INES Mapper 227: Difference between revisions

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The Chinese unlicensed game <i>[NJXXX] Xiang Shuai Chuan Qi</i> will fail to load pattern data if the below notes on write protection are employed. Is this feature only on some 227 carts (more likely multicarts)? The write protection has been temporarily disabled in fceux and bizhawk until more evidence is gathered. It should be noted that VirtuaNES doesn't use the write protection.
{{DEFAULTSORT:227}}[[Category:iNES Mappers]][[Category:Multicart mappers]][[Category:Mappers with CHR RAM]]
'''iNES Mapper 227''' denotes an address-latch-based multicart circuit board (PCB code '''810449-C-A1''' among others) mounting 1 MiB of PRG-ROM plus 8 KiB of unbanked CHR-RAM.


[[Category:iNES Mappers]][[Category:Multicart mappers]]
A variant used by Chinese RPGs from Nanjing, Waixing (PCB code '''FW-01''') and Yancheng adds 8 KiB battery-backed WRAM and does not implement the UNROM-like bankswitching modes.
  Here are Disch's original notes: 
 
  ========================
Other PCB that use this mapper :
  =  Mapper 227          =
* '''N120-72''' : ''[[1992 Contra 120 in 1]]'' multicart.
  ========================
 
 
Nestopia Plus! has defined submappers 0 and 1, '''submapper 0''' denoting that CHR-RAM is ''not'' write-protected in NROM modes (for use with Chinese RPGs), '''submapper 1''' denoting that CHR-RAM ''is'' write-protected in NROM modes (for use with multicarts).
 
 
  Example Game:
==Address Latch ($8000-$FFFF, write)==
  --------------------------
  [A~1... .mLQ OQQP PpMS]
  1200-in-1
          ||| |||| |||+-0: PRG A14=p
 
          ||| |||| |||  1: PRG A14=CPU A14
 
          ||| |||| ||+- 0: Vertical mirroring
  Notes:
          ||| |||| ||   1: Horizontal mirroring
  ---------------------------
          ||| |||+-++-- PRG A16..A14 (inner bank)
  This mapper has 8k CHR-RAM, and also has the ability to write protect it's CHR-RAM!
          ||+-|++------ PRG A19..A17 (outer bank)
 
          || +-------- 0: When CPU A14=1: PRG A16..14=LLL
 
          ||           1: When CPU A14=1: PRG A16..14=PPp
  Registers:
          |+----------- Value for PRG A16..14 when CPU A14=1 and O=0
  ---------------------------
          +------------ 0: PRG A3..A0=CPU A3..A0
 
                        1: PRG A3..A0=Solder pad 3-0
    $8000-FFFF: A~[.... ..LP  OPPP PPMS]
Power-on value: 0
      L = Last PRG Page Mode
 
      P = PRG Reg
Effective meaning:
      O = Mode
  Bit 9  Bit 7  Bit 0   Meaning
      M = Mirroring (0=Vert, 1=Horz)
$200s   $080s   $001s
      S = PRG Size
   (L)    (O)    (S)
    
  0      0      0    Switchable inner 16 KiB bank PPp at CPU $8000-$BFFF, fixed inner bank #0 at CPU $C000-$FFFF (UNROM-like with fixed bank 0)
 
  0      0      1    Switchable inner 16 KIB bank PP0 at CPU $8000-$BFFF, fixed inner bank #0 at CPU $C000-$FFFF (UNROM-like with only even banks reachable, pointless)
  Setup:
  1      0       0     Switchable inner 16 KiB bank PPp at CPU $8000-$BFFF, fixed inner bank #7 at CPU $C000-$FFFF (UNROM)
  ---------------------------
  1      0       1    Switchable inner 16 KIB bank PP0 at CPU $8000-$BFFF, fixed inner bank #7 at CPU $C000-$FFFF (UNROM with only even banks reachable, pointless)
 
  ?      1      0    Switchable 16 KiB inner bank PPp at CPU $8000-$BFFF, mirrored at CPU $C000-$FFFF (NROM-128)
  When 'O' is set, CHR-RAM is write protected (writes have no effect).  'O' also changes the PRG mode.
  ?      1      1    Switchable 32 KiB inner bank PP at CPU $8000-$FFFF (NROM-256)
 
 
  Note there is funky ANDs and ORs going on below depending on the modes:
* On multicart PCBs (no battery or '''submapper 1'''), CHR-RAM is write-protected when O=1 and write-enabled when O=0, i.e. write-protected in the NROM-128 and NROM-256 modes.
 
* When the ''m'' bit is set, PRG A3-A0 are replaced with the values of four solder pads, which when the menu code reads particular ROM locations effectively selects one of up to sixteen menus with different game counts.
 
* Because all bits are cleared on reset, both CPU $8000-$BFFF and $C000-$FFFF are set to 16 KiB bank #0 on reset.
                    $8000  $A000  $C000  $E000  
 
                  +---------------+---------------+
==Similar mappers==
  O=1, S=0:      |      P      |       P      |
* [[INES Mapper 242]] is a variant with only up to 512 KiB PRG-ROM that moves the ''m'' bit to a different bit location. A variant with two PRG-ROM chips exists as well.
                  +-------------------------------+
* [[NES 2.0 Mapper 375]] is a variant with up to 2 MiB PRG-ROM that allows the UNROM-like switchable bank to be changed via a data latch.
  O=1, S=1:       |            < P >            |
* [[NES 2.0 Mapper 380]] is an incompatible variant with similar functionality.
                  +-------------------------------+
* [[NES 2.0 Mapper 449]] is an incompatible variant that adds 32 KiB CHR-RAM bankswitching functionality.
  O=0, S=0, L=0:  |      P      |  P AND $38  |
 
                  +---------------+---------------+
==See also==
  O=0, S=1, L=0:  |   P AND $3E   |   P AND $38   |
* Dumping thread: https://forums.nesdev.org/viewtopic.php?f=9&t=15271
                  +---------------+---------------+
  O=0, S=0, L=1:  |       P       |  P  OR $07  |
                  +---------------+---------------+
  O=0, S=1, L=1: |  P AND $3E  |  P  OR $07  |
                  +---------------+---------------+

Latest revision as of 15:23, 26 March 2023

iNES Mapper 227 denotes an address-latch-based multicart circuit board (PCB code 810449-C-A1 among others) mounting 1 MiB of PRG-ROM plus 8 KiB of unbanked CHR-RAM.

A variant used by Chinese RPGs from Nanjing, Waixing (PCB code FW-01) and Yancheng adds 8 KiB battery-backed WRAM and does not implement the UNROM-like bankswitching modes.

Other PCB that use this mapper :

Nestopia Plus! has defined submappers 0 and 1, submapper 0 denoting that CHR-RAM is not write-protected in NROM modes (for use with Chinese RPGs), submapper 1 denoting that CHR-RAM is write-protected in NROM modes (for use with multicarts).

Address Latch ($8000-$FFFF, write)

[A~1... .mLQ OQQP PpMS]
         ||| |||| |||+-0: PRG A14=p
         ||| |||| |||  1: PRG A14=CPU A14
         ||| |||| ||+- 0: Vertical mirroring
         ||| |||| ||   1: Horizontal mirroring
         ||| |||+-++-- PRG A16..A14 (inner bank)
         ||+-|++------ PRG A19..A17 (outer bank)
         ||  +-------- 0: When CPU A14=1: PRG A16..14=LLL
         ||            1: When CPU A14=1: PRG A16..14=PPp
         |+----------- Value for PRG A16..14 when CPU A14=1 and O=0
         +------------ 0: PRG A3..A0=CPU A3..A0
                       1: PRG A3..A0=Solder pad 3-0
Power-on value: 0

Effective meaning: 

Bit 9   Bit 7   Bit 0   Meaning
$200s   $080s   $001s
 (L)     (O)     (S)
  0       0       0     Switchable inner 16 KiB bank PPp at CPU $8000-$BFFF, fixed inner bank #0 at CPU $C000-$FFFF (UNROM-like with fixed bank 0)
  0       0       1     Switchable inner 16 KIB bank PP0 at CPU $8000-$BFFF, fixed inner bank #0 at CPU $C000-$FFFF (UNROM-like with only even banks reachable, pointless)
  1       0       0     Switchable inner 16 KiB bank PPp at CPU $8000-$BFFF, fixed inner bank #7 at CPU $C000-$FFFF (UNROM)
  1       0       1     Switchable inner 16 KIB bank PP0 at CPU $8000-$BFFF, fixed inner bank #7 at CPU $C000-$FFFF (UNROM with only even banks reachable, pointless)
  ?       1       0     Switchable 16 KiB inner bank PPp at CPU $8000-$BFFF, mirrored at CPU $C000-$FFFF (NROM-128)
  ?       1       1     Switchable 32 KiB inner bank PP at CPU $8000-$FFFF (NROM-256)
  • On multicart PCBs (no battery or submapper 1), CHR-RAM is write-protected when O=1 and write-enabled when O=0, i.e. write-protected in the NROM-128 and NROM-256 modes.
  • When the m bit is set, PRG A3-A0 are replaced with the values of four solder pads, which when the menu code reads particular ROM locations effectively selects one of up to sixteen menus with different game counts.
  • Because all bits are cleared on reset, both CPU $8000-$BFFF and $C000-$FFFF are set to 16 KiB bank #0 on reset.

Similar mappers

  • INES Mapper 242 is a variant with only up to 512 KiB PRG-ROM that moves the m bit to a different bit location. A variant with two PRG-ROM chips exists as well.
  • NES 2.0 Mapper 375 is a variant with up to 2 MiB PRG-ROM that allows the UNROM-like switchable bank to be changed via a data latch.
  • NES 2.0 Mapper 380 is an incompatible variant with similar functionality.
  • NES 2.0 Mapper 449 is an incompatible variant that adds 32 KiB CHR-RAM bankswitching functionality.

See also

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