NES 2.0 Mapper 540

NES 2.0 Mapper 540 is a variant of NES 2.0 Mapper 359 that rewires the PPU/CHR address lines to select 2 KiB instead of 1 KiB banks in order to address 512 KiB of CHR-RAM with 8 bit CHR banking registers. It is used on a "Super Boy" mapper hack of Master Fighter VI', originally for NES 2.0 Mapper 264. Its UNIF board name is UNL-82112C.

Pin            Connected to
PPU A10        CHR-ROM A10
PPU A11        ASIC PA10
PPU A12        ASIC PA11+PA12
ASIC CHR A10   CHR-ROM A11
    :             :
ASIC CHR A17   CHR-ROM A18

So that the ASIC sees the followings addresses:

Real PPU Addr  ASIC PPU Addr
$0000          $0000 -> reg $A000
$0400          $0000 -> reg $A000
$0800          $0400 -> reg $A001
$0C00          $0400 -> reg $A001
$1000          $1800 -> reg $B002
$1400          $1800 -> reg $B002
$1800          $1C00 -> reg $B003
$1C00          $1C00 -> reg $B003

CHR Bank Select ($A000-$B003, write)

Mask: $F003

• $A000: Select 2 KiB CHR-ROM bank at PPU $0000-$07FF
• $A001: Select 2 KiB CHR-ROM bank at PPU $0800-$0FFF
• $A002: No function
• $A003: No function
• $B000: No function
• $B001: No function
• $B002: Select 2 KiB CHR-ROM bank at PPU $1000-$17FF
• $B003: Select 2 KiB CHR-ROM bank at PPU $1800-$1FFF