EN 61158-4-18:2012

SLOVENSKI STANDARD
01-julij-2012
1DGRPHãþD
SIST EN 61158-4-18:2008
Industrijska komunikacijska omrežja - Specifikacije za procesna vodila - 4-18. del:
Specifikacija protokola na nivoju podatkovnih povezav - Elementi tipa 18 (IEC
61158-4-18:2010)
Industrial communication networks - Fieldbus specifications -- Part 4-18: Data-link layer
protocol specification - Type 18 elements (IEC 61158-4-18:2010)
Industrielle Kommunikationsnetze - Feldbusse - Teil 4-18: Protokollspezifikation des
Data Link Layer (Sicherungsschicht) - Typ 18-Elemente (IEC 61158-4-18:2010)
Réseaux de communication industriels - Spécifications de bus de terrain - Partie 4-18:
Spécification du protocole de couche de liaison de données - Eléments de type 18 (CEI
61158-4-18:2010)
Ta slovenski standard je istoveten z: EN 61158-4-18:2012
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 61158-4-18
NORME EUROPÉENNE
May 2012
EUROPÄISCHE NORM
ICS 25.040.40; 35.100.20; 35.110 Supersedes EN 61158-4-18:2008

English version
Industrial communication networks -
Fieldbus specifications -
Part 4-18: Data-link layer protocol specification -
Type 18 elements
(IEC 61158-4-18:2010)
Réseaux de communication industriels -  Industrielle Kommunikationsnetze -
Spécifications de bus de terrain - Feldbusse -
Partie 4-18: Spécification du protocole de Teil 4-18: Protokollspezifikation des Data
couche de liaison de données - Link Layer (Sicherungsschicht) -
Eléments de type 18 Typ 18-Elemente
(CEI 61158-4-18:2010) (IEC 61158-4-18:2010)

This European Standard was approved by CENELEC on 2012-03-28. 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61158-4-18:2012 E
Foreword
The text of document 65C/605/FDIS, future edition 2 of IEC 61158-4-18, 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 EN 61158-4-18:2012.

The following dates are fixed:
(dop) 2012-12-28
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2015-03-28

standards conflicting with the
document have to be withdrawn
This document supersedes EN 61158-4-18:2008.
18:2008:
• Editorial improvements;
• Addition of cyclic data segmenting.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent
rights.
Endorsement notice
The text of the International Standard IEC 61158-4-18:2010 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 standards indicated:
IEC/TR 61158-1:2010 NOTE  Harmonized as CLC/TR 61158-1:2010 (not modified).
IEC 61158-2:2010 NOTE  Harmonized as EN 61158-2:2010 (not modified).
IEC 61158-3-18 NOTE  Harmonized as EN 61158-3-18.
IEC 61158-5-18:2010 NOTE  Harmonized as EN 61158-5-18:2012 (not modified).
IEC 61158-6-18:2010 NOTE  Harmonized as EN 61158-6-18:2012 (not modified).

- 3 - EN 61158-4-18:2012
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

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 13239 2002 Information technology - Telecommunications - -
and information exchange between systems -
High-level data link control (HDLC)
procedures
IEC 61158-4-18 ®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 4-18: Data-link layer protocol specification – Type 18 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
V
ICS 25.04.40; 35.100.20; 35.110 ISBN 978-2-88912-089-5
– 2 – 61158-4-18 © IEC:2010(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
1.1 General .8
1.2 Specifications.8
1.3 Procedures.8
1.4 Applicability.9
1.5 Conformance.9
2 Normative references .9
3 Terms, definitions, symbols, abbreviations and conventions .9
3.1 Reference model terms and definitions.9
3.2 Type 18: Symbols.10
3.3 Type 18: Additional conventions .10
4 DL-protocol overview.10
4.1 Introduction .10
4.2 Polled DLE classes .11
4.3 Packed DLE classes.11
5 DLPDU encoding and transmission.11
5.1 DL – PhL interface .11
5.2 DLPDU transmission encoding .12
6 DLPDU – basic structure .14
6.1 Overview .14
6.2 Address field .14
6.3 Status field .15
6.4 Data field.17
7 DLPDU – Detailed structure, segmenting and reassembly .19
8 Data transmission methods .23
8.1 Overview .23
8.2 Master-polled method.23
8.3 Level A slave-polled method.24
8.4 Level B slave-polled method.25
8.5 Level C slave-polled method .25
8.6 Master-packed method .26
8.7 Slave-packed method .27
9 DL-management – procedures.28
9.1 Overview .28
9.2 Establish master-polled DLE procedure.28
9.3 Establish slave-polled DLE procedure .29
9.4 Establish master-packed DLE procedure .31
9.5 Establish slave-packed DLE procedure .32
9.6 Release connection procedure .33
9.7 Suspend connection procedure .33
9.8 Resume connection procedure .33
9.9 Activate standby Master procedure.34
Bibliography.35

61158-4-18 © IEC:2010(E) – 3 –

Figure 1 – HDLC flag .12

Table 1 – HDLC convention summary .13
Table 2 – HDLC exception summary .14
Table 3 – Master-polled DLE address octet 0.14
Table 4 – Slave-polled DLE address octet 0.15
Table 5 – Master-packed DLE address octet 0 .15
Table 6 – Master-polled DLE status octet 0.16
Table 7 – Master-polled DLE status octet 1.16
Table 8 – Slave-polled DLE status octet 0.17
Table 9 – slave-polled DLE status octet 1 .17
Table 10 – Slave-packed DLE status .17
Table 11 – DLPDU – Master-polled DLE acyclic data field .18
Table 12 – DLPDU – Slave-polled DLE acyclic data field .19
Table 13 – Example master-polled DLE RY contiguous data field .20
Table 14 – Example slave-polled DLE RX contiguous data field.20
Table 15 – Example master-polled DLE RWw contiguous data field .20
Table 16 – Example slave-polled DLE RWr contiguous data field.20
Table 17 – Bit-oriented segment header .21
Table 18 – Polled DLE acyclic segment number field .22
Table 19 – Slave-polled DLE acyclic data type and sequence field .22
Table 20 – DLPDU – Polled class poll with data.23
Table 21 – Slave-polled DLE response timeout.23
Table 22 – DLPDU – Poll .24
Table 23 – DLPDU – End of cycle.24
Table 24 – slave-polled DLE request timeout .24
Table 25 – DLPDU – Level A poll response.25
Table 26 – DLPDU – Level B poll response.25
Table 27 – DLPDU – Level C poll response .26
Table 28 – DLPDU – Packed class poll with data .26
Table 29 – Slave-packed DLE response timeout .26
Table 30 – Slave-packed DLE request timeout.27
Table 31 – DLPDU – Packed class poll response.27
Table 32 – Slave-packed DLE time constraints .28
Table 33 – DLPDU – Poll with test data .28
Table 34 – Slave-polled DLE response timeout.29
Table 35 – DLPDU – Poll test .29
Table 36 – Slave-polled DLE request timeout .29
Table 37 – DLPDU – Poll test response .30
Table 38 – Slave-polled DLE configuration parameter.30
Table 39 – DLPDU – Baud rate synchronization.31
Table 40 – DLPDU – Poll test .31
Table 41 – Slave-packed DLE response timeout .31

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Table 42 – Slave-packed DLE number of occupied DLE station slots .32
Table 43 – Slave-packed DLE baud rate synchronization timeout .32
Table 44 – Slave-packed DLE Master timeout.33
Table 45 – DLPDU – Packed poll test response .33

61158-4-18 © IEC:2010(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 4-18: Data-link layer protocol specification –
Type 18 elements
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
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
misinterpretation by any end user.
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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
International Standard IEC 61158-4-18 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are listed below:
• Editorial improvements
• Addition of cyclic data segmenting

– 6 – 61158-4-18 © IEC:2010(E)
The text of this standard is based on the following documents:
FDIS Report on voting
65C/605/FDIS 65C/619/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.
A list of all the parts of the IEC 61158 series, published under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.

61158-4-18 © IEC:2010(E) – 7 –
INTRODUCTION
This part of IEC 61158 is one of a series produced to facilitate the interconnection of
automation system components. It is related to other standards in the set as defined by the
“three-layer” fieldbus reference model described in IEC 61158-1.
The data-link protocol provides the data-link service by making use of the services available
from the physical layer. The primary aim of this standard is to provide a set of rules for
communication expressed in terms of the procedures to be carried out by peer data-link
entities (DLEs) at the time of communication. These rules for communication are intended to
provide a sound basis for development in order to serve a variety of purposes:
a) as a guide for implementors and designers;
b) for use in the testing and procurement of equipment;
c) as part of an agreement for the admittance of systems into the open systems environment;
d) as a refinement to the understanding of time-critical communications within OSI.
This standard is concerned, in particular, with the communication and interworking of sensors,
effectors and other automation devices. By using this standard together with other standards
positioned within the OSI or fieldbus reference models, otherwise incompatible systems may
work together in any combination.
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 profile parts. Use of the various protocol types in other combinations
may require permission from their respective intellectual-property-right holders.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is
claimed that compliance with this document may involve the use of patents concerning Type
18 elements and possibly other types given in 7.1.2 as follows:
3343036/Japan [MEC] Network System for a Programmable Controller
5896509/USA [MEC] Network System for a Programmable Controller
246906/Korea [MEC] Network System for a Programmable Controller
19650753/Germany [MEC] Network System for a Programmable Controller

IEC takes no position concerning the evidence, validity and scope of these patent rights.
The holder of thess patent rights has assured the IEC that he/she is willing to negotiate
licences either free of charge or under reasonable and non-discriminatory terms and
conditions with applicants throughout the world. In this respect, the statement of the holder of
thess patent rights is registered with IEC. Information may be obtained from:
[MEC] Mitsubishi Electric Corporation
Corporate Licensing DeivsionDivision
7-3, Marunouchi 2-chome, Chiyoda-ku,
Tokyo 100-8310, Japan
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those identified above. IEC shall not be held responsible for
identifying any or all such patent rights.
ISO (www.iso.org/patents) and IEC (http://www.iec.ch/tctools/patent_decl.htm) maintain on-
line data bases of patents relevant to their standards. Users are encouraged to consult the
data bases for the most up to date information concerning patents.

– 8 – 61158-4-18 © IEC:2010(E)
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 4-18: Data-link layer protocol specification –
Type 18 elements
1 Scope
1.1 General
The data-link layer provides basic time-critical messaging communications between devices in
an automation environment.
This protocol provides communication opportunities to all participating data-link entities
a) in a synchronously-starting cyclic manner, according to a pre-established schedule, and
b) in a cyclic or acyclic asynchronous manner, as requested each cycle by each of those
data-link entities.
Thus this protocol can be characterized as one which provides cyclic and acyclic access
asynchronously but with a synchronous restart of each cycle.
1.2 Specifications
This part of IEC 61158 specifies
a) 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;
b) procedures for giving communications opportunities to all participating DL-entities,
sequentially and in a cyclic manner for deterministic and synchronized transfer at cyclic
intervals up to one millisecond;
c) procedures for giving communication opportunities available for time-critical data
transmission together with non-time-critical data transmission without prejudice to the
time-critical data transmission;
d) procedures for giving cyclic and acyclic communication opportunities for time-critical data
transmission with prioritized access;
e) procedures for giving communication opportunities based on standard ISO/ IEC 8802-3
medium access control, with provisions for nodes to be added or removed during normal
operation;
f) the structure of the fieldbus DLPDUs used for the transfer of data and control information
by the protocol of this standard, and their representation as physical interface data units.
1.3 Procedures
The procedures are defined in terms of
a) the interactions between peer DL-entities (DLEs) through the exchange of fieldbus
DLPDUs;
b) the interactions between a DL-service (DLS) provider and a DLS-user in the same system
through the exchange of DLS primitives;
c) the interactions between a DLS-provider and a Ph-service provider in the same system
through the exchange of Ph-service primitives.

61158-4-18 © IEC:2010(E) – 9 –
1.4 Applicability
These procedures are applicable to instances of communication between systems which
support time-critical communications services within the data-link layer of the OSI or fieldbus
reference models, and which require the ability to interconnect in an open systems
interconnection environment.
Profiles provide a simple multi-attribute means of summarizing an implementation’s
capabilities, and thus its applicability to various time-critical communications needs.
1.5 Conformance
This part of IEC 61158 does not specify individual implementations or products, nor do they
constrain the implementations of data-link entities within industrial automation systems.
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 18 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 Interconnectionl – Basic Reference
Model: Naming and addressing
ISO/IEC 13239:2002, Information technology – Telecommunications and information
exchange between systems – High-level data link control (HDLC) procedures
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 additional terms:
3.1.1
DLE station identifier
network address assigned to a DLE
3.1.2
DLE station slot
unit (granularity of one) of position dependent mapping (for cyclic data field) of which a DLE
may occupy one or more, delineated by the range beginning at the DLE station identifier with
a length equal to the configured number of occupied slots
3.1.3
Master DLE
DLE that performs the functions of network master

– 10 – 61158-4-18 © IEC:2010(E)
3.1.4
Master-packed DLE
master DLE that uses the packed response access protocol
3.1.5
Master-polled DLE
master DLE that uses the polled response access protocol
3.1.6
Packed response
transmission of data managed by the process of a master broadcasting a trigger message
whereupon each slave waits a time period unique to its DLE station identifier then transmits
its response resulting in a time-sliced packing of all slave responses triggered by a single
master request
3.1.7
Polled response
transmission of data managed by the process of a master individually interrogating each slave
in a request/response paradigm
3.1.8
Slave DLE
DLE that performs the functions of network slave
3.1.9
Slave-packed DLE
slave DLE that uses the packed response access protocol
3.1.10
Slave-polled DLE
slave DLE that uses the polled response access protocol
3.2 Type 18: Symbols
RX DLS-user visible register containing bit-oriented cyclic data of type input data that is transmitted from a
slave DLE to a master DLE
RY DLS-user visible register containing bit-oriented cyclic data of type output data that is transmitted from a
master DLE to a slave DLE
RWr DLS-user visible register containing word-oriented cyclic data of type input data that is transmitted from
a slave DLE to a master DLE
RWw DLS-user visible register containing word-oriented cyclic data of type input data that is transmitted from
a master DLE to a slave DLE
3.3 Type 18: Additional conventions
3.3.1 DLE support level
There are three levels of data transmission support for a DLE.
• Level A – supports only bit-oriented cyclic data transmission
• Level B – includes level A as well as word-oriented cyclic data transmission
• Level C – includes level B as well as acyclic data transmission
4 DL-protocol overview
4.1 Introduction
There are four classes of Type 18 DLE:
a) Master-polled DLE
61158-4-18 © IEC:2010(E) – 11 –
b) Slave-polled DLE
c) Master-packed DLE
d) Slave-packed DLE.
Only the master DLE classes are able to initiate traffic. Slave DLEs only transmit in response
to master DLE requests.
4.2 Polled DLE classes
A slave-polled DLE transmits a response immediately upon receipt of an explicitly coded poll
request addressed to the slave-polled DLE from a master-polled DLE. The polled classes
support both cyclic and acyclic data transport.
4.3 Packed DLE classes
A slave-packed DLE transmits a response after a unique time has elapsed following a receipt
of an explicitly coded poll request broadcast from a master-packed DLE. This results in a
time-sliced packing of all slave-packed DLE responses to a single master-packed DLE
request. The packed classes support cyclic data transport only.
5 DLPDU encoding and transmission
5.1 DL – PhL interface
5.1.1 Overview
The polled DLE classes employ the Type 18 Ph-MDS standard type. The packed DLE classes
employ the Type 18 Ph-MDS high-density type.
In order to effect transmission, reception and management via the PhE, the DLE assumes a
requisite set of support services as described in the following subclauses.
5.1.2 Transmission
A Type 18 DLE uses the following procedure to transmit data:
1) Segment DLPDUs into PhSDUs (single bits) using the HDLC protocol specified in 5.1
2) PH-DATA request (START-OF-ACTIVITY)
3) PH-DATA request (PhSDU)
4) PH-DATA confirm (SUCCESS)
5) repeat steps ( 3) and ( 4)
6) PH-DATA request (END-OF-ACTIVITY).
The DLE must sustain a rate of PhS requests that supports the configured baud rate as
regulated by the PH-DATA success confirmation.
5.1.3 Reception
A Type 18 DLE uses the following procedure to receive data:
1) Ph-Data indication (START-OF-ACTIVITY)
2) Ph-Data indication (PhSDU)
3) If not Ph-Data indication (END-OF-ACTIVITY), repeat step ( 2), otherwise proceed to step
( 4)
4) Reassemble PhSDUs (single bits) into a DLPDU using the HDLC protocol specified in 5. 1.

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The DLE must sustain a rate of PhS indications that supports the configured baud rate.
5.1.4 Management
A Type 18 DLE assumes that the PhE supports the following services:
• PH-RESET
• PH-SET-VALUE (baud-rate)
5.2 DLPDU transmission encoding
5.2.1 General
The Type 18 DL implements a subset of the High-level Data Link Control (HDLC) protocol
corresponding to ISO/IEC 13239:2002, named HDLC throughout the remainder of this clause,
with some exceptions as noted.
5.2.2 Polled DLE
5.2.2.1 Preamble
A preamble of three consecutive HDLC flags is transmitted as defined by ISO/IEC 13239:2002
and shown in Figure 1.
0 1 1 1 1 1 1 0
Figure 1 – HDLC flag
5.2.2.2 End of activity
An end-of-frame (EOF) of three consecutive HDLC flags is transmitted as defined by
ISO/IEC 13239:2002 and shown in Figure 1.
5.2.3 Packed DLE
5.2.3.1 Start of activity
A preamble of one HDLC flag is transmitted as defined by ISO/IEC 13239:2002 and shown in
Figure 1.
5.2.3.2 End of activity
An end-of-frame (EOF) of one HDLC flag is transmitted as defined by ISO/IEC 13239:2002
and shown in Figure 1.
5.2.4 HDLC conventions
5.2.4.1 Data encoding
Data is encoded using NRZI encoding as defined by ISO/IEC 9314-1.
5.2.4.2 Frame format
The non-basic frame format is specified with a non-standard address field, as specified in
5.2.5.1, and a non-standard control field, as specified in 5.2 . 5. 2.
5.2.4.3 Frame checking sequence field
The 16-bit frame checking sequence (Cyclic Redundancy Check, CRC) option shall be
implemented for all DLEs of the polled class. The 8-bit frame checking sequence (CRC)
option shall be implemented for all DLEs of the packed class.

61158-4-18 © IEC:2010(E) – 13 –
5.2.4.4 Header check sequence field
The header check sequence field shall not be implemented.
5.2.4.5 Operational mode
The Normal Response Mode (NRM) shall be implemented.
5.2.4.6 Start/stop transmission – basic transparency
The protocol for basic transparency shall not be implemented.
5.2.4.7 Summary
The HDLC conventions implemented by the DL are summarized in Table 1.
Table 1 – HDLC convention summary
Component Implementation
Data encoding NRZI
Frame format non-basic frame
Frame checking sequence field 16-bit / 8-bit
Header check sequence field not implemented
Operational mode normal response mode
Start/stop transmission – basic transparency not implemented

5.2.5 HDLC exceptions
5.2.5.1 Address field
The DLE implements a two-octet address field the encoding of which does not conform to
HDLC. A special subset of the response type messages are defined that exclude the address
field entirely (field length = 0).
5.2.5.2 Control field
The DLE implements a two-octet control field the encoding of which does not conform to
HDLC. Throughout the remainder of this clause, the control field is named the status field.
A special subset of the request type transmissions are defined that exclude the status field
entirely. Another special subset of the response type transmissions are defined with an
abbreviated 4-bit status field.
5.2.5.3 Inter-frame time fill
The polled DLE class implements an inter-frame time fill the encoding of which does not
conform to HDLC. The polled DLE class inter-frame time fill shall be accomplished by
transmitting a continuous stream of alternating zeros and ones.
5.2.5.4 Summary
The HDLC exceptions implemented by the DLE are summarized in Table 2.

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Table 2 – HDLC exception summary
Component Implementation
Address field conditional 16-bit field with non-standard encoding
Control field conditional 16-bit/4-bit field with non-standard encoding
Inter-frame time fill alternating zero-one data fill / one followed by high
impedance
5.2.6 Error handling
The HDLC frame encoding and decoding for data transmission and reception may, as
appropriate, send one or more Error indication to the DLS-user, as listed in the following list,
and as explained by ISO/IEC 13239:2002.
a) frame-error – any framing related error
b) crc-error – a received transmission contained an invalid CRC value
c) abort-error – an abort flag was received during transmission or reception
d) buffer-overflow – a DLE implementation has exceeded its allocated memory for data
reception
e) invalid-address – an unexpected source address or destination address was received
6 DLPDU – basic structure
6.1 Overview
Described in this clause is the basic structure of the DLPDU. In general, the Type 18 DLPDU
includes an address field, a status field and a data field. There are cases explained in the
Type 18 DL-protocol where one or more of these fields are zero length. The specific formats
of the DLPDU are detailed in Clause 7.
6.2 Address field
6.2.1 Master-polled DLE generated address field
The address field contains two octets. The first octet (octet 0) identifies the transmission type
as specified in Table 3. The second octet (octet 1) specifies the destination address (DLE
station identifier).
Table 3 – Master-polled DLE address octet 0
Value Transmission type
(hexadecimal)
FF Poll-with-data
FE Poll
FD Poll-with-test-data
FC Poll-test
FA End-of-cycle
6.2.2 Slave-polled DLE generated address field
The address field contains two octets. The first octet (octet 0) specifies the source address
(DLE station identifier). The second octet (octet 1) identifies the transmission type as
specified in Table 4.
61158-4-18 © IEC:2010(E) – 15 –
Table 4 – Slave-polled DLE address octet 0
Value Transmission type
(hexadecimal)
FF Poll-with-data-response
FE Poll-response
FD Poll-with-test-data-response
FC Poll-test-response
NOTE The response transmission type is an echo of the requesting transmission type.
6.2.3 Master-packed DLE generated address field
The address field contains two octets.
The first octet (octet 0) identifies the transmission type as specified in Table 5. The values to
identify the transmission types are correlated to the configured bit width of the master-packed
DLE as noted.
The second octet (octet 1) specifies the highest DLE station identifier included in the list of
slave-packed DLE. For the purposes of the baud-rate-synchronization type and initial poll-
with-test-data type transmissions, this value is set to 64.
Table 5 – Master-packed DLE address octet 0
Value Corresponding Transmission type
(hexadecimal) bit width
DE all Baud rate synchronization
9E 4 Poll-with-test-data
AE 8
BE 16
9A 4 Connected slave-packed DLE list
AA 8
BA 16
5E 4 Poll-with-data
6E 8
7E 16
6.2.4 Slave-packed DLE generated address field
The address field for the slave-packed DLE class is zero length.
6.3 Status field
6.3.1 Master-polled DLE generated status field
The status field contains two octets. These are specified in Table 6 and Table 7. The
specific values are updated from the most recent DLSDUs of corresponding DL-services.

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Table 6 – Master-polled DLE status octet 0
Bit Definition
0 DLS-user state (0 = Stop; 1 = Run)
1 DLS-user status (0 = Normal, 1 = Fault)
2 Cyclic refresh status (0 = Stop; 1 = Run)
3 Acyclic status (0 = Normal; 1 = Error)
4 Acyclic enabled (0 = Disabled; 1 = Enabled)
5 - 6 Bit 6 (0), Bit 5 (0) = Cyclic data segmenting not supported
Bit 6 (0), Bit 5 (1) = Cyclic data segmenting supported
Bit 6 (1), Bit 5 (0) = reserved
Bit 6 (1), Bit 5 (1) = reserved
7 Master DLE type (0 = Active; 1 = Standby)

Table 7 – Master-polled DLE status octet 1
Bit Value Definition
3 – 0 0 0 octets of bit oriented data in cyclic data field
1 32
2 64
3 96
4 128
5 160
6 192
7 224
8 256
9 – 15 reserved
7 – 4 0 0 octets of word oriented data in cyclic data field
1 64
2 128
3 192
4 256
5 320
6 384
7 448
8 512
9 – 15 reserved
6.3.2 Slave-polled DLE generated status field
The status field contains two octets. These are specified in Table 8 and Table 9. The
specific values are updated from the most recent DLSDUs of corresponding DL-services.

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Table 8 – Slave-polled DLE status octet 0
Bit Definition
0 DSL-user fuse status (0 = Normal; 1 = Abnormal)
1 DLS-user status (0 = Normal, 1 = Fault)
2 Cyclic refresh status (0 = Complete; 1 = Not received)
3 Slave DLE parameter receive status (0 = Complete; 1 = Not received)
4 DLS-user switch status (0 = No change; 1 = Changed)
5 Cyclic transmission enabled (0 = Enabled; 1 = Disabled)
6 reserved
7 DLS-user watchdog timer status (0 = Normal; 1 = WDT error detected)

Table 9 – slave-polled DLE status octet 1
Bit Definition
0 Acyclic status
...