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out period that is selected by software, please refer to the example program.
A tolerance of at least 5% must be maintained to avoid unknown routines within the operating
system (DOS), such as disk I/Os that can be very time consuming. Therefore, if the timeout
period has been set to 10 seconds, the I/O port 443H must be read within 7 seconds.
NOTE:
When exiting a program it is necessary to disable the Watchdog Timer,
otherwise the system will reset.
Example Assembly Program:
TIMER_PORT = 443H
TIMER_START = 443H
TIMER_STOP = 843H
;;INITIAL TIME PERIOD COUNTER
MOV DX, TIME_PORT
MOV AL, 8: ;;8 SECONDS
OUT DX, AL
;;ADD YOUR APPLICATION HERE
MOV DX, TIMER START
IN AL, DX. ;;START COUNTER
ADD YOUR APPLICATION HERE
W_LOOP:
MOV DX, TIMER_START
IN AL, DX. ;RESTART COUNTER
;ADD YOUR APPLICATION HERE
CMP EXIT_AP, 0
JNEW_LOOP
MOV DX, TIMER_STOP
A-3
