MicroLogix 1400 connection via modbus RTU

Hello,
I'm a newbie to PLC's and network protocols, and I need your help with setting up a modbus rtu network.

Hardware 1: Micrologix 1400
Hardware 2: Stepping motor driver
Software: RSLogix Micro Starter
Communication label: 1763-NC01

First I just want to establish communication between PLC and Driver. I'm having problems with setting up "MSG" function and data files.

Any help would be appreciated!
Thank you,
Bryan

Welcome to the Forum !

Post details about what you've already configured; either ZIP and post the *.RSS file itself or use screenshots.

Post details about the stepper motor controller and its Modbus interface, both physical and addressing.

Since you're using RS-485 and the 1763-NC01 cable, be sure to set the Channel 0 handshaking mode for "No Handshaking (485 Network)". No two manufacturers seem to label Data A and Data B the same, so be ready to try swapping them.

And of course make sure you've configured Channel 1 to be a Modbus RTU Master !

The MSG instruction always requires three data table entries: the MSG Instruction Control Block (MGx:y), the Destination or Source data table (usually Nx:y), and a Routing Information element (RIx:y).

The User Manual and Online Help really are useful for the MSG instruction and the configuration of the communication ports.

MicroLogix 1400 connection via modbus RT

As for the NC01, I have A and B connected to transmission line and Term connected to A.

Remove the SVC rung

Change "MSG File" argument to MG9:0

Then you'll be able to start the setup of the message by double clicking "Setup Screen" - though it may come up automatically with a correct MSG File argument.

Add a normally closed (XIO) of MG9:0/DN in the rung before the message to repetedly call the message. You'll have to modify this as you add more message blocks though but it's fine for a test.

Edit - if you need later I'll reference our method of controlling and sequencing multiple messages.

Actually this line

Add a normally closed (XIO) of MG9:0/DN in the rung before the message to repetedly call the message.

Click to expand...

May not work. Instead of that contact ...

Add a rung after your MSG with an XIC of MG9:0/DN in parallel with an XIC of MG9:0/ER ending with an unlatch (OTU) of MG:9/EN

Hello Bernie,
I removed the original contact and added the what you recommended to the next rung. I'm still getting communication error with my driver. I checked the baud rate, stop bit, parity, data bit and everything matches up. Anything else I should look at?

Thanks.

If everything matches try flipping the two data lines.

9If that doesn't do it open the 'Setup' of the message, do a screen shot then post it here.)
Instead just repost your small program.

I switched the data lines and it works! Thanks

Glad you got it. As Ken Roach noted this seems to be a standard troubleshooting tool when first setting up an RS485 connection. As usual, if it's a 50/50 chance you'l get it wrong 90% of the time - it seems.