Chip select (CS) is an active-low input that selects the device for SPI communication and controls the beginning and end of a data frame in asynchronous interrupt mode. CS must remain low for the entire duration of the serial communication to complete a command or data readback. When CS is taken high, the serial interface (including the data frame) is reset, SCLK and DIN are ignored, and DOUT enters a high-impedance state. DRDY transitions low when data conversion is complete, regardless of whether CS is high or low. As with other SPI devices, multiple ADS131A0x devices in asynchronous interrupt mode can be controlled at the same time but each device requires its own CS line.