INES Mapper 045

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 Here are Disch's original notes:  
 ========================
 =  Mapper 045          =
 ========================
 
 Example Games:
 --------------------------
 Super 8-in-1
 Super 4-in-1
 Super 1000000-in-1
 
 
 Notes:
 ---------------------------
 
 This mapper is another MMC3 multicart, only it works a bit strangely.  The multicart selects PRG/CHR blocks
 independently through 4 internal registers (accessed via $6000-7FFF).  MMC3 registers then operate normally
 within the current block.
 
 For info on MMC3, see mapper 004.
 
 
 Registers:
 ---------------------------
 
   $6000-7FFF:  Multicart regs
   $8000-FFFF:  Same as MMC3 for selected blocks
 
 When Multicart regs are locked, writes to $6000-7FFF proceed to PRG-RAM, as normal.
 
 Where the game writes in the $6000-7FFF range doesn't matter.  An internal counter selects which reg gets
 written to.  ie:
 
   LDA #$00
   STA $6000 ; first write, goes to reg 0
   STA $6000 ; second write, goes to reg 1
   STA $6000 ; reg 2
   STA $6000 ; reg 3
   STA $6000 ; back to reg 0, etc
 
 
   Reg 0:  [CCCC CCCC]   Low 8 bits of CHR-OR
   Reg 1:  [PPPP PPPP]   PRG-OR
   Reg 2:  [CCCC SSSS]
           S = CHR-AND block size
           C = High 4 bits of CHR-OR
   Reg 3:  [.LAA AAAA]
           L = Lock Multicart regs (1=locked)
           A = Inverted PRG-AND
 
 Once multicart regs are locked, the only way to unlock is to Reset the system.
 
 
 CHR Setup:
 --------------------------
 
 'S' bits are somewhat strange.  They seem to select the size of the CHR block to mask out:
   'S'   Block size     CHR-AND
   ----------------------------
   $F       256k          $FF
   $E       128k          $7F
   $D        64k          $3F
        ...
   $8         2k          $01
   7-0        1k          $00
 
 
 An easy way to emulate this:
 
    chr_and = 0xFF >> ~S_bits;
 
 CHR-OR is straightforward
 
 
 
 PRG Setup:
 -------------------------
 
 PRG-OR is straightforward.
 
 PRG-AND is inverted.  XOR written value with $3F for actual PRG-AND.
 
 
 
 Odd game behavior:
 -------------------------
 
 Games seem to set the multicart registers in a loop that runs 256 times.  Why it does this isn't known,
 neither is whether or not it is actually necessary.
 
 
 
 Powerup and reset:
 -------------------------
 
 Block 0 must be selected on powerup and reset.  Regs must be unlocked, as well... and they must be reset so
 that the next write will write to reg 0.