I have noticed that the datasheets for various PICs indicate a
specific sequence of moving Vdd up slightly and then raising Vpp
from Vdd to high voltage, then programming the chip, then cycling
back down.

Yet, in the DIY programmer schematics I've seen, it looks like
they're getting away with just turning on Vdd and leaving it at
+5V without changing it at all, and just turning Vpp from 0V to
+13V in one step.

So how picky are the PICs really about following the programming
specs in this respect?  Should I expect that building a simple
programmer which just turns on/off Vdd and Vpp (at high voltage)
would be sufficient?

How important is it for Vpp to sit at +5V (as opposed to 0) when
not in program mode?  (I'm assuming it should stay at +5V or +13V,
but as long as I'm asking questions, I'll toss that one in too).

Thanks,
steve
--
Steve Willoughby     | "It is our choices... that show what we truly
<steve@alchemy.com>  | are, far more than our abilities."
                     |     --Albus Dumbledore, in Harry Potter and the
                     |            Chamber of Secrets, by J. K. Rowling

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