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Redundant I/O, failure behaviour

Created by: BilalD at: 2/8/2010 12:04 PM (9 Replies)

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2/8/2010 12:04 PM	Rate (0)
BilalD Posts: 157 Rating: (10)	Dear Experts, If i have a S7-400H CPUs, Redundant, and one station (Two ET200M (Redundant), Three DO modules) each CPU is connected to ET200M module. In case of a failure of one ET200M, What will happen? Is the CPU connected to the Failure ET200M will be Reserve? or not? Can I control what will happen? please any details.. Thanks in advance,,, Regards,
BilalD Posts: 157 Rating: (10)
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2/9/2010 8:00 AM	Rate (1)
Nil96 Posts: 325 Rating: (14)	Hi BilalD, Upon failure of one of ET200M, the CPU switches over to the other and thereby the communication between ur DO modules and CPU will not get affected. Make sure that that you download all required OBs which will keep the CPU in runtime even if one of ET200M is faulty. Hope this helps.... Regards Nil
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2/9/2010 12:26 PM	Rate (0)
BilalD Posts: 157 Rating: (10)	Dear Nil96, Thank you for your reply,but are you sure for that info? somebody told me that if the master CPU was connected to the failure ET200M, the CPU keeps the master, and the reading from the I/O modules are done through the Reserve CPU..Is that correct?? and isn't there any documentation?? Thanks in advance,,,
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2/9/2010 1:56 PM	Rate (0)
Saravana kumar Gold Member Joined: 2/6/2009 Last visit: 8/19/2024 Posts: 939 Rating: (118)	HI, If the DP slave fails which is connect to the Master CPU then the CPU will switch over to the reserve one. Please see the pages 44&45 for your reference in the attached manual. Attachment Swr_english.pdf (316 Downloads)
	_______________________________________________________________ Best Regards T.Saravana Kumar "All for the Best"
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2/9/2010 3:19 PM	Rate (0)
BilalD Posts: 157 Rating: (10)	Thank you saravana very much But, is this manual applies also for S7-400 H??? I think the redundancy rules is different, isn't it?? Regards,
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2/9/2010 11:45 PM

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Dear all,

BilalD
In case of a failure of one ET200M, What will happen? Is the CPU connected to the Failure ET200M will be Reserve? or not?

What will happen is stated in S7-400H manualin Chapter13 (13.3.2 Failure and replacement of a redundant PROFIBUS DP interface module).

SIMATIC Fault-tolerant systems S7-400H manual

Starting situation
Failure How does the system react?
The S7-400H is in redundant system mode and a PROFIBUS DP interface module (IM 153–2, IM 157) fails. Both CPUs report the event in the diagnostic buffer and via OB 70.

So, a Master/Reserve change over doesn't take place.
You can also read in the manual page 82,

SIMATIC Fault-tolerant systems S7-400H manual
Master/reserve assignment
When the S7-400H is initially switched on, the CPU that started up first assumes master mode, and the partner CPU assumes reserve mode.
The preset master/reserve assignment is retained when both CPUs power up simultaneously.

The master/reserve assignment changes when:

1. The reserve CPU starts up before the master CPU (interval of at least 3 s)
2. The master CPU fails or goes into STOP in redundant system mode
3. No error was found in ERROR-SEARCH mode.

Best regards.

H-H

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2/10/2010 7:41 AM	Rate (0)
BilalD Posts: 157 Rating: (10)	Dear H-H, Thank you very much, you are great.. But, i have some questions please, if the master CPU was the connected to the failure ET200M, then it will read the I/O through the reserve CPU,isn'tit? what happens if more that one station is connected, the master CPU continues reading from its connected ET200Ms or not? can't we program the changeover to beoccur in these situations? Regards,
BilalD Posts: 157 Rating: (10)
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2/10/2010 10:56 AM	Rate (0)
Nil96 Posts: 325 Rating: (14)	Hi BilalD, 1) What u said is right. When the 1st IM fails, the master CPU gets the data from the 2nd IM via slave CPU. 2) When there are more no of IMs, the CPU reads all the data in the normal way. Only if u get any failure as described in point 1, data is read from 2nd IM via slave CPU. Also make a note that if in case master CPU fails and both IMs are healthy, then there will not be any change over in IM. Regards Nil
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2/12/2010 5:23 PM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 9/30/2024 Posts: 928 Rating: (309)	Hello Bilal, BilalD Thank you very much, you are great.. I'm glad I could help you. Thanks for your nice words. BilalD what happens if more that one station is connected, the master CPU continues reading from its connected ET200Ms or not? In Addition to what Nil had already said, I had the chance to testit yesterday andpulled out the Profibus bus connector from the master CPU and it was still the master. BilalD can't we program the changeover to beoccur in these situations? No. Why would you do this?! This thread will show you an idea of how to stopthe masterCPU but Techyand Arethad totally different applicationsfrom what you have. In your case, I would never stop any of the 2 CPUs. Just let it work the way it's designed. Best regards. H-H

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2/13/2010 8:07 AM	Rate (0)
BilalD Posts: 157 Rating: (10)	Thank you very much Nil96 & H-H That was very helpful for me.. Regards,
BilalD Posts: 157 Rating: (10)
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Redundant I/O, failure behaviour

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