dolbyinside

Hi guys, I am trying to make a S7 connection for a Profibus communication between master CPU and a slave CPU. I can't add a new connection in the NETPRO ("Insert->New Connection" is grayed), I tried to add a PUT and GET (BSEND and BRCV also) in the OB1 and in the Connections (right click on a PUT function for example) I also tried to add a new S7 connection. But the problem is that I got the message:

"No valid connection could be established between the local and remote partners (for example, due to incomplete network or there are no more connection resources)".

So in the hardware configuration of both CPUs under the Communication tab I have changed the resources number for "S7 basic Communication" to 1, but for the "S7 Communication" there is 0 resources and it says "already configured". The problem is that the number of Resources for S7 Communication can't be changed.

 Hello dolby,

Why not use this example just change the type of CPU:

DP link between CPU 315-2DP (slave) and S7-400 (master) with ...

or this:

What master/slave communication options are available on ...   19449428

Hello dolby;

S7 connections are not linked to a protocol, you are right. But when using a S7 Connection for S7 communication blocks (PUT/GET, BSend/BRecv...) you are using a client/server exchange.

So first of all, both partners must be masters (this cannot be done with a master-slave exchange) and a client must be a CP (CP 342-5 for a S7-300) Integrated Profibus ports on the CPU do not support client functionalities. See the following FAQ, copied in the attachment:

https://support.industry.siemens.com/cs/ww/en/view/24352751

You can find more explanations from other members on the following discussion:

Master--to--Master Communication on Profibus

https://support.industry.siemens.com/tf/ww/en/posts/84804/

So, in resumé: to establish S7 connections you will need 2 Profibus masters; to setup S7 Commiunication blocks on that connection, you must have at least one CP 342-5 in the PLC that will initiate the exchange.

Hope this helps,

Daniel Chartier

Daniel,

I had the same exact problem  as dolby and I have been looking hard all night on the internet trying to understand these concepts.

I found your reply on almost every post i opened and they were helpful until i hit the jackpot with this thread.

Thank you very much for your efforts