SPI Slave select

The SPI block provides for one Slave Select input in slave mode or output in master mode. The SSEL can be set for normal polarity (active low), or can be inverted (active high). Representation of the SSEL in a register is always active low. If the SSEL is inverted, this is done as the signal leaves/enters the SPI block.

In slave mode, the asserted SSEL that is connected to a pin will activate the SPI. In master mode, the SSEL that is connected to a pin will be output as defined in the SPI registers.

In master mode, the Slave Select is configured by the TXSSELN field, which appears in both the TXCTL and TXDATCTL registers. In slave mode, the state of the SSEL is saved along with received data in the RXSSEL_N field of the RXDAT register.