IEC TR 61158-1:2010

IEC/TR 61158-1 ®
Edition 3.0 2010-08
TECHNICAL
REPORT
colour
inside
Industrial communication networks – Fieldbus specifications –
Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series
IEC/TR 61158-1:2010(E)
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IEC/TR 61158-1 ®
Edition 3.0 2010-08
TECHNICAL
REPORT
colour
inside
Industrial communication networks – Fieldbus specifications –
Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 25.040; 35.100; 35.240.50 ISBN 978-2-88912-137-3
– 2 – TR 61158-1 © IEC:2010(E)
CONTENTS
FOREWORD.5
1 Scope.7
2 Normative references .7
3 Abbreviations .7
4 Guidelines for implementers and users.7
4.1 Background and purpose.7
4.2 Supported options .8
4.3 Benefits from using a common and formal style.8
5 Concept of the IEC 61158 series .9
6 Mapping onto the OSI Basic Reference Model.10
6.1 Overview .10
6.2 Physical layer service and protocol.11
6.3 Data-link layer service.12
6.4 Data-link layer protocol .13
6.5 Application layer service.13
6.6 Application layer protocol .14
7 Structure of IEC 61158 and IEC 61784 series.15
7.1 The IEC 61158 physical layer .15
7.2 The IEC 61158 data-link layer .15
7.3 The IEC 61158 application layer.16
7.4 IEC 61784-1 and IEC 61784-2 fieldbus profiles .16
7.5 IEC 61784-3 functional safety communication profiles .20
7.6 IEC 61784-5 installation profiles.21
8 Brief summary of the characteristics of each service and protocol for each type of
fieldbus .23
8.1 Summary of the physical layer service and protocol characteristics .23
8.1.1 Type 1: media.23
8.1.2 Type 2: Coaxial wire and optical media.23
8.1.3 Type 3: Twisted-pair wire and optical media .23
8.1.4 Type 4: Wire medium.24
8.1.5 Type 5: Wire and optical media .24
8.1.6 Type 7: Wire and optical media .24
8.1.7 Type 8: Twisted-pair wire and optical media .24
8.1.8 Type 10: Wire and optical media.24
8.1.9 Type 11: Wire and optical media.24
8.1.10 Type 12: Wire and optical media.24
8.1.11 Type 13: Wire and optical media.24
8.1.12 Type 14: Wire and optical media.24
8.1.13 Type 15: Wire and optical media.24
8.1.14 Type 16: Optical media.25
8.1.15 Type 17: Wire and optical media.25
8.1.16 Type 18 media.25
8.1.17 Type 19: Wire and optical media.25
8.2 Summary of data-link layer service characteristics .25
8.3 Summary of data-link layer protocol characteristics .26
8.4 Summary of application layer service characteristics .28

TR 61158-1 © IEC:2010(E) – 3 –
8.5 Summary of application layer protocol characteristics.29
9 Application layer service description concepts .31
9.1 Overview .31
9.2 Architectural relationships .32
9.2.1 Relationship to the application layer of the OSI Basic Reference
Model .32
9.2.2 Relationships to other fieldbus entities .32
9.3 Fieldbus application layer structure .34
9.3.1 Overview .34
9.3.2 Fundamental concepts.34
9.3.3 Fieldbus application processes.34
9.3.4 Application process objects .38
9.3.5 Application entities .40
9.3.6 Fieldbus application service elements.40
9.3.7 Application relationships.44
9.4 Fieldbus application layer naming and addressing.46
9.4.1 General .46
9.4.2 Identifying objects accessed through the FAL .46
9.4.3 Addressing APs accessed through the FAL .47
9.5 Architecture summary.47
9.6 Notional FAL service procedures .47
9.6.1 Notional FAL confirmed service procedures.47
9.6.2 Notional FAL unconfirmed service procedures .48
9.7 Common FAL attributes.48
9.8 Common FAL service parameters.49
9.9 APDU size.50
10 Data type ASE.50
10.1 Overview .50
10.1.1 General .50
10.1.2 Overview of basic types.51
10.1.3 Overview of fixed-length types.52
10.1.4 Overview of constructed types.52
10.1.5 Specification of user-defined data types .52
10.1.6 Transfer of user data .53
10.2 Formal definition of data type objects .53
10.2.1 Data type class.53
Annex A (informative) Trade name declarations.55
Bibliography.57

Figure 1 – Generic fieldbus network.9
Figure 2 – Concept of DL/AL to separate service and protocol parts .10
Figure 3 – Basic fieldbus reference model .11
Figure 4 – General model of physical layer .12
Figure 5 – Relationship of the IEC 61158-3 and IEC 61158-4 series to other fieldbus
layers and to users of the fieldbus data-link service .13
Figure 6 – Relationship of the IEC 61158-5 and IEC 61158-6 series to other fieldbus
layers and to users of the fieldbus application service.14
Figure 7 – Structure of communication profile families .17

– 4 – TR 61158-1 © IEC:2010(E)
Figure 8 – Example of a CPF structure .18
Figure 9 – Document structure of IEC 61918 and the IEC 61784-5 series .22
Figure 10 – Relationship to the OSI Basic Reference Model .32
Figure 11 – Architectural positioning of the fieldbus application layer.33
Figure 12 – Client/server interactions.35
Figure 13 – Pull model interactions .36
Figure 14 – Push model interactions .37
Figure 15 – APOs services conveyed by the FAL .38
Figure 16 – Application entity structure .40
Figure 17 – Example FAL ASEs .42
Figure 18 – FAL management of objects .42
Figure 19 – ASE service conveyance.43
Figure 20 – Defined and established AREPs.46
Figure 21 – FAL architectural components .47
Figure 22 – Data-type class hierarchy example.51

Table 1 – OSI and IEC 61158 layers .11
Table 2 – CPF, CP, and type relations .19
Table 3 – Types of timeliness defined for publisher/subscriber interactions.37
Table A.1 – Trade names of CPFs and CPs .55

TR 61158-1 © IEC:2010(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 1: Overview and guidance
for the IEC 61158 and IEC 61784 series

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
NOTE Use of some of the associated protocol types is restricted by their intellectual-property-right holders. In all
cases, the commitment to limited release of intellectual-property-rights made by the holders of those rights permits
a particular data-link layer protocol Type to be used with physical layer and application layer protocols in Type
combinations as specified explicitly in its profile parts. Use of the various protocol types in other combinations may
require permission of their respective intellectual-property-right holders.
IEC 61158-1, which is a technical report, has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This third edition cancels and replaces the second edition published in 2007. It constitutes a
technical revision.
– 6 – TR 61158-1 © IEC:2010(E)
This edition includes the following significant changes with respect to the previous edition:
• Updates of the references to the IEC 61158 series, IEC 61784-1, IEC 61784-3,
IEC 61784-5 series and IEC 61918 throughout the document;
• new Type 21 and the related profile family CPF 17;
• new Type 22 and the related profile family CPF 18.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
65C/590A/DTR 65C/608/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61158 series, published under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
NOTE The revision of this technical report will be synchronized with the other parts of the IEC 61158 series.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
TR 61158-1 © IEC:2010(E) – 7 –
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 1: Overview and guidance
for the IEC 61158 and IEC 61784 series

1 Scope
This technical report presents an overview and guidance for the IEC 61158 series by:
• explaining the structure and content of the IEC 61158 series;
• relating the structure of the IEC 61158 series to the ISO/IEC 7498 OSI Basic Reference
Model;
• showing the logical structure of the IEC 61784 series;
• showing how to use parts of the IEC 61158 series in combination with the IEC 61784
series;
• providing explanations of some aspects of the IEC 61158 series that are common to the
parts of the IEC 61158-5 series.
2 Normative references
None
3 Abbreviations
For the purposes of this document, the following abbreviations, based partially on the
concepts developed in ISO/IEC 7498-1, apply:
AL Application layer (N = 7)
AR Application relationship
AREP Application relationship endpoint
DL- Data-link layer (as a prefix)
DLL Data-link layer (N = 2)
IETF Internet Engineering Task Force
IP Internet Protocol (see RFC 791)
(n)-layer Layer n of the OSI Basic Reference Model
OSI Open systems interconnection
Ph- Physical layer (as a prefix)
PhL Physical layer (N = 1)
4 Guidelines for implementers and users
4.1 Background and purpose
Communication in global markets requires a global understanding of a specification (standard
or not). ISO/OSI related specifications provide a common basis for understanding and
acceptance between international experts (manufacturers and end-users). Examples are

– 8 – TR 61158-1 © IEC:2010(E)
• ISO/IEC 7498 series for general layering and structuring;
• ISO/IEC 9545 for general application layer modeling;
• ISO/IEC 8886 for data-link layer modeling.
The IEC 61158 series specifies a number of different fieldbus types in each of the parts of the
series (part 2 and the parts of part 3 through part 6). As a result of the editorial harmonization
work done by IEC, each PhL, DLL and AL specification within IEC 61158 is shown in a
homogeneous way. The description of each layer offers, as far as possible, common views,
concepts, definitions, and descriptive methods.
This common approach has been adopted to assist users and implementers in understanding
the several specifications. It is also intended to assist in comparing available products and
their communications-related features.
4.2 Supported options
Most of the fieldbus types specified in the IEC 61158 series include a range of selectable and
configurable options within their detailed specifications. In general, only certain restricted
combinations of options will interwork or interoperate correctly.
The recommended combinations of options are collected in IEC 61784-1 and IEC 61784-2.
IEC 61784-1 and IEC 61784-2 provide users and implementers with details of supported
fieldbus specifications based on selected options that are intended to work together
consistently and correctly. In most cases, available product demonstrations and working plant
experience support these profiles.
Annex A of IEC 61784-1 and IEC 61784-2 help select the needed fieldbus by showing the key
features of each of the profiled fieldbus protocol families.
As a result, the route map recommended to select a fieldbus is:
• Clause 5 to Clause 8 of this Technical Report
• IEC 61784-1, Annex A: Communication concepts
• IEC 61784-2, Annex A: Performance indicator calculations
• IEC 61784-1 and IEC 61784-2, Communication profile family
• IEC 61158 series as appropriate for the particular fieldbus type of interest.
4.3 Benefits from using a common and formal style
The benefits gained from using a common and formal style to specify the communication
system are:
• the common look and feel of a specification saves effort during evaluation;
• a common structure helps to identify and to specify common parts and contents;
• the common approach represents a first step to ensure long-term quality and stability;
• the missing parts and items of any specification are more readily identified by comparison
with the other specifications, leading to a simplified review and evaluation procedure;
• a common basis facilitates the development of test and certification procedures;
• the modular concepts support future enhancements, extensions and adaptation of new
technologies.
TR 61158-1 © IEC:2010(E) – 9 –
5 Concept of the IEC 61158 series
Conceptually, a fieldbus is a digital, serial, multidrop, data bus for communication with
industrial control and instrumentation devices such as – but not limited to – transducers,
actuators and controllers.
The IEC 61158 series specifies a number of fieldbus protocol types. Each protocol type is
designed to permit multiple measurement and control devices to communicate on a shared
medium. Devices communicate directly only with other devices of the same protocol type.
NOTE 1 Devices which use the same lower-layer protocols in a compatible fashion but differ in their higher-layer
protocols may be able to share a lower-layer medium.
NOTE 2 In all cases, a particular data-link layer protocol type may be used without restriction when coupled with
physical layer and application layer protocols of the same type or with other combinations as specified in
IEC 61784-1 and IEC 61784-2. Use of the various protocol types in other combinations may require permission
from their respective copyright holders.
These protocol types have been engineered to support information processing, monitoring
and control systems for any industrial sector and related domains. An example application for
high-integrity low-level communication between sensors, actuators and local controllers in a
process plant, together with the interconnection of programmable controllers, is shown in
Figure 1.
Information systems network
Gateway Gateway
Fieldbus
Process plant Factory shop floor
segment
Controllers
Programmable
ControlleProrsgra mmable
Controllers
Programmable
Sensors
Controllers
Actuators
Fieldbus
Monitoring
segment
system
Bridge
Fieldbus
segment
Figure 1 – Generic fieldbus network
A number of fieldbus types are specified in the IEC 61158 series using the following concepts
for decomposition.
a) First concept: The complex communication task is divided into different layers based on
an adaptation of ISO/IEC 7498, the ISO/OSI Basic Reference Model, thereby facilitating
well-structured functions and interfaces (see Clause 6). This has the following benefits:
• decomposition of complex tasks;
• modular structure to adapt different technologies.
b) Second concept: Each fieldbus type is composed of one or more layer specifications.
Most types include a number of services and protocol options that require an appropriate
selection to support a working system. Compatible selections of options and services
within one of the IEC 61158 fieldbus types are specified as standardized communication

– 10 – TR 61158-1 © IEC:2010(E)
profiles in IEC 61784-1 and IEC 61784-2. Most of these profiles are supported by
consortia or trade associations which are identified in the profile specification.
c) Third concept: The physical, data-link and application layers are described in
complementary ways, in terms of the offered services and the protocol which provides
those services.
Figure 2 illustrates the differences between service and protocol viewpoints of the data-link
and application layers. The protocol parts show the layer implementer’s view and the service
parts show the layer user’s view.
Layer user Layer implementer
Oriented view Oriented view
AL services AL protocol
Part 5 of IEC 61158 Part 6 of IEC 61158
- Model and concepts - Syntax definition and coding
- Data type definitions - Application relationships
- Application objects procedures
- Service description - Protocol machines (state machines)
- Communication end-point
management.
DL services DL protocol
Part 3 of IEC 61158 Part 4 of IEC 61158
- Model and concepts -Coding
- Service description - Medium access
- Management services - Protocol machines (state machines)

Figure 2 – Concept of DL/AL to separate service and protocol parts
The application layer structure is as follows:
– the "what“ is described by application layer service elements (ASE); and
– the "how“ is described by application layer relationships (AR).
The data-link layer structure is as follows:
– the "what“ is described by data-link layer services and models; and
– the "how“ is described by data-link layer protocol machines and medium access principles.
The physical layer is structured similarly, but, because its services are readily described, they
occur in the same specification (IEC 61158-2) as the definitions of the physical protocols:
– the "what“ is described by physical layer services and models, and
– the "how“ is described by physical layer electromagnetic and mechanical specifications.
6 Mapping onto the OSI Basic Reference Model
6.1 Overview
IEC 61158 protocol types are described using the principles, methodology and model of
ISO/IEC 7498. The OSI model provides a layered approach to communications standards,

TR 61158-1 © IEC:2010(E) – 11 –
whereby the layers can be developed and modified independently. IEC 61158 specifies
functionality from top to bottom of a full OSI stack and, potentially, some functions for the
users of the stack. Functions of the intermediate OSI layers, layers 3 through 6, may be
consolidated into either the IEC 61158 data-link layer or the IEC 61158 application layer, or
may be realized by a separate layer. Likewise, some features common to users of the fieldbus
application layer may be provided by the IEC 61158 application layer to simplify user
operation.
Table 1 shows the OSI layers, their functions, and the equivalent layers in the IEC 61158
basic fieldbus reference model (see Figure 3).
Table 1 – OSI and IEC 61158 layers
OSI layer Function IEC 61158 layer
Translates demands placed on the communications stack into a form Application
7 Application
understood by the lower layers and vice versa (IEC 61158-5-tt,
IEC 61158-6-tt)
6 Presentation Converts data to/from standardized network formats
↑
5 Session Creates and manages dialogue among lower layers ↑
4 Transport Provides transparent reliable data transfer (end-to-end transfer across a
↓ or ↑
network which may include multiple links)
3 Network Performs message routing ↓ or ↑
2 Data-link Controls access to the communication medium. Performs error Data-link
detection, (point-to-point transfer on a link) (IEC 61158-3-tt,
IEC 61158-4-tt)
Encodes/decodes signals for transmission/reception in a form
Physical
appropriate to the communications medium. Specifies communication
1 Physical
(IEC 61158-2)
media characteristics
-tt is a placeholder for the part numbers representing types.
NOTE  ↓ and ↑ indicate that the functionality of this layer, when present, may be included in the fieldbus layer
that is nearest in the direction of the arrow. Thus network and transport functionality may be included in either the
data-link or application layers, while session and presentation functionality may be included in the application layer
but not in the data-link layer.

Application layer
Data-link layer
Physical layer
Medium
Figure 3 – Basic fieldbus reference model
6.2 Physical layer service and protocol
This technical report comprises physical layer specifications corresponding to many of the
different DL-Layer protocol types specified in IEC 61158-4-1 to IEC 61158-4-19.
NOTE 1 The protocol type numbers used are consistent throughout the IEC 61158 series.
NOTE 2 Some specifications for types 1, 2, 3, 4, 8, 12, 16 and 18 are included. Some of these types also use
ISO/IEC 8802-3. Type 7 uses Type 1 specifications. The other types do not use any of the specifications given in
this report.
Systems
management
– 12 – TR 61158-1 © IEC:2010(E)
NOTE 3 For ease of reference, type numbers are given in clause names. This means that the specification given
therein applies to this type but does not exclude its use for other types.
NOTE 4 It is up to the user of this report to select interoperating sets of provisions. Refer to the IEC 61784 series
for standardized communication profiles based on the IEC 61158 series.
A general model of the physical layer is shown in Figure 4.

DLL
DL-Ph Interface
Systems Systems
Ph DIS
Management
DCE Independent Sublayer
Management
–Ph interface
DTE - DCE
Interface
Ph MDS
Medium Dependent Sublayer
MDS MAU Interface
-
Ph MAU
Medium Attachment Unit
Medium Interface
Medium
Figure 4 – General model of physical layer
NOTE 5 The protocol types use a subset of the structure elements.
NOTE 6 Since Type 8 uses a more complex DIS than the other types, it uses the term MIS to differentiate.
The common characteristics for all variants and types are as follows:
– digital data transmission;
– no separate clock transmission;
– either half-duplex communication (bi-directional but in only one direction at a time) or full-
duplex communication
6.3 Data-link layer service
The data-link service is provided by the data-link protocol making use of the services
available from the physical layer. This and related parts of the IEC 61158 series defines the
data-link service characteristics that the immediately higher-level protocol may exploit. The
relationship between the international standards for fieldbus data-link service, fieldbus data-
link protocol, fieldbus application protocol and systems management is illustrated in Figure 5.
NOTE Systems management, as used in the IEC 61158 series, is a local mechanism for managing the layer
protocols.
Alternative
Ph MAU variant
Alternative
PH MAU variant
Alternative
Ph MAU variant
Alternative
Ph MAU variant
DCE DTE
MDS MIS
Physical Layer
TR 61158-1 © IEC:2010(E) – 13 –

Application layer
Data-link
Data-link
services
management
Data-link layer
services
Physical layer
Medium
Figure 5 – Relationship of the IEC 61158-3 and IEC 61158-4 series
to other fieldbus layers and to users of the fieldbus data-link service
Throughout the set of fieldbus standards, the term “service” refers to the abstract capability
provided by one layer of the OSI Basic Reference Model to the layer immediately above. Thus,
the data-link service defined in this report is a conceptual architectural service, independent
of administrative and implementation divisions.
6.4 Data-link layer protocol
The data-link protocol provides the data-link service by making use of the services available
from the physical layer. The relationship between the International Standards for fieldbus
data-link service, fieldbus data-link protocol, fieldbus physical service and systems
management is illustrated in Figure 5.
NOTE Systems management, as used in the IEC 61158 series, is a local mechanism for managing the layer
protocols.
The primary aim of the data-link protocol standards is to provide a set of rules for
communication expressed in terms of the procedures to be carried out by peer data-link
entities (DLEs) at the time of communication. These rules for communication are intended to
provide a sound basis for development in order to serve a variety of purposes:
a) as a guide for implementers and designers;
b) for use in the testing and procurement of equipment;
c) as part of an agreement for the admittance of systems into the open systems
environment;
d) as a refinement to the understanding of time-critical communications within OSI.
These data-link protocol standards are concerned, in particular, with the communication and
interworking of sensors, effectors and other automation devices, using these standards,
together with other standards positioned within the OSI or fieldbus reference models;
otherwise, incompatible systems may work together in any combination.
6.5 Application layer service
The application service is provided by the application protocol making use of the services
available from the data-link or other immediately lower layer. Each part of the IEC 61158-5
series defines the application service characteristics that any immediately higher-level
protocols may exploit. The relationship between the international standards for fieldbus
application service, fieldbus application protocol and systems management is illustrated in
Figure 6.
NOTE Systems management, as used in the IEC 61158 series of standards, is a local mechanism for managing
the layer protocols.
Sys tems
Manag ement
– 14 – TR 61158-1 © IEC:2010(E)
Application
S M
services
FIELDBUS
Y A
Application
S N
APPLICATION
management
T A
LAYER
services
E G
Data-link
M E
services
M
DATA-LINK
E
LAYER
N
T
PHYSICAL
LAYER
MEDIUM
Figure 6 – Relationship of the IEC 61158-5 and IEC 61158-6 series
to other fieldbus layers and to users of the fieldbus application service
6.6 Application layer protocol
The application protocol provides the application service by making use of the services
available from the data-link layer or other immediately lower layer. The relationship between
the International Standards for fieldbus application service, fieldbus application protocol,
Figure 6.
fieldbus data-link service and system management is illustrated in
NOTE Systems management, as used in the IEC 61158 standards, is a local mechanism for managing the layer
protocols.
An application process uses the fieldbus application layer services to exchange information
with other application processes. The services define the abstract interface between the
application process and the application layer.
The application layer protocol is the set of rules that governs the format and meaning of the
information exchange between the application layers in various devices. The application layer
uses the protocol to implement the application layer services definitions.
The protocol machine defines the various states of an application layer and the valid
transitions between the states. It may be considered as a finite state machine. The protocol
machine is described using state tables. The information is exchanged between the
application process and the protocol machine through application service data units. The
protocol machine exchanges information with other protocol machines through application
protocol data units (APDU).
This set of application layer standards does not specify individual implementations or
products, nor does it constrain the implementations of application entities (AEs) and
interfaces within the industrial automation system.
This set of application layer standards does not contain test procedures to ensure compliance
with such requirements.
The primary aim of this report is to provide a set of rules for communication expressed in
terms of the procedures to be carried out by peer data-link entities at the time of
communication. These rules for communication are intended to provide a sound basis for
development in order to serve a variety of purposes:
a) as a guide for implementers and designers;
b) for use in the testing and procurement of equipment;
c) as part of an agreement for the admittance of systems into the open systems environment;
d) as a refinement to the understanding of time-critical communications within OSI.

TR 61158-1 © IEC:2010(E) – 15 –
This report is concerned, in particular, with the communication and interworking of sensors,
effectors and other automation devices, by using this report together with other standards
positioned within the OSI or fieldbus reference models; otherwise, incompatible systems may
work together in any combination.
7 Structure of IEC 61158 and IEC 61784 series
7.1 The IEC 61158 physical layer
The IEC 61158 physical layer receives data units from the data-link layer, encapsulates them
if necessary by adding communications framing information, encodes the bits and framing
information into signals, and transmits the resulting physical signals to the transmission
medium connected to the transmitting node.
Signals are then received at one or more other node(s) and decoded, and any
communications framing information is checked and removed, before the data units are
passed to the data-link layer of the receiving device.
IEC 61158-2 comprises physical layer specifications to support the DL-protocol types
specified in the IEC 61158 data-link layer. It defines the services provided
a) to the various types of fieldbus data-link layer at the boundary between the data-link and
physical layers of the fieldbus reference model;
b) to systems management at the boundary between the physical layer and systems
management of the fieldbus reference model.
NOTE  This combination of physical service definition and physical protocol specification into a single standard is
an historic anomaly; it is not common standards practice.
7.2 The IEC 61158 data-link layer
In the absence of persistent errors, the IEC 61158 data-link layers (see IEC 61158-3-tt and
IEC 61158-4-tt) provide basic time-critical support for data communications among devices in
an automation environment. The term “time-critical” is used to describe applications having a
time-window, within which one or more specified actions are required to be completed with
some defined level of certainty. Failure to complete specified actions within the time window
risks failure of the applications requesting the actions, with attendant risk to equipment, plant
and possibly human life.
IEC 611
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