MMM01 documentation up

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I just put up a more readable MMM01 documentation on my wiki, check it out. While I implemented the mapper already in MESS, I found some small issues with it that I’ll send a pull request over soon.

If you have any idea what the unknown bit might be there for, drop me a line as my test setup is still in one piece 🙂 I’ve already tried:

  • it’s not part of the #WE for the lower 5 bits of RA
  • it’s not part of the mask for the lower 5 bits of RA, i.e. cannot fix RA14 and trick zero-adjust
  • setting the bit does not prevent #RAM_CS (and RAM_CS) from asserting when RAMG == 0x0A
  • setting the bit does not automatically make the mux bit toggle when mapped and switching MBC1 modes
  • setting the bit does not allow writing to RA22..RA21, RA20..RA19, AA16..AA15 when mapped
  • setting the bit does not allow changing the multiplexer bit
  • setting the bit does not allow resetting the map enable bit
  • setting the bit does not ‘capture’ the MBC1 mode from the first write to the MODE register after mapping