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9/9/2010 10:24 PM | |
Joined: 9/27/2006 Last visit: 9/25/2024 Posts: 12283 Rating: (2685)
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Hello mnada; I believe you are mixing 2 issues here. All S7-300 CPUs support up to 8 SMs, FM,s CPs... on the central rack, where the CPU resides. You can also have up to 3 secondary racks, using adequate IM 360/361 modules; each rack can also hold up to 8 modules. There is where the limit of 32 "local" modules is taken from. See the attached screenshot, from theinstallation manual for S7-300 CPUs: http://support.automation.siemens.com/WW/view/en/13008499 Profibus-DP, on the other hand, is a communication protocol based on the RS-485 physical layer. RS-485 supports up to 31 nodes (PLCs, remote I/O islands, drives, SCADA and HMI panels, etc...) per segment, with up to 123 totalnodes allowed if you use repeaters. A segment is defined as the first of these limits to be reached: 31 nodes, or the maximum distance allowed at the selected bus speed (100m at 12 MB, 200 m at 1,5 MB, 1,2 km at 9600 baud).
The IM 360/361 actually use MPI to transfer the data and diagnostics from the local modules to the CPU, through the backplane. The CPUs actually support both Profibus DPV0 and DPV1, when communicating over Profibus-DP DPV0 (cyclic)is supported directly though the standard Profibus configuration. DPV1 (acyclic) services are supported by special functions (SFB52/53/541, for example). See chapter 8 of the following manual: System and Standard Functions. http://support.automation.siemens.com/WW/view/en/44240604 Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 9/9/2010 10:29 PM |
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9/10/2010 12:00 AM | |
Posts: 76 Rating: (0) |
Thank you clarify any doubts I actually a bit confused terminology |
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