SpaceWire Scope Standard ECSS-E-50-12, Draft-1 Layers above the Standard Space vs commercial digital technologies

SpaceWire Networks Point-to-point links Nodes Routers 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

Point-to-point serial links Example Router Cascaded routers Nodes Network Node Point-to-point serial links SpaceWire Interface Devices (chips)

Basic Communications infrastructure SpaceWire Basic Communications infrastructure SpaceWire Router SpaceWire links SpaceWire Network Computer Unit Instrument Mass Memory Module Digital Processing Unit Electrical Ground Support Equipment (EGSE) Processor EM

Board for On-Board Processing In red : 1355 / SpaceWire related modules 8kx32 DPRAM TSC 21020 (DSP) Two SMCS-332 Encoder / Decoder Support FPGA Back side: 128kx40 (DM) 128kx48 (PM) SRAM LVDS BOOT PROM SpaceWire connectors

Device for a SpaceWire node (Simple: approximately 5000 gates) SpaceWire Interface (part of a chip) Channel 1 Ch. 2 Ch. 3 Glue logic (e.g. FIFO, Checksum) C O M I H JT AG Device for a SpaceWire node SMCS332 RxDS TxDS Space Wire SpcW (Simple: approximately 5000 gates) ENCODER DECODER RECEIVE FIFO TRANSMIT Interface to Host Data Strobe STATE MACHINE 8 bits Node Cascaded routers Node Additional logic for System on a Chip

SpaceWire Standard Physical Level Signal Level Character Level Exchange Level Packet Level Network Level Recovery Schemes (Recommendations)

TOPNET Layers Application Application Presentation Software Session UDP / TCP-like ? IP-like CCSDS-SOIF (131.176.19.123) Transport Network Physical Signal Character Exchange Network Packet SpaceWire Levels (legacy from IEEE 1355) Data-Link Physical

Physical Level Physical Level covers Cables Connectors 4 screened twisted pairs with overall shield Connectors 9 pin micro-miniature D-types Cable Assemblies PCB / backplane tracking

Cable Construction Conductor 28 AWG (7 x 36 AWG) Insulating layer Filler Twisted pair Inner shield around twisted pair (40AWG) Jacket Filler Binder Outer shield (38AWG) Outer Jacket

Signal Level Signal Level covers:- Electrical characteristics Signal coding Signal timing EMC recommendations

SpaceWire Links LINK (LVDS + Cable/PCB) Point to point FIFO TYPE INTERFACE 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

SpaceWire Link Interface Micro- Miniature D-Type Data Strobe LVDS 8 bits ENCODER TRANSMIT FIFO Interface to Host STATE MACHINE Data Strobe LVDS DECODER RECEIVE FIFO 8 bits

SpaceWire Link Interface (as it is presented in the Standard) Figure 7-1 of the SpaceWire Std, Draft-1 ENCODER DECODER RECEIVE FIFO TRANSMIT Data Strobe STATE MACHINE 8 bits Receiver Transmitter State Machine Tx Clock Rx clock Recovery D S 8 // bits =

Data-Link Physical Application Software SpaceWire Levels Exchange Network Packet SpaceWire Levels (legacy from IEEE 1355) Application Software Intelligent node Local-EGSE On-Board Physical Signal Character

SpaceWire Network Interconnected with SpaceWire links Node 1 Node 2 Router 1 Router 2 Router 3 Interconnected with SpaceWire links Alternative paths give the redundancy

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)

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

Similar Standards for On-Board Space Interfaces IEEE 1394 (FireWire) same Data-Strobe Scheme and LVDS => data rates 100 – 200 and 400 Mbit/s

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

Methodology SpaceWire provides the high-speed network infrastructure for communications 1) within the unit SpaceWire Router SpaceWire links 2) between units EGSE 3) directly with EGSE TOPNET complements the OSI (CCSDS-SOIF) model with Network / Transport Layers 4) as a gateway to the Internet Internet => many other features (see next presentation)

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

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

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