IBT Technologies CI7BM, User Manual

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Chapter 2 Installations
36 CI7BM User’s Manual
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