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54 TPC-1260 User's Manual
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
Step 2: clear the watchdog timer
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:
Notice: the utility to enable/disable the watchdog timer under
Windows CE is built in the Advantech Windows CE
for TPC-1260.
mov dx, 404Ch
in al, dx
and al, NOT 80h ; GPO7 to low
out dx, al
mov dx, 404Ch
in al, dx
or al, 80h ; GPO7 to high
out dx, al
mov dx, 404Ch
in al, dx
and al, NOT 80h ; GPO7 to low
out dx, al