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Behaviour of the FM458 when two S7-400 CPU are on the rack.

Created by: Kramps at: 12/6/2006 4:03 PM (3 Replies)

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12/6/2006 4:03 PM	Rate (0)
Kramps Posts: 66 Rating: (2)	Hi, I would like to know how the FM458 works when there are two S7_CPUs on the same rack and especially for communication via P-bus and virtual connections. Can the FM458 send to both CPUs (as we do not specify a CPU address) ? Does it only depend on the record number we declared ? Can two CPUs receive the same record ? Or is it limited to the CPU which is the nearest on the rack from the FM ? Thank you in advance for your response, Best Regards, Kramps
Kramps Posts: 66 Rating: (2)
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12/7/2006 7:15 PM	Rate (0)
miami Platinum Expert Joined: 8/31/2005 Last visit: 11/13/2024 Posts: 2198 Rating: (330)	Hello, the FM458 can only "talk" to one S7-CPU. See http://support.automation.siemens.com/WW/view/en/14952610Chapter 4.3 for details

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12/8/2006 11:12 AM	Rate (0)
Kramps Posts: 66 Rating: (2)	Hi, Thanks for your answer miami. Can I have two CPUs on the same rack if i use a FM458 too ? In this case, how do I define which CPU controls the FM ? Does it depends on the position of the FM on the RACK ? Best Regards, Kramps
Kramps Posts: 66 Rating: (2)
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12/20/2006 10:39 AM	Rate (0)
miami Platinum Expert Joined: 8/31/2005 Last visit: 11/13/2024 Posts: 2198 Rating: (330)	As far as I know, yes With one S7-CPU you can write/read the address for the FM. The standard address of the FM458 is 512. So the FM talks to the S7-CPU who is asking. When two S7-CPU are asking the handshake will not work. Therefor you must only use one S7-CPU communicating with the FM.

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