In this method of data retrieval, ADC conversion data are shifted out directly from the output shift register. No command is necessary. Read data direct requires that no serial activity occur from the falling edge of DRDY to the readback, or the data are invalid. The serial interface is full duplex in the read data direct mode; meaning that commands are decoded during the data readback. If no command is intended, keep DIN low during readback. If an input command is sent during readback, the ADC executes the command, and data corruption can result. Synchronize the data readback to DRDY or to DOUT/DRDY to make sure the data are read before the next DRDY update, or the old data are overwritten with new data.
As shown in Figure 90, the ADC data field is 2, 3, or 4 bytes long. The data field consists of an optional STATUS byte, three bytes of conversion data, and an optional CRC byte. After all bytes are read, the data-byte sequence (including the STATUS byte and CRC byte, if selected) is repeated when continued SCLKs are sent. The byte sequence repeats starting with the first byte. In order to help verify error-free communication, read the same data multiple times in each conversion interval or use the optional CRC byte.