>Why does the fuction is just run every 0.2 seconds in the simulation time?
You must be using a Variable-step solver. It changes the step size during the simulation, reducing the step size to increase accuracy when model states are changing rapidly and increasing the step size to avoid taking unnecessary steps when model states are changing slowly. You can set expected step size as "Fixed-step size" below.
>Next question is why is simulink generating alwys the same "random" signal? I want to implement a random noise signal in a bigger model, but i think i did not understand how it works.
When you set the same seed value like zero as default, the rand function always return the same set of value. You need changing the seed value of the rand function.
Example: Each time you run the model, you will get different seed values depending on the time of day.
rng(sum(clock))
