At 02:56 PM 1/27/04 -0700, you wrote:
>At 01:49 PM 1/27/2004, Jan-Erik Soderholm XA (TN/PAC) wrote:
>>Dwayne Reid wrote :

>In fact, I'd like to pose that same question to the members of the PIClist
>- Has anyone ever had a PIC verify at the normal Vdd voltage but fail to
>verify at the supply limits (either above or below the programming
>voltage)?  In other words, Vdd normal: pass, Vdd low: pass, Vdd high: fail
>(or vice versa).


Anecdotal evidence: Over the last 10 years, maybe 500 to 600 (or more) pics
programmed with a "single voltage programmer" that have never shown
indications of problems.  Of that total, maybe 2 or 3 parts failed to
program at all and of those, 1 or 2 might have been due to flakey contacts
while programming.

Yes, the manufacturer says you get a higher confidence rating if you check
at different voltages. But as with many things in this industry, I willing
to bet that PIC chips made 20 years ago *did have* problems and in the
intervening time, the process control has improved enough to not require it.

But always remember: I *could* be wrong and your mileage *will* vary...

Tom

ps: It wouldn't surprise me to find out that application ambient
temperature range is a more important factor here. If so, you would need to
test over temperature...

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