The correlator output binary data format applies to the output data stream of the fast formatter component of the WIDAR correlator backend. The data produced in the binary data format are primarily spectral in nature, although limited supplemental, non-spectral data are also a part of the format. Typically, the data stream is sent to the EVLA archive and TelCal, while header data are also sent to DCAF for inclusion in the science data model. Note that there may be other data products produced by the correlator backend; however, their specification is not addressed by the present document.

As of this writing, the fast formatter will write its output data stream to a shared filesystem. In the EVLA design, the backend consists of a cluster of computers that accepts the correlator hardware-produced lag frames as input, processes the lag sets, and writes the output data files. One node in the cluster will have the role of the fast formatter, which will initialize the output files prior to access by the other cluster nodes, provide output data not available to individual nodes, and send the completed files to the EVLA archive (additionally, the fast formatter node will also provide data to DCAF, but that data is not of concern here.) Cluster nodes handling the lag frames will write data to the output file(s) concurrently as needed. Of course, nothing in this specification prohibits sending the data stream over a network rather than being produced as a file.