> There was something wierd the orther day about my 16F628 based
prototype...
> I could simply not get the thing to execute code!
> After going through all the docs again I still hadn't found what was
wrong
> so I did something that shouldn't have solved the issue according to
specs.
> I tied MCLR to VDD *even* if it was already tied to VDD internally.
(Yes, I
> had disabled it because I didn't need it, and I was using LVP ICSP.)
> Now, everything worked as it was supposed to?

What were you doing with MCLR before tying it to Vdd, floating?  If so,
that could easly be the problem.  MCLR is a CMOS input, which should never
be left floating.  Any stray noise or static electricity could drive it in
any direction.  Disabling master clear internally only keeps a low level
on the MCLR pin from causing a reset.  It doesn't mean the MCLR pin is
driven low (if it was, it would still be useless as an input).  Since MCLR
has no protection diode to Vdd, it could have picked up noise and driven
the chip in to high voltage programming mode.


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