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Multi master systems in profibus communication
Created by: thinhbi89 at: 10/3/2011 2:05 PM (15 Replies)
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| 10/3/2011 2:05 PM | |
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Posts: 6 Rating:
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Dear, I want to creat a systems with 2 masters in profibus line and send/receive data to them. But I don't know how to do it. Please help me. Thanks all. |
| 10/3/2011 11:41 PM | |
Joined: 9/27/2006 Last visit: 3/20/2025 Posts: 12344 Rating:
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Hello thinhbi; The easiest way to set multimaster operation in Step 7 is to insert the different masters (PLCs and HMI/SCADAs) in the same Step 7 project, and then connect them to the same bus in Netpro. This allows the Profibus configurator to set the timing parameters for the busso that all masters have access to the Profibus token at theirspecified time(which allows each one to have control and priority on the bus). Now, understand that there are Masters Class 1 (PLCs: they hold a very strict configuration of their slaves) and Masters Class 2 (HMIs/SCADAs/OPC servers: they do not hold a configuration of slaves, they interrogate other masters Class 1 on the bus) in Profibus. They operate differently than Masters Class 1 when they hold the token. And what you can do with each type depends on how they are configured. For example, 2 PLCs on the same bus (multimaster setup) will each have their own dedicated slaves, to which they will read and write when they have the token. You can never write to another master's slaves, but with the right equipment and configuration you can read values from another master's slaves: Reading the input data of a DP slave configured by a different DP master Direct data exchange (internode communication) between two CPU modules A second example: 2 PLCs can read and write to each other only if you are using a CP 342-5 on each one, not through their integrated Profibus port. You must then use communication blocks available in Step 7: How do you program communication blocks FB14 "GET" and FB15 "PUT" for data exchange in the S7 program of an S7-300 CPU?
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Last edited by: dchartier at: 10/4/2011 2:34 PM |
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| 10/4/2011 6:58 AM | |
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Posts: 6 Rating:
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Thanks both, your ideas is very helpful for me. I going to try it. |
| 10/5/2011 7:56 AM | |
Joined: 10/7/2005 Last visit: 3/20/2025 Posts: 3042 Rating:
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Yes it is dear thinhbi89and dchartieralready provided you with a detailedanswer concerning this, so all that's left to do for me is torepeat his answer here:
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Last edited by: fritz at: 10/5/2011 7:57 AMCheers |
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| 10/7/2011 3:18 AM | |
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Posts: 6 Rating:
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Thanks all ! I did it. But you know, I can read data only in the input of slaves. Can I read data in their output? |
| 10/7/2011 3:37 AM | |
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Posts: 6 Rating:
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Hello Dchartier! I know that the module CP 342-5 is Profibus module, but in your links, the systems is using Ethernet communication and module CP 343-1. So, I still don't understand this one! Please tell me about this.Thanks! |
Last edited by: thinhbi89 at: 10/7/2011 2:37 PMLast edited by: thinhbi89 at: 10/7/2011 3:37 AM |
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| 10/7/2011 4:57 PM | |
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Joined: 9/27/2006 Last visit: 3/20/2025 Posts: 12344 Rating:
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Hello thinhbi; Sorry, my bad. Siemens S7-communication can be handle data exchangeby CPs over different networks, such as Industrial Ethernet and Profibus-DP. In the following link, you will find a few sample projects showing how to exchange data between CPs over Profibus, using S7-communication blocks: https://www.automation.siemens.com/net-static/Quickstart2009/quickstart012003/html_76/profibus/pb_s7_s7_s7.htm Look at the last project (CP 342-5 to CP 342-5); you can download a pdf (Documentation) that explains the concept and the basic programming, and also the sample program, as an .exe file. This should help clear up the issue. Hope this helps, Danioel Chartier |
Last edited by: dchartier at: 10/7/2011 6:06 PM |
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