User`s manual

Appendix A – Watchdog Timer
Multi-Tech Systems, Inc. Single Board Computer IAC-F696 User’s Guide (S000349A) 43
APPENDIX A – WATCHDOG TIMER
You can enable the watchdog when your application software monitors an unexpected or not respond, then
the timer generates a reset to reboot your system. During the period of enable to reset, you could still
cancel reset by disabling the watchdog. Decide the way you want to set the period for reset by selecting
hardware or software watchdog (if both of them are available). For hardware setting period, select period by
jumper. For software setting period, normally setting hardware watchdog timer period to 2 sec.
Software watchdog using example.
EX.1: For DOS
Enable Disable
C:\DOS> DEBUG C:\DOS>DEBUG
-o443 D -o441 F
EX.2: For assemble Language
Enable: Disable:
MOV DX, 443H MOV DX, 441H
MOV AL, 0FH MOV AL, 0FH
OUT DX, AL OUT DX, AL
Note: F is the period of software watchdog timer (normally F indicated 0 sec.). 0 to 9 and A to F
are used for represent different period. Normally, the step is 2 sec. That means E is 2, D is
4, 2 is 26, 1 is 28 and 0 is 30 seconds.