DLMS COSEM communication protocol

Supported device types and versions
Communication line configuration
Station configuration
Station parameters
Settings of transmission parameters
I/O tag configuration
I/O tag address
Literature
Changes and modifications
Document revisions

Supported device types and versions

This protocol implements a serial communication with the devices by binary HDLC protocol according to the DLMS/COSEM standard.

Two modes of addressing I/O tags are supported:

• "Short Name (SN) referencing" using 16-bit object addresses
• "Logical Name (LN) referencing" using 6-byte OBIS codes

Communication was tested with the following devices:

• EMH LZQJ (SN referencing)
• Landis ZMD400 (SN referencing)
• Iskraemeco Iskra MT880-M (LN referencing)
• ADDAX NP73E.2-18-1 (LN referencing)

The protocol supports time synchronization, the period is configured in the station configuration dialog.

Communication line configuration

• Supported line categories: Serial, SerialOverUDP Device Redundant, TCP/IP-TCP, TCP/IP-TCP Redundant, MOXA IP Serial Library, RFC2217 Client, MODEM.

Station configuration

• Communication protocol "DLMS/COSEM".

The station address (DLMS Server HDLC/MAC Address) consists of two parts: Upper MAC Address and Lower MAC Address. Each of them is in the range from 0 to 16383 (3FFFH).

As per a specification, DLMS UA 1000-2 Ed. 7.0 (Green Book) represents:

• Upper MAC Address is used for Logical Device addressing, i.e. separately addressable entity within the physical device.
• Lower MAC Address is used for Physical Device addressing, i.e. multi-drop address on the line.

Upper MAC Address is required. An implicit value, which is set when the station address is missing, is a reserved address Upper MAC Address = 1 (Management Logical Device).

In ordinary situations, when the physical device is identical with the logical one (one physical device = one logical device), this address does not need to be changed. If the physical device integrates more logical devices, you should monitor content or "0-0:41.0.0" register of "SAP assignment" class (class_id=17, attribute 2 "SAP_assignment_list") in the "DLMS SN Object List" dialog box. This dialog box shows the list of logical devices that are integrated in a physical one.

This is the example of a value representation of the "SAP_assignment_list" attribute of the "SAP assignment" class in the device which contains one logical device with Upper MAC Address 16.
See also the protocol parameter "Client MAC address" and a document "DLMS UA 1000-2 Ed. 7.0", chapter 8.4.2.3 "Reserved special HDLC addresses".

Note: for Iskraemec Iskra MT880, Upper MAC Address = 1, Lower MAC Address = 16 + last two digits of the serial number (if, for example, the serial number is 72211943, then Lower MAC Address = 16 + 43 = 59).

Station parameters

Communication station configuration dialog box - Protocol parameters tab.
They influences some optional protocol parameters. The following station protocol parameters can be set:

Table 1

Parameter	Meaning	Unit / Size	Default value
--- DLMS/HDLC parameters ---
Application Context	The setting of the "Application Context" parameter of the DLMS/COSEM protocol. Short_Name_Referencing_No_Ciphering context is supported for "Short Name (SN) referencing". Logical_Name_Referencing_No_Ciphering context is supported for "Logical Name (LN) referencing". The next two contexts with encryption are not supported.	Logical_Name_Referencing_No_Ciphering Short_Name_Referencing_No_Ciphering Logical_Name_Referencing_With_Ciphering Short_Name_Referencing_With_Ciphering	Short_Name_Referencing_No_Ciphering
Client MAC Address	HDLC MAC address of a client (i.e. D2000 KOM process). The default value is 10H which is the reserved value "Public client". See "DLMS UA 1000-2 Ed. 7.0" document, chapter 8.4.2.3 "Reserved special HDLC addresses". For ADDAX NP73E.2-18-1 a different value than 10H had to be configured (1 or 2).	0 .. 7FH	10H
HDLC Max_info_field_length-receive parameter	The maximum length of one HDLC frame packet on the receiver's side. When communication problems occur (e.g. checksum error etc.), we recommend decreasing the value of this parameter.		250
HDLC Max_info_field_length-transmit parameter	The maximum length of one HDLC frame packet on the transmitter's side. When communication problems occur (e.g. checksum error etc.), we recommend decreasing the value of this parameter.		250
Client Max Receive PDU Size	The maximum length of PDU (data packet). One PDU can be divided into more HDLC frame packets according to settings of protocol parameters HDLC Max_info_field_length-receive and HDLC Max_info_field_length-transmit. Note: a specific electrometer (Landis  ZMD400) only accepted a value of 0, otherwise it returned a rejected-permanent error during connection establishment.	0 .. 65535	1200
No Disconnect	A Disconnect request will not be used after the readout of values from a device is finished. During the next readout, a connection establishment phase is omitted (HDLC mode-setting request and AARQ negotiation request). This allows for greater data throughput and an increase in the frequency of reading values from the device.	YES/NO	NO
Password	Device password. If entered, the "Low Level Security" authentication with the entered password is used within the AARQ Association Request.
No Browsing	Online address selection from the list of objects, directly on the device, through the DLMS Object List dialog box in the configuration of the I/O tag address will be disabled. Disabling of browsing makes sense in a production environment if values are to be read on a several-seconds basis and reading a list of objects, which can take up to several minutes, is not acceptable. Some devices (e.g. ADDAX NP73E.2-18-1) do not support reading of the object list.	YES/NO	NO
Profile Data Optimization	Several electrometers implement optimization of time data when reading from profiles (class_id=7). The optimization means that only the first row of data contains a timestamp, others contain null. The timestamp of each row is equal to the previous row's timestamp plus the value of the capture_period (4) attribute. If the value of this parameter is YES, the value of the capture_period attribute is read prior to reading the profile data. If the value of this parameter is NO, the content of the capture_period attribute is not read, but the KOM process relies on all profile rows to contain timestamps. If this is not the case, the profile data is not read, and the line logs contain error messages "turn on station parameter 'Profile Data Optimization".	YES/NO	YES
Opening Mode	Opening mode of connection with the device. If the device is configured so that it directly uses DLMS/COSEM protocol on the given interface, set this parameter to "Direct HDLC". Mostly (e.g. when reading through IR optical interface by an optical reading head) you must open the connection in IEC protocol in so-called "mode E" and then transfer to HDLC binary protocol (i.e. DLMS/COSEM). "Mode E", according to the specification of IEC protocol, uses the following settings of the transmission parameters: baud rate 300 Baud, 7 data bits, even parity, 1 stop bit. If "Opening Mode" is set to "IEC mode E", the above-mentioned transmission parameters must be set. As for the Serial communication line, the parameters must be set in the line parameters "Mode 1". See the protocol parameter "Software 7E1". The setting of the baud rate to 300 Baud is usually not required when using the line of MODEM category. A so-called DTE speed is used between a PC and a modem. If this speed is higher than 300 Baud, you have to activate the "handshaking" parameter on RTS/CTS in proper line mode. If the parameter value is set to "Direct HDLC", a dynamic change of transmission parameters is not expected. You can use any Serial line mode and set it by the "Line mode" parameter on the station. More information is mentioned in IEC 62056-21, Electricity metering - Data exchange for meter reading, tariff and load control - Part 21: Direct local data exchange, Annex E: "METERING HDLC protocol using protocol mode E for direct local data exchange". See also chapter "Setting of transmission parameters".	Direct HDLC IEC mode E	Direct HDLC
--- IEC Parameters ---
IEC Device Address	It is an address of a station (device) and is used only if the Opening mode is set to "IEC Mode E". This parameter is optional. It identifies the address of the device at the beginning of communication via the IEC protocol. If this parameter is not defined, the address will not be set at the communication via the IEC protocol and the device must always respond. If several devices are connected to one line (e.g. RS485 bus), the IEC address of a device must be set so that the devices could be identified and avoid a collision. A device address is max. 32 characters consisting of figures (0...9), capital letters (A...Z), small letters (a...z), or a blank space ( ). Zeros in front of valid figure are ignored (i.e. address 10203 = 010203 = 000010203). "IEC Device Address" is a serial number of the device. In OBIS addressing, this register has an address "0-0:C.1.0" - Device ID 1, manufacturing number. The picture below shows the front panel of the EMH LZQJ device. There is a serial number, i.e. IEC address (563911). If the device contains a display, this value may be usually displayed as you can see in the picture.		-
Baudrate Changeover (Z)	This parameter is used only if the Opening mode is set to "IEC Mode E". It defines baud rate for the communication through HDLC protocol DLMS/COSEM after the changeover from IEC mode E to the HDLC binary communication. As for the Serial line, this parameter must set the baud rate to "Mode 2" of the line. AUTO option sets the baud rate according to the value offered by a device. If this baud rate can not be identified, you should check the diagnostic communication logs. The following message can be found there: 10:46:05.809 30-05-2011|D|DLMS> Z Detected: '4' = 4800 Bd and set the baud rate according to it. HDLC binary communication through DLMS/COSEM protocol, unlike the opening IEC step, is realized by different parameters which have to be set in "Mode 2" of the Serial line category: 8 data bits, none parity, 1 stop bit. See also the "Software 7E1" parameter and the chapter Settings of transmission parameters.	300 600 1200 2400 4800 9600 19200 AUTO	AUTO
Software 7E1	This parameter is used if "Opening mode" is set to "IEC Mode E". Setting it to YES activates an SW emulation of transmission parameters of 7 data bits and even parity when the transmission parameters of 8 data bits and none parity are set (i.e. emulation of 7E1 when 8N1 is set). It enables the use of the "IEC mode E" option for SerialOverUDP lines that do not support dynamic changes of transmission parameters. See the chapter Settings of transmission parameters.	YES/NO	NO
Wake-up Message Length	This parameter is used if "Opening mode" is set to "IEC Mode E". Nonzero value activates the sending of a so-called "wake-up message" which activates the communication interface of battery-powered devices. The null characters (0x00) are sent according to the quantity that is defined by the parameter value. The baud rate must be 300 Baud (configured in "Mode 1" for Serial lines). More information is available in IEC 62056-21, Electricity metering - Data exchange for meter reading, tariff and load control - Part 21: Direct local data exchange, Annex B: "Wake-up methods for battery-operated tariff devices".	0 .. 120	0
Delay After Wake-up Message	This parameter is used if "Opening mode" is set to "IEC Mode E". If a so-called "wake-up" message is activated, this parameter defines a delay after sending a "wake-up" message, before the beginning of communication. In the case of a Serial line, we recommend setting the "WaitTxEMPTY" parameter in a specific line mode. According to the document IEC 62056-21, you should set this parameter between 1,5 and 1,7 seconds.	ms	0
--- Send/receive parameters ---
Wait First Timeout	The delay after sending the request but before reading the response.	ms	100 ms
Wait Timeout	The delay between readings of the response until its completion.	ms	200 ms
Max. Wait Retry	A retry count of reading response until its completion.	1 .. 100	20
Retry Timeout	The delay between the request retries if a communication error occurs.	ms	500 ms
Retry Count	A retry count of a request if a communication error occurs.	1 .. 20	3
--- Modem parameters ---
Modem Telephone Number	The phone number for modem connection with a device (only for MODEM lines).
Dial Timeout	Maximum waiting time for dial-up modem connection (only for MODEM lines).	1 .. 600 s	60 s
Dial Retry Count	A maximum retry count of dial-up modem connection (only for MODEM lines).	1 .. 20	1
Dial Retry Timeout	Delay before attempting to dial after an unsuccessful connection attempt (only for MODEM lines).	1 .. 600 s	30 s
After Connect Delay	Time delay after the dial-up connection has been established (only for MODEM lines) but before the beginning of communication. It is used to stabilize the modem connection for old types of modems. After this timeout elapses, all the redundant received data (the residues of AT modem communication) will be read and ignored.	0 .. 30 s	5 s
AT Command 1	A special initial string of modem 1 (only for MODEM lines).		AT&FE0V1Q0B0X3L0M0
AT Command 2	A special initial string of modem 2 (only for MODEM lines). Explanation of recommended settings: S37=5   1200bps DTE-DTE speed - limits the speed for modems. Many devices use modems with limited transmission speeds and this setting can speed-up the connection establishment process. Higher transmission speeds must be negotiated individually. &D2   DTR drop to hangup - for matching with the parameter of modem line (line configuration, tab "Modem - parameters", check the "Use DTR for Hangup" option). S0=0   Disable auto-answer. Auto-answer will not be used. S30=2   20 sec inactivity timeout - automatic hangup after idle timeout expired. Necessary for assuring connection termination after the communication with the last device is over.		ATS37=5&D2S0=0S7=60S30=2
--- Debug parameters ---
HDLC Debug	This parameter activates debug information from the HDLC protocol level.	YES/NO	NO
Full Debug	This parameter activates full communication monitoring. It enables displaying of the I/O tag values and other debug information.	YES/NO	NO

Settings of transmission parameters

Example 1 - line category Serial, the communication through IR optical head.

Example 2 - line category Serial, communication through IR optical head.

Example 3 - line category Serial, communication through RS232/RS485 interface.

I/O tag configuration

Possible I/O tag types: Ai, Ci, Di, TxtI, TiA, TiR.

I/O tag address

To understand the object addressing in DLMS/COSEM protocol, you should know a so-called OBIS standard according to the IEC standard 62056-61 Object Identification system (OBIS), chapter "Annex A - Code presentation".

The "Logical Name (LN) referencing" mode directly uses the OBIS address of objects.

The "Short Name (SN) referencing" mode does not use the OBIS address but a 16-bit numerical address.

The individual data entities are presented in so-called COSEM objects (Companion Specification for Energy Metering), which are the instances of COSEM classes (COSEM interface classes, COSEM IC). Individual types of COSEM classes are specified in the document "COSEM Identification System and Interface Classes, Ed. 10.0", i.e. so-called DLMS Blue Book. Each type of COSEM class has its own identification number ("class_id"). Each class has a set of attributes that have sequence numbers. The attribute facilitates the reading of a specific parameter of a data entity.
Each instance has its beginning SN address (base_name), which is also the address of the first attribute of a class. The "logical_name" is the first attribute of all COSEM classes. By reading this attribute, an OBIS address of a data entity that is presented by a specific class can be obtained. The addresses of further attributes are calculated according to this formula in the "Short Name referencing" mode:

short_name = base_name + ((attribute_index - 1) * 0x08)

The attributes can be static or dynamic depending on whether their value is static (i.e. unchanging, set by a producer or in the configuration of the device) or dynamic (changing). In the D2000 System, we recommend configuring only the dynamic attributes, as the value of the measured data entity is in dynamic attributes. If it is necessary for the interpretation of a value in a dynamic attribute (mostly the "value" attribute), other static or dynamic attributes are read automatically. See more information in the section Supported COSEM classes.

In the following tables, you can find the supported COSEM classes. The attributes that represent the value of the data entity (i.e. value that is important for a user) are marked as "Yes, the value of an entity" in the column "Support in D2000". The static attributes are read automatically and characterized as "Automatically read".

Supported COSEM classes

Historical data reading from load profiles

The reading of historical data from load profiles is performed using the instances of COSEM classes "Profile generic" (class_id = 7), i.e. by configuring an I/O tag with an attribute 2 ("buffer"). This I/O tag always contains an invalid value in D2000 System, however, it enables reading a buffer of a specific instance of COSEM class "Profile generic".

Data about objects that are accessible by the reading of attribute "capture_objects" are stored in the buffer. D2000 System automatically searches for I/O tags that match the objects from attribute "capture_objects" (by their address parameters). The objects are searched by parameters "logical_name", "class_id", and "attribute_index".

The TELL command GETOLDVAL or ESL action GETOLDVAL start the reading of all the configured load profiles on the station. The time interval with data is always read from the load profile according to the parameters of the TELL command or ESL action.

Example: I/O tag with address::

• class_id = 7
• attribute_index = 2
• logical_name = 1-0:P.1.0

After a tell command GETOLDVAL B.ELMER_125 "06-07-2020 00:00:00" "06-07-2020 01:00:00", the KOM process queries a list of objects in a profile (by reading attribute 3):

09:44:39.558 06-07-2020|D|DLMS> Composing getRequest for LN ClassID=0007 InstanceID=1-0:P.1.0 AttributeId 3, InvokeID 65

and displays a list of received objects:

09:44:40.710 06-07-2020|D|DLMS> Received capture_objects attribute for I/O tag 'M.ELMERY_T125_1_25_PROFILE' (class_id=7, logical_name=1-0:P.1.0, attribute_index=3) are:
09:44:40.710 06-07-2020|D|DLMS> 1. logical_name=1-0:1.5.0, class_id=4, attribute_index=2
09:44:40.710 06-07-2020|D|DLMS> 2. logical_name=1-0:2.5.0, class_id=4, attribute_index=2
09:44:40.710 06-07-2020|D|DLMS> 3. logical_name=1-0:32.7.0, class_id=3, attribute_index=2
09:44:40.711 06-07-2020|D|DLMS> 4. logical_name=1-0:3.5.0, class_id=4, attribute_index=2

this reading is performed only once and the result is cached. Subsequently, data blocks containing historical values are read:

09:44:42.924 06-07-2020|D|DLMS> Block 1 complete, reading next
09:44:42.925 06-07-2020|D|DLMS> Composing Get-Request-Next for block-number 2
..
09:44:51.203 06-07-2020|D|DLMS> Get-Data-Block-Result: raw-data [0], length 88: 
09:44:51.203 06-07-2020|D|DLMS> Last Block complete, going to parse 1614 bytes

The values are parsed and assigned to the I/O tags. If the  I/O tag with the required address does not exist, a warning is displayed:

09:44:51.205 06-07-2020|D|DLMS> > Old value for I/O tag 'M.ELMERY_T125_1_25_APm_15p', (double_long_unsigned) 992660, Re=99266, Tm=06-07-2020 00:00:00 Local
09:44:51.205 06-07-2020|D|DLMS> > Old value for I/O tag 'M.ELMERY_T125_1_25_APm_15m', (double_long_unsigned) 0, Re=0, Tm=06-07-2020 00:00:00 Local
09:44:51.205 06-07-2020|W|DLMS> Cannot find I/O tag logical_name=1-0:32.7.0, class_id=3, attribute_index=2 to assign profile data!
09:44:51.205 06-07-2020|W|DLMS> Cannot find I/O tag logical_name=1-0:3.5.0, class_id=4, attribute_index=2 to assign profile data!

Note: it is necessary to configure a non-zero delay in the time parameters of the station, otherwise the reading of profiles will never get to the run (periodic reading has a higher priority). If there are several stations on the line, the delay must be higher than the duration of the periodic reading of the values of all the stations.

Supported value types of class attributes

I/O tag address - configuration dialog box

The following picture shows a configuration dialog box of the I/O tag address.

Example for Short Name (SN) referencing:

Example for Logical Name (LN) referencing:

The meaning of the parameters in the dialog box:

DLMS Object List dialog box

If these conditions are fulfilled - the device is connected to D2000 System, a communication station exists and the device communicates, you can define the parameters of the I/O tag address by the selection of the object from the list of all objects on the device. A list of objects is queried from the device:

• in SN referencing mode: from a special class "Association SN" with predefined address base_name 0xFA00
• in LN referencing mode: from a special class "Association LN" with predefined address logical_name 0.0.40.0.0.255

There is no need to configure any other I/O tags, just click on the Browse button.

The first reading of the list takes up to several minutes depending on the baud rate. The window displays the information "Waiting for data...".

After data is read, the list of objects and their descriptions will show in the window:

You can find the following information in the list:

• each row represents one instance of COSEM class,
• the OBIS address of the object follows the icon of class,
• then there is the information about the SN address (base_name) of a particular instance of COSEM class and about its type (class_id and version),
• COSEM classes, which are supported in the D2000 System, can be expanded by clicking on the symbol (+).

When expanding a specific instance of the COSEM class, the supported attributes of the class will be displayed:

The information about attribute includes:

• attribute index (attribute_index) - a sequential number of the attribute, it is displayed next to the icon,
• attribute name (e.g. logical_name, value, scaler_unit, time_zone ...),
• static or dynamic attribute.

There can be an "expand" symbol (+) near the icon. When opening it and clicking on the "Attribute value=" row, the current value of the attribute will be retrieved from the device:

This feature enables fast browsing of the attributes of all supported COSEM classes. The dialog window works as both "Object List" and "Value Browser".

The bottom part of the dialog box contains these check-boxes:

• Show hexadecimal - shows all the addresses of base_name classes as hexadecimal numbers or decimal ones.
• Show inactive objects
• Show unsupported classes - enables to display the instances of unsupported COSEM classes.

To close the dialog box without any changes, click the Cancel button.

To insert the addressing parameters of the attribute of an instance into the address of I/O tag, double-click on the particular row. This closes the "DLMS SN Object List" dialog and the parameters of the I/O tag will be configured based on the selection.

OBIS address specification

The definition of OBIS address according to IEC 62056-61 is following:

• Value group A defines the energy type (0=abstract objects, 1=electricity, 7=gas),
• Value group B defines a channel number,
• Value group C defines a measured physical value,
• Value group D defines a type of processing,
• Value group E defines further processing or classification according to the algorithm,
• Value group F defines the storage of processed historical data.

Value group A up to F represents a positive number in the range 0 up to 255.

For Value group C and D you can enter also the character values:

• character 'C' represents 96,
• character 'F' represents 97,
• character 'L' represents 98,
• character 'P' represents 99.

The address is written in  text format:

A-B:C.D.E*F

Value groups C, D, and E must always contain the value. Other unspecified values will be set to zero (0).

For more information see "List of standard OBIS codes and COSEM objects" on http://www.dlms.com, the document "List of standardized OBIS codes, DLMS UA, V2.3, (c) Copyright 1997-2005 DLMS User Association".

Literature

• DLMS User Association, COSEM Architecture and Protocols, Seventh Edition, (c) Copyright 1997-2009 DLMS User Association (Green book).
• DLMS User Association, COSEM Identification System and Interface Classes, Ed. 10.0, (c) Copyright 1997-2010 DLMS User Association (Blue book).
• International Standard IEC 62056-21, Direct Data Local Exchange, First edition 2002-05.
• International Standard IEC 62056-61, Object Identification System (OBIS), Second edition 2006-11.
• List of standardized OBIS codes, DLMS UA, V2.3, (c) Copyright 1997-2005 DLMS User Association.

Changes and modifications

-

Document revisions

• Ver. 1.0 - May 30, 2011 - document created.
• Ver. 1.1 - January 30, 2019 - support for LN referencing.