Polled points

Polled PI points are grouped by scan class. If possible, the interface reads groups using the scan class rate configured for the point. Configure scan class rates using PI ICU.

Note: The OPC server does not guarantee that scan rates match between the OPC server and the interface. PI Interface for OPC DA sends a request to the OPC server to use an update rate that matches the scan class, but the OPC server determines its own update rate for scanning its data sources. The scan class offset has no effect on the OPC server, unless the interface is configured for staggered group activation and the OPC server uses the activation of the group to initiate the scanning cycle.

For more information about polled points, see the OPC Foundation document Data Access Custom Interface Standard v2.05a.

Configure the following PI point attributes to create polled points:

• location3

  Set to 0 for polled points.

• location4

  Assigns the scan class for a point.

  Note: Do not assign the same scan class to both advise and polled points. Use a separate class for each point type.