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S7 communications protocol

Thread Starter: MagicWolf   Started: 5/18/2009 12:16 PM   Replies: 12

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  5/18/2009, 12:16 PM
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Hello Everyone,

Where to find the description of S7 communications protocol between CPU 315-2 PN/DP and PC with the sockets TCP/IP? Not using OPC, prodave, libnodave, sapi, SoftNet-S7.

Can somebody help!

Thanks




=== Edited by MagicWolf @ 5/18/2009 1:35 PM [GMT ] ===


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  5/18/2009, 3:05 PM
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Hello,

I think S7 protocol is not open-source and generally you don't find any specific info on it. You still should use Siemens drivers like OPC (Simatic.NET) or something similar.

Regards,
--------------------------------
Darius
Automation engineer/programmer
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  5/19/2009, 7:36 AM
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Hello,

I description of the protocol seems to me has found, but it is possible not the full description!

So whether or not I can not understand it.

https://support.automation.siemens.com/WW/llisapi.dll/csfetch/1673972/mn_sendreceiveapi_76.pdf?func=cslib.csFetch&nodeid=1673974&forcedownload=true

https://support.automation.siemens.com/WW/llisapi.dll/csfetch/1172423/iethb_e.pdf?func=cslib.csFetch&nodeid=1172846&forcedownload=true

Can somebody help!

Thanks

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  5/19/2009, 7:47 AM
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Hi,

These manuals are about S7 communication drivers in SIMATIC.NET, but not detailed description about how to write your own S7 drivers. I can tell you one more time that S7 protocol is not open source and you can't find detailed info on this.
What you want to achieve ? If you want to write your own program with visual basic, C++ or C# to communicate with S7 PLCs then these manuals you provided is ok, but remember that you must buy SIMATIC.NET OPC server for this.

Regards,
--------------------------------
Darius
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  5/19/2009, 9:52 AM
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Hello,

Many thanks for the answer. Really, this document contains the description of library. Also there is a question: where it is possible download SEND/RECEIVE function library (S7_SR.DLL)?

And still the question library prodave works on tcp?

Can somebody help!

Thanks

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  5/19/2009, 10:03 AM
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MagicWolf wrote:

a question: where it is possible download SEND/RECEIVE function library (S7_SR.DLL)?



You don't need to download anything. When you buy license for SIMATIC.NET OPC then you get DVD with all needed libraries and drivers.

Regards,
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Darius
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  5/19/2009, 11:04 AM
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Hello,

In document Send-Receive Programming Interface it is written that it is library can work under Ms-DOS. I.e. it can work without an OPC-server. How the software product which includes SEND/RECEIVE library is called?

Can somebody help!

Thanks

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  5/19/2009, 5:28 PM
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Hello,

I am sorry but the MS-DOS version of this software was discontinued in the year 1998 or 99. There is no DOS driver available anymore. The Send / Receive interface you found is the C interface for the nowadays available drivers as part of the SOFTNET S7 or SOFTNET S7-Lean packages for Windows.

There you have the Send / Receive interface also in C. If you want to use Fetch / Write, as Service on the Send / Receive interface you may handle the Appendix as mentioned in the Document you posted first. But be aware the OPC Server extension of the Fetch / Write is pretty fast, maybe even faster than your Dos Window app.

Needless to say that Send / Receive is not the S7-Protocol... just to remember.

Best regards

J_Bell
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  5/20/2009, 11:19 AM
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Hello,

Many thanks for the answer!!!

J_Bell wrote:
I am sorry but the MS-DOS version of this software was discontinued in the year 1998 or 99. There is no DOS driver available anymore. The Send / Receive interface you found is the C interface for the nowadays available drivers as part of the SOFTNET S7 or SOFTNET S7-Lean packages for Windows.

If I correctly have understood you, free libraries for an exchange with controllers S7<->PC (TCP/IP) do not exist?

 

J_Bell wrote:
There you have the Send / Receive interface also in C. If you want to use Fetch / Write, as Service on the Send / Receive interface you may handle the Appendix as mentioned in the Document you posted first.

 

Thanks, but I cannot understand - CPU 315-2 PN/DP supports an exchange on S5 protocol which is described in "SIMATIC NET NCM for Industrial Ethernet" C "Linking to Other Systems with FETCH/WRITE" and "SEND/RECEIVE Programming Interface" 2 "Communication with SIMATIC S5 Programmable Controllers"???

 

J_Bell wrote:
But be aware the OPC Server extension of the Fetch / Write is pretty fast, maybe even faster than your Dos Window app.

 

I worked with several OPC-servers, unfortunately, experience not always was positive. Therefore, if there is a possibility I try to write the driver of an exchange with the controller (for me a wide experience of a spelling of drivers with controllers). But in case to write the exchange driver it is impossible or very long, I use an OPC-server.

 

And please understand me correctly, I do not think that your OPC-server bad, simply I should ensure functioning a SCADA&OPC-server together and to me to write the driver easier and to be responsible for its working capacity.

 

J_Bell wrote:
Needless to say that Send / Receive is not the S7-Protocol... just to remember.

 

Yes, it S5 the protocol or as it name on another: FETCH/WRITE, and sometimes Send/Receive. To me not important what protocol, the main thing that by means of it I could receive values of parametres and control them.

 

Best regards

Thanks

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  5/26/2009, 6:07 PM
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Hello,


well I think we have to differentiate this in certain points.

First of all let us talk about S7-Communication or better S7-Protocoll. This is a proprietary protocol for S7 Systems by Siemens. This Protocol is not freely available and only runs with drivers just like the SIMATIC NET Software.

If you would like to have TCP/IP or UDP/IP you may surely use the standard socket interface of your OS. The Libraries for these sockets are usually documented with your OS or your API.
If you would like to use RFC1006 (ISO on TCP) you may surely also use SIMATIC NET Software or you use any other implementation of this RFC for your OS. In this case you have the choice.

The Protocol FETCH / WRITE you mention is actually no standard Protocol on the S7. It is usable with the Ethernet CP’s, as it is embedded as a Server Protocol, with the TCP/IP, ISO on TCP or ISO TP protocol.
On the CPU this protocol is not natively supported at all. Here you may receive some help by Function blocs published for the use with the PN interface of the PN CPUs. The support of basic protocols is restricted here to TCP/IP and ISO on TCP.

In your case, as you want to use the CPU 315 PN/DP you may use these blocks, right. But you have to consider the documentation of these blocks too.
Send / Receive, as it is supported with the SIMATIC NET CP’s on the S7, is not possible. Here you may only use the open communication blocks, also known as T-Functions.

If you want I can offer you to post the link to the FETCH / WRITE Blocks for the PN CPU.

I hope I could bring some light into your thoughts.

Best regards

J_Bell
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