4. Configuration
132
Maximum number of variables
communicating with a single
PLC
Maximum number of variables
declared in a single POU or GVL
Maximum number of PLCs in a
OPC Server
Maximum number of
simultaneous connections of an
OPC Server in a single PLC
Table 4-91. OPC Server Communication Limits
ATTENTION:
The Maximum number of simultaneous connections of an OPC Server in a single PLC is shared
with connections made with the MasterTool IEC XE. I.e. the sum of connections of OPC Server and
MasterTool IEC XE should not exceed the maximum quantity defined in Table 4-91.
The communication between the OPC 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 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 5.000 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.
Accessing data Through an OPC Client
After the configuration of the OPC 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 Server must be selected. In
this case the name is CoDeSys.OPC.DA. The Figure 4-47 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. Depending 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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