NES 2.0 Mapper 351

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NES 2.0 Mapper 351 is used for a 9-in-1 multicart originally released by J.Y. Company and later Techline. It's an MMC3 clone with outer bank registers.

Set CHR-ROM Base ($5000, write)

Mask: unknown

D~7654 3210
  ---------
  BBBB BB..
  ++++-++--- Select 8 KiB CHR-ROM base to be OR'ed with MMC3 bank number

Set PRG-ROM Base ($5001, write)

Mask: unknown

D~7654 3210
  ---------
  BBBB BB..
  ++++-++--- Select 16 KiB PRG-ROM base to be OR'ed with MMC3 bank number

Set Banking Mode ($5002, write)

Mask: unknown

D~7654 3210
  ---------
  MMmm .?..
  ||||  +--- Unknown
  ||++------ Select outer bank size for CHR-ROM (and PRG-ROM in MMC3 mode)
  ||          0: 256 KiB
  ||          1: 32 KiB
  ||          2: 128 KiB
  ||          3: unknown, not used
  ++-------- PRG banking mode
              0: MMC3
              1: same as 0
              2: NROM-256
              3: NROM-128

Note

The circuit board detects Reset via interruption of the M2 signal to return to the multicart menu. This makes it difficult to dump the cartridge using a Kazzo device.