PIC12F635/PIC16F636/639
REGISTER 5-1:
OPTION_REG: OPTION REGISTER
R/W-1
RAPU
R/W-1
R/W-1
T0CS
R/W-1
T0SE
R/W-1
PSA
R/W-1
PS2
R/W-1
PS1
R/W-1
PS0
INTEDG
bit 7
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
RAPU: PORTA Pull-up Enable bit
1= PORTA pull-ups are disabled
0= PORTA 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 12.11 “Watchdog Timer (WDT)” for more
information.
TABLE 5-1:
Name
SUMMARY OF REGISTERS ASSOCIATED WITH TIMER0
Value on
all other
Resets
Value on:
POR, BOR
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
TMR0
Timer0 Module Register
GIE PEIE T0IE
xxxx xxxx uuuu uuuu
INTCON
INTE
T0SE
RAIE
PSA
T0IF
PS2
INTF
PS1
RAIF 0000 000x 0000 000x
PS0 1111 1111 1111 1111
OPTION_REG RAPU INTEDG T0CS
TRISA
—
—
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.
DS41232D-page 63
MICROCHIP [ MICROCHIP ]
