Data Exchange - WAGO -I/O-SYSTEM 750 Manual

86 Function Description
7.3

Data Exchange

With the fieldbus controller, data is exchanged via the MODBUS/TCP protocol
and/or the MODBUS/UDP protocol or EtherNet/IP.
MODBUS/TCP works according to the master/slave principle. The master
controller can be a PC or a PLC.
The fieldbus controllers of the WAGO-I/O-SYSTEM 750 are usually slave
devices. Thanks to the programming with IEC 61131-3, however, these
controllers can also assume the master function.
The master requests communication. This request can be directed to certain
nodes by addressing. The nodes receive the request and, depending on the
request type, send a reply to the master.
A controller can set up a defined number of simultaneous connections (socket
connections) to other network subscribers:
• 3 connections for HTTP (to read HTML pages from the controller)
• 15 connections via MODBUS/TCP (to read or write input and output data of
the controller)
• 128 connections for EtherNet/IP
• 5 connections (using the Ethernet.lib) via PFC (available in the PLC
function for IEC 61131-3 application programs)
• 2 connections for WAGO-I/O-PRO (these connections are reserved for
debugging the application program via ETHERNET. WAGO-I/O-PRO
needs 2 connections at the same time for the debugging. However, only
one programming tool can have access to the controller).
• 10 connections for FTP
• 2 connections for SNMP
The maximum number of simultaneous connections can not be exceeded.
Existing connections must first be terminated before new ones can be set up.
The Media Redundancy ETHERNET Controller is essentially equipped with three
interfaces for data exchange:
• the interface to the fieldbus (Master),
• the PLC function of the PFC (CPU) and
• the interface to the I/O modules.
Data exchange takes place between
• the fieldbus master and the I/O modules,
Manual
1.5.0
750-882 Media Redundancy ETHERNET Controller
WAGO-I/O-SYSTEM 750