5. CONFIGURATION
5.5.10.5. Limits of Communication with OPC DA Server
To communicate with the OPC DA Server, there are some limitations that must be respected for the correct functioning
of the application. There can’t be more than 20000 variables configured as available in the OPC DA Server for each PLC.
Therefore, 20000 variables is the maximum limit to communicate with a single PLC.
Furthermore, when configuring the variables to be available in the OPC DA Server, the quantity of declared variables in
each POU or GVL can’t exceed the limit of 5000. The table below presents the OPC DA Server configuration limits.
Maximum number of variables communicating with
a single PLC
20000
Maximum number of variables declared in a single
POU or GVL
5000
Maximum number of PLCs in an OPC DA Server 16
Maximum number of simultaneous connections of an
OPC DA Server in a single PLC
8
Table 131: OPC DA Server Communication Limits
ATTENTION
The Maximum number of simultaneous connections of an OPC DA Server in a single PLC
is shared with connections made with the MasterTool IEC XE. I.e. the sum of connections of
OPC DA Server and MasterTool IEC XE should not exceed the maximum quantity defined
in Table 131.
The communication between the OPC DA Server and the PLC uses the same protocol used in the MasterTool IEC XE
communication with the PLC. This protocol is only available for the Ethernet interfaces of the Nexto Series CPUs, it’s not
possible to establish this kind of communication with the Ethernet expansion modules.
When a communication between the OPC DA Server and the PLC is established, these two elements start a series of
transactions aimed at solving the addresses of each declared variables, optimizing the communication in data reading regime.
Besides, it’s also resolved in this stage the communication groups used by some Clients in order to optimize the communication.
This initial process demands some time and depends on the quantity of mapped variables.
The approximate time of this initial stage, with 5000 variables is about 2 minutes. In cases in which more variables are
used, this time can raise to up to 4 minutes, depending on the data type and network settings.
5.5.10.6. Accessing Data Through an OPC DA Client
After the configuration of the OPC DA Server, the available data on all PLCs can be accessed via an OPC Client. In the
configuration of the OPC Client, the name of the OPC DA Server must be selected. In this case the name is CoDeSys.OPC.DA.
The figure below shows the server selection on the client driver of the BluePlant SCADA software.
ATTENTION
The same way that in MasterTool IEC XE, some tools must be executed with administrator
privileges in the Operational System for the correct functioning of the OPC Client. Depend-
ing on the OS version, this privilege must be activated in the moment that the program is
executed. To do this, right-click MasterTool IEC XE icon and choose Run as Administrator.
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