My P16PRO (cheap programmer board not designed for ICSP) would only
program in-circuit with 470ohm resistors in series with the programming
lines (NOT Vdd, Gnd).  Also it will almost never work if it is asked to
power the circuit on its own (which only consists of a PIC and
decoupling caps directly connected to Vdd), but with the resistors, a
very short cable, and 4.5V+ put to the target I get pretty decent
results.  Doing a full power down to the PIC (make sure you fully
discharge any caps) and then powering up right before beginning
programming (almost at the same time) seems to be a key sometimes as
well.  It is definitely a weak point in my setup though and I would like
to get a legitimate in-circuit programmer or add better drivers to what
I have.

Hope this helps.
Nick

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Eisermann, Phil [Ridg/CO]
Sent: Monday, March 15, 2004 12:12 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [pic]: ICSP

pic microcontroller discussion list wrote:
> Ok but it is necessary tu have some isolators( resistors i think ) on
> the target's pins do you know exactly what ?
>=20
> Mike Hord a =E9crit:
>=20
>> Sure, just make a header with the same pinout as the PIC and
>> run the leads out to your target board.
>>=20
>> Just make sure to keep the current consumption down and
>> probably don't connect the VCC on your target to the VCC
>> on the PICSTART+.  Keep the wires short, as short as possible.
>>=20

the isolation circuit depends on what else the pins are connected
to. Maybe some jumpers if it's a hobby project. you could use
the same thing for isolation Vdd.

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