IEC 61158-1:2023

Industrial communication networks - Fieldbus specifications - Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series

IEC 61158-1:2023 specifies the generic concept of fieldbuses. This document also presents an overview and guidance for the IEC 61158 eries by:
explaining the structure and content of the IEC 61158 series;
relating the structure of the IEC 61158 series to the ISO/IEC 7498-1 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 type specific parts of the IEC 61158‑5 series including the application layer service description concepts and the generic fieldbus data types.

Réseaux de communication industriels - Spécifications des bus de terrain - Partie 1 : Vue d’ensemble et recommandations pour les séries IEC 61158 et IEC 61784

l'IEC 61158-1:2023 précise le concept générique de bus de terrain. Le présent document donne également une vue d’ensemble et des recommandations relatives à la série IEC 61158 en:
expliquant la structure et le contenu de la série IEC 61158;
associant la structure de la série IEC 61158 à l’ISO/IEC 7498-1 Modèle de référence de base OSI;
présentant la structure logique de la série IEC 61784;
présentant la manière d’utiliser les parties de la série IEC 61158 en combinaison avec la série IEC 61784;
donnant des explications relatives à certains aspects de la série IEC 61158 communs aux parties spécifiques au type de la série IEC 61158‑5, y compris les concepts de description de la couche d’application de service et les types de données de bus de terrain génériques.

General Information

• Status: Published
• Publication Date: 15-Mar-2023
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 33.040.40 - Data communication networks
• ICS: 35.100.05 - Multilayer applications
• Technical Committee: SC 65C - Industrial networks
• Drafting Committee: WG 9 - TC 65/SC 65C/WG 9
• Current Stage: PPUB - Publication issued
• Start Date: 31-Mar-2023
• Completion Date: 16-Mar-2023

Relations

• Revises: IEC 61158-1:2019 - Industrial communication networks - Fieldbus specifications - Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series
• Effective Date: 05-Sep-2023
• Revises: IEC TR 61158-1:2010 - Industrial communication networks - Fieldbus specifications - Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series
• Effective Date: 05-Sep-2023
• Revises: IEC TR 61158-1:2007 - Industrial communication networks - Fieldbus specifications - Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61158-1 ®
Edition 3.0 2023-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Fieldbus specifications –
Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series

Réseaux de communication industriels – Spécifications des bus de terrain –
Partie 1: Vue d’ensemble et recommandations pour les séries IEC 61158 et
IEC 61784
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IEC 61158-1 ®
Edition 3.0 2023-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Fieldbus specifications –

Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series

Réseaux de communication industriels – Spécifications des bus de terrain –

Partie 1: Vue d’ensemble et recommandations pour les séries IEC 61158 et

IEC 61784
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 33.040.40; 35.100.05 ISBN 978-2-8322-6543-7

– 2 – IEC 61158-1:2023 © IEC 2023
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviations ans symbols . 9
4 Guidelines for implementers and users . 10
4.1 Background and purpose . 10
4.2 Supported options . 10
4.3 Benefits from using a common and formal style . 11
5 Concept of the IEC 61158 series . 11
6 Mapping onto the OSI Basic Reference Model . 13
6.1 Overview. 13
6.2 Physical layer service and protocol . 14
6.3 Data-link layer service . 15
6.4 Data-link layer protocol . 16
6.5 Application layer service . 16
6.6 Application layer protocol . 17
7 Structure of the IEC 61158 and IEC 61784 series . 18
7.1 The IEC 61158 physical layer . 18
7.2 The IEC 61158 data-link layer . 18
7.3 The IEC 61158 application layer . 18
7.4 IEC 61784-1 series and IEC 61784-2 series fieldbus profiles . 19
7.5 IEC 61784-3 series functional safety communication profiles . 23
7.5.1 General . 23
7.5.2 General concepts and technology-specific profiles . 24
7.5.3 Assessment Guideline . 25
7.6 IEC 61784-5 series installation profiles . 25
7.7 Communication profiles for wireless communication networks . 27
8 Brief summary of the characteristics of service and protocol for each fieldbus type . 28
8.1 Summary of the physical layer service and protocol and media used
characteristics . 28
8.1.1 General . 28
8.1.2 Type 1: media . 28
8.1.3 Type 2: Coaxial wire and optical media . 29
8.1.4 Type 3: Twisted-pair wire and optical media . 29
8.1.5 Type 4: Wire medium . 29
8.1.6 Type 5: Wire and optical media . 29
8.1.7 Type 6: Void . 29
8.1.8 Type 7: Wire and optical media . 29
8.1.9 Type 8: Twisted-pair wire and optical media . 29
8.1.10 Type 9: Wire and optical media . 29
8.1.11 Type 10: Wire, optical media and wireless . 30
8.1.12 Type 11: Wire and optical media . 30
8.1.13 Type 12: Wire and optical media . 30
8.1.14 Type 13: Wire and optical media . 30

8.1.15 Type 14: Wire and optical media . 30
8.1.16 Type 15: Wire and optical media . 30
8.1.17 Type 16: Optical media . 30
8.1.18 Type 17: Wire and optical media . 30
8.1.19 Type 18: Wire media . 30
8.1.20 Type 19: Wire and optical media . 30
8.1.21 Type 20: Wire media . 30
8.1.22 Type 21: Wire and optical media . 30
8.1.23 Type 22: Wire and optical media . 30
8.1.24 Type 23: Wire and optical media . 31
8.1.25 Type 24: Twisted-pair wire media . 31
8.1.26 Type 25: Wire media . 31
8.1.27 Type 26: Wire and optical media . 31
8.1.28 Type 27: Wire media . 31
8.1.29 Type 28: Twisted-pair wire and coaxial media . 31
8.2 Summary of data-link layer service characteristics . 31
8.3 Summary of data-link layer protocol characteristics . 33
8.4 Summary of application layer service characteristics. 34
8.5 Summary of application layer protocol characteristics . 36
9 Application layer service description concepts . 39
9.1 Overview. 39
9.2 Architectural relationships . 39
9.2.1 Relationship to the application layer of the OSI Basic Reference Model . 39
9.2.2 Relationships to other fieldbus entities. 40
9.3 Fieldbus application layer structure . 41
9.3.1 Overview . 41
9.3.2 Fundamental concepts . 42
9.3.3 Fieldbus application processes . 42
9.3.4 Application process objects . 46
9.3.5 Application entities . 48
9.3.6 Fieldbus application service elements . 48
9.3.7 Application relationships . 52
9.4 Fieldbus application layer naming and addressing . 54
9.4.1 General . 54
9.4.2 Identifying objects accessed through the FAL . 54
9.4.3 Addressing APs accessed through the FAL. 55
9.5 Architecture summary . 55
9.6 Notional FAL service procedures . 55
9.6.1 Notional FAL confirmed service procedures . 55
9.6.2 Notional FAL unconfirmed service procedures . 56
9.7 Common FAL attributes . 56
9.8 Common FAL service parameters . 57
9.9 APDU size . 58
10 Data type ASE . 58
10.1 Overview. 58
10.1.1 General . 58
10.1.2 Overview of basic types . 59
10.1.3 Overview of fixed-length types . 60
10.1.4 Overview of constructed types . 60

– 4 – IEC 61158-1:2023 © IEC 2023
10.1.5 Specification of user-defined data types . 60
10.1.6 Transfer of user data . 60
10.2 Formal definition of data type objects . 61
10.2.1 Data type class . 61
10.2.2 Void . 62
11 Fieldbus system requirements . 63
11.1 General . 63
11.2 Industrial control network . 63
11.3 Communication between industrial control networks and other networks . 63
11.4 Quality of service features of an industrial control network . 64
11.4.1 General . 64
11.4.2 Control data transfer mechanisms . 64
11.5 Special requirements for wireless networks . 65
Annex A (informative) Trade name declarations . 66
Annex B (informative) Media selection for fieldbus systems . 69
B.1 General . 69
B.2 Cabled media . 69
B.3 Wireless media . 69
B.4 Media needing special consideration . 69
B.5 Performance characteristics of open and public networks . 69
B.5.1 Public network types . 69
B.5.2 Performance characteristics of public networks . 70
Bibliography . 71

Figure 1 – Example of a fieldbus system . 12
Figure 2 – Concept of DL/AL to separate service and protocol parts . 13
Figure 3 – Basic fieldbus reference model . 14
Figure 4 – General model of physical layer . 15
Figure 5 – Relationship of the Data-link layer to other fieldbus layers and to users of

the fieldbus data-link service. 16
Figure 6 – Relationship of the fieldbus Application layer to other fieldbus layers and to
users of the fieldbus application service . 17
Figure 7 – Structure of communication profile families . 20
Figure 8 – Example of a CPF structure . 21
Figure 9 – Document structure of IEC 61918 and the CPF specific part of the
IEC 61784-5 series . 27
Figure 10 – Relationship to the OSI Basic Reference Model . 40
Figure 11 – Architectural positioning of the fieldbus application layer . 40
Figure 12 – Client/server interactions . 43
Figure 13 – Pull model interactions . 44
Figure 14 – Push model interactions . 45
Figure 15 – APOs services conveyed by the FAL . 46
Figure 16 – Application entity structure . 48
Figure 17 – Example FAL ASEs . 50
Figure 18 – FAL management of objects . 50
Figure 19 – ASE service conveyance . 51

Figure 20 – Defined and established AREPs . 54
Figure 21 – FAL architectural components . 55
Figure 22 – Data-type class hierarchy example . 59

Table 1 – OSI and IEC 61158 layers . 14
Table 2 – CPF, CP, and type relations . 22
Table 3 – Types of timeliness defined for publisher/subscriber interactions . 45
Table A.1 – Trade names of CPFs and CPs . 66

– 6 – IEC 61158-1:2023 © IEC 2023
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 this end and
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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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
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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.
Attention is drawn to the fact that the 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 layer protocol type to
be used with other layer protocols of the same type, or in other type combinations explicitly
authorized by their respective intellectual property right holders.
NOTE Combinations of protocol types are specified in the IEC 61784-1 series and the IEC 61784-2 series.
IEC 61158-1 has been prepared by subcommittee 65C: Industrial networks, of IEC technical
committee 65: Industrial-process measurement, control and automation. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2019. This edition
constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous
edition:
a) added the new technology AUTBUS specified in Type 28;
b) additional profile within IEC 61784-2-8 referring to Type 23 (CP 8/6, CC-Link IE TSN);
c) additional profile referring to Type 24 (CP 19/3, Σ-LINKII);
d) additional profile within IEC 61784-2-19 referring to a new Type 27 (CP 19/4,
MECHATROLINK-4).
The text of this International Standard is based on the following documents:
Draft Report on voting
65C/1199/FDIS 65C/1240/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document
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.

– 8 – IEC 61158-1:2023 © IEC 2023
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 1: Overview and guidance for the IEC 61158 and IEC 61784 series

1 Scope
This part of IEC 61158 specifies the generic concept of fieldbuses.
This document also 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 7498-1 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
type specific parts of the IEC 61158-5 series including the application layer service
description concepts and the generic fieldbus data types.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms, definitions and abbreviated terms apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
communication system
arrangement of hardware, software and propagation media to allow the transfer of messages
from one application to another
3.1.2
fieldbus
communication system based on serial data transfer as typically used in industrial automation
and process control applications
___________
In the following pages of this document, “IEC 61158” will be used as a qualifier for “IEC 61158 (all parts)”.
In the following pages of this document, “IEC 61784” will be used as a qualifier for “IEC 61784 (all parts)”.

3.1.3
fieldbus system
system using a fieldbus with connected devices
3.1.4
message
ordered series of octets intended to convey information
3.1.5
network
all of the media, connectors, repeaters, routers, gateways and associated node communication
elements by which a given set of communicating devices are interconnected
3.2 Abbreviations and symbols
For the purposes of this document, the following abbreviations, based partially on the concepts
developed in ISO/IEC 7498-1, apply:
AE application entity
AL application layer (N = 7)
APDU application layer protocol data unit
APO application process object
AR application relationship
AREP application relationship endpoint
ASE application service element
CP communication profile
CPF communication profile family
DL- data-link layer (as a prefix)
DLL data-link layer (N = 2)
FAL fieldbus application layer
FSCP functional safety communication profile
IETF Internet Engineering Task Force
IO input output
IP Internet protocol (see IETF RFC 791)
kbit/s thousand bit per second
Mbit/s million bit per second
LME layer management entity
(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)
SIL safety integrity level
– 10 – IEC 61158-1:2023 © IEC 2023
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
• ISO/IEC 7498-1 for general layering and structuring;
• ISO/IEC 9545 for general application layer modeling;
• ISO/IEC 8886 for data-link layer modeling.
IEC 61158 series specifies a number of different fieldbus types in each of its parts (IEC 61158-2
and the type specific parts of IEC 61158-3-tt, IEC 61158-4-tt, IEC 61158-5-tt and
IEC 61158-6-tt). As a result of the editorial harmonization work done by IEC, each PhL, DLL
and AL specification within IEC 61158 series is shown in a homogeneous way. The description
of each layer offers, as far as possible, common views, concepts, definitions, and descriptive
methods.
NOTE The lists of parts in the IEC 61158 series are abbreviated as IEC 61158-3-tt, IEC 61158-4-tt, IEC 61158-5-tt,
or IEC 61158-6-tt, where tt represents one or more type numbers.
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.
The added value of having more than one fieldbus standardized in IEC 61158 series,
IEC 61784-1 series and IEC 61784-2 series is provided in IEC 61784-1-0, Annex A.
4.2 Supported options
Most of the fieldbus types specified in 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 series and
IEC 61784-2 series.
IEC 61784-1 series and IEC 61784-2 series 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.
IEC 61784-1-0 and IEC 61784-2-0 provide the common elements of the communication profile
families (CPF) specified in the subparts 1 to n of the IEC 61784-1 and IEC 61784-2 series
corresponding to the CPF numbers 1 to n.
Annex A of each CPF part of the IEC 61784-1 series and Annex A of each CPF part of the
IEC 61784-2 series help selecting 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 document;
• IEC 61784-1 series, Annex A of each CPF part: Communication concepts;
• IEC 61784-2 series, Annex A of each CPF part: Performance indicator calculation;

• the parts of the IEC 61784-1 and IEC 61784-2 series that specify the CPF;
• the parts of the IEC 61158 series as referenced in the relevant CPF parts of the IEC 61784-1
and IEC 61784-2 series for the selected communication profile 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.
5 Concept of the IEC 61158 series
Conceptually, a fieldbus is an industrial digital communication network for integration of
industrial control and instrumentation devices into a system. Examples of such devices are
transducers, sensors, actuators and controllers.
IEC 61158 series specifies a number of fieldbus protocol types. Each protocol type is designed
to permit multiple measurement and control devices to communicate. Devices communicate
directly only with other devices of the same protocol type. The basic requirements of industrial
communication networks for measurement and control are given in Clause 11.
Devices which use the same lower-layer protocols in a compatible fashion but differ in their
higher-layer protocols could be able to share a lower-layer medium.
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 series and IEC 61784-2 series. Use of the various
protocol types in other combinations could require permission from their respective copyright
holders.
The protocol types in IEC 61158 series 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.
– 12 – IEC 61158-1:2023 © IEC 2023

Figure 1 – Example of a fieldbus system
A number of fieldbus types are specified in 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 7498-1, 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 profiles
in IEC 61784-1 series and IEC 61784-2 series. 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 oriented view and the
service parts show the layer user’s oriented view.

Figure 2 – Concept of DL/AL to separate service and protocol parts
The application layer structure is as follows:
– the user layer view (the what) is described by application layer service elements (ASE) in
the type specific parts of the IEC 61158-5 series; and
– the implementer oriented view (the how) is described by application layer relationships (AR)
in the type specific parts of the IEC 61158-6 series.
The data-link layer structure is as follows:
– the user layer view (the what) is described by data-link layer services and models in the
type specific parts of the IEC 61158-3 series; and
– the implementer oriented view (the how) is described by data-link layer protocol machines
and medium access principles in the type specific parts of the IEC 61158-4 series.
The physical layer is structured similarly, but, because its services are readily described, they
are described in IEC 61158-2 together with the definitions of the physical protocols:
– the "what" is described by physical layer services and models, and
– the "how" is described by physical layer electrical 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 7498-1. The OSI model provides a layered approach to communications standards,
whereby the layers can be developed and modified independently. IEC 61158 series 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 (Figure 3).

– 14 – IEC 61158-1:2023 © IEC 2023
Table 1 – OSI and IEC 61158 layers
OSI layer Function IEC 61158 layer
7 Application Translates demands placed on the communications stack into a form 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)
1 Physical Encodes/decodes signals for transmission/reception in a form
Physical
appropriate to the communications medium. Specifies communication
(IEC 61158-2)
media characteristics
NOTE 1 -tt is a placeholder for the part numbers representing types.
NOTE 2 ↓ and ↑ indicate that the functionality of this layer, when present, is included in the fieldbus layer that is
nearest in the direction of the arrow. Thus it is possible that the network and transport functionality are included in
either the data-link or application layers, and it is possible that the session and presentation functionality are
included in the application layer but not in the data-link layer.

Figure 3 – Basic fieldbus reference model
6.2 Physical layer service and protocol
IEC 61158-2 comprises physical layer specifications corresponding to many of the different DL-
Layer protocol types specified in the type specific parts of the IEC 61158-4 series.
NOTE 1 The type numbers used are consistent throughout IEC 61158 series.
NOTE 2 Not all types have a physical layer specification in IEC 61158-2. In that case the communication profile in
IEC 61784-1 series or IEC 61784-2 series provides appropriate references to other standards.
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 IEC 61158 series to select interoperating sets of provisions. Refer to IEC 61784-1
serie
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