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LOOP problem in STL, Step7.

Created by: Najsel at: 1/28/2011 12:29 PM (4 Replies)

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1/28/2011 12:29 PM	Rate (0)
Najsel Posts: 19 Rating: (0)	I have some problems with my loop, for example: SET SAVE L 100 LOP1: T #loopcounter (BYTE > located in TEMP) L #test (BYTE > located in TEMP) + 1 T #test L #loopcntr LOOP LOP1 END: BE This statements will actually cause "#test" to constantly loop between 0-255(DEC), but in my thoughts I want it to loop between 0-100 because I transferred "100" to the #loopcounter. What's the problem? Seems like these loops is really hard to figure out how they really works because I've followed some examples.
Najsel Posts: 19 Rating: (0)
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1/28/2011 1:51 PM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 10/9/2024 Posts: 3024 Rating: (1054)	Hello Najsel you use a variable called "#loopcounter" as the loop counter at the start of the loop and one called "#loopcntr" at the end, is this just a typing mistake and they are in fact the same variable (which they need to be)? Let's assume they are and lets further assume that you are only calling this piece of logic in OB1, your observation would be correct! What happens is that the value of variable "#test"will be incremented to 100 in the first OB1 scan, followed by a count up to 200 in the secondOB1 scan, followed by a count to 45 in the thirdOB1 scan (its a BYTE which go back to zero once its reachesa value of 255) etc. etc.. All of the above will happen very fast ifyou were to observe the logic online that you may think the loop is doing something wrong when in fact it is working as it should. I hope this helps, but of not please upload your whole S7 project here for evaluation.
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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This contribution was helpful to 1 thankful Users hdhosseini

1/28/2011 2:46 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/6/2024 Posts: 6852 Rating: (1365)	Dear member One solution to the case fritz mentioned is to call the loop only for one time.The parameter "run" , when true guide the CPU to execute the loop only once and it is made to false in first execution round of loop.Check the following codes. Codes can be optimize but it is similiar to original codes provided. [code] A "reset" JCN RUN L 0 T "sum" RUN: A "run" JCN END L 100 LOP1: T "counter" CLR = "run" L "sum" + 1 T "sum" L "counter" LOOP LOP1 END: NOP 0[/code] BR
	Demo Channel on Youtube
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1/28/2011 3:59 PM	Rate (0)
Najsel Posts: 19 Rating: (0)	Thank u for answering me this fast! I see that I typed #loopcntr wrong in the beginning, just a mistake. But anyway, thank u guys for all the help. It's can be really hard sometimes when it goes to fast for the human eye. :) But loops is really great to have, saves alot of time.
Najsel Posts: 19 Rating: (0)
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This contribution was helpful to 2 thankful Users fritz hdhosseini

6/20/2017 9:08 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4767 Rating: (123)	New question published by Siemens- STL? is split to a separate thread with the subject STL, find a minimum value after which it ramps up. Best regards Min_Moderator

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