WATCHDOG TIMER SECTION 11
Page 11-1 RPC-320
DESCRIPTION
The watchdog timer is used to reset the RPC-320 if the
program or CPU "crashes". The timer is built into the
80C320 CPU. Timed access requirem ents built into the
CPU make it highly unlikely an errant processor would
cancel a watchdog timer.
The watchdog should not be used in loops which do not
end quickly or are of indeterminate duration unless a
WDOG command is included. An example of an
indeterminate loop is one that waits for a port condition
to change.
The timer is set by executing a WDOG n command. n is
0, 1, or 2. 0 turns off the timer. 1 sets the watch dog
time to 380 ms while 2 sets it to 2.8 seconds. Executing
WDOG by itself resets the timer. WD OG must be
executed periodically to prevent a reset.
When the watchdog times out, a software reset is
performed. The effect is lines at J3 do not change as in
a power-up or hardware reset. Lines at P6, display, and
keypad port are reset to power -up conditions.
EXTERNAL RESET
The card is reset externally by momentarily shorting
W10[1-2]. Reset is also achieved by shor ting W10-2 to
ground. Maintain this short for at least 10 ms. The card
will then reset for about 350 ms.
