Lenze I/O system 1000 - Modbus TCP communication; 10.1 About Modbus TCP

10 Modbus TCP communication
10.1 About Modbus TCP
569
Lenze · I/O system 1000 · Reference Manual · DMS 5.0 EN · 09/2016 · TD17
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
10 Modbus TCP communication
10.1 About Modbus TCP
Typical fieldbus systems are divided into master and slave systems. Master systems are CPs coupled
to the CPU that which allow remote programming and visualisation of the corresponding CPU and
a data exchange between several TCP/IP nodes.
Slave systems are "data collectors" which provide the requesting master with the I/O data of the
connected modules.
The Modbus TCP bus coupler module described here is a slave system. Since, however,
communication is executed out via TCP/IP, the slave system is called server and the master is called
client.
The Modbus TCP bus coupler module serves to connect up to 64 I/O compound modules via
Ethernet. Up to 8 clients can communicate simultaneously with the bus coupler.
Automatic address mapping
After switch-on, the bus coupler module identifies the I/O compound modules connected via the
backplane bus and adds them to the address range. Address mapping provides one area for input
data and one area for output data. The integrated web server provides access to the current
mapping. Here, you can also parameterise your modules.
Communication
The Modbus TCP bus coupler module is connected to the I/O compound modules via the backplane
bus. It collects their data and makes them available as "server" (slave) to a higher-level "client"
(master system).
Communication is executed via TCP/IP Modbus TCP protocol where TCP/IP packets are transmitted.
In reverse, the bus coupler module receives the data addressed via IP address and port and transmits
them to its output peripherals.
Protocol
Protocols define regulations or standards for communication. A generally accepted model for the
standardisation of the complete computer communication is the ISO/OSI layer model consisting of
seven layers which manage the use of hardware and software.
Layer Function Protocol
7 Application layer Modbus TCP
6 Presentation layer
5 Session layer
4 Transport layer TCP
3 Network layer IP
2 Data link layer (protection)
1 Physical layer (bit transmission)