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RT FIFO Write (G Dataflow)

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Last Modified: February 27, 2020

Writes an element to an RT FIFO. If the RT FIFO does not have empty elements, this node waits for an amount of time equal to the value of timeout in ms for an element to become available. If an empty element does not become available before the value of timeout in ms expires and overwrite on timeout is True, this node overwrites the oldest element in the RT FIFO and returns True in timed out?.

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Note

If you use an RT FIFO to transfer waveform data, the variant element of the waveform does not transfer because variants are variable-sized and therefore incompatible with the RT FIFO.

Programming Patterns
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rt fifo

References an existing RT FIFO.

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element

The data to write to the RT FIFO. This data type changes to match the type of the value you want to write.

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timeout in ms

Time, in milliseconds, that the node waits for an empty slot to write the data in the RT FIFO. Wire a -1 to the timeout in ms input to wait infinitely.

Default: 0

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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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overwrite on timeout

Defines whether to overwrite the oldest value in the RT FIFO if the FIFO does not have an available open slot and the value of the timeout in ms input expires. Use the timeout in ms input to specify an amount of time to wait for an open slot before overwriting the oldest value.

True The RT FIFO overwrites the oldest value and returns True in the timed out? output if the FIFO times out.
False The RT FIFO does not overwrite the oldest value if the FIFO times out.

Default: True

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rt fifo out

A reference to the RT FIFO defined in rt fifo.

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timed out?

A Boolean that indicates whether the FIFO times out before an empty slot becomes available for the write operation.

True The FIFO timed out before an empty slot became available.
False The FIFO did not time out.
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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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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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