IEC 62769-115-2:2020

Field device integration (FDI) - Part 115-2: Profiles - Modbus-RTU

IEC 62769-115-2:2020 defines the protocol-specific definitions (PSDs) as defined in IEC 62769-7 on generic protocol extensions for the Modbus® -RTU protocol in accordance with CPF 15 in IEC 61784 2.

Intégration des appareils de terrain (FDI) - Partie 115-2: Profils - Modbus-RTU

L'IEC 62769-115-2:2020 spécifie les définitions spécifiques au protocole (PSD – Protocol Specific Definition) telles que définies dans l'IEC 62769-7 relative aux extensions de protocole générique pour le protocole Modbus® -RTU conformément au CPF 15 de l'IEC 61784-2.

General Information

• Status: Published
• Publication Date: 24-Sep-2020
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.05 - Multilayer applications
• Technical Committee: SC 65E - Devices and integration in enterprise systems
• Drafting Committee: WG 7 - TC 65/SC 65E/WG 7
• Current Stage: PPUB - Publication issued
• Start Date: 25-Sep-2020
• Completion Date: 09-Oct-2020

Standards Content (Sample)

IEC 62769-115-2 ®
Edition 1.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Field device integration (FDI) –
Part 115-2: Profiles – Modbus-RTU

Intégration des appareils de terrain (FDI) –
Partie 115-2: Profils – Modbus-RTU

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IEC 62769-115-2 ®
Edition 1.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Field device integration (FDI) –

Part 115-2: Profiles – Modbus-RTU

Intégration des appareils de terrain (FDI) –

Partie 115-2: Profils – Modbus-RTU

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 35.100.05 ISBN 978-2-8322-8859-7

– 2 – IEC 62769-115-2:2020 © IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative References . 5
3 Terms, definitions, abbreviated terms and conventions . 5
3.1 Terms and definitions . 5
3.2 Abbreviated terms . 6
3.3 Conventions . 6
3.3.1 EDDL syntax. 6
3.3.2 Capitalizations . 6
4 PSDs for ModbusRTU . 7
4.1 General . 7
4.2 Header . 7
4.3 ProtocolIdentifier . 9
4.4 Address . 9
4.5 Manufacturer . 9
4.6 DeviceModel . 9
4.7 DeviceRevision . 9
4.8 SerialNumber . 9
4.9 Tag . 9
4.10 ProfileId . 9
4.11 Version . 9
4.12 ProtocolSupportFile . 9
5 Example for ModbusRTU . 10
5.1 General . 10
5.2 Called functionality (success) . 10
5.3 Called functionality (Error) . 10
5.4 EDD command . 11
6 Scanning . 11
Bibliography . 12

Table 1 – Modbus functions and their representation in an EDD HEADER . 7
Table 2 – Example Modbus PDU . 10
Table 3 – Example Modbus PDU with error response . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIELD DEVICE INTEGRATION (FDI) –

Part 115-2: Profiles – Modbus-RTU

FOREWORD
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International Standard IEC 62769-115-2 has been prepared by subcommittee 65E: Devices
and integration in enterprise systems, of IEC technical committee 65: Industrial-process
measurement, control and automation.
FCG_TS62769-115-2_Profiles_PSD ModbusRTU_1.1.0.4, a specification of the FieldComm
Group, PROFIBUS Nutzerorganisation e. V., OPC Foundation and FDT Group, has served as
a basis for the elaboration of this standard.
The text of this International Standard is based on the following documents:
FDIS Report on voting
65E/740/FDIS 65E/744/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.

– 4 – IEC 62769-115-2:2020 © IEC 2020
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62769 series, published under the general title Field Device
Integration (FDI), can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
FIELD DEVICE INTEGRATION (FDI) –

Part 115-2: Profiles – Modbus-RTU

1 Scope
This part of IEC 62769 defines the protocol-specific definitions (PSDs) as defined in
IEC 62769-7 on generic protocol extensions for the Modbus® -RTU protocol in accordance
with CPF 15 in IEC 61784-2.
2 Normative References
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 61784-1, Industrial communication networks – Profiles – Part 1: Fieldbus profiles
IEC 61804 (all parts), Function blocks (FB) for process control and Electronic Device
Description Language (EDDL)
IEC 62541-100, OPC Unified Architecture – Part 100: Device Interface
IEC 62769-2, Field Device Integration (FDI) – Part 2: FDI Client
IEC 62769-4, Field Device Integration (FDI) – Part 4: FDI Packages
IEC 62769-5, Field Device Integration (FDI) – Part 5: FDI Information Model
IEC 62769-7, Field Device Integration (FDI) – Part 7: FDI Communication Devices
MOD06, Modbus.org: MODBUS over serial line specification and implementation guide V1.02
MOD12, Modbus.org: MODBUS APPLICATION PROTOCOL SPECIFICATION, V1.1b3
3 Terms, definitions, abbreviated terms and conventions
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61784-1, the
IEC 61804 series, IEC 62541-100, IEC 62769-4, IEC 62769-5, and IEC 62769-7 apply.
___________
Modbus is the trademark of a product supplied by Schneider Electric USA, INC. This information is given for the
convenience of users of this document and does not constitute an endorsement by IEC of the product named.
Equivalent products may be used if they can be shown to lead to the same results.

– 6 – IEC 62769-115-2:2020 © IEC 2020
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addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Abbreviated terms
For the purposes of this specification, the following abbreviated terms apply.
EDD electronic device description
EDDL Electronic Device Description Language (see IEC 61804)
FDI™ Field Device Integration
FCG FieldComm Group
XML Extensible Markup Language (see REC-xml-2081126)
3.3 Conventions
3.3.1 EDDL syntax
This document specifies content for the EDD component that is part of FDI Communication
Packages. The specification content using EDDL syntax uses the font Courier New. The
EDDL syntax is used for method signature, variable, data structure and component
declarations.
3.3.2 Capitalizations
The IEC 62769 series uses capitalized terms to emphasize that these terms have an FDI-
specific meaning.
Some of these terms use an initialism as a prefix, for example:
• FDI Client, or
• FDI Server.
Some of these terms are compound terms such as:
• Communication Servers, or
• Profile Package.
Parameter names or attributes are concatenated into a single term, where the original terms
start in this term with a capital letter, such as:
• ProtocolSupportFile or
• ProtocolType.
Parameter names or attributes can also be constructed by using an underscore character to
concatenate two or more terms, such as:
• DEVICE_REV or
• DEVICE_MODEL
___________
Field Device Integration (FDI) is the trademark of a product supplied by FieldComm Group. This information is
given for the convenience of users of this document and does not constitute an endorsement by IEC of the
product named. Equivalent products may be used if they can be shown to lead to the same results.

4 PSDs for ModbusRTU
4.1 General
Clause 4 defines the protocol-specific definitions for Modbus-RTU, which is the Modbus over
serial line protocol using the transmission method RTU (remote terminal unit) in accordance
with MOD06.
4.2 Header
The HEADER string used to define EDD commands contains the information about what
Modbus function is called and what is addressed by the function. It shall contain the attribute
FUNCTION and may, depending on the FUNCTION, contain the attribute SUBFUNCTION,
READ_ADDRESS, READ_COUNT, WRITE_ADDRESS and WRITE_COUNT. The syntax is
= "" per attribute; attributes are separated by a space. The value is
provided as a decimal value, not as a hexadecimal value. For example, to read the device
identification (function 43 (0x2B) and sub-function 14 (0x0E)), the HEADER string is
"FUNCTION=\"43\" SUBFUNCTION=\"14\"".
NOTE The character \ is used as an escape character that allows " in the HEADER string.
The values for READ_ADDRESS, READ_COUNT, WRITE_ADDRESS, WRITE_COUNT are
restricted to numeric values between 0 and 65 535. Table 1 specifies the allowed Modbus
FUNCTION values and the usage of the attributes, as well as the used EDD COMMAND
OPERATION.
Table 1 – Modbus functions and their representation in an EDD HEADER
Read coils 01 - Starting Quantity - - R - Coil status
address of coils
Read 02 - Starting Quantity - - R - Input
discrete address of inputs status
inputs
Read holding 03 - Starting Quantity - - R - Reg. value
registers address of
registers
Read input 04  Starting Quantity - - R - Input
registers address of input register
registers
Write single 05 - - - Output - W Output Output
coil address value value
Write single 06 - - - Reg.  W Register Register
register address value value
Read 07 - - - - - R - Output
exception data
status
b)
Diagnostics 08 2 - - - - R, C Data Data
Get comm 11 - - - - - R - Status +
event counter Event
count
Functionality
FUNCTION
SUBFUNCTION
(Byte)
READ_ADDRESS
READ_COUNT
WRITE_ADDRESS
WRITE_COUNT
Operation (in
a)
EDD)
Request (in EDD)
Response (in EDD)
– 8 – IEC 62769-115-2:2020 © IEC 2020
Get comm 12 - - - - - R - Status +
event log Event
count +
Message
count +
Events
Write Starting Quantity Output
15 - - - W -
multiple coils address of outputs values
Write 16 -  - - Starting Quantity W Register -
multiple address of value
registers registers
Report server 17 - - - - - R - Server ID
ID + Run
indicator
status +
Additional
data
Read file 20 - - - - - R Sub- Sub-
record Req … Req …
Write file 21 - - - - - W Sub- Sub-
record Req … Req …
Mask write 22 - - - Ref. - W And_Mask -
register address +
Or_Mask
c)
Read/write 23 - Read Quantity Write Write R, W, C Write Read
multiple starting to read starting starting register register
registers address address quality value value
Read FIFO 24 - FIFO - - - R - FIFO
queue pointer Count +
address FIFO
value
register
Read device 43 14 Read - - - R - Conformit
identification device ID y level +
code + More
Object follows +
d)
Next
ID
object ID
+ Number
of objects
+ List of
object ID,
Object
length,
Object
value
a)
R = READ, W = WRITE, C = COMMAND
b)
Depending on the SUBFUNCTION, either READ or COMMAND (e.g. for 01 – Restart communication options)
c)
Depending on whether the function EDD has to choose between READ, WRITE, or COMMAND, since this
function allows independent READ and WRITE operations.
d)
Those two-byte values need to be combined to get a numeric value. For example, when Read device ID code
0x04 is chosen together with ObjectId 0x00 the value is 0x0400 = 1 024.

Functionality
FUNCTION
SUBFUNCTION
(Byte)
READ_ADDRESS
READ_COUNT
WRITE_ADDRESS
WRITE_COUNT
Operation (in
a)
EDD)
Request (in EDD)
Response (in EDD)
Table 1 also identifies what data shall be provided in the REQUEST of an EDD command. The
CRC information is never included in the REQUEST or RESPONSE and needs to be handled
by the communication infrastructure (FDI Gateway or FDI Communication Server). Also,
length information (e.g. byte count) is excluded from REQUEST or RESPONSE and needs to
be handled by the communication infrastructure.
4.3 ProtocolIdentifier
ProtocolIdentifier for ModbusRTU shall be "urn:fdipsd:ModbusRTU".
4.4 Address
Address shall be a value between 1 and 247. It shall be represented in the string as a decimal
number without leading zeros (e.g. using the regular expression
"(1\d?\d?)|((24[0-7]?)|(2[0-3]\d?)|2\d?)|([1-9]\d?)". Address maps to the slave
node address in accordance with MOD06. SetAddress is not supported.
4.5 Manufacturer
Manufacturer is mapped to VendorName (ObjectId 0x00) received with Function 43 in
Modbus. For FDI Gateways, the EDD data type EUC of length 256 shall be used and therefore
the length of the string is limited to 256. For devices providing a longer string, the end of the
string is truncated.
4.6 DeviceModel
DeviceModel is mapped to ProductCode (ObjectId 0x01) received with Function 43 in Modbus.
For FDI Gateways, the EDD data type EUC of length 256 shall be used and therefore the
length of the string is limited to 256. For devices providing a longer string, the end of the
string is truncated.
4.7 DeviceRevision
Modbus contains a place to manage a device revision in MajorMinorRevision (ObjectId 0x02)
received with Function 43. As this is an ASCII string, there is no mapping defined to
DeviceRevision and DeviceRevision shall not be used.
4.8 SerialNumber
No mapping is defined for SerialNumber and SerialNumber shall not be used.
4.9 Tag
No mapping is defined for Tag and Tag shall not be used.
4.10 ProfileId
No mapping is defined for ProfileId and ProfileId shall not be used.
4.11 Version
The ModbusRTU Protocol Version 1.02 shall be mapped to Version "1.02.00".
4.12 ProtocolSupportFile
There shall be no use of ProtocolSupportFiles.

– 10 – IEC 62769-115-2:2020 © IEC 2020
5 Example for ModbusRTU
5.1 General
In order to illustrate how the PSDs can be used to create EDDs for ModbusRTU, Subclauses
5.2 to 5.4 give the definition of an EDD command and the corresponding resulting Modbus
Serial Line PDU is provided, as well as a successful return and an error returned, and how
this affects the EDD.
5.2 Called functionality (success)
To illustrate the usage of EDD commands, the case should be considered of an EDD
developer who wants to read some data from the Modbus device in the input registers.
Via a scan, the FDI application has already identified the device address as 1. So the actual
PDU that should be generated is 0x 01 04 00 08 00 01 C2 95 (reading Input Register 9) and
the response would be 0x 01 04 02 00 0A D3 20 (value 10) (see also Table 2).
Table 2 – Example Modbus PDU
Request Response
Field Hex Field Hex
Device Address 01 Device Address 01
Function 04 Function 04
Starting Address Hi 00 Byte Count 02
Starting Address Lo 08 Input Req. 9 Hi 00
Quantity of Input Req. Hi 00 Input Register 9 Lo 0A
Quantity of Input Req. Lo 01 CRC Hi D3
CRC Hi C2 CRC Lo 20
CRC Lo 95
5.3 Called functionality (Error)
To illustrate a failed communication, an error case is also shown in Table 3. So the same
request as described in 5.2 could also lead to an error response 0x 01 84 04 73 63 indicating
a "SERVER DEVICE FAILURE" in accordance with MOD12.
Table 3 – Example Modbus PDU with error response
Request Response
Field Hex Field Hex
Device Address 01 Device Address 01
Function 04 Error Code 84
Starting Address Hi 00 Exception Code 04
Starting Address Lo 08 CRC Hi 73
Quantity of Input Req. Hi 00 CRC Lo 63
Quantity of Input Req. Lo 01
CRC Hi C2
CRC Lo 95
5.4 EDD command
In the following, an EDD command to generate such a Modbus communication is defined.
COMMAND ReadRegister9
{
OPERATION READ;
HEADER "FUNCTION=\"4\" READ_ADDRESS=\"8\" READ_COUNT=\"1\"";
//Function 04 – Read Input Registers

TRANSACTION
{
REQUEST
{
}
REPLY
{
VariableA // Variable of type Int(2), receiving value of Register 09
}
}
RESPONSE_CODES
{
0, SUCCESS, "No Errors";
1, MISC_ERROR, "ILLEGAL FUNCTION";
2, DATA_ENTRY_ERROR, "ILLEGAL DATA ADDRESS";
3, DATA_ENTRY_ERROR, "ILLEGAL DATA VALUE";
4, MISC_ERROR, "SERVER DEVICE ERROR";
}
}
The address is managed by the EDD application outside the EDD and needs to be put into the
PDU by the communication infrastructure (FDI Communication Server or FDI Gateway).
The Modbus function information as well as the starting address and the quantity of registers
is put into the HEADER attribute.
The CRC information is not defined in the EDD command and needs to be added by the
communication infrastructure (FDI Gateway or FDI Communication Server) managing the
ModbusRTU communication.
A successful response is put into the VariableA, as defined in the REPLY, and the response
code 0 is used. The CRC information is not provided but checked by the communication
infrastructure and handled as a communication error.
In the case of an error, the exception code is put into the RESPONSE_CODES. Identical to a
successful response, the CRC information is not provided but handled as in the success case.
Remark concerning the byte order: in ModbusRTU, the byte order is in general Big-Endian in
accordance with MOD12, so no transformation needs to be done by the communication
infrastructure.
6 Scanning
In order to scan for ModbusRTU devices and receive information about the type of devi
...