INES Mapper 224

From Nesdev wiki
Jump to: navigation, search

iNES Mapper 224 is used for the 晶科泰 (Jncota) KT-008 PCB. It's an MMC3 clone that supports 1024 KiB of PRG-ROM through an additional outer bank register at $5000.


MMC3-compatible Registers

Mask: $E001

$8000, $8001, $A000, $A001, $C000, $C001, $E000, $E001: As normal MMC3.

Outer Bank Register ($5000)

Mask: unknown, but probably $F003.

7654 3210
.... .P..
      +-- Select outer 512 KiB PRG-ROM bank

Other registers ($5001-$5003)

Mask: unknown, but probably $F003.

Meaning unknown; games just write $00 to them.


  • Because the outer bank register is initialized to $00 at power-on, these games boot with the $E000 bank from the first 512 KiB half.
  • Most of these ROM images are incorrectly set to Mapper 4, thus sharing a mapper number with oversize TNROM images having 1024 KiB of PRG-ROM. Oversize TNROM switches 512 KiB banks through bits 6-7 of MMC3 bank registers 6 and 7 and initializes them to $FE and $FF, causing them to boot with the $E000 bank from the second 512 KiB half.