Data required for

1. DATA BUS

2. DATA BUS

3. DATA BUS

4. DATA BUS
• Data buses are the principal means by which
information is exchanged among the navigation
and other systems
• They are the paths by which
– Necessary inputs are received by a system or
subsystem to perform its process(es) and
– Outputs from the process(es) are sent to users
• They are the foundation of modern integrated
avionics system

5. DATA BUS
• Data buses can be classified into two categories
– Simplex
• One way communication
• Has single transmitter and multiple receivers
– Duplex
• Two way communication
• Has multiple transmitters and receivers
• There are at least two possible transmission
media
– Wire or
– Optical cable

6. DATA BUS
• Other important features of data buses are
– Bus control
– Bit rate, and
– Word and message structure

7. DATA BUS
• They can be either
– Serial
• One bit of data transmitted at a time or
– Parallel
• Where often 8, 16 or 32 bits of data appear as a group on
a number of data lines at the same time
• Early data buses were
– Single-source, single-sink (point-to-point),
– Half-duplex (unidirectional) buses
– Relatively low data rates of the order (10 to 100 Kb)

8. OBJECTIVES OF DATA BUS
• To acquire data
• To use the data efficiently with minimal
processing loss
• Processing should be as per end user
requirements with precision, accuracy,
resolution and speed
• Flexibility of operation and feasibility of
expansion
• Reliable
• Economical

9. PROTOCOL OF DATA BUS
• Set of formal rules and conventions governing
the flow of information among the system
• Low level protocols define the electrical and
physical standards
• High level protocols deal with the data
formatting, including the syntax of messages
and its format

10. DATA BUS
• Aircraft data bus system allows number
of instruments and sensor to share the data with
each other or with the central Flight
Management System computer
• The bus architecture defines a protocol to
send/receive data as well as a common
interface
• A general depiction of instruments and data bus
system is as shown

11. DATA BUS

12. DATA BUS FOR
MILTARY AIRCRAFT
• For military aircraft the principal data bus is the
MIL-STD-1553
• It is a Time Division Command/Response
Multiplex data bus
• The standard describes
– Method of communication and
– Electrical interface for the subsystems connected in the
data bus

13. DATA BUS FOR
MILTARY AIRCRAFT
• Used in many types of military aircraft including
F-15, F-22 and C-17
• It is also been used on older generation aircraft as
a part of retrofitting upgraded avionics

14. MIL-STD-1553 DATA BUS
• There are three types of terminals on a
MIL-STD-1553 bus
– Bus controller
– Remote terminal (RT)
– Bus monitor
• Bus controller manages all activities on the bus
• It directs a designated RT to transmit a
message back to the bus controller or to
another designated RT

15. MIL-STD-1553 DATA BUS
• A RT is the interface between the bus and the
RT’s host system or subsystem
• It can be a separate line replaceable unit (LRU)
embedded in its host
• Bus monitor, if used records all messages on
the bus

16. BUS ARCHITECTURE

17. MIL-STD-1553A/B DATA BUS
• MIL-STD-1553B, superseded MIL-STD-1553A
• The basic difference between the 1553A and
1553B revisions is that in the latter, the options
are defined rather than being left for the user to
define as required
• It was found that when the standard did not
define an item, there was no coordination in its
use

18. MIL-STD-1553A/B DATA BUS
• Hardware and software had to be redesigned
for each new application
• The primary goal of the 1553B was to provide
flexibility without creating new designs for each
new user

19. MIL-STD-1553 SPECIFICATIONS
Data Rate 1 MBPS
Word Length 20 Bits
Message Length 32 Word Strings (Maximum)
Data Bits Per Word 16 Bits
Transmission Technique Half Duplex
Encoding Manchester II Bi-Phase
Protocol Command Response
Transmission Mode Voltage Mode

20. ?