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Industrial Communication ProtocolsWhite Paper
Introduction to ModbusModbus communication protocol is a messaging structure developed by
Modicon in 1979. It is used to establish a master-slave or client-server
communication between intelligent devices. The intelligent devices
can be a PLC, HMI, PC, Distributed Control Systems (DCS), Supervisory
Control and Data Acquisition Systems (SCADA) etc. Modbus protocol is
not industry specific and can be used in a wide variety of industries such as
factory automation, building automation, process control, oil & gas, traffic
& parking, agriculture & irrigation, water & wastewater, pharmaceutical and
medical, material handling etc.
Modbus protocol can be operated via the
following communication methods:
• Modbus RTU or Modbus over serial – This
communication method or interface can
be RS-485, RS-232, RS-422 and RS-423.
Generally, in this interface, the Modbus
devices would require the receive wire (RX),
the transmit wire (TX) and the ground wire
(GND) to exchange data between the Modbus
devices. The interface can be either half
duplex or full duplex. Typically, all intelligent
devices can be configured for both half duplex
and full duplex.
• Modbus™ TCP/IP – In this communication
method, the Modbus data is wrapped around
TCP/IP internet protocols and then the data is
transmitted over standard internet. A standard
RJ45 Ethernet port can be used to connect
the various devices for data transfer. Modbus™
TCP/IP can be defined as an open standard
implementation of Modbus on internet
protocols.
• EtherNet/IP™ - EtherNet/IP™ is an
application layer/industrial protocol that is
built on the standard TCP/IP stack, where
TCP means transport control protocol and
IP means internet protocol (IP). EtherNet/
IP™ uses standard Ethernet hardware and
operates over Ethernet using the common
industrial protocols (CIP) – ControlNet &
DeviceNet and the TCP/IP protocol stack.
Although EtherNet/IP™ was developed by
Rockwell Automation for its Allen Bradley
line of controls, it is now considered an open
standard and is managed by Open DeviceNet
Vendors Association (ODVA).
FIGURE 1. ETHERNET/IP™ APPLICATION LAYERS
FTP HTTP OPC CIP Modbus SNMP
UDP
OSPF
ARP
IGMP
RARPIP
IEEE 802.3 Ethernet
IExplicitMessaging
ImplicitMessaging
EthernE 802 33
ExplicitMessaging
TCP
Application
Transport
Network
Data LinkPhysical
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Industrial Communication Protocol White Paper
It is to be noted that the WMPR receiver only uses “Explicit Messaging” for
exchange of non-cyclic and non-time critical data between the devices
in the EtherNet/IP™ network. Explicit messaging uses the TCP/IP stack
and has a request/reply or client/server relationship. The client sends a
request to the server and the server responds to the request. This request
can be either read/write in nature. In our world, the client device can be
either a fieldbus coupler module or a host controller device and the server
device is the WMPR receiver module.
Note: For more information on Modbus™ RTU, Modbus™ TCP/IP and
EtherNet/IP™ please refer to www.modbus.org; www.rockwellautomation.
com & www.odva.org
Data Exchange between wireless receivers – WDRR/WMPR and Fieldbus Couplers WMPR Series: The WMPR Series is a reliable DIN rail or panel-mountable
wireless receiver that can accept 14 digital signals (PNP or NPN type) from
wireless Limitless™ switches or accept 14 analog signals from wireless
analog sensors. The WMPR receiver is menu driven through the use of
function buttons and an easy-to-read LCD display. The LCD menu allows
the user to see the nodes status, configure nodes and update receiver
functionality.
The WMPR receiver has EtherNet/IP™ as the
communication protocol. That means, it can
push all of the relevant information such as
nodes I/O Status (both digital and analog), unit
types of analog signals, battery level indication,
radio frequency signal strength, radio transmit
power type, field device type, radio transmitter
type, sensor update rate, IP address etc. through
the EtherNet/IP™ output. It has a standard RJ45
Ethernet port which needs to be connected to
the RJ45 port of the fieldbus coupler via a Cat5e
(twisted pair) or Cat 6 (standard) Ethernet cable
to establish data communication between the
two devices.
If the end user wants to display the data in a
host controller such as a PLC or HMI that has
Modbus™ TCP/IP protocol, then it is required
to connect the fieldbus coupler to the host
controller via a Cat5e or Cat 6 (standard)
Ethernet cable.
FIGURE 2: DATA EXCHANGE BETWEEN WMPR AND ETHERNET/IP™ OR
MODBUS™ TCP/IP NETWORK
Fieldbus CouplerEthernet IP or
Modbus TCP/IPNetwork
Honeywell WirelessSystem
PLC
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Industrial Communication Protocol White Paper
To interface the WMPR with a host controller device, it is required that the
WMPR is connected to an EtherNet/IP™ compliant host controller and
upload the electronic data sheet (EDS) of the WMPR to the host controller
device. This step allows the object model of the WMPR to transition into
the electronic datasheet (EDS) which allows the unique MAC ID of the
WMPR to be associated with the various parameters of the object model.
The WMPR Object Model (Figure 3 - WMPR Object Model) describes the
different object models such as common objects, the application objects
and the assembly objects.
Common Objects include: Identity Object, Message Router Object,
Connection Manager Object, Parameter Object and Link Objects
FIGURE 3: WMPR OBJECT MODEL
Note: For more information on the WMPR Object
Model, please refer to the document “EtherNet/
IP™ Object Mode, P/N 32308916” on the
Honeywell website.
For the latest version of the EDS file, please refer
to the Honeywell website.
WDRR Series: The WDRR Series is a reliable DIN
rail or panel-mountable wireless receiver that
can accept 14 digital signals (PNP or NPN type)
from wireless limitless switches. The WDRR
receiver then communicates the digital signals
which is basically the wireless limitless switch’s
status i.e. whether the switch is open or closed to
a host controller device such as a PLC, DCS and
SCADA that has physical I/O modules. It also
has an output for lost RF communication and
another output for low battery voltage.
Once the WDRR receiver obtains the status
of the digital input of the Limitless™ switch,
the information is replicated in the WDRR’s
output terminals. Then it is required to hardwire
the output terminals of the WDRR receiver
to individual input terminals on the WAGO or
Beckhoff fieldbus coupler or any host controller
device with physical I/O modules.
Connection Manager Object(06)
IdentityObject
(01)
ParameterObject Instances
(0F)
MessageRouter Object
(02)
Link Object F6TCP/IP F5
AssemblyObject Instances
(04)
ApplicationObject Instances
(various)
ExplicitMsg I/O
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Industrial Communication Protocol White Paper
FIGURE 4: DATA EXCHANGE BETWEEN WDRR AND MODBUS™ TCP/IP
NETWORK
Inpu
ts
Out
puts
WDRR Receiver Modbus TCP/IP
SS3(Sensing/Switching Device 3)
SS2(Sensing/Switching Device 2)
SS1(Sensing/Switching Device 1)
Modbus TCP/IP Network
PLC
Note: For more technical information on the WDRR and WMPR receiver
modules, please refer to the device’s datasheet on the Honeywell website
http://sensing.honeywell.com
When to use WMPR vs WDRRThe usage of WMPR vs WDRR is very application specific and may be
dependent on an existing control systems layout. To understand this
better, let’s take a look at the following real time application scenarios.
• If a customer already has a Fieldbus Coupler or some type of host
controller device such as a PLC or HMI, almost 90 percent of the time,
a Fieldbus Coupler/PLC/HMI will have some type of communication
protocol such as EtherNet/IP™, Modbus™ TCP/IP, Modbus™ RTU or
Profinet. In these types of system settings, the WMPR would be an ideal
candidate as it supports EtherNet/IP™ protocol.
However, there are many generic PLCs and Fieldbus Couplers out there
in the market that do not support any type of communication protocols.
These PLCs/Fieldbus Couplers can only support hardwire I/O signals
whether it is digital, analog, temperature, etc. In this type of scenario the
WDRR would be a good alternative.
• Generally, the cabinets which house control system hardware such as
Fieldbus Couplers, PLCs, I/O Modules, Power Supplies, Relay Module,
etc. are very heavily wired (Figure 5). In these types of settings, the
WMPR would be perfect as there is no wiring involved for Inputs and
Outputs. The status of all of the 14 digital/analog outputs from the
WMPR will be communicated to the host controller via a single standard
Ethernet cable. Less wiring will make the control system cabinet safer,
easy to identify parts and less time consuming for troubleshooting if
necessary.
However, if there is ample space available
for wiring in the control cabinet and if the
existing controllers do not support any type of
communication protocols, then WDRR would be
a very good alternative.
• Say a customer has a Fieldbus Coupler or
a PLC that is currently running on protocol
EtherNet/IP™, then another option might be
needed. Typically, these types of devices have
two to four RJ45 ports available per device.
If there are other Ethernet systems such as
a VLAN Networks, PC, DCS system, SCADA,
etc. already plugged in to the 4 available RJ45
ports of the Fieldbus Coupler/PLC, then there
is no RJ45 port available for the WMPR device.
In this scenario, the WDRR would come in
handy, as the Fieldbus Couplers/PLCs has
the ability to add I/O racks into an existing
controller.
• WMPR can support both analog and digital
signals. WDRR can only support digital
signals. So, for wireless applications involving
Honeywell’s wireless pressure sensors
(WPS Series), the WMPR would be the
recommended receiver module. Furthermore,
the WMPR would enable an operator to
change the update rate of the WPS series
analog sensors over wireless. This can be
a huge benefit especially if the sensors
are installed in places that are not easily
accessible.
– PAGE 5 –
Industrial Communication Protocol White Paper
• For autonomous time-critical applications, the WMPR would be a
perfect fit. The WMPR receiver module supports EtherNet/IP™ protocol
which is much faster than any existing serial communication protocols.
The WMPR can provide a wide variety of data points such as nodes
device status, I/O status, battery life indication, and network signal
strength which is typically required by a host controller to automate a
wireless network.
FIGURE 5: CONTROL SYSTEM HARDWARE
WAGO fieldbus coupler specifications: Fieldbus coupler part numbers (Factory recommended)
• Bus controller module: 750-352
• Power supply module: 750-602
• I/O module: 750-1405
• End module: 750-600
• Protocols: EtherNet/IP™, Modbus™ TCP/IP
• Baud rate: 10/100 Mbit/sec, full or half duplex
• Buscoupler connection: 2 x RJ45
• Number of I/O modules: 64
• Number of digital inputs per I/O module: 16
(PNP or NPN)
Note: For more technical information on the
WAGO fieldbus coupler, please refer to the
device’s datasheet at WAGO website http://www.
wago.us. There are many options available for the
bus controller module, power supply module, I/O
module and the end module.
FIGURE 6: WAGO FIELDBUS COUPLER WAGO Modbus™ TCP Coupler
Ethernet cable tomodbus network
Ethernet O/P fromHoneywell WMPRreceiver to WAGOcoupler RJ45
Digital input wired from HoneywellWDRR receiver
WAGO PN 750-352ETHERNET™ TCP/IP FIELDBUS
CONTROLLER WAGO PN 750-60224 VDC POWER SUPPLY MODULE WAGO PN 750-1405
16 CHANNEL DIGITAL INPUT MODULE(Can accept up to 64 I/O modules, thereby
supporting up to 1024 digital inputs)
WAGO PN 750-600END MODULE
For more informationsensing.honeywell.com
Honeywell Sensing and Productivity Solutions 1985 Douglas Drive North
Golden Valley, MN 55422
1-800-537-6945
www.honeywell.com
Beckhoff Fieldbus coupler specifications: Fieldbus coupler part numbers (Factory recommended)
• Bus controller module: BK9000/BK9050
• Power supply module: Built into the bus controller module
• I/O module: KL1154
• End module: KL9010
• Protocols: EtherNet/IP™, Modbus™ TCP/IP
• Baud rate: 10/100 Mbit/sec, full or half duplex
• Buscoupler connection: 1 x RJ45
• Number of I/O modules: 64
• Number of digital inputs per I/O module: 4 (PNP/NPN - configurable)
Note: For more technical information on the Beckhoff fieldbus coupler,
please refer to the device’s datasheet at the Beckhoff website https://www.
beckhoff.com . There are many options available for the bus controller
module, I/O module and the end module.
FIGURE 7: BECKHOFF FIELDBUS COUPLER
KL9010BECKHOFF
Ethernet O/P from Honeywell WMPRreceiver to Beckhoff coupler RJ45
Digital input wired from HoneywellWDRR receiver
Output to modbusnetwork
Beckhoff Modbus™ TCP Coupler
Ethernet TCP/IP BK9000,BK9050 Digital Input KL1154, KL1164
Configuration interface
Address selector
Ethernet RJ 45
BK9000, BK9050 I Ethernet TCP/IP Bus Couplers
Beckhoff PN BK9050(Can accept up to 64 I/O terminals and
one end terminal)
Beckhoff PN KL1154(4-channel digital input terminal)
Beckhoff PN KL9010(End terminal)
Top view Top view
Power-LEDs
K-bus
Power contacts
Input forpower contacts
Ethernet RJ 45
Signal LED1Signal LED3
Input 1
Power contact+24 V
Power contact DV
Input 3 Input 4
DV
+24V
Input 2
Signal LED4Signal LED2
KL9010System Terminals
BK9000 BK9050
+60° C
-25° C
Both of the fieldbus couplers namely – WAGO
and Beckhoff have the ability to accept digital
signals from the WDRR receiver. All of these
fieldbus couplers are designed for fieldbus
communication in both EtherNet/IP™ and
Modbus™ networks. The fieldbus couplers have
standard RJ45 Ethernet ports. So it is possible
to transfer the Limitless™ switches I/O status to
a host controller via protocols EtherNet/IP™ or
Modbus™ TCP/IP as long as the host controller
supports either of these two protocols. A Cat5e
(standard) or a Cat 6 (twisted pair) cable can be
used to connect the fieldbus couplers to a host
controller device.
Limitless™ is a registered trademark of Honeywell International Inc. EtherNet/IP™ is a registered trademark of ODVA, Inc.Modbus™ is a registered trademark of Schneider Automation Inc.
002415-1-EN | 1 | 02/2016© 2016 Honeywell International Inc.
Industrial Communication Protocol White Paper