'90 Calpaks and PROMs

[Roger Heflin]

On Mon, 1 May 2000, Keith wrote:

> is it possible to have an eprom in the eraser too long and damage it?
> Keith
> 
> Roger Heflin wrote:
> > 
> > Under the blue cover there is a black chip with about 28 pins, there
> > is a sticker on the top of it, it is covering a window in the chip,
> > you cannot erase the chip with this window covered, as the light won't
> > get to the circuits that are the eprom.
> > 
> > Also, if you do not recover the window sunlight can erase/degrade the
> > chip and it will lose its data and if exposed for long enough will no
> > longer be programmable at all, so it is very important to keep it
> > covered.
> > 
> >                         Roger

I was told that there was, but someone did find a technote from
National Sems that said not.  The note was dated in around the 1987,
the ones I was warned about having the problem probably predated 1987
by at least 5 years, so they may have had the problem at one time, but
have long since fixed it.  

THe technode also talked about the UV lamps inthe eraser aging badly
when it was on, so it gets weaker, so even if you did not damage the
chip you would be using up the light.   The indications were that the
UV lamp was in the low 1000's of hours, so unless you were doing alot
of erasing it probably won't affect any of us.

			Roger

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