ML1400 Modbus RTU Slave extended files

[OkiePC]

If I set up a ML1400 as a Modbus RTU slave, and click the extended files tickbox, then set up my files with 200 elements, will the Modbus addressing span those files correctly?

I selected file N20 and 200 elements, so N20:0 = Modbus holding register 1 or 40001, N20:199=40200

Next I want to create a second file N21 with 200 elements.
Will N21:0=40201?

I have seen this done and worked on systems that used 5 files but they were all 256 elements in length so I was curious if that was required and what would happen if I made it a nice round 200 elements each.

I will run a test later this week and update this thread but if someone knows for sure the answer to this, I can prepare my code correctly now before the panels are ready to test.

 

[OkiePC]

FYI for future finders of this thread:

The answer is no. If you make use of the extended Modbus RTU addresses, the PLC apparently still starts the second file first address corresponding to Modbus Holding Register 40257.

I made my first file 200 elements and got errors for "illegal data address" when I tried to poll addresses between Holding Register 201 and 256.

Why the hello would i use Modbus RTU to connect two Micrologix 1400 serially?

Because Phoenix Contact did away with the TWE series radio modems, the newer, faster, and allegedly better RadioLine series has no ethernet port, but does support Modbus serially so you can poll add on I/O modules as well as RTU slaves connected to any of the radio slaves serial ports.

This system we are setting up uses some Radioline slave nodes as purely remote I/O except this one station with a PLC and HMI...so to make all these features fit together I have to use Modbus RTU protocol at all nodes and the "PLC/Modbus dual mode" in the PSI-CONF setup for Radioline.

Now that I have this sorted out, I get to go back and massage all my message blocks and address comments.