David Schmidt <PICLIST@MITVMA.MIT.EDU> wrote:

> I've programmed and debugged my code using a PIC12C508/JW part.
> Everything works fine.  I then put in a OTP '508 in my programmer.
> It programmed and verified fine but when I put it in my target
> circuit it doesn't work at all!

Dave:

What's happening is that you're relying on the fact that light
impinging on the JW die will tend to zero its RAM.  I discuss the
issue in some detail on my company's web page... I think it may even
be the answer to Question #1 in the "Microchip PIC" section of the
"Answers" area.

To prove to yourself that this is the problemm, cover the JW's
window with something OPAQUE (like black electrical tape or one of
those silvered floppy-disk write-protect labels) and try it again.
You'll undoubtedly find that it immediately starts behaving just like
the OTP part (i.e., it won't work anymore).

To solve the problem, you'll need to add some code at the start of
your program to initialize all the registers you use.

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com                 ===
=== Fast Forward Engineering - Vista, California          ===
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