>  I need to program a 16c84 part soldered to the PCB, and I've built two
> homemade programmers: a "ludipipo" for the serial port and a "topic" for
> the parallel port.
>  None of them are able to program the pic in the circuit, but they work
> fine with a "off-circuit" PIC.  I've read in this List some things to try:
>
>    - Stop the PIC oscillator grounding the OSC1 pin.
>    - Shield the cables to the PIC.
>    - Cables as short as possible.
>
>  My questions is: It's really needed to stop the PIC oscillator? What else
> can I try?
>  Thanks in advance.

  I have used my Tait programmer to program 16F84s in-circuit (well,
in bread/pref board) without modification.  I DID NOT stop the
ceramic resonator, and I am using a short non-shielded cable.  I even
use the switched programmer power to power the device.  However, my
circuit does not yet use RB6 and RB7, so I can dedicate them to
programming.    If there is interest, I can share information on my
setup further.  I am very happy with my Tait programmer, it let me
start experimenting with PICs for very little cost!

Byon
________________________________________
 Byon Garrabrant  N6BG  byon@netcom.com