VRC1: Difference between revisions

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== Overview ==
== Overview ==
* PRG ROM bank size: 8 KB at $8000, $A000, and $C000
* PRG ROM bank size: 8 KB at $8000, $A000, and $C000
* PRG RAM: Unknown (none?)
* PRG RAM: None
* CHR bank size: 4 KB
* CHR bank size: 4 KB
* Nametable [[mirroring]]: Controlled by mapper
* Nametable [[mirroring]]: Controlled by mapper

Revision as of 21:47, 4 September 2012

The Konami VRC1 is an ASIC mapper.



Overview

  • PRG ROM bank size: 8 KB at $8000, $A000, and $C000
  • PRG RAM: None
  • CHR bank size: 4 KB
  • Nametable mirroring: Controlled by mapper
  • Subject to bus conflicts: No

Registers

PRG Select 0 ($8000-$8FFF)

7  bit  0
---------
.... PPPP
     ||||
     ++++- Select 8 KB PRG ROM at $8000

PRG Select 1 ($A000-$AFFF)

7  bit  0
---------
.... PPPP
     ||||
     ++++- Select 8 KB PRG ROM at $A000


PRG Select 2 ($C000-$CFFF)

7  bit  0
---------
.... PPPP
     ||||
     ++++- Select 8 KB PRG ROM at $C000


Mirroring Control, CHR bits ($9000-$9FFF)

7  bit  0
---------
.... .BAM
      |||
      ||+- Mirroring  (0: Vertical; 1: Horizontal)
      |+-- High Bit of 4 KB CHR bank at PPU $0000
      +--- High Bit of 4 KB CHR bank at PPU $1000


CHR Select 0 ($E000-$EFFF)

7  bit  0
---------
.... CCCC
     ||||
     ++++- Low 4 bits of 4 KB CHR bank at PPU $0000

These bits combined with bit 1 of $9000 make a 5-bit CHR selection.


CHR Select 1 ($F000-$FFFF)

7  bit  0
---------
.... CCCC
     ||||
     ++++- Low 4 bits of 4 KB CHR bank at PPU $1000

These bits combined with bit 2 of $9000 make a 5-bit CHR selection.