PIC16F631/677/685/687/689/690
REGISTER 5-1:
OPTION_REG: OPTION REGISTER
R/W-1 R/W-1 R/W-1 R/W-1
INTEDG T0CS T0SE PSA
R/W-1
RABPU
bit 7
R/W-1
PS2
R/W-1
PS1
R/W-1
PS0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
RABPU: PORTA/PORTB Pull-up Enable bit
1= PORTA/PORTB pull-ups are disabled
0= PORTA/PORTB pull-ups are enabled by individual PORT latch values
INTEDG: Interrupt Edge Select bit
1= Interrupt on rising edge of INT pin
0= Interrupt on falling edge of INT pin
T0CS: TMR0 Clock Source Select bit
1= Transition on T0CKI pin
0= Internal instruction cycle clock (FOSC/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
PSA: Prescaler Assignment bit
1= Prescaler is assigned to the WDT
0= Prescaler is assigned to the Timer0 module
PS<2:0>: Prescaler Rate Select bits
BIT VALUE TMR0 RATE
WDT RATE
000
001
010
011
100
101
110
111
1 : 2
1 : 1
1 : 4
1 : 2
1 : 8
1 : 4
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Note 1: A dedicated 16-bit WDT postscaler is available. See Section 14.5 “Watchdog Timer (WDT)” for more
information.
TABLE 5-1:
SUMMARY OF REGISTERS ASSOCIATED WITH TIMER0
Value on
all other
Resets
Value on
POR, BOR
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
INTCON
GIE
PEIE
T0IE
INTE RABIE
T0SE PSA
T0IF
PS2
INTF RABIF 0000 0000 0000 0000
OPTION_REG RABPU INTEDG T0CS
PS1
PS0 1111 1111 1111 1111
TMR0
TRISA
Timer0 Module Register
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.
© 2007 Microchip Technology Inc.
DS41262D-page 83
MICROCHIP [ MICROCHIP ]
