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I²S/TDM
=======

I²S/TDM is typically fundamental to most products and is built into the ``XUA_AudioHub()`` thread.

:numref:`opt_i2s_defines` lists the defines that affect the I²S implementation.

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.. _opt_i2s_defines:

.. list-table:: I²S defines
   :header-rows: 1
   :widths: 20 40 20

   * - Define
     - Description
     - Default
   * - ``I2S_CHANS_DAC``
     - The desired number of output channels via I2S (0 for disabled)
     - N/A (Must be defined)
   * - ``I2S_CHANS_ADC``
     - The desired number of input channels via I2S (0 for disabled)
     - N/A (Must be defined)
   * - ``XUA_PCM_FORMAT``
     - Enables either TDM or I2S mode
     - ``XUA_PCM_FORMAT_I2S``
   * - ``CODEC_MASTER``
     - Sets if `xcore` is I2S master or slave
     - ``0`` (`xcore` is master)
   * - ``XUA_I2S_N_BITS``
     - I2S/TDM word length (16, 32-bit supported)
     - ``32``

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The I²S code expects that the ports required for I²S (master clock, LR-clock, bit-clock and data lines) are defined in the application XN file on the relevant ``Tile``.
For example::

    <Tile Number="0" Reference="tile[0]">
        <Port Location="XS1_PORT_1A"  Name="PORT_MCLK_IN"/>
        <Port Location="XS1_PORT_1B"  Name="PORT_I2S_LRCLK"/>
        <Port Location="XS1_PORT_1C"  Name="PORT_I2S_BCLK"/>
        <Port Location="XS1_PORT_1D"  Name="PORT_I2S_DAC0"/>
        <Port Location="XS1_PORT_1E"  Name="PORT_I2S_DAC1"/>
        <Port Location="XS1_PORT_1F"  Name="PORT_I2S_ADC0"/>
        <Port Location="XS1_PORT_1G"  Name="PORT_I2S_ADC1"/>
    </Tile>

All of the I²S/TDM related ports must be 1-bit ports.

.. note::

    TDM mode allows 8 channels (rather than 2) to be supplied on each data-line.

.. note::

    Data output/input is in "I²S" format, rather than, say "left-justified" or "right-justified" formats.
    I²S format specifies a single bit-clock delay after the LR-clock transition before sample-data is driven/received.
    This also applies to TDM mode. TDM support in ADC/DAC hardware is quite varied, an "offset" value may need to be programmed into
    the external device for compatible operation.

