Watchdog Timer Configuration - IBT Technologies IB770 User Manual

INSTALLATIONS

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
1 1F
2 1E
3 1D
4 1C
5 1B
6 1A
7 19
8 18
Level Value
17 0F
18 0E
19 0D
20 0C
21 0B
22 0A
23 09
24 08
26
Time/sec Level Value
0
1 10
2 11
3 12
4 13
5 14
6 15
7 16
Time/sec Level Value
16 25
17 26
18 27
19 28
20 29
21 30
22 31
23 32
IB770 User' s Manual
Time/sec
9 17
16
15
14
13
12
11
10
Time/sec
07
06
05
04
03
02
01
00
8
9
10
11
12
13
14
15
24
25
26
27
28
29
30
31