Process Data Architecture; Data Exchange - WAGO 750 Series Manual

48 • Fieldbus coupler 750-342

Data exchange

3.1.4.3 Process Data Architecture

With some I/O modules, the structure of the process data is fieldbus specific.
In the case of an Ethernet TCP/IP coupler/controller, the process image uses a
word structure (with word alignment). The internal mapping method for data
greater than one byte conforms to the Intel format.
More Information
You can find the fieldbus specific process data architecture for all I/O
Modules of the WAGO-I/O-SYSTEM 750 and 753 in the chapter „ Process
Data Architecture for ETHERNET".
3.1.5 Data Exchange
Process data exchange with the ETHERNET TCP/IP fieldbus coupler occurs
via the MODBUS/TCP protocol.
MODBUS/TCP works according to the master/slave principle. The master is a
superimposed control unit, i.e. a PC or a PLC device. The ETHERNET
TCP/IP couplers of the WAGO-I/O-SYSTEM are slave devices.
The master makes a query for communication. Through adressing, this query
can be sent to a specific node. The nodes receive the query and return a
response to the master, depending on the kind of query.
A coupler can communicate with a certain number of simultaneous connections
(socket connections) to other network subscribers:
The maximum number of simultaneous connections cannot be exceeded. If
further connections are to be made, terminate existing connections beforehand.
For a data exchange, the ETHERNET TCP/IP fieldbus coupler is equipped with
two interfaces:
•
•
Data exchange takes place between MODBUS master and the bus modules.
The master accesses the bus module data via implemented MODBUS
functions.
• 1 connection for HTTP (reading HTML pages from coupler) and
• 5 connections via MODBUS/TCP (reading or writing input and output
data from coupler).
the interface to fieldbus (-master) and
the interface to the bus modules.
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP