Watchdog Timer
W atchdog Output
The onboard watchdog timer can be disable by jumper setting or enable for
either reboot by system RESET .The Jumper is on the carrier board.
Even if enabled by jumper setting upon boot the watchdog timer is always
inactive. To initialize or refresh the watchdog timer writing of port 444H is
sufficient. To disable the watchdog time read port 44H.
Status
Acti on
Enable/refresh the Watchdog Timer
I/O Write 444H
Disable the Watchdog Timer.
I/O Read 044H
After the watchdog timer has been initialized by reading port 444H, it has to
be strobed at preconfigured intervals to keep it from issuing a RESET or NMI.
The watchdog timer timeout intervals are set by software programming.
Timeout
Values
Timout values are programmed. The watchdog timer supports 255 steps.
use the table on the next page to find the hexidecimal value that needs to be
passed on to get the correct timer interval. Look subsequntly at the program
example how to pass the value to the watchdog timer.
Timeout Table
Level
Value
Seconds
Level
Value
Seconds
Level
Value
Seconds
1
1
1
2
2
2
3
3
3
4
4
4
5
5
5
6
6
6
7
7
7
8
8
8
9
9
9
10
A
10
11
B
11
12
C
12
13
D
13
14
E
14
15
F
15
16
10
16
17
11
17
18
12
18
19
13
19
20
14
20
21
15
21
12
3312400 User's Manual
