NES 2.0 Mapper 368

PCB front

PCB back (mirrored, pin 31 on the left)

NES 2.0 Mapper 368 denotes the Yung-8 cartridge conversion PCB of the disk system game Super Mario Bros. 2 (Japan). It is very similar to INES Mapper 043 and likely the "parent" to the versions denoted under that mapper.

There are two 32 KiB PRG-ROM chips, one 2 KiB PRG-ROM, and one 8 KiB CHR-ROM chip. The ROM image's 128 KiB PRG-ROM part is arranged as follows:

1. Offset $00000: First PRG-ROM chip (64 KiB)
2. Offset $08000: Second PRG-ROM chip (64 KiB)
3. Offset $10000: Third PRG-ROM chip, repeated 32 times (64 KiB)

Banks

• CPU $6000-$7FFF: 8 KiB PRG-ROM bank, fixed to #2
• CPU $8000-$9FFF: 8 KiB PRG-ROM bank, fixed to #1
• CPU $A000-$BFFF: 8 KiB PRG-ROM bank, fixed to #0
• CPU $C000-$DFFF: 8 KiB PRG-ROM bank, switchable
• CPU $E000-$FFFF: 8 KiB PRG-ROM bank, fixed to #8 (2 KiB PRG-ROM repeated four times)
• PPU $0000-$1FFF: unbanked 8 KiB CHR-ROM

Registers

PRG Bank Select ($4022, write)

Mask: $F1FF

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      5
3      3
4      6
5      3
6      7
7      3

Latch write/IRQ Control ($4122, write)

Mask: $F1FF

D~7654 3210
  ---------
  ..LL .L.I
    ||  | +- 0: Acknowledge and disable IRQ, reset counter
    ||  | |  1: Enable IRQ
    ++--+-+- Bits to be read-back

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

Latch read ($4122, read)

Mask: $F1FF

D~7654 3210
  ---------
  10LL 1L1L
    ++--+-+- Latched bits

When holding the A button while pressing START to begin in World A-1, the game checks the latch's functionality and returns to the title screen if the check fails.