State Models

The following figures show the state model for the NI-XNET session and the associated NI-XNET interface.

The session controls the transfer of frame values between the interface (network) and the data structures that Read or Write access. In other words, the session controls the receipt or transmission of specific frames for the session.

The interface controls communication on the physical network cluster. Multiple sessions can share the interface. For example, you can use one session for input on interface CAN1 and a second session for output on interface CAN1.

Although most state transitions occur automatically when you call the XNET Read or Write VI (LabVIEW) or the appropriate nxRead or nxWrite function (C), you can perform a more specific transition using XNET Start and XNET Stop IVs (LabVIEW) or nxStart and nxStop (C). If you invoke a transition that has already occurred, the transition is not repeated, and no error is returned.

Session State Model

For a description of each state, refer to Session States. For a description of each transition, refer to Session Transitions.

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Note Starting a Signal Input Waveform session discards any previous samples and frames--the same result as running the XNET Flush VI (LabVIEW) or nxFlush (C). Note that when calling the XNET Read (Signal Waveform) VI (LabVIEW) or nxReadSignalWaveform function for the first time on the session, the session will be started if it was not already. Stopping the session after the first start requires the session to be explicitly started in the future.

Interface State Model

For a description of each state, refer to Interface States. For a description of each transition, refer to Interface Transitions.

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