9/19/2008 2:05 PM | |
Joined: 9/6/2008 Last visit: 9/14/2024 Posts: 177 Rating: (1) |
We have an application coming up which has 15x S7-400 PLC all connected via MPI Network and Industrial Ethernet. My plan is to use the MPI bus for the PLC to PLC Comms and the Ethernet for WinCC Comms. This is not a PCS7 Solution. Here is my question:- Each PLC has a SEND DB and a RECEIVE DB and each PLC sends 30bytes of info to every other PLC. ie all PLC's have a small "area" of communication to every other PLC, basic interlocking. I have configured this on MPI Global Data and it amounts to 210 Rows of Packets. Is there any way to calculate the mean turnaround time for this communications method? I want to keep the SCADA comms and PLC to PLC comms seperate and I really do feel like buying 15x Industrial Ethernet CP's to do this job if the MPI Bus can handle it with a reasonable amount of speed. I have include my hardware setup with Global Data config for anyones perusal. Am I nuts or is this feasible. AttachmentCisa.zip (283 Downloads) |
9/20/2008 4:54 PM | |
Posts: 196 Rating: (12) |
Hi A guess is that the Globadata functionis in the S7 is because of the possibility very easy to transfer data between to plc. I personal think the GD function should only if have to replace a old unit or implement a new PLC in old GD ring. But now the Ethernet is widely used and the advantage with the SEND /RECIVE functions lot better. I don’t remember there is any diagnostics function if you using GD functions. Depending of the “speed” you need you can use Bsend/Berecive or Put/Get function. The Bsend/Berecive has a hand shake function that prevent you from send data before you have Scan the NW that has the receive function in the receiver CPU. The put/Get function here can you read / write data from and other CPU but you have no acknowledge that the data has been scanned before you “put” again. I can see you using the multi project function so it should be very easy to setup the S7 connection. Then defined a send / received UDT you can use in all our your PLC’s Here is a link where you can get some idea of the transmission time on the Ethernet https://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&lang=en&siteid=cseus&aktprim=4&extranet=standard&viewreg=WW&objid=20229805&treeLang=en |
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