Thanks Dwayne...a good tip. the m'chip doc is very helpful - it really
validates all the replies tha cme from the list .

Interestingly I can get a program into one 16f, but not another  - even
though it has the same apparent conditions.
I'll have to see if there is something that's not so apparent.....
I will build a buffer on Monday and will also check on Vpp.

Thanks to all.

Chris
>
> If the power supply rise time does turn out to be the
> problem, Microchip
> has published an active buffer circuit for that as well.  Its
> in lots of
> places: I simply did a search for the 2 terms PLUS ICSP (plus
> was shorthand
> for picstart plus) - one of the first hits was for the 12c508 but the
> buffer schematic was the same:
> <http://www.microchip.com/download/appnote/devspec/12cxxx/misc
/91017b.pdf>

Have a look at the buffer circuit in appendix A: it has the advantage that
it allows Vdd to go to zero for those PICs that require Vpp to be applied
before Vdd.

dwayne

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