SpaceWire Higher Layer Protocols

Authors: 
S. Parkes, S. Mills, C. McClements
Conference/Journal Name: 
57th IAC (International Astronautical Congress)
Date Published: 
October 2006

The SpaceWire standard was written with the aim of providing a communications network for use onboard spacecraft, which not only provides high bandwidth, but also reduces cost through compatibility and reusability. SpaceWire has a simple interface meaning that it can be readily implemented in a range of different technologies. The standard defines “links, nodes and routers”, but does not define any higher level communications protocols other than packet encapsulation. This helps to keep SpaceWire interfaces simple, but the lack of standardization at these higher layers does not improve reusability above the lower layers. This paper describes the protocol identifier field to be added to SpaceWire to provide support for higher layer protocols. It then goes on to describe the Remote Memory Access Protocol, a protocol which provides a standard method of reading and writing to registers and memory within a SpaceWire unit, and the first protocol to make use of SpaceWire’s protocol identifier field.