Reading cycle time on a TwinCAT 3 PLC

Question

Is there a way for a PLC program to know its own cycle time?

As a workaround, I can just add a persistent variable or a constant to tell it manually, but that's obviously error prone.

Answer 1

For TwinCAT3 this is available in PlcTaskSystemInfo (variable CycleTime). Combine it with the FB GETCURTASKINDEX to get the data you want.

See one example (though not cycle-time, but still same FB) here at AllTwinCAT.