[Coco] EPROM question

[jdaggett at gate.net]

On 7 Feb 2008 at 1:31, Joef6809 wrote:

> Interesting, The window has a sticky label over it as most do. I'll
> probably take a dump of it just in case anyway. Its not like its
> valuable or anything but its part of the collection now so it need to
> be taken care of. BTW are you saying alpha particals will also erase
> an EPROM? -----

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Not alpha particles but UV light in the 235 nM range or what is often refered to as UVC light 
will erase the UVEprom.  It is the programming voltage that causes charge to bore through 
the oxide layer in a tunnelling mode known as the Fowler-Nordheim tunneling process. This 
allows the charge to drain off the floating gate transistor and thus result in the bit to read 
"zero". UV light restores the oxide boring hole and the charge and the bit will read a logic 
"one". You can over erase an UV EPROM also with to much UVC exposure. This can  yield 
in the bit not properly reprogrmming.