NES 2.0 Mapper 554

NES 2.0 Mapper 554 denotes the Kaiser KS-7010 circuit board, used for one of several cartridge conversions of the FDS version of 悪魔城 Dracula, the Japanese version of Castlevania. Bankswitching is unusual in being triggered entirely through reads from "magic" addresses. The board mounts 128 KiB PRG-ROM, 128 KiB CHR-ROM, a KS-201 ASIC and a 74'32.

Banks

• CPU $6000-$7FFF: Switchable 8 KiB PRG-ROM bank
• CPU $8000-$9FFF: Fixed 8 KiB PRG-ROM bank #10
• CPU $A000-$BFFF: Fixed 8 KiB PRG-ROM bank #11
• CPU $C000-$DFFF: Fixed 8 KiB PRG-ROM bank #6
• CPU $E000-$FFFF: Fixed 8 KiB PRG-ROM bank #7
• PPU $0000-$1FFF: Switchable 8 KiB CHR-ROM bank
• Nametable mirroring: hard-wired (to vertical)

Bankswitching Reads

The 8 KiB PRG-ROM bank at $6000, and the 8 KiB CHR-ROM bank, are both switched to the same bank number whenever certain addresses are read from.

A~FEDC BA98 7654 3210
  -------------------
  .??? ???? ??DC BA1.
              ++-++--- PRG/CHR A16..13

The exact address mask is not known; the following addresses have been verified to trigger a bankswitch, and are used by the game:

• CAB6-CAD6
• EBE2, EE32
• FFFC

ASIC connection

KS-201  connected
pin#    to
 1      CPU M2
 2      CPU A1
 3      CPU A2
 4      CPU A3
 5      CPU A4
 6      CPU A5
 7      CPU A6
 8      CPU A7
 9      CPU A8
 10     CPU A9
 11     CPU A10
 12     CPU A11
 13     CPU A12
 14     GND
 15     CPU A13
 16     CPU A14
 17     /CE
 18     VCC
 19     PRG ROM /CE
 20     CHR ROM A16
 21     CHR ROM A15
 22     CHR ROM A14
 23     CHR ROM A13
 24     PRG ROM A16
 25     PRG ROM A15
 26     PRG ROM A14
 27     PRG ROM A13
 28     VCC