INES Mapper 227: Difference between revisions

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[[Category:iNES Mappers|227]][[Category:Multicart mappers|227]]
{{DEFAULTSORT:227}}[[Category:iNES Mappers]][[Category:Multicart mappers]][[Category:Mappers with CHR RAM]]
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.
'''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.


In r2750 of fceux this support was rewritten; it should still work. It supposedly works in nestopia as well.
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 :
  Menu information added by Zepper, thanks to zxbdragon. 
* '''N120-72''' : ''[[1992 Contra 120 in 1]]'' multicart.
  ========================
  =  Mapper 227          =
  ========================
 
 
  Example Game:
  --------------------------
  1200-in-1
  600-in-1
 
 
  Notes:
  ---------------------------
  This mapper has 8k CHR-RAM, and also has the ability to write protect it's CHR-RAM!
 
 
  Registers:
  ---------------------------
  This mapper uses the address written for its setup. The value is irrelevant.
 
    $8000-FFFF:  A~[.... .mLP  OPPP PPMS]
      L = Last PRG Page Mode
      P = PRG Reg
      O = Mode
      M = Mirroring (0=Vert, 1=Horz)
      S = PRG Size
      m = Menu list (see below)
 
  Setup:
  ---------------------------
 
  When 'O' is set, CHR-RAM is write protected (writes have no effect). 'O' also changes the PRG mode.
 
  Note there is funky ANDs and ORs going on below depending on the modes:
 
 
                    $8000  $A000  $C000  $E000 
                  +---------------+---------------+
  O=1, S=0:      |      P      |      P      |
                  +-------------------------------+
  O=1, S=1:      |            < P >            |
                  +-------------------------------+
  O=0, S=0, L=0:  |      P      |  P AND $38  |
                  +---------------+---------------+
  O=0, S=1, L=0:  |  P AND $3E  |  P AND $38  |
                  +---------------+---------------+
  O=0, S=0, L=1:  |      P      |  P  OR $07  |
                  +---------------+---------------+
  O=0, S=1, L=1:  |  P AND $3E  |  P  OR $07  |
                  +---------------+---------------+


  Menu list:
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),
  The following information does not work for the 1200in1 cartridge!
* '''submapper 1''' denoting that CHR-RAM ''is'' write-protected in NROM modes (for use with multicarts), and a solder pad read mode is available.
  Bit 11 of the address written activates the menu list selection. When activated, reading anywhere
* '''submapper 2''' denoting that CHR-RAM ''is'' write-protected in NROM modes (for use with multicarts), and "inner bank #0" also means "outer bank #0".
  at $8000-$FFFF returns the menu list type (value x 8) described below; otherwise, returns PRG ROM
  data at $8000-$FFFF.
  +-------+----------------------------+
  | value | number of selectable games |
  +-------+----------------------------+
  |  0  | 860 in 1                  |
  |  1  | 460 in 1                  |
  |  2   | 500 in 1                  |
  |  3  | 560 in 1                  |
  |  4  | 600 in 1                  |
  |  5  | 660 in 1                  |
  |  6  | 700 in 1                  |
  |  7  | 860 in 1                  |
  |  8  | 900 in 1                  |
  |  9  | 920 in 1                  |
  |  10  | 940 in 1                  |
  |  11  | 960 in 1                  |
  |  12  | 980 in 1                  |
  |  13  | 400 in 1                  |
  |  14  | 380 in 1                  |
  |  15  | 360 in 1                  |
  +-------+----------------------------+
  | 16~19 | blue screen                |
  | 20    | up to 980, 981+ bugged    |
  | 21    | same of 21                |
  | 22    | 40 in 1, clipped list      |
  | 23~31 | blue screen                |
  | 32    | 420 in 1                  |
  | 33    | 460 in 1 (same of 1) $21  |
  | 34    | 500 in 1 (same of 2) $22  |
  +-------+----------------------------+


The hardware on this board appears to be two [[74157]]s, a [[74153]], two [[74174]]s, a [[7402]], and a [[7432]]. When the 'm' bit is set, one of the 74157s replaces the 4 LSbits of the CPU's address bus with a fixed constant. Evidently, this allowed the pirates to make multiple different seeming multicarts from the same physical ROMs, just by using different PCBs.
==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 (submapper 1 only)
Power-on value: 0


All bits of the banking register (meaning both 74174s) are most likely cleared on reset.
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)


See also: [https://forums.nesdev.org/viewtopic.php?f=9&t=15271 dumping thread]
* 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==
* Dumping thread: https://forums.nesdev.org/viewtopic.php?f=9&t=15271

Latest revision as of 08:20, 3 June 2024

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), and a solder pad read mode is available.
  • submapper 2 denoting that CHR-RAM is write-protected in NROM modes (for use with multicarts), and "inner bank #0" also means "outer bank #0".

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 (submapper 1 only)
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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