Appendix A Watch-Dog Timer
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User’s Manual
APPENDIX A. Watch-Dog Timer
You can enable the watch-dog 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 watch-dog. Decide the way you want to set the period for reset by
selecting hardware or software watch-dog (if both of them are available). For hardware setting period,
select period by jumper. For software setting period, normally setting hardware watch-dog timer period to
16 sec.
Software watch-dog 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
OUTDX, AL OUT DX, AL
Note: “F” is the period of software watch-dog 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.
