[sdiy] EPROM replacement?

[Rainer Buchty]

>Has anyone looked at making a new EEPROM or FLASH based replacement for 
>old 2708/16/32/64 EPROMs?

What would that be good for? Also EEPROM and FlashROMs have no infinite 
data retention times, which seems to be your concern.

Plus, I personally prefer a programming process where I need programming 
voltages way above normal operation voltage, a certain time per byte 
(like 50ms), and considerable energy/time for erasing that thing again 
(several minutes of UV).

There are tons of EPROMs around and they will stay for probably longer 
times than CEMs, so I honestly don't see the benefits of a universal 
adapter board:  The EPROM pinout is (almost) the same among different 
sizes, so for most of them it's enough to either place N copies of the 
content sequentially into the EPROM, or just do it once and ground / 
pull-down the remaining address lines. Gives *me* a safer feeling 
compared to EE/Flash.

Back in the days, failing EPROMs were mostly caused by homebrew 
"ultra-speed" algorithms and not caring about the vendor's programming 
algorithm and times.

>I was thinking something along the lines of a carrier board for a TSOP 
>Atmel AT28C256 or AT29C256.  With a few solder pads it could be easily 
>reconfigured after programming to any one of the 2708/16/32/64/128/256 
>parts.  I'm also wondering how much longer 5V EEPROM or FLASH parts 
>will be available from Atmel, etc.  With 3.3 and now 1.8v parts 
>becoming the norm it can't be long.

3.3V probably won't be much of a problem, usually those were designed 
"5V-tolerant", i.e. you can drive the inputs with 5V, and 3.3V will 
usually be "high" enough for 5V applications.

Rainer