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12/17/2012 3:22 PM | |
Posts: 2 Rating: (0) |
ThanksMarko Bursicfor your reply. The plc is connected through serial RS485 cable. As per the client spec they require Moxa Converters to convert these RS485 to Ethernet. But i dont think this is the issue. The real issue is that I am not able to find out the Modbus Data (starting) address which i need to configure in the scada. The scada is accepting a range of 400000(four hundred thousand) . Therefore i need to cross check the Modbus data address in the S7 Plc. I have looked over the Logic to find the Starting address. Can you please guide on where to find the Starting Modbus Data Address. please advice
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12/17/2012 6:37 PM | |
Posts: 3093 Rating: (323) |
Hello Haishkm4u, address mapping with Modbus is sometimes hard, as there are different ways to do it. The specification of the Modbus user organization defines the addressing for the data link layer. Theydefine function codes which access different memory types (holding register, input registers, inputs and coil) and register/coil addresses from 0 to FFFF hex. The application layer of different vendors - especially the older ones - talk about addresses from 40001 to 49999. This implys data type "holding register". The address transferred on the linestarts from 0 to 9998 dec, as this address belongs to the data link layer. Newer systems use address 400001 to 465536, it implys as well "holding register" and the address transferred on the line is as well 0 to FFFF hex. So application layer 40001 and 400001 and data link layer address 0 (with function code 3) always access the identical memory. Regards, Kaulquappe |
Last edited by: Kaulquappe at: 12/17/2012 6:40 PM |
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