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XNET Start (G Dataflow)

Last Modified: November 2, 2017

Starts communication for the specified XNET session.

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session in

The session to start. This session is selected from the LabVIEW project or returned from XNET Create Session.

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scope

An input that describes the impact of this operation on the underlying state models for the session and its interface.

Normal (0) The session is started followed by starting the interface. This is equivalent to calling XNET Start with the Session Only scope followed by calling XNET Start with the Interface Only scope.

This is the default value for scope if it is unwired.

Session Only (1) The session is placed into the Started state . If the interface is in the Stopped state before this node runs, the interface remains in the Stopped state, and no communication occurs with the bus. To have multiple sessions start at exactly the same time, start each session with the Session Only scope. When you are ready for all sessions to start communicating on the associated interface, call XNET Start with the Interface Only scope. Starting a previously started session is considered a no-op. This operation sends the command to start the session, but does not wait for the session to be started. It is ideal for a real-time application where performance is critical.
Interface Only (2) If the underlying interface is not previously started, the interface is placed into the Started state . After the interface starts communicating, all previously started sessions can transfer data to and from the bus. Starting a previously started interface is considered a no-op.
Session Only Blocking (3) The session is placed into the Started state . If the interface is in the Stopped state before this node runs, the interface remains in the Stopped state, and no communication occurs with the bus. To have multiple sessions start at exactly the same time, start each session with the Session Only scope. When you are ready for all sessions to start communicating on the associated interface, call XNET Start with the Interface Only scope. Starting a previously started session is considered a no-op. This operation waits for the session to start before completing.
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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

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session out

An output that is the same as session in, provided for use with subsequent nodes.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Description

Because the session is started automatically by default, this node is optional. This node is for more advanced applications to start multiple sessions in a specific order. For more information about the automatic start feature, refer to the Auto Start? property.

For each physical interface, the NI-XNET hardware is divided into two logical units:

  • Sessions: You can create one or more sessions, each of which contains frames or signals to be transmitted (or received) on the bus.
  • Interface: The interface physically connects to the bus and transmits (or receives) data for the sessions.

You can start each logical unit separately. When a session is started, all contained frames or signals are placed in a state where they are ready to communicate. When the interface is started, it takes data from all started sessions to communicate with other nodes on the bus.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Supported

Web Server: Not supported in VIs that run in a web application


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