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Flush FIFO (Clock-Driven Logic)

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Last Modified: September 14, 2017

Empties data from the FIFO and sends the data to the recipient. For DMA target-to-host FIFOs, the recipient is the host. For peer-to-peer writer FIFOs, the recipient is the peer-to-peer reader FIFO.

You must enable the peer-to-peer stream when flushing a peer-to-peer writer FIFO. Otherwise, this node executes but does not flush the FIFO.

Use Flush FIFO when the need for lower latency outweighs the need for higher data transfer rates. If you overuse Flush FIFO, you may reduce data transfer rates.

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Note  

Flush FIFO must be in the same clock domain as the Write FIFO node. Otherwise, the program returns a code generation error when you try to compile the FPGA VI.

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reference in

The FIFO to flush.

You can wire a FIFO control, FIFO constant, or the reference out terminal of another FIFO node to reference in.

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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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reference out

The FIFO that you specify.

reference out returns the value wired to reference in.

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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.

Behavior with Write FIFO

You can use Flush FIFO to flush FIFOs regardless of whether Write FIFO uses a handshaking interface or a timeout interface. Flush FIFO works regardless of the status of the Write FIFO node. For example, the flush still works in the following situations:

  • The Timed Out? output of the Write FIFO node returns True when you use Flush FIFO.
  • The Ready for Input output of the Write FIFO node returns False when you use Flush FIFO.

Simultaneous Flushes

If you use Flush FIFO when another FIFO flush is in progress, the two flushes merge.

Where This Node Can Run:

Desktop OS: none

FPGA: All devices

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

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