The AD1852’s flexible serial data input port accepts data in twos-complement, MSB-first format. The left channel data field always precedes the right channel data field. The serial mode is set by using either the external mode pins (IDPM0 Pin 21 and IDPM1 Pin 20) or the mode select bits (Bits 4 and 5) in the SPI control register. To control the serial mode using the external mode pins, the SPI mode select bits should be set to zero (default at power-up). To control the serial mode using the SPI mode select bits, the external mode control pins should be grounded.