M. S. Ramaiah School of Advanced Studies 1

M. Sc. (Engg.) in Electronics System Design

Engineering

GREESHMA SCWB0913004 , FT-2013

8th Module Presentation

Module code : ESE2512

Module name : Data Communication and Networks

Module leader : Ms. Nireeksha

Presentation on : 14/07/2014

FlexRay

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• INTRODUCTION

• FLEXRAY ARCHITECTURE

• FLEXRAY FRAME FORMAT

• COMPARISON : OVERVIEW

• FLEXRAY : ACCESS SCHEME

• FLEXRAY V2.1 AND V3.0

• FLEXRAY V3.0 : TT-E

• FLEXRAY : WAKEUP

• FLEXRAY : APPLICATIONS

• FLEXRAY : ROADMAP

• CONCLUSION

Overview

• REFERENCES

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Introduction

►FlexRay is an automotive network communications

protocol developed by the FlexRay Consortium to govern on-board

automotive computing

►It is designed to be faster and more reliable than CAN and TTP,

but it is also more expensive

►VisualSim FlexRay library enables a system designer to

construct models of complex standard and non-standard FlexRay

topologies

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Figure 1: Layered structure of

FlexRay communication node

►The Physical layer defines how signals are actually

Transmitted

►The transfer layer is responsible for timing,

synchronization, message framing, error detection and

signaling, and fault confinement

► The presentation Layer is concerned with frame

filtering and masking, frame status handling and

contains the communication controller host interface

► The Application Layer is a user-programmed

application for expected operations

Layered Architecture of the FlexRay

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FlexRay: Architecture of Node

Figure 2 : FlexRay architecture

►MCU: Microcontroller

►CC: FlexRay Communication Controller: • embedded (e) • standalone (s)

►BD: FlexRay Bus Driver

►AS: FlexRay Active Star

►Cabling: twisted pair unshielded

►Two channels

►Topology: bus or star

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►Frame ID is a identifier, which is 12 bits, and defines the slot position in the static segment

and the priority in the dynamic segment

►H-CRC is a Cyclic Redundancy Check, which is 9 bits, and is calculated over the SYNC and

DLC field

►NF is a Null Frame field, which is 1 bit, and indicates whether the corresponding data buffer

is not updated by the host before sending

►CYCO is a Cycle Counter, which is 6 bits, and is increased simultaneously in all nodes by the

controller at the start of each new communication cycle

Figure 3 : FlexRay frame format

FlexRay frame format

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Comparison: Overview

Table 1 : Comparison

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FlexRay : Access Scheme

►Static Segment: Slots with fixed length. Fixed assignment between slots and nodes

Time division multiple access: TDMA

►Dynamic Segment: Minislots with fixed length. Minislots can be combined to contain

frames with variable length. No fixed assigned between slots and nodes

►Max. payload per frame (static and dynamic segment): 254 bytes

►Symbol Window: Used for wake-up symbols

►Network Idle Time (NIT): Clock correction

Figure 4 : FlexRay Access Scheme and flexray communication cycle example

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►Coldstart/sync node: Dedicated node for startup of the FlexRay cluster + providing sync

frames

►FlexRay V2.1: At least two coldstart nodes are required

►FlexRay V3.0: Single special coldstart node is allowed (TT-L node)

FlexRay V2.1 and V3.0

Figure 5 : FlexRay V2.1 and V3.0 Versions

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FlexRay V3.0: TT-E

►Single gateway node connects both FlexRay clusters

►Gateway node: time gateway source node + time gateway sink node

►Time gateway interface: Clock synchronization

►Time gateway sink node: TT-L node, i.e., single node which drives synchronization in

sink cluster

Figure 6 : FlexRay V3.0

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FlexRay V3.0: TT-E

►Same cycle length in both clusters

►Fixed cycle offset between clusters

►Clusters can have different schedules

Figure 7 : FlexRay V3.0

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FlexRay V3.0: Wake-up

►FlexRay V2.1: Wake-up before startup/communication only

►FlexRay V3.0: Wake-up also during operation possible: WUDOP

Figure 8 : FlexRay V3.0 : Wake-up

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FlexRay : Applications

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FlexRay : Roadmap

Figure 9 : FlexRay Roadmap

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Conclusion

►FlexRay:

•Built-in time triggered: deterministic communication

•V3.0: downward compatible + interesting new features

•Best for medium data rates (~10 Mbit/s)

►CAN:

•Event triggered, not deterministic

•Best for low data rates (~1 Mbit/s)

•Extensions available

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Reference

1. Paret, D. (2012) Flexray And Its Applications. 1st edn. Hoboken, NJ: Wiley

2. Anon. (2010) available from <http://Flexray> [13 July 2014]

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Thank You