The DNP3 protocol supports the ‘transparent’ transmission of data between DNP3 devices, through the use of DNP3 Virtual Terminals (VT).
If the servers on your system are being used to route communications in this way, you need to use the Virtual Terminal Support section of the DNP3 tab to specify the virtual terminal settings of the outstation. You also need to configure the required Virtual Terminal(s) and Service Port(s) (see Configuring DNP3 Virtual Terminals) that are required to allow a virtual, transparent, connection between a serial communications port on the ClearSCADA server and a serial communications port on the outstation.
Use the fields in the Virtual Terminal Support section of the DNP3 tab to specify whether ClearSCADA is to provide a virtual link between one of its serial ports and a serial port on the outstation:
- Configure VT on Startup—For Virtual Terminal functionality to operate, it is necessary to send a message to enable VT functionality when communications are initiated with an outstation. Select this check box if Virtual Terminal functionality is being used and the outstation is to generate unsolicited messages that contain DNP3 VT data. The outstation will send any data that it receives on its designated serial port, back to ClearSCADA. The DNP3 Event Class used for VT event data is determined by the outstation. For example, SCADAPack E outstations specify VT event data as Class 3.
Clear this check box if Virtual Terminal functionality is not required and the outstation is not providing a virtual serial port.
- Poll for VT Events—Use this check box to specify whether ClearSCADA is to poll the outstation for VT event data.
To retrieve VT event data from an outstation, ClearSCADA must has to poll the outstation for the event class for which the outstation logs VT events. For example, ClearSCADA has to perform a Class 3 poll to retrieve VT event data from a SCADAPack E outstation. Select this check box if ClearSCADA is to poll the outstation for VT event data and the outstation is not to generate unsolicited responses containing VT event data.
Leave the check box clear if the outstation is to generate unsolicited responses that contain VT event data.