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CaRnO

Modbus Widget needed

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Hi Guys, I'll try at my best to be the most clear and understandable as possible with my level of english. Here is the situation. I got a Master device A who speaks ModbusRTU . The message pass through Device B who translates it to Modbus TCP. Then Device C recieves the message through the network. (pic1) The problem is that the Device A is not configurable and it always point at the same register address. So, if there is more than one Device A in the same système, there is a register address conflict. I want to know: is there a device, let's call it D, that can take a message and shift the register address inside ? Exemple: The first Device A need to read the register 0 to 9. it get over the TCP network with the help of the Device B and it read the address 0 to 9 in the Device C then the seconde Device A need to read the 0-9 address ( but those are already use by the first Device A) so in the Device C we reserve 10 to 19. So the Second device A will ask for the 0-9 to the DEVICE D. Device D will shift the address for 10 to 19 and the Device C will provide that through the network with the help of the device B.(pic 2) So, does it exist ? thank you.

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Device A is the master. Device C is the slave. If device D is on an ethernet network, it has an IP address. The IP address (not the slave node ID number) is used for identifying the slave. For reading registers 0-9 from any device, Device A master needs to query each device by its IP address, for instance, first Device D at 192.168.xxx.xxx and the second Device D at 192.168.xxx.yyy

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Thank you for the answer. Actually, I got multiple Device A (master on Modbus RTU) and a single device C (PLC on Modbus TCP). All the Device A try to read and write on the same register address (ex: 0 to 9) and THAT is the problem. I want to shift the address on some device A to prevent the address conflict. The Device D would be between Device A and Device B.

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My original reply should have read: ------------------------- If device C (not D) is on an ethernet network, it has an IP address. The IP address (not the slave node ID number) is used for identifying the slave. ------------------------- Your device A can not specify more than one transaction, where each transaction uses a different IP address?

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And if it's all the same slave ? I need each Master to read different register in the unique Slave.

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That's a good diagram of what you're looking for. You should have started with that. I'd suggest you inquire of Red Lion Controls to see if their Data Station Plus can remap the data as required. The Data Station Plus has Master/slave capabilities along with some remapping abilities. I'd email them the last diagram, because that diagram does a good job describing the task at hand. I can't recall how many serial ports a Data Station plus, it might not have 3 serial ports to handle all 3 masters on the RTU side, but you could use a serial-to-ethernet server on one master's output to convert to ethernet, while using serial ports for the remaining two masters.

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Yeah, I knew it existed. I'll give it a try. Thanks alot.

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