ISO 17458-1:2013

INTERNATIONAL ISO
STANDARD 17458-1
First edition
2013-02-01
Road vehicles— FlexRay
communications system —
Part 1:
General information and use case
definition
Véhicules routiers — Système de communications FlexRay —
Partie 1: Information générale et définition de cas d'utilisation

Reference number
©
ISO 2013
©  ISO 2013
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ii © ISO 2013 – All rights reserved

Contents Page
1 Scope . 1
2 Terms, definitions, symbols and abbreviated terms . 1
2.1 Terms and definitions . 1
2.2 Abbreviated terms . 4
3 Conventions . 4
4 Document overview . 4
4.1 General . 4
4.2 Document overview and structure . 5
4.3 Open Systems Interconnection (OSI) model . 5
4.4 Document reference according to OSI model . 6
5 Use case overview and principles . 7
5.1 Basic principles for use case definition . 7
5.2 Use case clusters . 7
6 FlexRay communications system use case definition . 8
6.1 UC 1 FlexRay processes . 8
6.2 UC 2 TT modes in clusters . 11
6.3 UC 3 Communication protocol . 17
6.4 UC 4 Electrical physical layer . 20

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17458-1 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3,
Electrical and electronic equipment.
ISO 17458 consists of the following parts, under the general title Road vehicles — FlexRay communications
system:
 Part 1: General information and use case definition
 Part 2: Data link layer specification
 Part 3: Data link layer conformance test specification
 Part 4: Electrical physical layer specification
 Part 5: Electrical physical layer conformance test specification
iv © ISO 2013 – All rights reserved

Introduction
The FlexRay communications system is an automotive focused high speed network and was developed with
several main objectives which were defined beyond the capabilities of established standardized bus systems
like CAN and some other proprietary bus systems. Some of the basic characteristics of the FlexRay protocol
are synchronous and asynchronous frame transfer, guaranteed frame latency and jitter during synchronous
transfer, prioritization of frames during asynchronous transfer, single or multi-master clock synchronization,
time synchronization across multiple networks, error detection and signalling, and scalable fault tolerance.
The FlexRay communications system is defined for advanced automotive control applications. It serves as a
communication infrastructure for future generation high-speed control applications in vehicles by providing:
 A message exchange service that provides deterministic cycle based message transport;
 Synchronization service that provides a common time base to all nodes;
 Start-up service that provides an autonomous start-up procedure;
 Error management service that provides error handling and error signalling;
 Wakeup service that addresses the power management needs;
Since start of development the automotive industry world-wide supported the specification development. The
FlexRay communications system has been successfully implemented in production vehicles today.
The ISO 17458 series specifies the use cases, the communication protocol and physical layer requirements of
an in-vehicle communication network called "FlexRay communications system".
This part of ISO 17458 has been established in order to define the use cases for vehicle communication
systems implemented on a FlexRay data link.
To achieve this, it is based on the Open Systems Interconnection (OSI) Basic Reference Model specified in
ISO/IEC 7498-1 and ISO/IEC 10731, which structures communication systems into seven layers. When
mapped on this model, the protocol and physical layer requirements specified by ISO 17458 are broken into:
 Diagnostic services (layer 7), specified in ISO 14229-1 [3], ISO 14229-4 [5];
 Presentation layer (layer 6), vehicle manufacturer specific;
 Session layer services (layer 5), specified in ISO 14229-2 [4];
 Transport layer services (layer 4), specified in ISO 10681-2 [1];
 Network layer services (layer 3), specified in ISO 10681-2 [1];
 Data link layer (layer 2), specified in ISO 17458-2, ISO 17458-3;
 Physical layer (layer 1), specified in ISO 17458-4, ISO 17458-5;
in accordance with Table 1.
Table 1 — FlexRay communications system specifications applicable to the OSI layers
ISO 17458 FlexRay communications Vehicle manufacturer enhanced
Applicability OSI 7 layers
system diagnostics
Application (layer 7)
vehicle manufacturer specific ISO 14229-1, ISO 14229-4
Presentation (layer 6) vehicle manufacturer specific vehicle manufacturer specific
Seven layer
Session (layer 5)
vehicle manufacturer specific ISO 14229-2
according to
ISO 7498-1
Transport (layer 4)
vehicle manufacturer specific
and
ISO 10681-2
ISO/IEC
Network (layer 3)
vehicle manufacturer specific
Data link (layer 2)
ISO 17458-2, ISO 17458-3
Physical (layer 1)
ISO 17458-4, ISO 17458-5
Table 1 shows ISO 17458 Parts 2 – 5 being the common standards for the OSI layers 1 and 2 for the FlexRay
communications system and the vehicle manufacturer enhanced diagnostics.
The FlexRay communications system column shows vehicle manufacturer specific definitions for OSI layers
3 – 7.
The vehicle manufacturer enhanced diagnostics column shows application layer services covered by
ISO 14229-4 which have been defined in compliance with diagnostic services established in ISO 14229-1, but
are not limited to use only with them. ISO 14229-4 is also compatible with most diagnostic services defined in
national standards or vehicle manufacturer's specifications. The presentation layer is defined vehicle
manufacturer specific. The session layer services are covered by ISO 14229-2. The transport protocol and
network layer services are specified in ISO 10681.

vi © ISO 2013 – All rights reserved

INTERNATIONAL STANDARD ISO 17458-1:2013(E)

Road vehicles — FlexRay communications system — Part 1:
General information and use case definition
1 Scope
This part of ISO 17458 gives an overview of the structure and the partitioning of ISO 17458 and shows the
relation between the different parts. In addition, it outlines the use case scenarios where the ISO 17458 series
will be used. The terminology defined in this part of ISO 17458 is common for all FlexRay communication
systems and is used throughout all parts of ISO 17458.
2 Terms, definitions, symbols and abbreviated terms
2.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1.1
active star
AS
active element which passes bus signals automatically from one input port to several output ports, where
usually a passive net is plugged to each port
NOTE1 An AS refreshes the bus signal slopes and levels; an AS does not refresh the bit-timing.
NOTE2 An AS may be implemented in a monolithic way or a non-monolithic way.
NOTE3 Optionally an AS may have a CC interface included.
2.1.2
branch
component within active star topologies
NOTE A branch can be built from a point-to-point connection, a linear bus or a passive star.
2.1.3
bus driver
BD
physical interface between the CC and the wiring harness
NOTE A BD is a mandatory FlexRay component that converts the data stream of the physical interface and supports
the node with a power mode controlling optionally.
2.1.4
cable
FlexRay transmission line.
2.1.5
cluster
communication system of multiple nodes connected via at least one communication channel directly (bus
topology), by active stars (star topology) or by a combination of bus and star connections (hybrid topologies)
NOTE Clusters can be coupled by gateways.
2.1.6
communication channel
node connection through which signals are conveyed for the purpose of communication
NOTE FlexRay allows a single CC to distribute data-frames independent from each other on two different hardware
paths or topologies. From an abstract view each path is named “communication channel” (short: "channel"). The two
channels are distinguished by using the extensions "A" and "B".
2.1.7
communication controller
CC
electronic component in a node that is responsible for implementing the protocol aspects of the FlexRay
communications system
2.1.8
communication element
symbol and frame
NOTE FlexRay distinguishes two types of communication elements which can be transmitted on the communication
channel: symbols and frames.
2.1.9
communication cycle
one complete instance of the communication structure that is periodically repeated to comprise the media
access method of the FlexRay system
NOTE The communication cycle consists of a static segment, an optional dynamic segment, an optional symbol
window, and a network idle time.
Figure 1 illustrates the segmentation of a communication cycle during FlexRay´s normal operation.
communication cycle
... ...
static dynamic symbol network
segment segment window idle time
time
Figure 1 — Segmentation of a communication cycle during normal operation

The static segment is configured into a selectable number of static slots. The segmentation in the time domain is based on
FlexRay´s distributed clock. FlexRay frames are transmitted synchronously during these static slots.
The dynamic segment is configured into mini slots. They support prioritised event driven transmission of FlexRay frames.
The symbol window is used to transmit FlexRay symbols which support e.g. wake-up of a FlexRay communication system.
The network idle time is used for clock correction.
2 © ISO 2013 – All rights reserved

2.1.10
gateway
node that is connected to two or more independent communication networks that allows information to flow
between the networks
2.1.11
host
part of an ECU where the application software is executed, separated by the CHI from the FlexRay protocol
engine
NOTE The host offers interfaces which enable the application software to control the CC and the BD.
2.1.12
hybrid topology
design of a communication cycle using various topology components
EXAMPLE An AS with one branch as point-to-point connection, one branch as linear bus and one branch as passive
star.
2.1.13
passive net
summary of all possible implementations of passive connections among FlexRay BDs and Ass
NOTE A passive summarizes all point-to-point connections, linear busses and passive stars.
2.1.14
physical layer
BDs, ASs, CC I/O stages, cables, connectors, common mode filters, ESD protection circuits, termination
networks etc.
NOTE All timing relevant hard-ware components are included which are needed to transfer communication elements
among the protocol machines.
2.1.15
point-to-point
two terminated FlexRay nodes which are linked by a single FlexRay cable without any stub
2.1.16
splice
implementation of a connection-point where 3 or more transmission lines are plugged together.
NOTE A splice may contain passive components to damp radiation, e.g.a splice in a linear bus allows connecting a
stub to a FlexRay node.
2.1.17
stub
single FlexRay cable connected to the centre of a passive star or to a linear bus (short: plugged to a splice)
NOTE1 A stub represents a component within passive nets. A stub consists of a single FlexRay cable connected to
the centre of a passive star or to a linear bus (short: plugged to a splice).
NOTE2 The stub ends at the BD pins within an FlexRay node.
2.1.18
topology
distributed FlexRay system which consists of several components like nodes, busses, active and passive
stars etc.
NOTE The topology represents the non-hierarchical flat geometric structure of a FlexRay communication channel.
2.1.19
wiring harness
summary of all components inside the component “vehicle wiring harness” to transmit FlexRay communication
elements
NOTE The FlexRay wiring harness consists of
 connectors to plug ECUs,
 in-line connectors,
 cables,
 splices etc.
2.2 Abbreviated terms
AM amplitude modulation
AS active star
BD bus driver
BD/AS bus driver or active star
CC communication controller
CW continuous wave
ECU electronic control unit
EMC electromagnetic compatibility
EPL electrical physical layer
ESD electro static discharge
SAP service access point
3 Conventions
ISO 17458, ISO 10681 [1] and ISO 14229-4 [5] are based on the conventions specified in the OSI Service
Conventions (ISO/IEC 10731) [2] as they apply for physical layer, protocol, network & transport protocol and
diagnostic services.
4 Document overview
4.1 General
ISO 17458 has been established in order to define common requirements for vehicle communication systems
implemented on a FlexRay communication data link.
4 © ISO 2013 – All rights reserved

4.2 Document overview and structure
The ISO 17458 series provides an implementer with all documents and references required to support the
implementation of the requirements related to.
 Part 1: General information and use case definitions
This part provides an overview of the document set and structure along with the use case definitions and
a common set of resources (definitions, references) for use by all subsequent parts.
 Part 2: Data link layer specification
This part specifies the requirements for implementations of the FlexRay protocol on the logical level of
abstraction. Hardware related properties are hidden in the defined constrains.
 Part 3: Data link layer conformance test specification
This part specifies tests to check the compliance of a given protocol implementation (logical level of
abstraction) to the Data link layer specification.
 Part 4: Electrical physical layer specification
This part specifies the requirements for implementations of active hardware components which are
necessary to interconnect several distributed protocol implementations. Requirements for necessary
passive components are specified partly.
 Part 5: Electrical physical layer conformance test specification
This part specifies tests to check the compliance of a given active hardware component implementation
to the electrical physical layer specification.
4.3 Open Systems Interconnection (OSI) model
ISO 17458 is based on the Open Systems Interconnection (OSI) Basic Reference Model as specified in
ISO/IEC 7498 which structures communication systems into seven layers.
All parts of ISO 17458 are guided by the OSI service conventions as specified in ISO/IEC 10731 to the extent
that they are applicable to diagnostic services. These conventions define the interaction between the service
user and the service provider through service primitives.
The aim of this subclause is to give an overview of the OSI model and show how it has been used as a
guideline for this part of ISO 17458. It also shows how the OSI service conventions have been applied to
ISO 17458.
The OSI model structures data communication into seven layers called (top down) Application layer (layer 7),
Presentation layer, Session layer, Transport layer, Network layer, Data Link layer and Physical layer (layer 1).
A subset of these layers is used in ISO 17458.
ISO 17458 specifies data link layer and physical layer for the FlexRay communications system.
The purpose of each layer is to provide services to the layer above. The active parts of each layer,
implemented in software, hardware or any combination of software and hardware, are called entities. In the
OSI model, communication takes place between entities of the same layer in different nodes. Such
communicating entities of the same layer are called peer entities.
The services provided by one layer are available at the Service Access Point (SAP) of that layer. The layer
above can use them by exchanging data parameters
ISO 17458 distinguishes between the services provided by a layer to the layer above it and the protocol used
by the layer to send a message between the peer entities of that layer. The reason for this distinction is to
make the services, especially the application layer services and the transport layer services, reusable also for
other types of networks than FlexRay. In this way the protocol is hidden from the service user and it is
possible to change the protocol if special system requirements demand it.
4.4 Document reference according to OSI model
Figure 2 illustrates the document references.
ISO 17458-1
FlexRay communications
system - General
information and
use case definition
Vehicle Manufacturer
Enhanced Diagnostics
specific
ISO 14229-1 UDS Vehicle
ISO 14229-4
subset
Specification and manufacturer
OSI Layer 7
UDSonFR
requirements specific
Application
Vehicle Vehicle
manufacturer manufacturer
OSI Layer 6
specific specific
Presentation
ISO 14229-2 UDS ISO 14229-2 UDS Vehicle
1 : 1
Session layer Session layer manufacturer
OSI Layer 5
services services specific
Session
Standardized Service Primitive Interface
FlexRay communications system
Vehicle
manufacturer
OSI Layer 4
specific
Transport
ISO 10681-2
Communication on
FlexRay –
Communication
layer services
Vehicle
manufacturer
OSI Layer 3
specific
Network
ISO 17458-3
ISO 17458-2
FlexRay
FlexRay
communications system
communications system
– Data link layer
OSI Layer 2
– Data link layer
conformance test
Data Link
specification
specification
ISO 17458-5
ISO 17458-4
FlexRay
FlexRay
communications system
communications system
OSI Layer 1
- Electrical physical
- Electrical physical
Physical
layer conformance test
layer specification
specification
Figure 2 — FlexRay document reference according to OSI model
6 © ISO 2013 – All rights reserved

5 Use case overview and principles
5.1 Basic principles for use case definition
Basic principles have been established as a guideline to define the use cases:
 pointing out features which support usual operating modes of networked systems in OEMs products;
 pointing out features which support future expected properties of networked systems in OEMs products;
 comparing the contrast between normal operating functionalities in the absence of errors and limp-home
operation functionalities in the presence of errors;
 distributed applications inside vehicles expect completely different properties of their interconnecting
networks. FlexRay systems are allowed being implemented and parameterized by taking use of various
features. These stress fields are reflected by several use cases.
5.2 Use case clusters
This chapter defines use case clusters of the FlexRay communications system.
Table 2 provides an overview of the main FlexRay use case clusters. A main FlexRay use case cluster may
have one or more use case definition.
Table 2 — FlexRay communications system main use case clusters
# Main title of use case cluster Brief description
1 FlexRay processes The purpose of these use cases requires basic functionalities of a FlexRay
system when being built in vehicles and when being used for the distribution of
application data during the various operating modes of vehicles.
2 TT-D, TT-L and TT-E clusters The purpose of these use cases is the description of various methods to
provide a common time base to all FlexRay nodes communicating among each
other.
3 Communication protocol The purpose of these use cases is the description of the protocol driven
property range of systems and applications when using FlexRay for their
internal communication.
4 Electrical physical layer The purpose of these use cases is the description of the electrical physical
layer properties when interconnecting the logical links of the distributed
FlexRay ECUs by electrical hardware components inside a vehicle.

6 FlexRay communications system use case definition
6.1 UC 1 FlexRay processes
6.1.1 UC 1.1 Execute normal communication cycle
Table 3 specifies the use case to execute normal communication cycle.
Table 3 — UC 1.1 Execute normal communication cycle
Actor
Communication module
Goal Run the communication and the observation procedures during the communication cycle (static
segment, the dynamic segment, the symbol window and the network idle time).
Use case input
Start-up complete
Use case output Data stream to and from the logical link (physical layer) ,
data stream to and from the host,
control stream to and from the host.
Brief description The use case includes the detailed functionality, behaviour and data structures of FlexRay in its
main operating mode when running the communication cycle. Examples are:
 receive communication elements;
 transmit communication elements.
The complete functionality is implemented inside the communication controller.

6.1.2 UC 1.2 Check for wakeup condition
Table 4 specifies the use case to check for wakeup condition.
Table 4 — UC 1.2 Check for wakeup condition
Actor
Bus driver module
Goal Monitoring for presence of wake-up events and signal them.
Use case input Low power mode active.
Use case output Signal available which announces a detected wake-up event.
Brief description
The bus-driver module monitors optionally the availability of wake-up conditions at its interfaces.
Several types are distinguished:
 remote wake-up from the bus due to wakeup symbols;
 remote wake-up from the bus due to payload;
 local wakeup.
8 © ISO 2013 – All rights reserved

6.1.3 UC 1.3 Configure communication module
Table 5 specifies the use case to configure communication module.
Table 5 — UC 1.3 Configure communication module
Actor
Host
Goal Configure the communication module to ensure the participation in the FlexRay communication.
Use case input Set of communication parameters
Use case output Communication module is parameterized faultless.
Brief description The communication module (hardware implementation of the FlexRay protocol) offers a broad
range of features to be a
...