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S/PDIF transmit
===============

The codebase supports a single, stereo, S/PDIF transmitter. This can be output over 75 Ω coaxial or optical fibre.
In order to provide S/PDIF transmit functionality ``lib_xua`` uses `lib_spdif <https://www.xmos.com/file/lib_spdif>`__.

Basic configuration of S/PDIF transmit functionality is achieved with the defines in :numref:`opt_spdif_tx_defines`.

.. _opt_spdif_tx_defines:

.. list-table:: S/PDIF tx defines
   :header-rows: 1
   :widths: 30 60 20

   * - Define
     - Description
     - Default
   * - ``XUA_SPDIF_TX_EN``
     - Enable S/PDIF transmit
     - ``0`` (Disabled)
   * - ``SPDIF_TX_INDEX``
     - Output channel offset to use for S/PDIF transmit
     - ``0``

In addition, the developer may choose which tile the S/PDIF transmitter runs on, see
:numref:`opt_spdif_tx_tile_defines`

.. _opt_spdif_tx_tile_defines:

.. list-table:: S/PDIF tile define
   :header-rows: 1
   :widths: 30 40 20

   * - Define
     - Description
     - Default
   * - ``XUA_SPDIF_TX_TILE_NUM``
     - Tile that S/PDIF tx is connected to
     - Derived from PORT_SPDIF_OUT define in the application XN file

The codebase expects the S/PDIF transmit port to be defined in the application XN file as ``PORT_SPDIF_OUT``.
This must be a 1-bit port, for example::

    <Port Location="XS1_PORT_1A"  Name="PORT_SPDIF_OUT"/>

