PIC16C55X_13 Datasheet, PDF (18/108 Pages) Microchip Technology – EPROM-Based 8-Bit CMOS Microcontrollers

PIC16C55X
4.2.2.2 OPTION Register
The OPTION register is a readable and writable
register which contains various control bits to configure
the TMR0/WDT prescaler, the external RB0/INT
interrupt, TMR0 and the weak pull-ups on PORTB.
Note 1: To achieve a 1:1 prescaler assignment for
TMR0, assign the prescaler to the WDT
(PSA = 1).
REGISTER 4-2:
OPTION REGISTER (ADDRESS 81H)
R/W-1
R/W-1
R/W-1 R/W-1
RBPU INTEDG T0CS T0SE
bit7
R/W-1
PSA
R/W-1
PS2
R/W-1
PS1
R/W-1
PS0
bit0
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
RBPU: PORTB Pull-up Enable bit
1 = PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RB0/INT pin
0 = Interrupt on falling edge of RB0/INT pin
T0CS: TMR0 Clock Source Select bit
1 = Transition on RA4/T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on RA4/T0CKI pin
0 = Increment on low-to-high transition on RA4/T0CKI pin
PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
PS2:PS0: 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 reset
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared x = Bit is unknown
DS40143E-page 18
Preliminary
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