
2009 Microchip Technology Inc.
DS41236E-page 25
PIC12F508/509/16F505
REGISTER 4-4:
OPTION REGISTER (PIC16F505)
W-1
RBWU
RBPU
T0CS
T0SE
PSA
PS2
PS1
PS0
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
RBWU: Enable Wake-up on Pin Change bit (RB0, RB1, RB3, RB4)
1
= Disabled
0
= Enabled
bit 6
RBPU: Enable Weak Pull-ups bit (RB0, RB1, RB3, RB4)
1
= Disabled
0
= Enabled
bit 5
T0CS: Timer0 clock Source Select bit
1
= Transition on T0CKI pin (overrides TRIS on the T0CKI pin)
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