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 Dreamcast motherboard:

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