I have a PC, a PLC and a Temperature Controller in the same modbus network. The PC requests information from the PLC (so PC is master), and the PLC requests information from the Temp Controller (so PLC must be master). Can this be done?

 

Why don't you make the PC a slave and have the PLC as the only master?

 

It cannot be done with all devices on the same physical connection.

It can be done with a box in the middle that can take care of the communication conflicts.

You might like to check out our Multii-Port module that will allow two (or more) Modbus masters to communicate with one or more Modbus slaves
http://www.miille.com/din366-10p.pdf

Jerry Miille

 

For this application was developed ModBus + (plus) this is the protocol that works as multi master and peer to peer. Other possibility is to find a PLC whit two comm ports, and configure one as ModBus Slave and the other one as ModBus Master.

Or if you can find a PLC with a comm port configurable by program one o various programs cycles as Master and then one o various programs cycles as Slave. Some time ago Modicon have offered this type of solution.
Hope this help you

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