TFROM

TFROM (NES-TFROM and HVC-TFROM) is a common board within the TxROM set. Like other TxROM boards, TFROM uses the Nintendo MMC3 ASIC.

Overview

• PRG ROM size: 128, 256 or 512 KB (DIP-28/32 Nintendo pinout)
• PRG ROM bank size: 8 KB
• PRG RAM: None
• CHR capacity: 32 or 64 KB ROM (DIP-28 standard pinout)
• CHR bank size: 1 KB and 2 KB
• Nametable mirroring: Solder pads select horizontal, vertical or controlled by mapper.
• Subject to bus conflicts: No

Solder pad configuration

• Normal mode : 'CL1' connected, 'H' disconnected, 'V' disconnected, 'CL2' connected.
• DEROM backward compatibility mode with Horizontal mirroring : 'CL1' disconnected, 'H' disconnected, 'V' connected, 'CL2' disconnected.
• DEROM backward compatibility mode with Vertical mirroring : 'CL1' disconnected, 'H' connected, 'V' disconnected, 'CL2' disconnected.

Note : In DEROM backward compatibility mode, mirroring is hardwired and IRQs are disabled. However, the additional bank switching modes available by the MMC3 that weren't available with the MIMIC-1 chip used on DEROM boards are still present.

Connecting 'CL1' enables MMC3-controlled mirroring, while connecting 'CL2' enables IRQs.

See also

• Nintendo MMC3