INES Mapper 221

iNES Mapper 221 is used for N625092 multicarts. They have 8 KiB of unbanked CHR-RAM at PPU $0000-$1FFF. Their UNIF board name is BMC-N625092.

Mode/Outer Bank Register ($8000-$BFFF)

A~FEDC BA98 7654 3210
  -------------------
  10.. ...p ...O OOPM
          |    | |||+- Select nametable mirroring type
          |    | |||    0: Vertical
          |    | |||    1: Horizontal
          |    | ||+-- Select NROM-128/Other PRG-ROM modes
          |    | ||     0: NROM-128 (Inner Bank selects 16 KiB PRG-ROM bank
          |    | ||        at CPU $8000-$BFFF mirrored at CPU $C000-$FFFF)
          |    | ||     1: Other mode (decided by bit 8)
          |    +-++--- Select 128 KiB Outer PRG-ROM bank.
          +----------- Select PRG-ROM mode if bit 1=1
                        0: NROM-128 (Inner Bank SHR 1 selects 32 KiB PRG-ROM
                           bank at CPU $8000-$FFFF)
                        1: UNROM (Inner Bank selects 16 KiB PRG-ROM bank at
                           CPU $8000-$BFFF, CPU $C000-$FFFF fixed to Inner Bank #7)

Inner Bank Register ($C000-$FFFF)

A~FEDC BA98 7654 3210
  -------------------
  11.. .... .... .III
                  +++- 16/32 KiB (depending on PRG-ROM mode) Inner Bank number