devicenet ,controlnet and ethernet/IP

[hamza 0]

I have question as Devicenet , ethernet/ip and controlnet use all the same protol to communication why we can not get data by connection decivenet I/O to ethernet module that is connected in the chassis(we suppose that devicenet I/O has ethernet port) thanks in advance

[HKU_MS 0]

All these use seprate and distinct protocols the physical layers are distinctly different none of them will (talk) to the others

[hamza 0]

but I watched youtuve video of RTS automation and they said all of them use CIP protocol and TCP could you clarify please

[Mark- 17]

Hello, CIP is made up of several different protocols. They share the same seven layer framework but are not all compatible with each other. TCP is the carrier protocol. CIP is wrapped in a TCP layer. Take the web that you used to post messages. The messages go out your computer on TCP but the browser was using the HTTP protocol to actually send and view the messages SMTP and POP3 are used to get/send your email, assuming you are not using a browser mail client. The wiring/signals is like the train tracks and the train is like TCP. The tracks and the train to do care what is in the train cars, they move the cars. CIP, MODBUS, DNP3, etc. can all ride on the train because the way TCP works.

[rswolff 9]

make it simple......there are hardware specifications and software specifications.......hardware defines the physical layer...Ethernet, RS232, etc.......software would describe the protocol being used to communicate.....that is how the information is formatted and packaged.......even if the protocol is same you can't simply connect devices with different hardware......similarly simply because two devices have the same hardware (an ethernet port) doesn't mean they can connect to each other if the protocol is different..........as an example......everyone is familiar withe TCP/IP.....its a transport protocol....it defines how the information (regardless of what that information is) will be packaged and transmitted from node to node....Ethernet defines the hardware.......so TCP/IP over Ethernet determines how the information passes from one place to another......it doesn't define what the information is...... I would suggest you Google '7 Layer Communication Model' for more information....... Bob

[hamza 0]

thanks guys is bit clear now in my mind still not 100 percent how about generic message or CIP message how controllogix can talk to Ethernet module modbus module controlnet module devicenet module using the same protocol (CIP)through backplane even tough they are different devices

[rswolff 9]

because the modules don't 'talk' across the backplane in any of those protocols.......... no offense.....its kinda like asking how your Microsoft windows 'understands' an excel spreadsheet and Itunes since we've told you Itunes can't open an Excel file...... you're asking for all intents and purposes unrelated questions....... The processor uses the data the module(s) supply it.....the method (protocol) the module(s) uses to either receive or transmit the data to the outside world has no specific reference to how the module(s) send and receive the data across the backplane. bob

[Mark- 17]

Hello, Just for discussion, why do you think the network does not extend across the backplane from card to card? Protocols, like CIP do not care or have any requirements about the media they are carried on. CIP/TCP/etc. are carried on wire, fiber, microwave, short wave, radio wave, etc.. You and I could have a string and two cans and use the CIP protocol. I would say the value of the bytes in the correct order and you would decode them and vice versa. The chassis could be an extension of the wiring in a TCP network. It is not uncommon for the backplane of the PLC to use a multi-drop serial bus to connect all the cards.

[HKU_MS 0]

Built in Protocol convertion nice idea you are already carring across to the back plane, it dosen't seem like it would be that hard to carry back out to the various media, but what about node addressing conventions for the various types of CIP protocols, I think this could get complicated if you skip the processor.

[Mark- 17]

Hello, > for the various types of CIP protocols, I think this could get complicated if you skip the processor. You need to separate the transport layer from the data the transport layer carriers. TCP/IP does not care about CIP addressing. In this discussion, each card on the backplane, that needs to, must decode the message and do whatever it does. Some message are not for the PLC or could be for a PLC in another rack that is accessed via another media type.