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Modbus Organization Newsletter, December 2012
Wireless Communications in the
Industrial Space
Member company connectBlue brings its expertise
in wireless communications to bear every day for its
customers. In this issue, connectBlue’s chief tech-
nology officer, Mats Andersson, offers a bird’s eye
view of the role of wireless in industrial communica-
tions. Links to a longer paper can be found at the
end of this article.
Wireless communication has been used in industrial
applications for more than 30 years. Among its first
applications was the wireless control of Automated
Guided Vehicles (AGV) and cranes in warehouses
where proprietary radios were used to achieve flexi-
ble control of the moving devices. During the last 10
years, standardized radio technologies such as
Wireless LAN (IEEE 802.11),
continued on page 3
Modbus Protocol V1.1b3 Posted
on Modbus Web Site
The Modbus Organization has posted a new ver-
sion of the Modbus protocol specification on the
web site. Modbus Protocol v1.1b3 corrects some
acronym misnomers and replaces the traditional
master/slave language with the more appropriate
client/server construct.
Expect similar changes to the implementation
guides in short order. Other updates are under-
way as well.
New Addition to Modbus
Resources Page
The Modbus Organization’s Technical Resources
list of resources
for Modbus developers and
users continues to grow.
The newest listing is an open-source multi-
platform Modbus library for .Net. Cet Electronics
offers a series of open-source Modbus libraries
written in C#. They support RTU (binary only),
TCP and UDP, both client and server. The librar-
ies target .Net Micro Framework, Windows
Phone, and standard .Net (incoming). High ab-
straction for easy pluggability, and extensibility.
Multi-threading and C# 5 are supported. Very
easy to use.
Wishing you all
the best in 2013!
News about the World’s Most Popular Protocol
Member News
Member News
Member News
Member News
Since 1990,
Hjelmslund Elec-
has been completing
industrial automation projects
according to customers’ specifica-
tions. Today the company works
with smaller and more complex
technologies, using ARM micro-
processors (Primarily ARM7),
USB, Bluetooth and other tech-
nologies in customer-specified
Member News
Member News
Elecsys Corporation
innovative machine-to-machine
(M2M) communication
technology solutions, custom
electronic equipment and
displays for critical industrial
applications worldwide. The
company’s primary markets
include energy production and
distribution, agriculture, water
management, aerospace,
military, safety and security
systems, and transportation. The
company’s culture and
philosophy place a high emphasis
on innovation, quality, reliability,
and customer support.
Elecsys Corporation’s
Industrial Communications
is a cost-effective
remote field data
communications device designed
for data acquisition and control
applications, which
communicates via Modbus TCP
or Modbus over serial line.
founded in 1998. The company is
a research, design and
manufacturing organization,
specializing in power
measurement meters and
software for the distribution,
control and management of
electric energy and other
dynamic processes.
Accuenergy’s Acuvim series of
energy meters include three-
phase multifunction power
meters, multi-circuit power and
energy meters, multifunctional
DC power meters, and single-
phase multifunction power
meters — used in energy
management, industrial
automation, wide area power
monitoring, power quality
analysis, substation automation,
and many other applications.
Hjelmslund Electronics’ own
products include the USB485
family of Modbus RTU-
compatible USB-to-RS485 con-
verters — unique because of
their isolation barrier and com-
pactness, typically found only in
much larger converters.
Modbus Newsletter
This is the newsletter of the Modbus
Organization, the international nonprofit
organization devoted to the evolution and
support of the Modbus protocols.
The Modbus Organization Mission
The Modbus Organization, Inc. is a group of
independent users and suppliers of automation
devices that seeks to drive the adoption of the
Modbus communication protocol suite and the
evolution to address architectures for distributed
automation systems across multiple market
segments. Modbus Organization also provides the
infrastructure to obtain and share information about
the protocols, their application, and certification to
simplify implementation by users resulting in
reduced costs.
For more information about membership and
other services, please refer to our website:
Newsletter Editor:
Lenore Tracey (lenore@modbus.org)
Copyright 2012
Modbus Organization, Inc.
PO Box 628
Hopkinton, MA 01748 USA
ph +1-508-435-7170
Member News
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Member News
Applications where rapid roam-
ing is required. Bluetooth tech-
nology is used for Human Ma-
chine Interfaces (HMI), program-
ming, service/maintenance as
well as real-time control tasks.
During the last few years, other
technologies such as IEEE
802.15.4 (ZigBee, Wireless Hart,
etc.) and Bluetooth low-energy
technology have become increas-
ingly used for sensors, actuators
and other small devices.
The adoption of wireless in an
industrial environment is typi-
cally a gradual process. Initial
requirements include the crea-
tion of islands of wireless en-
abled devices connected to an
existing wired network. The
wired network may be a stan-
dard IP-based network or a field-
bus network, such as Modbus
TCP, Profinet, Devicenet,
Controlnet or Interbus-S.
connectBlue’s white paper
describes some of the specific
requirements for wireless com-
munication technology in indus-
trial applications. The paper con-
siders the following topics in
more detail:
Serial cable replacement
Ethernet cable replacement
and Ethernet infrastructure
Seamless roaming
Fieldbus cable replacement
Smart phone/other mobile
device applications
Wireless sensors and actua-
tors network
Industrial requirements for
wireless technologies
Coexistence of multiple wire-
less technologies.
Member News
Member News
Wireless Communications, cont’d...
IEEE 802.15.4 and Bluetooth
technology (IEEE 802.15.1) have
become the dominant technolo-
Wireless solutions offer several
advantages in industrial applica-
tions. They are used to increase
mobility, eliminate expensive and
high-maintenance transmission
media (such as flexible cables
and swivels), and overcome the
problems associated with large or
problematic zones, such as public
Moxa’s new Profibus-to
-Modbus TCP gateway
Moxa recently released its MGate
5101-PBM-MN Profibus-to-
Modbus TCP gateways series with
PI certification. The MGate 5101-
PBM-MN gateway features enable
bridging Profibus devices
(Profibus drives or masters) to
Modbus TCP masters (SCADA or
PLCs) with ease.
Industrial plants typically consist
of multiple devices intercon-
nected in different ways. These
devices may include simple I/Os,
intelligent sensors, single-loop
controllers or programmable con-
trollers, and devices for data log-
ging and supervisory control.
The devices may be intercon-
nected using different communi-
cation protocols and media types,
which, in some cases, can be re-
placed by wireless technologies.
No one wireless technology offers
all the features and strengths
that fit the various industrial
application requirements; there-
fore, standardized wireless tech-
nologies Wireless LAN, Bluetooth
technology and IEEE 802.15.4, as
well as number of proprietary
technologies, are all used. The
main requirement could be high
data throughput, robustness or
low power (the latter especially
for battery-operated devices).
Wireless LAN is often used for
production planning and data
acquisition, as well as
Its rugged design with optional
built-in optical isolation, and -40
to 75°C wide-temperature opera-
tion, ensure reliable performance
for use in industrial applications
such as oil/gas, power, process
automation and factory automa-
With a little help from
our friends...
Modbus member company
Acromag, recently pointed out a
helpful Wiki page
with explicit
instructions for taking raw Mod-
bus data and uploading it to
iDigi as “Dia Data” for access by
Web services.
Many thanks to Lynn Linse at
Digi for his continuous support to
the Modbus community. A fre-
quent contributor to the Modbus
discussion forums, he seems to
always be there with useful
advice for those with Modbus
questions and quandaries.
Member News
Modbus Discussion
Modbus Discussion
Member News
Member News
Modbus Discussion
Q&A from the Modbus Discussion Forum...
Using Modbus data packets and setting up the
registers to be read from a Modbus master...
New user posted this message
to the forum:
I’m new using Modbus and would
like some help, if possible. I have
an application where I need to
output data in Modbus format
over Ethernet to Experion Soft-
ware. I believe Automation Di-
rect’s H2-ECOM 100 module is
all I need, but not sure.
Once the PLC process is done, I
need to download all my user in-
puts (recipe data) to Experion. It
appears all I need is to use a con-
version sheet that targets V
memory. Specifically, I just enter
the V memory into the spread-
sheet and it tells me the Modbus
number to use.
I have not worked with Experion,
but am assuming this Modbus
“number” is what the Master
needs to pull that data. From a
PLC ladder logic point of view I
don’t have to write any additional
logic beside the Load and Output
for assigning user inputs to re-
ceipt V memory. Correct?
William Sturm replied:
Sounds to me like you have the
overall right idea...
Steve Myres concurred:
Correct. With the 205 PLC, Mod-
bus/TCP comms to an H2-
ECOM100 (or Modbus RTU
comms to Port 2) target the same
block of V-Memory you address
in ladder, so you don’t have to
move the data you’re interested
in to a special location or any-
thing like that.
To make it even easier, the ad-
dresses (for Modbus FCs 3 and
16) are even the same, once you
allow for the fact that ADC mem-
ory addresses are in octal. V2000
is Modbus 1024, for example (you
might see it as 1025, depending
on Experion’s implementation of
Coils are almost as easy. Convert
the “C” address to decimal and
add 3072, IIRC.
You don’t even need to use ADC’s
spreadsheet if you don’t want to.
Excel has the DEC2OCT() func-
tion in the Analysis Toolkit, and
between that and drag-and-fill,
you pretty much have everything
you need.
Read more or add your com-
to this thread.
IBM responded:
You need to provide a more infor-
mation! Biggest factor in deter-
mining the update time is the
communications speed (baud
rate). Modbus RTU is a reasona-
bly compact protocol; you can re-
quest up to 127 consecutive regis-
ters of data using an eight (8)
byte command; the response could
be up to 259 bytes long. At
19,200, 8, N, 1 that string would
take less than 2 seconds to trans-
VSS added:
Here is more information:
Baud rate: 9600
Request: 32
Parity: None
Stop Bit: 1
Length of cable around 1km
Master: Honeywell DCS through
SI card
Slave: IVT OilMist System
Patrick Lansdorf suggested:
I would actually say that [the]
most influential factor is/can be
the response time of the slave. In
some cases up to 300ms.
I have an excel sheet, that calcu-
lates the line times for Modbus
Read more or add your com-
to this thread.
Modbus comms &
total time scan...
VSS asked:
Both analog and discrete values
are fetched from a PLC via
RS485 2W Modbus. How much
time does it take to read value
for analog (numeric) value and
digital (holding register) value
till the values are displayed in
DCS system?
I read somewhere that it takes 5
sec for numeric and 1 sec for dis-
crete value.
What effect it will have if sev-
eral devices are put using multi-
Can anyone confirm this?
The Modbus Community
Active technical discussions
Knowledge aggregation
Contact with Modbus users
Discussion supported by...
We’re with you. The Modbus Or-
ganization is there to help suppli-
ers and users of the Modbus proto-
col succeed. Our members range
from Modbus device suppliers, to
system integrators, end users, and
educational institutions.
The common link? They all value
the information and services pro-
vided by the Modbus Organization,
and they all play a role in deter-
mining the future of the world’s
most broadly applied protocol.
Visibility: Your Company &
Your Products
Your membership in the Modbus
Organization also opens the door
to a powerful range of visibility
options to highlight your company
as a supplier of Modbus-based
Exposure on our website, our
newsletter, and through our vari-
ous trade show appearances are
all options that allow you to make
the most of your Modbus Organi-
zation membership.
Your company will also value the
opportunity to participate in our
technical committees. There, your
company’s knowledge, experience
and technology can help guide
future enhancements, extensions,
and adaptations of Modbus to
keep it the world’s leader for dec-
ades to come.
Modbus TCP Toolkit v3.0
The Modbus TCP Toolkit provides
all the necessary pieces to develop
a Modbus-compliant device, in-
cluding documentation, diagnostic
tools, sample source code, and pre-
test software to prepare for Mod-
bus conformance certification.
Designing with Modbus
Modbus developers rely on the
Modbus Organization for valued
assistance with their projects:
Start by downloading specifica-
tions and other design documents
from the modbus.org website.
To save time,
purchase the Mod-
bus TCP Toolkit
general members); it contains
source code and a myriad of other
If you come across technical is-
sues that have you stumped, post
your question on the
One of the many experi-
enced Modbus implementers who
frequent this forum will likely
have your answer.
Time to Apply
When it comes time to get your
Modbus network up and running,
it’s comforting to know that hun-
dreds of thousands of applications
have preceded yours. But what if
things don’t go as planned?
Again, the
modbus.org forum
ready to answer your questions
and provide guidance. Thousands
of users from diverse backgrounds
participate in the forum, giving
you a powerful base of experience
from which to draw.
The Future is Yours
Whatever your role in the use of
Modbus, consider joining the Mod-
bus Organization. You’ll get the
support you need today, and have
opportunities to help guide Mod-
bus to a dynamic future.
Download the Modbus Organiza-
tion Membership Application
learn about the different member-
ship levels and their associated
The toolkit is available as a bene-
fit of corporate-level membership
in the Modbus Organization or can
be purchased separately for
US$500 plus shipping and han-
dling. The toolkit contains the fol-
lowing items:
Modbus Documentation
Modbus Application Protocol
Specification, v1.1b
Modbus Messaging on TCP Im-
plementation Guide, v1.0b
Modbus TCP Client & Server
Diagnostic Tools
Conformance Testing
When your project’s done, how do
you know it really conforms to the
Modbus specification? How do your
users know?
The answer starts with running the
conformance test suite included
with your Modbus TCP Toolkit.
This self-test helps you check your
design assumptions and catch the
subtle “gotchas” that might other-
wise slip through your design re-
submit your product for test-
to the Modbus Organization for
conformance testing. We’ll certify
your product as compliant, and
post that information on the Mod-
bus website for the world to see.
Sample Source Code
Modbus TCP Sample Client
Code for Visual Basic Win32
Modbus TCP Sample Client
Code for C/C++ Win32
Modbus TCP Sample Server
Code for C/C++ Win32
Modbus TCP Sample Server
Code for C VxWorks
Modbus TCP Sample Server
Code for C++ VxWorks
Modbus Conformance Testing
Conformance Test Tool v3.0
Conformance Test Tool v2.1
Additional Resources
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