PIC16C770 Microchip Technology Inc., PIC16C770 Datasheet - Page 17

• Manufacturer Part Number: PIC16C770
• Description: 18/20-pin, 8-bit Cmos Microcontrollers With 10/12-bit A/d
• Manufacturer: Microchip Technology Inc.

2.2.2.2
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 also as the prescaler), the External
INT Interrupt, TMR0 and the weak pull-ups on PORTB.
REGISTER 2-2:
2002 Microchip Technology Inc.
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
OPTION_REG REGISTER
OPTION REGISTER (OPTION_REG: 81h, 181h)
RBPU: PORTB Pull-up Enable bit
1 = PORTB weak pull-ups are disabled
0 = PORTB weak pull-ups are enabled by the WPUB register
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
PS<2:0>: Prescaler Rate Select bits
bit 7
Legend:
R = Readable bit
- n = Value at POR
R/W-1
RBPU
Note 1: Individual weak pull-up on RB pins can be enabled/disabled from the weak pull-up
Bit Value
PORTB Register (WPUB).
INTEDG
000
001
010
011
100
101
110
111
R/W-1
TMR0 Rate
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
R/W-1
T0CS
W = Writable bit
’1’ = Bit is set
(1)
WDT Rate
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
R/W-1
T0SE
Note:
PIC16C717/770/771
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared
R/W-1
To achieve a 1:1 prescaler assignment for
the TMR0 register, assign the prescaler to
the Watchdog Timer.
PSA
R/W-1
PS2
x = Bit is unknown
R/W-1
PS1
DS41120B-page 15
R/W-1
PS0
bit 0