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| 5/26/2010 3:01 AM | |
Joined: 9/27/2006 Last visit: 1/22/2025 Posts: 12330 Rating:
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Hello Jeebs; Maybe you could look at the following link, it will take you to a group of Siemens application notes on network update calculations. http://support.automation.siemens.com/WW/view/en/34677186/136000&cspltfrm=0&cssw=0&csbinh=5 One of them is named: <Determining the transfer time for typical configurations in PROFIBUS>, so it looks like it could help you out. Hope this helps, Daniel Chartier |
| 5/26/2010 9:33 AM | |
Joined: 10/7/2005 Last visit: 1/23/2025 Posts: 3032 Rating:
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Hello Jeebs over and top of Daniel's advise, a couple of other ways to find out the the "typical" Profibus DP updatetime are: 1.) Do asetup of your ProfibusNetwork in HWconfig of Step 7 and check the "Ttr typical" valuewhich is the bus update time that you can "typically" expect (to be found in Properties-->Network settings-->Bus Parameters of the Profibus). 2.) Use the following simplified rule of thumb formula to calculate the Ttr (courtesy of Siemens, more useful stuff about this can be found in THIS technical brochure): Ttr = NbDP * [OvPB + BitDP * (NbI + NbQ)]/BdsDP NbDP = Number of Slaves OvPB = 317 = Profibus message frame "overhead" BitDP = 11 = Bits per Message Byte NbI =(Average) Numberof Input Bytesper DP Slave NbQ =(Average) Number of Output Bytesper DP Slave BdsDP =Baudrate Both method will give you a good idea of what "typcial" to update to expect (neither method takes into accountcycle time extensions due to diagnostic messages or additional acyclic data requests). I hope this helps |
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