Datasheet

 1999-2012 Microchip Technology Inc. DS40192D-page 15
PIC16C505
4.4 OPTION Register
The OPTION register is a 8-bit wide, write-only
register, which contains various control bits to
configure the Timer0/WDT prescaler and Timer0.
By executing the OPTION instruction, the contents of
the W register will be transferred to the OPTION
register. A RESET sets the OPTION<7:0> bits.
Note: If TRIS bit is set to ‘0’, the wake-up on
change and pull-up functions are disabled
for that pin (i.e., note that TRIS overrides
OPTION control of RBPU
and RBWU).
REGISTER 4-2: OPTION REGISTER
W-1 W-1 W-1 W-1 W-1 W-1 W-1 W-1
RBWU
RBPU T0CS T0SE PSA PS2 PS1 PS0 R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
bit7 6 5 4 3 2 1 bit0
bit 7: RBWU
: Enable wake-up on pin change (RB0, RB1, RB3, RB4)
1 = Disabled
0 = Enabled
bit 6: RBPU
: Enable weak pull-ups (RB0, RB1, RB3, RB4)
1 = Disabled
0 = Enabled
bit 5: T0CS: Timer0 clock source select bit
1 = Transition on T0CKI pin (overrides TRIS <RC57>
0 = Transition on internal instruction cycle clock, Fosc/4
bit 4: T0SE: Timer0 source edge select bit
1 = Increment on high to low transition on the T0CKI pin
0 = Increment on low to high transition on the T0CKI pin
bit 3: PSA: Prescaler assignment bit
1 = Prescaler assigned to the WDT
0 = Prescaler assigned to Timer0
bit 2-0: PS<2:0>: Prescaler rate select bits
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Bit Value Timer0 Rate WDT Rate