Due to the constraint on the number of channels and phase bins, the array of visibilities in each heap will have the same structure and maximum dimensions as for the continuum and spectral line imaging mode.

The SPEAD protocol has successfully been implemented in KAT7 and MeerKAT. A Python implementation containing example applications can be download from [RD8] and the FPGA implementation for MeerKAT is available (from Jason Manley at SKA-SA).

The SPEAD-64-48 flavour was chosen in order to support 48bit immediate values and is currently used in the MeerKAT implementation.

In general it’s prefered to use immediate addressing for the metadata items as it’s simpler to implement in FGPAs and more efficient to decode on the receiving end.

11: List of Item Names and their rationale