IEC 61158-4-21:2019

Industrial communication networks - Fieldbus specifications - Part 4-21: Data-link layer protocol specification - Type 21 elements

IEC 61158-4-21:2019 describes 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 data link service provider and procedures for giving communication opportunities based on standard ISO/IEC 8802-3 MAC, with provisions for nodes to be added or removed during normal operation; structure of the fieldbus data link protocol data units (DLPDUs) used for the transfer of data and control information by the protocol of this standard, and their representation as physical interface data units. This second edition cancels and replaces the first edition published in 2010. This edition constitutes a technical revision. The main changes are:
• added Frame control Value, DLM function and DLL constants;
• changed NCM_RETRY_RNMS to NCM_CHECK_NET_INTEGRITY_REQ;
• updated DLM state table;
• miscellaneous editorial corrections.

Réseaux de communication industriels - Spécifications des bus de terrain - Partie 4-21: Spécification du protocole de la couche liaison de données - Éléments de type 21

L'IEC 61158-4-21:2019 décrit:
a) des procédures de transfert en temps opportun de données et d'informations de commande d'une entité utilisateur de liaison de données à une entité utilisateur homologue ainsi qu'entre entités de liaison de données qui constituent le fournisseur de services distribués de la liaison;
b) des procédures offrant des moyens de communication, fondées sur la commande d’accès au support (MAC) de l’ISO/IEC 8802 3, ainsi que des dispositions permettant d'ajouter et de retirer des nœuds au cours du fonctionnement normal;
c) la structure des unités de données de protocole de liaison de données (DLPDU) de bus de terrain utilisées pour le transfert des données et les informations de commande par le protocole objet du présent document, ainsi que leur représentation en tant qu'unité de données d'interface de couche physique.

General Information

• Status: Published
• Publication Date: 09-Apr-2019
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.20 - Data link layer
• ICS: 35.110 - Networking
• Technical Committee: SC 65C - Industrial networks
• Drafting Committee: WG 9 - TC 65/SC 65C/WG 9
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 28-Mar-2023

Relations

• Revises: IEC 61158-4-21:2010 - Industrial communication networks - Fieldbus specifications - Part 4-21: Data-link layer protocol specification - Type 21 elements
• Effective Date: 05-Sep-2023
• Revised: IEC 61158-4-21:2023 - Industrial communication networks - Fieldbus specifications - Part 4-21: Data-link layer protocol specification - Type 21 elements
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61158-4-21 ®
Edition 2.0 2019-04
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 4-21: Data-link layer protocol specification – Type 21 elements

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
IEC 61158-4-21 ®
Edition 2.0 2019-04
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 978-2-8322-6777-6

– 2 – IEC 61158-4-21:2019 © IEC 2019
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 abbreviations . 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 . 19
4.1 General . 19
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 . 23
4.5.5 Octet String . 23
4.5.6 Visible String . 23
4.5.7 Time of day . 24
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 . 26
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

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 . 50
6.4 DL-SPDATA Transfer . 53
6.4.1 SPDT DLPDU . 53
6.5 Network control messages . 54
6.5.1 General . 54
6.5.2 NCM_LA DLPDU . 54
6.5.3 NCM_AT DLPDU . 56
6.5.4 NCM_LS DLPDU . 57
6.5.5 NCM_RS DLPDU . 58
6.5.6 NCM_AR_DLPDU . 59
6.5.7 NCM_AR DLPDU structure . 59
7 DLE elements of procedure . 60
7.1 Overall structure . 60
7.2 DL-protocol machine (DLPM) . 61
7.2.1 Overview . 61
7.2.2 Primitive definitions . 61
7.2.3 DLPM state table . 64
7.2.4 DLPM functions . 68
7.3 DLL management Protocol . 69
7.3.1 Overview . 69
7.3.2 Primitive definitions . 69
7.3.3 DLM state table . 72
7.3.4 DLM functions . 96
8 Constants and error codes . 105
8.1 General . 105
8.2 Constants . 106
8.3 Data-link layer error codes . 107
Bibliography . 108

Figure 1 – Interaction of PhS primitives with DLE . 20
Figure 2 – Data-link layer architecture . 21
Figure 3 – Relationships of DLSAPs, DLSAP-addresses, and group DL-addresses . 26
Figure 4 – Common MAC frame format for Type 21 DLPDU . 40
Figure 5 – MAC frame format for other protocols . 40
Figure 6 – Version and Length field . 41
Figure 7 – DST_addr field . 42

– 4 – IEC 61158-4-21:2019 © IEC 2019
Figure 8 – SRC_addr field. 43
Figure 9 – Frame Control Field . 43
Figure 10 – Extension field .
...

IEC 61158-4-21 ®
Edition 2.0 2019-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –
Part 4-21: Data-link layer protocol specification – Type 21 elements

Réseaux de communication industriels – Spécifications des bus de terrain –
Partie 4-21: Spécification du protocole de la couche liaison de données –
Éléments de type 21
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - Electropedia - www.electropedia.org
webstore.iec.ch/advsearchform Le premier dictionnaire d'électrotechnologie en ligne au
La recherche avancée permet de trouver des publications IEC monde, avec plus de 22 000 articles terminologiques en
en utilisant différents critères (numéro de référence, texte, anglais et en français, ainsi que les termes équivalents dans
comité d’études,…). Elle donne aussi des informations sur les 16 langues additionnelles. Egalement appelé Vocabulaire
projets et les publications remplacées ou retirées. Electrotechnique International (IEV) en ligne.

IEC Just Published - webstore.iec.ch/justpublished Glossaire IEC - std.iec.ch/glossary
Restez informé sur les nouvelles publications IEC. Just 67 000 entrées terminologiques électrotechniques, en anglais
Published détaille les nouvelles publications parues. et en français, extraites des articles Termes et Définitions des
Disponible en ligne et une fois par mois par email. publications IEC parues depuis 2002. Plus certaines entrées
antérieures extraites des publications des CE 37, 77, 86 et
Service Clients - webstore.iec.ch/csc CISPR de l'IEC.

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
[e-mail].
IEC 61158-4-21 ®
Edition 2.0 2019-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –

Part 4-21: Data-link layer protocol specification – Type 21 elements

Réseaux de communication industriels – Spécifications des bus de terrain –

Partie 4-21: Spécification du protocole de la couche liaison de données –

Éléments de type 21
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 35.100.20; 35.110 ISBN 978-2-8322-9146-7

– 2 – IEC 61158-4-21:2019 © IEC 2019
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 abbreviations . 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 . 19
4.1 General . 19
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 . 23
4.5.5 Octet String . 23
4.5.6 Visible String . 23
4.5.7 Time of day . 24
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 . 26
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

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 . 50
6.4 DL-SPDATA Transfer . 53
6.4.1 SPDT DLPDU . 53
6.5 Network control messages . 54
6.5.1 General . 54
6.5.2 NCM_LA DLPDU . 54
6.5.3 NCM_AT DLPDU . 56
6.5.4 NCM_LS DLPDU . 57
6.5.5 NCM_RS DLPDU . 58
6.5.6 NCM_AR_DLPDU . 59
6.5.7 NCM_AR DLPDU structure . 59
7 DLE elements of procedure . 60
7.1 Overall structure . 60
7.2 DL-protocol machine (DLPM) .
...