Home > Support > NI Product Manuals > LabVIEW Communications System Design Suite 1.0 Manual

Handshaking refers to communication between two nodes that establishes the parameters for continued communication.

For a given node F in a Clock-Driven Loop, handshaking determines when the following actions occur:

  • F discards data from upstream nodes. An upstream node is any node that sends data to F.
  • F accepts data from upstream nodes.
  • Downstream nodes discard data from F. A downstream node is any node that receives data from F.
  • Downstream nodes accept data from F.

In a Clock-Driven Loop, handshaking is necessary because some nodes need more than one cycle to compute valid data, but the Clock-Driven Loop requires all nodes to return data every clock cycle. To ensure the numeric accuracy of an algorithm, nodes that depend on this data must know whether the data is invalid or valid. National Instruments has established a handshaking protocol you can use with certain nodes inside a Clock-Driven Loop. This protocol involves the following terminals:

  • input valid—The next data point has arrived for processing.
  • output valid—The current data point produced by the node is valid and ready to be used by downstream nodes.
  • ready for output—The downstream node can accept a new data point.
  • ready for input—The node can accept a new data point during the next clock cycle.