Logix5000 & Modbus (slave) over ethernet

Hey gang -

I can't seem to locate any decent sample code for accomplishing what i need to do.

I have a CompactLogix L23E, connected via ethernet to the rest of the network. I wish to poll the PLC and read various modbus registers, and i'm not having a great deal of success.

I have some sample code (Modbus_EZ_v2..) that makes it a Modbus Slave, but evidently only in the serial port(because I have to assign it a modbus address), and I need the ethernet port, as a distinct 485 network is coming into the serial port. I don't have a Prosoft card.

So, in one line, I'd like to read Local:*:I:* over Modbus via Ethernet.

Thanks for the push.

What you are requesting cannot be done with the built-in Ethernet port of the CompactLogix.

The most straightforward solution is the Prosoft Technology MVI69 module for Modbus/TCP.

Another possible solution is to use a Modbus/TCP to EtherNet/IP gateway device. Vendors include Prosoft (ProLinx gateways), RTA Automation, Digi, and HMS Fieldbus (Anybus-X).

well, then i have been misinformed by my rep from the start. This is probably the worst news I've heard this quarter.

So, the L23E can be a modbus slave, but NOT through the ethernet port, for some reason. The RS-232 port is being used up by a 422 network, so, evidently, I have no current way to get the information out of the PLC??

Jeez.

In general, Allen-Bradley controllers only use Allen-Bradley protocols on Ethernet.

Only the SLC-5/0x and MicroLogix 1100/1200/1400/1500 support Modbus RTU on the serial port natively; the ControlLogix family resorts to that ASCII-processing application routine.

Prosoft is always the go-to company for Modbus interfaces to RA controllers. I have yet to find a Modbus application I couldn't do with a Prosoft module.

Does your communication application only support Modbus/TCP ? What is the device that you need to use to poll the controller ?

Well I don't know much but I do know I need to cover this more closely.
You have an AB Contrologix 5000 series PLC right? an L32E?
And you need a Modbus Slave driver for TCPIP? Or do you need it for another port which you don't have because it's a distinct 485 port.
I guess I am now confused, what "distinct" 485 is that port doing?

Bitmore

There is a few different networks, from which data is to be read and stored onto an on-site computer. The data sources are:

a 485 network to about a dozen Multitek meters
a 422 network to three gensets
a CompactLogix L23E, to pick up various discrete and analog signals

The current plan has the 422 network connected to the serial port of the PLC, and the 485 network connected to the serial port of a Spectrum Controls Webport.. The Webport and the PLC are both on the same ethernet LAN as the computer, which can speak Modbus through some custom scripts, and the computer is intended to poll data from each device.

In the event I couldn't poll the PLC directly to obtain the data, I was going to use the Webport and Modbus/TCP to poll the PLC, and allow the Webport to be the data concentrator for the project. The local PC would then obtain the complete data from the webport (which is currently working).

The breakdown appears to be that the ethernet port on the L23E is rather single-minded, leaving me with a bit of a puzzle to get the data out of it. Perhaps I need to connect the PLC to the 485 network through it's serial port, and put in a 422->485 converter and put the Gensets on the 485 loop as well, so EVERYTHING will be talking 485 to the Webport.

http://www.prosoft-technology.com/content/view/full/6458

That guy will fix this issue, yeah?

Or, I'll likely convert everything to 485, including the PLC (via serial port), and then talk to the PLC over 485, leaving the ethernet port as a programming port only.

Can't help with L32E, but will work with L4x and ControlLogix using EWEB modules
http://rockwellautomation.custhelp....ion.cfg/php/enduser/std_adp.php?p_faqid=33697

I'm getting a 1768-EWEB, as it says you can access all the tags over ethernet this way, using XML. That'll be fine for my purposes.

However, I STILL can't seem to find, online, any sort of documentation about the capabilities of the onboard ethernet port on the L23E. Lots of documentation about modbus, lots about "embedded EtherNet/IP capabilities for ease of use," but nothing really talks about what the ethernet port CAN do.

Can anyone more experienced point me in the right direction?

-- edit
http://www.ab.com/en/epub/catalogs/12762/2181376/2416247/407648/7921716/

Here, I guess. "Modbus" is only listed under Serial. So, no Modbus/TCP at all.

lots about "embedded EtherNet/IP capabilities for ease of use," but nothing really talks about what the ethernet port CAN do.

Click to expand...

Ethernet/IP is a protocol (read language), same as Modbus TCP - this is a protocol.

L32E, L35E,1756-ENBT,1756-EN2T,1768-ENBT only support Ethernet/IP (CIP) communication protocol. They do not support Modbus TCP or any other protocols.

1768-EWEB, 1756-EWEB support Modbus TCP via sample application - link above - this is untested, unsupported sample.

1768-EWEB can be used only with L4x controllers, it can't be used with L32E.

Bottom line- if you need Modbus TCP - use Prosoft card.

I guess it could have been another application of the G3 Data Station from Red Lion, but now it seems there are enough 3rd party interfaces to get the job done, albeit in a round about way.

digi one iap. should be cheaper than a prosoft card.

Yeah, now that I have a CompactLogix -EWEB in my hands, I notice it's not compatible with my CompactLogix processor. System reqs for the -EWEB kept talking about browsers and stuff. Only when I get to the installation instructions do I notice it won't work. Man, I'm really screwed. How can it be so difficult to move data off of the PLC - through any means necessary.

So, the -L23E has an ethernet port, which can't read the data, and it's not possible to install the -EWEB on it to accomplish that task, so now it's back to using a Prosoft card, pushing every tag through modbus to another device (the Webport) so that I can read it over ethernet. I wish I had more time to research this stuff.

Contr_Conn said:

....
Bottom line- if you need Modbus TCP - use Prosoft card.

Click to expand...

I don't, i need the data, via ethernet. It's just coming into the PLC via modbus, and physical inputs.

mainstreetmark said:

Yeah, now that I have a CompactLogix -EWEB in my hands, I notice it's not compatible with my CompactLogix processor. System reqs for the -EWEB kept talking about browsers and stuff. Only when I get to the installation instructions do I notice it won't work. Man, I'm really screwed. How can it be so difficult to move data off of the PLC - through any means necessary.

So, the -L23E has an ethernet port, which can't read the data, and it's not possible to install the -EWEB on it to accomplish that task, so now it's back to using a Prosoft card, pushing every tag through modbus to another device (the Webport) so that I can read it over ethernet. I wish I had more time to research this stuff.

Click to expand...

check out the digi one iap. its pretty easy to do. you just map the data to an array, tell the digi the array and then it converts it to modbus. I believe it will go both ways, in and out over ethernet in case you need to bring modbus data into the plc.