W78LE812 Datasheet, PDF (10/25 Pages) Winbond – 8-BIT MTP MICROCONTROLLER

W78LE812
PS2, PS1, PS0 : Watch-dog prescaler timer select. Prescaler is selected when set PS2−0 as follows:
PS2 PS1 PS0 PRESCALER SELECT
00 0
2
00 1
4
01 0
8
01 1
16
10 0
32
10 1
64
11 0
128
11 1
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.
WIDL
IDLE
OSC
1/12
ENW
EXTERNAL
RESET
PRESCALER
14-BIT TIMER
CLEAR
INTERNAL
RESET
Watchdog Timer Block Diagram
CLRW
Typical Watch-Dog time-out period when OSC = 20 MHz
PS2 PS1 PS0
00 0
00 1
01 0
01 1
10 0
10 1
11 0
11 1
WATCHDOG TIME-OUT PERIOD
19.66 mS
39.32 mS
78.64 mS
157.28 mS
314.57 mS
629.14 mS
1.25 s
2.50 s
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