NES 2.0 Mapper 324

NES 2.0 Mapper 324 is used for Farid's homebrew 8-in-1 UNROM multicart board. It consists of an UNROM latch with an additional outer bank register. Mirroring is hard-wired. Its UNIF board name is FARID_UNROM_8-IN-1.

Bank Register ($8000-$FFFF, write)

Mask: $8000

D~7654 3210  **BUS CONFLICTS**
  ---------
  Cooo kIII
  |||| ||||
  |||| |+++- Standard UNROM inner bank (select 16K at $8000-$BFFF)
  |||| +---- 1=Lock Outer Bank
  |+++------ Select 128 KiB outer PRG-ROM bank
  +--------- Clock Generator ("oook" bits latched only when this changes from 0 to 1 if k had been 0)

The middle four bits ($78, lowercase) are one 74'161; their contents are explicitly zeroed on power-up or reset. The outer four bits ($87, uppercase) are the other 74'161; their contents are NOT.

UNROM latch ($8000-$FFFF)

See INES Mapper 002.

See also

• NesDev discussion
• Mapper 72 uses a similar "one latch's output clocks another latch" structure.