IEC 62056-46:2002+AMD1:2006 CSV

Electricity metering - Data exchange for meter reading, tariff and load control - Part 46: Data link layer using HDLC protocol

Specifies the data link layer for connection-oriented, HDLC-based, asynchronous communication profile. This consolidated version consists of the first edition (2002) and its amendment 1 (2006). Therefore, no need to order amendment in addition to this publication.
This publication is of high relevance for Smart Grid.

General Information

• Status: Published
• Publication Date: 14-Feb-2007
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 35.100.20 - Data link layer
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 13 - Electrical energy measurement and control
• Current Stage: PPUB - Publication issued
• Start Date: 15-Feb-2007
• Completion Date: 15-Feb-2007

Standards Content (Sample)

INTERNATIONAL IEC


STANDARD 62056-46



Edition 1.1
2007-02

Edition 1:2002 consolidated with amendment 1:2006
Electricity metering –
Data exchange for meter reading,
tariff and load control –
Part 46:
Data link layer using HDLC protocol


Reference number
IEC 62056-46:2002+A1:2006(E)

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INTERNATIONAL IEC


STANDARD 62056-46





Edition 1.1

2007-02

Edition 1:2002 consolidated with amendment 1:2006
Electricity metering –
Data exchange for meter reading,
tariff and load control –
Part 46:
Data link layer using HDLC protocol


© IEC 2007 ⎯ Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
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Commission Electrotechnique Internationale CR
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

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CONTENTS

FOREWORD .4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Terms, definitions and abbreviations .8
4 Overview .9
4.1 The LLC sub-layer.9
4.2 The MAC sub-layer.9
4.3 Specification method .10
5 The LLC sub-layer .10
5.1 The role of the LLC sub-layer .10
5.2 Service specification for the LLC sub-layer.11
5.2.1 Setting up the Data Link Connection.11
5.2.2 Disconnecting the Data Link Connection.14
5.2.3 Data communication .18
5.3 Protocol specification for the LLC sub-layer.22
5.3.1 Overview .22
5.3.2 LLC protocol data unit (LPDU) structure .22
5.3.3 State transition tables for the LLC sub-layer .23
6 The MAC sub-layer.24
6.1 HDLC selections.24
6.2 Service specification for the MAC sub-layer.25
6.2.1 Setting up the MAC connection.25
6.2.2 Disconnecting the MAC connection.28
6.2.3 Data communication .33
6.3 Physical layer services used by the MAC sub-layer .35
6.3.1 Overview .35
6.3.2 Setting up a physical link .36
6.3.3 Disconnecting the physical link .36
6.3.4 Data communication .36
6.4 Protocol specification for the MAC sub-layer .36
6.4.1 The MAC PDU and the HDLC frame .36
6.4.2 MAC addressing .38
6.4.3 Command and response frames .42
6.4.4 Elements of the procedures .45
6.4.5 State transition diagram for the server MAC sub-layer .60
Annex A (informative) FCS calculation .62
Annex B (informative) Data model and protocol .65
Annex C (informative) Data link layer management services .66

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62056-46 © IEC:2002+A1:2006(E) – 3 –
Figure 1 – Data Link (LLC) services for setting up the Data Link Connection .11
Figure 2 – Data Link (LLC) services for disconnecting the Data Link Connection .15
Figure 3 – Data link layer data communication services .19
Figure 4 – The ISO/IEC 8802-2 LLC protocol data unit format.22
Figure 5 – The used LLC protocol data unit format.22
Figure 6 – MAC sub-layer services for setting up the MAC (DL) connection at the client
and server sides .25
Figure 7 – MAC sub-layer services for disconnecting the MAC (DL) connection at the
client and server sides .29
Figure 8 – MAC sub-layer data communication services .33
Figure 9 – Physical layer services used by the MAC sub-layer.36
Figure 10 – MAC sub-layer frame format (HDLC frame format type 3).36
Figure 11 – Multiple frames .37
Figure 12 – The frame format field .37
Figure 13 – MSC for long MSDU transfer in a transparent manner .54
Figure 14 – Example configuration to illustrate broadcasting.55
Figure 15 – Sending out a pending UI frame with a .response data .56
Figure 16 – Sending out a pending UI frame with a response to a RR frame .57
Figure 17 – Sending out a pending UI frame on receipt of an empty UI frame .57
Figure 18 – State transition diagram for the server MAC sub-layer.61
Figure B.1 – The three-step approach of COSEM .65
Figure C.1 – Layer management services .66

Table 1 – State transition table of the client side LLC sub-layer .23
Table 2 – State transition table of the server side LLC sub-layer.24
Table 3 – Table of reserved client addresses .40
Table 4 – Table of reserved server addresses .40
Table 5 – Handling inopportune address lengths.42
Table 6 – Command and response frames .42
Table 7 – Control field format.43
Table 8 – Example for parameter negotiation values with the SNRM/UA frames .50
Table 9 – Summary of MAC Addresses for the example.55
Table 10 – Broadcast UI frame handling .55

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________

ELECTRICITY METERING – DATA EXCHANGE
FOR METER READING, TARIFF AND LOAD CONTROL –

Part 46: Data link layer using HDLC protocol



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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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.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is claimed that compliance
with this International Standard may involve the use of a maintenance service concerning the stack of protocols on
which the present standard IEC 62056-46 is based.
The IEC takes no position concerning the evidence, validity and scope of this maintenance service.
The provider of the maintenance service has assured the IEC that he is willing to provide services under
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1
DLMS User Association
Geneva / Switzerland
www.dlms.ch
Attention is drawn to the possibility that some of the elements of this International Standard 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.
________
1
Device Language Message Specification.

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62056-46 © IEC:2002+A1:2006(E) – 5 –
International Standard IEC 62056-46 has been prepared by IEC technical committee 13:
Equipment for electrical energy measurement and load control.
This consolidated version of IEC 62056 consists of the first edition (2002) [documents
13/1267/FDIS and 13/1273/RVD] and its amendment 1 (2006) [documents 13/1376/FDIS and
13/1401/RVD].
The technical content is therefore identical to the base edition and its amendment and has
been prepared for user convenience.
It bears the edition number 1.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
Annexes A, B and C are for information only.
The committee has decided that the contents of the base publication and its amendments 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.

A bilingual version of this publication may be issued at a later date.

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INTRODUCTION (to amendment 1)
The amendment takes into account that in the third edition of ISO/IEC 13239, frame type 3
has been added as Annex H.4, as requested by IEC TC 13 WG 14, and that second editions
of some parts of the IEC 62056 series are under preparation.
It specifies now that a secondary station may use more than one addressing scheme.
It contains some changes concerning the negotiation of the maximum information length field
HDLC parameter for better efficiency.
References have been updated and some editorial errors have also been corrected.

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62056-46 © IEC:2002+A1:2006(E) – 7 –
ELECTRICITY METERING – DATA ECHANGE
FOR METER READING, TARIFF AND LOAD CONTROL –

Part 46: Data link layer using HDLC protocol



1 Scope
This part of IEC 62056 specifies the data link layer for connection-oriented, HDLC-based,
asynchronous communication profile.
In order to ensure a coherent data link layer service specification for both connection-oriented
and connectionless operation modes, the data link layer is divided into two sub-layers: the
Logical Link Control (LLC) sub-layer and the Medium Access Control (MAC) sub-layer.
This specification supports the following communication environments:
• point-to-point and point-to-multipoint configurations;
• dedicated and switched data transmission facilities;
• half-duplex and full-duplex connections;
• asynchronous start/stop transmission, with 1 start bit, 8 data bits, no parity, 1 stop bit.
Two special procedures are also defined:
• transferring of separately received Service User layer PDU parts from the server to
the client in a transparent manner. The server side Service user layer can give its PDU to
the data link layer in fragments and the data link layer can hide this fragmentation from the
client;
• event reporting, by sending UI frames from the secondary station to the primary station.
Annex B gives an explanation of the role of data models and protocols in electricity meter
data exchange.
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.
IEC 60050-300:2001, International Electrotechnical Vocabulary – Electrical and electronic
measurements and measuring instruments – Part 311: General terms relating to
measurements – Part 312: General terms relating to electrical measurements – Part 313:
Types of electrical measuring instruments – Part 314: Specific terms according to the type of
instrument
IEC/TR 62051:1999, Electricity metering – Glossary of terms
IEC 62051-1:2004, Electricity metering – Data exchange for meter reading, tariff and load
control – Glossary of Terms – Part 1, Terms related to data exchange with metering
equipment using DLMS/COSEM

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IEC 62056-42, Electricity metering – Data exchange for meter reading, tariff and load control –
Part 42: Physical layer services and procedures for connection oriented asynchronous data
1)
exchange
IEC 62056-53:2006, Electricity metering – Data exchange for meter reading, tariff and load
control – Part 53: COSEM Application layer
IEC 62056-61:2006, Electricity metering – Data exchange for meter reading, tariff and load
control – Part 61: OBIS Object identification system
IEC 62056-62:2006, Electricity metering – Data exchange for meter reading, tariff and load
control – Part 62: Interface classes
ISO/IEC 8802-2:1998, Information technology – Telecommunications and information exchange
between systems – Local and metropolitan area networks – Specific requirements – Part 2:
Logical link control
ISO/IEC 13239:2002, Information technology – Telecommunications and information
exchange between systems – High-level data link control (HDLC) procedures
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the definitions given in IEC 60050-300, IEC 62051 and
IEC 62051-1 apply.
3.2 Abbreviations
APDU Application layer Protocol Data Unit
COSEM COmpanion Specification for Energy Metering
DISC DISConnect (an HDLC frame type)
DL Data Link
DM Disconnected Mode (an HDLC frame type)
DPDU Data link Protocol Data Unit
DSAP Data link Service Access Point
DSDU Data link Service Data Unit
FCS Frame Check Sequence
FRMR FRaMe Reject (an HDLC frame type)
HCS Header Check Sequence
HDLC High-level Data Link Control
I Information (an HDLC frame type)
LLC Logical Link Control (Sub-layer)
LSAP LLC sub-layer Service Access Point
LPDU LLC Protocol Data Unit
LSB Least Significant Bit
LSDU LLC Service Data Unit
MAC Medium Access Control (sub-layer)
MSAP MAC sub-layer Service Access Point (here it is equal to the HDLC address)
MSB Most Significant Bit
MSDU MAC Service Data Unit
________
1)
 To be published.

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62056-46 © IEC:2002+A1:2006(E) – 9 –
NDM Normal Disconnected Mode
NRM Normal Response Mode
N(R) Receive sequence Number
N(S) Send sequence Number
P/F Poll/Final bit
PDU Protocol Data Unit
PH Physical layer
PSDU Physical layer Service Data Unit
RNR Receive Not Ready (an HDLC frame type)
RR Receive Ready (an HDLC frame type)
SAP Service Access Point
SDU Service Data Unit
SNRM Set Normal Response Mode (an HDLC frame type)
TWA Two Way Alternate
UA Unnumbered Acknowledgement (an HDLC frame type)
UI Unnumbered Information (an HDLC frame type)
UNC Unbalanced operation Normal response mode Class
USS Unnumbered Send Status
V(R) Receive state Variable
V(S) Send state Variable
4 Overview
4.1 The LLC sub-layer
In the connection-oriented profile the only role of the LLC sub-layer is to ensure consistent
Data Link addressing. It can be considered that the LLC sub-layer, defined in ISO/IEC 8802-2
is used in an extended class I operation, where the LLC sub-layer provides the standard
connectionless data services via a connection-oriented MAC sub-layer.
The LLC sub-layer provides Data Link (DL) connection/disconnection services to the Service
User layer, but it uses the services of the MAC sub-layer to execute these services.
The LLC sub-layer is specified in clause 5.
4.2 The MAC sub-layer
The MAC sub-layer – the major part of this data link layer specification – is based on ISO/IEC
13239 concerning high-level data link control (HDLC) procedures.
This standard includes a number of enhancements compared to the original HDLC, for
example in the areas of addressing, error protection and segmentation. These enhancements
have been incorporated in a new frame format, which meets the requirements of the
environment found in telemetry applications for electricity metering and similar industries.
The MAC sub-layer is specified in clause 6.       0

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4.3 Specification method
Sub-layers of the data link layer are specified in terms of services and protocol.
Service specifications cover the services required of, or by, the given sub-layer at the logical
interfaces with the neighbouring other sub-layer or layer, using connection oriented
procedures. Services are the standard way to specify communications between protocol
layers. Through the use of four types of transactions, commonly known as service primitives
(Request, Indication, Response and Confirm) the service provider co-ordinates and manages
the communication between the users. Using service primitives is an abstract, imple-
mentation-independent way to specify the transactions between protocol layers. Given this
abstract nature of the primitives, their use makes good sense for the following reasons:
• they permit a common convention to be used between layers, without regard to specific
operating systems and specific languages;
• they give the implementers a choice of how to implement the service primitives on a
specific machine.
Service primitives include service parameters. There are three classes of service parameters:
• parameters transmitted to the peer layer, becoming part of the transmitted frame, for
example addresses, control information;
• parameters which have only local significance;
• parameters which are transmitted transparently across the data link layer to the user of
the data link.
NOTE Data link layer management services are explained in Annex C.
This standard specifies values for parameters of the first category only.
The protocol specification for a protocol layer includes:
• the specification of the procedures for the transmission of the set of messages exchanged
between peer-layers;
• the procedures for the correct interpretation of protocol control information;
• the layer behaviour.
The protocol specification for a protocol layer does not include:
• the structure and the meaning of the information which is transmitted by means of the
layer (Information field, User data subfield);
• the identity of the Service User layer;
• the manner in which the Service User layer operation is accomplished as a result of
exchanging Data Link messages;
• the interactions that are the result of using the protocol layer.
5 The LLC sub-layer
5.1 The role of the LLC sub-layer
The LLC sub-layer used in this profile is based on ISO/IEC 8802-2. The presence of this sub-
layer in the connection-oriented profile is somewhat artificial: the LLC sub-layer is used as a
kind of protocol selector, and the ‘real’ data link layer connection is ensured by the MAC sub-
layer. It can be considered that the standard LLC sub-layer is used in an extended class I
operation, where the LLC sub-layer provides the standard data-link-connectionless services
via a connection-oriented MAC sub-layer. In order to be able to establish the data link
connection, the LLC sub-layer provides transparent MAC connection/disconnection services
to the service user protocol layer.

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62056-46 © IEC:2002+A1:2006(E) – 11 –
5.2 Service specification for the LLC sub-layer
This subclause specifies the services required of, or by, the LLC sub-layer at the logical
interfaces with the Service User layer and the MAC sub-layer, using connection-oriented
procedures. As the Service User layer ‘sees’ the services of the LLC sub-layer as the services
of the data link layer, in this standard these services are called data link layer services and
the prefix “DL” to designate these services is used.
5.2.1 Setting up the Data Link Connection
Overview
Figure 1 shows the services provided by the primary station (client side) and secondary
station (server side) data link layers to the service user layer for data link connection
establishment.
Primary station / Client side Secondary station / Server side
Service user layer
Data Link Layer
LLC sub-layer
MAC sub-layer
Physical Layer
IEC  248/02

Figure 1 – Data Link (LLC) services for setting up the Data Link Connection
Data link connection establishment can only be requested by the primary station, so the DL-
CONNECT.request and .confirm services are provided only at the client (primary station) side.
On the other hand, the DL-CONNECT.indication and .response services are provided only at
the server (secondary station) side.
The DL-CONNECT.request service primitive – in case of a locally detected error – can be also
locally confirmed.
All these services are in fact, provided by the MAC sub-layer: the LLC sub-layer shall
transparently transmit these services to/from the “real” service provider MAC sub-layer as the
appropriate MA-CONNECT.xxx service primitive.
DL-CONNECT.req
DL-CONNECT.cnf
DL-CONNECT.ind
DL-CONNECT.res

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5.2.1.1 DL-CONNECT.request
Function
This service primitive is provided only at the client side. The Service User layer invokes this
primitive to request set-up of a data link connection.
Service parameters
The semantics of the primitive is as follows:
DL-CONNECT.request
(
1)
Destination_MSAP ,
Source_MSAP,
User_Information
)
The Destination_MSAP and Source_MSAP parameters identify the referenced data link layer
connection. The addressing scheme for the MAC layer is discussed in 6.4.2. The specification
of the contents of the optional User_information parameter is not within the scope of this
standard.
Use
The client side Service User layer entity invokes the DL-CONNECT.request primitive, when it
wants to set up a connection with a peer data link layer.
5.2.1.2 DL-CONNECT.indication
Function
This service primitive is provided only at the server side. The LLC sub-layer uses
...