SPI
A synchronous full-duplex serial interface that uses a clock, separate data lines, and chip-select signals for high-speed peripheral communication.
Embedded-System Context
SPI uses a shared clock, separate data directions, and chip-select lines for synchronous peripheral communication. At higher clock rates, signal integrity, CPOL/CPHA mode, bus loading, trace length, and chip-select timing become part of protocol correctness.
Protocol Boundary
SPI defines the electrical transfer mechanism but not one universal message format. Register maps, commands, framing, and error handling are device-specific.