.. _dev-sample:

Device Sample Format
=====================

Data passed over the read or write streams are transmitted in unit packets,
or "samples".

Read Samples
-------------
These are the samples produced by the devices and sent through the
:ref:`read stream <com-channels>` to the controller.
Read samples MUST have the following format:

::

    uint64    hubclk_cnt
    var       payload

- ``hubclk_cnt``: Hub Clock Counter. This is the common counter for all devices in
  a :ref:`Hub <hub>`, indicating the time of sample capture.
- ``payload``: :ref:`Device-specific<dev-datasheet-read-format>` data. This data MUST be
  :ref:`Read Sample Size <dev-desc>` - 8 bytes long.

Write samples
-------------
These are the samples generated by the host and sent to the devices
trough the :ref:`write stream <com-channels>`.
Write samples MUST have the following format.

::

  var payload

- ``payload``: :ref:`Device-specific<dev-datasheet-write-format>` data. This data MUST be
  :ref:`Write Sample Size <dev-desc>` bytes long.