Flush (FIFO Method)

LabVIEW 2018 FPGA Module Help

Edition Date: March 2018
Part Number: 371599P-01
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Requires: FPGA Module

Flushes data from a DMA target-to-host FIFO to the host or from a peer-to-peer writer FIFO to the peer-to-peer reader FIFO. You must enable the peer-to-peer stream when flushing a peer-to-peer writer FIFO. Otherwise, the Flush method does nothing. To flush a peer-to-peer writer FIFO and then disable the peer-to-peer writer and reader FIFOs, use the Flush and Disable method.

Note  Use the Flush method only when low latency is important to you. Excessive use of the Flush method might reduce data transfer rates.

Use the FIFO Method Node to implement this method.


FIFO In specifies the FIFO. You can wire a FIFO control, FIFO constant, VI-Defined FIFO Configuration node, or the FIFO Out terminal of another FIFO Method Node to FIFO In.
FIFO Out returns FIFO In if FIFO In is wired. Otherwise, FIFO Out returns the FIFO that you specify in the FIFO Method Node.

Flush (FIFO Method) Details

You can use the Flush method to flush FIFOs with the handshaking interface and the timeout interface. The Flush method functions regardless of the status of the Write method. For example, the flush still works in the following situations:

  • The Timed Out? output of the Write method returns TRUE when you use the Flush method.
  • The Ready for Input output of the Write method returns FALSE when you use the Flush method.

If you use the Flush method when another FIFO flush is in progress, LabVIEW merges both flushes.

Considerations for Single-Cycle Timed Loops

If you use the Flush method in a single-cycle Timed Loop, the Flush method must be in the same clock domain as the Write method. Otherwise, LabVIEW returns a code generation error when you try to compile the FPGA VI.


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