avionics buses
TRANSCRIPT
AVIONICS BUSES
Presented By:YASIR MUNIR
HAZIQ AMJAD
COLLEGE OF AERONAUTICAL ENGG.
AVIONICS ENGINEERING DEPTT.
TABLE OF CONTENTS
INTRODUCTION
• BUS
• EVOLUTION OF BUSES
• TYPES OF TRANSMISSION
TYPES OF AVIONIC BUSES
• ARINC 429
• ARINC 629
• MIL-STD 1553
• MIL-STD-1773
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BUSES
What is a BUS?
In computer architecture, a bus is a communication
system that transfers data between components inside a
computer, or between computers.
The specification for data transmission is drawn by
Aeronautical Radio, Incorporated (ARINC).
EVOLUTION OF AVIONICS BUSES
COMMON TYPES OF SERIAL DIGITAL DATA
TRANSMISSION ARE:
Single source-single sink
Single source-multiple sink
Multiple source-multiple sink.
SINGLE SOURCE-SINGLE SINK
Earliest application
Comprises a dedicated link from one piece of equipment
to another
Developed in the 1970s for use on Tornado and Sea
Harrier avionics systems
SINGLE SOURCE-MULTIPLE SINK
One transmitting source transmits 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.
MULTIPLE SOURCE-MULTIPLE SINK
Multiple transmitting sources transmits data to multiple
receivers.
This is known as a full-duplex system and is widely
employed by military users
(MIL-STD-1553B) and by the B777 (ARINC 629).
MAJOR DIGITAL DATA BUSES
ARINC 429
ARINC 629
MIL STD 1553
ARINC-429
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ARINC-429
Topology
Bit rates
Encoding
Word Format
Data Format
TOPOLOGY
&
BIT RATE
Single source multiple sink
Limitation of input impedance on no. of receivers
Maximum up to 20 receivers
Two ranges of transmission rates are defined
High Speed at 100 kbps ±1%
Low Speed in the range 12 to 14.5 kbps
BUS TOPOLOGY
STAR TOPOLOGY
ENCODING
The signal has three states 'HI', 'NULL' and 'LOW'
represented by the differential voltage between the two
wires of the cable.
A logical ‘1’ is signaled by transmission of a +10 ±1V
pulse followed by a 0±0.5V null period.
A logical ‘0’ is signaled by transmission of a –10 ±1V
pulse also followed by a 0 ±0.5V null period.
WORD FORMAT
Organizes data in 32 bit words
Typical word consisting of five parts:
Label
Source/Destination Identifier (SDI)
Data field
Sign/Status Matrix (SSM)
Parity bit
DATA
Two’s complement binary data
BCD (2/10) data
Discrete bits
Maintenance data
Special Alphabet (Symbol and numeric)
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LABEL
Encoded in octal
Each sink is required to inspect the Label field to
represent the type of information
Each data item is assigned a label code and each
source may have up to 255 Labels
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SOURCE/ DESTINATION
IDENTIFIER (SDI)
Contains just two bits
Main functions are to:
indicate the intended destination on a multi-sink bus
identify the source on a multi-source bus
add an extension to Label
SIGN/STATUS MATRIX (SSM)
&
PARITY
Indicate sign information
Unique implementation of the SSM Sign function
Indicate the source equipment status
Imposes odd parity on the word
If even – mistake!!!
ARINC 429
ARINC-629
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HISTORY
Relatively new and not widely used
Boeing Commercial Airplane Group (BCAG)
Digital Autonomous Terminal Access Communication
(DATAC) protocol
Recognized as an air transport standard by ARINC in
spec 629
Boeing 777
ARINC 629
Source transmits either broadcast or address specific
message to all or specific receiver or sinks
If the sinks equipment needs to reply, each will need to
be fitted with own transmitter and a specific physical bus
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BUS TOPOLOGY
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ARINC-629
Multi-transmitter Data Bus
Serial data bus with distributed media access
Bit rate
Encoding
Message length
Number of nodes
BIT RATE
&
ENCODING
2 Mbps
Bipolar Manchester doublets
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WORD FORMAT
A message has variable length and is comprised of up to
31 word strings
Each word string has variable length and contains
one (20 bit) label word
up to 256 (20 bit) data words
MESSAGE STRUCTURE
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Message
Max 31 word string /
gap 4 bits
Each label
20bits/label-12/ext-4/3 sync/1
parity
Each data word
20bits/ 16 data/ 3 sync/ 1
parity
Each word string
Label + 256 data words
ARINC-429 VS ARINC-629
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ARINC-429 VS ARINC-629
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ARINC-429 VS ARINC-629
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MIL-STD-1553
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HISTORY
Developed at Wright Patterson Air Force Base since
1970s
Published First Version 1553A in 1975
Introduced in service on F-15 Program
Published Second version 1553B in 1978
OVERVIEW
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1553A vs 1553B
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Data Rate
Message Length
Data Bits per Word
Transmission Technique
Encoding
Protocol
1 Mbps
32 Word Strings(maximum)
16 Bits
Half - Duplex
Manchester II Bi-phase
Transmission Mode
Word Length 20 Bits
Voltage Mode
Command Response
Operation Asynchronous
SPECIFICATIONS OVERVIEW
BUS CONTROLLER (BC)
REMOTE TERMINAL (RT)
BUS MONITOR (BM)
TRANSMISSION MEDIA
ELEMENTS
BUS CONTROLLER
Main function is to provide data flow control for all
transmissions on the bus.
It must transmit , receive and coordinate the transfer of
information on the data bus.
All information is communicated in command/response
mode - the BC sends a command to the RTs, which
replies with a response.
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REMOTE TERMINAL
Device designed to interface various subsystems with the
1553 data bus.
May be embedded within the subsystem itself, or be an
external interface to tie a non-1553 compatible device to
the bus.
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BUS MONITOR
Listens to all messages on the bus and records selected
activities
A passive device that collects data for real-time or post
capture analysis
Store all or portions of traffic on the bus, including
electrical and protocol errors
BMs are primarily used for instrumentation and data bus
testing
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TRANSMISSION MEDIA
BUS ARCHITECTURE
TRANSMISSION METHOD
Modulation
The signal shall be transferred over the data bus in
serial digital pulse code modulation form.
Data Code
Manchester II bi-phase level.
A logic one shall be transmitted as a
bipolar coded signal 1/0 (i.e., a positive pulse followed by a
negative pulse). A logic zero
shall be a bipolar coded signal 0/1 (i.e., a negative pulse followed
by a positive pulse).
A transition through zero occurs at the midpoint of each bit time
(see Figure 3-2).
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COMMAND WORD
DATA WORD
STATUS WORD
WORD FORMAT
19181716151413121110987654321 20
COMMAND WORD
SYNCTERMINAL
ADDRESS
T
R
SUBADDRESS
OR MODE
WORD COUNT
MODE CODEPARITY
19181716151413121110987654321 20
PARITY16 BIT DATASYNC
DATA WORD
19181716151413121110987654321 20
TERMINAL
ADDRESSSYNC
Messag
e E
rror
Instru
men
tatio
n
Serv
ice R
eq
uest
Reserved
Bu
sy
STATUS WORD
TERMINAL
ADDRESSSYNC
Messag
e E
rror
Instru
men
tatio
n
Serv
ice R
eq
uest
Reserved
Bu
sy
MIL-STD-1773
Optical cabling
Identical Data encoding and word formats
Exception
–Pulses are defined as transitions b/w 0 (off) and 1
(on)
–Not b/w + and - voltage transitions since light cannot
have a negative value
MIL-STD-1773
THANK YOU
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QUESTIONS?
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