On Thu, 7 Aug 1997 21:45:23 +0200 Agrico LTX <agrilltx@IAFRICA.COM>
writes:
>Hello everyone!!
>
>I hope that I will at least save someone some time waiting for the
>configuration bits on a PIC17c44 or similar to erase some time.  I was
>quite shocked to have my erase time jump from about 3 mins to 25 mins
>when
>I moved from the 16C71 to the 17C44.
>Main problem is that the configuration bits take two to three times
>longer
>than the program memory to erase.
>I have just figured out that as long as I don't want to change the
>config
>bits, I don't have to wait for them to erase!! Silly me!! My picstart
>is
>friendly enough to tell me whether the program memory, config bits of
>both
>are unerased when I do a blank check - as long as it doesn't moan
>about the
>program memory, I can reprogram right away.
>I know it is obvious, but if I save one person 15 mins for every
>reprogram
>this message was worth it...

Be careful cutting back the erase time.  The PICSTART only checks at 5V
if the chip is blank.  If not completely erased there will be some ghosts
of the old program that will pass the 5V check but come back to haunt you
at low voltage and/or high temperature (these conditions move the EPROM
read margin toward "programmed") or just at random.  Do a few tests to
see how long it takes to get the PICSTART to first report the program
array is "erased" then use about 2x that time for quick tests.  But if
the chip is going to get (you) into a critical situation, e.g. near a
customer, investor, boss, etc. give it a good dose of UV, like 4-5x the
minimum to be sure it is really blank, then reprogram.  (of course,
always squirrel away an older, but well-known, version of the program for
such demonstrations.)

Another note about erasing: clean off the chip's window before putting it
under the light.  Seemingly innocent smudges of fingerprint or old
adhesive can block a lot of UV.  It is also normal for the eraser's
intensity to decrease as it wears out.  Repeat the minimum erase time
test every few months to be sure your eraser is still strong enough.

>
>One question - the new MPLab picstart programmer status window has a
>button
>to program directly without having to pull down the top menu. Is there
>any
>way to configure this button to only program the first say 500h
>locations,
>as one can when using the top (pulldown) menu??

I don't think so.  It would be nice.  Usually I leave the programmer
window minimized and open the other one from the pulldown.  On '84
projects I usually don't want to change the EEPROM when changing the
program.