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Execuation order

Created by: Per Olof at: 10/3/2010 10:43 PM (1 Replies)

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10/3/2010 10:43 PM	Rate (0)
Per Olof Posts: 311 Rating: (3)	Hello all, I have a question about the execution order in LAD. See attachement, my question is: In which order does the code run ? Is it correct to write like this ? Does the XOR function run before the compare functions ? Thanks Per Olof Attachment STEP 7 CPU 315.JPG (525 Downloads)
Per Olof Posts: 311 Rating: (3)
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10/4/2010 1:22 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 10/9/2024 Posts: 3024 Rating: (1054)	Per Olof ... my question is: In which order does the code run ? Is it correct to write like this ? Does the XOR function run before the compare functions ? Hello Per Olof Ladder logic execution in an S7 follows the "Left to right, Top to bottom" rule which in your case means that the XOR function does execute before the compare functions (and the "compare if MW4 if equal to 1" is executed before the "compare if MW4 if equal to 0") and yes, it is permissible to program like you did. Hint: If you change the view to STL you'll only have to read the statements top to bottom and toget a "clear" view of the execution sequence(albeit with some"odd" looking local memory usage and RLO/BR bit releated jumps and checks in it). You may also find the LAD/FBD/STL training video useful which you download from HERE. I hope this helps
	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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