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| 6/9/2009 9:51 AM | |
Joined: 10/7/2005 Last visit: 10/6/2024 Posts: 3024 Rating:
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Hello gumis have a look at the attached pdf which is straight fromthe inbuilt S7help and should contain all the answers you were seeking (I hope). Cheers Fritz AttachmentConfiguring Short and Equal-Length Process Reaction Times on PROFIBUS DP.pdf (403 Downloads) |
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| 6/10/2009 2:24 PM | |
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Joined: 10/7/2005 Last visit: 10/6/2024 Posts: 3024 Rating:
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Hello again gumis sure can, open up the help from within Simatic Manager, go to the index tab and copy "Configuring Short and Equal-Length Process Reaction Times on PROFIBUS DP" into the keywordsearch box of it. As for what you measured, here are also some more "ideas" on things to checktoget abettter understanding on how "trustworthy" your measurement results are (assuming a setup with one PLC and one Simoreg 6RA70 DP Slave and nothing else on the bus): 1.) Find out thethe reaction time of your S7DQ card(e.g. a 322-1BL00 needs up 0.1 ms for a 0-1 transition, a 322-5GH00 can take up to 6ms for a 0-1 transition). 2.)Find out the reactiontime of your 6RA70 DQ. 3.) What type of instrument do you use to measure the times and what is its accuracy (and/or input detection reaction time)? All of the above can very well explain the difference in times for your 12Mbit/s measurement As for your9.6Kbits/s measurement, I'm not too sure how you manage to actually get it down to 40.4 ms. Ttr typical (typical/average response time as calculated by Step7(see bus paramter tab in HWconfig)) is some 87 ms for this baudrate in the assumend configuration (1 DP slave with PPO3). Anyway, I hope this helps at least somewhat and please keep us posted as it is a rather interesting piece of research you are doing (and ideally you'll connect a busanlayser tool (e.g. Profitrace) to verify that you have no repeats/illegal messagesand the likes happenning while you measure). Cheers Fritz |
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| 6/15/2009 6:39 AM | |
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Joined: 10/7/2005 Last visit: 10/6/2024 Posts: 3024 Rating:
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Hello again gumis since a picture tells more than a thousands words, please see attached one way on how to get to the bus parameters in Step 7. From experience (and verification of actual Ttr via Profitrace) the Step 7 calculated "Ttr typcial" valueis quite accurate (factors likes retries, acyclic data exhange, diagnostic messages etc. obviously can lead to longer Ttr's). The calculated "Ttr typical"in your case are: 12 Mbps: 0.3 ms 9.6 Kbps: 87.1 ms Ihope this helps Cheers Fritz |
Last edited by: fritz at: 6/15/2009 1:24 PMReplaced "The calculated response time in your case are:" with "The calculated "Ttr typical" in your case are:" Cheers |
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| 6/15/2009 7:59 AM | |
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Posts: 116 Rating:
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Hi Fritz, Can you tell me which PLC cycles are included in this TTR time? Regards Paresh |
Last edited by: Paresh at: 6/15/2009 8:01 AM |
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| 6/15/2009 10:57 AM | |
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Joined: 10/7/2005 Last visit: 10/6/2024 Posts: 3024 Rating:
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Hello Paresh I'm not too sure if I uderstand your question correctly. The cycle time of your PLC program has nothing to do with the Profibus Ttr (unless you use"Configuring Short and Equal-Length Process Reaction Times on PROFIBUS DP", seemy earlier post for more on this). As for the calculation of the "Ttr typical" the following applies (see also the"HELP" button from the bus parameter screen"): All configured Slaves are in "pure" cyclic data exchange (i.eNone of the Slaves has diagnostic messages,noacyclic comms are taking place (e.g. no use of dataset readouts via SFC58/59 or SFB 52/53 etc.),no other active nodes like HMI system or programming device are on the busetc.) There is also a simplified generic formula available for calculating this time (in case you don't have Step7) which is (courtesy of Siemens, see also attached screendump from the Siemens Profibus brochure): DPt = NbDP · [OvPB + BitDP · (NbE + NbA)] / BdsDP NbDP: Number of DP slaves OvPB: Overhead of PROFIBUS message frame= 317 bit BitDP: Data format = 11 bit/byte NbE: Number of Input bytes:(max. 244) NbA: Number of Output bytes: (max. 244) BdsDP: Transmission speed I hope this helps Cheers Fritz |
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Cheers |
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| 6/15/2009 11:03 AM | |
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Posts: 45 Rating:
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Dear fritz: Could you define the term 'response time' in case of this topic? Regards, gumis |
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