Cycle time for PROFIBUS configuration

For the PROFIBUS configuration, it is recommended to use a separate PROFIBUS task to retrieve the data as quickly as possible from the PROFIBUS controller's (PBS) receive memory.

The task should be as fast as possible (short cycle time), otherwise the task cannot pick up the PROFIBUS data in time. However, a cycle time that is too short is also not recommended, as otherwise the cycle time will be exceeded. If the task is slow (long cycle time), the data cannot be retrieved from the receive memory and errors occur on the PROFIBUS side (No Resources - RR).

With one to two slaves, the PROFIBUS task should take 2 ms, with three to four slaves 4 ms. Use the settings to check the CPU load of the task; you can then optimize it if necessary. These settings apply to a PROFIBUS velocity of 12 Mbit/s. If you are allowed to use lower PROFIBUS speeds, the cycle time may be higher than recommended.

In addition, if you use acyclic PROFIBUS communication, you should not run this via the PROFIBUS task, but create a low-priority task with a higher cycle time, e.g. from 20 ms.

Never go to the limit, give the system enough leeway, approx. 60...70 % CPU load should be the limit.