Establishment Scan

When the Geo SCADA Expert server has not been in communications with a DNP3 outstation, Geo SCADA Expert performs an Establishment Scan rather than a Normal Scan. Geo SCADA Expert performs an Establishment Scan, for example, at system start-up, or when communications to an outstation has previously failed.

Geo SCADA Expert also performs an Establishment Scan whenever it opens a connection to a DNP3 outstation for which direct communications is available:

• On Demand (see Specify Whether the Direct Communications Connection is Always Online or only Available on Demand in the Geo SCADA Expert Guide to Advanced Drivers)
• On a Periodic basis, when establishing communications with the outstation at the start of each period during which communications are available (see Specify the Availability of Communications Between the Outstation and Geo SCADA Expert in the Geo SCADA Expert Guide to Advanced Drivers).
• (With an outstation for which Communications Availability is on a Periodic basis, comms persists for the period and then ceases at the end of that period.)
• On Demand on a Periodic basis, whenever an action necessitates a connection to be opened.

Performing an action such as a Refresh or Control on an On Demand outstation that is currently offline will trigger Geo SCADA Expert to perform an Establishment Scan, execute the required actions, and then close the connection. Such actions are only available during the outstation’s Communications Availability period—any attempt to trigger the actions outside of the outstation’s Communications Availability period will result in the requests being rejected.

With an Establishment Scan, the driver:

1. Disables the outstation’s Unsolicited Messages feature (if that feature is supported by the outstation).
2. Restores the values of the outstation’s output points if the Restart IIN flag is set in the outstation (and if configured to do so—see Configure the DNP3-Specific Control Properties on DNP3 Output Points).
3. Reads the outstation’s Device Attributes (if configured to do so—see Configure the Actions that Occur on Communications Startup).
4. Set the outstation’s clock (if configured to do so)—see Define Whether Geo SCADA Expert Updates the Outstation Clock.
5. Performs an Integrity Poll of the outstation.
6. The poll requests the outstation to send its Class 1, 2, and 3 event data and Class 0 static (current value) data in chronological order, to the server.

6. Re-enables the outstation’s Unsolicited Messages feature (if supported by the outstation, unless that outstation is configured not to send unsolicited messages).