PIC16F88

Manufacturer Part NumberPIC16F88
ManufacturerMicrochip Technology Inc.
PIC16F88 datasheet
 
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Page 20/228:

Watchdog Timer (WDT) for further

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PIC16F87/88
2.2.2.2
OPTION_REG Register
The OPTION_REG register is a readable and writable
register that contains various control bits to configure
the TMR0 prescaler/WDT postscaler (single assign-
able register known also as the prescaler), the external
INT interrupt, TMR0 and the weak pull-ups on PORTB.
REGISTER 2-2:
OPTION_REG: OPTION CONTROL REGISTER (ADDRESS 81h, 181h)
R/W-1
R/W-1
RBPU
INTEDG
bit 7
bit 7
RBPU
PORTB Pull-up Enable bit
:
1 = PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
bit 6
INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RB0/INT pin
0 = Interrupt on falling edge of RB0/INT pin
bit 5
T0CS: TMR0 Clock Source Select bit
1 = Transition on RA4/T0CKI/C2OUT pin
0 = Internal instruction cycle clock (CLKO)
bit 4
T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on RA4/T0CKI/C2OUT pin
0 = Increment on low-to-high transition on RA4/T0CKI/C2OUT pin
bit 3
PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0
PS<2:0>: Prescaler Rate Select bits
Bit Value
TMR0 Rate
000
001
010
011
100
101
110
111
Legend:
R = Readable bit
-n = Value at POR
DS30487C-page 18
Note:
To achieve a 1:1 prescaler assignment for
the TMR0 register, assign the prescaler to
the Watchdog Timer. Although the pres-
caler can be assigned to either the WDT or
Timer0, but not both, a new divide counter
is implemented in the WDT circuit to give
multiple WDT time-out selections. This
allows TMR0 and WDT to each have their
own scaler. Refer to Section 15.12
“Watchdog Timer (WDT)” for further
details.
R/W-1
R/W-1
R/W-1
T0CS
T0SE
PSA
WDT Rate
1 : 2
1 : 1
1 : 4
1 : 2
1 : 8
1 : 4
1 : 16
1 : 8
1 : 32
1 : 16
1 : 64
1 : 32
1 : 128
1 : 64
1 : 256
1 : 128
W = Writable bit
U = Unimplemented bit, read as ‘0’
‘1’ = Bit is set
‘0’ = Bit is cleared
R/W-1
R/W-1
R/W-1
PS2
PS1
PS0
bit 0
x = Bit is unknown
 2005 Microchip Technology Inc.