.. _headlabel-refx-cmd-hmc:

HMC (Hour Meter Count)
======================

The `AT@HMC` is used to count the accumulated ignition time of the vehicle, which can be understood as the accumulated working time of the vehicle.

.. code-block:: none

   Example:
   AT@HMC=gv500cna,,0,,012F$
   +ACK:HMC,123456789012345,8203,3,0,,012F,20210407101530,1234$
   AT@HMC?gv500cna,,0C37$
   +QRY:HMC,123456789012345,8203,3,0,1,1,,0,,0C37,20210407101530,1234$

.. tabularcolumns:: |p{2.2em}|p{14.2em}|p{5.8em}|p{12em}|p{4.8em}|

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

   +-------+-----------------------------+---------------+----------------------------------+--------------------+
   | Parts | Fields                      | Length (Byte) | Range/Format                     | Default            |
   +=======+=============================+===============+==================================+====================+
   | Head  | Header                      | 3             | AT@                              | AT@                |
   +       +-----------------------------+---------------+----------------------------------+--------------------+
   |       | Command Word                | 3             | HMC                              | HMC                |
   +       +-----------------------------+---------------+----------------------------------+--------------------+
   |       | Leading Symbol              | 1             | =                                | =                  |
   +       +-----------------------------+---------------+----------------------------------+--------------------+
   |       | Password                    | 8-16          |                                  | gv500cna           |
   +-------+-----------------------------+---------------+----------------------------------+--------------------+
   | Body  | Reserved                    | 0             |                                  |                    |
   +       +-----------------------------+---------------+----------------------------------+--------------------+
   |       | `Initial Hour Meter Count`  | <=8           | 0-16777215 (minutes)             | 0                  |
   +       +-----------------------------+---------------+----------------------------------+--------------------+
   |       | Reserved                    | 0             |                                  |                    |
   +-------+-----------------------------+---------------+----------------------------------+--------------------+
   | Tail  | Sequence Number             | 4             | 0000-FFFF ('0'-'9', 'A'-'F')     |                    |
   +       +-----------------------------+---------------+----------------------------------+--------------------+
   |       | Tail                        | 1             | $                                | $                  |
   +-------+-----------------------------+---------------+----------------------------------+--------------------+

- `Initial Hour Meter Count`

  The initial value for calculating the total hour meter count.

  **Note**: When the terminal receives the `AT@HMC` command, it checks the `Initial Hour Meter Count` parameter: Only if this parameter is not empty and its value is different from the value stored in the terminal, the terminal will perform the operation "Initialize the Total Hour Meter Count (refer to :ref:`Data 34 <headlabel-refx-data-34>`) and clear the Current Hour Meter Count (refer to :ref:`Data 35 <headlabel-refx-data-35>`)".