CPROM

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Revision as of 20:38, 26 November 2010 by Bregalad (talk | contribs) (Apparently there is no H/V solder pads on CPROM boards (or are they hidden under a chip ?))
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NES-CPROM (and HVC-CPROM) is a particular Nintendo cartridge board which uses discrete logic to provide up to four 4 KB banks of CHR RAM. The iNES format assigns mapper 13 to this board.

Overview

  • PRG ROM size: 32 KB (DIP-28 standard pinout)
  • PRG ROM bank size: Not bankswitched
  • PRG RAM: None
  • CHR capacity: 16 KB RAM
  • CHR bank size: 4 KB
  • Nametable mirroring: Vertical
  • Subject to bus conflicts: Yes

Banks

  • PPU $0000-$0FFF: 4 KB fixed CHR RAM bank (first page)
  • PPU $1000-$1FFF: 4 KB swappable CHR RAM page

Registers

Bank select ($8000-$FFFF)

7  bit  0
---- ----
xxxx xxCC
       ||
       ++- Select 4 KB CHR RAM bank for PPU $1000-$1FFF

Hardware

The CPROM board uses a 74HC161 (4-bit latch), 74HC04 (hex inverter), and 74HC08 (quad 2-input AND gate).