Technical information

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Modicon M580 automation
platform
PlantStruxure Ethernet architectures
Industrial Ethernet communication services
Functions (continued)
Modbus standard communication protocol
Modbus, the industry communication standard since 1979, has been combined with
Ethernet Modbus/TCP, the medium for the Internet revolution, to form Modbus/TCP,
a completely open Ethernet protocol. The development of a connection to Modbus/
TCP does not require any proprietary component, nor purchase of a license.
This protocol can easily be combined with any product supporting a standard TCP/IP
communication stack. The specications can be obtained free of charge from the
following website: www.modbus.org.
Modbus/TCP, simple and open
The Modbus application layer is very simple and universally familiar with its 9 million
installed connections. Thousands of manufacturers have already implemented this
protocol. Many have already developed a Modbus/TCP connection and numerous
products are presently available.
The simplicity of Modbus/TCP enables any eld device, such as an I/O module, to
communicate on Ethernet without the need for a powerful microprocessor or a lot of
internal memory.
Modbus/TCP, high-performance
Due to the simplicity of its protocol and the fast speed of 100 Mbps Ethernet,
Modbus/TCP performance is excellent. This allows this type of network to be used in
real-time applications such as I/O scanning.
Modbus/TCP, a standard
The application protocol is identical on Modbus serial link, Modbus Plus, or Modbus/
TCP. This means that messages can be routed from one network to the other without
converting protocol.
Since Modbus is implemented on top of the TCP/IP layer, users can also benet from
IP routing, enabling devices located anywhere in the world to communicate without
worrying about the distance between them.
Schneider Electric offers a complete range of gateways for interconnecting a
Modbus/TCP network to existing Modbus Plus or Modbus serial link networks.
The IANA organization (Internet Assigned Numbers Authority) has allocated the
xed, well-known port 502 to the Modbus protocol. Thus Modbus has become an
Internet standard.
Modbus and Modbus/TCP are recognized by the IEC/EN 61158 international
standard as a eldbus. They are also compliant with the “Chinese National Standard”
managed by ITEI.
Interfacing CANopen with Modbus/TCP
CiA DSP 309-2 provides standardized mapping of CANopen data for transport on
Ethernet Modbus/TCP networks. The specication reserves Modbus function code
43/13 for this purpose. This function code is reserved exclusively for CANopen.
Modbus TCP/IP characteristics
Maximum size of data:
b Read: 125 words or registers
b Write: 100 words or registers
Functions (continued)
Modbus/TCP function codes dec hex
Bit
access
Read n input bits 02 02
Read n output bits 01 01
Read exception status 07 07
Write 1 output bit 05 05
Write n output bits 15 0F
Read 1 input word 04 04
Read n input words 03 03
Write 1 output word 06 06
Write n output words 16 10
Read device ID 43/14 2B/0E
Examples of Modbus/TCP function codes for accessing data
and diagnostics
Processors:
page 1/18
I/O architectures:
page 2/2
Software:
page 4/2
Ruggedized Modicon M580
modules: page 5/2
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