VLAC. Chip erasing question

superba superba at comcast.net
Tue Dec 16 01:52:34 EST 2003


Hi,

I apologize in advance if I offend anyone, but I haven't seen a UV erasable
EPROM for years except in my parts box.  So, (I'm ducking), be sure it's an
EPROM which has a clear quartz window which is probably, and ought to be,
covered by an opaque label, when not being erased, of course.

HST, I have the directions for a cheap UV eraser I bought years ago;  it's 2
typewritten pages and deals with the physics of erasing EPROMs, etc.  I'll
be happy to scan it and send a copy to anyone that wants a copy, or, perhaps
someone might want to post it to the web site.  It's sufficiently generic to
be of use.  Please request copies directly from me.

EPROM manufacturers state that their products ought to be good for about 500
erase cycles,   erasure times vary from about 2 to 20 minutes, and that
"full erasure should be done by exposure to 15 watt seconds per square
centimeter of 254 nano meter wavelength radiation".  In practice, some units
require much less exposure.  For example, Fujitsu and Hitachi units(at the
time of the paper) show complete erasure after 60 to 100 seconds.  Faster
erase times can be achieved by Xenon flash lamps achieving erasure in less
than 1 second, with no damage to the EPROM.

HTH.

Cheers!

Jim Jordan

>  Date: Tue, 16 Dec 2003 01:02:54 -0500
>  From: Huw Powell <audi at humanspeakers.com>
>  Subject: Re: VLAC.  Chip erasing question
>  To: Robert Myers <robert at s-cars.org>
>  Cc: s-car-list at audifans.com, Quattro list <quattro at audifans.com>
>  Message-ID: <3FDEA00E.7070109 at humanspeakers.com>
>  Content-Type: text/plain; charset=us-ascii; format=flowed
>
>  > I've been having difficulty erasing EPROM chips using an improvised
>  > battery powered 4 watt UV fluorescent light.  This apparatus
>  has worked well for quite a while.  New batteries for the light have not
helped.
>  > Do these little 4 watt germicidal UV bulbs start putting out
>  less light
>  > as they age a little?  Perhaps I need a new bulb.
>
>  In my distant memory of aquarium keeping and such, where UV lights are
>  sometimes used to kill bacteria in a water jacket around them, they do
>  lose their effectiveness... as I recall a year (although, always on for
>  that year) would be enough to see a serious reduction in effectiveness.
>
>  Not a particularly useful reply, but I guess it's also on of those
>  ****fans things, too...
>  --
>  Huw Powell
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