NES 2.0 Mapper 381

NES 2.0 Mapper 381 denotes the KN-42 PCB, used by the 2-in-1 High Standard Game (BC-019) reset-based multicart containing two (modified) UOROM games, in this case, the two Codemasters "Bignose" titles.

Data Latch ($8000-$FFFF, write)

Mask: $8000

D~7654 3210
  ---------
  ...b .aaa
     |  +++- PRG A15..A17
     +------ PRG A14

The actual 16 KiB bank number is therefore aaab. PRG A14..A17 are forced to $F if CPU A14=1, just like UOROM. PRG A18 is flipped on each reset cycle, which is detected through interruption of the M2 signal. The data latch exhibits bus conflicts.