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SCL For cycle duration

Created by: JkRa at: 8/3/2018 2:42 PM (3 Replies)

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8/3/2018 2:42 PM	Rate (0)
JkRa Regular Member Joined: 2/4/2016 Last visit: 3/29/2023 Posts: 8 Rating: (0)	Hi, Please, how long does it take to perform all 100 iterations of the FOR cycle written as SCL function (theoretically)? Or better: How many iterations of FOR cycle can be processed in one OB cycle? Single or all? Is the return value then available in next call, or "somehow later"? Thank you. -- JkRa
	Last edited by: JkRa at: 8/3/2018 2:42:41 PM
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This contribution was helpful to 1 thankful Users hdhosseini

8/3/2018 5:02 PM	Rate (1)
KFoldesi Silver Member Joined: 9/8/2011 Last visit: 5/26/2023 Posts: 485 Rating: (74)	it will process all 100 iterations and PLC will hold up while it is happening (like windows freezing). Possibly causing a cycle time exceeded fault and stopping the PLC. Better to do the task over several cycles:
	A smart person learns from their mistakes A wise person learns from others mistakes
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8/3/2018 6:08 PM	Rate (1)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 6/8/2023 Posts: 6805 Rating: (1346)	Dear user, Please, how long does it take to perform all 100 iterations of the FOR cycle written as SCL function (theoretically)? Or better: How many iterations of FOR cycle can be processed in one OB cycle? Single or all? Is the return value then available in next call, or "somehow later"? Thank you. All iterations of a loop(in STL) that is FOR in SCL is performed in one cycle of CPU and the result is available at the end of 100 iterations calculation.If you try extensive code section on a large number of iterations, the overall cycle time of CPU will be extended dramatically if it is not strong enough.To calculate the rough execution time, convert the SCL FOR loop program t o STL , find the instruction list(OP list) for the CPU you are using and calculate the values.Check THIS for execution time required for each instruction. The other easy way to calculate the execution time is testing the only loop section on a real CPU and check the cycle time each time that is a parameter in OB1. I hope it helps, hdhosseini
	Last edited by: hdhosseini at: 8/3/2018 6:42:30 PM Last edited by: hdhosseini at: 8/3/2018 7:04:04 PM Demo Channel on Youtube
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8/7/2018 6:06 AM	Rate (0)
JkRa Regular Member Joined: 2/4/2016 Last visit: 3/29/2023 Posts: 8 Rating: (0)	Great, thank you both for aswers and explanations (I thought that LOOP in STL decreases its counter once per cycle until today). Cheers. --

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