INES Mapper 043

iNES Mapper 043 is used for the TONY-I and YS-612 circuit boards, both containing conversions of Super Mario Brothers 2 (Japanese) from Famicom Disk System to ROM cartridge. There are two 32 KiB, one 2 KiB and one 8 KiB PRG-ROM chip. iNES-format ROM images first include the data of both 32 KiB ROM chips, then the data of the 2 KiB chip repeated four times, then the data of the 8 KiB ROM chip, for a total of 80 KiB of PRG-ROM.

Banks

• CPU $5000-$5FFF: 2 KiB PRG-ROM bank, repeated once, from 2 KiB PRG-ROM chip
• CPU $6000-$7FFF: 8 KiB PRG-ROM bank, fixed to #2, from 2x32 KiB PRG-ROM chips
• CPU $8000-$9FFF: 8 KiB PRG-ROM bank, fixed to #1, from 2x32 KiB PRG-ROM chips
• CPU $A000-$BFFF: 8 KiB PRG-ROM bank, fixed to #0, from 2x32 KiB PRG-ROM chips
• CPU $C000-$DFFF: 8 KiB PRG-ROM bank, switchable, from 2x32 KiB PRG-ROM chips
• CPU $E000-$FFFF: 8 KiB PRG-ROM bank from 8 KiB PRG-ROM chip
• PPU $0000-$1FFF: unbanked 8 KiB CHR-ROM

Registers

PRG Bank Select ($4022)

Mask: $71FF

Bit 7654 3210
    ---------
    .... .CCC
          +++- Select 8 KiB PRG-ROM bank at CPU $C000-$DFFF.

The actual bank number is:

Value  Bank#
------------
0      4
1      3
2      4
3      4
4      4
5      7
6      5
7      6

IRQ Control ($4122 on TONY-I, $8122 on YS-612)

Mask: $71FF?

Bit 7654 3210
    ---------
    .... ...I
            +- 0: Acknowledge and disable IRQ, reset counter
               1: Enable IRQ

When enabled, the 12-bit IRQ counter increases on every M2 cycle until it overflows, upon which an IRQ is fired.

Notes

• FCEUX emulates a multicart extract of Mr. Mary 2 under this mapper number. Since that particular SMB2J conversion was never released in single-cartridge form, its description of is part of the multicarts' description.
• A modified iNES ROM file of YS-612 has different title screen variants in the four representations of the 2 KiB ROM chip. Nintendulator implements a dialog to switch between two of them.