Chapter 2 Installations
CI5TTV User’s Manual
31
Watchdog Timer Configuration
The function of the watchdog timer is to reset the system automatically
and is defined at I/O port 0443H. To enable the watchdog timer and allow
the system to reset, write I/O port 0443H. To disable the timer, write I/O
port 0441H for the system to stop the watchdog function. The timer has a
tolerance of 20% for its intervals.
The following describes how the timer should be programmed.
Enabling Watchdog:
MOV
AX, 000FH (Choose the values from 0)
MOV DX,
0443H
OUT
DX, AX
Disabling Watchdog
MOV
AX, 00FH (Any value is fine.)
MOV DX, 0441H
OUT
DX, AX
WATCHDOG TIMER CONTROL TABLE
Level
Value
Time/sec
Level
Value
Time/sec
1 F 0 9 7 16
2 E 2 10 6 18
3 D 4 11 5 20
4 C 6 12 4 22
5 B 8 13 3 24
6 A 10 14 2 26
7 9 12 15 1 28
8 8 14 16 0 30
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