INES Mapper 184

This is part of a family of Sunsoft mappers used largely by Japanese games: (iNES Mapper 089, iNES Mapper 093, iNES Mapper 184)

This mapper is for a few games which use the Sunsoft-1 mapper.

Fantasy Zone (J), despite using the Sunsoft-1 chip, is more easily emulated by Mapper 093 because it was written to support execution using either the Sunsoft-2 IC and a variant board that used the Sunsoft-1 IC.

Despite the mapper existing as a single IC, its functionality is describable using a 74139, a 74174, and a 74157, and so should probably be considered discrete logic.

Here is the documentation in disch's original style:

 Registers:
 --------------------------
   $6000-7FFF:  [.HHH .LLL]
     H = Selects 4k CHR @ $1000
     L = Selects 4k CHR @ $0000
 
 The most significant bit of H is always set in hardware. (i.e. its range is 4 to 7)
 (There can be no SRAM because the register is mapped into $6000-7FFF)

fwNES, a NES emulator for DOS, originally assigned mapper 122 for this.