NES 2.0 Mapper 383

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NES 2.0 Mapper 383 denotes J.Y. Company's YY840708C circuit board. It consists of an AX5202P MMC3 clone together with a 16V8 PAL. It is used for only one known multicart:

  • 1995 Soccer 6-in-1 足球小将專輯 (JY-014)

The PAL maintains four signals for bankswitching and responds both to reads and writes:

  • PAL PRG A15: Set by writing to CPU $8000-$FFFF.
  • PAL PRG A16: Set by reading from CPU $8000-$BFFF while PAL PRG A17/A18 are 0,
  • PAL PRG/CHR A17: Set by writing to CPU $8000-$FFFF.
  • PAL PRG/CHR A18: Set by writing to CPU $8000-$FFFF.

16V8 Write ($8100-$FFFF)

Mask: $8100

A~FEDC BA98 7654 3210
  1.u. ...1 ..vw ....
    |         |+------ PAL PRG/CHR A17
    |         +------- PAL PRG/CHR A18
    +----------------- PAL PRG A15 in some configurations

This register overlays the MMC3's registers in the same address range.

16V8 Read ($8000-$BFFF)

Mask: $C000

When reading from the CPU $8000-$BFFF area while PAL PRG/CHR A17/A18 are zero, PAL PRG A16 is updated with the MMC3 clone's MMC3 PRG A16 output.

Effective PRG-ROM banks

The four PAL signals not only provide additional address bits, but also modify the masking of other address bits and which 8 KiB CPU bank the MMC3 clone sees. The following table shows how the 8 KiB PRG-ROM bank coming from the MMC3 clone is first ANDed and then ORed depending on the PAL PRG signals and the CPU bank (all $xx numbers represent 8 KiB bank numbers):

  PAL PRG      CPU      MMC3
------------           ------
A17/A18  A16   Bank*    AND   OR
---------------------- ------ ---------------
$00      $00   **       $03   A15|A16|A17|A18
$00      $08   **       $07       A16|A17|A18
$10/$20  -     **       $0F           A17|A18
$30      -     $6->$E   $0B           A17|A18
$30      -     $8->$C   $0F           A17|A18
$30      -     $A->$E   $0F           A17|A18
$30      -     $C->$8   $0F           A17|A18
$30      -     $E->$A   $0F           A17|A18

*  CPU banks to which this applies, and which CPU bank the MMC3 clone sees.
** Applies to all CPU banks, which are input to the MMC3 clone unchanged.

Therefore, PAL PRG/CHR A17/A18 not only select a 128 KiB outer bank, but also select one of three bankswitching modes:

  • Setting 0 provides a round-about means of dividing the first 128 KiB bank into two 32 KiB and one 64 KiB bank. PAL PRG A16 is updated with the content of the corresponding MMC3 PRG bank bit by reading from the respective address range, which in turn will then be applied across the entire ROM address range. The content of this bit furthermore selects two bankswitching sub-modes:
    • When clear, the MMC3 only selects within one of the two 32 KiB banks of the first 64 KiB half of 128 KiB bank #0, which one is decided by PAL PRG A15. This is used for the CNROM/NROM-256 games Power Soccer and Nintendo's Soccer.
    • When set, the MMC3 selects within the second 64 KiB bank of 128 KiB bank #0. This is used for the game Tecmo World Cup Soccer (renamed "Goal 5").
  • Settings 1 and 2 provide normal 128 KiB MMC3 banking, used for the games Kunio-kun no Nekketsu Soccer League (renamed "Goal 3") and Nekketsu Koukou Dodgeball Bu - Soccer Hen (renamed "Heroes Soccer").
  • Setting 3 provides 128 KiB MMC3 banking with the CPU A14 line fed to the MMC3 clone reversed. This is used for the game Tecmo Cup: Soccer Game (renamed "Tecmo Cup Soccer"), originally an MMC1 game with the fixed bank at $8000-$BFFF and the switchable bank at $C000-$FFFF, a configuration that could not be reproduced with an MMC3 alone. It is also used for the menu, which in part executes from PRG-ROM mapped to the CPU $6000-$7FFF address range on the MMC3 clone's fixed banks alone, as no MMC3 PRG bank register is written to before JMPing to this address range.

See also

PCB image and analysis by Krzysiobal