try putting a (misc small signal) diode between MCLR switch
and the + rail to prevent voltage on mclr going up to the +
pic supply thru the switch.  My toasted pic rate went way
down after i started doing this.

alice

> Hi,
> I definately am not missing a ground. The power supply has correct polarity
> and voltage. Definatley checked out many times. There are only four grounds
> and two 5v connections. If it is latch, up under those conditions would it
> not also latch-up the 'c84 thats in there now? I'm only loading it with a
> CRO and logic probe which have input impedance of several hundred k. Would
> it be safe to say they're throw-away items?
>
> -----Original Message-----
> From: Spehro Pefhany [mailto:speff@INTERLOG.COM]
> Sent: Monday, 8 May 2000 11:36
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: ?? Short ??
>
>
> At 12:28 PM 5/8/00 +1000, you wrote:
> >Hi Spehro,
> >And thanks for your reply. I have a 7805 reg in there thats good for about
> >an amp. It shares the common ground and positive 5V with the '55. The
> >control lines are accounted for at either 0V or 5V. The chip would probably
> >get hot as if I let it go for longer than 2 - 3 seconds. For latch-up to
> >occur, would I not need a bias from somewhere? Apart from porta and control
> >lines, everything else is floating. I don't quite understand.
>
> I've seen it happen with a multimeter test probe (when it is first
> connected).
>
> I've also seen it with power supply connection problems (like a missing
> ground wire).
>
> Could be something else, of course, but it sounds like the classic symptoms.
>
> Best regards,
>
>
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> =
> Spehro Pefhany --"it's the network..."            "The Journey is the
> reward"
> speff@interlog.com             Info for manufacturers: http://www.trexon.com
> Embedded software/hardware/analog  Info for designers:  http://www.speff.com
> Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
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> =