The SPI Bus

Fast, simple, and one chip-select per device.

SPI uses a clock, a data line out, a data line in, and a chip-select for each peripheral. The controller pulls one chip-select low to talk to that device.

Data shifts in and out at the same time, one bit per clock pulse. Speeds of several megahertz are common, making SPI a good fit for displays and memory cards.

The cost is extra pins: each added device needs another chip-select.