Frequently Asked Question

System CPU is a general purpose processor which can be utilized for different assignments:

• Simulation of low dynamics phenomena of certain electrical domain components
• Executing Signal processing portion of the model

A few examples of electrical domain components with low dynamics phenomena that utilize by default System CPU are Voltage RMS, Single Phase Constant Power Load and Current RMS. It is possible to free System CPU and map these components to User CPUs as well. This can be done by setting Pin to System CPU property in their properties box under Signal processing tab.

If Pin to System CPU is checked, signal processing code in the component will be mapped to the System CPU. In this case, execution rates for signal processing code inside the component are defined in: Model settings dialog box ⇒ Signal processing settings tab ⇒ System SP settings.

Execution rate 1 defines the fast execution rate for the system signals. This means that some functions in the component, such as integration and derivation, are operating on a faster execution rate. The default value is 100 µs and it can be changed.

Execution rate 2 defines the slow execution rate for the system signal. This means that some functions in the component, such as basic mathematical operations, are operating on slower execution rate. The default value is 50 ms and it can be changed.

Usage of faster or slower execution rate depends on the algorithm. For example, in the components such as RMS measurement, the integrator part operates on a faster execution rate and square root operation operates on a slower execution rate.

These two execution rates can be changed by the user to fine tune the performance of the simulated system. However, we don't recommend changing the default settings unless you know exactly what you want to achieve.

If Pin to System CPU is unchecked, signal processing code in the component will be mapped to the CPU according to standard CPU partitioning algorithm. In this case, it is possible to specify Fast and Slow execution rates for the component directly in its property box.

Using CPU marker component, it is possible to distribute evenly the Signal processing domain on all available CPUs. This component allows user tomap certain part of Signal processing domain on System CPU. Nevertheless, it is important to distinguish System CPU in different HIL devices. System architecture for HIL devices shows following:

• For HIL 402/602+/604 device, System CPU has significantly less processing power than User CPU and therefore, user should be careful with mapping Signal processing component group on the System CPU
• For HIL 404/606 device, System CPU is equivalent processor like User CPU.

For more information about partitioning Signal processing domain, please refer to the Signal processing circuit partitioning and Signal processing device partitioning videos.