Sega Dreamcast & NAOMI SCI-SPI Mod

This guide explains how to access the SH-4 SCI port on Sega Dreamcast and NAOMI systems in both UART/SPI communication modes. It can be used for debugging or connecting an SD card. In SPI-like mode, the SCI port can transfer data at speeds up to 1.5 MB/s, which is twice as fast as using the SCIF port for bit-bang SPI. Sega Dreamcast Motherboard Solder wires directly to the following points on the…