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MIL-STD-1553

MIL-STD-1553. David Koppel. Excalibur Systems. Introduction. Review of MIL-STD-1553 Specification WHY? What need does it fill WHAT? What does the spec say HOW? How is it implemented. First Session. General Background on Avionics Buses Different Approaches ARINC-429 MIL-STD-1553

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MIL-STD-1553

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  1. MIL-STD-1553 David Koppel ExcaliburSystems

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

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

  4. Second Session • Specification Details • Message Types • Mode Codes • Broadcast

  5. Third Session • Implementation Issues • Prioritizing Messages • Maximizing Throughput

  6. Fourth Session • Hardware Issues • Connections and Terminations • Using an Oscilloscope

  7. Fifth Session • Software Applications

  8. INTRODUCTIONTOAVIONICBUSES

  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 Passive Device Active and Passive

  11. First GenerationAnalog Devices One Device Altimeter Speedometer Compass One Display Gauge Gauge

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

  13. Wiring Diagram Altimeter Display Auto Pilot Engine Flight 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 ApplicationARINC-429 Wiring Multiple Device Missile # 1 Missile # 2 Missile # 3 Missile # 4 Multiple Sink Display Trigger Weapons Test Flight Recorder

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

  17. 1553 Advantages Low Weight Easy Bus Installation Easy to Add RT’s

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

  19. 1553 Problem Solution 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. Firewire / AS5643 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

  21. ARINC-664 Part 7 / AFDX 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

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

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

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

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

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

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

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

  29. Command Word 5 Bits 1 Bit 5 Bits 5 Bits 15 11 10 9 5 4 0 RT Address T/R Bit Subaddress Word Count

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

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

  32. Command Fields • 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

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

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

  35. Status Bit Fields • 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 can’t respond - discouraged by spec

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

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

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

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

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

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

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

  43. Session 3 • Implementation Issues • Timing • Major / Minor Frames • Implementation Examples

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

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

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

  47. Major Frame 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

  48. Minor Frames 10 Mill 10 Mill 10 Mill 10 Mill ABC AB A AB Some Messages Are High Priority We can alter frequency of specific messages

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

  50. RT’s in Test Self Test Button on Console RT2 Missile RT3 Heads Up Display (HUD) RT4

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