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Modbus communication inquiry

Created by: woop_ass at: 4/4/2010 10:01 AM (5 Replies)

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4/4/2010 10:01 AM	Rate (0)
woop_ass Posts: 68 Rating: (0)	Dear All :) I'm using the IM 151 7 F CPU. I'm using the Simatic Manager V5.4 SP5 I've encountered a problem during communication that I've failed to solve : I'm using the F CPU along with standard I/O's . In the Simatic I'm using FB81, FB2, FB3. While trying to reach I/O's that do not exist or trying to write to location in the DB that doesn't exist the CPU goes in to stop mode, I managed to partially solve this issue by implementing the designated OB in the Simatic and now every time this error occur the SF lights and turn off as soon as the requested address is valid. My question is : How can I limit the communication areas and thus solving my problem? Best Regards, Woop ass
woop_ass Posts: 68 Rating: (0)
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4/4/2010 2:28 PM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 3/15/2025 Posts: 3042 Rating: (1061)	woop_ass In the Simatic I'm using FB81, FB2, FB3. While trying to reach I/O's that do not exist or trying to write to location in the DB that doesn't exist the CPU goes in to stop mode, My question is : How can I limit the communication areas and thus solving my problem? Hello woop_ass I can only assume that your S7 is the Modbus Slave (you wouldn't need to use FB81 otherwise), so the simple fix is to make sure that the Modbus Master does NOT request data and/or I/O's which don't exist in your S7. The "trouble" with Modbus is of course that its Function codes as well as addressing scheme "belongs" to the modicon world and that the Modbus Master expects a Modbus Slave (your S7) to have the requested data areas. This is where FB81 comes in who will essentially "fake" the existence of Modicon data areas in yourS7. As such your problem could also be caused by an incorrect or incompletesetup/configuration of the "faked" data areas and/orby the way you handle S_SEND/S_RECV (hard to say without looking at your S7 program as well as not knowing what data the Modbus Master wants or needs). I suggest you have good read of theET200S1SI manual (see link below) as well as the other link below: Function Blocks, Examples and User Manuals for the ET200S 1SI Serial Interface Module What should you watch out for in particular in the parameters of the S_SEND function block for the serial interface module ET 200S 1SI during the processing of a job? 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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4/6/2010 9:13 AM	Rate (0)
woop_ass Posts: 68 Rating: (0)	Hey Frirtz :) I haveaquestion regarding youranswer : * How can I limit the Master to not access areas which don't exist in my S7? Best Regards, Woop ass
woop_ass Posts: 68 Rating: (0)
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4/6/2010 9:55 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 3/15/2025 Posts: 3042 Rating: (1061)	Hello woop_ass There's only way as far as I'm concerned: Be really nice to the theperson who programs the Modbus Master and ask him to NOT request datawhich you haveNOT set up in your S7.
	Last edited by: fritz at: 4/6/2010 9:58 AM 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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4/6/2010 11:14 AM	Rate (0)
woop_ass Posts: 68 Rating: (0)	will it be more easier to send you my program and thus finding my problam?
woop_ass Posts: 68 Rating: (0)	Last edited by: woop_ass at: 4/6/2010 11:16 AM the master is the DCS and the slave is the S7. can a firmware update to the ET 200S 1SI will help?
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4/12/2010 2:39 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 3/15/2025 Posts: 3042 Rating: (1061)	woop_ass will it be more easier to send you my program and thus finding my problam? Hello woop_ass I suggest you post the following here: 1.) Your S7 program 2.) A document that shows what data areas (Modbus Registers and Function codes) the Modbus Master is requesting from the S7. 3.) A description of which requested data areas work and which ones don't. As for your other question: "can a firmware update to the ET 200S 1SI will help?" The answer at this stage can only be: It can. if your problem is firmware related.
	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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