NSBE Seminar1 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 Seminar2 Command and Data Handling System (C&DH) C&DH Facts: 54 Multiplexer DeMultiplexers ((MDM) – ESSMDM & SSMDM) MIL-STD-1553 data buses A/B channel redundancy MIL-STD-1553 remote terminal (RT) address assignments 190 payload 1553 RT addresses International partners and firmware controller 1553 devices 90 unique types devices 100 (approximately) Software Interface Control Documents 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.

NSBE Seminar3 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.

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7 Architecture Overview Data Rate1 MHz Word Length20 bits/word Data Bits/Word16 bits Transmission TechniqueHalf-duplex OperationAsynchronous, self-clocking waveform EncodingManchester II bi-phase Bus TopologyLinear multi-drop bus, with stub-coupled terminals Bus CouplingTransformer or direct coupled Transmission MediaTwisted-shielded-pair cable terminated in its characteristic impedance ProtocolTime-division, command/response Bus ControlSingle or multiple

NSBE Seminar8 MIL-STD-1553 Simple Multiplex Architecture Subsystem with Embedded Remote Terminal Remote Terminal Subsystem(s) Bus Controller Optional Redundant Cables Cable Coupler

NSBE Seminar9 Bus Topology Examples Bus Controller Single Level Topology Single Level, with Functional Separation Sensor ASensor B Comp 1 Sensor C Bus A Bus B Sensors Bus A Bus B Bus A Bus B Bus A Bus B Sensors Controls and Display Bus Navigation Bus Stores Bus

NSBE Seminar10 Transformer Coupled Bus Network Main Bus ZoZo ZoZo R = 0.75 Z o ohm Terminal 1 Terminal 2 Terminal N RRRRRR Stubs

NSBE Seminar11 Transmission Line Characteristics Cable TypeTwisted-shielded-pair Capacitance30 pFd./ft Max Characteristic70 to 85 OHMS at 1 MHz, nominal Impedance(actual, per notice 2) Attenuation1.5 db/100 ft Max at 1MHz Bus LengthNot specified in 1553B (300 ft suggested max) Stub LengthDirect coupled - less than 1 ft Transformer coupled - 20 ft (suggested max) TerminationEnds terminated with resistors of Z 0 +/-2% Cable Shielding75% coverage (90% coverage, per notice 2) 1553 Requirement

NSBE Seminar12 Bus Coupler Characteristics Direct Coupled Transformer Coupled Shield Data Bus RR 1: ohm  2% 55 ohm  2% Transceiver Terminal Isolation resistors: R = 0.75 Z O  2% Isolation transformer: turns ratio 1:1.41  3% (1 – terminal winding) (1.41 – bus winding) Z OC > 3K at 75 kHz to 1 MHz 1V rms sine wave Droop: 45 dB at 1 MHz Nominal characteristic impedance of bus cable: Z O = 70 to 85 at 1 MHz At 27v P-P 250-kHz sq wave

NSBE Seminar13 Data Bus Networks—Stub Impedance vs. Length Direct Coupled Stub Length (ft) Stub Impedance, Z 1 (ohms) Transformer Coupled (Ideal Transformer) Transformer Coupled (1553B Transformer) Direct Coupled (Z 1 = 2000 ohms) Terminal input impedance (Z 1 ): 1000 ohms, except where noted Coupler transformer: 1:1.41 turns ratio Isolation resistors: 52.5 ohms Cable capacitance: 30 pF/ft

NSBE Seminar14 MIL-STD-1553 Data Encoding One Bit Time (+) – (0) – (+) – (0) – (+) – (0) – (-) – 1 MHz Clock NRZ Data Manchester II Bi-Phase L

NSBE Seminar15 MIL-STD-1553B Intermessage Gap and Response Timing Command/Status Sync Parity Bit Bit Time Volts 0 – Volts Gap Time: Min 4.0 microsecResponse Time:Min 4.0 microsec Max 12.0 microsec

NSBE Seminar16 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 Seminar17 MIL-STD-1553B Word Formats P 1 P Remote Terminal Address Subaddress/ Mode Data Word Count/Mode Code Sync Remote Terminal Address Bit Times Command Word Data Word Status Word T/R Data Reserved Broadcast Command Received Busy Subsystem Flag Dynamic Bus Control Acceptance Terminal FlagParityService RequestInstrumentation Message Error

NSBE Seminar18 Information Transfer Formats Receive Command Data Word Data Word Data Word Status Word Command Word Controller-to- RT Transfer Transmit Command Status Word Data Word Data Word Data Word Command Word RT-to- Controller Transfer Receive Command Transmit Command Status Word Data Word Data Word Data Word Status Word Command Word RT-to-RT Transfer Mode Command Status Word Command Word Mode Command Without Data Word Mode Command Status Word Data Word Command Word Mode Command With Data Word (Transmit) Mode Command Data Word Status Word Command Word Mode Command With Data Word (Receive) Next # # # # # # Intermessage gap Response time #

NSBE Seminar19 Receive Command Transit Command Status Word Data Word Data Word Data Word Command Word RT-to-RT Transfer # Broadcast Information Transfer Formats Receive Command Data Word Data Word Data Word Command Word Controller-to- RT(s) Transfer Mode Command Word Mode Command Without Data Word Mode Command Data Word Command Word Mode Command With Data Word Next # # # Intermessage gap Response time # Next

NSBE Seminar20 MIL-STD-1553B Terminal Block Diagram Computer Subsystem I/F Encode Decode I/O Process Power Supply Transceiver Internal Buses 1553 Terminal 1553B Data Bus Subsystem Memory Encode Decode Protocol Control

NSBE Seminar21 Generalized 1553B Terminal Functions D Subsystem Interface Circuits Subsystem or Host Processor Interface Data Bus Interface C Word/ Message Processor B Bit/Word Processor (Encoder/ Decoder) A Analog Transmit/ Receive Word Processor Receive –Signal limiting –Filter –Threshold detection Transmit –Driver –Transmitter control –Timer Common –Bus coupling Receive –Receiver –Sync detection –Data detection –Manchester error detection –Parity check –Bits and word count Transmit –Transmit control –Sync and data encoder –Parity generation Clock generation Receive –Command word code –Status word decode –Address recognition –Mode execution –Word count recognition –Message error detection Transmit –Word count (BC) –Status register Built-in test Subsystem interface control –Data address –Control registers Memory buffers Channel selection Data sampling Conversation Subsystem timing Buffer registers Calibration Self-test DMA to host memory Interrupt lines Control lines Message Processor

NSBE Seminar22 GNC2 Local Bus – PRESTO analysis

NSBE Seminar23 GNC2 Local Bus – PRESTO analysis - result

NSBE Seminar24 JEM Local Bus – PRESTO analysis (1 of 2)

NSBE Seminar25 JEM Local Bus – PRESTO analysis (2 of 2)

NSBE Seminar26 JEM Local Bus – PRESTO analysis - result

NSBE Seminar27 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-HDBK- 1553A. Test Duration: 2 working days allocated for each RT. Mil-Std-1553 Remote Terminal Validation Testing

NSBE Seminar28 ORU Test Support Equipment Main Power BUS TESTER PC and Test Equipment TYPICAL TEST SET-UP Address Box 6 A B Main Power Mil-Std-1553 Remote Terminal Validation Testing

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NSBE Seminar31 Control Moment Gyroscopes CMG – Facts The speeds available for commanding: 6269, 6319, 6364, 6410, 6456, 6504, 6552, 660, 6639, 6683, 6722, , 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 …

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NSBE Seminar36 Control Moment Gyroscope (CMG) interface

NSBE Seminar37 Control Moment Gyroscope (CMG) interface

NSBE Seminar38 Control Moment Gyroscope (CMG) interface

NSBE Seminar39 Control Moment Gyroscope (CMG) interface

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NSBE Seminar41 Useful web links Command and Data Handling Architecture Control Document (D ) Command and Control Software site: MIL STD 1553 tutorial MDM User’s Guide ( Volume I)X , Rev D MIL-STD-1553 Details drawing contributed by: Mack McCall, Boeing Primus E. Jackson Jr. work cell