INES Mapper 176: Difference between revisions

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{{DEFAULTSORT:176}}[[Category:iNES Mappers]][[Category:Multicart mappers]][[Category:MMC3-like mappers]][[Category:MMC3 with CHR ROM and CHR RAM]][[Category:Mappers with scanline IRQs]][[Category:Mappers with large PRG RAM]][[Category:NES 2.0 mappers with submappers]]
{{DEFAULTSORT:176}}[[Category:iNES Mappers]][[Category:Multicart mappers]][[Category:MMC3-like mappers]][[Category:MMC3 with CHR ROM and CHR RAM]][[Category:Mappers with scanline IRQs]][[Category:Mappers with large PRG RAM]][[Category:NES 2.0 mappers with submappers]]
'''iNES Mapper 176''' denotes an enhanced [[MMC3]] chipset used by many multicarts as well as Chinese single-game carrtidges, mostly from Waixing.
'''iNES Mapper 176''' denotes the '''8025''' enhanced [[MMC3]] chipset. It used by many multicarts, Chinese single-game and educational computer cartridges, and Techno Source's ''Intellivision X2'' Plug-and-Play console. Incompatible variations exist that are denoted via NES 2.0 Submapper.
 
Three incompatible variations exist that are denoted via NES 2.0 Submapper:
* '''Submapper 0''': UNIF '''BMC-FK23C'''/'''BMC-FK23CA'''/'''BMC-Super24in1SC03''': Extended MMC3 mode ''disabled'' on reset, MMC3 registers $46 and $47 function normally.
* '''Submapper 1''': UNIF '''BMC-FK23C'''/'''BMC-FK23CA'''/'''BMC-Super24in1SC03''': Extended MMC3 mode ''enabled'' on reset, MMC3 registers $46 and $47 function normally.
* '''Submapper 2''': UNIF '''WAIXING-FS005''': Extended MMC3 mode ''disabled'' on reset, MMC3 registers $46 and $47 swapped.
Extended MMC3 mode being ''disabled'' on reset implies that the last 8 KiB in the ''first 512 KiB'' is mapped to CPU $E000-$FFFF, being ''enabled'' on reset implies that the last 8 KiB in the ''first 2 MiB'' is mapped to CPU $E000-$FFFF.


{| class="wikitable"
! colspan="13" | Submappers
|-
! rowspan="2" | # !! rowspan="2" | PCB codes !! rowspan="2" | [[UNIF]] MAPR !! colspan="5" | MMC3 !! colspan="4" | Outer bank registers !! rowspan="2" | Example
|-
! Ext. mode !! PRG bits !! $46/47 !! [[Mirroring#Single-Screen|1SM]] !! Extra WRAM !! Address mask !! PRG A21+ !! CHR A21+ !! CNROM latch
|-
| 0 || LP-8002KB, SFC-12B || '''BMC-Super24in1SC03'''  || - || 6 || normal || - || - || $Fxx3 || - || - || - || ''YH-xxx'' multicarts, ''Rockman 6-in-1''
|-
| 1 || FK-xxx/BS-xxx || '''BMC-FK23C'''/'''BMC-FK23CA''' || $5FF3.1 || 8 || normal || - || - || $Fxx3 || - || - || yes || ''FK-xxxx'' multicarts
|-
| 2 || FS005/FS006 || '''WAIXING-FS005''' || $5FF3.1 || 6 || swapped || yes || $A001.0-1 || $Fxx3 || $5xx0.3/7, $5xx2.6-7/5 || - || - || Waixing 2005+ re-releases, ''245-in-1 Real Game''
|-
| 3 || JX9003B || - || - || 8 || normal || - || - || $Fxx7 || $5xx5 || $5xx6 || - || ''Super Mario 160-in-1 Funny Time''
|-
| 4 || ? || - || - || 6 || normal || - || - || $Fxx3 || $5xx2.7 || - || - || ''GameStar Smart Genius Deluxe''
|-
| 5 || HST-162|| - || - || 6 || normal || - || - || $Fxx3 || $4800 || - || - || ''Game 500-in-1''
|-
|}
* The '''SFC-12B''' PCB (submapper 0) mounts both CHR-ROM and CHR-RAM that are selected via $5xx0.5.
* Eight MMC3 PRG bits mean that bit 6 and 7 of $8000.6/7 are applied, and the fixed banks are $FE/$FF rather than $3E/$3F. This implies that the multicart's reset vector lies at address PRG-ROM address $1FFFFC rather than $7FFFC if the PRG-ROM is that large.
=Registers=
=Registers=
Registers in the $5000-$5FFF range can be temporarily disabled through the [[#RAM Configuration Register ($A001)|RAM Configuration Register ($A001)]].
'''FS005 (Submapper 2)''' can disable the registers in the $5000-$5FFF range using the [[#RAM Configuration Register ($A001)|RAM Configuration Register ($A001)]]. The same register also enables a mixed CHR-ROM/CHR-RAM mode that is similar to [[INES Mapper 195]].


==Mode Register ($5xx0)==
==Mode Register ($5xx0)==
Mask: $5''xx''3, ''x'' determined by [[#Solder Pad|solder pad setting]]
Mask: $F''xx''7 ('''Submapper 3'''), $5''xx''3 (all others), ''x'' determined by [[#Solder Pad|solder pad setting]]
 
  7654 3210
  7654 3210
  ---- ----
  ---- ----
Line 19: Line 34:
  |||| ||||
  |||| ||||
  |||| |+++- Select PRG Banking Mode (ignored in Extended MMC3 Mode)
  |||| |+++- Select PRG Banking Mode (ignored in Extended MMC3 Mode)
  |||| |      0: MMC3 PRG Mode, 512 KiB Outer PRG Bank Size
  |||| |      0: MMC3 PRG Mode, 2 MiB/512 KiB Outer PRG Bank Size
  |||| |      1: MMC3 PRG Mode, 256 KiB Outer PRG Bank Size
  |||| |      1: MMC3 PRG Mode, 256 KiB Outer PRG Bank Size
  |||| |      2: MMC3 PRG Mode, 128 KiB Outer PRG Bank Size
  |||| |      2: MMC3 PRG Mode, 128 KiB Outer PRG Bank Size
  |||| |      3: NROM-128 PRG Mode, 16 KiB PRG at $8000-$BFFF mirrored at $C000-$FFFF
  |||| |      3: NROM-128 PRG Mode, 16 KiB PRG at $8000-$BFFF mirrored at $C000-$FFFF
  |||| |      4: NROM-256 PRG Mode, 32 KiB PRG at $8000-$FFFF
  |||| |      4: NROM-256 PRG Mode, 32 KiB PRG at $8000-$FFFF
  |||| |      5-7: Never used
  |||| |      5: UNROM PRG Mode, 16 KiB PRG at $8000-$BFFF, inner bank #7 at $C000-$FFFF
  |||| +---- PRG Base A21
|||| |      6-7: Never used
  |||| +---- PRG A21 ('''Submapper 2''' only)
  |||+------ Select Outer CHR Bank Size
  |||+------ Select Outer CHR Bank Size
  |||        0: In MMC3 CHR Mode: 256 KiB
  |||        0: In MMC3 CHR Mode: 256 KiB
  |||            In CNROM CHR Mode: 32 KiB
  |||            In CNROM CHR Mode: 32 KiB ('''Submapper 1''' only)
  |||        1: In MMC3 CHR Mode: 128 KiB
  |||        1: In MMC3 CHR Mode: 128 KiB
  |||            In CNROM CHR Mode: 16 KiB
  |||            In CNROM CHR Mode: 16 KiB ('''Submapper 1''' only)
  ||+------- Select CHR Memory Type
  ||+------- '''Submappers 0/1''' with both CHR-ROM and CHR-RAM (e.g. '''SFC-12B''' PCB):
  ||          0: CHR-ROM
  ||          0: Select CHR-ROM
  ||          1: CHR-RAM
  ||          1: Select CHR-RAM
  |+-------- CHR Mode
||        '''Submapper 1''' with $5xx0.6=1:
  |          0: MMC3 CHR Mode
||          0: Enable CNROM latch (CNROM mode)
  |          1: NROM/CNROM CHR Mode
||          1: Disable CNROM latch (NROM mode)
  +--------- PRG Base A22
  |+-------- CHR A10-12 Mode
  |          0: from MMC3
  |          1: from PPU
  +--------- PRG A22 ('''Submapper 2''' only)
   
   
  Power-on value: $00
  Power-on value: $00
* It is possible to use NROM mode for PRG banking and MMC3 mode for CHR banking.
* NROM versus CNROM CHR Mode is decided in the Extended Mode Register ($5xx3).
* Bit 5 applies to CHR Memory in its entirety, while Bit 2 of the [[#RAM Configuration Register ($A001)|RAM Configuration Register ($A001)]] selects mixed CHR-ROM/RAM mode.
* The inner and outer bank numbers are combined ...
** ... in MMC3 PRG/CHR modes: by masking the MMC3 bank register content according to the specified size (128 or 256 KiB) and OR'ing with the opposite-masked content of the PRG ($5xx1)/CHR ($5xx2) Base;
** ... in NROM PRG/CHR mode: by using the PRG ($5xx1)/CHR Base ($5xx2) directly.
** ... in CNROM CHR mode: by masking the CNROM Latch according to the selected Outer CHR Bank Size, and OR'ing with the ''unmasked'' content of the CHR Base ($5xx2);
** ... in [[#Extended Mode Register ($5xx3)|Extended MMC3 mode]] by OR'ing the ''unmasked'' (extended) bank register content with the ''unmasked'' content of the PRG ($5xx1)/CHR ($5xx2) Base.
==PRG Base Register ($5xx1)==
Mask: $5''xx''3, ''x'' determined by [[#Solder Pad|solder pad setting]]


==PRG Base Register LSB ($5xx1)==
Mask: $F''xx''7 ('''Submapper 3'''), $F''xx''3 (all others), ''x'' determined by [[#Solder Pad|solder pad setting]]
  7654 3210
  7654 3210
  ---- ----
  ---- ----
  .PPP PPPP
  .PPP PPPP
   ||| ||||
   ||| ||||
   +++-++++- PRG Base A20..A14
   +++-++++- PRG A20..A14
Power-on value: $00
Depending on the PRG banking mode set via $5xx0, only the higher bits of this register are applied:
PRG A..
21111111
09876543
--------
MMMMMMMM  Submappers 1/3 in PRG Mode 0 (MMC3 2 MiB) or Extended MMC3 Mode
BBMMMMMM  Submappers 0/2/4 in PRG Mode 0 (MMC3 512 KiB)
BBBMMMMM  PRG Mode 1 (MMC3 256 KiB)
BBBBMMMM  PRG Mode 2 (MMC3 128 KiB)
BBBBBBBC  PRG Mode 3 (NROM-128)
BBBBBBCC  PRG Mode 4 (NROM-256)
BBBBLLLC  PRG Mode 5 (UNROM)
M: Bit comes from MMC3 ($8000.6/7 or fixed bank)
B: Bit comes from PRG Base Register ($5xx1)
L: Bit comes from UNROM Latch ($8000-$FFFF or fixed bank)
C: Bit comes from CPU
 
'''Submapper 5''' only selects PRG A14-A18 (i.e. 512 KiB) via this register, selecting upper PRG bits via register [[#PRG Base Register MSB ($4800), Submapper 5 only|$4800]].
==PRG Base Register MSB ($5xx5), Submapper 3 only==
Mask: $F''xx''7 ('''Submapper 3'''), ''x'' determined by [[#Solder Pad|solder pad setting]]
7654 3210
---- ----
.... PPPP
      ||||
      ++++- PRG Base A24..A21
Power-on value: $00
==PRG Base Register MSB ($4800), Submapper 5 only==
Mask: $F800
7654 3210
---- ----
..PP PPPP
  || ||||
  ++-++++- PRG Base A24..A19
   
   
  Power-on value: $00
  Power-on value: $00
==CHR Base Register ($5xx2)==
Mask: $5''xx''3, ''x'' determined by [[#Solder Pad|solder pad setting]]


==CHR Base Register LSB ($5xx2)==
Mask: $F''xx''7 ('''Submapper 3'''), $5''xx''3 (all others), ''x'' determined by [[#Solder Pad|solder pad setting]]
  7654 3210
  7654 3210
  ---- ----
  ---- ----
  ccdC CCCC
  ccdC CCCC
  |||| ||||
  |||| ||||
  ++++-++++- CHR Base A20..A13
  ++++-++++- CHR A20..A13
  ||+------- PRG Base A25
  ||+------- PRG A25 ('''Submapper 2''' only)
  ++-------- PRG Base A24..A23
  ++-------- PRG A24..A23 ('''Submapper 2''' only)
+--------- PRG A21 ('''Submapper 4''')
   
   
  Power-on value: $00
  Power-on value: $00
Writing to the CHR Base Register also resets the CNROM latch.


==Extended Mode Register ($5xx3)==
Depending on the CHR banking mode set via $5xx0, only the higher bits of this register are applied:
Mask: $5''xx''3, ''x'' determined by [[#Solder Pad|solder pad setting]]
CHR A..
21111111111
09876543210
-----------
BBBMMMMMMMM  MMC3 CHR Mode ($5xx0.6=0), 256 KiB ($5xx0.4=0)
BBBBMMMMMMM  MMC3 CHR Mode ($5xx0.6=0), 128 KiB ($5xx0.4=1)
BBBBBBLLPPP  CNROM CHR Mode ($5xx0.6=1, $5xx0.5=0), 32 KiB ($5xx0.4=0), '''Submapper 1''' only
BBBBBBBLPPP  CNROM CHR Mode ($5xx0.6=1, $5xx0.5=0), 16 KiB ($5xx0.4=1), '''Submapper 1''' only
BBBBBBBBPPP  NROM CHR Mode ($5xx0.6=1, $5xx0.5=1 or '''Submapper''' other than '''1''')
M: Bit comes from MMC3 ($8000.0-5)
B: Bit comes from CHR Base Register ($5xx2)
L: Bit comes from CNROM Latch ($8000-$FFFF)
P: Bit comes from PPU
 
==CHR Base Register MSB ($5xx6), Submapper 3 only==
Mask: $F''xx''7 ('''Submapper 3'''), ''x'' determined by [[#Solder Pad|solder pad setting]]


  7654 3210
  7654 3210
  ---- ----
  ---- ----
  .C.. .CE.
  .... PPPP
  |   ||  
      ||||
  |    |+- [[#MMC3-compatible registers ($8000/$8001, $A000, $C000/$C001, $E000/$E001)|Extended MMC3 Mode]]
      ++++- CHR Base A24..A21
  |    |    0: disable
  |    |    1: enable
  +----+-- Select NROM/CNROM CHR Mode
            0: NROM
            1: CNROM
   
   
  Power-on value: $02 (Submapper 1), $00 (otherwise)
  Power-on value: $00
Since all games that use CNROM mode always set both bits 2 and 6 simultaneously, it's not clear which one of these bits actually triggers the CNROM mode, and what the function of the other bit would be.


==Extended Mode Register ($5xx3), Submappers 1-2 only==
Mask: $F''xx''3, ''x'' determined by [[#Solder Pad|solder pad setting]]
7654 3210
---- ----
.?.. .?E.
        |
        +- [[#MMC3-compatible registers ($8000/$8001, $A000, $C000/$C001, $E000/$E001)|Extended MMC3 Mode]]
            0: disable
            1: enable
Power-on value: $00
Most multicarts write value $44 rather than $00 to disable Extended MMC3 Mode. Hardware tests do not indicate any difference in behavior between writing $00 and $44.
==Mirroring Register ($A000)==
==Mirroring Register ($A000)==
  Mask: $E001
  Mask: $E003
   
   
  7654 3210
  7654 3210
Line 99: Line 169:
             0: Vertical
             0: Vertical
             1: Horizontal
             1: Horizontal
             2: Single-screen, page 0
             2: Single-screen, page 0 ('''Submapper 2''' only)
             3: Single-screen, page 1
             3: Single-screen, page 1 ('''Submapper 2''' only)
  Power-on value: $00
  Power-on value: $00


Single-screen mirroring is only available when the RAM Configuration Register is enabled ($A001.5).
Single-screen mirroring is only available when the RAM Configuration Register is enabled ($A001.5).


==RAM Configuration Register ($A001)==
==RAM Configuration Register ($A001), Submapper 2 only==
Mask: $E001
Mask: $E003


This register functions like MMC3 register $A001 until bit 5 is set, which turns it into the RAM Configuration Register. It is only present on later chipset revisions.
This register functions like MMC3 register $A001 until bit 5 is set, which turns it into the RAM Configuration Register.


  7654 3210
  7654 3210
Line 122: Line 192:
  ||          0: RAM Configuration Register disabled, $A001 functions as on MMC3, 8 KiB of WRAM
  ||          0: RAM Configuration Register disabled, $A001 functions as on MMC3, 8 KiB of WRAM
  ||          1: RAM Configuration Register enabled, 32 KiB of WRAM
  ||          1: RAM Configuration Register enabled, 32 KiB of WRAM
  |+-------- FK23C Registers Enable. Ignored if Bit 5 is clear.
  |+-------- Outer Bank Registers Enable. Ignored if Bit 5 is clear.
  |          0: FK23C Registers disabled, $5000-$5FFF maps to the second 4 KiB of the 8 KiB WRAM bank 2
  |          0: Outer Bank Registers disabled, $5000-$5FFF maps to the second 4 KiB of the 8 KiB WRAM bank 2
  |          1: FK23C Registers enabled in the $5000-$5FFF range
  |          1: Outer Bank Registers enabled in the $5000-$5FFF range
  +--------- PRG RAM enable (0: disable, 1: enable)
  +--------- PRG RAM enable (0: disable, 1: enable)
   
   
  Power-on value: $00
  Power-on value: $00
==CNROM latch ($8000-$9FFF, $C000-$FFFF)==
 
In CNROM Mode, writing to these address ranges changes the inner CHR bank.
==UNROM latch ($8000-$FFFF)==
In UNROM Mode (PRG Mode 5), writing to this address range changes the 16 KiB inner PRG bank at $8000-$BFFF.
 
==CNROM latch ($8000-$FFFF), Submapper 1 only==
In CNROM Mode, writing to this address range changes the inner CHR bank.


==MMC3-compatible registers, Extended MMC3 Mode ($8000/$8001, $C000/$C001, $E000/$E001)==
==MMC3-compatible registers, Extended MMC3 Mode ($8000/$8001, $C000/$C001, $E000/$E001)==
If the "Extended MMC3 Mode" bit in register $5xx3 is clear, then these registers function identically to the [[MMC3]]. If the "Extended MMC3 Mode" bit is set, four more bank registers become available at [[MMC3#Bank_select_.28.248000-.249FFE.2C_even.29|$8000/$8001]], so that the original two 2 KiB CHR banks become four 1 KiB CHR banks, and the two fixed 8 KiB PRG banks become selectable, similar to the [[RAMBO-1]]. Furthermore, all eight bits of the PRG-ROM bank numbers will then be used, allowing up to 2 MiB to be bankedswitched, and all "mask" settings of register $5000 are ignored.
Mask: $E003 (verified on real hardware)
  Register $8000 if $5xx3 bit 1 is set (Mask: $E001):
 
Some multicart games depend on writes to $9FFF not doing anything as a result of the MMC3 address mask being $E003 rather than the standard $E001.
 
If the "Extended MMC3 Mode" bit in register $5xx3 is clear, then these registers function identically to the [[MMC3]]. On '''Submappers 1 and 2''', if the "Extended MMC3 Mode" bit is set, four more bank registers become available at [[MMC3#Bank_select_.28.248000-.249FFE.2C_even.29|$8000/$8001]], so that the original two 2 KiB CHR banks become four 1 KiB CHR banks, and the two fixed 8 KiB PRG banks become selectable, similar to the [[RAMBO-1]].  Register $8000 if $5xx3 bit 1 is set:
  7  bit  0
  7  bit  0
  ---- ----
  ---- ----
Line 157: Line 234:
  * Standard MMC3 Registers $0-$7: $00, $02, $04, $05, $06, $07, $00, $01
  * Standard MMC3 Registers $0-$7: $00, $02, $04, $05, $06, $07, $00, $01
  * Extended MMC3 Registers $8-$B: $FE, $FF, $FF, $FF
  * Extended MMC3 Registers $8-$B: $FE, $FF, $FF, $FF
=Solder Pad=
=Solder Pad=
The address mask in the $5000-$5FFF range is determined by the solder pad setting:
The address mask in the $5000-$5FFF range is determined by the solder pad setting:
Line 172: Line 250:
* Some multicarts only display their menu at settings other than 0.
* Some multicarts only display their menu at settings other than 0.


=Protection=
=Protection (Submapper 2 only)=
Later Waixing games (and re-releases of earlier games) use the RAM Configuration Register for copy-protection purposes:
Later Waixing games (and re-releases of earlier games) use the RAM Configuration Register for copy-protection purposes:
* Write $A1 to $A001: Address range $5000-$5FFF to second half of 8 KiB WRAM bank 2, mapper registers there are disabled.
* Write $A1 to $A001: Address range $5000-$5FFF to second half of 8 KiB WRAM bank 2, mapper registers there are disabled.
Line 182: Line 260:
* Execute code at CPU $0100.
* Execute code at CPU $0100.
Hacked ROMs can be detected by them writing to $5000/$5010/$5013 but then no longer jumping to $0100.
Hacked ROMs can be detected by them writing to $5000/$5010/$5013 but then no longer jumping to $0100.
=See also=
* [[NES 2.0 Mapper 523]] is a variant of this mapper with hard-wired mirroring that connects CHR-ROM differently to produce 4/2 KiB instead of 2/1 KiB banks.

Latest revision as of 18:48, 17 December 2021

iNES Mapper 176 denotes the 8025 enhanced MMC3 chipset. It used by many multicarts, Chinese single-game and educational computer cartridges, and Techno Source's Intellivision X2 Plug-and-Play console. Incompatible variations exist that are denoted via NES 2.0 Submapper.

Submappers
# PCB codes UNIF MAPR MMC3 Outer bank registers Example
Ext. mode PRG bits $46/47 1SM Extra WRAM Address mask PRG A21+ CHR A21+ CNROM latch
0 LP-8002KB, SFC-12B BMC-Super24in1SC03 - 6 normal - - $Fxx3 - - - YH-xxx multicarts, Rockman 6-in-1
1 FK-xxx/BS-xxx BMC-FK23C/BMC-FK23CA $5FF3.1 8 normal - - $Fxx3 - - yes FK-xxxx multicarts
2 FS005/FS006 WAIXING-FS005 $5FF3.1 6 swapped yes $A001.0-1 $Fxx3 $5xx0.3/7, $5xx2.6-7/5 - - Waixing 2005+ re-releases, 245-in-1 Real Game
3 JX9003B - - 8 normal - - $Fxx7 $5xx5 $5xx6 - Super Mario 160-in-1 Funny Time
4 ? - - 6 normal - - $Fxx3 $5xx2.7 - - GameStar Smart Genius Deluxe
5 HST-162 - - 6 normal - - $Fxx3 $4800 - - Game 500-in-1
  • The SFC-12B PCB (submapper 0) mounts both CHR-ROM and CHR-RAM that are selected via $5xx0.5.
  • Eight MMC3 PRG bits mean that bit 6 and 7 of $8000.6/7 are applied, and the fixed banks are $FE/$FF rather than $3E/$3F. This implies that the multicart's reset vector lies at address PRG-ROM address $1FFFFC rather than $7FFFC if the PRG-ROM is that large.

Registers

FS005 (Submapper 2) can disable the registers in the $5000-$5FFF range using the RAM Configuration Register ($A001). The same register also enables a mixed CHR-ROM/CHR-RAM mode that is similar to INES Mapper 195.

Mode Register ($5xx0)

Mask: $Fxx7 (Submapper 3), $5xx3 (all others), x determined by solder pad setting 

7654 3210
---- ----
PCTm PMMM
|||| ||||
|||| |+++- Select PRG Banking Mode (ignored in Extended MMC3 Mode)
|||| |      0: MMC3 PRG Mode, 2 MiB/512 KiB Outer PRG Bank Size
|||| |      1: MMC3 PRG Mode, 256 KiB Outer PRG Bank Size
|||| |      2: MMC3 PRG Mode, 128 KiB Outer PRG Bank Size
|||| |      3: NROM-128 PRG Mode, 16 KiB PRG at $8000-$BFFF mirrored at $C000-$FFFF
|||| |      4: NROM-256 PRG Mode, 32 KiB PRG at $8000-$FFFF
|||| |      5: UNROM PRG Mode, 16 KiB PRG at $8000-$BFFF, inner bank #7 at $C000-$FFFF
|||| |      6-7: Never used
|||| +---- PRG A21 (Submapper 2 only)
|||+------ Select Outer CHR Bank Size
|||         0: In MMC3 CHR Mode: 256 KiB
|||            In CNROM CHR Mode: 32 KiB (Submapper 1 only)
|||         1: In MMC3 CHR Mode: 128 KiB
|||            In CNROM CHR Mode: 16 KiB (Submapper 1 only)
||+------- Submappers 0/1 with both CHR-ROM and CHR-RAM (e.g. SFC-12B PCB):
||          0: Select CHR-ROM
||          1: Select CHR-RAM
||         Submapper 1 with $5xx0.6=1:
||          0: Enable CNROM latch (CNROM mode)
||          1: Disable CNROM latch (NROM mode)
|+-------- CHR A10-12 Mode
|           0: from MMC3
|           1: from PPU
+--------- PRG A22 (Submapper 2 only)

Power-on value: $00

PRG Base Register LSB ($5xx1)

Mask: $Fxx7 (Submapper 3), $Fxx3 (all others), x determined by solder pad setting 

7654 3210
---- ----
.PPP PPPP
 ||| ||||
 +++-++++- PRG A20..A14

Power-on value: $00

Depending on the PRG banking mode set via $5xx0, only the higher bits of this register are applied: 

PRG A..
21111111
09876543
--------
MMMMMMMM  Submappers 1/3 in PRG Mode 0 (MMC3 2 MiB) or Extended MMC3 Mode
BBMMMMMM  Submappers 0/2/4 in PRG Mode 0 (MMC3 512 KiB)
BBBMMMMM  PRG Mode 1 (MMC3 256 KiB)
BBBBMMMM  PRG Mode 2 (MMC3 128 KiB)
BBBBBBBC  PRG Mode 3 (NROM-128)
BBBBBBCC  PRG Mode 4 (NROM-256)
BBBBLLLC  PRG Mode 5 (UNROM)

M: Bit comes from MMC3 ($8000.6/7 or fixed bank)
B: Bit comes from PRG Base Register ($5xx1)
L: Bit comes from UNROM Latch ($8000-$FFFF or fixed bank)
C: Bit comes from CPU

Submapper 5 only selects PRG A14-A18 (i.e. 512 KiB) via this register, selecting upper PRG bits via register $4800.

PRG Base Register MSB ($5xx5), Submapper 3 only

Mask: $Fxx7 (Submapper 3), x determined by solder pad setting 

7654 3210
---- ----
.... PPPP
     ||||
     ++++- PRG Base A24..A21

Power-on value: $00

PRG Base Register MSB ($4800), Submapper 5 only

Mask: $F800 

7654 3210
---- ----
..PP PPPP
  || ||||
  ++-++++- PRG Base A24..A19

Power-on value: $00

CHR Base Register LSB ($5xx2)

Mask: $Fxx7 (Submapper 3), $5xx3 (all others), x determined by solder pad setting 

7654 3210
---- ----
ccdC CCCC
|||| ||||
++++-++++- CHR A20..A13
||+------- PRG A25 (Submapper 2 only)
++-------- PRG A24..A23 (Submapper 2 only)
+--------- PRG A21 (Submapper 4)

Power-on value: $00

Depending on the CHR banking mode set via $5xx0, only the higher bits of this register are applied: 

CHR A..
21111111111
09876543210
-----------
BBBMMMMMMMM  MMC3 CHR Mode ($5xx0.6=0), 256 KiB ($5xx0.4=0)
BBBBMMMMMMM  MMC3 CHR Mode ($5xx0.6=0), 128 KiB ($5xx0.4=1)
BBBBBBLLPPP  CNROM CHR Mode ($5xx0.6=1, $5xx0.5=0), 32 KiB ($5xx0.4=0), Submapper 1 only
BBBBBBBLPPP  CNROM CHR Mode ($5xx0.6=1, $5xx0.5=0), 16 KiB ($5xx0.4=1), Submapper 1 only
BBBBBBBBPPP  NROM CHR Mode ($5xx0.6=1, $5xx0.5=1 or Submapper other than 1)

M: Bit comes from MMC3 ($8000.0-5)
B: Bit comes from CHR Base Register ($5xx2)
L: Bit comes from CNROM Latch ($8000-$FFFF)
P: Bit comes from PPU

CHR Base Register MSB ($5xx6), Submapper 3 only

Mask: $Fxx7 (Submapper 3), x determined by solder pad setting 

7654 3210
---- ----
.... PPPP
     ||||
     ++++- CHR Base A24..A21

Power-on value: $00

Extended Mode Register ($5xx3), Submappers 1-2 only

Mask: $Fxx3, x determined by solder pad setting 

7654 3210
---- ----
.?.. .?E.
       | 
       +- Extended MMC3 Mode
           0: disable
           1: enable

Power-on value: $00

Most multicarts write value $44 rather than $00 to disable Extended MMC3 Mode. Hardware tests do not indicate any difference in behavior between writing $00 and $44.

Mirroring Register ($A000)

Mask: $E003

7654 3210
---- ----
.... ..MM
       ++- Select nametable mirroring 
           0: Vertical
           1: Horizontal
           2: Single-screen, page 0 (Submapper 2 only)
           3: Single-screen, page 1 (Submapper 2 only)
Power-on value: $00

Single-screen mirroring is only available when the RAM Configuration Register is enabled ($A001.5).

RAM Configuration Register ($A001), Submapper 2 only

Mask: $E003

This register functions like MMC3 register $A001 until bit 5 is set, which turns it into the RAM Configuration Register. 

7654 3210
---- ----
RFE. SCWW
|||  ||||
|||  ||++- Select 8 KiB PRG-RAM bank at $6000-$7FFF. Ignored if Bit 5 is clear.
|||  |+--- Select the memory type in the first 8 KiB of CHR space. Ignored if Bit 5 is clear.
|||  |      0: First 8 KiB are CHR-ROM
|||  |      1: First 8 KiB are CHR-RAM
|||  +---- Unknown
||+------- RAM Configuration Register Enable
||          0: RAM Configuration Register disabled, $A001 functions as on MMC3, 8 KiB of WRAM
||          1: RAM Configuration Register enabled, 32 KiB of WRAM
|+-------- Outer Bank Registers Enable. Ignored if Bit 5 is clear.
|           0: Outer Bank Registers disabled, $5000-$5FFF maps to the second 4 KiB of the 8 KiB WRAM bank 2
|           1: Outer Bank Registers enabled in the $5000-$5FFF range
+--------- PRG RAM enable (0: disable, 1: enable)

Power-on value: $00

UNROM latch ($8000-$FFFF)

In UNROM Mode (PRG Mode 5), writing to this address range changes the 16 KiB inner PRG bank at $8000-$BFFF.

CNROM latch ($8000-$FFFF), Submapper 1 only

In CNROM Mode, writing to this address range changes the inner CHR bank.

MMC3-compatible registers, Extended MMC3 Mode ($8000/$8001, $C000/$C001, $E000/$E001)

Mask: $E003 (verified on real hardware)

Some multicart games depend on writes to $9FFF not doing anything as a result of the MMC3 address mask being $E003 rather than the standard $E001.

If the "Extended MMC3 Mode" bit in register $5xx3 is clear, then these registers function identically to the MMC3. On Submappers 1 and 2, if the "Extended MMC3 Mode" bit is set, four more bank registers become available at $8000/$8001, so that the original two 2 KiB CHR banks become four 1 KiB CHR banks, and the two fixed 8 KiB PRG banks become selectable, similar to the RAMBO-1. Register $8000 if $5xx3 bit 1 is set: 

7  bit  0
---- ----
CP.. RRRR
||   ||||
||   ++++- Specify which bank register to update on next write to Bank Data register
||         $0: Select 1 KB CHR bank at PPU $0000-$03FF (or $1000-$13FF)
||         $1: Select 1 KB CHR bank at PPU $0800-$0BFF (or $1800-$1BFF)
||         $2: Select 1 KB CHR bank at PPU $1000-$13FF (or $0000-$03FF)
||         $3: Select 1 KB CHR bank at PPU $1400-$17FF (or $0400-$07FF)
||         $4: Select 1 KB CHR bank at PPU $1800-$1BFF (or $0800-$0BFF)
||         $5: Select 1 KB CHR bank at PPU $1C00-$1FFF (or $0C00-$0FFF)
||         $6: Select 8 KB PRG ROM bank at $8000-$9FFF (or $C000-$DFFF)
||         $7: Select 8 KB PRG ROM bank at $A000-$BFFF
||         $8: Select 8 KB PRG ROM bank at $C000-$DFFF (or $8000-$9FFF)
||         $9: Select 8 KB PRG ROM bank at $E000-$FFFF
||         $A: Select 1 KB CHR bank at PPU $0400-$07FF (or $1400-$17FF)
||         $B: Select 1 KB CHR bank at PPU $0C00-$0FFF (or $1C00-$1FFF)
|+-------- Invert PRG A14
+--------- Invert CHR A12

Power-on values:
* Standard MMC3 Registers $0-$7: $00, $02, $04, $05, $06, $07, $00, $01
* Extended MMC3 Registers $8-$B: $FE, $FF, $FF, $FF

Solder Pad

The address mask in the $5000-$5FFF range is determined by the solder pad setting: 

Pad setting  Address mask
-----------  ------------
0            $5013
1            $5023
2            $5043
3            $5083
4            $5103
5            $5203
6            $5403
7            $5803
  • A solder pad setting of zero (address mask $5013) will produce a usable result for any ROM image.
  • Some multicarts only display their menu at settings other than 0.

Protection (Submapper 2 only)

Later Waixing games (and re-releases of earlier games) use the RAM Configuration Register for copy-protection purposes:

  • Write $A1 to $A001: Address range $5000-$5FFF to second half of 8 KiB WRAM bank 2, mapper registers there are disabled.
  • Write three values to $5000, $5010 and $5013.
  • Do further initialization.
  • Write $E2 to $A001. Mapper registers in address range $5000-$5FFF; WRAM at CPU $6000-$7FFF points to 8 KiB WRAM bank 2.
  • Copy 20 bytes from $7000 to $6000.
  • Copy and XOR bytes from $6000, $6010 and $6013 to $0100-$0102.
  • Execute code at CPU $0100.

Hacked ROMs can be detected by them writing to $5000/$5010/$5013 but then no longer jumping to $0100.

See also

  • NES 2.0 Mapper 523 is a variant of this mapper with hard-wired mirroring that connects CHR-ROM differently to produce 4/2 KiB instead of 2/1 KiB banks.
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