Task configuration

The PROFINET controller protocol must always be linked with a task. The protocol is also processed with the set task time. Theoretically the controller can also be jointly processed, for example, via a PLC or NC task. However, if a PLC project, for example, is stopped (e.g. by restart or debugging), this results in the PROFINET part also being stopped. In order to avoid such a side effect is it advisable to always create a free-running SyncTask.

It must be ensured that the task cycle lies in a PROFINET cycle, i.e. for PROFINET the basic cycle is 31.25 µs. This cycle is then always multiplied by the SendClockFactor (SCF) to obtain the basic cycle. The SendClockFactor is usually set to 32 for RTClass1. This is also the minimum PN cycle for RTClass1 for the Beckhoff PROFINET controller and results in the smallest cycle time of 1 ms. Further reductions take place using a ReductionRatioFactor. This always corresponds to a multiple of the minimum PN cycle.  For RTClass1 the smallest cycle must always be doubled (permissible cycle times (for RTC1) with an SCF of 32 are 1, 2, 4, 8,…, 512).

The SCF can and must be reduced in order to achieve faster cycle times for RTClass3 as well. This is presently at least 16 for a Beckhoff IRT controller (EL6632), which corresponds in turn to a basic cycle of 500 µs. In the case of such a decrease of the PROFINET cycle, it must be noted that the time of the triggering task must also be adapted accordingly.