NES 2.0 Mapper 331: Difference between revisions
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[[Category:Multicart mappers]]NES 2.0 mapper 331 is used for the ''7-in-1 (NS03)'' multicart. Its UNIF board name is '''BMC-12-IN-1'''. | {{DEFAULTSORT:331}}[[Category:Multicart mappers]]NES 2.0 mapper 331 is used for the ''7-in-1 (NS03)'' multicart. Its UNIF board name is '''BMC-12-IN-1'''. | ||
==Inner Bank Register A ($A000-$BFFF)== | ==Inner Bank Register A ($A000-$BFFF)== | ||
Latest revision as of 06:48, 26 May 2020
NES 2.0 mapper 331 is used for the 7-in-1 (NS03) multicart. Its UNIF board name is BMC-12-IN-1.
Inner Bank Register A ($A000-$BFFF)
Mask: probably $E000 D~7654 3210 --------- CCCC CPPP |||| |+++- Select 16 KiB inner PRG-ROM bank at CPU $8000-$BFFF and CPU $C000-$FFFF |||| | active when the PPU is rendering from $0000-$0FFF, subject to A14-A16 modification ++++-+---- Select 4 KiB inner CHR-ROM bank at PPU $0000-$0FFF
Inner Bank Register B ($C000-$DFFF)
Mask: probably $E000 D~7654 3210 --------- CCCC CPPP |||| |+++- Select 16 KiB inner PRG-ROM bank at CPU $8000-$BFFF and CPU $C000-$FFFF |||| | active when the PPU is rendering from $1000-$1FFF, subject to A14-A16 modification ++++-+---- Select 4 KiB inner CHR-ROM bank at PPU $1000-$1FFF
Outer Bank and Mode Register ($E000-$FFFF)
Mask: probably $E000
D~7654 3210
---------
.... PMOO
||++- Select 128 KiB outer PRG-ROM and CHR-ROM bank
|+--- Select nametable mirroring type
| 0: Vertical
| 1: Horizontal
+---- Select PRG A14-A16 mode
0: Force PRG A14-A16 to 111b if CPU A14=1 (UNROM-like)
1: PRG A14=CPU A14 (NROM-256)
It's probably a good idea to initialize the PPP bits of both inner bank registers to the same value to prevent the PRG-ROM bank at $8000-$BFFF from changing back and forth as the PPU is rendering.
