The CS pin is an active low input that enables the ADC serial interface for communication. CS must be low during the entire data transaction. When CS is high, the serial interface is reset, SCLK input activity is ignored (blocking input commands), and the DOUT/DRDY output pin enters a high-impedance state. ADC conversions are not affected by the state of CS. If the serial bus is dedicated to the ADC, the CS pin can be optionally tied low to reduce the serial interface from four I/Os to three I/Os. Tying the CS pin low permanently enables the ADC serial interface. The DRDY output asserts low when conversion data are ready and is not affected by CS.