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| [[Category:iNES Mappers|009]][[Category:in NesCartDB|009]][[Category:Nintendo licensed mappers]] | | #REDIRECT [[MMC2]] |
| | | {{DEFAULTSORT:009}}[[Category:iNES Mappers]][[Category:in NesCartDB]][[Category:Nintendo licensed mappers]] |
| [[iNES Mapper 009]] represents the [[PxROM]] boards, which use the [[Nintendo MMC2]] chip.
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| Here are Disch's original notes:
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| ========================
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| = Mapper 009 =
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| ========================
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|
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| aka
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| --------------------------
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| [[MMC2]]
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| [[PxROM]]
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|
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|
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| Example Game:
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| --------------------------
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| Mike Tyson's Punch Out!!
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|
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|
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| Registers:
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| ---------------------------
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|
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| Range,Mask: $A000-FFFF, $F000
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|
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|
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| $A000: PRG Reg
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| $B000: CHR Reg 0A
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| $C000: CHR Reg 0B
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| $D000: CHR Reg 1A
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| $E000: CHR Reg 1B
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| $F000: [.... ...M] Mirroring:
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| 0 = Vert
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| 1 = Horz
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| PRG Setup:
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| ---------------------------
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| $8000 $A000 $C000 $E000
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| +-------+-------+-------+-------+
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| | $A000 | { -3} | { -2} | { -1} |
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| +-------+-------+-------+-------+
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| CHR Setup:
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| ---------------------------
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| $0000 $0400 $0800 $0C00 $1000 $1400 $1800 $1C00
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| +-------------------------------+-------------------------------+
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| | $B000 or $C000 | $D000 or $E000 |
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| +-------------------------------+-------------------------------+
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| Which reg is used depends on the state of the respective latch. See below.
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| Latch:
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| ---------------------------
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| There are two latches on the MMC2. One associated with the left pattern table ($0xxx) and another associated
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| with right ($1xxx). Each latch operates independently.
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|
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| Whenever tile $FD is fetched, the appropriate latch is cleared, and whenever tile $FE is fetched, the
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| appropriate latch is set. This allows games to do mid-scanline swapping automatically by having $FD and $FE
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| be special marker tiles.
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| When the $0xxx latch is clear, $B000 is used. When set, $C000 is used.
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| When the $1xxx latch is clear, $D000 is used. When set, $E000 is used.
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|
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| The swap occurs after the tile is fetched, not before. So if the latch is clear, and tile $FE is loaded,
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| tile $FE from the first reg will be drawn to the screen, but the next tile drawn will be from the second reg.
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| Latches can be manipulated by hand by reading from the appropriate PPU address ($0FDx, $0FEx, $1FDx, $1FEx)
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| via $2007.
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