MIL-STD 1553 on the International Space Station’s Command and Data Handling System NSBE training seminar September 25, 2003 P.Eugene Jackson Jr. NSBE Seminar 1 Command and Data Handling System (C&DH) ESSMDMs and SSMDMs are used in the Space Station Command and Data Handling system design which is a “layered” approach providing difference levels of processing and communication capabilities for each layer. The ESSMDM provide control and data processing, communication control, and mass resources to support control and management function of onboard functions. The SSMDM are used to provide embedded control processing at the lower level and at the main interface to on board sensors and effectors via analog and discrete input/output. C&DH Facts: 54 Multiplexer DeMultiplexers ((MDM) – ESSMDM & SSMDM) 100 + MIL-STD-1553 data buses A/B channel redundancy 1200 + MIL-STD-1553 remote terminal (RT) address assignments • 190 payload 1553 RT addresses • 600 + International partners and firmware controller 1553 devices • 90 unique types devices 100 (approximately) Software Interface Control Documents NSBE Seminar 2 Both MDM type are designed to host User Application Software (UAS) to control all functionally. Functional Space Station Architecture (figure on the left) represents a”vertical slice” of The C&DH system defining the Control Processing, Local Processing, and the User Processing as they relate to MDMs. The top two layers, the Control Buses and the Local Buses are often referenced to as Local Bus. The lower layer of MIL-STD-1553 is referenced As User Bus layer, because the communicate Can be either Local bus protocol or a custom User Protocol connected directly to the user equipment. NSBE Seminar 3 NSBE Seminar 4 NSBE Seminar 5 NSBE Seminar 6 Architecture Overview • Data Rate 1 MHz • Word Length 20 bits/word • Data Bits/Word 16 bits • Transmission Technique Half-duplex • Operation Asynchronous, self-clocking waveform • Encoding Manchester II bi-phase • Bus Topology Linear multi-drop bus, with stub-coupled terminals • Bus Coupling Transformer or direct coupled • Transmission Media Twisted-shielded-pair cable terminated in its characteristic impedance • Protocol Time-division, command/response • Bus Control Single or multiple NSBE Seminar 7 MIL-STD-1553 Simple Multiplex Architecture Cable Coupler Optional Redundant Cables Bus Controller Remote Terminal Subsystem(s) NSBE Seminar Subsystem with Embedded Remote Terminal 8 Bus Topology Examples Sensor A Sensor B Sensor C Bus A Bus B Single Level Topology Comp 1 Sensors Controls and Display Bus Bus A Bus B Bus A Bus B Navigation Bus Single Level, with Functional Separation Bus Controller Sensors Bus A Bus B Stores Bus Sensors NSBE Seminar 9 Transformer Coupled Bus Network Terminal 1 Terminal 2 Terminal N Stubs R 1 1 1 1.41 1.41 1.41 R R R R R Main Bus Zo Zo R = 0.75 • Zo ohm NSBE Seminar 10 Transmission Line Characteristics 1553 Requirement • Cable Type Twisted-shielded-pair • Capacitance 30 pFd./ft Max • Characteristic Impedance 70 to 85 OHMS at 1 MHz, nominal (actual, per notice 2) • Attenuation 1.5 db/100 ft Max at 1MHz • Bus Length Not specified in 1553B (300 ft suggested max) • Stub Length Direct coupled - less than 1 ft Transformer coupled - 20 ft (suggested max) • Termination Ends terminated with resistors of Z0 +/-2% • Cable Shielding 75% coverage (90% coverage, per notice 2) NSBE Seminar 11 Bus Coupler Characteristics Direct Coupled Transformer Coupled Shield Data Bus • Isolation resistors: R = 0.75 ZO 2% • Isolation transformer: turns ratio 1:1.41 3% (1 – terminal winding) At 27v (1.41 – bus winding) P-P 250-kHz wave ZOC > 3K at 75 kHz to 1sq MHz 1V rms sine wave Droop: < 20% Overshooting/ringing: < 1V CMR: > 45 dB at 1 MHz • Nominal characteristic impedance of bus cable: ZO = 70 to 85 at 1 MHz R R 1:1.41 55 ohm 2% 55 ohm 2% Transceiver Transceiver Terminal Terminal NSBE Seminar 12 Data Bus Networks—Stub Impedance vs. Length 2200 •Terminal input impedance (Z1): 1000 ohms, except where noted •Coupler transformer: 1:1.41 turns ratio •Isolation resistors: 52.5 ohms •Cable capacitance: 30 pF/ft 2000 Stub Impedance, Z1 (ohms) 1800 1600 1400 Transformer Coupled (Ideal Transformer) Transformer Coupled (1553B Transformer) 1200 1000 Direct Coupled (Z1 = 2000 ohms) 800 600 400 Direct Coupled 200 0 0 2 4 6 8 10 12 14 16 18 Stub Length (ft) NSBE Seminar 20 22 24 26 28 30 13 MIL-STD-1553 Data Encoding One Bit Time 1 MHz Clock NRZ Data (+) – (0) – (+) – (0) – (+) – 1 0 1 1 0 0 0 Manchester (0) – II Bi-Phase L (-) – NSBE Seminar 14 MIL-STD-1553B Intermessage Gap and Response Timing Bit Time 19 Bit Time 20 1 2 3 Command/Status Sync Parity Bit + Volts 0 – Volts Gap Time: Min 4.0 microsec Response Time: Min 4.0 microsec Max 12.0 microsec NSBE Seminar 15 MIL-STD-1553B Word Formats • Command Word – Command/status sync, 16 data bits, odd party – Transmitted only by the active bus controller – Contains unique address of RT or broadcast address (11111) – Contains transmit or receive data indicator – Contains subaddress (or mode code indicator) – Contains word count of 1 to 32 (or mode code) • Status Word – Command/status sync, 16 data bits, odd party – Transmitted only by the commanded remote terminal – Contains own address and terminal health information • Data Words – Data word sync, 16 data bits, odd parity – Transmitted or received by bus controllers or remote terminals – Received by bus monitors NSBE Seminar 16 MIL-STD-1553B Word Formats Bit Times 1 2 Command Word 3 4 5 6 7 8 5 Sync 9 10 11 12 13 14 15 16 17 18 19 20 1 5 Remote Terminal T/R Address Subaddress/ Mode Data Word Sync 1 Data P 1 1 3 1 1 1 1 1 Reserved Busy Subsystem Flag Dynamic Bus Control Acceptance Terminal Flag NSBE Seminar 1 Parity 1 Broadcast Command Received Remote Terminal Address 16 Service Request Sync P Data Word Count/Mode Code Instrumentation 5 1 Message Error Status Word 5 17 Information Transfer Formats Controller-toRT Transfer Receive Command Data Word RT-toController Transfer Transmit Command RT-to-RT Transfer Receive Transmit Command Command Mode Command Mode Command Without Data Word Mode Command Mode With Data Word Command (Transmit) Mode Command Mode With Data Word Command (Receive) •• •• •• Data Word Data Word •••• Data Word •• Status Word Data Word Data Word •••• •• Status Word Data Word Data Word Status Word Status Word •• # Data Word Status Word # Next Command Word Data Word # Next Command Word •••• Data Word Status Word •• Status Word Next Command # Word Next Command Word # # Next Command Word Next Command Word # Intermessage gap • • Response time NSBE Seminar 18 Broadcast Information Transfer Formats Controller-toRT(s) Transfer RT-to-RT Transfer Receive Command Data Word Receive Transit Command Command Mode Mode Command Command Without Data Word Mode Mode Command With Data Word Command # Data Word Data Word •• •••• Status Word Data Word Data Word # Data Word Next Command Word •••• Data Word # Next Command Word Next Command Word # Next Command Word # Intermessage gap • • Response time NSBE Seminar 19 MIL-STD-1553B Terminal Block Diagram 1553B Data Bus 1553 Terminal Protocol Control Internal Buses Subsystem Computer Transceiver Encode Decode Subsystem I/F Transceiver Subsystem Encode Decode Memory Power Supply I/O Process Subsystem NSBE Seminar 20 Generalized 1553B Terminal Functions Word Processor Data Bus Interface A Analog Transmit/ Receive • Receive –Signal limiting –Filter –Threshold detection • Transmit –Driver –Transmitter control –Timer • Common –Bus coupling B Bit/Word Processor (Encoder/ Decoder) • Receive –Receiver –Sync detection –Data detection –Manchester error detection –Parity check –Bits and word count • Transmit Message Processor C Word/ Message Processor • Receive –Command word code –Status word decode –Address recognition –Mode execution –Word count recognition –Message error detection • Transmit –Transmit control NSBE Seminar –Word count (BC) –Sync and D Subsystem Interface Circuits Subsystem or Host Processor Interface • Channel selection • Data sampling • Conversation • Subsystem timing • Buffer registers • Calibration • Self-test • DMA to host memory • Interrupt lines • Control lines 21 GNC2 Local Bus – PRESTO analysis NSBE Seminar 22 GNC2 Local Bus – PRESTO analysis - result NSBE Seminar 23 JEM Local Bus – PRESTO analysis (1 of 2) NSBE Seminar 24 JEM Local Bus – PRESTO analysis (2 of 2) NSBE Seminar 25 JEM Local Bus – PRESTO analysis - result NSBE Seminar 26 Mil-Std-1553 Remote Terminal Validation Testing Requirement: all ORUs connecting to ISS cross-boundary buses must meet MIL-STD-1553B, Notice 2. Purpose: to verify that Remote Terminal designed to meet the requirements of MIL-STD-1553B, Notice 2. Test will be performed on stand-alone ORU. • Physical Layer: input and output electrical characteristics, noise rejection. • Protocol Layer: subaddress legalization, error detection and handling, transmission rate, mode code implementation ….. Test Plan: Appendix A of MIL-HDBK-1553 or Section 100 of MIL-HDBK1553A. Test Duration: 2 working days allocated for each RT. NSBE Seminar 27 Mil-Std-1553 Remote Terminal Validation Testing TYPICAL TEST SET-UP A Test Support Equipment ORU B BUS TESTER PC and Test Equipment 6 Address Box Main Power Main Power NSBE Seminar 28 NSBE Seminar 29 NSBE Seminar 30 Control Moment Gyroscopes CMG – Facts The speeds available for commanding: 6269, 6319, 6364, 6410, 6456, 6504, 6552, 660, 6639, 6683, 6722, 6768 6808, 6849, 6890, and 6932 rpm. The spin motor is used to spin up the wheel and maintain a constant wheel speed. At a nominal line voltage of 120 vdc, the maximum possible wheel speed is 8290 rpm. Gimbal Torquers – Used to rotate the gimbal assembly. CMG health and status – Temperatures, electronics voltages, inner and out gimbals positions and rates … NSBE Seminar 31 NSBE Seminar 32 NSBE Seminar 33 NSBE Seminar 34 NSBE Seminar 35 Control Moment Gyroscope (CMG) interface NSBE Seminar 36 Control Moment Gyroscope (CMG) interface NSBE Seminar 37 Control Moment Gyroscope (CMG) interface NSBE Seminar 38 Control Moment Gyroscope (CMG) interface NSBE Seminar 39 NSBE Seminar 40 Useful web links Command and Data Handling Architecture Control Document (D684-10500-02) http://iss-www.jsc.nasa.gov/ss/issapt/cdhait/resources/add_master15.PDF Command and Control Software site: http://iss-www.jsc.nasa.gov/ss/issapt/vehipt/sspt7ipt/cdhipt/ccipt/grp/ccsdev/ccs.htm MIL STD 1553 tutorial http://www.condoreng.com/support/downloads/tutorials/index.shtml MDM User’s Guide ( Volume I) X8264868, Rev D MIL-STD-1553 Details drawing contributed by: Mack McCall, Boeing Primus E. Jackson Jr. primus.e.jackson1@jsc.nasa.gov work 281 488 5551 cell 281 788 7663 . 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