INES Mapper 174: Difference between revisions

From NESdev Wiki
Jump to navigationJump to search
m (+consistency in arithmetic)
m (links to ICs)
 
(15 intermediate revisions by 3 users not shown)
Line 1: Line 1:
[[Category:iNES Mappers]]
[[Category:iNES Mappers|174]][[Category:Discrete logic mappers|174]][[Category:Multicart mappers|174]]
   Here are Bisqwit's original notes:   
   Here are Bisqwit's original notes:   
   ========================
   ========================
   =  Mapper 252         =
   =  Mapper 174         =
   ========================
   ========================
    
    
   Example Game:
   Example Game:
   --------------------------
   --------------------------
   NTDec 5-in-1 (PAL), Famicom cartridge format
   NTDec 5-in-1 (NTSC), Famicom cartridge format
    
    
   PRG ROM size: 128 kB
   PRG ROM size: 128 kB
Line 15: Line 15:
   ---------------------------
   ---------------------------
    
    
   $8000-FFFF:    A~[.... .... HLLL CCCM]
   $8000-FFFF:    A~[.... .... OPPP CCCM]
       M = Mirroring (1=Horizontal, 0=Vertical)
       M = Mirroring (1=Horizontal, 0=Vertical)
       L = Selects 16 kB page for PRG memory $8000 as L*0x4000
       P = when O=0 selects 16k both @ $8000 and @ $C000
       H = Selects 16 kB page for PRG memory $C000: If 1, selects L+0x4000, else selects same as L
          when O=1, the top two bits select 32k @ $8000 and the bottom bit is ignored
       O = PRG mode: selects 16 kB (when 0) or 32 kB mode (when 1).
       C = Selects 8 kB page for CHR memory $0000
       C = Selects 8 kB page for CHR memory $0000
    
    
   All of the mapper register access seems to be done in $FF00-$FFFF range.
   All of the mapper register access seems to be done in $FF00-$FFFF range, however the entire range works.
  It is unknown what is the exact range of memory where writes are trapped.
  It is also unknown where exactly the PRG memory page $8000 is mapped when H=0,
  because when H=0, the games on the cartridge only access memory range $C000-$FFFF.
  Additionally, it is unknown what happens if H=1 and L&1 = 1, because none of
  the cartridge's code ever invokes that situation.
    
    
   The cartridge powers on in a state where L=0, H=0.
   The cartridge powers on in a state where all registers are 0.
  (It is not known whether M, C are also 0 after poweron.)
    
    
   The cartridge expect the RAM contents to be kept when reset is pressed,
   The cartridge expect the RAM contents to be kept when reset is pressed,
   whereupon it boots the game. The only way to return to the main menu after
   whereupon it boots the game. The only way to return to the main menu after
   selecting a game is to powercycle the console (cold reboot).
   selecting a game is to power cycle the console (cold reboot).
    
    
  This mapper is functionally identical to [[iNES Mapper 058|mapper 58]] except the bits are moved around.
    
    
   Notes:
   Notes:
   ---------------------------
   ---------------------------
   This mapper is probably unique to that board, constructed from
   This mapper is probably unique to that board, constructed from
   two GD74LS161As (4-bit binary counter) and one GD74LS153 (dual 4-input multiplexer).
   two [[74161|GD74LS161A]]s (4-bit binary counter) and one [[74153|GD74LS153]] (dual 4-input multiplexer).
    
    
   It is a multicart that consists of games of different sizes.
   It is a multicart that consists of games of different sizes.
Line 46: Line 42:
   - One game with PRG size = 8 kB (Galaxian), which shares a 16 kB page together with the main menu.
   - One game with PRG size = 8 kB (Galaxian), which shares a 16 kB page together with the main menu.
    
    
  All the games have been edited to remove any copyright information from rendering
   The main menu does some writes to $4028 once in a while, and one of
  (the ROM data still does contain some of the trademark and copyright strings).
   the games (Urban Champion) writes to $4025. The purpose of these writes
  They also have been edited to access the cartridge's memory remapping I/O rather
   is unknown, as the cartridge does not trap those writes, and there is
  than the original mapper I/O of those respective games.
  (probably) no hardware in the NTDec famiclone that responds at those addresses.
 
  It can be noted though, that $4025 is the [[FDS]] motor control register,
   The main menu also does some writes to $4025 once in a while, and one of
  and the value written would safely stop a disk system motor.
   the games (Urban Champion) writes to $4028. The purpose of these writes
  It is possibly a leftover from porting the game or its library routines
   is unknown, as the cartridge does not trap those writes.
  from the FDS to the Famicom.
 
More information: [http://forums.nesdev.org/viewtopic.php?p=96276#p96276]


More information: http://nesdev.parodius.com/bbs/viewtopic.php?p=96276#96276
Similar mappers: [[INES_Mapper_058|58]], [[INES_Mapper_060|60]], [[INES_Mapper_212|212]], [[INES_Mapper_231|231]]

Latest revision as of 01:32, 13 July 2017

 Here are Bisqwit's original notes:  
 ========================
 =  Mapper 174          =
 ========================
 
 Example Game:
 --------------------------
 NTDec 5-in-1 (NTSC), Famicom cartridge format
 
 PRG ROM size: 128 kB
 CHR ROM size: 64 kB 
 
 Registers:
 ---------------------------
 
  $8000-FFFF:     A~[.... .... OPPP CCCM]
     M = Mirroring (1=Horizontal, 0=Vertical)
     P = when O=0 selects 16k both @ $8000 and @ $C000
         when O=1, the top two bits select 32k @ $8000 and the bottom bit is ignored
     O = PRG mode: selects 16 kB (when 0) or 32 kB mode (when 1).
     C = Selects 8 kB page for CHR memory $0000
 
 All of the mapper register access seems to be done in $FF00-$FFFF range, however the entire range works.
 
 The cartridge powers on in a state where all registers are 0.
 
 The cartridge expect the RAM contents to be kept when reset is pressed,
 whereupon it boots the game. The only way to return to the main menu after
 selecting a game is to power cycle the console (cold reboot).
 
 This mapper is functionally identical to mapper 58 except the bits are moved around.
 
 Notes:
 ---------------------------
 This mapper is probably unique to that board, constructed from
 two GD74LS161As (4-bit binary counter) and one GD74LS153 (dual 4-input multiplexer).
 
 It is a multicart that consists of games of different sizes.
 - Three games with PRG size = 32 kB (The Legend of Kage, The Goonies, Arkanoid)
 - One game with PRG size = 16 kB (Urban Champion)
 - One game with PRG size = 8 kB (Galaxian), which shares a 16 kB page together with the main menu.
 
 The main menu does some writes to $4028 once in a while, and one of
 the games (Urban Champion) writes to $4025. The purpose of these writes
 is unknown, as the cartridge does not trap those writes, and there is
 (probably) no hardware in the NTDec famiclone that responds at those addresses.
 It can be noted though, that $4025 is the FDS motor control register,
 and the value written would safely stop a disk system motor.
 It is possibly a leftover from porting the game or its library routines
 from the FDS to the Famicom.

More information: [1]

Similar mappers: 58, 60, 212, 231