In message , "Tapani T. Salmi" writes >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. >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? Serial ports do seem to vary a lot. I have the same problem with my new P133+ system with the I/O on the M/B, whereas my old 486 system with a simple I/O card works fine, as does my 486 system at work. I'd try adding the 555 voltage doubler circuit. I'll be trying this myself. Leon -- Leon Heller, G1HSM leon@lfheller.demon.co.uk Tel: +44 (0) 118 947 1424 (home) +44 (0) 1344 385556 (work)