Siemens Protocol Questions

[Corsair]

I need some clarification.

Do they have something called Fetch/Write that is different from Get/Put? How do they differ? Are they serial or Ethernet?

What's the proper name for the Ethernet protocol that hit the S7-300 and 400 processors? Is there a Siemens protocol document for it? Can you tell me how to get that document?

Thanks to all.

 

[JesperMP]

Yes there is a protocol that is called Fetch/Write.
It is used to communicate between old S5 PLCs or between old S5 PLCs and new S7 PLCs.
It is possible to use Fetch/Write between new S7 PLCs, but it is never done.

The protocol that is mostly used with S7-300/400 is called S7-Protocol. As far as I know there is no open document detailing the internals of the S7 Protocol. There is plenty of documentation on how to configure an S7 connection in an S7 PLC or by Simatic Net software on a PC though.

What are you intending to do, and to achieve what ?

 

[chud]

https://www.youtube.com/watch?v=xiJE2_flTAc

This might help for TIA Portl

 

[JesperMP]

I forgot to say that there are several other methods and protocols that can be used.
It is best if you describe what you want to achieve, then we can provide meaningful advice.

 

[Corsair]

My HMI is written in C. I wrote a driver years ago that talks to S7-300, 400, and I've used it with an early 1200.

I had it using Snap7 for awhile but I quit going that route since I want to maintain source code compatibility with my Raspberry PI version. That's why I'm looking for an actual protocol document if one is available somewhere. I think originally I used some of the Snap7 documentation since I didn't have anything from Siemens - I'm not sure how I got it to work.

A project has come up where I have to match protocols with an existing system so I need to revisit the protocol. It looks like what I'm looking for is not available as an official Siemens thing. The assistance is still appreciated.

 

[mk42]

The protocol that is mostly used with S7-300/400 is called S7-Protocol. As far as I know there is no open document detailing the internals of the S7 Protocol.

Everything Jesper said is absolutely correct; it is a proprietary standard, but I'll add that folks have reverse engineered it. There is a Wireshark dissector for the S7 protocol (S7comm), which can help show you what is going on. There are also at least 2 open source libraries that can be used on PCs to access S7 data: Snap7 and libnodave. You could dig into the source code to learn the details.