RT FIFO Read (G Dataflow)

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Version:

LabVIEW NXG 5.0 Real-Time Module

Last Modified: November 4, 2020

Reads the oldest element in an RT FIFO.

If no new data exists in the RT FIFO or if the RT FIFO is empty, this node waits for the amount of time specified in timeout in ms for new data. If the value of timeout in ms expires, the node returns the value wired to element in the element out output and returns True in the empty? output.

Programming Patterns

Transferring Data to Deterministic Code

Inputs/Outputs
Compatibility

rt fifo

References an existing RT FIFO.

element

Sets the default return value of an empty RT FIFO. This data type changes to match the type of the default return value you wire.

timeout in ms

Time, in milliseconds, that the node waits to receive a new value if the RT FIFO is empty. Wire a -1 to the timeout in ms input to wait indefinitely.

Default: 0

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

rt fifo out

A reference to the RT FIFO defined in rt fifo.

element out

The data read from the RT FIFO. If the node does not read new data, the node returns the default element.

empty?

A Boolean that indicates whether the RT FIFO is empty when you read it.

True	The RT FIFO is empty and the FIFO timed out.
False	The RT FIFO is not empty.

error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

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.

number of elements

Number of elements remaining in the RT FIFO after the read or write operation.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

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

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