Dave, it sounds like the problem is the interface. I've designed a
variety of devices that connect to a PC parallel port and grounding was a
big problem. Next was noise on the signal lines. I normally use a 74HC
buffer with a R/C filters. As far as the Parallax programmer, the main
problem I've seen was related to timing and how the parallel port was
implented on the PC. In my case, I got errors when running under Windows 95.
I get 100% reliability when I reboot to the MSDOS mode. Other folks with
faster and slower machines have no problem. I'm using SIIG cards with
EPP/ECP parallel ports.

   Carmacon is providing an upgrade to the Parallax programmer that uses the
serial port. It costs around $30 if you want to build your own RS232 interface
or $50 if you buy one from them. It runs in Windows. The update includes a new
firmawre chip, software, and serial interface that plugs into the RJ11 jack on
the Parallax programmer.

   Andy Kunz and I have the upgrade and have been providing feedback to
Carmacon. While I'm certainly not in a position to speak for Carmacon, I think
that their product will be very robust within the next few weeks. They have
been very responsive to suggestions and bug reports. Also, their update
supports more recent PICs compared with SPEP v4.7. Parallax is still
supporting the PIC (not just the Stamp) and the Carmacon update will provide
good support for those of us who prefer the Intel-style syntax of the Parallax
and TDE assembler.

   - Tom

At 12:36 PM 1/30/98 EST, you wrote:
>In a message dated 98-01-30 05:18:48 EST, you write:
>
><<
> Tom, thanks for the advise. I bought a 16F84, programmed a few 1's and 2's:
> the result was the same as with the 12c508.
> I got a brand new programmer from my distributer, still the same problem.
> So, the problems are caused by faul communications with the parallel port of
> the 286 computer. A known problem??
>
> Leo van Loon
>  >>
>Leo and Tom,
>I have had the same problem with my parralax programmer.  My problems started
>when I upgraded my unit to version 4.xx of the firmware.  The only way I get
>it to reliably function now is to use my ZIP drive as a buffer.  If I plug
>directly into the parrallel port of my laptop I get all kinds of errors.  If I
>plug my ZIP drive into the laptop and plug the programmer into the ZIP drive
>it works fine.
>
>Go figure
>
>Dave Duley
>
>