28 HMIs, PM583 ETH & SCADA on Modbus TCP/IP

Hi Flavio Mussolin,

You replied to my querry.

I want to keep 28 HMIs as master & PM583 as as slave on Modbus TCP/IP.

Also I have to communicate the same PLC on SCADA.

I have doubt regarding the load on PLC & if there would be any other issues??


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asked 10 months ago




AFAIK, the CPU PM583 must be every  time as master and HMI as slave

Flavio Mussolin   

answered 10 months ago


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An AC500 PLC ethernet port in modbus server mode will allow a maximum of 12 simultaneous client connections.For example,12 instances of Modscan 32 software can simultaneously read and write data to the AC500 PLC via its onboard ETH port. In order to meet your requirement of 28 modbus tcp/ip clients connected to a single CPU,you will have to use two CM597 coupler modules.These two modules, in theory,will allow 24 additional clients to communicate simulaneously with the AC500 PLC.Hence, a total of 36 sockets for Modbus client connections to the PLC.

The onboard ETH port has sufficient sockets to allow connections for other protocols as well,which includes OPC server communication with the PLC.

As far as loading is concerned,we can assume that since provision is available for the said requirement,by design the PLC would be capable of handling the load.

There may be some practical limitations to this.For more info,kindly navigate to the below link.






answered 10 months ago


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