The document discusses digital data buses used in avionics systems. It describes several common data bus architectures, including single source-single sink, single source-multiple sink, and multiple source-multiple sink. It then discusses three major digital data buses used in avionics: ARINC 429, MIL-STD-1553B, and ARINC 629.

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Avionics, Lecture, Ivan, 2011 1
AVIONICS
Digital data buses

2. References
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«ARINC»:
www.arinc.com
Avionics Systems Standardization Committee:
www.era.co.uk/assc
Avionics data buses:
http://www.interfacebus.com/Design_Connector_Avionics.html
Avionics, Lecture, Ivan, 2011

3. summary
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 Digital data buses
 Development of DDB
 ARING 429
 MIL-STD-1553B
 ARINC 629
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4. Data Bus, DB
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Data bus is a subsystem that
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transfers data between
computer components inside
a computer or between
computers.
Consists of
• Wire
• Information Packing equipment
• algorithms and formats of data
transition
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5. DB
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•inside LRU;
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•Between LRU;
•Transmit data from sensors to system;
•Between systems.
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Do you recall
functional
integration?
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7. Distributed analog architecture
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1950s, 1960s
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Lots of wire, no
bus
Very difficult to
modify
electro-
mechanical
parts
heavy, large
space, many
pieces
Boeing 707,
VC10, DC-9,
Boeing 737
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8. Distributed digital architecture
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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
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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)
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Integrated modular architecture
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Interchangeable modules can
realize diffrent system
functions
Permits on-board
repairs/swaps, that can
automatically reconfigure
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11. 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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12. Common types of serial digital
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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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13. Common types of serial digital
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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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Avionics, Lecture, Ivan, 2011

14. The major digital data buses in
widespread use today in avionics
are:
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 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.
IEEE 1355
SpaceWire, based on the HIC (IEEE-1355) bus, and Low
Voltage Differential Signaling.
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Other buses include:
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 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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20 ARING 429
1977
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Key attributes
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 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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27. Return to Zero Bipolar Tri-state
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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
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 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
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ARINC 429 Word Format
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Label (data name)(1-8)
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 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)
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 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
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 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)
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 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
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 The parity bit is set to impose odd parity on the
word.
 If even – mistake!!!!!
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38 MIL-STD-1553B
1973
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Key attributes
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 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
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Note that a
module can be
both a bus
controller and a
remote terminal
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Кодування кодом «Манчестер ІІ»
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Manchester Encoding
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Manchester on a twisted pair
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Signal
Subtractor
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MIL-STD-1553B formats
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CW
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 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)
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 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)
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 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.
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Data Words
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 Data Words may be transmitted either by the BC or
RT.
 Bits 1 – 3 are used for an invalid Manchester
synchronising pattern.
 Bits 4 – 19 contain the data to be conveyed. Bit 20
is the parity bit.
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Status Words
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 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
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 Bit times 1 – 3 are used for an invalid Manchester
synchronising pattern.
 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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56 ARINC 629
B-777
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Key attributes
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 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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60. 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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