EN IEC 61158-4-24:2023

SLOVENSKI STANDARD
01-november-2023
Nadomešča:
SIST EN IEC 61158-4-24:2019
Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-24. del:
Specifikacija protokola na ravni podatkovnih povezav - Elementi tipa 24 (IEC 61158
-4-24:2023)
Industrial communication networks - Fieldbus specifications - Part 4-24: Data-link layer
protocol specification - Type 24 elements (IEC 61158-4-24:2023)
Industrielle Kommunikationsnetze - Feldbusse – Teil 4-24: Protokollspezifikation des
Data Link Layer (Sicherungsschicht) - Typ 24-Elemente (IEC 61158-4-24:2023)
Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-24:
Spécification du protocole de la couche liaison de données - Éléments de type 24 (IEC
61158-4-24:2023)
Ta slovenski standard je istoveten z: EN IEC 61158-4-24:2023
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.100.20 Podatkovni povezovalni sloj Data link layer
35.110 Omreževanje Networking
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61158-4-24

NORME EUROPÉENNE
EUROPÄISCHE NORM May 2023
ICS 25.040.40; 35.100.20; 35.110 Supersedes EN IEC 61158-4-24:2019
English Version
Industrial communication networks - Fieldbus specifications -
Part 4-24: Data-link layer protocol specification - Type 24
elements
(IEC 61158-4-24:2023)
Réseaux de communication industriels - Spécifications des Industrielle Kommunikationsnetze - Feldbusse – Teil 4-24:
bus de terrain - Partie 4-24: Spécification du protocole de la Protokollspezifikation des Data Link Layer
couche liaison de données - Éléments de type 24 (Sicherungsschicht) - Typ 24-Elemente
(IEC 61158-4-24:2023) (IEC 61158-4-24:2023)
This European Standard was approved by CENELEC on 2023-05-02. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61158-4-24:2023 E

European foreword
The text of document 65C/1202/FDIS, future edition 3 of IEC 61158-4-24, prepared by SC 65C
"Industrial networks" of IEC/TC 65 "Industrial-process measurement, control and automation" was
submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-02-02
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-05-02
document have to be withdrawn
This document supersedes EN IEC 61158-4-24:2019 and all of its amendments and corrigenda (if
any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61158-4-24:2023 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 61784-1 (series) NOTE Approved as EN IEC 61784-1 (series)
IEC 61784-2 (series) NOTE Approved as EN IEC 61784-2 (series)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 61158-2 2023 Industrial communication networks - Fieldbus EN IEC 61158-2 2023
specifications - Part 2: Physical layer
specification and service definition
IEC 61158-3-24 2023 Industrial communication networks - Fieldbus EN IEC 61158-3-24 2023
specifications - Part 3-24: Data-link layer
service definition - Type 24 elements
ISO/IEC 7498-1 - Information technology - Open Systems - -
Interconnection - Basic reference model: The
basic model
ISO/IEC 7498-3 - Information technology - Open Systems - -
Interconnection - Basic reference model:
Naming and addressing
ISO/IEC/IEEE 2021 Telecommunications and exchange between - -
8802-3 information technology systems -
Requirements for local and metropolitan area
networks - Part 3: Standard for Ethernet
ISO/IEC 9899 - Information technology - Programming - -
languages - C
ISO/IEC 10731 - Information technology - Open Systems - -
Interconnection - Basic Reference Model -
Conventions for the definition of OSI services
ISO/IEC 13239 2002 Information technology - Telecommunications - -
and information exchange between systems -
High-level data link control (HDLC)
procedures
ISO/IEC 19501 2005 Information technology - Open Distributed - -
Processing - Unified Modeling Language
(UML) Version 1.4.2
IEC 61158-4-24 ®
Edition 3.0 2023-03
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 4-24: Data-link layer protocol specification – Type 24 elements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.20; 35.110 ISBN 978-2-8322-6556-7
– 2 – IEC 61158-4-24:2023 © IEC 2023
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
1.1 General . 10
1.2 Specifications . 10
1.3 Procedures . 10
1.4 Applicability . 11
1.5 Conformance . 11
2 Normative references . 11
3 Terms, definitions, symbols, abbreviated terms and conventions . 12
3.1 Reference model terms and definitions . 12
3.2 Service convention terms and definitions . 13
3.3 Common terms and definitions . 13
3.4 Symbols and abbreviations . 16
3.5 Additional Type 24 symbols and abbreviations . 16
3.6 Common conventions . 16
3.7 Additional Type 24 conventions. 17
3.7.1 Primitive conventions . 17
3.7.2 State machine conventions . 17
4 Overview of DL-protocol . 18
4.1 Characteristic feature of the DL-protocol . 18
4.2 DL layer component . 19
4.2.1 Cyclic transmission control (CTC) . 20
4.2.2 Send receive control (SRC) . 20
4.2.3 DL-management . 20
4.3 Timing sequence . 20
4.3.1 Overview . 20
4.3.2 Cyclic transmission mode . 20
4.3.3 Acyclic transmission mode . 34
4.4 Service assumed from the PhL. 34
4.4.1 General requirement . 34
4.4.2 DL_Symbols . 34
4.4.3 Assumed primitives of the PhS . 35
4.5 Local parameters, variables, counters, timers . 35
4.5.1 Overview . 35
4.5.2 Variables, parameters, counters and timers to support DLE function. 35
5 DLPDU structure . 40
5.1 Overview. 40
5.1.1 Transfer syntax for bit sequences . 40
5.1.2 Data type encodings . 41
5.1.3 Frame format . 41
5.2 Basic format DLPDU structure . 41
5.2.1 General . 41
5.2.2 Synchronous frame . 45
5.2.3 Output data or Input data frame . 46
5.2.4 Delay measurement start frame . 46

IEC 61158-4-24:2023 © IEC 2023 – 3 –
5.2.5 Delay measurement frame . 47
5.2.6 Message token frame . 47
5.2.7 Status frame . 48
5.2.8 Cycle Information frame . 49
5.2.9 Message frame . 50
5.3 Short format DLPDU structure . 51
5.3.1 General . 51
5.3.2 Synchronous frame . 53
5.3.3 Output data or Input data frame . 53
5.3.4 Message frame . 54
5.4 Short format II DLPDU structure . 54
5.4.1 General . 54
5.4.2 Asynchronous frame . 56
5.4.3 Synchronous frame . 57
5.4.4 Output data or Input data frame . 57
6 DLE element procedure . 58
6.1 Overview. 58
6.2 Cyclic transmission control sublayer . 58
6.2.1 General . 58
6.2.2 DLS-user interface . 58
6.2.3 Protocol machines in CTC . 59
6.2.4 CTC-DLM interface . 112
6.3 Send Receive Control . 113
6.3.1 General . 113
6.3.2 SRC-CTC interface . 114
6.3.3 Detailed specification of SRC . 114
6.3.4 SRC-DLM interface . 119
7 DL-management layer (DLM) . 120
7.1 Overview. 120
7.2 Primitive definitions . 120
7.2.1 Primitives exchanged between DLMS-user and DLM . 120
7.2.2 Parameters used with DLM primitives . 121
7.3 DLM protocol machine . 121
7.3.1 C1 master . 121
7.3.2 Slave and C2 master . 126
7.4 Functions . 130
7.5 DLM protocol machine for no time slot type . 131
7.5.1 C1 master . 131
7.5.2 C2 master and Slave . 133
7.6 Functions for no time slot type . 134
Bibliography . 135

Figure 1 – Data-link layer component . 20
Figure 2 – Timing chart of fixed-width time slot type cyclic communication . 21
Figure 3 – Timing chart of configurable time slot type cyclic communication . 23
Figure 4 – Schematic diagram of cyclic event occurrence . 25
Figure 5 – Timing relationship between cyclic transmission and data processing . 28

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Figure 6 – Timing chart of no time slot type cyclic communication (Master send
common address) . 28
Figure 7 – Timing chart for multiple transmission cycle setting . 29
Figure 8 – Timing chart for multiple transmission cycle setting igure title . 30
Figure 9 – Schematic diagram for connection. 31
Figure 10 – Schematic diagram of INPUT data response timing at the same interval . 32
Figure 11 – Schematic diagram of INPUT data response timing at the same time . 33
Figure 12 – Timing chart example of acyclic communication . 34
Figure 13 – Basic format DLPDU structure . 42
Figure 14 – Short format DLPDU structure . 51
Figure 15 – Short format II DLPDU structure . 54
Figure 16 – Acyclic transmission frame address field . 55
Figure 17 – Cyclic transmission frame address . 55
Figure 18 – Asynchronous frame . 56
Figure 19 – Synchronous frame (to be used by C1). 57
Figure 20 – Synchronous frame (to be used by C2 or slave) . 57
Figure 21 – The state diagram of the C1 master for fixed-width time slot . 60
Figure 22 – The state diagram of the C2 master for fixed-width time slot . 67
Figure 23 – The state diagram of the slave for fixed-width time slot . 71
Figure 24 – The state diagram of the C1 master for configurable time slot . 73
Figure 25 – The state diagram of the C2 master for configurable time slot . 82
Figure 26 – The state diagram of slave for configurable time slot . 85
Figure 27 – The state diagram of the C1 master for no time slot type . 89
Figure 28 – The state diagram of the C2 master for no time slot type . 90
Figure 29 – The state diagram of the Slave for no time slot type . 92
Figure 30 – The state diagram of message initiator for basic format . 93
Figure 31 – The state diagram of message responder for basic format. 97
Figure 32 – The state diagram of message initiator for short format . 101
Figure 33 – The state diagram of message responder for short format . 106
Figure 34 – The state diagram of the acyclic transmission protocol machine . 111
Figure 35 – Internal architecture of one-port SRC . 115
Figure 36 – Internal architecture of multi-port SRC . 115
Figure 37 – Internal architecture of serializer . 115
Figure 38 – Internal architecture of deserializer . 117
Figure 39 – State diagram of the C1 master DLM . 122
Figure 40 – State diagram of the Slave and the C2 master DLM . 127
Figure 41 – State diagram of the C1 master DLM for no time slot type . 132
Figure 42 – State diagram of the C2 master and slaves DLM for no time slot type . 133

Table 1 – State transition descriptions . 18
Table 2 – Description of state machine elements . 18
Table 3 – Conventions used in state machines . 18
Table 4 – Characteristic features of the fieldbus data-link protocol . 19

IEC 61158-4-24:2023 © IEC 2023 – 5 –
Table 5 – List of the values of the variable Cyc_sel. 36
Table 6 – List of the values of the variable Tunit . 37
Table 7 – List of the values of the variable PDUType . 38
Table 8 – List of the values of the variable SlotType . 38
Table 9 – Transfer syntax for bit sequences . 40
Table 10 – Bit order . 41
Table 11 – Destination and source address format . 42
Table 12 – Station address . 42
Table 13 – Extended address . 43
Table 14 – Message control field format (Information transfer format) . 43
Table 15 – Message control field format (Supervisory format) . 44
Table 16 – The list of Supervisory function bits . 44
Table 17 – Frame type and data length format . 44
Table 18 – The list of Frame type . 45
Table 19 – Data format of the Synchronous frame . 45
Table 20 – The field list of the Synchronous frame . 46
Table 21 – Data format of the Output data or the Input data frame . 46
Table 22 – The field list of the Output data or the Input data frame . 46
Table 23 – Data format of Delay measurement start frame . 47
Table 24 – The field list of Delay measurement start frame . 47
Table 25 – Data format of Delay measurement frame . 47
Table 26 – The field list of Delay measurement frame . 47
Table 27 – Data format of Status frame . 48
Table 28 – The field list of Status frame . 48
Table 29 – The list of the DLE status . 48
Table 30 – The list of Repeater status. 49
Table 31 – Data format of Delay measurement frame . 49
Table 32 – The field list of Cycle Information frame . 50
Table 33 – Data format of Message frame . 50
Table 34 – The field list of Message frame . 50
Table 35 – Range of Station address field . 51
Table 36 – Control field format (I/O data exchange format) . 52
Table 37 – Control field format (Message format). 52
Table 38 – The field list of Message format . 52
Table 39 – Data format of the Synchronous frame . 53
Table 40 – The field list of the Synchronous frame . 53
Table 41 – Data format of the Output data frame . 53
Table 42 – The field list of the Output data frame . 54
Table 43 – Data format of the Input data frame . 54
Table 44 – The field list of the Input data frame . 54
Table 45 – Range of Station address field . 55
Table 46 – Cycle scale counter field format . 56
Table 47 – The list of frame type . 56

– 6 – IEC 61158-4-24:2023 © IEC 2023
Table 48 – Data format of the Output data frame . 57
Table 49 – The field list of the Output data frame . 57
Table 50 – Data format of the Input data frame . 57
Table 51 – The field list of the Input data frame . 58
Table 52 – Primitives and parameters for the DLS-user interface issued by the
DLS‑user . 58
Table 53 – Primitives and parameters for the DLS-user interface issued by the CTC . 59
Table 54 – The state table of the C1 master for fixed-width time slot. 61
Table 55 – The state table of the C2 master for fixed-width time slot. 67
Table 56 – The state table of the slave for fixed-width time slot . 71
Table 57 – The state table of the C1 master for configurable time slot . 74
Table 58 – The state table of the C2 master for configurable time slot . 82
Table 59 – The state table of slave for configurable time slot . 86
Table 60 – The list of functions used by cyclic transmission machine . 87
Table 61 – The state table of the C1 master for no time slot type . 90
Table 62 – The state table of the C2 master for no time slot type . 91
Table 63 – The state table of the Slave for no time slot type . 92
Table 64 – The state table of message initiator for basic format . 94
Table 65 – The state table of message responder for basic format . 98
Table 66 – The state table of message initiator for short format . 102
Table 67 – The state table of message responder for short format . 106
Table 68 – List of functions used by the message segmentation machine . 110
Table 69 – The state table of the acyclic transmission protocol machine . 112
Table 70 – The list of functions used acyclic transmission protocol machine . 112
Table 71 – Primitives and parameters exchanged between CTC and DLM . 113
Table 72 – Error event primitive and parameters . 113
Table 73 – primitives and parameters for SRC-CTC interface . 114
Table 74 – Send frame primitive and parameters . 114
Table 75 – Receive frame primitives and parameters . 114
Table 76 – Primitives and parameters exchanged between SRC and DLM . 119
Table 77 – Get value primitive and parameters . 120
Table 78 – Error event primitive and parameters . 120
Table 79 – The list of primitives and parameters (DLMS-user source) . 121
Table 80 – The list of primitives and parameters (DLM source) . 121
Table 81 – State table of the C1 Master DLM . 122
Table 82 – State table of the Slave and the C2 master DLM . 127
Table 83 – The list of the functions used by DLM protocol machine . 130
Table 84 – State table of the C1 Master DLM for no time slot type . 132
Table 85 – State table of the C2 master and slaves DLM for no time slot type . 133

IEC 61158-4-24:2023 © IEC 2023 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 4-24: Data-link layer protocol specification –
Type 24 elements
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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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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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misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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.
Attention is drawn to the fact that the use of the associated protocol type is restricted by its
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 its intellectual-property-right holders.
NOTE Combinations of protocol types are specified in the IEC 61784-1 series and the IEC 61784-2 series.
IEC 61158-4-24 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.

– 8 – IEC 61158-4-24:2023 © IEC 2023
This edition includes the following significant technical changes with respect to the previous
edition:
• addition of a new cyclic transmission mode which called "no time slot type" in Subclause
4.3.2.4;
• addition of a new frame format for no time slot type in Subclause 5.4;
• addition of a new DLE element procedure for no time slot type in Subclause 6.2.3.2.4,
6.3.3.2.2.4, 6.3.3.3.2.4;
• addition of a new DLM protcol machine for no time slot type in Subclause 7.5, 7.6; and
• spelling and grammar.
The text of this International Standard is based on the following documents:
Draft Report on voting
65C/1202/FDIS 65C/1243/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.
A list of all parts of the IEC 61158 series, 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 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.
IEC 61158-4-24:2023 © IEC 2023 – 9 –
INTRODUCTION
This part of IEC 61158 is one of a series produced to facilitate the interconnection of automation
system components. It is related to other standards in the set as defined by the "three-layer"
fieldbus reference model described in IEC 61158-1.
The data-link protocol provides the data-link service by making use of the services available
from the physical layer. The primary aim of this document 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:
• as a guide for implementers and designers;
• for use in the testing and procurement of equipment;
• as part of an agreement for the admittance of systems into the open systems environment;
• as a refinement to the understanding of time-critical communications within OSI.
This document is concerned, in particular, with the communication and interworking of sensors,
effectors and other automation devices. By using this document together with other standards
positioned within the OSI or fieldbus reference models, otherwise incompatible systems could
work together in any combination.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent. IEC takes no position
concerning the evidence, validity, and scope of this patent right.
The holder of this patent right has assured IEC that s/he is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world.
In this respect, the statement of the holder of this patent right is registered with IEC. Information
may be obtained from the patent database available at patents.iec.ch.
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those in the patent database. IEC shall not be held
responsible for identifying any or all such patent rights.

– 10 – IEC 61158-4-24:2023 © IEC 2023
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 4-24: Data-link layer protocol specification –
Type 24 elements
1 Scope
1.1 General
The data-link layer provides basic time-critical messaging communications between devices in
an automation environment.
This protocol provides communication opportunities to all participating data-link entities:
• in a synchronously-starting cyclic manner, according to a pre-established schedule, or
• in an acyclic manner, as requested by each of those data-link entities.
Thus, this protocol can be characterized as one which provides cyclic and acyclic access
asynchronously but with a synchronous restart of each cycle.
1.2 Specifications
This part of IEC 61158 provides specifies
• procedures for the timely transfer of data and control information from one data-link user
entity to a peer user entity, and among the data-link entities forming the distributed datalink
service provider;
• procedures for giving communications opportunities to all participating DL-entities (DLEs),
sequentially and in a cyclic manner for deterministic and synchronized transfer at cyclic
intervals up to 64 ms;
• procedures for giving communication opportunities available for time-critical data
transmission together with non-time-critical data transmission without prejudice to the time-
critical data transmission;
• procedures for giving cyclic and acyclic communication opportunities for time-critical data
transmission with prioritized access;
• procedures for giving communication opportunities based on ISO/IEC/IEEE 8802-3 medium
access control, with provisions for nodes to be added or removed during normal operation;
• the structure of the fieldbus DLPDUs used for the transfer of data and control information
by the protocol of this document, and their representation as physical interface data units.
1.3 Procedures
The procedures are defined in terms of
• the interactions between peer DL-entities through the exchange of fieldbus DLPDUs;
• the interactions between a DL-service (DLS) provider and a DLS-user in the same system
through the exchange of DLS primitives;
• the interactions between a DLS-provider and a Ph-service provider in the same system
through the exchange of Ph-service primitives.

IEC 61158-4-24:2023 © IEC 2023 – 11 –
1.4 Applicability
These procedures are applicable to instances of communication between systems which
support time-critical communications services within
...