INES Mapper 205

From Nesdev wiki
Jump to: navigation, search
 Here are Disch's original notes:  
 ========================
 =  Mapper 205          =
 ========================
 
 
 Example Games:
 --------------------------
 15-in-1
 3-in-1
 
 
 Registers:
 ---------------------------
 Regs at $6000-7FFF means no SRAM
 
   $6000-7FFF:   [.... ..MM]  Game Mode / Block
 
   $8000-FFFF:   MMC3
 
 
 Notes:
 ---------------------------
 These multicarts select the game mode by writing to $6000-7FFF, the individual games then use traditional
 MMC3 style regs at $8000-FFFF.  The MMC3 regs only swap to pages *within* the block specifed by the game
 mode.  This can be easily emulated by ANDing the page numbers written to MMC3 with certain values, and then
 ORing them with other values, based on the selected block.
 
 Chart below to illustrate:
 
   Block    PRG-AND     PRG-OR    CHR-AND    CHR-OR
   -------------------------------------------------
    0         $1F        $00        $FF       $000
    1         $1F        $10        $FF       $080
    2         $0F        $20        $7F       $100
    3         $0F        $30        $7F       $180
 
 
 For details on MMC3, see mapper 004

This mapper is extremely similar to iNES Mapper 037. Q1 directly connects to PRG A18 and CHR A18, and both ROMs' A17 pins are Q0 + A17·/Q1 or NAND(NAND(Q0,Q0),NAND(A17,NAND(Q1,Q1)))