SPI (Serial Peripheral Interface) Explained

SPI, short for Serial Peripheral Interface, is primarily used for high-speed data communication over short distances. It’s a synchronous serial communication link where, typically, one slave device is connected to one master device, as illustrated below. The master device generates the clock signal for data transfer synchronization.

It’s also possible to connect multiple slave devices to a single master for communication. The SPI interface can operate in either half-duplex or full-duplex mode.

The SPI interface has four primary signal lines:

• MOSI (Master Output Slave Input): This line is used to transmit data from the master device to the slave device.
• MISO (Master Input Slave Output): This line is used to transmit data from the slave device to the master device.
• SCLK (Serial Clock): This is the clock signal generated by the master device, used for synchronization during data transfer.
• SS (Slave Select): The master device uses this line to select a specific slave device when multiple slaves are connected. It asserts an active-low signal to select the desired slave.