IEC 61158-3-2:2007

Industrial communication networks - Fieldbus specifications - Part 3-2: Data-link layer service definition - Type 2 elements

IEC 61158-3-2:2007 defines in an abstract way the externally visible service provided by the Type 2 fieldbus data-link layer in terms of:
- the primitive actions and events of the service;
- the parameters associated with each primitive action and event, and the form which they take;
- the interrelationship between these actions and events, and their valid sequences. This first edition and its companion parts of the IEC 61158-3 subseries cancel and replace IEC 61158-3:2003. This edition of this part constitutes a minor revision. This part and its companion Type 2 parts also cancel and replace IEC/PAS 62410, published in 2005. This edition includes the following changes:
- deletion of the former Type 6 fieldbus, and the placeholder for a Type 5 fieldbus data-link layer, for lack of market relevance;
- addition of new types of fieldbuses;
- division of this part into multiple parts numbered 3-1, 3-2,..., 3-19. This bilingual version (2013-07) corresponds to the monolingual English version, published in 2007-12.

Réseaux de communication industriels - Spécifications de bus de terrain - Partie 3-2: Définition du service de la couche de liaison de données - Eléments de type 2

La CEI 61158-3-2:2007 définit de manière abstraite le service visible externe fourni par la couche de liaison de données de bus de terrain de type 2, en termes:
- des actions et événements primitifs du service;
- des paramètres associés à chaque action et à chaque événement primitifs,
- ainsi que la forme de ces derniers, de l'interrelation entre ces actions et événements, et leurs séquences valides. Cette première édition et les parties associées de la sous-série CEI 61158-3 annulent et remplacent la CEI 61158-3:2003. L'édition de la présente partie constitue une révision mineure. La présente partie et les parties de type 2 associées annulent et remplacent également la CEI/PAS 62410 publiée en 2005. La présente édition comporte les modifications importantes suivantes par rapport à l'édition précédente:
- suppression du bus de terrain de type 6 précédent, et du paramètre fictif applicable à une couche de liaison de données de bus de terrain de type 5, pour défaut de pertinence de commercialisation;
- ajout de nouveaux types de bus de terrain;
- division de la présente partie en plusieurs parties numérotées 3-1, 3-2,..., 3-19. La présente version bilingue (2013-07) correspond à la version anglaise monolingue publiée en 2007-12.

General Information

• Status: Published
• Publication Date: 13-Dec-2007
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.20 - Data link layer
• Technical Committee: SC 65C - Industrial networks
• Drafting Committee: WG 9 - TC 65/SC 65C/WG 9
• Current Stage: DELPUB - Deleted Publication
• Start Date: 13-Aug-2014
• Completion Date: 26-Oct-2025

Relations

• Replaces: IEC PAS 62410:2005 - Real-time Ethernet SERCOS III
• Effective Date: 05-Sep-2023
• Replaces: IEC 61158-3:2003 - Digital data communications for measurement and control - Fieldbus for use in industrial control systems - Part 3: Data link service definition
• Effective Date: 05-Sep-2023
• Revised: IEC 61158-3-2:2014 - Industrial communication networks - Fieldbus specifications - Part 3-2: Data-lonk layer service definition - Type 2 elements
• Effective Date: 05-Sep-2023

Overview

IEC 61158-3-2:2007 - "Industrial communication networks - Fieldbus specifications - Part 3‑2: Data‑link layer service definition - Type 2 elements" - defines, in an abstract and protocol‑neutral way, the externally visible service that a Type 2 fieldbus data‑link layer provides to the layer above. The standard focuses on basic time‑critical messaging for automation systems: the primitive actions and events, associated parameters and data formats, and the valid sequencing and interrelationship of those primitives. This edition (2007) is a minor revision that replaces earlier 2003/2005 documents and is part of the IEC 61158 fieldbus family.

Key topics

The standard documents the data‑link service semantics and management features relevant to Type 2 fieldbuses, including:

• Service primitives and events: abstract definitions of actions the data‑link layer offers and the events it reports to users.
• Parameters and data formats: the parameters associated with each primitive and the forms they take.
• Primitive sequencing and state models: rules and valid sequences for using primitives (connection‑mode and connectionless‑mode).
• Connection‑mode vs connectionless‑mode data transfer: behavior, success/failure sequences and related primitives.
• DL‑management services: link synchronization, synchronized parameter changes, event reporting, bad‑FCS handling, moderator enable/current moderator, power‑up/online, listen‑only mode, time distribution.
• Queue maintenance and tag filtering: message queuing models, maintenance primitives and tag‑based filtering services.
• Relation to the OSI reference model and fieldbus three‑layer model (conceptual service interface).

Applications

IEC 61158-3-2 is intended for any implementation or evaluation of Type 2 fieldbus data‑link behavior where predictable, time‑constrained messaging is required:

• Industrial automation networks (factory and process automation)
• PLC and I/O device vendors implementing data‑link layers
• System integrators designing deterministic communication for control loops
• Safety and time‑synchronization critical systems requiring defined DL service semantics
• Test houses and conformance labs validating compliance with Type 2 data‑link behavior

Who uses this standard

• Automation engineers and system architects
• Device and stack implementers (data‑link layer developers)
• Certification bodies and test laboratories
• Standards experts mapping DL services to physical and application layer protocols

Related standards

• IEC 61158 series (other parts covering protocol specification, physical layers and profiles)
• IEC/TR 61158‑1 (fieldbus reference model)
• IEC 61784 (type combinations and use of protocol types)
• IEC/PAS 62410 (superseded by this part)

This concise service definition is essential when designing, implementing or validating deterministic fieldbus communications based on Type 2 data‑link semantics.

Standards Content (Sample)

IEC 61158-3-2
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 3-2: Data-link layer service definition – Type 2 elements
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IEC 61158-3-2
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 3-2: Data-link layer service definition – Type 2 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 35.100.20; 25.040.40 ISBN 2-8318-9411-5

– 2 – 61158-3-2 © IEC:2007(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
1.1 Overview .7
1.2 Specifications .7
1.3 Conformance.7
2 Normative references.8
3 Terms, definitions, symbols, abbreviations and conventions .8
3.1 Reference model terms and definitions .8
3.2 Service convention terms and definitions .10
3.3 Common data-link service terms and definitions.11
3.4 Additional Type 2 data-link specific definitions.12
3.5 Common symbols and abbreviations .15
3.6 Additional Type 2 symbols and abbreviations .15
3.7 Common conventions .15
4 Connection-mode and connectionless-mode data-link service .16
4.1 Overview .16
4.2 Facilities of the data-link service .20
4.3 Model of the data-link service .21
4.4 Sequence of primitives .23
4.5 Connection-mode data transfer .25
4.6 Connectionless-mode data transfer.27
4.7 Queue maintenance.30
4.8 Tag filter.32
5 DL-management Services .33
5.1 Sequence of primitives .33
5.2 Link synchronization .34
5.3 Synchronized parameter change .34
5.4 Event reports.36
5.5 Bad FCS.38
5.6 Current moderator .38
5.7 Enable moderator .39
5.8 Power-up and online .40
5.9 Listen only.41
5.10 Time distribution.42
Bibliography .44
INDEX .45

Figure 1 – Relationships of DLSAPs, DLSAP-addresses and group DL-addresses .11
Figure 2 – NUT structure.17
Figure 3 – Medium access during scheduled time.18
Figure 4 – Medium access during unscheduled time .19
Figure 5 – Queue model for the peer and multipoint DLS, DLSAPs and their DLCEPs .20
Figure 6 – Queue model of a multipoint DLS between a sending DLS-user and one or
more receiving DLS-users .22
Figure 7 – DLS primitive time-sequence diagram .24

61158-3-2 © IEC:2007(E) – 3 –
Figure 8 – State transition diagram for sequences of DLS primitives at one DLSAP.25
Figure 9 – Sequence of primitives for a successful connection-mode transfer .27
Figure 10 – Sequence of primitives for an unsuccessful connection-mode transfer.27
Figure 11 – Sequence of primitives for a successful connectionless-mode transfer .30
Figure 12 – Sequence of primitives for an unsuccessful connectionless-mode transfer.30
Figure 13 – Sequence of primitives for a queue maintenance request .32
Figure 14 – Sequence of primitives for a tag filter request.33
Figure 15 – Sequence of primitives for a local link synchronization .34
Figure 16 – Sequence of primitives for a DLM-get/set parameters request .36
Figure 17 – Sequence of primitives for a DLM-tMinus change request.36
Figure 18 – Sequence of primitives for a DLM-event indication .38
Figure 19 – Sequence of primitives for a DLM-bad-FCS indication .38
Figure 20 – Sequence of primitives for a DLM-current-moderator indication .39
Figure 21 – Sequence of primitives for a DLM-enable-moderator request.40
Figure 22 – Sequence of primitives for a DLM-power-up indication.41
Figure 23 – Sequence of primitives for a DLM-online request.41
Figure 24 – Sequence of primitives for a DLM-listen-only request .42

Table 1 – Summary of connection-mode and connectionless-mode primitives and
parameters .24
Table 2 – DL-connection-mode transfer primitives and parameters .26
Table 3 – DL-connectionless-mode transfer primitives and parameters .28
Table 4 – Fixed tag services available to the DLS-user .29
Table 5 – DL-queue maintenance primitives and parameters .31
Table 6 – DL-connectionless-mode tag filter primitives and parameters .32
Table 7 – Summary of DL-management primitives and parameters .33
Table 8 – Link synchronization primitives and parameters.34
Table 9 – Synchronized parameter change primitives and parameters .35
Table 10 – DLMS-configuration-data .36
Table 11 – Event report primitives and parameters .37
Table 12 – DLMS events being reported .37
Table 13 – Bad FCS primitives and parameters .38
Table 14 – Current moderator primitives and parameters.39
Table 15 – Enable moderator primitives and parameters.39
Table 16 – Power-up and online primitives and parameters.40
Table 17 – Listen-only primitives and parameters .41
Table 18 – DLMS time and time quality parameters .42
Table 19 – Time distribution source quality.43

– 4 – 61158-3-2 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 3-2: Data-link layer service definition – Type 2 elements

FOREWORD
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
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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.
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 the IEC 61784 series. Use of the various protocol types in other combinations
may require permission of their respective intellectual-property-right holders.
International Standard IEC 61158-3-2 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This first edition and its companion parts of the IEC 61158-3 subseries cancel and replace
IEC 61158-3:2003. This edition of this part constitutes a minor revision. This part and its
companion Type 2 parts also cancel and replace IEC/PAS 62410, published in 2005.
This edition includes the following significant changes with respect to the previous edition:
a) deletion of the former Type 6 fieldbus, and the placeholder for a Type 5 fieldbus data-link
layer, for lack of market relevance;
b) addition of new types of fieldbuses;

61158-3-2 © IEC:2007(E) – 5 –
c) division of this part into multiple parts numbered 3-1, 3-2, …, 3-19.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/473/FDIS 65C/484/RVD
Full information on the voting for the approval of this standard 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.
The committee has decided that the contents of this publication will remain unchanged until the
maintenance result 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 standard will be synchronized with the other parts of the IEC 61158 series.
The list of all the parts of the IEC 61158 series, under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.

– 6 – 61158-3-2 © IEC:2007(E)
INTRODUCTION
This standard 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/TR 61158-1.
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 layer service defined in this standard is a conceptual architectural service,
independent of administrative and implementation divisions.

61158-3-2 © IEC:2007(E) – 7 –
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 3-2: Data-link layer service definition – Type 2 elements

1 Scope
1.1 Overview
This part of IEC 61158 provides common elements for basic time-critical messaging
communications between devices in an automation environment. The term “time-critical” is
used to represent the presence of 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.
This standard defines in an abstract way the externally visible service provided by the Type 2
fieldbus data-link layer in terms of
a) the primitive actions and events of the service;
b) the parameters associated with each primitive action and event, and the form which they
take; and
c) the interrelationship between these actions and events, and their valid sequences.
The purpose of this standard is to define the services provided to:
• the Type 2 fieldbus application layer at the boundary between the application and data-link
layers of the fieldbus reference model;
• systems management at the boundary between the data-link layer and systems
management of the fieldbus reference model.
Type 2 DL-service provides both a connected and a connectionless subset of those services
specified in ISO/IEC 8886.
1.2 Specifications
The principal objective of this standard is to specify the characteristics of conceptual data-link
layer services suitable for time-critical communications and thus supplement the OSI Basic
Reference Model in guiding the development of data-link protocols for time-critical
communications. A secondary objective is to provide migration paths from previously-existing
industrial communications protocols.
This specification may be used as the basis for formal DL-Programming-Interfaces.
Nevertheless, it is not a formal programming interface, and any such interface will need to
address implementation issues not covered by this specification, including:
a) the sizes and octet ordering of various multi-octet service parameters;
b) the correlation of paired request and confirm, or indication and response, primitives.
1.3 Conformance
This standard does not specify individual implementations or products, nor does it constrain the
implementations of data-link entities within industrial automation systems.

– 8 – 61158-3-2 © IEC:2007(E)
There is no conformance of equipment to this data-link layer service definition standard.
Instead, conformance is achieved through implementation of the corresponding data-link
protocol that fulfills the Type 1 data-link layer services defined in this standard.
2 Normative references
The following referenced documents are indispensable for the application 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.
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 8886, Information technology – Open Systems Interconnection – Data link service
definition
ISO/IEC 10731:1994, Information technology – Open Systems Interconnection – Basic
Reference Model – Conventions for the definition of OSI services
3 Terms, definitions, symbols, abbreviations and conventions
For the purposes of this document, the following terms, definitions, symbols, abbreviations and
conventions apply.
3.1 Reference model terms and definitions
This standard is based in part on the concepts developed in ISO/IEC 7498-1 and
ISO/IEC 7498-3, and makes use of the following terms defined therein:
[ISO/IEC 7498-3]
3.1.1 DL-address
[ISO/IEC 7498-1]
3.1.2 DL-address-mapping
3.1.3 called-DL-address [ISO/IEC 7498-3]
3.1.4 calling-DL-address [ISO/IEC 7498-3]
3.1.5 centralized multi-end-point-connection [ISO/IEC 7498-1]
3.1.6 DL-connection [ISO/IEC 7498-1]
3.1.7 DL-connection-end-point [ISO/IEC 7498-1]
3.1.8 DL-connection-end-point-identifier [ISO/IEC 7498-1]
3.1.9 DL-connection-mode transmission [ISO/IEC 7498-1]
3.1.10 DL-connectionless-mode transmission [ISO/IEC 7498-1]
3.1.11 correspondent (N)-entities [ISO/IEC 7498-1]
correspondent DL-entities  (N=2)
correspondent Ph-entities  (N=1)
3.1.12 DL-duplex-transmission [ISO/IEC 7498-1]

61158-3-2 © IEC:2007(E) – 9 –
3.1.13 (N)-entity [ISO/IEC 7498-1]
DL-entity  (N=2)
Ph-entity  (N=1)
3.1.14 DL-facility [ISO/IEC 7498-1]
3.1.15 flow control [ISO/IEC 7498-1]
3.1.16 (N)-layer [ISO/IEC 7498-1]
DL-layer  (N=2)
Ph-layer  (N=1)
[ISO/IEC 7498-1]
3.1.17 layer-management
[ISO/IEC 7498-3]
3.1.18 DL-local-view
[ISO/IEC 7498-3]
3.1.19 DL-name
3.1.20 naming-(addressing)-domain [ISO/IEC 7498-3]
3.1.21 peer-entities [ISO/IEC 7498-1]
3.1.22 primitive name [ISO/IEC 7498-3]
3.1.23 DL-protocol [ISO/IEC 7498-1]
3.1.24 DL-protocol-connection-identifier [ISO/IEC 7498-1]
3.1.25 DL-protocol-data-unit [ISO/IEC 7498-1]
3.1.26 DL-relay [ISO/IEC 7498-1]
3.1.27 reset [ISO/IEC 7498-1]
3.1.28 responding-DL-address [ISO/IEC 7498-3]
3.1.29 routing [ISO/IEC 7498-1]
3.1.30 segmenting [ISO/IEC 7498-1]
3.1.31 (N)-service [ISO/IEC 7498-1]
DL-service  (N=2)
Ph-service  (N=1)
[ISO/IEC 7498-1]
3.1.32 (N)-service-access-point
DL-service-access-point  (N=2)
Ph-service-access-point  (N=1)
3.1.33 DL-service-access-point-address [ISO/IEC 7498-3]
3.1.34 DL-service-connection-identifier [ISO/IEC 7498-1]
3.1.35 DL-service-data-unit [ISO/IEC 7498-1]
3.1.36 DL-simplex-transmission [ISO/IEC 7498-1]
3.1.37 DL-subsystem [ISO/IEC 7498-1]
3.1.38 systems-management [ISO/IEC 7498-1]
3.1.39 DLS-user-data [ISO/IEC 7498-1]

– 10 – 61158-3-2 © IEC:2007(E)
3.2 Service convention terms and definitions
This standard also makes use of the following terms defined in ISO/IEC 10731 as they apply to
the data-link layer:
3.2.1 acceptor
3.2.2 asymmetrical service
3.2.3 confirm (primitive);
requestor.deliver (primitive)
3.2.4 deliver (primitive)
3.2.5 DL-confirmed-facility
3.2.6 DL-facility
3.2.7 DL-local-view
3.2.8 DL-mandatory-facility
3.2.9 DL-non-confirmed-facility
3.2.10 DL-provider-initiated-facility
3.2.11 DL-provider-optional-facility
3.2.12 DL-service-primitive;
primitive
3.2.13 DL-service-provider
3.2.14 DL-service-user
3.2.15 DLS-user-optional-facility
3.2.16 indication (primitive);
acceptor.deliver (primitive)
3.2.17 multi-peer
3.2.18 request (primitive);
requestor.submit (primitive)
3.2.19 requestor
3.2.20 response (primitive);
acceptor.submit (primitive)
3.2.21 submit (primitive)
3.2.22 symmetrical service
61158-3-2 © IEC:2007(E) – 11 –
3.3 Common data-link service terms and definitions
NOTE  Many definitions are common to more than one protocol Type; they are not necessarily used by all protocol
Types.
3.3.1
DL-segment, link, local link
single DL-subnetwork in which any of the connected DLEs may communicate directly, without
any intervening DL-relaying, whenever all of those DLEs that are participating in an instance of
communication are simultaneously attentive to the DL-subnetwork during the period(s) of
attempted communication
3.3.2
DLSAP
distinctive point at which DL-services are provided by a single DL-entity to a single higher-layer
entity
NOTE  This definition, derived from ISO/IEC 7498-1, is repeated here to facilitate understanding of the critical
distinction between DLSAPs and their DL-addresses.
DLS-user-entity
DLS-user-entity
DLS-users
DLSAP DLSAP DLSAP
DLSAP-
address DLSAP-
DLSAP-
group DL-
address
addresses
address
DL-layer
DL-entity
PhSA P PhSA P
Ph-layer
NOTE 1  DLSAPs and PhSAPs are depicted as ovals spanning the boundary between two adjacent layers.
NOTE 2  DL-addresses are depicted as designating small gaps (points of access) in the DLL portion of a DLSAP.
NOTE 3  A single DL-entity may have multiple DLSAP-addresses and group DL-addresses associated with a single
DLSAP.
Figure 1 – Relationships of DLSAPs, DLSAP-addresses and group DL-addresses
3.3.3
DL(SAP)-address
either an individual DLSAP-address, designating a single DLSAP of a single DLS-user, or a
group DL-address potentially designating multiple DLSAPs, each of a single DLS-user
NOTE  This terminology is chosen because ISO/IEC 7498-3 does not permit the use of the term DLSAP-address to
designate more than a single DLSAP at a single DLS-user.

– 12 – 61158-3-2 © IEC:2007(E)
3.3.4
(individual) DLSAP-address
DL-address that designates only one DLSAP within the extended link
NOTE  A single DL-entity may have multiple DLSAP-addresses associated with a single DLSAP.
3.3.5
extended link
DL-subnetwork, consisting of the maximal set of links interconnected by DL-relays, sharing a
single DL-name (DL-address) space, in which any of the connected DL-entities may
communicate, one with another, either directly or with the assistance of one or more of those
intervening DL-relay entities
NOTE  An extended link may be composed of just a single link.
3.3.6
frame
denigrated synonym for DLPDU
3.3.7
group DL-address
DL-address that potentially designates more than one DLSAP within the extended link
NOTE  A single DL-entity may have multiple group DL-addresses associated with a single DLSAP. A single
DL-entity also may have a single group DL-address associated with more than one DLSAP.
3.3.8
node
single DL-entity as it appears on one local link
3.3.9
receiving DLS-user
DL-service user that acts as a recipient of DLS-user-data
NOTE  A DL-service user can be concurrently both a sending and receiving DLS-user.
3.3.10
sending DLS-user
DL-service user that acts as a source of DLS-user-data
3.4 Additional Type 2 data-link specific definitions
3.4.1
application
function or data structure for which data is subscribed or published
3.4.2
behavior
indication of how the object responds to particular events. Its description includes the
relationship between attribute values and services
3.4.3
bridge, DL-router
DL-relay entity which performs selective store-and-forward and routing functions to connect two
or more separate DL-subnetworks (links) to form a unified DL-subnetwork (the extended link)
3.4.4
cyclic
term used to describe events which repeat in a regular and repetitive manner

61158-3-2 © IEC:2007(E) – 13 –
3.4.5
device
physical hardware connection to the link
NOTE  A device may contain more than one node.
3.4.6
DL-subnetwork
series of nodes connected by PhEs and, where appropriate, DL-routers
3.4.7
DLPDU
Data-link Protocol Data unit
NOTE  A DLPDU consists of a source MAC ID, zero or more Lpackets, and an FCS, as transmitted or received by
an associated PhE.
3.4.8
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.4.9
fixed tag
two octet identifier (tag) which identifies a specific service to be performed by either
a) that receiving node on the local link which has a specified MAC ID, or
b) all receiving nodes on the local link.
NOTE  Identification of the target node(s) is included in the two octet tag
3.4.10
generic tag
three octet identifier (tag) which identifies a specific piece of application information
3.4.11
guardband
time slot allocated for the transmission of the moderator DLPDU
3.4.12
link
collection of nodes with unique MAC IDs
NOTE  Ph-segments connected by Ph-repeaters make up a link; links connected by DL-routers make up an
extended link (sometimes called a local area network)
3.4.13
Lpacket
well-defined sub-portion of a DLPDU containing (among other things)
a) a fixed tag or a generic tag, and
b) DLS-user data or, when the tag has DL-significance, DL-data
3.4.14
moderator
node with the lowest MAC ID that is responsible for transmitting the moderator DLPDU
3.4.15
moderator DLPDU
DLPDU transmitted by the node with the lowest MAC ID for the purpose of synchronizing the
nodes and distributing the link configuration parameters

– 14 – 61158-3-2 © IEC:2007(E)
3.4.16
multipoint DLC
centralized multi-end-point DL-connection offering DL-simplex-transmission between a single
distinguished DLS-user, known as the publisher or publishing DLS-user, and a set of peer but
undistinguished DLS-users, known collectively as the subscribers or subscribing DLS-users,
where the publishing DLS-user can send to the subscribing DLS-users as a group (but not
individually). A multipoint DLC always provides asymmetrical service.
3.4.17
node
logical connection to a local link, requiring a single MAC ID
NOTE  A single physical device may appear as many nodes on the same local link. For the purposes of this
protocol, each node is considered to be a separate DLE.
3.4.18
peer-to-peer DLC
point-to-point DL-connection offering DL-simplex-transmission between a single distinguished
sending DLS-user and a single distinguished receiving DLS-user
NOTE  A peer-to-peer DLC always provides asymmetrical service.
3.4.19
rogue
node that has received a moderator DLPDU that disagrees with the link configuration currently
used by this node
3.4.20
scheduled
data transfers that occur in a deterministic and repeatable manner on predefined NUTs.
3.4.21
tMinus
number of NUTs before a new set of link configuration parameters are to be used
3.4.22
tone
instant of time which marks the boundary between two NUTs
3.4.23
unscheduled
data transfers that use the remaining allocated time in the NUT after the scheduled transfers
have been completed
61158-3-2 © IEC:2007(E) – 15 –
3.5 Common symbols and abbreviations
NOTE  Many symbols and abbreviations are common to more than one protocol Type; they are not necessarily
used by all protocol Types.
Data-link layer (as a prefix)
DL-
DL-connection
DLC
DLCEP DL-connection-end-point
DLE DL-entity (the local active instance of the data-link layer)
DLL DL-layer
DLPCI DL-protocol-control-information
DLPDU DL-protocol-data-unit
DL-management
DLM
DL-management Entity (the local active instance of DL-management)
DLME
DL-management Service
DLMS
DLS DL-service
DLSAP DL-service-access-point
DLSDU DL-service-data-unit
FIFO First-in first-out (queuing method)
OSI Open systems interconnection
Physical layer (as a prefix)
Ph-
Ph-entity (the local active instance of the physical layer)
PhE
Ph-layer
PhL
QoS Quality of service
3.6 Additional Type 2 symbols and abbreviations
MAC ID DL-address of a node
MDS Medium dependent sublayer
NUT Network (actually, local link) update time
NOTE  The use of the term “network” in the preceding definition is maintained for historic reasons, even though the
scope involved is only a portion of a single DL-subnetwork.
r.m.s. root mean square
SMAX MAC ID of the maximum scheduled node
Tx Transmit
TUI Table unique identifier
UCMM Unconnected message manager
UMAX MAC ID of maximum unscheduled node
Unscheduled start register
USR
3.7 Common conventions
This standard uses the descriptive conventions given in ISO/IEC 10731.
The service model, service primitives, and time-sequence diagrams used are entirely abstract
descriptions; they do not represent a specification for implementation.

– 16 – 61158-3-2 © IEC:2007(E)
Service primitives, used to represent service user/service provider interactions (see
ISO/IEC 10731), convey parameters that indicate information available in the user/provider
interaction.
This standard uses a tabular format to describe the component parameters of the DLS
primitives. The parameters that apply to each group of DLS primitives are set out in tables
throughout the remainder of this standard. Each table consists of up to six columns, containing
the name of the service parameter, and a column each for those primitives and parameter-
transfer directions used by the DLS:
⎯ the request primitive’s input parameters;
⎯ the request primitive’s output parameters;
⎯ the indication primitive’s output parameters;
⎯ the response primitive’s input parameters; and
⎯ the confirm primitive’s output parameters.
NOTE  The request, indication, response and confirm primitives are also known as requestor.submit,
acceptor.deliver, acceptor.submit, and requestor.deliver primitives, respectively (see ISO/IEC 10731).
One parameter (or part of it) is listed in each row of each table. Under the appropriate service
primitive columns, a code is used to specify the type of usage of the parameter on the primitive
and parameter direction specified in the column:
M — parameter is mandatory for the primitive.
U — parameter is a User option, and may or may not be provided depending on
the dynamic usage of the DLS-user. When not provided, a default value
for the parameter is assumed.
C — parameter is conditional upon other parameters or upon the environment
of the DLS-user.
(blank) — parameter is never present.
Some entries are further qualified by items in brackets. These may be
a) a parameter-specific constraint
(=) indicates that the parameter is semantically equivalent to the parameter in the
service primitive to its immediate left in the table.
b) an indication that some note applies to the entry
(n) indicates that the following note n contains additional information pertaining to the
parameter and its use.
In any particular interface, not all parameters need be explicitly stated. Some may be implicitly
associated with the DLSAP at which the primitive is issued.
In the diagrams which illustrate these interfaces, dashed lines indicate cause-and-effect or
time-sequence relationships, and wavy lines indicate that events are roughly
contemporaneous.
4 Connection-mode and connectionless-mode data-link service
4.1 Overview
4.1.1 Data transfer services
The primary task of a DLE is to determine, in co-operation with other DLEs on the same local
link, the granting of permission to transmit on the medium. At its upper interface, the DLL
provides services to receive and deliver service data units (DLSDUs) for higher level entities.

61158-3-2 © IEC:2007(E) – 17 –
NOTE 1  The following access mechanisms are not visible to the higher level entities. They are described here as
an aid to understanding the purpose and use of DLS parameters and services that are visible to higher layer
entities.
This DLL protocol is based on a fixed repetitive time cycle, called the network update time
(NUT). The NUT is maintained in close synchronism among all nodes on the local link. A node
is not permitted access to transmit if its configured NUT does not agree with the NUT currently
being used on the local link. Different local links within the extended link may have different
NUT durations.
Each node contains its own timer synchronized to the local link’s NUT. Medium access is
determined by local sub-division of the NUT into variable-duration access slots. Access to the
medium is in sequential order based on the MAC ID of the node. Specific behaviors have been
incorporated into the access protocol allowing a node which temporarily assumes a MAC ID of
zero to perform link maintenance. The MAC ID numbers of all nodes on a link are unique. Any
DLE detecting the presence of a MAC ID duplicating its own MAC ID immediately stops
transmitting.
An implicit token passing mechanism is used to grant access to the medium. Each node
monitors the source MAC ID of each DLPDU received. At the end of a DLPDU, each DLE sets
an “implicit token register” to the received source MAC ID + 1. If the implicit token register is
equal to the local MAC ID, then the DLE transmits one DLPDU containing zero or more
Lpackets with data. In all other cases, the node watches for either a new DLPDU from the node
identified by the “implicit token register” or a time-out value if the identified node fails to
transmit. In each case, the “implicit token” is automatically advanced to the next MAC ID. All
nodes have the same value in their “implicit token register” preventing collisions on the
medium.
The time-out period (called the “slot time”) is based on the amount of time required for
a) the current node to hear the end of the transmission from the previous node, and
b) the current node to begin transmitting, and
c) the next node to hear the beginning of the transmission from the current node.
The slot time is adjusted to compensate for the total length of the medium since the
propagation delay of the medium effects the first and last item on the previous list.
NOTE 2  The calculation of slot time is the responsibility of System Management.
Each NUT is divided into three major parts: scheduled, unscheduled, and guardband as shown
in Figure 2. This sequence is repeated in every NUT. The implicit token passing mechanism is
used to grant access to the medium during both the unscheduled and scheduled intervals.
Data-link layer protocol
Scheduled
Guardband
Network update time (NUT)
Unscheduled
Figure 2 – NUT structure
– 18 – 61158-3-2 © IEC:2007(E)
During the scheduled part of the NUT, each node, starting with node 0 and ending with node
SMAX, gets a chance to transmit time-critical (scheduled) data. SMAX is the MAC ID of the
highest numbered node that has access to the medium during the scheduled part of the NUT.
Every node between 0 and SMAX has only one opportunity to send one DLPDU of scheduled
data in each NUT. The opportunity to access the medium during the scheduled time is the
same for each node in every NUT. This allows data that is transmitted during the scheduled
portion of the NUT to be sent in a predictable and deterministic manner.
Figure 3 shows how the permission to transmit is granted during the scheduled time. The DLS-
user regulates the amount of data that each node may transmit during this scheduled token
pass.
Time
Scheduled
Unscheduled
Guardband
1  1
2   2
3     3
n
n       n
n = SMAX
maximum scheduled
Each node is allowed to transmit
network address
Example:
exactly once during scheduled time
node #3 waits one
slot time
(implied token)
This boundary moves from NUT to NUT
because node #2 was
depending on the utilization
missing
Nodes wait one slot time for each missing
of scheduled time
node (MAC ID) from 0 to SMAX
Figure 3 – Medium access during scheduled time
During the unscheduled part of the NUT, each node from 0 to UMAX shares the opportunity to
transmit one DLPDU of non-time-critical data in a round robin fashion, until the allocated NUT
duration is exhausted. UMAX is the MAC ID of the highest numbered node that has access to
the medium during the unscheduled part of the NUT. The round robin method of access
opportunity enables every node between 0 and UMAX to have zero, one or many opportunities
to send unscheduled data depending on how much of the NUT remains after the completion of
the scheduled time. Variations in scheduled traffic means the opportunity to access the
medium during the unscheduled time may be different for each node in every NUT.
Figure 4 shows how the permission to transmit is granted during the unscheduled time. The
MAC ID of the node that goes first in the unscheduled part of the NUT is incremented by 1 for
each NUT. The unscheduled token begins at the MAC ID specified in the unscheduled start
register (USR) of the previous moderator DLPDU. The USR increments by one modulo
(UMAX+1) each NUT. If the USR reaches UMAX before the guardband, it returns to zero and
the token pass continues.
61158-3-2 © IEC:2007(E) – 19 –
Time
9 9
10   10
11     11
12 UMAX
(maximum unscheduled
MAC ID)
Permission to transmit is passed
Each node gets several or no
on a round-robin basis
MAC ID from start of previous
opportunities to transmit,
interval plus one gets first
based on available NUT time
opportunity to transmit
and other unscheduled traffic
Nodes wait one slot time for each
one MAC frame in interval
missing node (MAC ID) from 0 to UMAX
plus one
Figure 4 – Medium access during unscheduled time
When the guardband is reached, all nodes stop transmitting. A node is not allowed to start a
transmission unless it can be completed before the beginning of the guardband. During the
guardband, the node with the lowest MAC ID (called the “moderator”) transmits a maintenance
message (called the “moderator DLPDU”) that accomplishes two things.
1) It keeps the NUT timers of all nodes synchronized.
2) It publishes critical link parameters enabling all DLEs on the local link to share a common
version of important
...

IEC 61158-3-2 ®
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –
Part 3-2: Data-link layer service definition – Type 2 elements

Réseaux de communications industriels – Spécifications des bus de terrain –
Partie 3-2 : Définition du service de la couche de liaison de données –
Eléments de type 2
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IEC 61158-3-2 ®
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –

Part 3-2: Data-link layer service definition – Type 2 elements

Réseaux de communications industriels – Spécifications des bus de terrain –

Partie 3-2 : Définition du service de la couche de liaison de données –

Eléments de type 2
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX X
ICS 25.040.40; 35.100.20 ISBN 978-2-8322-0987-5

– 2 – 61158-3-2 © IEC:2007
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
1.1 Overview . 7
1.2 Specifications . 7
1.3 Conformance . 7
2 Normative references. 8
3 Terms, definitions, symbols, abbreviations and conventions . 8
3.1 Reference model terms and definitions . 8
3.2 Service convention terms and definitions . 10
3.3 Common data-link service terms and definitions . 11
3.4 Additional Type 2 data-link specific definitions. 12
3.5 Common symbols and abbreviations . 15
3.6 Additional Type 2 symbols and abbreviations . 15
3.7 Common conventions . 15
4 Connection-mode and connectionless-mode data-link service . 16
4.1 Overview . 16
4.2 Facilities of the data-link service . 20
4.3 Model of the data-link service . 21
4.4 Sequence of primitives . 23
4.5 Connection-mode data transfer . 25
4.6 Connectionless-mode data transfer . 27
4.7 Queue maintenance . 30
4.8 Tag filter . 32
5 DL-management Services . 33
5.1 Sequence of primitives . 33
5.2 Link synchronization . 34
5.3 Synchronized parameter change . 34
5.4 Event reports . 36
5.5 Bad FCS . 38
5.6 Current moderator . 38
5.7 Enable moderator . 39
5.8 Power-up and online . 40
5.9 Listen only . 41
5.10 Time distribution . 42
Bibliography . 44
INDEX . 45

Figure 1 – Relationships of DLSAPs, DLSAP-addresses and group DL-addresses . 11
Figure 2 – NUT structure . 17
Figure 3 – Medium access during scheduled time . 18
Figure 4 – Medium access during unscheduled time . 19
Figure 5 – Queue model for the peer and multipoint DLS, DLSAPs and their DLCEPs . 20
Figure 6 – Queue model of a multipoint DLS between a sending DLS-user and one or
more receiving DLS-users . 22
Figure 7 – DLS primitive time-sequence diagram . 24

61158-3-2 © IEC:2007 – 3 –
Figure 8 – State transition diagram for sequences of DLS primitives at one DLSAP . 25
Figure 9 – Sequence of primitives for a successful connection-mode transfer . 27
Figure 10 – Sequence of primitives for an unsuccessful connection-mode transfer . 27
Figure 11 – Sequence of primitives for a successful connectionless-mode transfer . 30
Figure 12 – Sequence of primitives for an unsuccessful connectionless-mode transfer. 30
Figure 13 – Sequence of primitives for a queue maintenance request . 32
Figure 14 – Sequence of primitives for a tag filter request . 33
Figure 15 – Sequence of primitives for a local link synchronization . 34
Figure 16 – Sequence of primitives for a DLM-get/set parameters request . 36
Figure 17 – Sequence of primitives for a DLM-tMinus change request . 36
Figure 18 – Sequence of primitives for a DLM-event indication . 38
Figure 19 – Sequence of primitives for a DLM-bad-FCS indication . 38
Figure 20 – Sequence of primitives for a DLM-current-moderator indication . 39
Figure 21 – Sequence of primitives for a DLM-enable-moderator request . 40
Figure 22 – Sequence of primitives for a DLM-power-up indication. 41
Figure 23 – Sequence of primitives for a DLM-online request . 41
Figure 24 – Sequence of primitives for a DLM-listen-only request . 42

Table 1 – Summary of connection-mode and connectionless-mode primitives and
parameters . 24
Table 2 – DL-connection-mode transfer primitives and parameters . 26
Table 3 – DL-connectionless-mode transfer primitives and parameters . 28
Table 4 – Fixed tag services available to the DLS-user . 29
Table 5 – DL-queue maintenance primitives and parameters . 31
Table 6 – DL-connectionless-mode tag filter primitives and parameters . 32
Table 7 – Summary of DL-management primitives and parameters . 33
Table 8 – Link synchronization primitives and parameters . 34
Table 9 – Synchronized parameter change primitives and parameters . 35
Table 10 – DLMS-configuration-data . 36
Table 11 – Event report primitives and parameters . 37
Table 12 – DLMS events being reported . 37
Table 13 – Bad FCS primitives and parameters . 38
Table 14 – Current moderator primitives and parameters . 39
Table 15 – Enable moderator primitives and parameters . 39
Table 16 – Power-up and online primitives and parameters. 40
Table 17 – Listen-only primitives and parameters . 41
Table 18 – DLMS time and time quality parameters . 42
Table 19 – Time distribution source quality . 43

– 4 – 61158-3-2 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 3-2: Data-link layer service definition – Type 2 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
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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
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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.
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 the IEC 61784 series. Use of the various protocol types in other combinations
may require permission of their respective intellectual-property-right holders.
International Standard IEC 61158-3-2 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This first edition and its companion parts of the IEC 61158-3 subseries cancel and replace
IEC 61158-3:2003. This edition of this part constitutes a minor revision. This part and its
companion Type 2 parts also cancel and replace IEC/PAS 62410, published in 2005.
This edition includes the following significant changes with respect to the previous edition:
a) deletion of the former Type 6 fieldbus, and the placeholder for a Type 5 fieldbus data-link
layer, for lack of market relevance;
b) addition of new types of fieldbuses;

61158-3-2 © IEC:2007 – 5 –
c) division of this part into multiple parts numbered 3-1, 3-2, …, 3-19.
This bilingual version (2013-07) corresponds to the monolingual English version, published in
2007-12.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/473/FDIS 65C/484/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until the
maintenance result 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 standard will be synchronized with the other parts of the IEC 61158 series.
The list of all the parts of the IEC 61158 series, under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.

– 6 – 61158-3-2 © IEC:2007
INTRODUCTION
This standard 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/TR 61158-1.
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 layer service defined in this standard is a conceptual architectural service,
independent of administrative and implementation divisions.

61158-3-2 © IEC:2007 – 7 –
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 3-2: Data-link layer service definition – Type 2 elements

1 Scope
1.1 Overview
This part of IEC 61158 provides common elements for basic time-critical messaging
communications between devices in an automation environment. The term “time-critical” is
used to represent the presence of 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.
This standard defines in an abstract way the externally visible service provided by the Type 2
fieldbus data-link layer in terms of
a) the primitive actions and events of the service;
b) the parameters associated with each primitive action and event, and the form which they
take; and
c) the interrelationship between these actions and events, and their valid sequences.
The purpose of this standard is to define the services provided to:
• the Type 2 fieldbus application layer at the boundary between the application and data-link
layers of the fieldbus reference model;
• systems management at the boundary between the data-link layer and systems
management of the fieldbus reference model.
Type 2 DL-service provides both a connected and a connectionless subset of those services
specified in ISO/IEC 8886.
1.2 Specifications
The principal objective of this standard is to specify the characteristics of conceptual data-link
layer services suitable for time-critical communications and thus supplement the OSI Basic
Reference Model in guiding the development of data-link protocols for time-critical
communications. A secondary objective is to provide migration paths from previously-existing
industrial communications protocols.
This specification may be used as the basis for formal DL-Programming-Interfaces.
Nevertheless, it is not a formal programming interface, and any such interface will need to
address implementation issues not covered by this specification, including:
a) the sizes and octet ordering of various multi-octet service parameters;
b) the correlation of paired request and confirm, or indication and response, primitives.
1.3 Conformance
This standard does not specify individual implementations or products, nor does it constrain the
implementations of data-link entities within industrial automation systems.

– 8 – 61158-3-2 © IEC:2007
There is no conformance of equipment to this data-link layer service definition standard.
Instead, conformance is achieved through implementation of the corresponding data-link
protocol that fulfills the Type 1 data-link layer services defined in this standard.
2 Normative references
The following referenced documents are indispensable for the application 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.
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 8886, Information technology – Open Systems Interconnection – Data link service
definition
ISO/IEC 10731:1994, Information technology – Open Systems Interconnection – Basic
Reference Model – Conventions for the definition of OSI services
3 Terms, definitions, symbols, abbreviations and conventions
For the purposes of this document, the following terms, definitions, symbols, abbreviations and
conventions apply.
3.1 Reference model terms and definitions
This standard is based in part on the concepts developed in ISO/IEC 7498-1 and
ISO/IEC 7498-3, and makes use of the following terms defined therein:
[ISO/IEC 7498-3]
3.1.1 DL-address
[ISO/IEC 7498-1]
3.1.2 DL-address-mapping
[ISO/IEC 7498-3]
3.1.3 called-DL-address
[ISO/IEC 7498-3]
3.1.4 calling-DL-address
3.1.5 centralized multi-end-point-connection [ISO/IEC 7498-1]
3.1.6 DL-connection [ISO/IEC 7498-1]
3.1.7 DL-connection-end-point [ISO/IEC 7498-1]
3.1.8 DL-connection-end-point-identifier [ISO/IEC 7498-1]
3.1.9 DL-connection-mode transmission [ISO/IEC 7498-1]
3.1.10 DL-connectionless-mode transmission [ISO/IEC 7498-1]
3.1.11 correspondent (N)-entities [ISO/IEC 7498-1]
correspondent DL-entities  (N=2)
correspondent Ph-entities  (N=1)
3.1.12 DL-duplex-transmission [ISO/IEC 7498-1]

61158-3-2 © IEC:2007 – 9 –
3.1.13 (N)-entity [ISO/IEC 7498-1]
DL-entity  (N=2)
Ph-entity  (N=1)
3.1.14 DL-facility [ISO/IEC 7498-1]
3.1.15 flow control [ISO/IEC 7498-1]
3.1.16 (N)-layer [ISO/IEC 7498-1]
DL-layer  (N=2)
Ph-layer  (N=1)
[ISO/IEC 7498-1]
3.1.17 layer-management
[ISO/IEC 7498-3]
3.1.18 DL-local-view
[ISO/IEC 7498-3]
3.1.19 DL-name
[ISO/IEC 7498-3]
3.1.20 naming-(addressing)-domain
[ISO/IEC 7498-1]
3.1.21 peer-entities
3.1.22 primitive name [ISO/IEC 7498-3]
3.1.23 DL-protocol [ISO/IEC 7498-1]
3.1.24 DL-protocol-connection-identifier [ISO/IEC 7498-1]
3.1.25 DL-protocol-data-unit [ISO/IEC 7498-1]
3.1.26 DL-relay [ISO/IEC 7498-1]
3.1.27 reset [ISO/IEC 7498-1]
3.1.28 responding-DL-address [ISO/IEC 7498-3]
3.1.29 routing [ISO/IEC 7498-1]
3.1.30 segmenting [ISO/IEC 7498-1]
3.1.31 (N)-service [ISO/IEC 7498-1]
DL-service  (N=2)
Ph-service  (N=1)
3.1.32 (N)-service-access-point [ISO/IEC 7498-1]
DL-service-access-point  (N=2)
Ph-service-access-point  (N=1)
[ISO/IEC 7498-3]
3.1.33 DL-service-access-point-address
[ISO/IEC 7498-1]
3.1.34 DL-service-connection-identifier
[ISO/IEC 7498-1]
3.1.35 DL-service-data-unit
3.1.36 DL-simplex-transmission [ISO/IEC 7498-1]
3.1.37 DL-subsystem [ISO/IEC 7498-1]
3.1.38 systems-management [ISO/IEC 7498-1]
3.1.39 DLS-user-data [ISO/IEC 7498-1]

– 10 – 61158-3-2 © IEC:2007
3.2 Service convention terms and definitions
This standard also makes use of the following terms defined in ISO/IEC 10731 as they apply to
the data-link layer:
3.2.1 acceptor
3.2.2 asymmetrical service
3.2.3 confirm (primitive);
requestor.deliver (primitive)
3.2.4 deliver (primitive)
3.2.5 DL-confirmed-facility
3.2.6 DL-facility
3.2.7 DL-local-view
3.2.8 DL-mandatory-facility
3.2.9 DL-non-confirmed-facility
3.2.10 DL-provider-initiated-facility
3.2.11 DL-provider-optional-facility
3.2.12 DL-service-primitive;
primitive
3.2.13 DL-service-provider
3.2.14 DL-service-user
3.2.15 DLS-user-optional-facility
3.2.16 indication (primitive);
acceptor.deliver (primitive)
3.2.17 multi-peer
3.2.18 request (primitive);
requestor.submit (primitive)
3.2.19 requestor
3.2.20 response (primitive);
acceptor.submit (primitive)
3.2.21 submit (primitive)
3.2.22 symmetrical service
61158-3-2 © IEC:2007 – 11 –
3.3 Common data-link service terms and definitions
NOTE Many definitions are common to more than one protocol Type; they are not necessarily used by all protocol
Types.
3.3.1
DL-segment, link, local link
single DL-subnetwork in which any of the connected DLEs may communicate directly, without
any intervening DL-relaying, whenever all of those DLEs that are participating in an instance of
communication are simultaneously attentive to the DL-subnetwork during the period(s) of
attempted communication
3.3.2
DLSAP
distinctive point at which DL-services are provided by a single DL-entity to a single higher-layer
entity
NOTE This definition, derived from ISO/IEC 7498-1, is repeated here to facilitate understanding of the critical
distinction between DLSAPs and their DL-addresses.

NOTE 1 DLSAPs and PhSAPs are depicted as ovals spanning the boundary between two adjacent layers.
NOTE 2 DL-addresses are depicted as designating small gaps (points of access) in the DLL portion of a DLSAP.
NOTE 3 A single DL-entity may have multiple DLSAP-addresses and group DL-addresses associated with a single
DLSAP.
Figure 1 – Relationships of DLSAPs, DLSAP-addresses and group DL-addresses
3.3.3
DL(SAP)-address
either an individual DLSAP-address, designating a single DLSAP of a single DLS-user, or a
group DL-address potentially designating multiple DLSAPs, each of a single DLS-user
NOTE This terminology is chosen because ISO/IEC 7498-3 does not permit the use of the term DLSAP-address to
designate more than a single DLSAP at a single DLS-user.

– 12 – 61158-3-2 © IEC:2007
3.3.4
(individual) DLSAP-address
DL-address that designates only one DLSAP within the extended link
NOTE A single DL-entity may have multiple DLSAP-addresses associated with a single DLSAP.
3.3.5
extended link
DL-subnetwork, consisting of the maximal set of links interconnected by DL-relays, sharing a
single DL-name (DL-address) space, in which any of the connected DL-entities may
communicate, one with another, either directly or with the assistance of one or more of those
intervening DL-relay entities
NOTE An extended link may be composed of just a single link.
3.3.6
frame
denigrated synonym for DLPDU
3.3.7
group DL-address
DL-address that potentially designates more than one DLSAP within the extended link
NOTE A single DL-entity may have multiple group DL-addresses associated with a single DLSAP. A single
DL-entity also may have a single group DL-address associated with more than one DLSAP.
3.3.8
node
single DL-entity as it appears on one local link
3.3.9
receiving DLS-user
DL-service user that acts as a recipient of DLS-user-data
NOTE A DL-service user can be concurrently both a sending and receiving DLS-user.
3.3.10
sending DLS-user
DL-service user that acts as a source of DLS-user-data
3.4 Additional Type 2 data-link specific definitions
3.4.1
application
function or data structure for which data is subscribed or published
3.4.2
behavior
indication of how the object responds to particular events. Its description includes the
relationship between attribute values and services
3.4.3
bridge, DL-router
DL-relay entity which performs selective store-and-forward and routing functions to connect two
or more separate DL-subnetworks (links) to form a unified DL-subnetwork (the extended link)
3.4.4
cyclic
term used to describe events which repeat in a regular and repetitive manner

61158-3-2 © IEC:2007 – 13 –
3.4.5
device
physical hardware connection to the link
NOTE A device may contain more than one node.
3.4.6
DL-subnetwork
series of nodes connected by PhEs and, where appropriate, DL-routers
3.4.7
DLPDU
Data-link Protocol Data unit
NOTE A DLPDU consists of a source MAC ID, zero or more Lpackets, and an FCS, as transmitted or received by
an associated PhE.
3.4.8
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.4.9
fixed tag
two octet identifier (tag) which identifies a specific service to be performed by either
a) that receiving node on the local link which has a specified MAC ID, or
b) all receiving nodes on the local link.
NOTE Identification of the target node(s) is included in the two octet tag
3.4.10
generic tag
three octet identifier (tag) which identifies a specific piece of application information
3.4.11
guardband
time slot allocated for the transmission of the moderator DLPDU
3.4.12
link
collection of nodes with unique MAC IDs
NOTE Ph-segments connected by Ph-repeaters make up a link; links connected by DL-routers make up an
extended link (sometimes called a local area network)
3.4.13
Lpacket
well-defined sub-portion of a DLPDU containing (among other things)
a) a fixed tag or a generic tag, and
b) DLS-user data or, when the tag has DL-significance, DL-data
3.4.14
moderator
node with the lowest MAC ID that is responsible for transmitting the moderator DLPDU
3.4.15
moderator DLPDU
DLPDU transmitted by the node with the lowest MAC ID for the purpose of synchronizing the
nodes and distributing the link configuration parameters

– 14 – 61158-3-2 © IEC:2007
3.4.16
multipoint DLC
centralized multi-end-point DL-connection offering DL-simplex-transmission between a single
distinguished DLS-user, known as the publisher or publishing DLS-user, and a set of peer but
undistinguished DLS-users, known collectively as the subscribers or subscribing DLS-users,
where the publishing DLS-user can send to the subscribing DLS-users as a group (but not
individually). A multipoint DLC always provides asymmetrical service.
3.4.17
node
logical connection to a local link, requiring a single MAC ID
NOTE A single physical device may appear as many nodes on the same local link. For the purposes of this
protocol, each node is considered to be a separate DLE.
3.4.18
peer-to-peer DLC
point-to-point DL-connection offering DL-simplex-transmission between a single distinguished
sending DLS-user and a single distinguished receiving DLS-user
NOTE A peer-to-peer DLC always provides asymmetrical service.
3.4.19
rogue
node that has received a moderator DLPDU that disagrees with the link configuration currently
used by this node
3.4.20
scheduled
data transfers that occur in a deterministic and repeatable manner on predefined NUTs.
3.4.21
tMinus
number of NUTs before a new set of link configuration parameters are to be used
3.4.22
tone
instant of time which marks the boundary between two NUTs
3.4.23
unscheduled
data transfers that use the remaining allocated time in the NUT after the scheduled transfers
have been completed
61158-3-2 © IEC:2007 – 15 –
3.5 Common symbols and abbreviations
NOTE Many symbols and abbreviations are common to more than one protocol Type; they are not necessarily
used by all protocol Types.
Data-link layer (as a prefix)
DL-
DL-connection
DLC
DLCEP DL-connection-end-point
DLE DL-entity (the local active instance of the data-link layer)
DLL DL-layer
DLPCI DL-protocol-control-information
DLPDU DL-protocol-data-unit
DLM DL-management
DL-management Entity (the local active instance of DL-management)
DLME
DL-management Service
DLMS
DL-service
DLS
DLSAP DL-service-access-point
DLSDU DL-service-data-unit
FIFO First-in first-out (queuing method)
OSI Open systems interconnection
Ph- Physical layer (as a prefix)
Ph-entity (the local active instance of the physical layer)
PhE
Ph-layer
PhL
Quality of service
QoS
3.6 Additional Type 2 symbols and abbreviations
MAC ID DL-address of a node
MDS Medium dependent sublayer
NUT Network (actually, local link) update time
NOTE The use of the term “network” in the preceding definition is maintained for historic reasons, even though the
scope involved is only a portion of a single DL-subnetwork.
root mean square
r.m.s.
SMAX MAC ID of the maximum scheduled node
Tx Transmit
TUI Table unique identifier
UCMM Unconnected message manager
UMAX MAC ID of maximum unscheduled node
Unscheduled start register
USR
3.7 Common conventions
This standard uses the descriptive conventions given in ISO/IEC 10731.
The service model, service primitives, and time-sequence diagrams used are entirely abstract
descriptions; they do not represent a specification for implementation.

– 16 – 61158-3-2 © IEC:2007
Service primitives, used to represent service user/service provider interactions (see
ISO/IEC 10731), convey parameters that indicate information available in the user/provider
interaction.
This standard uses a tabular format to describe the component parameters of the DLS
primitives. The parameters that apply to each group of DLS primitives are set out in tables
throughout the remainder of this standard. Each table consists of up to six columns, containing
the name of the service parameter, and a column each for those primitives and parameter-
transfer directions used by the DLS:
 the request primitive’s input parameters;
 the request primitive’s output parameters;
 the indication primitive’s output parameters;
 the response primitive’s input parameters; and
 the confirm primitive’s output parameters.
NOTE The request, indication, response and confirm primitives are also known as requestor.submit,
acceptor.deliver, acceptor.submit, and requestor.deliver primitives, respectively (see ISO/IEC 10731).
One parameter (or part of it) is listed in each row of each table. Under the appropriate service
primitive columns, a code is used to specify the type of usage of the parameter on the primitive
and parameter direction specified in the column:
M — parameter is mandatory for the primitive.
U — parameter is a User option, and may or may not be provided depending on
the dynamic usage of the DLS-user. When not provided, a default value
for the parameter is assumed.
C — parameter is conditional upon other parameters or upon the environment
of the DLS-user.
(blank) — parameter is never present.
Some entries are further qualified by items in brackets. These may be
a) a parameter-specific constraint
(=) indicates that the parameter is semantically equivalent to the parameter in the
service primitive to its immediate left in the table.
b) an indication that some note applies to the entry
(n) indicates that the following note n contains additional information pertaining to the
parameter and its use.
In any particular interface, not all parameters need be explicitly stated. Some may be implicitly
associated with the DLSAP at which the primitive is issued.
In the diagrams which illustrate these interfaces, dashed lines indicate cause-and-effect or
time-sequence relationships, and wavy lines indicate that events are roughly
contemporaneous.
4 Connection-mode and connectionless-mode data-link service
4.1 Overview
4.1.1 Data transfer services
The primary task of a DLE is to determine, in co-operation with other DLEs on the same local
link, the granting of permission to transmit on the medium. At its upper interface, the DLL
provides services to receive and deliver service data units (DLSDUs) for higher level entities.

61158-3-2 © IEC:2007 – 17 –
NOTE 1 The following access mechanisms are not visible to the higher level entities. They are described here as
an aid to understanding the purpose and use of DLS parameters and services that are visible to higher layer
entities.
This DLL protocol is based on a fixed repetitive time cycle, called the network update time
(NUT). The NUT is maintained in close synchronism among all nodes on the local link. A node
is not permitted access to transmit if its configured NUT does not agree with the NUT currently
being used on the local link. Different local links within the extended link may have different
NUT durations.
Each node contains its own timer synchronized to the local link’s NUT. Medium access is
determined by local sub-division of the NUT into variable-duration access slots. Access to the
medium is in sequential order based on the MAC ID of the node. Specific behaviors have been
incorporated into the access protocol allowing a node which temporarily assumes a MAC ID of
zero to perform link maintenance. The MAC ID numbers of all nodes on a link are unique. Any
DLE detecting the presence of a MAC ID duplicating its own MAC ID immediately stops
transmitting.
An implicit token passing mechanism is used to grant access to the medium. Each node
monitors the source MAC ID of each DLPDU received. At the end of a DLPDU, each DLE sets
an “implicit token register” to the received source MAC ID + 1. If the implicit token register is
equal to the local MAC ID, then the DLE transmits one DLPDU containing zero or more
Lpackets with data. In all other cases, the node watches for either a new DLPDU from the node
identified by the “implicit token register” or a time-out value if the identified node fails to
transmit. In each case, the “implicit token” is automatically advanced to the next MAC ID. All
nodes have the same value in their “implicit token register” preventing collisions on the
medium.
The time-out period (called the “slot time”) is based on the amount of time required for
a) the current node to hear the end of the transmission from the previous node, and
b) the current node to begin transmitting, and
c) the next node to hear the beginning of the transmission from the current node.
The slot time is adjusted to compensate for the total length of the medium since the
propagation delay of the medium effects the first and last item on the previous list.
NOTE 2 The calculation of slot time is the responsibility of System Management.
Each NUT is divided into three major parts: scheduled, unscheduled, and guardband as shown
in Figure 2. This sequence is repeated in every NUT. The implicit token passing mechanism is
used to grant access to the medium during both the unscheduled and scheduled intervals.
Data-link layer protocol
Scheduled
Network update time (NUT) Guardband
Unscheduled
Figure 2 – NUT structure
– 18 – 61158-3-2 © IEC:2007
During the scheduled part of the NUT, each node, starting with node 0 and ending with node
SMAX, gets a chance to transmit time-critical (scheduled) data. SMAX is the MAC ID of the
highest numbered node that has access to the medium during the scheduled part of the NUT.
Every node between 0 and SMAX has only one opportunity to send one DLPDU of scheduled
data in each NUT. The opportunity to access the medium during the scheduled time is the
same for each node in every NUT. This allows data that is transmitted during the scheduled
portion of the NUT to be sent in a predictable and deterministic manner.
Figure 3 shows how the permission to transmit is granted during the scheduled time. The DLS-
user regulates the amount of data that each node may transmit during this scheduled token
pass.
Time
Scheduled
Unscheduled
Guardband
1  1
...