INES Mapper 200

iNES Mapper 200 denotes the circuit boards of simple address-latch-based NROM-128 multicarts, i.e. CPU $8000-$BFFF is always a mirror of CPU $C000-$FFFF. The mapper number is used for two variants that differ in the bit that selects nametable mirroring.

Address Latch ($8000-$FFFF, write)

Submapper 0

A~[1... .... .... bBBB]
                  |+++- PRG A16..A14, CHR A15..A13
                  +---- PRG A17, CHR A16, Mirroring:
                         0: Vertical
                         1: Horizontal

Submapper 1

A~[1... .... .... .bBB]
                   |++- PRG A15..A14, CHR A14..A13
                   +--- PRG A16, CHR A15, Mirroring:
                         0: Vertical
                         1: Horizontal

Notes

• Some menus select bank numbers beyond the PRG ROM size, expecting to read back a solder pad value to select one of several displayed game counts.
• NES 2.0 Mapper 338 flips the meaning of the mirroring bit.