PIC16F688 DATA SHEET (08/21/2009) DOWNLOAD

PIC16F688
Data Sheet
14-Pin Flash-Based, 8-Bit
CMOS Microcontrollers with
nanoWatt Technology
© 2009 Microchip Technology Inc.
DS41203E
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•
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•
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•
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•
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•
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Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART,
rfPIC and UNI/O are registered trademarks of Microchip
Technology Incorporated in the U.S.A. and other countries.
FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
MXDEV, MXLAB, SEEVAL and The Embedded Control
Solutions Company are registered trademarks of Microchip
Technology Incorporated in the U.S.A.
Analog-for-the-Digital Age, Application Maestro, CodeGuard,
dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
ECONOMONITOR, FanSense, HI-TIDE, In-Circuit Serial
Programming, ICSP, Mindi, MiWi, MPASM, MPLAB Certified
logo, MPLIB, MPLINK, mTouch, Octopus, Omniscient Code
Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit,
PICtail, PIC32 logo, REAL ICE, rfLAB, Select Mode, Total
Endurance, TSHARC, UniWinDriver, WiperLock and ZENA
are trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2009, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received ISO/TS-16949:2002 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
DS41203E-page ii
© 2009 Microchip Technology Inc.
PIC16F688
14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology
High-Performance RISC CPU:
Low-Power Features:
• Only 35 Instructions to Learn:
- All single-cycle instructions except branches
• Operating Speed:
- DC – 20 MHz oscillator/clock input
- DC – 200 ns instruction cycle
• Interrupt Capability
• 8-level Deep Hardware Stack
• Direct, Indirect and Relative Addressing modes
• Standby Current:
- 50 nA @ 2.0V, typical
• Operating Current:
- 11 μA @ 32 kHz, 2.0V, typical
- 220 μA @ 4 MHz, 2.0V, typical
• Watchdog Timer Current:
- 1 μA @ 2.0V, typical
Peripheral Features:
Special Microcontroller Features:
• Precision Internal Oscillator:
- Factory calibrated to ±1%
- Software selectable frequency range of
8 MHz to 125 kHz
- Software tunable
- Two-Speed Start-Up mode
- Crystal fail detect for critical applications
- Clock mode switching during operation for
power savings
• Power-Saving Sleep mode
• Wide Operating Voltage Range (2.0V-5.5V)
• Industrial and Extended Temperature Range
• Power-on Reset (POR)
• Power-up Timer (PWRT) and Oscillator Start-up
Timer (OST)
• Brown-out Reset (BOR) with Software Control
Option
• Enhanced Low-Current Watchdog Timer (WDT)
with on-chip oscillator (software selectable nominal 268 seconds with full prescaler) with software
enable
• Multiplexed Master Clear with Weak Pull-up or
Input Only Pin
• Programmable Code Protection
• High-Endurance Flash/EEPROM Cell:
- 100,000 write Flash endurance
- 1,000,000 write EEPROM endurance
- Flash/Data EEPROM retention: > 40 years
© 2009 Microchip Technology Inc.
• 12 I/O Pins with Individual Direction Control:
- High-current source/sink for direct LED drive
- Interrupt-on-change pin
- Individually programmable weak pull-ups
- Ultra Low-Power Wake-up
• Analog Comparator module with:
- Two analog comparators
- Programmable On-chip Voltage Reference
(CVREF) module (% of VDD)
- Comparator inputs and outputs externally
accessible
• A/D Converter:
- 10-bit resolution and 8 channels
• Timer0: 8-bit Timer/Counter with 8-bit
Programmable Prescaler
• Enhanced Timer1:
- 16-bit timer/counter with prescaler
- External Timer1 Gate (count enable)
- Option to use OSC1 and OSC2 in LP mode as
Timer1 oscillator if INTOSC mode selected
• Enhanced USART Module:
- Supports RS-485, RS-232, LIN 2.0/2.1 and
J2602
- Auto-Baud Detect
- Auto-wake-up on Start bit
• In-Circuit Serial Programming™ (ICSP™) via two
pins
DS41203E-page 1
PIC16F688
Program
Memory
Data Memory
Device
Flash
(words)
SRAM
(bytes)
EEPROM
(bytes)
4096
256
256
PIC16F688
I/O
10-bit A/D
(ch)
Comparators
Timers
8/16-bit
12
8
2
1/1
Pin Diagram (PDIP, SOIC, TSSOP)
14-pin PDIP, SOIC, TSSOP
1
14
VSS
RA5/T1CKI/OSC1/CLKIN
2
13
RA0/AN0/C1IN+/ICSPDAT/ULPWU
RA4/AN3/T1G/OSC2/CLKOUT
3
12
RA1/AN1/C1IN-/VREF/ICSPCLK
RA3/MCLR/VPP
4
11
RA2/AN2/T0CKI/INT/C1OUT
RC5/RX/DT
5
10
RC0/AN4/C2IN+
RC4/C2OUT/TX/CK
6
9
RC1/AN5/C2IN-
RC3/AN7
7
8
RC2/AN6
TABLE 1:
I/O
PIC16F688
VDD
PIC16F688 14-PIN SUMMARY (PDIP, SOIC, TSSOP)
Pin
Analog
Comparators
Timers
EUSART
Interrupt
Pull-up
Basic
RA0
13
AN0/ULPWU
C1IN+
—
—
IOC
Y
ICSPDAT
RA1
12
AN1
C1IN-
—
—
IOC
Y
VREF/ICSPCLK
RA2
11
AN2
C1OUT
T0CKI
—
IOC/INT
Y
—
RA3
4
—
—
—
—
IOC
Y(1)
MCLR/VPP
RA4
3
AN3
—
T1G
—
IOC
Y
OSC2/CLKOUT
RA5
2
—
—
T1CKI
—
IOC
Y
OSC1/CLKIN
RC0
10
AN4
C2IN+
—
—
—
—
—
RC1
9
AN5
C2IN-
—
—
—
—
—
RC2
8
AN6
—
—
—
—
—
—
RC3
7
AN7
—
—
—
—
—
—
RC4
6
—
C2OUT
—
TX/CK
—
—
—
RC5
5
—
—
—
RX/DT
—
—
—
—
1
—
—
—
—
—
—
VDD
—
14
—
—
—
—
—
—
VSS
Note 1:
Pull-up activated only with external MCLR configuration.
DS41203E-page 2
© 2009 Microchip Technology Inc.
PIC16F688
Pin Diagram (QFN)
TABLE 2:
NC
VSS
14
13
2
NC
RA4/AN3/T1G/OSC2/CLKOUT
15
1
VDD
RA5/T1CKI/OSC1/CLKIN
16
16-pin QFN
PIC16F688
12
RA0/AN0/C1IN+/ICSPDAT/ULPWU
11
RA1/AN1/C1IN-/VREF/ICSPCLK
RA2/AN2/T0CKI/INT/C1OUT
7
8
RC1/AN5/C2IN-
9
RC2/AN6
4
6
RC5/RX/DT
RC3/AN7
10
5
3
RC4/C2OUT/TX/CK
RA3/MCLR/VPP
RC0/AN4/C2IN+
PIC16F688 16-PIN SUMMARY (QFN)
I/O
Pin
Analog
Comparators
Timers
EUSART
Interrupt
Pull-up
Basic
RA0
12
AN0/ULPWU
C1IN+
—
—
IOC
Y
ICSPDAT
RA1
11
AN1
C1IN-
—
—
IOC
Y
VREF/ICSPCLK
RA2
10
AN2
C1OUT
T0CKI
—
IOC/INT
Y
—
MCLR/VPP
—
—
IOC
Y(1)
—
T1G
—
IOC
Y
OSC2/CLKOUT
—
T1CKI
—
IOC
Y
OSC1/CLKIN
RA3
3
—
—
RA4
2
AN3
RA5
1
—
RC0
9
AN4
C2IN+
—
—
—
—
—
RC1
8
AN5
C2IN-
—
—
—
—
—
RC2
7
AN6
—
—
—
—
—
—
RC3
6
AN7
—
—
—
—
—
—
RC4
5
—
C2OUT
—
TX/CK
—
—
—
RC5
4
—
—
—
RX/DT
—
—
—
—
16
—
—
—
—
—
—
VDD
—
13
—
—
—
—
—
—
VSS
—
14
—
—
—
—
—
—
NC
—
15
—
—
—
—
—
—
NC
Note 1:
Pull-up activated only with external MCLR configuration.
© 2009 Microchip Technology Inc.
DS41203E-page 3
PIC16F688
Table of Contents
1.0 Device Overview ......................................................................................................................................................................... 5
2.0 Memory Organization .................................................................................................................................................................. 7
3.0 Clock Sources ........................................................................................................................................................................... 21
4.0 I/O Ports .................................................................................................................................................................................... 33
5.0 Timer0 Module .......................................................................................................................................................................... 45
6.0 Timer1 Module with Gate Control.............................................................................................................................................. 49
7.0 Comparator Module................................................................................................................................................................... 55
8.0 Analog-to-Digital Converter (A/D) Module ................................................................................................................................. 65
9.0 Data EEPROM and Flash Program Memory Control ................................................................................................................ 77
10.0 Enhanced Universal Asynchronous Receiver Transmitter (EUSART) ...................................................................................... 83
11.0 Special Features of the CPU ................................................................................................................................................... 109
12.0 Instruction Set Summary ......................................................................................................................................................... 129
13.0 Development Support .............................................................................................................................................................. 139
14.0 Electrical Specifications........................................................................................................................................................... 143
15.0 DC and AC Characteristics Graphs and Tables ...................................................................................................................... 163
16.0 Packaging Information............................................................................................................................................................. 185
Appendix A: Data Sheet Revision History......................................................................................................................................... 193
Appendix B: Migrating from other PIC® Devices............................................................................................................................... 193
Index ................................................................................................................................................................................................. 195
On-line Support ................................................................................................................................................................................. 199
Systems Information and Upgrade Hot Line ..................................................................................................................................... 199
Reader Response ............................................................................................................................................................................. 200
Product Identification System............................................................................................................................................................ 201
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DS41203E-page 4
© 2009 Microchip Technology Inc.
PIC16F688
1.0
DEVICE OVERVIEW
The PIC16F688 is covered by this data sheet. It is
available in 14-pin PDIP, SOIC, TSSOP and QFN
packages. Figure 1-1 shows a block diagram of the
PIC16F688
device. Table 1-1 shows the pinout
description.
FIGURE 1-1:
PIC16F688 BLOCK DIAGRAM
INT
Configuration
13
8
Data Bus
PORTA
Program Counter
Flash
4k x 14
Program
Memory
Program
Bus
RA0
RA1
RA2
RAM
256 bytes
File
Registers
8-Level Stack
(13 bit)
14
RAM Addr
RA3
RA4
RA5
9
Addr MUX
Instruction Reg
7
Direct Addr
PORTC
Indirect
Addr
8
RC0
RC1
FSR Reg
RC2
RC3
STATUS Reg
8
RC4
RC5
3
MUX
Power-up
Timer
Instruction
Decode &
Control
Oscillator
Start-up Timer
Power-on
Reset
Timing
Generation
OSC1/CLKIN
ALU
8
Watchdog
Timer
W Reg
Brown-out
Reset
OSC2/CLKOUT
Internal
Oscillator
Block
T1G
RX/DT
MCLR
VDD
TX/CK
VSS
T1CKI
Timer0
Timer1
EUSART
T0CKI
Analog-to-Digital Converter
2
Analog Comparators
and Reference
EEDAT
8
256 bytes
DATA
EEPROM
EEADDR
VREF
AN0 AN1 AN2 AN3 AN4 AN5 AN6 AN7 C1IN- C1IN+ C1OUT C2IN- C2IN+ C2OUT
© 2009 Microchip Technology Inc.
DS41203E-page 5
PIC16F688
TABLE 1-1:
PIC16F688 PINOUT DESCRIPTION
Name
Function
Input
Type
Output
Type
RA0/AN0/C1IN+/ICSPDAT/ULPWU
RA0
TTL
CMOS
AN0
AN
—
A/D Channel 0 input
C1IN+
AN
—
Comparator 1 input
ICSPDAT
TTL
CMOS
ULPWU
AN
—
RA1
TTL
CMOS
RA1/AN1/C1IN-/VREF/ICSPCLK
RA2/AN2/T0CKI/INT/C1OUT
RA3/MCLR/VPP
RA4/AN3/T1G/OSC2/CLKOUT
RA5/T1CKI/OSC1/CLKIN
RC0/AN4/C2IN+
RC1/AN5/C2IN-
RC2/AN6
RC3/AN7
RC4/C2OUT/TX/CK
RC5/RX/DT
Description
PORTA I/O w/prog pull-up and interrupt-on-change
Serial Programming Data I/O
Ultra Low-Power Wake-up input
PORTA I/O w/prog pull-up and interrupt-on-change
AN1
AN
—
A/D Channel 1 input
C1IN-
AN
—
Comparator 1 input
VREF
AN
—
External Voltage Reference for A/D
ICSPCLK
ST
—
Serial Programming Clock
RA2
ST
CMOS
AN2
AN
—
PORTA I/O w/prog pull-up and interrupt-on-change
A/D Channel 2 input
T0CKI
ST
—
Timer0 clock input
INT
ST
—
External Interrupt
C1OUT
—
CMOS
RA3
TTL
—
MCLR
ST
—
Master Clear w/internal pull-up
VPP
HV
—
Programming voltage
RA4
TTL
CMOS
AN3
AN
—
T1G
ST
—
OSC2
—
XTAL
Crystal/Resonator
CLKOUT
—
CMOS
FOSC/4 output
PORTA I/O w/prog pull-up and interrupt-on-change
Comparator 1 output
PORTA input with interrupt-on-change
PORTA I/O w/prog pull-up and interrupt-on-change
A/D Channel 3 input
Timer1 gate
RA5
TTL
CMOS
T1CKI
ST
—
Timer1 clock
OSC1
XTAL
—
Crystal/Resonator
External clock input/RC oscillator connection
CLKIN
ST
—
RC0
TTL
CMOS
AN4
AN
—
C2IN+
AN
RC1
TTL
CMOS
AN5
AN
—
PORTC I/O
A/D Channel 4 input
Comparator 2 input
PORTC I/O
A/D Channel 5 input
C2IN-
AN
RC2
TTL
CMOS
Comparator 2 input
AN6
AN
—
RC3
TTL
CMOS
AN7
AN
—
RC4
TTL
CMOS
PORTC I/O
C2OUT
—
CMOS
Comparator 2 output
PORTC I/O
A/D Channel 6 input
PORTC I/O
A/D Channel 7 input
TX
—
CMOS
USART asynchronous output
CK
ST
CMOS
USART asynchronous clock
RC5
TTL
CMOS
Port C I/O
RX
ST
CMOS
USART asynchronous input
USART asynchronous data
DT
ST
CMOS
VSS
VSS
Power
—
Ground reference
VDD
VDD
Power
—
Positive supply
Legend:
AN
TTL
HV
DS41203E-page 6
= Analog input or output
= TTL compatible input
= High Voltage
CMOS = CMOS compatible input or output
ST
= Schmitt Trigger input with CMOS levels
XTAL = Crystal
OC = Open collector output
© 2009 Microchip Technology Inc.
PIC16F688
2.0
MEMORY ORGANIZATION
2.1
Program Memory Organization
The PIC16F688 has a 13-bit program counter capable
of addressing a 4K x 14 program memory space. Only
the first 4K x 14 (0000h-01FFF) for the PIC16F688 is
physically implemented. Accessing a location above
these boundaries will cause a wrap-around within the
first 4K x 14 space. The Reset vector is at 0000h and
the interrupt vector is at 0004h (see Figure 2-1).
FIGURE 2-1:
PROGRAM MEMORY MAP
AND STACK FOR THE
PIC16F688
PC<12:0>
CALL, RETURN
RETFIE, RETLW
13
Stack Level 1
2.2
Data Memory Organization
The data memory is partitioned into multiple banks,
which contain the General Purpose Registers (GPR)
and the Special Function Registers (SFR). Bits RP0
and RP1 are bank select bits.
RP1
RP0
0
0
→
Bank 0 is selected
0
1
→
Bank 1 is selected
1
0
→
Bank 2 is selected
1
1
→
Bank 3 is selected
Each bank extends up to 7Fh (128 bytes). The lower
locations of each bank are reserved for the Special
Function Registers. Above the Special Function Registers are the General Purpose Registers, implemented
as static RAM. All implemented banks contain Special
Function Registers. Some frequently used Special
Function Registers from one bank are mirrored in
another bank for code reduction and quicker access.
Stack Level 2
2.2.1
Stack Level 8
The register file is organized as 256 x 8 in the
PIC16F688. Each register is accessed, either directly
or indirectly, through the File Select Register (FSR)
(see Section 2.4 “Indirect Addressing, INDF and
FSR Registers”).
Reset Vector
0000h
Interrupt Vector
0004h
SPECIAL FUNCTION REGISTERS
0005h
The Special Function Registers are registers used by
the CPU and peripheral functions for controlling the
desired operation of the device (see Tables 2-1, 2-2,
2-3 and 2-4). These registers are static RAM.
01FFh
The special registers can be classified into two sets:
core and peripheral. The Special Function Registers
associated with the “core” are described in this section.
Those related to the operation of the peripheral
features are described in the section of that peripheral
feature.
On-chip Program
Memory
02000h
Wraps to 0000h-07FFh
1FFFh
© 2009 Microchip Technology Inc.
2.2.2
GENERAL PURPOSE REGISTER
FILE
DS41203E-page 7
PIC16F688
FIGURE 2-2:
PIC16F688 SPECIAL FUNCTION REGISTERS
File
Address
Indirect addr. (1) 00h
TMR0
01h
PCL
02h
STATUS
03h
FSR
04h
PORTA
05h
06h
PORTC
07h
08h
09h
PCLATH
0Ah
INTCON
0Bh
PIR1
0Ch
0Dh
TMR1L
0Eh
TMR1H
0Fh
T1CON
10h
BAUDCTL
11h
SPBRGH
12h
SPBRG
13h
RCREG
14h
TXREG
15h
TXSTA
16h
RCSTA
17h
WDTCON
18h
CMCON0
19h
CMCON1
1Ah
1Bh
1Ch
1Dh
ADRESH
1Eh
ADCON0
1Fh
20h
File
Address
Indirect addr. (1) 80h
OPTION_REG 81h
PCL
82h
STATUS
83h
FSR
84h
TRISA
85h
86h
TRISC
87h
88h
89h
PCLATH
8Ah
INTCON
8Bh
PIE1
8Ch
8Dh
PCON
8Eh
OSCCON
8Fh
OSCTUNE
90h
ANSEL
91h
92h
93h
94h
WPUA
95h
IOCA
96h
EEDATH
97h
EEADRH
98h
VRCON
99h
EEDAT
9Ah
EEADR
9Bh
EECON1
9Ch
EECON2(1)
9Dh
ADRESL
9Eh
ADCON1
9Fh
A0h
File
Address
Indirect addr. (1) 100h
TMR0
101h
PCL
102h
STATUS
103h
FSR
104h
PORTA
105h
106h
PORTC
107h
108h
109h
PCLATH
10Ah
INTCON
10Bh
10Ch
10Dh
10Eh
10Fh
110h
111h
112h
113h
114h
115h
116h
117h
118h
119h
11Ah
11Bh
11Ch
11Dh
11Eh
11Fh
120h
General
Purpose
Register
General
Purpose
Register
General
Purpose
Register
80 Bytes
96 Bytes
7Fh
Bank 0
accesses
Bank 0
File
Address
Indirect addr. (1) 180h
OPTION_REG 181h
PCL
182h
STATUS
183h
FSR
184h
TRISA
185h
186h
TRISC
187h
188h
189h
PCLATH
18Ah
INTCON
18Bh
18Ch
18Dh
18Eh
18Fh
190h
191h
192h
193h
194h
195h
196h
197h
198h
199h
19Ah
19Bh
19Ch
19Dh
19Eh
19Fh
1A0h
80 Bytes
EFh
F0h
FFh
Bank 1
accesses
Bank 0
Bank 2
16Fh
170h
17Fh
accesses
Bank 0
1EFh
1F0h
1FFh
Bank 3
Unimplemented data memory locations, read as ‘0’.
Note 1:
Not a physical register.
DS41203E-page 8
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 2-1:
Addr
Name
PIC16F688 SPECIAL REGISTERS SUMMARY BANK 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR/BOR
Page
Bank 0
00h
INDF
Addressing this location uses contents of FSR to address data memory (not a physical register)
xxxx xxxx
20, 117
01h
TMR0
Timer0 Module’s register
xxxx xxxx
45, 117
02h
PCL
Program Counter’s (PC) Least Significant Byte
0000 0000
19, 117
03h
STATUS
13, 117
04h
FSR
05h
PORTA
06h
07h
IRP
RP1
TO
PD
Z
DC
C
0001 1xxx
xxxx xxxx
20, 117
RA5
RA4
RA3
RA2
RA1
RA0
--x0 x000
33, 117
—
—
RC5
RC4
RC3
RC2
RC1
RC0
--xx 0000
42, 117
—
RP0
Indirect Data Memory Address Pointer
—
PORTC
—
—
Unimplemented
—
—
08h
—
Unimplemented
—
09h
—
Unimplemented
—
—
---0 0000
19, 117
0Ah
PCLATH
—
—
—
0Bh
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF(2)
0000 000x
15, 117
0Ch
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
17, 117
Write Buffer for upper 5 bits of Program Counter
0Dh
—
0Eh
TMR1L
Unimplemented
Holding Register for the Least Significant Byte of the 16-bit TMR1
0Fh
TMR1H
Holding Register for the Most Significant Byte of the 16-bit TMR1
10h
T1CON
T1GINV
TMR1GE
T1CKPS1
T1CKPS0
T1OSCEN
T1SYNC
TMR1CS
TMR1ON
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
—
—
xxxx xxxx
48, 117
xxxx xxxx
48, 117
0000 0000
51, 117
11h
BAUDCTL
ABDOVF
01-0 0-00
94, 117
12h
SPBRGH
USART Baud Rate High Generator
0000 0000
95, 117
13h
SPBRG
USART Baud Rate Generator
0000 0000
95, 117
14h
RCREG
USART Receive Register
0000 0000
87, 117
15h
TXREG
USART Transmit Register
0000 0000
87, 117
16h
TXSTA
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
0000 0010
92, 117
17h
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
0000 000x
93, 117
18h
WDTCON
—
—
—
WDTPS3
WDTPS2
WDTPS1
WDTPS0
SWDTEN
---0 1000
124, 117
19h
CMCON0
C2OUT
C1OUT
C2INV
C1INV
CIS
CM2
CM1
CM0
0000 0000
61, 117
1Ah
CMCON1
—
—
—
—
—
—
T1GSS
C2SYNC
---- --10
62, 117
1Bh
—
Unimplemented
—
—
1Ch
—
Unimplemented
—
—
1Dh
—
Unimplemented
—
—
xxxx xxxx
72, 117
00-0 0000
71, 117
1Eh
ADRESH
1Fh
ADCON0
Legend:
Note 1:
2:
Most Significant 8 bits of the left shifted A/D result or 2 bits of right shifted result
ADFM
VCFG
—
CHS2
CHS1
CHS0
GO/DONE
ADON
– = Unimplemented locations read as ‘0’, u = unchanged, x = unknown, q = value depends on condition, shaded = unimplemented
Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.
MCLR and WDT Reset does not affect the previous value data latch. The RAIF bit will be cleared upon Reset but will set again if the
mismatched exists.
© 2009 Microchip Technology Inc.
DS41203E-page 9
PIC16F688
TABLE 2-2:
Addr
PIC16F688 SPECIAL FUNCTION REGISTERS SUMMARY BANK 1
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR/BOR
Page
xxxx xxxx
20, 117
1111 1111
14, 117
Bank 1
80h
INDF
81h
OPTION_REG
82h
PCL
83h
STATUS
84h
FSR
85h
TRISA
RAPU
INTEDG
T0CS
T0SE
PSA
PS2
PS1
PS0
Program Counter’s (PC) Least Significant Byte
IRP
RP1
—
TRISC
—
—
—
19, 117
13, 117
PD
Z
DC
C
0001 1xxx
xxxx xxxx
20, 117
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
--11 1111
33, 117
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
42, 117
—
Unimplemented
—
0000 0000
TO
RP0
Indirect Data Memory Address Pointer
86h
87h
Addressing this location uses contents of FSR to address data memory (not a physical register)
88h
—
Unimplemented
—
89h
—
Unimplemented
—
—
8Ah
PCLATH
—
—
—
---0 0000
19, 117
8Bh
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF(3)
0000 000x
15, 117
8Ch
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
16, 117
8Dh
—
Write Buffer for upper 5 bits of Program Counter
Unimplemented
POR
—
BOR
--01 --qq
18, 117
PCON
—
—
ULPWUE
SBOREN
—
8Fh
OSCCON
—
IRCF2
IRCF1
IRCF0
OSTS
HTS
LTS
SCS
-110 x000
22, 118
90h
OSCTUNE
—
—
—
TUN4
TUN3
TUN2
TUN1
TUN0
---0 0000
26, 118
91h
ANSEL
ANS7
ANS6
ANS5
ANS4
ANS3
ANS2
ANS1
ANS0
1111 1111
34, 118
8Eh
—
—
92h
—
Unimplemented
—
—
93h
—
Unimplemented
—
—
94h
—
Unimplemented
—
—
95h
WPUA(2)
—
—
WPUA0
--11 -111
35, 118
WPUA5
WPUA4
—
WPUA2
WPUA1
96h
IOCA
—
—
IOCA5
IOCA4
IOCA3
IOCA2
IOCA1
IOCA0
--00 0000
35, 118
97h
EEDATH
—
—
EEDATH5
EEDATH4
EEDATH3
EEDATH2
EEDATH1
EEDATH0
--00 0000
78, 118
98h
EEADRH
—
—
—
—
EEADRH3 EEADRH2 EEADRH1 EEADRH0 ---- 0000
78, 118
99h
VRCON
VREN
—
VRR
—
VR3
VR2
VR1
VR0
0-0- 0000
63, 118
9Ah
EEDAT
EEDAT7
EEDAT6
EEDAT5
EEDAT4
EEDAT3
EEDAT2
EEDAT1
EEDAT0
0000 0000
78, 118
9Bh
EEADR
EEADR7
EEADR6
EEADR5
EEADR4
EEADR3
EEADR2
EEADR1
EEADR0
0000 0000
78, 118
9Ch
EECON1
EEPGD
—
—
—
WRERR
WREN
WR
RD
x--- x000
79, 118
9Dh
EECON2
EEPROM Control 2 Register (not a physical register)
---- ----
77, 118
9Eh
ADRESL
Least Significant 2 bits of the left shifted result or 8 bits of the right shifted result
xxxx xxxx
72, 118
9Fh
ADCON1
-000 ----
71, 118
Legend:
Note 1:
2:
3:
—
ADCS2
ADCS1
ADCS0
—
—
—
—
– = Unimplemented locations read as ‘0’, u = unchanged, x = unknown, q = value depends on condition, shaded = unimplemented
Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.
RA3 pull-up is enabled when pin is configured as MCLR in the Configuration Word register.
MCLR and WDT Reset does not affect the previous value data latch. The RAIF bit will be cleared upon Reset but will set again if the
mismatched exists.
DS41203E-page 10
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 2-3:
Addr
Name
PIC16F688 SPECIAL REGISTERS SUMMARY BANK 2
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR/BOR
Page
Bank 2
100h
INDF
Addressing this location uses contents of FSR to address data memory (not a physical register)
xxxx xxxx
20, 117
101h
TMR0
Timer0 Module’s register
xxxx xxxx
45, 117
102h
PCL
Program Counter’s (PC) Least Significant Byte
103h
STATUS
104h
FSR
105h
PORTA
106h
—
107h
IRP
RP1
RP0
TO
PD
Z
DC
C
RA4
RA3
RA2
RA1
RA0
Indirect Data Memory Address Pointer
PORTC
—
—
RA5
Unimplemented
—
—
RC5
RC4
RC3
RC2
RC1
RC0
0000 0000
19, 117
0001 1xxx
13, 117
xxxx xxxx
20, 117
--x0 x000
33, 117
—
—
--xx 0000
42, 117
—
108h
—
Unimplemented
—
109h
—
Unimplemented
—
—
---0 0000
19, 117
10Ah
PCLATH
—
—
—
10Bh
INTCON
GIE
PEIE
T0IE
Write Buffer for upper 5 bits of Program Counter
INTE
RAIE
T0IF
INTF
RAIF(2)
0000 000x
15, 117
10Ch
—
Unimplemented
—
—
10Dh
—
Unimplemented
—
—
10Eh
—
Unimplemented
—
—
10Fh
—
Unimplemented
—
—
110h
—
Unimplemented
—
—
111h
—
Unimplemented
—
—
112h
—
Unimplemented
—
—
113h
—
Unimplemented
—
—
114h
—
Unimplemented
—
—
115h
—
Unimplemented
—
—
116h
—
Unimplemented
—
—
117h
—
Unimplemented
—
—
118h
—
Unimplemented
—
—
119h
—
Unimplemented
—
—
11Ah
—
Unimplemented
—
—
11Bh
—
Unimplemented
—
—
11Ch
—
Unimplemented
—
—
11Dh
—
Unimplemented
—
—
11Eh
—
Unimplemented
—
—
11Fh
—
Unimplemented
—
—
Legend:
Note 1:
2:
– = Unimplemented locations read as ‘0’, u = unchanged, x = unknown, q = value depends on condition, shaded = unimplemented
Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.
MCLR and WDT Reset does not affect the previous value data latch. The RAIF bit will be cleared upon Reset but will set again if the
mismatched exists.
© 2009 Microchip Technology Inc.
DS41203E-page 11
PIC16F688
TABLE 2-4:
Addr
PIC16F688 SPECIAL FUNCTION REGISTERS SUMMARY BANK 3
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR/BOR
Page
xxxx xxxx
20, 117
Bank 3
180h
INDF
181h
OPTION_REG
182h
PCL
183h
STATUS
184h
FSR
185h
TRISA
186h
187h
Addressing this location uses contents of FSR to address data memory (not a physical register)
RAPU
INTEDG
T0CS
T0SE
PSA
PS2
PS1
PS0
Program Counter’s (PC) Least Significant Byte
IRP
RP1
RP0
TO
PD
Z
DC
C
Indirect Data Memory Address Pointer
—
TRISC
—
—
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
Unimplemented
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
1111 1111
14, 117
0000 0000
19, 117
0001 1xxx
13, 117
xxxx xxxx
20, 117
--11 1111
33, 117
—
—
--11 1111
42, 117
—
188h
—
Unimplemented
—
189h
—
Unimplemented
—
—
18Ah
PCLATH
---0 0000
19, 117
—
—
—
GIE
PEIE
T0IE
Write Buffer for upper 5 bits of Program Counter
RAIF(2)
18Bh
INTCON
0000 000x
15, 117
18Ch
—
Unimplemented
—
—
18Dh
—
Unimplemented
—
—
190h
—
Unimplemented
—
—
191h
—
Unimplemented
—
—
192h
—
Unimplemented
—
—
193h
—
Unimplemented
—
—
194h
—
Unimplemented
—
—
195h
—
Unimplemented
—
—
196h
—
Unimplemented
—
—
19Ah
—
Unimplemented
—
—
19Bh
—
Unimplemented
—
—
199h
—
Unimplemented
—
—
19Ah
—
Unimplemented
—
—
19Bh
—
Unimplemented
—
—
19Ch
—
Unimplemented
—
—
19Dh
—
Unimplemented
—
—
19Eh
—
Unimplemented
—
—
19Fh
—
Unimplemented
—
—
Legend:
Note 1:
2:
INTE
RAIE
T0IF
INTF
– = Unimplemented locations read as ‘0’, u = unchanged, x = unknown, q = value depends on condition, shaded = unimplemented
Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.
MCLR and WDT Reset does not affect the previous value data latch. The RAIF bit will be cleared upon Reset but will set again if the
mismatched exists.
DS41203E-page 12
© 2009 Microchip Technology Inc.
PIC16F688
2.2.2.1
STATUS Register
The STATUS register, shown in Register 2-1, contains:
• the arithmetic status of the ALU
• the Reset status
• the bank select bits for data memory (SRAM)
The STATUS register can be the destination for any
instruction, like any other register. If the STATUS
register is the destination for an instruction that affects
the Z, DC or C bits, then the write to these three bits is
disabled. These bits are set or cleared according to the
device logic. Furthermore, the TO and PD bits are not
writable. Therefore, the result of an instruction with the
STATUS register as destination may be different than
intended.
REGISTER 2-1:
For example, CLRF STATUS will clear the upper three
bits and set the Z bit. This leaves the STATUS register
as ‘000u u1uu’ (where u = unchanged).
It is recommended, therefore, that only BCF, BSF,
SWAPF and MOVWF instructions are used to alter the
STATUS register, because these instructions do not
affect any Status bits. For other instructions not
affecting any Status bits (see Section 12.0
“Instruction Set Summary”).
Note 1: The C and DC bits operate as a Borrow
and Digit Borrow out bit, respectively, in
subtraction.
STATUS: STATUS REGISTER
R/W-0
R/W-0
R/W-0
R-1
R-1
R/W-x
R/W-x
R/W-x
IRP
RP1
RP0
TO
PD
Z
DC(1)
C(1)
bit 7
bit 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
bit 7
IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h-1FFh)
0 = Bank 0, 1 (00h-FFh)
bit 6-5
RP<1:0>: Register Bank Select bits (used for direct addressing)
00 = Bank 0 (00h-7Fh)
01 = Bank 1 (80h-FFh)
10 = Bank 2 (100h-17Fh)
11 = Bank 3 (180h-1FFh)
bit 4
TO: Time-out bit
1 = After power-up, CLRWDT instruction or SLEEP instruction
0 = A WDT time-out occurred
bit 3
PD: Power-down bit
1 = After power-up or by the CLRWDT instruction
0 = By execution of the SLEEP instruction
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 (ADDWF, ADDLW,SUBLW,SUBWF instructions)(1)
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
bit 0
C: Carry/Borrow bit(1) (ADDWF, ADDLW, SUBLW, SUBWF instructions)(1)
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 1:
x = Bit is unknown
For Borrow, the polarity is reversed. A subtraction is executed by adding the two’s complement of the second operand.
For rotate (RRF, RLF) instructions, this bit is loaded with either the high-order or low-order bit of the source register.
© 2009 Microchip Technology Inc.
DS41203E-page 13
PIC16F688
2.2.2.2
OPTION Register
Note:
The OPTION register is a readable and writable
register, which contains various control bits to
configure:
•
•
•
•
Timer0/WDT prescaler
External RA2/INT interrupt
Timer0
Weak pull-ups on PORTA
REGISTER 2-2:
To achieve a 1:1 prescaler assignment for
Timer0, assign the prescaler to the WDT
by setting PSA bit of the OPTION register
to ‘1’. See Section 5.1.3 “Software
Programmable Prescaler”.
OPTION_REG: OPTION 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
RAPU
INTEDG
T0CS
T0SE
PSA
PS2
PS1
PS0
bit 7
bit 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
bit 7
RAPU: PORTA Pull-up Enable bit
1 = PORTA pull-ups are disabled
0 = PORTA pull-ups are enabled by individual PORT latch values
bit 6
INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RA2/INT pin
0 = Interrupt on falling edge of RA2/INT pin
bit 5
T0CS: Timer0 Clock Source Select bit
1 = Transition on RA2/T0CKI pin
0 = Internal instruction cycle clock (FOSC/4)
bit 4
T0SE: Timer0 Source Edge Select bit
1 = Increment on high-to-low transition on RA2/T0CKI pin
0 = Increment on low-to-high transition on RA2/T0CKI pin
bit 3
PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0
PS<2:0>: Prescaler Rate Select bits
DS41203E-page 14
Bit Value
Timer0 Rate
WDT Rate
000
001
010
011
100
101
110
111
1:2
1:4
1:8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1:1
1:2
1:4
1:8
1 : 16
1 : 32
1 : 64
1 : 128
x = Bit is unknown
© 2009 Microchip Technology Inc.
PIC16F688
2.2.2.3
INTCON Register
Note:
The INTCON register is a readable and writable
register, which contains the various enable and flag bits
for TMR0 register overflow, PORTA change and
external RA2/INT pin interrupts.
REGISTER 2-3:
Interrupt flag bits are set when an interrupt
condition occurs, regardless of the state of
its corresponding enable bit or the global
enable bit, GIE of the INTCON register.
User software should ensure the appropriate interrupt flag bits are clear prior to
enabling an interrupt.
INTCON: INTERRUPT 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-x
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
bit 7
bit 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
bit 7
GIE: Global Interrupt Enable bit
1 = Enables all unmasked interrupts
0 = Disables all interrupts
bit 6
PEIE: Peripheral Interrupt Enable bit
1 = Enables all unmasked peripheral interrupts
0 = Disables all peripheral interrupts
bit 5
T0IE: Timer0 Overflow Interrupt Enable bit
1 = Enables the Timer0 interrupt
0 = Disables the Timer0 interrupt
bit 4
INTE: RA2/INT External Interrupt Enable bit
1 = Enables the RA2/INT external interrupt
0 = Disables the RA2/INT external interrupt
bit 3
RAIE: PORTA Change Interrupt Enable bit(1)
1 = Enables the PORTA change interrupt
0 = Disables the PORTA change interrupt
bit 2
T0IF: Timer0 Overflow Interrupt Flag bit(2)
1 = Timer0 register has overflowed (must be cleared in software)
0 = Timer0 register did not overflow
bit 1
INTF: RA2/INT External Interrupt Flag bit
1 = The RA2/INT external interrupt occurred (must be cleared in software)
0 = The RA2/INT external interrupt did not occur
bit 0
RAIF: PORTA Change Interrupt Flag bit
1 = When at least one of the PORTA <5:0> pins changed state (must be cleared in software)
0 = None of the PORTA <5:0> pins have changed state
Note 1:
2:
IOCA register must also be enabled.
T0IF bit is set when TMR0 rolls over. TMR0 is unchanged on Reset and should be initialized before
clearing T0IF bit.
© 2009 Microchip Technology Inc.
DS41203E-page 15
PIC16F688
2.2.2.4
PIE1 Register
The PIE1 register contains the interrupt enable bits, as
shown in Register 2-4.
REGISTER 2-4:
Note:
Bit PEIE of the INTCON register must be
set to enable any peripheral interrupt.
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
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
bit 7
bit 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
bit 7
EEIE: EE Write Complete Interrupt Enable bit
1 = Enables the EE write complete interrupt
0 = Disables the EE write complete interrupt
bit 6
ADIE: A/D Converter (ADC) Interrupt Enable bit
1 = Enables the ADC interrupt
0 = Disables the ADC interrupt
bit 5
RCIE: EUSART Receive Interrupt Enable bit
1 = Enables the EUSART receive interrupt
0 = Disables the EUSART receive interrupt
bit 4
C2IE: Comparator 2 Interrupt Enable bit
1 = Enables the Comparator C2 interrupt
0 = Disables the Comparator C2 interrupt
bit 3
C1IE: Comparator 1 Interrupt Enable bit
1 = Enables the Comparator C1 interrupt
0 = Disables the Comparator C1 interrupt
bit 2
OSFIE: Oscillator Fail Interrupt Enable bit
1 = Enables the oscillator fail interrupt
0 = Disables the oscillator fail interrupt
bit 1
TXIE: EUSART Transmit Interrupt Enable bit
1 = Enables the EUSART transmit interrupt
0 = Disables the EUSART transmit interrupt
bit 0
TMR1IE: Timer1 Overflow Interrupt Enable bit
1 = Enables the Timer1 overflow interrupt
0 = Disables the Timer1 overflow interrupt
DS41203E-page 16
x = Bit is unknown
© 2009 Microchip Technology Inc.
PIC16F688
2.2.2.5
PIR1 Register
The PIR1 register contains the interrupt flag bits, as
shown in Register 2-5.
REGISTER 2-5:
Note:
Interrupt flag bits are set when an interrupt
condition occurs, regardless of the state of
its corresponding enable bit or the global
enable bit, GIE bit of the INTCON register.
User software should ensure the appropriate interrupt flag bits are clear prior to
enabling an interrupt.
PIR1: PERIPHERAL INTERRUPT REQUEST REGISTER 1
R/W-0
R/W-0
R-0
R/W-0
R/W-0
R/W-0
R-0
R/W-0
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
bit 7
bit 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
bit 7
EEIF: EEPROM Write Operation Interrupt Flag bit
1 = The write operation completed (must be cleared in software)
0 = The write operation has not completed or has not been started
bit 6
ADIF: A/D Converter Interrupt Flag bit
1 = A/D conversion complete (must be cleared in software)
0 = A/D conversion has not completed or has not been started
bit 5
RCIF: EUSART Receive Interrupt Flag bit
1 = The EUSART receive buffer is full (cleared by reading RCREG)
0 = The EUSART receive buffer is not full
bit 4
C2IF: Comparator C2 Interrupt Flag bit
1 = Comparator output (C2OUT bit) has changed (must be cleared in software)
0 = Comparator output (C2OUT bit) has not changed
bit 3
C1IF: Comparator C1 Interrupt Flag bit
1 = Comparator output (C1OUT bit) has changed (must be cleared in software)
0 = Comparator output (C1OUT bit) has not changed
bit 2
OSFIF: Oscillator Fail Interrupt Flag bit
1 = System oscillator failed, clock input has changed to INTOSC (must be cleared in software)
0 = System clock operating
bit 1
TXIF: EUSART Transmit Interrupt Flag bit
1 = The EUSART transmit buffer is empty (cleared by writing to TXREG)
0 = The EUSART transmit buffer is full
bit 0
TMR1IF: Timer1 Overflow Interrupt Flag bit
1 = The TMR1 register overflowed (must be cleared in software)
0 = The TMR1 register did not overflow
© 2009 Microchip Technology Inc.
DS41203E-page 17
PIC16F688
2.2.2.6
PCON Register
The Power Control (PCON) register (see Register 2-6)
contains flag bits to differentiate between a:
•
•
•
•
Power-on Reset (POR)
Brown-out Reset (BOR)
Watchdog Timer Reset (WDT)
External MCLR Reset
The PCON register also controls the Ultra Low-Power
Wake-up and software enable of the BOR.
REGISTER 2-6:
PCON: POWER CONTROL REGISTER
U-0
U-0
R/W-0
R/W-1
U-0
U-0
R/W-0
R/W-x
—
—
ULPWUE
SBOREN(1)
—
—
POR
BOR
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5
ULPWUE: Ultra Low-Power Wake-up Enable bit
1 = Ultra low-power wake-up enabled
0 = Ultra low-power wake-up disabled
bit 4
SBOREN: Software BOR Enable bit(1)
1 = BOR enabled
0 = BOR disabled
bit 3-2
Unimplemented: Read as ‘0’
bit 1
POR: Power-on Reset Status bit
1 = No Power-on Reset occurred
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 = No Brown-out Reset occurred
0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset occurs)
Note 1:
BOREN<1:0> = 01 in the Configuration Word register for this bit to control the BOR.
DS41203E-page 18
© 2009 Microchip Technology Inc.
PIC16F688
2.3
2.3.2
PCL and PCLATH
The Program Counter (PC) is 13 bits wide. The low byte
comes from the PCL register, which is a readable and
writable register. The high byte (PC<12:8>) is not
directly readable or writable and comes from PCLATH.
On any Reset, the PC is cleared. Figure 2-3 shows the
two situations for the loading of the PC. The upper
example in Figure 2-3 shows how the PC is loaded on a
write to PCL (PCLATH<4:0> → PCH). The lower example in Figure 2-3 shows how the PC is loaded during a
CALL or GOTO instruction (PCLATH<4:3> → PCH).
FIGURE 2-3:
LOADING OF PC IN
DIFFERENT SITUATIONS
PCH
PCL
12
8
7
0
PC
8
PCLATH<4:0>
5
Instruction with
PCL as
Destination
ALU Result
PCLATH
PCH
12
11 10
PCL
8
STACK
The PIC16F688 family has an 8-level x 13-bit wide
hardware stack (see Figure 2-1). The stack space is
not part of either program or data space and the Stack
Pointer is not readable or writable. The PC is PUSHed
onto the stack when a CALL instruction is executed or
an interrupt causes a branch. The stack is POPed in
the event of a RETURN,
RETLW or a RETFIE
instruction execution. PCLATH is not affected by a
PUSH or POP operation.
The stack operates as a circular buffer. This means that
after the stack has been PUSHed eight times, the ninth
push overwrites the value that was stored from the first
push. The tenth push overwrites the second push (and
so on).
Note 1: There are no Status bits to indicate Stack
Overflow or Stack Underflow conditions.
2: There are no instructions/mnemonics
called PUSH or POP. These are actions
that occur from the execution of the
CALL, RETURN, RETLW and RETFIE
instructions or the vectoring to an
interrupt address.
0
7
PC
GOTO, CALL
2
PCLATH<4:3>
11
OPCODE<10:0>
PCLATH
2.3.1
COMPUTED GOTO
A computed GOTO is accomplished by adding an offset
to the program counter (ADDWF
PCL). When
performing a table read using a computed GOTO
method, care should be exercised if the table location
crosses a PCL memory boundary (each 256-byte
block). Refer to the Application Note AN556,
“Implementing a Table Read” (DS00556).
© 2009 Microchip Technology Inc.
DS41203E-page 19
PIC16F688
2.4
Indirect Addressing, INDF and
FSR Registers
A simple program to clear RAM location 20h-2Fh using
indirect addressing is shown in Example 2-1.
The INDF register is not a physical register. Addressing
the INDF register will cause indirect addressing.
EXAMPLE 2-1:
MOVLW
MOVWF
NEXT CLRF
INCF
BTFSS
GOTO
CONTINUE
Indirect addressing is possible by using the INDF
register. Any instruction using the INDF register
actually accesses data pointed to by the File Select
Register (FSR). Reading INDF itself indirectly will
produce 00h. Writing to the INDF register indirectly
results in a no operation (although Status bits may be
affected). An effective 9-bit address is obtained by
concatenating the 8-bit FSR register and the IRP bit of
the STATUS register, as shown in Figure 2-4.
FIGURE 2-4:
INDIRECT ADDRESSING
0x20
FSR
INDF
FSR
FSR,4
NEXT
;initialize pointer
;to RAM
;clear INDF register
;inc pointer
;all done?
;no clear next
;yes continue
DIRECT/INDIRECT ADDRESSING PIC16F688
Direct Addressing
RP1
RP0
Indirect Addressing
From Opcode
6
Bank Select
0
7
IRP
Bank Select
Location Select
00
01
10
File Select Register
0
Location Select
11
00h
180h
Data
Memory
7Fh
1FFh
Bank 0
Note:
Bank 1
Bank 2
Bank 3
For memory map detail, see Figure 2-2.
DS41203E-page 20
© 2009 Microchip Technology Inc.
PIC16F688
3.0
OSCILLATOR MODULE (WITH
FAIL-SAFE CLOCK MONITOR)
The oscillator module can be configured in one of eight
clock modes.
3.1
Overview
1.
2.
3.
The oscillator module has a wide variety of clock
sources and selection features that allow it to be used
in a wide range of applications while maximizing performance and minimizing power consumption. Figure 3-1
illustrates a block diagram of the oscillator module.
4.
5.
Clock sources can be configured from external
oscillators, quartz crystal resonators, ceramic resonators
and Resistor-Capacitor (RC) circuits. In addition, the
system clock source can be configured from one of two
internal oscillators, with a choice of speeds selectable via
software. Additional clock features include:
6.
7.
8.
• Selectable system clock source between external
or internal via software.
• Two-Speed Start-Up mode, which minimizes
latency between external oscillator start-up and
code execution.
• Fail-Safe Clock Monitor (FSCM) designed to
detect a failure of the external clock source (LP,
XT, HS, EC or RC modes) and switch
automatically to the internal oscillator.
FIGURE 3-1:
EC – External clock with I/O on OSC2/CLKOUT.
LP – 32 kHz Low-Power Crystal mode.
XT – Medium Gain Crystal or Ceramic
Resonator Oscillator mode.
HS – High Gain Crystal or Ceramic Resonator
mode.
RC – External Resistor-Capacitor (RC) with
FOSC/4 output on OSC2/CLKOUT.
RCIO – External Resistor-Capacitor (RC) with
I/O on OSC2/CLKOUT.
INTOSC – Internal oscillator with FOSC/4 output
on OSC2 and I/O on OSC1/CLKIN.
INTOSCIO – Internal oscillator with I/O on
OSC1/CLKIN and OSC2/CLKOUT.
Clock source modes are configured by the FOSC<2:0>
bits in the Configuration Word register (CONFIG). The
internal clock can be generated from two internal
oscillators. The HFINTOSC is a calibrated highfrequency oscillator. The LFINTOSC is an uncalibrated
low-frequency oscillator.
PIC® MCU CLOCK SOURCE BLOCK DIAGRAM
FOSC<2:0>
(Configuration Word Register)
SCS<0>
(OSCCON Register)
External Oscillator
OSC2
Sleep
MUX
LP, XT, HS, RC, RCIO, EC
OSC1
IRCF<2:0>
(OSCCON Register)
8 MHz
Internal Oscillator
4 MHz
System Clock
(CPU and Peripherals)
INTOSC
111
110
101
1 MHz
100
500 kHz
250 kHz
125 kHz
LFINTOSC
31 kHz
31 kHz
011
MUX
HFINTOSC
8 MHz
Postscaler
2 MHz
010
001
000
Power-up Timer (PWRT)
Watchdog Timer (WDT)
Fail-Safe Clock Monitor (FSCM)
© 2009 Microchip Technology Inc.
DS41203E-page 21
PIC16F688
3.2
Oscillator Control
The Oscillator Control (OSCCON) register (Figure 3-1)
controls the system clock and frequency selection
options. The OSCCON register contains the following
bits:
• Frequency selection bits (IRCF)
• Frequency Status bits (HTS, LTS)
• System clock control bits (OSTS, SCS)
REGISTER 3-1:
OSCCON: OSCILLATOR CONTROL REGISTER
U-0
R/W-1
R/W-1
R/W-0
R-1
R-0
R-0
R/W-0
—
IRCF2
IRCF1
IRCF0
OSTS(1)
HTS
LTS
SCS
bit 7
bit 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
bit 7
Unimplemented: Read as ‘0’
bit 6-4
IRCF<2:0>: Internal Oscillator Frequency Select bits
111 = 8 MHz
110 = 4 MHz (default)
101 = 2 MHz
100 = 1 MHz
011 = 500 kHz
010 = 250 kHz
001 = 125 kHz
000 = 31 kHz (LFINTOSC)
bit 3
OSTS: Oscillator Start-up Time-out Status bit(1)
1 = Device is running from the external clock defined by FOSC<2:0> of the Configuration Word
0 = Device is running from the internal oscillator (HFINTOSC or LFINTOSC)
bit 2
HTS: HFINTOSC Status bit (High Frequency – 8 MHz to 125 kHz)
1 = HFINTOSC is stable
0 = HFINTOSC is not stable
bit 1
LTS: LFINTOSC Stable bit (Low Frequency – 31 kHz)
1 = LFINTOSC is stable
0 = LFINTOSC is not stable
bit 0
SCS: System Clock Select bit
1 = Internal oscillator is used for system clock
0 = Clock source defined by FOSC<2:0> of the Configuration Word
Note 1:
Bit resets to ‘0’ with Two-Speed Start-up and LP, XT or HS selected as the Oscillator mode or Fail-Safe
mode is enabled.
DS41203E-page 22
© 2009 Microchip Technology Inc.
PIC16F688
3.3
Clock Source Modes
Clock source modes can be classified as external or
internal.
External Clock Modes
3.4.1
OSCILLATOR START-UP TIMER (OST)
If the oscillator module is configured for LP, XT or HS
modes, the Oscillator Start-up Timer (OST) counts
1024 oscillations from OSC1. This occurs following a
Power-on Reset (POR) and when the Power-up Timer
(PWRT) has expired (if configured), or a wake-up from
Sleep. During this time, the program counter does not
increment and program execution is suspended. The
OST ensures that the oscillator circuit, using a quartz
crystal resonator or ceramic resonator, has started and
is providing a stable system clock to the oscillator
module. When switching between clock sources, a
delay is required to allow the new clock to stabilize.
These oscillator delays are shown in Table 3-1.
• External Clock modes rely on external circuitry for
the clock source. Examples are: oscillator modules (EC mode), quartz crystal resonators or
ceramic resonators (LP, XT and HS modes) and
Resistor-Capacitor (RC) mode circuits.
• Internal clock sources are contained internally
within the oscillator module. The oscillator module
has two internal oscillators: the 8 MHz HighFrequency Internal Oscillator (HFINTOSC) and
the 31 kHz Low-Frequency Internal Oscillator
(LFINTOSC).
The system clock can be selected between external or
internal clock sources via the System Clock Select
(SCS) bit of the OSCCON register. See Section 3.6
“Clock Switching” for additional information.
TABLE 3-1:
3.4
In order to minimize latency between external oscillator
start-up and code execution, the Two-Speed Clock
Start-up mode can be selected (see Section 3.7 “TwoSpeed Clock Start-up Mode”).
OSCILLATOR DELAY EXAMPLES
Switch From
Switch To
Frequency
Oscillator Delay
Sleep/POR
LFINTOSC
HFINTOSC
31 kHz
125 kHz to 8 MHz
Sleep/POR
EC, RC
DC – 20 MHz
2 instruction cycles
LFINTOSC (31 kHz)
EC, RC
DC – 20 MHz
1 cycle of each
Oscillator Warm-Up Delay (TWARM)
Sleep/POR
LP, XT, HS
32 kHz to 20 MHz
1024 Clock Cycles (OST)
LFINTOSC (31 kHz)
HFINTOSC
125 kHz to 8 MHz
1 μs (approx.)
3.4.2
EC MODE
The External Clock (EC) mode allows an externally
generated logic level as the system clock source. When
operating in this mode, an external clock source is
connected to the OSC1 input and the OSC2 is available
for general purpose I/O. Figure 3-2 shows the pin
connections for EC mode.
The Oscillator Start-up Timer (OST) is disabled when
EC mode is selected. Therefore, there is no delay in
operation after a Power-on Reset (POR) or wake-up
from Sleep. Because the PIC® MCU design is fully
static, stopping the external clock input will have the
effect of halting the device while leaving all data intact.
Upon restarting the external clock, the device will
resume operation as if no time had elapsed.
© 2009 Microchip Technology Inc.
FIGURE 3-2:
EXTERNAL CLOCK (EC)
MODE OPERATION
OSC1/CLKIN
Clock from
Ext. System
PIC® MCU
I/O
Note 1:
OSC2/CLKOUT(1)
Alternate pin functions are listed in
Section 1.0 “Device Overview”.
DS41203E-page 23
PIC16F688
3.4.3
LP, XT, HS MODES
The LP, XT and HS modes support the use of quartz
crystal resonators or ceramic resonators connected to
OSC1 and OSC2 (Figure 3-3). The mode selects a low,
medium or high gain setting of the internal inverteramplifier to support various resonator types and speed.
LP Oscillator mode selects the lowest gain setting of
the internal inverter-amplifier. LP mode current
consumption is the least of the three modes. This mode
is best suited to drive resonators with a low drive level
specification, for example, tuning fork type crystals.
This mode is designed to drive only 32.768 kHz tuning
fork type crystals (watch crystals).
Note 1: Quartz crystal characteristics vary according
to type, package and manufacturer. The
user should consult the manufacturer data
sheets for specifications and recommended
application.
2: Always verify oscillator performance over
the VDD and temperature range that is
expected for the application.
3: For oscillator design assistance, reference
the following Microchip Applications Notes:
• AN826, “Crystal Oscillator Basics and
Crystal Selection for rfPIC® and PIC®
Devices” (DS00826)
• AN849, “Basic PIC® Oscillator Design”
(DS00849)
• AN943, “Practical PIC® Oscillator
Analysis and Design” (DS00943)
• AN949, “Making Your Oscillator Work”
(DS00949)
XT Oscillator mode selects the intermediate gain
setting of the internal inverter-amplifier. XT mode
current consumption is the medium of the three modes.
This mode is best suited to drive resonators with a
medium drive level specification.
HS Oscillator mode selects the highest gain setting of the
internal inverter-amplifier. HS mode current consumption
is the highest of the three modes. This mode is best
suited for resonators that require a high drive setting.
FIGURE 3-4:
CERAMIC RESONATOR
OPERATION
(XT OR HS MODE)
Figure 3-3 and Figure 3-4 show typical circuits for
quartz crystal and ceramic resonators, respectively.
FIGURE 3-3:
PIC® MCU
QUARTZ CRYSTAL
OPERATION (LP, XT OR
HS MODE)
OSC1/CLKIN
C1
To Internal
Logic
PIC® MCU
RP(3)
RF(2)
OSC1/CLKIN
C1
To Internal
Logic
Quartz
Crystal
RF(2)
Sleep
C2 Ceramic
RS(1)
Resonator
Note 1:
C2
RS(1)
OSC2/CLKOUT
Note 1:
A series resistor (RS) may be required for
quartz crystals with low drive level.
2:
The value of RF varies with the Oscillator mode
selected (typically between 2 MΩ to 10 MΩ).
DS41203E-page 24
Sleep
OSC2/CLKOUT
A series resistor (RS) may be required for
ceramic resonators with low drive level.
2: The value of RF varies with the Oscillator mode
selected (typically between 2 MΩ to 10 MΩ).
3: An additional parallel feedback resistor (RP)
may be required for proper ceramic resonator
operation.
© 2009 Microchip Technology Inc.
PIC16F688
3.4.4
EXTERNAL RC MODES
3.5
The external Resistor-Capacitor (RC) modes support
the use of an external RC circuit. This allows the
designer maximum flexibility in frequency choice while
keeping costs to a minimum when clock accuracy is not
required. There are two modes: RC and RCIO.
In RC mode, the RC circuit connects to OSC1. OSC2/
CLKOUT outputs the RC oscillator frequency divided
by 4. This signal may be used to provide a clock for
external circuitry, synchronization, calibration, test or
other application requirements. Figure 3-5 shows the
external RC mode connections.
FIGURE 3-5:
VDD
EXTERNAL RC MODES
PIC® MCU
REXT
OSC1/CLKIN
Internal
Clock
CEXT
VSS
FOSC/4 or
I/O(2)
OSC2/CLKOUT(1)
Recommended values: 10 kΩ ≤ REXT ≤ 100 kΩ, <3V
3 kΩ ≤ REXT ≤ 100 kΩ, 3-5V
CEXT > 20 pF, 2-5V
Note 1:
2:
Alternate pin functions are listed in
Section 1.0 “Device Overview”.
Output depends upon RC or RCIO clock mode.
In RCIO mode, the RC circuit is connected to OSC1.
OSC2 becomes an additional general purpose I/O pin.
The RC oscillator frequency is a function of the supply
voltage, the resistor (REXT) and capacitor (CEXT) values
and the operating temperature. Other factors affecting
the oscillator frequency are:
• threshold voltage variation
• component tolerances
• packaging variations in capacitance
The user also needs to take into account variation due
to tolerance of external RC components used.
Internal Clock Modes
The oscillator module has two independent, internal
oscillators that can be configured or selected as the
system clock source.
1.
2.
The HFINTOSC (High-Frequency Internal
Oscillator) is factory calibrated and operates at
8 MHz. The frequency of the HFINTOSC can be
user-adjusted via software using the OSCTUNE
register (Register 3-2).
The LFINTOSC (Low-Frequency Internal
Oscillator) is uncalibrated and operates at 31 kHz.
The system clock speed can be selected via software
using the Internal Oscillator Frequency Select bits
IRCF<2:0> of the OSCCON register.
The system clock can be selected between external or
internal clock sources via the System Clock Selection
(SCS) bit of the OSCCON register. See Section 3.6
“Clock Switching” for more information.
3.5.1
INTOSC AND INTOSCIO MODES
The INTOSC and INTOSCIO modes configure the
internal oscillators as the system clock source when
the device is programmed using the oscillator selection
or the FOSC<2:0> bits in the Configuration Word
register (CONFIG). See Section 11.0 “Special
Features of the CPU” for more information.
In INTOSC mode, OSC1/CLKIN is available for general
purpose I/O. OSC2/CLKOUT outputs the selected
internal oscillator frequency divided by 4. The CLKOUT
signal may be used to provide a clock for external
circuitry, synchronization, calibration, test or other
application requirements.
In INTOSCIO mode, OSC1/CLKIN and OSC2/CLKOUT
are available for general purpose I/O.
3.5.2
HFINTOSC
The High-Frequency Internal Oscillator (HFINTOSC) is
a factory calibrated 8 MHz internal clock source. The
frequency of the HFINTOSC can be altered via
software using the OSCTUNE register (Register 3-2).
The output of the HFINTOSC connects to a postscaler
and multiplexer (see Figure 3-1). One of seven
frequencies can be selected via software using the
IRCF<2:0> bits of the OSCCON register. See
Section 3.5.4 “Frequency Select Bits (IRCF)” for
more information.
The HFINTOSC is enabled by selecting any frequency
between 8 MHz and 125 kHz by setting the IRCF<2:0>
bits of the OSCCON register ≠ 000. Then, set the
System Clock Source (SCS) bit of the OSCCON
register to ‘1’ or enable Two-Speed Start-up by setting
the IESO bit in the Configuration Word register
(CONFIG) to ‘1’.
The HF Internal Oscillator (HTS) bit of the OSCCON
register indicates whether the HFINTOSC is stable or not.
© 2009 Microchip Technology Inc.
DS41203E-page 25
PIC16F688
3.5.2.1
OSCTUNE Register
The HFINTOSC is factory calibrated but can be
adjusted in software by writing to the OSCTUNE
register (Register 3-2).
The default value of the OSCTUNE register is ‘0’. The
value is a 5-bit two’s complement number.
REGISTER 3-2:
When the OSCTUNE register is modified, the
HFINTOSC frequency will begin shifting to the new
frequency. Code execution continues during this shift.
There is no indication that the shift has occurred.
OSCTUNE does not affect the LFINTOSC frequency.
Operation of features that depend on the LFINTOSC
clock source frequency, such as the Power-up Timer
(PWRT), Watchdog Timer (WDT), Fail-Safe Clock
Monitor (FSCM) and peripherals, are not affected by the
change in frequency.
OSCTUNE: OSCILLATOR TUNING REGISTER
U-0
U-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
—
—
—
TUN4
TUN3
TUN2
TUN1
TUN0
bit 7
bit 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
bit 7-5
Unimplemented: Read as ‘0’
bit 4-0
TUN<4:0>: Frequency Tuning bits
01111 = Maximum frequency
01110 =
•
•
•
00001 =
00000 = Oscillator module is running at the calibrated frequency.
11111 =
•
•
•
10000 = Minimum frequency
DS41203E-page 26
x = Bit is unknown
© 2009 Microchip Technology Inc.
PIC16F688
3.5.3
LFINTOSC
The Low-Frequency Internal Oscillator (LFINTOSC) is
an uncalibrated 31 kHz internal clock source.
The output of the LFINTOSC connects to a postscaler
and multiplexer (see Figure 3-1). Select 31 kHz, via
software, using the IRCF<2:0> bits of the OSCCON
register. See Section 3.5.4 “Frequency Select Bits
(IRCF)” for more information. The LFINTOSC is also the
frequency for the Power-up Timer (PWRT), Watchdog
Timer (WDT) and Fail-Safe Clock Monitor (FSCM).
The LFINTOSC is enabled by selecting 31 kHz
(IRCF<2:0> bits of the OSCCON register = 000) as the
system clock source (SCS bit of the OSCCON
register = 1), or when any of the following are enabled:
• Two-Speed Start-up IESO bit of the Configuration
Word register = 1 and IRCF<2:0> bits of the
OSCCON register = 000
• Power-up Timer (PWRT)
• Watchdog Timer (WDT)
• Fail-Safe Clock Monitor (FSCM)
The LF Internal Oscillator (LTS) bit of the OSCCON
register indicates whether the LFINTOSC is stable or
not.
3.5.4
FREQUENCY SELECT BITS (IRCF)
The output of the 8 MHz HFINTOSC and 31 kHz
LFINTOSC connects to a postscaler and multiplexer
(see Figure 3-1). The Internal Oscillator Frequency
Select bits IRCF<2:0> of the OSCCON register select
the frequency output of the internal oscillators. One of
eight frequencies can be selected via software:
•
•
•
•
•
•
•
•
8 MHz
4 MHz (Default after Reset)
2 MHz
1 MHz
500 kHz
250 kHz
125 kHz
31 kHz (LFINTOSC)
Note:
3.5.5
HF AND LF INTOSC CLOCK
SWITCH TIMING
When switching between the LFINTOSC and the
HFINTOSC, the new oscillator may already be shut
down to save power (see Figure 3-6). If this is the case,
there is a delay after the IRCF<2:0> bits of the
OSCCON register are modified before the frequency
selection takes place. The LTS and HTS bits of the
OSCCON register will reflect the current active status
of the LFINTOSC and HFINTOSC oscillators. The
timing of a frequency selection is as follows:
1.
2.
3.
4.
5.
6.
IRCF<2:0> bits of the OSCCON register are
modified.
If the new clock is shut down, a clock start-up
delay is started.
Clock switch circuitry waits for a falling edge of
the current clock.
CLKOUT is held low and the clock switch
circuitry waits for a rising edge in the new clock.
CLKOUT is now connected with the new clock.
LTS and HTS bits of the OSCCON register are
updated as required.
Clock switch is complete.
See Figure 3-1 for more details.
If the internal oscillator speed selected is between
8 MHz and 125 kHz, there is no start-up delay before
the new frequency is selected. This is because the old
and new frequencies are derived from the HFINTOSC
via the postscaler and multiplexer.
Start-up delay specifications are located in the
Section 14.0 “Electrical Specifications”, under the
AC Specifications (Oscillator Module).
Following any Reset, the IRCF<2:0> bits of
the OSCCON register are set to ‘110’ and
the frequency selection is set to 4 MHz.
The user can modify the IRCF bits to
select a different frequency.
© 2009 Microchip Technology Inc.
DS41203E-page 27
PIC16F688
FIGURE 3-6:
INTERNAL OSCILLATOR SWITCH TIMING
LF(1)
HF
HFINTOSC
LFINTOSC (FSCM and WDT disabled)
HFINTOSC
Start-up Time
2-cycle Sync
Running
LFINTOSC
≠0
IRCF <2:0>
=0
System Clock
Note 1:
When going from LF to HF.
HFINTOSC
LFINTOSC (Either FSCM or WDT enabled)
HFINTOSC
2-cycle Sync
Running
LFINTOSC
≠0
IRCF <2:0>
=0
System Clock
LFINTOSC
HFINTOSC
LFINTOSC turns off unless WDT or FSCM is enabled
LFINTOSC
Start-up Time 2-cycle Sync
Running
HFINTOSC
IRCF <2:0>
=0
≠0
System Clock
DS41203E-page 28
© 2009 Microchip Technology Inc.
PIC16F688
3.6
Clock Switching
The system clock source can be switched between
external and internal clock sources via software using
the System Clock Select (SCS) bit of the OSCCON
register.
3.6.1
SYSTEM CLOCK SELECT (SCS) BIT
The System Clock Select (SCS) bit of the OSCCON
register selects the system clock source that is used for
the CPU and peripherals.
• When the SCS bit of the OSCCON register = 0,
the system clock source is determined by
configuration of the FOSC<2:0> bits in the
Configuration Word register (CONFIG).
• When the SCS bit of the OSCCON register = 1,
the system clock source is chosen by the internal
oscillator frequency selected by the IRCF<2:0>
bits of the OSCCON register. After a Reset, the
SCS bit of the OSCCON register is always
cleared.
Note:
3.6.2
Any automatic clock switch, which may
occur from Two-Speed Start-up or Fail-Safe
Clock Monitor, does not update the SCS bit
of the OSCCON register. The user can
monitor the OSTS bit of the OSCCON
register to determine the current system
clock source.
OSCILLATOR START-UP TIME-OUT
STATUS (OSTS) BIT
The Oscillator Start-up Time-out Status (OSTS) bit of
the OSCCON register indicates whether the system
clock is running from the external clock source, as
defined by the FOSC<2:0> bits in the Configuration
Word register (CONFIG), or from the internal clock
source. In particular, OSTS indicates that the Oscillator
Start-up Timer (OST) has timed out for LP, XT or HS
modes.
3.7
Two-Speed Clock Start-up Mode
Two-Speed Start-up mode provides additional power
savings by minimizing the latency between external
oscillator start-up and code execution. In applications
that make heavy use of the Sleep mode, Two-Speed
Start-up will remove the external oscillator start-up
time from the time spent awake and can reduce the
overall power consumption of the device.
When the oscillator module is configured for LP, XT or
HS modes, the Oscillator Start-up Timer (OST) is
enabled (see Section 3.4.1 “Oscillator Start-up Timer
(OST)”). The OST will suspend program execution until
1024 oscillations are counted. Two-Speed Start-up
mode minimizes the delay in code execution by
operating from the internal oscillator as the OST is
counting. When the OST count reaches 1024 and the
OSTS bit of the OSCCON register is set, program
execution switches to the external oscillator.
3.7.1
TWO-SPEED START-UP MODE
CONFIGURATION
Two-Speed Start-up mode is configured by the
following settings:
• IESO (of the Configuration Word register) = 1;
Internal/External Switchover bit (Two-Speed Startup mode enabled).
• SCS (of the OSCCON register) = 0.
• FOSC<2:0> bits in the Configuration Word
register (CONFIG) configured for LP, XT or HS
mode.
Two-Speed Start-up mode is entered after:
• Power-on Reset (POR) and, if enabled, after
Power-up Timer (PWRT) has expired, or
• Wake-up from Sleep.
If the external clock oscillator is configured to be
anything other than LP, XT or HS mode, then TwoSpeed Start-up is disabled. This is because the external
clock oscillator does not require any stabilization time
after POR or an exit from Sleep.
3.7.2
1.
2.
3.
4.
5.
6.
7.
TWO-SPEED START-UP
SEQUENCE
Wake-up from Power-on Reset or Sleep.
Instructions begin execution by the internal
oscillator at the frequency set in the IRCF<2:0>
bits of the OSCCON register.
OST enabled to count 1024 clock cycles.
OST timed out, wait for falling edge of the
internal oscillator.
OSTS is set.
System clock held low until the next falling edge
of new clock (LP, XT or HS mode).
System clock is switched to external clock
source.
This mode allows the application to wake-up from
Sleep, perform a few instructions using the INTOSC
as the clock source and go back to Sleep without
waiting for the primary oscillator to become stable.
Note:
Executing a SLEEP instruction will abort
the oscillator start-up time and will cause
the OSTS bit of the OSCCON register to
remain clear.
© 2009 Microchip Technology Inc.
DS41203E-page 29
PIC16F688
3.7.3
CHECKING TWO-SPEED CLOCK
STATUS
Checking the state of the OSTS bit of the OSCCON
register will confirm if the microcontroller is running
from the external clock source, as defined by the
FOSC<2:0> bits in the Configuration Word register
(CONFIG), or the internal oscillator.
FIGURE 3-7:
TWO-SPEED START-UP
HFINTOSC
TOST
OSC1
0
1
1022 1023
OSC2
Program Counter
PC - N
PC
PC + 1
System Clock
DS41203E-page 30
© 2009 Microchip Technology Inc.
PIC16F688
3.8
3.8.3
Fail-Safe Clock Monitor
The Fail-Safe Clock Monitor (FSCM) allows the device
to continue operating should the external oscillator fail.
The FSCM can detect oscillator failure any time after
the Oscillator Start-up Timer (OST) has expired. The
FSCM is enabled by setting the FCMEN bit in the
Configuration Word register (CONFIG). The FSCM is
applicable to all external oscillator modes (LP, XT, HS,
EC, RC and RCIO).
FIGURE 3-8:
FSCM BLOCK DIAGRAM
Clock Monitor
Latch
External
Clock
LFINTOSC
Oscillator
÷ 64
31 kHz
(~32 μs)
488 Hz
(~2 ms)
S
Q
R
Q
The Fail-Safe condition is cleared after a Reset,
executing a SLEEP instruction or toggling the SCS bit
of the OSCCON register. When the SCS bit is toggled,
the OST is restarted. While the OST is running, the
device continues to operate from the INTOSC selected
in OSCCON. When the OST times out, the Fail-Safe
condition is cleared and the device will be operating
from the external clock source. The Fail-Safe condition
must be cleared before the OSFIF flag can be cleared.
3.8.4
3.8.1
Clock
Failure
Detected
FAIL-SAFE DETECTION
The FSCM module detects a failed oscillator by
comparing the external oscillator to the FSCM sample
clock. The sample clock is generated by dividing the
LFINTOSC by 64. See Figure 3-8. Inside the fail
detector block is a latch. The external clock sets the
latch on each falling edge of the external clock. The
sample clock clears the latch on each rising edge of the
sample clock. A failure is detected when an entire halfcycle of the sample clock elapses before the primary
clock goes low.
3.8.2
RESET OR WAKE-UP FROM SLEEP
The FSCM is designed to detect an oscillator failure
after the Oscillator Start-up Timer (OST) has expired.
The OST is used after waking up from Sleep and after
any type of Reset. The OST is not used with the EC or
RC Clock modes so that the FSCM will be active as
soon as the Reset or wake-up has completed. When
the FSCM is enabled, the Two-Speed Start-up is also
enabled. Therefore, the device will always be executing
code while the OST is operating.
Note:
Sample Clock
FAIL-SAFE CONDITION CLEARING
Due to the wide range of oscillator start-up
times, the Fail-Safe circuit is not active
during oscillator start-up (i.e., after exiting
Reset or Sleep). After an appropriate
amount of time, the user should check the
OSTS bit of the OSCCON register to verify
the oscillator start-up and that the system
clock
switchover
has
successfully
completed.
FAIL-SAFE OPERATION
When the external clock fails, the FSCM switches the
device clock to an internal clock source and sets the bit
flag OSFIF of the PIR2 register. Setting this flag will
generate an interrupt if the OSFIE bit of the PIE2
register is also set. The device firmware can then take
steps to mitigate the problems that may arise from a
failed clock. The system clock will continue to be
sourced from the internal clock source until the device
firmware successfully restarts the external oscillator
and switches back to external operation.
The internal clock source chosen by the FSCM is
determined by the IRCF<2:0> bits of the OSCCON
register. This allows the internal oscillator to be
configured before a failure occurs.
© 2009 Microchip Technology Inc.
DS41203E-page 31
PIC16F688
FIGURE 3-9:
FSCM TIMING DIAGRAM
Sample Clock
Oscillator
Failure
System
Clock
Output
Clock Monitor Output
(Q)
Failure
Detected
OSCFIF
Test
Note:
Test
Test
The system clock is normally at a much higher frequency than the sample clock. The relative frequencies in
this example have been chosen for clarity.
TABLE 3-2:
SUMMARY OF REGISTERS ASSOCIATED WITH CLOCK SOURCES
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets(1)
CONFIG(2)
CPD
CP
MCLRE
PWRTE
WDTE
FOSC2
FOSC1
FOSC0
—
—
Name
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
OSCCON
—
IRCF2
IRCF1
IRCF0
OSTS
HTS
LTS
SCS
-110 x000
-110 x000
OSCTUNE
—
—
—
TUN4
TUN3
TUN2
TUN1
TUN0
---0 0000
---u uuuu
0000 0000
0000 0000
PIE1
PIR1
Legend:
Note 1:
2:
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
x = unknown, u = unchanged, – = unimplemented locations read as ‘0’. Shaded cells are not used by oscillators.
Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.
See Configuration Word register (CONFIG) for operation of all register bits.
DS41203E-page 32
© 2009 Microchip Technology Inc.
PIC16F688
4.0
I/O PORTS
Therefore, a write to a port implies that the port pins are
read, this value is modified and then written to the
PORT data latch. RA3 reads ‘0’ when MCLRE = 1.
There are as many as twelve general purpose I/O pins
available. Depending on which peripherals are enabled,
some or all of the pins may not be available as general
purpose I/O. In general, when a peripheral is enabled,
the associated pin may not be used as a general
purpose I/O pin.
4.1
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. I/O pins configured as analog input
always read ‘0’.
PORTA and the TRISA Registers
Note:
PORTA is a 6-bit wide, bidirectional port. The
corresponding 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).
The exception is RA3, which is input only and its TRISA
bit will always read as ‘1’. Example 4-1 shows how to
initialize PORTA.
EXAMPLE 4-1:
BANKSEL
CLRF
MOVLW
MOVWF
BANKSEL
CLRF
MOVLW
MOVWF
Reading the PORTA register reads the status of the
pins, whereas writing to it will write to the PORT latch.
All write operations are read-modify-write operations.
REGISTER 4-1:
The ANSEL and CMCON0 registers must
be initialized to configure an analog
channel as a digital input. Pins configured
as analog inputs will read ‘0’.
INITIALIZING PORTA
PORTA
PORTA
07h
CMCON0
ANSEL
ANSEL
0Ch
TRISA
;
;Init PORTA
;Set RA<2:0> to
;digital I/O
;
;digital I/O
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
PORTA: PORTA REGISTER
U-0
U-0
R/W-x
R/W-0
R-x
R/W-0
R/W-0
R/W-0
—
—
RA5
RA4
RA3
RA2
RA1
RA0
bit 0
bit 7
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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
RA<5:0>: PORTA I/O Pin bit
1 = Port pin is > VIH
0 = Port pin is < VIL
REGISTER 4-2:
x = Bit is unknown
TRISA: PORTA TRI-STATE REGISTER
U-0
U-0
R/W-1
R/W-1
R-1
R/W-1
R/W-1
R/W-1
—
—
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
TRISA<5:0>: PORTA Tri-State Control bits
1 = PORTA pin configured as an input (tri-stated)
0 = PORTA pin configured as an output
Note 1:
2:
x = Bit is unknown
TRISA<3> always reads ‘1’.
TRISA<5:4> always reads ‘1’ in XT, HS and LP Oscillator modes.
© 2009 Microchip Technology Inc.
DS41203E-page 33
PIC16F688
4.2
4.2.3
Additional Pin Functions
INTERRUPT-ON-CHANGE
Every PORTA pin on the PIC16F688 has an interrupton-change option and a weak pull-up option. PORTA
also provides an Ultra Low-Power Wake-up option. The
next three sections describe these functions.
Each of the PORTA pins is individually configurable as
an interrupt-on-change pin. Control bits IOCAx enable
or disable the interrupt function for each pin. Refer to
Register 4-5. The interrupt-on-change is disabled on a
Power-on Reset.
4.2.1
For enabled interrupt-on-change pins, the values are
compared with the old value latched on the last read of
PORTA. The ‘mismatch’ outputs of the last read are
OR’d together to set the PORTA Change Interrupt Flag
bit (RAIF) in the INTCON register.
ANSEL REGISTER
The ANSEL register is used to configure the Input
mode of an I/O pin to analog. Refer to Register 4-3.
Setting the appropriate ANSEL bit high will cause all
digital reads on the pin to be read as ‘0’ and allow
analog functions on the pin to operate correctly.
The state of the ANSEL bits has no affect on digital
output functions. A pin with TRIS clear and ANSEL set
will still operate as a digital output, but the Input mode
will be analog. This can cause unexpected behavior
when executing read-modify-write instructions on the
affected port.
4.2.2
WEAK PULL-UPS
Each of the PORTA pins, except RA3, has an
individually configurable internal weak pull-up. Control
bits WPUAx enable or disable each pull-up. Refer to
Register 4-4. Each 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 by the
RAPU bit of the OPTION register. A weak pull-up is
automatically enabled for RA3 when configured as
MCLR and disabled when RA3 is an I/O. There is no
software control of the MCLR pull-up.
REGISTER 4-3:
This interrupt can wake the device from Sleep. The user,
in the Interrupt Service Routine, clears the interrupt by:
a)
Any read or write of PORTA. This will end the
mismatch condition, then
Clear the flag bit RAIF.
b)
A mismatch condition will continue to set flag bit RAIF.
Reading PORTA will end the mismatch condition and
allow flag bit RAIF to be cleared. The latch holding the
last read value is not affected by a MCLR nor BOR
Reset. After these Resets, the RAIF flag will continue
to be set if a mismatch is present.
Note:
If a change on the I/O pin should occur
when the read operation is being executed
(start of the Q2 cycle), then the RAIF
interrupt flag may not get set.
ANSEL: ANALOG SELECT 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
ANS7
ANS6
ANS5
ANS4
ANS3
ANS2
ANS1
ANS0
bit 7
bit 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
bit 7-0
Note 1:
x = Bit is unknown
ANS<7:0>: Analog Select bits
Analog select between analog or digital function on pins AN<7:0>, respectively.
1 = Analog input. Pin is assigned as analog input(1).
0 = Digital I/O. Pin is assigned to port or special function.
Setting a pin to an analog input automatically disables the digital input circuitry, weak pull-ups and
interrupt-on-change, if available. The corresponding TRIS bit must be set to Input mode in order to allow
external control of the voltage on the pin.
DS41203E-page 34
© 2009 Microchip Technology Inc.
PIC16F688
REGISTER 4-4:
WPUA: WEAK PULL-UP PORTA REGISTER
U-0
U-0
R/W-1
R/W-1
U-0
R/W-1
R/W-1
R/W-1
—
—
WPUA5
WPUA4
—
WPUA2
WPUA1
WPUA0
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-4
WPUA<5:4>: Weak Pull-up Control bits
1 = Pull-up enabled
0 = Pull-up disabled
bit 3
Unimplemented: Read as ‘0’
bit 2-0
WPUA<2:0>: Weak Pull-up Control bits
1 = Pull-up enabled
0 = Pull-up disabled
Note 1:
2:
3:
4:
x = Bit is unknown
Global RAPU must be enabled for individual pull-ups to be enabled.
The weak pull-up device is automatically disabled if the pin is in Output mode (TRISA = 0).
The RA3 pull-up is enabled when configured as MCLR and disabled as an I/O in the Configuration Word.
WPUA<5:4> always reads ‘1’ in XT, HS and LP OSC modes.
REGISTER 4-5:
IOCA: INTERRUPT-ON-CHANGE PORTA REGISTER
U-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
—
—
IOCA5
IOCA4
IOCA3
IOCA2
IOCA1
IOCA0
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
IOCA<5:0>: Interrupt-on-change PORTA Control bits
1 = Interrupt-on-change enabled
0 = Interrupt-on-change disabled
Note 1:
2:
x = Bit is unknown
Global Interrupt Enable (GIE) must be enabled for individual interrupts to be recognized.
IOCA<5:4> always reads ‘1’ in XT, HS and LP OSC modes.
© 2009 Microchip Technology Inc.
DS41203E-page 35
PIC16F688
4.2.4
ULTRA LOW-POWER WAKE-UP
The Ultra Low-Power Wake-up (ULPWU) on RA0
allows a slow falling voltage to generate an interrupton-change on RA0 without excess current consumption. The mode is selected by setting the ULPWUE bit
of the PCON register. This enables a small current sink
which can be used to discharge a capacitor on RA0.
To use this feature, the RA0 pin is configured to output
‘1’ to charge the capacitor, interrupt-on-change for RA0
is enabled, and RA0 is configured as an input. The
ULPWUE bit is set to begin the discharge and a SLEEP
instruction is performed. When the voltage on RA0
drops below VIL, an interrupt will be generated which
will cause the device to wake-up. Depending on the
state of the GIE bit of the INTCON register, the device
will either jump to the interrupt vector (0004h) or
execute the next instruction when the interrupt event
occurs.
See
Section 4.2.3
“INTERRUPT-ONCHANGE” and Section 11.3.3 “PORTA Interrupt” for
more information.
EXAMPLE 4-2:
BANKSEL
BSF
MOVLW
MOVWF
BANKSEL
BCF
BANKSEL
BCF
CALL
BSF
BSF
BSF
MOVLW
MOVWF
SLEEP
NOP
ULTRA LOW-POWER
WAKE-UP INITIALIZATION
PORTA
PORTA,0
H’7’
CMCON0
ANSEL
ANSEL,0
TRISA
TRISA,0
CapDelay
PCON,ULPWUE
IOCA,0
TRISA,0
B’10001000’
INTCON
;
;Set RA0 data latch
;Turn off
; comparators
;
;RA0 to digital I/O
;
;Output high to
; charge capacitor
;Enable ULP Wake-up
;Select RA0 IOC
;RA0 to input
;Enable interrupt
; and clear flag
;Wait for IOC
;
This feature provides a low-power technique for
periodically waking up the device from Sleep. The
time-out is dependent on the discharge time of the RC
circuit on RA0. See Example 4-2 for initializing the
Ultra Low-Power Wake-up module.
The series resistor provides overcurrent protection for
the RA0 pin and can allow for software calibration of the
time-out. (see Figure 4-1). A timer can be used to
measure the charge time and discharge time of the
capacitor. The charge time can then be adjusted to
provide the desired interrupt delay. This technique will
compensate for the affects of temperature, voltage and
component accuracy. The Ultra Low-Power Wake-up
peripheral can also be configured as a simple
programmable low voltage detect or temperature sensor.
Note:
For more information, refer to Application
Note AN879, “Using the Microchip Ultra
Low-Power
Wake-up
Module”
(DS00879).
DS41203E-page 36
© 2009 Microchip Technology Inc.
PIC16F688
4.2.5
PIN DESCRIPTIONS AND
DIAGRAMS
4.2.5.1
Figure 4-1 shows the diagram for this pin. The RA0 pin
is configurable to function as one of the following:
Each PORTA pin is multiplexed with other functions.
The pins and their combined functions are briefly
described here. For specific information about individual functions such as the comparator or the A/D, refer
to the appropriate section in this data sheet.
FIGURE 4-1:
RA0/AN0/C1IN+/ICSPDAT/ULPWU
•
•
•
•
•
a general purpose I/O
an analog input for the A/D
an analog input to the comparator
an analog input to the Ultra Low-Power Wake-up
In-Circuit Serial Programming™ data
BLOCK DIAGRAM OF RA0
Analog(1)
Input Mode
VDD
Data Bus
D
Q
Weak
CK Q
WR
WPUDA
RAPU
RD
WPUDA
VDD
D
WR
PORTA
Q
I/O PIN
CK Q
VSS
+
D
WR
TRISA
VT
Q
CK Q
IULP
0
RD
TRISA
1
Analog(1)
Input Mode
Vss
ULPWUE
RD
PORTA
D
Q
Q
CK Q
WR
IOCA
D
EN
RD
IOCA
Q
Q3
D
EN
Interrupt-onChange
RD PORTA
To Comparator
To A/D Converter
Note
1:
Comparator mode and ANSEL determines analog Input mode.
© 2009 Microchip Technology Inc.
DS41203E-page 37
PIC16F688
4.2.5.2
RA1/AN1/C1IN-/VREF/ICSPCLK
4.2.5.3
RA2/AN2/T0CKI/INT/C1OUT
Figure 4-2 shows the diagram for this pin. The RA1 pin
is configurable to function as one of the following:
Figure 4-3 shows the diagram for this pin. The RA2 pin
is configurable to function as one of the following:
•
•
•
•
•
•
•
•
•
•
a general purpose I/O
an analog input for the A/D
an analog input to the comparator
a voltage reference input for the A/D
In-Circuit Serial Programming™ clock
FIGURE 4-2:
Data Bus
D
WR
WPUA
BLOCK DIAGRAM OF RA1
Q
Analog(1)
Input Mode
a general purpose I/O
an analog input for the A/D
the clock input for Timer0
an external edge triggered interrupt
a digital output from the comparator
FIGURE 4-3:
Data Bus
D
VDD
CK Q
WR
WPUA
Weak
Q
CK
Analog(1)
Input Mode
VDD
Q
Weak
RAPU
RD
WPUA
RAPU
RD
WPUA
BLOCK DIAGRAM OF RA2
C1OUT
Enable
D
WR
PORTA
VDD
Q
WR
PORTA
CK Q
VDD
Q
D
CK
Q
C1OUT 1
0
I/O pin
D
WR
TRISA
D
Q
CK Q
VSS
WR
TRISA
CK
Q
VSS
(1)
Analog
Input Mode
RD
TRISA
Analog(1)
Input Mode
RD
TRISA
RD
PORTA
I/O pin
Q
RD
PORTA
D
Q
Q
D
Q
CK Q
WR
IOCA
D
EN
RD
IOCA
Q
Q3
D
CK
WR
IOCA
Q
EN
RD
IOCA
Q
EN
Interrupt-onchange
D
Q
Q3
D
EN
Interrupt-onchange
RD PORTA
RD PORTA
To Comparator
To Timer0
To A/D Converter
To INT
To A/D Converter
Note
1:
Comparator mode and ANSEL determines analog
Input mode.
DS41203E-page 38
Note
1:
Analog Input mode is based upon ANSEL.
© 2009 Microchip Technology Inc.
PIC16F688
4.2.5.4
RA3/MCLR/VPP
4.2.5.5
RA4/AN3/T1G/OSC2/CLKOUT
Figure 4-4 shows the diagram for this pin. The RA3 pin
is configurable to function as one of the following:
Figure 4-5 shows the diagram for this pin. The RA4 pin
is configurable to function as one of the following:
• a general purpose input
• as Master Clear Reset with weak pull-up
•
•
•
•
•
FIGURE 4-4:
BLOCK DIAGRAM OF RA3
VDD
MCLRE
Data Bus
RD
TRISA
MCLRE
MCLRE
RD
PORTA
WR
IOCA
Input
pin
VSS
D
CK
FIGURE 4-5:
Weak
Reset
VSS
Q
Q
a general purpose I/O
an analog input for the A/D
a Timer1 gate input
a crystal/resonator connection
a clock output
BLOCK DIAGRAM OF RA4
Analog(3)
Input Mode
Data Bus
WR
WPUA
D
CK
Q
VDD
Q
Weak
RAPU
RD
WPUA
D
Oscillator
Circuit
Q
EN
CLK(1)
Modes
OSC1
Q3
VDD
CLKOUT
Enable
RD
IOCA
Q
D
D
EN
Interrupt-onchange
WR
PORTA
CK
Q
Fosc/4
1
0
I/O pin
Q
CLKOUT
Enable
RD PORTA
VSS
D
WR
TRISA
CK
Q
Q
INTOSC/
RC/EC(2)
CLKOUT
Enable
RD
TRISA
Analog(3)
Input Mode
RD
PORTA
D
WR
IOCA
CK
Q
Q
D
Q
EN
RD
IOCA
Q
Q3
D
EN
Interrupt-onchange
RD PORTA
To T1G
To A/D Converter
Note 1: CLK modes are XT, HS, LP, LPTMR1 and CLKOUT
Enable.
2: With CLKOUT option.
3: Analog Input mode is ANSEL.
© 2009 Microchip Technology Inc.
DS41203E-page 39
PIC16F688
4.2.5.6
RA5/T1CKI/OSC1/CLKIN
FIGURE 4-6:
BLOCK DIAGRAM OF RA5
Figure 4-6 shows the diagram for this pin. The RA5 pin
is configurable to function as one of the following:
•
•
•
•
a general purpose I/O
a Timer1 clock input
a crystal/resonator connection
a clock input
INTOSC
Mode
Data Bus
WR
WPUA
TMR1LPEN(1)
VDD
Q
D
CK
Weak
Q
RAPU
RD
WPUA
Oscillator
Circuit
OSC2
WR
PORTA
CK
D
WR
TRISA
VDD
Q
D
Q
Q
CK
I/O pin
Q
VSS
INTOSC
Mode
RD
TRISA
RD
PORTA
(2)
D
WR
IOCA
Q
CK
Q
D
Q
EN
Q3
RD
IOCA
Q
D
EN
Interrupt-onchange
RD PORTA
To Timer1 or CLKGEN
Note
1:
Timer1 LP oscillator enabled.
2: When using Timer1 with LP oscillator, the
Schmitt Trigger is bypassed.
DS41203E-page 40
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 4-1:
Name
SUMMARY OF REGISTERS ASSOCIATED WITH PORTA
Bit 7
ANSEL
CMCON0
PCON
INTCON
IOCA
OPTION_REG
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
1111 1111
ANS7
ANS6
ANS5
ANS4
ANS3
ANS2
ANS1
ANS0
1111 1111
C2OUT
C1OUT
C2INV
C1INV
CIS
CM2
CM1
CM0
0000 0000
0000 0000
—
—
ULPWUE
SBOREN
—
—
POR
BOR
--01 --qq
--0u --uu
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
—
—
IOCA5
IOCA4
IOCA3
IOCA2
IOCA1
IOCA0
--00 0000
--00 0000
RAPU
INTEDG
T0CS
T0SE
PSA
PS2
PS1
PS0
1111 1111
1111 1111
PORTA
—
—
RA5
RA4
RA3
RA2
RA1
RA0
--x0 x000
--x0 x000
TRISA
—
—
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
--11 1111
--11 1111
WPUA
—
—
WPUA5
WPUA4
—
WPUA2
WPUA1
WPUA0
--11 -111
--11 -111
Legend:
x = unknown, u = unchanged, – = unimplemented locations read as ‘0’. Shaded cells are not used by PORTA.
© 2009 Microchip Technology Inc.
DS41203E-page 41
PIC16F688
4.3
EXAMPLE 4-3:
PORTC
PORTC is a general purpose I/O port consisting of 6
bidirectional pins. The pins can be configured for either
digital I/O or analog input to A/D converter or comparator. For specific information about individual functions
such as the EUSART or the A/D converter, refer to the
appropriate section in this data sheet.
Note:
The ANSEL and CMCON0 registers must
be initialized to configure an analog
channel as a digital input. Pins configured
as analog inputs will read ‘0’.
REGISTER 4-6:
BANKSEL
CLRF
MOVLW
MOVWF
BANKSEL
CLRF
MOVLW
MOVWF
PORTC
PORTC
07h
CMCON0
ANSEL
ANSEL
0Ch
TRISC
INITIALIZING PORTC
;
;Init PORTC
;Set RC<4,1:0> to
;digital I/O
;
;digital I/O
;Set RC<3:2> as inputs
;and set RC<5:4,1:0>
;as outputs
PORTC: PORTC REGISTER
U-0
U-0
R/W-x
R/W-x
R/W-0
R/W-0
R/W-0
R/W-0
—
—
RC5
RC4
RC3
RC2
RC1
RC0
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
RC<5:0>: PORTC I/O Pin bit
1 = PORTC pin is > VIH
0 = PORTC pin is < VIL
REGISTER 4-7:
x = Bit is unknown
TRISC: PORTC TRI-STATE REGISTER
U-0
U-0
R/W-1
R/W-1
R/W-1
R/W-1
R/W-1
R/W-1
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
TRISC<5:0>: PORTC Tri-State Control bits
1 = PORTC pin configured as an input (tri-stated)
0 = PORTC pin configured as an output
DS41203E-page 42
x = Bit is unknown
© 2009 Microchip Technology Inc.
PIC16F688
4.3.1
RC0/AN4/C2IN+
4.3.3
RC2/AN6
Figure 4-7 shows the diagram for this pin. The RC0 is
configurable to function as one of the following:
Figure 4-8 shows the diagram for this pin. The RC2 is
configurable to function as one of the following:
• a general purpose I/O
• an analog input for the A/D Converter
• an analog input to the comparator
• a general purpose I/O
• an analog input for the A/D Converter
4.3.2
Figure 4-8 shows the diagram for this pin. The RC3 is
configurable to function as one of the following:
4.3.4
RC1/AN5/C2IN-
Figure 4-7 shows the diagram for this pin. The RC1 is
configurable to function as one of the following:
• a general purpose I/O
• an analog input for the A/D Converter
• an analog input to the comparator
FIGURE 4-7:
• a general purpose I/O
• an analog input for the A/D Converter
FIGURE 4-8:
BLOCK DIAGRAM OF RC0
AND RC1
D
D
CK
WR
PORTC
VDD
Q
WR
TRISC
Q
VSS
Analog Input
Mode(1)
RD
TRISC
CK
D
Q
CK
VDD
Q
Q
I/O Pin
Q
I/O Pin
D
BLOCK DIAGRAM OF RC2
AND RC3
Data Bus
Data Bus
WR
PORTC
RC3/AN7
WR
TRISC
Q
CK
Q
VSS
Analog Input
Mode(1)
RD
TRISC
RD
PORTC
To A/D Converter
RD
PORTC
To Comparators
Note
1:
Analog Input mode comes from ANSEL.
To A/D Converter
Note
1:
Analog Input mode is based upon Comparator mode
and ANSEL.
© 2009 Microchip Technology Inc.
DS41203E-page 43
PIC16F688
4.3.5
4.3.6
RC4/C2OUT/TX/CK
RC5/RX/DT
Figure 4-9 shows the diagram for this pin. The RC4 is
configurable to function as one of the following:
The RC5 is configurable to function as one of the
following:
• a general purpose I/O
• a digital output from the comparator
• a digital I/O for the EUSART
• a general purpose I/O
• a digital I/O for the EUSART
FIGURE 4-10:
FIGURE 4-9:
Data Bus
USART Select(1)
C2OUT EN
EUSART Out
Enable
D
EUSART
TX/CLKOUT
Data Bus
C2OUT
WR
PORTC
VDD
WR
PORTC
WR
TRISC
Q
EUSART
DT Out
1
0
0
D
1
Q
WR
TRISC
I/O Pin
CK Q
CK
I/O Pin
Q
Q
VSS
RD
TRISC
VSS
D
CK
VDD
Q
0
1
D
BLOCK DIAGRAM OF RC5
PIN
BLOCK DIAGRAM OF RC4
Q
RD
PORTC
CK Q
To EUSART RX/DT In
RD
TRISC
RD
PORTC
To EUSART CLK Input
Note
1:
USART Select signals selects between port
data and peripheral output.
TABLE 4-2:
Name
ANSEL
CMCON0
PORTC
TRISC
Legend:
SUMMARY OF REGISTERS ASSOCIATED WITH PORTC
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
1111 1111
ANS7
ANS6
ANS5
ANS4
ANS3
ANS2
ANS1
ANS0
1111 1111
C2OUT
C1OUT
C2INV
C1INV
CIS
CM2
CM1
CM0
0000 0000
0000 0000
—
—
RC5
RC4
RC3
RC2
RC1
RC0
--xx 0000
--xx 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
x = unknown, u = unchanged, – = unimplemented locations read as ‘0’. Shaded cells are not used by PORTC.
DS41203E-page 44
© 2009 Microchip Technology Inc.
PIC16F688
5.0
TIMER0 MODULE
5.1
Timer0 Operation
The Timer0 module is an 8-bit timer/counter with the
following features:
When used as a timer, the Timer0 module can be used
as either an 8-bit timer or an 8-bit counter.
•
•
•
•
•
5.1.1
8-bit timer/counter register (TMR0)
8-bit prescaler (shared with Watchdog Timer)
Programmable internal or external clock source
Programmable external clock edge selection
Interrupt on overflow
8-BIT TIMER MODE
When used as a timer, the Timer0 module will
increment every instruction cycle (without prescaler).
Timer mode is selected by clearing the T0CS bit of the
OPTION register to ‘0’.
Figure 5-1 is a block diagram of the Timer0 module.
When TMR0 is written, the increment is inhibited for
two instruction cycles immediately following the write.
Note:
5.1.2
The value written to the TMR0 register can
be adjusted, in order to account for the two
instruction cycle delay when TMR0 is
written.
8-BIT COUNTER MODE
When used as a counter, the Timer0 module will
increment on every rising or falling edge of the T0CKI
pin. The incrementing edge is determined by the T0SE
bit of the OPTION register. Counter mode is selected by
setting the T0CS bit of the OPTION register to ‘1’.
FIGURE 5-1:
BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
FOSC/4
Data Bus
0
8
1
Sync
2 Tcy
1
T0CKI
pin
TMR0
0
0
T0SE
T0CS
Set Flag bit T0IF
on Overflow
8-bit
Prescaler
PSA
1
8
PSA
WDTE
SWDTEN
PS<2:0>
16-bit
Prescaler
31 kHz
INTOSC
1
WDT
Time-out
0
16
Watchdog
Timer
PSA
WDTPS<3:0>
Note
1:
T0SE, T0CS, PSA, PS<2:0> are bits in the OPTION register.
2:
SWDTEN and WDTPS<3:0> are bits in the WDTCON register.
3:
WDTE bit is in the Configuration Word register.
© 2009 Microchip Technology Inc.
DS41203E-page 45
PIC16F688
5.1.3
SOFTWARE PROGRAMMABLE
PRESCALER
A single software programmable prescaler is available
for use with either Timer0 or the Watchdog Timer
(WDT), but not both simultaneously. The prescaler
assignment is controlled by the PSA bit of the OPTION
register. To assign the prescaler to Timer0, the PSA bit
must be cleared to a ‘0’.
There are 8 prescaler options for the Timer0 module
ranging from 1:2 to 1:256. The prescale values are
selectable via the PS<2:0> bits of the OPTION register.
In order to have a 1:1 prescaler value for the Timer0
module, the prescaler must be assigned to the WDT
module.
The prescaler is not readable or writable. When
assigned to the Timer0 module, all instructions writing to
the TMR0 register will clear the prescaler.
When the prescaler is assigned to WDT, a CLRWDT
instruction will clear the prescaler along with the WDT.
5.1.3.1
Switching Prescaler Between
Timer0 and WDT Modules
As a result of having the prescaler assigned to either
Timer0 or the WDT, it is possible to generate an
unintended device Reset when switching prescaler
values. When changing the prescaler assignment from
Timer0 to the WDT module, the instruction sequence
shown in Example 5-1, must be executed.
EXAMPLE 5-1:
BANKSEL
CLRWDT
CLRF
BANKSEL
BSF
CLRWDT
MOVLW
ANDWF
IORLW
MOVWF
TMR0
CHANGING PRESCALER
(TIMER0 → WDT)
;
;Clear WDT
TMR0
;Clear TMR0 and
;prescaler
OPTION_REG
;
OPTION_REG,PSA ;Select WDT
;
;
b’11111000’
;Mask prescaler
OPTION_REG,W
;bits
b’00000101’
;Set WDT prescaler
OPTION_REG
;to 1:32
DS41203E-page 46
When changing the prescaler assignment from the
WDT to the Timer0 module, the following instruction
sequence must be executed (see Example 5-2).
EXAMPLE 5-2:
CHANGING PRESCALER
(WDT → TIMER0)
CLRWDT
;Clear WDT and
;prescaler
BANKSEL OPTION_REG
;
MOVLW
b’11110000’ ;Mask TMR0 select and
ANDWF
OPTION_REG,W ;prescaler bits
IORLW
b’00000011’ ;Set prescale to 1:16
MOVWF
OPTION_REG
;
5.1.4
TIMER0 INTERRUPT
Timer0 will generate an interrupt when the TMR0
register overflows from FFh to 00h. The T0IF interrupt
flag bit of the INTCON register is set every time the
TMR0 register overflows, regardless of whether or not
the Timer0 interrupt is enabled. The T0IF bit must be
cleared in software. The Timer0 interrupt enable is the
T0IE bit of the INTCON register.
Note:
5.1.5
The Timer0 interrupt cannot wake the
processor from Sleep since the timer is
frozen during Sleep.
USING TIMER0 WITH AN
EXTERNAL CLOCK
When Timer0 is in Counter mode, the synchronization
of the T0CKI input and the Timer0 register is accomplished by sampling the prescaler output on the Q2 and
Q4 cycles of the internal phase clocks. Therefore, the
high and low periods of the external clock source must
meet the timing requirements as shown in
Section 14.0 “Electrical Specifications”.
© 2009 Microchip Technology Inc.
PIC16F688
REGISTER 5-1:
OPTION_REG: OPTION 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
RAPU
INTEDG
T0CS
T0SE
PSA
PS2
PS1
PS0
bit 7
bit 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
bit 7
RAPU: PORTA Pull-up Enable bit
1 = PORTA pull-ups are disabled
0 = PORTA pull-ups are enabled by individual PORT latch values
bit 6
INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of INT pin
0 = Interrupt on falling edge of INT pin
bit 5
T0CS: TMR0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (FOSC/4)
bit 4
T0SE: TMR0 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: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0
PS<2:0>: Prescaler Rate Select bits
Note 1:
TMR0 RATE
WDT RATE
000
001
010
011
100
101
110
111
1:2
1:4
1:8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1:1
1:2
1:4
1:8
1 : 16
1 : 32
1 : 64
1 : 128
A dedicated 16-bit WDT postscaler is available. See Section 11.5 “Watchdog Timer (WDT)” for more
information.
TABLE 5-1:
Name
TMR0
INTCON
OPTION_REG
TRISA
BIT VALUE
x = Bit is unknown
SUMMARY OF REGISTERS ASSOCIATED WITH TIMER0
Bit 7
Bit 6
Bit 5
PEIE
RAPU INTEDG
—
—
Value on
all other
Resets
Bit 3
Bit 2
Bit 1
Bit 0
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x 0000 000x
T0CS
T0SE
PSA
PS2
PS1
PS0
1111 1111 1111 1111
Timer0 Module Register
GIE
Value on
POR, BOR
Bit 4
xxxx xxxx uuuu uuuu
TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 --11 1111 --11 1111
Legend: – = Unimplemented locations, read as ‘0’, u = unchanged, x = unknown. Shaded cells are not used by the
Timer0 module.
© 2009 Microchip Technology Inc.
DS41203E-page 47
PIC16F688
6.0
TIMER1 MODULE WITH GATE
CONTROL
6.1
The Timer1 module is a 16-bit incrementing counter
which is accessed through the TMR1H:TMR1L register
pair. Writes to TMR1H or TMR1L directly update the
counter.
The Timer1 module is a 16-bit timer/counter with the
following features:
•
•
•
•
•
•
16-bit timer/counter register pair (TMR1H:TMR1L)
Programmable internal or external clock source
3-bit prescaler
Optional LP oscillator
Synchronous or asynchronous operation
Timer1 gate (count enable) via comparator or
T1G pin
• Interrupt on overflow
• Wake-up on overflow (external clock,
Asynchronous mode only)
When used with an internal clock source, the module is
a timer. When used with an external clock source, the
module can be used as either a timer or counter.
6.2
Clock Source Selection
The TMR1CS bit of the T1CON register is used to select
the clock source. When TMR1CS = 0, the clock source
is FOSC/4. When TMR1CS = 1, the clock source is
supplied externally.
Clock Source
Figure 6-1 is a block diagram of the Timer1 module.
FIGURE 6-1:
Timer1 Operation
TMR1CS
Clock Source
FOSC/4
0
FOSC/4
T1CKI pin
1
T1CKI pin
TIMER1 BLOCK DIAGRAM
TMR1GE
T1GINV
TMR1ON
Set flag bit
TMR1IF on
Overflow
To C2 Comparator Module
Timer1 Clock
TMR1(2)
TMR1H
TMR1L
Synchronized
clock input
0
EN
1
Oscillator
(1)
T1SYNC
OSC1/T1CKI
OSC2/T1G
1
FOSC/4
Internal
Clock
Synchronize(3)
Prescaler
1, 2, 4, 8
det
0
2
T1CKPS<1:0>
TMR1CS
1
INTOSC
Without CLKOUT
T1OSCEN
C2OUT
0
T1GSS
Note 1:
2:
3:
DS41203E-page 48
ST Buffer is low power type when using LP oscillator, or high speed type when using T1CKI.
Timer1 register increments on rising edge.
Synchronize does not operate while in Sleep.
© 2009 Microchip Technology Inc.
PIC16F688
6.2.1
INTERNAL CLOCK SOURCE
When the internal clock source is selected the
TMR1H:TMR1L register pair will increment on multiples
of TCY as determined by the Timer1 prescaler.
6.2.2
EXTERNAL CLOCK SOURCE
When the external clock source is selected, the Timer1
module may work as a timer or a counter.
When counting, Timer1 is incremented on the rising
edge of the external clock input T1CKI. In addition, the
Counter mode clock can be synchronized to the
microcontroller system clock or run asynchronously.
6.5
If control bit T1SYNC of the T1CON register is set, the
external clock input is not synchronized. The timer
continues to increment asynchronous to the internal
phase clocks. The timer will continue to run during
Sleep and can generate an interrupt on overflow,
which will wake-up the processor. However, special
precautions in software are needed to read/write the
timer (see Section 6.5.1 “Reading and Writing
Timer1 in Asynchronous Counter Mode”).
Note:
If an external clock oscillator is needed (and the
microcontroller is using the INTOSC without CLKOUT),
Timer1 can use the LP oscillator as a clock source.
Note:
6.3
In Counter mode, a falling edge must be
registered by the counter prior to the first
incrementing rising edge.
6.4
Timer1 Oscillator
A low-power 32.768 kHz crystal oscillator is built-in
between pins OSC1 (input) and OSC2 (amplifier
output). The oscillator is enabled by setting the
T1OSCEN control bit of the T1CON register. The
oscillator will continue to run during Sleep.
The Timer1 oscillator is shared with the system LP
oscillator. Thus, Timer1 can use this mode only when
the primary system clock is derived from the internal
oscillator or when in LP oscillator mode. The user must
provide a software time delay to ensure proper oscillator start-up.
TRISA5 and TRISA4 bits are set when the Timer1
oscillator is enabled. RA5 and RA4 bits read as ‘0’ and
TRISA5 and TRISA4 bits read as ‘1’.
Note:
6.5.1
Timer1 Prescaler
Timer1 has four prescaler options allowing 1, 2, 4 or 8
divisions of the clock input. The T1CKPS bits of the
T1CON register control the prescale counter. The
prescale counter is not directly readable or writable;
however, the prescaler counter is cleared upon a write to
TMR1H or TMR1L.
The oscillator requires a start-up and
stabilization time before use. Thus,
T1OSCEN should be set and a suitable
delay observed prior to enabling Timer1.
Timer1 Operation in
Asynchronous Counter Mode
When switching from synchronous to
asynchronous operation, it is possible to
skip an increment. When switching from
asynchronous to synchronous operation,
it is possible to produce a single spurious
increment.
READING AND WRITING TIMER1 IN
ASYNCHRONOUS COUNTER
MODE
Reading TMR1H or TMR1L while the timer is running
from an external asynchronous clock will ensure a valid
read (taken care of in hardware). However, the user
should keep in mind that reading the 16-bit timer in two
8-bit values itself, poses certain problems, since the
timer may overflow between the reads.
For writes, it is recommended that the user simply stop
the timer and write the desired values. A write
contention may occur by writing to the timer registers,
while the register is incrementing. This may produce an
unpredictable value in the TMR1H:TTMR1L register
pair.
6.6
Timer1 Gate
Timer1 gate source is software configurable to be the
T1G pin or the output of Comparator 2. This allows the
device to directly time external events using T1G or
analog events using Comparator 2. See the CMCON1
register (Register 7-2) for selecting the Timer1 gate
source. This feature can simplify the software for a
Delta-Sigma A/D converter and many other applications.
For more information on Delta-Sigma A/D converters,
see the Microchip web site (www.microchip.com).
Note:
TMR1GE bit of the T1CON register must
be set to use either T1G or C2OUT as the
Timer1 gate source. See Register 7-2 for
more information on selecting the Timer1
gate source.
Timer1 gate can be inverted using the T1GINV bit of
the T1CON register, whether it originates from the T1G
pin or Comparator 2 output. This configures Timer1 to
measure either the active-high or active-low time
between events.
© 2009 Microchip Technology Inc.
DS41203E-page 49
PIC16F688
6.7
Timer1 Interrupt
The Timer1 register pair (TMR1H:TMR1L) increments
to FFFFh and rolls over to 0000h. When Timer1 rolls
over, the Timer1 interrupt flag bit of the PIR1 register is
set. To enable the interrupt on rollover, you must set
these bits:
• Timer1 interrupt enable bit of the PIE1 register
• PEIE bit of the INTCON register
• GIE bit of the INTCON register
The interrupt is cleared by clearing the TMR1IF bit in
the Interrupt Service Routine.
Note:
The TMR1H:TTMR1L register pair and the
TMR1IF bit should be cleared before
enabling interrupts.
FIGURE 6-2:
6.8
Timer1 Operation During Sleep
Timer1 can only operate during Sleep when setup in
Asynchronous Counter mode. In this mode, an external
crystal or clock source can be used to increment the
counter. To set up the timer to wake the device:
• TMR1ON bit of the T1CON register must be set
• TMR1IE bit of the PIE1 register must be set
• PEIE bit of the INTCON register must be set
The device will wake-up on an overflow and execute
the next instruction. If the GIE bit of the INTCON
register is set, the device will call the Interrupt Service
Routine (0004h).
TIMER1 INCREMENTING EDGE
T1CKI = 1
when TMR1
Enabled
T1CKI = 0
when TMR1
Enabled
Note 1:
2:
Arrows indicate counter increments.
In Counter mode, a falling edge must be registered by the counter prior to the first incrementing rising edge of
the clock.
DS41203E-page 50
© 2009 Microchip Technology Inc.
PIC16F688
6.9
Timer1 Control Register
The Timer1 Control register (T1CON), shown in
Register 6-1, is used to control Timer1 and select the
various features of the Timer1 module.
REGISTER 6-1:
R/W-0
R/W-0
(1)
T1GINV
T1CON: TIMER 1 CONTROL REGISTER
(2)
TMR1GE
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
T1CKPS1
T1CKPS0
T1OSCEN
T1SYNC
TMR1CS
TMR1ON
bit 7
bit 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
bit 7
T1GINV: Timer1 Gate Invert bit(1)
1 = Timer1 gate is active high (Timer1 counts when gate is high)
0 = Timer1 gate is active low (Timer1 counts when gate is low)
bit 6
TMR1GE: Timer1 Gate Enable bit(2)
If TMR1ON = 0:
This bit is ignored
If TMR1ON = 1:
1 = Timer1 is on if Timer1 gate is active
0 = Timer1 is on
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: LP Oscillator Enable Control bit
If INTOSC without CLKOUT oscillator is active:
1 = LP oscillator is enabled for Timer1 clock
0 = LP oscillator is off
Else:
This bit is ignored. LP oscillator is disabled.
bit 2
T1SYNC: Timer1 External Clock Input Synchronization Control bit
TMR1CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock
bit 1
TMR1CS: Timer1 Clock Source Select bit
1 = External clock from T1CKI pin (on the rising edge)
0 = Internal clock (FOSC/4)
bit 0
TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1
Note 1:
2:
x = Bit is unknown
T1GINV bit inverts the Timer1 gate logic, regardless of source.
TMR1GE bit must be set to use either T1G pin or C2OUT, as selected by the T1GSS bit of the CM2CON1
register, as a Timer1 gate source.
© 2009 Microchip Technology Inc.
DS41203E-page 51
PIC16F688
TABLE 6-1:
Name
SUMMARY OF REGISTERS ASSOCIATED WITH TIMER1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
00-- --10
CMCON1
—
—
—
—
—
—
T1GSS
C2SYNC
---- --10
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
xxxx xxxx
uuuu uuuu
xxxx xxxx
uuuu uuuu
0000 0000
uuuu uuuu
PIR1
TMR1H
Holding Register for the Most Significant Byte of the 16-bit TMR1 Register
TMR1L
Holding Register for the Least Significant Byte of the 16-bit TMR1 Register
T1CON
Legend:
T1GINV
TMR1GE
T1CKPS1
T1CKPS0
T1OSCEN
T1SYNC
TMR1CS
TMR1ON
x = unknown, u = unchanged, – = unimplemented, read as ‘0’. Shaded cells are not used by the Timer1 module.
DS41203E-page 52
© 2009 Microchip Technology Inc.
PIC16F688
7.0
COMPARATOR MODULE
Comparators are used to interface analog circuits to a
digital circuit by comparing two analog voltages and
providing a digital indication of their relative magnitudes.
The comparators are very useful mixed signal building
blocks because they provide analog functionality
independent of the program execution. The analog
comparator module includes the following features:
• Dual comparators
• Multiple comparator configurations
• Comparator outputs are available internally/externally
• Programmable output polarity
• Interrupt-on-change
• Wake-up from Sleep
• Timer1 gate (count enable)
• Output synchronization to Timer1 clock input
• Programmable voltage reference
Note:
7.1
Comparator Overview
A comparator is shown in Figure 7-1 along with the
relationship between the analog input levels and the
digital output. When the analog voltage at VIN+ is less
than the analog voltage at VIN-, the output of the
comparator is a digital low level. When the analog
voltage at VIN+ is greater than the analog voltage at
VIN-, the output of the comparator is a digital high level.
FIGURE 7-1:
SINGLE COMPARATOR
VIN+
+
VIN-
–
Output
VINVIN+
Only Comparator C2 can be linked to
Timer1.
Output
Note:
The black areas of the output of the
comparator represents the uncertainty
due to input offsets and response time.
This device contains two comparators as shown in
Figure 7-2 and Figure 7-3. The comparators are not
independently configurable.
© 2009 Microchip Technology Inc.
DS41203E-page 53
PIC16F688
FIGURE 7-2:
COMPARATOR C1 OUTPUT BLOCK DIAGRAM
MULTIPLEX
Port Pins
C1INV
To C1OUT pin
C1
D
Q1
To Data Bus
Q
EN
RD CMCON0
Set C1IF bit
D
Q3*RD CMCON0
Q
EN
CL
Reset
Note 1:
2:
FIGURE 7-3:
Q1 and Q3 are phases of the four-phase system clock (FOSC).
Q1 is held high during Sleep mode.
COMPARATOR C2 OUTPUT BLOCK DIAGRAM
C2SYNC
Port Pins
MULTIPLEX
To Timer1 Gate
C2INV
0
C2
To C2OUT pin
D
Q
D
Q
1
Timer1
clock source(1)
Q1
EN
To Data Bus
RD CMCON0
Set C2IF bit
D
Q3*RD CMCON0
Q
EN
CL
Reset
Note 1:
DS41203E-page 54
Comparator output is latched on falling edge of Timer1 clock source.
2:
Q1 and Q3 are phases of the four-phase system clock (FOSC).
3:
Q1 is held high during Sleep mode.
© 2009 Microchip Technology Inc.
PIC16F688
7.1.1
ANALOG INPUT CONNECTION
CONSIDERATIONS
A simplified circuit for an analog input is shown in
Figure 7-4. Since the analog input pins share their
connection with a digital input, they have reverse
biased ESD protection 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 may occur.
Note 1: When reading a PORT register, all pins
configured as analog inputs will read as a
‘0’. Pins configured as digital inputs will
convert as an analog input, according to
the 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.
A maximum source impedance of 10 kΩ is recommended
for the analog sources. Also, any external component
connected to an analog input pin, such as a capacitor or
a Zener diode, should have very little leakage current to
minimize inaccuracies introduced.
FIGURE 7-4:
ANALOG INPUT MODEL
VDD
VT ≈ 0.6V
Rs < 10K
RIC
To ADC Input
AIN
VA
CPIN
5 pF
VT ≈ 0.6V
ILEAKAGE
±500 nA
Vss
Legend: CPIN
= Input Capacitance
ILEAKAGE = Leakage Current at the pin due to various junctions
= Interconnect Resistance
RIC
= Source Impedance
RS
VA
= Analog Voltage
= Threshold Voltage
VT
© 2009 Microchip Technology Inc.
DS41203E-page 55
PIC16F688
7.2
Comparator Configuration
There are eight modes of operation for the comparator.
The CM<2:0> bits of the CMCON0 register are used to
select these modes as shown in Figure 7-5. I/O lines
change as a function of the mode and are designated
as follows:
• Analog function (A): digital input buffer is disabled
• Digital function (D): comparator digital output,
overrides port function
• Normal port function (I/O): independent of
comparator
The port pins denoted as “A” will read as a ‘0’
regardless of the state of the I/O pin or the I/O control
TRIS bit. Pins used as analog inputs should also have
the corresponding TRIS bit set to ‘1’ to disable the
digital output driver. Pins denoted as “D” should have
the corresponding TRIS bit set to ‘0’ to enable the
digital output driver.
Note:
Comparator interrupts should be disabled
during a Comparator mode change to
prevent unintended interrupts.
DS41203E-page 56
© 2009 Microchip Technology Inc.
PIC16F688
FIGURE 7-5:
COMPARATOR I/O OPERATING MODES
Comparators Reset (POR Default Value)
CM<2:0> = 000
A
VINC1INVIN+
C1IN+ A
C2IN-
C1
Off(1)
C2
(1)
Two Independent Comparators
CM<2:0> = 100
VINC1IN- A
C1IN+
VIN-
A
VIN+
C2IN+ A
C2INOff
C2IN+
Three Inputs Multiplexed to Two Comparators
CM<2:0> = 001
C1INC1IN+
C2INC2IN+
A
A
VIN-
CIS = 0
CIS = 1
VIN+
C1
C1OUT
C2
C2OUT
VIN-
A
VIN+
A
C1INC1IN+
A
A
VIN-
CIS = 0
CIS = 1
VIN+
C1
C1IN+
C2IN+
C2IN-
C2IN+
A
VIN-
CIS = 0
CIS = 1
VIN+
VIN+
I/O
VIN+
A
VIN-
A
VIN+
VIN+
C2INC2
C2OUT
I/O
VIN+
A
VIN-
A
VIN+
C1
C1OUT
C2IN+
C2OUT(pin)
C2
C2OUT
C1
Off(1)
C2
C2OUT
C1
C1OUT
C2
C2OUT
D
C2
C2OUT
I/O = Normal port I/O
A
VIN-
A
VIN+
D
Comparators Off (Lowest Power)
CM<2:0> = 111
C1IN-
I/O
C1IN+ I/O
C2IN-
Legend: A = Analog Input, ports always reads ‘0’
Note 1:
A
C1OUT
A
Two Common Reference Comparators
CM<2:0> = 011
A
VINC1IN-
C2IN-
VIN-
C1OUT
From CVREF Module
C1IN+
A
C1
Two Common Reference Comparators with Outputs
CM<2:0> = 110
A
VINC1INC1OUT(pin)
C2IN+
VIN+
One Independent Comparator
CM<2:0> = 101
I/O
VINC1IN-
C2IN-
Four Inputs Multiplexed to Two Comparators
CM<2:0> = 010
A
C2IN+
VINVIN+
I/O
VIN-
I/O
VIN+
C1
Off(1)
C2
Off(1)
CIS = Comparator Input Switch (CMCON0<3>)
D = Comparator Digital Output
Reads as ‘0’, unless CxINV = 1.
© 2009 Microchip Technology Inc.
DS41203E-page 57
PIC16F688
7.3
Comparator Control
The CMCON0 register (Register 7-1) provides access
to the following comparator features:
•
•
•
•
Mode selection
Output state
Output polarity
Input switch
7.3.1
COMPARATOR OUTPUT STATE
Each comparator state can always be read internally
via the associated CxOUT bit of the CMCON0 register.
The comparator outputs are directed to the CxOUT
pins when CM<2:0> = 110. When this mode is
selected, the TRIS bits for the associated CxOUT pins
must be cleared to enable the output drivers.
7.3.2
COMPARATOR OUTPUT POLARITY
Inverting the output of a comparator is functionally
equivalent to swapping the comparator inputs. The
polarity of a comparator output can be inverted by setting the CxINV bits of the CMCON0 register. Clearing
CxINV results in a non-inverted output. A complete
table showing the output state versus input conditions
and the polarity bit is shown in Table 7-1.
TABLE 7-1:
OUTPUT STATE VS. INPUT
CONDITIONS
Input Conditions
CxINV
CxOUT
VIN- > VIN+
0
0
VIN- < VIN+
0
1
VIN- > VIN+
1
1
VIN- < VIN+
1
0
Note:
CxOUT refers to both the register bit and
output pin.
DS41203E-page 58
© 2009 Microchip Technology Inc.
PIC16F688
7.3.3
COMPARATOR INPUT SWITCH
The inverting input of the comparators may be switched
between two analog pins in the following modes:
• CM<2:0> = 001 (Comparator C1 only)
• CM<2:0> = 010 (Comparators C1 and C2)
In the above modes, both pins remain in analog mode
regardless of which pin is selected as the input. The CIS
bit of the CMCON0 register controls the comparator
input switch.
7.4
Comparator Response Time
The comparator output is indeterminate for a period of
time after the change of an input source or the selection
of a new reference voltage. This period is referred to as
the response time. The response time of the
comparator differs from the settling time of the voltage
reference. Therefore, both of these times must be
considered when determining the total response time
to a comparator input change. See the Comparator and
Voltage Reference specifications in Section 14.0
“Electrical Specifications” for more details.
7.5
Comparator Interrupt Operation
The comparator interrupt flag is set whenever there is
a change in the output value of the comparator.
Changes are recognized by means of a mismatch
circuit which consists of two latches and an exclusiveor gate (see Figure 7-2 and Figure 7-3). One latch is
updated with the comparator output level when the
CMCON0 register is read. This latch retains the value
until the next read of the CMCON0 register or the
occurrence of a Reset. The other latch of the mismatch
circuit is updated on every Q1 system clock. A
mismatch condition will occur when a comparator
output change is clocked through the second latch on
the Q1 clock cycle. The mismatch condition will persist,
holding the CxIF bit of the PIR1 register true, until either
the CMCON0 register is read or the comparator output
returns to the previous state.
Note:
A write operation to the CMCON0 register
will also clear the mismatch condition
because all writes include a read
operation at the beginning of the write
cycle.
Software will need to maintain information about the
status of the comparator output to determine the actual
change that has occurred.
The CxIF bit of the PIR1 register is the comparator
interrupt flag. This bit must be reset in software by
clearing it to ‘0’. Since it is also possible to write a ‘1’ to
this register, a simulated interrupt may be initiated.
The CxIE bit of the PIE1 register and the PEIE and GIE
bits of the INTCON register must all be set to enable
comparator interrupts. If any of these bits are cleared,
the interrupt is not enabled, although the CxIF bit of the
PIR1 register 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)
b)
Any read or write of CMCON0. This will end the
mismatch condition. See Figures 7-6 and 7-7
Clear the CxIF interrupt flag.
A persistent mismatch condition will preclude clearing
the CxIF interrupt flag. Reading CMCON0 will end the
mismatch condition and allow the CxIF bit to be
cleared.
© 2009 Microchip Technology Inc.
DS41203E-page 59
PIC16F688
FIGURE 7-6:
COMPARATOR
INTERRUPT TIMING W/O
CMCON0 READ
Q1
Q3
CIN+
TRT
COUT
Set CMIF (level)
CMIF
reset by software
FIGURE 7-7:
COMPARATOR
INTERRUPT TIMING WITH
CMCON0 READ
Q1
Q3
CIN+
7.6
Operation During Sleep
The comparator, if enabled before entering Sleep mode,
remains active during Sleep. The additional current
consumed by the comparator is shown separately in
Section 14.0 “Electrical Specifications”. If the
comparator is not used to wake the device, power
consumption can be minimized while in Sleep mode by
turning off the comparator. The comparator is turned off
by selecting mode CM<2:0> = 000 or CM<2:0> = 111
of the CMCON0 register.
A change to the comparator output can wake-up the
device from Sleep. To enable the comparator to wake
the device from Sleep, the CxIE bit of the PIE1 register
and the PEIE bit of the INTCON register must be set.
The instruction following the Sleep instruction always
executes following a wake from Sleep. If the GIE bit of
the INTCON register is also set, the device will then
execute the Interrupt Service Routine.
TRT
7.7
COUT
Set CMIF (level)
CMIF
cleared by CMCON0 read
reset by software
Note 1: If a change in the CM1CON0 register
(CxOUT) occurs when a read operation is
being executed (start of the Q2 cycle),
then the CxIF Interrupt Flag bit of the
PIR1 register may not get set.
Effects of a Reset
A device Reset forces the CMCON0 and CMCON1
registers to their Reset states. This forces the
comparator module to be in the Comparator Reset
mode (CM<2:0> = 000). Thus, all comparator inputs
are analog inputs with the comparator disabled to
consume the smallest current possible.
2: When either comparator is first enabled,
bias circuitry in the comparator module
may cause an invalid output from the
comparator until the bias circuitry is stable.
Allow about 1 μs for bias settling then clear
the mismatch condition and interrupt flags
before enabling comparator interrupts.
DS41203E-page 60
© 2009 Microchip Technology Inc.
PIC16F688
REGISTER 7-1:
CMCON0: COMPARATOR CONFIGURATION REGISTER
R-0
R-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
C2OUT
C1OUT
C2INV
C1INV
CIS
CM2
CM1
CM0
bit 7
bit 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
bit 7
C2OUT: Comparator 2 Output bit
When C2INV = 0:
1 = C2 VIN+ > C2 VIN0 = C2 VIN+ < C2 VINWhen C2INV = 1:
1 = C2 VIN+ < C2 VIN0 = C2 VIN+ > C2 VIN-
bit 6
C1OUT: Comparator 1 Output bit
When C1INV = 0:
1 = C1 VIN+ > C1 VIN0 = C1 VIN+ < C1 VINWhen C1INV = 1:
1 = C1 VIN+ < C1 VIN0 = 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> = 010:
1 = C1IN+ connects to C1 VINC2IN+ connects to C2 VIN0 = C1IN- connects to C1 VINC2IN- connects to C2 VINWhen CM<2:0> = 001:
1 = C1IN+ connects to C1 VIN0 = C1IN- connects to C1 VIN-
bit 2-0
CM<2:0>: Comparator Mode bits (See Figure 7-5)
000 = Comparators off. CxIN pins are configured as analog
001 = Three inputs multiplexed to two comparators
010 = Four inputs multiplexed to two comparators
011 = Two common reference comparators
100 = Two independent comparators
101 = One independent comparator
110 = Two common reference comparators with outputs
111 = Comparators off. CxIN pins are configured as digital I/O
© 2009 Microchip Technology Inc.
x = Bit is unknown
DS41203E-page 61
PIC16F688
7.8
Comparator C2 Gating Timer1
7.9
This feature can be used to time the duration or interval
of analog events. Clearing the T1GSS bit of the
CMCON1 register will enable Timer1 to increment
based on the output of Comparator C2. This requires
that Timer1 is on and gating is enabled. See
Section 6.0 “Timer1 Module with Gate Control” for
details.
It is recommended to synchronize Comparator C2 with
Timer1 by setting the C2SYNC bit when the comparator
is used as the Timer1 gate source. This ensures Timer1
does not miss an increment if the comparator changes
during an increment.
REGISTER 7-2:
Synchronizing Comparator C2
Output to Timer1
The output of Comparator C2 can be synchronized with
Timer1 by setting the C2SYNC bit of the CMCON1
register. When enabled, the comparator output is
latched on the falling edge of the Timer1 clock source.
If a prescaler is used with Timer1, the comparator
output is latched after the prescaling function. To
prevent a race condition, the comparator output is
latched on the falling edge of the Timer1 clock source
and Timer1 increments on the rising edge of its clock
source. Reference the comparator block diagrams
(Figure 7-2 and Figure 7-3) and the Timer1 Block
Diagram (Figure 6-1) for more information.
CMCON1: COMPARATOR CONFIGURATION REGISTER
U-0
U-0
U-0
U-0
U-0
U-0
R/W-1
R/W-0
—
—
—
—
—
—
T1GSS
C2SYNC
bit 7
bit 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
bit 7-2
Unimplemented: Read as ‘0’
bit 1
T1GSS: Timer1 Gate Source Select bit(1)
1 = Timer1 gate source is T1G pin (pin should be configured as digital input)
0 = Timer1 gate source is Comparator C2 output
bit 0
C2SYNC: Comparator C2 Output Synchronization bit(2)
1 = Output is synchronized with falling edge of Timer1 clock
0 = Output is asynchronous
Note 1:
2:
Refer to Section 6.6 “Timer1 Gate”.
Refer to Figure 7-3.
DS41203E-page 62
© 2009 Microchip Technology Inc.
PIC16F688
7.10
EQUATION 7-1:
Comparator Voltage Reference
The Comparator Voltage Reference module provides
an internally generated voltage reference for the
comparators. The following features are available:
•
•
•
•
V RR = 1 (low range):
CVREF = (VR<3:0>/24) × V DD
V RR = 0 (high range):
CV REF = (VDD/4) + (VR<3:0> × VDD/32)
Independent from Comparator operation
Two 16-level voltage ranges
Output clamped to VSS
Ratiometric with VDD
The full range of VSS to VDD cannot be realized due to
the construction of the module. See Figure 7-8.
The VRCON register (Figure 7-3) controls the Voltage
Reference module shown in Figure 7-8.
7.10.1
CVREF OUTPUT VOLTAGE
INDEPENDENT OPERATION
7.10.3
OUTPUT CLAMPED TO VSS
The CVREF output voltage can be set to Vss with no
power consumption by configuring VRCON as follows:
The comparator voltage reference is independent of
the comparator configuration. Setting the VREN bit of
the VRCON register will enable the voltage reference.
• VREN = 0
• VRR = 1
• VR<3:0> = 0000
7.10.2
This allows the comparator to detect a zero-crossing
while not consuming additional CVREF module current.
OUTPUT VOLTAGE SELECTION
The CVREF voltage reference has 2 ranges with 16
voltage levels in each range. Range selection is
controlled by the VRR bit of the VRCON register. The
16 levels are set with the VR<3:0> bits of the VRCON
register.
The CVREF output voltage is determined by the
following equations:
REGISTER 7-3:
7.10.4
OUTPUT RATIOMETRIC TO VDD
The comparator voltage reference is VDD derived and
therefore, the CVREF output changes with fluctuations in
VDD. The tested absolute accuracy of the Comparator
Voltage Reference can be found in Section 14.0
“Electrical Specifications”.
VRCON: VOLTAGE REFERENCE CONTROL REGISTER
R/W-0
U-0
R/W-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
VREN
—
VRR
—
VR3
VR2
VR1
VR0
bit 7
bit 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
bit 7
VREN: CVREF Enable bit
1 = CVREF circuit powered on
0 = CVREF circuit powered down, no IDD drain and CVREF = VSS.
bit 6
Unimplemented: Read as ‘0’
bit 5
VRR: CVREF Range Selection bit
1 = Low range
0 = High range
bit 4
Unimplemented: Read as ‘0’
bit 3-0
VR<3:0>: CVREF Value Selection bits (0 ≤ VR<3:0> ≤ 15)
When VRR = 1: CVREF = (VR<3:0>/24) * VDD
When VRR = 0: CVREF = VDD/4 + (VR<3:0>/32) * VDD
© 2009 Microchip Technology Inc.
x = Bit is unknown
DS41203E-page 63
PIC16F688
FIGURE 7-8:
COMPARATOR VOLTAGE REFERENCE BLOCK DIAGRAM
16 Stages
8R
R
R
R
R
VDD
VRR
8R
16-1 Analog
MUX
VREN
15
14
CVREF to
Comparator
Input
2
1
0
VR<3:0>(1)
VREN
VR<3:0> = 0000
VRR
Note 1:
TABLE 7-2:
Name
ANSEL
CMCON0
Care should be taken to ensure VREF remains
within the comparator common mode input
range. See Section 14.0 “Electrical Specifications” for more detail.
SUMMARY OF REGISTERS ASSOCIATED WITH THE COMPARATOR AND
VOLTAGE REFERENCE MODULES
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
ANS7
ANS6
ANS5
ANS4
ANS3
ANS2
ANS1
ANS0
1111 1111
1111 1111
C2OUT
C1OUT
C2INV
C1INV
CIS
CM2
CM1
CM0
0000 0000
0000 0000
CMCON1
—
—
—
—
—
—
T1GSS
C2SYNC
---- --10
---- --10
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
PORTA
—
—
RA5
RA4
RA3
RA2
RA1
RA0
--x0 x000
--x0 x000
PORTC
—
—
RC5
RC4
RC3
RC2
RC1
RC0
--xx 0000
--xx 0000
TRISA
—
—
TRISA5 TRISA4 TRISA3 TRISA2
TRISA1
TRISA0
--11 1111
--11 1111
TRISC
—
—
TRISC5 TRISC4 TRISC3 TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
VREN
—
VR1
VR0
0-0- 0000
0-0- 0000
VRCON
Legend:
VRR
—
VR3
VR2
x = unknown, u = unchanged, – = unimplemented, read as ‘0’. Shaded cells are not used for comparator.
DS41203E-page 64
© 2009 Microchip Technology Inc.
PIC16F688
8.0
ANALOG-TO-DIGITAL
CONVERTER (ADC) MODULE
The Analog-to-Digital Converter (ADC) allows
conversion of an analog input signal to a 10-bit binary
representation of that signal. This device uses analog
inputs, which are multiplexed into a single sample and
hold circuit. The output of the sample and hold is
connected to the input of the converter. The converter
generates a 10-bit binary result via successive
approximation and stores the conversion result into the
ADC result registers (ADRESL and ADRESH).
The ADC voltage reference is software selectable to
either VDD or a voltage applied to the external reference
pins.
The ADC can generate an interrupt upon completion of
a conversion. This interrupt can be used to wake-up the
device from Sleep.
Figure 8-1 shows the block diagram of the ADC.
FIGURE 8-1:
ADC BLOCK DIAGRAM
VDD
VCFG = 0
VREF
RA0/AN0
000
RA1/AN1/VREF
RA2/AN2
001
010
011
RA4/AN3
RC0/AN4
VCFG = 1
A/D
10
GO/DONE
100
RC1/AN5
RC2/AN6
101
110
111
RC3/AN7
ADFM
0 = Left Justify
1 = Right Justify
ADON
10
VSS
ADRESH
ADRESL
CHS
© 2009 Microchip Technology Inc.
DS41203E-page 65
PIC16F688
8.1
ADC Configuration
When configuring and using the ADC the following
functions must be considered:
•
•
•
•
•
•
Port configuration
Channel selection
ADC voltage reference selection
ADC conversion clock source
Interrupt control
Results formatting
8.1.1
For correct conversion, the appropriate TAD specification
must be met. See A/D conversion requirements in
Section 14.0 “Electrical Specifications” for more
information. Table 8-1 gives examples of appropriate
ADC clock selections.
Note:
Unless using the FRC, any changes in the
system clock frequency will change the
ADC clock frequency, which may
adversely affect the ADC result.
PORT CONFIGURATION
The ADC can be used to convert both analog and digital
signals. When converting analog signals, the I/O pin
should be configured for analog by setting the associated
TRIS and ANSEL bits. See the corresponding Port
section for more information.
Note:
8.1.2
Analog voltages on any pin that is defined
as a digital input may cause the input
buffer to conduct excess current.
CHANNEL SELECTION
The CHS bits of the ADCON0 register determine which
channel is connected to the sample and hold circuit.
When changing channels, a delay is required before
starting the next conversion. Refer to Section 8.2
“ADC Operation” for more information.
8.1.3
ADC VOLTAGE REFERENCE
The VCFG bit of the ADCON0 register provides control
of the positive voltage reference. The positive voltage
reference can be either VDD or an external voltage
source. The negative voltage reference is always
connected to the ground reference.
8.1.4
CONVERSION CLOCK
The source of the conversion clock is software
selectable via the ADCS bits of the ADCON1 register.
There are seven possible clock options:
•
•
•
•
•
•
•
FOSC/2
FOSC/4
FOSC/8
FOSC/16
FOSC/32
FOSC/64
FRC (dedicated internal oscillator)
The time to complete one bit conversion is defined as
TAD. One full 10-bit conversion requires 11 TAD periods
as shown in Figure 8-3.
DS41203E-page 66
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 8-1:
ADC CLOCK PERIOD (TAD) VS. DEVICE OPERATING FREQUENCIES (VDD > 3.0V)
ADC Clock Period (TAD)
ADC Clock Source
Device Frequency (FOSC)
ADCS<2:0>
20 MHz
FOSC/2
000
100 ns
FOSC/4
100
200 ns(2)
001
400 ns
(2)
800 ns
(2)
FOSC/8
FOSC/16
101
FOSC/32
010
1.6 μs
FOSC/64
110
3.2 μs
FRC
x11
2-6 μs(1,4)
Legend:
Note 1:
2:
3:
4:
8 MHz
(2)
4 MHz
1 MHz
(2)
2.0 μs
1.0 μs(2)
4.0 μs
2.0 μs
8.0 μs(3)
2.0 μs
4.0 μs
16.0 μs(3)
4.0 μs
8.0 μs(3)
32.0 μs(3)
(3)
16.0 μs
64.0 μs(3)
2-6 μs(1,4)
2-6 μs(1,4)
250 ns
(2)
500 ns
500 ns(2)
1.0 μs
(2)
8.0 μs
(3)
2-6 μs(1,4)
Shaded cells are outside of recommended range.
The FRC source has a typical TAD time of 4 μs for VDD > 3.0V.
These values violate the minimum required TAD time.
For faster conversion times, the selection of another clock source is recommended.
When the device frequency is greater than 1 MHz, the FRC clock source is only recommended if the
conversion will be performed during Sleep.
FIGURE 8-2:
ANALOG-TO-DIGITAL CONVERSION TAD CYCLES
TCY to TAD TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8 TAD9 TAD10 TAD11
b9
b8
b7
b6
b5
b4
b3
b2
b1
b0
Conversion Starts
Holding Capacitor is Disconnected from Analog Input (typically 100 ns)
Set GO/DONE bit
© 2009 Microchip Technology Inc.
ADRESH and ADRESL registers are loaded,
GO bit is cleared,
ADIF bit is set,
Holding capacitor is connected to analog input
DS41203E-page 67
PIC16F688
8.1.5
INTERRUPTS
8.1.6
The ADC module allows for the ability to generate an
interrupt upon completion of an Analog-to-Digital
Conversion. The ADC interrupt flag is the ADIF bit in
the PIR1 register. The ADC interrupt enable is the ADIE
bit in the PIE1 register. The ADIF bit must be cleared in
software.
Note:
RESULT FORMATTING
The 10-bit A/D Conversion result can be supplied in
two formats, left justified or right justified. The ADFM bit
of the ADCON0 register controls the output format.
Figure 8-4 shows the two output formats.
The ADIF bit is set at the completion of
every conversion, regardless of whether
or not the ADC interrupt is enabled.
This interrupt can be generated while the device is
operating or while in Sleep. If the device is in Sleep, the
interrupt will wake-up the device. Upon waking from
Sleep, the next instruction following the SLEEP
instruction is always executed. If the user is attempting
to wake-up from Sleep and resume in-line code
execution, the global interrupt must be disabled. If the
global interrupt is enabled, execution will switch to the
Interrupt Service Routine.
Please see Section 8.1.5 “Interrupts” for more
information.
FIGURE 8-3:
10-BIT A/D CONVERSION RESULT FORMAT
ADRESH
(ADFM = 0)
ADRESL
MSB
LSB
bit 7
bit 0
bit 7
10-bit A/D Result
(ADFM = 1)
Unimplemented: Read as ‘0’
MSB
bit 7
Unimplemented: Read as ‘0’
DS41203E-page 68
bit 0
LSB
bit 0
bit 7
bit 0
10-bit A/D Result
© 2009 Microchip Technology Inc.
PIC16F688
8.2
8.2.1
ADC Operation
STARTING A CONVERSION
To enable the ADC module, the ADON bit of the
ADCON0 register must be set to a ‘1’. Setting the GO/
DONE bit of the ADCON0 register to a ‘1’ will start the
Analog-to-Digital Conversion.
Note:
8.2.2
The GO/DONE bit should not be set in the
same instruction that turns on the ADC.
Refer to Section 8.2.5 “A/D Conversion
Procedure”.
8.2.5
This is an example procedure for using the ADC to
perform an Analog-to-Digital Conversion:
1.
2.
COMPLETION OF A CONVERSION
When the conversion is complete, the ADC module will:
3.
• Clear the GO/DONE bit
• Set the ADIF flag bit
• Update the ADRESH:ADRESL registers with new
conversion result
8.2.3
TERMINATING A CONVERSION
If a conversion must be terminated before completion,
the GO/DONE bit can be cleared in software. The
ADRESH:ADRESL registers will not be updated with
the partially complete Analog-to-Digital Conversion
sample. Instead, the ADRESH:ADRESL register pair
will retain the value of the previous conversion. Additionally, a 2 TAD delay is required before another acquisition can be initiated. Following this delay, an input
acquisition is automatically started on the selected
channel.
Note:
8.2.4
A device Reset forces all registers to their
Reset state. Thus, the ADC module is
turned off and any pending conversion is
terminated.
ADC OPERATION DURING SLEEP
A/D CONVERSION PROCEDURE
4.
5.
6.
7.
8.
Configure Port:
• Disable pin output driver (See TRIS register)
• Configure pin as analog
Configure the ADC module:
• Select ADC conversion clock
• Configure voltage reference
• Select ADC input channel
• Select result format
• Turn on ADC module
Configure ADC interrupt (optional):
• Clear ADC interrupt flag
• Enable ADC interrupt
• Enable peripheral interrupt
• Enable global interrupt(1)
Wait the required acquisition time(2).
Start conversion by setting the GO/DONE bit.
Wait for ADC conversion to complete by one of
the following:
• Polling the GO/DONE bit
• Waiting for the ADC interrupt (interrupts
enabled)
Read ADC Result
Clear the ADC interrupt flag (required if interrupt
is enabled).
Note 1: The global interrupt can be disabled if the
user is attempting to wake-up from Sleep
and resume in-line code execution.
2: See Section 8.3
Requirements”.
“A/D
Acquisition
The ADC module can operate during Sleep. This
requires the ADC clock source to be set to the FRC
option. When the FRC clock source is selected, the
ADC waits one additional instruction before starting the
conversion. This allows the SLEEP instruction to be
executed, which can reduce system noise during the
conversion. If the ADC interrupt is enabled, the device
will wake-up from Sleep when the conversion
completes. If the ADC interrupt is disabled, the ADC
module is turned off after the conversion completes,
although the ADON bit remains set.
When the ADC clock source is something other than
FRC, a SLEEP instruction causes the present conversion to be aborted and the ADC module is turned off,
although the ADON bit remains set.
© 2009 Microchip Technology Inc.
DS41203E-page 69
PIC16F688
EXAMPLE 8-1:
A/D CONVERSION
;This code block configures the ADC
;for polling, Vdd reference, Frc clock
;and AN0 input.
;
;Conversion start & polling for completion
; are included.
;
BANKSEL ADCON1
;
MOVLW
B’01110000’ ;ADC Frc clock
MOVWF
ADCON1
;
BANKSEL TRISA
;
BSF
TRISA,0
;Set RA0 to input
BANKSEL ANSEL
;
BSF
ANSEL,0
;Set RA0 to analog
BANKSEL ADCON0
;
MOVLW
B’10000001’ ;Right justify,
MOVWF
ADCON0
;Vdd Vref, AN0, On
CALL
SampleTime
;Acquisiton delay
BSF
ADCON0,GO
;Start conversion
BTFSC
ADCON0,GO
;Is conversion done?
GOTO
$-1
;No, test again
BANKSEL ADRESH
;
MOVF
ADRESH,W
;Read upper 2 bits
MOVWF
RESULTHI
;store in GPR space
BANKSEL ADRESL
;
MOVF
ADRESL,W
;Read lower 8 bits
MOVWF
RESULTLO
;Store in GPR space
DS41203E-page 70
© 2009 Microchip Technology Inc.
PIC16F688
8.2.6
ADC REGISTER DEFINITIONS
The following registers are used to control the operation of the ADC.
REGISTER 8-1:
ADCON0: A/D CONTROL REGISTER 0
R/W-0
R/W-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
ADFM
VCFG
—
CHS2
CHS1
CHS0
GO/DONE
ADON
bit 7
bit 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
bit 7
ADFM: A/D Conversion Result Format Select bit
1 = Right justified
0 = Left justified
bit 6
VCFG: Voltage Reference bit
1 = VREF pin
0 = VDD
bit 5
Unimplemented: Read as ‘0’
bit 4-2
x = Bit is unknown
CHS<2:0>: Analog Channel Select bits
000 = AN0
001 = AN1
010 = AN2
011 = AN3
100 = AN4
101 = AN5
110 = AN6
111 = AN7
bit 1
GO/DONE: A/D Conversion Status bit
1 = A/D Conversion cycle in progress. Setting this bit starts an A/D Conversion cycle.
This bit is automatically cleared by hardware when the A/D Conversion has completed.
0 = A/D Conversion completed/not in progress
bit 0
ADON: ADC Enable bit
1 = ADC is enabled
0 = ADC is disabled and consumes no operating current
REGISTER 8-2:
ADCON1: A/D CONTROL REGISTER 1
U-0
R/W-0
R/W-0
R/W-0
U-0
U-0
U-0
U-0
—
ADCS2
ADCS1
ADCS0
—
—
—
—
bit 7
bit 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
bit 7
Unimplemented: Read as ‘0’
bit 6-4
ADCS<2:0>: A/D Conversion Clock Select bits
000 = FOSC/2
001 = FOSC/8
010 = FOSC/32
x11 = FRC (clock derived from a dedicated internal oscillator = 500 kHz max)
100 = FOSC/4
101 = FOSC/16
110 = FOSC/64
bit 3-0
Unimplemented: Read as ‘0’
© 2009 Microchip Technology Inc.
DS41203E-page 71
PIC16F688
REGISTER 8-3:
ADRESH: ADC RESULT REGISTER HIGH (ADRESH) ADFM = 0
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
ADRES9
ADRES8
ADRES7
ADRES6
ADRES5
ADRES4
ADRES3
ADRES2
bit 7
bit 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
bit 7-0
x = Bit is unknown
ADRES<9:2>: ADC Result Register bits
Upper 8 bits of 10-bit conversion result
REGISTER 8-4:
ADRESL: ADC RESULT REGISTER LOW (ADRESL) ADFM = 0
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
ADRES1
ADRES0
—
—
—
—
—
—
bit 7
bit 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
bit 7-6
ADRES<1:0>: ADC Result Register bits
Lower 2 bits of 10-bit conversion result
bit 5-0
Reserved: Do not use.
REGISTER 8-5:
x = Bit is unknown
ADRESH: ADC RESULT REGISTER HIGH (ADRESH) ADFM = 1
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
—
—
—
—
—
—
ADRES9
ADRES8
bit 7
bit 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
bit 7-2
Reserved: Do not use.
bit 1-0
ADRES<9:8>: ADC Result Register bits
Upper 2 bits of 10-bit conversion result
REGISTER 8-6:
x = Bit is unknown
ADRESL: ADC RESULT REGISTER LOW (ADRESL) ADFM = 1
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
ADRES7
ADRES6
ADRES5
ADRES4
ADRES3
ADRES2
ADRES1
ADRES0
bit 7
bit 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
bit 7-0
x = Bit is unknown
ADRES<7:0>: ADC Result Register bits
Lower 8 bits of 10-bit conversion result
DS41203E-page 72
© 2009 Microchip Technology Inc.
PIC16F688
8.3
A/D Acquisition Requirements
For the ADC 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 8-4. 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), see Figure 8-4.
The maximum recommended impedance for analog
sources is 10 kΩ. As the source impedance is
decreased, the acquisition time may be decreased.
After the analog input channel is selected (or changed),
an A/D acquisition must be done before the conversion
EQUATION 8-1:
can be started. To calculate the minimum acquisition
time, Equation 8-1 may be used. This equation
assumes that 1/2 LSb error is used (1024 steps for the
ADC). The 1/2 LSb error is the maximum error allowed
for the ADC to meet its specified resolution.
ACQUISITION TIME EXAMPLE
Temperature = 50°C and external impedance of 10k Ω 5.0V V DD
Assumptions:
T ACQ = Amplifier Settling Time + Hold Capacitor Charging Time + Temperature Coefficient
= T AMP + T C + T COFF
= 2µs + T C + [ ( Temperature - 25°C ) ( 0.05µs/°C ) ]
The value for TC can be approximated with the following equations:
1
V AP PLIE D ⎛⎝ 1 – ------------⎞⎠ = V CHOLD
2047
;[1] VCHOLD charged to within 1/2 lsb
–TC
----------⎞
⎛
RC
V AP P LI ED ⎜ 1 – e ⎟ = V CHOLD
⎝
⎠
;[2] VCHOLD charge response to VAPPLIED
– Tc
---------⎞
⎛
1
RC
V AP P LIED ⎜ 1 – e ⎟ = V A P PLIE D ⎛⎝ 1 – ------------⎞⎠
2047
⎝
⎠
;combining [1] and [2]
Solving for TC:
T C = – C HOLD ( R IC + R SS + R S ) ln(1/2047)
= – 10pF ( 1k Ω + 7k Ω + 10k Ω ) ln(0.0004885)
= 1.37 µs
Therefore:
T ACQ = 2ΜS + 1.37 ΜS + [ ( 50°C- 25°C ) ( 0.05ΜS /°C ) ]
= 4.67 ΜS
Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself out.
2: The charge holding capacitor (CHOLD) is not discharged after each conversion.
3: The maximum recommended impedance for analog sources is 10 kΩ. This is required to meet the pin
leakage specification.
© 2009 Microchip Technology Inc.
DS41203E-page 73
PIC16F688
FIGURE 8-4:
ANALOG INPUT MODEL
VDD
ANx
Rs
CPIN
5 pF
VA
VT = 0.6V
VT = 0.6V
RIC ≤ 1k
Sampling
Switch
SS Rss
I LEAKAGE
± 500 nA
CHOLD = 10 pF
VSS/VREF-
Legend: CPIN
= Input Capacitance
= Threshold Voltage
VT
I LEAKAGE = Leakage current at the pin due to
various junctions
RIC
= Interconnect Resistance
SS
= Sampling Switch
CHOLD
= Sample/Hold Capacitance
FIGURE 8-5:
6V
5V
VDD 4V
3V
2V
RSS
5 6 7 8 9 10 11
Sampling Switch
(kΩ)
ADC TRANSFER FUNCTION
Full-Scale Range
3FFh
3FEh
ADC Output Code
3FDh
3FCh
1 LSB ideal
3FBh
Full-Scale
Transition
004h
003h
002h
001h
000h
Analog Input Voltage
1 LSB ideal
VSS/VREF-
DS41203E-page 74
Zero-Scale
Transition
VDD/VREF+
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 8-2:
SUMMARY OF ASSOCIATED ADC REGISTERS
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
ADCON0
ADFM
VCFG
—
CHS2
CHS1
CHS0
GO/DONE
ADON
00-0 0000
00-0 0000
—
ADCS2
ADCS1
ADCS0
—
—
—
—
-000 ----
-000 ----
ANS7
ANS6
ANS5
ANS4
ANS3
ANS2
ANS1
ANS0
1111 1111
1111 1111
ADCON1
ANSEL
ADRESH
A/D Result Register High Byte
xxxx xxxx
uuuu uuuu
ADRESL
A/D Result Register Low Byte
xxxx xxxx
uuuu uuuu
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
PORTA
—
—
RA5
RA4
RA3
RA2
RA1
RA0
--x0 x000
--x0 x000
PORTC
—
—
RC5
RC4
RC3
RC2
RC1
RC0
--xx 0000
--xx 0000
TRISA
—
—
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
--11 1111
--11 1111
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
TRISC
Legend:
x = unknown, u = unchanged, — = unimplemented read as ‘0’. Shaded cells are not used for ADC module.
© 2009 Microchip Technology Inc.
DS41203E-page 75
PIC16F688
NOTES:
DS41203E-page 76
© 2009 Microchip Technology Inc.
PIC16F688
9.0
DATA EEPROM AND FLASH
PROGRAM MEMORY
CONTROL
Data EEPROM memory is readable and writable and
the Flash program memory is readable during normal
operation (full VDD range). These memories are not
directly mapped in the register file space. Instead, they
are indirectly addressed through the Special Function
Registers. There are six SFRs used to access these
memories:
•
•
•
•
•
•
EECON1
EECON2
EEDAT
EEDATH
EEADR
EEADRH
When interfacing the data memory block, EEDAT holds
the 8-bit data for read/write, and EEADR holds the
address of the EE data location being accessed. This
device has 256 bytes of data EEPROM with an address
range from 0h to 0FFh.
When interfacing the program memory block, the
EEDAT and EEDATH registers form a 2-byte word that
holds the 14-bit data for read/write, and the EEADR
and EEADRH registers form a 2-byte word that holds
the 12-bit address of the EEPROM location being
accessed. This device has 4K words of program
EEPROM with an address range from 0h to 0FFFh.
The program memory allows one word reads.
The EEPROM data memory allows byte read and write.
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. The
write/erase voltages are generated by an on-chip
charge pump rated to operate over the voltage range of
the device for byte or word operations.
When the device is code-protected, the CPU may
continue to read and write the data EEPROM memory
and read the program memory. When code-protected,
the device programmer can no longer access data or
program memory.
© 2009 Microchip Technology Inc.
9.1
EEADR and EEADRH Registers
The EEADR and EEADRH registers can address up to
a maximum of 256 bytes of data EEPROM or up to a
maximum of 4K words of program EEPROM.
When selecting a program address value, the MSB of
the address is written to the EEADRH register and the
LSB is written to the EEADR register. When selecting a
data address value, only the LSB of the address is
written to the EEADR register.
9.1.1
EECON1 AND EECON2 REGISTERS
EECON1 is the control register for EE memory
accesses.
Control bit EEPGD determines if the access will be a
program or data memory access. When clear, as it is
when reset, any subsequent operations will operate on
the data memory. When set, any subsequent
operations will operate on the program memory.
Program memory can only be read.
Control bits RD and WR initiate read and write,
respectively. These bits cannot be cleared, only set, in
software. They are cleared in hardware at completion
of the read or write operation. The inability to clear the
WR bit in software prevents the accidental, premature
termination of a write operation.
The WREN bit, when set, will allow a write operation to
data EEPROM. On power-up, the WREN bit is clear.
The WRERR bit is set when a write operation is interrupted by a MCLR or a WDT Time-out Reset during
normal operation. In these situations, following Reset,
the user can check the WRERR bit and rewrite the
location. The data and address will be unchanged in
the EEDAT and EEADR registers.
Interrupt flag bit EEIF of the PIR1 register is set when
write is complete. It must be cleared in the software.
EECON2 is not a physical register. Reading EECON2
will read all ‘0’s. The EECON2 register is used
exclusively in the data EEPROM write sequence.
DS41203E-page 77
PIC16F688
REGISTER 9-1:
EEDAT: EEPROM DATA 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
EEDAT7
EEDAT6
EEDAT5
EEDAT4
EEDAT3
EEDAT2
EEDAT1
EEDAT0
bit 7
bit 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
bit 7-0
x = Bit is unknown
EEDATn: Byte Value to Write to or Read from Data EEPROM bits
REGISTER 9-2:
EEADR: EEPROM ADDRESS 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
EEADR7
EEADR6
EEADR5
EEADR4
EEADR3
EEADR2
EEADR1
EEADR0
bit 7
bit 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
EEADR<7:0>: 8 Least Significant Address bits for EEPROM Read/Write Operation(1) or Read from program memory
bit 7-0
REGISTER 9-3:
EEDATH: EEPROM DATA HIGH BYTE REGISTER
U-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
—
—
EEDATH5
EEDATH4
EEDATH3
EEDATH2
EEDATH1
EEDATH0
bit 7
bit 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
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
EEDATH<5:0>: 6 Most Significant Data bits from program memory
REGISTER 9-4:
x = Bit is unknown
EEADRH: EEPROM ADDRESS HIGH BYTE REGISTER
U-0
U-0
U-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
—
—
—
—
EEADRH3
EEADRH2
EEADRH1
EEADRH0
bit 7
bit 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
bit 7-4
Unimplemented: Read as ‘0’
bit 3-0
EEADRH<3:0>: Specifies the 4 Most Significant Address bits or high bits for program memory reads
DS41203E-page 78
© 2009 Microchip Technology Inc.
PIC16F688
REGISTER 9-5:
EECON1: EEPROM CONTROL REGISTER
R/W-x
U-0
U-0
U-0
R/W-x
R/W-0
R/S-0
R/S-0
EEPGD
—
—
—
WRERR
WREN
WR
RD
bit 7
bit 0
Legend:
S = Bit can only be set
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
bit 7
EEPGD: Program/Data EEPROM Select bit
1 = Accesses program memory
0 = Accesses data memory
bit 6-4
Unimplemented: Read as ‘0’
bit 3
WRERR: EEPROM Error Flag bit
1 = A write operation is prematurely terminated (any MCLR Reset, any WDT Reset during
normal operation or BOR Reset)
0 = The write operation completed
bit 2
WREN: EEPROM Write Enable bit
1 = Allows write cycles
0 = Inhibits write to the data EEPROM
bit 1
WR: Write Control bit
EEPGD = 1:
This bit is ignored
EEPGD = 0:
1 = Initiates a write cycle (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 data EEPROM is complete
bit 0
RD: Read Control bit
1 = Initiates a memory read (the RD is cleared in hardware and can only be set, not cleared, in
software.)
0 = Does not initiate a memory read
© 2009 Microchip Technology Inc.
DS41203E-page 79
PIC16F688
9.1.2
READING THE DATA EEPROM
MEMORY
9.1.3
WRITING TO 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 of the EECON1 register, and then set control
bit RD of the EECON1 register. The data is available in
the very next cycle, in the EEDAT register; therefore, it
can be read in the next instruction. EEDAT will hold this
value until another read or until it is written to by the
user (during a write operation).
To write an EEPROM data location, the user must first
write the address to the EEADR register and the data
to the EEDAT register. Then the user must follow a
specific sequence to initiate the write for each byte.
EXAMPLE 9-1:
Additionally, the WREN bit in EECON1 must be set to
enable write. This mechanism prevents accidental
writes to data EEPROM due to errant (unexpected)
code execution (i.e., lost programs). The user should
keep the WREN bit clear at all times, except when
updating EEPROM. The WREN bit is not cleared
by hardware.
DATA EEPROM READ
BANKSEL EEADR
MOVLW
DATA_EE_ADDR
MOVWF
EEADR
BCF
EECON1, EEPGD
BSF
MOVF
EECON1, RD
EEDAT, W
;
;
;Data Memory
;Address to read
;Point to DATA
;memory
;EE Read
;W = EEDAT
The write will not initiate if the above sequence is not
followed exactly (write 55h to EECON2, write AAh to
EECON2, then set WR bit) for each byte. Interrupts
should be disabled during this code segment.
After a write sequence has been initiated, clearing the
WREN bit will not affect this write cycle. The WR bit will
be inhibited from being set unless the WREN bit is set.
At the completion of the write cycle, the WR bit is
cleared in hardware and the EE Write Complete
Interrupt Flag bit (EEIF) is set. The user can either
enable this interrupt or poll this bit. EEIF must be
cleared by software.
Required
Sequence
EXAMPLE 9-2:
DATA EEPROM WRITE
BANKSEL
MOVLW
MOVWF
MOVLW
MOVWF
BANKSEL
BCF
BSF
EEADR
DATA_EE_ADDR
EEADR
DATA_EE_DATA
EEDAT
EECON1
EECON1, EEPGD
EECON1, WREN
;
;
;Data Memory Address to write
;
;Data Memory Value to write
;
;Point to DATA memory
;Enable writes
BCF
BTFSC
GOTO
MOVLW
MOVWF
MOVLW
MOVWF
BSF
BSF
INTCON,
INTCON,
$-2
55h
EECON2
AAh
EECON2
EECON1,
INTCON,
GIE
GIE
;Disable INTs.
;SEE AN576
WR
GIE
;
;Write 55h
;
;Write AAh
;Set WR bit to begin write
;Enable INTs.
SLEEP
BCF
EECON1, WREN
DS41203E-page 80
;Wait for interrupt to signal write complete
;Disable writes
© 2009 Microchip Technology Inc.
PIC16F688
9.1.4
READING THE FLASH PROGRAM
MEMORY
To read a program memory location, the user must
write two bytes of the address to the EEADR and
EEADRH registers, set the EEPGD control bit of the
EECON1 register, and then set control bit RD of the
EECON1 register. Once the read control bit is set, the
program memory Flash controller will use the second
instruction cycle to read the data. This causes the second instruction immediately following the “BSF
EECON1,RD” instruction to be ignored. The data is
available in the very next cycle, in the EEDAT and
EEDATH registers; therefore, it can be read as two
bytes in the following instructions.
Required
Sequence
EXAMPLE 9-3:
BANKSEL
MOVLW
MOVWF
MOVLW
MOVWF
BANKSEL
BSF
BSF
EEDAT and EEDATH registers will hold this value until
another read or until it is written to by the user (during
a write operation).
Note 1: The two instructions following a program
memory read are required to be NOP’s.
This prevents the user from executing a
two-cycle instruction on the next
instruction after the RD bit is set.
2: If the WR bit is set when EEPGD = 1, it
will be immediately reset to ‘0’ and no
operation will take place.
FLASH PROGRAM READ
EEADR
MS_PROG_EE_ADDR
EEADRH
LS_PROG_EE_ADDR
EEADR
EECON1
EECON1, EEPGD
EECON1, RD
;
;
;MS Byte of Program Address to read
;
;LS Byte of Program Address to read
;
;Point to PROGRAM memory
;EE Read
;
;First instruction after BSF EECON1,RD executes normally
NOP
NOP
;Any instructions here are ignored as program
;memory is read in second cycle after BSF EECON1,RD
;
BANKSEL
MOVF
MOVWF
MOVF
MOVWF
BCF
EEDAT
EEDAT, W
LOWPMBYTE
EEDATH, W
HIGHPMBYTE
STATUS, RP1
© 2009 Microchip Technology Inc.
;
;W = LS Byte of Program Memory
;
;W = MS Byte of Program EEDAT
;
;Bank 0
DS41203E-page 81
PIC16F688
FIGURE 9-1:
FLASH PROGRAM MEMORY READ CYCLE EXECUTION
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
PC
Flash ADDR
Flash Data
PC + 1
INSTR (PC)
INSTR(PC - 1)
executed here
EEADRH,EEADR
INSTR (PC + 1)
BSF EECON1,RD
executed here
PC
+3
PC+3
EEDATH,EEDAT
INSTR(PC + 1)
executed here
PC + 5
PC + 4
INSTR (PC + 3)
Forced NOP
executed here
INSTR (PC + 4)
INSTR(PC + 3)
executed here
INSTR(PC + 4)
executed here
RD bit
EEDATH
EEDAT
Register
EERHLT
TABLE 9-1:
Name
EECON1
EECON2
EEADR
EEADRH
EEDAT
EEDATH
INTCON
SUMMARY OF REGISTERS ASSOCIATED WITH DATA EEPROM
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
EEPGD
—
—
—
WRERR
WREN
WR
RD
x--- x000
0--- q000
---- ----
---- ----
EEPROM Control Register 2 (not a physical register)
EEADR7
EEADR6
EEADR5
EEADR4
EEADR3
EEADR2
EEADR1
EEADR0
0000 0000
0000 0000
—
—
—
—
EEADRH3
EEADRH2
EEADRH1
EEADRH0
---- 0000
---- 0000
EEDAT7
EEDAT6
EEDAT5
EEDAT4
EEDAT3
EEDAT2
EEDAT1
EEDAT0
0000 0000
0000 0000
—
—
EEDATH5
EEDATH4
EEDATH3
EEDATH2
EEDATH1
EEDATH0
--00 0000
--00 0000
GIE
PEIE
T0IE
INTE
RABIE
T0IF
INTF
RABIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
Legend:
x = unknown, u = unchanged, — = unimplemented read as ‘0’, q = value depends upon condition.
Shaded cells are not used by data EEPROM module.
DS41203E-page 82
© 2009 Microchip Technology Inc.
PIC16F688
10.0
ENHANCED UNIVERSAL
SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (EUSART)
The EUSART module includes the following capabilities:
•
•
•
•
•
•
•
•
•
•
The Enhanced Universal Synchronous Asynchronous
Receiver Transmitter (EUSART) module is a serial I/O
communications peripheral. It contains all the clock
generators, shift registers and data buffers necessary
to perform an input or output serial data transfer
independent of device program execution. The
EUSART, also known as a Serial Communications
Interface (SCI), can be configured as a full-duplex
asynchronous system or half-duplex synchronous
system.
Full-Duplex
mode
is
useful
for
communications with peripheral systems, such as CRT
terminals and personal computers. Half-Duplex
Synchronous mode is intended for communications
with peripheral devices, such as A/D or D/A integrated
circuits, serial EEPROMs or other microcontrollers.
These devices typically do not have internal clocks for
baud rate generation and require the external clock
signal provided by a master synchronous device.
FIGURE 10-1:
Full-duplex asynchronous transmit and receive
Two-character input buffer
One-character output buffer
Programmable 8-bit or 9-bit character length
Address detection in 9-bit mode
Input buffer overrun error detection
Received character framing error detection
Half-duplex synchronous master
Half-duplex synchronous slave
Programmable clock polarity in synchronous
modes
The EUSART module implements the following
additional features, making it ideally suited for use in
Local Interconnect Network (LIN) bus systems:
• Automatic detection and calibration of the baud rate
• Wake-up on Break reception
• 13-bit Break character transmit
Block diagrams of the EUSART transmitter and
receiver are shown in Figure 10-1 and Figure 10-2.
EUSART TRANSMIT BLOCK DIAGRAM
Data Bus
TXIE
Interrupt
TXIF
TXREG Register
8
TX/CK pin
MSb
LSb
(8)
0
Pin Buffer
and Control
TRMT
SPEN
• • •
Transmit Shift Register (TSR)
TXEN
Baud Rate Generator
FOSC
TX9
n
BRG16
+1
SPBRGH
÷n
SPBRG
Multiplier
x4
x16 x64
SYNC
1 X 0 0
0
BRGH
X 1 1 0
0
BRG16
X 1 0 1
0
© 2009 Microchip Technology Inc.
TX9D
DS41203E-page 83
PIC16F688
FIGURE 10-2:
EUSART RECEIVE BLOCK DIAGRAM
SPEN
CREN
RX/DT pin
Baud Rate Generator
Data
Recovery
FOSC
BRG16
SPBRGH
SPBRG
Multiplier
x4
x16 x64
SYNC
1 X 0 0
0
BRGH
X 1 1 0
0
BRG16
X 1 0 1
0
Stop
RCIDL
RSR Register
MSb
Pin Buffer
and Control
+1
OERR
(8)
•••
7
1
LSb
0 START
RX9
÷n
n
FERR
RX9D
RCREG Register
FIFO
8
Data Bus
RCIF
RCIE
Interrupt
The operation of the EUSART module is controlled
through three registers:
• Transmit Status and Control (TXSTA)
• Receive Status and Control (RCSTA)
• Baud Rate Control (BAUDCTL)
These registers are detailed in Register 10-1,
Register 10-2 and Register 10-3, respectively.
DS41203E-page 84
© 2009 Microchip Technology Inc.
PIC16F688
10.1
EUSART Asynchronous Mode
The EUSART transmits and receives data using the
standard non-return-to-zero (NRZ) format. NRZ is
implemented with two levels: a VOH mark state which
represents a ‘1’ data bit, and a VOL space state which
represents a ‘0’ data bit. NRZ refers to the fact that
consecutively transmitted data bits of the same value
stay at the output level of that bit without returning to a
neutral level between each bit transmission. An NRZ
transmission port idles in the mark state. Each character
transmission consists of one Start bit followed by eight
or nine data bits and is always terminated by one or
more Stop bits. The Start bit is always a space and the
Stop bits are always marks. The most common data
format is 8 bits. Each transmitted bit persists for a period
of 1/(Baud Rate). An on-chip dedicated 8-bit/16-bit Baud
Rate Generator is used to derive standard baud rate
frequencies from the system oscillator. See Table 10-5
for examples of baud rate configurations.
The EUSART transmits and receives the LSb first. The
EUSART’s transmitter and receiver are functionally
independent, but share the same data format and baud
rate. Parity is not supported by the hardware, but can
be implemented in software and stored as the ninth
data bit.
10.1.1
EUSART ASYNCHRONOUS
TRANSMITTER
The EUSART transmitter block diagram is shown in
Figure 10-1. The heart of the transmitter is the serial
Transmit Shift Register (TSR), which is not directly
accessible by software. The TSR obtains its data from
the transmit buffer, which is the TXREG register.
10.1.1.1
Enabling the Transmitter
The EUSART transmitter is enabled for asynchronous
operations by configuring the following three control
bits:
• TXEN = 1
• SYNC = 0
• SPEN = 1
All other EUSART control bits are assumed to be in
their default state.
Setting the TXEN bit of the TXSTA register enables the
transmitter circuitry of the EUSART. Clearing the SYNC
bit of the TXSTA register configures the EUSART for
asynchronous operation. Setting the SPEN bit of the
RCSTA register enables the EUSART and
automatically configures the TX/CK I/O pin as an output.
If the TX/CK pin is shared with an analog peripheral the
analog I/O function must be disabled by clearing the
corresponding ANSEL bit.
© 2009 Microchip Technology Inc.
Note 1: When the SPEN bit is set, the RX/DT I/O
pin is automatically configured as an input,
regardless of the state of the corresponding
TRIS bit and whether or not the EUSART
receiver is enabled. The RX/DT pin data
can be read via a normal PORT read but
PORT latch data output is precluded.
2: The TXIF transmitter interrupt flag is set
when the TXEN enable bit is set.
10.1.1.2
Transmitting Data
A transmission is initiated by writing a character to the
TXREG register. If this is the first character, or the
previous character has been completely flushed from
the TSR, the data in the TXREG is immediately
transferred to the TSR register. If the TSR still contains
all or part of a previous character, the new character
data is held in the TXREG until the Stop bit of the
previous character has been transmitted. The pending
character in the TXREG is then transferred to the TSR
in one TCY immediately following the Stop bit
transmission. The transmission of the Start bit, data bits
and Stop bit sequence commences immediately
following the transfer of the data to the TSR from the
TXREG.
10.1.1.3
Transmit Interrupt Flag
The TXIF interrupt flag bit of the PIR1 register is set
whenever the EUSART transmitter is enabled and no
character is being held for transmission in the TXREG.
In other words, the TXIF bit is only clear when the TSR
is busy with a character and a new character has been
queued for transmission in the TXREG. The TXIF flag
bit is not cleared immediately upon writing TXREG.
TXIF becomes valid in the second instruction cycle
following the write execution. Polling TXIF immediately
following the TXREG write will return invalid results. The
TXIF bit is read-only, it cannot be set or cleared by
software.
The TXIF interrupt can be enabled by setting the TXIE
interrupt enable bit of the PIE1 register. However, the
TXIF flag bit will be set whenever the TXREG is empty,
regardless of the state of TXIE enable bit.
To use interrupts when transmitting data, set the TXIE
bit only when there is more data to send. Clear the
TXIE interrupt enable bit upon writing the last character
of the transmission to the TXREG.
DS41203E-page 85
PIC16F688
10.1.1.4
TSR Status
10.1.1.6
The TRMT bit of the TXSTA register indicates the
status of the TSR register. This is a read-only bit. The
TRMT bit is set when the TSR register is empty and is
cleared when a character is transferred to the TSR
register from the TXREG. The TRMT bit remains clear
until all bits have been shifted out of the TSR register.
No interrupt logic is tied to this bit, so the user has to
poll this bit to determine the TSR status.
Note:
10.1.1.5
1.
2.
3.
The TSR register is not mapped in data
memory, so it is not available to the user.
4.
Transmitting 9-Bit Characters
The EUSART supports 9-bit character transmissions.
When the TX9 bit of the TXSTA register is set the
EUSART will shift 9 bits out for each character transmitted. The TX9D bit of the TXSTA register is the ninth,
and Most Significant, data bit. When transmitting 9-bit
data, the TX9D data bit must be written before writing
the 8 Least Significant bits into the TXREG. All nine bits
of data will be transferred to the TSR shift register
immediately after the TXREG is written.
5.
6.
7.
Asynchronous Transmission Set-up:
Initialize the SPBRGH, SPBRG register pair and
the BRGH and BRG16 bits to achieve the desired
baud rate (see Section 10.3 “EUSART Baud
Rate Generator (BRG)”).
Enable the asynchronous serial port by clearing
the SYNC bit and setting the SPEN bit.
If 9-bit transmission is desired, set the TX9 control bit. A set ninth data bit will indicate that the 8
Least Significant data bits are an address when
the receiver is set for address detection.
Enable the transmission by setting the TXEN
control bit. This will cause the TXIF interrupt bit
to be set.
If interrupts are desired, set the TXIE interrupt
enable bit. An interrupt will occur immediately
provided that the GIE and PEIE bits of the INTCON register are also set.
If 9-bit transmission is selected, the ninth bit
should be loaded into the TX9D data bit.
Load 8-bit data into the TXREG register. This
will start the transmission.
A special 9-bit Address mode is available for use with
multiple receivers. See Section 10.1.2.7 “Address
Detection” for more information on the Address mode.
FIGURE 10-3:
ASYNCHRONOUS TRANSMISSION
Write to TXREG
BRG Output
(Shift Clock)
Word 1
RC4/C2OUT/TX/CK
pin
Start bit
FIGURE 10-4:
bit 1
bit 7/8
Stop bit
Word 1
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
bit 0
1 TCY
Word 1
Transmit Shift Reg
ASYNCHRONOUS TRANSMISSION (BACK-TO-BACK)
Write to TXREG
BRG Output
(Shift Clock)
Word 1
RC4/C2OUT/TX/CK
pin
TXIF bit
(Interrupt Reg. Flag)
Word 2
Start bit
bit 0
1 TCY
bit 1
Word 1
bit 7/8
Stop bit
Start bit
bit 0
Word 2
1 TCY
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Note:
Word 1
Transmit Shift Reg.
Word 2
Transmit Shift Reg.
This timing diagram shows two consecutive transmissions.
DS41203E-page 86
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 10-1:
REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION
Name
Bit 7
Bit 6
BAUDCTL
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
0000 0000
0000 0000
PIR1
RCREG
EUSART Receive Data Register
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
0000 000x
0000 000x
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
0000 0000
0000 0000
0000 0010
0000 0010
TRISC
TXREG
TXSTA
Legend:
EUSART Transmit Data Register
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for Asynchronous Transmission.
© 2009 Microchip Technology Inc.
DS41203E-page 87
PIC16F688
10.1.2
EUSART ASYNCHRONOUS
RECEIVER
The Asynchronous mode would typically be used in
RS-232 systems. The receiver block diagram is shown
in Figure 10-2. The data is received on the RX/DT pin
and drives the data recovery block. The data recovery
block is actually a high-speed shifter operating at 16
times the baud rate, whereas the serial Receive Shift
Register (RSR) operates at the bit rate. When all 8 or 9
bits of the character have been shifted in, they are
immediately transferred to a two character First-InFirst-Out (FIFO) memory. The FIFO buffering allows
reception of two complete characters and the start of a
third character before software must start servicing the
EUSART receiver. The FIFO and RSR registers are not
directly accessible by software. Access to the received
data is via the RCREG register.
10.1.2.1
Enabling the Receiver
The EUSART receiver is enabled for asynchronous
operation by configuring the following three control bits:
• CREN = 1
• SYNC = 0
• SPEN = 1
All other EUSART control bits are assumed to be in
their default state.
Setting the CREN bit of the RCSTA register enables the
receiver circuitry of the EUSART. Clearing the SYNC bit
of the TXSTA register configures the EUSART for
asynchronous operation. Setting the SPEN bit of the
RCSTA register enables the EUSART and
automatically configures the RX/DT I/O pin as an input.
If the RX/DT pin is shared with an analog peripheral the
analog I/O function must be disabled by clearing the
corresponding ANSEL bit.
Note:
When the SPEN bit is set the TX/CK I/O
pin is automatically configured as an
output, regardless of the state of the
corresponding TRIS bit and whether or not
the EUSART transmitter is enabled. The
PORT latch is disconnected from the
output driver so it is not possible to use the
TX/CK pin as a general purpose output.
10.1.2.2
Receiving Data
The receiver data recovery circuit initiates character
reception on the falling edge of the first bit. The first bit,
also known as the Start bit, is always a zero. The data
recovery circuit counts one-half bit time to the center of
the Start bit and verifies that the bit is still a zero. If it is
not a zero then the data recovery circuit aborts
character reception, without generating an error, and
resumes looking for the falling edge of the Start bit. If
the Start bit zero verification succeeds then the data
recovery circuit counts a full bit time to the center of the
next bit. The bit is then sampled by a majority detect
circuit and the resulting ‘0’ or ‘1’ is shifted into the RSR.
This repeats until all data bits have been sampled and
shifted into the RSR. One final bit time is measured and
the level sampled. This is the Stop bit, which is always
a ‘1’. If the data recovery circuit samples a ‘0’ in the
Stop bit position then a framing error is set for this
character, otherwise the framing error is cleared for this
character. See Section 10.1.2.4 “Receive Framing
Error” for more information on framing errors.
Immediately after all data bits and the Stop bit have
been received, the character in the RSR is transferred
to the EUSART receive FIFO and the RCIF interrupt
flag bit of the PIR1 register is set. The top character in
the FIFO is transferred out of the FIFO by reading the
RCREG register.
Note:
10.1.2.3
If the receive FIFO is overrun, no additional
characters will be received until the overrun
condition is cleared. See Section 10.1.2.5
“Receive Overrun Error” for more
information on overrun errors.
Receive Interrupts
The RCIF interrupt flag bit of the PIR1 register is set
whenever the EUSART receiver is enabled and there is
an unread character in the receive FIFO. The RCIF
interrupt flag bit is read-only, it cannot be set or cleared
by software.
RCIF interrupts are enabled by setting the following
bits:
• RCIE interrupt enable bit of the PIE1 register
• PEIE peripheral interrupt enable bit of the INTCON register
• GIE global interrupt enable bit of the INTCON
register
The RCIF interrupt flag bit will be set when there is an
unread character in the FIFO, regardless of the state of
interrupt enable bits.
DS41203E-page 88
© 2009 Microchip Technology Inc.
PIC16F688
10.1.2.4
Receive Framing Error
Each character in the receive FIFO buffer has a
corresponding framing error Status bit. A framing error
indicates that a Stop bit was not seen at the expected
time. The framing error status is accessed via the
FERR bit of the RCSTA register. The FERR bit
represents the status of the top unread character in the
receive FIFO. Therefore, the FERR bit must be read
before reading the RCREG.
The FERR bit is read-only and only applies to the top
unread character in the receive FIFO. A framing error
(FERR = 1) does not preclude reception of additional
characters. It is not necessary to clear the FERR bit.
Reading the next character from the FIFO buffer will
advance the FIFO to the next character and the next
corresponding framing error.
The FERR bit can be forced clear by clearing the SPEN
bit of the RCSTA register which resets the EUSART.
Clearing the CREN bit of the RCSTA register does not
affect the FERR bit. A framing error by itself does not
generate an interrupt.
Note:
10.1.2.5
10.1.2.7
Address Detection
A special Address Detection mode is available for use
when multiple receivers share the same transmission
line, such as in RS-485 systems. Address detection is
enabled by setting the ADDEN bit of the RCSTA
register.
Address detection requires 9-bit character reception.
When address detection is enabled, only characters
with the ninth data bit set will be transferred to the
receive FIFO buffer, thereby setting the RCIF interrupt
bit. All other characters will be ignored.
Upon receiving an address character, user software
determines if the address matches its own. Upon
address match, user software must disable address
detection by clearing the ADDEN bit before the next
Stop bit occurs. When user software detects the end of
the message, determined by the message protocol
used, software places the receiver back into the
Address Detection mode by setting the ADDEN bit.
If all receive characters in the receive
FIFO have framing errors, repeated reads
of the RCREG will not clear the FERR bit.
Receive Overrun Error
The receive FIFO buffer can hold two characters. An
overrun error will be generated If a third character, in its
entirety, is received before the FIFO is accessed. When
this happens the OERR bit of the RCSTA register is
set. The characters already in the FIFO buffer can be
read but no additional characters will be received until
the error is cleared. The error must be cleared by either
clearing the CREN bit of the RCSTA register or by
resetting the EUSART by clearing the SPEN bit of the
RCSTA register.
10.1.2.6
Receiving 9-bit Characters
The EUSART supports 9-bit character reception. When
the RX9 bit of the RCSTA register is set the EUSART
will shift 9 bits into the RSR for each character
received. The RX9D bit of the RCSTA register is the
ninth and Most Significant data bit of the top unread
character in the receive FIFO. When reading 9-bit data
from the receive FIFO buffer, the RX9D data bit must
be read before reading the 8 Least Significant bits from
the RCREG.
© 2009 Microchip Technology Inc.
DS41203E-page 89
PIC16F688
10.1.2.8
1.
2.
3.
4.
5.
6.
7.
8.
9.
Asynchronous Reception Set-up:
10.1.2.9
Initialize the SPBRGH, SPBRG register pair and
the BRGH and BRG16 bits to achieve the
desired baud rate (see Section 10.3 “EUSART
Baud Rate Generator (BRG)”).
Enable the serial port by setting the SPEN bit.
The SYNC bit must be clear for asynchronous
operation.
If interrupts are desired, set the RCIE interrupt
enable bit and set the GIE and PEIE bits of the
INTCON register.
If 9-bit reception is desired, set the RX9 bit.
Enable reception by setting the CREN bit.
The RCIF interrupt flag bit will be set when a
character is transferred from the RSR to the
receive buffer. An interrupt will be generated if
the RCIE interrupt enable bit was also set.
Read the RCSTA register to get the error flags
and, if 9-bit data reception is enabled, the ninth
data bit.
Get the received 8 Least Significant data bits
from the receive buffer by reading the RCREG
register.
If an overrun occurred, clear the OERR flag by
clearing the CREN receiver enable bit.
FIGURE 10-5:
Rcv Shift
Reg
Rcv Buffer Reg
RCIDL
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 register pair and
the BRGH and BRG16 bits to achieve the
desired baud rate (see Section 10.3 “EUSART
Baud Rate Generator (BRG)”).
2. Enable the serial port by setting the SPEN bit.
The SYNC bit must be clear for asynchronous
operation.
3. If interrupts are desired, set the RCIE interrupt
enable bit and set the GIE and PEIE bits of the
INTCON register.
4. Enable 9-bit reception by setting the RX9 bit.
5. Enable address detection by setting the ADDEN
bit.
6. Enable reception by setting the CREN bit.
7. The RCIF interrupt flag bit will be set when a
character with the ninth bit set is transferred
from the RSR to the receive buffer. An interrupt
will be generated if the RCIE interrupt enable bit
was also set.
8. Read the RCSTA register to get the error flags.
The ninth data bit will always be set.
9. Get the received 8 Least Significant data bits
from the receive buffer by reading the RCREG
register. Software determines if this is the
device’s address.
10. If an overrun occurred, clear the OERR flag by
clearing the CREN receiver enable bit.
11. If the device has been addressed, clear the
ADDEN bit to allow all received data into the
receive buffer and generate interrupts.
ASYNCHRONOUS RECEPTION
Start
bit
bit 0
RX/DT pin
9-bit Address Detection Mode Set-up
bit 1
bit 7/8 Stop
bit
Start
bit
Word 1
RCREG
bit 0
bit 7/8 Stop
bit
Start
bit
bit 7/8 Stop
bit
Word 2
RCREG
Read Rcv
Buffer Reg
RCREG
RCIF
(Interrupt Flag)
OERR bit
CREN
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.
DS41203E-page 90
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 10-2:
REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION
Name
Bit 7
Bit 6
BAUDCTL
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
0000 0000
0000 0000
PIR1
RCREG
EUSART Receive Data Register
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
0000 000x
0000 000x
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
0000 0000
0000 0000
0000 0010
0000 0010
TRISC
TXREG
TXSTA
Legend:
EUSART Transmit Data Register
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for Asynchronous Reception.
© 2009 Microchip Technology Inc.
DS41203E-page 91
PIC16F688
10.2
Clock Accuracy with
Asynchronous Operation
The factory calibrates the internal oscillator block
output (INTOSC). However, the INTOSC frequency
may drift as VDD or temperature changes, and this
directly affects the asynchronous baud rate. Two
methods may be used to adjust the baud rate clock, but
both require a reference clock source of some kind.
REGISTER 10-1:
The first (preferred) method uses the OSCTUNE
register to adjust the INTOSC output. Adjusting the
value in the OSCTUNE register allows for fine resolution
changes to the system clock source. See Section 3.5
“Internal Clock Modes” for more information.
The other method adjusts the value in the Baud Rate
Generator. This can be done automatically with the
Auto-Baud Detect feature (see Section 10.3.1 “AutoBaud Detect”). There may not be fine enough
resolution when adjusting the Baud Rate Generator to
compensate for a gradual change in the peripheral
clock frequency.
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(1)
SYNC
SENDB
BRGH
TRMT
TX9D
bit 7
bit 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
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)
1 = Transmit enabled
0 = Transmit disabled
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: Ninth bit of Transmit Data
Can be address/data bit or a parity bit.
Note 1:
SREN/CREN overrides TXEN in Sync mode.
DS41203E-page 92
© 2009 Microchip Technology Inc.
PIC16F688
REGISTER 10-2:
RCSTA: RECEIVE STATUS AND CONTROL REGISTER(1)
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
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
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, enable interrupt and load 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 8-bit (RX9 = 0):
Don’t care
bit 2
FERR: Framing Error bit
1 = Framing error (can be updated by reading RCREG register and receive 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: Ninth bit of Received Data
This can be address/data bit or a parity bit and must be calculated by user firmware.
© 2009 Microchip Technology Inc.
DS41203E-page 93
PIC16F688
REGISTER 10-3:
BAUDCTL: BAUD RATE CONTROL REGISTER
R-0
R-1
U-0
R/W-0
R/W-0
U-0
R/W-0
R/W-0
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
bit 7
bit 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
bit 7
ABDOVF: Auto-Baud Detect Overflow bit
Asynchronous mode:
1 = Auto-baud timer overflowed
0 = Auto-baud timer did not overflow
Synchronous mode:
Don’t care
bit 6
RCIDL: Receive Idle Flag bit
Asynchronous mode:
1 = Receiver is Idle
0 = Start bit has been received and the receiver is receiving
Synchronous mode:
Don’t care
bit 5
Unimplemented: Read as ‘0’
bit 4
SCKP: Synchronous Clock Polarity Select bit
Asynchronous mode:
1 = Transmit inverted data to the RB7/TX/CK pin
0 = Transmit non-inverted data to the RB7/TX/CK pin
Synchronous mode:
1 = Data is clocked on rising edge of the clock
0 = Data is clocked on falling edge of the clock
bit 3
BRG16: 16-bit Baud Rate Generator bit
1 = 16-bit Baud Rate Generator is used
0 = 8-bit Baud Rate Generator is used
bit 2
Unimplemented: Read as ‘0’
bit 1
WUE: Wake-up Enable bit
Asynchronous mode:
1 = Receiver is waiting for a falling edge. No character will be received byte RCIF will be set. WUE will
automatically clear after RCIF is set.
0 = Receiver is operating normally
Synchronous mode:
Don’t care
bit 0
ABDEN: Auto-Baud Detect Enable bit
Asynchronous mode:
1 = Auto-Baud Detect mode is enabled (clears when auto-baud is complete)
0 = Auto-Baud Detect mode is disabled
Synchronous mode:
Don’t care
DS41203E-page 94
© 2009 Microchip Technology Inc.
PIC16F688
10.3
EUSART Baud Rate Generator
(BRG)
The Baud Rate Generator (BRG) is an 8-bit or 16-bit
timer that is dedicated to the support of both the
asynchronous and synchronous EUSART operation.
By default, the BRG operates in 8-bit mode. Setting the
BRG16 bit of the BAUDCTL register selects 16-bit
mode.
If the system clock is changed during an active receive
operation, a receive error or data loss may result. To
avoid this problem, check the status of the RCIDL bit to
make sure that the receive operation is Idle before
changing the system clock.
EXAMPLE 10-1:
For a device with FOSC of 16 MHz, desired baud rate
of 9600, Asynchronous mode, 8-bit BRG:
The SPBRGH, SPBRG register pair determines the
period of the free running baud rate timer. In
Asynchronous mode the multiplier of the baud rate
period is determined by both the BRGH bit of the TXSTA
register and the BRG16 bit of the BAUDCTL register. In
Synchronous mode, the BRGH bit is ignored.
F OS C
Desired Baud Rate = --------------------------------------------------------------------64 ( [SPBRGH:SPBRG] + 1 )
Solving for SPBRGH:SPBRG:
FOSC
--------------------------------------------Desired Baud Rate
X = --------------------------------------------- – 1
64
Table 10-3 contains the formulas for determining the
baud rate. Example 10-1 provides a sample calculation
for determining the baud rate and baud rate error.
Typical baud rates and error values for various
asynchronous modes have been computed for your
convenience and are shown in Table 10-3. It may be
advantageous to use the high baud rate (BRGH = 1),
or the 16-bit BRG (BRG16 = 1) to reduce the baud rate
error. The 16-bit BRG mode is used to achieve slow
baud rates for fast oscillator frequencies.
16000000
-----------------------9600
= ------------------------ – 1
64
= [ 25.042 ] = 25
16000000
Calculated Baud Rate = --------------------------64 ( 25 + 1 )
= 9615
Writing a new value to the SPBRGH, SPBRG register
pair causes the BRG timer to be reset (or cleared). This
ensures that the BRG does not wait for a timer overflow
before outputting the new baud rate.
TABLE 10-3:
CALCULATING BAUD
RATE ERROR
Calc. Baud Rate – Desired Baud Rate
Error = -------------------------------------------------------------------------------------------Desired Baud Rate
( 9615 – 9600 )
= ---------------------------------- = 0.16%
9600
BAUD RATE FORMULAS
Configuration Bits
BRG/EUSART Mode
Baud Rate Formula
0
8-bit/Asynchronous
FOSC/[64 (n+1)]
0
1
8-bit/Asynchronous
0
1
0
16-bit/Asynchronous
0
1
1
16-bit/Asynchronous
1
0
x
8-bit/Synchronous
1
x
16-bit/Synchronous
SYNC
BRG16
BRGH
0
0
0
FOSC/[16 (n+1)]
1
Legend:
FOSC/[4 (n+1)]
x = Don’t care, n = value of SPBRGH, SPBRG register pair
TABLE 10-4:
REGISTERS ASSOCIATED WITH THE BAUD RATE GENERATOR
Name
Bit 7
Bit 6
BAUDCTL
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
0000 000x
0000 000x
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
TXSTA
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
0000 0010
0000 0010
Legend:
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for the Baud Rate Generator.
© 2009 Microchip Technology Inc.
DS41203E-page 95
PIC16F688
TABLE 10-5:
BAUD RATES FOR ASYNCHRONOUS MODES
SYNC = 0, BRGH = 0, BRG16 = 0
BAUD
RATE
FOSC = 20.000 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 18.432 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 11.0592 MHz
Actual
Rate
%
Error
FOSC = 8.000 MHz
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
300
—
—
—
—
—
—
—
—
—
—
—
—
1200
1221
1.73
255
1200
0.00
239
1200
0.00
143
1202
0.16
103
2400
2404
0.16
129
2400
0.00
119
2400
0.00
71
2404
0.16
51
9600
9470
-1.36
32
9600
0.00
29
9600
0.00
17
9615
0.16
12
10417
10417
0.00
29
10286
-1.26
27
10165
-2.42
16
10417
0.00
11
19.2k
19.53k
1.73
15
19.20k
0.00
14
19.20k
0.00
8
—
—
—
57.6k
—
—
—
57.60k
0.00
7
57.60k
0.00
2
—
—
—
115.2k
—
—
—
—
—
—
—
—
—
—
—
—
SYNC = 0, BRGH = 0, BRG16 = 0
BAUD
RATE
FOSC = 4.000 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 3.6864 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 2.000 MHz
Actual
Rate
FOSC = 1.000 MHz
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
300
300
0.16
207
300
0.00
191
300
0.16
103
300
0.16
51
1200
1202
0.16
51
1200
0.00
47
1202
0.16
25
1202
0.16
12
2400
2404
0.16
25
2400
0.00
23
2404
0.16
12
—
—
—
9600
—
—
—
9600
0.00
5
—
—
—
—
—
—
10417
10417
0.00
5
—
—
—
10417
0.00
2
—
—
—
19.2k
—
—
—
19.20k
0.00
2
—
—
—
—
—
—
57.6k
—
—
—
57.60k
0.00
0
—
—
—
—
—
—
115.2k
—
—
—
—
—
—
—
—
—
—
—
—
SYNC = 0, BRGH = 1, BRG16 = 0
BAUD
RATE
FOSC = 20.000 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 18.432 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 11.0592 MHz
Actual
Rate
%
Error
FOSC = 8.000 MHz
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
300
—
—
—
—
—
—
—
—
—
—
—
—
1200
—
—
—
—
—
—
—
—
—
—
—
—
2400
—
—
—
—
—
—
—
—
—
2404
0.16
207
9600
9615
0.16
129
9600
0.00
119
9600
0.00
71
9615
0.16
51
10417
10417
0.00
119
10378
-0.37
110
10473
0.53
65
10417
0.00
47
19.2k
19.23k
0.16
64
19.20k
0.00
59
19.20k
0.00
35
19231
0.16
25
57.6k
56.82k
-1.36
21
57.60k
0.00
19
57.60k
0.00
11
55556
-3.55
8
115.2k
113.64k
-1.36
10
115.2k
0.00
9
115.2k
0.00
5
—
—
—
DS41203E-page 96
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 10-5:
BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED)
SYNC = 0, BRGH = 1, BRG16 = 0
BAUD
RATE
FOSC = 4.000 MHz
FOSC = 3.6864 MHz
FOSC = 2.000 MHz
FOSC = 1.000 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
300
1200
—
1202
—
0.16
—
207
—
1200
—
0.00
—
191
—
1202
—
0.16
—
103
300
1202
0.16
0.16
207
51
2400
2404
0.16
103
2400
0.00
95
2404
0.16
51
2404
0.16
25
—
Actual
Rate
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
9600
9615
0.16
25
9600
0.00
23
9615
0.16
12
—
—
10417
10417
0.00
23
10473
0.53
21
10417
0.00
11
10417
0.00
5
19.2k
19.23k
0.16
12
19.2k
0.00
11
—
—
—
—
—
—
57.6k
—
—
—
57.60k
0.00
3
—
—
—
—
—
—
115.2k
—
—
—
115.2k
0.00
1
—
—
—
—
—
—
SYNC = 0, BRGH = 0, BRG16 = 1
BAUD
RATE
FOSC = 20.000 MHz
Actual
Rate
FOSC = 18.432 MHz
%
Error
SPBRG
value
(decimal)
Actual
Rate
FOSC = 11.0592 MHz
%
Error
SPBRG
value
(decimal)
Actual
Rate
FOSC = 8.000 MHz
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
1666
300
300.0
-0.01
4166
300.0
0.00
3839
300.0
0.00
2303
299.9
-0.02
1200
1200
-0.03
1041
1200
0.00
959
1200
0.00
575
1199
-0.08
416
2400
2399
-0.03
520
2400
0.00
479
2400
0.00
287
2404
0.16
207
51
9600
9615
0.16
129
9600
0.00
119
9600
0.00
71
9615
0.16
10417
10417
0.00
119
10378
-0.37
110
10473
0.53
65
10417
0.00
47
19.2k
19.23k
0.16
64
19.20k
0.00
59
19.20k
0.00
35
19.23k
0.16
25
57.6k
56.818
-1.36
21
57.60k
0.00
19
57.60k
0.00
11
55556
-3.55
8
115.2k
113.636
-1.36
10
115.2k
0.00
9
115.2k
0.00
5
—
—
—
SYNC = 0, BRGH = 0, BRG16 = 1
BAUD
RATE
FOSC = 4.000 MHz
Actual
Rate
%
Error
FOSC = 3.6864 MHz
SPBRG
value
(decimal)
Actual
Rate
%
Error
FOSC = 2.000 MHz
SPBRG
value
(decimal)
Actual
Rate
%
Error
FOSC = 1.000 MHz
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
300
300.1
0.04
832
300.0
0.00
767
299.8
-0.108
416
300.5
0.16
207
1200
1202
0.16
207
1200
0.00
191
1202
0.16
103
1202
0.16
51
2400
2404
0.16
103
2400
0.00
95
2404
0.16
51
2404
0.16
25
9600
9615
0.16
25
9600
0.00
23
9615
0.16
12
—
—
—
10417
10417
0.00
23
10473
0.53
21
10417
0.00
11
10417
0.00
5
19.2k
19.23k
0.16
12
19.20k
0.00
11
—
—
—
—
—
—
57.6k
—
—
—
57.60k
0.00
3
—
—
—
—
—
—
115.2k
—
—
—
115.2k
0.00
1
—
—
—
—
—
—
© 2009 Microchip Technology Inc.
DS41203E-page 97
PIC16F688
TABLE 10-5:
BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED)
SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1
BAUD
RATE
FOSC = 20.000 MHz
FOSC = 18.432 MHz
FOSC = 11.0592 MHz
FOSC = 8.000 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
300
1200
300.0
1200
0.00
-0.01
16665
4166
300.0
1200
0.00
0.00
15359
3839
300.0
1200
0.00
0.00
9215
2303
300.0
1200
0.00
-0.02
6666
1666
2400
2400
0.02
2082
2400
0.00
1919
2400
0.00
1151
2401
0.04
832
9600
9597
-0.03
520
9600
0.00
479
9600
0.00
287
9615
0.16
207
10417
10417
0.00
479
10425
0.08
441
10433
0.16
264
10417
0
191
Actual
Rate
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
19.2k
19.23k
0.16
259
19.20k
0.00
239
19.20k
0.00
143
19.23k
0.16
103
57.6k
57.47k
-0.22
86
57.60k
0.00
79
57.60k
0.00
47
57.14k
-0.79
34
115.2k
116.3k
0.94
42
115.2k
0.00
39
115.2k
0.00
23
117.6k
2.12
16
SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1
BAUD
RATE
FOSC = 4.000 MHz
Actual
Rate
%
Error
SPBRG
value
(decimal)
FOSC = 3.6864 MHz
Actual
Rate
FOSC = 2.000 MHz
%
Error
SPBRG
value
(decimal)
Actual
Rate
FOSC = 1.000 MHz
%
Error
SPBRG
value
(decimal)
Actual
Rate
%
Error
SPBRG
value
(decimal)
832
300
300.0
0.01
3332
300.0
0.00
3071
299.9
-0.02
1666
300.1
0.04
1200
1200
0.04
832
1200
0.00
767
1199
-0.08
416
1202
0.16
207
2400
2398
0.08
416
2400
0.00
383
2404
0.16
207
2404
0.16
103
9600
9615
0.16
103
9600
0.00
95
9615
0.16
51
9615
0.16
25
10417
10417
0.00
95
10473
0.53
87
10417
0.00
47
10417
0.00
23
19.2k
19.23k
0.16
51
19.20k
0.00
47
19.23k
0.16
25
19.23k
0.16
12
57.6k
58.82k
2.12
16
57.60k
0.00
15
55.56k
-3.55
8
—
—
—
115.2k
111.1k
-3.55
8
115.2k
0.00
7
—
—
—
—
—
—
DS41203E-page 98
© 2009 Microchip Technology Inc.
PIC16F688
10.3.1
AUTO-BAUD DETECT
The EUSART module supports automatic detection
and calibration of the baud rate.
In the Auto-Baud 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.
The Baud Rate Generator is used to time the period of
a received 55h (ASCII “U”) which is the Sync character
for the LIN bus. The unique feature of this character is
that it has five rising edges including the Stop bit edge.
Setting the ABDEN bit of the BAUDCTL register starts
the auto-boot sequence (Figure 10-6). While the ABD
sequence takes place, the EUSART state machine is
held in Idle. On the first rising edge of the receive line,
after the Start bit, the SPBRG begins counting up using
the BRG counter clock as shown in Table 10-6. The
fifth rising edge will occur on the RX pin at the end of
the eighth bit period. At that time, an accumulated
value totaling the proper BRG period is left in
SPBRGH, SPBRG register pair, the ABDEN bit is
automatically cleared and the RCIF interrupt flag is set.
The value in the RCREG needs to be read to clear the
RCIF interrupt. RCREG content should be discarded.
When calibrating for modes that do not use the
SPBRGH register the user can verify that the SPBRG
register did not overflow by checking for 00h in the
SPBRGH register.
The BRG auto-baud clock is determined by the BRG16
and BRGH bits as shown in Table 10-6. During ABD,
both the SPBRGH and SPBRG registers are used as a
16-bit counter, independent of the BRG16 bit setting.
While calibrating the baud rate period, the SPBRGH
and SPBRG registers are clocked at 1/8th the BRG
base clock rate. The resulting byte measurement is the
average bit time when clocked at full speed.
Note 1: If the WUE bit is set with the ABDEN bit,
auto-baud detection will occur on the byte
following the Break character (see
Section 10.3.3
“Auto-Wake-up
on
Break”).
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 Detect feature.
3: During the auto-baud process, the autobaud counter starts counting at 1. Upon
completion of the auto-baud sequence, to
achieve maximum accuracy, subtract 1
from the SPBRGH:SPBRG register pair.
TABLE 10-6:
BRG16
BRGH
BRG Base
Clock
BRG ABD
Clock
0
0
FOSC/64
FOSC/512
0
1
FOSC/16
FOSC/128
1
0
FOSC/16
FOSC/128
1
1
FOSC/4
FOSC/32
Note:
FIGURE 10-6:
During the ABD sequence, SPBRG and
SPBRGH registers are both used as a 16-bit
counter, independent of BRG16 setting.
AUTOMATIC BAUD RATE CALCULATION
XXXXh
BRG Value
BRG COUNTER CLOCK RATES
RX pin
0000h
001Ch
Start
Edge #1
bit 1
bit 0
Edge #2
bit 3
bit 2
Edge #3
bit 5
bit 4
Edge #4
bit 7
bit 6
Edge #5
Stop bit
BRG Clock
Auto Cleared
Set by User
ABDEN bit
RCIDL
RCIF bit
(Interrupt)
Read
RCREG
SPBRG
XXh
1Ch
SPBRGH
XXh
00h
Note 1:
The ABD sequence requires the EUSART module to be configured in Asynchronous mode.
© 2009 Microchip Technology Inc.
DS41203E-page 99
PIC16F688
10.3.2
AUTO-BAUD OVERFLOW
During the course of automatic baud detection, the
ABDOVF bit of the BAUDCTL register will be set if the
baud rate counter overflows before the fifth rising edge
is detected on the RX pin. The ABDOVF bit indicates
that the counter has exceeded the maximum count that
can fit in the 16 bits of the SPBRGH:SPBRG register
pair. After the ABDOVF has been set, the counter continues to count until the fifth rising edge is detected on
the RX pin. Upon detecting the fifth RX edge, the hardware will set the RCIF interrupt flag and clear the
ABDEN bit of the BAUDCTL register. The RCIF flag
can be subsequently cleared by reading the RCREG.
The ABDOVF flag can be cleared by software directly.
To terminate the auto-baud process before the RCIF
flag is set, clear the ABDEN bit then clear the ABDOVF
bit. The ABDOVF bit will remain set if the ABDEN bit is
not cleared first.
10.3.3
AUTO-WAKE-UP ON BREAK
During Sleep mode, all clocks to the EUSART are
suspended. Because of this, the Baud Rate Generator
is inactive and a proper character reception cannot be
performed. The Auto-Wake-up feature allows the
controller to wake-up due to activity on the RX/DT line.
This feature is available only in Asynchronous mode.
The Auto-Wake-up feature is enabled by setting the
WUE bit of the BAUDCTL register. Once set, the normal
receive sequence on RX/DT is disabled, and the
EUSART remains in an Idle state, monitoring for a wakeup 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 protocol.)
The EUSART module generates an RCIF interrupt
coincident with the wake-up event. The interrupt is
generated synchronously to the Q clocks in normal CPU
operating modes (Figure 10-7), and asynchronously if
the device is in Sleep mode (Figure 10-8). The interrupt
condition is cleared by reading the RCREG register.
FIGURE 10-7:
The WUE bit is automatically cleared by the low-to-high
transition on the RX line at the end of the Break. This
signals to the user that the Break event is over. At this
point, the EUSART module is in Idle mode waiting to
receive the next character.
10.3.3.1
Special Considerations
Break Character
To avoid character errors or character fragments
during a wake-up event, the wake-up character must
be all zeros.
When the wake-up is enabled the function works
independent of the low time on the data stream. If the
WUE bit is set and a valid non-zero character is
received, the low time from the Start bit to the first rising
edge will be interpreted as the wake-up event. The
remaining bits in the character will be received as a
fragmented character and subsequent characters can
result in framing or overrun errors.
Therefore, the initial character in the transmission must
be all ‘0’s. This must be 10 or more bit times, 13-bit
times recommended for LIN bus, or any number of bit
times for standard RS-232 devices.
Oscillator Start-up Time
Oscillator start-up time must be considered, especially
in applications using oscillators with longer start-up
intervals (i.e., LP, 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.
WUE Bit
The wake-up event causes a receive interrupt by
setting the RCIF bit. The WUE bit is cleared in
hardware by a rising edge on RX/DT. The interrupt
condition is then cleared in software by reading the
RCREG register and discarding its contents.
To ensure that no actual data is lost, check the RCIDL.
AUTO-WAKE-UP BIT (WUE) TIMING DURING NORMAL OPERATION
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 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
Auto Cleared
Bit set by user
WUE bit
RX/DT Line
RCIF
Note 1:
Cleared due to User Read of RCREG
The EUSART remains in Idle while the WUE bit is set.
DS41203E-page 100
© 2009 Microchip Technology Inc.
PIC16F688
FIGURE 10-8:
AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP
Q1Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1Q2 Q3 Q4
Q1
Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4
OSC1
Auto Cleared
Bit Set by User
WUE bit
RX/DT Line
Note 1
RCIF
Sleep Command Executed
Note 1:
2:
10.3.4
If the wake-up event requires long oscillator warm-up time, the automatic clearing of the WUE bit can occur while the stposc signal is
still active. This sequence should not depend on the presence of Q clocks.
The EUSART remains in Idle while the WUE bit is set.
BREAK CHARACTER SEQUENCE
The EUSART module has the capability of sending the
special Break character sequences that are required by
the LIN bus standard. A Break character consists of a
Start bit, followed by 12 ‘0’ bits and a Stop bit.
To send a Break character, set the SENDB and TXEN
bits of the TXSTA register. The Break character transmission is then initiated by a write to the TXREG. 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 specification).
The TRMT bit of the TXSTA register indicates when the
transmit operation is active or Idle, just as it does during
normal transmission. See Figure 10-9 for the timing of
the Break character sequence.
10.3.4.1
Break and Sync Transmit Sequence
The following sequence will start a message frame
header made up of a Break, followed by an auto-baud
Sync byte. This sequence is typical of a LIN bus
master.
1.
2.
3.
4.
5.
Cleared due to User Read of RCREG
Sleep Ends
10.3.5
RECEIVING A BREAK CHARACTER
The Enhanced EUSART module can receive a Break
character in two ways.
The first method to detect a Break character uses the
FERR bit of the RCSTA register and the Received data
as indicated by RCREG. The Baud Rate Generator is
assumed to have been initialized to the expected baud
rate.
A Break character has been received when;
• RCIF bit is set
• FERR bit is set
• RCREG = 00h
The second method uses the Auto-Wake-up feature
described in Section 10.3.3 “Auto-Wake-up on
Break”. 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 Detect feature.
For both methods, the user can set the ABDEN bit of
the BAUDCTL register before placing the EUSART in
Sleep mode.
Configure the EUSART for the desired mode.
Set the TXEN and SENDB bits to enable the
Break sequence.
Load the TXREG with a dummy character to
initiate transmission (the value is ignored).
Write ‘55h’ to TXREG to load the Sync character
into the transmit FIFO buffer.
After the Break has been sent, the SENDB bit is
reset by hardware and the Sync character is
then transmitted.
When the TXREG becomes empty, as indicated by the
TXIF, the next data byte can be written to TXREG.
© 2009 Microchip Technology Inc.
DS41203E-page 101
PIC16F688
FIGURE 10-9:
Write to TXREG
SEND BREAK CHARACTER SEQUENCE
Dummy Write
BRG Output
(Shift Clock)
TX (pin)
Start bit
bit 0
bit 1
bit 11
Stop bit
Break
TXIF bit
(Transmit
interrupt Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
SENDB Sampled Here
Auto Cleared
SENDB
(send Break
control bit)
DS41203E-page 102
© 2009 Microchip Technology Inc.
PIC16F688
10.4
EUSART Synchronous Mode
Synchronous serial communications are typically used
in systems with a single master and one or more
slaves. The master device contains the necessary
circuitry for baud rate generation and supplies the clock
for all devices in the system. Slave devices can take
advantage of the master clock by eliminating the
internal clock generation circuitry.
There are two signal lines in Synchronous mode: a
bidirectional data line and a clock line. Slaves use the
external clock supplied by the master to shift the serial
data into and out of their respective receive and transmit shift registers. Since the data line is bidirectional,
synchronous operation is half-duplex only. Half-duplex
refers to the fact that master and slave devices can
receive and transmit data but not both simultaneously.
The EUSART can operate as either a master or slave
device.
Start and Stop bits are not used in synchronous
transmissions.
10.4.1
SYNCHRONOUS MASTER MODE
The following bits are used to configure the EUSART
for Synchronous Master operation:
•
•
•
•
•
SYNC = 1
CSRC = 1
SREN = 0 (for transmit); SREN = 1 (for receive)
CREN = 0 (for transmit); CREN = 1 (for receive)
SPEN = 1
Setting the SYNC bit of the TXSTA register configures
the device for synchronous operation. Setting the CSRC
bit of the TXSTA register configures the device as a
master. Clearing the SREN and CREN bits of the RCSTA
register ensures that the device is in the Transmit mode,
otherwise the device will be configured to receive. Setting
the SPEN bit of the RCSTA register enables the
EUSART. If the RX/DT or TX/CK pins are shared with an
analog peripheral the analog I/O functions must be
disabled by clearing the corresponding ANSEL bits.
10.4.1.1
10.4.1.3
Synchronous Master Transmission
Data is transferred out of the device on the RX/DT pin.
The RX/DT and TX/CK pin output drivers are automatically enabled when the EUSART is configured for
synchronous master transmit operation.
A transmission is initiated by writing a character to the
TXREG register. If the TSR still contains all or part of a
previous character, the new character data is held in
the TXREG until the last bit of the previous character
has been transmitted. If this is the first character, or the
previous character has been completely flushed from
the TSR, the data in the TXREG is immediately transferred to the TSR. The transmission of the character
commences immediately following the transfer of the
data to the TSR from the TXREG.
Each data bit changes on the leading edge of the
master clock and remains valid until the subsequent
leading clock edge.
Note:
The TSR register is not mapped in data
memory, so it is not available to the user.
10.4.1.4
Synchronous Master Transmission
Set-up:
1.
2.
3.
4.
5.
6.
Master Clock
Synchronous data transfers use a separate clock line,
which is synchronous with the data. A device
configured as a master transmits the clock on the TX/
CK line. The TX/CK pin is automatically configured as
an output when the EUSART is configured for
synchronous transmit operation. Serial data bits
change on the leading edge to ensure they are valid at
the trailing edge of each clock. One clock cycle is
generated for each data bit. Only as many clock cycles
are generated as there are data bits.
10.4.1.2
the clock Idle state as high. When the SCKP bit is set,
the data changes on the falling edge of each clock.
Clearing the SCKP bit sets the Idle state as low. When
the SCKP bit is cleared, the data changes on the rising
edge of each clock.
7.
8.
Initialize the SPBRGH, SPBRG register pair and
the BRGH and BRG16 bits to achieve the
desired baud rate (see Section 10.3 “EUSART
Baud Rate Generator (BRG)”).
Enable the synchronous master serial port by
setting bits SYNC, SPEN and CSRC.
Disable Receive mode by clearing bits SREN
and CREN.
Enable Transmit mode by setting the TXEN bit.
If 9-bit transmission is desired, set the TX9 bit.
If interrupts are desired, set the TXIE, GIE and
PEIE interrupt enable bits.
If 9-bit transmission is selected, the ninth bit
should be loaded in the TX9D bit.
Start transmission by loading data to the
TXREG register.
Clock Polarity
A clock polarity option is provided for Microwire
compatibility. Clock polarity is selected with the SCKP
bit of the BAUDCTL register. Setting the SCKP bit sets
© 2009 Microchip Technology Inc.
DS41203E-page 103
PIC16F688
FIGURE 10-10:
SYNCHRONOUS TRANSMISSION
RX/DT
pin
bit 0
bit 1
Word 1
bit 2
bit 7
bit 0
bit 1
Word 2
bit 7
TX/CK pin
(SCKP = 0)
TX/CK pin
(SCKP = 1)
Write to
TXREG Reg
Write Word 1
Write Word 2
TXIF bit
(Interrupt Flag)
TRMT bit
TXEN bit
‘1’
Note:
‘1’
Sync Master mode, SPBRG = 0, continuous transmission of two 8-bit words.
FIGURE 10-11:
SYNCHRONOUS TRANSMISSION (THROUGH TXEN)
RX/DT pin
bit 0
bit 2
bit 1
bit 6
bit 7
TX/CK pin
Write to
TXREG reg
TXIF bit
TRMT bit
TXEN bit
TABLE 10-7:
REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER TRANSMISSION
Name
Bit 7
Bit 6
BAUDCTL
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
0000 0000
0000 0000
RX9D
0000 000x
0000 000x
RCREG
RCSTA
EUSART Receive Data Register
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
0000 0000
0000 0000
0000 0010
0000 0010
TRISC
TXREG
TXSTA
Legend:
EUSART Transmit Data Register
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for Synchronous Master Transmission.
DS41203E-page 104
© 2009 Microchip Technology Inc.
PIC16F688
10.4.1.5
Synchronous Master Reception
Data is received at the RX/DT pin. The RX/DT and TX/
CK pin output drivers are automatically disabled when
the EUSART is configured for synchronous master
receive operation.
In Synchronous mode, reception is enabled by setting
either the Single Receive Enable bit (SREN of the
RCSTA register) or the Continuous Receive Enable bit
(CREN of the RCSTA register).
When SREN is set and CREN is clear, only as many
clock cycles are generated as there are data bits in a
single character. The SREN bit is automatically cleared
at the completion of one character. When CREN is set,
clocks are continuously generated until CREN is
cleared. If CREN is cleared in the middle of a character
the CK clock stops immediately and the partial character is discarded. If SREN and CREN are both set, then
SREN is cleared at the completion of the first character
and CREN takes precedence.
To initiate reception, set either SREN or CREN. Data is
sampled at the RX/DT pin on the trailing edge of the
TX/CK clock pin and is shifted into the Receive Shift
Register (RSR). When a complete character is
received into the RSR, the RCIF bit is set and the character is automatically transferred to the two character
receive FIFO. The Least Significant eight bits of the top
character in the receive FIFO are available in RCREG.
The RCIF bit remains set as long as there are un-read
characters in the receive FIFO.
10.4.1.6
10.4.1.8
Synchronous Master Reception Setup:
1.
Initialize the SPBRGH, SPBRG register pair for
the appropriate baud rate. Set or clear the
BRGH and BRG16 bits, 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 using interrupts, set the GIE and PEIE bits of
the INTCON register and set RCIE.
5. If 9-bit reception is desired, set bit RX9.
6. Start reception by setting the SREN bit or for
continuous reception, set the CREN bit.
7. Interrupt flag bit RCIF will be set when reception
of a character is complete. An interrupt will be
generated if the enable bit RCIE was set.
8. Read the RCSTA register to get the ninth 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 an overrun error occurs, clear the error by
either clearing the CREN bit of the RCSTA
register or by clearing the SPEN bit which resets
the EUSART.
Receive Overrun Error
The receive FIFO buffer can hold two characters. An
overrun error will be generated if a third character, in its
entirety, is received before RCREG is read to access
the FIFO. When this happens the OERR bit of the
RCSTA register is set. Previous data in the FIFO will
not be overwritten. The two characters in the FIFO
buffer can be read, however, no additional characters
will be received until the error is cleared. The OERR bit
can only be cleared by clearing the overrun condition.
If the overrun error occurred when the SREN bit is set
and CREN is clear then the error is cleared by reading
RCREG. If the overrun occurred when the CREN bit is
set then the error condition is cleared by either clearing
the CREN bit of the RCSTA register or by clearing the
SPEN bit which resets the EUSART.
10.4.1.7
Receiving 9-bit Characters
The EUSART supports 9-bit character reception. When
the RX9 bit of the RCSTA register is set the EUSART
will shift 9-bits into the RSR for each character
received. The RX9D bit of the RCSTA register is the
ninth, and Most Significant, data bit of the top unread
character in the receive FIFO. When reading 9-bit data
from the receive FIFO buffer, the RX9D data bit must
be read before reading the 8 Least Significant bits from
the RCREG.
© 2009 Microchip Technology Inc.
DS41203E-page 105
PIC16F688
FIGURE 10-12:
SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
RX/DT
pin
bit 0
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
TX/CK pin
(SCKP = 0)
TX/CK pin
(SCKP = 1)
Write to
bit SREN
SREN bit
CREN bit ‘0’
‘0’
RCIF bit
(Interrupt)
Read
RXREG
Note:
Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0.
TABLE 10-8:
REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER RECEPTION
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
BAUDCTL
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
RCREG
EUSART Receive Data Register
FERR
OERR
0000 0000
RX9D
0000 000x
0000 000x
RCSTA
SPEN
RX9
SREN
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
0000 0000
0000 0000
SYNC
SENDB
BRGH
TRMT
TX9D
0000 0010
0000 0010
TRISC
TXREG
TXSTA
Legend:
CREN
ADDEN
0000 0000
EUSART Transmit Data Register
CSRC
TX9
TXEN
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for Synchronous Master Reception.
DS41203E-page 106
© 2009 Microchip Technology Inc.
PIC16F688
10.4.2
SYNCHRONOUS SLAVE MODE
The following bits are used to configure the EUSART
for Synchronous slave operation:
•
•
•
•
•
SYNC = 1
CSRC = 0
SREN = 0 (for transmit); SREN = 1 (for receive)
CREN = 0 (for transmit); CREN = 1 (for receive)
SPEN = 1
1.
2.
3.
4.
Setting the SYNC bit of the TXSTA register configures
the device for synchronous operation. Clearing the
CSRC bit of the TXSTA register configures the device as
a slave. Clearing the SREN and CREN bits of the RCSTA
register ensures that the device is in the Transmit mode,
otherwise the device will be configured to receive. Setting
the SPEN bit of the RCSTA register enables the
EUSART. If the RX/DT or TX/CK pins are shared with an
analog peripheral the analog I/O functions must be
disabled by clearing the corresponding ANSEL bits.
10.4.2.1
If two words are written to the TXREG and then the
SLEEP instruction is executed, the following will occur:
5.
10.4.2.2
1.
2.
3.
EUSART Synchronous Slave
Transmit
The operation of the Synchronous Master and Slave
modes
are
identical
(see
Section 10.4.1.3
“Synchronous Master Transmission”), except in the
case of the Sleep mode.
4.
5.
6.
7.
TABLE 10-9:
Synchronous Slave Transmission
Set-up:
Set the SYNC and SPEN bits and clear the
CSRC bit.
Clear the CREN and SREN bits.
If using interrupts, ensure that the GIE and PEIE
bits of the INTCON register are set and set the
TXIE bit.
If 9-bit transmission is desired, set the TX9 bit.
Enable transmission by setting the TXEN bit.
If 9-bit transmission is selected, insert the Most
Significant bit into the TX9D bit.
Start transmission by writing the Least
Significant 8 bits to the TXREG register.
REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION
Name
Bit 7
Bit 6
BAUDCTL
ABDOVF
GIE
INTCON
The first character will immediately transfer to
the TSR register and transmit.
The second word will remain in TXREG register.
The TXIF bit will not be set.
After the first character has been shifted out of
TSR, the TXREG register will transfer the second
character to the TSR and the TXIF bit will now be
set.
If the PEIE and TXIE bits are set, the interrupt
will wake the device from Sleep and execute the
next instruction. If the GIE bit is also set, the
program will call the Interrupt Service Routine.
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
0000 0000
Bit 5
Bit 4
Bit 3
RCIDL
—
SCKP
PEIE
T0IE
INTE
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
0000 0000
0000 0000
RCREG
EUSART Receive Data Register
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
0000 000x
0000 000x
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
--11 1111
--11 1111
0000 0000
0000 0000
SYNC
SENDB
BRGH
TRMT
TX9D
0000 0010
0000 0010
TRISC
TXREG
TXSTA
Legend:
EUSART Transmit Data Register
CSRC
TX9
TXEN
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for Synchronous Slave Transmission.
© 2009 Microchip Technology Inc.
DS41203E-page 107
PIC16F688
10.4.2.3
EUSART Synchronous Slave
Reception
10.4.2.4
The operation of the Synchronous Master and Slave
modes is identical (Section 10.4.1.5 “Synchronous
Master Reception”), with the following exceptions:
• Sleep
• CREN bit is always set, therefore the receiver is
never Idle
• SREN bit, which is a “don’t care” in Slave mode
A character may be received while in Sleep mode by
setting the CREN bit prior to entering Sleep. 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 device from Sleep
and execute the next instruction. If the GIE bit is also
set, the program will branch to the interrupt vector.
1.
2.
3.
4.
5.
6.
7.
8.
Synchronous Slave Reception Setup:
Set the SYNC and SPEN bits and clear the
CSRC bit.
If using interrupts, ensure that the GIE and PEIE
bits of the INTCON register are set and set the
RCIE bit.
If 9-bit reception is desired, set the RX9 bit.
Set the CREN bit to enable reception.
The RCIF bit will be set when reception is
complete. An interrupt will be generated if the
RCIE bit was set.
If 9-bit mode is enabled, retrieve the Most
Significant bit from the RX9D bit of the RCSTA
register.
Retrieve the 8 Least Significant bits from the
receive FIFO by reading the RCREG register.
If an overrun error occurs, clear the error by
either clearing the CREN bit of the RCSTA
register or by clearing the SPEN bit which resets
the EUSART.
TABLE 10-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION
Name
Bit 7
Bit 6
BAUDCTL
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
all other
Resets
Value on
POR, BOR
ABDOVF
RCIDL
—
SCKP
BRG16
—
WUE
ABDEN
01-0 0-00
01-0 0-00
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
RCREG
EUSART Receive Data Register
0000 0000
0000 0000
RCSTA
SPEN
RX9
SREN
CREN
ADDEN
FERR
OERR
RX9D
0000 000x
0000 000x
SPBRG
BRG7
BRG6
BRG5
BRG4
BRG3
BRG2
BRG1
BRG0
0000 0000
0000 0000
SPBRGH
BRG15
BRG14
BRG13
BRG12
BRG11
BRG10
BRG9
BRG8
0000 0000
0000 0000
—
—
TRISC5
TRISC4
TRISC3
TRISC2
TRISC1
TRISC0
TRISC
TXREG
TXSTA
Legend:
EUSART Transmit Data Register
CSRC
TX9
TXEN
SYNC
SENDB
BRGH
TRMT
TX9D
--11 1111
--11 1111
0000 0000
0000 0000
0000 0010
0000 0010
x = unknown, – = unimplemented read as ‘0’. Shaded cells are not used for Synchronous Slave Reception.
DS41203E-page 108
© 2009 Microchip Technology Inc.
PIC16F688
11.0
SPECIAL FEATURES OF THE
CPU
The PIC16F688 has a host of features intended to
maximize system reliability, minimize cost through
elimination of external components, provide
power-saving features and offer code protection.
These features are:
• Reset
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
• Interrupts
• Watchdog Timer (WDT)
• Oscillator Selection
• Sleep
• Code Protection
• ID Locations
• In-Circuit Serial Programming™
© 2009 Microchip Technology Inc.
The PIC16F688 has two timers that offer necessary
delays on power-up. One is the Oscillator Start-up
Timer (OST), intended to keep the chip in Reset until
the crystal oscillator is stable. The other is the
Power-up Timer (PWRT), which provides a fixed
delay of 64 ms (nominal) on power-up only, designed
to keep the part in Reset while the power supply
stabilizes. There is also circuitry to reset the device if
a brown-out occurs, which can use the Power-up
Timer to provide at least a 64 ms Reset. With these
three functions-on-chip, most applications need no
external Reset circuitry.
The Sleep mode is designed to offer a very low-current
Power-Down mode. The user can wake-up from Sleep
through:
• External Reset
• Watchdog Timer Wake-up
• An interrupt
Several oscillator options are also made available to
allow the part to fit the application. The INTOSC option
saves system cost while the LP crystal option saves
power. A set of Configuration bits are used to select
various options (see Register 11-1).
DS41203E-page 109
PIC16F688
11.1
Configuration Bits
The Configuration bits can be programmed (read as
‘0’), or left unprogrammed (read as ‘1’) to select various
device configurations as shown in Register 11-1.
These bits are mapped in program memory location
2007h.
Note:
Address 2007h is beyond the user program
memory space. It belongs to the special
configuration
memory
space
(2000h-3FFFh), which can be accessed
only
during
programming.
See
“PIC12F6XX/16F6XX Memory Programming Specification” (DS41204) for more
information.
DS41203E-page 110
© 2009 Microchip Technology Inc.
PIC16F688
REGISTER 11-1:
Reserved
CONFIG: CONFIGURATION WORD REGISTER
Reserved
Reserved
Reserved
FCMEN
BOREN1(1)
IESO
BOREN0(1)
bit 15
bit 8
CPD(2)
CP(3)
MCLRE(4)
PWRTE
WDTE
FOSC2
FOSC1
FOSC0
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
P = Programmable’
U = Unimplemented bit, read
as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 15-12
Reserved: Reserved bits. Do Not Use.
bit 11
FCMEN: Fail-Safe Clock Monitor Enabled bit
1 = Fail-Safe Clock Monitor is enabled
0 = Fail-Safe Clock Monitor is disabled
bit 10
IESO: Internal External Switchover bit
1 = Internal External Switchover mode is enabled
0 = Internal External Switchover mode is disabled
bit 9-8
BOREN<1:0>: Brown-out Reset Selection bits(1)
11 = BOR enabled
10 = BOR enabled during operation and disabled in Sleep
01 = BOR controlled by SBOREN bit of the PCON register
00 = BOR disabled
bit 7
CPD: Data Code Protection bit(2)
1 = Data memory code protection is disabled
0 = Data memory code protection is enabled
bit 6
CP: Code Protection bit(2)
1 = Program memory code protection is disabled
0 = Program memory code protection is enabled
bit 5
MCLRE: MCLR Pin Function Select bit(3)
1 = MCLR pin function is MCLR
0 = MCLR pin function is digital input, MCLR internally tied to VDD
bit 4
PWRTE: Power-up Timer Enable bit
1 = PWRT disabled
0 = PWRT enabled
bit 3
WDTE: Watchdog Timer Enable bit
1 = WDT enabled
0 = WDT disabled
bit 2-0
FOSC<2:0>: Oscillator Selection bits
111 = EXTRC oscillator: External RC on RA5/OSC1/CLKIN, CLKOUT function on RA4/OSC2/CLKOUT pin
110 = EXTRCIO oscillator: External RC on RA5/OSC1/CLKIN, I/O function on RA4/OSC2/CLKOUT pin
101 = INTOSC oscillator: CLKOUT function on RA4/OSC2/CLKOUT pin, I/O function on
RA5/OSC1/CLKIN
100 = INTOSCIO oscillator: I/O function on RA4/OSC2/CLKOUT pin, I/O function on
RA5/OSC1/CLKIN
011 = EC: I/O function on RA4/OSC2/CLKOUT pin, CLKIN on RA5/OSC1/CLKIN
010 = HS oscillator: High-speed crystal/resonator on RA4/OSC2/CLKOUT and RA5/OSC1/CLKIN
001 = XT oscillator: Crystal/resonator on RA4/OSC2/CLKOUT and RA5/OSC1/CLKIN
000 = LP oscillator: Low-power crystal on RA4/OSC2/CLKOUT and RA5/OSC1/CLKIN
Note 1:
2:
3:
4:
Enabling Brown-out Reset does not automatically enable Power-up Timer.
The entire data EEPROM will be erased when the code protection is turned off.
The entire program memory will be erased when the code protection is turned off.
When MCLR is asserted in INTOSC or RC mode, the internal clock oscillator is disabled.
© 2009 Microchip Technology Inc.
DS41203E-page 111
PIC16F688
11.2
Reset
The PIC16F688 differentiates between various kinds of
Reset:
a)
b)
c)
d)
e)
f)
Power-on Reset (POR)
WDT Reset during normal operation
WDT Reset during Sleep
MCLR Reset during normal operation
MCLR Reset during Sleep
Brown-out Reset (BOR)
Some registers are not affected in any Reset condition;
their status is unknown on POR and unchanged in any
other Reset. Most other registers are reset to a “Reset
state” on:
•
•
•
•
•
They are not affected by a WDT wake-up since this is
viewed as the resumption of normal operation. TO and
PD bits are set or cleared differently in different Reset
situations, as indicated in Table 11-2. These bits are
used in software to determine the nature of the Reset.
See Table 11-4 for a full description of Reset states of
all registers.
A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 11-1.
The MCLR Reset path has a noise filter to detect and
ignore small pulses. See Section 14.0 “Electrical
Specifications” for pulse width specifications.
Power-on Reset
MCLR Reset
MCLR Reset during Sleep
WDT Reset
Brown-out Reset (BOR)
FIGURE 11-1:
SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
External
Reset
MCLR/VPP pin
Sleep
WDT
Module
WDT
Time-out
Reset
VDD Rise
Detect
Power-on Reset
VDD
Brown-out(1)
Reset
BOREN
SBOREN
S
OST/PWRT
OST
Chip_Reset
10-bit Ripple Counter
R
Q
OSC1/
CLKI pin
PWRT
LFINTOSC
11-bit Ripple Counter
Enable PWRT
Enable OST
Note
1:
Refer to the Configuration Word register (Register 11-1).
DS41203E-page 112
© 2009 Microchip Technology Inc.
PIC16F688
11.2.1
POWER-ON RESET
FIGURE 11-2:
The on-chip POR circuit holds the chip in Reset until
VDD has reached a high enough level for proper
operation. To take advantage of the POR, simply
connect the MCLR pin through a resistor to VDD. This
will eliminate external RC components usually needed
to create Power-on Reset. A maximum rise time for
VDD is required. See Section 14.0 “Electrical Specifications” for details. If the BOR is enabled, the maximum rise time specification does not apply. The BOR
circuitry will keep the device in Reset until VDD reaches
VBOD (see Section 11.2.4 “Brown-Out Reset
(BOR)”).
Note:
The POR circuit does not produce an
internal Reset when VDD declines. To
re-enable the POR, VDD must reach Vss
for a minimum of 100 μs.
When the device starts normal operation (exits the
Reset condition), device operating parameters (i.e.,
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.
For additional information, refer to Application Note
AN607, “Power-up Trouble Shooting” (DS00607).
11.2.2
MCLR
PIC16F688 has a noise filter in the MCLR Reset path.
The filter will detect and ignore small pulses.
It should be noted that a WDT Reset does not drive
MCLR pin low.
The behavior of the ESD protection on the MCLR pin
has been altered from early devices of this family.
Voltages applied to the pin that exceed its specification
can result in both MCLR Resets and excessive current
beyond the device specification during the ESD event.
For this reason, Microchip recommends that the MCLR
pin no longer be tied directly to VDD. The use of an RC
network, as shown in Figure 11-2, is suggested.
An internal MCLR option is enabled by clearing the
MCLRE bit in the Configuration Word register. When
MCLRE = 0, the Reset signal to the chip is generated
internally. When the MCLRE = 1, the RA3/MCLR pin
becomes an external Reset input. In this mode, the
RA3/MCLR pin has a weak pull-up to VDD.
© 2009 Microchip Technology Inc.
RECOMMENDED MCLR
CIRCUIT
VDD
PIC16F688
R1
1 kΩ (or greater)
MCLR
C1
0.1 μF
(optional, not critical)
11.2.3
POWER-UP TIMER (PWRT)
The Power-up Timer provides a fixed 64 ms (nominal)
time-out on power-up only, from POR or Brown-out
Reset. The Power-up Timer operates from the 31 kHz
LFINTOSC oscillator. For more information, see
Section 3.5 “Internal Clock Modes”. The chip is kept
in Reset as long as PWRT is active. The PWRT delay
allows the VDD to rise to an acceptable level. A Configuration bit, PWRTE, can disable (if set) or enable (if
cleared or programmed) the Power-up Timer. The
Power-up Timer should be enabled when Brown-out
Reset is enabled, although it is not required.
The Power-up Timer delay will vary from chip-to-chip
and vary due to:
• VDD variation
• Temperature variation
• Process variation
See DC parameters for details
“Electrical Specifications”).
Note:
(Section 14.0
Voltage spikes below VSS at the MCLR
pin, inducing currents greater than 80 mA,
may cause latch-up. Thus, a series resistor of 50-100 Ω should be used when
applying a “low” level to the MCLR pin,
rather than pulling this pin directly to VSS.
DS41203E-page 113
PIC16F688
11.2.4
BROWN-OUT RESET (BOR)
This will occur regardless of VDD slew rate. A Reset is
not insured to occur if VDD falls below VBOD for less
than parameter (TBOD).
The BOREN0 and BOREN1 bits in the Configuration
Word register selects one of four BOR modes. Two
modes have been added to allow software or hardware
control of the BOR enable. When BOREN<1:0> = 01,
the SBOREN bit of the PCON register enables/disables
the BOR, allowing it to be controlled in software. By
selecting BOREN<1:0>, the BOR is automatically
disabled in Sleep to conserve power and enabled on
wake-up. In this mode, the SBOREN bit is disabled.
See Register 11-1 for the Configuration Word
definition.
On any Reset (Power-on, Brown-out Reset, Watchdog
Timer, etc.), the chip will remain in Reset until VDD rises
above VBOD (see Figure 11-3). The Power-up Timer
will now be invoked, if enabled and will keep the chip in
Reset an additional 64 ms.
Note:
If VDD drops below VBOD while the Power-up Timer is
running, the chip will go back into a Brown-out Reset
and the Power-up Timer will be re-initialized. Once VDD
rises above VBOD, the Power-up Timer will execute a
64 ms Reset.
If VDD falls below VBOD for greater than parameter
(TBOD) (see Section 14.0 “Electrical Specifications”), the Brown-out situation will reset the device.
FIGURE 11-3:
BROWN-OUT SITUATIONS
VDD
Internal
Reset
VBOD
64 ms(1)
VDD
Internal
Reset
VBOD
< 64 ms
64 ms(1)
VDD
Internal
Reset
Note 1:
The Power-up Timer is enabled by the
PWRTE bit in the Configuration Word
register.
VBOD
64 ms(1)
64 ms delay only if PWRTE bit is programmed to ‘0’.
DS41203E-page 114
© 2009 Microchip Technology Inc.
PIC16F688
11.2.5
TIME-OUT SEQUENCE
11.2.6
On power-up, the time-out sequence is as follows: first,
PWRT time-out is invoked after POR has expired, then
OST is activated after the PWRT time-out has expired.
The total time-out will vary based on oscillator configuration and PWRTE bit status. For example, in EC mode
with PWRTE bit erased (PWRT disabled), there will be
no time-out at all. Figure 11.2.1, Figure 11-5 and
Figure 11-6 depict time-out sequences. The device can
execute code from the INTOSC while OST is active by
enabling Two-Speed Start-up or Fail-Safe Monitor (see
Section 3.7.2 “Two-Speed Start-up Sequence” and
Section 3.8 “Fail-Safe Clock Monitor”).
The Power Control (PCON) register (address 8Eh) has
two Status bits to indicate what type of Reset that last
occurred.
Bit 0 is BOR (Brown-out). BOR is unknown on
Power-on Reset. It must then be set by the user and
checked on subsequent Resets to see if BOR = 0,
indicating that a Brown-out has occurred. The BOR
Status bit is a “don’t care” and is not necessarily
predictable if the brown-out circuit is disabled
(BOREN<1:0> = 00 in the Configuration Word
register).
Since the time-outs occur from the POR pulse, if MCLR
is kept low long enough, the time-outs will expire. Then,
bringing MCLR high will begin execution immediately
(see Figure 11-5). This is useful for testing purposes or
to synchronize more than one PIC16F688 device
operating in parallel.
Bit 1 is POR (Power-on Reset). It is a ‘0’ on Power-on
Reset and unaffected otherwise. The user must write a
‘1’ to this bit following a Power-on Reset. On a
subsequent Reset, if POR is ‘0’, it will indicate that a
Power-on Reset has occurred (i.e., VDD may have
gone too low).
Table 11-5 shows the Reset conditions for some
special registers, while Table 11-4 shows the Reset
conditions for all the registers.
TABLE 11-1:
POWER CONTROL (PCON)
REGISTER
For more information, see Section 4.2.4 “Ultra
Low-Power
Wake-up”
and
Section 11.2.4
“Brown-Out Reset (BOR)”.
TIME-OUT IN VARIOUS SITUATIONS
Power-up
Brown-out Reset
Wake-up
from Sleep
Oscillator Configuration
XT, HS, LP
PWRTE = 0
PWRTE = 1
PWRTE = 0
PWRTE = 1
TPWRT + 1024
• TOSC
1024 • TOSC
TPWRT + 1024
• TOSC
1024 • TOSC
1024 • TOSC
TPWRT
—
TPWRT
—
—
RC, EC, INTOSC
TABLE 11-2:
PCON BITS AND THEIR SIGNIFICANCE
POR
BOR
TO
PD
0
u
1
1
Power-on Reset
1
0
1
1
Brown-out Reset
u
u
0
u
WDT Reset
u
u
0
0
WDT Wake-up
u
u
u
u
MCLR Reset during normal operation
u
u
1
0
MCLR Reset during Sleep
Condition
Legend: u = unchanged, x = unknown
TABLE 11-3:
SUMMARY OF REGISTERS ASSOCIATED WITH BROWN-OUT RESET
Name
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets(1)
CONFIG(2)
BOREN1
BOREN0
CPD
CP
MCLRE
PWRTE
WDTE
FOSC2
FOSC1
FOSC0
—
—
—
—
POR
BOR
--01 --qq
--0u --uu
PD
Z
DC
C
0001 1xxx
000q quuu
PCON
STATUS
Legend:
Note 1:
2:
—
—
IRP
RP1
ULPWUE SBOREN
RP0
TO
u = unchanged, x = unknown, – = unimplemented bit, reads as ‘0’, q = value depends on condition. Shaded cells are not used by BOR.
Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.
See Configuration Word register (Register 11-1) for operation of all register bits.
© 2009 Microchip Technology Inc.
DS41203E-page 115
PIC16F688
FIGURE 11-4:
TIME-OUT SEQUENCE ON POWER-UP (DELAYED MCLR)
VDD
MCLR
Internal POR
TPWRT
PWRT Time-out
TOST
OST Time-out
Internal Reset
FIGURE 11-5:
TIME-OUT SEQUENCE ON POWER-UP (DELAYED MCLR)
VDD
MCLR
Internal POR
TPWRT
PWRT Time-out
TOST
OST Time-out
Internal Reset
FIGURE 11-6:
TIME-OUT SEQUENCE ON POWER-UP (MCLR WITH VDD)
VDD
MCLR
Internal POR
TPWRT
PWRT Time-out
TOST
OST Time-out
Internal Reset
DS41203E-page 116
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 11-4:
INITIALIZATION CONDITION FOR REGISTERS
Address
Power-on
Reset
MCLR Reset
WDT Reset
Brown-out Reset(1)
Wake-up from Sleep
through Interrupt
Wake-up from Sleep
through WDT Time-out
—
xxxx xxxx
uuuu uuuu
uuuu uuuu
INDF
00h/80h/100h/180h
xxxx xxxx
uuuu uuuu
uuuu uuuu
TMR0
01h/101h
xxxx xxxx
uuuu uuuu
uuuu uuuu
PCL
02h/82h/102h/182h
0000 0000
0000 0000
PC + 1(3)
STATUS
03h/83h/103h/183h
0001 1xxx
000q quuu(4)
uuuq quuu(4)
FSR
04h/84h/104h/184h
xxxx xxxx
uuuu uuuu
uuuu uuuu
PORTA
05h/105h
--x0 x000
--00 0000
--uu uuuu
PORTC
07h/107h
--xx 0000
--00 0000
--uu uuuu
PCLATH
0Ah/8Ah/10Ah/18Ah
---0 0000
---0 0000
---u uuuu
INTCON
0Bh/8Bh/10Bh/18Bh
0000 000x
0000 000x
uuuu uuuu(2)
PIR1
0Ch
0000 0000
0000 0000
uuuu uuuu(2)
TMR1L
0Eh
xxxx xxxx
uuuu uuuu
uuuu uuuu
TMR1H
0Fh
xxxx xxxx
uuuu uuuu
uuuu uuuu
T1CON
10h
0000 0000
uuuu uuuu
-uuu uuuu
BAUDCTL
11h
01-0 0-00
01-0 0-00
uu-u u-uu
SPBRGH
12h
-000 0000
-000 0000
-uuu uuuu
SPBRG
13h
0000 0000
0000 0000
uuuu uuuu
RCREG
14h
0000 0000
0000 0000
uuuu uuuu
TXREG
15h
0000 0000
0000 0000
uuuu uuuu
TXSTA
16h
0000 0010
0000 0010
uuuu uuuu
RCSTA
17h
000x 000x
000x 000x
uuuu uuuu
WDTCON
18h
---0 1000
---0 1000
---u uuuu
CMCON0
19h
0000 0000
0000 0000
uuuu uuuu
CMCON1
1Ah
---- --10
---- --10
---- --uu
ADRESH
1Eh
xxxx xxxx
uuuu uuuu
uuuu uuuu
ADCON0
1Fh
00-0 0000
00-0 0000
uu-u uuuu
OPTION_REG
81h/181h
1111 1111
1111 1111
uuuu uuuu
TRISA
85h/185h
--11 1111
--11 1111
--uu uuuu
TRISC
87h/187h
--11 1111
--11 1111
--uu uuuu
8Ch
0000 0000
0000 0000
uuuu uuuu
Register
W
PIE1
PCON
Legend:
Note 1:
2:
3:
4:
5:
8Eh
--01 --0x
--0u
--uu(1,5)
--uu --uu
u = unchanged, x = unknown, – = unimplemented bit, reads as ‘0’, q = value depends on condition.
If VDD goes too low, Power-on Reset will be activated and registers will be affected differently.
One or more bits in INTCON and/or PIR1 will be affected (to cause wake-up).
When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt
vector (0004h).
See Table 11-5 for Reset value for specific condition.
If Reset was due to brown-out, then bit 0 = 0. All other Resets will cause bit 0 = u.
© 2009 Microchip Technology Inc.
DS41203E-page 117
PIC16F688
TABLE 11-4:
INITIALIZATION CONDITION FOR REGISTERS (CONTINUED)
Address
Power-on
Reset
• MCLR Reset
• WDT Reset
• Brown-out Reset(1)
OSCCON
8Fh
-110 q000
-110 q000
-uuu uuuu
OSCTUNE
90h
---0 0000
---u uuuu
---u uuuu
ANSEL
91h
1111 1111
1111 1111
uuuu uuuu
WPUA
95h
--11 -111
--11 -111
uuuu uuuu
IOCA
96h
--00 0000
--00 0000
--uu uuuu
EEDATH
97h
--00 0000
--00 0000
--uu uuuu
EEADRH
98h
---- 0000
---- 0000
---- uuuu
VRCON
99h
0-0- 0000
0-0- 0000
u-u- uuuu
EEDAT
9Ah
0000 0000
0000 0000
uuuu uuuu
EEADR
9Bh
0000 0000
0000 0000
uuuu uuuu
EECON1
9Ch
x--- x000
u--- q000
u--- uuuu
EECON2
9Dh
---- ----
---- ----
---- ----
ADRESL
9Eh
xxxx xxxx
uuuu uuuu
uuuu uuuu
ADCON1
9Fh
-000 ----
-000 ----
-uuu ----
Register
Legend:
Note 1:
2:
3:
4:
5:
• Wake-up from Sleep
through interrupt
• Wake-up from Sleep
through WDT time-out
u = unchanged, x = unknown, – = unimplemented bit, reads as ‘0’, q = value depends on condition.
If VDD goes too low, Power-on Reset will be activated and registers will be affected differently.
One or more bits in INTCON and/or PIR1 will be affected (to cause wake-up).
When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt
vector (0004h).
See Table 11-5 for Reset value for specific condition.
If Reset was due to brown-out, then bit 0 = 0. All other Resets will cause bit 0 = u.
TABLE 11-5:
INITIALIZATION CONDITION FOR SPECIAL REGISTERS
Program
Counter
Status
Register
PCON
Register
Power-on Reset
000h
0001 1xxx
--01 --0x
MCLR Reset during normal operation
000h
000u uuuu
--0u --uu
MCLR Reset during Sleep
000h
0001 0uuu
--0u --uu
Condition
WDT Reset
WDT Wake-up
Brown-out Reset
Interrupt Wake-up from Sleep
000h
0000 uuuu
--0u --uu
PC + 1
uuu0 0uuu
--uu --uu
000h
0001 1uuu
--01 --10
uuu1 0uuu
--uu --uu
PC + 1
(1)
Legend: u = unchanged, x = unknown, – = unimplemented bit, reads as ‘0’.
Note 1: When the wake-up is due to an interrupt and Global Interrupt Enable bit, GIE, is set, the PC is loaded with
the interrupt vector (0004h) after execution of PC + 1.
DS41203E-page 118
© 2009 Microchip Technology Inc.
PIC16F688
11.3
Interrupts
The PIC16F688 has multiple sources of interrupt:
•
•
•
•
•
•
•
•
•
External Interrupt RA2/INT
TMR0 Overflow Interrupt
PORTA Change Interrupts
2 Comparator Interrupts
A/D Interrupt
Timer1 Overflow Interrupt
EEPROM Data Write Interrupt
Fail-Safe Clock Monitor Interrupt
EUSART Receive and Transmit interrupts
The Interrupt Control (INTCON) register and Peripheral
Interrupt Request 1 (PIR1) register record individual
interrupt requests in flag bits. The INTCON register
also has individual and global interrupt enable bits.
A Global Interrupt Enable bit, GIE bit of the INTCON
register, enables (if set) all unmasked interrupts, or disables (if cleared) all interrupts. Individual interrupts can
be disabled through their corresponding enable bits in
the INTCON register and PIE1 register. GIE is cleared
on Reset.
For external interrupt events, such as the INT pin or
PORTA change interrupt, the interrupt latency will be
three or four instruction cycles. The exact latency
depends upon when the interrupt event occurs (see
Figure 11-8). The latency is the same for one or
two-cycle instructions. Once in the Interrupt Service
Routine, the source(s) of the interrupt can be
determined by polling the interrupt flag bits. The
interrupt flag bit(s) must be cleared in software before
re-enabling interrupts to avoid multiple interrupt
requests.
Note 1: Individual interrupt flag bits are set,
regardless of the status of their
corresponding mask bit or the GIE bit.
2: When an instruction that clears the GIE
bit is executed, any interrupts that were
pending for execution in the next cycle
are ignored. The interrupts, which were
ignored, are still pending to be serviced
when the GIE bit is set again.
For additional information on Timer1, A/D or data
EEPROM modules, refer to the respective peripheral
section.
The Return from Interrupt instruction, RETFIE, exits
the interrupt routine, as well as sets the GIE bit, which
re-enables unmasked interrupts.
The following interrupt flags are contained in the
INTCON register:
• INT Pin Interrupt
• PORTA Change Interrupt
• TMR0 Overflow Interrupt
The peripheral interrupt flags are contained in the
special register, PIR1. The corresponding interrupt
enable bit is contained in special register, PIE1.
The following interrupt flags are contained in the PIR1
register:
•
•
•
•
•
•
EEPROM Data Write Interrupt
A/D Interrupt
EUSART Receive and Transmit Interrupts
2 Comparator Interrupts
Timer1 Overflow Interrupt
Fail-Safe Clock Monitor Interrupt
When an interrupt is serviced:
• The GIE is cleared to disable any further interrupt.
• The return address is pushed onto the stack.
• The PC is loaded with 0004h.
© 2009 Microchip Technology Inc.
DS41203E-page 119
PIC16F688
11.3.1
RA2/INT INTERRUPT
11.3.2
External interrupt on RA2/INT pin is edge-triggered;
either rising if the INTEDG bit of the OPTION register is
set, or falling if the INTEDG bit is clear. When a valid
edge appears on the RA2/INT pin, the INTF bit of the
INTCON register is set. This interrupt can be disabled
by clearing the INTE control bit of the INTCON register.
The INTF bit must be cleared in software in the Interrupt Service Routine before re-enabling this interrupt.
The RA2/INT interrupt can wake-up the processor from
Sleep if the INTE bit was set prior to going into Sleep.
The status of the GIE bit decides whether or not the
processor branches to the interrupt vector following
wake-up (0004h). See Section 11.6 “Power-Down
Mode (Sleep)” for details on Sleep and Figure 11-10
for timing of wake-up from Sleep through RA2/INT
interrupt.
Note:
TIMER0 INTERRUPT
An overflow (FFh → 00h) in the TMR0 register will set
the T0IF of the INTCON register bit. The interrupt can
be enabled/disabled by setting/clearing T0IE bit of the
INTCON register. See Section 5.0 “Timer0 Module”
for operation of the Timer0 module.
11.3.3
PORTA INTERRUPT
An input change on PORTA change sets the RAIF bit
of the INTCON register. The interrupt can be
enabled/disabled by setting/clearing the RAIE bit of the
INTCON register. Plus, individual pins can be
configured through the IOCA register.
Note:
If a change on the I/O pin should occur
when the read operation is being executed
(start of the Q2 cycle), then the RAIF
interrupt flag may not get set.
The ANSEL (91h) and CMCON0 (19h)
registers must be initialized to configure
an analog channel as a digital input. Pins
configured as analog inputs will read ‘0’.
FIGURE 11-7:
INTERRUPT LOGIC
IOC-RA0
IOCA0
IOC-RA1
IOCA1
IOC-RA2
IOCA2
IOC-RA3
IOCA3
IOC-RA4
IOCA4
IOC-RA5
IOCA5
TXIF
TXIE
TMR1IF
TMR1IE
C1IF
C1IE
C2IF
C2IE
T0IF
T0IE
INTF
INTE
RAIF
RAIE
Wake-up (If in Sleep mode)
Interrupt to CPU
PEIE
GIE
ADIF
ADIE
EEIF
EEIE
OSFIF
OSFIE
RCIF
RCIE
DS41203E-page 120
© 2009 Microchip Technology Inc.
PIC16F688
FIGURE 11-8:
INT PIN INTERRUPT TIMING
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
OSC1
CLKOUT (3)
(4)
INT pin
(1)
(1)
INTF Flag
(INTCON<1>)
Interrupt Latency (2)
(5)
GIE bit
(INTCON<7>)
Instruction Flow
PC
PC
Instruction
Fetched
Inst (PC)
Instruction
Executed
Inst (PC - 1)
Note 1:
2:
3:
4:
5:
0004h
PC + 1
PC + 1
—
Inst (PC + 1)
Dummy Cycle
Inst (PC)
0005h
Inst (0004h)
Inst (0005h)
Dummy Cycle
Inst (0004h)
INTF flag is sampled here (every Q1).
Asynchronous interrupt latency = 3-4 TCY. Synchronous latency = 3 TCY, where TCY = instruction cycle time.
Latency is the same whether Inst (PC) is a single cycle or a two-cycle instruction.
CLKOUT is available only in INTOSC and RC Oscillator modes.
For minimum width of INT pulse, refer to AC specifications in Section 14.0 “Electrical Specifications”.
INTF is enabled to be set any time during the Q4-Q1 cycles.
TABLE 11-6:
SUMMARY OF REGISTERS ASSOCIATED WITH INTERRUPTS
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
INTCON
GIE
PEIE
T0IE
INTE
RAIE
T0IF
INTF
RAIF
0000 000x
0000 000x
PIE1
EEIE
ADIE
RCIE
C2IE
C1IE
OSFIE
TXIE
TMR1IE
0000 0000
0000 0000
PIR1
EEIF
ADIF
RCIF
C2IF
C1IF
OSFIF
TXIF
TMR1IF
0000 0000
0000 0000
Name
Legend:
x = unknown, u = unchanged, — = unimplemented read as ‘0’, q = value depends upon condition.
Shaded cells are not used by the Interrupt module.
© 2009 Microchip Technology Inc.
DS41203E-page 121
PIC16F688
11.4
Context Saving During Interrupts
During an interrupt, only the return PC value is saved
on the stack. Typically, users may wish to save key
registers during an interrupt (e.g., W and Status
registers). This must be implemented in software.
Since the lower 16 bytes of all banks are common in the
PIC16F688 (see Figure 2-2), temporary holding
registers, W_TEMP and STATUS_TEMP, should be
placed in here. These 16 locations do not require
banking and therefore, make it easier to context save
and restore. The same code shown in Example 11-1
can be used to:
•
•
•
•
•
Store the W register
Store the Status register
Execute the ISR code
Restore the Status (and Bank Select Bit register)
Restore the W register
Note:
The PIC16F688 normally does not require
saving the PCLATH. However, if
computed GOTO’s are used in the ISR and
the main code, the PCLATH must be
saved and restored in the ISR.
EXAMPLE 11-1:
MOVWF
SWAPF
SAVING STATUS AND W REGISTERS IN RAM
W_TEMP
STATUS,W
MOVWF
STATUS_TEMP
:
:(ISR)
:
SWAPF
STATUS_TEMP,W
MOVWF
SWAPF
SWAPF
STATUS
W_TEMP,F
W_TEMP,W
DS41203E-page 122
;Copy W to TEMP
;Swap status to
;Swaps are used
;Save status to
register
be saved into W
because they do not affect the status bits
bank zero STATUS_TEMP register
;Insert user code here
;Swap STATUS_TEMP register into W
;(sets bank to original state)
;Move W into STATUS register
;Swap W_TEMP
;Swap W_TEMP into W
© 2009 Microchip Technology Inc.
PIC16F688
11.5
Watchdog Timer (WDT)
The WDT has the following features:
•
•
•
•
•
Operates from the LFINTOSC (31 kHz)
Contains a 16-bit prescaler
Shares an 8-bit prescaler with Timer0
Time-out period is from 1 ms to 268 seconds
Configuration bit and software controlled
WDT is cleared under certain conditions described in
Table 11-7.
11.5.1
WDT OSCILLATOR
The WDT derives its time base from the 31 kHz
LFINTOSC. The LTS bit does not reflect that the
LFINTOSC is enabled.
The value of WDTCON is ‘---0 1000’ on all Resets.
This gives a nominal time base of 16 ms, which is
compatible with the time base generated with previous
PIC16F688 microcontroller versions.
Note:
A new prescaler has been added to the path between
the INTRC and the multiplexers used to select the path
for the WDT. This prescaler is 16 bits and can be
programmed to divide the INTRC by 32 to 65536,
giving the WDT a nominal range of 1 ms to 268s.
11.5.2
WDT CONTROL
The WDTE bit is located in the Configuration Word
register. When set, the WDT runs continuously.
When the WDTE bit in the Configuration Word register
is set, the SWDTEN bit of the WDTCON register has no
effect. If WDTE is clear, then the SWDTEN bit can be
used to enable and disable the WDT. Setting the bit will
enable it and clearing the bit will disable it.
The PSA and PS<2:0> bits of the OPTION register
have the same function as in previous versions of the
PIC16F688 family of microcontrollers. See Section 5.0
“Timer0 Module” for more information.
When the Oscillator Start-up Timer (OST)
is invoked, the WDT is held in Reset,
because the WDT Ripple Counter is used
by the OST to perform the oscillator delay
count. When the OST count has expired,
the WDT will begin counting (if enabled).
FIGURE 11-9:
WATCHDOG TIMER BLOCK DIAGRAM
From TMR0 Clock Source
0
Prescaler(1)
16-bit WDT Prescaler
1
8
PSA
31 kHz
LFINTOSC Clock
PS<2:0>
WDTPS<3:0>
To TMR0
0
1
PSA
WDTE from Configuration Word Register
SWDTEN from WDTCON
WDT Time-out
Note 1: This is the shared Timer0/WDT prescaler. See Section 5.1.3 “Software Programmable Prescaler” for more information.
TABLE 11-7:
WDT STATUS
Conditions
WDTE = 0
CLRWDT Command
Oscillator Fail Detected
Exit Sleep + System Clock = T1OSC, EXTRC, INTRC, EXTCLK
Exit Sleep + System Clock = XT, HS, LP
© 2009 Microchip Technology Inc.
WDT
Cleared
Cleared until the end of OST
DS41203E-page 123
PIC16F688
REGISTER 11-2:
WDTCON: WATCHDOG TIMER CONTROL REGISTER
U-0
U-0
U-0
R/W-0
R/W-1
R/W-0
R/W-0
R/W-0
—
—
—
WDTPS3
WDTPS2
WDTPS1
WDTPS0
SWDTEN
bit 7
bit 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
bit 7-5
Unimplemented: Read as ‘0’
bit 4-1
WDTPS<3:0>: Watchdog Timer Period Select bits
Bit Value = Prescale Rate
0000 = 1:32
0001 = 1:64
0010 = 1:128
0011 = 1:256
0100 = 1:512 (Reset value)
0101 = 1:1024
0110 = 1:2048
0111 = 1:4096
1000 = 1:8192
1001 = 1:16384
1010 = 1:32768
1011 = 1:65536
1100 = Reserved
1101 = Reserved
1110 = Reserved
1111 = Reserved
bit 0
SWDTEN: Software Enable or Disable the Watchdog Timer(1)
1 = WDT is turned on
0 = WDT is turned off (Reset value)
Note 1:
If WDTE Configuration bit = 1, then WDT is always enabled, irrespective of this control bit. If WDTE
Configuration bit = 0, then it is possible to turn WDT on/off with this control bit.
TABLE 11-8:
Name
WDTCON
Legend:
Note 1:
SUMMARY OF REGISTERS ASSOCIATED WITH WATCHDOG TIMER
Bit 7
OPTION_REG
CONFIG
x = Bit is unknown
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
WDTPS3 WDTPS2 WSTPS1 WDTPS0 SWDTEN
Value on
POR, BOR
Value on
all other
Resets
—
—
—
---0 1000
---0 1000
RAPU
INTEDG
T0CS
T0SE
PSA
PS2
PS1
PS0
1111 1111
1111 1111
CPD
CP
MCLRE
PWRTE
WDTE
FOSC2
FOSC1
FOSC0
—
—
Shaded cells are not used by the Watchdog Timer.
See Register 11.0 for operation of all Configuration Word register bits.
DS41203E-page 124
© 2009 Microchip Technology Inc.
PIC16F688
11.6
Power-Down Mode (Sleep)
The Power-down mode is entered by executing a
SLEEP instruction.
If the Watchdog Timer is enabled:
•
•
•
•
•
WDT will be cleared but keeps running.
PD bit in the Status register is cleared.
TO bit is set.
Oscillator driver is turned off.
I/O ports maintain the status they had before SLEEP
was executed (driving high, low or high-impedance).
For lowest current consumption in this mode, all I/O
pins should be either at VDD or VSS, with no external
circuitry drawing current from the I/O pin, and the
comparators and CVREF should be disabled. I/O pins
that are high-impedance inputs should be pulled high
or low externally to avoid switching currents caused by
floating inputs. The T0CKI input should also be at VDD
or VSS for lowest current consumption. The
contribution from on-chip pull-ups on PORTA should be
considered.
The MCLR pin must be at a logic high level.
Note:
11.6.1
It should be noted that a Reset generated
by a WDT time-out does not drive MCLR
pin low.
WAKE-UP FROM SLEEP
The device can wake-up from Sleep through one of the
following events:
1.
2.
3.
External Reset input on MCLR pin.
Watchdog Timer wake-up (if WDT was
enabled).
Interrupt from RA2/INT pin, PORTA change or a
peripheral interrupt.
The first event will cause a device Reset. The two latter
events are considered a continuation of program
execution. The TO and PD bits in the Status register
can be used to determine the cause of device Reset.
The PD bit, which is set on power-up, is cleared when
Sleep is invoked. TO bit is cleared if WDT wake-up
occurred.
The following peripheral interrupts can wake the device
from Sleep:
1.
2.
3.
4.
5.
6.
7.
8.
Timer1 interrupt. Timer1 must be operating as
an asynchronous counter.
A/D conversion (when A/D clock source is FRC).
EEPROM write operation completion.
Comparator output changes state.
Interrupt-on-change.
External Interrupt from INT pin.
EUSART Receive Interrupt.
ULPWU Interrupt.
© 2009 Microchip Technology Inc.
Other peripherals cannot generate interrupts since
during Sleep, no on-chip clocks are present.
When the SLEEP instruction is being executed, the next
instruction (PC + 1) is prefetched. For the device to
wake-up through an interrupt event, the corresponding
interrupt enable bit must be set (enabled). Wake-up is
regardless of the state of the GIE bit. If the GIE bit is
clear (disabled), the device continues execution at the
instruction after the SLEEP instruction. If the GIE bit is
set (enabled), the device executes the instruction after
the SLEEP instruction, then branches to the interrupt
address (0004h). In cases where the execution of the
instruction following SLEEP is not desirable, the user
should have a NOP after the SLEEP instruction.
Note:
If the global interrupts are disabled (GIE is
cleared), but any interrupt source has both
its interrupt enable bit and the corresponding interrupt flag bits set, the device will
immediately wake-up from Sleep. The
SLEEP instruction is completely executed.
The WDT is cleared when the device wakes up from
Sleep, regardless of the source of wake-up.
11.6.2
WAKE-UP USING INTERRUPTS
When global interrupts are disabled (GIE cleared) and
any interrupt source has both its interrupt enable bit
and interrupt flag bit set, one of the following will occur:
• If the interrupt occurs before the execution of a
SLEEP instruction, the SLEEP instruction will
complete as a NOP. Therefore, the WDT and WDT
prescaler and postscaler (if enabled) will not be
cleared, the TO bit will not be set and the PD bit
will not be cleared.
• If the interrupt occurs during or after the
execution of a SLEEP instruction, the device will
immediately wake-up from Sleep. The SLEEP
instruction will be completely executed before the
wake-up. Therefore, the WDT and WDT prescaler
and postscaler (if enabled) will be cleared, the TO
bit will be set and the PD bit will be cleared.
Even if the flag bits were checked before executing a
SLEEP instruction, it may be possible for flag bits to
become set before the SLEEP instruction completes.
To determine whether a SLEEP instruction executed,
test the PD bit. If the PD bit is set, the SLEEP instruction
was executed as a NOP.
To ensure that the WDT is cleared, a CLRWDT instruction
should be executed before a SLEEP instruction.
DS41203E-page 125
PIC16F688
FIGURE 11-10:
WAKE-UP FROM SLEEP THROUGH INTERRUPT
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
TOST(2)
CLKOUT(4)
INT pin
INTF flag
(INTCON<1>)
Interrupt Latency (3)
GIE bit
(INTCON<7>)
Processor in
Sleep
Instruction Flow
PC
Instruction
Fetched
Instruction
Executed
Note
11.7
1:
2:
3:
4:
PC
Inst(PC) = Sleep
Inst(PC - 1)
PC + 1
PC + 2
PC + 2
Inst(PC + 1)
Inst(PC + 2)
Sleep
Inst(PC + 1)
PC + 2
Dummy Cycle
0004h
0005h
Inst(0004h)
Inst(0005h)
Dummy Cycle
Inst(0004h)
XT, HS or LP Oscillator mode assumed.
TOST = 1024 TOSC (drawing not to scale). This delay does not apply to EC and RC Oscillator modes.
GIE = 1 assumed. In this case after wake-up, the processor jumps to 0004h. If GIE = 0, execution will continue in-line.
CLKOUT is not available in XT, HS, LP or EC Oscillator modes, but shown here for timing reference.
Code Protection
If the code protection bit(s) have not been
programmed, the on-chip program memory can be
read out using ICSP for verification purposes.
Note:
11.8
The entire data EEPROM and Flash
program memory will be erased when the
code protection is turned off. See the
“PIC12F6XX/16F6XX Memory Programming Specification” (DS41204) for more
information.
ID Locations
Four memory locations (2000h-2003h) are designated
as ID locations where the user can store checksum or
other code identification numbers. These locations are
not accessible during normal execution but are
readable and writable during Program/Verify mode.
Only the Least Significant 7 bits of the ID locations are
used.
DS41203E-page 126
© 2009 Microchip Technology Inc.
PIC16F688
11.9
In-Circuit Serial Programming
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.
The device is placed into a Program/Verify mode by
holding the RA0 and RA1 pins low, while raising the
MCLR (VPP) pin from VIL to VIHH. See the
“PIC12F6XX/16F6XX
Memory
Programming
Specification” (DS41204) for more information. RA0
becomes the programming data and RA1 becomes the
programming clock. Both RA0 and RA1 are Schmitt
Trigger inputs in Program/Verify mode.
A typical In-Circuit Serial Programming connection is
shown in Figure 11-11.
FIGURE 11-11:
TYPICAL IN-CIRCUIT
SERIAL PROGRAMMING
CONNECTION
To Normal
Connections
External
Connector
Signals
*
11.10 In-Circuit Debugger
Since in-circuit debugging requires access to the data
and MCLR pins, MPLAB® ICD 2 development with an
14-pin device is not practical. A special 20-pin
PIC16F688 ICD device is used with MPLAB ICD 2 to
provide separate clock, data and MCLR pins and frees
all normally available pins to the user.
A special debugging adapter allows the ICD device to
be used in place of a PIC16F688 device. The
debugging adapter is the only source of the ICD device.
When the ICD pin on the PIC16F688 ICD device is held
low, the In-Circuit Debugger functionality is enabled.
This function allows simple debugging functions when
used with MPLAB ICD 2. When the microcontroller has
this feature enabled, some of the resources are not
available for general use. Table 11-9 shows which
features are consumed by the background debugger:
TABLE 11-9:
DEBUGGER RESOURCES
Resource
Description
I/O pins
ICDCLK, ICDDATA
Stack
1 level
Program Memory
Address 0h must be NOP
700h-7FFh
PIC16F688
+5V
VDD
0V
VSS
VPP
MCLR/VPP/RA3
CLK
RA1
Data I/O
RA0
For more information, see “MPLAB® ICD 2 In-Circuit
Debugger User’s Guide” (DS51331), available on
Microchip’s web site (www.microchip.com).
FIGURE 11-12:
20-PIN ICD PINOUT
20-Pin PDIP
In-Circuit Debug Device
*
*
To Normal
Connections
* Isolation devices (as required)
© 2009 Microchip Technology Inc.
1
20
2
19
3
4
5
6
7
8
9
10
PIC16F688 -ICD
*
NC
ICDMCLR/VPP
VDD
RA5
RA4
RA3
RC5
RC4
RC3
ICD
18
17
16
15
14
13
12
11
ICDCLK
ICDDATA
Vss
RA0
RA1
RA2
RC0
RC1
RC2
NC
DS41203E-page 127
PIC16F688
NOTES:
DS41203E-page 128
© 2009 Microchip Technology Inc.
PIC16F688
12.0
INSTRUCTION SET SUMMARY
The PIC16F688 instruction set is highly orthogonal and
is comprised of three basic categories:
• Byte-oriented operations
• Bit-oriented operations
• Literal and control operations
Each PIC16 instruction is a 14-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 formats for each of the categories
is presented in Figure 12-1, while the various opcode
fields are summarized in Table 12-1.
TABLE 12-1:
Field
The destination designator specifies where the result of
the operation is to be placed. If ‘d’ is zero, the result is
placed in the W register. If ‘d’ is one, the result is placed
in the file register specified in the instruction.
For bit-oriented instructions, ‘b’ represents a bit field
designator, which selects the bit affected by the
operation, while ‘f’ represents the address of the file in
which the bit is located.
For literal and control operations, ‘k’ represents an
8-bit or 11-bit constant, or literal value.
One instruction cycle consists of four oscillator periods;
for an oscillator frequency of 4 MHz, this gives a
nominal instruction execution time of 1 μs. All
instructions are executed within a single instruction
cycle, unless a conditional test is true, or the program
counter is changed as a result of an instruction. When
this occurs, the execution takes two instruction cycles,
with the second cycle executed as a NOP.
All instruction examples use the format ‘0xhh’ to
represent a hexadecimal number, where ‘h’ signifies a
hexadecimal digit.
Description
Register file address (0x00 to 0x7F)
f
W
Working register (accumulator)
b
Bit address within an 8-bit file register
k
Literal field, constant data or label
x
Don’t care location (= 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.
d
Destination select; d = 0: store result in W,
d = 1: store result in file register f.
Default is d = 1.
Table 12-2 lists the instructions recognized by the
MPASMTM assembler.
For byte-oriented instructions, ‘f’ represents a file
register designator and ‘d’ represents a destination
designator. The file register designator specifies which
file register is to be used by the instruction.
OPCODE FIELD
DESCRIPTIONS
PC
Program Counter
TO
Time-out bit
Carry bit
C
DC
Digit carry bit
Zero bit
Z
PD
Power-down bit
FIGURE 12-1:
GENERAL FORMAT FOR
INSTRUCTIONS
Byte-oriented file register operations
13
8 7 6
OPCODE
d
f (FILE #)
0
d = 0 for destination W
d = 1 for destination f
f = 7-bit file register address
Bit-oriented file register operations
13
10 9
7 6
OPCODE
b (BIT #)
f (FILE #)
0
b = 3-bit bit address
f = 7-bit file register address
Literal and control operations
General
12.1
Read-Modify-Write Operations
13
8
7
OPCODE
Any instruction that specifies a file register as part of
the instruction performs a Read-Modify-Write (R-M-W)
operation. The register is read, the data is modified,
and the result is stored according to either the instruction, or the destination designator ‘d’. A read operation
is performed on a register even if the instruction writes
to that register.
For example, a CLRF PORTA instruction will read
PORTA, clear all the data bits, then write the result
back to PORTA. This example would have the
unintended consequence of clearing the condition that
set the RAIF flag.
© 2009 Microchip Technology Inc.
0
k (literal)
k = 8-bit immediate value
CALL and GOTO instructions only
13
11
OPCODE
10
0
k (literal)
k = 11-bit immediate value
DS41203E-page 129
PIC16F688
TABLE 12-2:
PIC16F684 INSTRUCTION SET
Mnemonic,
Operands
14-Bit Opcode
Description
Cycles
MSb
LSb
Status
Affected
Notes
BYTE-ORIENTED FILE REGISTER OPERATIONS
ADDWF
ANDWF
CLRF
CLRW
COMF
DECF
DECFSZ
INCF
INCFSZ
IORWF
MOVF
MOVWF
NOP
RLF
RRF
SUBWF
SWAPF
XORWF
f, d
f, d
f
–
f, d
f, d
f, d
f, d
f, d
f, d
f, d
f
–
f, d
f, d
f, d
f, d
f, d
Add W and f
AND W with f
Clear f
Clear W
Complement f
Decrement f
Decrement f, Skip if 0
Increment f
Increment f, Skip if 0
Inclusive OR W with f
Move f
Move W to f
No Operation
Rotate Left f through Carry
Rotate Right f through Carry
Subtract W from f
Swap nibbles in f
Exclusive OR W with f
BCF
BSF
BTFSC
BTFSS
f, b
f, b
f, b
f, b
Bit Clear f
Bit Set f
Bit Test f, Skip if Clear
Bit Test f, Skip if Set
1
1
1
1
1
1
1(2)
1
1(2)
1
1
1
1
1
1
1
1
1
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
dfff
dfff
lfff
0xxx
dfff
dfff
dfff
dfff
dfff
dfff
dfff
lfff
0xx0
dfff
dfff
dfff
dfff
dfff
ffff
ffff
ffff
xxxx
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
0000
ffff
ffff
ffff
ffff
ffff
00bb
01bb
10bb
11bb
bfff
bfff
bfff
bfff
ffff
ffff
ffff
ffff
111x
1001
0kkk
0000
1kkk
1000
00xx
0000
01xx
0000
0000
110x
1010
kkkk
kkkk
kkkk
0110
kkkk
kkkk
kkkk
0000
kkkk
0000
0110
kkkk
kkkk
kkkk
kkkk
kkkk
0100
kkkk
kkkk
kkkk
1001
kkkk
1000
0011
kkkk
kkkk
0111
0101
0001
0001
1001
0011
1011
1010
1111
0100
1000
0000
0000
1101
1100
0010
1110
0110
C, DC, Z
Z
Z
Z
Z
Z
Z
Z
Z
C
C
C, DC, Z
Z
1, 2
1, 2
2
1, 2
1, 2
1, 2, 3
1, 2
1, 2, 3
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
BIT-ORIENTED FILE REGISTER OPERATIONS
1
1
1 (2)
1 (2)
01
01
01
01
1, 2
1, 2
3
3
LITERAL AND CONTROL OPERATIONS
ADDLW
ANDLW
CALL
CLRWDT
GOTO
IORLW
MOVLW
RETFIE
RETLW
RETURN
SLEEP
SUBLW
XORLW
Note 1:
2:
3:
k
k
k
–
k
k
k
–
k
–
–
k
k
Add literal and W
AND literal with W
Call Subroutine
Clear Watchdog Timer
Go to address
Inclusive OR literal with W
Move literal to W
Return from interrupt
Return with literal in W
Return from Subroutine
Go into Standby mode
Subtract W from literal
Exclusive OR literal with W
1
1
2
1
2
1
1
2
2
2
1
1
1
11
11
10
00
10
11
11
00
11
00
00
11
11
C, DC, Z
Z
TO, PD
Z
TO, PD
C, DC, Z
Z
When an I/O register is modified as a function of itself (e.g., MOVF GPIO, 1), 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’.
If this instruction is executed on the TMR0 register (and where applicable, d = 1), the prescaler will be cleared if
assigned to the Timer0 module.
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.
DS41203E-page 130
© 2009 Microchip Technology Inc.
PIC16F688
12.2
Instruction Descriptions
ADDLW
Add literal and W
Syntax:
[ label ] ADDLW
Operands:
0 ≤ k ≤ 255
Operation:
(W) + k → (W)
Status Affected:
C, DC, Z
Description:
The contents of the W register
are added to the eight-bit literal ‘k’
and the result is placed in the
W register.
k
BCF
Bit Clear f
Syntax:
[ label ] BCF
Operands:
0 ≤ f ≤ 127
0≤b≤7
Operation:
0 → (f<b>)
Status Affected:
None
Description:
Bit ‘b’ in register ‘f’ is cleared.
BSF
Bit Set f
Syntax:
[ label ] BSF
f,b
ADDWF
Add W and f
Syntax:
[ label ] ADDWF
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
0 ≤ f ≤ 127
0≤b≤7
Operation:
(W) + (f) → (destination)
Operation:
1 → (f<b>)
Status Affected:
C, DC, Z
Status Affected:
None
Description:
Add the contents of the W register
with register ‘f’. If ‘d’ is ‘0’, the
result is stored in the W register. If
‘d’ is ‘1’, the result is stored back
in register ‘f’.
Description:
Bit ‘b’ in register ‘f’ is set.
ANDLW
AND literal with W
BTFSC
Bit Test f, Skip if Clear
Syntax:
[ label ] ANDLW
Syntax:
[ label ] BTFSC f,b
Operands:
0 ≤ k ≤ 255
Operands:
Operation:
(W) .AND. (k) → (W)
0 ≤ f ≤ 127
0≤b≤7
Status Affected:
Z
Operation:
skip if (f<b>) = 0
Description:
The contents of W register are
AND’ed with the eight-bit literal
‘k’. The result is placed in the W
register.
Status Affected:
None
Description:
If bit ‘b’ in register ‘f’ is ‘1’, the next
instruction is executed.
If bit ‘b’, in register ‘f’, is ‘0’, the
next instruction is discarded, and
a NOP is executed instead, making
this a two-cycle instruction.
ANDWF
f,d
k
AND W with f
Syntax:
[ label ] ANDWF
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operation:
(W) .AND. (f) → (destination)
f,d
Status Affected:
Z
Description:
AND the W register with register
‘f’. If ‘d’ is ‘0’, the result is stored in
the W register. If ‘d’ is ‘1’, the
result is stored back in register ‘f’.
© 2009 Microchip Technology Inc.
f,b
DS41203E-page 131
PIC16F688
BTFSS
Bit Test f, Skip if Set
CLRWDT
Clear Watchdog Timer
Syntax:
[ label ] BTFSS f,b
Syntax:
[ label ] CLRWDT
Operands:
0 ≤ f ≤ 127
0≤b<7
Operands:
None
Operation:
00h → WDT
0 → WDT prescaler,
1 → TO
1 → PD
Status Affected:
TO, PD
Description:
CLRWDT instruction resets the
Watchdog Timer. It also resets the
prescaler of the WDT.
Status bits TO and PD are set.
Operation:
skip if (f<b>) = 1
Status Affected:
None
Description:
If bit ‘b’ in register ‘f’ is ‘0’, the next
instruction is executed.
If bit ‘b’ is ‘1’, then the next
instruction is discarded and a NOP
is executed instead, making this a
two-cycle instruction.
CALL
Call Subroutine
COMF
Complement f
Syntax:
[ label ] CALL k
Syntax:
[ label ] COMF
Operands:
0 ≤ k ≤ 2047
Operands:
Operation:
(PC)+ 1→ TOS,
k → PC<10:0>,
(PCLATH<4:3>) → PC<12:11>
0 ≤ f ≤ 127
d ∈ [0,1]
f,d
Operation:
(f) → (destination)
Status Affected:
Z
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’.
DECF
Decrement f
Syntax:
[ label ] DECF f,d
Status Affected:
None
Description:
Call Subroutine. First, return
address (PC + 1) is pushed onto
the stack. The eleven-bit
immediate address is loaded into
PC bits <10:0>. The upper bits of
the PC are loaded from PCLATH.
CALL is a two-cycle instruction.
CLRF
Clear f
Syntax:
[ label ] CLRF
Operands:
0 ≤ f ≤ 127
Operands:
Operation:
00h → (f)
1→Z
0 ≤ f ≤ 127
d ∈ [0,1]
Operation:
(f) - 1 → (destination)
Status Affected:
Z
Status Affected:
Z
Description:
The contents of register ‘f’ are
cleared and the Z bit is set.
Description:
Decrement register ‘f’. If ‘d’ is ‘0’,
the result is stored in the W
register. If ‘d’ is ‘1’, the result is
stored back in register ‘f’.
CLRW
Clear W
Syntax:
[ label ] CLRW
f
Operands:
None
Operation:
00h → (W)
1→Z
Status Affected:
Z
Description:
W register is cleared. Zero bit (Z)
is set.
DS41203E-page 132
© 2009 Microchip Technology Inc.
PIC16F688
DECFSZ
Decrement f, Skip if 0
INCFSZ
Increment f, Skip if 0
Syntax:
[ label ] DECFSZ f,d
Syntax:
[ label ]
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operation:
(f) - 1 → (destination);
skip if result = 0
Operation:
(f) + 1 → (destination),
skip if result = 0
Status Affected:
None
Status Affected:
None
Description:
The contents of register ‘f’ are
decremented. If ‘d’ is ‘0’, the result
is placed in the W register. If ‘d’ is
‘1’, the result is placed back in
register ‘f’.
If the result is ‘1’, the next
instruction is executed. If the
result is ‘0’, then a NOP is
executed instead, making it a
two-cycle instruction.
Description:
The contents of register ‘f’ are
incremented. If ‘d’ is ‘0’, the result
is placed in the W register. If ‘d’ is
‘1’, the result is placed back in
register ‘f’.
If the result is ‘1’, the next
instruction is executed. If the
result is ‘0’, a NOP is executed
instead, making it a two-cycle
instruction.
GOTO
Unconditional Branch
IORLW
Syntax:
[ label ]
Syntax:
[ label ]
Operands:
0 ≤ k ≤ 2047
Operands:
0 ≤ k ≤ 255
Operation:
k → PC<10:0>
PCLATH<4:3> → PC<12:11>
Operation:
(W) .OR. k → (W)
Status Affected:
Z
Status Affected:
None
Description:
Description:
GOTO is an unconditional branch.
The eleven-bit immediate value is
loaded into PC bits <10:0>. The
upper bits of PC are loaded from
PCLATH<4:3>. GOTO is a
two-cycle instruction.
The contents of the W register are
OR’ed with the eight-bit literal ‘k’.
The result is placed in the
W register.
INCF
Increment f
IORWF
Inclusive OR W with f
Syntax:
[ label ]
Syntax:
[ label ]
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operation:
(f) + 1 → (destination)
Operation:
(W) .OR. (f) → (destination)
Status Affected:
Z
Status Affected:
Z
Description:
The contents of register ‘f’ are
incremented. If ‘d’ is ‘0’, the result
is placed in the W register. If ‘d’ is
‘1’, the result is placed back in
register ‘f’.
Description:
Inclusive OR the W register with
register ‘f’. If ‘d’ is ‘0’, the result is
placed in the W register. If ‘d’ is
‘1’, the result is placed back in
register ‘f’.
GOTO k
INCF f,d
© 2009 Microchip Technology Inc.
INCFSZ f,d
Inclusive OR literal with W
IORLW k
IORWF
f,d
DS41203E-page 133
PIC16F688
MOVF
Move f
Syntax:
[ label ]
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
MOVF f,d
MOVWF
Move W to f
Syntax:
[ label ]
MOVWF
Operands:
0 ≤ f ≤ 127
Operation:
(W) → (f)
f
Operation:
(f) → (dest)
Status Affected:
None
Status Affected:
Z
Description:
Description:
The contents of register f is
moved to a destination dependent
upon the status of d. If d = 0,
destination is W register. If d = 1,
the destination is file register f
itself. d = 1 is useful to test a file
register since status flag Z is
affected.
Move data from W register to
register ‘f’.
Words:
1
Cycles:
1
Words:
1
Cycles:
1
Example:
MOVF
Example:
MOVW
F
OPTION
Before Instruction
OPTION =
W
=
After Instruction
OPTION =
W
=
FSR, 0
0xFF
0x4F
0x4F
0x4F
After Instruction
W =
value in FSR
register
Z = 1
MOVLW
Move literal to W
NOP
No Operation
Syntax:
[ label ]
Syntax:
[ label ]
Operands:
0 ≤ k ≤ 255
Operands:
None
Operation:
k → (W)
Operation:
No operation
Status Affected:
None
Status Affected:
None
Description:
The eight-bit literal ‘k’ is loaded into
W register. The “don’t cares” will
assemble as ‘0’s.
Description:
No operation.
Words:
1
Cycles:
1
Words:
1
Cycles:
1
Example:
MOVLW k
Example:
MOVLW
NOP
0x5A
After Instruction
W =
DS41203E-page 134
NOP
0x5A
© 2009 Microchip Technology Inc.
PIC16F688
RETFIE
Return from Interrupt
RETLW
Return with literal in W
Syntax:
[ label ]
Syntax:
[ label ]
Operands:
None
Operands:
0 ≤ k ≤ 255
Operation:
TOS → PC,
1 → GIE
Operation:
k → (W);
TOS → PC
Status Affected:
None
Status Affected:
None
Description:
Return from Interrupt. Stack is
POPed and Top-of-Stack (TOS) is
loaded in the PC. Interrupts are
enabled by setting Global
Interrupt Enable bit, GIE
(INTCON<7>). This is a two-cycle
instruction.
Description:
The W register is loaded with the
eight bit literal ‘k’. The program
counter is loaded from the top of
the stack (the return address).
This is a two-cycle instruction.
Words:
1
Cycles:
2
Example:
RETFIE
Words:
1
Cycles:
2
Example:
RETFIE
After Interrupt
PC =
GIE =
TABLE
TOS
1
RETLW k
CALL TABLE;W contains
table
;offset value
•
;W now has table value
•
•
ADDWF PC ;W = offset
RETLW k1 ;Begin table
RETLW k2 ;
•
•
•
RETLW kn ; End of table
Before Instruction
W = 0x07
After Instruction
W = value of k8
RETURN
© 2009 Microchip Technology Inc.
Return from Subroutine
Syntax:
[ label ]
Operands:
None
RETURN
Operation:
TOS → PC
Status Affected:
None
Description:
Return from subroutine. The stack
is POPed and the top of the stack
(TOS) is loaded into the program
counter. This is a two-cycle
instruction.
DS41203E-page 135
PIC16F688
RLF
Rotate Left f through Carry
SLEEP
Enter Sleep mode
Syntax:
[ label ]
Syntax:
[ label ] SLEEP
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
None
Operation:
Operation:
See description below
Status Affected:
C
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 the W register.
If ‘d’ is ‘1’, the result is stored
back in register ‘f’.
00h → WDT,
0 → WDT prescaler,
1 → TO,
0 → PD
RLF
f,d
C
Words:
1
Cycles:
1
Example:
Status Affected:
TO, PD
Description:
The power-down Status bit, PD is
cleared. Time-out Status bit, TO
is set. Watchdog Timer and its
prescaler are cleared.
The processor is put into Sleep
mode with the oscillator stopped.
Register f
RLF
REG1,0
Before Instruction
REG1
C
=
=
1110 0110
0
=
=
=
1110 0110
1100 1100
1
After Instruction
REG1
W
C
RRF
Rotate Right f through Carry
SUBLW
Syntax:
[ label ]
Syntax:
[ label ] SUBLW k
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
0 ≤ k ≤ 255
Operation:
k - (W) → (W)
Operation:
See description below
Status Affected: C, DC, Z
Status Affected:
C
Description:
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 the W register.
If ‘d’ is ‘1’, the result is placed
back in register ‘f’.
RRF f,d
C
DS41203E-page 136
Register f
Subtract W from literal
The W register is subtracted (2’s
complement method) from the
eight-bit literal ‘k’. The result is
placed in the W register.
C=0
W>k
C=1
W≤k
DC = 0
W<3:0> > k<3:0>
DC = 1
W<3:0> ≤ k<3:0>
© 2009 Microchip Technology Inc.
PIC16F688
SUBWF
Subtract W from f
XORLW
Exclusive OR literal with W
Syntax:
[ label ] SUBWF f,d
Syntax:
[ label ] XORLW k
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
0 ≤ k ≤ 255
(f) - (W) → (destination)
Operation:
(W) .XOR. k → (W)
Operation:
Status Affected: C, DC, Z
Description:
SWAPF
Status Affected:
Z
Description:
The contents of the W register
are XOR’ed with the eight-bit
literal ‘k’. The result is placed in
the W register.
Subtract (2’s complement method)
W register from register ‘f’. If ‘d’ is
‘0’, the result is stored in the W
register. If ‘d’ is ‘1’, the result is
stored back in register ‘f.
C=0
W>f
C=1
W≤f
DC = 0
W<3:0> > f<3:0>
DC = 1
W<3:0> ≤ f<3:0>
Swap Nibbles in f
XORWF
Exclusive OR W with f
Syntax:
[ label ] SWAPF f,d
Syntax:
[ label ] XORWF
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operands:
0 ≤ f ≤ 127
d ∈ [0,1]
Operation:
(f<3:0>) → (destination<7:4>),
(f<7:4>) → (destination<3:0>)
Operation:
(W) .XOR. (f) → (destination)
Status Affected:
Z
Status Affected:
None
Description:
Description:
The upper and lower nibbles of
register ‘f’ are exchanged. If ‘d’ is
‘0’, the result is placed in the W
register. If ‘d’ is ‘1’, the result is
placed in register ‘f’.
Exclusive OR the contents of the
W register with register ‘f’. If ‘d’ is
‘0’, the result is stored in the W
register. If ‘d’ is ‘1’, the result is
stored back in register ‘f’.
© 2009 Microchip Technology Inc.
f,d
DS41203E-page 137
PIC16F688
NOTES:
DS41203E-page 138
© 2009 Microchip Technology Inc.
PIC16F688
13.0
DEVELOPMENT SUPPORT
The PIC® microcontrollers are supported with a full
range of hardware and software development tools:
• Integrated Development Environment
- MPLAB® IDE Software
• Assemblers/Compilers/Linkers
- MPASMTM Assembler
- MPLAB C18 and MPLAB C30 C Compilers
- MPLINKTM Object Linker/
MPLIBTM Object Librarian
- MPLAB ASM30 Assembler/Linker/Library
• Simulators
- MPLAB SIM Software Simulator
• Emulators
- MPLAB ICE 2000 In-Circuit Emulator
- MPLAB REAL ICE™ In-Circuit Emulator
• In-Circuit Debugger
- MPLAB ICD 2
• Device Programmers
- PICSTART® Plus Development Programmer
- MPLAB PM3 Device Programmer
- PICkit™ 2 Development Programmer
• Low-Cost Demonstration and Development
Boards and Evaluation Kits
13.1
MPLAB Integrated Development
Environment Software
The MPLAB IDE software brings an ease of software
development previously unseen in the 8/16-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)
- 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
• Visual device initializer for easy register
initialization
• 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
HI-TECH Software C Compilers and IAR
C Compilers
The MPLAB IDE allows you to:
• Edit your source files (either assembly or C)
• One touch assemble (or compile) and download
to PIC MCU emulator and simulator tools
(automatically updates all project information)
• Debug using:
- Source files (assembly or C)
- Mixed assembly and C
- 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.
© 2009 Microchip Technology Inc.
DS41203E-page 139
PIC16F688
13.2
MPASM Assembler
The MPASM Assembler is a full-featured, universal
macro assembler for all PIC 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
13.5
MPLAB ASM30 Assembler produces relocatable
machine code from symbolic assembly language for
dsPIC30F devices. MPLAB C30 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 dsPIC30F instruction set
Support for fixed-point and floating-point data
Command line interface
Rich directive set
Flexible macro language
MPLAB IDE compatibility
13.6
13.3
MPLAB C18 and MPLAB C30
C Compilers
The MPLAB C18 and MPLAB C30 Code Development
Systems are complete ANSI C compilers for
Microchip’s PIC18 and PIC24 families of microcontrollers and the dsPIC30 and dsPIC33 family of digital
signal controllers. These compilers provide powerful
integration capabilities, superior code optimization and
ease of use not found with other compilers.
For easy source level debugging, the compilers provide
symbol information that is optimized to the MPLAB IDE
debugger.
13.4
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.
MPLAB ASM30 Assembler, Linker
and Librarian
MPLAB SIM Software Simulator
The MPLAB SIM Software Simulator allows code
development in a PC-hosted environment by simulating 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 C18 and
MPLAB C30 C Compilers, and the MPASM and
MPLAB ASM30 Assemblers. The software simulator
offers the flexibility to develop and debug code outside
of the hardware laboratory environment, making it an
excellent, economical software development tool.
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
DS41203E-page 140
© 2009 Microchip Technology Inc.
PIC16F688
13.7
MPLAB ICE 2000
High-Performance
In-Circuit Emulator
The MPLAB ICE 2000 In-Circuit Emulator is intended
to provide the product development engineer with a
complete microcontroller design tool set for PIC
microcontrollers. Software control of the MPLAB ICE
2000 In-Circuit Emulator is advanced by the MPLAB
Integrated Development Environment, which allows
editing, building, downloading and source debugging
from a single environment.
The MPLAB ICE 2000 is a full-featured emulator
system with enhanced trace, trigger and data monitoring features. Interchangeable processor modules allow
the system to be easily reconfigured for emulation of
different processors. The architecture of the MPLAB
ICE 2000 In-Circuit Emulator allows expansion to
support new PIC microcontrollers.
The MPLAB ICE 2000 In-Circuit Emulator system has
been designed as a real-time emulation system with
advanced features that are typically found on more
expensive development tools. The PC platform and
Microsoft® Windows® 32-bit operating system were
chosen to best make these features available in a
simple, unified application.
13.8
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 MPLAB REAL ICE probe 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 the popular MPLAB ICD 2 system
(RJ11) or with the new high-speed, noise tolerant, LowVoltage Differential Signal (LVDS) interconnection
(CAT5).
13.9
MPLAB ICD 2 In-Circuit Debugger
Microchip’s In-Circuit Debugger, MPLAB ICD 2, is a
powerful, low-cost, run-time development tool,
connecting to the host PC via an RS-232 or high-speed
USB interface. This tool is based on the Flash PIC
MCUs and can be used to develop for these and other
PIC MCUs and dsPIC DSCs. The MPLAB ICD 2 utilizes
the in-circuit debugging capability built into the Flash
devices. This feature, along with Microchip’s In-Circuit
Serial ProgrammingTM (ICSPTM) protocol, offers costeffective, in-circuit Flash debugging from the graphical
user interface of the MPLAB Integrated Development
Environment. This enables a designer to develop and
debug source code by setting breakpoints, single stepping and watching variables, and CPU status and
peripheral registers. Running at full speed enables
testing hardware and applications in real time. MPLAB
ICD 2 also serves as a development programmer for
selected PIC devices.
13.10 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 modular, 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 SD/MMC card for
file storage and secure data applications.
MPLAB REAL ICE is field upgradeable through future
firmware downloads in MPLAB IDE. In upcoming
releases of MPLAB IDE, new devices will be supported,
and new features will be added, such as software breakpoints and assembly code trace. MPLAB REAL ICE
offers significant advantages over competitive emulators
including low-cost, full-speed emulation, real-time
variable watches, trace analysis, complex breakpoints, a
ruggedized probe interface and long (up to three meters)
interconnection cables.
© 2009 Microchip Technology Inc.
DS41203E-page 141
PIC16F688
13.11 PICSTART Plus Development
Programmer
13.13 Demonstration, Development and
Evaluation Boards
The PICSTART Plus Development Programmer is an
easy-to-use, low-cost, prototype programmer. It
connects to the PC via a COM (RS-232) port. MPLAB
Integrated Development Environment software makes
using the programmer simple and efficient. The
PICSTART Plus Development Programmer supports
most PIC devices in DIP packages up to 40 pins.
Larger pin count devices, such as the PIC16C92X and
PIC17C76X, may be supported with an adapter socket.
The PICSTART Plus Development Programmer is CE
compliant.
A wide variety of demonstration, development and
evaluation boards for various PIC MCUs and dsPIC
DSCs allows quick application development on fully functional systems. Most boards include prototyping areas for
adding custom circuitry and provide application firmware
and source code for examination and modification.
13.12 PICkit 2 Development Programmer
The PICkit™ 2 Development Programmer is a low-cost
programmer and selected Flash device debugger with
an easy-to-use interface for programming many of
Microchip’s baseline, mid-range and PIC18F families
of Flash memory microcontrollers. The PICkit 2 Starter
Kit includes a prototyping development board, twelve
sequential lessons, software and HI-TECH’s PICC™
Lite C compiler, and is designed to help get up to speed
quickly using PIC® microcontrollers. The kit provides
everything needed to program, evaluate and develop
applications using Microchip’s powerful, mid-range
Flash memory family of microcontrollers.
DS41203E-page 142
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™ demonstration/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.
Check the Microchip web page (www.microchip.com)
for the complete list of demonstration, development
and evaluation kits.
© 2009 Microchip Technology Inc.
PIC16F688
14.0
ELECTRICAL SPECIFICATIONS
Absolute Maximum Ratings(†)
Ambient temperature under bias..........................................................................................................-40° to +125°C
Storage temperature ........................................................................................................................ -65°C to +150°C
Voltage on VDD with respect to VSS ................................................................................................... -0.3V to +6.5V
Voltage on MCLR with respect to Vss ............................................................................................... -0.3V to +13.5V
Voltage on all other pins with respect to VSS ........................................................................... -0.3V to (VDD + 0.3V)
Total power dissipation(1) ............................................................................................................................... 800 mW
Maximum current out of VSS pin ...................................................................................................................... 95 mA
Maximum current into VDD pin ......................................................................................................................... 95 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 PORTA and PORTC (combined) ........................................................................... 90 mA
Maximum current sourced PORTA and PORTC (combined) ........................................................................... 90 mA
Note 1:
Power dissipation is calculated as follows: PDIS = VDD x {IDD – ∑ IOH} + ∑ {(VDD – VOH) x IOH} + ∑(VOl x
IOL).
† 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 above maximum rating conditions for
extended periods may affect device reliability.
© 2009 Microchip Technology Inc.
DS41203E-page 143
PIC16F688
FIGURE 14-1:
PIC16F688 VOLTAGE-FREQUENCY GRAPH,
-40°C ≤ TA ≤ +125°C
5.5
5.0
VDD (V)
4.5
4.0
3.5
3.0
2.5
2.0
0
8
10
20
Frequency (MHz)
Note 1: The shaded region indicates the permissible combinations of voltage and frequency.
HFINTOSC FREQUENCY ACCURACY OVER DEVICE VDD AND TEMPERATURE
FIGURE 14-2:
125
± 5%
Temperature (°C)
85
± 2%
60
± 1%
25
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
DS41203E-page 144
© 2009 Microchip Technology Inc.
PIC16F688
14.1
DC Characteristics: PIC16F688 -I (Industrial)
PIC16F688 -E (Extended)
DC 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.
Min Typ† Max Units
Sym
Characteristic
Conditions
VDD
Supply Voltage
2.0
2.0
3.0
4.5
—
—
—
—
5.5
5.5
5.5
5.5
V
V
V
V
FOSC < = 8 MHz: HFINTOSC, EC
FOSC < = 4 MHz
FOSC < = 10 MHz
FOSC < = 20 MHz
D002*
VDR
RAM Data Retention
Voltage(1)
1.5
—
—
V
Device in Sleep mode
D003
VPOR
VDD Start Voltage to
ensure internal Power-on
Reset signal
—
VSS
—
V
See Section 11.2.1 “Power-On Reset”
for details.
D004*
SVDD
VDD Rise Rate to ensure
internal Power-on Reset
signal
0.05
—
—
D001
D001C
D001D
V/ms See Section 11.2.1 “Power-On Reset”
for details.
* These parameters are characterized but not tested.
† 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: This is the limit to which VDD can be lowered in Sleep mode without losing RAM data.
© 2009 Microchip Technology Inc.
DS41203E-page 145
PIC16F688
14.2
DC Characteristics: PIC16F688 -I (Industrial)
PIC16F688 -E (Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +85°C for industrial
-40°C ≤ TA ≤ +125°C for extended
DC CHARACTERISTICS
Param
No.
D010
Conditions
Device Characteristics
Min
Typ†
Max
Units
VDD
Supply Current (IDD)
D011*
D012
D013*
D014
D015
D016*
D017
D018
D019
(1, 2)
—
16
23
μA
2.0
—
27
38
μA
3.0
—
47
75
μA
5.0
—
180
250
μA
2.0
—
290
400
μA
3.0
—
490
650
μA
5.0
—
280
380
μA
2.0
—
480
670
μA
3.0
—
0.9
1.4
mA
5.0
—
130
220
μA
2.0
—
215
360
μA
3.0
—
360
520
μA
5.0
—
220
340
μA
2.0
—
375
550
μA
3.0
—
0.65
1.0
mA
5.0
—
8
20
μA
2.0
—
16
40
μA
3.0
—
31
65
μA
5.0
—
320
400
μA
2.0
—
490
640
μA
3.0
—
0.87
1.2
mA
5.0
—
0.5
0.7
mA
2.0
—
0.78
1
mA
3.0
5.0
—
1.43
1.8
mA
—
340
580
μA
2.0
—
550
950
μA
3.0
—
0.92
1.6
mA
5.0
—
2.9
3.7
mA
4.5
—
3.1
3.8
mA
5.0
Note
FOSC = 32 kHz
LP Oscillator mode
FOSC = 1 MHz
XT Oscillator mode
FOSC = 4 MHz
XT Oscillator mode
FOSC = 1 MHz
EC Oscillator mode
FOSC = 4 MHz
EC Oscillator mode
FOSC = 31 kHz
LFINTOSC mode
FOSC = 4 MHz
HFINTOSC mode
FOSC = 8 MHz
HFINTOSC mode
FOSC = 4 MHz
EXTRC mode(3)
FOSC = 20 MHz
HS Oscillator mode
* These parameters are characterized but not tested.
† 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: 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; MCLR = VDD; WDT disabled.
2: The supply current is mainly a function of the operating voltage and frequency. Other factors, such as I/O
pin loading and switching rate, oscillator type, internal code execution pattern and temperature, also have
an impact on the current consumption.
3: For RC oscillator configurations, current through REXT is not included. The current through the resistor can
be extended by the formula IR = VDD/2REXT (mA) with REXT in kΩ.
DS41203E-page 146
© 2009 Microchip Technology Inc.
PIC16F688
14.3
DC Characteristics: PIC16F688-I (Industrial)
DC CHARACTERISTICS
Param
No.
D020
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +85°C for industrial
Conditions
Device Characteristics
Power-down Base
Current(IPD)(2)
D021
Min
Typ†
Max
Units
VDD
Note
WDT, BOR, Comparators, VREF and
T1OSC disabled
—
0.05
1.2
μA
2.0
—
0.15
1.5
μA
3.0
—
0.35
1.8
μA
5.0
—
150
500
nA
3.0
-40°C ≤ TA ≤ +25°C
—
1.0
2.2
μA
2.0
WDT Current(1)
—
2.0
4.0
μA
3.0
—
3.0
7.0
μA
5.0
D022
—
42
60
μA
3.0
—
85
122
μA
5.0
D023
—
32
45
μA
2.0
D024
D025*
D026
D027
—
60
78
μA
3.0
—
120
160
μA
5.0
—
30
36
μA
2.0
—
45
55
μA
3.0
—
75
95
μA
5.0
—
39
47
μA
2.0
—
59
72
μA
3.0
—
98
124
μA
5.0
—
4.5
7.0
μA
2.0
—
5.0
8.0
μA
3.0
—
6.0
12
μA
5.0
—
0.30
1.6
μA
3.0
—
0.36
1.9
μA
5.0
BOR Current(1)
Comparator Current(1), both
comparators enabled
CVREF Current(1) (high range)
CVREF Current(1) (low range)
T1OSC Current(1), 32.768 kHz
A/D Current(1), no conversion in
progress
* These parameters are characterized but not tested.
† 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: The peripheral current is the sum of the base IDD or IPD and the additional current consumed when this
peripheral is enabled. The peripheral Δ current can be determined by subtracting the base IDD or IPD
current from this limit. Max values should be used when calculating total current consumption.
2: 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.
© 2009 Microchip Technology Inc.
DS41203E-page 147
PIC16F688
14.4
DC Characteristics: PIC16F688-E (Extended)
DC CHARACTERISTICS
Param
No.
D020E
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +125°C for extended
Conditions
Device Characteristics
Power-down Base
Current (IPD)(2)
D021E
Min
—
Typ†
0.05
Max
9
Units
μA
VDD
Note
2.0
WDT, BOR, Comparators, VREF and
T1OSC disabled
—
0.15
11
μA
3.0
—
0.35
15
μA
5.0
—
1
28
μA
2.0
—
2
30
μA
3.0
—
3
35
μA
5.0
D022E
—
42
65
μA
3.0
—
85
127
μA
5.0
D023E
—
32
45
μA
2.0
D024E
D025E*
D026E
D027E
—
60
78
μA
3.0
—
120
160
μA
5.0
—
30
70
μA
2.0
—
45
90
μA
3.0
—
75
120
μA
5.0
—
39
91
μA
2.0
—
59
117
μA
3.0
—
98
156
μA
5.0
—
4.5
25
μA
2.0
—
5
30
μA
3.0
—
6
40
μA
5.0
—
0.30
12
μA
3.0
—
0.36
16
μA
5.0
WDT Current(1)
BOR Current(1)
Comparator Current(1), both
comparators enabled
CVREF Current(1) (high range)
CVREF Current(1) (low range)
T1OSC Current(1), 32.768 kHz
A/D Current(1), no conversion in
progress
* These parameters are characterized but not tested.
† 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: The peripheral current is the sum of the base IDD or IPD and the additional current consumed when this
peripheral is enabled. The peripheral Δ current can be determined by subtracting the base IDD or IPD
current from this limit. Max values should be used when calculating total current consumption.
2: 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.
DS41203E-page 148
© 2009 Microchip Technology Inc.
PIC16F688
14.5
DC Characteristics:
PIC16F688 -I (Industrial)
PIC16F688 -E (Extended)
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +85°C for industrial
-40°C ≤ TA ≤ +125°C for extended
DC CHARACTERISTICS
Param
No.
Sym
VIL
Characteristic
Min
Typ†
Max
Units
Vss
Vss
Conditions
—
0.8
V
4.5V ≤ VDD ≤ 5.5V
—
0.15 VDD
V
2.0V ≤ VDD ≤ 4.5V
Vss
—
0.2 VDD
V
2.0V ≤ VDD ≤ 5.5V
Input Low Voltage
I/O Port:
D030
with TTL buffer
D030A
D031
with Schmitt Trigger buffer
(1)
D032
MCLR, OSC1 (RC mode)
VSS
—
0.2 VDD
V
D033
OSC1 (XT and LP modes)
VSS
—
0.3
V
OSC1 (HS mode)
VSS
—
0.3 VDD
V
2.0
—
VDD
V
4.5V ≤ VDD ≤ 5.5V
0.25 VDD + 0.8
—
VDD
V
2.0V ≤ VDD ≤ 4.5V
0.8 VDD
—
VDD
V
2.0V ≤ VDD ≤ 5.5V
0.8 VDD
—
VDD
V
1.6
—
VDD
V
D033A
VIH
Input High Voltage
I/O ports:
D040
—
with TTL buffer
D040A
D041
with Schmitt Trigger buffer
D042
MCLR
D043
OSC1 (XT and LP modes)
D043A
OSC1 (HS mode)
0.7 VDD
—
VDD
V
D043B
OSC1 (RC mode)
0.9 VDD
—
VDD
V
—
± 0.1
±1
μA
VSS ≤ VPIN ≤ VDD,
Pin at high-impedance
(Note 1)
(2)
Input Leakage Current
IIL
D060
I/O ports
D061
MCLR(3)
—
± 0.1
±5
μA
VSS ≤ VPIN ≤ VDD
D063
OSC1
—
± 0.1
±5
μA
VSS ≤ VPIN ≤ VDD, XT, HS and
LP oscillator configuration
IPUR
PORTA Weak Pull-up Current
50
250
400
μA
VDD = 5.0V, VPIN = VSS
VOL
Output Low Voltage(5)
—
—
0.6
V
IOL = 8.5 mA, VDD = 4.5V (Ind.)
VDD – 0.7
—
—
V
IOH = -3.0 mA, VDD = 4.5V (Ind.)
D070*
D080
I/O ports
VOH
D090
Output High Voltage(5)
I/O ports
*
†
Note 1:
2:
3:
4:
5:
These parameters are characterized but not tested.
Data in “Typ” column is at 5.0V, 25°C unless otherwise stated. These parameters are for design guidance only and are
not tested.
In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended to use an external
clock in RC mode.
Negative current is defined as current sourced by the pin.
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.
See Section 9.0 “Data EEPROM and Flash Program Memory Control” for additional information.
Including OSC2 in CLKOUT mode.
© 2009 Microchip Technology Inc.
DS41203E-page 149
PIC16F688
14.5
DC Characteristics:
PIC16F688 -I (Industrial)
PIC16F688 -E (Extended) (Continued)
DC CHARACTERISTICS
Param
No.
Sym
D100
IULP
Characteristic
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +85°C for industrial
-40°C ≤ TA ≤ +125°C for extended
Min
Typ†
Max
Units
—
200
—
nA
See Application Note AN879,
“Using the Microchip Ultra
Low-Power Wake-up Module”
(DS00879)
OSC2 pin
—
—
15
pF
In XT, HS and LP modes when
external clock is used to drive
OSC1
All I/O pins
—
—
50
pF
Ultra Low-Power Wake-Up
Current
Conditions
Capacitive Loading Specs on
Output Pins
D101*
COSC2
D101A* CIO
Data EEPROM Memory
-40°C ≤ TA ≤ +85°C
D120
ED
Byte Endurance
100K
1M
—
E/W
D120A
ED
Byte Endurance
10K
100K
—
E/W
D121
VDRW
VDD for Read/Write
VMIN
—
5.5
V
D122
TDEW
Erase/Write Cycle Time
—
5
6
D123
TRETD
Characteristic Retention
40
—
—
Year Provided no other specifications
are violated
D124
TREF
Number of Total Erase/Write
Cycles before Refresh(4)
1M
10M
—
E/W
-40°C ≤ TA ≤ +85°C
-40°C ≤ TA ≤ +85°C
+85°C ≤ TA ≤ +125°C
Using EECON1 to read/write
VMIN = Minimum operating
voltage
ms
Program Flash Memory
D130
EP
Cell Endurance
10K
100K
—
E/W
D130A
ED
Cell Endurance
1K
10K
—
E/W
D131
VPR
VDD for Read
VMIN
—
5.5
V
D132
VPEW
VDD for Erase/Write
4.5
—
5.5
V
D133
TPEW
Erase/Write cycle time
—
2
2.5
ms
D134
TRETD
Characteristic Retention
40
—
—
*
†
Note 1:
2:
3:
4:
5:
+85°C ≤ TA ≤ +125°C
VMIN = Minimum operating
voltage
Year Provided no other specifications
are violated
These parameters are characterized but not tested.
Data in “Typ” column is at 5.0V, 25°C unless otherwise stated. These parameters are for design guidance only and are
not tested.
In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended to use an external
clock in RC mode.
Negative current is defined as current sourced by the pin.
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.
See Section 9.0 “Data EEPROM and Flash Program Memory Control” for additional information.
Including OSC2 in CLKOUT mode.
DS41203E-page 150
© 2009 Microchip Technology Inc.
PIC16F688
14.6
Thermal Considerations
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +125°C
Param
No.
TH01
TH02
TH03
TH04
TH05
TH06
TH07
Note 1:
2:
3:
Sym
θJA
Characteristic
Thermal Resistance
Junction to Ambient
Typ
Units
69.8
85.0
100.4
46.3
32.5
31.0
31.7
2.6
150
—
—
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C
W
W
Conditions
14-pin PDIP package
14-pin SOIC package
14-pin TSSOP package
16-pin QFN 4x0.9mm package
θJC
Thermal Resistance
14-pin PDIP package
Junction to Case
14-pin SOIC package
14-pin TSSOP package
16-pin QFN 4x0.9mm package
TJ
Junction Temperature
For derated power calculations
PD
Power Dissipation
PD = PINTERNAL + PI/O
PINTERNAL Internal Power Dissipation
PINTERNAL = IDD x VDD
(NOTE 1)
PI/O
I/O Power Dissipation
—
W
PI/O = Σ (IOL * VOL) + Σ (IOH * (VDD - VOH))
PDER
Derated Power
—
W
PDER = (TJ - TA)/θJA
(NOTE 2, 3)
IDD is current to run the chip alone without driving any load on the output pins.
TA = Ambient Temperature.
Maximum allowable power dissipation is the lower value of either the absolute maximum total power
dissipation or derated power (PDER).
© 2009 Microchip Technology Inc.
DS41203E-page 151
PIC16F688
14.7
Timing Parameter Symbology
The timing parameter symbols have been created with
one of the following formats:
1. TppS2ppS
2. TppS
T
F
Frequency
Lowercase letters (pp) and their meanings:
pp
cc
CCP1
ck
CLKOUT
cs
CS
di
SDI
do
SDO
dt
Data in
io
I/O PORT
mc
MCLR
Uppercase letters and their meanings:
S
F
Fall
H
High
I
Invalid (High-impedance)
L
Low
FIGURE 14-3:
T
Time
osc
rd
rw
sc
ss
t0
t1
wr
OSC1
RD
RD or WR
SCK
SS
T0CKI
T1CKI
WR
P
R
V
Z
Period
Rise
Valid
High-impedance
LOAD CONDITIONS
Load Condition
Pin
CL
VSS
Legend: CL = 50 pF for all pins
15 pF for OSC2 output
DS41203E-page 152
© 2009 Microchip Technology Inc.
PIC16F688
14.8
AC Characteristics: PIC16F688 (Industrial, Extended)
FIGURE 14-4:
CLOCK TIMING
Q4
Q1
Q2
Q3
Q4
Q1
OSC1/CLKIN
OS02
OS04
OS04
OS03
OSC2/CLKOUT
(LP, XT, HS Modes)
OSC2/CLKOUT
(CLKOUT Mode)
TABLE 14-1:
CLOCK OSCILLATOR TIMING REQUIREMENTS
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +125°C
Param
No.
OS01
Sym
FOSC
Characteristic
External CLKIN Frequency(1)
Oscillator Frequency(1)
OS02
TOSC
External CLKIN Period(1)
Oscillator Period(1)
OS03
OS04*
TCY
TosH,
TosL
Min
Typ†
Max
Units
DC
DC
DC
DC
—
0.1
1
DC
27
250
50
50
—
250
50
250
—
—
—
—
32.768
—
—
—
—
—
—
—
30.5
—
—
—
37
4
20
20
—
4
20
4
•
•
•
•
—
10,000
1,000
—
kHz
MHz
MHz
MHz
kHz
MHz
MHz
MHz
μs
ns
ns
ns
μs
ns
ns
ns
Conditions
LP Oscillator mode
XT Oscillator mode
HS Oscillator mode
EC Oscillator mode
LP Oscillator mode
XT Oscillator mode
HS Oscillator mode
RC Oscillator mode
LP Oscillator mode
XT Oscillator mode
HS Oscillator mode
EC Oscillator mode
LP Oscillator mode
XT Oscillator mode
HS Oscillator mode
RC Oscillator mode
Instruction Cycle Time(1)
External CLKIN High,
External CLKIN Low
200
TCY
DC
ns
TCY = 4/FOSC
2
—
—
μs
LP oscillator
100
—
—
ns
XT oscillator
20
—
—
ns
HS oscillator
OS05* TosR, External CLKIN Rise,
0
—
•
ns
LP oscillator
TosF
External CLKIN Fall
0
—
•
ns
XT oscillator
0
—
•
ns
HS oscillator
* These parameters are characterized but not tested.
† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and
are not tested.
Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period. 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 OSC1 pin. When an external clock input is used, the “max” cycle time limit is “DC” (no clock) for
all devices.
© 2009 Microchip Technology Inc.
DS41203E-page 153
PIC16F688
TABLE 14-2:
OSCILLATOR PARAMETERS
Standard Operating Conditions (unless otherwise stated)
Operating Temperature
-40°C ≤ TA ≤ +125°C
Param
No.
Sym
Characteristic
Freq
Tolerance
Min
Typ†
Max
Units
Conditions
OS06
TWARM
Internal Oscillator Switch
when running(3)
—
—
—
2
TOSC
Slowest clock
OS07
TSC
Fail-Safe Sample Clock
Period(1)
—
—
21
—
ms
LFINTOSC/64
OS08
HFOSC
Internal Calibrated
HFINTOSC Frequency(2)
±1%
7.92
8.0
8.08
MHz
VDD = 3.5V, 25°C
±2%
7.84
8.0
8.16
MHz
2.5V ≤ VDD ≤ 5.5V,
0°C ≤ TA ≤ +85°C
±5%
7.60
8.0
8.40
MHz
2.0V ≤ VDD ≤ 5.5V,
-40°C ≤ TA ≤ +85°C (Ind.),
-40°C ≤ TA ≤ +125°C (Ext.)
—
15
31
45
kHz
OS09*
LFOSC
Internal Uncalibrated
LFINTOSC Frequency
OS10*
TIOSC
HFINTOSC Oscillator
Wake-up from Sleep
Start-up Time
ST
—
5.5
12
24
μs
VDD = 2.0V, -40°C to +85°C
—
3.5
7
14
μs
VDD = 3.0V, -40°C to +85°C
—
3
6
11
μs
VDD = 5.0V, -40°C to +85°C
* These parameters are characterized but not tested.
† 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: Instruction cycle period (TCY) equals four times the input oscillator time base period. 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 pin. When an external clock input is used, the “max” cycle time limit is “DC” (no clock)
for all devices.
2: To ensure these oscillator frequency tolerances, VDD and VSS must be capacitively decoupled as close to the
device as possible. 0.1 μF and 0.01 μF values in parallel are recommended.
3: By design.
DS41203E-page 154
© 2009 Microchip Technology Inc.
PIC16F688
FIGURE 14-5:
CLKOUT AND I/O TIMING
Cycle
Write
Fetch
Read
Execute
Q4
Q1
Q2
Q3
FOSC
OS12
OS11
OS20
OS21
CLKOUT
OS19
OS18
OS16
OS13
OS17
I/O pin
(Input)
OS14
OS15
I/O pin
(Output)
New Value
Old Value
OS18, OS19
TABLE 14-3:
CLKOUT AND I/O TIMING PARAMETERS
Standard Operating Conditions (unless otherwise stated)
Operating Temperature -40°C ≤ TA ≤ +125°C
Param
No.
Sym
Characteristic
Min
Typ†
Max
Units
Conditions
TOSH2CKL
FOSC↑ to CLKOUT↓ (1)
—
—
70
ns
VDD = 5.0V
OS12
TOSH2CKH
FOSC↑ to CLKOUT↑
—
—
72
ns
VDD = 5.0V
OS13
TCKL2IOV
CLKOUT↓ to Port out valid(1)
—
—
20
ns
OS14
TIOV2CKH
Port input valid before CLKOUT↑(1)
TOSC + 200 ns
—
—
ns
OS15*
TOSH2IOV
FOSC↑ (Q1 cycle) to Port out valid
—
50
70
ns
VDD = 5.0V
OS16
TOSH2IOI
FOSC↑ (Q2 cycle) to Port input invalid
(I/O in hold time)
50
—
—
ns
VDD = 5.0V
OS17
TIOV2OSH
Port input valid to FOSC↑ (Q2 cycle)
(I/O in setup time)
20
—
—
ns
OS18
TIOR
Port output rise time(2)
—
—
15
10
72
32
ns
VDD = 2.0V
VDD = 5.0V
OS19
TIOF
Port output fall time(2)
—
—
28
15
55
30
ns
VDD = 2.0V
VDD = 5.0V
OS20*
TINP
INT pin input high or low time
25
—
—
ns
OS21*
TRAP
PORTA interrupt-on-change new input
level time
TCY
—
—
ns
OS11
*
†
Note 1:
2:
(1)
These parameters are characterized but not tested.
Data in “Typ” column is at 5.0V, 25°C unless otherwise stated.
Measurements are taken in RC mode where CLKOUT output is 4 x TOSC.
Includes OSC2 in CLKOUT mode.
© 2009 Microchip Technology Inc.
DS41203E-page 155
PIC16F688
FIGURE 14-6:
RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER AND
POWER-UP TIMER TIMING
VDD
MCLR
30
Internal
POR
33
PWRT
Time-out
32
OSC
Start-Up Time
Internal Reset(1)
Watchdog Timer
Reset(1)
31
34
34
I/O pins
Note 1:
Asserted low.
FIGURE 14-7:
BROWN-OUT RESET TIMING AND CHARACTERISTICS
VDD
VBOR + VHYST
VBOR
(Device in Brown-out Reset)
(Device not in Brown-out Reset)
37
Reset
(due to BOR)
*
33*
64 ms delay only if PWRTE bit in the Configuration Word register is programmed to ‘0’.
DS41203E-page 156
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 14-4:
RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER, POWER-UP TIMER
AND BROWN-OUT RESET PARAMETERS
Standard Operating Conditions (unless otherwise stated)
Operating Temperature -40°C ≤ TA ≤ +125°C
Param
No.
Sym
Characteristic
Min
Typ†
Max
Units
Conditions
30
TMCL
MCLR Pulse Width (low)
2
5
—
—
—
—
μs
μs
VDD = 5V, -40°C to +85°C
VDD = 5V
31
TWDT
Watchdog Timer Time-out
Period (No Prescaler)
10
10
16
16
29
31
ms
ms
VDD = 5V, -40°C to +85°C
VDD = 5V
32
TOST
Oscillation Start-up Timer
Period(1, 2)
—
1024
—
33*
TPWRT
Power-up Timer Period
40
65
140
ms
34*
TIOZ
I/O High-impedance from
MCLR Low or Watchdog Timer
Reset
—
—
2.0
μs
35
VBOR
Brown-out Reset Voltage
2.0
—
2.2
V
36*
VHYST
Brown-out Reset Hysteresis
—
50
—
mV
37*
TBOR
Brown-out Reset Minimum
Detection Period
100
—
—
μs
TOSC (NOTE 3)
(NOTE 4)
VDD ≤ VBOR
* These parameters are characterized but not tested.
† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance
only and are not tested.
Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period. 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 pin. When an external clock input is used, the “max” cycle time
limit is “DC” (no clock) for all devices.
2: By design.
3: Period of the slower clock.
4: To ensure these voltage tolerances, VDD and VSS must be capacitively decoupled as close to the device as
possible. 0.1 μF and 0.01 μF values in parallel are recommended.
© 2009 Microchip Technology Inc.
DS41203E-page 157
PIC16F688
FIGURE 14-8:
TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS
T0CKI
40
41
42
T1CKI
45
46
49
47
TMR0 or
TMR1
TABLE 14-5:
TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS
Standard Operating Conditions (unless otherwise stated)
Operating Temperature
-40°C ≤ TA ≤ +125°C
Param
No.
40*
Sym
TT0H
Characteristic
T0CKI High Pulse Width
No Prescaler
With Prescaler
41*
TT0L
T0CKI Low Pulse Width
No Prescaler
42*
TT0P
T0CKI Period
45*
TT1H
T1CKI High Synchronous, No Prescaler
Time
Synchronous,
with Prescaler
With Prescaler
Asynchronous
46*
TT1L
T1CKI Low
Time
Synchronous, No Prescaler
Synchronous,
with Prescaler
Asynchronous
47*
TT1P
T1CKI Input Synchronous
Period
48
FT1
Timer1 Oscillator Input Frequency Range
(oscillator enabled by setting bit T1OSCEN)
49*
TCKEZTMR1 Delay from External Clock Edge to Timer
Increment
Asynchronous
*
†
Min
Typ†
Max
Units
0.5 TCY + 20
—
—
ns
10
—
—
ns
0.5 TCY + 20
—
—
ns
10
—
—
ns
Greater of:
20 or TCY + 40
N
—
—
ns
0.5 TCY + 20
—
—
ns
15
—
—
ns
30
—
—
ns
0.5 TCY + 20
—
—
ns
15
—
—
ns
30
—
—
ns
Greater of:
30 or TCY + 40
N
—
—
ns
60
—
—
ns
—
32.768
—
kHz
2 TOSC
—
7 TOSC
—
Conditions
N = prescale value
(2, 4, ..., 256)
N = prescale value
(1, 2, 4, 8)
Timers in Sync
mode
These parameters are characterized but not tested.
Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not
tested.
DS41203E-page 158
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 14-6:
COMPARATOR SPECIFICATIONS
Standard Operating Conditions (unless otherwise stated)
Operating Temperature -40°C ≤ TA ≤ +125°C
Param
No.
Sym
Characteristics
CM01
VOS
Input Offset Voltage
CM02
VCM
Input Common Mode Voltage
CM03* CMRR
Common Mode Rejection Ratio
CM04* TRT
Response Time
Min
Typ†
Max
Units
—
± 5.0
± 10
mV
0
—
VDD – 1.5
V
+55
—
—
dB
Falling
—
150
600
ns
Rising
—
200
1000
ns
—
—
10
μs
CM05* TMC2COV Comparator Mode Change to
Output Valid
Comments
(VDD - 1.5)/2
(NOTE 1)
* These parameters are characterized but not tested.
† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance
only and are not tested.
Note 1: Response time is measured with one comparator input at (VDD - 1.5)/2 - 100 mV to (VDD - 1.5)/2 + 20 mV.
TABLE 14-7:
COMPARATOR VOLTAGE REFERENCE (CVREF) SPECIFICATIONS
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +125°C
Param
No.
Sym
Characteristics
Min
Typ†
Max
Units
Comments
CV01*
CLSB
Step Size(2)
—
—
VDD/24
VDD/32
—
—
V
V
Low Range (VRR = 1)
High Range (VRR = 0)
CV02*
CACC
Absolute Accuracy
—
—
—
—
± 1/2
± 1/2
LSb
LSb
Low Range (VRR = 1)
High Range (VRR = 0)
CV03*
CR
Unit Resistor Value (R)
—
2k
—
Ω
CV04*
CST
Settling Time(1)
—
—
10
μs
* These parameters are characterized but not tested.
† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design
guidance only and are not tested.
Note 1: Settling time measured while VRR = 1 and VR<3:0> transitions from ‘0000’ to ‘1111’.
2: See Section 7.10 “Comparator Voltage Reference” for more information.
© 2009 Microchip Technology Inc.
DS41203E-page 159
PIC16F688
TABLE 14-8:
PIC16F688 A/D CONVERTER (ADC) CHARACTERISTICS
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +125°C
Param
Sym
No.
Characteristic
Min
Typ†
Max
Units
Conditions
AD01
NR
Resolution
—
—
10 bits
AD02
EIL
Integral Error
—
—
±1
LSb VREF = 5.12V
AD03
EDL
Differential Error
—
—
±1
LSb No missing codes to 10 bits
VREF = 5.12V
AD04
EOFF
Offset Error
—
—
±1
LSb VREF = 5.12V
AD07
EGN
LSb VREF = 5.12V
bit
Gain Error
—
—
±1
AD06 VREF
AD06A
Reference Voltage(1)
2.2
2.7
—
—
VDD
V
AD07
VAIN
Full-Scale Range
VSS
—
VREF
V
AD08
ZAIN
Recommended
Impedance of Analog
Voltage Source
—
—
10
kΩ
AD09* IREF
VREF Input Current(1)
10
—
1000
μA
During VAIN acquisition.
Based on differential of VHOLD to VAIN.
—
—
50
μA
During A/D conversion cycle.
Absolute minimum to ensure 1 LSb
accuracy
* These parameters are characterized but not tested.
† 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: ADC VREF is from external VREF or VDD pin, whichever is selected as reference input.
DS41203E-page 160
© 2009 Microchip Technology Inc.
PIC16F688
TABLE 14-9:
PIC16F688 A/D CONVERSION REQUIREMENTS
Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +125°C
Param
No.
Sym
AD130* TAD
Characteristic
A/D Clock Period
A/D Internal RC
Oscillator Period
AD131 TCNV
Conversion Time
(not including
Acquisition Time)(1)
Min
Typ†
1.6
—
9.0
μs
TOSC-based, VREF ≥ 3.0V
3.0
—
9.0
μs
TOSC-based, VREF full range
3.0
6.0
9.0
μs
ADCS<1:0> = 11 (ADRC mode)
At VDD = 2.5V
1.6
4.0
6.0
μs
At VDD = 5.0V
—
11
—
TAD
Set GO/DONE bit to new data in A/D
Result register
11.5
—
μs
Amplifier Settling Time
—
—
5
μs
Q4 to A/D Clock Start
—
TOSC/2
—
—
—
TOSC/2 + TCY
—
—
AD132* TACQ Acquisition Time
AD133*
TAMP
AD134 TGO
Max Units
Conditions
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.
* These parameters are characterized but not tested.
† 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: ADRESH and ADRESL registers may be read on the following TCY cycle.
2: See Section 8.3 “A/D Acquisition Requirements” for minimum conditions.
© 2009 Microchip Technology Inc.
DS41203E-page 161
PIC16F688
FIGURE 14-9:
PIC16F688 A/D CONVERSION TIMING (NORMAL MODE)
BSF ADCON0, GO
AD134
1 TCY
(TOSC/2(1))
AD131
Q4
AD130
A/D CLK
9
A/D Data
8
7
6
3
2
1
0
NEW_DATA
OLD_DATA
ADRES
1 TCY
ADIF
GO
DONE
Note 1:
Sampling Stopped
AD132
Sample
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.
FIGURE 14-10:
PIC16F688 A/D CONVERSION TIMING (SLEEP MODE)
BSF ADCON0, GO
AD134
(TOSC/2 + TCY(1))
1 TCY
AD131
Q4
AD130
A/D CLK
9
A/D Data
8
7
6
OLD_DATA
ADRES
3
2
1
0
NEW_DATA
ADIF
1 TCY
GO
DONE
Sample
Note 1:
AD132
Sampling Stopped
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.
DS41203E-page 162
© 2009 Microchip Technology Inc.
PIC16F688
15.0
DC AND AC CHARACTERISTICS GRAPHS AND TABLES
The graphs and tables provided in this section are for design guidance and are not tested.
In some graphs or tables, the data presented are outside specified operating range (i.e., outside specified VDD
range). This is for information only and devices are ensured to operate properly only within the specified range.
Note:
The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein are
not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore, outside the warranted range.
“Typical” represents the mean of the distribution at 25°C. “Maximum” or “minimum” represents
(mean + 3σ) or (mean - 3σ) respectively, where σ is a standard deviation, over each temperature range.
FIGURE 15-1:
TYPICAL IDD vs. FOSC OVER VDD (EC MODE)
3.5
3.0
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
5.5V
5.0V
IDD (mA)
2.5
2.0
4.0V
1.5
3.0V
1.0
2.0V
0.5
0.0
1 MHz
2 MHz
4 MHz
6 MHz
8 MHz
10 MHz
12 MHz
14 MHz
16 MHz
18 MHz
20 MHz
FOSC
© 2009 Microchip Technology Inc.
DS41203E-page 163
PIC16F688
FIGURE 15-2:
MAXIMUM IDD vs. FOSC OVER
VDD (EC MODE)
EC Mode
4.0
3.5
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
5.5V
5.0V
3.0
IDD (mA)
2.5
4.0V
2.0
3.0V
1.5
2.0V
1.0
0.5
0.0
1 MHz
2 MHz
4 MHz
6 MHz
8 MHz
10 MHz
12 MHz
14 MHz
16 MHz
18 MHz
20 MHz
FOSC
FIGURE 15-3:
TYPICAL IDD vs. FOSC OVER VDD (HS MODE)
4.0
3.5
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C
to 125°C)
Temp)+
5.5V
5,0V
3.0
4.5V
IDD (mA)
2.5
2.0
1.5
4.0V
3.5V
3.0V
1.0
0.5
0.0
4 MHz
10 MHz
16 MHz
20 MHz
FOSC
© 2009 Microchip Technology Inc.
DS41203E-page 164
PIC16F688
FIGURE 15-4:
MAXIMUM IDD vs. FOSC OVER VDD (HS MODE)
5.0
4.5
Typical:
Typical: Statistical
Statistical Mean
Mean @25°C
@25×C
Maximum:
Maximum: Mean
Mean (Worst-case
(Worst CaseTemp) + 3σ
(-40°C
Temp)+to
3 125°C)
4.0
5.5V
5.0V
IDD (mA)
3.5
4.5V
3.0
2.5
2.0
4.0V
3.5V
3.0V
1.5
1.0
0.5
0.0
4 MHz
10 MHz
16 MHz
20 MHz
FOSC
TYPICAL IDD vs. VDD OVER FOSC (XT MODE)
FIGURE 15-5:
1200
@25°C
Typical: Statistical Mean @25×C
Maximum: Mean (Worst
Case Temp)
Temp) ++ 3σ
(Worst-case
1000
IDD (uA)
800
600
4 MHz
400
1 MHz
200
0
2
2.5
3
3.5
4
4.5
5
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 165
PIC16F688
FIGURE 15-6:
MAXIMUM IDD vs. VDD OVER FOSC (XT MODE)
1,800
1,600
1,400
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
IDD (uA)
1,200
1,000
4 MHz
800
600
400
1 MHz
200
0
2
2.5
3
3.5
4
4.5
5
5.5
VDD (V)
FIGURE 15-7:
TYPICAL IDD vs. VDD OVER FOSC (EXTRC MODE)
1,200
1,000
Typical:
Mean
@25×C
Typical:Statistical
Statistical
Mean
@25°C
Maximum: Mean (Worst Case Temp) +
Maximum:
Mean
(Worst-case
Temp) + 3σ
3
125°C)
((-40°C
40×Ct to
125×C)
4 MHz
IDD (uA)
800
600
1 MHz
400
200
0
2
2.5
3
3.5
4
4.5
5
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 166
PIC16F688
FIGURE 15-8:
MAXIMUM IDD vs. VDD (EXTRC MODE)
2,000
Typical: Statistical Mean @25°C
Maximum:
Maximum:Mean
Mean(Worst-case
(Worst CaseTemp)
Temp)+ +3s3
(-40×Ctoto125°C)
125×C)
(-40°C
1,800
1,600
1,400
4 MHz
IDD (uA)
1,200
1,000
800
1 MHz
600
400
200
0
2
2.5
3
3.5
4
4.5
5
5.5
VDD (V)
FIGURE 15-9:
IDD vs. VDD OVER FOSC (LFINTOSC MODE, 31 kHz)
LFINTOSC Mode, 31KHZ
80
70
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
60
IDD (μA)
50
Maximum
40
30
Typical
20
10
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 167
PIC16F688
FIGURE 15-10:
IDD vs. VDD (LP MODE)
90
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
80
70
IDD (uA)
60
32 kHz Maximum
50
40
30
32 kHz Typical
20
10
0
2
2.5
3
3.5
4
4.5
5
5.5
VDD (V)
FIGURE 15-11:
TYPICAL IDD vs. FOSC OVER
VDD (HFINTOSC MODE)
HFINTOSC
1,800
1,600
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
5.5V
5.0V
1,400
1,200
IDD (uA)
4.0V
1,000
3.0V
800
600
2.0V
400
200
0
125 kHz
250 kHz
500 kHz
1 MHz
2 MHz
4 MHz
8 MHz
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 168
PIC16F688
FIGURE 15-12:
MAXIMUM IDD vs. FOSC OVER VDD (HFINTOSC MODE)
2,500
2,000
Typical: Statistical Mean @ 25°C
Maximum: Mean (Worst-case Temp) +3σ
(-40°C to 125°C)
5.5V
5.0V
IDD (uA)
1,500
4.0V
3.0V
1,000
2.0V
500
0
125 kHz
250 kHz
500 kHz
1 MHz
2 MHz
4 MHz
8 MHz
VDD (V)
FIGURE 15-13:
TYPICAL IPD vs. VDD (SLEEP MODE, ALL PERIPHERALS DISABLED)
Typical
(Sleep Mode all Peripherals Disabled)
0.45
0.40
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
0.35
IPD (μA)
0.30
0.25
0.20
0.15
0.10
0.05
0.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 169
PIC16F688
FIGURE 15-14:
MAXIMUM IPD vs. VDD (SLEEP MODE, ALL PERIPHERALS DISABLED)
Maximum
(Sleep Mode all Peripherals Disabled)
18.0
16.0
Typical: Statistical Mean @25°C
Maximum:
Mean +
3σ
Maximum: Mean
(Worst-case
Temp) + 3σ
(-40°C to 125°C)
14.0
Max. 125°C
IPD (μA)
12.0
10.0
8.0
6.0
4.0
Max. 85°C
2.0
0.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-15:
COMPARATOR IPD vs. VDD (BOTH COMPARATORS ENABLED)
180
160
140
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
IPD (μA)
120
Maximum
100
Typical
80
60
40
20
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 170
PIC16F688
FIGURE 15-16:
BOR IPD vs. VDD OVER TEMPERATURE
160
140
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
120
IPD (μA)
100
Maximum
80
Typical
60
40
20
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-17:
TYPICAL WDT IPD vs. VDD (25°C)
3.0
2.5
IPD (uA)
2.0
1.5
1.0
0.5
0.0
2.0V
2.5V
3.0V
3.5V
4.0V
4.5V
5.0V
5.5V
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 171
PIC16F688
FIGURE 15-18:
MAXIMUM WDT IPD vs. VDD OVER TEMPERATURE
40.0
35.0
Max. 125°C
30.0
IPD (uA)
25.0
20.0
15.0
10.0
Max. 85°C
5.0
0.0
2.0V
2.5V
3.0V
3.5V
4.0V
4.5V
5.0V
4.5
5.0
5.5V
VDD (V)
FIGURE 15-19:
WDT PERIOD vs. VDD OVER TEMPERATURE
30
28
Typical: Statistical Mean @25°C
Maximum: Mean + 3σ (-40°C to 125°C)
Maximum: Mean + 3σ
Max. (125°C)
26
Max. (85°C)
24
Time (ms)
22
20
Typical
18
16
14
Minimum
12
10
2.0
2.5
3.0
3.5
4.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 172
PIC16F688
FIGURE 15-20:
WDT PERIOD vs. TEMPERATURE
Vdd = 5V
30
28
Typical: Statistical Mean @25°C
Maximum: Mean + 3σ
26
Maximum
24
Time (ms)
22
20
Typical
18
16
Minimum
14
12
10
-40°C
25°C
85°C
125°C
Temperature (°C)
FIGURE 15-21:
CVREF IPD vs. VDD OVER TEMPERATURE (HIGH RANGE)
High Range
140
120
Typical: Statistical Mean @25°C
Maximum: Mean + 3σ (-40°C to 125°C)
100
IPD (μA)
Max. 125°C
80
Max. 85°C
60
Typical
40
20
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 173
PIC16F688
FIGURE 15-22:
CVREF IPD vs. VDD OVER TEMPERATURE (LOW RANGE)
180
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
160
140
120
IPD (μA)
Max. 125°C
100
Max. 85°C
80
Typical
60
40
20
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-23:
VOL vs. IOL OVER TEMPERATURE (VDD = 3.0V)
(VDD = 3V, -40×C TO 125×C)
0.8
0.7
Typical: Statistical Mean @25°C
Maximum: Mean + 3σ
Max. 125°C
0.6
VOL (V)
0.5
Max. 85°C
0.4
Typical 25°C
0.3
0.2
Min. -40°C
0.1
0.0
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
IOL (mA)
© 2009 Microchip Technology Inc.
DS41203E-page 174
PIC16F688
FIGURE 15-24:
VOL vs. IOL OVER TEMPERATURE (VDD = 5.0V)
0.45
Typical: Statistical Mean @25°C
Typical:
Statistical
Maximum:
Mean
+ 3σ Mean
Maximum: Means + 3
0.40
Max. 125°C
0.35
Max. 85°C
VOL (V)
0.30
0.25
Typ. 25°C
0.20
0.15
Min. -40°C
0.10
0.05
0.00
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
IOL (mA)
FIGURE 15-25:
VOH vs. IOH OVER TEMPERATURE (VDD = 3.0V)
3.5
3.0
Max. -40°C
Typ. 25°C
2.5
Min. 125°C
VOH (V)
2.0
1.5
1.0
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
0.5
0.0
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
IOH (mA)
© 2009 Microchip Technology Inc.
DS41203E-page 175
PIC16F688
FIGURE 15-26:
VOH vs. IOH OVER TEMPERATURE
(VDD = 5.0V)
(
,
)
5.5
5.0
Max. -40°C
Typ. 25°C
VOH (V)
4.5
Min. 125°C
4.0
3.5
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
3.0
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
-4.5
-5.0
IOH (mA)
FIGURE 15-27:
TTL INPUT THRESHOLD VIN vs. VDD OVER TEMPERATURE
(TTL Input, -40×C TO 125×C)
1.7
1.5
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
Max. -40°C
VIN (V)
1.3
Typ. 25°C
1.1
Min. 125°C
0.9
0.7
0.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 176
PIC16F688
FIGURE 15-28:
SCHMITT TRIGGER INPUT THRESHOLD VIN vs. VDD OVER TEMPERATURE
(ST Input, -40×C TO 125×C)
4.0
VIH Max. 125°C
3.5
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
VIH Min. -40°C
VIN (V)
3.0
2.5
2.0
VIL Max. -40°C
1.5
VIL Min. 125°C
1.0
0.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-29:
T1OSC IPD vs. VDD OVER TEMPERATURE (32 kHz)
45.0
40.0
Typical: Statistical Mean @25°C
Maximum: Mean
Mean
(Worst-case
Temp) + 3σ
Maximum:
(-40×C
+
3 to 125×C)
(-40°C to 125°C)
35.0
Max. 125°C
IPD (mA)
30.0
25.0
20.0
15.0
Max. 85°C
10.0
5.0
Typ. 25°C
0.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 177
PIC16F688
FIGURE 15-30:
COMPARATOR RESPONSE TIME (RISING EDGE)
531
806
1000
900
Max. 125°C
Response Time (nS)
800
700
600
Note:
500
VCM = VDD - 1.5V)/2
V+ input = VCM
V- input = Transition from VCM + 100MV to VCM - 20MV
Max. 85°C
400
300
Typ. 25°C
200
Min. -40°C
100
0
2.0
2.5
4.0
5.5
VDD (V)
FIGURE 15-31:
COMPARATOR RESPONSE TIME (FALLING EDGE)
1000
900
Max. 125°C
800
Response Time (nS)
700
600
500
Note:
VCM = VDD - 1.5V)/2
V+ input = VCM
V- input = Transition from VCM - 100MV to VCM + 20MV
Max. 85°C
400
300
Typ. 25°C
200
Min. -40°C
100
0
2.0
2.5
4.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 178
PIC16F688
FIGURE 15-32:
LFINTOSC FREQUENCY vs. VDD OVER TEMPERATURE (31 kHz)
LFINTOSC 31Khz
45,000
40,000
Max. -40°C
35,000
Typ. 25°C
Frequency (Hz)
30,000
25,000
20,000
Min. 85°C
Min. 125°C
15,000
10,000
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
5,000
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-33:
ADC CLOCK PERIOD vs. VDD OVER TEMPERATURE
8
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
125°C
6
Time (μs)
85°C
4
25°C
-40°C
2
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 179
PIC16F688
FIGURE 15-34:
TYPICAL HFINTOSC START-UP TIMES vs. VDD OVER TEMPERATURE
16
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
14
85°C
12
25°C
Time (μs)
10
-40°C
8
6
4
2
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-35:
MAXIMUM HFINTOSC START-UP TIMES vs. VDD OVER TEMPERATURE
-40C to +85C
25
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
Time (μs)
20
15
85°C
25°C
10
-40°C
5
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 180
PIC16F688
FIGURE 15-36:
MINIMUM HFINTOSC START-UP TIMES vs. VDD OVER TEMPERATURE
-40C to +85C
10
9
Typical: Statistical Mean @25°C
Maximum: Mean (Worst-case Temp) + 3σ
(-40°C to 125°C)
8
7
Time (μs)
85°C
6
25°C
5
-40°C
4
3
2
1
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-37:
TYPICAL HFINTOSC FREQUENCY CHANGE vs. VDD (25°C)
5
4
Change from Calibration (%)
3
2
1
0
-1
-2
-3
-4
-5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 181
PIC16F688
FIGURE 15-38:
TYPICAL HFINTOSC FREQUENCY CHANGE OVER DEVICE VDD (85°C)
5
4
Change from Calibration (%)
3
2
1
0
-1
-2
-3
-4
-5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
FIGURE 15-39:
TYPICAL HFINTOSC FREQUENCY CHANGE vs. VDD (125°C)
5
4
Change from Calibration (%)
3
2
1
0
-1
-2
-3
-4
-5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 182
PIC16F688
FIGURE 15-40:
TYPICAL HFINTOSC FREQUENCY CHANGE vs. VDD (-40°C)
5
4
Change from Calibration (%)
3
2
1
0
-1
-2
-3
-4
-5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
© 2009 Microchip Technology Inc.
DS41203E-page 183
PIC16F688
NOTES:
© 2009 Microchip Technology Inc.
DS41203E-page 184
PIC16F688
16.0
PACKAGING INFORMATION
16.1
Package Marking Information
14-Lead PDIP (Skinny DIP)
XXXXXXXXXXXXXX
XXXXXXXXXXXXXX
YYWWNNN
14-Lead SOIC (3.90 mm)
XXXXXXXXXXX
XXXXXXXXXXX
YYWWNNN
14-Lead TSSOP
XXXXXXXX
YYWW
NNN
16-Lead QFN
Legend: XX...X
Y
YY
WW
NNN
e3
*
*
PIC16F688
-I/P e3
0610017
Example
PIC16C688
-I/SL e3
0610017
Example
688/ST e3
0610
017
Example
XXXXXX
XXXXXX
YWWNNN
Note:
Example
16F688
-I/ML e3
610017
Customer-specific information
Year code (last digit of calendar year)
Year code (last 2 digits of calendar year)
Week code (week of January 1 is week ‘01’)
Alphanumeric traceability code
Pb-free JEDEC designator for Matte Tin (Sn)
This package is Pb-free. The Pb-free JEDEC designator ( e3 )
can be found on the outer packaging for this package.
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.
Standard PIC® device marking consists of Microchip part number, year code, week code, and traceability
code. For PIC device marking beyond this, certain price adders apply. Please check with your Microchip
Sales Office. For QTP devices, any special marking adders are included in QTP price.
© 2009 Microchip Technology Inc.
DS41203E-page 185
PIC16F688
16.2
Package Details
The following sections give the technical details of the packages.
3
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NOTE 1
E1
1
3
2
D
E
A2
A
L
A1
c
b1
b
e
eB
6%
& 9&%
7!&(
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%
0
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,0
0
0
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0
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0
9"4
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0
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DS41203E-page 186
© 2009 Microchip Technology Inc.
PIC16F688
14-Lead Plastic Small Outline (SL) – Narrow, 3.90 mm Body [SOIC]
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
D
N
E
E1
NOTE 1
1
2
3
e
h
b
α
h
A
A2
c
φ
L
A1
β
L1
Units
Dimension Limits
Number of Pins
MILLMETERS
MIN
N
NOM
MAX
14
Pitch
e
Overall Height
A
–
1.27 BSC
–
Molded Package Thickness
A2
1.25
–
–
Standoff §
A1
0.10
–
0.25
Overall Width
E
Molded Package Width
E1
3.90 BSC
Overall Length
D
8.65 BSC
1.75
6.00 BSC
Chamfer (optional)
h
0.25
–
0.50
Foot Length
L
0.40
–
1.27
Footprint
L1
1.04 REF
Foot Angle
φ
0°
–
8°
Lead Thickness
c
0.17
–
0.25
Lead Width
b
0.31
–
0.51
Mold Draft Angle Top
α
5°
–
15°
Mold Draft Angle Bottom
β
5°
–
15°
Notes:
1. Pin 1 visual index feature may vary, but must be located within the hatched area.
2. § Significant Characteristic.
3. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side.
4. Dimensioning and tolerancing per ASME Y14.5M.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
REF: Reference Dimension, usually without tolerance, for information purposes only.
Microchip Technology Drawing C04-065B
© 2009 Microchip Technology Inc.
DS41203E-page 187
PIC16F688
3
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DS41203E-page 188
© 2009 Microchip Technology Inc.
PIC16F688
14-Lead Plastic Thin Shrink Small Outline (ST) – 4.4 mm Body [TSSOP]
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
D
N
E
E1
NOTE 1
1 2
e
b
c
φ
A2
A
A1
Units
Dimension Limits
Number of Pins
L
L1
MILLIMETERS
MIN
N
NOM
MAX
14
Pitch
e
Overall Height
A
–
0.65 BSC
–
Molded Package Thickness
A2
0.80
1.00
1.05
Standoff
A1
0.05
–
0.15
1.20
Overall Width
E
Molded Package Width
E1
4.30
6.40 BSC
4.40
Molded Package Length
D
4.90
5.00
5.10
Foot Length
L
0.45
0.60
0.75
Footprint
L1
4.50
1.00 REF
Foot Angle
φ
0°
–
8°
Lead Thickness
c
0.09
–
0.20
Lead Width
b
0.19
–
0.30
Notes:
1. Pin 1 visual index feature may vary, but must be located within the hatched area.
2. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15 mm per side.
3. Dimensioning and tolerancing per ASME Y14.5M.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
REF: Reference Dimension, usually without tolerance, for information purposes only.
Microchip Technology Drawing C04-087B
© 2009 Microchip Technology Inc.
DS41203E-page 189
PIC16F688
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
DS41203E-page 190
© 2009 Microchip Technology Inc.
PIC16F688
16-Lead Plastic Quad Flat, No Lead Package (ML) – 4x4x0.9 mm Body [QFN]
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
D2
D
EXPOSED
PAD
e
E2
E
2
2
1
1
b
TOP VIEW
K
N
N
NOTE 1
L
BOTTOM VIEW
A3
A
A1
Units
Dimension Limits
Number of Pins
MILLIMETERS
MIN
N
NOM
MAX
16
Pitch
e
Overall Height
A
0.80
0.65 BSC
0.90
1.00
Standoff
A1
0.00
0.02
0.05
Contact Thickness
A3
0.20 REF
Overall Width
E
Exposed Pad Width
E2
Overall Length
D
Exposed Pad Length
D2
2.50
2.65
2.80
b
0.25
0.30
0.35
Contact Length
L
0.30
0.40
0.50
Contact-to-Exposed Pad
K
0.20
–
–
Contact Width
4.00 BSC
2.50
2.65
2.80
4.00 BSC
Notes:
1. Pin 1 visual index feature may vary, but must be located within the hatched area.
2. Package is saw singulated.
3. Dimensioning and tolerancing per ASME Y14.5M.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
REF: Reference Dimension, usually without tolerance, for information purposes only.
Microchip Technology Drawing C04-127B
© 2009 Microchip Technology Inc.
DS41203E-page 191
PIC16F688
3
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DS41203E-page 192
© 2009 Microchip Technology Inc.
PIC16F688
APPENDIX A:
DATA SHEET
REVISION HISTORY
Revision A
APPENDIX B:
MIGRATING FROM
OTHER PIC®
DEVICES
This is a new data sheet.
This discusses some of the issues in migrating from
other PIC devices to the PIC16F6XX family of devices.
Revision B
B.1
Rewrites of the Oscillator and Special Features of the
CPU Sections. General corrections to Figures and
formatting.
TABLE B-1:
Revision C
Revised Electrical Section and added Char Data.
Added Golden Chapters.
PIC16F676 to PIC16F688
FEATURE COMPARISON
Feature
PIC16F676
PIC16F688
Max Operating Speed
20 MHz
20 MHz
Max Program Memory
(Words)
1024
4K
SRAM (Bytes)
64
256
A/D Resolution
10-bit
10-bit
Revision D
Data EEPROM (bytes)
128
256
Replaced Package Drawings; Revised Product ID (SL
Package to 3.90 mm); Replaced PICmicro with PIC;
Replaced Dev. Tool Section.
Timers (8/16-bit)
1/1
1/1
Oscillator Modes
8
8
Revision E
Updated Peripheral Features, page 1; Deleted Note 1,
page 13; Updated the Typical Info. in Param. OS18,
Table 14-3; Added sub-section 10.3.2 (Auto-Baud
Overflow, page 100) to Chapter 10; Added SOIC,
TSSOP, QFN Package Land Patterns.
Brown-out Reset
Y
Y
Internal Pull-ups
RA0/1/2/4/5
RA0/1/2/4/5,
MCLR
RA0/1/2/3
/4/5
RA0/1/2/3/4/5
Interrupt-on-change
Comparator
1
2
EUSART
N
Y
Ultra Low-Power
Wake-up
N
Y
Extended WDT
N
Y
Software Control
Option of WDT/BOR
N
Y
INTOSC Frequencies
4 MHz
32 kHz 8 MHz
N
Y
Clock Switching
Note:
© 2009 Microchip Technology Inc.
This device has been designed to perform
to the parameters of its data sheet. It has
been tested to an electrical specification
designed to determine its conformance
with these parameters. Due to process
differences in the manufacture of this
device, this device may have different
performance characteristics than its earlier
version. These differences may cause this
device to perform differently in your
application than the earlier version of this
device.
DS41203E-page 193
PIC16F688
NOTES:
DS41203E-page 194
© 2009 Microchip Technology Inc.
PIC16F688
INDEX
A
A/D
Specifications.................................................... 160, 161
Absolute Maximum Ratings .............................................. 143
AC Characteristics
Industrial and Extended ............................................ 153
Load Conditions ........................................................ 152
ADC .................................................................................... 65
Acquisition Requirements ........................................... 73
Associated registers.................................................... 75
Block Diagram............................................................. 65
Calculating Acquisition Time....................................... 73
Channel Selection....................................................... 66
Configuration............................................................... 66
Configuring Interrupt ................................................... 69
Conversion Clock........................................................ 66
Conversion Procedure ................................................ 69
Internal Sampling Switch (RSS) Impedance................ 73
Interrupts..................................................................... 68
Operation .................................................................... 69
Operation During Sleep .............................................. 69
Port Configuration ....................................................... 66
Reference Voltage (VREF)........................................... 66
Result Formatting........................................................ 68
Source Impedance...................................................... 73
Starting an A/D Conversion ........................................ 68
ADCON0 Register............................................................... 71
ADCON1 Register............................................................... 71
ADRESH Register (ADFM = 0) ........................................... 72
ADRESH Register (ADFM = 1) ........................................... 72
ADRESL Register (ADFM = 0)............................................ 72
ADRESL Register (ADFM = 1)............................................ 72
Analog Front-end (AFE)
Power-On Reset ....................................................... 113
Analog Input Connection Considerations............................ 55
Analog-to-Digital Converter. See ADC
ANSEL Register .................................................................. 34
Assembler
MPASM Assembler................................................... 140
B
BAUDCTL Register ............................................................. 94
Block Diagrams
ADC ............................................................................ 65
ADC Transfer Function ............................................... 74
Analog Input Model ............................................... 55, 74
Clock Source............................................................... 21
Comparator 1 .............................................................. 54
Comparator 2 .............................................................. 54
Comparator Modes ..................................................... 57
Crystal Operation ........................................................ 24
EUSART Receive ....................................................... 84
EUSART Transmit ...................................................... 83
External RC Mode....................................................... 25
Fail-Safe Clock Monitor (FSCM) ................................. 31
In-Circuit Serial Programming Connections.............. 127
Interrupt Logic ........................................................... 120
MCLR Circuit............................................................. 113
On-Chip Reset Circuit ............................................... 112
PIC16F688.................................................................... 5
RA1 Pins ..................................................................... 38
RA2 Pin....................................................................... 38
RA3 Pin....................................................................... 39
RA4 Pin....................................................................... 39
© 2009 Microchip Technology Inc.
RA5 Pin ...................................................................... 40
RC0 and RC1 Pins ..................................................... 43
RC2 and RC3 Pins ..................................................... 43
RC4 Pin ...................................................................... 44
RC5 Pin ...................................................................... 44
Resonator Operation .................................................. 24
Timer1 ........................................................................ 48
TMR0/WDT Prescaler ................................................ 45
Watchdog Timer (WDT)............................................ 123
Break Character (12-bit) Transmit and Receive ............... 101
Brown-out Reset (BOR).................................................... 114
Associated ................................................................ 115
Specifications ........................................................... 157
Timing and Characteristics ....................................... 156
C
C Compilers
MPLAB C18.............................................................. 140
MPLAB C30.............................................................. 140
Clock Accuracy with Asynchronous Operation ................... 92
Clock Sources
External Modes........................................................... 23
EC ...................................................................... 23
HS ...................................................................... 24
LP ....................................................................... 24
OST .................................................................... 23
RC ...................................................................... 25
XT ....................................................................... 24
Internal Modes............................................................ 25
Frequency Selection........................................... 27
HFINTOSC ......................................................... 25
INTOSC .............................................................. 25
INTOSCIO .......................................................... 25
LFINTOSC.......................................................... 27
Clock Switching .................................................................. 29
CMCON0 Register.............................................................. 61
CMCON1 Register.............................................................. 62
Code Examples
A/D Conversion .......................................................... 70
Assigning Prescaler to Timer0.................................... 46
Assigning Prescaler to WDT....................................... 46
Indirect Addressing..................................................... 20
Initializing PORTA ...................................................... 33
Initializing PORTC ...................................................... 42
Saving Status and W Registers in RAM ................... 122
Ultra Low-Power Wake-up Initialization...................... 36
Code Protection ................................................................ 126
Comparator......................................................................... 53
C2OUT as T1 Gate..................................................... 62
Configurations ............................................................ 56
Interrupts .................................................................... 59
Operation.............................................................. 53, 58
Operation During Sleep .............................................. 60
Response Time .......................................................... 59
Synchronizing COUT w/Timer1 .................................. 62
Comparator Module
Associated registers ................................................... 64
Comparator Voltage Reference (CVREF)............................ 63
Effects of a Reset ....................................................... 60
Response Time .......................................................... 59
Specifications ........................................................... 159
Comparators
C2OUT as T1 Gate..................................................... 49
Effects of a Reset ....................................................... 60
DS41203E-page 195
PIC16F688
Specifications ............................................................ 159
CONFIG Register.............................................................. 111
Configuration Bits.............................................................. 110
CPU Features ................................................................... 109
Customer Change Notification Service ............................. 199
Customer Notification Service........................................... 199
Customer Support ............................................................. 199
D
Data EEPROM Memory ...................................................... 77
Associated Registers .................................................. 82
Reading....................................................................... 80
Writing ......................................................................... 80
Data Memory......................................................................... 7
DC and AC Characteristics
Graphs and Tables ................................................... 163
DC Characteristics
Extended and Industrial ............................................ 149
Industrial and Extended ............................................ 145
Development Support ....................................................... 139
Device Overview ................................................................... 5
E
EEADR Register ................................................................. 78
EEADR Registers................................................................ 77
EEADRH Registers ............................................................. 77
EECON1 Register ......................................................... 77, 79
EECON2 Register ............................................................... 77
EEDAT Register.................................................................. 78
EEDATH Register ............................................................... 78
Electrical Specifications .................................................... 143
Enhanced Universal Synchronous Asynchronous
Receiver Transmitter (EUSART)................................. 83
Errata .................................................................................... 4
EUSART.............................................................................. 83
Associated Registers
Baud Rate Generator.......................................... 95
Asynchronous Mode ................................................... 85
12-bit Break Transmit and Receive................... 101
Associated Registers
Receive ....................................................... 91
Transmit ...................................................... 87
Auto-Baud Overflow.......................................... 100
Auto-Wake-up on Break.................................... 100
Baud Rate Generator (BRG)............................... 95
Clock Accuracy ................................................... 92
Receiver.............................................................. 88
Setting up 9-bit Mode with Address Detect......... 90
Transmitter.......................................................... 85
Baud Rate Generator (BRG)
Auto Baud Rate Detect ....................................... 99
Baud Rate Error, Calculating .............................. 95
Baud Rates, Asynchronous Modes..................... 96
Formulas ............................................................. 95
High Baud Rate Select (BRGH Bit)..................... 95
Synchronous Master Mode ............................... 103, 107
Associated Registers
Receive ..................................................... 106
Transmit .................................................... 104
Reception.......................................................... 105
Transmission..................................................... 103
Synchronous Slave Mode
Associated Registers
Receive ..................................................... 108
Transmit .................................................... 107
Reception.......................................................... 108
DS41203E-page 196
Transmission .................................................... 107
F
Fail-Safe Clock Monitor ...................................................... 31
Fail-Safe Condition Clearing....................................... 31
Fail-Safe Detection ..................................................... 31
Fail-Safe Operation..................................................... 31
Reset or Wake-up from Sleep .................................... 31
Firmware Instructions ....................................................... 129
Flash Program Memory ...................................................... 77
Fuses. See Configuration Bits
G
General Purpose Register File ............................................. 7
I
I/O Ports.............................................................................. 33
ID Locations...................................................................... 126
In-Circuit Debugger........................................................... 127
In-Circuit Serial Programming (ICSP)............................... 127
Indirect Addressing, INDF and FSR Registers ................... 20
Instruction Format............................................................. 129
Instruction Set................................................................... 129
ADDLW..................................................................... 131
ADDWF..................................................................... 131
ANDLW..................................................................... 131
ANDWF..................................................................... 131
MOVF ....................................................................... 134
BCF .......................................................................... 131
BSF........................................................................... 131
BTFSC ...................................................................... 131
BTFSS ...................................................................... 132
CALL......................................................................... 132
CLRF ........................................................................ 132
CLRW ....................................................................... 132
CLRWDT .................................................................. 132
COMF ....................................................................... 132
DECF ........................................................................ 132
DECFSZ ................................................................... 133
GOTO ....................................................................... 133
INCF ......................................................................... 133
INCFSZ..................................................................... 133
IORLW ...................................................................... 133
IORWF...................................................................... 133
MOVLW .................................................................... 134
MOVWF .................................................................... 134
NOP .......................................................................... 134
RETFIE ..................................................................... 135
RETLW ..................................................................... 135
RETURN................................................................... 135
RLF ........................................................................... 136
RRF .......................................................................... 136
SLEEP ...................................................................... 136
SUBLW ..................................................................... 136
SUBWF..................................................................... 137
SWAPF ..................................................................... 137
XORLW .................................................................... 137
XORWF .................................................................... 137
Summary Table ........................................................ 130
INTCON Register................................................................ 15
Internal Oscillator Block
INTOSC
Specifications ........................................... 154, 155
Internal Sampling Switch (RSS) Impedance........................ 73
Internet Address ............................................................... 199
Interrupts........................................................................... 119
© 2009 Microchip Technology Inc.
PIC16F688
ADC ............................................................................ 69
Associated Registers ................................................ 121
Comparator ................................................................. 59
Context Saving.......................................................... 122
Interrupt-on-Change.................................................... 34
PORTA Interrupt-on-Change .................................... 120
RA2/INT .................................................................... 120
Timer0....................................................................... 120
TMR1 .......................................................................... 50
INTOSC Specifications ............................................. 154, 155
IOCA Register ..................................................................... 35
L
Load Conditions ................................................................ 152
M
MCLR ................................................................................ 113
Internal ...................................................................... 113
.............................................................................................. 7
Data .............................................................................. 7
Program ........................................................................ 7
.......................................... 199, 193, 140, 141, 139, 141, 140
O
OPCODE Field Descriptions ............................................. 129
OPTION Register ................................................................ 14
OPTION_REG Register ...................................................... 47
OSCCON Register ........................................................ 10, 22
Oscillator
Associated registers.............................................. 32, 52
Oscillator Module ................................................................ 21
EC ............................................................................... 21
HFINTOSC.................................................................. 21
HS ............................................................................... 21
INTOSC ...................................................................... 21
INTOSCIO................................................................... 21
LFINTOSC .................................................................. 21
LP................................................................................ 21
RC............................................................................... 21
RCIO ........................................................................... 21
XT ............................................................................... 21
Oscillator Parameters ....................................................... 154
Oscillator Specifications .................................................... 153
Oscillator Start-up Timer (OST)
Specifications............................................................ 157
Oscillator Switching
Fail-Safe Clock Monitor............................................... 31
Two-Speed Clock Start-up.......................................... 29
OSCTUNE Register ............................................................ 26
P
Packaging ......................................................................... 185
Marking ..................................................................... 185
PDIP Details.............................................................. 186
PCL and PCLATH ............................................................... 19
Computed GOTO........................................................ 19
Stack ........................................................................... 19
PCON Register ........................................................... 18, 115
PICSTART Plus Development Programmer ..................... 142
PIE1 Register ...................................................................... 16
Pin Diagram ...................................................................... 2, 3
Pinout Description
PIC16F688.................................................................... 6
PIR1 Register...................................................................... 17
PORTA................................................................................ 33
Additional Pin Functions ............................................. 34
© 2009 Microchip Technology Inc.
ANSEL Register ................................................. 34
Interrupt-on-Change ........................................... 34
Ultra Low-Power Wake-up............................ 34, 36
Weak Pull-up ...................................................... 34
Associated registers ................................................... 41
Pin Descriptions and Diagrams .................................. 37
RA0............................................................................. 37
RA1............................................................................. 38
RA2............................................................................. 38
RA4............................................................................. 39
RA5............................................................................. 40
Specifications ........................................................... 155
PORTA Register ................................................................. 33
PORTC ............................................................................... 42
Associated registers ................................................... 44
PA/PB/PC/PD.See Enhanced Universal Asynchronous
Receiver Transmitter (EUSART) ........................ 42
Specifications ........................................................... 155
PORTC Register................................................................. 42
Power-Down Mode (Sleep)............................................... 125
Power-up Timer (PWRT) .................................................. 113
Specifications ........................................................... 157
Precision Internal Oscillator Parameters .......................... 155
Prescaler
Shared WDT/Timer0................................................... 46
Switching Prescaler Assignment ................................ 46
Program Memory .................................................................. 7
Map and Stack.............................................................. 7
Programming, Device Instructions.................................... 129
R
RA3/MCLR/VPP .................................................................. 39
RCREG............................................................................... 90
RCSTA Register ................................................................. 93
Reader Response............................................................. 200
Read-Modify-Write Operations ......................................... 129
Register
RCREG Register ........................................................ 99
Registers
ADCON0 (ADC Control 0) .......................................... 71
ADCON1 (ADC Control 1) .......................................... 71
ADRESH (ADC Result High) with ADFM = 0) ............ 72
ADRESH (ADC Result High) with ADFM = 1) ............ 72
ADRESL (ADC Result Low) with ADFM = 0).............. 72
ADRESL (ADC Result Low) with ADFM = 1).............. 72
ANSEL (Analog Select) .............................................. 34
BAUDCTL (Baud Rate Control).................................. 94
CMCON0 (Comparator Control 0) .............................. 61
CMCON1 (Comparator Control 1) .............................. 62
CONFIG (Configuration Word) ................................. 111
EEADR (EEPROM Address) ...................................... 78
EECON1 (EEPROM Control 1) .................................. 79
EEDAT (EEPROM Data) ............................................ 78
EEDATH (EEPROM Data High Byte) ......................... 78
INTCON (Interrupt Control) ........................................ 15
IOCA (Interrupt-on-Change PORTA).......................... 35
OPTION_REG (OPTION)........................................... 14
OPTION_REG (Option) .............................................. 47
OSCCON (Oscillator Control)..................................... 22
OSCTUNE (Oscillator Tuning).................................... 26
PCON (Power Control Register)................................. 18
PCON (Power Control) ............................................. 115
PIE1 (Peripheral Interrupt Enable 1) .......................... 16
PIR1 (Peripheral Interrupt Register 1) ........................ 17
PORTA ....................................................................... 33
PORTC ....................................................................... 42
DS41203E-page 197
PIC16F688
RCSTA (Receive Status and Control)......................... 93
Reset Values............................................................. 117
Reset Values (Special Registers) ............................. 118
Special Function Register Map ..................................... 8
Special Register Summary ........................................... 9
STATUS ...................................................................... 13
T1CON ........................................................................ 51
TRISA (Tri-State PORTA) ........................................... 33
TRISC (Tri-State PORTC) .......................................... 42
TXSTA (Transmit Status and Control) ........................ 92
VRCON (Voltage Reference Control) ......................... 63
WDTCON (Watchdog Timer Control)........................ 124
WPUA (Weak Pull-Up PORTA) .................................. 35
Reset................................................................................. 112
Revision History ................................................................ 193
S
Software Simulator (MPLAB SIM)..................................... 140
SPBRG................................................................................ 95
SPBRGH ............................................................................. 95
Special Function Registers ................................................... 7
STATUS Register................................................................ 13
T
T1CON Register.................................................................. 51
Thermal Considerations .................................................... 151
Time-out Sequence........................................................... 115
Timer0 ................................................................................. 45
Associated Registers .................................................. 47
External Clock ............................................................. 46
Interrupt....................................................................... 47
Operation .............................................................. 45, 48
Specifications ............................................................ 158
T0CKI .......................................................................... 46
Timer1 ................................................................................. 48
Associated registers.................................................... 52
Asynchronous Counter Mode ..................................... 49
Reading and Writing ........................................... 49
Interrupt....................................................................... 50
Modes of Operation .................................................... 48
Operation During Sleep .............................................. 50
Oscillator ..................................................................... 49
Prescaler ..................................................................... 49
Specifications ............................................................ 158
Timer1 Gate
Inverting Gate ..................................................... 49
Selecting Source........................................... 49, 62
Synchronizing COUT w/Timer1 .......................... 62
TMR1H Register ......................................................... 48
TMR1L Register .......................................................... 48
Timers
Timer1
T1CON................................................................ 51
Timing Diagrams
A/D Conversion ......................................................... 162
A/D Conversion (Sleep Mode) .................................. 162
Asynchronous Reception ............................................ 90
Asynchronous Transmission ....................................... 86
Asynchronous Transmission (Back to Back) .............. 86
Auto Wake-up Bit (WUE) During Normal Operation . 100
Auto Wake-up Bit (WUE) During Sleep .................... 101
Automatic Baud Rate Calculator ................................. 99
Brown-out Reset (BOR) ............................................ 156
Brown-out Reset Situations ...................................... 114
CLKOUT and I/O....................................................... 155
Clock Timing ............................................................. 153
DS41203E-page 198
Comparator Output ..................................................... 53
Fail-Safe Clock Monitor (FSCM)................................. 32
INT Pin Interrupt ....................................................... 121
Internal Oscillator Switch Timing ................................ 28
Reset, WDT, OST and Power-up Timer ................... 156
Send Break Character Sequence ............................. 102
Synchronous Reception (Master Mode, SREN) ....... 106
Synchronous Transmission ...................................... 104
Synchronous Transmission (Through TXEN) ........... 104
Time-out Sequence .................................................. 116
Case 3 .............................................................. 116
Timer0 and Timer1 External Clock ........................... 158
Timer1 Incrementing Edge ......................................... 50
Two Speed Start-up.................................................... 30
Wake-up from Interrupt............................................. 126
Timing Parameter Symbology .......................................... 152
TRISA ................................................................................. 33
TRISA Register................................................................... 33
TRISC Register................................................................... 42
Two-Speed Clock Start-up Mode........................................ 29
TXREG ............................................................................... 85
TXSTA Register.................................................................. 92
BRGH Bit .................................................................... 95
U
Ultra Low-Power Wake-up........................................ 6, 34, 36
V
Voltage Reference. See Comparator Voltage
Reference (CVREF)
Voltage References
Associated registers ................................................... 64
VREF. SEE ADC Reference Voltage
W
Wake-up on Break ............................................................ 100
Wake-up Using Interrupts ................................................. 125
Watchdog Timer (WDT).................................................... 123
Associated Registers ................................................ 124
Clock Source ............................................................ 123
Modes ....................................................................... 123
Period ....................................................................... 123
Specifications ........................................................... 157
WDTCON Register ....................................................... 9, 124
WPUA Register................................................................... 35
WWW Address ................................................................. 199
WWW, On-Line Support ....................................................... 4
© 2009 Microchip Technology Inc.
PIC16F688
THE MICROCHIP WEB SITE
CUSTOMER SUPPORT
Microchip provides online support via our WWW site at
www.microchip.com. This web site is used as a means
to make files and information easily available to
customers. Accessible by using your favorite Internet
browser, the web site contains the following
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Users of Microchip products can receive assistance
through several channels:
• Product Support – Data sheets and errata,
application notes and sample programs, design
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Questions (FAQ), technical support requests,
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representatives
•
•
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•
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Local Sales Office
Field Application Engineer (FAE)
Technical Support
Development Systems Information Line
Customers
should
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support. Local sales offices are also available to help
customers. A listing of sales offices and locations is
included in the back of this document.
Technical support is available through the web site
at: http://support.microchip.com
CUSTOMER CHANGE NOTIFICATION
SERVICE
Microchip’s customer notification service helps keep
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To register, access the Microchip web site at
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Notification and follow the registration instructions.
© 2009 Microchip Technology Inc.
DS41203E-page 199
PIC16F688
READER RESPONSE
It is our intention to provide you with the best documentation possible to ensure successful use of your Microchip product. If you wish to provide your comments on organization, clarity, subject matter, and ways in which our documentation
can better serve you, please FAX your comments to the Technical Publications Manager at (480) 792-4150.
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Device: PIC16F688
Y
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Literature Number: DS41203E
Questions:
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2. How does this document meet your hardware and software development needs?
3. Do you find the organization of this document easy to follow? If not, why?
4. What additions to the document do you think would enhance the structure and subject?
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6. Is there any incorrect or misleading information (what and where)?
7. How would you improve this document?
DS41203E-page 200
© 2009 Microchip Technology Inc.
PIC16F688
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
Device
Temperature
Range
Package
Pattern
Examples:
a)
b)
Device
PIC16F688, PIC16F688T(1)
VDD range 2.0V to 5.5V
Temperature Range
I
E
Package
ML
P
SL
ST
Pattern
QTP, SQTPSM or ROM Code; Special Requirements
(blank otherwise)
= -40°C to +85°C
= -40°C to +125°C
PIC16F688-E/P 301 = Extended Temp., PDIP
package, 20 MHz, QTP pattern #301
PIC16F688-I/SO = Industrial Temp., SOIC
package, 20 MHz.
(Industrial)
(Extended)
= Quad Flat No Leads (QFN)
= Plastic DIP
= 16-lead Small Outline (3.90 mm)
= Thin Shrink Small Outline (4.4 mm)
Note
© 2009 Microchip Technology Inc.
1:
T=In tape and reel TSSOP, SOIC and
QFN packages only.
DS41203E-page 201
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China - Nanjing
Tel: 86-25-8473-2460
Fax: 86-25-8473-2470
Malaysia - Kuala Lumpur
Tel: 60-3-6201-9857
Fax: 60-3-6201-9859
China - Qingdao
Tel: 86-532-8502-7355
Fax: 86-532-8502-7205
Malaysia - Penang
Tel: 60-4-227-8870
Fax: 60-4-227-4068
China - Shanghai
Tel: 86-21-5407-5533
Fax: 86-21-5407-5066
Philippines - Manila
Tel: 63-2-634-9065
Fax: 63-2-634-9069
China - Shenyang
Tel: 86-24-2334-2829
Fax: 86-24-2334-2393
Singapore
Tel: 65-6334-8870
Fax: 65-6334-8850
China - Shenzhen
Tel: 86-755-8203-2660
Fax: 86-755-8203-1760
Taiwan - Hsin Chu
Tel: 886-3-6578-300
Fax: 886-3-6578-370
China - Wuhan
Tel: 86-27-5980-5300
Fax: 86-27-5980-5118
Taiwan - Kaohsiung
Tel: 886-7-536-4818
Fax: 886-7-536-4803
China - Xiamen
Tel: 86-592-2388138
Fax: 86-592-2388130
Taiwan - Taipei
Tel: 886-2-2500-6610
Fax: 886-2-2508-0102
China - Xian
Tel: 86-29-8833-7252
Fax: 86-29-8833-7256
Thailand - Bangkok
Tel: 66-2-694-1351
Fax: 66-2-694-1350
Italy - Milan
Tel: 39-0331-742611
Fax: 39-0331-466781
Netherlands - Drunen
Tel: 31-416-690399
Fax: 31-416-690340
Spain - Madrid
Tel: 34-91-708-08-90
Fax: 34-91-708-08-91
UK - Wokingham
Tel: 44-118-921-5869
Fax: 44-118-921-5820
China - Zhuhai
Tel: 86-756-3210040
Fax: 86-756-3210049
03/26/09
DS41203E-page 202
© 2009 Microchip Technology Inc.