PIC16F627A_05 Datasheet, PDF (25/180 Pages) Microchip Technology – Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F627A/628A/648A
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 RB0/INT interrupt,
TMR0 and the weak pull-ups on PORTB.
Note:
To achieve a 1:1 prescaler assignment for
TMR0, assign the prescaler to the WDT
(PSA = 1). See Section 6.3.1 “Switching
Prescaler Assignment”.
REGISTER 4-2:
OPTION_REG – OPTION REGISTER (ADDRESS: 81h, 181h)
R/W-1 R/W-1 R/W-1 R/W-1
R/W-1
R/W-1
RBPU INTEDG T0CS T0SE
PSA
PS2
bit 7
R/W-1
PS1
R/W-1
PS0
bit 0
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
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/CMP2 pin
0 = Internal instruction cycle clock (CLKOUT)
T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on RA4/T0CKI/CMP2 pin
0 = Increment on low-to-high transition on RA4/T0CKI/CMP2 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 Value TMR0 Rate WDT Rate
000
1:2
1:1
001
1:4
1:2
010
1:8
1:4
011
1 : 16
1:8
100
1 : 32
1 : 16
101
1 : 64
1 : 32
110
1 : 128 1 : 64
111
1 : 256 1 : 128
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
© 2005 Microchip Technology Inc.
DS40044D-page 23