PIC16F688 Datasheet, PDF (16/174 Pages) Microchip Technology – 14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F688
2.2.2.2 Option Register
The Option register is a readable and writable register,
which contains various control bits to configure:
• TMR0/WDT prescaler
• External RA2/INT interrupt
• TMR0
• Weak pull-ups on PORTA
Note:
To achieve a 1:1 prescaler assignment for
TMR0, assign the prescaler to the WDT by
setting PSA bit to ‘1’ (Option<3>). See
Section 5.4 “Prescaler”.
REGISTER 2-2:
OPTION_REG – OPTION REGISTER (ADDRESS: 81h OR 181h)
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RAPU INTEDG T0CS
T0SE
PSA
PS2
PS1
bit 7
R/W-1
PS0
bit 0
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
RAPU: PORTA Pull-up Enable bit
1 = PORTA pull-ups are disabled
0 = PORTA pull-ups are enabled by individual port latch values
INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RA2/INT pin
0 = Interrupt on falling edge of RA2/INT pin
T0CS: TMR0 Clock Source Select bit
1 = Transition on RA2/T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on RA2/T0CKI pin
0 = Increment on low-to-high transition on RA2/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 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
DS41203B-page 14
Preliminary
 2004 Microchip Technology Inc.