NES 2.0 Mapper 270: Difference between revisions

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[[Category:Multicart mappers]]
{{DEFAULTSORT:270}}[[Category:Multicart mappers]][[Category:NES 2.0 mappers with submappers]][[Category:MMC3-like mappers]][[Category:Mappers with scanline IRQs]]
NES 2.0 Mapper 270 is used for the ''Game Prince RS-16'' plug-and-play console's multicart. It uses [[VTxx]] OneBus bankswitching all similar to [[NES 2.0 Mapper 256|Mapper 256]], but has an additional bankswitch register.
'''NES 2.0 Mapper 270''' denotes [[NES 2.0 Mapper 256|OneBus]] console multicarts that use the consoles' universal input/output (UIO) register $412C to bankswitch higher-order PRG address lines or several PRG chips, and select CHR-RAM via $4242.
==Outer Bank Register ($412C)==
 
$412C is a general "UIO output data" port on the VTxx consoles. In this case, the value written to this register selects an 8 MiB base address (A23) for all [[VT02%2B_PRG-ROM_Bankswitching|PRG-ROM]] and [[VT02%2B_CHR-ROM_Bankswitching|CHR-ROM]] banks.
=Submapper 0: Combination=
Responds to all bank bits of submappers 1-3 at the same time. This is permissible, since the only bit that is used by several submappers has the same function in each of them.
 
=Submapper 1: Game Prince RS-16=
==Outer PRG Bank ($412C, write)==
D~7654 3210
  ---------
  .... ..A.
          +-- PRG/CHR A24
 
=Submapper 2: Family Pocket 638-in-1=
==Outer PRG Bank ($412C, write)==
D~7654 3210
  ---------
  .... ..AB
          |+- PRG/CHR A25
          +-- PRG/CHR A24
 
==Jumper Cartridge Detection ($412C, read)==
D~7654 3210
  ---------
  .... B...
        +---- 0: Jumper cartridge not inserted
              1: Jumper cartridge inserted
 
==CHR-RAM enable ($4242, write)==
D~7654 3210
  ---------
  .... ...C
          +- 0: Use normal [[VT02%2B_CHR-ROM_Bankswitching|OneBus CHR banking]]
              1: Use 8 KiB of unbanked CHR-RAM
 
=Submapper 3: Bittboy 300-in-1=
==Outer PRG Bank ($412C, write)==
D~7654 3210
  ---------
  .... .A..
        +--- PRG/CHR A24
=Notes=
* Any $412C bit can only be read from if the corresponding bit in register $412B (UIO input/output selector) is set to "0" (input).
* Any $412C bit can only be written to if the corresponding bit in register $412B (UIO input/output selector) is set to "1" (output).

Latest revision as of 06:37, 26 May 2020

NES 2.0 Mapper 270 denotes OneBus console multicarts that use the consoles' universal input/output (UIO) register $412C to bankswitch higher-order PRG address lines or several PRG chips, and select CHR-RAM via $4242.

Submapper 0: Combination

Responds to all bank bits of submappers 1-3 at the same time. This is permissible, since the only bit that is used by several submappers has the same function in each of them.

Submapper 1: Game Prince RS-16

Outer PRG Bank ($412C, write)

D~7654 3210
  ---------
  .... ..A.
         +-- PRG/CHR A24

Submapper 2: Family Pocket 638-in-1

Outer PRG Bank ($412C, write)

D~7654 3210
  ---------
  .... ..AB
         |+- PRG/CHR A25
         +-- PRG/CHR A24

Jumper Cartridge Detection ($412C, read)

D~7654 3210
  ---------
  .... B...
       +---- 0: Jumper cartridge not inserted
             1: Jumper cartridge inserted

CHR-RAM enable ($4242, write)

D~7654 3210
  ---------
  .... ...C
          +- 0: Use normal OneBus CHR banking
             1: Use 8 KiB of unbanked CHR-RAM

Submapper 3: Bittboy 300-in-1

Outer PRG Bank ($412C, write)

D~7654 3210
  ---------
  .... .A..
        +--- PRG/CHR A24

Notes

  • Any $412C bit can only be read from if the corresponding bit in register $412B (UIO input/output selector) is set to "0" (input).
  • Any $412C bit can only be written to if the corresponding bit in register $412B (UIO input/output selector) is set to "1" (output).
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