EPROMS - Page 1
Forum section: electronics / projects

author: Squarewave
author_rank: Frequent Contributor
timestamp: September 11, 2024, 02:44:03 pm
content: If there is such a thing, do you know if anyone has created a list for EPROMS and what will work in place of them. For example, if there is one which is obsolete, which one can be used in its place?I have a stash of old EPROMs, mostly pulls, some NOS from work also. So looking to see where they may be useful.Thanks.

author: bson
author_rank: Unknown
timestamp: September 11, 2024, 05:21:35 pm
content: Most parallel 8/16 bit wide PROMs, EPROMs, SRAMs, NOR flash/EEPROMs, etc, are mostlyfunctionally interchangeable. Meaning signal definitions and timing is such that they're pretty much mutually exchangeable even if different packages.For devices that have the same number of data and address pins, in the same package) they're often interchangeable. This is easily verified by checking the datasheets.The exception is for programming purposes, programming requires device specifics. Sometimes voltages, sometimes erase sequences (pins or special writes, use of a command pin for NOR flash), sometimes the write procedure itself.

author: Benta
author_rank: Super Contributor
timestamp: September 11, 2024, 05:46:53 pm
content: You'll have to go back in time to the late 80's, when different suppliers would give out comparison tables.That being said, they're mostly compatible on the supply, address and data bus pinning. The small group of signals comprising R/W, OE and Vpp vary.You can safely assume they are 5 V devices. Programming voltage varies, but is normally stamped on the package.Erasing is UV, of course. You need an appropriate eraser, they can still be bought.

author: bson
author_rank: Unknown
timestamp: September 11, 2024, 06:51:10 pm
content: I think replacing old EPROMs with modern EEPROMs or NOR flash on a carrier is desirable. The other way is bound to be problematic as those old windowed EPROMs are very slow.

author: Gyro
author_rank: Super Contributor
timestamp: September 11, 2024, 07:14:19 pm
content: I wonder which, ultimately, have the longest data retention time. I've certainly seen plenty of 40yr+ uncorrupted UVEPROMs.

author: Squarewave
author_rank: Frequent Contributor
timestamp: September 11, 2024, 07:26:22 pm
content: Thanks for the suggestions so far, I've not yet had a failure, but just in case I ever needed to replace an EPROM, it's nice to know what I can use or not. In the meanwhile I should copy the programs from the EPROMS I do have.

author: m k
author_rank: Super Contributor
timestamp: September 12, 2024, 01:53:17 pm
content: Reprogram some and put them in a box with not reprogrammed ones and some new ones with old and new version of a program.Add a note that somebody should check them around 2070.Generally there are two chip possibilities, JEDEC and not.28 pin 2764 to 27256 are very standard, maybe 27512 also.That includes 28x E2PROMS.After that it's different.Small ones can be many things and some bigger ones were also before the standard catched up.

author: Squarewave
author_rank: Frequent Contributor
timestamp: September 12, 2024, 03:51:51 pm
content: I need to get lots of boxes. The ones I've pulled so far are in anti static bags. There's a lot more to come also, loads of boards from an old control system, loads of EPROMS, 8088 processors etc, I'm saving them all and putting them away as they're mostly rare now I think. The ones I've looked up aren't obtainable anymore.