.. _headlabel-refx-cmd-hbd:

HBD (Heartbeat Settings)
========================

The `AT@HBD` command is used to configure the :ref:`HBD <headlabel-refx-frames-heartbeat>` feature.

.. code-block:: none

   Example:
   AT@HBD=gl601###,,,,10,,,,012F$
   +ACK:HBD,123456789012345,C031,10,0,,012F,20210407101530,1234$
   AT@HBD?gl601###,,0C37$
   +QRY:HBD,123456789012345,C031,10,0,1,1,,,,10,,,,0C37,20210407101530,1234$

.. tabularcolumns:: |p{2.2em}|p{7.2em}|p{5.8em}|p{19em}|p{4.8em}|

.. table::
   :width: 100%
   :widths: auto

   +-------+--------------------------+---------------+---------------------------------------+--------------------+
   | Parts |              Fields      | Length (Byte) |                  Range/Format         |    Default         |
   +=======+==========================+===============+=======================================+====================+
   | Head  | Header                   | 3             | AT@                                   | AT@                |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Command Word             | 3             | HBD                                   | HBD                |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Leading Symbol           | 1             | =                                     | =                  |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Password                 | 8-16          |                                       | gl601###           |
   +-------+--------------------------+---------------+---------------------------------------+--------------------+
   | Body  | Reserved                 | 0             |                                       |                    |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Reserved                 | 0             |                                       |                    |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Reserved                 | 0             |                                       |                    |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | `Heartbeat Interval`     | <=2           | 3 - 99 (minutes)                      | 10                 |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Reserved                 | 0             |                                       |                    |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Reserved                 | 0             |                                       |                    |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Reserved                 | 0             |                                       |                    |
   +-------+--------------------------+---------------+---------------------------------------+--------------------+
   | Tail  | Sequence Number          | 4             | 0000-FFFF ('0'-'9', 'A'-'F')          |                    |
   +       +--------------------------+---------------+---------------------------------------+--------------------+
   |       | Tail                     | 1             | $                                     | $                  |
   +-------+--------------------------+---------------+---------------------------------------+--------------------+

- `Heartbeat Interval`

  The interval for the terminal to send the HBD frame to the backend server.

  **Note**: Only when the terminal has not sent any information to the backend server within the time indicated by 'Heartbeat Interval', the terminal will send the HBD frame to the backend server.