At 01:37 AM 26/2/97 +0200, you wrote:
>Does someone know the common problems & solutions for the COM84
>programmer? My attempts to program PIC16F84 with COM84 has been
>very unsuccesful.
>
>I build my COM84 with instructions found from
>http://hobbes.king.ac.uk/matt/pic/prog.html. Is that circuit ok? When I
>write something with pip02 program (I use com84.exe driver, does it work
>with 16F84) I get programming error. Reading the chip always tells me 3f
>ff stuff.
>
>Even that the circuit is very simple, I tried it again: I asked my friend
>to make the COM84, we used a fresh PIC and his computer. Nada, same
>symptoms.
>
>But I think that there is something strange going on, because while
>programming, my multimeter shows only about 5-6V as the voltage of MCLR.

this is the problem, unless the voltage is >= 10.5 the programmer will not
program or read any chips.
I suggest you make a simple LPT programmer. PIP02 now supports NOPPP
almost simpliest LPT programmer.

>As far as I know, it can't be right? It should be higher? Is the problem
>too low voltage, possibly caused by lame serial ports? (but if it's so,
>lame RS ports are very common; I have tried two different mother board
>integrated and one separate adapter card) Or is MCLR switched on/off
>during write procedure?
>
>Please, can you tell me what is going wrong?

maybe you use 7805 on your programmer? it takes too much current
78L05 or zener can be used.

antti

The COM84 hardware or whatever a-like is not our design, we only wrote
a driver for our programming software.

-- Silicon Studio Ltd.
-- http://www.sistudio.com