Preliminary W78E51B
Watchdog Timer Control Register
Bit:
7
6
5
4
-
3
-
2
1
0
ENW CLRW WIDL
Mnemonic: WDTC
PS2
PS1
PS0
Address: 8FH
ENW : Enable watch-dog if set.
CLRW: Clear watch-dog timer and prescaler if set. This flag will be cleared automatically
WIDL : If this bit is set, watch-dog is enabled under IDLE mode. If cleared, watch-dog is disabled
under IDLE mode. Default is cleared.
PS2, PS1, PS0: Watch-dog prescaler timer select. Prescaler is selected when set PS2~0 as follows:
PS2 PS1 PS0
PRESCALER SELECT
0
0
0
0
1
1
1
1
0
1
0
1
0
0
1
1
0
0
1
1
0
1
0
1
2
4
8
16
32
64
128
256
The time-out period is obtained using the following equation :
1
214 PRESCALER 1000 12 mS
´
´
´
´
OSC
Before Watchdog time-out occurs, the program must clear the 14-bit timer by writing 1 to WDTC.6
(CLRW). After 1 is written to this bit, the 14-bit timer , prescaler and this bit will be reset on the next
instruction cycle. The Watchdog timer is cleared on reset.
ENW
WIDL
IDLE
EXTERNAL
RESET
INTERNAL
14-BIT TIMER
RESET
PRESCALER
OSC
1/12
CLEAR
CLRW
Watchdog Timer Block Diagram
Publication Release Date: December 1998
Revision A1
- 7 -
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