INES Mapper 037: Difference between revisions
(Traced board, got extended register function from Kinopio, said hi to Karnaugh and DeMorgan.) |
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This game, like [[iNES Mapper 047|Super Spike V'Ball + Nintendo World Cup]], replaces PRG RAM with a single register to enforce multiple "jail cells" containing each game. | This game, like [[iNES Mapper 047|Super Spike V'Ball + Nintendo World Cup]], replaces PRG RAM with a single register to enforce multiple "jail cells" containing each game. | ||
The Outer Bank Select register | The Outer Bank Select register is not cleared on reset, so the reset button is not necessarily sufficient to allow the user to choose a different game. | ||
=== Outer Bank Select ($6000-$7FFF) === | === Outer Bank Select ($6000-$7FFF) === | ||
7 bit 0 | 7 bit 0 | ||
Revision as of 04:40, 25 July 2012
iNES Mapper 037 represents the Nintendo of Europe multicart "Super Mario Bros. + Tetris + Nintendo World Cup". It glues together 3 MMC3-compatible games in a single pak.
Overview
- PRG ROM size: 256 KiB
- PRG ROM bank size: 8 KiB inner / 64 or 128 KiB outer
- PRG RAM: Impossible
- CHR capacity: 256 KiB ROM
- CHR bank size: 1 and 2 KiB inner / 128 KiB outer
- Nametable mirroring: Controlled by mapper.
- Subject to bus conflicts: No
Registers
This game, like Super Spike V'Ball + Nintendo World Cup, replaces PRG RAM with a single register to enforce multiple "jail cells" containing each game.
The Outer Bank Select register is not cleared on reset, so the reset button is not necessarily sufficient to allow the user to choose a different game.
Outer Bank Select ($6000-$7FFF)
7 bit 0
xxxx xQBB
│││
│└┴── if 3, forces PRG A16 high regardless of Q bit
└──── A17 to both PRG and CHR ROM. Additionally, the MMC3's PRG A16
is ANDed with this bit before going to PRG ROM (but see above!)
In case that wasn't clear:
| Value written | PRG window | 128kB CHR window |
|---|---|---|
| 0,1,2 | $00000-$0FFFF (64kB) | $00000-$1FFFF |
| 3 | $10000-$1FFFF (64kB) | $00000-$1FFFF |
| 4,5,6 | $20000-$3FFFF (128kB) | $20000-$3FFFF |
| 7 | $30000-$3FFFF (64kB) | $20000-$3FFFF |
All other registers ($8000-$FFFF)
See MMC3.
Hardware
Since this pak was only ever released with epoxy covering wirebonded silicon dice, the following is guesswork:
It is likely that the support hardware is a 74HC161 and a 74HC00, based on the specific order that the traces enter the epoxy blob. The NAND gates are arranged to calculate
(PRG ROM A16 in) = Q0·Q1 + Q2·(MMC3 PRG A16 out) = Q̿0̿·̿Q̿1̿ ̅·̅ ̅Q̿2̿·̿M̿1̿6̿ (PRG ROM A17 in) = (CHR ROM A17 in) = Q2
