-----Original Message-----
From: George A. Silvis <gsilvis@CHANNEL1.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Monday, May 18, 1998 11:45 AM
Subject: Windowed part works, OTP don't


>'m having trouble with the PIC16C924 part. The code works in the windowed
>part but won't run when I put it in an OTP part. I'm using the Picstart to
>do the programming.
>
>One suggestion I've found is to make sure all of the file registers are
>initialized. I believe I've done that, but maybe I don't understand exactly
>what a "file register" is.
>
>Any suggestions?
>
>Many thanks.
>
>George
>   come visit my choral music midi page, the "Woodshed", at
>         http://www.channel1.com/users/gsilvis/
>                      00 FF 2F 00

I had this problem with 16C71. It worked for a windowed part, but not for an
OTP. All Microchip could tell me is that it's exactly the same die, so it
shouldn't be any difference. I did make sure that all registers are
initialized at start-up.
Even more weird - OTP worked when I lifted VDD pin!
Finally I've found the problem - one of inputs had about 3.4V rails on it.
When I raised it to 5V, everything came to normal. It looks like specs for
reprogrammable and OTP parts are not exactly the same.
Another thing they told me to check: voltage on any pin should not be higher
that VDD - it can cause latch-up. But I think it would be the same for both
parts?
I hope it may help a bit.

Gennady Palitsky
Jefferson Audio Video Systems
gennadyp@mainlink.net