EPROM erase times and lifespan

Tony Duell wrote: I'd go with "maybe, but it isn't guaranteed". To my knowledge, no EPROM manufacturer (if there are any left, I seem to recall STMicroelectronics were one of the last) guarantee that their chips will work under UV light -- I suspect the expectation is that you hit them with UV light for one reason only -- to erase them. There may be a little bit of shielding over the more sensitive circuitry, but I wouldn't bet any money on it. One thing that's sometimes worth a quick demo is the propensity of EPROMs to temporarily lose their programming when nailed with high-intensity light from, say, a camera flash. That caught me out a few times -- I've got a couple of old HTEC "Kitty Card" 8052 microcontroller boards (formerly sold by Greenweld). Basically, it's a board with an 8032, an EPROM, a bit of RAM, an RS232 line-driver and a few I/Os (notably a HD44780 LCD driver). The original code in the EPROMs contained text referring to the old Argos "Premier Points" scheme. Anyway, I finished hooking the board up, and figured it'd be nice to have a photo of the whole arrangement. The camera flash fired and the software promptly crashed. A nice explanation as to why semiconductors tend to come in light-proof packages, and why you really should put reflective labels on windowed ICs when you're done playing with the software... -- Phil. classiccmp at philpem.me.uk http://www.philpem.me.uk/