SpaceWire Architectures
Steve ParkesSpace Technology Centre,
University of Dundee, Scotland, UK
Parkes MAPLD2006 2222
Point to point link
InstrumentMemory
OrProcessor
SpaceWire
Parkes MAPLD2006 2223
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
Parkes MAPLD2006 2224
Redundant point to point links
InstrumentMemory
OrProcessor
SpaceWire
Prime
Redundant
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
Parkes MAPLD2006 2225
Redundancy at physical level
SpaceWireInterface
2x2LVDS
CrossPoint
LVDSDriver
Receiver
LVDSLVDS
LVDS
SpaceWireInterface
LVDSDriver
Receiver
LVDS
LVDS
CMOS
Parkes MAPLD2006 2226
Redundant point to point links
InstrumentPrime
Memory /Processor
Prime
SpaceWire
Prime
Redundant
InstrumentRedundant
Memory /ProcessorRedundant
Redundant
Redundant
Parkes MAPLD2006 2227
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
Parkes MAPLD2006 2228
Router
Instrument1
Memory
Instrument2
Processor
Router
Parkes MAPLD2006 2229
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
Parkes MAPLD2006 22210
Router with redundant links
Instrument1
Memory
Instrument2
Processor
Router
Parkes MAPLD2006 22211
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
Parkes MAPLD2006 22212
Redundant routers
Instrument1
Memory
Instrument2
Processor
Router
Router
Parkes MAPLD2006 22213
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
Parkes MAPLD2006 22214
Prime
Redundant
Routers in data-handling unit
InstrumentPrime
Memory
InstrumentRedundant
ProcessorRouter
RouterMemory
Processor
Parkes MAPLD2006 22215
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
Parkes MAPLD2006 22216
Prime
Redundant
Multiple Instruments to data-handling unit
Instrument1
Memory
Instrument2
ProcessorRouter
RouterMemory
ProcessorInstrument
3
Parkes MAPLD2006 22217
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
Parkes MAPLD2006 22218
Prime
Redundant
Routers in instruments
Instrument1
Memory
Instrument2
ProcessorRouter
RouterMemory
ProcessorInstrument
3
Router
Router
Router
Parkes MAPLD2006 22219
Routers in instruments
Advantages None
Disadvantages Routers do not give any redundancy benefits Added power of routers
Applications None
Parkes MAPLD2006 22220
Prime
Redundant
Instruments concentrator
Instrument1
High Rate
Memory
Instrument2
ProcessorRouter
RouterMemory
Processor
Instrument3
RouterInstrument
4
Instrument5
Parkes MAPLD2006 22221
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
Parkes MAPLD2006 22222
Prime
Redundant
Instruments concentrator redundant
Instrument1
High Rate
Memory
Instrument2
ProcessorRouter
RouterMemory
Processor
Instrument3
Router
Instrument4
Instrument5
Router
Parkes MAPLD2006 22223
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
Parkes MAPLD2006 22224
Prime
Redundant
Group adaptive routing
Instrument1
High Rate
Memory
Instrument2
ProcessorRouter
RouterMemory
Processor
Instrument3
Router
Instrument4
Instrument5
Router
GAR
Parkes MAPLD2006 22225
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
Parkes MAPLD2006 22226
Prime
Redundant
Bridge to low data rate bus
Instrument1
High Rate
Memory
Instrument2
ProcessorRouter
RouterMemory
Processor
Instrument3
Router
Instrument4
SensorA
RTCSensor
BSensor
C
Parkes MAPLD2006 22227
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
Parkes MAPLD2006 22228
Integrated architecture
Prime
Redundant
Instrument1
High Rate
Memory
Instrument2
ProcessorRouter
RouterMemory
Processor
Instrument3
Router
Instrument4
SensorA
RTCSensor
BSensor
C
Telemetry / TelecommandPrime
Telemetry / TelecommandRedundant
Parkes MAPLD2006 22229
Summary
SpaceWire can support a wide range of data-handling system architectures
Point to point links Redundant point to point links Networks Redundant networks