Dan Michaels wrote:

> Hi Tony,
>=20
> Some of these issues are touched in DS31028A - Section 28. In-Circu=
it
> Serial Programming=99 (ICSP=99). Says:

I'll download and check that out - thanks.


> Sounds difficult to achieve total versatility, in being able to
> handle virtually "any" app board operating over full Vcc range.

CUMP can do it - kidding ;-)

> I had another question regards your ckt. I assume [rightly??]
> that you have some kinda control PIC on your programmer bd. So,
> when you vary verification voltage over 2 - 6v, are you also
> varying Vcc to the control PIC?

No.

> If no, then how are you interfacing to the pins of the target PIC,
> to deal with the large Vcc differences? 2v <-> 5v and 5v <-> 6v.

I am using open collector drivers for RB6/7 with pullups to the VccP
rail.

The data pin (RB7) has an input circuit as well, so it can be read.

I tested the circuit over a 1 meter cable length and all seems ok.

According to the ICSP sheet mentioned above, RB6/RB7 'may' need
isolation depending on the target circuit connections. If that's the
case then my circuit should work. As you mention, you can't hope to
please everyone.


--=20
Best regards

Tony

mICro's
http://www.picnpoke.com
mailto:sales@picnpoke.com

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