Roger told us:

> Just out of interest, this is directly from page 9 of the datasheet for
> ST's
> 27C256B EPROM.
>
> "Research shows that constant exposure to room level fluorescent lighting
> could erase a typical M27C256B in about 3 years, while it would take
> approximately 1
> week to cause erasure when exposed to direct sunlight."
>

This is a favorite quote of mine, which I used to lay on folks who insisted
on covering the EPROM windows.  (In fact I was tempted to post it here.)  I
have to say that at the time, I didn't know about the photoelectric effects=
,
but I'm not aware we ever had a problem.

Per Russell's adventures:

AFAIR we used to put 2716s in the sun for an afternoon on the aforementione=
d
> brick window ledge....
> NZ does have a very high solar UV level, which helps...
>

S. California does, too, as I learned whilst exposing PC boards for etch.  =
I
tried the erase-the-EPROMs stunt once, and all I got was a batch of dead
EPROMs.  My guess was the heat did it.  (They "appeared" blank but would no=
t
program.)
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.