Thank you for the fixes NewRisingSun!
Sadly I haven't got any other device like this but if I get one in my hand I would be happy to dump it.
So...is the content encrypted ? I wanted to make a custom rom with official NES games in it , instead of bootleg ones, I noticed that the roms are saved in "banks" , I tried to replace one with Super Mario Bros. 3 but that did't work (I guess the mapper is unsupported?) perhaps with the emulator now I can try the edits before burning the eeprom
Edit: Nevermind, I re-read your answer, I guess , I either swap the opcodes in the rom I want to paste in or I disable the scrambling in the eeprom ? (if is even possible?)