YOKOGAWA STARDOM FCN-500, Engineering Manual

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<2. Basic Design and Function Design>
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TI 34P02K35-02E Jun. 6, 2018-00
2.2.3 Checking FCN-500, FCN-RTU Performance
Estimate the execution time of an FCN-500 or FCN-RTU control application from
the requirement specification and determine the CPU load.
SEE ALSO
For details on how to estimate performance, see Section 4.5.3, “Confirmation of Performance" of TI
"FCN-500 Technical Guide", Section 4.5.3, “Confirmation of Performance" of TI "FCN-RTU Technical
Guide".
The checking items described in this section is based on calculated values, which
should be verified by checking the actual CPU load during function test.
SEE ALSO
For details, see Section 5.5.1, “Checking CPU Load."
● Calculating Execution Time and CPU load of Control Application
The method for estimating the execution time of a control application depends on
whether the project uses NPAS POUs.
• For projects using NPAS POUs
For a project using NPAS POUs, determine the execution time as described in
the above-mentioned TI document, and calculate the CPU load using the
following formula:
NPAS_POU's execution time
Control task interval
CPU load (%) = x 100%
• For projects not using NPAS POUs
The above-mentioned TI document does not describe how to calculate the
execution time of a project not using NPAS POUs. This is because the
execution time of non-NPAS_POU blocks are very short and hence need not
be considered during the estimation phase.
TIP
In the CPU function specification description of the GS document “FCN Autonomous Controller
Functions (FCN-500)” or “FCN-RTU Low Power Autonomous Controller Functions”, the execution
speed is given as:
FCN-500s Execution speed: Approx. 10 µs per kilosteps in an IL program
FCN-RTUs Execution speed: Approx. 50 µs per kilosteps in an IL program
This means that about 10 µs (FCN-500) or 50 µs (FCN-RTU) is required to process 1 kilosteps of an
IL program block.
Each function such as AND or OR coded in IL is equivalent to 3 steps.
Therefore, the execution time of 1000 functions is about 30 µs (FCN-500) or about 150 µs (50 µs x
3, FCN-RTU).
Based on this calculation, about 195,000 functions (FCN-500) or about 65,000 functions (FCN-RTU)
can be processed within 10 milliseconds.