Harold Hallikainen wrote:

>>alan smith wrote:
>>
>>>Tim,
>>>
>>>  From my experiance, you need to do at least ONE bulk erase with 5V,
>>>and then forever more, it will work fine with 3.3V.  Its hit and miss
>>>if you don't do the one time bulk erase, but
>>>  try that and see if it works for you.
>>
>>I can confirm the same bizarre requirement. 16F876As. Would not verify
>>using ICSP @ 3.3V.
>>After one bulk erase at 5V (all parts were tolerant of 5V) loaded fine,
>>and bootloader
>>then worked correctly. Weird, but now I just put in the bootloader
>>(ROMZap) @ 5V
>>and then all is well.
>>
>>Robert
> 
> Is there a chance the chips were code protected? It seems the only way to
> get rid of that is a bulk erase, which, of course, requires 5V. You can,
> however bootload at 3.3V with code protect enabled.
> 
> Harold

I didn't specifically look at the state of the config.
These were factory fresh parts, already mounted, and I just needed to
'make them go' yesterday. The default for an erased CONFIG is NOT code protected,
but I suppose it was possible that factory testing left them with CP set.
I'll see if I still have one lying around from that batch to see what state it
was in. Seems to be a logical explanation for the observed problem.

Robert



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