5. CONFIGURATION
5.6.3. OPC UA Server
For the performance tests of communication with OPC UA Server, projects were created for the PLC by declaring variables
of type INT.
All test scenarios have the following characteristics in common:
Projects with Machine Profile and MainTask Interval configured in 100 ms;
All variables of type INT are being modified every 100 ms interval. In the OPC UA protocol, only the variables that are
modified are reported to the OPC UA clients. In applications where few variables change frequently the performance of
OPC UA communication improves significantly;
The MainTask duration has been set to consume 10%, 30% and 60% of the configured interval of 100 ms. When
the duration of the MainTask is very high, there is little processing capacity for OPC UA communication, which can
significantly reduce its performance;
The “Publishing Interval” parameter was configured on the client in 1000 ms, which means that the variables that change
its value should be reported to the client every 1000 ms. A very low value in this parameter can significantly reduce the
performance of OPC UA communication;
The “Sampling Interval” parameter has been configured on the client in 500 ms, which means that the controller (server)
will detect changes of values in the variables every 500 ms to know which ones should be reported to the client. A very
low value in this parameter can significantly reduce the performance of OPC UA communication. It is recommended
that it be at least half of the “Publishing Interval”, and at most equal to “Publishing Interval”;
Encryption was not configured. If configured, there would be a slight reduction in the performance of OPC UA commu-
nication;
Only one OPC UA client was connected. Connecting multiple clients can significantly reduce the performance of OPC
UA communication.
The table below shows the interval between communications (which value should be 1000 ms according to the Publishing
Interval configured):
Total number of INT
variables in PLC
project
Variable update time in OPC UA Client
10% of CPU Busy 30% of CPU Busy 60% of CPU Busy
1000 1010 ms 1014 ms 1040 ms
2000 1013 ms 1017 ms 1472 ms
5000 1321 ms 1405 ms 2351 ms
Table 154: Communication Rate of an OPC UA Server
ATTENTION
The NAP165 application note analyzes the performance of OPC UA communication in
greater detail, including addressing the consumption of Ethernet communication bandwidth.
This application note also discusses concepts about the operation of the OPC UA protocol.
5.6.4. IEC60870-5-104 Server
The IEC 60870-5-104 Server driver is executed by the CPU in the same way as the other communication drivers Servers,
that is, in the background, with a priority below the user application and cyclically. The task of this The driver specifically
executes every 50 ms, and 1 driver execution cycle is enough to process and respond to requests. However, as it is a low priority
task, it is not guaranteed to be able to run at this frequency because depends on the percentage of free CPU (difference between
the MainTask interval and the time that the user application takes to be executed) and also concurrency with tasks from other
protocols configured in the CPU.
To help in the comprehension of the driver IEC 60870-5-104 Server performance are presented the result of some test done
with an IEC 60870-5-104 Client simulator, connected to a NX3030 running an IEC 60870-5-104 Server. The configured data
base was compose of 900 digital points and 100 analog points (all with quality and time stamp), and the MainTask was using
70 ms (of the 100 ms interval).
Time to complete a general interrogation command: less than one second
Time to transfer 900 digital events + 100 analog events: 6 seconds
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