Greetings. In order for my function block (written in ST) to work properly, I need to get the cycle time during which it is called. How can I do this?

Hi Pavel, Welcome to the Community! You can use the RTInfo function block from the BRSystem library to get the task’s cycle time.

Thanks Marcus! RTInfo inside the function block will be called every cycle, although 1 time would be enough for me. Or should I not worry about it?

Hi Pavel @Pavel_Bezrodnyi , that should be a ‘cheap’ operation, but you can check this with the profiler. btw: an elegant way to call such ‘one time operations’ would be to check the rising edge of an ‘Enable’ or ‘Execute’ input of your function block.

Hi, I want to add: Usually inside a FUB you implement a state machine, so doing such an operation is a thing of one step only. Also, you can always remember the value somewhere in some “Internal” structure and only call the FUB in case the value is still zero. Note: Often times I see people who us…

Yes, I agree, I will highlight the INIT state in the internal finite automaton to get the cycle time and validate the input parameters. TON / TOF and other timers will not work for me, because I need to change the output value from 0 to MAX in a given time (input parameter) by ramp. For this purpos…

I guess you could still use a TON :smiley: TON_Ramp.PT := InputTime; TON_Ramp(); IF TON_Ramp.IN THEN OutputValue := TIME_TO_REAL(TON_Ramp.ET)/TIME_TO_REAL(TON_Ramp.PT); ELSE OutputValue := 0.0; END_IF Edit: See Christophs answer below: Only precise down to 10ms (TON base)

Hi, there are, as your usecase shows, cases where it’s definitely legit to do those calculations. I just often enough stumbled upon the highlighted wrong (imo) usage of it and wanted to point to it :slight_smile: I have also seen people count cycles to implement timings, which is even worse since i…

Marcel, thanks for the interesting solution! Hmm, maybe I should really stop using cycle time, I’ll think about it, thanks!

don’t underestimate the counting of cycles. TON works on a 10ms base so it is less precise. B&R Online Help (br-automation.com)

If you need the exact information of time exceeded between 2 calls, you also could use the AsIoTimestamp() function, which delivers a actual system time counter in microseconds. This then has to be done cyclic, and you always have to store the timestamp value of the last call also. As it’s a DINT v…

Cycle time in FB

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Pavel_Bezrodnyi (Pavel Bezrodnyi) September 24, 2024, 6:20am 5

Thank you, Christoph.
I’ll think about it.

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Cycle time in FB

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