unit3 avionics
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Unit 3, Digital Avionics
ArchitectureAvionics system architectureData
buses MILSTD 1553 BARINC429ARINC 629.
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Syllabus
Avionics system architecture
Data buses
MILSTD 1553 BARINC 429
ARINC 629.
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OSI Model
Data unit Layer Function
Hostlayers
Data 7. Application Network process to application
6. Presentation Data representation and encryption
5. Session Interhost communication
Segment 4. Transport End-to-end connections and reliability
Medialayers
Packet 3. Network Path determination and logical addressing
Frame 2. Data Link Physical addressing
Bit 1. Physical Media, signal
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Pave Pillar Architecture
An Hypothetical Architecture for an highperformance Aircraft
Which has the following performance
requirement1. Paying attention to take off and landing on
flight controls
2. Having Two level maintenance & that has
MTBF=70 Hrs & MTTR=1.25 hr3.High percentage of Fault Detection & Fault
Isolation=99 & 98%
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Major Avionic Architecture
Types, features and comparison
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Scheme of General Avionic ControlSystem
ACS
Effector To DisplaysFor Pilot Alerting
SensorsACS-Avionic Control System
Inputs from Sensor1.Positional Data2.Environmental data3.Aircraaft State Data
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Types
I. Federated Architecture= Dedicated& independent processing andcommunication system with no Data
Sharing eg. Arinc 429 and Saras of NAL
II. Integrated Modular Architecture- Areal time computer system with data
sharing between Sensors and Effectorsintegrated to flight control, landinggear, display control. - 1553 A/B eg.
Airbus & Arinc 629 (partially IMA & Fed)
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Features -Federated
1. Stand-alone independent system withsensors, processing units and Effectors
2. No Data Sharing between sensors,
effectors and processing units3. Each system having own interfaces
(CPU, I/O) to sensors and actuators
(Effectors)4. Functions partitioned
Eg. ARINC 429
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Federated Architecture Schematic
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Components of FederatedArchitecture
User Interface for controlling the Effector
3 CPU-s each CPU for Sensor, Effectors,
5 I/O modules 4 Physical Communication Channel (1.User
Interface to Effector, 2. UI to Sensor,
3.Sensor to Effector and 4. a Feedbackfrom Sensor to UI)
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Components of FederatedArchitecturecontd
1. User interface = landing gear,processing unit, display and control
2. Effector Used interface used forcontrolling the effector based uponfeedback collected from a sensor
3. Sensor
4. 3 Units connected by dedicatedcommunication channels.
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Advantages of Federated Architecture
Each Function has its own fault tolerantcomputer and each box has a specificfunction, with specifically developed
hardware and software
Failure of one function has no effect onthe other system
Every system is a stand alone system
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Disadvantages of FederatedArchitecture system
Developed from scratch, with the lack oftechnology re-use
Suffering from obsolescence issues for hardwarecomponents
Increased weight and power consumption
Hence increasing the weight of the aircraftresulting in poor fuel efficiency this introducesdedicated communication channels and also
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Integrated Modular Architecture
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Features of IMA
1. Sensor data shared between several systems2. In Core computer several modules identified
performing a specific function like the flight control,landing gear, display control, etc.
3. Multiple Federated application integrated into a singleplatform4. Strong Partitioning of Software & Two layer Software
Architecture5. Inter partitioning of Communication Facility & Client
Server inter partition Protocol6. Displaying of Status Messages7. Input/Output message handling by Message Handler
and System Executive
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Advantages of IMA
Each Avionic Computer has Open SystemInterface called Application Program Interface
API with Plug and Play
Flexible communication having a logical channeland communication channel
Flexibility in Hardware Architecture
All LRM lightening protected,EMC and
environmentally protected Fault Tolerance in IMA
Full Duplex Switched Ethernet
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Disdvantages of IMA
Specific function for each LRM ( autopilotmodule, flight management module notinterchangable)
Modules not field replacable
Multiple suppliers-not my problem
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Air crtafts using IMA
1. F22 Raptor
2. Airbus 380 & Airbus A400
3. Boeing 7874. Sukhoi Super Jet 100
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Two layer Software Architecture
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Examples of IMA architecture
Airbus A350
Airbus A380
Boeing 787 Dassault Falcon 900
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Comparison between IMA & Fed
1. Open Systemarchitecture with P&P
2. Fully Duplex
3.Only One CoreComputer
4. Field Replacable(LRM)except FM andAutopilot
5. Highly fuel efficient andlight weight
1. Closed Systemarchitecture with no P&P
2. Not Duplex
3. Many DistributedComputers
4. Not Field Replacable
5.Poor Fuel efficient andBulky.
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Aeronautical Standards
ARINC, 1553 1773
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Aeronautical Standards
ARINC-Aeronautical Radio Incorporated-Arinc 400 series and Arinc 600,700 and800 series, used by Boeing
MIL Military, MIL 1553 standard Airbus
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ARINC 429
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ARINC 429 in brief
An Old, Simplex, Dedicated I/O Opensystem
Point to Multipoint, Asynchronous system
Operate on both discrete and analogsignals
Sub Systems include FMS,ILS, VHF,Displaysystem
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ARINC-429
Unidirectional Bus operating at either 12.514.5 kbps or 100 kbps
A Simplex Bus ( one TX and manyReceivers)
No Bus Controller, RT, or Bus Monitorcontrary to 1553
ARINC use 32 Bit word with Odd Parity
Waveform for ARINC is RTZ Bipolar
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RTZ Bipolar Format
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ARINC Avionic Data Bus in Boeing
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Features of ARINC 429
A standard that communicates betweenavionics equipment and systemsconnected with Twisted Pair wires
Employs a Unidirectional Data BusStandard called Mark 33 DigitalInformation system
Data speed =12.5 or 100 kbps Transmission and reception on separate
ports so that many wires required
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ARINC 429 Architecture
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ARINC 429 INTERFACE thru RS232
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Word Format for Arinc 429
32 bit word by two wire transmissioncontaining 5 fields
Protocol= Point to Multi- Point Protocol
Has both low speed and high speed
Parity Bit = MSB
Five fields ; 2 for numerical data, 1 fordiscrete data, 2 for alphanumeric data
Data = BCD
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Arinc Word Format
32 BIT Format
1-8 for Label (type of Data-BCD)
9 & 10 for SDI ( Source DestinationIdentifier)-1 TX and 20 RX
11 to 29 Data
30 & 31 for SSM( Sign/Status Matrix) 32 for Parity
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Word Format for Arinc 429
3230 3181 9 10
0-32 bits for Arinc 4291-8 bit for Label
Bit 9 & 10 Station Identifier11-29 for Data
30 & 31 bit =Sign and Status BitBit 32 for Parity
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Arinc 429 Word Format
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Other ARINC Protocols
1. Arinc 419
2. Arinc 453 in Inertial Navigation system
3. Arinc 568 in Flight Recorder4. Arinc 619
5. Arinc 629 used in Boeing 777
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ARINC 629
General Features,Protocol Layer,TimingDiagram (Periodic and Aperiodic)
Comparison between 429 & 629
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General Features of ARINC 629
1. ARINC629- Multi transmitter to Multi receivers
2. ARINC 629 = two independent MAC protocolsfor communications across a 20 Mbps Serialdata bus
3. High Speed Bi directional Bus (used in latestBoeing 777)
4. ARINC 629- periodic and a-periodictransmissions
5.2 Protocols-Basic Protocol and Combinedprotocol;
6. Basic protocol for flight controls,
7. Combined protocol for flight managementsystem
8. No bus Controller required
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4 Protocol Layers of 629
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4 Protocol layers of Arinc 629
1.Physical layer- Layer-Main computational componentinteracting with shared memory, using 2 Mbps SerialData Transmission on Twister pair cable-
Multiple timers and circuitry employed for collisionavoidance on twisted pair cable with 20 Mbps serial
data 2.Data Link Layer-dealing with single source to many
terminals for data Using TDMA Has Basic Protocol and Combined protocol existing
individually in the same bus due to their differences. Using Collision Avoidance logic, for accessing a
channel across all terminals 3. Network Layer-dealing with networks for 20 bit
words upto 256 data words 4.Upper Layer-presenting application, session,
presentation and transport layer
l ( f l h
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Basic Protocol-BP ( for Flightcontrol)
CSMA/CA scheme defined in BP
Operate either on periodic or aperidic, butnot simultaneously
Variable 31 Word Strings
Used in Flight control long messagesdriving the bus from periodic to aperiodicmode
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Protocol Layer-contd
Basic Protocol (DL):All transmissions fixedfor periodic mode and individualtransmissions vary for a-periodic mode-
have Terminal Gap, Synchronization gap
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Combined Protocol-CP ( FMS system)
CAMA/CA defined in CP
Shortfalls in BP for Periodic and Sporadicdata transmissions.
Sporadic data serviced when all periodicdata have been completed
Unique TG pre-assigned
Periodic Data compressed into Burst,separated by TG
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Difference between BP & CP
BP CP
Transmitting either
Periodic or aperiodic
Transmitting both
periodic and aperiodicTerminals transmit atconst speed, if there isno overload
Terminals transmit atperiodic mode even ifthere is overload
If there is overload,data switched to a-periodic mode
Terminals given equalopportunity to switchfor overload
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ARINC 629 card
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Arinc 629 Interface
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Word Format for ARINC 629
20 bit word using CSMA/CA protocol
11 bits as Label
1 Bit for Parity 4 bits for CID
4 Bits for Synchronization(High Low
Synchronization)
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Word Format in Arinc 629
11911
12 15
11 to 1 Labels (numberedin reverse)
0
0 for Parity 12-15 for ChannelIdentification CID
16
16-19-4 bits for sync
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Channel Identification CID
629 messages -series of word strings
Label- the First word in a string (11-1)marked in reverse
Channel identification-the word stringafter a Label (12-15)
CID-to identify a unit in a word string
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Label Word
16 Bits assigned between Synchronizationbits and parity bit- are Labels
Synchronization bits to identify a Label
Word
Label bits numbered in reverse
3 Ti i C diti f ARINC 629
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3 Timing Conditions of ARINC 629to access a terminal
1. Transit timing condition T1- themoment the terminal starts transmitting-T1 starts
2. Synchronization gap-SG conditionSG-starts the moment the terminal isquiet
3. Terminal Gap condition TG-anunique timer assigned to the terminal;TG begins when SG is elapsed. TG & SGcannot overlap
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Timing diagram-Periodic mode
Constant T1
TnT2T1
Delay until T1 elapse
TG2 SG
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Timing diagram-Periodic mode
When terminal starts Transmission, T1timer starts
SG timer starts when the Bus is quiet
TG timer starts when SG has elapsed
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Timing Diagram-Aperiodic Mode
Variable T1
startstopT1 T2
Tn
SG
TG1 TG2TGn
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Comparison between 429 & 629
No
Parameter ARINC429
ARINC629
1 Architecture On Federated On IMA
2 Flow of Data Unidirectional
Simplex
Bi DirectionalDuplex
3 Word Size 32 bit in RTZ 20 bit word
4 Protocol SP-MP
Asynch.
Basic &Combined
MP-MP
Sync & Async
5 Transmission Speed 12.5 Kbps or
100 kbps
2 Mbps Serial
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1553 B
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1553 B Salient Features
A Serial TDMA 1 Mbps Data Bus commonly usedin Civil Aircrafts, ships, submarines
Using both Twisted Pair and Transformer forcoupling
3 Devices ( BC,RT & BM) to the bus, RT-standalone Unit
A dual redundant Balanced physical layer,Differential Network Interface, TDM, Half-duplex
command/response protocol witho 31 remoteterminals
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1553 A & 1553 B
1553 AMIL std, not fully defined fromthe user point
1553 Bfully defined from the user point
of view for both hardware and software-two types of Coupling (STP andTransformer) to the data bus
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1553 Block diagram
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1553 B in an Aircraft
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1553 Architecture
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1553 Bus Structure
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1) Bus controller- the Master Device responsiblefor directing the flow of data into the bus
2) Remote Terminal-responsible for receiving
the data and storing the data for flight test,maintenance and mission analysis
3) Bus Monitor-Responding to the commandsaddressed to Bus Monitor where 31 RT-s
connected, but cannot transmit data
Architecture of 1553 B
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Architecture of 1553 B
RemoteTerminal 1
RemoteTerminal 2
RemoteTerminal 3
Bus Monitor
Channel A
Channel B
BUSCO
N
Data Encoding in 1553 B-
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Data Encoding in 1553 B-Manchestor
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Industry MIL Standard 1553 B
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Components of 1553 B
A dual-redundant MIL-STD-1553B busA Bus Controller responsible for initiating
message communication over the bus, detectingand correcting errors
Three Remote TerminalsResponsible foracquiring data from one Subsystem andtransferring to another subsystem(eg, data frominertial navigation to cockpit display)
A Bus Monitor-Responsible for monitoring alltransactions over the bus and storing the datafor later analysis, but does not transmit
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Technical Features of 1553 B
Data Speed 1 Mbps
Data Encoding by Manchestor
Modulation of data by PCM
Access by TDMA
Data Size=16 bit word
3 types of data transfers between RT andBC
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Types of Data Transfer in 1553 B
Bus Controller to Remote Terminal- BC toRT
Remote Terminal to Bus Controller-RT to
BC
Remote Terminal to Remote Terminal- RTto RT
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1553 B Bus Controller Summary
Supporting 128 kBytes memory
Synchronous or Asynchronous interface
Clock rate 12, 14, 16 or 24 MHz
Verilog Source Code
Use Ma nchestor Encoding
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Components of 1553B
1. Encoder/Decodeer-input serial data usingManchestor coding with 12,16 or 24 Mhzclock
2. Protocol Controller for messagesequencing and error control
3. CPU access the Block controller withinthe system
4. Backend interface enabling theconnection to a memory device
Simple Remote Terminal ( Redundant
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Simple Remote Terminal ( RedundantBus)
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Word Format of 1553B
3 Types of Words in 1553 B of 20 bitswith 3 bits for synchronization, 16 bitsdata and 1 bit for parity
1. Command Word CW transmitted by BC
2. Status Words SW transmitted by RT
3. Data Word DW transmitted by BC or RT
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1553 B Bus Word Format
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Status Word=20 bits(Tx by BC)
Transmitted by RT from BC
3 bit-time sync pattern (same as for acommand word)
16 bits for Data in Status
1 parity check bit.
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Status Word=20 bits
1163
One word=20 Bits
Sync Data Parity
d d ( b )
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Command Word ( Tx by BC)
20 bit word Transmitted by Bus Controller ofwhich (no BC address)
3 bits for sync using Manchestor coding 5 bits for address of RT
1bit Transmit/Receive (T/R) indicating datadirection (T means Data recd by RT)
5 bits for sub address under RT address tomemory etc
5 bit for data word count,indicating the wordcount after the sub address. 1 bit for parity check (using Odd parity)
Command Word ( Transmitted by
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Command Word ( Transmitted byBC)
One Command word=20 Bits
35 1 5 5 1
Sync RT Address T/R Sub address Word Count Parity
D W d (b RT/BC)
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Data Word (by RT/BC)
20 bit Data Word transmitted by RT or BCagainst a BC request
3 bits for sync pattern (opposite in
polarity from command and status words)
16 bit for data field
1 bit for parity check bit.
D t W d ( T b RT/BC)
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Data Word ( Tx by RT/BC)
3 16 1
Sync Data Parity
Di ti ti b t 629 & 1553
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Distinction between 629 & 1553No Description 629 1553
1 Architecture IMA IMA
2 Word Format in Sync &
Parity
RTZ
Odd
Manchestor
Odd
3 Terminals on Data Bus 2(RT & BM) 3 (RT,BC,BM)
4 Coupling by STP STP&Transformer
5 Data System & speed Multiplex
2 Mbps
Multiplex
1 Mbps
6 Data Word Size 20 Bit 16 bit