Can someone can teach me how to communicate a DCS to Allen Bradley PLC thru modbus.

Thanks in advance

 

Hi Joel,

We often get questions like this posted to the forum. It would help if you explained what it is that you need to know. Your question takes in a broad area.

Can anyone point this gentleman to a good general reference to get him started?

Thanks,
Peg, one of your friendly moderators

 

First you need define which of dozens of AB models of PLC you are using. Some require external add-on products/slot-cards. A FEW support Modbus directly (some of the higher-end MicroLogix).

So no one answer can be offered yet.

 

I think all of the micrologix. compact logix, and control logix processors that have an RS232 serial port support modbus.

if your cpu does not have a serial port, or it is a different model, there are 3rd party (such as Prosoft) modbus modules that can be added.

the manuals that come with these processors or modules are pretty self explanatory as far as implementing modbus.

--
Bob
http://ilbob.blogspot.com/

 

If the Allen Bradley PLC is the master without any serial ports available, then they make the 1769-SM2 card which can also be used as a Modbus RTU Master over RS485, see link below for manual.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1769-um013_-en-p.pdf

This card can be used on a Micrologix 1500, Compact Logix and Control Logix PLCs. These are cheaper than the Prosoft cards, but the trade off is that the setup of card is a little bit more involved than the Prosoft cards...

 

We have a controllogix plc and need to communicate with a DCS that uses controlnet for I/O communications. do i need to connect the prosoft Modbus to the controlnet to receive data from the DCS or i can just use a controlnet module for the controllogix to receive data from the DCS?

Thanks for your kind replies. Sorry for the newbie question, because i am just new in AB programming and DCS communication.

 

the prosoft modbus module has nothing to do with the controlnet network. it is a separate I/O module that goes into a controllogix I/O rack.

if your dcs supports controlnet it may not need any other module at all at the PLC end to communicate with the PLC.

--
Bob
http://ilbob.blogspot.com/

 

Thanks for the info.

can you teach me how do i get data from the dcs by using controlnet to control bits or words in my AB PLC. thanks in advance for your answers.

 

Joel,

To get data from DCS means that your controllogix read data from DCS through Controlnet,

so, there are 2 methods for Controllogix read data through Controlnet:

1. Message

http://literature.rockwellautomation.com/idc/groups/literature/documents/ap/1756-ap002_-en-e.pdf

2. Produce-consume

http://www.e-applied.com.tw/technol...uced and Consumed Tags Programming Manual.pdf

<b>Moderator's note:</b> the forum software places spaces in long urls. Please delete them when copying and pasting them in your browser.

But above documents only details setup, configuration and programming on Controllogix side only. In order to get Controllogix and third party communicate through Controlnet, you need to consult also with DCS manual. Please check which method (message/produce-condume) your DCS supported

Hope this help
Ikhtiander