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Communication between Safety and non-safety programs

Created by: PAUL H at: 6/23/2009 8:09 AM (14 Replies)

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2/21/2012 8:15 AM	Rate (0)
h2_504 Experienced Member Joined: 11/8/2011 Last visit: 9/19/2023 Posts: 89 Rating: (1)	Hi fritz, Thanks for the reply. I read the rules layed down in Chapter 7, but what about the safety program itself? You cannot use M bits in this program because this memory is not fail safe. What memory can you use as intermediate values in the fail safe program? For instance in the standard program you can store result of an operation in a M bit and use the same bit in the following networks several times. How can you do this in a fail safe program? Best regards, h2_504

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2/21/2012 8:24 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 10/8/2024 Posts: 3024 Rating: (1054)	h2_504 What memory can you use as intermediate values in the fail safe program? Hello h2_504 simple answer: F-DB's (and chapter 4.3.3 of the previously linked manual has more on this)
	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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2/21/2012 9:28 AM	Rate (0)
h2_504 Experienced Member Joined: 11/8/2011 Last visit: 9/19/2023 Posts: 89 Rating: (1)	Hi fritz, Thanks for clearing this up. Somehow related to this problem (using memory in F-programs), can you read an F-output during F-program (from process image)? Also can you read an F-input during F-program (with peripheral addressing)? Best regards, h2_504

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2/21/2012 9:06 PM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 10/8/2024 Posts: 3024 Rating: (1054)	Hello h2_504 the answers are No and No and can also found in the previously mentioned manual. On that note, while there is of course nothing wrong with asking questions, allow me to suggest that you do spend some time study theSIMATIC Industrial Software S7 Distributed Safety - configuring and programming as well as theSIMATIC Industrial Software Safety Engineering in SIMATIC S7 manuals in detail as there are a few things to note about Safety programming. I hope this helps
	Last edited by: fritz at: 2/21/2012 9:19 PM fixed up advise 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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2/23/2012 11:41 AM	Rate (0)
h2_504 Experienced Member Joined: 11/8/2011 Last visit: 9/19/2023 Posts: 89 Rating: (1)	Hi fritz, Thanks for the answers and the patience. Actually I read the first manual you mentioned, but it's my first project in the safety area and I have some doubts (I am not sure that I understand and interpret correctly everything I read in these manuals). I found in the manual where it was said that you cannot read outputs prom process image (they are write only), but I wanted a confirmation from someone with experience in this field. I am puzzled because you cannot read outputs from process image (it is mentioned that they are write only), but if I define an F-FB i can read the outputs of this F-FB inside the block. How can be this possible when I eventualy apply this function to some outputs (in process image)? I have some guesses (maybe the function copies in RAM all parameters) but I am not sure if the CPU does this. Also I don't know if the F-compiler will always stop me from doing some unallowed operations in safety program if the same operations are allowed in a stadard program, operations which could lead the program to an error after commissioning. Best regards, h2_504

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