NES 2.0 Mapper 348

NES 2.0 Mapper 348 is used for multicarts using 830118C-numbered PCBs such as 1994 New Series Red Pig 7-in-1. Its UNIF board name is BMC-830118C.

Registers

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

These registers function identically to a normal MMC3, except in GNROM mode.

Outer Bank Register ($6800, write)

Mask: probably $E000

D~7654 3210
  ---------
  .... OO..
       ++--- Select 128 KiB outer PRG-ROM bank (i.e. PRG A17-A18)
             and 128 KiB outer CHR-ROM bank (i.e. CHR A17-A18)

• This bank register functions as a substitute for WRAM and can only be written to if $A001 bit 7 is set and $A001 bit 6 is clear.
• The Outer Bank Register's PRG/CHR A17-A18 replace the MMC3's.

GNROM-like Mode

If PRG A17 and PRG A18 are both 1 (i.e. if $6800 AND $0C==$0C), standard MMC3 PRG-ROM banking is replaced with an odd GNROM-ish mode, in which the MMC3's CPU A14 input is held low and PRG A14 is directly connected to CPU A14, resulting in the following bank layout:

• CPU $8000-$BFFF: MMC3 banks effective in the $8000-$BFFF range but as if their bank register values were AND'd with $FD
• CPU $C000-$FFFF: MMC3 banks effective in the $8000-$BFFF range but as if their bank register values were OR'd with $02

Similar Mappers

NES 2.0 Mapper 315 is similar but with the Outer Bank Register bits being arranged slightly differently.