> > 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 lighti=
ng
> > 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 insist=
ed
> on covering the EPROM windows. =A0(In fact I was tempted to post it here.=
) =A0I
> have to say that at the time, I didn't know about the photoelectric effec=
ts,
> but I'm not aware we ever had a problem.

And yet, a number of people, including me, have reported problems
which were definitely caused by light. In my case it was office
fluorescent lighting.
Covering with a sheet of paper was enough to prevent the effect (or,
to prevent it being obvious :-) ).

    R

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