A.1 Programming the Watchdog Timer
To program the watchdog timer, you must write a program which writes a value to I/O port address 443 (hex). This output value represents time interval. The value range is from 01 (hex) to FF (hex), and the related time interval is 1 sec. to 255 sec.
Data Time Interval
01 1 sec.
02 2 sec.
03 3 sec.
04 4 sec.
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3F 63 sec.
After data entry, your program must refresh the watchdog timer by rewriting the I/O port 443 and 043 (hex) while simultaneously setting it. When you want to disable the watchdog timer, your program should read I/O port 043 (hex). The following example shows how you might program the watchdog timer in BASIC:
10 REM Watchdog timer example program
20 OUT &H443, data REM Start and restart the watchdog 30 GOSUB 1000 REM Your application task #1,
40 OUT &H443, data REM Reset the timer
50 GOSUB 2000 REM Your application task #2,
60 OUT &H443, data REM Reset the timer
70 X=INP (&H043) REM, Disable the watchdog timer
80 END
1000 REM Subroutine #1, your application task
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1070 RETURN
2000 REM Subroutine #2, your application task
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2090 RETURN.
