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PICList Thread
'16C7x, Codeprotection, and UV erase'
1999\03\16@185450 by Marc

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Well, it was topic on the list often enough to know that setting
code protection bits on a JW device is not recommended.


According to the programming specs, a normal cell receives up to
25 programming pulses. If it still doesn't read back correctly,
the chip is considered bad. Another 3N cycles are applied then,
to be on the safe side for the whole voltage range.

That would make for a max of 100 pulses for a normal cell.


Someone on the list pointed out that his PIC12 actually reads back
correctly after one single programming pulse, and that he skips
the 3N overprogram pulses to speed up his development cycle (reduced
erase time).

If that holds true for the C7x, a normal cell receives just 4
programming pulses or maybe 8, but no near to the max of 100.


The config word (code protection) however does _always_ receive
100 pulses (making up a total of 10ms programming time), according
to the programming specs.


I wonder whether the UV erase problems with code protected devices
are caused by UV resistant coverings on the chip surface, or
simply by _overprogrammed_ code protection bits?!

Has anyone noticed if programmed XTAL or WDOG bits expose the same
resistance to erasure as code protection does? ("No" would speak
for UV opaque covers)

Can you confirm that these devices really verify OK after just one
single programming pulse usually?


I'm looking forward to your comments on the matter..

1999\03\16@190110 by Ryan Pogge

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Trying to do a little reverse engineering?
=)


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