Erasing EPROMs - was Re: '90 Calpaks and PROMs

[Peter Gargano]

TK wrote:
> 
> Yes, you can damage eproms. I usually start at 1 minute then check for blank
> and keep increasing it until I get a blank then add 2 minutes. It all
> depends on the eraser and eprom manufacturer.

   It does not harm an EPROM to over erase for a few hours.
   Thus, if uncertain about the lamp intensity the safe thing to
   do is erase two or three times the minimum erase time.

That was an extract from page 4 of:

   National Semiconductor Application Note 472
   Merrill Johnson, March 1987
   Programming National UV EPROMs

This is worth reading as it further points out the problems of under erasing
EPROMs. I'd suggest erasing for "as long again" as it takes for a blank check.
Also, UV lamps degrade over time, and it's worth doing a "blank check time"
test if you use your lamp a lot.

I could *not* find AN-472 at:

   http://www.national.com/apnotes/apnotes_all_1.html

So, if anyone wants a copy, I'll send it to /incoming. Note also: a lot of
GM EPROMs are Natsemi parts, and are identified by an 014 as the part prefix.

Peter
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