Intel OPEN (660) 120/140/150 II - Manual (Page 149)

User Manual version 2.1
OPEN (660) 120/140/150
9-139
B: Programming the Watchdog Timer
The OPEN (660) system features a watchdog timer which
can generate a system reset if the CPU processing comes
to a halt. This feature ensures the system dependability
during unattended operation. The watchdog timer is
programmable. In order to program the watchdog timer,
a program writing I/O port address 443 (hex) needs to be
written first. The output data is a value of time interval.
The value ranges from 01(hex) to 3F(hex), and the
related time interval ranges from 0 to 30 seconds.
Data Time Interval
00 0 sec.
01 2 sec.
02 4 sec.
03 6 sec.
0F 30 sec.
After entering the data, the program has to refresh the
watchdog timer by rewriting the I/O port 443 (hex) and
setting it at the same time. To disable the watchdog
timer, the program should read I/O port 143 (hex).