On Apr 3, 11:02am, James Musselman wrote:
> Subject: Power Brown Outs
> 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.
> Thanks.
>
> --
> Regards, James Musselman, President
>
>  Radix/Cobalt Instruments, Inc.
>  PO Box 897
>  Clovis, CA  93613 USA
>  tel  209-297-9000
>  fax  209-297-9400
>
>  Check out my home page  http://rdx.com
>-- End of excerpt from James Musselman

Sounds like a tough day at the office!

You could try enough bulk capacitance on your board to ride through the short.
 Or add circuitry to hold the PIC in reset until the supply voltage recovers.
 Motorola makes a part for micro-processor resets.


Regards,

Brad Morrow

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Brad Morrow                                      Advanced Systems Division
Product Design                                  e-mail: morrow@asd.sgi.com
Silicon Graphics, Inc.                      voice-mail:      (415)390-1311
2011 N. Shoreline Blvd.                            fax:      (415)961-9075
Mountain View, CA 94039-7311
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