NES 2.0 Mapper 393

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NES 2.0 Mapper 393 denotes the 820720C multicart PCB.

Registers

MMC3-compatible registers ($8000-$FFFF, write)

These registers function identically to a normal MMC3, except in UNROM/BNROM mode.

Outer Bank Register ($6000-$7FFF, write)

Mask: $E000
 
A~FEDC BA98 7654 3210
  --------- ---------
  011. .... ..MM CPPP
              || |+++- PRG A19..A17
              || +---- CHR Mode
              ||        0: CHR-ROM with MMC3 banking
              ||        1: 8 KiB unbanked CHR-RAM
              ++------ PRG Mode
                        0: MMC3 (PRG A13-A16)
                        1: same as 0
                        2: BNROM (PRG A15-A16 from MMC3 R6,
                           PRG A13-A14=CPU A13-A14)
                        3: UNROM (PRG A14-A16 from $8000-$FFFF latch,
                           PRG A13=CPU A13) 

Selected by the MMC3's PRG-RAM /CE, WRAM must be enabled and writable in the MMC3's A001 register for Outer Bank Register writes to be recognized.