4/12/2013 2:40 PM | |
Joined: 9/27/2006 Last visit: 6/3/2024 Posts: 12259 Rating: (2670) |
Hello Shaka; First, about the bus parameters of the DP master: Beckhoffpresents a verynice table illustrating and explaining the various bus parameters for Profibus-DP. http://infosys.beckhoff.com/italiano.php?content=../content/1040/el6731/html/pb_dialog_busparameter.htm&id= The values are expressed in terms of “tbit”, or time-bits: this is the period of a bit in the transmission, which varies according to the bus speed. Now, this is valid for Profibus-DP, Profibus-PA uses a very distinct set of tranmission parameters, since it does not use RS-485 as a transmission medium (it uses MBP, Manchester Bus-Powered coding, based on IEC 1158-2). Please tell us howyou haveconnected the PA slaves to the Profibus-DP line (through a PA coupler or a PA link), at what speed you run the DP bus, and what errors you face. Make sure you have followed the guidelines of PA installation, such as can be encountered in Chap. 3 of the following document:: Profibus PA Installation Guideline Hope this helps, Daniel Chartier |
4/12/2013 4:24 PM | |
Posts: 21 Rating: (0) |
Hi dchartier and Rated X Thanks. I am using the IM157 DP to PA Coupler. I have setup a network with the DP master system at 45.45Kbps(31.25Kbps) and 4 Profibus PA nodes with a 5Byte input. This was working ok with the standard bus parameters. Now i needed to add 5 more nodes making it 9 nodes in total and whats happing is that the node are alternating between ready and not ready quite quikly. Very unstable communication. So i need to find out the right bus parameters to get the timing correct? Is there any formulas or solutions for this problem? |
4/12/2013 6:10 PM | |
Joined: 9/27/2006 Last visit: 6/3/2024 Posts: 12259 Rating: (2670) |
Hello Shaka; I really doubt that your problem comes from the DP bus parameters. They normally adjust to the requirements of the process speed, and they are mostly critical when you have a multimaster system or you operate at the higher end of the allowable bus speeds. Start with this: Have a look at our friend fritz’ answer to this similar question: Lossing Data Intermitantly over the PA/DP Coupler. Also examine the contents of the following FAQ: What must you watch out for when connecting PROFIBUS PA devices to the PROFIBUS DP? Could you tell us: - Have you added the new slaves at the end of the PA trunkline of the original coupler, or have you inserted a new DP/PA coupler on the Profibus-DP line? - Have you setup the trunkline termination properly after the new last PA-slave? - Have you made sure the addresses of the new PA-slaves do not match any existing DP or PA slave in your network? If you could show us a screencapture of the new Profibus configuration, with the addresses used for the slaves, it might show something. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 4/12/2013 6:10 PM |
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This contribution was helpful to1 thankful Users |
4/15/2013 10:57 AM | |
Posts: 21 Rating: (0) |
Hi dchartier Thanks for the information. >>Could you tell us: >>-Have you added the new slaves at the end of the PA trunkline of the original coupler, or have you >> inserted a new DP/PA coupler on the Profibus-DP line? I added the slaves to the end of the original DP/PA Coupler. >>-Have you setup the trunkline termination properly after the new last PA-slave? I made sure that the termination on the profibus DP and PA side is correct. >>- Have you made sure the addresses of the new PA-slaves do not match any existing DP or PA >> slave in your network? All slaves have unique address. Please see attached. Im not sure why the default settings are not working but when i started playing a round with Siemens Forum : Correction to Bus time calculations I was able to get 5 nodes to work correctly. But when i connect all 9 it does not work i get a lot of diagnostic counts. Any thoughts? |
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