> > > So, is there any unusual or it is always
> necessary to
> > > provide for a switch to disconnect the quartz
> when
> > > programming.
> >
> > Something doesn't sound right.  The crystal
> oscillator should
> > have no effect on programming unless the
> programmer has a VERY
> > long Vpp rise time.
>
> In my experience this is a normal effect for
> primitive programming
> hardware that is not designed for in-circuit
> programming.
>
> Wouter van Ooijen

Maybe the culprit is the programmer I have.It is a kit
bourd which is an universal programmer for PIC,AVR and
EEPROMs with corresponding attachments and probably it
is not designed for ICSP.
The most likely reason for the flaw is,as Olin said,
too long rise time of Vpp.This is discribed in TB016 -
"How to implement ICSP using pic16f8X flash MCUs".
To solve this problem I'm going to use a switch to
connect crystal osc. to ground when programming.
But I'm not completely convinced that this is the
right solution because with the previous circuits I
have made there weren't such problems.I suspect that
the other parts influence to the pic although there
are not powered.But I leave that to you to consider.I
attach the circuit.

Stefan




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