iNES Mapper 221 is used for multicarts using the NTDEC N625092 PCB. They have 8 KiB of unbanked CHR-RAM at PPU $0000-$1FFF. Their UNIF board name is BMC-N625092.
A~FEDC BA98 7654 3210
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10.. ..Bp ...O OOPM
|| | |||+- Select nametable mirroring type
|| | ||| 0: Vertical
|| | ||| 1: Horizontal
|| | ||+-- Select NROM-128/Other PRG-ROM modes
|| | || 0: NROM-128 (Inner Bank selects 16 KiB PRG-ROM bank
|| | || at CPU $8000-$BFFF mirrored at CPU $C000-$FFFF)
|| | || 1: Other mode (decided by bit 8)
|| +-++--- Select 128 KiB Outer PRG-ROM bank (PRG A17-A19)
|+----------- Select PRG-ROM mode if bit 1=1
| 0: NROM-128 (Inner Bank SHR 1 selects 32 KiB PRG-ROM
| bank at CPU $8000-$FFFF)
| 1: UNROM (Inner Bank selects 16 KiB PRG-ROM bank at
| CPU $8000-$BFFF, CPU $C000-$FFFF fixed to Inner Bank #7)
+------------ Select 1 MiB Outer PRG-ROM bank (PRG A20)
A~FEDC BA98 7654 3210
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11.. .... .... CIII
|+++- 16/32 KiB (depending on PRG-ROM mode) Inner Bank number
+---- Select CHR-RAM write-protection
0: Disabled, CHR-RAM write-enabled
1: Enabled, CHR-RAM write-protected
Categories: Multicart mappers