ianlesnet@cwazy.co.uk wrote:
>The program works great at 5 volts, but I get nothing at 3.3volts.
>Does anyone have experience working with PICs under 5 volts?  Is there
>something obvious I have missed?

Have you remembered to clear the Brown-Out Detect Enable bit (BODEN) in
the configuration word (see section 14.1 of the data sheet)?  If it is
set, then the BOD circuit holds the PIC in reset when running off 3.3V.
In the PIC16F628, the BOD trips below a *fixed* threshold of around 4.0V.

It caught me out first time around!
-- 
Ian Chapman
Chapmip Technology, UK
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