And what it looks like:
Past few days I tried to get it working and I finally got it working (lots of software problems, and datasheet misunderstandings).
All EEPROM access is done by writing to and reading from address $A130F1.
I made this thing, so that people who want to get their game that uses batter back-up RAM into production, would use this instead, so that cartridge gets lot cheaper, as 2 logic chips and one EEPROM chip are lot more cheaper than battery and SRAM chip.
Here's the source required (TIMEPIN = $A130F1):
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