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Modbus Organization Newsletter, December 2011

WCT Makes Modbus

Mapping Progress

The Modbus Subcommittee of the Wireless Coop-

eration Team (WCT) continues to work on the pro-

ject and has made strides in conceptualizing the

gateway parameters. Committee members have

made some initial decisions to design a gateway

specification that will be as straightforward and

simple as possible.

Look for regular updates on the gateway specifica-

tion development over the coming year.

Blog Focuses on Security

Modbus Organization member company Byres

Security (a Belden company) last week reported

on a hacker who showed how he could easily

hack into a SCADA system controlling the wa-

ter utility in the City of South Houston.

this blog entry,

Eric Byres discusses the vul-

nerability of passwords and the inherent risk

password protection poses to critical systems.

With tips for choosing "memorable yet effec-

tive" passwords, there's good advice here for

everyone.

Welcome to New Members!



Advanced Micro Controls Inc (AMCI)

Bentek Systems Ltd.

Define Instruments

Domat Control System s.r.o.

Trebing & Himstedt Prozeßautomation

Modbus Device

Directory Expanding

The Modbus Organization has maintained a

directory of Modbus products — hardware de-

vices and software programs — since launch-

ing its current website in 2008. Today there are

almost 1200 listings, affording users the ability

to search for products for their projects based

on a variety of criteria.

Recent entries include an increase in the num-

ber of wireless devices, well as the number of

devices and programs focusing on energy man-

agement.

The directory lists Modbus Conformance-tested

devices first, followed by member companies'

products. Non-member listings are also in-

cluded, but do not include either spec. sheets or

links.

to inquire about adding your com-

pany's Modbus products to the directory or how

to find the right Modbus device for your appli-

cation.

Wishing you all peace

and good fortune

in the new year!

News about the World’s Most Popular Protocol

Member News

Trebing + Himstedt

is an

international supplier of products

and services for the optimal use

of IT in the production

environment. The company

supports customers in their

manufacturing processes,

allowing targeted access to

Member News

Bentek Systems,

based in

Calgary, Canada, is a company

dedicated to the design and

manufacture of industrial

Advanced Micro Controls Inc

(AMCI)

is a U.S.-based

manufacturer with a global

presence. Its industrial controls

are sold all over the world,

including eight different product

families: Stepper Motor Controls,

PLC Modules, Rotary Sensors,

Networked Devices, Standalone

Solutions, Packaging Systems

Controls, and Stamping Press

Technologies.

Founded in 1985, AMCI leverages

an international network of

distributors, so customers can

quickly and conveniently

purchase products, no matter

where in the world they are

located.

In May, AMCI announced

Modbus TCP support for the

company’s robust NR25 series

encoders.

production and process

information through continuous

integration across different

communication levels – from the

automation level to the ERP

system.

In its Industrial Communication

business unit, Trebing +

Himstedt's products ensure the

availability of industrial

networks. The Manufacturing

Integration business unit

encompasses solutions for

production IT, particularly for

Manufacturing Execution

Systems in SAP environments.

wireless SCADA and telemetry

solutions. The company provides

products and services to

industries including oil and gas,

water and wastewater, mining

and manufacturing.

SCADALink is Bentek Systems'

own line of SCADA & automation

products. The SCADALink line

includes integrated RTU/

Radiomodems, cellular- and

Internet-enabled RTU/

Radiomodems, wireless Ethernet

radios, serial Ethernet gateways,

wireless I/O telemetry, solar-

powered RTU systems, alarm

callout systems, and protocol

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.

For more information about

membership and other services,

please refer to our website:

www.modbus.org

Newsletter Editor:

Lenore Tracey

(lenore@modbus.org)

Modbus Organization, Inc.

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.

Member News

Reliability: High and Costs: Low

For a wastewater treatment

plant, reliability is of great im-

portance. The removal of waste-

water and stormwater in extreme

situations must happen when

required. Costs are also impor-

tant, and the key is to ensure

cost-effectiveness without com-

promising the reliability and sus-

tainability of the wastewater

treatment plant.

At Bjerringbro Wastewater

Treatment Plant in Denmark,

data registered by Dedicated

Controls is effectively transmit-

ted wirelessly via a CIM 250

communication interface module.

This has reduced the need for

manual inspection, improved pre-

ventive maintenance and en-

sured reliability of the wastewa-

ter facility.

Bjerringbro is located in mid-

Jutland, Denmark. The Bjerring-

bro Wastewater Treatment Plant

is one of 22 wastewater treat-

ment plants serving 250 pumping

stations operated by Energi Vi-

borg. Bjerringbro Wastewater

Treatment Plant has 35 pumping

stations, four of which run

Grundfos pumps transmitting

data wirelessly via CIM 250.

The Situation

Prior to the installation of the

wireless solution at the pumping

stations connected to the Bjer-

ringbro Wastewater Treatment

Plant, manual inspections were

necessary on a weekly basis for

local pumping stations and daily

for main pumping stations, to

ensure correct operation and to

detect possible faults. This re-

quired that staff be present at

the treatment plant every day of

the week, all year round.

Previously, the warning sys-

tem at one of the local pump-

ing stations consisted of

lamp placed high up on a

lamppost; and reaction to a

warning depended on the

lamp being seen and reported!

Today, wireless transmission

sends the full register of

pump pit activity every ten

minutes to the SCADA system

at Bjerringbro Wastewater

Treatment Plant.

The Grundfos solution

Using the terrain cabinet at

the Engvej Øst local pumping

station as an example, the

robust cabinet includes a me-

Sewage pump controller with a CIM 250 mod-

ter and a sewage pump con-

ule and GSM/GPRS modem are to the right.

troller (Dedicated Controls)

with a CIM 250 module that

has a GSM/ GPRS modem with

Winpager software – a log pro-

its own IP address and mobile

gram for SCADA on the com-

phone number. The use of a SIM

puter at the treatment plant –

card to establish the wireless

sets the schedule, ensuring the

connection makes installation

alarm is sent to the correct per-

easy, as the GSM/GPRS operator

sonnel at the right time, accord-

delivers the communication in-

ing to five pre-determined levels

frastructure.

of alarm situations and response

times.

“Wireless transmission

means we get data here and

now – and that’s data we

can use,”

says Kaj Lorenzen,

Driftsleder, Bjerringbro Ren-

seanlæg.

The data transmitted includes

the main status of the pump pit

and pumps and users can re-

quest active alarms and warn-

ings.

The types of alarms include sew-

age overflow, low flow, dry run-

ning, under-voltage, blocked mo-

tor/pump, over-temperature, and

others that can be adapted ac-

cording to the user's needs.

Currently, there are about 200

of these cabinets installed in

Denmark with Dedicated Con-

trols transmitting wirelessly via

the CIM 250 module.

Data is communicated wirelessly

every 10 minutes to the central

SCADA system. In an alarm

situation, the SCADA system

ensures correct alarm handling.

Member News

Wireless Water...

Member News

Comtrol Announces

Modbus Router

Comtrol Corporation

an-

nounced Modbus Router, the lat-

est firmware application for its

DeviceMaster UP Industrial

Gateway family of products. The

Modbus Router firmware was

developed to provide network-

wide Modbus connectivity be-

tween a wide variety of Modbus

masters and local and remote

Modbus slaves. Modbus Router

provides a highly flexible and

easy-to-use connectivity solution.

What can Modbus Router do?



Simultaneously connect up to

123 Modbus masters to as

many as 255 Modbus slave

device(s)

Member News

cont’d from pg 3

The Outcome

The immediate benefits of the

wireless communication offered

by the CIM 250 arise from the

system showing how a pumping

station is running over an entire

day. This helps save time and

money by reducing the need for

manual inspections and helping

make better planning possible.

In time, this means greater reli-

ability from better preventive

maintenance.

Two-port version of

Anybus CompactCom

HMS Network's

two-port ver-

sion of Anybus CompactCom for

Modbus TCP is a fast and easy

way for industrial device manu-

facturers to achieve connectivity

to Modbus TCP. It also reduces

the need for expensive external

switches and cuts down on fac-

tory wiring since the module

comes with a built-in switch of

its own.

The new two-port Modbus TCP

module includes an integrated

switch that makes it possible to

build networks in normal field-

bus style (daisy chain) rather

than connecting all devices

through an external switch. This

reduces the need for expensive

external switches.

Personnel only get called out if

absolutely necessary and they

can act earlier. In addition, the

wireless system provides opera-

tional data for control and statis-

tics. This increases the possibil-

ity of even greater measures for

ensuring maintenance planning,

operational reliability, and also

for optimising efficiency in the

future, because all data is saved

in a database.



Automatically detect local

slave devices and route mes-

sages



Connect serial Modbus mas-

ters to Modbus TCP net-

works and remote Modbus

slave devices



Convert Modbus protocols,

such as Modbus/TCP to Mod-

bus RTU/ASCII



Deliver diagnostics and

status pages to enhance

maintenance and problem-

solving capabilities



Solve common problems such

as relocating devices or con-

necting additional Modbus

masters to an existing instal-

lation

See

Comtrol’s Modbus Solu-

tions web page

for more info.

Advertise on the

Modbus.org Website

With

a half million pages served to

almost 30,000 unique visitors each

month,

what better place to advertise

your Modbus devices and software ?

for a rate sheet. A special

member's discount makes banner

advertising an even better deal when

you join the Modbus Organization.

The

Anybus CompactCom

mod-

ule acts as a slave on the Modbus

TCP network. It is available with

and without housing and is about

the size of a compact flash card.

The core of the module is com-

posed of HMS's NP30 microproc-

essor with its integrated fast

Ethernet controller along with

RAM and Flash memory for the

Modbus TCP device software

stack.

Member News

Modbus Discussion

Member News

Modbus Discussion

Q&A from the Modbus Discussion Forum...

Modbus writing 16-bit signed (-) values

neilrudds asked:

Hi, I'm new to the forum and

quite new to the Modbus protocol

and I'm hoping someone can help

me with my Modbus problem.

I am using RS485 to communi-

cate with a generator engine con-

troller. The controller stores a

series of event records across sev-

eral string type registers that

contain firstly date, time and

event log reason; secondly the

state of all inputs/outputs of the

engine (this works well and is not

the issue).

The issue is:

To acquire this data I must first

write to a 16-bit signed register

the actual ID of the event record

before I can read out the data.

The record ID's range from 0 to

approx. -1200 depending on the

records logged.

I have had success writing from 0

to -128 and the correct records

are then contained in the appro-

priate registers, but after -128, I

have many problems. For exam-

ple, when trying to write -384, I

am actually given record -128 but

-385 is ok and gives me the cor-

rect record. And again writing -

256 give me -256 but -257 gives

me -1. I have looked at the binary

values etc. and cannot see a prob-

lem.

Any help is greatly appreciated!

Rob replied :

It sounds like something some-

where is getting 8-bit and 16-bit

words confused.

8-bit signed numbers range from

-127 to +128

16-bit signed numbers range

from -32766 to +32767

If you are familiar with the "2s

Compliment" notation you will

understand how negative num-

bers are encoded - i.e. if the MSB

is SET then the number is nega-

tive. http://en.wikipedia.org/wiki/

Two%27s_complement.

In your case it appears that when

you write a value where bit 8 is

set (i.e. the MSB of an 8-bit word)

it will appear as a negative inte-

ger value. I suspect from your

symptoms that you are either

writing 8-bit words or your device

is expecting 8 bits instead of 16.

Lynn Linse suggested:

This isn't really a Modbus prob-

lem as Modbus literally moves all

registers as 'unsigned 16-bit'.

Modbus is the delivery truck &

doesn't care what's in the pack-

age.

The problem is in how your code

is packing your signed integer

into that unsigned 16-bit word.

Your signed INT is likely 32-bit if

a PC or modern embedded sys-

tem, but perhaps 8-bit if your

system is trying to highly mini-

mize data memory usage.

Since a PC is also little-byte first

and Modbus is big-byte first, this

makes packing a signed integer

from 'host form' to 'Modbus form'

tricky.

I can't explain how you accom-

plish this, but since the most

common design is something

like:

modbus[0] = (X >> 8) AND 0xFF

modbus[1] = (X AND 0xFF)

Your symptom sounds like your

first equation is always resulting

in 0xFF. The shift-right (>>) op-

eration may have unexpected

consequences on a signed inte-

ger in some systems.

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