Adolfo Cobo (Ingenieria Fotonica) wrote:
>
>  Hello to all,
>  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 had to isolate the programming pins with a switch even though the
circuits the pins were connected to were relatively high in impedance I
suspect rise time problems due to capacitive loading.Afterwords it
occured to me that I probably could have built a cmos buffer into a dip
clip and succeded but I did'nt try it.There's no doubt others on the
list with more usable advice but I just could'nt help myself..Tony M.