How to program this eprom? 27C512-25 - Page 1
Forum section: electronics / beginners

author: RichardM
author_rank: Frequent Contributor
timestamp: September 19, 2019, 09:24:13 pm
content: Hi allI am seeking suggestions on how to program an 27-C512-25 eprom from an HP calculator module. I have attached some photos. I dont really want to desolder the eprom unless i have to. These eproms can be flashed using a vintage device made just fot the purpose 30+ years ago by CMT microtechnologies, the CMT-71-P01https://www.hpmuseum.org/forum/thread-5913.htmlSo I guess my questions are, could this be programmed in place by soldering wires to the underside ? What type of programmer woyld be required? I assume an older parallel port programmer like thishttps://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.au%2Fulk%2Fitm%2F123911761403Any suggestions much appreciatedRichard

author: james_s
author_rank: Super Contributor
timestamp: September 19, 2019, 09:29:00 pm
content: The TL866 can handle the eprom, but what's the black blob? You may have to desolder the eprom.

author: RichardM
author_rank: Frequent Contributor
timestamp: September 19, 2019, 10:35:23 pm
content: Ok good to hear. I have tried to do some reading before posting and wasn't sure if this eprom needed higher voltages etc Have you programmed one of these in that programmer ?Cheers

author: james_s
author_rank: Super Contributor
timestamp: September 19, 2019, 10:40:52 pm
content: The 27C512 is a very common part, not sure if I've programmed that specific type but I have done lots of 27C256. The TL866 like any other eprom programmer supplies the various programming voltages.

author: ArthurDent
author_rank: Super Contributor
timestamp: September 20, 2019, 01:49:42 am
content: I suspect what you show is a specialized module with the square with the glass cover being a special version of the eprom chip in a very small package and the black blob is the calculator chip. It looks like you scraped the black paint covering the eprom window off the eprom. You may be out of luck.

author: RichardM
author_rank: Frequent Contributor
timestamp: September 20, 2019, 02:18:38 am
content: This module plugs into the calculator. Not sure what is under the black blob. Maybe a cap or something.The module has a black sticker to keep light from erasing the eprom, easy to just stick back on when it is erased via UV.I thougjt this was just a standard eprom in PLCC form ? What do you mean by out of luck ?

author: james_s
author_rank: Super Contributor
timestamp: September 20, 2019, 02:53:33 am
content: The black blob is an IC, but what purpose it serves I don't know. You may be able to make up an adapter to program the EPROM in circuit but the blob IC may interfere with it.It's actually quite hard to accidentally erase an EPROM, even in direct tropical sun it takes hours. The black stickers are more to prevent light from interfering with operation, if you shine a bright light on an EPROM while the circuit is operating it will malfunction.

author: Circlotron
author_rank: Super Contributor
timestamp: September 20, 2019, 03:20:59 am
content: Quote from: james_s on September 20, 2019, 02:53:33 amVery true!Ages ago I made a Selcall tone generator with a 'HC705 microcontroller that had an erase window and it would work great in my workroom but every time i took it over to the phone to demonstrate it to my brother it simply refused to work. Just couldn't work it out until I realised that the kitchen was much much brighter and sunnier than the workroom. Piece of black tape fixed everything.