INES Mapper 002

iNES Mapper 002 is used to designate the most common configuration of the UxROM boardset, generalized to support up to 2048 KB of PRG ROM (iNES) or 4096 KB of PRG ROM (NES 2.0).

 Here are Disch's original notes:
 ========================
 =  Mapper 002          =
 ========================
 
 aka
 --------------------------
 UxROM (and compatible)
 
 
 Example Games:
 --------------------------
 Mega Man
 Castlevania
 Contra
 Duck Tales
 Metal Gear
 
 
 Notes:
 ---------------------------
 UxROM has bus conflicts, however mapper 002 is meant to be UxROM and compatible.  So some mappers which were
 similar in function, but did not have bus conflicts are included.
 
 Additionally, UxROM does not have an 8 bit reg.  UNROM is capped at 128k PRG, and UOROM is capped at 256k.
 
 So to be "safe":
  - for homebrewing:  assume bus conflicts, do not exceed 256k
  - for emudev:  assume no bus conflicts, use all 8 PRG reg bits
 
 There is no CHR swapping.  Every mapper 002 game I've ever seen has CHR-RAM.
 
 
 Registers (**BUS CONFLICTS** sometimes):
 --------------------------
   $8000-FFFF:  [PPPP PPPP]
     PRG Reg
 
 
 
 PRG Setup:
 --------------------------
 
       $8000   $A000   $C000   $E000  
     +---------------+---------------+
     |     $8000     |     { -1}     |
     +---------------+---------------+