EEPROM writer for AT28C256 using Arduino Mega

Quick and dirty breadboard circuit and Arduino sketch to make possible write in the AT28C256 EEPROM

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When making my pet project JACA homebrew Computer I quickly realize that I would need some way to write in the ROM chips (for microcode and for the programs itself). Obviously I could buy an EEPROM writer but I prefer to have some fun doing my own. Besides this I was learning Arduino and it looks like a great way to acomplish this. (For this same reason pardon me if there is some shame bad programming technique.

Source code:

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mitchgollub wrote 10/22/2020 at 12:37 point

Has anyone gotten this to work?  I hooked up my Mega to match the sketch and the picture, but I'm still unable to write to the memory of my AT28C256 chip.

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jamesaharrisonuk wrote 12/27/2019 at 05:34 point

Do you have a schematic? I've guestimated wire up by looking at the pictures, but its not working. The Sketch code uses 16 (0-15) address lines, but the AT28C256 only has 15 (A0-A14 and there is no A15). Where does the extra address line hook up to. Ive changed the sketch to ADDRESS_BUS_SIZE variable to 14.

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Marcel van Kervinck wrote 04/02/2018 at 10:37 point

I made one like this as well, it is a great tool for learning these chips. After a while I rebased the code on MEEPROMMER. You have to play around with the cycle times and retry-scheme to speed-up things. The code can get tricky from there. Still it is worth looking at it.

When I got to the point of locking/unlocking ATmel EEPROMs I found some issues with that. I debugged them (there is a problem in MEEPROMMER). I got it to work, but I had a "proper" programmer shipped from China as well and never looked back. They are so much faster, easy to use, and quite cheap.

I just saw "The 8-bit Guy" just unbox exactly the programmer I'm using!

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Dylan Brophy wrote 03/10/2018 at 07:04 point

I did something like this before! Pain to do, and I only got it working once :P  Cool to see this on HaD

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