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Updating the Data Interface

The data source variables are updated cyclically at runtime. Only the data is updated that either is used in the current visualization or has the property Update always.

You can define the time interval. Moreover, you can define variables whose data is transferred in each update interval, and therefore they are always update. To update variables that are not used in the application code, you can implement an update programmatically with the help of interface functions from the data source manager.

Important

If data traffic between the remote and local device is too high, then the refresh rate is reduced automatically. This can lead to an incomplete transfer.

Setting the refresh rate

  1. Open the editor of the data source.

  2. Click the General and Diagnosis tab.

  3. Specify a value in the Refresh rate field.

    Example: 100

    The data from the remote device to the local device is transferred every 100 ms.

Selecting the variable for Update always

Important

Avoid updating too many variables always. Each update produces additional data traffic at the connection between the remote and local devices. When data traffic is too high, the refresh rate is reduced automatically. This can lead to an incomplete transfer.

  1. Open the editor of the data source.

  2. Activate the option Update always for a variable.

    The data of the variables is transferred at each update cycle, even when the data has not changed.

Updating data programmatically

The data source manager provides interface functions in the Datasources library. If a data source manager is integrated in the application code, then the global variable g_Datasources is instantiated automatically. This provides access to the interface functions.

Then you can update individual variables that are not called in the active visualization.

Example 7. Example

The variable ivar is activated and deactivated by means of methods from the Datasources library so that its value is transferred. Furthermore, you can configure that the variable is updated only over a defined duration in order to save transfer capacity.

//Synchronize with DatasourcesTask and block until access is possible
//Regard the feedback in ERR_OK or in ERR_DE_MULTITASKING_LOCKED
g_Datasources.BeginDataConfiguration(TRUE);
// Activate variable
g_Datasources.UseData(ADR('RemoteDevice.Application.PLC_PRG.iVar'));
// Deactivate variable
//g_Datasources.ReleaseData(ADR('RemoteDevice.Application.PLC_PRG.iVar'));
g_Datasources.EndDataConfiguration();

The data configuration is started with BeginDataConfiguration(TRUE), thus initializing the synchronization of the task DatasourceTask with the application task. The value TRUE blocks the processing until the access to the variable is possible; FALSE repeats access attempts without blocking. The return values ERR_OK and ERR_DS_MULTITASKING_LOCKED provide feedback about the access attempts.

When synchronization is successful, the variable is activated by means of the UseData method. Then the data configuration is completed with the EndDataConfiguration method and the synchronization triggered again with the task DatasourceTask.

The ReleaseData method is used in the same way for deactivating the variable again at the desired processing time.



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