PIC16C774 Microchip Technology Inc., PIC16C774 Datasheet - Page 17

• Manufacturer Part Number: PIC16C774
• Description: 28/40-pin, 8-bit Cmos Microcontrollers W/ 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.
FIGURE 2-4:
bit7
1999 Microchip Technology Inc.
bit 7:
bit 6:
bit 5:
bit 4:
bit 3:
bit 2-0: PS2:PS0: Prescaler Rate Select bits
R/W-1
RBPU
OPTION_REG REGISTER
RBPU: PORTB Pull-up Enable bit
1 = PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
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
INTEDG
Bit Value
R/W-1
000
001
010
011
100
101
110
111
OPTION_REG REGISTER (ADDRESS 81h, 181h)
R/W-1
T0CS
TMR0 Rate
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
R/W-1
T0SE
WDT Rate
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
R/W-1
Advance Information
PSA
R/W-1
PS2
R/W-1
Note:
PS1
To achieve a 1:1 prescaler assignment for
the TMR0 register, assign the prescaler to
the Watchdog Timer.
R/W-1
PS0
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
- n = Value at POR reset
PIC16C77X
read as ‘0’
DS30275A-page 17