Get Number of Elements to Read (FIFO Method)

Returns the number of elements remaining to be read in the FPGA FIFO. You must use this node in the same clock domain as the clock domain containing the FIFO Method Node configured with the Read method.

Use the FIFO Method Node to invoke this method.

Inputs/Outputs

Option Description
FIFO In 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 FIFO Out returns FIFO In if FIFO In is wired. Otherwise, FIFO Out returns the FIFO that you specify in the FIFO Method Node.
Number of Elements to Read Number of Elements to Read—Returns the number of remaining elements for the application to read from the FIFO.

The number of elements that this method returns is less than or equal to the actual number of elements remaining in the FIFO.

You can use the following types of FIFOs in this method:

  • Target-scoped
  • VI-defined
  • DMA
  • Peer-to-peer

(Xilinx Vivado) This method does not support FIFOs with the built-in control logic or implemented using UltraRAM.

The sum of the values returned from this method and Get Number of Elements to Write method is less than or equal to the total number of elements in the FIFO. You can use this method to ensure that the FIFO can handle bursts of elements before the Read method times out.

Note Within a single-cycle Timed Loop, the Get Number of Elements to Write and Get Number of Elements to Read FIFO methods will always return the number of elements available at the beginning of the cycle, prior to the occurrence of any Read or Write methods.