W78E51B Winbond, W78E51B Datasheet - Page 7

• Manufacturer Part Number: W78E51B
• Description: 8-BIT MTP MICROCONTROLLER
• Manufacturer: Winbond

Watchdog Timer Control Register
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
PS2, PS1, PS0: Watch-dog prescaler timer select. Prescaler is selected when set PS2~0 as follows:
The time-out period is obtained using the following equation :
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.
OSC
WIDL
IDLE
1
Watchdog Timer Block Diagram
OSC
2
14
under IDLE mode. Default is cleared.
PRESCALER 1000 12 mS
1/12
Bit:
PS2 PS1 PS0
0
0
0
0
1
1
1
1
0
1
0
1
0
0
1
1
ENW
Mnemonic: WDTC
ENW
7
0
0
1
1
0
1
0
1
CLRW
6
PRESCALER SELECT
PRESCALER
WIDL
- 7 -
5
CLRW
128
256
16
32
64
2
4
8
EXTERNAL
Address: 8FH
RESET
4
-
Preliminary W78E51B
14-BIT TIMER
Publication Release Date: December 1998
CLEAR
3
-
PS2
2
PS1
1
INTERNAL
Revision A1
RESET
PS0
0