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SpaceWire Architectures

SpaceWire Architectures. Steve Parkes Space Technology Centre, University of Dundee, Scotland, UK. Point to point link. Instrument. Memory Or Processor. SpaceWire. Point to point link. Advantages Simple interface Low power per Mbit/s No problem with router blocking

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SpaceWire Architectures

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  1. SpaceWire Architectures Steve ParkesSpace Technology Centre,University of Dundee, Scotland, UK

  2. Point to point link Instrument Memory Or Processor SpaceWire

  3. Point to point link • Advantages • Simple interface • Low power per Mbit/s • No problem with router blocking • Full bandwidth of link available to application • Disadvantages • No redundancy • May be inefficient if link bandwidth not fully utilised • But can use auto-start, disable on silence • Applications • Direct connection of instrument to memory or processor

  4. Redundant point to point links • Redundancy of SpaceWire links only • Could do this with one SpaceWire interface • And a 2x2 LVDS switch or two LVDS drivers/receivers • Alternatively two SpaceWire interfaces at each end • To provide redundancy of the interfaces SpaceWire Prime Instrument Memory Or Processor Redundant

  5. Redundancy at physical level LVDS SpaceWire Interface 2x2 LVDS CrossPoint LVDS LVDS LVDS Driver Receiver CMOS LVDS SpaceWire Interface LVDS Driver Receiver LVDS

  6. Redundant point to point links SpaceWire Prime Instrument Prime Memory / Processor Prime Redundant Redundant Instrument Redundant Memory / Processor Redundant Redundant

  7. Redundant point to point links • Advantages • As single point to point link • Redundancy • Simple architecture • Disadvantages • Mass penalty as several links needed for redundancy • Inefficient if bandwidth not fully utilised • Applications • Direct connection of instrument to memory or process • Redundancy used where single point failure not acceptable

  8. Router Instrument 1 Router Memory Instrument 2 Processor

  9. Router • Advantages • Versatile architecture • All units can talk to one another through router • Control and data can be sent over network • Control flow generally opposite direction to data flow • Disadvantages • Have to be aware of potential blocking in router • Need to consider traffic on network • Router is single point failure • Applications • Payload data-handling systems • With more than one instrument • Or multiple possible destinations for data • Instrument to memory to processor to memory

  10. Router with redundant links Instrument 1 Router Memory Instrument 2 Processor

  11. Router with redundant links • Advantages • Redundancy of SpaceWire links • Router can auto-start and disable on silence • To support rapid switching to redundant links • Group Adaptive Routing • To support higher bandwidths • Disadvantages • Router is single point failure • Applications • None

  12. Redundant routers Instrument 1 Router Memory Instrument 2 Router Processor

  13. Redundant routers • Advantages • No single point failures • Disadvantages • Routers not really giving any advantage • Over system without routers • Mass penalty with number of links • Power penalty with routers • Applications • None

  14. Routers in data-handling unit Instrument Prime Router Memory Processor Prime Instrument Redundant Router Memory Processor Redundant

  15. Routers in data-handling unit • Advantages • Supports multiplexing of several instruments • Support prime/redundant instruments • No single point failures • Lower mass penalty of links • Since several links embedded in data-handling units • Disadvantages • None • Applications • Payload data-handling systems • With redundancy

  16. Multiple Instruments to data-handling unit Instrument 1 Router Memory Processor Instrument 2 Prime Router Memory Instrument 3 Processor Redundant

  17. Multiple Instruments to data-handling unit • Advantages • Supports multiplexing of several instruments • Support prime/redundant data-handling units • No single point failures (except instruments) • Lower mass penalty of links • Since several links embedded in data-handling units • Disadvantages • None • Applications • Payload data-handling systems • For multiple instruments

  18. Routers in instruments Instrument 1 Router Router Memory Processor Instrument 2 Router Prime Router Memory Instrument 3 Router Processor Redundant

  19. Routers in instruments • Advantages • None • Disadvantages • Routers do not give any redundancy benefits • Added power of routers • Applications • None

  20. Instruments concentrator Instrument 1 High Rate Router Memory Processor Prime Instrument 2 Instrument 3 Router Memory Router Processor Instrument 4 Redundant Instrument 5

  21. Instrument concentrator • Advantages • Reduced cable mass • High rate instrument(s) • Direct connection to data-handling unit • Low to moderate rate instruments • Connected via concentrating router • Disadvantages • Concentrating Router is not redundant • Applications • Payload data-handling systems • With distributed clusters of instruments • Being served by centralised data-handling unit

  22. Instruments concentrator redundant Instrument 1 High Rate Router Memory Processor Prime Instrument 2 Router Instrument 3 Router Memory Processor Instrument 4 Router Redundant Instrument 5

  23. Instrument concentrator redundant • Advantages • Reduced cable mass • High rate instrument(s) • Direct connection to data-handling unit • Low to moderate rate instruments • Connected via concentrating routers • Concentrating routers are redundant • Both concentrating routers could be active • Provide graceful degradation • Disadvantages • Concentrated instruments in same unit or large number of links • Applications • Payload data-handling systems • With distributed clusters of instruments • Being served by centralised data-handling unit

  24. Group adaptive routing GAR Instrument 1 High Rate Router Memory Processor Prime Instrument 2 Router Instrument 3 Router Memory Processor Instrument 4 Router Redundant Instrument 5

  25. Group Adaptive Routing • Advantages • Increased bandwidth to memory and/or processor • Provides instant graceful degradation in case of a link failure • Disadvantages • Extra cable mass • Unless inside a unit • Applications • High data rate payload data-handling systems

  26. Bridge to low data rate bus Instrument 1 High Rate Router Memory Processor Prime Instrument 2 Router Instrument 3 Router Memory Processor Instrument 4 Redundant RTC Sensor A Sensor B Sensor C

  27. Bridging • Advantages • Multiple low data rate sensors attached to low speed bus • Sensor data packed and sent to data-handling unit over SpaceWire • Legacy devices supported • E.g. Mil-Std 1553 • Disadvantages • Two types of bus/network used • Applications • Data handling systems • Legacy device support

  28. Integrated architecture Instrument 1 High Rate Router Memory Processor Instrument 2 Prime Router Router Memory Instrument 3 Processor Instrument 4 Redundant RTC Telemetry / Telecommand Prime Sensor A Sensor B Sensor C Telemetry / Telecommand Redundant

  29. Summary • SpaceWire can support a wide range of data-handling system architectures • Point to point links • Redundant point to point links • Networks • Redundant networks

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