A possible answer to:
>Here's a brain buster.
>We have a stand alone CO gas monitor (safety equipment) that uses a
>PIC16C74.
>If the power supply is momentarily shorted (milliseconds), the PIC does
>not recover, but locks up in random modes.
>We have the Watchdog timer ON and CLRWDT is only given one time in the
>main program loop.
>Any ideas?  I was massacred today in an engineering meeting as this
>instrument was on the verge of its first major shipment.

James:

What type of oscillator are you using? TTL clock,crystal,etc. Is it still
oscillating after the power glitch? I mention this because if the program
counter (instruction pointer) is being loaded with garbage that is outside
your program loop, the watchdog timer should fire and reset the PIC unless
the clock/oscillator has stopped.

Any more info on what state it is locking up in? How long do you have to
power down to reset the processor?  What value of bypass capacitors are on
the PIC?

Good luck,
Todd Peterson


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