S7 Ethernet protocol ??

RussB

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I have a customer who wants to communicate to an S7 PLC with an ethernet port. We would like to know what protocol the port supports. The distributor can only tell me that it is TCP/IP. The programming software that my customer has works serial only, so it does not help.
Spcifically we would like to talk to an operator interface device that has these ethernet protocols available: GE SRTP, GE EGD, Modbus TCP/IP, AB TCP/IP. Can any one verify that one of these is available for the S7?
TIA
 
From what I have been able to gather, the Siemens Ethernet offerings will just encapsulate other Siemens protocols (MPI, Profibus, etc) into TCP/IP or UDP packets and transfer those. So unless your HMI has Siemens Ehternet support you are out of luck as far as I can tell.

Keith
 
Your are out of luck

Siemens has their own protocol. Actually it is a ISO protocol. The CP343-1 I have can package the ISO protocol in a TCP/IP packet. Siemens Ethernet is not easy to initiate from a PLC. It is fairly easy to read or write Ethernet packets from a PC. It may be possible to build a Modbus/TCP packet inside a TCP/IP packet but that is a lot of work. Even if you could I don't think you should. It would be cheaper to buy a bridge or use a PC as a bridge.

Shame an on all the PLC companies for setting the high bar only high enough to trip over. The PLC companies should have their Ethernet modules support mulitple application layers so they can talk to different brands. We do it.

Isn't there a CP341-? card that can communicate using Modbus over a serial line? I think may be the best/cheapest solution. I don't have any experience with serial comms with a S7 though.

JRW, Roy, where are you?

BTW, JRW or Roy, can I program a S7-315 over the Ethernet using the CP343-1? Please say yes. Programming a S7-300 over serial/MPI is too slow and for some reason my CP5511 doesn't work.
 
Peter-
Thought I would jump in. Yes, you can program the S7-315 over Ethernet using the CP343-1. However, you will also need Simatic NET on the computer you are programming from.

Keith
 
Peter

Don't let anyone tell you that you have to buy one of those cursed Siemens CP1613. They are expensive.. Softnet is better. you
can use a standard ethernet card


BTW, has the CP5511 ever worked? That puppy is too expensive to be sitting in a drawer
 
Last edited:
PC to PLC Data Transfer

I need to send about a dozen words continously 100 times / sec to A Customer PC running a custom C++ written GUI and receive 1 or 2 words back not as fast. The customer prefers to use Ethernet. I was hoping to setup a datablock and just send/receive from/to it as transferred as an ethernet packet. It looks like I'll need an ethernet CP343-1 and softnet to do so. Even with this it doesn't look to be straight forward Send Data / Recieve Data. My rep is pushing Profibus. Is softnet & OPC required to transfer a simple datablock? Is Profibus easier to setup in this case? Either way how does the customer's GUI tie in.
 
It won't be possible

The Siemens CP343-1 can't update that much data that quickly. Neither can Profibus DP. You need to make some choices. Profibus DP can update data at the PLC scan rate but the number of words it can update this quickly is limited to about 16 in and 16 out. More data can be sent back and forth in one transfer but then the data isn't consistant. Our motion controller can communicate with the S7 using Profibus DP and Ethernet. The fastest the Ethernet can update is about 18 milliseconds for small packets. The limiting factor is the S7 back plane and even after the data gets to the CP343-1 card it still must be transfered across the backplane.

It is not easy to initiate Ethernet transfers from the S7. It takes two blocks. One to initiate the transfer and another to receive the data. On top of that the message header needs to be built. I may have some examples around. I am just recovering from my laptop crashing.

We have a S7 315DP with a CP343-1. We use this to test communications with our motion controller.
 
Russ, I concur with what Peter said. There is no way you will be able to update a GUI every 10ms. Which brings up the obvious question: Why do they need to update a GUI that often? Is there some kind of other process running behind it? Are they doing some kind of machine control at the PC level? It sounds to me like the approach may be inherently flawed, so you may want to look at that first.
 
In looking closer into it I see the obvious that even if data was sent at 10ms intervals it would only be updated at the 20-30ms scan rate. There was originally going to be a significant amount of control at the GUI but now it's mostly monitoring that does need to be recorded at a fast rate but probably not at the rate in the specification. Bottom line I still have to come up with a fast communication method but probably not as bad as first percieved. My Siemens rep says the 343-1 will send Native Ethernet, I'm hoping this will work as the data transfer is only a block of values & always the same values in the same order.
 
What is 'Native Ethernet'

I think what he is trying to say is that the S7 can send TCP/IP packets. If so the Siemens rep is correct. However this is what makes Ethernet communications such a pain in the rear. Siemens does not have an application layer like Modbus TCP/IP or Rockwell's CSP or Ethernet/IP. You must build the application headers yourself. This is tedious and you WILL be testing your STL skills. This is where both Modicon and Rockwell have Siemens beat.

Profibus would be much faster for 16 words in and 16 words out. If you use consistant Profibus DP transfers then you are limited only by the PLC scan time as the Profibus itself is MUCH faster than the plc.
 
Re: What is 'Native Ethernet'

Peter Nachtwey said:
Profibus would be much faster for 16 words in and 16 words out. If you use consistant Profibus DP transfers then you are limited only by the PLC scan time as the Profibus itself is MUCH faster than the plc.

How do you access the Profibus data on the PC side. The're hoping that they can use sockets and COM, DCOM since they are writing the GUI themselves. Either way I'm afraid this will be the biggest hurdle for me to overcome in the whole project. Always something new to learn.
 
It depends on Profibus DP master

Each manufacturer has its own set of DLLs or ActiveX for accessing the Profibus DP master from the PC. Normally they try to make it easy to access this data using VB or Excel. Do you know what Profibus DP master you are using? It would be good to know if the Profibus DP master you plan to use will be easy to interface to. It is time for you to do some research.

Roy or JRW should be able to tell you what is available from Siemens.
 
I just want to pull the data in through a socket connection with DCOM. Do you still need DLL's and Drivers, and ActiveX? The're not looking to use a HMI development package, just C++.
 
I got what you need. I have attached an example of Native TCP, a small VB ap and the VB source so you can "Roll your own". Be aware, to get the speed you are looking at, you must leave the port open. I had a customer that complained about the time that it took to open and close the port. Why he insisted on closing it, oh well..... If you have a CP343-1, you won't need Softnet ot Simatic Net, just VB 6.0. I like to use this demo over the internet to a PLC setup in the office and then give it away on a floppy, blows their mind, that they can have it for free. Keep in mind the CP343-1 communicates across the backplane at 187.5k serial. The 443-1 (s7-400) is parrallel. As far as Modbus, you would be better off with a CP340/341 and run serially. Ethernet I/p is propritary and neither are supported in the CP343. I am working on putting Modbus TCP in a wrapper for the CP343/443. I am also working on the new CP443-1 IT that has web pages and will send FTP packages, from a DB to any PC in an ASCII packet. Once there, you can parse the data. Yes you can program over the internet with ethernet. Peter, my guess is, someone connected the CP5511 with a serial cable, instead of the 485 cable and burned the dongle up. I've seen it a few times. The dongle HAS to be attached to the card for the computer to see the PCMCIA card.
 

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