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| 2/18/2011 1:30 AM | |
Joined: 10/7/2005 Last visit: 9/14/2025 Posts: 3049 Rating:
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Hello Johnny77 I'm afraid to say it is not neccessarily as simple as Pegaiasuggested and you need to be very careful when using data from the standard program (e.g. M,DB, I/Omemory)in your safety program. Your safety program is actually executed twice inside yourF-Call (first execution is the safety logic that your programmed, followed by an execution of the safety compiler generated inverted and Word based logic of it, this is a so called "time based redundancy with diversity" execution and happens "behind the scenes"). Once both execution are done, the result of both executions are compared (the safety program takes care of this "behind the scenes") and must deliver an exact opposite result of each other. If you now for example use anM bit from the standard program that can changestatus while the safety program is executed (e.g. acyclically changing clock memory bit), your safety program will come to grinding hold with the error that you observed. To overcome this, you woudl marshall thisM bit into anotherM bits in just before you do your F-Call and then use it inside the safety logic. Have a look too at chapter 7 of the SIMATIC Industrial Software S7 Distributed Safety - configuring and programming manual, which has more on this subject I hope this helps |
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Cheers |
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| 2/18/2011 1:26 PM | |
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Joined: 10/7/2005 Last visit: 9/14/2025 Posts: 3049 Rating:
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Hello Johnny77 go to your Start menu -> Simatic -> Documentation -> English and you should find a"S7 Distributed Safety - Getting started guide" pdf which usesa standard input for the acknowledgement. The other place where you'll find plenty of well documented and pre-programmed examples is in the Application and Tools section. By the way, usageof a standard Digital inputdirectly in your safety program can be donewithout problemsasit is part of the process image and won't change state throughout the scan, so this is possibly NOT the cause for your safety program Data corruption. I hope this helps |
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Cheers |
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| 2/19/2011 12:35 AM | |
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Joined: 10/7/2005 Last visit: 9/14/2025 Posts: 3049 Rating:
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Hello Johnny77 what do you mean by "this standard input assigned to F-DB" ? (are you writing into an F-DB from the standard program? I hope not because that is NOT allowed). Anyway, it's hard to debug a program problemwithout seeing the program, so pelase upload your S7 project here, tell us what addresses, FC's, FB's etc. you believe are giving you grief and most importantly tell us what the password is for your safety application. I hope this helps |
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Cheers |
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