EN IEC 61158-4-21:2023

SLOVENSKI STANDARD
01-november-2023
Nadomešča:
SIST EN IEC 61158-4-21:2019
Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-21. del:
Specifikacija protokola na ravni podatkovnih povezav - Elementi tipa 21 (IEC 61158
-4-21:2023)
Industrial communication networks - Fieldbus specifications - Part 4-21: Data-link layer
protocol specification - Type 21 elements (IEC 61158-4-21:2023)
Industrielle Kommunikationsnetze - Feldbusse - Teil 4-21: Protokollspezifikation des
Data Link Layer (Sicherungsschicht) - Typ 21-Elemente (IEC 61158-4-21:2023)
Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-21:
Spécification du protocole de la couche de liaison de données - Eléments de type 21
(IEC 61158-4-21:2023)
Ta slovenski standard je istoveten z: EN IEC 61158-4-21:2023
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 61158-4-21

NORME EUROPÉENNE
EUROPÄISCHE NORM May 2023
ICS 25.040.40; 35.100.20; 35.110 Supersedes EN IEC 61158-4-21:2019
English Version
Industrial communication networks - Fieldbus specifications -
Part 4-21: Data-link layer protocol specification - Type 21
elements
(IEC 61158-4-21:2023)
Réseaux de communication industriels - Spécifications des Industrielle Kommunikationsnetze - Feldbusse - Teil 4-21:
bus de terrain - Partie 4-21: Spécification du protocole de la Protokollspezifikation des Data Link Layer
couche de liaison de données - Eléments de type 21 (Sicherungsschicht) - Typ 21-Elemente
(IEC 61158-4-21:2023) (IEC 61158-4-21:2023)
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 61158-4-21:2023 E

European foreword
The text of document 65C/1202/FDIS, future edition 3 of IEC 61158-4-21, 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 61158-4-21:2019 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 61158-4-21:2023 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 61158-1 NOTE Approved as EN IEC 61158-1
IEC 61158-2 NOTE Approved as EN IEC 61158-2
IEC 61158-5-21 NOTE Approved as EN IEC 61158-5-21
IEC 61158-6-21 NOTE Approved as EN IEC 61158-6-21
IEC 61784-1 (series) NOTE Approved as EN IEC 61784-1 (series)
IEC 61784-2 (series) NOTE Approved as EN IEC 61784-2 (series)
IEC 61784-2-0:2023 NOTE Approved as EN IEC 61784-2-0:2023 (not modified)
IEC 61918:2018 NOTE Approved as EN IEC 61918:2018 (not modified) + A11:2019
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 61158-3-21 2019 Industrial communication networks - EN IEC 61158-3-21 2019
Fieldbus specifications - Part 3-21: Data-
link layer service definition - Type 21
elements
ISO/IEC 7498-1 1994 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 8802-3 2021 Telecommunications and exchange - -
between information technology systems -
Requirements for local and metropolitan
area networks - Part 3: Standard for
Ethernet
ISO/IEC 10731 - Information technology - Open Systems - -
Interconnection - Basic Reference Model -
Conventions for the definition of OSI
services
IEC 61158-4-21 ®
Edition 3.0 2023-03
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 4-21: Data-link layer protocol specification – Type 21 elements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.20; 35.110 ISBN 978-2-8322-6555-0
– 2 – IEC 61158-4-21:2023 © 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 . 10
1.5 Conformance . 10
2 Normative references . 11
3 Terms, definitions, symbols and abbreviated terms . 11
3.1 Reference model terms and definitions . 11
3.2 Service convention terms and definitions . 13
3.3 Common terms and definitions . 14
3.4 Additional Type 21 definitions . 17
3.5 Common symbols and abbreviations . 17
3.6 Additional Type 21 symbols and abbreviations . 18
4 Overview of the data-link protocol . 18
4.1 General . 18
4.2 Overview of medium access control . 19
4.3 Service assumed from the physical layer . 19
4.4 DLL architecture . 20
4.4.1 General . 20
4.4.2 DLL management (DLM) interface support function . 21
4.5 Data type . 22
4.5.1 General . 22
4.5.2 Boolean . 22
4.5.3 Unsigned integer . 22
4.5.4 Signed integer . 22
4.5.5 Octet String . 23
4.5.6 Visible String . 23
4.5.7 Time of day . 23
4.6 Local parameters and variables . 24
4.6.1 General . 24
4.6.2 DLE configuration parameters . 24
4.6.3 Queues to support data transfer . 25
4.6.4 Variables to support SAP management . 25
4.6.5 Variables to support local device information management . 27
4.6.6 Variables and counter to support network information management . 31
4.6.7 Variables and counter to support a device path information
management . 35
4.6.8 Variables, counters, timers, and queues to support path table
management . 39
5 General structure and encoding . 39
5.1 Overview. 39
5.2 MAPDU structure and encoding . 39
5.3 Common MAC frame structure, encoding and elements of procedure . 40
5.3.1 MAC frame structure . 40

IEC 61158-4-21:2023 © IEC 2023 – 3 –
5.3.2 Elements of the MAC frame . 40
5.3.3 Elements of the Type 21 DLPDU . 41
5.4 Order of bit transmission . 49
5.5 Invalid DLPDU . 49
6 DLPDU structure and procedure . 49
6.1 General . 49
6.2 Common DLPDU Field . 49
6.2.1 General . 49
6.2.2 Version . 50
6.2.3 Length . 50
6.3 DL-DATA Transfer . 50
6.3.1 DT DLPDU . 5
...