The PCM9211 includes an SPI-compatible serial port, which operates asynchronously to the audio serial interface. The control interface consists of these data sources: MDI/SDA, MS/ADR1, MC/SCL, and MDO/ADR0.
- MDI is the serial data input to program the mode control registers. In other applications, this source may be known as MOSI.
- MDO is the serial data output to read back register settings and some flags. In other applications, this source may be known as MISO.
- MC is the serial bit clock to shift the data into the control port. In other applications, this clock may be known as SCK.
- MS is the select input to enable the mode control port. In other applications, this control may be known as an active-low Chip Select (
CS).