Gennady,

The obvious difference between an OTP & a windowed part is the window.  If you l
eave the
window uncovered you will get leakage from photon induced carriers - this may be
 enough
to cause the differences indicated below.  Try covering the window or shining br
ighter,
more UV light, on a windowed part & see what effect that has.  A covered windowe
d part
ought to behave the same as the OTP.

Scott

----------
> From: Gennady Palitsky <gennadyp@MAINLINK.NET>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Windowed part works, OTP don't
> Date: Monday, May 18, 1998 12:16 PM
>
> -----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