Using Modbus IO server to talk to MicroLogix 1400

[JimMacD]

Just wondering,

Has anyone used the MODBUS I/O Server (DSC and RT module) to communicate with a Allen Bradley MicroLogix 1400 using Modbus TCP/IP?

[Peter_W]

Hi Jim,

I can't say that I have personally done so but you shouldn't have any trouble with it, the PLC has two COM ports with Modbus RTU support. Is this something you're having trouble with or just potentially looking to do in the future?

Regards,

Peter W.

[JimMacD]

Looking at doing in the future.

I was planning on using COM Port 1 (RJ-45 Ethernet) to talk over MODBUS TCP/IP. Would like to avoid RS-232/485 if possible

[Daniel-H]

Jim,

I would have to agree with Peter. You should be able to accomplish this.

Daniel

[JimMacD]

I'm going to go to our local Allen Bradley distributor next week and try it out on their test system. Will have to let you know how it goes.

Thanks

[JimMacD]

Status Update:

Was able to setup a MODBUS IO Server on a Laptop and talk to the MicroLogix 1400 using the RS232 Serial Interface. Was pretty easy once we figured out how to set up the modbus registers on the micrologix.

Apparently there are multiple revisions of the MicroLogix 1400, and it is only the latest one that has the MODBUS TCP capability, this was a 1st gen model. Working to get my hands on the newest revision to test.

[Daniel-H]

Jim,

Great to hear. Keep us posted with your progress.

Daniel

[dmoradi]

I am trying to read and write to the micrologix PLC 1400 REV B that has modbus/TCP. I can write to the PLC, but for some reason I can't read from PLC.

I have used the same cod to comunicate with other devices like festo valves, ABB drives... over modbus/TCP. it works with other devices but doesnt work with AB PLC.

If anyone knows why? Please help.

thanks    

Davood  

[JimMacD]

Communications successful between MicroLogix 1400 Series B and LabVIEW Modbus I/O Server using Modbus TCP. Same as modbus serial interface on MicroLogix 1400.

As a note: do NOT read/write to modbus addresses that do not exist. This will cause all addresses to come back "disconnected"

[JimMacD]

dmoradi,

Are you using the Modbus API vi's or the Modbus I/O Server built into the DSC and Real-time modules?