NES 2.0 Mapper 301

NES 2.0 Mapper 301 is used for GG1 multicarts. Its UNIF board name is BMC-8157.

Address latch ($8000-$FFFF)

Mask: $8000

A~FEDC BA98 7654 3210
  -------------------
  .... ..PD POOI IIM.
         || |||| ||+- Select nametable mirroring type
         || |||| ||    0: Vertical
         || |||| ||    1: Horizontal
         || |||+-++-- Select 16 KiB inner PRG-ROM bank at CPU $8000-$BFFF        
         || |++------ Select 128 KiB outer PRG-ROM bank
         +|-+-------- Select 16 KiB inner PRG-ROM bank at CPU $C000-$FFFF
          |           0: bank 0
          |           1: same as CPU $8000-$BFFF (NROM-128)
          |           2/3: bank 7 (UNROM)
          +---------- Select 512 KiB outer PRG-ROM bank
          

Notes

• On carts with 512 KiB PRG-ROM or less, a jumper or DIP switch selects whether setting bit 8 will result in wrapped-around PRG-ROM data or open bus. This switches between a short menu with no and a long menu with repeats.
• CHR pattern data is stored in 8 KiB of unbanked CHR-RAM.