The serial audio interface
consists of two or three clock signals and one or two data signals(AD0,AD1),
depending on how the I2S module is used. The clock
signals(MCLK,BCLK,WCLK) can be generated either internally (by the I2S module)
or externally (by the audio device or another clock source).
The ADx pins cannot be dynamically placed in a tri-state condition. Therefore,
TDM mode is supported for ADx input pins where only external audio devices drive
these signals, but TDM mode is not supported for ADx output pins.