Glossary · Automation fundamentals, platforms and components
Serial Peripheral Interface (SPI)
Also known as: SPI, SPI bus
German: Serial Peripheral Interface (SPI)
In embedded electronics, the Serial Peripheral Interface (SPI) is a synchronous serial bus in which a controller device exchanges data with one or more peripheral devices over a clock line, two data lines (MOSI, controller out/peripheral in, and MISO, controller in/peripheral out) and one chip select line per peripheral, typically to read and write registers of ICs on the same board.
- Automation components
In one sentence
SPI is a synchronous board-level serial bus with clock, two data lines and chip select, used to read and write registers of ICs.
Example
A microcontroller configures a motion control IC over SPI, writing 40-bit datagrams that set the motor current and read back the status flags.
How it applies
- Engineering: SPI is fast and simple but meant for short distances on a board or between nearby boards. Newer documents call the lines SDO/SDI or COPI/CIPO, and the roles controller/peripheral instead of the older master/slave.
- Commissioning: Clock polarity and phase (SPI mode 0–3), bit order, word length and maximum clock rate must match the peripheral's datasheet.
- Operation: SPI has no built-in error detection; some ICs add a CRC or status bits to each datagram.
- Documentation: Document the SPI mode, clock rate, datagram format and register map with addresses, bit fields, reset values and access (read/write). State which line names you use and map them once to the alternatives.
SPI vs. UART
SPI is synchronous: a shared clock line times every bit, the controller always starts the transfer, and each peripheral needs a chip select. A Universal asynchronous receiver-transmitter (UART) is asynchronous with two data lines and no clock; both sides must agree on the baud rate.