PIC16F639 Microchip Technology Inc., PIC16F639 Datasheet - Page 29

• Manufacturer Part Number: PIC16F639
• Description: 8/14-pin Flash-based, 8-bit Cmos Microcontrollers With Nanowatt Technology
• Manufacturer: Microchip Technology Inc.

2.2.2.2
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-up/pull-downs on PORTA
REGISTER 2-2:
© 2007 Microchip Technology Inc.
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
R/W-1
RAPU
OPTION Register
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: Timer0 Clock Source Select bit
1 = Transition on RA2/T0CKI pin
0 = Internal instruction cycle clock (F
T0SE: Timer0 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
INTEDG
R/W-1
OPTION_REG: OPTION REGISTER
Bit Value
000
001
010
011
100
101
110
111
W = Writable bit
‘1’ = Bit is set
R/W-1
T0CS
Timer0 Rate
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
R/W-1
T0SE
PIC12F635/PIC16F636/639
WDT Rate
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
OSC
/4)
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
R/W-1
PSA
Note:
To achieve a 1:1 prescaler assignment for
Timer0, assign the prescaler to the WDT by
setting the PSA bit of the OPTION register
to ‘1’. See Section 5.1.3 “Software
Programmable Prescaler”.
R/W-1
PS2
x = Bit is unknown
R/W-1
PS1
DS41232D-page 27
R/W-1
PS0
bit 0