The SPI (Serial Peripheral Interface)  bus is a full-duplex synchronous serial data link, using three common lines (SCLK, MOSI, MISO) and a select line per slave device. It offers higher throughput than I²C, at the cost of using more pins, and is primarily used to access nonvolatile storage (eg. SD cards, on-board NOR) or peripheral devices (eg. the AD7888 ADC ).
On the Rig 200 development board, SPI is available for communicating with a SPI boot ROM (Snapper CL15 only), SD/MMC cards, and SPI-based LCDs. On Rig 200 it is also provided to expansion boards via the riser connectors, and to end users via Mictor 11 on the debug expansion board for debugging and prototyping use.