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

2. SpaceWire Networks Point-to-point links Nodes Routers
Serial digital links : 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

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

4. 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

5. 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

6. 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

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

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

9. 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

10. 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

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

12. 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 Mbps)
Cable or PCB trace / backplane
LVDS
Data-Strobe encoding

13. 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

14. 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 =

15. 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

16. 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

17. 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)

18. 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

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

20. 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 < @ 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

21. 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)

22. 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

23. 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

24. 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