CPROM

NES-CPROM (no HVC-CPROM known) 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. Only Videomation, a paint program for NES, is known to use it.

Overview

• PRG ROM size: 32 KiB (DIP-28 standard pinout)
• PRG ROM bank size: Not bankswitched
• PRG RAM: None
• CHR capacity: 16 KiB RAM (in two 8KiB RAMs)
• CHR bank size: 4 KiB
• Nametable mirroring: Vertical
• Subject to bus conflicts: Yes

Banks

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

Registers

Bank select ($8000-$FFFF)

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

Hardware

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

See also

• Kevtris's notes
• The NROM-368 proposal is also compatible with this board.