Dear experts, 

I need to design a control loop with PID which I want to place in OB35 with default interrupt interval 100 ms.

The CPU is 315-2DP. Of course it cannot be guaranteed that cycle interrupt will always be 100 ms. Usually it is 100 ms with + or - some jitter value. I know the jitter is random in its nature, but I'd like to know this:

1. Is jitter dependant on specific CPU or the main cause is the user program OB1 and other logic?

2. Is there any document in which I can find out the worst case for the jitter, is it for example 100, 200 or 300 us?

Thank you.

Jasner

1. Is jitter dependant on specific CPU or the main cause is the user program OB1 and other logic?

Main cause are higher priority level OBs.

Jasner

2. Is there any document in which I can find out the worst case for the jitter, is it for example 100, 200 or 300 us?

No (because of the above). You can find best case here.