Beijer Electronics (formerly QSI Corporation)
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Qlarity terminal as a Modbus/TCP Master and Slave
http://www.qsiforums.com/viewtopic.php?f=6&t=4765
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Author:  Dano.oh [ Thu Jul 18, 2013 1:36 pm ]
Post subject:  Qlarity terminal as a Modbus/TCP Master and Slave

I am getting requests from customers that want to have both a local and remote HMI using the same Modbus/TCP network. Is there a way to use the local HMI screen to send Modbus information to a second screen using MBSlaveV2, or additional MBComV2 objects?

Dan

Author:  Jeremy [ Thu Jul 18, 2013 11:14 pm ]
Post subject:  Re: Qlarity terminal as a Modbus/TCP Master and Slave

Normally in the scenario you describe, I would suggest having the remote HMI talk to the directly modbus PLC using Modbus TCP and forgo using the local HMI as a middle device.

It is possible to have one HMI using both Modbus Master and Modbus slave protocols, however setting up the Modbus slave communication is a fair amount of work.

Author:  Dano.oh [ Fri Jul 19, 2013 1:06 pm ]
Post subject:  Re: Qlarity terminal as a Modbus/TCP Master and Slave

Usually we do have only a remote HMI talking to a PLC however, lately we have been getting requests to have two HMIs communicating with the PLC. They would like to have the Modbus information available in two locations.

I dont mind doing some work to get the Modbus slave communications if it will do the trick. What is the best way for me to begin trying this out?

Author:  Jeremy [ Fri Jul 26, 2013 1:16 pm ]
Post subject:  Re: Qlarity terminal as a Modbus/TCP Master and Slave

My suggestion would be to forgo the Modbus slave entirely. Instead, have both the local and the remote HMI talk Modbus TCP directly to the PLC. The only reason you should need to get Modbus slave involved on the local HMI would be if you want the remote HMI to have additional information about the local HMI in addition to the PLC.

This will be dramatically easier to set up and ensure that the remote HMI has up-to-date information about the PLC, instead of possibly out-of-date information from the local HMI.

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