You can find this informatio in almost any data book related to audio
It is a serial interface for audio converters. It consists of the
following signals (ony 4 are necessary for either direction):
Master Clock - Typically the sampling rate x oversmapling.
e.g. 48kHz sampling x 256 times oversampling will be 12.288MHz
Data Clock - one cycle per data bit in or out. Alignment and phse
are important here, see a data book.
L/R signal - identifies if right or left channel information
is currently being sent/recieved.
Data out - data sent to DAC
Data in - data in from ADC.
There are dozens of variations in use by various people. The newer
codec's are actually giving you quite a number of options, such as
positive clock or negative clock, data starts with L/R or is delayed by
one cycle, 16, 24, or 32 bit lengths, etc.....