EPROM erase times and lifespan

Tony Duell ard at p850ug1.demon.co.uk
Thu Jan 29 13:34:18 CST 2009


> 
> --- On Thu, 1/29/09, Jules Richardson <jules.richardson99 at gmail.com> wrote:
>  
> > Presumably more expensive erasers do things in-place - i.e.
> > periodically do a blank-check during the erase cycle?
> 
> Hmm, I've never even heard of such a device. Even the professional 
> EPROM erasers are little more than what I've built, a box with a UV 
> light and a timer. I've never heard of an eraser in which the chip was 
> actually connected to anything while being erased.
> 
> If a machine like this exists, however, it would be quite cool! But 
> probably very expensive, and a pain in the neck to use, as you'd have to 
> tell it what kind of chip you were erasing, and it would need ZIF 
> sockets and all kinds of electronics to read the chips.

I've never seen a commerical one (but then I've never seriously looked), 
ut I am pretty sure there was a design for ome in one of the magazines 
over here <mumble> years ago. Probably Elektor. Given the time, it 
probaly only worked with 2764/27128/27256 devices which have essentially 
the same pinout, so telling it what sort of device it was erasing is not 
a problem.

>From what I rememebr, the cirucit just read through all the addresses of 
the EPROM until all of them read as FF. And then geve <n> times more 
erasure time. In other words what you expect. I think it was built from 
TTL (no microcotnroller, no PLDs of any type), so it should still be 
possible to make one.

-tony



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