IBM 100/10 - Manual (Page 122)

TPC-642 User’s Manual 112
Appendix A Programming the Watchdog
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.
04 4 sec.
.
.
.
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).