The document discusses data hierarchy and the structure of data buses, including concepts of bits, bytes, words, fields, and records. It specifically details the ARINC 429 and ARINC 629 data buses used in avionics, highlighting their specifications, data transmission characteristics, and message structures. The ARINC 429 operates on a 32-bit serial bus with one-way data flow, while ARINC 629 can handle multiple terminals and supports higher data rates.

1. 5.4 DATA BUSES
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2. BITS, BYTES,WORD
• The traditional data hierarchy are:
– Bit – either 0 or 1
– Bytes – a collection of bits to make a character
– Word – a collection of bytes to have a meaningful
word.
– Field – a collection of words
– A record – a collections of field on a related
subject.
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3. Traditional Example – STUDENTS FILE
• Student’s File – consist of 100 records of student.
• A record – for example – information on a
student.
• Fields – example students name or address or
telephone number e.g Abraham Maslow
• Word – the name of a student e.g Abraham
• Bytes – e.g A is represented by 10000001
• Bit – either 0 or 1
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4. ARINC 429 DATA WORD
• In computing, word is the natural unit of data
used by a particular processor design.
• It is basically a fixed sized group of bits that
are handled as a unit by the instruction
• The number of bits in a word (the word
size, word width, or word length) is
determined by the computer architecture.
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5. INTRODUCTION TO DATA BUSES
• Data buses are used to transmit data from one
component to another.
• The buses can be electrical or fibre optic.
• The specification for data transmission is
drawn by ARINC.
• The standard used in aircrafts is the ARINC
429.
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6. ABOUT ARINC 429
• It defines how avionics equipment should talk
with each other.
• Defines the electrical and data characteristics and
protocol.
• A 32 bits serial bus with data flow in one
direction. If two directions are required, then two
sets of buses are required. (max 20 receivers)
• The signal uses three level -10v, 0 and +10v.
(measured between 2 wires)
• High speed 100k and low speed of 12-14k/sec
(cannot be mixed)
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7. ARINC 429 DATA WORD
• Five Basic Parts
– Label (e.g True air speed, TAT)
– Source /Destination Identifier (SDI)
– Data Field (bit 11-28)
– Sign Status Matrix (SSM) (e.g +, - , North)
– Parity Bit ( Odd parity)
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8. 8

9. DATA TRANSMISSION
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10. ARINC DATA WORD
1- 8 Label – information about the data
9-10 SDI – Source Destination Information
11-28 – Data
29-31 – SSM Sign Status Matrix
32 – Parity bit - sum of all logic is ODD
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11. DATA FORMAT
• It is using Bipolar return to zero (RZ)
modulation.
– The data in 3 states, hi, null, lo (1, null, 0)
– A 4 null period separate the words.
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12. DATA BUS
• Operates on one of the two speeds
– High - 100kbits/sec
– Low - 12.0kbits/sec
• Self clocking – the receiver receives the null
between the bits to generate its internal clock.
• Self synchronous – the 4 bits null is recognized
and used to generate word synchronisation.
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13. VOLTAGE LEVEL
• The voltage used is +10 , 0 and -10 volts.
• +10volts signifies logic 1 and (-10v) is logic 0
(obsolute voltage +- 5 )
• The second half of the bit is always null.
• The shield is grounded at both end of he wire.
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14. INSTALLATION
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15. 1977 => Boeing began to work on “DATAC”
project
1977 - 85 => DATAC Emerged as ARINC 629
1989 => ARINC 629 was adopted by AEEC
1990 => ARINC 629 was first implemented
in BOEING-777
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16. Triple-Triple Redundant
777 Primary Flight Computer
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17. Time Division Multiplex
Linear Bus
Multiple Transmitter Access
2 Mbps Data Rate
Current Mode Coupling
(Present implementation)
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18. ARINC 629
• ARINC 629 introduced in May 1995
• Used on B777, A330 andA340 .
• Multiple-source, multiple sink system
• Each terminal can transmit receive data
• ARINC 629 can handle total of 120 terminals
• It supports a data rate of 2 Mbps
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19. ARINC 629 SYSTEM - COMPONENTS
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20. ARINC 629 DATA BUS CABLE
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21. ARINC 629
BUS INSTALLATION BUS COUPLER
• Most of the wires are in • The coupler is used to
electronics compartment. connect the LRU to the data
This to enable the black bus.
boxes to talk to each other. • A maximum of 120 couplers
can be connected.
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22. 429 V 629 BUSES
• A pair if wire per link • Shared buses – max 120
• One way flow • Two ways
• Max 100kb • Max 2 mega
• Receiver max 20 • Receiver – max 120
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23. ARINC 629 MESSAGE STRUCTURE
Message
Max 31 word string /
gap 4 bits
Each word string
Label + 256 datawords
Each label Each data word
20bits/label-12/ext-4/3 syncro/1 parity 20bits/ 16 data/ 3 syn/ 1 parity
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24. MESSAGE STRUCTURE
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