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