Add an OPC DA server as a tag integration source

This task describes how to add an OPC server as a tag integration source in your project.

Before you begin this task, you should be familiar with the OPC DA specification (also known as OPC Classic). For more information, go to: opcfoundation.org/about/opc-technologies/opc-classic/

You should also review the documentation for your specific OPC server software. Make sure the server is running and accessible on your network, and then note its network address.

Note: This task applies to OPC DA servers only. If you have an OPC UA server, see Add an OPC UA server as a tag integration source.

To add an OPC DA server as a tag integration source in your project:

1. On the Project tab of the ribbon, in the Settings group, click Communication.

   The Project Settings dialog is displayed, with the Communication tab selected.

   

2. In the Tag Integration area, click Add.

   The Tag Integration Source dialog box is displayed.

3. In the Type box, select Integrated if it is not already selected.

4. In the Provider box, select OPC DA.

5. In the Name box, type an appropriate name for the tag integration source.

   This name will be added as a prefix to the names of the integrated tags. The default is DEV, which is short for "device".

6. Click Add.

   The OPC DA Tag Integration dialog box is displayed.

   

7. In the Server box, select the connection to the OPC server.

8. In the Publish rate box, type the frequency (in milliseconds) at which the OPC server should publish updates to the client (that is, your project).

   The publish rate is actually set when the client establishes its connection to the server.

9. In the Group size box, type the maximum number of items that may be read or written in a single operation.

   The default group size is 0, which means there is no limit and changes in item values will be immediately read and written (according to the publish rate). This is acceptable in most cases, but if you use a large number of items in your project and the values of those items change frequently, then read/write operations might overload the project and decrease runtime performance. You can specify a group size (for example, 64) in order to moderate those read/write operations and restore runtime performance.

10. If the OPC server is configured to handle array elements as separate items, select the Use array index in browse path option. Conversely, if the OPC server is configured to handle each array as a single item with multiple elements, make sure the option is cleared.

    You can review the project runtime log (for example, in the Output window) to see if there are any OPC communication errors when your project tries to read/write arrays. If there are, you might need to toggle the Use array index in browse path option.

11. In the Root node or view box, specify the server node that will serve as the root for all items. You can click the "more" button (…) to the right of the box in order to browse the server and then select a node.

    This step is optional, but specifying a root node makes it easier to find items and increases runtime performance.

12. Click OK to finish the configuration and add the source.

If the OPC server is successfully added as a tag integration source, its items will be immediately available for selection in the Object Finder. For more information, see Use the Object Finder to select integrated tags.