ICSP + reset circuit + WARP13a

[Darth Freudius]

Hello,

I'm new here and this is my first post.

I use a Warp13a to program the PIC18F452 chip through ICSP port (High voltage programming mode).

I use the couple resistor + diode to MCLR pin, I can program the PIC without any problem. But when I add a capacitor (classic RC reset circuit + diode), the PIC can't be programmed properly (some data missed at the beginning, the time the high voltage goes to high due to this capacitor => not sure but seems to be that).

The resistor is about 10k, and the capacitor 10uF.

Do you have any idea how to fix this issue ?

Thank you !!

Best Regards,

(sorry for my bad english)

David from France

[valemike]

In the past, i just had 1 pull-up resistor (10K) on MCLR, and that was it. What would happen is that noise would get into there, causing me to reset. In fact it would happen more so with one custom transformer than another of the same transformer specs, but different manufacturers.

I fixed this by following the recommended Reset circuit on MCLR commonly found in the PIC datasheet manual. I'm pretty sure your're following the same thing.

MCLR ---(1) 100ohm (2) ---(3) 47kohm (4) ---- +5V
and

47 kohm (3) --- 0.1uf --- GND

and
47Kohm (3) --- ICSP

Think of the numbers in parenthesis as nodes, since i don't have a picture.
That circuit above got rid of any noise problems i was having. I tried adding a diode, and I found I couldn't program it with the ICD anymore! So i just left the diode off.

I think the diode is for a quick discharge. This is screwing up our icsp. I was able to get a quick discharge when i removed power because i've got so many other discharge paths in my circuit anyways, so i can get away without a diode.