Heinzmann GmbH & Co.

KG
Engine & Turbine Management

Am Haselbach 1
D-79677 Schönau/Germany

Phone: +49 7673 8208-0

Fax: +49 7673 8208-188
Email: info@heinzmann.de
www.heinzmann.com

V.A.T. No.: DE145551926

HEINZMANN®
Engine & Turbine Controls

MODBUS

Operating Instructions

Copyright 2014 by Heinzmann GmbH & Co. KG. All rights reserved.
This publication may not be reproduced by any means whatsoever or passed on to any third parties.

6878 Manual DG 05 002-e / 08-14

The appropriate manuals must be thoroughly studied before
installation, initial start-up and maintenance.
All instructions pertaining to the system and safety must be followed in
full. Non-observance of the instructions may lead to injury to persons
and/or material damage.
HEINZMANN shall not be held liable for any damage caused through
non-observance of instructions.
Independent tests and inspections are of particular importance for all
applications in which a malfunction could result in injury to persons or
material damage.
All examples and data, as well as all other information in this manual
are there solely for the purpose of instruction and they may not be used
for special application without the operator running independent tests
and inspections beforehand.
HEINZMANN does not guarantee, neither expressly nor tacitly, that
the examples, data or other information in this manual is free from
error, complies with industrial standards or fulfils the requirements of
any special application.

To avoid any injury to persons and damage to systems, the

following monitoring and protective systems must be provided:
Overspeed protection independent of the rpm controller
HEINZMANN shall not be held liable for any damage caused through
missing or insufficiently rated overspeed protection.
thermal overload protection
The following must also be provided for alternator systems:
Overcurrent protection
Protection against faulty synchronisation for excessively-large
frequency, voltage or phase difference
Directional contactor
The reasons for overspeeding may be:
Failure of positioning device, control unit or its auxiliary devices
Linkage sluggishness and jamming

The following must be observed before an installation:

Always disconnect the electrical mains supply before any
interventions to the system.
Only use cable screening and mains supply connections that
correspond with the European Union EMC Directive
Check the function of all installed protection and monitoring
systems
Please observe the following for electronically controlled injection
(MVC):
For common rail systems each injector line must be equipped with
a separate mechanical flow-rate limiter
For unit pump (PLD) and pump-injector unit (PDE) systems, the
fuel enable is first made possible by the solenoid valve’s control
plunger motion. This means that in the event of the control plunger
sticking, the fuel supply to the injection valve is stopped.

As soon as the positioning device receives power, it can actuate the

controller output shaft automatically at any given time. The range of the
controller shaft or control linkage must therefore be secured against
unauthorised access.

HEINZMANN expressly rejects any implied guarantee pertaining to

any marketability or suitability for a special purpose, including in the
event that HEINZMANN was notified of such a special purpose or the
manual contains a reference to such a special purpose.

HEINZMANN shall not be held liable for any indirect and direct
damage nor for any incidental and consequential damage that results
from application of any of the examples, data or miscellaneous
information as given in this manual.

HEINZMANN shall not provide any guarantee for the design and
planning of the overall technical system. This is a matter of the operator
its planners and its specialist engineers. They are also responsible for
checking whether the performances of our devices match the intended
purpose. The operator is also responsible for a correct initial start-up of
the overall system.
 Version Information

Version Information

Version Description of Changes Date Edited by

02-05 created 2004-11-30 DeM
Supplemented by chapter 3 Installation 2005-02-03 ShD

11-07 Chapter 3.3 RS485-two-wire-system corrected 2007-11-19 ShD

Front page and page header updated 2007-11-20 DeM
Chapter Order Specifications for Manuals, appendixes FAX
2007-11-20 DeM
Replay and Subsidiaries deleted
Minor changes 2007-11-20 DeM
Chapter 4.2 Supported function codes and 0
08-14 2014-07-08 EnJ
Supported exception codes updated
Parameter for Modbus Extended in Chapter 5.1 Configuration of
2014-07-08 EnJ
interface added
Chapter 5.3 Write data and subchapter revised 2014-07-08 EnJ
Chapter Overview Table deleted 2014-08-08 DeM
Front page and warning notices updated 2014-08-08 DeM
Minor changes 2014-08-08 DeM

Operating Instructions Modbus

 Table of Contents

Table of Contents
Page

1 Safety instructions and related symbols .............................................................................. 9

1.1 Basic safety measures for normal operation .................................................................. 10
1.2 Basic safety measures for servicing and maintenance................................................... 10
1.3 Before putting an installation into service after naintenance and repair works ............ 10

2 Introduction ......................................................................................................................... 11
2.1 Message format of data transmission ............................................................................ 11
2.2 Example of a data transmission ..................................................................................... 12

3 Installation ........................................................................................................................... 14
3.1 Bus topology .................................................................................................................. 14
3.2 Bus configuration .......................................................................................................... 15
3.3 RS485-two-wire-system ................................................................................................ 16
3.3.1 Bus cable in RS485-two-wire-systems .................................................................. 18
3.3.2 Derivation cable in RS485-two-wire-systems ....................................................... 18
3.4 RS485-Four-wire-system .............................................................................................. 19
3.4.1 Bus cable in RS485-four-wire-systems ................................................................. 20
3.4.2 Derivation cable in RS485-four-wire-system ........................................................ 21
3.5 RS232 Operation ........................................................................................................... 21
3.6 Slave participant ............................................................................................................ 22
3.7 Master participant .......................................................................................................... 22
3.8 Reference potential ........................................................................................................ 22
3.9 Shield ............................................................................................................................. 23
3.10 Line termination .......................................................................................................... 25
3.11 Line polarization .......................................................................................................... 26
3.12 Bus accessories ............................................................................................................ 27
3.13 Device side connection module ................................................................................... 27
3.14 Connector plug and socket .......................................................................................... 27

4 Module functions ................................................................................................................. 28

4.1 Device address ............................................................................................................... 28
4.2 Supported function codes .............................................................................................. 28
4.3 Supported exception codes ............................................................................................ 30

5 Parameterization and commissioning ............................................................................... 31

5.1 Configuration of interface ............................................................................................. 31
5.2 Reading data .................................................................................................................. 33
5.3 Write data ...................................................................................................................... 35
5.3.1 Basic version .......................................................................................................... 36
5.3.2 Extended version.................................................................................................... 36

Operating Instructions Modbus

Table of Contents

5.3.3 Timeout monitoring ............................................................................................... 37

5.3.4 Assignment of sensor values to sensors ................................................................. 38
5.3.5 Assignment of binary values to switching functions ............................................. 39
5.3.6 Assignment of Modbus functions (extended version only) ................................... 40
5.4 Diagnostic counter ......................................................................................................... 41

6 Technical data ...................................................................................................................... 42

7 Parameter description......................................................................................................... 43
7.1 List 1: Parameters .......................................................................................................... 43
7.2 List 2: Measurements .................................................................................................... 43
7.3 List 3: Functions ............................................................................................................ 45
7.4 List 4: Curves and maps ................................................................................................ 45

8 Index of Figures ................................................................................................................... 46

9 Index of Tables .................................................................................................................... 47

10 Index ................................................................................................................................... 48

Operating Instructions Modbus

 1 Safety instructions and related symbols

1 Safety instructions and related symbols

This publication offers wherever necessary practical safety instructions to indicate inevitable
residual risks when operating the engine. These residual risks imply dangers to
- Personnel

- Product and machine

- The environment

The primary aim of the safety instructions is to prevent personal injury!

The signal words used in this publication are specifically designed to direct your attention to
possible damage extent!

DANGER indicates a hazardous situation the consequence of which could

be fatal or severe injuries if it is not prevented.

WARNING indicates a hazardous situation which could lead to fatal injury

or severe injuries if it is not prevented.

CAUTION indicates a hazardous situation which could lead to minor

injuries if it is not prevented.

NOTICE indicates possible material damage.

Safety instructions are not only denoted by a signal word but also by hazard
warning triangles. Hazard warning triangles can contain different symbols
to illustrate the danger. However, the symbol used is no substitute for the
actual text of the safety instructions. The text must therefore always be read
in full!

This symbol does not refer to any safety instructions but offers important
notes for better understanding the functions that are being discussed. They
should by all means be observed and practiced.

Operating Instructions Modbus 9

1 Safety instructions and related symbols

1.1 Basic safety measures for normal operation

The installation may be operated only by authorized persons who have been duly
trained and who are fully acquainted with the operating instructions so that they are
capable of working in accordance with them.
Before turning the installation on please verify and make sure that
- only authorized persons are present within the working range of the engine;
- nobody will be in danger of suffering injuries by starting the engine.
Before starting the engine always check the installation for visible damages and make
sure it is not put into operation unless it is in perfect condition. On detecting any faults
please inform your superior immediately!
Before starting the engine remove any unnecessary material and/or objects from the
working range of the installation/engine.
Before starting the engine check and make sure that all safety devices are working
properly!

1.2 Basic safety measures for servicing and maintenance

Before performing any maintenance or repair work make sure the working area of the
engine has been closed to unauthorized persons. Put on a sign warning that maintenance
or repair work is being done.
Before performing any maintenance or repair work switch off the master switch of the
power supply and secure it by a padlock! The key must be kept by the person
performing the maintenance and repair works.
Before performing any maintenance and repair work make sure that all parts of engine
to be touched have cooled down to ambient temperature and are dead!
Refasten loose connections!
Replace at once any damaged lines and/or cables!
Keep the cabinet always closed. Access should be permitted only to authorized persons
having a key or tools.
Never use a water hose to clean cabinets or other casings of electric equipment!

1.3 Before putting an installation into service after naintenance and

repair works
Check on all slackened screw connections to have been tightened again!
Make sure the control linkage has been reattached and all cables have been reconnected.
Make sure all safety devices of the installation are in perfect order and are working
properly!

10 Operating Instructions Modbus

 2 Introduction

2 Introduction
Modbus is a serial Master-Slave-protocol. This protocol is open and therefore freely
accessible for any user. It provides two transmission modes RTU and ASCII and can be used
on RS232 and RS485 or RS422.
For application of the Modbus protocol, the HEINZMANN control units of the THESEUS
and HELENOS series must be equipped with an add-on pc board. The HEINZMANN
Connection Module uses exclusively RTU mode. Throughout this document, it will therefore
be only this mode that is made reference to. As a connection an RS485 or RS422 interface is
provided. Hence an additional level converter will be required for connection to an RS232
interface.
Any details concerning the design and operation of the interface relate to the below
specifications which can be downloaded from www.modbus.org.
Hardware reference: Modbus over Serial Line Specification and Implementation Guide
V1.02 – Dec 20, 2006
Protocol reference: Modbus Application Protocol Specification V1.1b3 – April 26, 2012
The following sections give a general overview of the functionality, concept and structure of
the Modbus protocol. Experienced Modbus users may skip them and continue with chapter
3 Installation.

2.1 Message format of data transmission

Modbus data transmission always consists of a request/reply cycle. Request and reply are
always executed sequentially, never simultaneously. To separate the individual messages
from each other transmission pauses are required as delimiters.
The following Figure 1 shows a typical request-reply-cycle.

Request
master

Reply
slave

Figure 1: Request-reply-cycle

The Modbus protocol defines a simple Protocol Data Unit (PDU) independent of the type
of network used and includes a function code indicating by which of the diverse actions the
data is to be processed.
Operating Instructions Modbus 11
2 Introduction

As additional information, the Application Data Unit (ADU) includes the participant
address (ID) allowing Master and Multi-Slave operation, and a so-called Error Check
defined as the check-sum over the characters to be transmitted. The address and the error
check are added before and behind the character string as shown in Figure 2 and are
transmitted together with it.

Figure 2: Protocol frame

In RTU Mode the error check is created by a well-defined procedure (Cyclical

Redundancy Check, in short CRC). The error check comprises two bytes.
Besides the error check that is to be evaluated for the totality of a message's characters, it is
also possible to set and perform a parity check for each individual byte of a message.
If checking any message for parity or CRC results in an error, processing the message is
aborted and no response is returned.
In contrast to errors that are detected by examining the error checks (parity, CRC) and that
are not responded to, there may occur errors caused by the user when the specifications for
the data to be transmitted exceed the internal address and data ranges of the device or when
a function code is not supported. In this case, the request is answered by an exception
message indicating the cause by means of an exception code.
To obtain an assessment of the quality of the data exchange, a number of diagnostic
counter have been implemented that are assigned to the various causes. These 16-bit
counters are incremented on the occurrence of the respective event and can be read out
both via Modbus and directly by a HEINZMANN diagnostics tool.

2.2 Example of a data transmission

The function code 0x03 “Read Holding Registers” is used to explain the sequence of
Master request and Slave reply / Slave exception reply by the following tables (Table 1,
Table 2 and Table 3). These tables show the formal structure of the transmitted character
strings. The last column contains a numeric example in hexadecimal notation.

12 Operating Instructions Modbus

 2 Introduction

ID 0 to 247 (decimal) Slave address 01

Function 1 to 255 (decimal) Function to be performed 03
Data Starting Address High Starting address of data register (high byte) 00
Starting Address Low Starting address of data register (low byte) 00
No. of Registers High Number of data (high byte) 00
No. of Registers Low Number of data (low byte) 01
CRC CRC Low Error check CRC (low byte) 84
CRC High Error check CRC (high byte) 0A

Table 1: Master request

ID 0 to 247 (decimal) Slave address 01

Function 1 to 255 (decimal) Function to be performed 03
ByteCount 2 to 255 (decimal) Number of data bytes 02
Data Register Value High Data value (high byte) 00
Register Value Low Data value (low byte) 00
CRC CRC Low Error check CRC (low byte) B8
CRC High Error check CRC (high byte) 44

Table 2: Slave reply

ID 0 to 247 (decimal) Slave-Adresse 01

Function 1 to 255 (decimal) Function to be performed + 0x80 83
Data Data Byte Exception code 02
CRC CRC Low Error check CRC (low byte) C0
CRC High Error check CRC (high byte) F1

Table 3: Slave exception reply

Operating Instructions Modbus 13

3 Installation

3 Installation
The installation of a Modbus data bus system requires particular care, especially with regard
to electromagnetic compatibility as well as to the data transmission rate to be obtained in
dependence on type and length of the conductor. In order to avoid errors in the pre-
commissioning phase, the most important points concerning the installation will be discussed
in advance. More details will be dealt with in later chapters or are to be found in the Modbus
Specification, see section 2 Introduction.

Connecting a HEINZMANN control unit to a serial data bus system according to

EIA/TIA-485/422 Standard for using the Modbus protocol requires that the
Note control unit be equipped with the Modbus connection module.

3.1 Bus topology

The bus topology of the Modbus consists of a straight data link cable as shown in Figure 3.
Basically, both point-to-point connections and multipoint connections are allowed.

Figure 3: Bus topology

A remote data cable (trunk) is running across some longer distance from a Modbus Master
to one or more Modbus Slaves. Preferably, the individual Slaves are to be connected to the
trunk directly by a linear structure (from node to node, Daisy-Chain structure) or by a short
derivation cable.
The elements of the bus are:
ITr – Trunk Interface – a bus cable. For different distances, cables with suitable properties
must be used, such as characteristic impedance, shield and line construction. The cable
lines form a bus of linear structure which is characterized by having two ends. Maximum

14 Operating Instructions Modbus

 3 Installation

length is 1,200 m. For more details see the sections 3.3.1 Bus cable in RS485-two-wire-
systems and 3.4.1 Bus cable in RS485-four-wire-systems.
IDv – Derivation Interface – a derivation cable. By the derivation cable all bus signals, the
reference potential and the shield must be conducted from the bus to the participant (Slave
or Master). A derivation cable may connect several participants, e.g., the devices in a
switch cabinet. Derivation cables must not be longer than 20 m. If there is a local tap with
more than one derivation cables connected, the cable length must be limited to 40 m
divided by the number of derivation cables. For more details see sections
3.3.2 Derivation cable in RS485-two-wire-systems and 3.4.2 Derivation cable in
RS485-four-wire-system.
Passive TAP – a passive tap. The tap connects the bus cable with the derivation cables,
i.e., the data lines, the line for the reference potential and the shield. Possibilities of
earthing and termination can be provided within the tap.
Active Tap – a tap having an integrated bus driver. The rest is very much the same as with
the passive tap.
AUI – Attachment Unit Interface – a data cable connecting active taps with the
participants.
Slave – a participant serving as a Slave device. The maximum number of participants of
the bus without repeater is 31. For more details see section 3.6 Slave participant.
Master - a participant serving as a Master device. Only one Master may be connected to
the bus. For more details see section 3.7 Master participant.
LT – Line Terminator – Bus terminator. At either extremity of the bus a line termination
must be provided. For more details see section 3.10 Line termination.

3.2 Bus configuration

The Modbus standard provides three communication configurations:
according to RS485 in a two-wire-system,
according to RS485 (or RS422) in a four-wire-system and
according to RS232 (requiring accessory devices for HEINZMANN units).
The first two configurations provide differential data transmission via a balanced twisted
pair (or pairs) of conductors. Communication is supported by a reference potential
(Common). Due to EMI, the standard Modbus requires using shielded cables. In these
operating modes both multiple connections and a point-to-point connection will be
allowed.
With RS232 operation, an unbalanced data transmission is basically given using a separate
signal line for either direction, i.e. for transmission from Master to Slave and from Slave to

Operating Instructions Modbus 15

3 Installation

Master. This will also require an additional line with the reference potential (Common).
RS232 operation is provided only for a point-to-point connection.
As communication equipment the following items will be of importance:
Slave participant,
Master participant ,
Bus cable,
Derivation cable,
Reference potential,
Shield,
Bus earthing,
Line termination, and
Line polarization.

3.3 RS485-two-wire-system
In a two-wire-system, bi-directional data are being transmitted, viz. Master-Slave and
Slave-Master, by a common balanced twisted pair of conductors. There is, in addition, a
separate conductor (e.g. a twisted pair of conductors) for the reference potential
(Common). The complete cable must have an external shield.
The 2-wire-system constitutes the configuration most frequently used in practice. The
layout of the bus must be about the same as shown in Figure 4. In a daisy-chain structure,
no derivation cables may be used.

16 Operating Instructions Modbus

 3 Installation

Master device
+5V
DC D

Pull Down
DC

Pull Up
R
PE

Passive Tap Passive Tap

150 Ohm

D1

150 Ohm
D0
Common

Shield

PE

DC R DC R DC R
DC D PE DC D PE DC D PE

Slave device l Slave device m Slave device n

Figure 4: RS485 – two-wire-system

The following Table 4 defines the signals as in Figure 4.

Contact EIA/TIA-
Designati at 485
for Device Description
on Participa Designati
nt on
D1 I/O yes B/B’ Transmitter-receiver-terminal 1 (+),
voltage V1
(V1 > V0 for binary 1 and OFF-state
respectively)
D0 I/O yes A/A’ Transmitter-receiver-terminal 0 (–),
voltage V0
(V0 > V1 for binary 0 and ON-state
respectively)
Common - yes C/C’ Reference potential
and optionally as supply potential
Shield - yes - Cable shield

Table 4 Signal definition – two-wire-system

Operating Instructions Modbus 17

3 Installation

The connectors A and A’ pin no. 8 and 9 respectively and B and B’ pin no. 4 and 5
respectively have to be shorted to use the two-wire-system with the Modbus connection
module for HEINZMANN devices.

3.3.1 Bus cable in RS485-two-wire-systems

There exist two variants:
a cable with one balanced twisted pair of conductors, a separate conductor, and with
external shield,
a cable with two balanced twisted pairs of conductors and with external shield.
The conductor size must generally be chosen for lengths of at least 1,000 m. Thus, for
all conductors, including the shield, a gauge of at least AWG 24 must be provided. The
characteristic impedance must be no less than 100 Ohms in the frequency range up to
100 kHz (for a baud rate of 19,200).
Basically, also cables with several twisted pairs of conductors can be used such as STP
category 5 cables (4 pairs).

3.3.2 Derivation cable in RS485-two-wire-systems

The derivation cable must consist of:
at least one balanced twisted pair of conductors for the differential data signal,
a separate conductor or twisted pair of conductors for the reference potential
(Common), and
an external shield.
For derivations, for instance, the same cable can be used as for the bus.
Generally, also cables with several twisted pairs of conductors can be used.
Every derivation cable connects one or more participants to the bus (by passive taps).
Therefore, the derivation cable includes
the connection to the passive tap (connector, screw terminals, etc.), and
the connection or connections to the participants (connectors, screws, terminals e.a.)
For every participant connection, attention should be paid to the device specific pin and
bridge assignments (e.g., 4-wire to 2-wire, see Figure 4). The connectors A and A’ pin
no. 8 and 9 respectively and B and B’ pin no. 4 and 5 respectively have to be shorted to
use the two-wire-system with the Modbus connection module for HEINZMANN
devices.

18 Operating Instructions Modbus

 3 Installation

3.4 RS485-Four-wire-system
With 4-wire-systems, data transmission in both directions, viz. Master-Slave and Slave-
Master, is made by two separate balanced twisted pairs of conductors. There is, in addition,
a separate conductor (e.g., a twisted pair of conductors) for the reference potential
(Common). The complete cable must have an external shield.
An example of the bus configuration is shown in Figure 5. In the daisy-chain structure no
derivation cable may be used.

Master device
+5V +5V

Pull Down

Pull Down
D DC
Pull Up

Pull Up
R DC PE

Passive Tap Passive Tap

TXD 1
150 Ohm TXD 0 150 Ohm
RXD 1
150 Ohm RXD 0 150 Ohm
Common

Shield

PE

DC R DC R DC R
DC D PE DC D PE DC D PE

Slave device l Slave device m Slave device n

Figure 5: Signal definition – four-wire-system

The following Table 5 defines the signals of Figure 5.

Contact EIA/TIA-485
for Device
Desig- at Designation
Description
nation Partici-
Master Slave pant Master Slave

TXD 1 In Out yes B’ B Transmitter terminal 1 (+),

voltage Vb
(Vb > Va for binary 1 and
OFF-state respectively)

Operating Instructions Modbus 19

3 Installation

Contact EIA/TIA-485
for Device
Desig- at Designation
Description
nation Partici-
Master Slave pant Master Slave

TXD 0 In Out yes A’ A Transmitter terminal 0 (–),

voltage Va
(Va > Vb for binary 0 and
ON- state respectively)
RXD 1 Out In yes B B’ Receiver terminal 1 (+),
voltage Vb’
(Vb’ > Va’ for binary 1 and
OFF-state respectively)
RXD 0 Out In yes A A’ Receiver terminal 0 (–),
voltage Va’
(Va’ > Vb’ for binary 0 and
ON- state respectively)
Common - - yes C/C’ C/C’ Reference potential,
optionally serving as supply
potential
Shield - - yes - - Cable shield

Table 5: Signal definition – four-wire-system

3.4.1 Bus cable in RS485-four-wire-systems

There exist two variants:
a cable with two balanced twisted pairs of conductors, a separate conductor and
external shield,
a cable with three balanced twisted pairs of conductors and with external shield.
The conductor size must generally be chosen for lengths of at least 1,000 m. Thus, for
all conductors including the shield a gauge of at least AWG 24 must be provided. The
characteristic impedance must be no less than 100 Ohms in the frequency range up to
100 kHz (with a baud rate of 19,200).
Basically, also cables with several twisted pairs of conductors may be used such as STP
category 5 cables (4 pairs).

20 Operating Instructions Modbus

 3 Installation

3.4.2 Derivation cable in RS485-four-wire-system

The derivation cable must have:
at least two balanced twisted pairs of conductors for the differential data signal,
a separate conductor or twisted pair of conductors for the reference potential
(common), and
an external shield.
For the derivation, for instance, the same cable can be used as for the bus.
Generally, also cables with several twisted pairs of conductors can be used.
Every derivation cable connects one or more participants to the bus (by passive taps).
Therefore, the derivation cable includes
the connection to the passive tap (connector, screw terminals, etc.), and
the connection and connections to the participants (connectors, screw
terminals, etc.) respectively.
For every participant connection, particular attention should be paid the device specific
pin assignments.

3.5 RS232 Operation

With RS232 operation, an unbalanced data transmission is basically given using a separate
signal line for either direction, i.e. for transmission from Master to Slave and from Slave to
Master. This will also require an additional line with the reference potential (Common).
In RS232 operation, the Modbus standard is characterized by the following peculiarities:
RS232 operation is only provided for point-to-point connections.
Only a shielded cable may be used as a bus line
Capacitance between the signal line and the Common line may not exceed 2,500 pF.
This implies that the length of the bus line will be limited.
Neither termination nor polarization of the bus.
The Slave devices by HEINZMANN support RS485 in two-wire and four-wire operation.
Applications in RS232 operation will require additional RS232-RS485 interface adapters.

Operating Instructions Modbus 21

3 Installation

3.6 Slave participant

The maximum number of devices to be connected to a bus without repeater is up to 31
Slave devices plus one Master device.
All Slave participants must support:
the 2-wire or 4-wire RS485 standard for two-wire-systems, and
the 4-wire RS485 standard for four-wire-systems
Every participant must have a potential separation. By this, an electrically isolated
communication is established offering these advantages:
it is suitable for relatively long distances (up to 1,200 m), especially for industrial
applications,
it provides increased immunity against electromagnetic noise, and
it inhibits larger currents from flowing in case of magnetic disturbances and different
earthing potentials.

3.7 Master participant

By principle, only one Master participant is allowed on the bus. It must support:
the 2-wire or 4-wire RS485 standard for two-wire-systems, and
the 4-wire RS485 standard for four-wire-systems
It must also have a potential isolation. Normally, the Master device implements a bus
polarization, see also section 3.11 Line polarization.

3.8 Reference potential

By means of a separate line all bus participants are pulled onto a common reference
potential.
The Modbus standard requires this line to be connected with the protective earthing
conductor (PE – Protective Earth) preferably on the Master or on its tap. There is only one
single earthing point allowed. This rule is observed by the examples in Figure 4, Figure 5,
Figure 7 and Figure 8.

Although symmetric data transmission as compared with RS232 (asymmetric

transmission) shows a relatively greater immunity against interferences and
Note the signal level is to be directly recognized at the data lines, communication is
additionally supported by the reference potential (Common).

22 Operating Instructions Modbus

 3 Installation

Master device Modbus Modbus Slave device

(e.g. SPS) module D D module
D1 and D0
R R

DC
DC

DC
DC
UCM1 UCM
CEMV Common
CEMV ≈ 1uF
GND1 CISO COMMON UCM2 COMMON CISO ≈ 50pF GND2

PE
PE PE

UCM1 – Common mode voltage from transmitter with interference induced among the conductors within the bus cable.
UCM2 – Interference induced between Common line and protective earthing conductor.

Figure 6: Reference potential

The indicated common mode voltage UCM must not exceed the level of -7/+12 V
(specific working range). The reference potential (Common) is to be connected
to all participants. Then UCM = UCM1 will hold for interferences.
Note

3.9 Shield
The Modbus standard requires a shielded cable.
According to this standard, the shield of every cable must be connected at one end to the
protective earthing conductor (PE). The shield of any cable is to be connected either to the
shield of the other cable or at one of its extremities to protective earthing. The admissible
variants are shown in Figure 4, Figure 5, Figure 7 and Figure 8.
According to our recommendations, the optimum shield configuration will be best as
follows:
A common shield for the bus cables. The only earthing point must preferably be
located on the Master or its tap.
A separate shield for the derivation cables. The only earthing point must be located in
the participant's cubicle.
These rules are observed by the examples in Figure 4, Figure 5 and Figure 8.

Operating Instructions Modbus 23

3 Installation

Cabinet 1
Master device
+5V
DC D

Pull Down
Pull Up
DC R
PE
150 Ohm

150 Ohm
Common

Shield
PE PE PE

DC R DC R R
DC
DC D DC D DC
PE PE D
PE
Slave device l Slave device m Slave device n
Cabinet 2 Cabinet 3 Cabinet 4
Figure 7: Reference potential and shield

Cabinet 1
Master device
+5V
DC D
Pull Down
Pull Up

DC R
PE
150 Ohm

150 Ohm

Common

Shield

PE

DC R DC R R
DC
DC D DC D DC
PE PE D
PE
Slave device l Slave device m Slave device n
Cabinet 2 Cabinet 3 Cabinet 4
Figure 8: Reference potential and shield

24 Operating Instructions Modbus

 3 Installation

The external shield serves as an electrostatic and electromagnetic shield and must not be
used as a conductor for the reference potential. The shield must not have a second electric
connection to the earthing bus or to the casing.

3.10 Line termination

Termination of the data line is a measure recommended according to Modbus standard.

Slave device Master Slave device

n device m
D R D R D R

TXD
L 1
TXD L
0RXD
T T
L 1RXD L
0
T T

In order to obtain optimum transmission quality and/or signal quality, particularly over
long distances, the data line is to have a termination as a twisted data conductor pair at both
extremities according to Figure 9. For this, termination load must correspond to the
characteristic impedance of the data line.

Figure 9: Line termination in four-wire-system

The Modbus standard permits two quasi optimum termination methods:

AC termination – on either end a serial RC element with capacitor: 1 nF, 10 V
minimum and with resistor 120 Ohms, 0.25 W.
Advantage: – maximum signal level up to 5 Vpp.
Disadvantage: – poor reflection behaviour.
DC termination – on either end a resistor 150 Ohm, 0.5 W.
Advantage: – good reflection behaviour.
Disadvantage: – smaller signal level (e.g., silent state of about 0.27 Vpp).
Preferably, DC termination should be chosen. It is depicted both in Figure 4 and Figure 5.
Termination can be implemented:
at the bus end in the device connection in the daisy-chain structure, for this see also
section 3.1 Bus topology.
at the bus end in the participant in the daisy-chain structure if this possibility is
provided in the participant,
in the passive tap at the bus end (see Figure 4 and Figure 5) or
in the active tap at the bus end.
The termination must not be installed in the derivation cable.

Operating Instructions Modbus 25

3 Installation

3.11 Line polarization

A remote data cable needs a polarization for each pair of data conductors which is to be
implemented preferably in the Master device or in its tap. Consequently, there is no need
for polarization in the Slave devices.
Polarization is to be built using the following components:
Pull-up resistors that are to be connected against 5 V DC and to signal + (TXD1,
RXD1 or D1), and
Pull down resistors that are to be connected against the reference potential (Common)
and to signal + (TXD1, RXD1 or D1).
For all polarization resistors identical values should be chosen that may range from
450 Ohms to 650 Ohms. Polarization requires a 5 V DC supply. A detailed configuration
of the polarization is depicted in Figure 10 and outlined in Figure 4 and Figure 5.

Master device
+5V +5V
Pull Down

Pull Down
D DC
Slave device n
Pull Up

Pull Up

R DC
D R

Figure 10: Line polarization in a four-wire-system

If the polarization is implemented in the active/passive tap of the Master device the tap
must be supplied 5 V DC either from the Master device or from an electrically separated
source.

Line polarization serves to set the OFF-state, where the OFF-state designates
the silent state when there is no transmission from any participant. Actually in
Note silent state, however, a polarization current between 3.6 and 5.1 mA DC must
be flowing. With a DC termination by 150 Ohms, this will in silent state cause
a differential signal of 0.27 to 0.38 V DC. The maximum polarization current
will increase interference immunity.

26 Operating Instructions Modbus

 3 Installation

3.12 Bus accessories

The taps constitute an important element of the bus. As a passive tap for Modbus every
suitable bus tap can be used (e.g., Fieldbus, CAN, Ethernet).
The possibility of termination and polarization is already provided in certain taps, such as
Schneider-Electric, TSX SCA 64 connection box,
Schneider-Electric, TSX SCA 50,
Phoenix Contact, PSM PTK (passive RS-485 T-tap),
Weidmüller, Fieldbus components.

3.13 Device side connection module

In accordance with the EIA/TIA-485/422 standard, the HEINZMANN connection module
is designed as a 4-wire interface with separate transmission and reception lines. Due to
this, both connection types as a 2-wire and a 4-wire interface can be used. For 2-wire
operation, this can be achieved by simply paralleling two lines RX and TX of identical
polarity in the connector.
Electrical isolation between bus connection and control unit is provided. On the
communication side, the Slave devices by HEINZMANN have no contacting between the
reference potential and protective earthing (PE) nor between the case of the connection and
protecting earthing (PE).

Electric shock hazard

Contact with communication lines, shield or reference potential might
cause electric shock.
Never touch communication lines, shield or the reference potential

3.14 Connector plug and socket

The device side connector socket is a:
9 pole Sub-D female connector.
The bus or cable side coupler is a:
9 pole Sub-D male connector.
Regarding the specifications concerning the pin assignment of the connectors see section
6 Technical data.

Operating Instructions Modbus 27

4 Module functions

4 Module functions
The HEINZMANN control unit is always defined as a Slave and by request from the
connected Master can be made to execute a data transfer as determined by the function code.
In accordance with the function code, the reply following this request may consist of a read-
out of data, an acknowledgement of data received, an exception response or no response.

4.1 Device address

The device addresses of the participants (ID) of the network must be set by the user in the
participant device. Every ID may be assigned only once within a bus segment.

In assigning device addresses it is particularly important to ensure that one

and the same address is not assigned to several devices. Such a failure may
Note result in abnormal bus performance so that the Master will not be able to
communicate with all Slaves connected to the bus.

Broadcast in Multi-Slave operation or in transmission only mode: Requests

under Slave address 0 are accepted by the HEINZMANN control unit but will
Note be without any function! The reaction of the control unit will be no response.

4.2 Supported function codes

The following Table 6 lists all supported functions from the Modbus function stock
together with a brief description. Whenever an unknown function code is requested by the
Master the corresponding exception response will be returned.

Function Code Function Designation Brief Description

0x03 Read Holding Register Read access to one or more data words,
for transmission of parameter values or
measurements of the control unit
0x06 Write Single Register Write access to a data word
0x08 Diagnostics Diagnostic function, e.g., reading out the
diagnostics counters
0x10 Write Multiple Register Write access to one or more data words

Table 6: Function codes

The diagnostics function is confined to the sub-function codes that are specified in Table 7;
any other sub-functions are not supported and are rejected through an exception response.
The request data field or data word is to be assigned the value 0x0000 except for the sub-
function code 0x0000 which supports any length and selectable values of the data words.

28 Operating Instructions Modbus

 4 Module functions

This functionality serves for diagnosing the communication result and allows to indivi-
dually or globally reading out and reset the counter states that are being incremented with
regard to success, error of communication, etc.

Sub-function Designation Brief Description

code
0x0000 Return Query Data Request is echoed back
0x0002 Return Diagnostics The data of the sub-functions codes 0x0B
Register to 0x12 are returned in this order
0x000A Clear Counters and The counter states of the sub-function
Diagnostic Registers codes 0x0B to 0x12 are reset to zero
0x000B Return Bus Message Quantity of valid messages received is
Count returned
0x000C Return Bus Quantity of errors encountered in
Communication Error receiving messages is returned
Count
0x000D Return Bus Exception Quantity of transmitted exception
Error Count responses is returned
0x000E Return Slave Message Quantity of transmitted messages is
Count returned
0x000F Return Slave No Quantity of received messages requiring
Response Count no response is returned
0x0010 Return Slave NAK Zero is returned
Count
0x0011 Return Slave Busy Zero is returned
Count
0x0012 Return Bus Character Quantity of messages is returned that due
Overrun Count to a character overrun condition were not
correctly received

Table 7: Sub-functions of the diagnostic function

Operating Instructions Modbus 29

4 Module functions

4.3 Supported exception codes

The possible exception codes that may be contained in an exception response derive from the
function codes that are supported. An exception response is returned as a reaction to any
request from the Master when the specifications concerning the data to be transmitted exceed
the device's internal address and data ranges or when a function code is not supported. Table 8
offers a list of the supported exception codes of a HEINZMANN control unit.

Exception Code Designation Brief Description

0x01 Illegal Function Function code is not supported
0x02 Illegal Data Address Data address exceeds the internal data
range as provided by the device
0x03 Illegal Data Value Quantity of data exceeds the internal data
range as provided by the device
0x04 Slave Device Failure Device can not process the data

Table 8: Exception codes

30 Operating Instructions Modbus

 5 Parameterization and commissioning

5 Parameterization and commissioning

Parameterization of the module is to be performed exclusively by means of the software of
the HEINZMANN basis device, which will require either DcDesk 2000 as a Windows®
programme for visualizing and configuring the input and output data of digital HEINZMANN
control devices, or the Hand Programmer HP-03-03 as a diagnostics tool. For more details,
please refer to
Operation Manual Communication Programme DcDesk 2000, Manual No. DG 00 003–e,
Operating Instructions Hand Programmer HP-03-03, Manual No. DG 04 002-e,
PRIAMOS / HELENOS Basic Information 2000 for Digital Governors Level 6, Manual
No. DG 00 001-e and
THESEUS Control Systems for Electronically Controlled Generator Sets in Isolated and
Mains Parallel Operation, Manual No. DG 97 002-e.

5.1 Configuration of interface

The configuration of the interface requires parameterizing the baud rate used, the
transmission type and the device address within the bus system. The transmission type
includes specifications concerning the parity bit and the number of stop bits. In addition, it
is necessary to activate the complete Modbus functionality within the HEINZMANN
control device. To do so, the user will have to pre-setting the following parameters and
function parameters:
21800 Modb:Baudrate Parameter baud rate,
21801 Modb:SlaveID Specific device address as Slave,
25800 ModbusOn On/Off switch for Modbus functionality,
25801 Modb:ParityBitOn Selection transmission type with or without
parity bit,
25802 Modb:ParityOddOrEven Selection of odd or even parity if parity bit is
selected
25803 Modb:OneOrTwoStopBit Selection of one or two stop bits
25804 Modb:ExtendedOn Selection of the Modbus functionality:
parameter values can also be set in the
extended version
The measurement
23800 Modb:Baudrate Indication value baud rate
will indicate whether the device was able to set the baud rate as selected by means of the
respective parameter.

Operating Instructions Modbus 31

5 Parameterization and commissioning

Any changes of the parameter 21800 Modb:Baudrate or of the function

parameters 25800 ModbusOn, 25801 Modb:ParityBitOn,
25802 Modb:ParityOddOrEven and25803 Modb:OneOrTwoStopBit will be
Note
effective only after saving the changes and resetting the control unit. The
function parameter 25804 Modb:ExtendedOn is only available in the Modbus
Extended Version.

Table 9 gives an overview of the options for setting the transmission types with regard to
parity bit and stop bits.

No parity No parity Even parity Odd parity

with one stop with two stop with one stop with one stop
bit bits bit bit
25801
0 0 1 1
Modb:ParityBitOn
25802
X X 0 1
Modb:ParityOddOrEven
25803
1 0 1 1
Modb:OneOrTwoStopBit

Table 9: Setting for transmission type

Example of parameterization:
Modbus functionality is to be activated with the baud rate set to 9600 Baud and the Slave
device address to 1. The data transmission type for a character is to be selected as
including one bit for even parity and one stop bit. It should be noted that after making
modifications to the settings for the baud rate, the activation of the functionality and the
transmission type these changes must be saved and the control unit reset.
Number Parameter Value Unit
21800 Modb:Baudrate 9.600 kBaud
21801 Modb:SlaveID 1
25800 ModbusOn 1
25801 Modb:ParityBitOn 1
25802 Modb:ParityOddOrEven 0
25803 Modb:OneOrTwoStopBit 1

Indication
23800 Modb:Baudrate 9.600 kBaud

32 Operating Instructions Modbus

 5 Parameterization and commissioning

The standard default settings on shipping the device are

Number Parameter Value Unit
21800 Modb:Baudrate 9.600 kBaud
21801 Modb:SlaveID 247
25800 ModbusOn 1
25801 Modb:ParityBitOn 1
25802 Modb:ParityOddOrEven 0
25803 Modb:OneOrTwoStopBit 1

On request, the shipping state can be modified in dependence of customer wishes and
project requirements.

5.2 Reading data

A read access to one or more data words serves for the transmission of parameter values or
measurements of the control unit to the Master device on the Modbus. For this purpose, the
function code 0x03 “Read Holding Register” is to be used, see also section
4.2 Supported function codes.
As regards curve parameters, a data array ranging from 29200 to 29299
Modb:TxParamSet(x) (or Modb:ParamSet(x) for Extended Version) is available for the
user and can be accessed via the function code 0x03. The start address specified in the
request message corresponds with the index of the data array which is limited to 100
entries. The quantity of data to be transmitted beginning with this index is given by the
number of registers specified in the request message.
The data field is to be assigned the parameter numbers whose measuring or parameter
values are to be transmitted. Particular care should be taken to enter the numbers
consecutively beginning with the index zero and without gaps. Note that from the first
invalid parameter number on all subsequent entries will be ignored. The following
parameter numbers are defined as invalid:
parameter number zero,
any parameter number unknown to the control unit, or
any parameter number associated with a parameter whose level is higher than the
access level for the Modbus which on principle is limited to four.

By being invariably set to four the access level for the Modbus allows to
transmit all measurements and indication values as well as all application
Note specific parameters.

Operating Instructions Modbus 33

5 Parameterization and commissioning

The user is informed about the maximum number of data words that can be read out by the
measurement
23810 Modb:NoOfTxParams Number of valid parameter numbers in the
data array.
Example of parameterization:
Speed, oil pressure and oil temperature are to be read out via Modbus. A control unit of the
HELENOS series is being used.
Number Parameter Value Unit
29200 Modb:TxParamSet(0) 2000
29201 Modb:TxParamSet(1) 2905
29202 Modb:TxParamSet(2) 2909
29202 Modb:TxParamSet(3) 0

Indication
23810 Modb:NoOfTxParams 3
2000 Speed 1500.2 1/min
2905 OilPressure 3.15 bar
2909 OilTemp -10.2 °C

External Value Ranges

2000 Speed 0.0..4000.0 1/min
2905 OilPressure 0.00..10.00 bar
2909 OilTemp -100.0..1000.0 °C

The data are transmitted by their external value ranges. As regards the value ranges of the
different parameters the user should refer to the publications describing the HEINZMANN
control devices or read them out directly from the control unit using one of the
HEINZMANN diagnostics tools. To interpret the data words transmitted correctly, account
must be taken of the number of decimal places and of whether the value range can also be
negative.
In the above example, the data word for speed will be transmitted by the value 15002 as
obtained from 1500.2 10 for one decimal place, that for oil pressure by the value 315 as
obtained from 3.15 100 for two decimal places, and that for oil temperature by –102 as
obtained from 10.2 10 for one decimal place.
Since speed and oil pressure can assume positive values only, it is but the number of digital
places that must be taken into account as powers of ten. Likewise, if oil temperature is
interpreted as already signed, it will also be the number of digital places that is to be
evaluated as power of ten.
If oil temperature is evaluated as not yet signed the above example will yield a data word
having the value 65,434. Any values greater than or equal to 32,768 are to be interpreted as
negative values provided the external value range admits of negative values. The correct
signed value is obtained as the difference between the data word and 65,536, and as a
34 Operating Instructions Modbus
 5 Parameterization and commissioning

second step it is but the number of digital places that must be taken into account to
calculate the final value.

If in the above example any request should include a start address equal or
greater than two or if the quantity of data to be read exceeds two data words,
Note an exception response will be transmitted.

5.3 Write data

A given data field can be written to by means of the function codes 0x06 “Write Single
Register” (single write mode) and 0x10 “Write Multiple Register” (multiple write mode), see
also section 4.2 Supported function codes. The write access to one or more data words
allows to further process received data within the control device as external input quantities.
The implementation of the HEINZMANN Modbus differs fundamentally between the
basic and the extended version. In contrast to the extended version, the basic version only
has write access rights for the Modbus switching functions and sensors, which are
predetermined and fixed. The following Table 10 provides information about the write
access rights associated with the different versions.

Parameter Lists Basic Extended

Parameter - X
Functions - X
Curves - X
Measurements (general) - -
Measurements (Modbus functions) - X
Measurements (Modbus binary values) X X
Measurements (Modbus sensor values) X X

Table 10: Write access rights

Measurements (Modbus functions)

23815 Modb:ResetDevice Force reset of the control unit
23816 Modb:SaveParameter Save parameter values in the control unit
Measurements (Modbus binary values)
23820 Modb:RxBinary Binary values 16 bits wide
Measurements (Modbus sensor values)
23821 Modb:RxSensor(0) to
23824 Modb:RxSensor(3) Sensor values

Operating Instructions Modbus 35

5 Parameterization and commissioning

5.3.1 Basic version

By standard, the size of the writeable data field is five words. Due to definition, the first
word can be used for 16 binary switch input values and every subsequent data word for
a sensor input value. This configuration is shown in Table 11 and may on request be
extended according to customer or application needs.

Data Field
Index Type
0 8 Bit (high) 8 Bit (low) switch
1 16 Bit sensor
2 16 Bit sensor
3 16 Bit sensor
4 16 Bit sensor

Table 11: Write data

The data received by the control unit can be viewed via these indication values
23820 Modb:RxBinary Binary values 16 bits wide, and
23821 Modb:RxSensor(0) to
23824 Modb:RxSensor(3) Sensor values.

5.3.2 Extended version

In the extended version, the sensor values and binary values are freely configurable via
the 29200 Modb:ParamSet(x) data field. In addition to sensor and switching functions,
parameters with an access level of less than or equal to 4 can also be specified. The data
field that is used to read out data (see 5.2 Reading data) should be populated with the
corresponding parameter numbers, the parameter values of which should also be
specified.
The data field can be activated using the function code 0x06 or 0x10, and the parameter
and measured values specific to Modbus can be set. The start address given in the
output corresponds to the data field index, for which the data field is limited to 100
entries. The number of data entries that will be transferred from the index is determined
by the number of registers that should be populated, which is given in the output. If an
array is to be populated, all of the registered parameters in the given array must possess
write access. If this requirement is not fulfilled, a corresponding exception code (0x04
Slave Device Failure) will be returned.

36 Operating Instructions Modbus

 5 Parameterization and commissioning

Example of parameterization:
As in the above example, the speed, oil pressure and oil temperature must be read via
Modbus. It must be possible to specify the PID parameters for the speed governor
100 Gain, 101 Stability and 102 Derivative using Modbus. A control unit of the
HELENOS series is being used.
Number Parameter Value Unit
29200 Modb:ParamSet(0) 2000
29201 Modb:ParamSet(1) 2905
29202 Modb:ParamSet(2) 2909
29203 Modb:ParamSet(3) 100
29204 Modb:ParamSet(4) 101
29205 Modb:ParamSet(5) 102
29206 Modb:ParamSet(6) 0

Activation
25804 Modb:ExtendedOn 1

Indication
23810 Modb:NoOfParams 6
2000 Speed 1500.2 1/min
2905 OilPressure 3.15 bar
2909 OilTemp -10.2 °C

5.3.3 Timeout monitoring

If binary and/or sensor values are to be transmitted to the HEINZMANN control unit in
write mode, it should be noted that these values must be transmitted periodically in
cyclical order to detect any failures or damages of the data transmission equipment. For
this purpose, a time-out is initiated with the first write access whose time limit is to be
set by means of the parameter 21820 Modb:RxTimeOut. With every valid reception of a
request via the functions codes 0x06 or 0x10 the time-out is re-initialized. If the write
access fails to occur within the pre-set reception time limit the error flag
3074 ErrModbusComm is set.

If a failure of Modbus communication occurs the standard reactions of the

HEINZMANN control units to sensor errors will be applied for the
Note respective sensor value. The binary values are assumed to be zero, and due
to this the assigned switching functions are reset.

If it is only parameters (e.g. at the start of communication) that are to be specified in

write mode, timeout monitoring is not strictly necessary. In this case, timeout
monitoring can be deactivated by setting the time limit parameter to zero.

Operating Instructions Modbus 37

5 Parameterization and commissioning

For further details concerning the parameterization of sensors and switching function,
refer to the chapters Sensors and Inputs and Outputs of the respective Basis
Information. In this brochure, it is only the specific extension of the particular
functionality required for Modbus that will be dealt with.

5.3.4 Assignment of sensor values to sensors

The assignment of sensor values as inputs to sensors via Modbus is achieved by
entering the desired channel numbers, in this case the respective index plus one, in the
associated parameters from 900 Assign… onward. The selection of the sensor as
Modbus sensor value is made by specifying the channel type in the parameters from
4900 ChanTyp… onward. For Modbus, it is always the value ‘6’ that is to be specified
as channel type.
49xx ChanTyp… = 6 Sensor value is being received via Modbus
The transmission of any sensor value from the Master to the HEINZMANN control unit
operating as a Slave will on principle be made within the internal value range which is
defined as ranging from 0 to 65535.

The scaling of the sensor value from 0% to 100% is equivalent to values

from 0 to 65535 being transmitted via Modbus. In the above example this
Note will yield the value 32767 for 50%.

Example of parameterization for basic version:

The power set point is to be received via Modbus as second sensor value. The sensor
value is to be updated cyclically every two seconds. A control unit of the THESEUS
series is being used.
Number Parameter Value Unit
900 Assign_PowerSetpoint 2
980 PowerSetpointLow 0.0 %
981 PowerSetpointHigh 100.0 %
4900 ChanType_PowerSetp 6
21820 Modb:RxTimeOut 2.5 s

Indication
2900 PowerSetpoint 50.0 %
3074 ErrModbusComm 0
23821 Modb:RxSensor(0) 0.0 %
23822 Modb:RxSensor(1) 50.0 %
23823 Modb:RxSensor(2) 0.0 %
23824 Modb:RxSensor(3) 0.0 %

38 Operating Instructions Modbus

 5 Parameterization and commissioning

Example of parameterization for extended version:

The power set point is to be received via Modbus as second sensor value. The sensor
value is to be updated cyclically every two seconds. A control unit of the THESEUS
series is being used.
Number Parameter Value Unit
900 Assign_PowerSetpoint 2
980 PowerSetpointLow 0.0 %
981 PowerSetpointHigh 100.0 %
4900 ChanType_PowerSetp 6
21820 Modb:RxTimeOut 2.5 s
29200 Modb:ParamSet(0) 23822

Activation
25804 Modb:ExtendedOn 1

Indication
2900 PowerSetpoint 50.0 %
3074 ErrModbusComm 0
23821 Modb:RxSensor(0) 0.0 %
23822 Modb:RxSensor(1) 50.0 %
23823 Modb:RxSensor(2) 0.0 %
23824 Modb:RxSensor(3) 0.0 %

5.3.5 Assignment of binary values to switching functions

The assignment parameters from parameter number 810 Funct… on may be used
exclusively for switching functions whose state is to be modified via digital hardware
inputs. With respect to the extended functionality of the switching functions the
assignment parameters have been doubled by introducing the parameter numbers from
20810 Comm… onward. These parameters can now be used for switching functions that
are to be set via some communication mode.
A binary value to be transmitted via Modbus can be easily assigned to a switching
function by entering the bit number in the corresponding assignment parameter.
Similarly to sensor assignment, the channel type of switching functions is to be
specified for Modbus by ‘6’.
248xx ChanTyp… = 6 Binary value is to be received via Modbus
If the parameterization of a switching functions admits of both the hardware and the
selected communication the two states will internally be combined by OR.
Example of parameterization for basic version:
By setting the binary input three via Modbus, operation is to be by fixed speed 1. The
binary value is to be updated cyclically every ten seconds. A control unit of the
HELENOS series is being used.

Operating Instructions Modbus 39

5 Parameterization and commissioning

Number Parameter Value Unit

20815 CommSpeedFix1 3
21820 Modb:RxTimeOut 11.0 s
24815 ChanType_SpeedFix1 6

Indication
2815 SwitchSpeedFix1 1
3074 ErrModbusComm 0
23820 Modb:RxBinary 04 Hex

Example of parameterization for extended version:

By setting the binary input three via Modbus, operation is to be by fixed speed 1. The
binary value is to be updated cyclically every ten seconds. A control unit of the
HELENOS series is being used.
Number Parameter Value Unit
20815 CommSpeedFix1 3
21820 Modb:RxTimeOut 11.0 s
24815 ChanType_SpeedFix1 6
29200 Modb:ParamSet(0) 23820

Activation
25804 Modb:ExtendedOn 1

Indication
2815 SwitchSpeedFix1 1
3074 ErrModbusComm 0
23820 Modb:RxBinary 04 Hex

5.3.6 Assignment of Modbus functions (extended version only)

The extended version offers the facility to carry out specific functions in the control
unit. The parameter number must be entered into the data field to enable the relevant
function to be carried out. The following Modbus functions are possible:
23815 Modb:ResetDevice Force reset of the control unit
23816 Modb:SaveParameter Save parameter values in the control unit
Example of parameterization:
The parameters must be stored in the control unit using Modbus.
Number Parameter Value Unit
29200 Modb:ParamSet(0) 23815

Activation
25804 Modb:ExtendedOn 1

40 Operating Instructions Modbus

 5 Parameterization and commissioning

Indication
3851 LastIdentifier 94
23816 Modb:SaveParameter 1

5.4 Diagnostic counter

For the HEINZMANN control devices the following diagnostic counters have been
implemented according to Modbus specification. They can also be read out via the function
code 0x08 “Diagnostics”, see also section 4.2 Supported function codes:
23801 Modb:BusMessageCnt Quantity of valid messages received,
23802 Modb:CommErrorCnt Quantity of faulty messages received,
23803 Modb:ExceptErrCnt Quantity of exception messages transmitted,
23804 Modb:SlaveMessageCnt Quantity of messages transmitted,
23805 Modb:SlaveNoRespCnt Quantity of No response messages,
23806 Modb:BusCharOvrCnt Quantity of messages not correctly received
due to character overrun.

Operating Instructions Modbus 41

6 Technical data

6 Technical data
Interface: EIA/TIA-485/422 standard
4-wire interface
Insulation: electrically separated
Insulation voltage: 1000 Volts(RMS), 1 min
Signal voltages against
reference potential (Common): –7 V to +12 V D.C.
Interference immunity (ESD): to EN 61000-4-2 (intended)
Connector: D-Sub 9 (male)
Signal assignment: according to Modbus Specification 4-wire interface

Pin Signal EIA/TIA- Description

485/422
8 RXD0 A’ Receiver connection 0
4 RXD1 B’ Receiver connection 1
9 TXD0 A Transmitter connection 0
5 TXD1 B Transmitter connection 1
2 VP --- +5 V DC (depending on version)
1 Common C/C’ Signal reference potential
Case --- --- potential free

Table 12: Signal assignment

Visual error indication: none

Data transmission: RTU Mode
Baud rate: 9,600, 19,200 Baud
Parity: no parity, even or odd parity
Stop bits one or two
Function codes: see section 4.2 Supported function codes
Exception codes: see section 4.3 Supported exception codes

42 Operating Instructions Modbus

 7 Parameter description

7 Parameter description

7.1 List 1: Parameters

21800 Modb:Baudrate
Level: 4 Modbus
Range: 9.6..19.2 kBaud Parameter baud rate, modification only effective after
Page(s): 32 reset
21801 Modb:SlaveID
Level: 4 Modbus
Range: 1..247 Unique device address as Slave
Page(s): 32
21820 Modb:RxTimeOut
Level: 4 Modbus
Range: 0..60 s Reception time limit for requests for writing binary
Page(s): 38 values or sensor values

7.2 List 2: Measurements

3074 ErrModbusComm
Level: 1 Modbus
Range: 0..1 Error indication Modbus communication
Page(s): 38
3174 SErrModbusComm
Level: 1 Modbus
Range: 0..255 or 0..1 Error Counter or sentinel for the occurrence of
3074 ErrModbusComm
23800 Modb:Baudrate
Level: 4 Modbus
Range: 9.6..19.2 kBaud Indication value for the pre-set baud rate
Page(s): 32
23801 Modb:BusMessageCnt
Level: 4 Modbus
Range: 0..65535 Quantity of valid received messages
Page(s): 42
23802 Modb:CommErrorCnt
Level: 4 Modbus
Range: 0..65535 Quantity of faulty received messages
Page(s): 42

Operating Instructions Modbus 43

7 Parameter description

23803 Modb:ExceptErrCnt
Level: 4 Modbus
Range: 0..65535 Quantity of exception messages transmitted
Page(s): 42
23804 Modb:SlaveMessageCnt
Level: 4 Modbus
Range: 0..65535 Quantity of messages transmitted
Page(s): 42
23805 Modb:SlaveNoRespCnt
Level: 4 Modbus
Range: 0..65535 Quantity of messages received requiring no response
Page(s): 42 (here: only transmission message from Master)
23806 Modb:BusCharOvrCnt
Level: 4 Modbus
Range: 0..65535 Quantity of messages not correctly received due to
Page(s): 42 character overrun
23810 Modb:NoOfTxParams
Level: 4 Modbus Basic Version
Range: 0..100 Number of valid parameter numbers entered in the data
Page(s): 35 field for read access
23810 Modb:NoOfParams
Level: 4 Modbus Extended Version
Range: 0..100 Number of valid parameter numbers entered in the data
Page(s): 35 field for read access and write access
23815 Modb:ResetDevice
Level: 4 Modbus Extended Version
Range: 0..1 Modbus function: Force reset of the control unit
Page(s): 36, 41
23816 Modb:SaveParameter
Level: 4 Modbus Extended Version
Range: 0..1 Modbus function: Save parameter values in the control
Page(s): 36, 41 unit
23820 Modb:RxBinary
Level: 4 Modbus
Range: 0000..FFFF Hex Binary values for write access
Page(s): 36
23821 Modb:RxSensor(x)
to Level: 4 Modbus
23824 Range: 0..65535 Sensor values for write access
Page(s): 36

44 Operating Instructions Modbus

 7 Parameter description

7.3 List 3: Functions

25800 ModbusOn
Level: 4 Modbus
Range: 0..1 On/Off switch Modbus functionality. Modification will
Page(s): 32 be effective after reset only
25801 Modb:ParityBitOn
Level: 4 Modbus
Range: 0..1 Selection transmission mode with or without parity bit.
Page(s): 32 Modification will be effective after reset only
0 = no parity bit
1 = with parity bit
25802 Modb:ParityOddOrEven
Level: 4 Modbus
Range: 0..1 Selection odd or even parity with parity bit set.
Page(s): 32 Modification will be effective after reset only
0 = even parity
1 = odd parity
25803 Modb:OneOrTwoStopBit
Level: 4 Modbus
Range: 0..1 Selection one or two stop bits. Modification will be
Page(s): 32 effective after reset only
0 = two stop bits
1 = one stop bit
25804 Modb:ExtendedOn
Level: 4 Modbus Extended Version
Range: 0..1 Activation of Modbus Extended Version
Page(s): 32

7.4 List 4: Curves and maps

29200 Modb:TxParamSet(x)
to Level: 4 Modbus Basic Version
29299 Range: 0..29999 Data field for read access
Page(s): 34 Any parameters or measurement numbers must be
entered whose values will be transmitted on request
29200 Modb:ParamSet (x)
to Level: 4 Modbus Extended Version
29299 Range: 0..29999 Data field for read access and write access
Page(s): 34 Any parameters or measurement numbers must be
entered whose values will be transmitted on request or
should be received

Operating Instructions Modbus 45

8 Index of Figures

8 Index of Figures
Figure 1: Request-reply-cycle .................................................................................................. 11
Figure 2: Protocol frame .......................................................................................................... 12
Figure 3: Bus topology ............................................................................................................. 14
Figure 4: RS485 – two-wire-system......................................................................................... 17
Figure 5: Signal definition – four-wire-system ........................................................................ 19
Figure 6: Reference potential ................................................................................................... 23
Figure 7: Reference potential and shield .................................................................................. 24
Figure 8: Reference potential and shield .................................................................................. 24
Figure 9: Line termination in four-wire-system ....................................................................... 25
Figure 10: Line polarization in a four-wire-system ................................................................. 26

46 Operating Instructions Modbus

 9 Index of Tables

9 Index of Tables
Table 1: Master request ............................................................................................................ 13
Table 2: Slave reply.................................................................................................................. 13
Table 3: Slave exception reply ................................................................................................. 13
Table 4 Signal definition – two-wire-system ........................................................................... 17
Table 5: Signal definition – four-wire-system ......................................................................... 20
Table 6: Function codes ........................................................................................................... 28
Table 7: Sub-functions of the diagnostic function ................................................................... 29
Table 8: Exception codes ......................................................................................................... 30
Table 9: Setting for transmission type...................................................................................... 32
Table 10: Write access rights ................................................................................................... 35
Table 11: Write data ................................................................................................................. 36
Table 12: Signal assignment .................................................................................................... 42

Operating Instructions Modbus 47

10 Index

10 Index
Access level ......................................................... 33 Interference Immunity .......................................... 42
Baud Rate ..................................................31, 42, 43 Line Termination.................................................. 16
Binary Value .......................................35, 37, 39, 44 Master ..................................... 15, 22, 23, 28, 30, 38
Broadcast.............................................................. 28 Master Participant ...........................................16, 22
Bus Cable ............................................ 14, 15, 16, 23 Parameterization .................................................. 31
Bus Topology ....................................................... 14 Parity ...............................................................12, 42
Channel Type ..................................................38, 39 Parity Bit ...................................................31, 32, 45
Connection Module ...................................11, 14, 27 Participant Address .............................................. 12
Connector ........................................................27, 42 Polarization ...............................................16, 22, 26
Data Transmission...........................................11, 42 Protocol Reference ............................................... 11
DcDesk 2000 ........................................................ 31 Read Access ........................................ 28, 33, 44, 45
Derivation Cable ............... 15, 16, 18, 19, 21, 23, 25 Reception Time Limit .....................................37, 43
Device Address .........................................28, 31, 43 Reference Potential15, 16, 18, 19, 21, 22, 26, 27, 42
Diagnostic Function ............................................. 28 Reset Control Unit ....................................35, 40, 44
Diagnostics Tool .......................................12, 31, 34 RTU Mode ................................................11, 12, 42
EIA/TIA-485/422 Standard.......................14, 27, 42 Save Parameter Values..............................35, 40, 44
Error Check .......................................................... 12 Sensor Value ....................................... 35, 37, 38, 44
Exception Code .........................................12, 30, 42 Shield .................................................. 14, 15, 23, 25
Four-Wire-System .....................................15, 19, 22 Signal Assignment ............................................... 42
Function Code ...........................................11, 28, 42 Signal Voltages .................................................... 42
0x03 ............................................................12, 33 Slave................................................................15, 28
0x06 ................................................................. 35 Slave Participant .............................................16, 22
0x08 ................................................................. 41 Socket................................................................... 27
0x10 ................................................................. 35 Stop Bits .............................................. 31, 32, 42, 45
Handprogrammer HP-03-03................................. 31 Sub-Function Code .............................................. 28
Hardware Reference ............................................. 11 Switching Functions ............................................. 39
Insulation.............................................................. 42 Tap .............................. 15, 18, 21, 22, 23, 25, 26, 27
Insulation Voltage ................................................ 42 Termination .......................................................... 25
Interface ..........................................................31, 42 Two-Wire-System .....................................15, 16, 22
RS232 ...................................................11, 15, 22 Visual Error Indication......................................... 42
RS422 .........................................................11, 15 Write Access ................................. 28, 35, 37, 44, 45
RS485 ...................................................11, 15, 22

48 Operating Instructions Modbus