estec/ tos-etd section 1 university of dundee applied computing spacewire 1.scope 2.standard...

ESTEC/ TOS-ETD sectionwww.estec.esa.nl/tech/spacewire

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UniversityOf DundeeAPPLIED COMPUTING

SpaceWire

1. Scope

2. Standard ECSS-E-50-12, Draft-1

3. Layers above the Standard

4. Space vs commercial digital technologies


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SpaceWire Networks

• Point-to-point links– Serial digital links : 2- 400 Mbit/s - typical distance: 10 meters

– Bi-directional (full-duplex)

– Good EMC characteristics – low power consumption -

– Scaleable, low cost, low latency

• Nodes– A source or a destination of a packet

(e.g. a processor, memory unit, sensor, Ground Support Equipment

• Routers– Switch connecting several links that routes packets from one link to another


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Node Node

Point-to-point serial linksSpaceWire Interface

Devices (chips)

Example

Cascaded routers

Nodes Nodes

Network

Router


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Electrical Ground Support Equipment (EGSE)

Computer UnitInstrument

Instrument

Mass MemoryModule

DigitalProcessing

Unit

SpaceWire Router

SpaceWire links

SpaceWire

Network

SpaceWire Basic Communications infrastructure

Processor EM


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Board for On-Board Processing

8kx32DPRAM

In red : 1355 / SpaceWire related modules

TSC21020(DSP)

BOOTPROM

Back side:128kx40 (DM)128kx48 (PM)

SRAM

SupportFPGA

SpaceWireconnectors

LVDS

Two SMCS-332Encoder /Decoder


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Node

SpaceWire Interface(part of a chip)

Node

Additional logic for System on a Chip

Channel 1

Ch. 2

Ch. 3

Gluelogic

(e.g. FIFO,Checksum)

COMI

HOCI

JTAG

Device for a SpaceWire nodeSMCS332

RxDS

TxDS SpaceWire

SpcW

SpcW

routersCascaded

(Simple: approximately 5000 gates)

ENCODER

DECODERRECEIVE

FIFO

TRANSMITFIFO

Interfaceto Host

Data

Strobe

Data

Strobe

STATEMACHINE

8 bits

8 bits


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SpaceWire Standard

• Physical Level

• Signal Level

• Character Level

• Exchange Level

• Packet Level

• Network Level• Recovery Schemes (Recommendations)


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ApplicationPresentation

Session

TOPNET Layers

Data-Link

Physical

ApplicationSoftware

Transport

Network

UDP /TCP-like ?

IP-likeCCSDS-SOIF

(131.176.19.123)

Physical

Signal

Character

Exchange

Network

Packet

SpaceWireLevels

(legacy from IEEE 1355)


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Physical Level

• Physical Level covers– Cables

• 4 screened twisted pairs with overall shield

– Connectors• 9 pin micro-miniature D-types

– Cable Assemblies

– PCB / backplane tracking


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Cable ConstructionConductor 28 AWG(7 x 36 AWG)

Insulating layer

Twisted pair

Inner shield aroundtwisted pair (40AWG)

Outer shield (38AWG)

Outer Jacket

Filler

Jacket

Filler

Binder


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Signal Level

• Signal Level covers:-– Electrical characteristics– Signal coding– Signal timing

– EMC recommendations


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SpaceWire Links

• Point to point

• Bi-directional (Full duplex)

• High-speed 2 Mbits/s to 400 Mbits/s

• Low power 0.5 W per link interface (~5mW/Mbps @100 Mbps)

• Cable or PCB trace / backplane

• LVDS

• Data-Strobe encoding

LINK(LVDS + Cable/PCB)FIFO TYPE

INTERFACEFIFO TYPE

INTERFACELINK

INTERFACELINK

INTERFACE


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SpaceWire Link Interface

ENCODER

DECODERRECEIVE

FIFO

TRANSMITFIFO

Interfaceto Host

SpaceWireLink

Micro-MiniatureD-Type

Data

Strobe

LVDS

Data

Strobe

LVDS

STATEMACHINE

8 bits

8 bits


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SpaceWire Link Interface (as it is presented in the Standard)

Receiver

Transmitter

StateMachine

TxClock

Rx clockRecovery

D

S

D

S

Clock

8 // bits

8 // bits

ENCODER

DECODERRECEIVE

FIFO

TRANSMITFIFO

Data

Strobe

Data

Strobe

STATEMACHINE

8 bits

8 bits

Figure 7-1 of the

SpaceWire Std, Draft-1

=


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PhysicalPhysical

Physical

Signal

Character

Data-LinkData-Link Exchange

Network

Packet

SpaceWireLevels

(legacy from

IEEE 1355)

SpaceWire

ApplicationSoftware

Intelligent nodeLocal-EGSE

ApplicationSoftware

Intelligent nodeOn-Board

ApplicationSoftware


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SpaceWire Network

• Interconnected with SpaceWire links• Alternative paths give the redundancy

Node 1 Node 2Router 1

Router 2

Router 3


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SpaceWire Error Recovery

• Link Errors– Disconnect error– Parity error– Escape sequence error– Credit error– Empty packet error

• Network Errors– Link error– EEP received– Destination address error

Recommendation of possible actions :– Examples : Disconnect link / Discard packet / report to higher level (e.g.

application)


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On-Board Buses for Command& Control

• Mil-Std-1553– Max. 1 Mbit/s – Asynchronous – Half-duplex (one-direction at a time)– American

• On-Board-Data-Handling– Max. 512 kbit/s– Synchronous– Full-duplex (bi-directional)– European


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Similar Standards for On-Board Space Interfaces

• IEEE 1394 (FireWire)• same Data-Strobe Scheme and LVDS => data rates 100 – 200 and

400 Mbit/s

Our perceptionFirewire SpaceWire

Cables, connectors defined Cables & connectors defined for commercial applications for space applicationsTopology: Bus Point-to-point (Network with routers)Shared memory Distributed processingIsochronous AsynchornousPacket content specified (overheads) Packet content not specifiedRedundancy possible (but not in the Std.) Redundancy: Dupplicate links100, 200, 400 Mbps Variable data rate

Coherent I/F to DSPs, SSMM, sensors.Not clear visibility Radiation Tolerant devices availableCommercial applications (as specified in Std) Harsh environment applications


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SpaceWire New generation of High Speed Serial Links

Unified high-speed interface all over the Spacecraft 2 Mbps < Variable data rates < 400 Mbps and scalable with number of cables

High-speed gives margin for above layers overheads => sort of Intranet possible in the S/C It is bi-directional: required for DSPs, and allows remote configuration/control of

camera/SSMM Routers allow dynamic switching (packets switched according to Header Content)

A large number of nodes can be reached with a reduced number of cables=> seamless communication intra-box (backplane) and inter-box (cable) => good for SW

It is reliable=> Robust physical level => BER < 10-14 @ 100 Mbps = 1 error every 11.5 days In addition: Detection of disconnect and Parity errors + Link restart Redundant paths are available On top of SpaceWire, Network / Transport Layers for further protection

Enabling end-to-end model (HW and SW) for high-speed interfaces

=> Facilitates SOFTWARE developments: message passing & Virtual Channels High speed links can talk to computers on-board => Intranet possible in the S/C Possibilities for integration / testing via Internet – Just a Gateway is needed


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Methodology

• 2) between units

EGSE

• 3) directly with EGSE

=> many other features (see next presentation)

TOPNET complements the OSI (CCSDS-SOIF) model with Network / Transport Layers

• 4) as a gateway to the Internet

Internet

SpaceWire provides the high-speed network infrastructure for communications

• 1) within the unit

SpaceWire Router

SpaceWire links


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Topnet: Features summary

TopNet at a glance– Provides an end to end solution

– SpaceWire infrastructure

– Network / Transport Layers & FDIR

– Frame for a de-centralised and progressive functional Integration.

– Interface to the Internet

Benefits to Users – Reduces development risks/costs by allowing early pre-integration

– Fosters complete compatibility and modules re-use


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Defying traditional mindset

Projects interested in– what other projects did before (reliability, cost)

– Availability of components and modules

– Standards => compatibility, re-use => cost, time to market

– Potential gains in the short term

More R&D budget needed to prove concepts first


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Conclusion• SpaceWire provides the infrastructure to have a sort of

Internet On-Board the Spacecraft• A large number of Spacecraft in the U.S. and Europe

– use SMCS devices based on IEEE 1355

– plan to use SpaceWire and its routers

• The Network/Transport Layers have to be further defined

estec/ tos-etd section 1 university of dundee applied computing spacewire 1.scope 2.standard...

Documents

university of dundee

estec tosetd section

spacewire std

fifo interface

computing board

encoder decoder slide

link lvds

spacewire related modules