NES 2.0 Mapper 429

NES 2.0 Mapper 429 denotes both the Milowork FCFC1 flash cartridge (in A mode) and several similar multicart PCBs.

• PRG ROM size: 512 KB (or 1024 KB, FCFC1 DIY)
• PRG ROM bank size: 32 KB
• PRG RAM: None
• CHR capacity: 32 KB RAM, optional battery-backup or FeRAM
• CHR bank size: 8 KB
• Nametable mirroring: vertical or horizontal selected by switch, or fixed (or Single-screen, FCFC1 DIY)
• Subject to bus conflicts: No (submapper 0-1), Yes (submapper 2)

7  bit  0
---- ----
xpPP PPCC
 ||| ||||
 ||| ||++- Select 8 KB CHR RAM bank for PPU $0000-$1FFF, initial bank 0
 +++-++--- Select 32 KB PRG ROM bank for CPU $8000-$FFFF, initial bank 1

7  bit  0
---- ----
MpPP PPCC
|||| ||||
|||| ||++- Select 8 KB CHR RAM bank for PPU $0000-$1FFF, initial bank 0
|+++-++--- Select 32 KB PRG ROM bank for CPU $8000-$FFFF, initial bank 1
+--------- Same as AxROM

7  bit  0
---- ----
.... BACC
     ||||
     ||++- CHR A14..A13
     ++--- CHR A15=A*B; meaning 1 if A=1 and B=1, otherwise 0
     ++--- Select 32 KB PRG ROM bank for CPU $8000-$FFFF, initial bank 0

• The A mode of FCFC1 has compatibility with CNROM/GxROM, but the compatibility is fragile, some games will switch back to the page where the firmware is located, causing problems such as crashes.
• The B mode of FCFC1 is a BNROM/AxROM with initial bank 4 and no bus conflict, and has compatibility with NROM/UNROM.
• To simplify the circuit implementation, the actual location of the page in ROM is shuffled.
• It is recommended to save the preserved data to a page other than 0 of CHR RAM, as this avoids being overwritten by the kazzo programming process, and it can also make the bank selection play a role similar to the WRAM lock bit.
• Some FCFC1 sold as game carriers do not have switches, or the switches do not have the W position. These FCFC1 are not compatible with kazzo.

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