Appendix A Watchdog Timer Programming
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
0.25sec. to 63.75sec.
Data Time Interval 01 0.25 sec.
02 0.50 sec.
03 0.75 sec.
04 1.00 sec.
••
••
FF 63.75 sec.
After data entry, your program must refresh the watchdog timer by rewriting the I/O port 443 (hex) while simultaneously setting it. When you want to dis- able the watchdog timer, your program should read I/O port 443 (hex). The fol- lowing shows how to 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 (&H443) REM, Disable the watchdog timer
80 END
1000 REM Subroutine #1, your application task
••
••
1070 RETURN
2000 REM Subroutine #2, your application task
••
••
2090 RETURN.
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