INES Mapper 228

iNES Mapper 228 represents the board used by Active Enterprises for Action 52 and Cheetahmen II.

Registers

Address           Data
FEDCBA98 76543210 76543210
1.MHHPPP PPS.CCCC ......CC
  |||||| ||| ||||       ||
  |||||| ||| ++++-------++- Select 8 KiB CHR ROM bank at PPU $0000
  |||||| ||+--------------- PRG bank size
  |||||| ||                 0: Put bank with bit 0 false in $8000 and
  |||||| ||                    bank with bit 0 true in $C000
  |||||| ||                 1: Put same 16 KiB bank in $8000 and $C000
  |||+++-++---------------- Select 16 KiB PRG ROM bank at CPU $8000
  |++---------------------- Select which 512 KiB PRG ROM chip to enable
  |                         (A52 uses 0, 1, and 3; bank 2 is open bus)
  +------------------------ 0: Vertical mirroring; 1: Horizontal mirroring

There are also four 4-bit RAM locations at $4020-$4023, mirrored throughout $4020-$5FFF

References

• Disch's mapper doc