NES 2.0 Mapper 298

From Nesdev wiki
Jump to: navigation, search

NES 2.0 Mapper is used for the unlicensed game Lethal Weapon, which is actually a backport of Lethal Enforcers, and not to be confused with the licensed game of the same name. Its UNIF board name is UNL-TF1201.

The board uses a VRC4 clone in the VRC4b configuration (CPU 0x02s to VRC4 A0, CPU 0x01s to VRC4 A1). The only difference is that register $F003 is implemented differently than on the original ASIC: writing to $F003 only acknowledges a pending IRQ, but it does not move the 'A' control bit to the 'E' control bit the way an original VRC4 does. This is relevant for emulation, as the game writes to $F003 immediately after enabling the IRQ by writing $02 to $F002.