Appendix A Programming the Watch- dog Timer
A.1 Supported Input Timing Modes
In order to program the watchdog timer, you must write a program which writes I/O port address 443 (hex). The output data is a value of time inter- val. The value range is from 01 (hex) to 3E (hex), and the related time interval is 1 sec. to 62 sec.
Data | Time Interval |
01 | 1 sec. |
02 | 2 sec. |
03 | 3 sec. |
044 sec.
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| . |
3E | 62 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 disable the watchdog timer, your program should read I/O port 443 (hex).
The following example shows how you might program the watchdog timer in BASIC:
10REM Watchdog timer example program
20OUT &H443, data REM Start and restart the watchdog
30GOSUB 1000 REM Your application task #1
40OUT &H443, data REM Reset the timer
50GOSUB 2000 REM Your application task #2
60OUT &H443, data REM Reset the timer
70X=INP (&H443) REM Disable the watchdog timer
80END
1000 REM Subroutine #1, your application task
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