NES 2.0 Mapper 389

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NES 2.0 Mapper 389 denotes the circuit board of the Caltron 9-in-1 multicart.

Mirroring/Outer PRG-ROM Bank register ($8000-$8FFF, write)

Mask: $F000

A~FEDC BA98 7654 3210
  -------------------
  1000 0000 .PPP P..M
             ||| |  +- Mirroring: 0=Vertical, 1=Horizontal
             +++-+---- PRG A15-A18

Power-up value: $00

PRG Mode/Outer CHR-ROM Bank register ($9000-$9FFF, write)

Mask: $F000

A~FEDC BA98 7654 3210
  -------------------
  1001 0000 ..CC C.U.
              || | +-- 0=NROM-256, 1=UNROM-064
              ++-+---- CHR A15-A17

Power-up value: $00

In NROM-256 mode, the Inner Bank register's PRG bits are ignored. In UNROM-064 mode, the Inner Bank register's PRG bits select one of four 16 KiB PRG-ROM banks at CPU $8000-$BFFF, while CPU $C000-$FFFF is hard-wired to inner bank #3, similarly to INES Mapper 081, used by the stand-alone version of the only game using this mode.

Inner Bank register ($A000-$FFFF, write)

Mask: $E000

A~FEDC BA98 7654 3210
  -------------------
  .... .... .... PPCC
                 ||++- CHR A13-A14
                 ++--- PRG A14-A15 in UNROM-064 mode when CPU A14=0

Power-up value: $00