Safety and Productivity Solutions
Industrial Communication Protocols
White Paper
Introduction to Modbus
Modbus protocol can be operated via the
Modbus communication protocol is a messaging structure developed by
following communication methods:
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.
FTP
HTTP
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
FIGURE 1. ETHERNET/IP™ APPLICATION LAYERS
Application
• Modbus RTU or Modbus over serial – This
OPC
CIP
devices can be configured for both half duplex
Modbus SNMP
and full duplex.
• Modbus™ TCP/IP – In this communication
TCP
Transport
method, the Modbus data is wrapped around
UDP
TCP/IP internet protocols and then the data is
transmitted over standard internet. A standard
OSPF
Network
ARP
Explicit
Messaging
Implicit
Messaging
IIGMP
RJ45 Ethernet port can be used to connect
the various devices for data transfer. Modbus™
TCP/IP can be defined as an open standard
IP
RARP
implementation of Modbus on internet
protocols.
Data Link
Physical
E 802
3 Ethern
IEEE
802.3
Ethernet
• 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).
Industrial Communication Protocol White Paper
It is to be noted that the WMPR receiver only uses “Explicit Messaging” for
The WMPR receiver has EtherNet/IP™ as the
exchange of non-cyclic and non-time critical data between the devices
communication protocol. That means, it can
in the EtherNet/IP™ network. Explicit messaging uses the TCP/IP stack
push all of the relevant information such as
and has a request/reply or client/server relationship. The client sends a
nodes I/O Status (both digital and analog), unit
request to the server and the server responds to the request. This request
types of analog signals, battery level indication,
can be either read/write in nature. In our world, the client device can be
radio frequency signal strength, radio transmit
either a fieldbus coupler module or a host controller device and the server
power type, field device type, radio transmitter
device is the WMPR receiver module.
type, sensor update rate, IP address etc. through
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
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
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
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.
functionality.
FIGURE 2: DATA EXCHANGE BETWEEN WMPR AND ETHERNET/IP™ OR
MODBUS™ TCP/IP NETWORK
Honeywell Wireless
System
Fieldbus Coupler
Ethernet IP or
Modbus TCP/IP
Network
PLC
– PAGE 2 –
Industrial Communication Protocol White Paper
To interface the WMPR with a host controller device, it is required that the
Note: For more information on the WMPR Object
WMPR is connected to an EtherNet/IP™ compliant host controller and
Model, please refer to the document “EtherNet/
upload the electronic data sheet (EDS) of the WMPR to the host controller
IP™ Object Mode, P/N 32308916” on the
device. This step allows the object model of the WMPR to transition into
Honeywell website.
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.
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)
Common Objects include: Identity Object, Message Router Object,
from wireless limitless switches. The WDRR
Connection Manager Object, Parameter Object and Link Objects
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
FIGURE 3: WMPR OBJECT MODEL
a host controller device such as a PLC, DCS and
SCADA that has physical I/O modules. It also
Identity
Object
(01)
Parameter
Object Instances
(0F)
Application
Object Instances
(various)
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
Message
Router Object
(02)
output terminals. Then it is required to hardwire
Assembly
Object Instances
(04)
Link Object F6
TCP/IP F5
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.
Explicit
Msg
I/O
Connection Manager Object
(06)
– PAGE 3 –
Industrial Communication Protocol White Paper
FIGURE 4: DATA EXCHANGE BETWEEN WDRR AND MODBUS™ TCP/IP
NETWORK
Modbus TCP/IP Network
SS3
(Sensing/Switching Device 3)
SS2
(Sensing/Switching Device 2)
WDRR Receiver
Inputs
(Sensing/Switching Device 1)
Outputs
PLC
SS1
Modbus TCP/IP
Note: For more technical information on the WDRR and WMPR receiver
However, if there is ample space available
modules, please refer to the device’s datasheet on the Honeywell website
for wiring in the control cabinet and if the
http://sensing.honeywell.com
existing controllers do not support any type of
communication protocols, then WDRR would be
a very good alternative.
When to use WMPR vs WDRR
• Say a customer has a Fieldbus Coupler or
The usage of WMPR vs WDRR is very application specific and may be
a PLC that is currently running on protocol
dependent on an existing control systems layout. To understand this
EtherNet/IP™, then another option might be
better, let’s take a look at the following real time application scenarios.
needed. Typically, these types of devices have
• 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.
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
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.
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
• 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.
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 4 –
Industrial Communication Protocol White Paper
WAGO fieldbus coupler specifications:
FIGURE 5: CONTROL SYSTEM HARDWARE
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)
• For autonomous time-critical applications, the WMPR would be a
perfect fit. The WMPR receiver module supports EtherNet/IP™ protocol
Note: For more technical information on the
WAGO fieldbus coupler, please refer to the
which is much faster than any existing serial communication protocols.
device’s datasheet at WAGO website http://www.
The WMPR can provide a wide variety of data points such as nodes
wago.us. There are many options available for the
device status, I/O status, battery life indication, and network signal
bus controller module, power supply module, I/O
strength which is typically required by a host controller to automate a
module and the end module.
wireless network.
FIGURE 6: WAGO FIELDBUS COUPLER
WAGO Modbus™ TCP Coupler
Digital input wired from Honeywell
WDRR receiver
Ethernet cable to
modbus network
Ethernet O/P from
Honeywell WMPR
receiver to WAGO
coupler RJ45
WAGO PN 750-352
ETHERNET™ TCP/IP FIELDBUS
CONTROLLER
WAGO PN 750-602
24 VDC POWER SUPPLY MODULE
WAGO PN 750-600
END 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)
– PAGE 5 –
Industrial Communication Protocol White Paper
Beckhoff Fieldbus coupler specifications:
Note: For more technical information on the
Fieldbus coupler part numbers (Factory recommended)
• Bus controller module: BK9000/BK9050 (to be used with WDRR
receiver)
• Bus controller module: EL6652 (to be used with WMPR receiver)
• Power supply module: Built into the bus controller module
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.
• I/O module: KL1154
• End module: KL9010 (to be used with BK9000/BK9050) and EL9011
Both of the fieldbus couplers namely – WAGO
and Beckhoff have the ability to accept digital
(to be used with EL6652)
• Protocols: EtherNet/IP™, Modbus™ TCP/IP
signals from the WDRR receiver. All of these
• Baud rate: 10/100 Mbit/sec, full or half duplex
fieldbus couplers are designed for fieldbus
• Buscoupler connection: 1 x RJ45
communication in both EtherNet/IP™ and
• Number of I/O modules: 64
Modbus™ networks. The fieldbus couplers have
• Number of digital inputs per I/O module: 4 (PNP/NPN - configurable)
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
Beckhoff Modbus™ TCP Coupler
FIGURE 7: BECKHOFF FIELDBUS COUPLER
used to connect the fieldbus couplers to a host
controller device.
Ethernet TCP/IP BK9000,
BK9050
Digital Input
System Terminals
KL1154, KL1164
KL9010
+60° C
Ethernet O/P from Honeywell WMPR
receiver to Beckhoff coupler RJ45
Power-LEDs
-25° C
K-bus
Ethernet RJ 45
Digital input wired from Honeywell
WDRR receiver
Signal LED1
Signal LED3
Signal LED2
Signal LED4
Input 1
Input 2
+24V
Power contact
+24 V
Input for
power contacts
Output to modbus
network
DV
Power contact DV
Address selector
Configuration interface
Power contacts
Input 3
Input 4
KL9010
BECKHOFF
Top view
BK9000
Top view
BK9050
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)
For more information
sensing.honeywell.com
Honeywell Safety and Productivity Solutions
9680 Old Bailes Road
Fort Mill, SC 29707
1.800.537.6945
www.honeywell.com
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.
002415-2-EN | 2 | 08/2016
© 2016 Honeywell International Inc.
Beckhoff PN KL9010
(End terminal)