Avionics

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AVIONICS

Avionics, Lecture, Ivan, 2011 1

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References

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«ARINC»:

www.arinc.com

Avionics Systems Standardization Committee: www.era.co.uk/assc

Avionics data buses:

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summary

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

Digital data buses



Development of DDB

 ARING 429  MIL-STD-1553B  ARINC 629 w w .O S T R O U M O V.c o.c c OS T R OUM O V I V AN

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Data Bus

, DB

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Data bus is a subsystem that transfers data between

computer components inside a computer or between

computers.

Consists of • Wire

• Information Packing equipment • algorithms and formats of data

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DB

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•inside LRU;

•Between LRU;

•Transmit data from sensors to system;

•Between systems. w w .O S T R O U M O V.c o.c c OS T R OUM O V I V AN

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6 Do you recall functional integration? www.OSTROUMOV.co.cc OSTROUMOV IVAN

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Distributed analog architecture

1950s, 1960s Lots of wire, no bus Very difficult to modify electro-mechanical parts heavy, large space, many pieces Boeing 707, VC10, DC-9, Boeing 737 w w .O S T R O U M O V.c o.c c OS T R OUM O V I V AN

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Distributed digital architecture

Digital systems, heavy, slow, difficult to reprogram

(AN/ALQ-162) Each component contains its own computer and memory

Uses a bus between components (less wire)

Each unit has a dedicated function Difficult to expand Boeing 737, 767 A330 (tanker),

Tornado, Sea Harrier

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Federated digital architecture

Systens communicate via a 1553B bus Additions are easy, only requires that the bus controller be reprogrammed

Can employ many buses to separate common equipment (ex : EW on the F-18 with its own MC)

www.OSTROUMOV.co.cc

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Integrated modular architecture

Interchangeable modules can realize diffrent system

functions

Permits on-board

repairs/swaps, that can automatically reconfigure

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Common types of serial digital data transmission are:

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Single source-single sink. This is the earliest application

and comprises a dedicated link from one piece of

equipment to another. This was developed in the 1970s for use on Tornado and Sea Harrier avionics systems.

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Common types of serial digital

data transmission are:



• Single source-multiple sink. This describes a

technique where one piece of transmitting

equipment can send data to a number of

recipient pieces of equipment (sinks). ARINC

429 is an example of this data bus which is

widely used by civil transport and business jets.

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Common types of serial digital

data transmission are:

 Multiple source-multiple sink. In this system, multiple

transmitting sources may transmit data to multiple

receivers. This is known as a full-duplex system and is widely employed by military users (M1L-STD-1553B) and by the B777 (ARINC 629).

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The major digital data buses in

widespread use today in avionics

are:

 ARINC 429 (A429).

 MIL-STD-1553B, also covered by UK Def Stan

00-18/Parts 1 and 2 and NATO STANAG 3838.

 ARINC629 (A629).

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SAE Standards

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AIR1189 Airborne Internal Interface Standards for Moderate Bit Rate Digital

Time Division - Multiplex Systems

AIR4013A Multiplex Data Bus Networks for Mil-Std-1760 Stores

ARP4258 Application of Low Speed Avionic System Discrete Signal Interfaces AS15531 Digital Time Division Command/Response Multiplex Data Bus

AS4075 High Speed Ring Bus (Hsrb) Standard

AS4075/1 Optical Implementation Relating to the High Speed Ring Bus (Hsrb)

Standard

AS4710 Pi-Bus

AS5370 Multi-Transmitter Bidirectional Fiber-Optic Data Bus for Distributed

Aircraft Control Systems

AS5643 IEEE-1394b Interface Requirements for Military and Aerospace

Vehicle Applications

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ARINC standards

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ARINC_{429. Digital Information Transfer System.}

Point-to-point, 2-wire Bi-Polar Return-to-Zero signal. 32 bit data. 100K or 12.5K bit rate.

ARINC _{629. Multi-Transmitter Data Bus. Serial data bus}

which operates over cable at 2Mbps. Developed by Boeing.

ARINC 659. Backplane Data Bus for IMA, operates at

60Mbps as a commercial aviation bus.

ARINC_{818. released in Jan. 07, is a video interface}

and protocol standard developed for high bandwidth, low latency, uncompressed digital video transmission.

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IEEE standarts

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IEEE_-std-1393

Spaceborne Fiber Optic Data Bus (SFODB); 1 Gb/s, fiber.

Std_1149.5

Standard for Module Test and Maintenance Bus (MTM-Bus)

Protocol.

IEEE₁₃₅₅

SpaceWire, based on the HIC (IEEE-1355) bus, and Low

Voltage Differential Signaling.

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Other buses include:

 Avionics Standard Communications Bus (ASCB), available in

several forms and based upon Ethernet protocols. ASCB was developed by Honeywell and is used in General Aviation (GA) and business jet applications.

 Commercial Standard Data Bus (CSDB) developed by

Rockwell Collins for use in GA applications.

 Avionics Full Duplex Ethernet (AFDX) based upon

commercial Fast Switched Ethernet (FDX) technology and adopted for the Airbus A380.

 In some applications, commercial RS 232 and RS 422 buses

are also used.

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Comparative DDB transmission rate

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1977

ARING 429

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Key attributes

 Simplex broadcast bus  Bit rates:

 'High Speed' 100kbps

 'Low Speed' 12 to 14.5kbps

 Encoding: return to zero bipolar tri-state modulation

 Message length: 32 bit word, 255 word data block in block transfer

mode

 Media access: simplex single source multiple sink plus full duplex  Topology: single source multiple sink either star or bus

 Number of nodes: 20 sinks, 1 source

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 The ARINC 429 specification defines the

requirements for a data transmission system based on the use of a single data source and reception of that data by up to 20 sinks or receivers. The

maximum number of receivers permitted for

connection to a source is limited by the specified minimum receiver input impedance.

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«Star» topology

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Bus drop topology

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Multiplex topology

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Full duplex link

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Return to Zero Bipolar Tri-state

Modulation

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 The signal has three states 'HI', 'NULL' and 'LO'

represented by the differential voltage between the two wires of the cable.

 A logical ‘1’ is signalled by transmission of a +10

±1V pulse followed by a 0±0.5V null period.

 A logical ‘0’ is signalled by transmission of a –10

±1V pulse also followed by a 0 ±0.5V null period.

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 Two ranges of transmission rate are defined.  'High Speed' at 100 kbps ±1% and

 'Low Speed' in the range 12 to 14.5 kbps.

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Word format

 ARINC 429 organizes data in 32 bit words.

 typical ARINC 429 word consisting of five parts: • Label

• Source/Destination Identifier (SDI) • Data field • Sign/Status Matrix (SSM) • Parity bit 30 www.OSTROUMOV.co.cc OSTROUMOV IVAN

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ARINC 429 Word Format

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Label (data name)(1-8)

 each sink is required to inspect the Label field which

is encoded in octal to represent the type of information contained within the 32-bit word.

 Each data item is assigned a label code listed in the

ARINC 429 specification and each source may have up to 255 Labels, assigned for its use.

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Source/ Destination Identifier (SDI)

 The SDI field contains just two bits.  The SDI’s functions are to:

 indicate the intended destination of the data on

a multi-sink bus

 identify the source of the data on a multi-source

bus (multi-system installation)

 to add an extension to the Label, in which case

receiving systems decode the Label/SDI combination.

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Data formats

 two’s complement binary data  BCD (2/10) data

 Discrete bits

 Maintenance data

 special Alphabet (Symbol and numeric)

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Sign/Status Matrix (SSM)

 It may be used to indicate sign information e.g. +, -,

compass direction etc. Each Label has its own unique implementation of the SSM Sign function.

 The SSM field may also be used to indicate the

source equipment status, operational mode or data validity.

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Parity

 The parity bit is set to impose odd parity on the

word.

 If even – mistake!!!!!

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1973

MIL-STD-1553B

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Key attributes

 Serial time division command response data bus  Bit rate: 1Mbps

 Encoding: baseband Manchester II bi-phase level  Message length: 1 to 32 16-bit words

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Структура MIL-STD-1553B

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A typical example

41 Note that a module can be both a bus controller and a remote terminal www.OSTROUMOV.co.cc OSTROUMOV IVAN

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Кодування кодом «Манчестер ІІ»

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Manchester Encoding

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Manchester on a twisted pair

44 Subtractor Signal www.OSTROUMOV.co.cc OSTROUMOV IVAN

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MIL-STD-1553B formats

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CW

 The standard defines three word formats  all words are 20 bit times long

 The Command Word is issued only by a bus

controller and is used to convey commands to RTs.

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CW (Bit times)

 1 – 3 are used for an invalid Manchester

synchronising pattern.

 4 – 8 contain the address of the RT that is to act on

the command (‘11111’ indicates a broadcast command).

 9 - the T/R bit, indicates to the receiving RT

whether it is to transmit (T/R = 1) or receive (T/R = 0) data words in response to the command.

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CW (Bit times)

 10 – 14, if set to ‘00000’ or ‘11111’, indicate that the

next 5 bits are to be interpreted as a mode code. If set to any other value they indicate a subaddress within the subsystem served by the RT that is to source or receive data.

 15 – 16 indicate either a mode code that requires the

RT to perform some control function (e.g. Reset, Initiate Self Test etc.) or the number of Data Words to be either received or transmitted by the RT.

 Bit 20 is a parity bit set for odd parity over the

previous 16 bits. 48

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Data Words

 Data Words may be transmitted either by the BC or

RT.

 Bits 1 – 3 are used for an invalid Manchester

 Bits 4 – 19 contain the data to be conveyed. Bit 20

is the parity bit.

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Status Words

 Status Words are transmitted only by RTs and are

used to indicate to the BC the state of the RT and the RT’s view of recent events on the bus. For

example, certain status bits are used to indicate

whether there is a fault in the subsystem or terminal and others the results of error checking, broadcast message reception and service request (latent

interrupt) conditions.

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Status Words

 Bit times 1 – 3 are used for an invalid Manchester

 Bits 4 – 8 contain the address of the RT transmitting

the Status word.

 Bits 9 – 11 and 15 – 19 are the status bits and bits

12 – 14 are reserved and unused (always ‘0’).

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Data Transfer Message Formats

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Принцип передачі даних MIL-STD-1553B

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Broadcast Message Formats

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Передача даних у широкомовному режимі

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B-777

ARINC

629

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Key attributes

 ARINC specification 629 Multi-transmitter Data Bus  Serial data bus with distributed media access.

 Bit rate: 2Mbps.

 Encoding: Manchester II bi-phase.

 Message length: up to 31 Word Strings each

containing one 16 bit label word and up to two hundred and fifty-six 16 bit data words

 Number of nodes: up to 120.

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ARINC

629 topology

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ARINC

629 topology

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ARINC 629 Message Structure

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Basic Protocol – Periodic Mode

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Передача повідомлень у ARINC 629

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