modbus over rs232 with slc 5/03

I have to test a modbus communication which is modbus over rs232 implemented with a slc 5/03 on channel 0.
I tried to connect with a PC using a null modem and modbus poll but I coundn`t.
How can I test the communication.
How can I realise which is the modbus configuration in the plc, I enter to the channel configuration cannel 0 and it says df1 full duplex, 1200 baud, I don`t see anywhere the modbus.

Thanks in advance,
dialc

What version of RSLogix do you have?
What firmware version do you have in your CPU?

Modbus Master was only a fairly recent addition to the SLC family. If it doesn't show up in your settings, it may not be available.

If ye have it, then here it be.



or if for some reason the image doesn't work, you can view it here.

http://imageshack.us/photo/my-images/705/modbusconfig.png/

Dialc, carefully check the Operating System Series and Firmware Revision (FRN) of your controller.

Only the newest SLC-5/03 controllers with OS Series C, FRN 11 support Modbus RTU Master. SLC-5/03 controllers can be upgraded in the field using a firmware upgrade kit; the price is a few hundred dollars and you can get it from your Rockwell Automation distributor.

You will need RSLogix 500 version 8.10 or higher to configure this processor.

You mentioned using "modbus poll" on a PC; that says that you expect the SLC-5/03 to be a Modbus RTU Slave. The controller does not support Slave Mode.

The excellent MVI46-MCM modules from Prosoft Technology support two channels of RS-232/422/485 Modbus RTU Master or Slave. These modules are the most common way of implementing a Modbus channel on an SLC-5/0x controller.

I am using RSLogix 500 5.50.00
The processor type: 1747-L532C/D %/03 CPU - 16K Mem. OS302 i dont remember the firmware revision.
The plc was working ok, but after a electrical shutdown i cant comunicate with it anymore.

I am confused; you could not possibly be using Modbus RTU (with modern OS302 Series C FRN 11 firmware) if you are using RSLogix 500 version 5.50, which is many years out of date.

What protcol were you using previously, before the power outage ?

Is the controller operating normally, other than the communications issue ?

Hi Ken,
Is it possible that the original programmer had it running and had the newer and greater software and DIALC may have uploaded the program with the older RSLogix, modified, re-downloaded and now messed up the modbus comms?

dialc

If possible use the Prosoft Technology MVI46-MCM

I have used the MVI46-MCM but have used the MVI46-MNET Module, its the modbus over ethernet. Easy setup. Sample program they give just works


I also used the MVI46-GSC RS232 comms with great results. Again easy set and communictions.

Damian,

Now I'm questioning my assumption that RSLogix 500 version 5.50 (released 2002 ) could not upload or go online with a Series C FRN 11 controller (released 2009 or so). Version 5.50 did support OS503 Series C firmware (FRN 5, I think) so it's not outside the realm of possibility that the software could upload but discard any instructions or configurations the compiler didn't understand.

The original post is moderately confusing because it implies that the SLC is a Modbus RTU Slave (he describes using a PC with a Modbus Poll software utility), but we know that SLC's can't be Modbus RTU Slaves, only Masters.

He also describes loss of connectivity after a power cycle. If he's looking for ordinary "go online and monitor", then he needs to be looking at DF1 or DH485 networking, not Modbus.

Dialc is going to have to post more information, preferably with some history or context.

In the company we have two laptop, the old one with Rslogix 5.50.00 and the newer one with Rslogix 8.10.00 (CPR 9).
Last time I connected to the plc with the older one, but still with the 8.10.00 version cannot see the rtu configuration.

It may be helpful if you can post processors program file ( the .RSS file) zip it first.

dialc said:

In the company we have two laptop, the old one with Rslogix 5.50.00 and the newer one with Rslogix 8.10.00 (CPR 9).
Last time I connected to the plc with the older one, but still with the 8.10.00 version cannot see the rtu configuration.

Click to expand...

The fact that you were "online" with the CPU using ver 5.50 is concerning. As Ken mentioned, your going to have to give us some history on what you have done to this point.

I assume that since you were "online" with ver 5 that you must have done an upload. If so, did you then at any time download using ver 5 software? If you did, you likely lost the configuration that was related to modbus. If you then went back online with ver 8.10 and again uploaded, I imagine it is possible that Modbus RTU will not show up as a selection.

Do you have the original program that was developed in ver 8.10 that has not been compromised by a recent upload?

The fact is, you MUST use 8.10 for RSLogix to recognize modbus. If you are using 8.10 now, and you still don't see the modbus selection in the spot that I show in the screen shot I posted earlier, then you likely have a compromised version of the program.