NES 2.0 Mapper 412
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NES 2.0 Mapper 412 denotes an "MMC3 plus NROM" multicart mapper, used for the Intellivision 10-in-1 Plug 'n Play 2nd Edition as well as assorted multicarts from Henggedianzi. It uses an MMC3 clone with additional outer bank registers at $6000-$7FFF that are accessible via the MMC3's WRAM interface, meaning that WRAM must be enabled via $A001 for them to be written to.
8 KiB CHR Bank Register ($6000, write)
D~[BBBB BB..] Mask: $E003, reset value: 0 ++++-++---- CHR A18..A13
Only applicable in NROM banking mode ($6002.1=1).
Mode Register ($6001, write)
D~[CARQ DBPL] Mask: $E003, reset value: 0 |||| |||+-- Lock register $6001 |||| ||+--- 0: PRG A17 from MMC3, 1: from A Bit |||| |+---- PRG A18 if Q=2 |||| +----- CHR A18 |||+------- 0: PRG A18 from MMC3, 1: from B Bit ||+-------- 0: CHR A17 from MMC3, 1: from C Bit |+--------- PRG A17 if P=1 +---------- CHR A17 if R=1
PRG Bank Register ($6002, write)
D~[BBBB bQP.] Mask: $E003, reset value: 0 |||| ||+--- 0: MMC3 banking, 1: NROM PRG/CHR banking |||| |+---- 0: NROM-128, 1: NROM-256 banking, only if P=1 |||| +----- PRG A14 if P=1 and Q=0 ++++------- PRG A18..A15 if P=1