IEC 62056 Series Explained: The Complete Guide to Every Part
The IEC 62056 series is the most comprehensive metering communication standard in existence. It covers everything from the physical optical port to application-layer security to companion profiles for specific meter types. This guide maps every part so you know exactly where to look.
What is IEC 62056?
IEC 62056 is the international standard for electricity metering data exchange. Published by the International Electrotechnical Commission (IEC), it is technically identical to the DLMS/COSEM specification maintained by the DLMS User Association. The two organisations co-publish the standard — IEC for the formal international standard, DLMS UA for the freely downloadable technical books.
The standard is divided into numbered parts, grouped into series:
IEC 62056-1x: Glossary and General Principles
| Part |
Title |
Key Content |
| 62056-1-0 |
Glossary of terms |
Definitions of all terms used across the series. Start here. |
IEC 62056-2x: System Architecture
| Part |
Title |
Key Content |
| 62056-2-0 |
Roles and procedures for management of the DLMS UA COSEM object model and OBIS |
How OBIS codes and COSEM classes are allocated and maintained |
IEC 62056-3x: Data Link and Physical Layers
| Part |
Title |
Key Content |
| 62056-21 |
Direct local data exchange |
The classic optical port standard. Defines Modes A–E, baud rate negotiation, protocol selection. Still in 100 million+ deployed meters. |
| 62056-31 |
Use of local area networks on twisted pair |
LAN-based local communication for meters |
| 62056-46 |
Data link layer using HDLC protocol |
HDLC framing for point-to-point meter communication — the basis for serial/optical DLMS |
| 62056-47 |
TCP-UDP/IP setup for meters |
How DLMS runs over TCP/IP: wrapper protocol, port numbers (4059 TCP for DLMS) |
| 62056-48 |
TCP-UDP/IP setup in multi-drop networks |
Extension for PLC and multi-drop environments |
IEC 62056-5x: COSEM Application Layer
This is the heart of the standard.
| Part |
Title |
Key Content |
| 62056-53 |
COSEM Application layer |
GET, SET, ACTION, NOTIFICATION services. Association setup (AARQ/AARE). The PDU structure for every DLMS request/response. |
| 62056-57 |
COSEM object classes |
Companion to the Blue Book. Formal ASN.1 definitions of all COSEM interface classes. |
IEC 62056-6x: Object Model and OBIS
| Part |
Title |
Key Content |
| 62056-6-1 |
Object identification system (OBIS) |
The complete OBIS code allocation. Every group A–F value is defined here. The authoritative OBIS reference. |
| 62056-6-2 |
COSEM interface classes |
All standard COSEM classes: Data (1), Register (3), Extended Register (4), Demand Register (5), Register Activation (6), Profile Generic (7), Clock (8), Script Table (9), Schedule (10), Special Days Table (11), Association (15), IEC Local Port Setup (19), Activity Calendar (20), Register Monitor (21), Single/Double Action Schedule (22/23), Image Transfer (18), and more. |
IEC 62056-7x: Transport Layers and Communication Profiles
| Part |
Title |
Key Content |
| 62056-7-5 |
Use of wired and wireless networks |
How to carry DLMS over any lower-layer network: S-FSK PLC, OFDM PLC, RF, cellular, Ethernet |
IEC 62056-8x: Security
| Part |
Title |
Key Content |
| 62056-8-1 |
Security suite 0 |
AES-128 in GCM mode for authenticated encryption. The baseline security suite for all modern DLMS deployments. Defines general ciphering, dedicated ciphering, and the key management framework. |
| 62056-8-2 |
Role-based access control |
How to assign read/write/action permissions per user/association |
IEC 62056-9x: Abstract Test Suites
| Part |
Title |
Key Content |
| 62056-9-7 |
Abstract test suite for COSEM application layer |
The test cases behind the DLMS CTT (Conformance Test Tool). If your meter passes 62056-9-7, it gets a DLMS certificate. |
The DLMS UA Books and Their IEC Equivalents
| DLMS UA Book |
Colour |
IEC Equivalent |
Content |
| Architecture & Protocols |
Green Book |
62056-1-0, 62056-2-0, 62056-5-3, 62056-7-5 |
System architecture, application layer, transport profiles |
| COSEM Object Model |
Blue Book |
62056-6-1, 62056-6-2 |
All OBIS codes, all COSEM interface classes |
| Conformance Testing |
Yellow Book |
62056-9-7 |
Test cases for CTT certification |
| Security |
White Book |
62056-8-1, 62056-8-2 |
Cryptographic suites, key management |
Where to Get the Standard
- DLMS UA books (free): dlms.com/home/documents/distr/technical-documents
- IEC formal publications (paid): webstore.iec.ch
- DLMS CTT certification: dlms.com/home/certification