Technical data

62 • BACnet/IP Controller 750-830
Data Exchange
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
3.1.6 Data Exchange
Exchange of process data takes place with BACnet/IP controllers using the
BACnet/IP protocol or the MODBUS protocol.
The BACnet/IP controller works according to the client server principle. The
client requests services from the server. It subscribes, for example, to changes
in value or sets limits for alarm/event reports. With its objects, the server maps
and executes the service requests of the client.
A controller can establish 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)
• 5 connections via PFC (available in the PLC function for IEC 61131-3 ap-
plication programs)
• 2 connections for WAGO-I/O-PRO CAA (these connections are reserved
for downloading and debugging the application program via ETHERNET.
WAGO-I/O-PRO CAA needs 2 connections at the same time for the de-
bugging. However, only a programming tool can have access to the con-
troller).
• 10 connections for FTP
• 2 connections for SNMP
The maximum number of simultaneous connections cannot be exceeded. Ex-
isting connections must first be terminated before new ones can be set up.
The BACnet/IP controller is essentially equipped with three interfaces for data
exchange:
• the interface to the fieldbus (master)
• the PLC function of the PFC (CPU)
• the interface to the bus modules
There is a data exchange between the fieldbus master and the bus modules, be-
tween the PLC function of the PFC (CPU) and the bus modules, and between
the fieldbus master and PLC function of the PFC (CPU). If the MODBUS
master is used as the fieldbus, access is made to the data using a MODBUS
function implemented in the controller.
Data access by the PFC is carried out with the aid of an IEC 61131-3 applica-
tion program. Data addressing varies greatly here.