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SOLVED> [S7-1200] Using more than 1 "OB1" - why?

Created by: William_B at: 11/3/2011 12:12 PM (2 Replies)

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11/3/2011 12:12 PM	Rate (0)
William_B Posts: 5225 Rating: (1198)	Hi all, The S7-1200 study continues for me. I read.. "Organization blocks for cyclic program execution" that "You can use multiple OBs (OB numbers >= 123)" That is like having more than 1 OB1. It would have made sens if the S7-1200 had more than one processor and the multiple cyclic OBs were running in parrallel. But this is not the case.. is it? Could someone please explain why you'd want to use more than one "OB1"? Does it have something to do with writing and re-using code?
William_B Posts: 5225 Rating: (1198)	Last edited by: William B. at: 11/4/2011 11:49 AM title: solved
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11/3/2011 12:40 PM	Rate (0)
fritz Diamond Member Joined: 10/7/2005 Last visit: 1/17/2025 Posts: 3030 Rating: (1058)	HelloWilliam B. here's my take on this: William B. That is like having more than 1 OB1. Correct William B. It would have made sens if the S7-1200 had more than one processor and the multiple cyclic OBs were running in parrallel. But this is not the case.. is it? No, it isn't. OB's that belong to the same priority class will be executed one after the other (i.e.when OB1 is done, the "second" cylic OB's will be called. William B. Could someone please explain why you'd want to use more than one "OB1"? Good question and something I wonder myself. Perhaps someone from the TIA Portal development team thought it would be a "cool" idea to allow this (coudl be sold as a "feature" that the classic Step 7/S7 PLC'sdo not have), perhapsit is because IEC61131 does not prohibit, perhaps the answer is as simple as "because you can"etc. etc. Truth be told, I can't think of any good reasons for this, but am open to suggestions. William B. Does it have something to do with writing and re-using code? Dont think so, that is the task of FC's and FB's. 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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11/3/2011 1:46 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/17/2025 Posts: 15541 Rating: (2465)	William B. Hi all, The S7-1200 study continues for me. I read.. "Organization blocks for cyclic program execution" that "You can use multiple OBs (OB numbers >= 123)" That is like having more than 1 OB1. It would have made sens if the S7-1200 had more than one processor and the multiple cyclic OBs were running in parrallel. But this is not the case.. is it? Could someone please explain why you'd want to use more than one "OB1"? Does it have something to do with writing and re-using code? It is not like having more than 1 OB1 in that only OB1 starts first during the normal cyclic scan. The other OBs process in the order of their OB #. I have numerous projects and they all have multiple OBs. I have OB1 as a supervisory and abort / startup / recovery handler, setting states of the system used by all the pieces. I have an OB for each main function that can be logicallybroken up. That OB calls related FBs/FCs. When I have that main function in another project, I drag and drop the OB and associated FBs/FCs (which I put into a group). It works very well, and I do not have to modify OB1 in any way to integrate the new functionality.
	Last edited by: huggy_d1 at: 11/3/2011 1:47 PM science guy
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