nanoprom VS TommyPROM

You might be interested in my NanoProm project: https://github.com/gfoot/nanoprom - or the Pico equivalent which is in github too. They're for programming EEPROMs without glue logic, feel free to use any of the code that you find useful.

It is actually possible to program the Atmel ones with a regular Arduino, or even a Nano, without needing shift registers, because the address pins are latched at the start of the write operation. This is how my NanoProm worked: https://github.com/gfoot/nanoprom

If you remove the shift registers and connect the pins directly to the EEPROM then it can be done just using PORT writes. This worked well for me in NanoPROM, see here: https://github.com/gfoot/nanoprom

I have an alternative setup here for Nano and Uno that you might want to try - it deals with SDP, writes much more quickly overall, and doesn't require external components: https://github.com/gfoot/nanoprom

I also made an Arduino Nano version here: https://github.com/gfoot/nanoprom

If you're interested, I have code here that does all the page writes, unlock codes, etc correctly: https://github.com/gfoot/nanoprom It only supports writing, not reading, and doesn't use shift registers like yours does, so you can't just switch to it, but maybe seeing the code can help with the timing issues.

I have tried the script from u/nib85 from his github here (https://github.com/TomNisbet/TommyPROM/blob/master/unlock-ben-eater-hardware/unlock-ben-eater-hardware.ino) His code is for the 256k rather than the 64k version and I changed the sequence of writes as required by the datasheet for the 64k version as follows:

Oh ok. I did upload the sketch from the arduino ide, but I was following the documentation at https://tomnisbet.github.io/TommyPROM/.

Which chip are you using? If it is the 28C256 and you built the Ben Eater programmer, try this sketch: https://github.com/TomNisbet/TommyPROM/tree/master/unlock-ben-eater-hardware

Also, although not necessarily the root cause based on the symptoms you are describing, the AT28C256 comes with a software data protection feature which, if it was somehow enabled prior to shipping, needs to be disabled. Ben's EEPROM code does not unlock these chips. If your testing reveals that the EEPROM was in fact not written to, then one option would be to implement u/nib85's TommyPROM arduino programmer, which supports unlocking. It uses a few different chips, but you can make it work with Ben's hardware. There is a section somewhere in the hardware notes that speaks to that.

Here is one of th3m that works with your setup: https://github.com/TomNisbet/TommyPROM I will search for the other one and send. Also, read the README of the github repository

When I encountered the problem I tried to find the solution and found references to TommyRom. After trying I had the same behaviour then before. From the Datasheet I couldn't find mutch about extra steps to writing the Chip. I haven't build the first thing where Ben programmed the Chip manually, but I will recreate it next.

Really not sure about that programmer... according to what I could read here it mostly supports micro-controllers and serial EEPROM chips. If you only run on Windows, then the XGecu T48 would be a safer bet, IMO. One of XGecu's official distributors has a store on AliExpress under the name of 'XGecu Official Store'. Most reliable source if you are willing to wait a bit. If you run Mac OS or Linux, then the older TL-866II-Plus model is best for compatibility as the minipro open source software works with it on these platforms. Still available out there, but good chance it will be a clone. A third option is a breadboard/arduino version like the TommyPROM from u/nib85.

I just added support for these chips to my programmer. Take a look at this project if you want to see some working code: https://github.com/TomNisbet/TommyPROM