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Profibus communication fails due to the last DP slave

Created by: Meritor at: 8/10/2008 1:26 PM (4 Replies)

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8/10/2008 1:26 PM	Rate (0)
Meritor Posts: 33 Rating: (2)	Dear All, I have the same problem what "Hans D" mentioned on 7/26/2008 and I need some more information about the ABT active bus terminator.. Existing system: - 315-2DP CPU - OP177B connected on Profibus network - ET-200 S (IM-151) profibus slave module (with some I/O on it) connected to the same network asthe last profibus components. Issue: As somobody swith the last slave module (ET200S) off all the profibus communication goes down. Even the OP panel is not able to communicate with the PLC because the profibus falut. I inserted all the necessary OB modules (OB86,...) into the PLC to avoid any stop on it but I need to maintain the communication between the OP and PLC in case of the last Profibus Slave (ET200S)module is missing. I check the profibus terminals and they are OK. I set a low speed (187.5)on the profibus network and the length of the cable is less then 50m. Can you suggest a sollution (ABT active bus terminator????) to avaid this profibus issue in case the last slave module is missing? Can you give me some more information about ABT if this is the right sollution? Thanks, Norbert
Meritor Posts: 33 Rating: (2)
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8/10/2008 2:13 PM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Dear Norbert, I think that the ABT is the right solution for you, as long as you provide a constant power supply on the ABT. As you mentioned the low baud rate and the "just" 50 m segment length over all I get some doubts. Is it possible that there are other reasons for interferences? Is it maybe more useful to use OLM instead of the Copper cable? Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
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8/10/2008 5:50 PM	Rate (0)
Meritor Posts: 33 Rating: (2)	Dear J_Bell, Can you give me more information about ABT? Where can I gain more detailed information about this active bus terminal? Thanks in advance! Norbert
Meritor Posts: 33 Rating: (2)
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8/11/2008 6:30 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 10/4/2024 Posts: 12283 Rating: (2685)	Hello Meritor; The active bus terminator (6ES7 972-0DA00-0AA0) description can be found on the Siemens Mall, for example here: There is also a 3-page section on the ABT in chapter 5 of the manual "Simatic Net Profibus Networks" (profn2_e.pdf). However, as suggested earlier, please look atthe physical setup of your bus, it is weird that you should have to use such a low speed for such a small length. Do you have any diagnostic information available on the diagnostic buffer of the CPU? Hope this helps, Daniel Chartier
	Last edited by: dchartier at: 8/11/2008 6:32 AM
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8/12/2008 3:40 PM	Rate (0)
Meritor Posts: 33 Rating: (2)	Hi dchartier, Thanks for the above mentined information. The Profibus network can work on 500K without any issue (except in case of a power issue on the last slave). The reason why I reduced the speed down to 187,5 was that in the previous topic (see my first comment) was mentioned that this reduction solved the problem on the profibus network. Anyway, thanks for your advise and comments! Norbert
Meritor Posts: 33 Rating: (2)
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