PIC16C62B/72A
2.2.2.2
OPTION_REG REGISTER
Note: To achieve a 1:1 prescaler assignment for
the TMR0 register, assign the prescaler to
the Watchdog Timer.
The OPTION_REG register is a readable and writable
register, which contains various control bits to configure
the TMR0 prescaler/WDT postscaler (single assign-
able register known as the prescaler), the External INT
Interrupt, TMR0 and the weak pull-ups on PORTB.
REGISTER 2-2: OPTION_REG REGISTER (ADDRESS 81h)
R/W-1
RBPU
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
R = Readable bit
W = Writable bit
- n = Value at POR reset
bit7
bit0
bit 7:
RBPU: PORTB Pull-up Enable bit
1= PORTB pull-ups are disabled
0= PORTB pull-ups are enabled for all PORTB inputs
bit 6:
bit 5:
bit 4:
bit 3:
INTEDG: Interrupt Edge Select bit
1= Interrupt on rising edge of RB0/INT pin
0= Interrupt on falling edge of RB0/INT pin
T0CS: TMR0 Clock Source Select bit
1= Transition on RA4/T0CKI pin
0= Internal instruction cycle clock (CLKOUT)
T0SE: TMR0 Source Edge Select bit
1= Increment on high-to-low transition on RA4/T0CKI pin
0= Increment on low-to-high transition on RA4/T0CKI pin
PSA: Prescaler Assignment bit
1= Prescaler is assigned to the WDT
0= Prescaler is assigned to the Timer0 module
bit 2-0: PS2:PS0: Prescaler Rate Select bits
Bit Value
TMR0 Rate WDT Rate
000
001
010
011
100
101
110
111
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
DS35008B-page 12
Preliminary
1999 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
