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Created by: ralphtang at: 9/11/2008 10:07 PM (4 Replies)

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9/11/2008 10:07 PM	Rate (0)
ralphtang Posts: 33 Rating: (1)	I have an old machine which contents three PLCs the Main is a S5 with IM304/IM314 link with some remote I/O, 2nd is a S7-400 with a groups of ET200 I/O and TP370 screen,the 3rd is safety PLC use ET200s with IM151-7S cpu+a wincc screen. the 3 plcs use I/O link with each others. now I would like upgrade S5 PLC to S7-300 and would like use Profibus link to the others, how I do thatsince Profibus only allow one master? Do I need to put two DP/DP coupler? thanks for any comments
ralphtang Posts: 33 Rating: (1)
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9/11/2008 10:20 PM	Rate (0)
JMJ Posts: 487 Rating: (45)	S7-300does not required to be DPmaster. You can have S7-400 as the master. IM151-7 is any way a slave and you can configure S7-300 as DP slave. This provided S7-300 does not require to be a master. If you remote IO has to be on profibus then it is not possible. But if is in the same panel, it can be on expansion rack. But it is also possible to have communication between CPUs onprofibus usingS7 communicationalso. Let me give an example: In this case we can have S7-400 as DP master with Address 2 and address 3-9 are slaves for S7-400. S7-300 as DP master with address 10 and it's slaves are address >10. This was you can have 2 masters in the same network but talking to different slaves. (A slave can have only have 1 master). Now, you can configure S7 communication between CPUs over profibus. DP-DP coupler is another possibility. That way you can still keep both the networks separate. So there are multiple possibilities.
JMJ Posts: 487 Rating: (45)	Last edited by: JMJ at: 9/11/2008 10:28 PM Last edited by: JMJ at: 9/11/2008 10:26 PM
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9/12/2008 4:13 AM	Rate (0)
ralphtang Posts: 33 Rating: (1)	Thanks JMJ. in your example, S7-400 cpu has an address 2 and slaves 3-9, S7-300 cpu has an address 10 and slaves 11-15. in this case how these 2 cpu exchange data? do i need write special programs to exchange the data? ralph
ralphtang Posts: 33 Rating: (1)
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9/12/2008 8:41 AM	Rate (0)
umencho Diamond Expert Joined: 3/21/2006 Last visit: 1/13/2025 Posts: 10239 Rating: (1182)	Hi May be is better to use DP/DP Coupler and keep separately both Profibus network, If I understood right, existing plc are separately.Example of a configuration of the DP/DP Coupler I/O in STEP 7 (part 4.3.4 in manual ) Manual DP/DP coupler. regards

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9/12/2008 2:15 PM	Rate (0)
JMJ Posts: 487 Rating: (45)	There are many possibilities. They all use communication blocks. Please see the link below. This has lot of information on communication functions available on S7. http://support.automation.siemens.com/WW/view/en/20982954 Openthe embeded PDF and goto section 2.2.3 which is CPU-CPU communication on profibus. This manual has some table that shows the possibilities between different CPUs and also the data length on different option. This should help you deside which function to use. The manual also has details about each possible communication. The same link also has link to other FAQs with example of each communication. I think this info should help you a lot. Let me know if you need any more help.
JMJ Posts: 487 Rating: (45)
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