NES 2.0 Mapper 373

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NES 2.0 Mapper 373 is used for a Super 4-in-1 multicart (PCB ID SFC-13). It is INES Mapper 045 but with one bit of outer bank register #2 working as a GNROM switch.

CHR-AND, CHR-OR/PRG-OR MSB, CHR source ($6000 #2, write)

Mask: $F001

D~7654 3210
  ---------
  PPRC cccc
  |||| ++++- Select number of CHR bits from MMC3
  ||||       ($F: 256 KiB, $E: 128 KiB ... $7-$0: 1 KiB)
  |||+------ Select CHR A18
  ||+------- Select MMC3 (0)/GNROM-like (1) PRG mode
  ++-------- Select CHR A20-A21 and PRG A21-22

In GNROM-like mode, the MMC3 clone's CPU A14 input is held low, so that MMC3 registers #6 and #7 apply both to $8000/$C000 and $A000/$E000, with the bank number ANDed with NOT $02 in the lower range and ORed with $02 in the upper range.