Watchdog Programming Guide
•
23
3
Watchdog Programming Guide
The NuPRO-760
implements a watchdog timer by the use of PLD, EPM7032.
It contains a one-second resolution down counter. Once setup a value to
WDT, the timer begins to count down. The Watchdog output is connected to
“reset” button. When the system hangs up without software re-trigger, the
system will be reset.
The watchdog timer would reset the system automatically if the system
program did not refresh the watchdog timer during the watchdog time out
interval. It is set at I/O port 440h and 443h to enable/disable the watchdog
time out function. Its clock source 1Hz, and then is divided into 1Hz base to
counter a 8 bits counter such that the timer range is from 1 sec to 256 sec
with resolution 1 sec.
Regarding to the watchdog function, users must have a program to set the
watchdog time out value, and refresh the watchdog timer cycle. If the system
programs goes into a dead loop or goes into an abnormal cycle, the
watchdog timer cannot be refreshed immediately. Meanwhile, the watchdog
timer will reset the system automatically. The watchdog timer will be
refreshed by “ disable watchdog output” then “enable watchdog output”.
