NES 2.0 Mapper 429

NES 2.0 Mapper 429 is for Milowork FCFC1 flash cartridge (in A mode). There is some doujin game in progress using this mapper.

Overview

• PRG ROM size: 512 KB
• 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
• Subject to bus conflicts: No

Registers

Bank select ($8000-$FFFF)

7  bit  0
---- ----
xxPP 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

FCFC1 Details

• 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.

Register value causes error	CNROM (A)	GxROM (A)	NROM (B) (Except using CHR RAM)
Firmware 2.1 and before	xxx1xx	xxx1xx	xxx1xx
Firmware 2.2 and after	xx01xx	xx01xx	xx01xx