Data Exchange - WAGO -I/O-SYSTEM 750 User's Installation And Configuration

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 re-
sponse 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.
Modular I/O System
ETHERNET TCP/IP
1 connection for HTTP (reading HTML pages from coupler) and
3 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.
Fieldbus coupler 750-342 • 31
Data exchange