INES Mapper 236

iNES Mapper 236 denotes the Realtec 8155 circuit board, used for a number of multicarts with 128 KiB PRG-ROM and 64 KiB CHR-ROM:

• 35-in-1 (HM5511)
• 56-in-1 (NT-009)
• 68-in-1 (HM5511)
• 70-in-1

A variant of this circuit board with 512 KiB PRG-ROM and 8 KiB of unbanked CHR-RAM is emulated under the same mapper number:

• 800-in-1

Due to the presence of four solder pads that select one of sixteen displayed game counts, the same ROM is bound to exist with different cartridge codes.

Lower Address Latch ($8000-$BFFF, write)

Mask: $C000

A~FEDC BA98 7654 3210
  -------------------
  10.. .... ..M. .CCC
              |   +++- CHR A15..A13 (with CHR-ROM)
              |        PRG A19..A17 (without CHR-ROM)
              +------- Nametable mirroring
                        0: Vertical
                        1: Horizontal

Upper Address Latch ($C000-$FFFF, write)

Mask: $C000

A~FEDC BA98 7654 3210
  -------------------
  11.. .... ..SS .PPP
              ||  +++- PRG A16..A14
              ++------ PRG Mode
                        0: UNROM (PRG A14..16=111 when CPU A14=1)
                        1: Read Solder Pad (like SS=0, plus
                           PRG A0..A3=solder pad value)
                        2: NROM-256 (PRG A14=CPU A14)
                        3: NROM-128