iNES Mapper 236 denotes the Realtec 8031 and 8155 circuit boards, used for a number of multicarts with 128 KiB PRG-ROM and 64 KiB CHR-ROM:
The Realtec 8099 PCB has twice the ROM size:
A variant of this circuit board (Realtec 8106 PCB) with 512 KiB PRG-ROM and 8 KiB of unbanked CHR-RAM is emulated under the same mapper number:
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.
Mask: $C000
Variant with CHR-ROM:
A~FEDC BA98 7654 3210
-------------------
10.. .... ..M. CCCC
| ++++- CHR A16..A13
+------- Nametable mirroring
0: Vertical
1: Horizontal
Variant with CHR-RAM:
A~FEDC BA98 7654 3210
-------------------
10.. .... ..M. .PPP
| +++- PRG A19..A17
+------- Nametable mirroring
0: Vertical
1: Horizontal
Mask: $C000
Variant with CHR-ROM:
A~FEDC BA98 7654 3210
-------------------
11.. .... ..SS PPPP
|| ++++- PRG A17..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
Variant with CHR-RAM:
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
Categories: INES Mappers, Multicart mappers