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
Current Stage
PPUB - Publication issued
Completion Date
25-Sep-2020
Ref Project

Buy Standard

Standard
IEC 62769-115-2:2020 - Field device integration (FDI) - Part 115-2: Profiles - Modbus-RTU
English and French language
25 pages
sale 15% off
Preview
sale 15% off
Preview

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
IEC 62769-115-2:2020-09(en-fr)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2020 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, 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

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC

copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite

ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie

et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des

questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez

les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org

The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,

variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English

committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.

and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary

details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and

once a month by email. French extracted from the Terms and Definitions clause of

IEC publications issued since 2002. Some entries have been

IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and

If you wish to give us your feedback on this publication or CISPR.
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC

La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des

Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC

Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la

plus récente, un corrigendum ou amendement peut avoir été publié.
Recherche de publications IEC - Electropedia - www.electropedia.org

webstore.iec.ch/advsearchform Le premier dictionnaire d'électrotechnologie en ligne au

La recherche avancée permet de trouver des publications IEC monde, avec plus de 22 000 articles terminologiques en

en utilisant différents critères (numéro de référence, texte, anglais et en français, ainsi que les termes équivalents dans

comité d’études,…). Elle donne aussi des informations sur les 16 langues additionnelles. Egalement appelé Vocabulaire

projets et les publications remplacées ou retirées. Electrotechnique International (IEV) en ligne.

IEC Just Published - webstore.iec.ch/justpublished Glossaire IEC - std.iec.ch/glossary

Restez informé sur les nouvelles publications IEC. Just 67 000 entrées terminologiques électrotechniques, en anglais

Published détaille les nouvelles publications parues. et en français, extraites des articles Termes et Définitions des

Disponible en ligne et une fois par mois par email. publications IEC parues depuis 2002. Plus certaines entrées

antérieures extraites des publications des CE 37, 77, 86 et
Service Clients - webstore.iec.ch/csc CISPR de l'IEC.
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
IEC 62769-115-2:2020 © IEC 2020 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIELD DEVICE INTEGRATION (FDI) –
Part 115-2: Profiles – Modbus-RTU
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

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC

Publication(s)"). 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. 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 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 IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

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.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

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.
---------------------- Page: 5 ----------------------
– 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.
---------------------- Page: 6 ----------------------
IEC 62769-115-2:2020 © IEC 2020 – 5 –
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.

---------------------- Page: 7 ----------------------
– 6 – IEC 62769-115-2:2020 © IEC 2020

ISO and IEC maintain terminological databases for use in standardization at the following

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.

---------------------- Page: 8 ----------------------
IEC 62769-115-2:2020 © IEC 2020 – 7 –
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
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
EDD)
Request (in EDD)
Response (in EDD)
---------------------- Page: 9 ----------------------
– 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
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 +
Next
object ID
+ Number
of objects
+ List of
object ID,
Object
length,
Object
value
R = READ, W = WRITE, C = COMMAND

Depending on the SUBFUNCTION, either READ or COMMAND (e.g. for 01 – Restart communication options)

Depending on whether the function EDD has to choose between READ, WRITE, or COMMAND, since this

function allows independent READ and WRITE operations.

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
EDD)
Request (in EDD)
Response (in EDD)
---------------------- Page: 10 ----------------------
IEC 62769-115-2:2020 © IEC 2020 – 9 –

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.
---------------------- Page: 11 ----------------------
– 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
---------------------- Page: 12 ----------------------
IEC 62769-115-2:2020 © IEC 2020 – 11 –
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 device

(Manufacturer and DeviceModel), the device needs to support ModbusRTU Function 43.

Since support for this function is optional, not all ModbusRTU devices support this function. In

that case, the FDI Communication Server or Gateway can only return a scan result having the

address, but no device identification. Hosts need to deal with this and cannot automatically

assign FDI Packages according to DeviceModel and Manufacturer, for example by asking the

user for this information. Therefore, it is strongly recommended for device vendors developing

FDI packages for ModbusRTU devices to implement ModbusRTU Function 43 in their devices

so that the normal FDI package assignment process is working.
---------------------- Page: 13 ----------------------
– 12 – IEC 62769-115-2:2020 © IEC 2020
Bibliography

IEC 61784-2, Industrial communication networks – Profiles – Part 2: Additional fieldbus

profiles for real-time networks based on IS
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.