This is old-hat.  I first saw this mentioned on Microchip's website 
many years ago.  Its one of the first tricks mentioned shortly after 
the 12c508 was released.

Note that it does NOT work with certain PICs (12f629/675, 16f630/676) 
because those PICs don't have weak pullups on the MCLR pin.

dwayne


At 02:53 AM 1/29/2008, Alan B. Pearce wrote:

>Ever need an extra output pin on a 10F2xx chip? It can be done apparently,
>though the data rate is probably slow - but good enough for debugging output
>to a LED.
>
>The technique would also have some reverse engineering types scratching
>their heads ...
>
>http://www.edn.com/contents/images/6515349.pdf
>
>Technique can also be used on some larger chips apparently.


-- 
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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