Datasheet

PIC16F8X
DS30430B-page 16  1996 Microchip Technology Inc.
4.2.2.2 OPTION REGISTER
The OPTION register is a readable and writable
register which contains various control bits to configure
the TMR0/WDT prescaler, the external INT interrupt,
TMR0, and the weak pull-ups on PORTB.
Note: When the prescaler is assigned to
the WDT (PSA = '1'), TMR0 has a 1:1
prescaler assignment.
FIGURE 4-6: OPTION REGISTER (ADDRESS 81h)
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RBPU
INTEDG T0CS T0SE PSA PS2 PS1 PS0 R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- 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 (by individual port latch values)
bit 6: INTEDG : Interrupt Edge Select bit
1 = Interrupt on rising edge of RB0/INT pin
0 = Interrupt on falling edge of RB0/INT pin
bit 5: T0CS : TMR0 Clock Source Select bit
1 = Transition on RA4/T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
bit 4: 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
bit 3: PSA : Prescaler Assignment bit
1 = Prescaler assigned to the WDT
0 = Prescaler assigned to TMR0
bit 2-0: PS2:PS0: Prescaler Rate Select bits
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
Bit Value TMR0 Rate WDT Rate