Advantech manual B.1 Watchdog timer programming example, clear the watchdog timer, for TPC-1260

B.1 Watchdog timer programming example

The watchdog timer built in the TPC-1260 is a useful aid to reduce system down time-especially for those operating systems not reliable enough. There is a counter inside the watchdog timer. If the system does not constantly clear the counter within the timeout period, the watchdog timer would initialize a system reset.

The following example program in assembly language gives hint to utilize the watchdog timer under operating systems such as DOS, Windows 9x/NT, etc.

Step 1: activate the watchdog timer

mov dx, 404Ch

in	al, dx
and	al, NOT 80h	; GPO7 to low
out	dx, al
Step 2: clear the watchdog timer
mov	dx, 404Ch
in	al, dx
or	al, 80h	; GPO7 to high

out dx, al

Step 3: re-trigger the watchdog timer

If the timer will not count the GP07 is kept high. To re-trigger the watch- dog timer:

mov	dx, 404Ch
in	al, dx
and	al,	NOT 80h	; GPO7 to low
out	dx,	al

Notice:	the utility to enable/disable the watchdog timer under
	Windows CE is built in the Advantech Windows CE
	for TPC-1260.

5 4 TPC-1260 User's Manual