On Sat, 18 Aug 2012 18:10:08 GMT, (Slater) wrote:

Jeff Liebermann wrote:

What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

It's a bad EPROM. If the blank check on your unspecified EPROM burner
says it's not blank, it's not blank.

I meant another thing: what will happen if a chip undergoes several
write/erase cycles where an area is intentionally left unprogrammed
every time? It's like erasing it over and over.

Nothing will happen. Erasing sets all the bits to a "1". If the bits
are already set to "1", then erasing won't change or wreck the bit.

EPROMs do have a limited number of erase cycles. It really depends on
the age and technology of your unspecified EPROM. Usually it's about
1000 erase cycles before the silicon dioxide wrapped around the gate
falls apart.

Probably nothing, I think. It must have happened quite often that some
byte (or bit, why not?) would always be unprogrammed at every cycle in
the prototyping process, so it shouln't be a problem.

Well, there's an easy test. Erase your unspecified EPROM. Verify
that every byte is set to FF with the blank check on your unspecified
model EPROM eraser. Create a bin file where all the bytes are
programmed to "OO". Write the file to the EPROM and compare the bin
file with a read from the EPROM. If they're identical, then the
programmer was able to change every cell and there are no bits stuck
at "1". If there are any bytes NOT set to "00", you have at least one
stuck bit.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558