SpaceFibre. Steve Parkes, Chris McClements, Martin Suess* Space Technology Centre University of Dundee *ESA, ESTEC

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1 SpaceFibre Steve Parkes, Chris McClements, Martin Suess* Space Technology Centre University of Dundee *ESA, ESTEC 1

2 Lessons Learnt from SpaceWire Cable Mass 87 g/m approximately Bi-directional Data strobe signalling No need for PLL Differentially encoded Good EMC performance 8 signal wires Individual screens on pairs Overall screen High cable mass To reduce cable mass need fewer wires 2

3 Lessons Learnt from SpaceWire Data Rate Limited by Cable attenuation Skew between data and strobe signals Longer cables Exacerbate these problems SpaceWire practically limited to 200 Mbits/s Up to 10m length Faster links require different signalling scheme 3

4 Lessons Learnt from SpaceWire Character Sizes FCT, EOP, EEP 4-bits Null 8-bits Data character 10-bits Time-code 14-bits Variable character size Makes CODEC design more difficult Keep characters all the same size 4

5 Lessons Learnt from SpaceWire Parity coverage Data Character EOP FCT P 0 X X X X X X X X P P Parity Coverage Parity Coverage Parity bit to cover just one character 5

6 Lessons Learnt from SpaceWire Transmitted DC Component SpaceWire characters All possible bit patters used Coding not DC balanced Degrades transmission characteristics Makes them broadband Prevents AC coupling Use DC balanced signalling scheme 6

7 Lessons Learnt from SpaceWire Galvanic Isolation No method of galvanic isolation provided in SpaceWire Various techniques possible Support galvanic isolation 7

8 Lessons Learnt from SpaceWire Matched Impedance Connectors 9-pin MDM connector Not impedance matched Becomes a problem for high data rates Alternative impedance matched connectors Have been developed Use impedance matched connector 8

9 Lessons Learnt from SpaceWire Initialisation Protocol SpaceWire does not use full handshake Part timing Part handshake Allowed backwards compatibility with IEEE1355 devices Can lead to false initialisation due to noise And erroneous flow of data External bias resistors can help with this A full handshake protocol is preferable 9

10 10 Requirements High data rate 2.5 G bits/s plus Over fibre and copper Fibre optic communications 100 m plus Copper Short length (1m) Galvanically isolated Light weight cables Low power per Gbit/s Radiation tolerant Rugged Able to integrate with SpaceWire network

11 R&D Team University of Dundee - CODEC VTT - Transceiver INO - Fibre Fibre Pulse - Connectors Gore Cable Patria New Systems Oy ESA study managers Martin Suess Iain MacKenzie 11

12 Key Problems 12 Fibre Blackening due to radiation Robustness Transceiver Radiation tolerance components 2.5 Gbits/s plus Rugged Connectors Rugged Materials CODEC 2.5 Gbits/s plus Transferable to radiation tolerant technologies

13 Current Status Radiation tolerant fibre Fibres evaluated by INO Fibre selected and tested Good radiation tolerance Rugged cable Gore developed sheathing for fibre Extremely rugged Lightweight Uses materials suitable for flight 13

14 Current Status Rugged connectors Connectors evaluated by Fibre Pulse Small, lightweight connectors selected Easy to mate Materials suitable for space flight Prototype transceiver Designed by VTT Using commercial devices Specially designed housing Radiation testing performed recently 14

15 15

16 Current Status Prototype CODEC Extensive evaluation of existing protocols CODEC specified and designed by UoD Prototyped using Xilinx FPGAs 16

17 Trade-offs Gigabit Ethernet Fibre Channel Serial ATA PCI Express Infiniband HyperTransport 17

18 SpaceFibre Approach Use the lower level of Fibre Channel as the basis for SpaceFibre Bit and word synchronisation, 8B/10B encoding Ordered Sets. Scrambling of data should be included for EM emission reduction Link speed negotiation protocol should follow the highest-speed first approach of Serial ATA Frame concept used in Fibre Channel, PCI Express and Serial ATA should be adopted Fine grained power management of the link interfaces should be supported Virtual channel and traffic class concepts of PCI Express should be adopted. 18

19 TXD<31:0> ORD_SET TX_EN SYS_CLK Port Interface STATE RXD<31:0> ORD_SET RX_DV RX_ER SYS_CLK Scrambler 8B/10B Encoder Coding & Link Control PHY Control PHY State Machine De-Scrambler 8B/10B Decoder RX Elastic Buffer Rx Code Synchronisation TX_CLK tx_code<9:0> RX_CLK rx_code<9:0> Serialiser Serialisation/ Deserialisation RX CLK Deserialiser 19 Driver tx_bit Transmit Physical Medium Dependent Medium Dependent Interface rx_bit Receiver Receive

20 SpaceFibre CODEC Implemented in Xilinx Virtex II Xilinx Virtex 4 Using Rocket IO Also implemented in VHDL Tested one implementation against the other 20

21 SpaceWire-SpaceFibre Router SpaceWire Links SpaceWire Router Frame Buffer Frame Buffer Frame Buffer Mux/ Demux SpaceFibre Port SpaceFibre Link Frame Buffer SpaceWire-SpaceFibre Router 21

22 22 Photo of test unit

23 SpaceWire-SpaceFibre Demo PC with SpaceWire Interfaces SpaceWire Links SpaceWire- SpaceFibre Router PC with SpaceWire Interfaces SpaceWire Links SpaceWire- SpaceFibre Router SpaceFibre Link 23

24 24 Photo of demo system

25 Conclusions 25 SpaceWire Very successful for spacecraft onboard data handling Now being widely used. Need for higher speed link (>>1Gbit/s) UoD developed appropriate SpaceFibre CODEC SpaceFibre demonstration system designed and tested Next step to provide draft SpaceFibre standard For review by SpaceWire working group

Martin Suess (TOS-EDP), Iain McKenzie (TOS-MME) martin.suess ESA-ESTEC, ESTEC, 2200AG Noordwijk,, The Netherlands

Martin Suess (TOS-EDP), Iain McKenzie (TOS-MME) martin.suess suess@esa.int, iain.mckenzie mckenzie@esa.int ESA-ESTEC, ESTEC, 2200AG Noordwijk,, The Netherlands ESTEC 19-20 July 2005 slide: 1 Overview Requirements