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Definition: SPI bus

(Serial Peripheral Interface bus) A four-line, synchronous, serial bus from Motorola that is widely used to connect a microcontroller to peripheral chips on a circuit board. Each device has one input line and one output line, and data are exchanged in full-duplex mode. SPI operates in a master-slave topology where the microcontroller is the master and clock controller, and the peripheral chips respond as slaves. SPI is typically faster than the I2C bus. See I2C bus.

SPI on a Microcontroller
This Ramtron microcontroller (MCU) includes controllers for both SPI and I2C buses for peripheral data transfer (note upper right of diagram). (Image courtesy of Ramtron International Corporation, www.ramtron.com)