This document discusses FlexRay, an automotive network communication protocol used for data communication in vehicles and other transportation systems. FlexRay uses a cluster of electronic control units (ECUs) connected to a physical bus to allow deterministic and asynchronous message transmission. Each ECU contains a FlexRay controller that handles framing, bus access, and error detection according to the FlexRay specification. The document also discusses how FlexRay supports fixed and dynamic scheduling and is used in aircraft through data bus systems like ARINC 629 which uses time division multiple access and a standardized data word format to enable communication between avionics equipment.

2. Introduction
 Developed by FlexRay consortium to govern on-board
automotive computing.
 FlexRay: Automotive Network Communication
Protocol.
 FlexRay is a serial communication technology used for
data communication in transportation media. E.g.,
civil and military aircrafts, modern cars.

3. FlexRay Architecture
 FlexRay cluster: A FlexRay communication system is
made up of FlexRay nodes.
 FlexRay Bus : A physical transmission medium
interconnecting all the nodes.

4. FlexRay Node
 A FlexRay node is an electronic control unit(ECU).
 Connected to FlexRay Bus via FlexRay interface.
 Examples of ECUs are electro - hydraulic and electro
mechanical brake system.
 The FlexRay controller executes communication
protocol defined by FlexRay specification.
 FlexRay controller primary tasks are framing, bus
access, error detection and handling.

5. ABS : FlexRay Node

6. Architecture cont.
 FlexRay Cluster consists of several nodes and two
communication channels, channel A and channel B.
 Supports both bus and star
Topologies.
 Uses Time Division Multiple Access.

7. The Communication Cycle
 FlexRay communication cycle is the fundamental
element of the media-access scheme.
 The duration of a cycle is fixed when the network is
designed, typically it varies around 1-5 ms.
 There are 4 parts of communication cycle.

8. Communication Cycle Cont.
 Static Segment: Reserved slots for deterministic data
that arrives at a fixed period.
 Dynamic Segment: is used for a wider variety of
event-based data that does not require determinism.
 Symbol Window
Typically used for network maintenance and signaling
for starting the network.
 Network Idle Time
A known "quiet" time used to maintain
synchronization between node clocks.

9. FlexRay in modern Aircrafts.
 In analog avionic systems, number of cables were used
to transfer information between components.
 Hence, in modern avionics the signals are transmitted
on a single pair of wires which makes data bus.
 Aircraft data bus systems allow a wide variety of
avionics equipment to communicate with one another
and exchange data.

11. Data Bus.
 A bus is a collection of wires through which data is
transmitted from one part of system to another.
 All analog signals are converted to digital systems and
assigned unique address labels to ensure no conflicts.
 All buses consists of two parts an address bus and a
data bus. On aircraft two parts are incorporated within
a single word.
 A bus can be either serial or parallel. In avionics serial
communication is used.

12. ARINC 629
 ARINC 629 was introduced in May 1995 and is
currently used on the Boeing 777, Airbus A330 and
A340 aircraft.
 The ARINC 629 bus operates as a multiple-source,
multiple sink system.
 ARINC 629 can accommodate up to a total of 128
terminals and supports a data rate of 2Mbps.

13. ARINC 629 cont.
 It uses Time Division Multiple Access(TDMA).
 Each terminal is allocated a time slot to access the bus.
 It uses 20 bit data word format.
 First 3 bits are used for time synchronization.
 Next 16 bits are data contents and last bit is Parity.