INES Mapper 246

iNES Mapper 246 denotes the G0151-1 circuit board, used only for the Taiwanese game 封神榜 (Fēngshénbǎng: Fúmó Sān Tàizǐ).

Banks

• CPU $6800-$6FFF: 2 KiB PRG-RAM, battery-banked
• CPU $8000-$9FFF: 8 KiB PRG-ROM bank, switchable via $6000
• CPU $A000-$BFFF: 8 KiB PRG-ROM bank, switchable via $6001
• CPU $C000-$DFFF: 8 KiB PRG-ROM bank, switchable via $6002
• CPU $E000-$FFFF: 8 KiB PRG-ROM bank, switchable via $6003
• PPU $0000-$07FF: 2 KiB CHR-ROM bank, switchable via $6004
• PPU $0800-$0FFF: 2 KiB CHR-ROM bank, switchable via $6005
• PPU $1000-$17FF: 2 KiB CHR-ROM bank, switchable via $6006
• PPU $1800-$1FFF: 2 KiB CHR-ROM bank, switchable via $6007

Nametable mirroring is hard-wired and set by the iNES header.

Registers

PRG-ROM bank select ($6000-$6003), write

A~[0110 0000 000. .0rr] D~[..bb bbbb]
                    ||       ++-++++- PRG A18..A13 of bank to select
                    ++--------------- CPU A14..A13 bank to switch

• When reading from CPU address $FFE4-$FFFF, PRG A17 is forced high, as if register $6003 were OR'd with $10.
• Register $6003 is set to $FF at power-on only.

CHR-ROM bank select ($6004-$6007), write

A~[0110 0000 000. .1rr] D~[bbbb bbbb]
                    ||     ++++-++++- CHR A18..A11 of bank to select
                    ++--------------- PPU A12..A11 bank to switch

See also

• http://forums.nesdev.org/viewtopic.php?t=13969 Why does Fong Shen Bang only work in Famiclones?