ATTENTION: If you configure a point in the outstation to generate DNP3 events (see DNP3 Integrity and Data Classes), it is not advisable to perform DNP3 Level 3 Scans for that point. (The DNP3 standard dictates that event data for a DNP3 point has to be transmitted in chronological order. As a DNP3 Level 3 Scan returns a point’s current value without any preceding DNP3 event data, the value of the point may be returned out-of-order.)
If point data is not retrieved from a DNP3 outstation by other means, such as an Integrity Poll, you can retrieve that data using the Perform Level 3 Scan pick action.
In order to retrieve Class 0 static (current value) data in this way, you need to:
- Enable Level 3 Scan functionality on the Point’s Form
- Configure the point to have a suitable Scan Group (Confidence Poll).
For more information on either of the above, see Configure General Point Properties.
- Use the Perform Level 3 Scan pick action to specify that the driver is to poll the outstation for the point data that is assigned the above Scan Group.
ClearSCADA retrieves any DNP3 Status Point data by performing a Level 3 scan.
Level 3 Scans do not apply to DNP3 Pulse Actions.
(With points that are assigned a Scan Group (Confidence Interval) but are excluded from Level 3 Scans, the DNP3 driver does not schedule a poll of the outstation when the Scan Group timer expires. Instead, it updates the point’s value with the response to the next scheduled Integrity Poll.)