Modbus Plus

[Camel]

Someone please help. I have 15 modbus plus devices that i want to connect to a TSX Quantum 140 CPU 534 14. First of all, do i have to assign the PLC an address, or does it do this automatically? Second, i do know that there can be only 4 read operations operations active at the same time. Third, should i use the EFB CREAD_REG or CREADREG? What is the difference? Fourth, how do i setup routing, all this network has are the 15 sensors on a twisted pair. There will be no outbound traffic from the PLC except the request for data. Any info will be greatly appreciated.

[Crossbow]

The Quantum's Modbus Plus address is in rotary switches on the BACK of the CPU module. I don't know what rocket scientist thought that up, and out of the box it's typically set to one. The only command you need is the MSTR. You can write the MSTR to poll the sensors. It is true only 4 will run at a time. As for routing, if they are all on the same network, there is no routing. Routing only comes into play if you have multiple Modbus Plus networks connected together with Bridge Plus BP85 devices. One thing you may want to try is Peer Cop. It's an automatic polling of devices. Set up Specific Inputs for each of the sensor node addresses, and specific outputs for any devices you need to write to. Then the extension manages communications and you don't have to code MSTR instructions.

[Camel]

Sweet! Thanks for the input. I guess i will try this on a weekend since i have to pull the cpu.

[Guest Guest_leon78]

See http://forums.mrplc.com/index.php?act=Downl...&CODE=02&id=278