Hi guys,

I'd like to communicate with some Siemens PLC outside my project. In order to do so, I chose to use a S7 communication and BSEND/BRCV blocks (we don't want I-Device nor GET/PUT).

However, upon creating the S7 communication link, the "one way link" is enabled AND grayed out (see attachment). For me to use BSEND/BRCV, I need a two way communication...

In the following documentation, chap. 2.2.2 :

https://support.industry.siemens.com/cs/us/en/view/18516182

It seems to be possible to have a two way unspecified S7 communication .

I'm using TIA Portal v16 and a CPU1513F.

Any help is welcome !

Thanks !

I tried to do the same in a random Step 7 project and I had the same result. However, Step7 documentation is more complete regarding the matter.

It seems that in order to have an unspecified two way communication using BSEND/BRCV, two S7 communication had to be used for each PLC. Each one of them is a one way communication (option is enabled and grayed out).

If anyone that ever came accross the same issue could confirm, would be great !

Hi Lucas. T,

an unspecified connection is a connection where one of the two partners is unspecified. That is possible, if the unspecified partner acts as server. An unspecified connection is always a one-way connection. Even thought, it is possible to create a specified one-way connection.

It's not possible, to create a two-way connection wothpout specifying it on both partners.

I can't explain why the checkbox is shown. In case of a S7 connection, the TSAP defines the connection type. So the checkbox is not needed.

Kind regards
Stefan

Hi Stefan,

Thanks for the explanation, much appreciated !

It's very odd that the documentation doesn't warn the readers that two different S7 connections have to be used in order to use BSEND/BRCV with unspecified partner.

Best regards

Edit : Ran some tests. BSEND/BRCV worked fine with one S7 communication link loaded in both partners.

Lucas.T

Hi Stefan,

Thanks for the explanation, much appreciated !

It's very odd that the documentation doesn't warn the readers that two different S7 connections have to be used in order to use BSEND/BRCV with unspecified partner.

Best regards

Edit : Ran some tests. BSEND/BRCV worked fine with one S7 communication link loaded in both partners.

 Is there any way you could post a screenshot of your Connection settings for both of these PLCs? I am struggling with the exact same issue and have not found a solution as of yet.