Read FIFO

Reads and removes the oldest element from the FIFO.

1378

Inputs/Outputs

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reference in

Reference to the FIFO.

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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

Default value: No error

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ready for output

Boolean value that specifies whether downstream nodes are ready for this node to return a new value.

Use Feedback Node to wire this input to the ready for input input of a downstream node. If this input is False during a given cycle, output valid returns False during that cycle.

True The downstream node is ready for the next data element.
False The downstream node is not ready for the next data element.

Default value: False

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reference out

Reference to the FIFO.

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data

Oldest data element in the FIFO.

If the FIFO is empty, data returns an undefined element.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

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output valid

Boolean value that indicates whether this node computes a result that downstream nodes can use.

Wire this output to the input valid input of a downstream node to transfer data from the node to the downstream node.

True Downstream nodes can use the result this node computes.
False This node returns an undefined value that downstream nodes cannot use.
Note This node may return different undefined values when executed in simulation mode versus when executed on hardware.

Programming Patterns

Transferring Data between Clock Domains Using FIFOs

Handshake Protocol

Because this node may return invalid data in certain cases, such as when the FIFO is being cleared or the FIFO is currently empty, this node uses the four-wire handshake protocol to alert you if this node returns invalid data. Check the status of output valid to ensure the data output is valid.