SpaceFibre/SpaceWire-RT implementation experience and evolution trends

The paper considers experience of SpaceFibre/SpaceWireRT implementation and analysis. Overheads are estimated and gaps in the SpaceFibre draft for implementation are considered, its refinement is proposed. The problems in the Retry level are discussed. In case of repeating a frame the virtual channels characteristics (priorities, timeslots) are not fully followed; it could corrupt required QoS of the traffic. Another problem with the Retry level is shown in a case study of streaming data traffic. For such type of traffic late frames transmission could be not only useless but harmful for the target traffic. To deal with the problems a modification of Retry is proposed. Another open problem is in disconnection of a link at the Lane and Encoding levels when there is a need to change virtual channels (VC) logical numbers. When one needs to switch on or change a logical number of a single VC the link disconnection and restart is done. Thus data transfer would be stopped for all the VC of the link. It leads to considerable delays in tuning logical structuring of networks, excessive delays in virtual channel transfers when other VC in the same controller are retuned, excessive complication and resources in processor-less nodes implementations. To deal with the problem a modification of link flow control crediting is proposed.