IEC 62056-3-1:2013

Electricity metering data exchange - The DLMS/COSEM suite - Part 3-1: Use of local area networks on twisted pair with carrier signalling

IEC 62056-3-1:2013 describes three profiles for local bus data exchange with stations either energized or not. For non-energized stations, the bus supplies energy for data exchange. Three different profiles are supported:
- base profile;
- profile with DLMS;
- profile with DLMS/COSEM. The three profiles use the same physical layer and they are fully compatible, meaning that devices implementing any of these profiles can be operated on the same bus. The transmission medium is twisted pair using carrier signalling and it is known as the Euridis Bus. This first edition cancels and replaces the first edition of IEC 62056-31, issued in 1999, and constitutes a technical revision. The main technical changes are:
- addition of a profile which makes use of the IEC 62056 DLMS/COSEM Application layer and COSEM object model,
- review of the data link layer which is split into two parts: a pure Data Link layer; a "Support Manager" entity managing the communication media;
- ability to negotiate the communication speed, bringing baud rate up to 9 600 bauds.

Echange des données de comptage de l'électricité - La suite DLMS/COSEM - Partie 3-1: Utilisation des réseaux locaux sur paire torsadée avec signal de porteuse

La CEI 62056-3-1:2013 décrit trois profils pour échange de données par bus en local avec des stations alimentées ou non en énergie. Pour les stations télé-alimentées, le bus fournit l'énergie pour l'échange des données. Trois différents profils sont supportés:
- Profil de base;
- Profil avec DLMS;
- Profil avec DLMS/COSEM. Les trois profils utilisent la même couche physique et ils sont entièrement compatibles, c'est-à-dire que des équipements ayant implémenté l'un de ces profils peuvent opérer sur le même bus. Le moyen de transmission est la paire torsadée par signal de porteuse et connue sous le nom de Bus Euridis. Cette première édition annule et remplace la première édition de la CEI 62056-31, parue en 1999, dont elle constitue une révision technique. Les modifications techniques sont:
- Ajout d'un profil qui permet l'utilisation de la couche Application et la modélisation objet DLMS/COSEM de la CEI 62056,
- Révision de la couche liaison de données qui est maintenant scindée en deux parties: la première est intégralement une couche de liaison de données; la dernière, nommée "Gestion du Support", gère le média de communication;
- Capacité de négocier la vitesse de communication, portant la vitesse maximale jusqu'à 9 600 bauds.

General Information

• Status: Published
• Publication Date: 19-Aug-2013
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• ICS: 35.110 - Networking
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 13 - Electrical energy measurement and control
• Drafting Committee: MT 62056-3-1 - TC 13/MT 62056-3-1
• Current Stage: DELPUB - Deleted Publication
• Start Date: 07-Jul-2021
• Completion Date: 26-Oct-2025

Relations

• Replaces: IEC 62056-31:1999 - Electricity metering - Data exchange for meter reading, tariff and load control - Part 31: Use of local area networks on twisted pair with carrier signalling
• Effective Date: 05-Sep-2023
• Revised: IEC 62056-3-1:2021 - Electricity metering data exchange - The DLMS/COSEM suite - Part 3-1: Use of local area networks on twisted pair with carrier signalling
• Effective Date: 05-Sep-2023

Overview

IEC 62056-3-1:2013 is an international standard published by the International Electrotechnical Commission (IEC) that specifies protocols for electricity metering data exchange using the DLMS/COSEM suite. This part (3-1) focuses specifically on the use of local area networks over twisted pair cables with carrier signalling, commonly known as the Euridis Bus.

This standard defines three profiles for local bus data exchange supporting stations that may or may not be energized by the bus itself. The profiles-base profile, profile with DLMS, and profile with DLMS/COSEM-share a unified physical layer, ensuring full compatibility across devices. Key improvements in this 2013 edition include support for the DLMS/COSEM Application layer and object model, enhanced Data Link layer separation, and communication speed negotiation up to 9600 baud.

Key Topics

• Local Bus Data Exchange Profiles
  IEC 62056-3-1:2013 covers three profiles for communication on local buses that operate on twisted pair cables:

  • Base profile without DLMS
  • Profile with DLMS protocol
  • Profile with DLMS/COSEM, aligned with IEC 62056 standards

• Physical Layer and Transmission Medium
  Communication uses twisted pair wiring coupled with a 50 kHz carrier signalling method. This physical setup supports both energized and non-energized stations, with energy supplied on the bus for non-energized devices.

• Data Link Layer Optimization
  The Data Link layer is split into two functional parts: a pure Data Link layer and a Support Manager entity responsible for media communication management, including bus initialization, discovery, and speed negotiation.

• Communication Speed Negotiation
  Devices can negotiate baud rates dynamically, allowing communication speeds up to 9600 baud, improving data transfer efficiency over the local bus.

• Application Layer Integration
  The profiles support the DLMS/COSEM Application layer and COSEM object model for standardized, interoperable metering data representation and exchange.

• Error Handling and System Management
  The standard includes detailed mechanisms for error detection, handling, and recovery across all layers to ensure robust communication.

Applications

IEC 62056-3-1:2013 is critical for utilities and metering system manufacturers involved in smart metering infrastructure, specifically:

• Smart Metering Networks
  Enables reliable data exchange between electricity meters and data concentrators or other primary stations in local area networks using existing twisted pair infrastructure.

• Energy Supply to Non-Energized Devices
  The specification allows the bus itself to power non-energized metering devices, reducing wiring complexity and installation costs.

• Interoperable Metering Systems
  By supporting DLMS/COSEM protocols, it facilitates the integration of devices from multiple manufacturers, enhancing system flexibility and future-proofing.

• Remote Meter Reading and Control
  Supports remote reading, programming, and transfer operations essential for automated meter data acquisition and management in advanced metering infrastructure (AMI).

• Legacy and New Installations
  Given its compatibility between base and DLMS-based profiles, the standard assists in transitioning older systems to modern metering solutions without full infrastructure overhaul.

Related Standards

• IEC 62056 Series
  The parent DLMS/COSEM suite of standards for electricity metering data exchange provides a comprehensive framework across different communication media and layers.

• IEC 62056-3-3
  Defines the use of local area networks with power line carrier (PLC) signalling complementing the twisted pair approach.

• IEC 62056-7-3
  Covers object identification and modeling which dovetails with COSEM profiles detailed in this standard.

• IEC 62056-8-3
  Addresses persistent data exchange mechanisms, which may be layered on top of the physical and data link protocols in IEC 62056-3-1.

Conclusion

IEC 62056-3-1:2013 plays a vital role in standardizing metering data communication over twisted pair local area networks using carrier signalling. Its backward compatibility and support for the DLMS/COSEM protocol suite enable utilities and device manufacturers to ensure interoperable, reliable, and efficient smart metering communications. By implementing this standard, organizations can optimize network performance, enhance remote meter management, and streamline deployment of intelligent electricity metering systems worldwide.

Keywords: IEC 62056-3-1, DLMS/COSEM, electricity metering data exchange, twisted pair communication, Euridis Bus, local area networks, carrier signalling, smart metering protocols, data link layer, communication speed negotiation

Standards Content (Sample)

IEC 62056-3-1 ®
Edition 1.0 2013-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electricity metering data exchange – The DLMS/COSEM suite –
Part 3-1: Use of local area networks on twisted pair with carrier signalling

Échange des données de comptage de l'électricité – La suite DLMS/COSEM –
Partie 3-1: Utilisation des réseaux locaux sur paire torsadée avec signal de
porteuse
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IEC 62056-3-1 ®
Edition 1.0 2013-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electricity metering data exchange – The DLMS/COSEM suite –

Part 3-1: Use of local area networks on twisted pair with carrier signalling

Échange des données de comptage de l'électricité – La suite DLMS/COSEM –

Partie 3-1: Utilisation des réseaux locaux sur paire torsadée avec signal de

porteuse
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XE
ICS 17.220; 35.110; 91.140.50 ISBN 978-2-8322-1046-8

– 2 – 62056-3-1 © IEC:2013
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Abbreviations . 10
4 General description . 11
4.1 Basic vocabulary . 11
4.2 Profiles, layers and protocols . 11
4.2.1 Overview . 11
4.2.2 Base profile (without DLMS) . 12
4.2.3 Profile with DLMS . 12
4.2.4 Profile with DLMS/COSEM . 13
4.3 Specification language . 13
4.4 Communication services for local bus data exchange without DLMS . 13
4.4.1 Overview . 13
4.4.2 Remote reading exchange . 14
4.4.3 Remote programming exchange . 14
4.4.4 Point to point remote transfer exchange . 16
4.4.5 Broadcast remote transfer frame . 16
4.4.6 Bus initialization frame . 16
4.4.7 Forgotten station call exchange . 17
4.4.8 Frame fields . 17
4.4.9 Principle of the energy remote supply . 18
4.4.10 Non-energized station preselection exchange . 19
4.4.11 Communication exchange after preselection . 20
4.4.12 Alarm function . 20
4.5 Communication services for local bus data exchange with DLMS . 21
4.6 Systems management . 22
5 Local bus data exchange without DLMS . 22
5.1 Physical layer . 22
5.1.1 Physical-62056-3-1 protocol . 22
5.1.2 Physical parameters . 23
5.1.3 Timing diagrams . 25
5.1.4 Physical services and service primitives . 26
5.1.5 State transitions . 27
5.1.6 List and processing of errors . 34
5.2 Data Link layer . 35
5.2.1 Link-62056-3-1 protocol . 35
5.2.2 Management of exchanges . 35
5.2.3 Data Link services and service primitives . 35
5.2.4 Data Link parameters . 36
5.2.5 State transitions . 36
5.2.6 List and processing of errors . 41
5.3 Application layer . 42
5.3.1 Application-62056-3-1 protocol . 42
5.3.2 Application services and service primitives . 42
5.3.3 Application parameters . 42

62056-3-1 © IEC:2013 – 3 –
5.3.4 State transitions . 43
5.3.5 List and processing of errors . 45
6 Local bus data exchange with DLMS . 45
6.1 Physical layer . 45
6.2 Data Link layer . 46
6.2.1 Link-E/D protocol . 46
6.2.2 Management of exchanges . 46
6.2.3 Data Link services and service primitives . 47
6.2.4 Data Link parameters . 47
6.2.5 State transitions . 48
6.2.6 List and processing of errors . 54
6.3 Application layer . 54
6.3.1 General . 54
6.3.2 Transport sub-layer . 54
6.3.3 Application sub-layer . 54
7 Local bus data exchange with DLMS/COSEM . 55
7.1 Model . 55
7.2 Physical Layer . 55
7.2.1 General . 55
7.2.2 Physical Parameters . 55
7.2.3 Speed negotiation. 55
7.2.4 E/COSEM Physical Services and service primitives . 56
7.2.5 State transitions . 57
7.3 Data Link layer . 65
7.3.1 General . 65
7.3.2 Identification of data units . 66
7.3.3 Role of the Data Link layer . 66
7.3.4 Management of exchanges . 66
7.3.5 Data Link services and service primitives . 66
7.3.6 Data Link parameters . 68
7.3.7 State transitions . 68
7.4 Support Manager layer . 75
7.4.1 Overview . 75
7.4.2 Initialisation of the bus . 75
7.4.3 Discover service . 76
7.4.4 Speed negotiation. 76
7.4.5 Support Manager parameters . 76
7.4.6 State transitions . 77
7.5 Transport Layer . 78
7.5.1 General . 78
7.5.2 Transport Data Units . 78
7.5.3 State transitions . 80
7.6 Application Layer . 82
7.6.1 General . 82
7.6.2 Broadcast Management . 82
7.6.3 Management of EventNotifications or InformationReports . 83
7.6.4 Priority Management . 83
7.6.5 Management of releasing Application Associations . 83
8 Local bus data exchange – Hardware . 83

– 4 – 62056-3-1 © IEC:2013
8.1 General . 83
8.2 General characteristics . 83
8.2.1 Signal transmission at 50 kHz . 83
8.2.2 Energy supply signal transmission . 84
8.2.3 Simple Secondary Station and multiple Secondary Station . 87
8.3 Bus specification . 88
8.3.1 General characteristics . 88
8.3.2 Cable characteristics . 88
8.3.3 Wiring . 89
8.4 Magnetic plug . 90
8.4.1 Function . 90
8.4.2 Common mechanical characteristics . 90
8.4.3 Electrical block diagram with simple plug . 91
8.4.4 Electrical Block Diagram with energy supply plug . 92
8.5 Functional specifications of Primary Station transmitter (for 50 kHz signal) . 93
8.6 Functional specifications of Primary Station receiver (for 50 kHz signal). 93
8.7 Functional specification of Secondary Station transmitter (for 50 kHz signal) . 94
8.8 Functional specifications of Secondary Station receiver (for 50 kHz signal) . 95
Annex A (normative) Specification language . 97
Annex B (normative) Timing types and characteristics . 100
Annex C (normative) List of fatal errors . 102
Annex D (normative) Coding the command code field of frames . 103
Annex E (normative) Principle of the CRC. 105
Annex F (normative) Random integer generation for response from forgotten stations . 106
Annex G (normative) Random number generation for authentication (profile without
DLMS) . 107
Annex H (normative) Systems management implementation . 108
Annex I (informative) Information about exchanges . 109
Bibliography . 113

Figure 1 – IEC 62056-3-1 communication profiles . 12
Figure 2 – Alarm mechanism. 21
Figure 3 – Exchanges in continuous operation . 25
Figure 4 – Alarm event without any communication in progress . 25
Figure 5 – Alarm event with a communication in progress . 25
Figure 6 – Signal envelope on the bus . 84
Figure 7 – Bus representation . 85
Figure 8 – Power supply characteristics . 85
Figure 9 – States associated to a session: for selected Secondary station . 86
Figure 10 – States associated to a session: for non-selected Secondary station . 86
Figure 11 – Simple and multiple Secondary stations . 87
Figure 12 – Equivalent diagram of the test equipment . 89
Figure 13 – Ferrite pot and bobbin . 90
Figure 14 – Associated components of the magnetic plug . 91
Figure 15 – Associated components of the energy supply plug . 92
Figure B.1 – Logical timing type . 100

62056-3-1 © IEC:2013 – 5 –
Figure B.2 – Physical timing type . 100
Figure B.3 – Results processing for timing defined with low and high limits . 101
Figure B.4 – Results processing for timing defined by a nominal value . 101
Figure I.1 – Non-energized station session . 109
Figure I.2 – Remote reading and programming exchanges . 110
Figure I.3 – Bus initialization . 111
Figure I.4 – Forgotten station call exchange . 112

Table 1 – Primary Station timing . 23
Table 2 – Secondary station timing . 24
Table 3 – Physical services and service primitives . 26
Table 4 – Physical-62056-3-1 state transitions: Primary station . 27
Table 5 – Power supply management state transitions (only for non-energized
secondary station) . 29
Table 6 – Physical-62056-3-1 state transitions: Secondary station . 31
Table 7 – Meaning of the states listed in the previous tables . 32
Table 8 – Definition of the procedures, functions and events classified in alphabetical
order . 33
Table 9 – Error summary table . 34
Table 10 – Data Link services and service primitives . 35
Table 11 – Link-62056-3-1 state transitions: Primary station . 36
Table 12 – Link-62056-3-1 State transitions: Secondary station . 39
Table 13 – Meaning of the states listed in the previous tables . 40
Table 14 – Definition of the procedures and functions classified in alphabetical order . 40
Table 15 – Error summary table . 41
Table 16 – Application services and service primitives . 42
Table 17 – Application-62056-3-1 state transitions: Primary station . 43
Table 18 – Application-62056-3-1 state transitions: Secondary station . 44
Table 19 – Meaning of the states listed in the previous tables . 44
Table 20 – Definition of the procedures and functions classified in alphabetical order . 45
Table 21 – Error summary table . 45
Table 22 – Data Link services and service primitives . 47
Table 23 – Link-E/D state transitions: Primary station . 48
Table 24 – Link-E/D state transitions: Secondary station. 50
Table 25 – Meaning of the states listed in the previous tables . 52
Table 26 – Definition of the procedures and functions classified in alphabetical order . 52
Table 27 – Error summary table . 54
Table 28 – Client_connect function definition . 54
Table 29 – E/COSEM Physical services and service primitives . 56
Table 30 – E/COSEM Physical state transitions: Primary station . 57
Table 31 – Power supply management state transitions (only for non-energized
Secondary station) . 60
Table 32 – E/COSEM Physical State transitions: Secondary station . 61
Table 33 – Meaning of the states listed in the previous tables . 63

– 6 – 62056-3-1 © IEC:2013
Table 34 – Definition of the procedures, functions and events classified in alphabetical
order . 64
Table 35 – Error summary table . 65
Table 36 – Data Link services and service primitives . 66
Table 37 – DLMS/COSEM Data Link E/D state transitions: Primary station . 68
Table 38 – DLMS/COSEM Link E/D state transitions: Secondary station . 71
Table 39 – Meaning of the states listed in the previous tables . 73
Table 40 – Definition of the procedures and functions classified in alphabetical order . 74
Table 41 – Commands managed by the Support Manager layer . 75
Table 42 – List of parameters . 76
Table 43 – Support Manager layer state transitions: Primary station . 77
Table 44 – Support Manager layer state transitions: Secondary station . 77
Table 45 – Meaning of the states listed in the previous table . 77
Table 46 – Definition of procedures, functions and events . 78
Table 47 – Transport services and services primitive . 79
Table 48 – Transport state transitions . 80
Table 49 – Meaning of the states listed in the previous table . 81
Table 50 – Definition of the procedures and functions classified in alphabetical order . 82
Table 51 – Primary station transmitter: Tev0 and Tev1 values . 93
Table 52 – Primary station receiver: Tev0 and Tev1 values . 94
Table 53 – Secondary station transmitter: Tev0 and Tev1 values . 94
Table 54 – Secondary station receiver: Tev0 and Tev1 values . 95
Table C.1 – FatalError error numbers . 102
Table D.1 – Command codes for local bus data exchange . 103
Table D.2 – Command codes with DLMS and DLMS/COSEM . 104
Table H.1 – Discovery service. 108
Table H.2 – Service specification . 108

62056-3-1 © IEC:2013 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICITY METERING DATA EXCHANGE –
THE DLMS/COSEM SUITE –
Part 3-1: Use of local area networks on twisted pair
with carrier signalling
FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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.
International Standard IEC 62056-3-1 has been prepared by IEC technical committee 13:
Electrical energy measurement, tariff- and load control.
This first edition cancels and replaces the first edition of IEC 62056-31, issued in 1999, and
constitutes a technical revision.
The main technical changes with regard to the previous edition are as follows:
• addition of a profile which makes use of the IEC 62056 DLMS/COSEM Application layer
and COSEM object model,
• review of the data link layer which is split into two parts:
– a pure Data Link layer;
– a “Support Manager” entity managing the communication media;
• ability to negotiate the communication speed, bringing baud rate up to 9 600 bauds.

– 8 – 62056-3-1 © IEC:2013
The text of this standard is based on the following documents:
FDIS Report on voting
13/1546/FDIS 13/1552/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.
A list of all parts of IEC 62056 series, published under the general title Electricity metering
data exchange – The DLMS/COSEM suite, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next eidition.
The numbering scheme has changes from IEC 62056-XY to IEC 62056-X-Y. For example,
IEC 62056-31 becomes IEC 62056-3-1.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
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.
62056-3-1 © IEC:2013 – 9 –
ELECTRICITY METERING DATA EXCHANGE –
THE DLMS/COSEM SUITE –
Part 3-1: Use of local area networks on twisted pair
with carrier signalling
1 Scope
This part of IEC 62056 describes three profiles for local bus data exchange with stations
either energized or not. For non-energized stations, the bus supplies energy for data
exchange.
Three different profiles are supported:
• base profile: this three-layer profile provides remote communication services;
NOTE This first profile has been published in IEC 61142:1993 and became known as the Euridis standard.
• profile with DLMS: this profile allows using DLMS services as specified in IEC 61334-4-41;
NOTE This second profile has been published in IEC 62056-31 Ed. 1.0:1999;
• profile with DLMS/COSEM: this profile allows using the DLMS/COSEM Application layer
and the COSEM object model as specified in IEC 62056-5-3 Ed. 1.0:— and in IEC 62056-
6-2 Ed. 1.0:— respectively.
The three profiles use the same physical layer and they are fully compatible, meaning that
devices implementing any of these profiles can be operated on the same bus.
The transmission medium is twisted pair using carrier signalling and it is known as the Euridis
Bus.
2 Normative references
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.
IEC 61334-4-41:1996, Distribution automation using distribution line carrier systems – Part 4:
Data communication protocol – Section 41: Application protocols – Distribution line message
specification
IEC 62056-51:1998 Electricity Metering – Data exchange for meter reading, tariff and load
control – Part 51: Application Layer Protocols
IEC 62056-5-3 Ed. 1.0:—, Electricity metering data exchange – The DLMS/COSEM suite –
Part 5-3: DLMS/COSEM application layer
ISO/IEC 8482:1993, Information technology – Telecommunications and information exchange
between systems – Twisted pair multipoint interconnections
EIA 485 – Standard for Electrical Characteristics of Generators and Receivers for Use in
Balanced Digital Multipoint Systems

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3 Abbreviations
Abbreviation English rendering
ADP Primary Station Address
ADG General Secondary Address. Broadcast Address
ADS Secondary Station Address
AGN Normal Wakeup
AGT General call for a General Energized Station
APDU Application Protocol Data Unit
APG General Primary Address
ARJ COM field value: Rejection of authentication in remote programming exchange
ASDU Application Service Data Unit
ASO COM field value: Call to Forgotten Stations
AUT COM field value: Authentication command
COM Control field of the Data Link layer
COSEM Companion Specification for Energy Metering
DAT COM field value: Response of remote reading exchange
DES Data Encryption Standard
DLMS Distribution Line Message Specification (IEC 61334-4-41)
Device Language Message Specification (IEC 62056-5-3)
DSDU Data link Service Data Unit
DRJ COM field value: Data Rejected
Value of COM notifying the rejection of remote programming exchange data
Dsap Transport data unit label. Coded over 3 bits. Its value is 6.
DTSAP Destination of Transport Service Access Point
ECH COM field value: Echo of remote programming exchange data
ENQ Remote reading exchange request
EOS COM field value: End of remote programming exchange
IB Initialisation of the bus
MaxRetry Maximum number retransmissions. Limited to 2.
MaxRSO Maximum number of RSO listening windows. Fixed at 3.
PDU Protocol Data Unit
PRE COM field value: Pre-selection of energised stations
REC COM field value: Remote programming exchange request
RSO COM field value: Response to a call to forgotten stations
SEL COM field value: Acknowledgement of the pre-selection of energized stations
STSAP Source Transport Service Access Point
TAB In the case of the Euridis profiles without DLMS and without DLMS/COSEM: data code.
In the case of profiles using DLMS or DLMS/COSEM: value at which the equipment is
programmed for Discovery
TABi List of TAB field
TASB Duration of an Alarm Signal on the Bus
TOAG Maximum wait time for an energized station once selected, to recognise a general call AGN
TOALR Wait before sending an AGN after reception of an AGN or AGT
TOL Maximum waiting time for a request from the upper layer

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Abbreviation English rendering
TOPRE Maximum waiting time for a response to a pre-selection.
TPDU Transport Protocol Data Unit
TSDU Transport Protocol Service Unit
TRA COM field value: Acknowledgement of point to point transfer
TRB COM field value: Broadcast remote transfer frame not acknowledged
TRF COM field value: Point to point remote transfer exchange
T1 Time out to wait for a response according to a request
XBA COM field value: Response to a change of speed request
XBR COM field value: Change of speed request
ZA1 Field reserved for bidirectional programming authentication
ZA2 Field reserved for bidirectional programming authentication
4 General description
4.1 Basic vocabulary
All communication calls upon two systems called Primary Station and Secondary Station. The
Primary Station is the system that decides to initialize a communication with a remote system
called Secondary Station; these designations remain valid throughout the duration of the
communication.
A communication is broken down into a certain number of transactions. Each transaction
consists of a transmission from the Transmitter to the Receiver. During the sequence of
transactions, the Primary Station and Secondary Station systems take turns to act as
Transmitter and Receiver.
For the local bus data exchange profile with DLMS or DLMS/COSEM, the terms Client and
Server have the same meaning as for the DLMS model (refer to IEC 61334-4-41 or
IEC 62056-5-3 Ed. 1.0:—). The Server (which is a Secondary Station) receives and processes
all submissions of specific service requests. The Client (which is a Primary Station) is the
system that uses the Server for a specific purpose by means of one or more service requests.
4.2 Profiles, layers and protocols
4.2.1 Overview
This standard specifies three profiles as shown in Figure 1.
• the base profile (without DLMS), see 4.2.2;
• the profile with DLMS, see 4.2.3;
• the profile with DLMS/COSEM; see 4.2.4.
The physical layer in the three profiles is the same except that in the DLMS/COSEM profile
speed negotiation is available. This common physical layer allows stations using different
profiles to be installed on the same bus.

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COSEM model
IEC 62056-6-2
Application layer Application layer
IEC 62056-5-3
Application-62056-3-1
Application layer
protocol DLMS/COSEM protocol
IEC 62056-51
DLMS+ protocol
Application+ protocol
Transport + protocol
Transport layer Support manager
Data link layer
Data link layer Data link layer
Link-62056-3-1 protocol
Link-E/D protocol Link-E/D protocol
Physical layer Physical layer Physical layer
Physical-62056-3-1 Physical-62056-3-1 Physical E/COSEM
protocol protocol protocol
Architecture with
Base architecture Architecture with DLMS
DLMS/COSEM
IEC  2066/13
Figure 1 – IEC 62056-3-1 communication profiles
4.2.2 Base profile (without DLMS)
The base profile (without DLMS) uses three protocol layers:
• the physical layer with the Physical-62056-3-1 protocol specified in 5.1;
• the data link layer with the Link-62056-3-1 protocol, specified in 5.2, and
• the application layer with the Application-62056-3-1 protocol specified in 5.3.
This profile allows remote reading, remote programming, point-to-point remote transfer –
which is a simplified remote programming service – broadcast remote transfer, remote supply
of secondary stations, detecting forgotten stations and alarm functions. The related
communication services are specified in 4.4.
4.2.3 Profile with DLMS
The profile with DLMS uses three protocol layers:
• the same physical layer as the base profile, specified in 5.1;
• the data link layer using the Link-E/D protocol, specified in 6.2; and
• the application layer specified in IEC 62056-51, using the Transport+, Application+ and
DLMS+ protocols, see 6.3.
This profile also allows using DLMS as specified in IEC 61334-4-41. The related
communication services are specified in 4.5.

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4.2.4 Profile with DLMS/COSEM
The profile with DLMS/COSEM uses four protocol layers:
• the physical layer, similar to the one used in the base profile and the profile with DLMS,
specified in 5.1, but with speed negotiation, see 7.2;
• the data link layer using the Link-E/D protocol. This is the same as
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