EN 62056-31:2000

SLOVENSKI STANDARD
01-junij-2000
Electricity metering - Data exchange for meter reading, fariff and load control - Part
31: Use of local area networks on twisted pair with carrier signalling
Electricity metering - Data exchange for meter reading, tariff and load control -- Part 31:
Use of local area networks on twisted pair with carrier signalling
Messung der elektrischen Energie - Zählerstandsübertragung, Tarif- und Laststeuerung -
- Teil 31: Nutzung örtlicher Bereichsnetze mit Trägerfrequenz-Signalübertragung auf
verdrillten Zweidrahtleitungen
Comptage de l'électricité - Echange de données pour la lecture des compteurs, le
contrôle des tarifs et de la charge -- Partie 31: Utilisation des réseaux locaux sur paire
torsadée avec signal de porteuse
Ta slovenski standard je istoveten z: EN 62056-31:2000
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
35.240.60 Uporabniške rešitve IT v IT applications in transport
transportu in trgovini and trade
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME CEI
INTERNATIONALE IEC
62056-31
INTERNATIONAL
Première édition
STANDARD
First edition
1999-11
Comptage de l'électricité – Echange de données
pour la lecture des compteurs, le contrôle des
tarifs et de la charge
Partie 31:
Utilisation des réseaux locaux sur paire torsadée
avec signal de porteuse
Electricity metering – Data exchange for meter
reading, tariff and load control
Part 31:
Use of local area networks on twisted pair with
carrier signalling
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62056-31 © IEC:1999 – 3 –
CONTENTS
Page
FOREWORD . 7
Clause
1 General. 11
1.1 Scope . 11
1.2 Normative references. 11
2 General description. 11
2.1 Basic vocabulary. 11
2.2 Layers and protocols. 13
2.3 Specification language. 13
2.4 Communication services for local bus data exchange without DLMS. 15
2.4.1 Remote reading exchange . 15
2.4.2 Remote programming exchange. 15
2.4.3 Point to point remote transfer exchange. 19
2.4.4 Broadcast remote transfer frame. 21
2.4.5 Bus initialization frame. 21
2.4.6 Forgotten station call exchange . 21
2.4.7 Frame fields. 23
2.4.8 Principle of the energy remote supply . 25
2.4.9 Non-energized station preselection exchange . 27
2.4.10 Communication exchange after preselection . 29
2.4.11 Alarm function. 29
2.5 Communication services for local bus data exchange with DLMS. 31
2.6 Systems management. 33
3 Local bus data exchange without DLMS. 33
3.1 Physical layer . 33
3.1.1 Physical-62056-31 protocol. 33
3.1.2 Physical parameters. 35
3.1.3 Timing diagrams . 39
3.1.4 Physical services and service primitives. 39
3.1.5 State transitions. 43
3.1.6 List and processing of errors. 61
3.2 Data Link layer. 63
3.2.1 Link-62056-31 protocol . 63
3.2.2 Management of exchanges . 63
3.2.3 Data Link services and service primitives. 63
3.2.4 Data Link parameters. 65
3.2.5 State transitions. 67
3.2.6 List and processing of errors. 81
3.3 Application layer . 81
3.3.1 Application-62056-31 protocol. 81
3.3.2 Application services and service primitives . 81
3.3.3 Application parameters . 83
3.3.4 State transitions. 85
3.3.5 List and processing of errors. 91

62056-31 © IEC:1999 – 5 –
Clause Page
4 Local bus data exchange with DLMS. 91
4.1 Physical layer . 91
4.2 Data Link layer. 91
4.2.1 Link-E/D protocol . 91
4.2.2 Management of exchanges . 93
4.2.3 Data Link services and service primitives. 93
4.2.4 Data Link parameters. 95
4.2.5 State transitions. 97
4.2.6 List and processing of errors. 113
4.3 Application layer . 113
4.3.1 Transport sub-layer. 113
4.3.2 Application sub-layer. 113
5 Local bus data exchange – Hardware . 115
5.1 General. 115
5.2 General characteristics . 115
5.2.1 Signal transmission at 50 kHz . 115
5.2.2 Energy supply signal transmission . 119
5.2.3 Simple Secondary Station and multiple Secondary Station. 123
5.3 Bus specification. 125
5.3.1 General characteristics . 125
5.3.2 Cable characteristics. 127
5.3.3 Wiring . 129
5.4 Magnetic plug . 129
5.4.1 Function. 129
5.4.2 Common mechanical characteristics . 131
5.4.3 Electrical Block diagram with simple plug. 133
5.4.4 Electrical Block Diagram with energy supply plug. 135
5.5 Functional specifications of Primary Station transmitter (for 50 kHz signal). 135
5.6 Functional specifications of Primary Station receiver (for 50 kHz signal) . 137
5.7 Functional specification of Secondary Station transmitter (for 50 kHz signal) . 139
5.8 Functional specifications of Secondary Station receiver (for 50 kHz signal) . 139
Annex A (normative) Specification language. 143
Annex B (normative) Timing types and characteristics. 149
Annex C (normative) List of fatal errors . 153
Annex D (normative) Coding the command code field of frames . 155
Annex E (normative) Principle of the CRC . 159
Annex F (normative) Random integer generation for response from forgotten stations. 161
Annex G (normative) Random number generation for authentication (architecture without
DLMS). 163
Annex H (normative) Systems management implementation. 165
Annex I (informative) Information about exchanges . 167

62056-31 © IEC:1999 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICITY METERING – DATA EXCHANGE FOR METER READING,
TARIFF AND LOAD CONTROL –
Part 31: Use of local area networks on twisted pair
with carrier signalling
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
International Standard IEC 62056-31 has been prepared by IEC technical committee 13:
Equipment for electrical energy measurement and load control.
This first edition of IEC 62056-31 cancels and replaces the first edition of IEC 61142,
published in 1993, and constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
13/1194/FDIS 13/1203/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 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 patent
concerning the stack of protocols on which the present standard IEC 62056-31 is based.
The IEC takes no position concerning the evidence, validity and scope of this patent right.

62056-31 © IEC:1999 – 9 –
The holder of this patent right has assured the IEC that he is willing to negotiate licences
under reasonable and non-discriminatory terms and conditions with applicants throughout the
world. In this respect, the statement of the holder of this patent right is registered with the
IEC. Information may be obtained from:
EURIDIS Association
Bureau P107, 1 Avenue du Général de GAULLE, 92141 Clamart Cedex, FRANCE
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.
This publication has been drafted in accordance with ISO/IEC Directives, Part 3.
The committee has decided that this publication remains valid until 2004.
At this date, in accordance with the committee's decision, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
Annexes A, B, C, D, E, F, G and H form an integral part of this standard.
Annex I is for information only.

62056-31 © IEC:1999 – 11 –
ELECTRICITY METERING – DATA EXCHANGE FOR METER READING,
TARIFF AND LOAD CONTROL –
Part 31: Use of local area networks on twisted pair
with carrier signalling
1 General
1.1 Scope
This part of IEC 62056 describes two new architectures for local bus data exchange with
stations either energized or not. For non-energized stations, the bus supplies energy for data
exchange.
The first architecture completes the base protocol (IEC 61142) with remote transfer services
while the second one allows operation of DLMS services using the same physical medium and
the same physical layer.
This complete compatibility guarantees the possibility of using IEC 61142 and IEC 62056-31
equipment on the same bus.
1.2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of IEC
and ISO maintain registers of currently valid International Standards.
IEC 62056-51:1998, Electricity metering – Data exchange for meter reading, tariff and load
control – Part 51: Application layer protocols
IEC 61334-4-41:1996, Distribution automation using distribution line carrier systems – Part 4:
Data communication protocols – Section 41: Application protocols – Distribution line message
specification
EIA 485: —, Standard for Electrical Characteristics of Generators and Receivers for Use in
Balanced Digital Multipoint Systems
ISO/IEC 8482:1993, Information technology – Telecommunications and information exchange
between systems – Twisted pair multipoint interconnections
2 General description
2.1 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.
62056-31 © IEC:1999 – 13 –
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 architecture with DLMS, the terms Client and Server have
the same meaning as for the DLMS model (refer to IEC 61334-4-41). The Server (which is a
Secondary Station) acts as a VDE (refer to IEC 61334-4-41) for the submission of special
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.
2.2 Layers and protocols
The local bus data exchange architecture uses a breakdown into three network layers:
Physical, Data Link and Application. The protocol corresponding to the Physical layer is the
same for both local bus data exchange architecture, with and without DLMS, allowing all kinds
of stations to be installed on the same bus.
The protocols corresponding to the Data Link and Application layers are defined in the table 1.
Table 1 – Architectures
Layers Protocols
Architecture Application Application-62056-31
Without DLMS Data Link Link-62056-31
Architecture DLMS+
Application Application+
Transport+
With DLMS Data Link Link-E/D
The Transport+ and Application+ protocols of the Transport and Application sub-layers of the
Application layer are described in IEC 62056-51.
The DLMS+ protocol of the DLMS sub-layer of the Application layer is described in
IEC 61334-4-41.
2.3 Specification language
In this standard, the protocol of each layer is described by state transitions represented in the
form of tables. The syntax used in making up these tables is defined by a specification
language described in annex A.
In the event of a difference in interpretation between part of the text and a state transition
table, the table is always taken as the reference.

62056-31 © IEC:1999 – 15 –
2.4 Communication services for local bus data exchange without DLMS
The list of available services is:
a) remote reading of data;
b) remote programming of data;
c) point to point remote transfer, which is a simplified remote programming service;
d) broadcast remote transfer;
e) bus initialization;
f) forgotten station call.
2.4.1 Remote reading exchange
The ENQ exchange consists of two frames arranged in one sequence:
remote reading frame containing the type of data to select in the TAB field
1 6 1 1 1 2
octet octets octet octet octet octets
-------------------> N ADS ADP COM TAB CRC
|
COM=ENQ (ENQuery)
positive acknowledgement frame with the selected data in the DATA field
1 6 1 1 1 0 to 116 2
octet octets octet octet octet octets octets
<------------------- N ADS ADP COM TAB DATA CRC
|
COM=DAT (DATa)
negative acknowledgement frame (TAB identifier unknown)
1 6 1 1 2
octet octets octet octet octets
<------------------- N ADS ADP COM CRC
|
COM=DRJ (Data ReJected)
2.4.2 Remote programming exchange
The REC exchange consists of four frames arranged in two sequences. Since there is an
internal sequence for authentication purpose, from the application point of view, it seems to
be only one sequence with two frames:
remote programming frame containing data in the DATA field and their type in the TAB field
1 6 1 1 8 8 1 0 to 100 2
octet octets octet octet octets octets octet octets octets
-------------------> N ADS ADP COM ZA1 ZA2 TAB DATA CRC
|    NA1    0
COM=REC (RECeive)
62056-31 © IEC:1999 – 17 –
positive acknowledgement frame (no authentication trouble)
1 6 1 1 8 8 2
octet octets octet octet octets octets octets
<------------------- N ADS ADP COM ZA1 ZA2 CRC
|      0     0
COM=EOS (End Of Session)
negative acknowledgement frame (no authentication trouble but remote programming data not
validated)
1 6 1 1 2
octet octets octet octet octets
<------------------- N ADS ADP COM CRC
|
COM=DRJ (Data ReJected)
Authentication is carried out by an exchange of random numbers cyphered using a secret key
specific to each Secondary Station. The random numbers are defined in 8 octets and they are
ciphered with the DES algorithm using an 8-octet ciphering key Ki known both to the Primary
and the Secondary station.
A random number NA1 is first generated by the Primary Station and transmitted into the ZA1
field of the remote programming frame while field ZA2 is set to zero.
On arrival at the Secondary Station, field ZA1 is ciphered by the DES algorithm with key Ki to
get the ciphered random number NA1K. Then occurs the internal sequence for authentication
which consists of two frames.
The first frame (from Secondary to Primary Station) contains this random number NA1K in
field ZA1 and a random number NA2 generated by the Secondary station in field ZA2.
On reception of this frame, the Primary Station compares the ZA1 field to an NA1´ number
obtained by ciphering the transmitted NA1 number using the DES algorithm with key Ki. If
NA1´ = ZA1, then the Primary Station considers the called Secondary Station as
authenticated. Otherwise, it considers the Secondary Station has not been authenticated and
aborts the communication session.
After correct authentication of the Secondary Station, the Primary Station first ciphers the
random number NA2 by the DES algorithm with key Ki to get the ciphered random number
NA2K and then transmits it into field ZA2 while field ZA1 is set to zero.
On reception of this response frame, the Secondary Station compares the ZA2 field to an
NA2´ number obtained by ciphering the transmitted NA2 number using the DES algorithm with
key Ki. If NA2´ = ZA2, then the Secondary Station considers the Primary Station as
authenticated. Otherwise, it considers the Primary Station has not been authenticated and
sends a negative acknowledgment frame.

62056-31 © IEC:1999 – 19 –
The internal authentication exchange is the following:
internal authentication frame containing the ciphered random number NA1K in field ZA1 and
the random number NA2 in field ZA2
1 6 1 1 8 8 1 0 to 100 2
octet octets octet octet octets octets octet octets octets
<------------------- N ADS ADP COM ZA1 ZA2 TAB DATA CRC
|    NA1K  NA2
COM=ECH (ECHo)
positive response frame containing the ciphered random number NA2K in field ZA2 (if the
Secondary Station is considered as authenticated)
1 6 1 1 8 8 2
octet octets octet octet octets octets octets
-------------------> N ADS ADP COM ZA1 ZA2 CRC
|      0    NA2K
COM=AUT (AUThentication)
an authentication rejection frame replaces the normal EOS or DRJ frame when the Primary
Station is not considered authenticated
1 6 1 1 2
octet octets octet octet octets
<------------------- N ADS ADP COM CRC
|
COM=ARJ (Authentication ReJected)
2.4.3 Point to point remote transfer exchange
This TRF exchange consists of two frames arranged in one sequence. From the application
point of view, it seems to be a remote programming exchange in a single sequence with no
authentication:
point to point remote transfer frame containing data in the DATA field and their type in the
TAB field
1 6 1 1 1 0 to 116 2
octet octets octet octet octet octets octets
-------------------> N ADS ADP COM TAB DATA CRC
|
COM=TRF (TRansFer)
positive acknowledgement frame
1 6 1 1 2
octet octets octet octet octets
<------------------- N ADS ADP COM CRC
|
COM=TRA (TRansfer Acknowledgement)
negative acknowledgement frame (remote transfer data not validated)
1 6 1 1 2
octet octets octet octet octets
<------------------- N ADS ADP COM CRC
|
COM=DRJ (Data ReJected)
62056-31 © IEC:1999 – 21 –
2.4.4 Broadcast remote transfer frame
This TRB frame does not involve any frame answer. From the application point of view, it
seems to be a point to point remote transfer, but without acknowledgement since it is a
broadcasting:
broadcast remote transfer frame containing data in the DATA field and their type in the TAB
field
1 6 1 1 1 0 to 116 2
octet octets octet octet octet octets octets
-------------------> N ADS ADP COM TAB DATA CRC
|
COM=TRB (Transfer Broadcast)
The secondary address (which defines the receiving Secondary Stations) shall be a broadcast
address.
2.4.5 Bus initialization frame
This IB frame does not involve any frame answer. From the application point of view, it seems
to be a broadcast remote transfer, but without data since its purpose is only to reset a special
flag (called forgotten station flag) to TRUE for all Secondary Stations that have been
programmed with the ADP address:
bus initialization frame
1 6 1 1 2
octet octets octet octet octets
-------------------> N ADS ADP COM CRC
|
COM=IB (Initialize Bus)
The secondary address (which defines the receiving Secondary Stations) shall be a broadcast
address.
After the bus initialization frame, any Secondary Station receiving a correct ENQ frame
containing a known TAB identifier will then no longer be considered as a “forgotten station”.
2.4.6 Forgotten station call exchange
This ASO exchange consists of two frames arranged in one sequence. At the end of a remote
reading sequence, the Primary Station can search for stations whose forgotten station flag is
TRUE (maximum 5 in 100).
As a correct remote reading exchange sets the forgotten station flag of the corresponding
station to FALSE, the ASO exchange normally occurs after the completion of a remote
reading sequence that is one or several remote reading exchanges preceded by a bus
initialization frame.
The Primary Station manages several time slots. When detecting a collision, it has to retry an
ASO exchange. Nevertheless, each time a correct Secondary Station answer is received, the
Primary Station shall eliminate it from the list of forgotten stations by operating a correct
remote reading exchange with this station.

62056-31 © IEC:1999 – 23 –
In order to assure the selection constraints (described in 2.4.9), the non-energized stations
shall answer in the first time slot of the first ASO exchange. Then, only the forgotten stations
are selected and the usual principle can be used for the following ASO exchanges.
forgotten station call frame containing selection criteria in the TABi field (1 to 40 TAB
identifiers)
1 6 1 1 1 to 40 2
octet octets octet octet octets octets
-------------------> N ADS ADP COM TABi CRC
|
COM=ASO (A forgotten StatiOn call)
The secondary address (which defines the receiving Secondary Stations) should be a
broadcast address.
acknowledgement frame containing the first TAB recognized by the unit and the ADS of the
station
1 6 1 1 1 6 2
octet octets octet octet octet octets octets
<------------------- N ADS ADP COM TAB ADS CRC
|
COM=RSO (Reply from forgotten StatiOn)
2.4.7 Frame fields
N total number of octets in the frame, including N.
ADS absolute physical address of the Secondary Station coded as a 48-bit string.
There is only one broadcast physical address which is the general broadcast ADG
1)
coded as "000000000000"in hexadecimal
The ADS also corresponds exactly to the System Title of the Secondary Station.
ADP physical address of the Primary Station coded as an 8-bit string. The value "00"H
2)
is reserved for the coding of the physical address of the general primary APG .
Any Secondary Station solicited by a Primary Station whose physical address is
APG, replies with the first primary physical address with which it has been
programmed
COM command code depending on the exchange and the frame direction (see annex D)
ZA1, ZA2 fields reserved for authentication operated during the remote programming
exchange
TAB type of data selected associated with some command codes (ENQ, DAT, REC,
TRF, TRB or RSO). The value "00"H is reserved for systems management, the
value "FF"H for alarm management.
DATA information packet from the host application. This field can be eventually empty
depending on the command code.
CRC Cyclic Redundancy Check field corresponds to the 16 redundant bits of the CRC
whose principle is described in annex E.
––––––––––
1)
Other broadcast addresses could be defined depending on the naming rules adopted in companion standards
for the semantics of the System Titles which are often based on a manufacturer code, a manufacture year and
an equipment type.
2)
Other general addresses could be defined depending on the naming rules adopted in companion standards for
the semantics of operator identifiers which are often based on a utility code.

62056-31 © IEC:1999 – 25 –
The frame fields are transmitted in an ascending order (from N to CRC). When a field contains
data over several octets, the transmission begins with the least significant octet and ends with
the most significant one. However, the DATA field is considered as an octet string and
transmitted in an ascending order.
2.4.8 Principle of the energy remote supply
The general principle of the data exchanges is preserved for the non-energized stations. The
notion of energy remote supply is only added for communication between a Primary Station
and one or more Secondary Stations.
To begin a communication session, the Primary Station should send a “Wakeup Call”
designed to alert the communications system of every Secondary Station connected to the
bus. This call is a continuous carrier for a nominal time depending on the energy remote
supply mechanism:
– the “Wakeup Call” signal duration is AGT to wake up non-energized stations;
– the “Wakeup Call” signal duration is AGN to wake up energized stations.
Remark: A Secondary Station can be configured in Alarm mode. It is then remote supplied
continuously and so can transmit the alarm to the Primary Station (see 2.4.11).
Then, whatever type of remote station is selected (energized or not), an intermediate AGN
“Wakeup Call” signal shall also be required at the Primary Station side in the following
circumstances:
– before the first ENQ or TRF exchange;
– before the sixth consecutive and successful ENQ or TRF exchange with the same
Secondary Station;
– before the first ENQ or TRF exchange with a different Secondary Station to the one
previously selected in the preceding ENQ or TRF exchange;
– before any REC exchange;
– before any TRB frame;
– before any IB frame;
– before any ASO exchange.
For non-energized stations, it means that the Primary Station can avoid to wake up all the
remote stations when not necessary, and then save its energy.
A Primary Station can use a specific modem ensuring both the energy remote supply as well
as the modulation and demodulation functions. The communication time and the number of
non-energized stations shall be optimized in order to save the battery of the Primary Station.
As another possibility, the Primary Station might only focus on the modulation and
demodulation functions. In this case, an auxiliary station continuously supplies the bus with
energy.
A Secondary Station generally contains only one logical application referenced by its ADS.
Such a station may or may not be energized.
A multiple Secondary Station (containing several logical applications corresponding to several
ADSs) should be a non-energized station. This feature is described more fully in clause 5.

62056-31 © IEC:1999 – 27 –
2.4.9 Non-energized station preselection exchange
To optimize the bus consumption, a preselection exchange enables the Primary Station to
select a non-energized Secondary Station.
The preselection exchange occurs after an AGT “Wakeup Call” signal addressed to all non-
energized stations of the bus. To limit the bus consumption, the first frame sent by the
Primary Station should be short enough and the addressed Secondary Station should answer
before the triggering of the TOPRE wakeup. Not seeing an answer in time, the modem of the
Seconday Station goes back in a low consumption state.
During the preselection exchange, all the non-energized stations consume energy. The bus
voltage and the energy storage capacitors decrease until the non selected stations goes back
in a low consumption state. Then the continuously sent energy charges the energy storage
capacitors and the bus voltage increase.
The modem of the Primary Station should store sufficient energy before the first preselection.
This step is guaranteed by a wait-time controlled thanks to the TICB wakeup. At the end of a
preselection, the energy storage capacitors are empty and the Primary Station shall wait for
the bus voltage increase before a second preselection.
As the preselection frame shall not be more than 18 bytes long, it can be
– an ENQ frame;
– a TRB or TRF frame, if and only if the data field is less than or equal to 6 octets long;
– an IB frame;
– an ASO frame, if and only if the number of TABi fields is less than or equal to 7.
As the first frame of REC and TRF exchanges may be too long, an additional service is
provided for preselection. This fully transparent PRE exchange consists of two frames
arranged in one sequence.
non-energized station preselection frame
1 6 1 1 2
octet octets octet octet octets
-------------------> N ADS ADP COM CRC
|
COM=PRE (PREselection)
acknowledgement frame
1 6 1 1 2
octet octets octet octet octets
<------------------- N ADS ADP COM CRC
|
COM=SEL (SELected)
To save the energy of the Primary Station, there is no retry during a preselection exchange. If
an addressed non-energized station does not answer correctly, it is not selected and the
Primary Station shall send a new AGT “Wakeup Call” signal.

62056-31 © IEC:1999 – 29 –
2.4.10 Communication exchange after preselection
After preselection, the modem of a non-energized station can stay awake for the continuing
communication and delays are not critical since the number of connected devices is limited.
The Primary Station supplies the selected station and charges the capacitive reservoirs of the
non-selected stations.
The normal end of the communication session occurs differently depending on the energy
remote supply mechanism:
– after a short period of inactivity during the communication session when no intermediate
AGN “Wakeup Call” signal is required for energized stations. This period is checked by the
wakeup TOL;
– after a longer period of inactivity during the communication session for non-energized
stations. This period is checked by the wakeup TOAG.
Note that for a non-energized station, as far as there is no timeout of TOAG wakeup, an
intermediate AGN “Wakeup Call” signal is enough to go on the current communication
session.
2.4.11 Alarm function
A device integreted in a simple or multiple Secondary Station (see 5.2.3) can transmit alarms
to the primary station, providing it can integrate functions of interface as described hereafter.
An alarm shall be fetched from the Secondary Station in 10 s maximum.
A programmable configuration on the Interface and one on each device selects the status of
Alarm mode: Active or Inactive.
When Alarm mode is active, the device can generate an alarm, inside the secondary station.
The Alarm function is effective only if the supply is present and permanent on the bus.
The device sends the alarm during TASB. TASB is long enough to force an “0” state on the
secondary bus and to be detected by the Interface, even if a communication is in progress.
Alarm mechanism is described in the figure 1.
IEC  1416/99
Figure 1 – Alarm mecanism
The alarm is not directly transmitted towards the primary station. The interface receives the
alarm and transmits it by sending a “0” (50 kHz carrier) during TAB on the bus when it is
possible:
a) No communication on the bus
When the interface receives the alarm on the secondary bus, it transmits it on the bus.

62056-31 © IEC:1999 – 31 –
b) On synchronization of AGN or AGT when a communication is in progress. When a
communication is in progress on the bus, the Interface memorises the alarm received. It
transmits it to the bus after one of the following events:
• TOALR after the end of AGN or AGT reception,
 when the normal end of the communication session occurs.
In this way, the interface can filter the alarm to avoid conflict on the bus.
After the alarm generation, the Secondary Station will be considered as a “forgotten station”
with a selection criteria equal to FF.
The primary station configured in Alarm mode listens to the bus when there is no
communication on the bus and after transmission of an AGN or AGT in order to detect an
alarm. When the primary station receives an alarm, it enters in Forgotten Station Call
procedure with a selection criteria in the TABi field equal to FF (see 2.4.6).
Timing diagrams explain Alarm management in 3.1.3.
2.5 Communication services for local bus data exchange with DLMS
DLMS does not offer services to operate the bus initialization and forgotten station call
mechanisms. Nevertheless, the IB frame and the ASO exchange are supported and managed
as they are with the local bus data exchange architecture without DLMS except that the
forgotten station flag is considered as a global variable shared with the Application
Programming Interface.
Remote reading of data and point to point remote transfer are directly foreseen by DLMS. But
the (redundant) remote programming of data is not supported since authentication is reserved
for the Application layer.
As data semantics is managed by DLMS, the frame format is very simple and only unmarked
frames are required. To ensure compatibility with the architecture without DLMS, this frame
format is defined by the following nine fields:
1 6 1 3 1 2 2 0 to 117 2
octets octet bits bit bits bits octets octets
octet
Size ADS ADP DATA+ Priority Send Confirm Text CRC
Size total number of octets in the frame, including Size. If its value is not 11, the Receiver
knows that the frame contains data in the Text field
ADS same rules as for local bus architecture without DLMS
ADP same rules as for local bus architecture without DLMS
DATA+ always coded "111"B
Priority transmission priority level of the current frame. The Application layer sets this priority
according to the requested service
Send number of the last frame sent
Confirm number of the last frame received without error

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Text DSDU (Data link Service Data Unit) from the higher level. A frame does not
necessarily contain text. If data from the Application layer is available when the
frame is sent, then the Text field will contain data, otherwise it will be empty. This
mechanism provides the conditions for balanced bi-directional data transmission. In
order not to confuse DATA+ frame with frames from the architecture without DLMS,
the DATA+, Priority, Send and Confirm fields make up a special command code COM
whose values shall be different from the already reserved COM values (see annex D)
CRC same rules as for local bus architecture without DLMS
The frame fields are transmitted in ascending order (from Size to CRC). When a field is coded
on several octets, the transmission begins with the least significant octet and ends with the
most significant one. However, the Text field is considered as an octet string and transmitted
in ascending order.
2.6 Systems management
The purpose of Systems management is to make an enrolment which includes an
identification of Secondary Stations on a bus. For that aim, it provides the Discover service.
The enrolment consists of a sequence of Discover requests issued by the active initiator
located inside the Primary Station. Each Discover service is provided to inform the remaining
new stations that they will have a chance to respond in the next time slots.
A Discover request conveys a specific response-probability argument as an integer in the
range [0, 100]. It expresses the probability, in per cent, that a new station responds. When it
is set to 100, all the new stations on the bus shall respond.
On reception of a Discover indication, each Secondary Station tests the value of its flag
Discovered. If it is set to TRUE, the indication is discarded else it draws a random number
between 1 and 100. If this number is smaller than or equal to the response-probability
argument, the new station will issue a Discover response and set its flag Discovered to TRUE.
The flag Discovered is always reset by an IB frame.
To ensure a maximum compatibility (for stations including DLMS or not), it is proposed to
implement the systems management as indicated in annex H.
3 Local bus data exchange without DLMS
3.1 Physical layer
3.1.1 Physical-62056-31 protocol
The Physical-62056-31 protocol of the Physical layer of the local bus data exchange
architecture without DLMS behaves asymmetrically. The state machine of the Primary Station
is therefore different from that of the Secondary Station.
The Physical-62056-31 protocol supports the Secondary Stations whether or not they are
energized. As already stated in the general description, the remote stations shall be woken up
either by an AGN or an AGT “Wakeup Call” signal and a communication session ends after
expiry of TOL or TOAG wakeup.
After a “Wakeup Call” signal, a communication session is then made asynchronously and by
half-duplex at 1 200 bits/s on the bus.

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3.1.2 Physical parameters
The value of the maximum size of a frame being received, MaxIndex, is set to 128.
The value of the maximum number of RSO time slots for the processing of a “Forgotten
Stations Call”, MaxRSO, is set to 3.
The AGN duration of an AGN “Wakeup Call” signal shall be in the range [
...