This input pin is used to select the device for a SPI transaction. The pin is active low, so while nCS is high the Serial Data Output (SDO) pin of the device is high impedance allowing an SPI bus to be designed. When nCS is low the SDO driver is activated and communication may be started. The nCS pin is held low for a SPI transaction. A special feature on this device allows the SDO pin to immediately show the Global Fault Flag on a falling edge of nCS.