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MIL-STD-1553 David Koppel Excalibur Systems. Review of MIL-STD-1553 Specification WHY?What need does it fill WHAT?What does the spec say HOW?How is it.

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Presentation on theme: "MIL-STD-1553 David Koppel Excalibur Systems. Review of MIL-STD-1553 Specification WHY?What need does it fill WHAT?What does the spec say HOW?How is it."— Presentation transcript:

1 MIL-STD-1553 David Koppel Excalibur Systems

2 Review of MIL-STD-1553 Specification WHY?What need does it fill WHAT?What does the spec say HOW?How is it implemented Introduction

3 General Background on Avionics Buses Different Approaches ARINC-429 MIL-STD-1553 Firewire AFDX First Session

4 Specification Details Message Types Mode Codes Broadcast Second Session

5 Implementation Issues Prioritizing Messages Maximizing Throughput Third Session

6 Fourth Session Hardware Issues Connections and Terminations Using an Oscilloscope

7 Software Applications Fifth Session


9 TERMS Avionics Bus Remote Terminal Bus Controller Bus Monitor Source Sink Data Coupler Dual Redundant Minor Frame Major Frame Message

10 Examples of Clients Altimeter …… Display …… Black Box …… Flight Computer …… Active Device Passive Device Active and Passive

11 First Generation Analog Devices One Device Altimeter Speedometer Compass One Display Gauge

12 Second Generation ARINC-429 One Device Altimeter Engine Multiple Sink Display Auto Pilot Flight Recorder Display Auto Pilot Flight Recorder Maintenance Log

13 Wiring Diagram AltimeterDisplay Auto Pilot EngineFlight Recorder Maintenance Log

14 Military Applications Multiple Device Missile # 1 Missile # 2 Missile # 3 Missile # 4 Multiple Sink Display Trigger Weapons Test Flight Recorder

15 Military Application ARINC-429 Wiring Multiple Device Missile # 1 Missile # 2 Missile # 3 Missile # 4 Multiple Sink Display Trigger Weapons Test Flight Recorder

16 Military Applications MIL-STD-1553 Wiring Mission Computer (Bus Controller) Missile # 1 Missile # 2 Missile # 3 Missile # 4 Display Trigger Weapons Test Flight Recorder

17 Low Weight Easy Bus Installation Easy to Add RTs 1553 Advantages

18 Determines Order of Transmission Is Source or Sink for almost all Data Can check for bus errors Bus Controller

19 1553 ProblemSolution Cable Cut = Crash Inefficiency Serial Transmission Xmt to / from BC BC Overhead BC Lost = Crash Dual Redundant Bus 1 Mhz speed vs. 100 Khz for 429 Minor Frames Backup BC

20 Used in Video equipment and the F35 Wiring uses a binary tree configuration, each node passes the message through to its other nodes. Requires specialized Link and Phy hardware Firewire / AS5643

21 Based on Ethernet Adds dual redundancy No multiple routes – packets arrive in the order they are sent ~1500 bytes per packet Detection of lost or repeated data Relatively high overhead for short messages ARINC-664 Part 7 / AFDX

22 Direct lines are simple and cheap Multiple Transmit/Multiple Sink need a Bus Buses simplify H/W & Complicate S/W Summary

23 Goals of MIL-STD-1553 Mindset of MIL-STD Design Message Types MIL-STD-1760 Session 2

24 Communication between <= 32 Boxes Low Data Requirement <= 32 Words High Reliability Ability to detect communication errors Ability to retry on error Goals of MIL-STD-1553

25 Military Approach 1 Commander in Control All others speak when spoken to Commander speaks to one at a time or to all together (Broadcast) Mindset of MIL-STD Design

26 All Communication is by Message All Messages are Initiated by the BC All Messages begin with a Command Word 1553 Message

27 Bus Controller to RT Bus Controller to All RTs (Broadcast) RT to Bus Controller Housekeeping messages (Mode Codes) RT to RT Commands Message Types

28 Messages Begin With A Command Word Data may flow to/from BC from/to RT RTs return a Status Word Message Format

29 Command Word 5 Bits 1 Bit5 Bits 5 Bits RT AddressT/R Bit Subaddress Word Count

30 RT Address Address range is Some Systems use Address 31 as Broadcast T/R Bit If T/R = 1, RT Transmits Data If T/R = 0, RT Receives Data Command Fields

31 RT Subaddress Additional Routing for Complex RTs May Correspond to Subsystems Subaddress 0 is for Mode Codes Subaddress 31 is MIL-STD-1553B Mode Code Command Fields

32 Word Count Range is 1 to 32 (field value 0 = 32 words) For Mode Codes this is Mode Code Type There are 16 Mode Codes with No Data There are 16 Mode Codes with 1 word of Data Command Fields

33 Status Word Bit #Description 15-11RT Address 10Message Error 8Service Request 4Broadcast Received 3Busy

34 RT Address Lets BC Know Correct RT is Responding Usually The Only Field Set Message Error Indicates a Communications Error Status Bit Fields

35 Service Request (SRQ) Indicates another Subaddress has info ready Used with Get Vector Mode Command Broadcast Received Set in response to the message following a broadcast command Busy When RT cant respond - discouraged by spec Status Bit Fields

36 Message Sequence Receive Command Transmit Command Data Word Status Word Data Word Next Command * … Data Word Status Word *. … * Data Word.

37 RT to RT Command Receive Command Tx Status Word Data Word Next Command * … Data Word * Rx Status Word. Transmit Command

38 Mode Commands Mode Command Status Word Data Word Status Word Data Word Next Command *. *. *.

39 Checksum SRQ Processing Header Word Checking MIL-STD-1760 Features

40 On selected messages in Bus Controller Mode On selected RT/Subaddresses in RT Mode For all messages in Monitor Mode Checksum

41 Send Vector Mode Command If hi vector bit ==0 vector is a status word else send transmit command based on vector word SRQ Processing

42 User selects which subaddress to check User Selects header value for each subaddress Default is based on 1760 standard Header Word Checking

43 Session 3 lImplementation Issues –Timing –Major / Minor Frames –Implementation Examples

44 Intermessage Gap Time Response Time Major Frame Minor Frame Timing Issues

45 Time Between Messages At Least 4 usec Mid Sync to Mid Parity No Maximum in Specification Intermessage Gap Time

46 Time Until RT Sends A Status Word MIL-STD-1553A Maximum = 7 usec MIL-STD-1553B Maximum = 12 usec Response Time

47 A Major Frame is the set of all messages in a single cycle Typical Cycle is 20 to 80 milliseconds Some messages may appear more than once in a single Major Frame Major Frame

48 Some Messages Are High Priority We can alter frequency of specific messages Minor Frames 10 Mill10 Mill10 Mill10 Mill ABCABAAB

49 Does Pilot Wish To Perform a Test Instruct Missile to Execute Self Test Get Results Of Self Test Display Results On HUD Example: Missile Test

50 Self Test Button on ConsoleRT2 MissileRT3 Heads Up Display (HUD)RT4 RTs in Test

51 Message Frame RT2BCButton to BC BCRT3BC to Missile RT3BCMissile to BC BCRT4BC to HUD

52 Synchronize Time Tags for All Terminals Check If Terminal Received the Command Example: Synchronize RTs

53 Set & Check Synch BCBroadcastSynchronize Mode Command BCRT1Last Command Mode BCRT2Last Command Mode

54 Session 4 Hardware Issues Manchester 2 coding Differential Signals Bus Termination

55 Signal moves between +3.75v and -3.75v Signal always crosses 0 v at mid bit Direction of cross determines bit value Data Bits are 1 microsecond mid bit after.5 microseconds Sync is 3 microseconds mid sync after 1.5 microseconds Manchester Properties

56 Manchester 2 Coding v -3.75v microseconds

57 Like preceding chart but less square Original spec has Trapezoidal signal MacAir introduced Sinusoidal signal Fewer harmonics Cleaner signal (less noise) Oscilloscope View

58 Oscilloscope View – 1553 word Sync 3 us Data 16 us Parity 1 us 20 us

59 Oscilloscope View 1553 message Transmit Command Data Word Status Word RT to BC Response Time Intermessage Gap time Command Sync Data Sync

60 1553 Bus is actually 2 wires The first is Manchester described above The second is the complement of the first During Bus Quiet both lines are 0 volts Differential Signals

61 Less Dependent On Ground Less Susceptible To Spikes Advantages

62 Hi frequency signals are sensitive to reflection At the end of the Bus the signal cant continue and tries to Bounce Back This is caused by Lo Resistance wire meeting Hi Resistance air Bus Termination

63 1553 Topology Point A, A and B represent junctions We put Terminators on A and A to make the bus appear infinitely long This prevents signal reflection RT1RT2RT3BC B B B B A

64 B Junctions Represent BCs RTs and BMs Connection To The Bus Two Methods Are Permitted By The Spec Direct Coupling Transformer Coupling Coupling

65 Simple Point To Point Connection Maximum Stub Length Is 1 Foot (30cm) Direct Coupling

66 Uses An Isolation Stub Coupler Filters out DC and Noise Prevents all Reflections May Be Used For Up To 20 Foot (6 m) Stubs Transformer Coupling

67 Direct Coupling is convenient when: Used in a lab Connecting Two Boxes Directly The US Air Force Prohibits Direct Coupling on Aircraft


69 Software Applications Session 5

70 MIL-STD-1553 Applications l Systems Integration l RT Development l Problem Isolation l Post Flight Analysis

71 Run multiple RTs in Lab Some RTs may be ready some not Simulate Bus Controller and some RTs Simulate Bus timing and errors Monitor responses for timing, quality and correctness Systems Integration

72 Simulate BC for single message response Simulate other RT for RT to RT commands Inject errors to check response Alter intermessage timing for stress testing RT Development

73 Reconstruct Bus activity in lab Selectively simulate RTs Match bus timing taken from in flight record Perform regression testing Problem Isolation

74 Analyze flight data for: Health analysis – error statistics Throughput analysis Engineering data patterns Indirect data analysis i.e., data comprised of other units, e.g., acceleration = speed Δ / time Correlations between different data elements, e.g. temperature relative to altitude Post Flight Analysis


76 Thank You! Excalibur Systems Phone: Fax:

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