Ethernet/IP

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Thread Starter

Asma

I want to know that the advantages/application of Ethernet/IP against Modbus TCP protocol.

Or can we use Modbus TCP integrated with the Ethernet/IP?

Where can we use Ethernet/IP to Serial gateways??
 
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Lynn August Linse

Hmm, quite a mouthful to answer.

I have written several ODVA Ethernet/Ip stacks in C and Python ... the main difference between Ethernet/IP and Modbus/TCP is about 3 to 4 weeks of development work - Modbus/TCP requiring an afternoon and Ethernet/IP 3-4 weeks if you own a ControlLogix PLC, pay for the ODVA spec and are good at network tracing to understand the difference between the spec and reality.

Lately, ODVA has included a Modbus object, which means some Ethernet/IP clients/hosts can indirectly query Modbus slaves via Ethernet/IP. A ControlLogix is *NOT* such a cient/host.

As for Ethernet/IP to serial, the primary market is for Ethernet/IP to DF1 serial. A few companies make what you could call "ASCII Import into PCCC via Ethernet/IP", but it has limitations and requires special decoding on the ControlLogix.

Anyway - bottom line is you rarely get to chose Ethernet/IP or Modbus/TCP - unless you are willing to spend serious money for a Modbus/TCP 'rack card/adapter' to convert your Rockwell PLC into a Modbus speaker. (Note: a fw of the MicroLogix PLC do speak Modbus).
 
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bob peterson

>(Note: a fw of the MicroLogix PLC do speak Modbus).

I think all the compactlogix, controllogix, and Micrologix units support Modbus on their serial ports as well. You have to set it up in logic, but it is relatively straightforward.

I don't believe any of the SLC500 or PLC5 units directly support Modbus unless you buy an expensive adder module from Prosoft, which works quite well. I have been told that someone has created a RLL implementation of Modbus on the SLC500 serial ports, but I have not seen it. I have used it for simple ASCII stuff and it works pretty good, so ASCII Modbus should be fairly easy to implement as long as you have a fairly simple network without demanding timing required.
 
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James Ingraham

"Modbus/TCP requiring an afternoon and Ethernet/IP 3-4 weeks..."

EtherNet/IP took us longer, actually. That's the annoying thing; Modbus/TCP is just so dead simple, but it appears to be dying off in the face of EtherNet/IP and Profinet (plus the "real-time" stuff like EtherCAT.)

"As for Ethernet/IP to serial, the primary market is for Ethernet/IP to DF1 serial. A few companies make what you could call 'ASCII Import into PCCC via Ethernet/IP', but it has limitations and requires special decoding on the ControlLogix."

Here I have to disagree. Moxa, digi, and RTI all make nice, easy serial to EtherNet/IP gateways.

"(Note: a fw of the MicroLogix PLC do speak Modbus)."

Actually, ALL of the Compact and ControlLogix versions can talk Modbus, with some AOIs you can download (or perhaps they're included in the install of RSLogix 5000.) Well, I say all; the newest processors don't have a built in serial port anymore. You could probably tweak the software example they give you to work with an add-on serial card or EIP to serial box, though.

-James Ingraham
Sage Automation, Inc.
 
S
"That's the annoying thing; Modbus/TCP is just so dead simple, but it appears to be dying off in the face of EtherNet/IP and Profinet"

That's a shame. I refuse to use an Ethernet product that won't support Modbus/TCP. It's standard, open, easy, and would be free (and incredibly simple) for mfgrs to implement.

Therefore the only reason left that a manufacturer would refuse to support it is intentionally adverse to my interests and those of my customer. They can peddle their buses elsewhere. Or not. I really don't care.
 
S
"I want to know that the advantages/application of Ethernet/IP against Modbus TCP protocol."

Well, you DO get the advantage of being locked into using only products that have paid ODVA the vig, and the advantage of not nearly as many confusing choices as with Modbus/TCP. Oh, and the advantage of a much more complicated protocol and license fees buried in the hardware.

AND, I guess you're more likely to get lunch from your local AB distributor.

That's about it, though.
 
SLC 500's do support modbus on the serial port if you upgrade the firmware to Rev 11

5/30 & 5/04's require a chio that will flash multiple processors to the new firmware.

5/05's have software to upgrade the firmware
You can update unlimited processors.

Fairly inexpensive.

Buy an old used PLC on e-bay and flash it to latest rev
 
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Martin Carangelo

I'm a control engineer doing some material handling work in the northeast. I've recently become interested in Python and would like to know if you would be interested in sharing any of your Python development regarding Ethernet/IP. I've written some crude code to talk to a Controllogix after reverse engineering the packet stream using wire shark. I'm not well versed in Python as of yet and would like to get a leg up. Thanks in advance.

Martin C.
Winchester Industrial Controls
[email protected]
 
I can't help you with Python, but what are you trying to do that you can't do in one of the supported IEC 61131-3 languages on your PLC? OK, so you use Python and create some code that only you can maintain. Would your customer/client appreciate that? If I were your client, I would insist on the use of a maintainable program. Are you configuring a system with unsupported hardware? Why?

Dick Caro
 
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Lynn August Linse

> I'm a control engineer doing some material handling work in the northeast.
> I've recently become interested in Python and would like to know if you
> would be interested in sharing any of your Python development regarding Ethernet/IP.

I'll send you a ZIP - I do a lot of product testing with Python including Ethernet/IP to/from Modbus mapping. My code works exclusively with the Rockwel Vendor-specific 'PCCC' object, so none of the ODVA objects, nor the multicast I/O messaging.

- LynnL at Digi.com
 
> I'll send you a ZIP - I do a lot of product testing with Python including
> Ethernet/IP to/from Modbus mapping.

Hi Lynn, can you send the python zip to me as well? Thank you in advance.
 
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