INES Mapper 176: Difference between revisions

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(Update based on some real hardware tests and additional dumps. 2 MiB PRG separate from Extended MMC3, CNROM latch only one some boards, UNROM mode added.)
 
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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 and educational computer cartridges. Curiously, it is also used by Techno Source's ''Intellivision X2'' Plug-and-Play console. At least four incompatible variations exist that are denoted via NES 2.0 Submapper. UNIF board names do not correspond exactly to them.
'''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.
 
{| class="wikitable"
{| class="wikitable"
! colspan="9" | Submappers
! 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''
|-
|-
! # !! MMC3 PRG limit !! PRG A21+ !! CHR A21+ !! $46/47 !! CNROM latch !! Extra WRAM !! 1-Screen Mirroring || UNIF
| 1 || FK-xxx/BS-xxx || '''BMC-FK23C'''/'''BMC-FK23CA''' || $5FF3.1 || 8 || normal || - || - || $Fxx3 || - || - || yes || ''FK-xxxx'' multicarts
|-
|-
| 0 || 512 KiB || CHR A20 bit in $5xx2 || - || normal || not present|| not supported || not supported || '''BMC-FK23C'''/'''BMC-FK23CA'''/'''BMC-Super24in1SC03'''
| 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''
|-
|-
| 1 || 2 MiB || $5xx5 || $5xx6 || normal || not present|| not supported || not supported || '''BMC-FK23C'''/'''BMC-FK23CA'''
| 3 || JX9003B || - || - || 8 || normal || - || - || $Fxx7 || $5xx5 || $5xx6 || - || ''Super Mario 160-in-1 Funny Time''
|-
|-
| 2 || 512 KiB || various bits in $5xx0/$5xx2 || - || swapped || not present|| supported via $A001 || supported || '''WAIXING-FS005'''
| 4 || ? || - || - || 6 || normal || - || - || $Fxx3 || $5xx2.7 || - || - || ''GameStar Smart Genius Deluxe''
|-
|-
| 3 || 512 KiB || - || - || - || present|| not supported || not supported || '''BMC-FK23CA'''
| 5 || HST-162|| - || - || 6 || normal || - || - || $Fxx3 || $4800 || - || - || ''Game 500-in-1''
|-
|-
|}
|}
* The Waixing variant swaps the meaning of MMC3's $8000 values $46 and $47.
* The '''SFC-12B''' PCB (submapper 0) mounts both CHR-ROM and CHR-RAM that are selected via $5xx0.5.
* Variants with no CHR-RAM and only CHR-RAM that repurpose higher CHR address lines as PRG-ROM address lines do not have their own submappers.
* 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.
* MMC3 PRG limit of 2 MiB means 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.
 
=Registers=
=Registers=
Submapper 2 can disable the registers in the $5000-$5FFF range using the [[#RAM Configuration Register ($A001)|RAM Configuration Register ($A001)]]. Writes to $5xx8-$5xxF have no effect.
'''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''F, ''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 30: Line 34:
  |||| ||||
  |||| ||||
  |||| |+++- Select PRG Banking Mode (ignored in Extended MMC3 Mode)
  |||| |+++- Select PRG Banking Mode (ignored in Extended MMC3 Mode)
  |||| |      0: MMC3 PRG Mode, 2 MiB (Submapper 1)/512 KiB (all others) 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
Line 37: Line 41:
  |||| |      5: UNROM PRG Mode, 16 KiB PRG at $8000-$BFFF, inner bank #7 at $C000-$FFFF
  |||| |      5: UNROM PRG Mode, 16 KiB PRG at $8000-$BFFF, inner bank #7 at $C000-$FFFF
  |||| |      6-7: Never used
  |||| |      6-7: Never used
  |||| +---- PRG Base A21 (Submapper 2 only)
  |||| +---- 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 (submapper 3 only)
  |||            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 (submapper 3 only)
  |||            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: CNROM (Submapper 3)/NROM (all others) CHR Mode
||          1: Disable CNROM latch (NROM mode)
  +--------- PRG Base A22 (Submapper 2 only)
  |+-------- CHR A10-12 Mode
  |          0: from MMC3
  |          1: from PPU
  +--------- PRG A22 ('''Submapper 2''' only)
   
   
  Power-on value: $00
  Power-on value: $00
* It is possible to use NROM mode for PRG banking and MMC3 mode for CHR banking.
* Bit 5 applies to CHR Memory in its entirety. Submapper 2 provides for mixed CHR_ROM/RAM mode using Bit 2 of its [[#RAM Configuration Register ($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 (Submapper 3 only): 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 LSB ($5xx1)==
==PRG Base Register LSB ($5xx1)==
Mask: $5''xx''F, ''x'' determined by [[#Solder Pad|solder pad setting]]
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
  Power-on value: $00
==PRG Base Register MSB ($5xx5), Submapper 1 only==
Depending on the PRG banking mode set via $5xx0, only the higher bits of this register are applied:
Mask: $5''xx''F, ''x'' determined by [[#Solder Pad|solder pad setting]]
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
  7654 3210
  ---- ----
  ---- ----
Line 80: Line 97:
   
   
  Power-on value: $00
  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)==
==CHR Base Register LSB ($5xx2)==
Mask: $5''xx''F, ''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
  ---- ----
  ---- ----
  ccdC CCCC
  ccdC CCCC
  |||| ||||
  |||| ||||
  ++++-++++- CHR Base A20..A13
  ++++-++++- CHR A20..A13
  ||+------- PRG Base A25 (submapper 2 only)
  ||+------- PRG A25 ('''Submapper 2''' only)
  ++-------- PRG Base A24..A23 (submapper 2 only)
  ++-------- PRG A24..A23 ('''Submapper 2''' only)
  +--------- PRG Base A21 (submapper 0 without CHR-ROM only)
  +--------- PRG A21 ('''Submapper 4''')
   
   
  Power-on value: $00
  Power-on value: $00
* Writing to the CHR Base Register also resets the CNROM latch in submapper 3.
* Submapper 0 and 2 boards that only use CHR-RAM reuse some of the higher CHR address lines as PRG address lines.


==CHR Base Register MSB ($5xx6), Submapper 1 only==
Depending on the CHR banking mode set via $5xx0, only the higher bits of this register are applied:
Mask: $5''xx''F, ''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
Line 107: Line 147:
  Power-on value: $00
  Power-on value: $00


==Extended Mode Register ($5xx3)==
==Extended Mode Register ($5xx3), Submappers 1-2 only==
Mask: $5''xx''F, ''x'' determined by [[#Solder Pad|solder pad setting]]
Mask: $F''xx''3, ''x'' determined by [[#Solder Pad|solder pad setting]]


  7654 3210
  7654 3210
  ---- ----
  ---- ----
  .... ..E.
  .?.. .?E.
         |  
         |  
         +- [[#MMC3-compatible registers ($8000/$8001, $A000, $C000/$C001, $E000/$E001)|Extended MMC3 Mode]]
         +- [[#MMC3-compatible registers ($8000/$8001, $A000, $C000/$C001, $E000/$E001)|Extended MMC3 Mode]]
Line 119: Line 159:
   
   
  Power-on value: $00
  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 129: Line 169:
             0: Vertical
             0: Vertical
             1: Horizontal
             1: Horizontal
             2: Single-screen, page 0 (Submapper 2 only)
             2: Single-screen, page 0 ('''Submapper 2''' only)
             3: Single-screen, page 1 (Submapper 2 only)
             3: Single-screen, page 1 ('''Submapper 2''' only)
  Power-on value: $00
  Power-on value: $00


Line 136: Line 176:


==RAM Configuration Register ($A001), Submapper 2 only==
==RAM Configuration Register ($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 152: 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
==UNROM latch ($8000-$FFFF)==
==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.
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 3 only==
==CNROM latch ($8000-$FFFF), Submapper 1 only==
In CNROM Mode, writing to this address range changes the inner CHR bank.
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]].  Register $8000 if $5xx3 bit 1 is set (Mask: $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 [[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 189: 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:
  Pad setting  Address mask
  Pad setting  Address mask
  -----------  ------------
  -----------  ------------
  0            $501F
  0            $5013
  1            $502F
  1            $5023
  2            $504F
  2            $5043
  3            $508F
  3            $5083
  4            $510F
  4            $5103
  5            $520F
  5            $5203
  6            $540F
  6            $5403
  7            $580F
  7            $5803
* A solder pad setting of zero (address mask $501F) will produce a usable result for any ROM image.
* 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.
* Some multicarts only display their menu at settings other than 0.


Line 214: 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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