PIC12F508/509/16F505
4.5
OPTION Register
Note:
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 GPPU/RBPU and
GPWU/RBWU).
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 regis-
ter. A Reset sets the OPTION<7:0> bits.
If the T0CS bit is set to ‘1’, it will override
the TRIS function on the T0CKI pin.
REGISTER 4-3:
OPTION REGISTER (PIC12F508/509)
W-1
GPWU
bit 7
W-1
W-1
W-1
T0SE
W-1
W-1
PS2
W-1
PS1
W-1
PS0
bit 0
GPPU
T0CS
PSA
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
GPWU: Enable Wake-up on Pin Change bit (GP0, GP1, GP3)
1= Disabled
0= Enabled
GPPU: Enable Weak Pull-ups bit (GP0, GP1, GP3)
1= Disabled
0= Enabled
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
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
PSA: Prescaler Assignment bit
1= Prescaler assigned to the WDT
0= Prescaler assigned to Timer0
PS<2:0>: Prescaler Rate Select bits
Bit Value Timer0 Rate WDT Rate
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
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
DS41236C-page 22
Preliminary
© 2007 Microchip Technology Inc.