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Read Variable with Timeout (G Dataflow)

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    Last Modified: March 15, 2017

    Returns the current variable value if the node has not previously read the value. Otherwise, the node waits for either a new value or for the specified timeout to elapse.

    Use this node to avoid reading data values that you already have read. If you need to read the current value regardless of whether the value changes, use the Read Variable node.

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    Note  

    NI recommends that you use Tag nodes instead of this node for new applications you create.

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    shared variable refnum in

    The reference to the PSP variable.

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    data type

    The data type of the PSP variable.

    If you specify the data type using shared variable refnum in, this node removes the data type input. If you specify the data type upon opening the connection, this input is unavailable for subsequent read nodes.

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    timeout ms

    Time, in milliseconds, that the node waits before timing out. Use the timed out? output to detect a timeout.

    Default: -1—Specifies no timeout.

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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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    shared variable refnum out

    The reference to the PSP variable.

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    data out

    The data read from the PSP variable.

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    timed out?

    A Boolean value that indicates whether an element became available within the timeout you specify.

    If the timeout expires, this node returns the last value written to the variable and does not return an error.

    True A new element did not become available within the timeout you specify.
    False A new element became available within the timeout you specify.
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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.
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    timestamp

    The timestamp indicating when the current data was written to the shared variable. This output is available only if you place a checkmark in the Read Timestamp checkbox on the Configuration page of the Properties dialog box for the variable refnum.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: This product does not support FPGA devices


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