
PIC16F8X
DS30430C-page 16
1998 Microchip Technology Inc.
4.2.2.2
OPTION_REG REGISTER
The OPTION_REG 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.
FIGURE 4-1:
OPTION_REG REGISTER (ADDRESS 81h)
Note:
When
the
prescaler
is
assigned to
the WDT (PSA = ’1’), TMR0 has a 1:1
prescaler assignment.
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