Deterministic Communication with Space Wire Martin Suess CCSDS

Deterministic Communication with Space. Wire Martin Suess CCSDS Spring Meeting 2015 23/03/2015 ESA UNCLASSIFIED – For Official Use

Overview • Introduction • Space. Wire-D Protocol Main Requirements • Scheduling of Space. Wire Traffic • Space. Wire-D Protocol Stack • Space. Wire-D Prototyping • Conclusion Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 2 ESA UNCLASSIFIED – For Official Use

Introduction • Space. Wire is a widely used on-board data link standard for payload communication. • The Space. Wire standard ECSS-E-ST-50 -12 C defines the point to point links as well as networks. • The communication over the bi-directional Space. Wire links and the network is asynchronous, i. e. no synchronization between data sources. • If communication channels share the same hardware resources the access is arbitrated. • • As result the message latency through the network is not fixed. • The maximum (worse case) latency has always an upper bound but this bound depends on many parameters. • This makes it difficult to manage the latency in a system. The mean latency and the jitter around the mean is a function of many parameters: link speed, network traffic, network topology, segment or packet size. Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 3 ESA UNCLASSIFIED – For Official Use

Space. Wire-D Main Protocol Requirements Provide deterministic data delivery • Using Remote Memory Access Protocol (RMAP) ECSS-E-ST-50 -52 C as the basic communication mechanism. • Operates on existing Space. Wire networks with current routing switches. • Compatible with existing Space. Wire RMAP target devices. • Space. Wire-D protocol initiator part can be implemented in software. • Other Space. Wire packets can be sent without disrupting deterministic traffic Allows Space. Wire to be used for • Time critical avionics applications (e. g. AOCS) • Concurrently with regular payload data handling Basic service shall be very simple to implement Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 4 ESA UNCLASSIFIED – For Official Use

Determinism with a Single Initiator Initiating Node Data. Handling Processor Read Reply Command Read Reply Read Space. Wire Router Inst. 1 Inst. 2 Inst. 3 Space. Wire Router Target Nodes Inst. 4 Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 5 ESA UNCLASSIFIED – For Official Use Inst. 5 Mass Memory

Multiple Initiators Data. Handling Processor Read Command Space. Wire Router Read Command Inst. 1 Inst. 2 Inst. 3 Space. Wire Router Inst. 4 Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 6 ESA UNCLASSIFIED – For Official Use Inst. 5 Mass Memory

Determinism through Scheduling Data. Handling Processor 0 1 2 3 4 . . . Y N N Y N . . . Each initiator has a schedule table Space. Wire Router Inst. 1 Inst. 2 Inst. 3 Specifies in which time-slots an initiator 0 is allowed to initiate an RMAP command N Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 7 ESA UNCLASSIFIED – For Official Use Mass Memory 1 2 3 4 . . . Y Y N N . . .

Time-Slot 0 Data. Handling Processor 0 1 2 3 4 . . . Y N N Y N . . . Write Command Write Reply Space. Wire Router Inst. 1 Inst. 2 Inst. 3 Mass Memory 0 1 2 3 4 . . . N Y Y N N . . . Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 8 ESA UNCLASSIFIED – For Official Use

Time-Slot 1 Data. Handling Processor 0 1 2 3 4 . . . Y N N Y N . . . Space. Wire Router Read Command Inst. 1 Read Reply Inst. 2 Inst. 3 Mass Memory 0 1 2 3 4 . . . N Y Y N N . . . Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 9 ESA UNCLASSIFIED – For Official Use

Concurrent Data Transfer Data. Handling Processor 0 1 2 3 4 . . . Y N Y Y N . . . Write Command Write Reply Space. Wire Router Read Command Inst. 1 Inst. 2 Read Reply Inst. 3 Mass Memory Doubles the effective network bandwidth 0 1 2 3 4 . . . N Y Y N N . . . Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 10 ESA UNCLASSIFIED – For Official Use

Schedule • Schedule arranged to avoid conflicting use of network resources • In a single slot can have a. Parallel Initiators with non conflicting Targets or groups of Targets b. Single Initiator that can send commands to any Target • The synchronization of the schedule between the Space. Wire-D initiators is achieved using Space. Wire Time-Codes. Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 11 11 ESA UNCLASSIFIED – For Official Use

Space. Wire-D Services q Static Bus • Deterministic. • Transaction group sent one specific slot per schedule round. q Dynamic Bus • Not fully deterministic. • Transaction group sent in one of several slots assigned to the virtual bus. Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 14 14 ESA UNCLASSIFIED – For Official Use

Space. Wire-D Services q Asynchronous Bus • Not deterministic. • Individual transactions with priority grouped into transaction group and sent in one of several assigned slots. q Packet Bus • Not deterministic. • Sends and receives Space. Wire packets using RMAP. • Packet segmented if necessary to fit into slot. • One or more or part of a packet sent in one of several assigned slots. Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 15 15 ESA UNCLASSIFIED – For Official Use

Space. Wire-D Protocol Stack Initiator User Application Space. Wire-D User Application Static Bus Initiator Dynamic Bus Initiator Async Bus Initiator User Application Static Bus Target Packet Bus Initiator Async Bus Target RMAP Target Space. Wire Network Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 21 21 Dynamic Bus Target RMAP Initiator RMAP Space. Wire Target ESA UNCLASSIFIED – For Official Use Packet Bus Target

Space. Wire-D FDIR q Fault Detection, Isolation and Recovery (FDIR) requirements have been considered from the beginning and addressed in Space. Wire-D. q Initiator can monitor the completion of all transactions within the time slot. q If an error is detected the network manager is informed to perform isolation and recovery. q For faster failure isolation a schedule conscious bus guarding function can be integrated in the Space. Wire routing switches. • This function is not yet available in current routing switches. Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 22 22 ESA UNCLASSIFIED – For Official Use

Space. Wire-D Prototype q AT 6981 Castor system-on-chip • Used for both RMAP initiators and targets • 8 -port Space. Wire router • Dedicated RMAP engines • LEON 2 -FT processor q Software built using the RTEMS real-time operating system • Board support package ports the OS to the AT 6981 board q Link Analyser Mk 2 used to monitor traffic q USB Brick Mk 2 used as time-code master Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 23 23 ESA UNCLASSIFIED – For Official Use

Space. Wire Prototype Link Castor-PXI Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 24 Analyser Mk 2 Castor-PXI 24 ESA UNCLASSIFIED – For Official Use Castor-PCIe Brick Mk 2

Space. Wire-D Protocol Definition q The Space. Wire-D protocol has been defined by the University of Dundee under ESA contract. q Protocol requirements have been established with active involvement of two major European System Integrators (TAS-F, Airbus Defense & Space) q The Space. Wire-D protocol specification has been regularly reviewed by • ESA • TAS-F • Airbus D&S • Space. Wire Working Group q The prototype implementation is performed by Uo. D q The protocol definition is very advanced • Space. Wire-D Standard Draft D v 0. 15 (July 2014) Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 25 ESA UNCLASSIFIED – For Official Use

Conclusion q Space. Wire-D addresses the need of deterministic data delivery over Space. Wire. q Based on currently existing Space. Wire devices • Routers • RMAP Target devices • RMAP Initiators q Additional software to handle the protocol only required on Initiators. q Further error resilience can be gained by introducing the bus guarding function in the routers. q Space. Wire-D is planned for standardization in ECSS in 2016 -2017 Sp. W-D | Martin Suess | CCSDS Spring Meeting 2015 | 23/03/2015 | TEC-EDP | Slide 26 26 ESA UNCLASSIFIED – For Official Use