IB Peter Feucht wrote:
> I now tried to flash the changed software, but for another part of my
> circuit can only be operated from no more than 3,3V I crashed this
> part by applying 5V (no big surprise!).

Right.  You have to design for ICSP up front.  The impact is usually minima=
l
when done right.  Doing it after the fact will usually cost a lot more and
field units may not be reprogrammable at all.

See http://www.embedinc.com/picprg/icsp.htm for more discussion of this.

> When looking at several application notes I only found the
> possibility of ICSP with Vdd=3D5V! Do I miss something?

Yes.  App notes aren't for providing specifications.  Specifications are in
the datasheeet and the programming spec.

I just looked, and the programming spec says that Vdd must be from 4.5 to
5.5 volts to perform a bulk erase.  Most programming specs tell you the Vdd
range of other operations, but this one is strangely quiet about that.  The
only safe thing to assume is that Vdd must 4.5 to 5.5 volts for all
programming operations unless you can find a definative spec to the
contrary.

> My ICSP hardware is a PICStart+ (I love it!)

That's a development, not production programmer according to Microchip's ow=
n
classification.  It's OK to use for programming one off versions for testin=
g
and debugging, but you really shouldn't be using it in production.

> with a self made adapter.

The Picstart+ is a in-socket programmer.  It therefore was not designed wit=
h
consideration of a target circuit connected to the PIC.  While I have heard
of people getting away with using a Picstart+ as a in-circuit programmer,
it's not a good idea.

> Is there a possibility to make flashing with Vdd=3D3,0V on a 12F519?

Not if that includes bulk erase, and probably not for other operations too.
See the programming spec.

> If possible at all, is it reliable, to just use a voltage divider for
> Vdd, ICSPCLK and ICSPDAT?

No.  More kludges are going to make things less reliable.  It's not clear
what signals from and to where you want to divide down, but I don't see how
readback is going to work, just to name one problem.

> I assume I have to keep the Vpp at those
> 12,5V (which makes no problem in my case)

Don't assume, know.  This is quite clearly shown in the programming spec.


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