SpaceWire Higher-Layer Protocols

Paper number

IAC-06-B5.7.03

Author

Dr. Steve Parkes, University of Dundee, United Kingdom

Coauthor

Mr. Chris McClements, University of Dundee, United Kingdom

Coauthor

Dr. Stuart Mills, University of Dundee, United Kingdom

Year

2006

Abstract

SpaceWire is now being used on many spacecraft by ESA, NASA and JAXA and on other space missions. SpaceWire provides a convenient means of connecting together sensors, processing systems, control units, memory units, telecommand and telemetry systems. It can be used in straightforward point-to-point links providing a data transfer rate of 140 Mbits/s when operating at a data signalling rate of 200 Mbits/s. It can also be used in more sophisticated data-handling system architectures using SpaceWire routers to switch data between many units attached to the router. Radiation tolerant ASICs are being developed by ESA, NASA and JAXA and validated SpaceWire IP is available from these agencies for use in radiation tolerant FPGAs. A wide range of SpaceWire to host computer interface units is available from various vendors for use during system development and STAR-Dundee Ltd provides equipment for monitoring the traffic across a SpaceWire link. Reference designs for flight equipment have been developed by many space organisations and SpaceWire in various forms is already flying on several spacecraft.
 
SpaceWire standardizes the physical and data-link levels of a high-speed communications network for spacecraft. Higher level protocols are now being developed by the SpaceWire Working Group and the Consultative Committee for Space Data Systems (CCSDS) Spacecraft Onboard Interface Services working groups. The aim of these protocols is to support software and hardware reuse further up the communications protocol stack. The first protocol being defined by the SpaceWire working group is a relatively low-level service called the remote memory access protocol (RMAP). The aim of the RMAP protocol is to standardize the way in which SpaceWire units are configured and to provide a low-level mechanism for the transfer of data between two SpaceWire nodes. It is used to write to and read from memory or registers in a destination node on a SpaceWire network. Input/output registers and control/status registers are assumed to be memory mapped so are accessed as memory. CCSDS are developing a set of networking protocols that will run over various buses and networks and which are being mapped to SpaceWire.

This paper introduces the higher layer protocols that are being developed for SpaceWire. First the SpaceWire Protocol Identifier is explained and then the Remote Memory Access Protocol (RMAP) is introduced. The CCSCS Time Critical Onboard Network Service protocols are then described with the mapping of these protocols onto SpaceWire being outlined. 

Abstract document

IAC-06-B5.7.03.pdf

Manuscript document

IAC-06-B5.7.03.pdf (🔒 authorized access only).

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