
f, d, a
f, d, a
f, d, a
f, a
f, d, a
Add WREG and f
Add WREG and Carry bit to f
AND WREG with f
Clear f
Complement f
Compare f with WREG, Skip =
Compare f with WREG, Skip >
Compare f with WREG, Skip <
Decrement f
Decrement f, Skip if 0
Decrement f, Skip if Not 0
Increment f
Increment f, Skip if 0
Increment f, Skip if Not 0
Inclusive OR WREG with f
Move f
Move fs (source) to 1st Word
fd (destination) 2nd Word
Move WREG to f
Multiply WREG with f
Negate f
Rotate Left f through Carry
Rotate Left f (No Carry)
Rotate Right f through Carry
Rotate Right f (No Carry)
Set f
Subtract f from WREG with
Borrow
Subtract WREG from f
Subtract WREG from f with
Borrow
Swap Nibbles in f
Test f, Skip if 0
Exclusive OR WREG with f
1
1
1
1
1
1 (2 or 3)
1 (2 or 3)
1 (2 or 3)
1
1 (2 or 3)
1 (2 or 3)
1
1 (2 or 3)
1 (2 or 3)
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1 (2 or 3)
1
0010
0010
0001
0110
0001
0110
0110
0110
0000
0010
0100
0010
0011
0100
0001
0101
1100
1111
0110
0000
0110
0011
0100
0011
0100
0110
0101
0101
0101
0011
0110
0001
01da0
0da
01da
101a
11da
001a
010a
000a
01da
11da
11da
10da
11da
10da
00da
00da
ffff
ffff
111a
001a
110a
01da
01da
00da
00da
100a
01da
11da
10da
10da
011a
10da
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
C, DC, Z, OV, N
C, DC, Z, OV, N
Z, N
Z
Z, N
None
None
None
C, DC, Z, OV, N
None
None
C, DC, Z, OV, N
None
None
Z, N
Z, N
None
None
None
C, DC, Z, OV, N
C, Z, N
Z, N
C, Z, N
Z, N
None
C, DC, Z, OV, N
C, DC, Z, OV, N
C, DC, Z, OV, N
None
None
Z, N
1, 2
1, 2
1,2
2
1, 2
4
4
1, 2
1, 2, 3, 4
1, 2, 3, 4
1, 2
1, 2, 3, 4
4
1, 2
1, 2
1
1, 2
1, 2
1, 2
1, 2
4
1, 2
Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value
present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an
external device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if
assigned.
3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second
cycle is executed as a NOP.
4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the
first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory
locations have a valid instruction.
PIC18F2221/2321/4221/4321 FAMILY
© 2009 Microchip Technology Inc. DS39689F-page 283
BIT-ORIENTED OPERATIONS
BCF
BSF
BTFSC
BTFSS
BTG
f, b, a
f, b, a
f, b, a
f, b, a
f, d, a
Bit Clear f
Bit Set f
Bit Test f, Skip if Clear
Bit Test f, Skip if Set
Bit Toggle f
1
1
1 (2 or 3)
1 (2 or 3)
1
1001
1000
1011
1010
0111
bbba
bbba
bbba
bbba
bbba
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
None
None
None
None
None
1, 2
1, 2
3, 4
3, 4
1, 2
CONTROL OPERATIONS
BC
BN
BNC
BNN
BNOV
BNZ
BOV
BRA
BZ
CALL
CLRWDT
DAW
GOTO
NOP
NOP
POP
PUSH
RCALL
RESET
RETFIE
RETLW
RETURN
SLEEP
n
n
n
n
n
n
n
n
n
n, s
n
n
s
k
s
Branch if Carry
Branch if Negative
Branch if Not Carry
Branch if Not Negative
Branch if Not Overflow
Branch if Not Zero
Branch if Overflow
Branch Unconditionally
Branch if Zero
Call Subroutine 1st Word
2nd Word
Clear Watchdog Timer
Decimal Adjust WREG
Go to Address 1st Word
2nd Word
No Operation
No Operation
Pop Top of Return Stack (TOS)
Push Top of Return Stack (TOS)
Relative Call
Software Device Reset
Return from Interrupt Enable
Return with Literal in WREG
Return from Subroutine
Go into Standby mode
1 (2)
1 (2)
1 (2)
1 (2)
1 (2)
1 (2)
1 (2)
2
1 (2)
2
1
1
2
1
1
1
1
2
1
2
2
2
1
1110
1110
1110
1110
1110
1110
1110
1101
1110
1110
1111
0000
0000
1110
1111
0000
1111
0000
0000
1101
0000
0000
0000
0000
0000
0010
0110
0011
0111
0101
0001
0100
0nnn
0000
110s
kkkk
0000
0000
1111
kkkk
0000
xxxx
0000
0000
1nnn
0000
0000
1100
0000
0000
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
kkkk
kkkk
0000
0000
kkkk
kkkk
0000
xxxx
0000
0000
nnnn
1111
0001
kkkk
0001
0000
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
nnnn
kkkk
kkkk
0100
0111
kkkk
kkkk
0000
xxxx
0110
0101
nnnn
1111
000s
kkkk
001s
0011
None
None
None
None
None
None
None
None
None
None
TO, PD
C
None
None
None
None
None
None
All
GIE/GIEH,
PEIE/GIEL
None
None
TO, PD
4
TABLE 25-2: PIC18FXXXX INSTRUCTION SET (CONTINUED)
Mnemonic,
Operands Description Cycles
16-Bit Instruction Word Status
Affected Notes
MSb LSb
Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value
present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an
external device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if
assigned.
3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second
cycle is executed as a NOP.
4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the
first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory
locations have a valid instruction.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 284 © 2009 Microchip Technology Inc.
LITERAL OPERATIONS
ADDLW
ANDLW
IORLW
LFSR
MOVLB
MOVLW
MULLW
RETLW
SUBLW
XORLW
k
k
k
f, k
k
k
k
k
k
k
Add Literal and WREG
AND Literal with WREG
Inclusive OR Literal with WREG
Move Literal (12-bit) 2nd Word
to FSR(f) 1st Word
Move Literal to BSR<3:0>
Move Literal to WREG
Multiply Literal with WREG
Return with Literal in WREG
Subtract WREG from Literal
Exclusive OR Literal with WREG
1
1
1
2
1
1
1
2
1
1
0000
0000
0000
1110
1111
0000
0000
0000
0000
0000
0000
1111
1011
1001
1110
0000
0001
1110
1101
1100
1000
1010
kkkk
kkkk
kkkk
00ff
kkkk
0000
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
kkkk
C, DC, Z, OV, N
Z, N
Z, N
None
None
None
None
None
C, DC, Z, OV, N
Z, N
DATA MEMORY PROGRAM MEMORY OPERATIONS
TBLRD*
TBLRD*+
TBLRD*-
TBLRD+*
TBLWT*
TBLWT*+
TBLWT*-
TBLWT+*
Table Read
Table Read with Post-Increment
Table Read with Post-Decrement
Table Read with Pre-Increment
Table Write
Table Write with Post-Increment
Table Write with Post-Decrement
Table Write with Pre-Increment
2
2
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
1000
1001
1010
1011
1100
1101
1110
1111
None
None
None
None
None
None
None
None
TABLE 25-2: PIC18FXXXX INSTRUCTION SET (CONTINUED)
Mnemonic,
Operands Description Cycles
16-Bit Instruction Word Status
Affected Notes
MSb LSb
Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value
present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an
external device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if
assigned.
3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second
cycle is executed as a NOP.
4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the
first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory
locations have a valid instruction.
PIC18F2221/2321/4221/4321 FAMILY
© 2009 Microchip Technology Inc. DS39689F-page 285
25.1.1 STANDARD INSTRUCTION SET
ADDLW ADD Literal to W
Syntax: ADDLW k
Operands: 0 k 255
Operation: (W) + k W
Status Affected: N, OV, C, DC, Z
Encoding: 0000 1111 kkkk kkkk
Description: The contents of W are added to the
8-bit literal ‘k’ and the result is placed in
W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to W
Example: ADDLW 15h
Before Instruction
W = 10h
After Instruction
W = 25h
ADDWF ADD W to f
Syntax: ADDWF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (W) + (f) dest
Status Affected: N, OV, C, DC, Z
Encoding: 0010 01da ffff ffff
Description: Add W to register ‘f’. If ‘d’ is 0’, the
result is stored in W. If ‘d’ is ‘1’, the
result is stored back in register ‘f’
(default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: ADDWF REG, 0, 0
Before Instruction
W = 17h
REG = 0C2h
After Instruction
W = 0D9h
REG = 0C2h
Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in
symbolic addressing. If a label is used, the instruction format then becomes: {label} instruction argument(s).
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ADDWFC ADD W and Carry bit to f
Syntax: ADDWFC f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (W) + (f) + (C) dest
Status Affected: N,OV, C, DC, Z
Encoding: 0010 00da ffff ffff
Description: Add W, the Carry flag and data memory
location ‘f’. If ‘d’ is 0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed in data memory location ‘f’.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: ADDWFC REG, 0, 1
Before Instruction
Carry bit = 1
REG = 02h
W=4Dh
After Instruction
Carry bit = 0
REG = 02h
W = 50h
ANDLW AND Literal with W
Syntax: ANDLW k
Operands: 0 k 255
Operation: (W) .AND. k W
Status Affected: N, Z
Encoding: 0000 1011 kkkk kkkk
Description: The contents of W are ANDed with the
8-bit literal ‘k’. The result is placed in W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
‘k’
Process
Data
Write to W
Example: ANDLW 05Fh
Before Instruction
W=A3h
After Instruction
W = 03h
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ANDWF AND W with f
Syntax: ANDWF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (W) .AND. (f) dest
Status Affected: N, Z
Encoding: 0001 01da ffff ffff
Description: The contents of W are ANDed with
register ‘f’. If ‘d’ is ‘0’, the result is stored
in W. If ‘d’ is ‘1’, the result is stored back
in register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: ANDWF REG, 0, 0
Before Instruction
W = 17h
REG = C2h
After Instruction
W = 02h
REG = C2h
BC Branch if Carry
Syntax: BC n
Operands: -128 n 127
Operation: If Carry bit is ‘1’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0010 nnnn nnnn
Description: If the Carry bit is ‘1’, then the program
will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BC 5
Before Instruction
PC = address (HERE)
After Instruction
If Carry = 1;
PC = address (HERE + 12)
If Carry = 0;
PC = address (HERE + 2)
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BCF Bit Clear f
Syntax: BCF f, b {,a}
Operands: 0 f 255
0 b 7
a [0,1]
Operation: 0 f<b>
Status Affected: None
Encoding: 1001 bbba ffff ffff
Description: Bit ‘b’ in register ‘f’ is cleared.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f’
Example: BCF FLAG_REG, 7, 0
Before Instruction
FLAG_REG = C7h
After Instruction
FLAG_REG = 47h
BN Branch if Negative
Syntax: BN n
Operands: -128 n 127
Operation: If Negative bit is ‘1’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0110 nnnn nnnn
Description: If the Negative bit is ‘1’, then the
program will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BN Jump
Before Instruction
PC = address (HERE)
After Instruction
If Negative = 1;
PC = address (Jump)
If Negative = 0;
PC = address (HERE + 2)
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BNC Branch if Not Carry
Syntax: BNC n
Operands: -128 n 127
Operation: If Carry bit is ‘0’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0011 nnnn nnnn
Description: If the Carry bit is ‘0’, then the program
will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BNC Jump
Before Instruction
PC = address (HERE)
After Instruction
If Carry = 0;
PC = address (Jump)
If Carry = 1;
PC = address (HERE + 2)
BNN Branch if Not Negative
Syntax: BNN n
Operands: -128 n 127
Operation: If Negative bit is ‘0’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0111 nnnn nnnn
Description: If the Negative bit is ‘0’, then the
program will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BNN Jump
Before Instruction
PC = address (HERE)
After Instruction
If Negative = 0;
PC = address (Jump)
If Negative = 1;
PC = address (HERE + 2)
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BNOV Branch if Not Overflow
Syntax: BNOV n
Operands: -128 n 127
Operation: If Overflow bit is ‘0’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0101 nnnn nnnn
Description: If the Overflow bit is ‘0’, then the
program will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BNOV Jump
Before Instruction
PC = address (HERE)
After Instruction
If Overflow = 0;
PC = address (Jump)
If Overflow = 1;
PC = address (HERE + 2)
BNZ Branch if Not Zero
Syntax: BNZ n
Operands: -128 n 127
Operation: If Zero bit is ‘0’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0001 nnnn nnnn
Description: If the Zero bit is ‘0’, then the program
will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BNZ Jump
Before Instruction
PC = address (HERE)
After Instruction
If Zero = 0;
PC = address (Jump)
If Zero = 1;
PC = address (HERE + 2)
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BRA Unconditional Branch
Syntax: BRA n
Operands: -1024 n 1023
Operation: (PC) + 2 + 2n PC
Status Affected: None
Encoding: 1101 0nnn nnnn nnnn
Description: Add the 2’s complement number ‘2n’ to
the PC. Since the PC will have
incremented to fetch the next instruction,
the new address will be PC + 2 + 2n. This
instruction is a two-cycle instruction.
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
Example: HERE BRA Jump
Before Instruction
PC = address (HERE)
After Instruction
PC = address (Jump)
BSF Bit Set f
Syntax: BSF f, b {,a}
Operands: 0 f 255
0 b 7
a [0,1]
Operation: 1 f<b>
Status Affected: None
Encoding: 1000 bbba ffff ffff
Description: Bit ‘b’ in register ‘f’ is set.
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f’
Example: BSF FLAG_REG, 7, 1
Before Instruction
FLAG_REG = 0Ah
After Instruction
FLAG_REG = 8Ah
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BTFSC Bit Test File, Skip if Clear
Syntax: BTFSC f, b {,a}
Operands: 0 f 255
0 b 7
a [0,1]
Operation: skip if (f<b>) = 0
Status Affected: None
Encoding: 1011 bbba ffff ffff
Description: If bit ‘b’ in register ‘f’ is ‘0’, then the next
instruction is skipped. If bit ‘b’ is ‘0’, then
the next instruction fetched during the
current instruction execution is discarded
and a NOP is executed instead, making
this a two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected. If
‘a’ is 1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates in
Indexed Literal Offset Addressing
mode whenever f 95 (5Fh).
See Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
No
operation
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE
FALSE
TRUE
BTFSC
:
:
FLAG, 1, 0
Before Instruction
PC = address (HERE)
After Instruction
If FLAG<1> = 0;
PC = address (TRUE)
If FLAG<1> = 1;
PC = address (FALSE)
BTFSS Bit Test File, Skip if Set
Syntax: BTFSS f, b {,a}
Operands: 0 f 255
0 b < 7
a [0,1]
Operation: skip if (f<b>) = 1
Status Affected: None
Encoding: 1010 bbba ffff ffff
Description: If bit ‘b’ in register ‘f’ is ‘1’, then the next
instruction is skipped. If bit ‘b’ is ‘1’, then
the next instruction fetched during the
current instruction execution is discarded
and a NOP is executed instead, making
this a two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected. If
‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh).
See Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f
Process
Data
No
operation
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE
FALSE
TRUE
BTFSS
:
:
FLAG, 1, 0
Before Instruction
PC = address (HERE)
After Instruction
If FLAG<1> = 0;
PC = address (FALSE)
If FLAG<1> = 1;
PC = address (TRUE)
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BTG Bit Toggle f
Syntax: BTG f, b {,a}
Operands: 0 f 255
0 b < 7
a [0,1]
Operation: (f<b>) f<b>
Status Affected: None
Encoding: 0111 bbba ffff ffff
Description: Bit ‘b’ in data memory location ‘f’ is
inverted.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f’
Example: BTG PORTC, 4, 0
Before Instruction:
PORTC = 0111 0101 [75h]
After Instruction:
PORTC = 0110 0101 [65h]
BOV Branch if Overflow
Syntax: BOV n
Operands: -128 n 127
Operation: If Overflow bit is ‘1’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0100 nnnn nnnn
Description: If the Overflow bit is ‘1’, then the
program will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BOV Jump
Before Instruction
PC = address (HERE)
After Instruction
If Overflow = 1;
PC = address (Jump)
If Overflow = 0;
PC = address (HERE + 2)
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BZ Branch if Zero
Syntax: BZ n
Operands: -128 n 127
Operation: If Zero bit is ‘1’,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1110 0000 nnnn nnnn
Description: If the Zero bit is ‘1’, then the program
will branch.
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will
have incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity:
If Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
If No Jump:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
Process
Data
No
operation
Example: HERE BZ Jump
Before Instruction
PC = address (HERE)
After Instruction
If Zero = 1;
PC = address (Jump)
If Zero = 0;
PC = address (HERE + 2)
CALL Subroutine Call
Syntax: CALL k {,s}
Operands: 0 k 1048575
s [0,1]
Operation: (PC) + 4 TOS,
k PC<20:1>;
if s = 1,
(W) WS,
(STATUS) STATUSS,
(BSR) BSRS
Status Affected: None
Encoding:
1st word (k<7:0>)
2nd word(k<19:8>)
1110
1111
110s
k19kkk
k7kkk
kkkk
kkkk0
kkkk8
Description: Subroutine call of entire 2-Mbyte
memory range. First, return address
(PC + 4) is pushed onto the return
stack. If ‘s’ = 1, the W, STATUS and
BSR registers are also pushed into their
respective shadow registers, WS,
STATUSS and BSRS. If ‘s’ = 0, no
update occurs (default). Then, the
20-bit value ‘k’ is loaded into PC<20:1>.
CALL is a two-cycle instruction.
Words: 2
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
‘k’<7:0>,
PUSH PC to
stack
Read literal
‘k’<19:8>,
Write to PC
No
operation
No
operation
No
operation
No
operation
Example: HERE CALL THERE, 1
Before Instruction
PC = address (HERE)
After Instruction
PC = address (THERE)
TOS = address (HERE + 4)
WS = W
BSRS = BSR
STATUSS = STATUS
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CLRF Clear f
Syntax: CLRF f {,a}
Operands: 0 f 255
a [0,1]
Operation: 000h f,
1 Z
Status Affected: Z
Encoding: 0110 101a ffff ffff
Description: Clears the contents of the specified
register.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f’
Example: CLRF FLAG_REG, 1
Before Instruction
FLAG_REG = 5Ah
After Instruction
FLAG_REG = 00h
CLRWDT Clear Watchdog Timer
Syntax: CLRWDT
Operands: None
Operation: 000h WDT,
000h WDT postscaler,
1 TO,
1 PD
Status Affected: TO, PD
Encoding: 0000 0000 0000 0100
Description: CLRWDT instruction resets the
Watchdog Timer. It also resets the
postscaler of the WDT. Status bits, TO
and PD, are set.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
Process
Data
No
operation
Example: CLRWDT
Before Instruction
WDT Counter = ?
After Instruction
WDT Counter = 00h
WDT Postscaler = 0
TO =1
PD =1
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COMF Complement f
Syntax: COMF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) dest
Status Affected: N, Z
Encoding: 0001 11da ffff ffff
Description: The contents of register ‘f’ are
complemented. If ‘d’ is ‘0’, the result is
stored in W. If ‘d’ is ‘1’, the result is
stored back in register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: COMF REG, 0, 0
Before Instruction
REG = 13h
After Instruction
REG = 13h
W=ECh
CPFSEQ Compare f with W, Skip if f = W
Syntax: CPFSEQ f {,a}
Operands: 0 f 255
a [0,1]
Operation: (f) – (W),
skip if (f) = (W)
(unsigned comparison)
Status Affected: None
Encoding: 0110 001a ffff ffff
Description: Compares the contents of data memory
location ‘f’ to the contents of W by
performing an unsigned subtraction.
If ‘f’ = W, then the fetched instruction is
discarded and a NOP is executed
instead, making this a two-cycle
instruction.
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
No
operation
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE CPFSEQ REG, 0
NEQUAL :
EQUAL :
Before Instruction
PC Address = HERE
W=?
REG = ?
After Instruction
If REG = W;
PC = Address (EQUAL)
If REG W;
PC = Address (NEQUAL)
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CPFSGT Compare f with W, Skip if f > W
Syntax: CPFSGT f {,a}
Operands: 0 f 255
a [0,1]
Operation: (f) – (W),
skip if (f) > (W)
(unsigned comparison)
Status Affected: None
Encoding: 0110 010a ffff ffff
Description: Compares the contents of data memory
location ‘f’ to the contents of the W by
performing an unsigned subtraction.
If the contents of ‘f’ are greater than the
contents of WREG, then the fetched
instruction is discarded and a NOP is
executed instead, making this a
two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
No
operation
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE CPFSGT REG, 0
NGREATER :
GREATER :
Before Instruction
PC = Address (HERE)
W= ?
After Instruction
If REG > W;
PC = Address (GREATER)
If REG W;
PC = Address (NGREATER)
CPFSLT Compare f with W, Skip if f < W
Syntax: CPFSLT f {,a}
Operands: 0 f 255
a [0,1]
Operation: (f) – (W),
skip if (f) < (W)
(unsigned comparison)
Status Affected: None
Encoding: 0110 000a ffff ffff
Description: Compares the contents of data memory
location ‘f’ to the contents of W by
performing an unsigned subtraction.
If the contents of ‘f’ are less than the
contents of W, then the fetched
instruction is discarded and a NOP is
executed instead, making this a
two-cycle instruction.
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
No
operation
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE CPFSLT REG, 1
NLESS :
LESS :
Before Instruction
PC = Address (HERE)
W= ?
After Instruction
If REG < W;
PC = Address (LESS)
If REG W;
PC = Address (NLESS)
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DAW Decimal Adjust W Register
Syntax: DAW
Operands: None
Operation: If [W<3:0> > 9] or [DC = 1] then,
(W<3:0>) + 6 W<3:0>;
else,
(W<3:0>) W<3:0>
If [W<7:4> + DC > 9] or [C = 1] then,
(W<7:4>) + 6 + DC W<7:4>;
else,
(W<7:4>) + DC W<7:4>
Status Affected: C
Encoding: 0000 0000 0000 0111
Description: DAW adjusts the eight-bit value in W
resulting from the earlier addition of two
variables (each in packed BCD format)
and produces a correct packed BCD
result.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register W
Process
Data
Write
W
Example 1:
DAW
Before Instruction
W=A5h
C=0
DC = 0
After Instruction
W = 05h
C=1
DC = 0
Example 2:
Before Instruction
W=CEh
C=0
DC = 0
After Instruction
W = 34h
C=1
DC = 0
DECF Decrement f
Syntax: DECF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) – 1 dest
Status Affected: C, DC, N, OV, Z
Encoding: 0000 01da ffff ffff
Description: Decrement register ‘f’. If ‘d’ is ‘0’, the
result is stored in W. If ‘d’ is ‘1’, the
result is stored back in register ‘f’
(default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: DECF CNT, 1, 0
Before Instruction
CNT = 01h
Z=0
After Instruction
CNT = 00h
Z=1
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DECFSZ Decrement f, Skip if 0
Syntax: DECFSZ f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) – 1 dest,
skip if result = 0
Status Affected: None
Encoding: 0010 11da ffff ffff
Description: The contents of register ‘f’ are
decremented. If ‘d’ is 0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
If the result is ‘0’, the next instruction,
which is already fetched, is discarded
and a NOP is executed instead, making
it a two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE DECFSZ CNT, 1, 1
GOTO LOOP
CONTINUE
Before Instruction
PC = Address (HERE)
After Instruction
CNT = CNT – 1
If CNT = 0;
PC = Address (CONTINUE)
If CNT 0;
PC = Address (HERE + 2)
DCFSNZ Decrement f, Skip if Not 0
Syntax: DCFSNZ f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) – 1 dest,
skip if result 0
Status Affected: None
Encoding: 0100 11da ffff ffff
Description: The contents of register ‘f’ are
decremented. If ‘d’ is 0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
If the result is not 0’, the next
instruction, which is already fetched, is
discarded and a NOP is executed
instead, making it a two-cycle
instruction.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE DCFSNZ TEMP, 1, 0
ZERO :
NZERO :
Before Instruction
TEMP = ?
After Instruction
TEMP = TEMP – 1
If TEMP = 0;
PC = Address (ZERO)
If TEMP 0;
PC = Address (NZERO)
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GOTO Unconditional Branch
Syntax: GOTO k
Operands: 0 k 1048575
Operation: k PC<20:1>
Status Affected: None
Encoding:
1st word (k<7:0>)
2nd word(k<19:8>)
1110
1111
1111
k19kkk
k7kkk
kkkk
kkkk0
kkkk8
Description: GOTO allows an unconditional branch
anywhere within entire
2-Mbyte memory range. The 20-bit
value ‘k’ is loaded into PC<20:1>.
GOTO is always a two-cycle
instruction.
Words: 2
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
‘k’<7:0>,
No
operation
Read literal
‘k’<19:8>,
Write to PC
No
operation
No
operation
No
operation
No
operation
Example: GOTO THERE
After Instruction
PC = Address (THERE)
INCF Increment f
Syntax: INCF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) + 1 dest
Status Affected: C, DC, N, OV, Z
Encoding: 0010 10da ffff ffff
Description: The contents of register ‘f’ are
incremented. If ‘d’ is ‘0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: INCF CNT, 1, 0
Before Instruction
CNT = FFh
Z=0
C=?
DC = ?
After Instruction
CNT = 00h
Z=1
C=1
DC = 1
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INCFSZ Increment f, Skip if 0
Syntax: INCFSZ f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) + 1 dest,
skip if result = 0
Status Affected: None
Encoding: 0011 11da ffff ffff
Description: The contents of register ‘f’ are
incremented. If ‘d’ is ‘0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
If the result is ‘0’, the next instruction,
which is already fetched, is discarded
and a NOP is executed instead, making
it a two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE INCFSZ CNT, 1, 0
NZERO :
ZERO :
Before Instruction
PC = Address (HERE)
After Instruction
CNT = CNT + 1
If CNT = 0;
PC = Address (ZERO)
If CNT 0;
PC = Address (NZERO)
INFSNZ Increment f, Skip if Not 0
Syntax: INFSNZ f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) + 1 dest,
skip if result 0
Status Affected: None
Encoding: 0100 10da ffff ffff
Description: The contents of register ‘f’ are
incremented. If ‘d’ is 0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
If the result is not 0’, the next
instruction, which is already fetched, is
discarded and a NOP is executed
instead, making it a two-cycle
instruction.
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE INFSNZ REG, 1, 0
ZERO
NZERO
Before Instruction
PC = Address (HERE)
After Instruction
REG = REG + 1
If REG 0;
PC = Address (NZERO)
If REG = 0;
PC = Address (ZERO)
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IORLW Inclusive OR Literal with W
Syntax: IORLW k
Operands: 0 k 255
Operation: (W) .OR. k W
Status Affected: N, Z
Encoding: 0000 1001 kkkk kkkk
Description: The contents of W are ORed with the
eight-bit literal ‘k’. The result is placed in
W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to W
Example: IORLW 35h
Before Instruction
W=9Ah
After Instruction
W=BFh
IORWF Inclusive OR W with f
Syntax: IORWF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (W) .OR. (f) dest
Status Affected: N, Z
Encoding: 0001 00da ffff ffff
Description: Inclusive OR W with register ‘f’. If ‘d’ is
0’, the result is placed in W. If ‘d’ is ‘1’,
the result is placed back in register ‘f
(default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: IORWF RESULT, 0, 1
Before Instruction
RESULT = 13h
W = 91h
After Instruction
RESULT = 13h
W = 93h
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LFSR Load FSR
Syntax: LFSR f, k
Operands: 0 f 2
0 k 4095
Operation: k FSRf
Status Affected: None
Encoding: 1110
1111
1110
0000
00ff
k7kkk
k11kkk
kkkk
Description: The 12-bit literal ‘k’ is loaded into the
File Select Register pointed to by ‘f’.
Words: 2
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
‘k’ MSB
Process
Data
Write
literal ‘k’
MSB to
FSRfH
Decode Read literal
‘k’ LSB
Process
Data
Write literal
‘k’ to FSRfL
Example: LFSR 2, 3ABh
After Instruction
FSR2H = 03h
FSR2L = ABh
MOVF Move f
Syntax: MOVF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: f dest
Status Affected: N, Z
Encoding: 0101 00da ffff ffff
Description: The contents of register ‘f’ are moved to
a destination dependent upon the
status of ‘d’. If ‘d’ is ‘0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
Location ‘f’ can be anywhere in the
256-byte bank.
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write W
Example: MOVF REG, 0, 0
Before Instruction
REG = 22h
W=FFh
After Instruction
REG = 22h
W = 22h
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MOVFF Move f to f
Syntax: MOVFF fs,fd
Operands: 0 fs 4095
0 fd 4095
Operation: (fs) fd
Status Affected: None
Encoding:
1st word (source)
2nd word (destin.)
1100
1111
ffff
ffff
ffff
ffff
ffffs
ffffd
Description: The contents of source register ‘fs’ are
moved to destination register ‘fd’.
Location of source ‘fs’ can be anywhere
in the 4096-byte data space (000h to
FFFh) and location of destination ‘fd
can also be anywhere from 000h to
FFFh.
Either source or destination can be W
(a useful special situation).
MOVFF is particularly useful for
transferring a data memory location to a
peripheral register (such as the transmit
buffer or an I/O port).
The MOVFF instruction cannot use the
PCL, TOSU, TOSH or TOSL as the
destination register.
Words: 2
Cycles: 2 (3)
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
(src)
Process
Data
No
operation
Decode No
operation
No dummy
read
No
operation
Write
register ‘f’
(dest)
Example: MOVFF REG1, REG2
Before Instruction
REG1 = 33h
REG2 = 11h
After Instruction
REG1 = 33h
REG2 = 33h
MOVLB Move Literal to Low Nibble in BSR
Syntax: MOVLW k
Operands: 0 k 255
Operation: k BSR
Status Affected: None
Encoding: 0000 0001 kkkk kkkk
Description: The eight-bit literal ‘k’ is loaded into the
Bank Select Register (BSR). The value of
BSR<7:4> always remains ‘0’, regardless
of the value of k7:k4.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write literal
‘k’ to BSR
Example: MOVLB 5
Before Instruction
BSR Register = 02h
After Instruction
BSR Register = 05h
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MOVLW Move Literal to W
Syntax: MOVLW k
Operands: 0 k 255
Operation: k W
Status Affected: None
Encoding: 0000 1110 kkkk kkkk
Description: The eight-bit literal ‘k’ is loaded into W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to W
Example: MOVLW 5Ah
After Instruction
W=5Ah
MOVWF Move W to f
Syntax: MOVWF f {,a}
Operands: 0 f 255
a [0,1]
Operation: (W) f
Status Affected: None
Encoding: 0110 111a ffff ffff
Description: Move data from W to register ‘f’.
Location ‘f’ can be anywhere in the
256-byte bank.
If ‘a’ is0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f
Example: MOVWF REG, 0
Before Instruction
W=4Fh
REG = FFh
After Instruction
W=4Fh
REG = 4Fh
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MULLW Multiply Literal with W
Syntax: MULLW k
Operands: 0 k 255
Operation: (W) x k PRODH:PRODL
Status Affected: None
Encoding: 0000 1101 kkkk kkkk
Description: An unsigned multiplication is carried
out between the contents of W and the
8-bit literal ‘k’. The 16-bit result is
placed in the PRODH:PRODL register
pair. PRODH contains the high byte.
W is unchanged.
None of the Status flags are affected.
Note that neither Overflow nor Carry is
possible in this operation. A Zero result
is possible but not detected.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write
registers
PRODH:
PRODL
Example: MULLW 0C4h
Before Instruction
W=E2h
PRODH = ?
PRODL = ?
After Instruction
W=E2h
PRODH = ADh
PRODL = 08h
MULWF Multiply W with f
Syntax: MULWF f {,a}
Operands: 0 f 255
a [0,1]
Operation: (W) x (f) PRODH:PRODL
Status Affected: None
Encoding: 0000 001a ffff ffff
Description: An unsigned multiplication is carried
out between the contents of W and the
register file location ‘f’. The 16-bit
result is stored in the PRODH:PRODL
register pair. PRODH contains the
high byte. Both W and ‘f’ are
unchanged.
None of the Status flags are affected.
Note that neither Overflow nor Carry is
possible in this operation. A Zero
result is possible but not detected.
If ‘a’ is ‘0’, the Access Bank is
selected. If ‘a’ is ‘1’, the BSR is used
to select the GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction
operates in Indexed Literal Offset
Addressing mode whenever
f 95 (5Fh). See Section 25.2.3
“Byte-Oriented and Bit-Oriented
Instructions in Indexed Literal Offset
Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
registers
PRODH:
PRODL
Example: MULWF REG, 1
Before Instruction
W=C4h
REG = B5h
PRODH = ?
PRODL = ?
After Instruction
W=C4h
REG = B5h
PRODH = 8Ah
PRODL = 94h
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NEGF Negate f
Syntax: NEGF f {,a}
Operands: 0 f 255
a [0,1]
Operation: (f) + 1 f
Status Affected: N, OV, C, DC, Z
Encoding: 0110 110a ffff ffff
Description: Location ‘f’ is negated using two’s
complement. The result is placed in the
data memory location ‘f’.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f’
Example: NEGF REG, 1
Before Instruction
REG = 0011 1010 [3Ah]
After Instruction
REG = 1100 0110 [C6h]
NOP No Operation
Syntax: NOP
Operands: None
Operation: No operation
Status Affected: None
Encoding: 0000
1111
0000
xxxx
0000
xxxx
0000
xxxx
Description: No operation.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
No
operation
No
operation
Example:
None.
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POP Pop Top of Return Stack
Syntax: POP
Operands: None
Operation: (TOS) bit bucket
Status Affected: None
Encoding: 0000 0000 0000 0110
Description: The TOS value is pulled off the return
stack and is discarded. The TOS value
then becomes the previous value that
was pushed onto the return stack.
This instruction is provided to enable
the user to properly manage the return
stack to incorporate a software stack.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
POP TOS
value
No
operation
Example: POP
GOTO NEW
Before Instruction
TOS = 0031A2h
Stack (1 level down) = 014332h
After Instruction
TOS = 014332h
PC = NEW
PUSH Push Top of Return Stack
Syntax: PUSH
Operands: None
Operation: (PC + 2) TOS
Status Affected: None
Encoding: 0000 0000 0000 0101
Description: The PC + 2 is pushed onto the top of
the return stack. The previous TOS
value is pushed down on the stack.
This instruction allows implementing a
software stack by modifying TOS and
then pushing it onto the return stack.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode PUSH
PC + 2 onto
return stack
No
operation
No
operation
Example: PUSH
Before Instruction
TOS = 345Ah
PC = 0124h
After Instruction
PC = 0126h
TOS = 0126h
Stack (1 level down) = 345Ah
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RCALL Relative Call
Syntax: RCALL n
Operands: -1024 n 1023
Operation: (PC) + 2 TOS,
(PC) + 2 + 2n PC
Status Affected: None
Encoding: 1101 1nnn nnnn nnnn
Description: Subroutine call with a jump up to 1K
from the current location. First, return
address (PC + 2) is pushed onto the
stack. Then, add the 2’s complement
number ‘2n’ to the PC. Since the PC will
have incremented to fetch the next
instruction, the new address will be
PC + 2 + 2n. This instruction is a
two-cycle instruction.
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read literal
‘n’
PUSH PC
to stack
Process
Data
Write to
PC
No
operation
No
operation
No
operation
No
operation
Example: HERE RCALL Jump
Before Instruction
PC = Address (HERE)
After Instruction
PC = Address (Jump)
TOS = Address (HERE + 2)
RESET Reset
Syntax: RESET
Operands: None
Operation: Reset all registers and flags that are
affected by a MCLR Reset.
Status Affected: All
Encoding: 0000 0000 1111 1111
Description: This instruction provides a way to
execute a MCLR Reset in software.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Start
Reset
No
operation
No
operation
Example: RESET
After Instruction
Registers = Reset Value
Flags* = Reset Value
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RETFIE Return from Interrupt
Syntax: RETFIE {s}
Operands: s [0,1]
Operation: (TOS) PC,
1 GIE/GIEH or PEIE/GIEL;
if s = 1,
(WS) W,
(STATUSS) STATUS,
(BSRS) BSR,
PCLATU, PCLATH are unchanged
Status Affected: GIE/GIEH, PEIE/GIEL
Encoding: 0000 0000 0001 000s
Description: Return from interrupt. Stack is popped
and Top-of-Stack (TOS) is loaded into
the PC. Interrupts are enabled by
setting either the high or low-priority
global interrupt enable bit. If ‘s’ = 1, the
contents of the shadow registers, WS,
STATUSS and BSRS, are loaded into
their corresponding registers, W,
STATUS and BSR. If ‘s’ = 0, no update
of these registers occurs (default).
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
No
operation
POP PC
from stack
Set GIEH or
GIEL
No
operation
No
operation
No
operation
No
operation
Example: RETFIE 1
After Interrupt
PC = TOS
W=WS
BSR = BSRS
STATUS = STATUSS
GIE/GIEH, PEIE/GIEL = 1
RETLW Return Literal to W
Syntax: RETLW k
Operands: 0 k 255
Operation: k W,
(TOS) PC,
PCLATU, PCLATH are unchanged
Status Affected: None
Encoding: 0000 1100 kkkk kkkk
Description: W is loaded with the eight-bit literal ‘k’.
The program counter is loaded from the
top of the stack (the return address).
The high address latch (PCLATH)
remains unchanged.
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
POP PC
from stack,
Write to W
No
operation
No
operation
No
operation
No
operation
Example:
CALL TABLE ; W contains table
; offset value
; W now has
; table value
:
TABLE
ADDWF PCL ; W = offset
RETLW k0 ; Begin table
RETLW k1 ;
:
:
RETLW kn ; End of table
Before Instruction
W = 07h
After Instruction
W = value of kn
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RETURN Return from Subroutine
Syntax: RETURN {s}
Operands: s [0,1]
Operation: (TOS) PC;
if s = 1,
(WS) W,
(STATUSS) STATUS,
(BSRS) BSR,
PCLATU, PCLATH are unchanged
Status Affected: None
Encoding: 0000 0000 0001 001s
Description: Return from subroutine. The stack is
popped and the top of the stack (TOS)
is loaded into the program counter. If
‘s’= 1, the contents of the shadow
registers, WS, STATUSS and BSRS,
are loaded into their corresponding
registers, W, STATUS and BSR. If
‘s’ = 0, no update of these registers
occurs (default).
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
Process
Data
POP PC
from stack
No
operation
No
operation
No
operation
No
operation
Example: RETURN
After Instruction:
PC = TOS
RLCF Rotate Left f through Carry
Syntax: RLCF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f<n>) dest<n + 1>,
(f<7>) C,
(C) dest<0>
Status Affected: C, N, Z
Encoding: 0011 01da ffff ffff
Description: The contents of register ‘f’ are rotated
one bit to the left through the Carry
flag. If ‘d’ is ‘0’, the result is placed in
W. If ‘d’ is ‘1’, the result is stored back
in register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank is
selected. If ‘a’ is ‘1’, the BSR is used to
select the GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction
operates in Indexed Literal Offset
Addressing mode whenever
f 95 (5Fh). See Section 25.2.3
“Byte-Oriented and Bit-Oriented
Instructions in Indexed Literal Offset
Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: RLCF REG, 0, 0
Before Instruction
REG = 1110 0110
C=0
After Instruction
REG = 1110 0110
W=1100 1100
C=1
Cregister f
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RLNCF Rotate Left f (No Carry)
Syntax: RLNCF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f<n>) dest<n + 1>,
(f<7>) dest<0>
Status Affected: N, Z
Encoding: 0100 01da ffff ffff
Description: The contents of register ‘f’ are rotated
one bit to the left. If ‘d’ is 0’, the result
is placed in W. If ‘d’ is 1’, the result is
stored back in register ‘f’ (default).
If ‘a’ is0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: RLNCF REG, 1, 0
Before Instruction
REG = 1010 1011
After Instruction
REG = 0101 0111
register f
RRCF Rotate Right f through Carry
Syntax: RRCF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f<n>) dest<n – 1>,
(f<0>) C,
(C) dest<7>
Status Affected: C, N, Z
Encoding: 0011 00da ffff ffff
Description: The contents of register ‘f’ are rotated
one bit to the right through the Carry
flag. If ‘d’ is ‘0’, the result is placed in W.
If ‘d’ is ‘1’, the result is placed back in
register ‘f’ (default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: RRCF REG, 0, 0
Before Instruction
REG = 1110 0110
C=0
After Instruction
REG = 1110 0110
W=0111 0011
C=0
Cregister f
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RRNCF Rotate Right f (No Carry)
Syntax: RRNCF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f<n>) dest<n – 1>,
(f<0>) dest<7>
Status Affected: N, Z
Encoding: 0100 00da ffff ffff
Description: The contents of register ‘f’ are rotated
one bit to the right. If ‘d’ is ‘0’, the result
is placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank will be
selected, overriding the BSR value. If ‘a’
is ‘1’, then the bank will be selected as
per the BSR value (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example 1: RRNCF REG, 1, 0
Before Instruction
REG = 1101 0111
After Instruction
REG = 1110 1011
Example 2: RRNCF REG, 0, 0
Before Instruction
W=?
REG = 1101 0111
After Instruction
W=1110 1011
REG = 1101 0111
register f
SETF Set f
Syntax: SETF f {,a}
Operands: 0 f 255
a [0,1]
Operation: FFh f
Status Affected: None
Encoding: 0110 100a ffff ffff
Description: The contents of the specified register
are set to FFh.
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write
register ‘f’
Example: SETF REG, 1
Before Instruction
REG = 5Ah
After Instruction
REG = FFh
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SLEEP Enter Sleep mode
Syntax: SLEEP
Operands: None
Operation: 00h WDT,
0 WDT postscaler,
1 TO,
0 PD
Status Affected: TO, PD
Encoding: 0000 0000 0000 0011
Description: The Power-Down status bit (PD) is
cleared. The Time-out status bit (TO)
is set. Watchdog Timer and its
postscaler are cleared.
The processor is put into Sleep mode
with the oscillator stopped.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
Process
Data
Go to
Sleep
Example: SLEEP
Before Instruction
TO =?
PD =?
After Instruction
TO =1
PD =0
† If WDT causes wake-up, this bit is cleared.
SUBFWB Subtract f from W with Borrow
Syntax: SUBFWB f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (W) – (f) – (C) dest
Status Affected: N, OV, C, DC, Z
Encoding: 0101 01da ffff ffff
Description: Subtract register ‘f’ and Carry flag
(borrow) from W (2’s complement
method). If ‘d’ is 0’, the result is stored
in W. If ‘d’ is ‘1’, the result is stored in
register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example 1: SUBFWB REG, 1, 0
Before Instruction
REG = 3
W=2
C=1
After Instruction
REG = FF
W=2
C=0
Z=0
N = 1 ; result is negative
Example 2: SUBFWB REG, 0, 0
Before Instruction
REG = 2
W=5
C=1
After Instruction
REG = 2
W=3
C=1
Z=0
N = 0 ; result is positive
Example 3: SUBFWB REG, 1, 0
Before Instruction
REG = 1
W=2
C=0
After Instruction
REG = 0
W=2
C=1
Z = 1 ; result is zero
N=0
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SUBLW Subtract W from Literal
Syntax: SUBLW k
Operands: 0 k 255
Operation: k – (W) W
Status Affected: N, OV, C, DC, Z
Encoding: 0000 1000 kkkk kkkk
Description W is subtracted from the eight-bit
literal ‘k’. The result is placed in W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to W
Example 1: SUBLW 02h
Before Instruction
W = 01h
C=?
After Instruction
W = 01h
C = 1 ; result is positive
Z=0
N=0
Example 2: SUBLW 02h
Before Instruction
W = 02h
C=?
After Instruction
W = 00h
C = 1 ; result is zero
Z=1
N=0
Example 3: SUBLW 02h
Before Instruction
W = 03h
C=?
After Instruction
W = FFh ; (2’s complement)
C = 0 ; result is negative
Z=0
N=1
SUBWF Subtract W from f
Syntax: SUBWF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) – (W) dest
Status Affected: N, OV, C, DC, Z
Encoding: 0101 11da ffff ffff
Description: Subtract W from register ‘f’ (2’s
complement method). If ‘d’ is0’, the
result is stored in W. If ‘d’ is ‘1’, the
result is stored back in register ‘f’
(default).
If ‘a’ is ‘0’, the Access Bank is
selected. If ‘a’ is ‘1’, the BSR is used
to select the GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction
operates in Indexed Literal Offset
Addressing mode whenever
f 95 (5Fh). See Section 25.2.3
“Byte-Oriented and Bit-Oriented
Instructions in Indexed Literal Offset
Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example 1: SUBWF REG, 1, 0
Before Instruction
REG = 3
W=2
C=?
After Instruction
REG = 1
W=2
C = 1 ; result is positive
Z=0
N=0
Example 2: SUBWF REG, 0, 0
Before Instruction
REG = 2
W=2
C=?
After Instruction
REG = 2
W=0
C = 1 ; result is zero
Z=1
N=0
Example 3: SUBWF REG, 1, 0
Before Instruction
REG = 1
W=2
C=?
After Instruction
REG = FFh ;(2’s complement)
W=2
C = 0 ; result is negative
Z=0
N=1
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SUBWFB Subtract W from f with Borrow
Syntax: SUBWFB f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f) – (W) – (C) dest
Status Affected: N, OV, C, DC, Z
Encoding: 0101 10da ffff ffff
Description: Subtract W and the Carry flag (borrow)
from register ‘f’ (2’s complement
method). If ‘d’ is ‘0’, the result is stored
in W. If ‘d’ is ‘1’, the result is stored back
in register ‘f’ (default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example 1: SUBWFB REG, 1, 0
Before Instruction
REG = 19h (0001 1001)
W=0Dh(0000 1101)
C=1
After Instruction
REG = 0Ch (0000 1011)
W=0Dh(0000 1101)
C=1
Z=0
N = 0 ; result is positive
Example 2: SUBWFB REG, 0, 0
Before Instruction
REG = 1Bh (0001 1011)
W=1Ah(0001 1010)
C=0
After Instruction
REG = 1Bh (0001 1011)
W = 00h
C=1
Z = 1 ; result is zero
N=0
Example 3: SUBWFB REG, 1, 0
Before Instruction
REG = 03h (0000 0011)
W=0Eh(0000 1101)
C=1
After Instruction
REG = F5h (1111 0100)
; [2’s comp]
W=0Eh(0000 1101)
C=0
Z=0
N = 1 ; result is negative
SWAPF Swap f
Syntax: SWAPF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (f<3:0>) dest<7:4>,
(f<7:4>) dest<3:0>
Status Affected: None
Encoding: 0011 10da ffff ffff
Description: The upper and lower nibbles of register
‘f’ are exchanged. If ‘d’ is ‘0’, the result
is placed in W. If ‘d’ is 1, the result is
placed in register ‘f’ (default).
If ‘a’ is ‘0, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: SWAPF REG, 1, 0
Before Instruction
REG = 53h
After Instruction
REG = 35h
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TBLRD Table Read
Syntax: TBLRD ( *; *+; *-; +*)
Operands: None
Operation: if TBLRD *,
(Prog Mem (TBLPTR)) TABLAT,
TBLPTR – No Change;
if TBLRD *+,
(Prog Mem (TBLPTR)) TABLAT,
(TBLPTR) + 1 TBLPTR;
if TBLRD *-,
(Prog Mem (TBLPTR)) TABLAT,
(TBLPTR) – 1 TBLPTR;
if TBLRD +*,
(TBLPTR) + 1 TBLPTR,
(Prog Mem (TBLPTR)) TABLAT
Status Affected: None
Encoding: 0000 0000 0000 10nn
nn=0 *
=1 *+
=2 *-
=3 +*
Description: This instruction is used to read the contents
of Program Memory (P.M.). To address the
program memory, a pointer called Table
Pointer (TBLPTR) is used.
The TBLPTR (a 21-bit pointer) points to
each byte in the program memory. TBLPTR
has a 2-Mbyte address range.
TBLPTR[0] = 0: Least Significant Byte of
Program Memory Word
TBLPTR[0] = 1: Most Significant Byte of
Program Memory Word
The TBLRD instruction can modify the value
of TBLPTR as follows:
no change
post-increment
post-decrement
pre-increment
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
No
operation
No
operation
No
operation
No operation
(Read Program
Memory)
No
operation
No operation
(Write
TABLAT)
TBLRD Table Read (Continued)
Example 1: TBLRD *+ ;
Before Instruction
TABLAT = 55h
TBLPTR = 00A356h
MEMORY (00A356h) = 34h
After Instruction
TABLAT = 34h
TBLPTR = 00A357h
Example 2: TBLRD +* ;
Before Instruction
TABLAT = AAh
TBLPTR = 01A357h
MEMORY (01A357h) = 12h
MEMORY (01A358h) = 34h
After Instruction
TABLAT = 34h
TBLPTR = 01A358h
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TBLWT Table Write
Syntax: TBLWT ( *; *+; *-; +*)
Operands: None
Operation: if TBLWT*,
(TABLAT) Holding Register,
TBLPTR – No Change;
if TBLWT*+,
(TABLAT) Holding Register,
(TBLPTR) + 1 TBLPTR;
if TBLWT*-,
(TABLAT) Holding Register,
(TBLPTR) – 1 TBLPTR;
if TBLWT+*,
(TBLPTR) + 1 TBLPTR,
(TABLAT) Holding Register
Status Affected: None
Encoding: 0000 0000 0000 11nn
nn=0 *
=1 *+
=2 *-
=3 +*
Description: This instruction uses the 3 LSBs of
TBLPTR to determine which of the
8 holding registers the TABLAT is written
to. The holding registers are used to
program the contents of Program
Memory (P.M.). (Refer to Section 7.0
“Flash Program Memory” for additional
details on programming Flash memory.)
The TBLPTR (a 21-bit pointer) points to
each byte in the program memory.
TBLPTR has a 2-Mbyte address range.
The LSb of the TBLPTR selects which
byte of the program memory location to
access.
TBLPTR[0] = 0: Least Significant Byte
of Program Memory
Word
TBLPTR[0] = 1: Most Significant Byte
of Program Memory
Word
The TBLWT instruction can modify the
value of TBLPTR as follows:
no change
post-increment
post-decrement
pre-increment
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No
operation
No
operation
No
operation
No
operation
No
operation
(Read
TABLAT)
No
operation
No
operation
(Write to
Holding
Register )
TBLWT Table Write (Continued)
Example 1: TBLWT *+;
Before Instruction
TABLAT = 55h
TBLPTR = 00A356h
HOLDING REGISTER
(00A356h) = FFh
After Instructions (table write completion)
TABLAT = 55h
TBLPTR = 00A357h
HOLDING REGISTER
(00A356h) = 55h
Example 2: TBLWT +*;
Before Instruction
TABLAT = 34h
TBLPTR = 01389Ah
HOLDING REGISTER
(01389Ah) = FFh
HOLDING REGISTER
(01389Bh) = FFh
After Instruction (table write completion)
TABLAT = 34h
TBLPTR = 01389Bh
HOLDING REGISTER
(01389Ah) = FFh
HOLDING REGISTER
(01389Bh) = 34h
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TSTFSZ Test f, Skip if 0
Syntax: TSTFSZ f {,a}
Operands: 0 f 255
a [0,1]
Operation: skip if f = 0
Status Affected: None
Encoding: 0110 011a ffff ffff
Description: If ‘f’ = 0, the next instruction fetched
during the current instruction execution
is discarded and a NOP is executed,
making this a two-cycle instruction.
If ‘a’ is0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
No
operation
If skip:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE TSTFSZ CNT, 1
NZERO :
ZERO :
Before Instruction
PC = Address (HERE)
After Instruction
If CNT = 00h,
PC = Address (ZERO)
If CNT 00h,
PC = Address (NZERO)
XORLW Exclusive OR Literal with W
Syntax: XORLW k
Operands: 0 k 255
Operation: (W) .XOR. k W
Status Affected: N, Z
Encoding: 0000 1010 kkkk kkkk
Description: The contents of W are XORed with
the 8-bit literal ‘k’. The result is placed
in W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to W
Example: XORLW 0AFh
Before Instruction
W=B5h
After Instruction
W=1Ah
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XORWF Exclusive OR W with f
Syntax: XORWF f {,d {,a}}
Operands: 0 f 255
d [0,1]
a [0,1]
Operation: (W) .XOR. (f) dest
Status Affected: N, Z
Encoding: 0001 10da ffff ffff
Description: Exclusive OR the contents of W with
register ‘f’. If ‘d’ is ‘0’, the result is stored
in W. If ‘d’ is1’, the result is stored back
in the register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 25.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: XORWF REG, 1, 0
Before Instruction
REG = AFh
W=B5h
After Instruction
REG = 1Ah
W=B5h
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25.2 Extended Instruction Set
In addition to the standard 75 instructions of the PIC18
instruction set, PIC18F2221/2321/4221/4321 family
devices also provide an optional extension to the core
CPU functionality. The added features include eight
additional instructions that augment indirect and
indexed addressing operations and the implementation
of Indexed Literal Offset Addressing mode for many of
the standard PIC18 instructions.
The additional features of the extended instruction set
are disabled by default. To enable them, users must set
the XINST Configuration bit.
The instructions in the extended set (with the exception
of CALLW, MOVSF and MOVSS) can all be classified as
literal operations, which either manipulate the File
Select Registers, or use them for indexed addressing.
Two of the instructions, ADDFSR and SUBFSR, each
have an additional special instantiation for using FSR2.
These versions (ADDULNK and SUBULNK) allow for
automatic return after execution.
The extended instructions are specifically implemented
to optimize re-entrant program code (that is, code that
is recursive or that uses a software stack) written in
high-level languages, particularly C. Among other
things, they allow users working in high-level
languages to perform certain operations on data
structures more efficiently. These include:
Dynamic allocation and deallocation of software
stack space when entering and leaving
subroutines
Function Pointer invocation
Software Stack Pointer manipulation
Manipulation of variables located in a software
stack
A summary of the instructions in the extended instruction
set is provided in Table 25-3. Detailed descriptions are
provided in Section 25.2.2 “Extended Instruction
Set”. The opcode field descriptions in Table 25-1
(page 280) apply to both the standard and extended
PIC18 instruction sets.
25.2.1 EXTENDED INSTRUCTION SYNTAX
Most of the extended instructions use indexed
arguments, using one of the File Select Registers and
some offset to specify a source or destination register.
When an argument for an instruction serves as part of
indexed addressing, it is enclosed in square brackets
(“[ ]”). This is done to indicate that the argument is used
as an index or offset. The MPASM™ Assembler will
flag an error if it determines that an index or offset value
is not bracketed.
When the extended instruction set is enabled, brackets
are also used to indicate index arguments in byte-
oriented and bit-oriented instructions. This is in addition
to other changes in their syntax. For more details, see
Section 25.2.3.1 “Extended Instruction Syntax with
Standard PIC18 Commands”.
TABLE 25-3: EXTENSIONS TO THE PIC18 INSTRUCTION SET
Note: The instruction set extension and the
Indexed Literal Offset Addressing mode
were designed for optimizing applications
written in C; the user may likely never use
these instructions directly in the assembler.
The syntax for these commands is
provided as a reference for users who may
be reviewing code that has been generated
by a compiler.
Note: In the past, square brackets have been
used to denote optional arguments in the
PIC18 and earlier instruction sets. In this
text and going forward, optional
arguments are denoted by braces (“{ }”).
Mnemonic,
Operands Description Cycles
16-Bit Instruction Word Status
Affected
MSb LSb
ADDFSR
ADDULNK
CALLW
MOVSF
MOVSS
PUSHL
SUBFSR
SUBULNK
f, k
k
zs, fd
zs, zd
k
f, k
k
Add Literal to FSR
Add Literal to FSR2 and Return
Call Subroutine using WREG
Move zs (source) to 1st Word
fd (destination) 2nd Word
Move zs (source) to 1st word
zd (destination) 2nd Word
Store Literal at FSR2,
Decrement FSR2
Subtract Literal from FSR
Subtract Literal from FSR2 and
Return
1
2
2
2
2
1
1
2
1110
1110
0000
1110
1111
1110
1111
1110
1110
1110
1000
1000
0000
1011
ffff
1011
xxxx
1010
1001
1001
ffkk
11kk
0001
0zzz
ffff
1zzz
xzzz
kkkk
ffkk
11kk
kkkk
kkkk
0100
zzzz
ffff
zzzz
zzzz
kkkk
kkkk
kkkk
None
None
None
None
None
None
None
None
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25.2.2 EXTENDED INSTRUCTION SET
ADDFSR Add Literal to FSR
Syntax: ADDFSR f, k
Operands: 0 k 63
f [ 0, 1, 2 ]
Operation: FSR(f) + k FSR(f)
Status Affected: None
Encoding: 1110 1000 ffkk kkkk
Description: The 6-bit literal ‘k’ is added to the
contents of the FSR specified by ‘f’.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to
FSR
Example: ADDFSR 2, 23h
Before Instruction
FSR2 = 03FFh
After Instruction
FSR2 = 0422h
ADDULNK Add Literal to FSR2 and Return
Syntax: ADDULNK k
Operands: 0 k 63
Operation: FSR2 + k FSR2,
(TOS) PC
Status Affected: None
Encoding: 1110 1000 11kk kkkk
Description: The 6-bit literal ‘k’ is added to the
contents of FSR2. A RETURN is then
executed by loading the PC with the
TOS.
The instruction takes two cycles to
execute; a NOP is performed during the
second cycle.
This may be thought of as a special
case of the ADDFSR instruction, where
f = 3 (binary ‘11’); it operates only on
FSR2.
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to
FSR
No
Operation
No
Operation
No
Operation
No
Operation
Example: ADDULNK 23h
Before Instruction
FSR2 = 03FFh
PC = 0100h
After Instruction
FSR2 = 0422h
PC = (TOS)
Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in
symbolic addressing. If a label is used, the instruction syntax then becomes: {label} instruction argument(s).
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CALLW Subroutine Call Using WREG
Syntax: CALLW
Operands: None
Operation: (PC + 2) TOS,
(W) PCL,
(PCLATH) PCH,
(PCLATU) PCU
Status Affected: None
Encoding: 0000 0000 0001 0100
Description First, the return address (PC + 2) is
pushed onto the return stack. Next, the
contents of W are written to PCL; the
existing value is discarded. Then, the
contents of PCLATH and PCLATU are
latched into PCH and PCU,
respectively. The second cycle is
executed as a NOP instruction while the
new next instruction is fetched.
Unlike CALL, there is no option to
update W, STATUS or BSR.
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
WREG
PUSH PC to
stack
No
operation
No
operation
No
operation
No
operation
No
operation
Example: HERE CALLW
Before Instruction
PC = address (HERE)
PCLATH = 10h
PCLATU = 00h
W = 06h
After Instruction
PC = 001006h
TOS = address (HERE + 2)
PCLATH = 10h
PCLATU = 00h
W = 06h
MOVSF Move Indexed to f
Syntax: MOVSF [zs], fd
Operands: 0 zs 127
0 fd 4095
Operation: ((FSR2) + zs) fd
Status Affected: None
Encoding:
1st word (source)
2nd word (destin.)
1110
1111
1011
ffff
0zzz
ffff
zzzzs
ffffd
Description: The contents of the source register are
moved to destination register ‘fd’. The
actual address of the source register is
determined by adding the 7-bit literal
offset ‘zs’ in the first word to the value of
FSR2. The address of the destination
register is specified by the 12-bit literal
‘fd’ in the second word. Both addresses
can be anywhere in the 4096-byte data
space (000h to FFFh).
The MOVSF instruction cannot use the
PCL, TOSU, TOSH or TOSL as the
destination register.
If the resultant source address points to
an indirect addressing register, the
value returned will be 00h.
Words: 2
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Determine
source addr
Determine
source addr
Read
source reg
Decode No
operation
No dummy
read
No
operation
Write
register ‘f’
(dest)
Example: MOVSF [05h], REG2
Before Instruction
FSR2 = 80h
Contents
of 85h = 33h
REG2 = 11h
After Instruction
FSR2 = 80h
Contents
of 85h = 33h
REG2 = 33h
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MOVSS Move Indexed to Indexed
Syntax: MOVSS [zs], [zd]
Operands: 0 zs 127
0 zd 127
Operation: ((FSR2) + zs) ((FSR2) + zd)
Status Affected: None
Encoding:
1st word (source)
2nd word (dest.)
1110
1111
1011
xxxx
1zzz
xzzz
zzzzs
zzzzd
Description The contents of the source register are
moved to the destination register. The
addresses of the source and destination
registers are determined by adding the
7-bit literal offsets ‘zs’ or ‘zd’,
respectively, to the value of FSR2. Both
registers can be located anywhere in
the 4096-byte data memory space
(000h to FFFh).
The MOVSS instruction cannot use the
PCL, TOSU, TOSH or TOSL as the
destination register.
If the resultant source address points to
an indirect addressing register, the
value returned will be 00h. If the
resultant destination address points to
an indirect addressing register, the
instruction will execute as a NOP.
Words: 2
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Determine
source addr
Determine
source addr
Read
source reg
Decode Determine
dest addr
Determine
dest addr
Write
to dest reg
Example: MOVSS [05h], [06h]
Before Instruction
FSR2 = 80h
Contents
of 85h = 33h
Contents
of 86h = 11h
After Instruction
FSR2 = 80h
Contents
of 85h = 33h
Contents
of 86h = 33h
PUSHL
Store Literal at FSR2, Decrement FSR2
Syntax: PUSHL k
Operands: 0k 255
Operation: k (FSR2),
FSR2 – 1 FSR2
Status Affected: None
Encoding: 1111 1010 kkkk kkkk
Description: The 8-bit literal ‘k’ is written to the data
memory address specified by FSR2. FSR2
is decremented by 1 after the operation.
This instruction allows users to push values
onto a software stack.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read ‘k’ Process
data
Write to
destination
Example: PUSHL 08h
Before Instruction
FSR2H:FSR2L = 01ECh
Memory (01ECh) = 00h
After Instruction
FSR2H:FSR2L = 01EBh
Memory (01ECh) = 08h
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SUBFSR Subtract Literal from FSR
Syntax: SUBFSR f, k
Operands: 0 k 63
f [ 0, 1, 2 ]
Operation: FSR(f – k) FSR(f)
Status Affected: None
Encoding: 1110 1001 ffkk kkkk
Description: The 6-bit literal ‘k’ is subtracted from
the contents of the FSR specified
by ‘f’.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: SUBFSR 2, 23h
Before Instruction
FSR2 = 03FFh
After Instruction
FSR2 = 03DCh
SUBULNK
Subtract Literal from FSR2 and Return
Syntax: SUBULNK k
Operands: 0 k 63
Operation: FSR2 – k FSR2,
(TOS) PC
Status
Affected:
None
Encoding: 1110 1001 11kk kkkk
Description: The 6-bit literal ‘k’ is subtracted from the
contents of the FSR2. A RETURN is then
executed by loading the PC with the TOS.
The instruction takes two cycles to
execute; a NOP is performed during the
second cycle.
This may be thought of as a special case of
the SUBFSR instruction, where f = 3 (binary
11’); it operates only on FSR2.
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
No
Operation
No
Operation
No
Operation
No
Operation
Example: SUBULNK 23h
Before Instruction
FSR2 = 03FFh
PC = 0100h
After Instruction
FSR2 = 03DCh
PC = (TOS)
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25.2.3 BYTE-ORIENTED AND
BIT-ORIENTED INSTRUCTIONS IN
INDEXED LITERAL OFFSET MODE
In addition to eight new commands in the extended set,
enabling the extended instruction set also enables
Indexed Literal Offset Addressing mode (Section 6.5.1
“Indexed Addressing with Literal Offset”). This has
a significant impact on the way that many commands of
the standard PIC18 instruction set are interpreted.
When the extended set is disabled, addresses embed-
ded in opcodes are treated as literal memory locations:
either as a location in the Access Bank (‘a’ = 0) or in a
GPR bank designated by the BSR (‘a’ = 1). When the
extended instruction set is enabled and ‘a’ = 0,
however, a file register argument of 5Fh or less is
interpreted as an offset from the pointer value in FSR2
and not as a literal address. For practical purposes, this
means that all instructions that use the Access RAM bit
as an argument – that is, all byte-oriented and bit-
oriented instructions, or almost half of the core PIC18
instructions – may behave differently when the
extended instruction set is enabled.
When the content of FSR2 is 00h, the boundaries of the
Access RAM are essentially remapped to their original
values. This may be useful in creating backward
compatible code. If this technique is used, it may be
necessary to save the value of FSR2 and restore it
when moving back and forth between C and assembly
routines in order to preserve the Stack Pointer. Users
must also keep in mind the syntax requirements of the
extended instruction set (see Section 25.2.3.1
“Extended Instruction Syntax with Standard PIC18
Commands”).
Although the Indexed Literal Offset Addressing mode
can be very useful for dynamic stack and pointer
manipulation, it can also be very annoying if a simple
arithmetic operation is carried out on the wrong
register. Users who are accustomed to the PIC18
programming must keep in mind that, when the
extended instruction set is enabled, register addresses
of 5Fh or less are used for Indexed Literal Offset
Addressing mode.
Representative examples of typical byte-oriented and
bit-oriented instructions in the Indexed Literal Offset
Addressing mode are provided on the following page to
show how execution is affected. The operand
conditions shown in the examples are applicable to all
instructions of these types.
25.2.3.1 Extended Instruction Syntax with
Standard PIC18 Commands
When the extended instruction set is enabled, the file
register argument, ‘f’, in the standard byte-oriented and
bit-oriented commands is replaced with the literal offset
value, ‘k’. As already noted, this occurs only when ‘f’ is
less than or equal to 5Fh. When an offset value is used,
it must be indicated by square brackets (“[ ]”). As with
the extended instructions, the use of brackets indicates
to the compiler that the value is to be interpreted as an
index or an offset. Omitting the brackets, or using a
value greater than 5Fh within brackets, will generate an
error in the MPASM Assembler.
If the index argument is properly bracketed for Indexed
Literal Offset Addressing mode, the Access RAM
argument is never specified; it will automatically be
assumed to be ‘0’. This is in contrast to standard
operation (extended instruction set disabled) when ‘a’
is set on the basis of the target address. Declaring the
Access RAM bit in this mode will also generate an error
in the MPASM Assembler.
The destination argument, ‘d’, functions as before.
In the latest versions of the MPASM Assembler,
language support for the extended instruction set must
be explicitly invoked. This is done with either the
command line option, /y, or the PE directive in the
source listing.
25.2.4 CONSIDERATIONS WHEN
ENABLING THE EXTENDED
INSTRUCTION SET
It is important to note that the extensions to the instruc-
tion set may not be beneficial to all users. In particular,
users who are not writing code that uses a software
stack may not benefit from using the extensions to the
instruction set.
Additionally, the Indexed Literal Offset Addressing
mode may create issues with legacy applications
written to the PIC18 assembler. This is because
instructions in the legacy code may attempt to address
registers in the Access Bank below 5Fh. Since these
addresses are interpreted as literal offsets to FSR2
when the instruction set extension is enabled, the
application may read or write to the wrong data
addresses.
When porting an application to the PIC18F2221/2321/
4221/4321 family, it is very important to consider the
type of code. A large, re-entrant application that is
written in ‘C’ and would benefit from efficient
compilation will do well when using the instruction set
extensions. Legacy applications that heavily use the
Access Bank will most likely not benefit from using the
extended instruction set.
Note: Enabling the PIC18 instruction set
extension may cause legacy applications
to behave erratically or fail entirely.
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ADDWF ADD W to Indexed
(Indexed Literal Offset mode)
Syntax: ADDWF [k] {,d}
Operands: 0 k 95
d [0,1]
Operation: (W) + ((FSR2) + k) dest
Status Affected: N, OV, C, DC, Z
Encoding: 0010 01d0 kkkk kkkk
Description: The contents of W are added to the
contents of the register indicated by
FSR2, offset by the value ‘k’.
If ‘d’ is ‘0’, the result is stored in W. If ‘d’
is ‘1’, the result is stored back in
register ‘f’ (default).
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read ‘k’ Process
Data
Write to
destination
Example: ADDWF [OFST] , 0
Before Instruction
W = 17h
OFST = 2Ch
FSR2 = 0A00h
Contents
of 0A2Ch = 20h
After Instruction
W = 37h
Contents
of 0A2Ch = 20h
BSF Bit Set Indexed
(Indexed Literal Offset mode)
Syntax: BSF [k], b
Operands: 0 f 95
0 b 7
Operation: 1 ((FSR2) + k)<b>
Status Affected: None
Encoding: 1000 bbb0 kkkk kkkk
Description: Bit ‘b’ of the register indicated by FSR2,
offset by the value ‘k’, is set.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
register ‘f’
Process
Data
Write to
destination
Example: BSF [FLAG_OFST], 7
Before Instruction
FLAG_OFST = 0Ah
FSR2 = 0A00h
Contents
of 0A0Ah = 55h
After Instruction
Contents
of 0A0Ah = D5h
SETF Set Indexed
(Indexed Literal Offset mode)
Syntax: SETF [k]
Operands: 0 k 95
Operation: FFh ((FSR2) + k)
Status Affected: None
Encoding: 0110 1000 kkkk kkkk
Description: The contents of the register indicated
by FSR2, offset by ‘k’, are set to FFh.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read ‘k’ Process
Data
Write
register
Example: SETF [OFST]
Before Instruction
OFST = 2Ch
FSR2 = 0A00h
Contents
of 0A2Ch = 00h
After Instruction
Contents
of 0A2Ch = FFh
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25.2.5 SPECIAL CONSIDERATIONS WITH
MICROCHIP MPLAB® IDE TOOLS
The latest versions of Microchip’s software tools have
been designed to fully support the extended instruction
set of the PIC18F2221/2321/4221/4321 family family of
devices. This includes the MPLAB C18 C Compiler,
MPASM Assembly language and MPLAB Integrated
Development Environment (IDE).
When selecting a target device for software
development, MPLAB IDE will automatically set default
Configuration bits for that device. The default setting for
the XINST Configuration bit is 0’, disabling the
extended instruction set and Indexed Literal Offset
Addressing mode. For proper execution of applications
developed to take advantage of the extended
instruction set, XINST must be set during
programming.
To develop software for the extended instruction set,
the user must enable support for the instructions and
the Indexed Addressing mode in their language tool(s).
Depending on the environment being used, this may be
done in several ways:
A menu option, or dialog box within the
environment, that allows the user to configure the
language tool and its settings for the project
A command line option
A directive in the source code
These options vary between different compilers,
assemblers and development environments. Users are
encouraged to review the documentation accompany-
ing their development systems for the appropriate
information.
© 2009 Microchip Technology Inc. DS39689F-page 329
PIC18F2221/2321/4221/4321 FAMILY
26.0 DEVELOPMENT SUPPORT
The PIC® microcontrollers and dsPIC® digital signal
controllers are supported with a full range of software
and hardware development tools:
Integrated Development Environment
- MPLAB® IDE Software
Compilers/Assemblers/Linkers
- MPLAB C Compiler for Various Device
Families
- HI-TECH C for Various Device Families
- MPASMTM Assembler
-MPLINK
TM Object Linker/
MPLIBTM Object Librarian
- MPLAB Assembler/Linker/Librarian for
Various Device Families
Simulators
- MPLAB SIM Software Simulator
•Emulators
- MPLAB REAL ICE™ In-Circuit Emulator
In-Circuit Debuggers
- MPLAB ICD 3
- PICkit™ 3 Debug Express
Device Programmers
- PICkit™ 2 Programmer
- MPLAB PM3 Device Programmer
Low-Cost Demonstration/Development Boards,
Evaluation Kits, and Starter Kits
26.1 MPLAB Integrated Development
Environment Software
The MPLAB IDE software brings an ease of software
development previously unseen in the 8/16/32-bit
microcontroller market. The MPLAB IDE is a Windows®
operating system-based application that contains:
A single graphical interface to all debugging tools
- Simulator
- Programmer (sold separately)
- In-Circuit Emulator (sold separately)
- In-Circuit Debugger (sold separately)
A full-featured editor with color-coded context
A multiple project manager
Customizable data windows with direct edit of
contents
High-level source code debugging
Mouse over variable inspection
Drag and drop variables from source to watch
windows
Extensive on-line help
Integration of select third party tools, such as
IAR C Compilers
The MPLAB IDE allows you to:
Edit your source files (either C or assembly)
One-touch compile or assemble, and download to
emulator and simulator tools (automatically
updates all project information)
Debug using:
- Source files (C or assembly)
- Mixed C and assembly
- Machine code
MPLAB IDE supports multiple debugging tools in a
single development paradigm, from the cost-effective
simulators, through low-cost in-circuit debuggers, to
full-featured emulators. This eliminates the learning
curve when upgrading to tools with increased flexibility
and power.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 330 © 2009 Microchip Technology Inc.
26.2 MPLAB C Compilers for Various
Device Families
The MPLAB C Compiler code development systems
are complete ANSI C compilers for Microchip’s PIC18,
PIC24 and PIC32 families of microcontrollers and the
dsPIC30 and dsPIC33 families of digital signal control-
lers. These compilers provide powerful integration
capabilities, superior code optimization and ease of
use.
For easy source level debugging, the compilers provide
symbol information that is optimized to the MPLAB IDE
debugger.
26.3 HI-TECH C for Various Device
Families
The HI-TECH C Compiler code development systems
are complete ANSI C compilers for Microchip’s PIC
family of microcontrollers and the dsPIC family of digital
signal controllers. These compilers provide powerful
integration capabilities, omniscient code generation
and ease of use.
For easy source level debugging, the compilers provide
symbol information that is optimized to the MPLAB IDE
debugger.
The compilers include a macro assembler, linker, pre-
processor, and one-step driver, and can run on multiple
platforms.
26.4 MPASM Assembler
The MPASM Assembler is a full-featured, universal
macro assembler for PIC10/12/16/18 MCUs.
The MPASM Assembler generates relocatable object
files for the MPLINK Object Linker, Intel® standard HEX
files, MAP files to detail memory usage and symbol
reference, absolute LST files that contain source lines
and generated machine code and COFF files for
debugging.
The MPASM Assembler features include:
Integration into MPLAB IDE projects
User-defined macros to streamline
assembly code
Conditional assembly for multi-purpose
source files
Directives that allow complete control over the
assembly process
26.5 MPLINK Object Linker/
MPLIB Object Librarian
The MPLINK Object Linker combines relocatable
objects created by the MPASM Assembler and the
MPLAB C18 C Compiler. It can link relocatable objects
from precompiled libraries, using directives from a
linker script.
The MPLIB Object Librarian manages the creation and
modification of library files of precompiled code. When
a routine from a library is called from a source file, only
the modules that contain that routine will be linked in
with the application. This allows large libraries to be
used efficiently in many different applications.
The object linker/library features include:
Efficient linking of single libraries instead of many
smaller files
Enhanced code maintainability by grouping
related modules together
Flexible creation of libraries with easy module
listing, replacement, deletion and extraction
26.6 MPLAB Assembler, Linker and
Librarian for Various Device
Families
MPLAB Assembler produces relocatable machine
code from symbolic assembly language for PIC24,
PIC32 and dsPIC devices. MPLAB C Compiler uses
the assembler to produce its object file. The assembler
generates relocatable object files that can then be
archived or linked with other relocatable object files and
archives to create an executable file. Notable features
of the assembler include:
Support for the entire device instruction set
Support for fixed-point and floating-point data
Command line interface
Rich directive set
Flexible macro language
MPLAB IDE compatibility
© 2009 Microchip Technology Inc. DS39689F-page 331
PIC18F2221/2321/4221/4321 FAMILY
26.7 MPLAB SIM Software Simulator
The MPLAB SIM Software Simulator allows code
development in a PC-hosted environment by simulat-
ing the PIC MCUs and dsPIC® DSCs on an instruction
level. On any given instruction, the data areas can be
examined or modified and stimuli can be applied from
a comprehensive stimulus controller. Registers can be
logged to files for further run-time analysis. The trace
buffer and logic analyzer display extend the power of
the simulator to record and track program execution,
actions on I/O, most peripherals and internal registers.
The MPLAB SIM Software Simulator fully supports
symbolic debugging using the MPLAB C Compilers,
and the MPASM and MPLAB Assemblers. The soft-
ware simulator offers the flexibility to develop and
debug code outside of the hardware laboratory envi-
ronment, making it an excellent, economical software
development tool.
26.8 MPLAB REAL ICE In-Circuit
Emulator System
MPLAB REAL ICE In-Circuit Emulator System is
Microchip’s next generation high-speed emulator for
Microchip Flash DSC and MCU devices. It debugs and
programs PIC® Flash MCUs and dsPIC® Flash DSCs
with the easy-to-use, powerful graphical user interface of
the MPLAB Integrated Development Environment (IDE),
included with each kit.
The emulator is connected to the design engineer’s PC
using a high-speed USB 2.0 interface and is connected
to the target with either a connector compatible with in-
circuit debugger systems (RJ11) or with the new high-
speed, noise tolerant, Low-Voltage Differential Signal
(LVDS) interconnection (CAT5).
The emulator is field upgradable through future firmware
downloads in MPLAB IDE. In upcoming releases of
MPLAB IDE, new devices will be supported, and new
features will be added. MPLAB REAL ICE offers signifi-
cant advantages over competitive emulators including
low-cost, full-speed emulation, run-time variable
watches, trace analysis, complex breakpoints, a rugge-
dized probe interface and long (up to three meters) inter-
connection cables.
26.9 MPLAB ICD 3 In-Circuit Debugger
System
MPLAB ICD 3 In-Circuit Debugger System is Micro-
chip's most cost effective high-speed hardware
debugger/programmer for Microchip Flash Digital Sig-
nal Controller (DSC) and microcontroller (MCU)
devices. It debugs and programs PIC® Flash microcon-
trollers and dsPIC® DSCs with the powerful, yet easy-
to-use graphical user interface of MPLAB Integrated
Development Environment (IDE).
The MPLAB ICD 3 In-Circuit Debugger probe is con-
nected to the design engineer's PC using a high-speed
USB 2.0 interface and is connected to the target with a
connector compatible with the MPLAB ICD 2 or MPLAB
REAL ICE systems (RJ-11). MPLAB ICD 3 supports all
MPLAB ICD 2 headers.
26.10 PICkit 3 In-Circuit Debugger/
Programmer and
PICkit 3 Debug Express
The MPLAB PICkit 3 allows debugging and program-
ming of PIC® and dsPIC® Flash microcontrollers at a
most affordable price point using the powerful graphical
user interface of the MPLAB Integrated Development
Environment (IDE). The MPLAB PICkit 3 is connected
to the design engineer's PC using a full speed USB
interface and can be connected to the target via an
Microchip debug (RJ-11) connector (compatible with
MPLAB ICD 3 and MPLAB REAL ICE). The connector
uses two device I/O pins and the reset line to imple-
ment in-circuit debugging and In-Circuit Serial Pro-
gramming™.
The PICkit 3 Debug Express include the PICkit 3, demo
board and microcontroller, hookup cables and CDROM
with user’s guide, lessons, tutorial, compiler and
MPLAB IDE software.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 332 © 2009 Microchip Technology Inc.
26.11 PICkit 2 Development
Programmer/Debugger and
PICkit 2 Debug Express
The PICkit™ 2 Development Programmer/Debugger is
a low-cost development tool with an easy to use inter-
face for programming and debugging Microchip’s Flash
families of microcontrollers. The full featured
Windows® programming interface supports baseline
(PIC10F, PIC12F5xx, PIC16F5xx), midrange
(PIC12F6xx, PIC16F), PIC18F, PIC24, dsPIC30,
dsPIC33, and PIC32 families of 8-bit, 16-bit, and 32-bit
microcontrollers, and many Microchip Serial EEPROM
products. With Microchip’s powerful MPLAB Integrated
Development Environment (IDE) the PICkit™ 2
enables in-circuit debugging on most PIC® microcon-
trollers. In-Circuit-Debugging runs, halts and single
steps the program while the PIC microcontroller is
embedded in the application. When halted at a break-
point, the file registers can be examined and modified.
The PICkit 2 Debug Express include the PICkit 2, demo
board and microcontroller, hookup cables and CDROM
with user’s guide, lessons, tutorial, compiler and
MPLAB IDE software.
26.12 MPLAB PM3 Device Programmer
The MPLAB PM3 Device Programmer is a universal,
CE compliant device programmer with programmable
voltage verification at VDDMIN and VDDMAX for
maximum reliability. It features a large LCD display
(128 x 64) for menus and error messages and a modu-
lar, detachable socket assembly to support various
package types. The ICSP™ cable assembly is included
as a standard item. In Stand-Alone mode, the MPLAB
PM3 Device Programmer can read, verify and program
PIC devices without a PC connection. It can also set
code protection in this mode. The MPLAB PM3
connects to the host PC via an RS-232 or USB cable.
The MPLAB PM3 has high-speed communications and
optimized algorithms for quick programming of large
memory devices and incorporates an MMC card for file
storage and data applications.
26.13 Demonstration/Development
Boards, Evaluation Kits, and
Starter Kits
A wide variety of demonstration, development and
evaluation boards for various PIC MCUs and dsPIC
DSCs allows quick application development on fully func-
tional systems. Most boards include prototyping areas for
adding custom circuitry and provide application firmware
and source code for examination and modification.
The boards support a variety of features, including LEDs,
temperature sensors, switches, speakers, RS-232
interfaces, LCD displays, potentiometers and additional
EEPROM memory.
The demonstration and development boards can be
used in teaching environments, for prototyping custom
circuits and for learning about various microcontroller
applications.
In addition to the PICDEM™ and dsPICDEM™ demon-
stration/development board series of circuits, Microchip
has a line of evaluation kits and demonstration software
for analog filter design, KEELOQ® security ICs, CAN,
IrDA®, PowerSmart battery management, SEEVAL®
evaluation system, Sigma-Delta ADC, flow rate
sensing, plus many more.
Also available are starter kits that contain everything
needed to experience the specified device. This usually
includes a single application and debug capability, all
on one board.
Check the Microchip web page (www.microchip.com)
for the complete list of demonstration, development
and evaluation kits.
© 2009 Microchip Technology Inc. DS39689F-page 333
PIC18F2221/2321/4221/4321 FAMILY
27.0 ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings(†)
Ambient temperature under bias.............................................................................................................-40°C to +125°C
Storage temperature .............................................................................................................................. -65°C to +150°C
Voltage on any pin with respect to VSS (except VDD and MCLR) ................................................... -0.3V to (VDD + 0.3V)
Voltage on VDD with respect to VSS ......................................................................................................... -0.3V to +7.5V
Voltage on MCLR with respect to VSS (Note 2) ......................................................................................... 0V to +13.25V
Total power dissipation (Note 1) ...............................................................................................................................1.0W
Maximum current out of VSS pin ...........................................................................................................................300 mA
Maximum current into VDD pin ..............................................................................................................................250 mA
Input clamp current, IIK (VI < 0 or VI > VDD)...................................................................................................................... ±20 mA
Output clamp current, IOK (VO < 0 or VO > VDD).............................................................................................................. ±20 mA
Maximum output current sunk by any I/O pin..........................................................................................................25 mA
Maximum output current sourced by any I/O pin ....................................................................................................25 mA
Maximum current sunk by all ports .......................................................................................................................200 mA
Maximum current sourced by all ports ..................................................................................................................200 mA
Note 1: Power dissipation is calculated as follows:
Pdis = VDD x {IDD IOH} + {(VDDVOH) x IOH} + (VOL x IOL)
2: Voltage spikes below VSS at the MCLR/VPP/RE3 pin, inducing currents greater than 80 mA, may cause
latch-up. Thus, a series resistor of 50-100Ω should be used when applying a “low” level to the MCLR/VPP/
RE3 pin, rather than pulling this pin directly to VSS.
NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at those or any other conditions above those
indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 334 © 2009 Microchip Technology Inc.
FIGURE 27-1: PIC18F2221/2321/4221/4321 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL)
FIGURE 27-2: PIC18F2221/2321/4221/4321 VOLTAGE-FREQUENCY GRAPH (EXTENDED)
Frequency
Voltage
6.0V
5.5V
4.5V
4.0V
2.0V
40 MHz
5.0V
3.5V
3.0V
2.5V
4.2V
Frequency
Voltage
6.0V
5.5V
4.5V
4.0V
2.0V
25 MHz
5.0V
3.5V
3.0V
2.5V
4.2V
© 2009 Microchip Technology Inc. DS39689F-page 335
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-3: PIC18LF2221/2321/4221/4321 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL)
Frequency
Voltage
6.0V
5.5V
4.5V
4.0V
2.0V
25 MHz
5.0V
3.5V
3.0V
2.5V
FMAX = (9.54 MHz/V) (VDDAPPMIN – 2.0V) + 4 MHz
Note: VDDAPPMIN is the minimum voltage of the PIC® device in the application.
4 MHz
4.2V
40 MHz
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 336 © 2009 Microchip Technology Inc.
27.1 DC Characteristics: Supply Voltage
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Symbol Characteristic Min Typ Max Units Conditions
D001 VDD Supply Voltage
PIC18LF2X21/4X21 2.0 5.5 V
PIC18F2X21/4X21 4.2 5.5 V
D001C AVDD Analog Supply Voltage VDD – 0.3V VDD + 0.3V V
D001D AVSS Analog Ground Voltage VSS – 0.3V VSS + 0.3V V
D002 VDR RAM Data Retention
Voltage(1)
1.5 V
D003 VPOR VDD Start Voltage
to Ensure Internal
Power-on Reset Signal
0.7 V See section on Power-on Reset for
details
D004 SVDD VDD Rise Rate
to Ensure Internal
Power-on Reset Signal
0.05 V/ms See section on Power-on Reset for
details
VBOR Brown-out Reset Voltage
D005 PIC18LF2X21/4X21
BORV<1:0> = 11 2.00 2.11 2.22 V
BORV<1:0> = 10 2.65 2.79 2.93 V
D005 All devices
BORV<1:0> = 01(2) 4.11 4.33 4.55 V
BORV<1:0> = 00 4.36 4.59 4.82 V
Legend: Shading of rows is to assist in readability of the table.
Note 1: This is the limit to which VDD can be lowered in Sleep mode, or during a device Reset, without losing RAM data.
2: With BOR enabled, full-speed operation (FOSC = 40 MHz) is supported until a BOR occurs. This is valid although
VDD may be below the minimum voltage for this frequency.
© 2009 Microchip Technology Inc. DS39689F-page 337
PIC18F2221/2321/4221/4321 FAMILY
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Power-Down Current (IPD)(1)
PIC18LF2X21/4X21 0.5 0.7 μA -40°C VDD = 2.0V
(Sleep mode)
0.5 0.7 μA +25°C
0.5 1.7 μA +85°C
PIC18LF2X21/4X21 0.6 0.9 μA-40°C VDD = 3.0V
(Sleep mode)
0.6 0.9 μA +25°C
0.6 1.9 μA +85°C
All Devices 0.9 2.0 μA-40°C
VDD = 5.0V
(Sleep mode)
0.9 2.0 μA +25°C
0.9 6.5 μA +85°C
Extended Devices Only 7.5 70 μA +125°C
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 338 © 2009 Microchip Technology Inc.
Supply Current (IDD)(2)
PIC18LF2X21/4X21 13 19 μA-40°C
VDD = 2.0V
FOSC = 31 kHz
(RC_RUN mode,
INTRC source)
13 19 μA+25°C
13 17 μA+85°C
PIC18LF2X21/4X21 41 45 μA-40°C
VDD = 3.0V34 38 μA+25°C
27 30 μA+85°C
All Devices 104 115 μA-40°C
VDD = 5.0V
86 95 μA+25°C
67 75 μA+85°C
Extended Devices Only 68 100 μA +125°C
PIC18LF2X21/4X21 0.31 0.35 mA -40°C
VDD = 2.0V
FOSC = 1 MHz
(RC_RUN mode,
INTOSC source)
0.31 0.35 mA +25°C
0.31 0.35 mA +85°C
PIC18LF2X21/4X21 0.55 0.60 mA -40°C
VDD = 3.0V0.51 0.60 mA +25°C
0.47 0.60 mA +85°C
All Devices 1.0 1.3 mA -40°C
VDD = 5.0V
0.94 1.3 mA +25°C
0.88 1.2 mA +85°C
Extended Devices Only 0.88 1.2 mA +125°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
© 2009 Microchip Technology Inc. DS39689F-page 339
PIC18F2221/2321/4221/4321 FAMILY
Supply Current (IDD)(2)
PIC18LF2X21/4X21 0.69 0.9 mA -40°C
VDD = 2.0V
FOSC = 4 MHz
(RC_RUN mode,
INTOSC source)
0.70 0.9 mA +25°C
0.71 0.9 mA +85°C
PIC18LF2X21/4X21 1.17 1.45 mA -40°C
VDD = 3.0V1.15 1.45 mA +25°C
1.14 1.45 mA +85°C
All Devices 2.24 2.9 mA -40°C
VDD = 5.0V
2.20 2.9 mA +25°C
2.16 2.8 mA +85°C
Extended Devices Only 2.18 2.8 mA +125°C
PIC18LF2X21/4X21 3 5 μA-40°C
VDD = 2.0V
FOSC = 31 kHz
(RC_IDLE mode,
INTRC source)
35μA+25°C
35.6μA+85°C
PIC18LF2X21/4X21 4 7 μA-40°C
VDD = 3.0V57μA+25°C
510μA+85°C
All Devices 10 12 μA-40°C
VDD = 5.0V
10 12 μA+25°C
10 16 μA+85°C
Extended Devices Only 17 50 μA +125°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 340 © 2009 Microchip Technology Inc.
Supply Current (IDD)(2)
PIC18LF2X21/4X21 160 230 μA-40°C
VDD = 2.0V
FOSC = 1 MHz
(RC_IDLE mode,
INTOSC source)
170 230 μA+25°C
170 230 μA+85°C
PIC18LF2X21/4X21 220 330 μA-40°C
VDD = 3.0V240 330 μA+25°C
250 330 μA+85°C
All Devices 410 500 μA-40°C
VDD = 5.0V
420 500 μA+25°C
430 500 μA+85°C
Extended Devices Only 450 500 μA+125°C
PIC18LF2X21/4X21 310 440 μA-40°C
VDD = 2.0V
FOSC = 4 MHz
(RC_IDLE mode,
INTOSC source)
330 440 μA+25°C
340 440 μA+85°C
PIC18LF2X21/4X21 480 750 μA-40°C
VDD = 3.0V500 750 μA+25°C
520 750 μA+85°C
All Devices 0.91 1.3 mA -40°C
VDD = 5.0V
0.93 1.3 mA +25°C
0.96 1.3 mA +85°C
Extended Devices Only 0.98 1.3 mA +125°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
© 2009 Microchip Technology Inc. DS39689F-page 341
PIC18F2221/2321/4221/4321 FAMILY
Supply Current (IDD)(2)
PIC18LF2X21/4X21 0.22 0.35 mA -40°C
VDD = 2.0V
FOSC = 1 MHz
(PRI_RUN mode,
EC oscillator)
0.22 0.35 mA +25°C
0.21 0.3 mA +85°C
PIC18LF2X21/4X21 0.51 0.55 mA -40°C
VDD = 3.0V0.45 0.50 mA +25°C
0.39 0.45 mA +85°C
All Devices 1.14 1.15 mA -40°C
VDD = 5.0V
0.99 1.1 mA +25°C
0.83 1.1 mA +85°C
Extended Devices Only 0.80 1.1 mA +125°C
PIC18LF2X21/4X21 610 870 μA-40°C
VDD = 2.0V
FOSC = 4 MHz
(PRI_RUN mode,
EC oscillator)
610 870 μA+25°C
610 870 μA+85°C
PIC18LF2X21/4X21 1.16 1.83 mA -40°C
VDD = 3.0V1.10 1.83 mA +25°C
1.07 1.83 mA +85°C
All Devices 2.35 2.85 mA -40°C
VDD = 5.0V
2.24 2.85 mA +25°C
2.14 2.85 mA +85°C
Extended Devices Only 2.14 2.85 mA +125°C
Extended Devices Only 9 15 mA +125°C VDD = 4.2V FOSC = 25 MHz
(PRI_RUN mode,
EC oscillator)
12 20 mA +125°C VDD = 5.0V
All Devices 16 19 mA -40°C
VDD = 4.2V
FOSC = 40 MHz
(PRI_RUN mode,
EC oscillator)
14 19 mA +25°C
14 19 mA +85°C
All Devices 17 22.7 mA -40°C
VDD = 5.0V17 22.7 mA +25°C
17 22.7 mA +85°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 342 © 2009 Microchip Technology Inc.
Supply Current (IDD)(2)
All Devices 7 10 mA -40°C
VDD = 4.2V
FOSC = 4 MHz,
16 MHz internal
(PRI_RUN HS+PLL)
610mA +25°C
610mA +85°C
Extended Devices Only 6 10 mA +125°C
All Devices 10 12 mA -40°C
VDD = 5.0V
FOSC = 4 MHz,
16 MHz internal
(PRI_RUN HS+PLL)
912mA +25°C
912mA +85°C
Extended Devices Only 9 12 mA +125°C
All Devices 17 19 mA -40°C
VDD = 4.2V
FOSC = 10 MHz,
40 MHz internal
(PRI_RUN HS+PLL)
15 19 mA +25°C
15 19 mA +85°C
All Devices 18 23 mA -40°C
VDD = 5.0V
FOSC = 10 MHz,
40 MHz internal
(PRI_RUN HS+PLL)
18 23 mA +25°C
18 23 mA +85°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
© 2009 Microchip Technology Inc. DS39689F-page 343
PIC18F2221/2321/4221/4321 FAMILY
Supply Current (IDD)(2)
PIC18LF2X21/4X21 51 75 μA-40°C
VDD = 2.0V
FOSC = 1 MHz
(PRI_IDLE mode,
EC oscillator)
54 75 μA+25°C
60 75 μA+85°C
PIC18LF2X21/4X21 83 123 μA-40°C
VDD = 3.0V88 123 μA+25°C
93 123 μA+85°C
All Devices 180 260 μA-40°C
VDD = 5.0V
180 260 μA+25°C
180 260 μA+85°C
Extended Devices Only 190 260 μA +125°C
PIC18LF2X21/4X21 210 290 μA-40°C
VDD = 2.0V
FOSC = 4 MHz
(PRI_IDLE mode,
EC oscillator)
220 290 μA+25°C
230 290 μA+85°C
PIC18LF2X21/4X21 350 480 μA-40°C
VDD = 3.0V360 480 μA+25°C
370 480 μA+85°C
All Devices 0.69 1 mA -40°C
VDD = 5.0V
0.70 1 mA +25°C
0.72 1 mA +85°C
Extended Devices Only 0.74 1 mA +125°C
Extended Devices Only 3.7 4.0 mA +125°C VDD = 4.2V FOSC = 25 MHz
(PRI_IDLE mode,
EC oscillator)
4.6 5.0 mA +125°C VDD = 5.0V
All Devices 6.0 7.3 mA -40°C
VDD = 4.2V
FOSC = 40 MHz
(PRI_IDLE mode,
EC oscillator)
6.2 7.3 mA +25°C
6.6 7.3 mA +85°C
All Devices 6.8 9.2 mA -40°C
VDD = 5.0V7.0 9.2 mA +25°C
7.1 9.2 mA +85°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 344 © 2009 Microchip Technology Inc.
Supply Current (IDD)(2)
PIC18LF2X21/4X21 12 19 μA -40°C(5)
VDD = 2.0V
FOSC = 32 kHz
(SEC_RUN mode,
Timer1 as clock)(3)
—19μA-10°C
13 19 μA+25°C
13 19 μA+85°C
PIC18LF2X21/4X21 40 45 μA -40°C(5)
VDD = 3.0V
—45μA-10°C
33 45 μA+25°C
27 45 μA+85°C
All Devices 101 115 μA -40°C(5)
VDD = 5.0V
—110μA-10°C
83 110 μA+25°C
65 88 μA+85°C
PIC18LF2X21/4X21 2.5 5 μA -40°C(5)
VDD = 2.0V
FOSC = 32 kHz
(SEC_IDLE mode,
Timer1 as clock)(3)
—5μA-10°C
3.0 5 μA+25°C
3.5 8 μA+85°C
PIC18LF2X21/4X21 3.9 7 μA -40°C(5)
VDD = 3.0V
—7μA-10°C
4.5 7 μA+25°C
5.2 10.7 μA+85°C
All Devices 7.5 10 μA -40°C(5)
VDD = 5.0V
—10μA-10°C
8.0 10 μA+25°C
8.6 15 μA+85°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
© 2009 Microchip Technology Inc. DS39689F-page 345
PIC18F2221/2321/4221/4321 FAMILY
Module Differential Currents (ΔIWDT, ΔIBOR, ΔILVD, ΔIOSCB, ΔIAD)
D022
(ΔIWDT)
Watchdog Timer 1.6 2.5 μA-40°C
VDD = 2.0V1.6 2.5 μA+25°C
1.5 2.5 μA+85°C
2.3 3.5 μA-40°C
VDD = 3.0V2.2 3.5 μA+25°C
2.1 3 μA+85°C
3.4 7.4 μA-40°C
VDD = 5.0V
3.9 7.4 μA+25°C
4.4 7.4 μA+85°C
4.5 7.4 μA +125°C
D022A
(ΔIBOR)
Brown-out Reset(4) 34 45 μA -40°C to +85°C VDD = 3.0V
40 62.6 μA -40°C to +85°C VDD = 5.0V
42 62.6 μA -40°C to +125°C
02μA -40°C to +85°C VDD = 3.0V Sleep mode,
BOREN<1:0> = 10
05μA -40°C to +125°C VDD = 5.0V
D022B
(ΔILVD)
High/Low-Voltage
Detect(4)
23 35 μA -40°C to +85°C VDD = 2.0V
23 35 μA -40°C to +85°C VDD = 3.0V
28 35 μA -40°C to +85°C VDD = 5.0V
30 40 μA -40°C to +125°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 346 © 2009 Microchip Technology Inc.
D025
(ΔIOSCB)
Timer1 Oscillator 2.1 4.5 μA -40°C(5)
VDD = 2.0V
32 kHz Tuning Fork,
Crystal on Timer1
Oscillator(3)
—4.5μA-10°C
1.8 4.5 μA+25°C
2.1 4.5 μA+85°C
2.2 6.0 μA -40°C(5)
VDD = 3.0V
—6μA-10°C
2.6 6.0 μA+25°C
2.9 6.0 μA+85°C
3.0 8.0 μA -40°C(5)
VDD = 5.0V
—8μA-10°C
3.2 8.0 μA+25°C
3.4 8.0 μA+85°C
D026
(ΔIAD)
A/D Converter 1.0 2.0 μA -40°C to +85°C VDD = 2.0V
A/D on, Not Converting
1.0 2.0 μA -40°C to +85°C VDD = 3.0V
1.0 2.0 μA -40°C to +85°C VDD = 5.0V
2.0 8.0 μA -40°C to +125°C
27.2 DC Characteristics: Power-Down and Supply Current
PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
PIC18LF2221/2321/4221/4321
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
PIC18F2221/2321/4221/4321
(Industrial, Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Typ Max Units Conditions
Legend: Shading of rows is to assist in readability of the table.
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured
with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that
add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).
2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin
loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have
an impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;
MCLR = VDD; WDT enabled/disabled as specified.
3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.
4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less
than the sum of both specifications.
5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.
© 2009 Microchip Technology Inc. DS39689F-page 347
PIC18F2221/2321/4221/4321 FAMILY
27.3 DC Characteristics: PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial)
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C TA +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Symbol Characteristic Min Max Units Conditions
VIL Input Low Voltage
I/O Ports:
D030 with TTL Buffer VSS 0.15 VDD VVDD < 4.5V
D030A 0.8 V 4.5V VDD 5.5V
D031 with Schmitt Trigger Buffer VSS 0.2 VDD V
D031A RC3 and RC4 VSS 0.3 VDD VI
2C™ enabled
D031B VSS 0.8 V SMBus enabled
D032 MCLR VSS 0.2 VDD V
D033 OSC1 VSS 0.3 VDD V HS, HSPLL modes
D033A
D033B
D034
OSC1
OSC1
T13CKI
VSS
VSS
VSS
0.2 VDD
0.3
0.3
V
V
V
RC, EC modes(1)
XT, LP modes
VIH Input High Voltage
I/O Ports:
D040 with TTL Buffer 0.25 VDD +
0.8V
VDD VVDD < 4.5V
D040A 2.0 VDD V4.5V VDD 5.5V
D041 with Schmitt Trigger Buffer 0.8 VDD VDD V
D041A RC3 and RC4 0.7 VDD VDD VI
2C™ enabled
D041B 2.1 VDD V SMBus enabled,
VSS 3V
D042 MCLR 0.8 VDD VDD V
D043 OSC1 0.7 VDD VDD V HS, HSPLL modes
D043A
D043B
D043C
D044
OSC1
OSC1
OSC1
T13CKI
0.8 VDD
0.9 VDD
1.6
1.6
VDD
VDD
VDD
VDD
V
V
V
V
EC mode
RC mode(1)
XT, LP modes
IIL Input Leakage Current(2,3)
D060 I/O Ports
±200
±50
nA
nA
VDD < 5.5V,
VSS VPIN VDD,
Pin at High-Impedance
VDD < 3V,
VSS VPIN VDD,
Pin at High-Impedance
D061 MCLR ±1 μAVss VPIN VDD
D063 OSC1 ±1 μAVss VPIN VDD
Note 1: In RC oscillator configuration, the OSC1/CLKI pin is a Schmitt Trigger input. It is not recommended that the
PIC® device be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified
levels represent normal operating conditions. Higher leakage current may be measured at different input
voltages.
3: Negative current is defined as current sourced by the pin.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 348 © 2009 Microchip Technology Inc.
IPU Weak Pull-up Current
D070 IPURB PORTB Weak Pull-up Current 50 400 μAVDD = 5V, VPIN = VSS
VOL Output Low Voltage
D080 I/O Ports 0.6 V IOL = 8.5 mA, VDD = 4.5V,
-40°C to +85°C
D083 OSC2/CLKO
(RC, RCIO, EC, ECIO modes)
—0.6VI
OL = 1.6 mA, VDD = 4.5V,
-40°C to +85°C
VOH Output High Voltage(3)
D090 I/O Ports VDD – 0.7 V IOH = -3.0 mA, VDD = 4.5V,
-40°C to +85°C
D092 OSC2/CLKO
(RC, RCIO, EC, ECIO modes)
VDD – 0.7 V IOH = -1.3 mA, VDD = 4.5V,
-40°C to +85°C
Capacitive Loading Specs
on Output Pins
D100 COSC2 OSC2 Pin 15 pF In XT, HS and LP modes
when external clock is used
to drive OSC1
D101 CIO All I/O Pins and OSC2
(in RC mode)
50 pF Maximum that allows the
AC Timing Specifications to
be met
D102 CBSCL, SDA 400 pF Maximum bus capacitance
permitted by I2C™
Specification
27.3 DC Characteristics: PIC18F2221/2321/4221/4321 (Industrial)
PIC18LF2221/2321/4221/4321 (Industrial) (Continued)
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C TA +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Symbol Characteristic Min Max Units Conditions
Note 1: In RC oscillator configuration, the OSC1/CLKI pin is a Schmitt Trigger input. It is not recommended that the
PIC® device be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified
levels represent normal operating conditions. Higher leakage current may be measured at different input
voltages.
3: Negative current is defined as current sourced by the pin.
© 2009 Microchip Technology Inc. DS39689F-page 349
PIC18F2221/2321/4221/4321 FAMILY
TABLE 27-1: MEMORY PROGRAMMING REQUIREMENTS
DC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C TA +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Sym Characteristic Min Typ† Max Units Conditions
Data EEPROM Memory
D120 EDByte Endurance 1M 10M E/W -40°C to +85°C
D121 VDRW VDD for Read/Write VMIN 5.5 V Using EECON to read/write,
VMIN = Minimum operating
voltage
D122 TDEW Erase/Write Cycle Time 4 ms
D123 TRETD Characteristic Retention 40 Year Provided no other
specifications are violated
D124 TREF Number of Total Erase/Write
Cycles before Refresh(1)
100K 1M E/W -40°C to +85°C
D125 IDDP Supply Current during
Programming
—10—mA
Program Flash Memory
D130 EPCell Endurance 10K 100K E/W -40°C to +85°C
D131 VPR VDD for Read VMIN —5.5VVMIN = Minimum operating
voltage
D132 VIE VDD for Block Erase 3.0 5.5 V Using ICSP™ port, 25°C
D132B VPEW VDD for Self-Timed Write VMIN —5.5VVMIN = Minimum operating
voltage
D133A TIW Self-Timed Write Cycle Time 2 ms
D134 TRETD Characteristic Retention 40 100 Year Provided no other
specifications are violated
D135 IDDP Supply Current during
Programming
—10—mA
Data in “Typ” column is at 5.0V, 25°C unless otherwise stated. These parameters are for design guidance
only and are not tested.
Note 1: Refer to Section 8.7 “Using the Data EEPROM for a more detailed discussion on data EEPROM
endurance.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 350 © 2009 Microchip Technology Inc.
TABLE 27-2: COMPARATOR SPECIFICATIONS
TABLE 27-3: VOLTAGE REFERENCE SPECIFICATIONS
Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C for industrial (unless otherwise stated)
-40°C < TA < +125°C for extended (unless otherwise stated)
Param
No. Sym Characteristics Min Typ Max Units Comments
D300 VIOFF Input Offset Voltage ±5.0 ±10 mV
D301 VICM Input Common Mode Voltage 0 VDD – 1.5 V
D302 CMRR Common Mode Rejection Ratio 55 dB
D303 TRESP Response Time(1) 150 400 ns PIC18FXXXX
D303A 150 600 ns PIC18LFXXXX,
VDD = 2.0V
D304 TMC2OV Comparator Mode Change to
Output Valid
—— 10μs
Note 1: Response time measured with one comparator input at (VDD1.5)/2, while the other input transitions
from VSS to VDD.
Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C for industrial (unless otherwise stated)
-40°C < TA < +125°C for extended (unless otherwise stated)
Param
No. Sym Characteristics Min Typ Max Units Comments
D310 VRES Resolution VDD/24 VDD/32 LSb
D311 VRAA Absolute Accuracy 1/2 LSb
D312 VRUR Unit Resistor Value (R) 2k Ω
D310 TSET Settling Time(1) — — 10 μs
Note 1: Settling time measured while CVRR = 1 and CVR<3:0> transitions from0000’ to1111’.
© 2009 Microchip Technology Inc. DS39689F-page 351
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-4: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS
TABLE 27-4: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C TA +85°C for industrial
-40°C TA +125°C for extended
Param
No. Symbol Characteristic Min Typ Max Units Conditions
D420 HLVD Voltage on VDD
Transition High-to-Low
LVV = 0000 2.06 2.17 2.28 V
LVV = 0001 2.12 2.23 2.34 V
LVV = 0010 2.24 2.36 2.48 V
LVV = 0011 2.32 2.44 2.56 V
LVV = 0100 2.47 2.60 2.73 V
LVV = 0101 2.65 2.79 2.93 V
LVV = 0110 2.74 2.89 3.04 V
LVV = 0111 2.96 3.12 3.28 V
LVV = 1000 3.22 3.39 3.56 V
LVV = 1001 3.37 3.55 3.73 V
LVV = 1010 3.52 3.71 3.90 V
LVV = 1011 3.70 3.90 4.10 V
LVV = 1100 3.90 4.11 4.32 V
LVV = 1101 4.11 4.33 4.55 V
LVV = 1110 4.36 4.59 4.82 V
LVV = 1111 1.10 1.20 1.30 V HLVDIN Input/Internal
Reference Voltage
VLVD
HLVDIF(1)
VDD
(HLVDIF set by hardware)
(HLVDIF can be
cleared in software)
Note 1: VDIRMAG = 0.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 352 © 2009 Microchip Technology Inc.
27.4 AC (Timing) Characteristics
27.4.1 TIMING PARAMETER SYMBOLOGY
The timing parameter symbols have been created
using one of the following formats:
1. TppS2ppS 3. TCC:ST (I2C specifications only)
2. TppS 4. Ts (I2C specifications only)
T
F Frequency T Time
Lowercase letters (pp) and their meanings:
pp
cc CCP1 osc OSC1
ck CLKO rd RD
cs CS rw RD or WR
di SDI sc SCK
do SDO ss SS
dt Data in t0 T0CKI
io I/O port t1 T13CKI
mc MCLR wr WR
Uppercase letters and their meanings:
S
F Fall P Period
HHigh RRise
I Invalid (High-impedance) V Valid
L Low Z High-impedance
I2C only
AA output access High High
BUF Bus free Low Low
T
CC:ST (I2C specifications only)
CC
HD Hold SU Setup
ST
DAT DATA input hold STO Stop condition
STA Start condition
© 2009 Microchip Technology Inc. DS39689F-page 353
PIC18F2221/2321/4221/4321 FAMILY
27.4.2 TIMING CONDITIONS
The temperature and voltages specified in Table 27-5
apply to all timing specifications unless otherwise
noted. Figure 27-5 specifies the load conditions for the
timing specifications.
TABLE 27-5: TEMPERATURE AND VOLTAGE SPECIFICATIONS – AC
FIGURE 27-5: LOAD CONDITIONS FOR DEVICE TIMING SPECIFICATIONS
Note: Because of space limitations, the generic
terms “PIC18FXXXX” and “PIC18LFXXXX”
are used throughout this section to refer to
the PIC18F2221/2321/4221/4321 and
PIC18LF2221/2321/4221/4321 families of
devices specifically and only those devices.
AC CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C TA +85°C for industrial
-40°C TA +125°C for extended
Operating voltage VDD range as described in DC spec Section 27.1 and
Section 27.3.
LF parts operate for industrial temperatures only.
VDD/2
CL
RL
Pin
Pin
VSS
VSS
CL
RL=464Ω
CL= 50 pF for all pins except OSC2/CLKO
and including D and E outputs as ports
Load Condition 1 Load Condition 2
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DS39689F-page 354 © 2009 Microchip Technology Inc.
27.4.3 TIMING DIAGRAMS AND SPECIFICATIONS
FIGURE 27-6: EXTERNAL CLOCK TIMING (ALL MODES EXCEPT PLL)
TABLE 27-6: EXTERNAL CLOCK TIMING REQUIREMENTS
Param.
No. Symbol Characteristic Min Max Units Conditions
1A FOSC External CLKI Frequency(1) DC 1 MHz XT, RC Oscillator mode
DC 25 MHz HS Oscillator mode
DC 40 MHz EC Oscillator mode
4 10 MHz HS+PLL Oscillator mode
DC 50 kHz LP Oscillator mode
Oscillator Frequency(1) DC 4 MHz RC Oscillator mode
0.1 4 MHz XT Oscillator mode
4 25 MHz HS Oscillator mode
5 200 kHz LP Oscillator mode
1T
OSC External CLKI Period(1) 1000 ns XT, RC Oscillator mode
40 ns HS Oscillator mode
25 ns EC Oscillator mode
100 250 ns HS+PLL Oscillator mode
32 μs LP Oscillator mode
Oscillator Period(1) 250 ns RC Oscillator mode
250 1 μs XT Oscillator mode
40 250 ns HS Oscillator mode
5209μs LP Oscillator mode
2T
CY Instruction Cycle Time(1) 100 ns TCY = 4/FOSC, Industrial
160 ns T
CY = 4/FOSC, Extended
3T
OSL,
T
OSH
External Clock in (OSC1)
High or Low Time
30 ns XT Oscillator mode
2.5 μs LP Oscillator mode
10 ns HS Oscillator mode
4T
OSR,
T
OSF
External Clock in (OSC1)
Rise or Fall Time
20 ns XT Oscillator mode
50 ns LP Oscillator mode
7.5 ns HS Oscillator mode
Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period for all configurations
except PLL. All specified values are based on characterization data for that particular oscillator type under
standard operating conditions with the device executing code. Exceeding these specified limits may result
in an unstable oscillator operation and/or higher than expected current consumption. All devices are tested
to operate at “min.” values with an external clock applied to the OSC1/CLKI pin. When an external clock
input is used, the “max.” cycle time limit is “DC” (no clock) for all devices.
OSC1
CLKO
Q4 Q1 Q2 Q3 Q4 Q1
1
2
3344
© 2009 Microchip Technology Inc. DS39689F-page 355
PIC18F2221/2321/4221/4321 FAMILY
TABLE 27-7: PLL CLOCK TIMING SPECIFICATIONS (VDD = 4.2V TO 5.5V)
TABLE 27-8: AC CHARACTERISTICS: INTERNAL RC ACCURACY
Param
No. Sym Characteristic Min Typ† Max Units Conditions
F10 FOSC Oscillator Frequency Range 4 10 MHz HS mode only
F11 FSYS On-Chip VCO System Frequency 16 40 MHz HS mode only
F12 trc PLL Start-up Time (Lock Time) 2 ms
F13 ΔCLK CLKO Stability (Jitter) -2 +2 %
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance
only and are not tested.
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C T
A +85°C for industrial
-40°C T
A +125°C for extended
Param
No. Device Min Typ Max Units Conditions
INTOSC Accuracy @ Freq = 8 MHz, 4 MHz, 2 MHz, 1 MHz, 500 kHz, 250 kHz, 125 kHz, 31 kHz(1)
PIC18LF2221/2321/4221/4321 -2 +/-1 2 % +25°C VDD = 2.0-5.5V
-5 5 % -10°C to +85°C VDD = 2.0-5.5V
-10 +/-1 10 % -40°C to +85°C VDD = 2.0-5.5V
PIC18F2221/2321/4221/4321 -2 +/-1 2 % +25°C VDD = 4.2-5.5V
-5 5 % -10°C to +85°C VDD = 4.2-5.5V
-10 +/-1 10 % -40°C to +85°C VDD = 4.2-5.5V
INTRC Accuracy @ Freq = 31 kHz
PIC18LF2221/2321/4221/4321 26.562 35.938 kHz -40°C to +85°C VDD = 2.0-5.5V
PIC18F2221/2321/4221/4321 26.562 35.938 kHz -40°C to +85°C VDD = 4.2-5.5V
Note 1: Frequency calibrated at 25°C. OSCTUNE register can be used to compensate for temperature drift.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 356 © 2009 Microchip Technology Inc.
FIGURE 27-7: CLKO AND I/O TIMING
TABLE 27-9: CLKO AND I/O TIMING REQUIREMENTS
Param
No. Symbol Characteristic Min Typ Max Units Conditions
10 TosH2ckL OSC1 to CLKO 75 200 ns (Note 1)
11 TosH2ckH OSC1 to CLKO 75 200 ns (Note 1)
12 TckR CLKO Rise Time 35 100 ns (Note 1)
13 TckF CLKO Fall Time 35 100 ns (Note 1)
14 TckL2ioV CLKO to Port Out Valid 0.5 T
CY + 20 ns (Note 1)
15 TioV2ckH Port In Valid before CLKO 0.25 T
CY + 25 ns (Note 1)
16 TckH2ioI Port In Hold after CLKO 0—ns(Note 1)
17 TosH2ioV OSC1 (Q1 cycle) to Port Out Valid 50 150 ns
18 TosH2ioI OSC1 (Q2 cycle) to
Port Input Invalid
(I/O in hold time)
PIC18FXXXX 100 ns
18A PIC18LFXXXX 200 ns VDD = 2.0V
19 TioV2osH Port Input Valid to OSC1 (I/O in setup time) 0 ns
20 TioR Port Output Rise Time PIC18FXXXX 10 25 ns
20A PIC18LFXXXX 60 ns VDD = 2.0V
21 TioF Port Output Fall Time PIC18FXXXX 10 25 ns
21A PIC18LFXXXX 60 ns VDD = 2.0V
22† TINP INTx Pin High or Low Time TCY ——ns
23† TRBP RB<7:4> Change INTx High or Low Time TCY ——ns
These parameters are asynchronous events not related to any internal clock edges.
Note 1: Measurements are taken in RC mode, where CLKO output is 4 x TOSC.
Note: Refer to Figure 27-5 for load conditions.
OSC1
CLKO
I/O pin
(Input)
I/O pin
(Output)
Q4 Q1 Q2 Q3
10
13
14
17
20, 21
19 18
15
11
12
16
Old Value New Value
© 2009 Microchip Technology Inc. DS39689F-page 357
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-8: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER AND
POWER-UP TIMER TIMING
FIGURE 27-9: BROWN-OUT RESET TIMING
TABLE 27-10: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER, POWER-UP TIMER
AND BROWN-OUT RESET REQUIREMENTS
Param.
No. Symbol Characteristic Min Typ Max Units Conditions
30 TmcL MCLR Pulse Width (low) 2 μs
31 TWDT Watchdog Timer Time-out Period
(no postscaler)
3.56 4.19 4.82 ms
32 TOST Oscillation Start-up Timer Period 1024 TOSC 1024 TOSC —TOSC = OSC1 period
33 TPWRT Power-up Timer Period 57 67 77 ms
34 TIOZ I/O High-Impedance from MCLR
Low or Watchdog Timer Reset
—2μs
35 TBOR Brown-out Reset Pulse Width 200 μsVDD BVDD (see D005)
36 TIRVST Time for Internal Reference
Voltage to become Stable
—2050 μs
37 TLVD High/Low-Voltage Detect Pulse Width 200 μsVDD VLVD
38 TCSD CPU Start-up Time 10 μs
39 TIOBST Time for INTOSC to Stabilize 1 μs
VDD
MCLR
Internal
POR
PWRT
Time-out
OSC
Time-out
Internal
Reset
Watchdog
Timer
Reset
33
32
30
31
34
I/O pins
34
VDD BVDD
35
VIRVST
Enable Internal
Internal Reference 36
Reference Voltage
Voltage Stable
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 358 © 2009 Microchip Technology Inc.
FIGURE 27-10: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS
TABLE 27-11: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS
Param
No. Symbol Characteristic Min Max Units Conditions
40 Tt0H T0CKI High Pulse Width No prescaler 0.5 T
CY + 20 ns
With prescaler 10 ns
41 Tt0L T0CKI Low Pulse Width No prescaler 0.5 TCY + 20 ns
With prescaler 10 ns
42 Tt0P T0CKI Period No prescaler TCY + 10 ns
With prescaler Greater of:
20 ns or
(TCY + 40)/N
ns N = prescale
value
(1, 2, 4,..., 256)
45 Tt1H T13CKI
High Time
Synchronous, no prescaler 0.5 TCY + 20 ns
Synchronous,
with prescaler
PIC18FXXXX 10 ns
PIC18LFXXXX 25 ns VDD = 2.0V
Asynchronous PIC18FXXXX 30 ns
PIC18LFXXXX 50 ns VDD = 2.0V
46 Tt1L T13CKI
Low Time
Synchronous, no prescaler 0.5 TCY + 5 ns
Synchronous,
with prescaler
PIC18FXXXX 10 ns
PIC18LFXXXX 25 ns VDD = 2.0V
Asynchronous PIC18FXXXX 30 ns
PIC18LFXXXX 50 ns VDD = 2.0V
47 Tt1P T13CKI
Input
Period
Synchronous Greater of:
20 ns or
(TCY + 40)/N
ns N = prescale
value (1, 2, 4, 8)
Asynchronous 60 ns
Ft1 T13CKI Oscillator Input Frequency Range DC 50 kHz
48 Tcke2tmrI Delay from External T13CKI Clock Edge to
Timer Increment
2 T
OSC 7 TOSC
46
47
45
48
41
42
40
T0CKI
T1OSO/T13CKI
TMR0 or
TMR1
© 2009 Microchip Technology Inc. DS39689F-page 359
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-11: CAPTURE/COMPARE/PWM TIMINGS (ALL CCP MODULES)
TABLE 27-12: CAPTURE/COMPARE/PWM REQUIREMENTS (ALL CCP MODULES)
Param
No. Symbol Characteristic Min Max Units Conditions
50 TccL CCPx Input Low
Time
No prescaler 0.5 TCY + 20 ns
With
prescaler
PIC18FXXXX 10 ns
PIC18LFXXXX 20 ns VDD = 2.0V
51 TccH CCPx Input
High Time
No prescaler 0.5 TCY + 20 ns
With
prescaler
PIC18FXXXX 10 ns
PIC18LFXXXX 20 ns VDD = 2.0V
52 TccP CCPx Input Period 3 TCY + 40
N
ns N = prescale
value (1, 4 or 16)
53 TccR CCPx Output Fall Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
54 TccF CCPx Output Fall Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
CCPx
(Capture Mode)
50 51
52
CCPx
53 54
(Compare or PWM Mode)
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 360 © 2009 Microchip Technology Inc.
FIGURE 27-12: PARALLEL SLAVE PORT TIMING (PIC18F4221/4321)
TABLE 27-13: PARALLEL SLAVE PORT REQUIREMENTS (PIC18F4221/4321)
Param.
No. Symbol Characteristic Min Max Units Conditions
62 TdtV2wrH Data In Valid before WR or CS (setup time) 20 ns
63 TwrH2dtI WR or CS to Data–In
Invalid (hold time)
PIC18FXXXX 20 ns
PIC18LFXXXX 35 ns VDD = 2.0V
64 TrdL2dtV RD and CS to Data–Out Valid 80 ns
65 TrdH2dtI RD or CS to Data–Out Invalid 10 30 ns
66 TibfINH Inhibit of the IBF Flag bit being Cleared from
WR or CS
—3 T
CY
Note: Refer to Figure 27-5 for load conditions.
RE2/CS
RE0/RD
RE1/WR
RD<7:0>
62
63
64
65
© 2009 Microchip Technology Inc. DS39689F-page 361
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-13: EXAMPLE SPI MASTER MODE TIMING (CKE = 0)
TABLE 27-14: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 0)
Param
No. Symbol Characteristic Min Max Units Conditions
73 TdiV2scH,
TdiV2scL
Setup Time of SDI Data Input to SCK Edge 20 ns
73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge
of Byte 2
1.5 TCY + 40 ns
74 TscH2diL,
TscL2diL
Hold Time of SDI Data Input to SCK Edge 40 ns
75 TdoR SDO Data Output Rise Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
76 TdoF SDO Data Output Fall Time 25 ns
78 TscR SCK Output Rise Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
79 TscF SCK Output Fall Time 25 ns
80 TscH2doV,
TscL2doV
SDO Data Output Valid after
SCK Edge
PIC18FXXXX 50 ns
PIC18LFXXXX 100 ns VDD = 2.0V
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
73
74
75, 76
78
79
80
79
78
MSb LSb
bit 6 - - - - - -1
MSb In LSb In
bit 6 - - - -1
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DS39689F-page 362 © 2009 Microchip Technology Inc.
FIGURE 27-14: EXAMPLE SPI MASTER MODE TIMING (CKE = 1)
TABLE 27-15: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 1)
Param.
No. Symbol Characteristic Min Max Units Conditions
73 TdiV2scH,
TdiV2scL
Setup Time of SDI Data Input to SCK Edge 20 ns
73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge
of Byte 2
1.5 TCY + 40 ns
74 TscH2diL,
Ts c L 2 d i L
Hold Time of SDI Data Input to SCK Edge 40 ns
75 TdoR SDO Data Output Rise Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
76 TdoF SDO Data Output Fall Time 25 ns
78 TscR SCK Output Rise Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
79 TscF SCK Output Fall Time 25 ns
80 TscH2doV,
TscL2doV
SDO Data Output Valid after
SCK Edge
PIC18FXXXX 50 ns
PIC18LFXXXX 100 ns VDD = 2.0V
81 TdoV2scH,
TdoV2scL
SDO Data Output Setup to SCK Edge TCY —ns
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
81
74
75, 76
78
80
MSb
79
73
MSb In
bit 6 - - - - - -1
LSb In
bit 6 - - - -1
LSb
© 2009 Microchip Technology Inc. DS39689F-page 363
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-15: EXAMPLE SPI SLAVE MODE TIMING (CKE = 0)
TABLE 27-16: EXAMPLE SPI MODE REQUIREMENTS (SLAVE MODE TIMING, CKE = 0)
Param
No. Symbol Characteristic Min Max Units Conditions
70 TssL2scH,
Ts s L 2s c L
SS to SCK or SCK Input 3 TCY —ns
71 TscH SCK Input High Time Continuous 1.25 TCY + 30 ns
71A Single Byte 40 ns (Note 1)
72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 ns
72A Single Byte 40 ns (Note 1)
73 TdiV2scH,
TdiV2scL
Setup Time of SDI Data Input to SCK Edge 20 ns
73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 ns (Note 2)
74 TscH2diL,
Ts c L 2 d iL
Hold Time of SDI Data Input to SCK Edge 40 ns
75 TdoR SDO Data Output Rise Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
76 TdoF SDO Data Output Fall Time 25 ns
77 TssH2doZ SS to SDO Output High-Impedance 10 50 ns
80 TscH2doV,
TscL2doV
SDO Data Output Valid after SCK Edge PIC18FXXXX 50 ns
PIC18LFXXXX 100 ns VDD = 2.0V
83 TscH2ssH,
Ts c L 2s s H
SS after SCK edge 1.5 TCY + 40 ns
Note 1: Requires the use of Parameter #73A.
2: Only if Parameter #71A and #72A are used.
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
70
71 72
73 74
75, 76 77
80
MSb LSb
bit 6 - - - - - -1
bit 6 - - - -1 LSb In
83
MSb In
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DS39689F-page 364 © 2009 Microchip Technology Inc.
FIGURE 27-16: EXAMPLE SPI SLAVE MODE TIMING (CKE = 1)
TABLE 27-17: EXAMPLE SPI SLAVE MODE REQUIREMENTS (CKE = 1)
Param
No. Symbol Characteristic Min Max Units Conditions
70 TssL2scH,
TssL2scL
SS to SCK or SCK Input 3 TCY —ns
71 TscH SCK Input High Time Continuous 1.25 TCY + 30 ns
71A Single Byte 40 ns (Note 1)
72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 ns
72A Single Byte 40 ns (Note 1)
73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 ns (Note 2)
74 TscH2diL,
TscL2diL
Hold Time of SDI Data Input to SCK Edge 40 ns
75 TdoR SDO Data Output Rise Time PIC18FXXXX 25 ns
PIC18LFXXXX 45 ns VDD = 2.0V
76 TdoF SDO Data Output Fall Time 25 ns
77 TssH2doZ SS to SDO Output High-Impedance 10 50 ns
80 TscH2doV,
TscL2doV
SDO Data Output Valid after SCK
Edge
PIC18FXXXX 50 ns
PIC18LFXXXX 100 ns VDD = 2.0V
82 TssL2doV SDO Data Output Valid after SS
Edge
PIC18FXXXX 50 ns
PIC18LFXXXX 100 ns VDD = 2.0V
83 TscH2ssH,
TscL2ssH
SS after SCK Edge 1.5 TCY + 40 ns
Note 1: Requires the use of Parameter #73A.
2: Only if Parameter #71A and #72A are used.
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
70
71 72
82
SDI
74
75, 76
MSb bit 6 - - - - - -1 LSb
77
MSb In bit 6 - - - -1 LSb In
80
83
© 2009 Microchip Technology Inc. DS39689F-page 365
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-17: I2C™ BUS START/STOP BITS TIMING
TABLE 27-18: I2C™ BUS START/STOP BITS REQUIREMENTS (SLAVE MODE)
FIGURE 27-18: I2C™ BUS DATA TIMING
Param.
No. Symbol Characteristic Min Max Units Conditions
90 TSU:STA Start Condition 100 kHz mode 4700 ns Only relevant for Repeated
Start condition
Setup Time 400 kHz mode 600
91 THD:STA Start Condition 100 kHz mode 4000 ns After this period, the first
clock pulse is generated
Hold Time 400 kHz mode 600
92 TSU:STO Stop Condition 100 kHz mode 4700 ns
Setup Time 400 kHz mode 600
93 THD:STO Stop Condition 100 kHz mode 4000 ns
Hold Time 400 kHz mode 600
91
92
93
SCL
SDA
Start
Condition
Stop
Condition
90
90
91 92
100
101
103
106 107
109 109
110
102
SCL
SDA
In
SDA
Out
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 366 © 2009 Microchip Technology Inc.
TABLE 27-19: I2C™ BUS DATA REQUIREMENTS (SLAVE MODE)
Param.
No. Symbol Characteristic Min Max Units Conditions
100 THIGH Clock High Time 100 kHz mode 4.0 μs
400 kHz mode 0.6 μs
MSSP Module 1.5 TCY
101 TLOW Clock Low Time 100 kHz mode 4.7 μs
400 kHz mode 1.3 μs
MSSP Module 1.5 TCY
102 TRSDA and SCL Rise
Time
100 kHz mode 1000 ns
400 kHz mode 20 + 0.1 CB300 ns CB is specified to be from
10 to 400 pF
103 TFSDA and SCL Fall
Time
100 kHz mode 300 ns
400 kHz mode 20 + 0.1 CB300 ns CB is specified to be from
10 to 400 pF
90 TSU:STA Start Condition
Setup Time
100 kHz mode 4.7 μs Only relevant for Repeated
Start condition
400 kHz mode 0.6 μs
91 THD:STA Start Condition
Hold Time
100 kHz mode 4.0 μs After this period, the first
clock pulse is generated
400 kHz mode 0.6 μs
106 THD:DAT Data Input Hold
Time
100 kHz mode 0 ns
400 kHz mode 0 0.9 μs
107 TSU:DAT Data Input Setup
Time
100 kHz mode 250 ns (Note 2)
400 kHz mode 100 ns
92 TSU:STO Stop Condition
Setup Time
100 kHz mode 4.7 μs
400 kHz mode 0.6 μs
109 TAA Output Valid from
Clock
100 kHz mode 3500 ns (Note 1)
400 kHz mode ns
110 TBUF Bus Free Time 100 kHz mode 4.7 μs Time the bus must be free
before a new transmission
can start
400 kHz mode 1.3 μs
D102 CBBus Capacitive Loading 400 pF
Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region
(min. 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.
2: A Fast mode I2C bus device can be used in a Standard mode I2C bus system, but the requirement
T
SU:DAT 250 ns must then be met. This will automatically be the case if the device does not stretch the
LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must
output the next data bit to the SDA line, TR max. + TSU:DAT = 1000 + 250 = 1250 ns (according to the
Standard mode I2C bus specification), before the SCL line is released.
© 2009 Microchip Technology Inc. DS39689F-page 367
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-19: MASTER SSP I2C™ BUS START/STOP BITS TIMING WAVEFORMS
TABLE 27-20: MASTER SSP I2C™ BUS START/STOP BITS REQUIREMENTS
FIGURE 27-20: MASTER SSP I2C™ BUS DATA TIMING
Param.
No. Symbol Characteristic Min Max Units Conditions
90 TSU:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) ns Only relevant for
Repeated Start
condition
Setup Time 400 kHz mode 2(TOSC)(BRG + 1)
1 MHz mode(1) 2(TOSC)(BRG + 1)
91 THD:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) ns After this period, the
first clock pulse is
generated
Hold Time 400 kHz mode 2(TOSC)(BRG + 1)
1 MHz mode(1) 2(TOSC)(BRG + 1)
92 TSU:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) ns
Setup Time 400 kHz mode 2(TOSC)(BRG + 1)
1 MHz mode(1) 2(TOSC)(BRG + 1)
93 THD:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) ns
Hold Time 400 kHz mode 2(TOSC)(BRG + 1)
1 MHz mode(1) 2(TOSC)(BRG + 1)
Note 1: Maximum pin capacitance = 10 pF for all I2C pins.
91 93
SCL
SDA
Start
Condition
Stop
Condition
90 92
90 91 92
100
101
103
106 107
109 109 110
102
SCL
SDA
In
SDA
Out
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 368 © 2009 Microchip Technology Inc.
TABLE 27-21: MASTER SSP I2C™ BUS DATA REQUIREMENTS
Param.
No. Symbol Characteristic Min Max Units Conditions
100 THIGH Clock High Time 100 kHz mode 2(TOSC)(BRG + 1) ms
400 kHz mode 2(TOSC)(BRG + 1) ms
1 MHz mode(1) 2(TOSC)(BRG + 1) ms
101 TLOW Clock Low Time 100 kHz mode 2(TOSC)(BRG + 1) ms
400 kHz mode 2(TOSC)(BRG + 1) ms
1 MHz mode(1) 2(TOSC)(BRG + 1) ms
102 TRSDA and SCL
Rise Time
100 kHz mode 1000 ns CB is specified to be from
10 to 400 pF
400 kHz mode 20 + 0.1 CB300 ns
1 MHz mode(1) 300 ns
103 TFSDA and SCL
Fall Time
100 kHz mode 300 ns CB is specified to be from
10 to 400 pF
400 kHz mode 20 + 0.1 CB 300 ns
1 MHz mode(1) 100 ns
90 T
SU:STA Start Condition
Setup Time
100 kHz mode 2(TOSC)(BRG + 1) ms Only relevant for
Repeated Start
condition
400 kHz mode 2(TOSC)(BRG + 1) ms
1 MHz mode(1) 2(TOSC)(BRG + 1) ms
91 THD:STA Start Condition
Hold Time
100 kHz mode 2(TOSC)(BRG + 1) ms After this period, the first
clock pulse is generated
400 kHz mode 2(TOSC)(BRG + 1) ms
1 MHz mode(1) 2(TOSC)(BRG + 1) ms
106 THD:DAT Data Input
Hold Time
100 kHz mode 0 ns
400 kHz mode 0 0.9 ms
107 T
SU:DAT Data Input
Setup Time
100 kHz mode 250 ns (Note 2)
400 kHz mode 100 ns
92 TSU:STO Stop Condition
Setup Time
100 kHz mode 2(TOSC)(BRG + 1) ms
400 kHz mode 2(TOSC)(BRG + 1) ms
1 MHz mode(1) 2(TOSC)(BRG + 1) ms
109 TAA Output Valid
from Clock
100 kHz mode 3500 ns
400 kHz mode 1000 ns
1 MHz mode(1) ——ns
110 TBUF Bus Free Time 100 kHz mode 4.7 ms Time the bus must be free
before a new transmission
can start
400 kHz mode 1.3 ms
D102 CBBus Capacitive Loading 400 pF
Note 1: Maximum pin capacitance = 10 pF for all I2C pins.
2: A Fast mode I2C bus device can be used in a Standard mode I2C bus system, but parameter 107 250 ns
must then be met. This will automatically be the case if the device does not stretch the LOW period of the
SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit
to the SDA line, parameter 102 + parameter 107 = 1000 + 250 = 1250 ns (for 100 kHz mode), before the
SCL line is released.
© 2009 Microchip Technology Inc. DS39689F-page 369
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-21: EUSART SYNCHRONOUS TRANSMISSION (MASTER/SLAVE) TIMING
TABLE 27-22: EUSART SYNCHRONOUS TRANSMISSION REQUIREMENTS
FIGURE 27-22: EUSART SYNCHRONOUS RECEIVE (MASTER/SLAVE) TIMING
TABLE 27-23: EUSART SYNCHRONOUS RECEIVE REQUIREMENTS
Param
No. Symbol Characteristic Min Max Units Conditions
120 TckH2dtV SYNC XMIT (MASTER & SLAVE)
Clock High to Data Out Valid PIC18FXXXX 40 ns
PIC18LFXXXX 100 ns VDD = 2.0V
121 Tckrf Clock Out Rise Time and Fall Time
(Master mode)
PIC18FXXXX 20 ns
PIC18LFXXXX 50 ns VDD = 2.0V
122 Tdtrf Data Out Rise Time and Fall Time PIC18FXXXX 20 ns
PIC18LFXXXX 50 ns VDD = 2.0V
Param.
No. Symbol Characteristic Min Max Units Conditions
125 TdtV2ckl SYNC RCV (MASTER & SLAVE)
Data Hold before CK (DT hold time) 10 ns
126 TckL2dtl Data Hold after CK (DT hold time) 15 ns
121 121
120 122
RC6/TX/CK
RC7/RX/DT
pin
pin
125
126
RC6/TX/CK
RC7/RX/DT
pin
pin
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 370 © 2009 Microchip Technology Inc.
TABLE 27-24: A/D CONVERTER CHARACTERISTICS
Param
No. Symbol Characteristic Min Typ Max Units Conditions
A01 NRResolution 10 bit ΔVREF 3.0V
A03 EIL Integral Linearity Error <±1 LSb ΔVREF 3.0V
A04 EDL Differential Linearity Error <±1 LSb ΔVREF 3.0V
A06 EOFF Offset Error <±2 LSb ΔVREF 3.0V
A07 EGN Gain Error <±1 LSb ΔVREF 3.0V
A10 Monotonicity Guaranteed(1) —VSS VAIN VREF
A20 ΔVREF Reference Voltage Range
(VREFH – VREFL)
1.8
3
V
V
VDD < 3.0V
VDD 3.0V
A21 VREFH Reference Voltage High VDD + 3.0V V
A22 VREFL Reference Voltage Low VSS – 0.3V V
A25 VAIN Analog Input Voltage VREFL —VREFH V
A30 ZAIN Recommended Impedance of
Analog Voltage Source
——2.5kΩ
A50 IREF VREF Input Current(2)
5
150
μA
μA
During VAIN acquisition.
During A/D conversion
cycle.
Note 1: The A/D conversion result never decreases with an increase in the input voltage and has no missing codes.
2: VREFH current is from RA3/AN3/VREF+ pin or VDD, whichever is selected as the VREFH source.
VREFL current is from RA2/AN2/VREF-/CVREF pin or VSS, whichever is selected as the VREFL source.
© 2009 Microchip Technology Inc. DS39689F-page 371
PIC18F2221/2321/4221/4321 FAMILY
FIGURE 27-23: A/D CONVERSION TIMING
TABLE 27-25: A/D CONVERSION REQUIREMENTS
Param
No. Symbol Characteristic Min Max Units Conditions
130 TAD A/D Clock Period PIC18FXXXX 0.7 25.0(1) μsTOSC based, VREF 3.0V
PIC18LFXXXX 1.4 25.0(1) μsVDD = 2.0V;
T
OSC based, VREF full range
PIC18FXXXX 1 μs A/D RC mode
PIC18LFXXXX 3 μsV
DD = 2.0V; A/D RC mode
131 TCNV Conversion Time
(not including acquisition time)(2)
11 12 TAD
132 TACQ Acquisition Time(3) 1.4 μs-40°C to +85°C
135 TSWC Switching Time from Convert Sample (Note 4)
137 TDIS Discharge Time 0.2 μs
Note 1: The time of the A/D clock period is dependent on the device frequency and the TAD clock divider.
2: ADRES register may be read on the following TCY cycle.
3: The time for the holding capacitor to acquire the “New” input voltage when the voltage changes full scale
after the conversion (VDD to VSS or VSS to VDD). The source impedance (RS) on the input channels is 50Ω.
4: On the following cycle of the device clock.
131
130
132
BSF ADCON0, GO
Q4
A/D CLK(1)
A/D DATA
ADRES
ADIF
GO
SAMPLE
OLD_DATA
SAMPLING STOPPED
DONE
NEW_DATA
(Note 2)
987 21 0
Note 1: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts.
This allows the SLEEP instruction to be executed.
2: This is a minimal RC delay (typically 100 ns), which also disconnects the holding capacitor from the analog input.
. . . . . .
TCY
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 372 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 373
PIC18F2221/2321/4221/4321 FAMILY
28.0 PACKAGING INFORMATION
28.1 Package Marking Information
28-Lead SPDIP
XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX
YYWWNNN
Example
PIC18F2321-I/SP
0910017
28-Lead SOIC
XXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXX
YYWWNNN
Example
PIC18F2321-E/SO
0910017
Legend: XX...X Customer-specific information
Y Year code (last digit of calendar year)
YY Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanumeric traceability code
Pb-free JEDEC designator for Matte Tin (Sn)
*This package is Pb-free. The Pb-free JEDEC designator ( )
can be found on the outer packaging for this package.
Note: In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line, thus limiting the number of available
characters for customer-specific information.
3
e
3
e
3
e
28-Lead QFN
XXXXXXXX
XXXXXXXX
YYWWNNN
Example
18F2321
/ML
0910017
3
e
28-Lead SSOP
XXXXXXXXXXXX
XXXXXXXXXXXX
YYWWNNN
Example
PIC18F2321
-I/SS
0910017
3
e
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 374 © 2009 Microchip Technology Inc.
28.1 Package Marking Information (Continued)
44-Lead TQFP
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
YYWWNNN
Example
PIC18F4321
-I/PT
0910017
XXXXXXXXXX
44-Lead QFN
XXXXXXXXXX
XXXXXXXXXX
YYWWNNN
PIC18F4321
Example
-I/ML
0910017
40-Lead PDIP
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
YYWWNNN
Example
PIC18F4321-I/P
0910017
3
e
3
e
3
e
© 2009 Microchip Technology Inc. DS39689F-page 375
PIC18F2221/2321/4221/4321 FAMILY
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NOTE 1
N
12
D
E1
eB
c
E
L
A2
eb
b1
A1
A
3
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PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 376 © 2009 Microchip Technology Inc.
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!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
6&! 99..
'!9'&! 7 7: ;
7"')%! 7 <
& 1,
: 8& = = ?
##44!!  = =
&#%%+   = -
: >#& . -1,
##4>#& . 1,
: 9& 1,
,'%@&A  = 
3&9& 9  = 
3&& 9 .3
3& IB = <B
9#4!! < = --
9#>#& ) - = 
#%& DB = B
#%&1&&' EB = B
c
h
h
L
L1
A2
A1
A
NOTE 1
123
b
e
E
E1
D
φ
β
α
N
  * ,1
© 2009 Microchip Technology Inc. DS39689F-page 377
PIC18F2221/2321/4221/4321 FAMILY
*+%!,-./.*+!
01'((),1
!"
  !"#$%&"' ()"&'"!&)&#*&&&#
 4!!*!"&#
- '!#&.0
1,2 1!'!&$& "!**&"&&!
.32 %'!("!"*&"&&(%%'&"!!
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
6&! 99..
'!9'&! 7 7: ;
7"')%! 7 <
& ?1,
: 8& <  
&#%%    
,&&4!! - .3
: >#& . ?1,
.$!##>#& . -? - 
: 9& ?1,
.$!##9&  -? - 
,&&>#& ) - - -
,&&9& 9   
,&&&.$!## C  = =
DEXPOSED D2
e
b
K
E2
E
L
N
NOTE 1
1
2
2
1
N
A
A1
A3
TOP VIEW BOTTOM VIEW
PAD
  * ,1
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 378 © 2009 Microchip Technology Inc.
*+%!,-./.*+!
01'((),1
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
© 2009 Microchip Technology Inc. DS39689F-page 379
PIC18F2221/2321/4221/4321 FAMILY
12#('#
!"
  !"#$%&"' ()"&'"!&)&#*&&&#
 '!!#.#&"#'#%!&"!!#%!&"!!!&$#''!#
- '!#&.0
1,2 1!'!&$& "!**&"&&!
.32 %'!("!"*&"&&(%%'&"!!
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
6&! 99..
'!9'&! 7 7: ;
7"')%! 7 <
& ?1,
: 8& = = 
##44!! ?  <
&#%%   = =
: >#& .  < <
##4>#& .  - ?
: 9&   
3&9& 9   
3&& 9 .3
9#4!!  = 
3& IB B <B
9#>#& )  = -<
L
L1
c
A2
A1
A
E
E1
D
N
12
NOTE 1
b
e
φ
  * ,-1
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 380 © 2009 Microchip Technology Inc.
3.
!"
  !"#$%&"' ()"&'"!&)&#*&&&#
 +%&,&!&
- '!!#.#&"#'#%!&"!!#%!&"!!!&$#/!#
 '!#&.0
1,2 1!'!&$& "!**&"&&!
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
6&! 7,8.
'!9'&! 7 7: ;
7"')%! 7 
& 1,
&& = = 
##44!!   = 
1!&&   = =
"#&"#>#& .  = ?
##4>#& . < = <
: 9& < = 
&& 9  = 
9#4!! < = 
69#>#& ) - = 
9*9#>#& )  = -
: *+ 1 = = 
N
NOTE 1
E1
D
123
A
A1 b1
be
c
eB
E
L
A2
  * ,?1
© 2009 Microchip Technology Inc. DS39689F-page 381
PIC18F2221/2321/4221/4321 FAMILY
33*+%!,-/*+!
!"
  !"#$%&"' ()"&'"!&)&#*&&&#
 4!!*!"&#
- '!#&.0
1,2 1!'!&$& "!**&"&&!
.32 %'!("!"*&"&&(%%'&"!!
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
6&! 99..
'!9'&! 7 7: ;
7"')%! 7 
& ?1,
: 8& <  
&#%%    
,&&4!! - .3
: >#& . <1,
.$!##>#& . ?- ? ?<
: 9& <1,
.$!##9&  ?- ? ?<
,&&>#& )  - -<
,&&9& 9 -  
,&&&.$!## C  = =
DEXPOSED
PAD
D2
e
b
K
L
E2
2
1
N
NOTE 1
2
1
E
N
BOTTOM VIEW
TOP VIEW
A3 A1
A
  * ,-1
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 382 © 2009 Microchip Technology Inc.
33*+%!,-/*+!
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
© 2009 Microchip Technology Inc. DS39689F-page 383
PIC18F2221/2321/4221/4321 FAMILY
3341*+546/6/6%'4*+
!"
  !"#$%&"' ()"&'"!&)&#*&&&#
 ,'%!&!&D!E' 
- '!!#.#&"#'#%!&"!!#%!&"!!!&$#''!#
 '!#&.0
1,2 1!'!&$& "!**&"&&!
.32 %'!("!"*&"&&(%%'&"!!
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
6&! 99..
'!9'&! 7 7: ;
7"')%9#! 7 
9#& <1,
: 8& = = 
##44!!   
&#%%   = 
3&9& 9  ? 
3&& 9 .3
3& IB -B B
: >#& . 1,
: 9& 1,
##4>#& . 1,
##49&  1,
9#4!!  = 
9#>#& ) - - 
#%& DB B -B
#%&1&&' EB B -B
A
E
E1
D
D1
e
b
NOTE 1 NOTE 2
N
123
c
A1
L
A2
L1
α
φ
β
  * ,?1
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 384 © 2009 Microchip Technology Inc.
3341*+546/6/6%'4*+
!" 3&'!&"&4#*!(!!&4%&&#&
&&255***''54
© 2009 Microchip Technology Inc. DS39689F-page 385
PIC18F2221/2321/4221/4321 FAMILY
APPENDIX A: REVISION HISTORY
Revision A (July 2005)
Original data sheet for PIC18F2221/2321/4221/4321
devices.
Revision B (August 2006)
Updated Section 26.0 “Electrical Characteristic”.
Revision C (October 2006)
This revision includes updates to the packaging
diagrams.
Revision D (January 2007)
This revision includes updates to the packaging
diagrams.
Revision E (February 2007)
This revision includes updates to the packaging
diagrams.
Revision F (September 2009)
This revision includes a new chapter, Section 2.0
“Guidelines for Getting Started with PIC18F
Microcontrollers. There are also updates to
Section 27.0 “Electrical Characteristics”,
Section 28.0 “Packaging Information” and minor
text edits throughout document.
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 386 © 2009 Microchip Technology Inc.
APPENDIX B: DEVICE
DIFFERENCES
The differences between the devices listed in this data
sheet are shown in Table B-1.
TABLE B-1: DEVICE DIFFERENCES
Features PIC18F2221 PIC18F2321 PIC18F4221 PIC18F4321
Program Memory (Bytes) 4096 8192 4096 8192
Program Memory (Instructions) 2048 4096 2048 4096
Interrupt Sources 19 19 20 20
I/O Ports Ports A, B, C, (E) Ports A, B, C, (E) Ports A, B, C, D, E Ports A, B, C, D, E
Capture/Compare/PWM Modules 2 2 1 1
Enhanced Capture/Compare/
PWM Modules
0011
Parallel Communications (PSP) No No Yes Yes
10-Bit Analog-to-Digital Module 10 input channels 10 input channels 13 input channels 13 input channels
Packages 28-pin SPDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
28-pin SPDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
40-pin PDIP
44-pin TQFP
44-pin QFN
40-pin PDIP
44-pin TQFP
44-pin QFN
© 2009 Microchip Technology Inc. DS39689F-page 387
PIC18F2221/2321/4221/4321 FAMILY
APPENDIX C: CONVERSION
CONSIDERATIONS
This appendix discusses the considerations for
converting from previous versions of a device to the
ones listed in this data sheet. Typically, these changes
are due to the differences in the process technology
used. An example of this type of conversion is from a
PIC16C74A to a PIC16C74B.
The PIC18F2221/2321/4221/4321 family of devices is
functionally the same as the PIC18F4320 family. Code
written for a PIC18F4320 will generally work on a
PIC18F4321 with few or no changes.
The following is a list of changes the user should be
aware of when migrating an application from the
PIC18F4320 to the PIC18F4321. Code written for the
PIC18F4321 may not run as expected due to these
differences.
1. Entry to power-managed modes has changed.
Modifying the SCS1:SCS0 bits (OSCCON<1:0>)
immediately changes the current clock source. It
is not necessary to execute a SLEEP instruction
to change clock sources. Refer to Section 4.1.2
“Entering Power-Managed Modes for details.
2. Exit from power-managed modes has changed.
A WDT wake or interrupt does not cause an
automatic return to PRI_RUN mode. The
controller will execute code while continuing to
use the current clock source. If the controller
was operating in RC_IDLE or RC_RUN mode,
an interrupt will cause entry to RC_RUN mode
until code selects another power-managed
mode. Refer to Section 4.4 “Idle Modes” for
details.
3. The extended instruction set can be con-
figured as enabled using the XINST bit
(CONFIG4L<6>). The access memory map is
also modified when the extended instruction set
is enabled. Refer to Section 6.5 “Data Memory
and the Extended Instruction Set” and
Section 24.2 “Extended Instruction Set” for
details.
4. There may also be changes to the electrical spec-
ifications. Refer to Section 27.0 “Electrical
Characteristics” for details.
APPENDIX D: MIGRATION FROM
BASELINE TO
ENHANCED DEVICES
This section discusses how to migrate from a Baseline
device (i.e., PIC16C5X) to an Enhanced MCU device
(i.e., PIC18FXXX).
The following are the list of modifications over the
PIC16C5X microcontroller family:
Not Currently Available
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 388 © 2009 Microchip Technology Inc.
APPENDIX E: MIGRATION FROM
MID-RANGE TO
ENHANCED DEVICES
A detailed discussion of the differences between the
mid-range MCU devices (i.e., PIC16CXXX) and the
Enhanced devices (i.e., PIC18FXXX) is provided in
AN716, “Migrating Designs from PIC16C74A/74B to
PIC18C442”. The changes discussed, while device
specific, are generally applicable to all mid-range to
Enhanced device migrations.
This Application Note is available as Literature Number
DS00716.
APPENDIX F: MIGRATION FROM
HIGH-END TO
ENHANCED DEVICES
A detailed discussion of the migration pathway and
differences between the high-end MCU devices (i.e.,
PIC17CXXX) and the Enhanced devices (i.e.,
PIC18FXXX) is provided in AN726, “PIC17CXXX to
PIC18CXXX Migration”.
This Application Note is available as Literature Number
DS00726.
© 2009 Microchip Technology Inc. DS39689F-page 389
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INDEX
A
A/D ................................................................................... 233
Acquisition Requirements ........................................ 238
ADCON0 Register .................................................... 233
ADCON1 Register .................................................... 233
ADCON2 Register .................................................... 233
ADRESH Register ............................................ 233, 236
ADRESL Register .................................................... 233
Analog Port Pins, Configuring .................................. 240
Associated Registers ............................................... 242
Configuring the Module ............................................ 237
Conversion Clock (TAD) ........................................... 239
Conversion Requirements ....................................... 371
Conversion Status (GO/DONE Bit) .......................... 236
Conversions ............................................................. 241
Converter Characteristics ........................................ 370
Converter Interrupt, Configuring .............................. 237
Discharge ................................................................. 241
Operation in Power-Managed Modes ...................... 240
Selecting and Configuring Acquisition Time ............ 239
Special Event Trigger (CCP) .................................... 242
Special Event Trigger (ECCP) ................................. 154
Use of the CCP2 Trigger .......................................... 242
Absolute Maximum Ratings ............................................. 333
AC (Timing) Characteristics ............................................. 352
Load Conditions for Device Timing
Specifications ................................................... 353
Parameter Symbology ............................................. 352
Temperature and Voltage Specifications ................. 353
Timing Conditions .................................................... 353
AC Characteristics
Internal RC Accuracy ............................................... 355
Access Bank
Mapping with Indexed Literal Offset
Addressing Mode ............................................... 77
ACKSTAT ........................................................................ 201
ACKSTAT Status Flag ..................................................... 201
ADCON0 Register ............................................................ 233
GO/DONE Bit ........................................................... 236
ADCON1 Register ............................................................ 233
ADCON2 Register ............................................................ 233
ADDFSR .......................................................................... 322
ADDLW ............................................................................ 285
ADDULNK ........................................................................ 322
ADDWF ............................................................................ 285
ADDWFC ......................................................................... 286
ADRESH Register ............................................................ 233
ADRESL Register .................................................... 233, 236
Analog-to-Digital Converter. See A/D.
ANDLW ............................................................................ 286
ANDWF ............................................................................ 287
Assembler
MPASM Assembler .................................................. 330
Auto-Wake-up on Sync Break Character ......................... 226
B
Bank Select Register (BSR) ............................................... 65
Baud Rate Generator ....................................................... 197
BC .................................................................................... 287
BCF .................................................................................. 288
BF .................................................................................... 201
BF Status Flag ................................................................. 201
Block Diagrams
A/D ........................................................................... 236
Analog Input Model .................................................. 237
Baud Rate Generator .............................................. 197
Capture Mode Operation ......................................... 147
Comparator Analog Input Model .............................. 247
Comparator I/O Operating Modes ........................... 244
Comparator Output .................................................. 246
Comparator Voltage Reference ............................... 250
Comparator Voltage Reference Output
Buffer Example ................................................ 251
Compare Mode Operation ....................................... 148
Device Clock .............................................................. 35
Enhanced PWM ....................................................... 155
EUSART Receive .................................................... 225
EUSART Transmit ................................................... 222
External Power-on Reset Circuit
(Slow VDD Power-up) ........................................ 49
Fail-Safe Clock Monitor ........................................... 272
Generic I/O Port ....................................................... 111
High/Low-Voltage Detect with External Input .......... 254
HSPLL ....................................................................... 31
Interrupt Logic ............................................................ 98
INTOSC and PLL ....................................................... 32
MSSP (I2C Master Mode) ........................................ 195
MSSP (I2C Mode) .................................................... 176
MSSP (SPI Mode) ................................................... 167
On-Chip Reset Circuit ................................................ 47
PIC18F2221/2321 ..................................................... 12
PIC18F4221/4321 ..................................................... 13
PORTD and PORTE (Parallel Slave Port) ............... 126
PWM Operation (Simplified) .................................... 150
Reads from Flash Program Memory ......................... 83
Single Comparator ................................................... 245
Table Read Operation ............................................... 79
Table Write Operation ............................................... 80
Table Writes to Flash Program Memory .................... 85
Timer0 in 16-Bit Mode ............................................. 130
Timer0 in 8-Bit Mode ............................................... 130
Timer1 ..................................................................... 134
Timer1 (16-Bit Read/Write Mode) ............................ 134
Timer2 ..................................................................... 140
Timer3 ..................................................................... 142
Timer3 (16-Bit Read/Write Mode) ............................ 142
Watchdog Timer ...................................................... 269
BN .................................................................................... 288
BNC ................................................................................. 289
BNN ................................................................................. 289
BNOV .............................................................................. 290
BNZ ................................................................................. 290
BOR. See Brown-out Reset.
BOV ................................................................................. 293
BRA ................................................................................. 291
Break Character (12-Bit) Transmit and Receive .............. 227
BRG. See Baud Rate Generator.
Brown-out Reset (BOR) ..................................................... 50
Detecting ................................................................... 50
Disabling in Sleep Mode ............................................ 50
Software Enabled ...................................................... 50
BSF .................................................................................. 291
BTFSC ............................................................................. 292
BTFSS ............................................................................. 292
BTG ................................................................................. 293
BZ .................................................................................... 294
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C
C Compilers
MPLAB C18 .............................................................330
MPLAB C30 .............................................................330
CALL ................................................................................ 294
CALLW .............................................................................323
Capture (CCP Module) ..................................................... 147
Associated Registers ............................................... 149
CCP Pin Configuration .............................................147
CCPRxH:CCPRxL Registers ................................... 147
Prescaler ..................................................................147
Software Interrupt .................................................... 147
Timer1/Timer3 Mode Selection ................................ 147
Capture (ECCP Module) .................................................. 154
Capture/Compare/PWM (CCP) ........................................145
Capture Mode. See Capture.
CCPRxH Register .................................................... 146
CCPRxL Register ..................................................... 146
Compare Mode. See Compare.
Interaction of Two CCP Modules ............................. 146
Module Configuration ............................................... 146
Pin Assignment ........................................................ 146
Timer Resources ...................................................... 146
Clock Sources .................................................................... 35
Selecting the 31 kHz Source ......................................36
Selection Using OSCCON Register ...........................36
CLRF ................................................................................295
CLRWDT ..........................................................................295
Code Examples
16 x 16 Signed Multiply Routine ................................ 96
16 x 16 Unsigned Multiply Routine ............................ 96
8 x 8 Signed Multiply Routine .................................... 95
8 x 8 Unsigned Multiply Routine ................................ 95
Address Masking ..................................................... 182
Changing Between Capture Prescalers ................... 147
Computed GOTO Using an Offset Value ................... 62
Data EEPROM Read .................................................91
Data EEPROM Refresh Routine ................................ 92
Data EEPROM Write .................................................91
Erasing a Flash Program Memory Row .....................84
Fast Register Stack .................................................... 62
How to Clear RAM (Bank 1) Using Indirect
Addressing ......................................................... 73
Implementing a Real-Time Clock Using a
Timer1 Interrupt Service .................................. 137
Initializing PORTA .................................................... 111
Initializing PORTB .................................................... 114
Initializing PORTC .................................................... 117
Initializing PORTD .................................................... 120
Initializing PORTE .................................................... 123
Loading the SSPBUF (SSPSR) Register ................. 170
Reading a Flash Program Memory Word .................. 83
Saving STATUS, WREG and BSR
Registers in RAM ............................................. 109
Writing to Flash Program Memory ....................... 86–87
Code Protection ....................................................... 259, 274
Associated Registers ............................................... 275
Configuration Register Protection ............................277
Data EEPROM ......................................................... 277
Program Memory ..................................................... 275
COMF ............................................................................... 296
Comparator ...................................................................... 243
Analog Input Connection Considerations ................. 247
Associated Registers ............................................... 247
Configuration ............................................................ 244
Effects of a Reset .................................................... 246
Interrupts ................................................................. 246
Operation ................................................................. 245
Operation During Sleep ........................................... 246
Outputs .................................................................... 245
Reference ................................................................ 245
External Signal ................................................ 245
Internal Signal .................................................. 245
Response Time ........................................................ 245
Comparator Specifications ............................................... 350
Comparator Voltage Reference ....................................... 249
Accuracy and Error .................................................. 250
Associated Registers ............................................... 251
Configuring .............................................................. 249
Connection Considerations ...................................... 250
Effects of a Reset .................................................... 250
Operation During Sleep ........................................... 250
Compare (CCP Module) .................................................. 148
CCPRx Register ...................................................... 148
Pin Configuration ..................................................... 148
Software Interrupt .................................................... 148
Special Event Trigger .............................. 143, 148, 242
Timer1/Timer3 Mode Selection ................................ 148
Compare (ECCP Module) ................................................ 154
Special Event Trigger .............................................. 154
Computed GOTO ............................................................... 62
Configuration Bits ............................................................ 259
Context Saving During Interrupts ..................................... 109
Conversion Considerations .............................................. 387
CPFSEQ .......................................................................... 296
CPFSGT .......................................................................... 297
CPFSLT ........................................................................... 297
Crystal Oscillator/Ceramic Resonator ................................ 29
Customer Change Notification Service ............................ 399
Customer Notification Service ......................................... 399
Customer Support ............................................................ 399
D
Data Addressing Modes .................................................... 73
Comparing Options with the Extended
Instruction Set Enabled ..................................... 76
Direct ......................................................................... 73
Indexed Literal Offset ................................................ 75
Instructions Affected .......................................... 75
Indirect ....................................................................... 73
Inherent and Literal .................................................... 73
Data EEPROM Memory ..................................................... 89
Associated Registers ................................................. 93
EEADR Register ........................................................ 89
EECON1 Register ...................................................... 89
EECON2 Register ...................................................... 89
EEDATA Register ...................................................... 89
Operation During Code-Protect ................................. 92
Protection Against Spurious Write ............................. 92
Reading ..................................................................... 91
Using ......................................................................... 92
Write Verify ................................................................ 91
Writing ....................................................................... 91
Data Memory ..................................................................... 65
Access Bank .............................................................. 67
and the Extended Instruction Set .............................. 75
Bank Select Register (BSR) ...................................... 65
General Purpose Registers ....................................... 67
Map for PIC18F2221/2321/4221/4321 Family ........... 66
Special Function Registers ........................................ 68
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DAW ................................................................................. 298
DC Characteristics ........................................................... 347
Power-Down and Supply Current ............................ 337
Supply Voltage ......................................................... 336
DCFSNZ .......................................................................... 299
DECF ............................................................................... 298
DECFSZ ........................................................................... 299
Development Support ...................................................... 329
Device Differences ........................................................... 386
Device Overview .................................................................. 9
Details on Individual Family Members ....................... 10
Features (table) .......................................................... 11
New Core Features ...................................................... 9
Other Special Features .............................................. 10
Device Reset Timers .......................................................... 51
Oscillator Start-up Timer (OST) ................................. 51
PLL Lock Time-out ..................................................... 51
Power-up Timer (PWRT) ........................................... 51
Time-out Sequence .................................................... 51
Direct Addressing ............................................................... 74
E
Effect on Standard PIC MCU Instructions ........................ 326
Effects of Power-Managed Modes on Various
Clock Sources ............................................................ 38
Electrical Characteristics .................................................. 333
Enhanced Capture/Compare/PWM (ECCP) .................... 153
Associated Registers ............................................... 166
Capture and Compare Modes .................................. 154
Capture Mode. See Capture (ECCP Module).
Outputs and Configuration ....................................... 154
Pin Configurations for ECCP1 ................................. 154
PWM Mode. See PWM (ECCP Module).
Standard PWM Mode ............................................... 154
Timer Resources ...................................................... 154
Enhanced PWM Mode. See PWM (ECCP Module). ........ 155
Enhanced Universal Synchronous Asynchronous Receiver
Transmitter (EUSART). See EUSART.
Equations
A/D Acquisition Time ................................................ 238
A/D Minimum Charging Time ................................... 238
Calculating the Minimum Required
Acquisition Time .............................................. 238
Errata ................................................................................... 8
EUSART
Asynchronous Mode ................................................ 221
12-Bit Break Transmit and Receive ................. 227
Associated Registers, Receive ........................ 225
Associated Registers, Transmit ....................... 223
Auto-Wake-up on Sync Break ......................... 226
Receiver ........................................................... 224
Setting up 9-Bit Mode with Address Detect ..... 224
Transmitter ....................................................... 221
Baud Rate Generator
Operation in Power-Managed Mode ................ 215
Baud Rate Generator (BRG) .................................... 215
Associated Registers ....................................... 216
Auto-Baud Rate Detect .................................... 219
Baud Rate Error, Calculating ........................... 216
Baud Rates, Asynchronous Modes ................. 217
High Baud Rate Select (BRGH Bit) ................. 215
Sampling .......................................................... 215
Synchronous Master Mode ...................................... 228
Associated Registers, Receive ........................ 230
Associated Registers, Transmit ....................... 229
Reception ........................................................ 230
Transmission ................................................... 228
Synchronous Slave Mode ........................................ 231
Associated Registers, Receive ........................ 232
Associated Registers, Transmit ....................... 231
Reception ........................................................ 232
Transmission ................................................... 231
Extended Instruction Set
ADDFSR .................................................................. 322
ADDULNK ............................................................... 322
and Using MPLAB Tools ......................................... 328
CALLW .................................................................... 323
Considerations for Use ............................................ 326
MOVSF .................................................................... 323
MOVSS .................................................................... 324
PUSHL ..................................................................... 324
SUBFSR .................................................................. 325
SUBULNK ................................................................ 325
Syntax ...................................................................... 321
External Clock Input ........................................................... 30
F
Fail-Safe Clock Monitor ........................................... 259, 272
Exiting Operation ..................................................... 272
Interrupts in Power-Managed Modes ...................... 273
POR or Wake From Sleep ....................................... 273
WDT During Oscillator Failure ................................. 272
Fast Register Stack ........................................................... 62
Firmware Instructions ...................................................... 279
Flash Program Memory ..................................................... 79
Associated Registers ................................................. 87
Control Registers ....................................................... 80
EECON1 and EECON2 ..................................... 80
TABLAT (Table Latch) Register ........................ 82
TBLPTR (Table Pointer) Register ...................... 82
Erase Sequence ........................................................ 84
Erasing ...................................................................... 84
Operation During Code-Protect ................................. 87
Reading ..................................................................... 83
Table Pointer
Boundaries ........................................................ 82
Boundaries Based on Operation ....................... 82
Operations with TBLRD and TBLWT (table) ..... 82
Table Reads and Table Writes .................................. 79
Write Sequence ......................................................... 85
Writing ....................................................................... 85
Protection Against Spurious Writes ................... 87
Unexpected Termination ................................... 87
Write Verify ........................................................ 87
FSCM. See Fail-Safe Clock Monitor.
G
GOTO .............................................................................. 300
H
Hardware Multiplier ............................................................ 95
Introduction ................................................................ 95
Operation ................................................................... 95
Performance Comparison .......................................... 95
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High/Low-Voltage Detect ................................................. 253
Applications .............................................................. 256
Associated Registers ............................................... 257
Characteristics ......................................................... 351
Current Consumption ...............................................255
Effects of a Reset ..................................................... 257
Operation .................................................................254
During Sleep .................................................... 257
Setup ........................................................................ 255
Start-up Time ........................................................... 255
Typical Application ................................................... 256
HLVD. See High/Low-Voltage Detect. ............................. 253
I
I/O Ports ........................................................................... 111
I2C Mode (MSSP)
Acknowledge Sequence Timing ............................... 204
Associated Registers ............................................... 210
Baud Rate Generator ...............................................197
Bus Collision
During a Repeated Start Condition .................. 208
During a Start Condition ................................... 206
During a Stop Condition ................................... 209
Clock Arbitration .......................................................198
Clock Stretching .......................................................190
10-Bit Slave Receive Mode (SEN = 1) ............. 190
10-Bit Slave Transmit Mode ............................. 190
7-Bit Slave Receive Mode (SEN = 1) ............... 190
7-Bit Slave Transmit Mode ............................... 190
Clock Synchronization and the CKP Bit ................... 191
Effects of a Reset ..................................................... 205
General Call Address Support ................................. 194
I2C Clock Rate w/BRG ............................................. 197
Master Mode ............................................................ 195
Operation ......................................................... 196
Reception ......................................................... 201
Repeated Start Condition Timing ..................... 200
Start Condition Timing ..................................... 199
Transmission .................................................... 201
Multi-Master Communication, Bus Collision
and Arbitration .................................................. 205
Multi-Master Mode ...................................................205
Operation .................................................................181
Read/Write Bit Information (R/W Bit) ....................... 181
Read/Write Bit Information (R/W Bit) ....................... 183
Registers .................................................................. 176
Serial Clock (RC3/SCK/SCL) ................................... 183
Slave Mode ..............................................................181
Address Masking ............................................. 182
Addressing ....................................................... 181
Reception ......................................................... 183
Transmission .................................................... 183
Sleep Operation ....................................................... 205
Stop Condition Timing ..............................................204
ID Locations ............................................................. 259, 277
INCF .................................................................................300
INCFSZ ............................................................................ 301
In-Circuit Debugger .......................................................... 277
In-Circuit Serial Programming (ICSP) ...................... 259, 277
Single-Supply ........................................................... 277
Indexed Literal Offset Addressing
and Standard PIC18 Instructions ............................. 326
Indexed Literal Offset Mode ............................................. 326
Indirect Addressing ............................................................ 74
INFSNZ ............................................................................301
Initialization Conditions for all Registers ...................... 55–58
Instruction Cycle ................................................................ 63
Clocking Scheme ....................................................... 63
Instruction Flow/Pipelining ................................................. 63
Instruction Set .................................................................. 279
ADDLW .................................................................... 285
ADDWF .................................................................... 285
ADDWF (Indexed Literal Offset Mode) .................... 327
ADDWFC ................................................................. 286
ANDLW .................................................................... 286
ANDWF .................................................................... 287
BC ............................................................................ 287
BCF ......................................................................... 288
BN ............................................................................ 288
BNC ......................................................................... 289
BNN ......................................................................... 289
BNOV ...................................................................... 290
BNZ ......................................................................... 290
BOV ......................................................................... 293
BRA ......................................................................... 291
BSF .......................................................................... 291
BSF (Indexed Literal Offset Mode) .......................... 327
BTFSC ..................................................................... 292
BTFSS ..................................................................... 292
BTG ......................................................................... 293
BZ ............................................................................ 294
CALL ........................................................................ 294
CLRF ....................................................................... 295
CLRWDT ................................................................. 295
COMF ...................................................................... 296
CPFSEQ .................................................................. 296
CPFSGT .................................................................. 297
CPFSLT ................................................................... 297
DAW ........................................................................ 298
DCFSNZ .................................................................. 299
DECF ....................................................................... 298
DECFSZ .................................................................. 299
Extended Instruction Set ......................................... 321
General Format ........................................................ 281
GOTO ...................................................................... 300
INCF ........................................................................ 300
INCFSZ .................................................................... 301
INFSNZ .................................................................... 301
IORLW ..................................................................... 302
IORWF ..................................................................... 302
LFSR ....................................................................... 303
MOVF ...................................................................... 303
MOVFF .................................................................... 304
MOVLB .................................................................... 304
MOVLW ................................................................... 305
MOVWF ................................................................... 305
MULLW .................................................................... 306
MULWF .................................................................... 306
NEGF ....................................................................... 307
NOP ......................................................................... 307
Opcode Field Descriptions ....................................... 280
POP ......................................................................... 308
PUSH ....................................................................... 308
RCALL ..................................................................... 309
RESET ..................................................................... 309
RETFIE .................................................................... 310
RETLW .................................................................... 310
RETURN .................................................................. 311
RLCF ....................................................................... 311
RLNCF ..................................................................... 312
RRCF ....................................................................... 312
© 2009 Microchip Technology Inc. DS39689F-page 393
PIC18F2221/2321/4221/4321 FAMILY
RRNCF .................................................................... 313
SETF ........................................................................ 313
SETF (Indexed Literal Offset Mode) ........................ 327
SLEEP ..................................................................... 314
Standard Instructions ............................................... 279
SUBFWB .................................................................. 314
SUBLW .................................................................... 315
SUBWF .................................................................... 315
SUBWFB .................................................................. 316
SWAPF .................................................................... 316
TBLRD ..................................................................... 317
TBLWT ..................................................................... 318
TSTFSZ ................................................................... 319
XORLW .................................................................... 319
XORWF .................................................................... 320
INTCON Registers ..................................................... 99–101
Inter-Integrated Circuit. See I2C.
Internal Oscillator Block ..................................................... 32
Adjustment ................................................................. 32
INTIO Modes .............................................................. 32
INTOSC Frequency Drift ............................................ 33
INTOSC Output Frequency ........................................ 32
OSCTUNE Register ................................................... 32
PLL in INTOSC Modes .............................................. 33
Internal RC Oscillator
Use with WDT .......................................................... 269
Internet Address ............................................................... 399
Interrupt Sources ............................................................. 259
A/D Conversion Complete ....................................... 237
Capture Complete (CCP) ......................................... 147
Compare Complete (CCP) ....................................... 148
Interrupt-on-Change (RB7:RB4) .............................. 114
INTx Pin ................................................................... 109
PORTB, Interrupt-on-Change .................................. 109
TMR0 ....................................................................... 109
TMR0 Overflow ........................................................ 131
TMR1 Overflow ........................................................ 133
TMR2 to PR2 Match (PWM) ............................ 150, 155
TMR3 Overflow ................................................ 141, 143
Interrupts ............................................................................ 97
INTOSC, INTRC. See Internal Oscillator Block.
IORLW ............................................................................. 302
IORWF ............................................................................. 302
IPR Registers ................................................................... 106
L
LFSR ................................................................................ 303
Low-Voltage ICSP Programming. See Single-Supply ICSP
Programming
M
Master Clear (MCLR) ......................................................... 49
Master Synchronous Serial Port (MSSP). See MSSP.
Memory Organization ......................................................... 59
Data Memory ............................................................. 65
Program Memory ....................................................... 59
Memory Programming Requirements .............................. 349
Microchip Internet Web Site ............................................. 399
Migration from Baseline to Enhanced Devices ................ 387
Migration from High-End to Enhanced Devices ............... 388
Migration from Mid-Range to Enhanced Devices ............ 388
MOVF ............................................................................... 303
MOVFF ............................................................................ 304
MOVLB ............................................................................ 304
MOVLW ........................................................................... 305
MOVSF ............................................................................ 323
MOVSS ............................................................................ 324
MOVWF ........................................................................... 305
MPLAB ASM30 Assembler, Linker, Librarian .................. 330
MPLAB ICD 2 In-Circuit Debugger .................................. 331
MPLAB ICE 2000 High-Performance Universal
In-Circuit Emulator ................................................... 331
MPLAB Integrated Development Environment
Software .................................................................. 329
MPLAB PM3 Device Programmer ................................... 331
MPLAB REAL ICE In-Circuit Emulator System ............... 331
MPLINK Object Linker/MPLIB Object Librarian ............... 330
MSSP
ACK Pulse ....................................................... 181, 183
Control Registers (general) ..................................... 167
I2C Mode. See I2C Mode.
Module Overview ..................................................... 167
SPI Master/Slave Connection .................................. 171
SPI Mode. See SPI Mode.
SSPBUF Register .................................................... 172
SSPSR Register ...................................................... 172
MULLW ............................................................................ 306
MULWF ............................................................................ 306
N
NEGF ............................................................................... 307
NOP ................................................................................. 307
O
Oscillator Configuration ..................................................... 29
EC .............................................................................. 29
ECIO .......................................................................... 29
HS .............................................................................. 29
HSPLL ....................................................................... 29
Internal Oscillator Block ............................................. 32
INTIO1 ....................................................................... 29
INTIO2 ....................................................................... 29
LP .............................................................................. 29
RC ............................................................................. 29
RCIO .......................................................................... 29
XT .............................................................................. 29
Oscillator Selection .......................................................... 259
Oscillator Start-up Timer (OST) ................................... 38, 51
Oscillator Switching ........................................................... 35
Oscillator Transitions ......................................................... 36
Oscillator, Timer1 ..................................................... 133, 143
Oscillator, Timer3 ............................................................. 141
P
Packaging Information ..................................................... 373
Marking .................................................................... 373
Parallel Slave Port (PSP) ......................................... 120, 126
Associated Registers ............................................... 127
CS (Chip Select) ...................................................... 126
PORTD .................................................................... 126
RD (Read Input) ...................................................... 126
Select (PSPMODE Bit) .................................... 120, 126
WR (Write Input) ...................................................... 126
PICSTART Plus Development Programmer .................... 332
PIE Registers ................................................................... 104
Pin Functions
MCLR/VPP/RE3 ................................................... 14, 18
OSC1/CLKI/RA7 .................................................. 14, 18
OSC2/CLKO/RA6 ................................................ 14, 18
RA0/AN0 .............................................................. 15, 19
RA1/AN1 .............................................................. 15, 19
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 394 © 2009 Microchip Technology Inc.
RA2/AN2/VREF-/CVREF ........................................ 15, 19
RA3/AN3/VREF+ ................................................... 15, 19
RA4/T0CKI/C1OUT .............................................. 15, 19
RA5/AN4/SS/HLVDIN/C2OUT ............................. 15, 19
RB0/INT0/FLT0/AN12 .......................................... 16, 20
RB1/INT1/AN10 ................................................... 16, 20
RB2/INT2/AN8 ..................................................... 16, 20
RB3/AN9/CCP2 ................................................... 16, 20
RB4/KBI0/AN11 ................................................... 16, 20
RB5/KBI1/PGM .................................................... 16, 20
RB6/KBI2/PGC .................................................... 16, 20
RB7/KBI3/PGD .................................................... 16, 20
RC0/T1OSO/T13CKI ...........................................17, 21
RC1/T1OSI/CCP2 ................................................ 17, 21
RC2/CCP1 .................................................................17
RC2/CCP1/P1A ......................................................... 21
RC3/SCK/SCL ..................................................... 17, 21
RC4/SDI/SDA ...................................................... 17, 21
RC5/SDO ............................................................. 17, 21
RC6/TX/CK .......................................................... 17, 21
RC7/RX/DT .......................................................... 17, 21
RD0/PSP0 .................................................................. 22
RD1/PSP1 .................................................................. 22
RD2/PSP2 .................................................................. 22
RD3/PSP3 .................................................................. 22
RD4/PSP4 .................................................................. 22
RD5/PSP5/P1B ..........................................................22
RD6/PSP6/P1C .......................................................... 22
RD7/PSP7/P1D .......................................................... 22
RE0/RD/AN5 .............................................................. 23
RE1/WR/AN6 ............................................................. 23
RE2/CS/AN7 .............................................................. 23
VDD ....................................................................... 17, 23
VSS ....................................................................... 17, 23
Pinout I/O Descriptions
PIC18F2221/2321 ...................................................... 14
PIC18F4221/4321 ...................................................... 18
PIR Registers ................................................................... 102
PLL Frequency Multiplier ...................................................31
HSPLL Oscillator Mode .............................................. 31
Use with INTOSC ....................................................... 31
POP .................................................................................. 308
POR. See Power-on Reset.
PORTA
Associated Registers ............................................... 113
LATA Register .......................................................... 111
PORTA Register ...................................................... 111
TRISA Register ........................................................ 111
PORTB
Associated Registers ............................................... 116
LATB Register .......................................................... 114
PORTB Register ...................................................... 114
TRISB Register ........................................................ 114
PORTC
Associated Registers ............................................... 119
LATC Register ......................................................... 117
PORTC Register ...................................................... 117
RC3/SCK/SCL Pin ...................................................183
TRISC Register ........................................................117
PORTD
Associated Registers ............................................... 122
LATD Register ......................................................... 120
Parallel Slave Port (PSP) Function .......................... 120
PORTD Register ...................................................... 120
TRISD Register ........................................................120
PORTE
Associated Registers ............................................... 125
LATE Register ......................................................... 123
PORTE Register ...................................................... 123
PSP Mode Select (PSPMODE Bit) .......................... 120
TRISE Register ........................................................ 123
Power-Managed Modes ..................................................... 39
and A/D Operation ................................................... 240
and EUSART Operation .......................................... 215
and PWM Operation ................................................ 165
and SPI Operation ................................................... 175
Clock Sources ............................................................ 39
Clock Transitions and Status Indicators .................... 40
Effects on Clock Sources ........................................... 38
Entering ..................................................................... 39
Exiting Idle and Sleep Modes .................................... 45
By Interrupt ........................................................ 45
By Reset ............................................................ 45
By WDT Time-out .............................................. 45
Without an Oscillator Start-up Delay ................. 46
Idle Modes ................................................................. 43
PRI_IDLE ........................................................... 44
RC_IDLE ........................................................... 45
SEC_IDLE ......................................................... 44
Multiple Sleep Commands ......................................... 40
Run Modes ................................................................ 40
PRI_RUN ........................................................... 40
RC_RUN ............................................................ 41
SEC_RUN ......................................................... 40
Sleep Mode ............................................................... 43
Summary (table) ........................................................ 39
Power-on Reset (POR) ...................................................... 49
Power-up Timer (PWRT) ........................................... 51
Time-out Sequence ................................................... 51
Power-up Delays ............................................................... 38
Power-up Timer (PWRT) ................................................... 38
Prescaler
Timer2 ..................................................................... 156
Prescaler, Timer0 ............................................................ 131
Prescaler, Timer2 ............................................................ 151
PRI_IDLE Mode ................................................................. 44
PRI_RUN Mode ................................................................. 40
Program Counter ............................................................... 60
PCL, PCH and PCU Registers .................................. 60
PCLATH and PCLATU Registers .............................. 60
Program Memory
and Extended Instruction Set .................................... 77
Instructions ................................................................ 64
Two-Word .......................................................... 64
Interrupt Vector .......................................................... 59
Look-up Tables .......................................................... 62
Map and Stack (diagram) .......................................... 59
Reset Vector .............................................................. 59
Program Verification ........................................................ 274
Programming, Device Instructions ................................... 279
PSP. See Parallel Slave Port.
Pulse-Width Modulation. See PWM (CCP Module) and
PWM (ECCP Module).
PUSH ............................................................................... 308
PUSH and POP Instructions .............................................. 61
PUSHL ............................................................................. 324
PWM (CCP Module)
Associated Registers ............................................... 152
Auto-Shutdown (CCP1 Only) ................................... 151
Duty Cycle ............................................................... 150
© 2009 Microchip Technology Inc. DS39689F-page 395
PIC18F2221/2321/4221/4321 FAMILY
Example Frequencies/Resolutions .......................... 151
Operation Setup ....................................................... 151
Period ....................................................................... 150
TMR2 to PR2 Match ........................................ 150, 155
PWM (ECCP Module) ...................................................... 155
CCPR1H:CCPR1L Registers ................................... 155
Duty Cycle ................................................................ 156
Effects of a Reset ..................................................... 165
Enhanced PWM Auto-Shutdown ............................. 162
Example Frequencies/Resolutions .......................... 156
Full-Bridge Application Example .............................. 160
Full-Bridge Mode ...................................................... 159
Direction Change ............................................. 160
Half-Bridge Mode ..................................................... 158
Half-Bridge Output Mode Applications
Example ........................................................... 158
Operation in Power-Managed Modes ...................... 165
Operation with Fail-Safe Clock Monitor ................... 165
Output Configurations .............................................. 156
Output Relationships (Active-High) .......................... 157
Output Relationships (Active-Low) ........................... 157
Period ....................................................................... 155
Programmable Dead-Band Delay ............................ 162
Setup for PWM Operation ........................................ 165
Start-up Considerations ........................................... 164
Q
Q Clock .................................................................... 151, 156
R
RAM. See Data Memory.
RC Oscillator
RCIO Oscillator Mode ................................................ 31
RC_IDLE Mode .................................................................. 45
RC_RUN Mode .................................................................. 41
RCALL ............................................................................. 309
RCON Register
Bit Status During Initialization .................................... 54
Reader Response ............................................................ 400
Register File ....................................................................... 67
Register File Summary ................................................ 69–71
Registers
ADCON0 (A/D Control 0) ......................................... 233
ADCON1 (A/D Control 1) ......................................... 234
ADCON2 (A/D Control 2) ......................................... 235
BAUDCON (Baud Rate Control) .............................. 214
CCP1CON (Enhanced Capture/Compare/PWM
Control 1) ......................................................... 153
CCPxCON (CCPx Control) ...................................... 145
CMCON (Comparator Control) ................................ 243
CONFIG1H (Configuration 1 High) .......................... 260
CONFIG2H (Configuration 2 High) .......................... 262
CONFIG2L (Configuration 2 Low) ............................ 261
CONFIG3H (Configuration 3 High) .......................... 263
CONFIG4L (Configuration 4 Low) ............................ 264
CONFIG5H (Configuration 5 High) .......................... 265
CONFIG5L (Configuration 5 Low) ............................ 265
CONFIG6H (Configuration 6 High) .......................... 266
CONFIG6L (Configuration 6 Low) ............................ 266
CONFIG7H (Configuration 7 High) .......................... 267
CONFIG7L (Configuration 7 Low) ............................ 267
CVRCON (Comparator Voltage
Reference Control) .......................................... 249
DEVID1 (Device ID 1) .............................................. 268
DEVID2 (Device ID 2) .............................................. 268
ECCP1AS (ECCP Auto-Shutdown Control) ............. 163
ECCP1DEL (PWM Dead-Band Delay) .................... 162
EECON1 (Data EEPROM Control 1) ................... 81, 90
HLVDCON (High/Low-Voltage Detect Control) ....... 253
INTCON (Interrupt Control) ....................................... 99
INTCON2 (Interrupt Control 2) ................................ 100
INTCON3 (Interrupt Control 3) ................................ 101
IPR1 (Peripheral Interrupt Priority 1) ....................... 106
IPR2 (Peripheral Interrupt Priority 2) ....................... 107
OSCCON (Oscillator Control) .................................... 37
OSCTUNE (Oscillator Tuning) ................................... 33
PIE1 (Peripheral Interrupt Enable 1) ....................... 104
PIE2 (Peripheral Interrupt Enable 2) ....................... 105
PIR1 (Peripheral Interrupt Request (Flag) 1) ........... 102
PIR2 (Peripheral Interrupt Request (Flag) 2) ........... 103
RCON (Reset Control) ....................................... 48, 108
RCSTA (Receive Status and Control) ..................... 213
SSPADD(MSSP Address) ....................................... 180
SSPCON1 (MSSP Control 1, I2C Mode) ................. 178
SSPCON1 (MSSP Control 1, SPI Mode) ................ 169
SSPCON2 (MSSP Control 2, I2C Mode) ................. 179
SSPSTAT (MSSP Status, I2C Mode) ...................... 177
SSPSTAT (MSSP Status, SPI Mode) ...................... 168
STATUS .................................................................... 72
STKPTR (Stack Pointer) ............................................ 61
T0CON (Timer0 Control) ......................................... 129
T1CON (Timer1 Control) ......................................... 133
T2CON (Timer2 Control) ......................................... 139
T3CON (Timer3 Control) ......................................... 141
TRISE (PORTE/PSP Control) ................................. 124
TXSTA (Transmit Status and Control) ..................... 212
WDTCON (Watchdog Timer Control) ...................... 270
RESET ............................................................................. 309
Reset State of Registers .................................................... 54
Resets ....................................................................... 47, 259
Brown-out Reset (BOR) ........................................... 259
Oscillator Start-up Timer (OST) ............................... 259
Power-on Reset (POR) ............................................ 259
Power-up Timer (PWRT) ......................................... 259
RETFIE ............................................................................ 310
RETLW ............................................................................ 310
RETURN .......................................................................... 311
Return Address Stack ........................................................ 60
Associated Registers ................................................. 60
Return Stack Pointer (STKPTR) ........................................ 61
Revision History ............................................................... 385
RLCF ............................................................................... 311
RLNCF ............................................................................. 312
RRCF ............................................................................... 312
RRNCF ............................................................................ 313
S
SCK ................................................................................. 167
SDI ................................................................................... 167
SDO ................................................................................. 167
SEC_IDLE Mode ............................................................... 44
SEC_RUN Mode ................................................................ 40
Serial Clock, SCK ............................................................ 167
Serial Data In (SDI) .......................................................... 167
Serial Data Out (SDO) ..................................................... 167
Serial Peripheral Interface. See SPI Mode.
SETF ............................................................................... 313
Single-Supply ICSP Programming.
Slave Select (SS) ............................................................. 167
SLEEP ............................................................................. 314
Sleep
OSC1 and OSC2 Pin States ...................................... 38
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DS39689F-page 396 © 2009 Microchip Technology Inc.
Software Simulator (MPLAB SIM) .................................... 330
Special Event Trigger. See Compare (CCP Mode).
Special Event Trigger. See Compare (ECCP Module).
Special Features of the CPU ............................................ 259
Special Function Registers ................................................ 68
Map ............................................................................68
SPI Mode (MSSP)
Associated Registers ............................................... 175
Bus Mode Compatibility ........................................... 175
Effects of a Reset ..................................................... 175
Enabling SPI I/O ...................................................... 171
Master Mode ............................................................ 172
Master/Slave Connection ......................................... 171
Operation .................................................................170
Operation in Power-Managed Modes ...................... 175
Serial Clock .............................................................. 167
Serial Data In ........................................................... 167
Serial Data Out ........................................................ 167
Slave Mode ..............................................................173
Slave Select .............................................................167
Slave Select Synchronization .................................. 173
SPI Clock ................................................................. 172
Typical Connection .................................................. 171
SS .................................................................................... 167
SSPOV ............................................................................. 201
SSPOV Status Flag .......................................................... 201
SSPSTAT Register
R/W Bit ............................................................. 181, 183
Stack Full/Underflow Resets .............................................. 62
SUBFSR ........................................................................... 325
SUBFWB ..........................................................................314
SUBLW ............................................................................315
SUBULNK ........................................................................325
SUBWF ............................................................................ 315
SUBWFB .......................................................................... 316
SWAPF ............................................................................316
T
Table Reads/Table Writes .................................................. 62
TBLRD .............................................................................317
TBLWT .............................................................................318
Time-out in Various Situations (table) ................................51
Timer0 .............................................................................. 129
Associated Registers ............................................... 131
Operation .................................................................130
Overflow Interrupt .................................................... 131
Prescaler ..................................................................131
Prescaler Assignment (PSA Bit) ..............................131
Prescaler Select (T0PS2:T0PS0 Bits) ..................... 131
Prescaler. See Prescaler, Timer0.
Reads and Writes in 16-Bit Mode ............................ 130
Source Edge Select (T0SE Bit) ................................ 130
Source Select (T0CS Bit) ......................................... 130
Switching Prescaler Assignment .............................. 131
Timer1 .............................................................................. 133
16-Bit Read/Write Mode ........................................... 135
Associated Registers ............................................... 137
Interrupt .................................................................... 136
Operation .................................................................134
Oscillator .......................................................... 133, 135
Layout Considerations ..................................... 136
Low-Power Option ........................................... 135
Overflow Interrupt .................................................... 133
Resetting, Using the CCP Special Event Trigger ..... 136
Special Event Trigger (ECCP) ................................. 154
TMR1H Register ...................................................... 133
TMR1L Register ....................................................... 133
Use as a Real-Time Clock ....................................... 136
Timer2 .............................................................................. 139
Associated Registers ............................................... 140
Interrupt ................................................................... 140
Operation ................................................................. 139
Output ...................................................................... 140
PR2 Register ................................................... 150, 155
TMR2 to PR2 Match Interrupt .................................. 155
TMR2-to-PR2 Match Interrupt ................................. 150
Timer3 .............................................................................. 141
16-Bit Read/Write Mode .......................................... 143
Associated Registers ............................................... 143
Operation ................................................................. 142
Oscillator .......................................................... 141, 143
Overflow Interrupt ............................................ 141, 143
Special Event Trigger (CCP) ................................... 143
TMR3H Register ...................................................... 141
TMR3L Register ....................................................... 141
Timing Diagrams
A/D Conversion ........................................................ 371
Acknowledge Sequence .......................................... 204
Asynchronous Reception ......................................... 225
Asynchronous Transmission .................................... 222
Asynchronous Transmission (Back to Back) ........... 222
Automatic Baud Rate Calculation ............................ 220
Auto-Wake-up Bit (WUE) During
Normal Operation ............................................ 226
Auto-Wake-up Bit (WUE) During Sleep ................... 226
Baud Rate Generator with Clock Arbitration ............ 198
BRG Overflow Sequence ......................................... 220
BRG Reset Due to SDA Arbitration During
Start Condition ................................................. 207
Brown-out Reset (BOR) ........................................... 357
Bus Collision During a Repeated Start
Condition (Case 1) ........................................... 208
Bus Collision During a Repeated Start
Condition (Case 2) ........................................... 208
Bus Collision During a Start Condition
(SCL = 0) ......................................................... 207
Bus Collision During a Stop Condition (Case 1) ...... 209
Bus Collision During a Stop Condition (Case 2) ...... 209
Bus Collision During Start Condition
(SDA Only) ...................................................... 206
Bus Collision for Transmit and Acknowledge .......... 205
Capture/Compare/PWM (All CCP Modules) ............ 359
CLKO and I/O .......................................................... 356
Clock Synchronization ............................................. 191
Clock/Instruction Cycle .............................................. 63
EUSART Synchronous Receive (Master/Slave) ...... 369
EUSART Synchronous Transmission
(Master/Slave) ................................................. 369
Example SPI Master Mode (CKE = 0) ..................... 361
Example SPI Master Mode (CKE = 1) ..................... 362
Example SPI Slave Mode (CKE = 0) ....................... 363
Example SPI Slave Mode (CKE = 1) ....................... 364
External Clock (All Modes Except PLL) ................... 354
Fail-Safe Clock Monitor ........................................... 273
First Start Bit Timing ................................................ 199
Full-Bridge PWM Output .......................................... 159
Half-Bridge PWM Output ......................................... 158
High/Low-Voltage Detect Characteristics ................ 351
High-Voltage Detect Operation (VDIRMAG = 1) ..... 256
I2C Bus Data ............................................................ 365
I2C Bus Start/Stop Bits ............................................ 365
© 2009 Microchip Technology Inc. DS39689F-page 397
PIC18F2221/2321/4221/4321 FAMILY
I2C Master Mode (7 or 10-Bit Transmission) ........... 202
I2C Master Mode (7-Bit Reception) .......................... 203
I2C Slave Mode (10-Bit Reception, SEN = 0,
ADMSK = 01001) ............................................. 187
I2C Slave Mode (10-Bit Reception, SEN = 0) .......... 188
I2C Slave Mode (10-Bit Reception, SEN = 1) .......... 193
I2C Slave Mode (10-Bit Transmission) ..................... 189
I2C Slave Mode (7-Bit Reception, SEN = 0,
ADMSK = 01011) ............................................. 185
I2C Slave Mode (7-Bit Reception, SEN = 0) ............ 184
I2C Slave Mode (7-Bit Reception, SEN = 1) ............ 192
I2C Slave Mode (7-Bit Transmission) ....................... 186
I2C Slave Mode General Call Address
Sequence (7 or 10-Bit Addressing Mode) ........ 194
I2C Stop Condition Receive or Transmit Mode ........ 204
Low-Voltage Detect Operation (VDIRMAG = 0) ...... 255
Master SSP I2C Bus Data ........................................ 367
Master SSP I2C Bus Start/Stop Bits ........................ 367
Parallel Slave Port (PIC18F4221/4321) ................... 360
Parallel Slave Port (PSP) Read ............................... 127
Parallel Slave Port (PSP) Write ............................... 127
PWM Auto-Shutdown (PRSEN = 0,
Auto-Restart Disabled) .................................... 164
PWM Auto-Shutdown (PRSEN = 1,
Auto-Restart Enabled) ..................................... 164
PWM Direction Change ........................................... 161
PWM Direction Change at Near
100% Duty Cycle ............................................. 161
PWM Output ............................................................ 150
Repeated Start Condition ......................................... 200
Reset, Watchdog Timer (WDT), Oscillator Start-up
Timer (OST), Power-up Timer (PWRT) ........... 357
Send Break Character Sequence ............................ 227
Slave Synchronization ............................................. 173
Slow Rise Time (MCLR Tied to VDD,
VDD Rise > TPWRT) ............................................ 53
SPI Mode (Master Mode) ......................................... 172
SPI Mode (Slave Mode, CKE = 0) ........................... 174
SPI Mode (Slave Mode, CKE = 1) ........................... 174
Synchronous Reception (Master Mode, SREN) ...... 230
Synchronous Transmission ...................................... 228
Synchronous Transmission (Through TXEN) .......... 229
Time-out Sequence on POR w/PLL Enabled
(MCLR Tied to VDD) ........................................... 53
Time-out Sequence on Power-up
(MCLR Not Tied to VDD, Case 1) ....................... 52
Time-out Sequence on Power-up
(MCLR Not Tied to VDD, Case 2) ....................... 52
Time-out Sequence on Power-up
(MCLR Tied to VDD, VDD Rise < TPWRT) ........... 52
Timer0 and Timer1 External Clock .......................... 358
Transition for Entry to Idle Mode ................................ 44
Transition for Entry to SEC_RUN Mode .................... 41
Transition for Entry to Sleep Mode ............................ 43
Transition for Two-Speed Start-up
(INTOSC to HSPLL) ........................................ 271
Transition for Wake from Idle to Run Mode ............... 44
Transition for Wake from Sleep (HSPLL) ................... 43
Transition from RC_RUN Mode to PRI_RUN Mode .. 42
Transition from SEC_RUN Mode to
PRI_RUN Mode (HSPLL) .................................. 41
Transition to RC_RUN Mode ..................................... 42
Timing Diagrams and Specifications ............................... 354
Capture/Compare/PWM Requirements
(All CCP Modules) ........................................... 359
CLKO and I/O Requirements ................................... 356
EUSART Synchronous Receive Requirements ....... 369
EUSART Synchronous Transmission Requirements ....
369
Example SPI Mode Requirements
(Master Mode, CKE = 0) .................................. 361
Example SPI Mode Requirements
(Master Mode, CKE = 1) .................................. 362
Example SPI Mode Requirements
(Slave Mode, CKE = 0) .................................... 363
Example SPI Mode Requirements
(Slave Mode, CKE = 1) .................................... 364
External Clock Requirements .................................. 354
I2C Bus Data Requirements (Slave Mode) .............. 366
I2C Bus Start/Stop Requirements (Slave Mode) ..... 365
Master SSP I2C Bus Data Requirements ................ 368
Master SSP I2C Bus Start/Stop Bits
Requirements .................................................. 367
Parallel Slave Port Requirements
(PIC18F4221/4321) ......................................... 360
PLL Clock ................................................................ 355
Reset, Watchdog Timer, Oscillator Start-up
Timer, Power-up Timer and
Brown-out Reset Requirements ...................... 357
Timer0 and Timer1 External Clock
Requirements .................................................. 358
Top-of-Stack Access .......................................................... 60
TRISE Register
PSPMODE Bit ......................................................... 120
TSTFSZ ........................................................................... 319
Two-Speed Start-up ................................................. 259, 271
Two-Word Instructions
Example Cases ......................................................... 64
TXSTA Register
BRGH Bit ................................................................. 215
V
Voltage Reference Specifications .................................... 350
W
Watchdog Timer (WDT) ........................................... 259, 269
Associated Registers ............................................... 270
Control Register ....................................................... 269
During Oscillator Failure .......................................... 272
Programming Considerations .................................. 269
WCOL ...................................................... 199, 200, 201, 204
WCOL Status Flag ................................... 199, 200, 201, 204
WWW Address ................................................................ 399
WWW, On-Line Support ...................................................... 8
X
XORLW ........................................................................... 319
XORWF ........................................................................... 320
PIC18F2221/2321/4221/4321 FAMILY
DS39689F-page 398 © 2009 Microchip Technology Inc.
NOTES:
© 2009 Microchip Technology Inc. DS39689F-page 399
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DS39689FPIC18F2221/2321/4221/4321 Family
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© 2009 Microchip Technology Inc. DS39689F-page 401
PIC18F2221/2321/4221/4321 FAMILY
PIC18F2221/2321/4221/4321 PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO. X/XX XXX
PatternPackageTemperature
Range
Device
Device PIC18F2221/2321(1), PIC18F4221/4321(1),
PIC18F2221/2321T(2), PIC18F4221/4321T(2);
VDD range 4.2V to 5.5V
PIC18LF2221/2321(1), PIC18LF4221/4321(1),
PIC18LF2221/2321T(2), PIC18LF4221/4321T(2);
VDD range 2.0V to 5.5V
Temperature Range I = -40°C to +85°C (Industrial)
E= -40°C to +125°C (Extended)
Package PT = TQFP (Thin Quad Flatpack)
SO = SOIC
SS = SSOP
SP = Skinny Plastic DIP
P=PDIP
ML = QFN
Pattern QTP, SQTP, Code or Special Requirements
(blank otherwise)
Examples:
a) PIC18F4321-I/P 301 = Industrial temp., PDIP
package, Extended VDD limits, QTP pattern
#301.
b) PIC18LF2321-I/SO = Industrial temp., SOIC
package, Extended VDD limits.
c) PIC18LF4321-I/P = Industrial temp., PDIP
package, normal VDD limits.
Note 1: F = Standard Voltage Range
LF = Wide Voltage Range
2: T = in tape and reel
DS39689F-page 402 © 2009 Microchip Technology Inc.
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03/26/09