Ethernet/IP Unconnected Message Format

Hi,

I'm trying to develop my own windows based application to communication to Contrologix via Ethernet/IP.

I've dug through the CIP specification and other documentation but I can't figure out how to derieve the very last part of Unconnected message.

In Chapter two of Vol. 1, CIP common specification, it states that message router request is composed of

1. service code
2. request path size
3. request path
4. request data

Does anyone know of any documentation that shows the format of request data?

Slim

First, my usual statement when folks are writing their own drivers: You will be money and time ahead licensing your driver from a software developer who has done it before. Pyramid Solutions (www.pyrasol.com) in particular are absolute experts with EtherNet/IP. Every EtherNet/IP implementor (except one*) that I have encountered spent more money and time on their work than they would have using Pyramid.

Now then, time for the geeky stuff.

Have you read the Logix 5000 Data Access Reference Manual ? You can get that, as well as a handful of other very helpful references from this website:

http://www.automation.rockwell.com/enabled/guides.html

Those might be the documents you mention as "other documentation".

continued.....

Look at the example on Page 19 of the Logix Data Access Manual.

For Service 0x4C (CIP Read Data) your message router request data to read a tag called "parts" would be:

04 91 05 70 61 72 74 73 00

04 is the length of the Internal Object Identifier (IOI) in Words

91 indicates a Symbolic IOI Segment

05 is the length of the Symbol in bytes (not including header or pad byte)

70 61 72 74 73 is "parts" in ASCII code

00 is a pad byte to make up the 4 Words designated at the beginning.

At least, that's my best interpretation of that manual. I am not a protocol engineer, just a technician, so I could be way off.

*

Oh, that one customer who was able to write their own EtherNet/IP driver without any help and faster and cheaper than licensing code from somebody else ? That was Peter Nachtwey and his in-house protocol genius. Those guys are good.

Re: *

Ken Roach said:

Oh, that one customer who was able to write their own EtherNet/IP driver without any help and faster and cheaper than licensing code from somebody else ? That was Peter Nachtwey and his in-house protocol genius. Those guys are good.

Click to expand...

I will tell Quinton you gave him an 'atta boy'. I don't mind telling all that it did cost a lot. Now we have the Ethernet/IP stack done and we can use it on future products. In addition, we (Quinton) developed a Ethernet/IP protocol analyzer. The protocol analyzer can be very handy for questions such as Slim's. I personally had nothing to do with the developement it except to pay for the costs.

I thought there were development kits available from ODVA.

I don't know what Pyramid Solutions charges to tell whether licensing or developing is the best option now. We didn't have an option as we were one of the first.

Got it

Hi...

Thank you for all your help. I finally figured it out. I now have a working visual application to read/write by tag names to the PLC.

The key was the Logix5000 data access reference manual.

If anyone needs help with this.. I'll be glad to help.

Sam

slim1976 said:

Hi...

Thank you for all your help. I finally figured it out. I now have a working visual application to read/write by tag names to the PLC.

The key was the Logix5000 data access reference manual.

If anyone needs help with this.. I'll be glad to help.

Sam

Click to expand...

Hello I'm trying to do the exact same thing in python. I don't know how to build the cip message. Please help me.

JEaglestone said:

Hello I'm trying to do the exact same thing in python. I don't know how to build the cip message. Please help me.

Click to expand...

This is a start.... This packet is an unconnected message that will read DINTTag from processor in slot 0. An unconnected message is service code 0x52 sent to the Connection Manager (Class 6, Instance 1). Within the Service 0x52 data payload is a service 0x4c for read tag