TQROM: Difference between revisions

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'''TQROM''' denotes Nintendo's NES-TQROM and [[Famicom|HVC]]-TQROM cartridge boards, which use the [[MMC3|Nintendo MMC3]] ASIC mapper.
#REDIRECT [[INES Mapper 119]]
This [[rare]] board, used only by ''Pinbot'' and ''High Speed'', is one of the few that have both CHR ROM and CHR RAM on the same board.
The [[iNES]] format assigns [[iNES Mapper 119|mapper 119]] to this board.
 
== Overview ==
* PRG ROM size: 128 KB (DIP-28 Nintendo pinout)
* PRG ROM bank size: 8 KB
* PRG RAM: Up to 8 KB
* CHR capacity: 32 or 64 KB ROM (DIP-28 standard pinout) and 8 KB RAM [[Category:Mappers with CHR RAM]]
* CHR bank size: 1 KB and 2 KB
* Nametable [[mirroring]]: Controlled by mapper
* Subject to [[bus conflict]]s: No
 
== Registers ==
See [[MM3]]
 
=== Bank data ($8001-$9FFF, odd) ===
Bit 6 of the CHR bank number is used to switch between the CHR ROM chip and the CHR RAM chip.
 
7  bit  0
---- ----
xCDD DDDD
  ||| ||||
  |++-++++- New bank value, based on last value written to Bank select register
  |        0: Select 2 KB CHR bank at PPU $0000-$07FF (or $1000-$17FF);
  |        1: Select 2 KB CHR bank at PPU $0800-$0FFF (or $1800-$1FFF);
  |        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, 7: As standard MMC3
  +-------- Chip select (for CHR banks)
            0: Select CHR ROM; 1: Select CHR RAM
 
Nintendo ''could'' have used bit 7 instead of bit 6, allowing 128 KiB of CHR ROM instead of 64 KiB.
However, using bit 7 would have precluded a hypothetical "TQSROM" board combining TQROM-style ROM/RAM mixing with [[TLSROM]]-style single-screen mirroring.
Rare developed both games on this board, and Rare was also a big fan of single-screen mirroring on the [[AxROM]] boards.
 
== Hardware ==
A [[7432|74HC32]] IC controls the CHR RAM's enable line.
 
== References ==
*[http://kevtris.org/mappers/mmc3/NES_TQROM.html NES-TQROM] by Kevin Horton

Revision as of 04:52, 15 November 2010

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