SPI Operation Modes

SPI Full Duplex Mode

In full duplex mode SPI master device simultaneously transmits data to a slave and receives data from a slave. This way only a single slave device can be engaged at one time. An SS line is used to select the particular SPI slave device.

SPI in full duplex mode

SPI Half Duplex Mode (Single Read)

In half duplex single read mode SPI master device only receives data from a slave. This way only a single slave device can be engaged at one time. An SS line is used to select the slave device.

SPI in half duplex single read mode

SPI Half Duplex Mode (Single Write)

In half duplex single write mode SPI master device only transmits data to a slave, and doesn't receive any data from the slave. This way simultaneous operation with several slave devices is possible.

When operating in Half Duplex (Single Write) mode users are strongly encouraged NOT to interconnect the MISO lines and not to connect them to the master. This precaution will prevent possible damage to equipment if several slaves accidentally start outputting data.

SPI in half duplex single write mode