> For the complete documentation index, see [llms.txt](https://developer.magtek.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.magtek.com/hardware/card-readers/mms-dyna-devices/dynaflex-ii-go/documents/developers-manuals/programmers-manual-commands/notifications/user-interface/host-action-request.md).

# Host Action Request

## Notification 0x1803 - User Interface Host Action Request

The host uses this command to request that the device display a message for the cardholder.

The sequence of events is as follows:

{% stepper %}
{% step %}
The host ensures the device is not currently running another command, for example, that it is not running a transaction using **Command 0x1001 - Start Transaction**.
{% endstep %}

{% step %}
The host selects the message it wants to display from the list of available pre-determined strings.
{% endstep %}

{% step %}
The host composes a command request in the format below, and sends it to the device.
{% endstep %}

{% step %}
The device displays the requested message.

* If the Timeout parameter is set to Infinite, the device returns a command response message with Response Status, Operation Status Summary byte set to 0x00 (OK, Done) after which the host is free to send further commands.
* If the Timeout parameter is not set to Infinite:
  * The device returns a command response message with its Response Status, Operation Status Summary byte set to 0x01 (OK, Started / Running).
  * While the host is waiting for the timeout to expire, it should not send any commands to the device, because the device is busy processing the current command.
  * After the timeout period expires, the device blanks the display and sends **Notification 0x1805 — User Interface Operation Complete** to inform the host.
    {% endstep %}
    {% endstepper %}

## Table - Request Data for Command 0x1803 - Display Message (Display Only)

<table><thead><tr><th>Tag</th><th width="75">Len</th><th width="239">Value / Description</th><th width="76.33331298828125">Typ</th><th width="75.333251953125">Req</th><th width="92.666748046875">Default</th></tr></thead><tbody><tr><td>Beginning of any wrappers, at minimum including <strong>Request Message</strong> </td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>1803 = <strong>Command 0x1803 - Display Message (Display Only)</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>81</td><td>01</td><td>Timeout<br>- 0x00 = Infinite. Device leaves the requested message on the display until the host initiates a change.</td><td>B</td><td>O</td><td>0x00</td></tr><tr><td></td><td></td><td>- All other values = Timeout in seconds for the device to display the message.</td><td></td><td></td><td></td></tr><tr><td>82</td><td>01</td><td>Message ID. Specify a Display String ID from section <strong>4.3 Display Strings</strong>.</td><td>B</td><td>O</td><td>0x14</td></tr><tr><td>End of any wrappers, at minimum including <strong>Request Message</strong> </td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

## Table - Response Data for Command 0x1803 - Display Message (Display Only)

<table><thead><tr><th width="196.6666259765625">Tag</th><th width="73.3333740234375">Len</th><th width="263.66668701171875">Value / Description</th><th width="76.3333740234375">Typ</th><th width="76.6666259765625">Req</th><th width="96">Default</th></tr></thead><tbody><tr><td>Beginning of any wrappers, at minimum including <strong>Response Message</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>1803 = <strong>Command 0x1803 - Display Message (Display Only)</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>No parameters.</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>End of any wrappers, at minimum including <strong>Response Message</strong> </td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

## Table - Request Example

Example (Hex):

```
AA00 810401551803 8408 1803 810102 820116
```

## Table - Response Example

{% code title="Example (Hex)" %}

```
AA00 810482551803 820401000000 84021803
```

{% endcode %}


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