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[Moved] EPROM and EEPROM chips does any light damage them?

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johnburford

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If any kind of LIGHT ( not UV light) just regular shop lighs gets through the Eprom labels or EEPROM labs, This can ruin and damage EPROM and EEPROM chips. I can READ the files on EPROM chips but I can't WRITE files to EPROM chips. I know I can read and write to EEPROM chips, but can I write files to EPROM chips. When using a universal programmer to check EPROM and EEPROM chips do you ever change the univeral programmers software settings about the test voltage, margins , etc. Each Universal programmer has different algorithms for testing the checksum. A Bad EEPROM chip can pass the checksum test on one universal programmer but fail on other universal programmers any reasons why?
 

dick_freebird

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Any light with wavelength short enough to free electrons in
silicon will provide carriers to cancel the stored charge. How
long this takes, depends.

I've never messed with settings on my Willem programmer,
that was the whole point of going with that one, it was
known-good for the EPROMs I was using. But I did find out
that there is a large variation in speed grades for those
EPROMs, the plastic un-erasable ones I got for cheap
were also way slow. Possible that write cycle time wants
changed?
 

betwixt

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EEPROMs don't normally have a window so light doesn't affect them. EPROMs are the ones with quartz windows and as Dick_freebird pointed out, ANY light with sufficient energy will cause degradation of the stored charge in the cells. It has to be taken in context though, a UV eraser with it's tube a few mm away from the window will produce thousands of times more discharge current than a room light and even a simple paper label will reduce the light level maybe a hundred times lower again. Most EPROMs will survive tens of hours of direct Sunshine on them before they show problems.

You should note that except for some very early types (before about 1990) the methods of programming EEPROMS and EPROMs is completely different so it isn't fair to compare your programmers performance in terms of one type or the other. Each EPROM manufacturer produced their own algorithms so if you can't program them, the chances are you have the right device but the wrong manufacturer selected.

Brian.
 

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