I posted initial question about it June 1^st. Since then ixo65 contributed greatly to the discussion. I thank ixo65 greatly for being so patient with me sharing knowledge and examples. Yet I still have questions.

• Assume LOGO is configured as Client and S7-1200 – Server. What process initiates data transfer/communications? In examples all I see is mapping data from LOGO to data blocks in S7-1200 and vice versa. And the data magically appears on the other side of the network, does it? There must be some hidden mechanism of data transfer.

Question related to the above: what is the periodicity of this data transfer? Can frequency of transfer be adjusted/controlled?

• Second question relates to the above as well: How does it happen that multiple LOGO’s configured as clients on the same network and not time-synchronized, yet data transfers from them do not collide?

AndreyGle

I posted initial question about it June 1^st. Since then ixo65 contributed greatly to the discussion. I thank ixo65 greatly for being so patient with me sharing knowledge and examples. Yet I still have questions.

• Assume LOGO is configured as Client and S7-1200 – Server. What process initiates data transfer/communications? In examples all I see is mapping data from LOGO to data blocks in S7-1200 and vice versa. And the data magically appears on the other side of the network, does it? There must be some hidden mechanism of data transfer.

Question related to the above: what is the periodicity of this data transfer? Can frequency of transfer be adjusted/controlled?

• Second question relates to the above as well: How does it happen that multiple LOGO’s configured as clients on the same network and not time-synchronized, yet data transfers from them do not collide?

Dear fellow,

Assume the whole forum did not follow your conversation with Mr. ixo65.  

• Link to your conversation (topic)
• Give some sample coding for both S7-1200 and LOGO! archived in a ZIP file.

At first glance your questions is about how the S7-1200 handles the communication -- not so much the LOGO! Then also we might think that you are using Modbus TCP while you speak of S7 communications. Mention also how many devices are used.

Thank you for your reply.

No specific code to share - I am still trying to understand how it works. The question is about LOGOs. If I make LOGO a server S7-1200 Client executes PUT/GET function and this transfers the data. If LOGO is a client nothing visibly gets executed but data gets transferred. 

I am trying to understand how this happens, how collisions are avoided with multiple LOGO clients (in my case it will be 4 LOGOS) and if the timing of data transfer can be controlled with LOGO clients.

Andrey,

When you make it easy for our volunteers to follow your thoughts then chances increase that field experts will come to discuss this case with you. Not providing linked information reduces your chances for constructive conversation.

The original topic you abandoned is published here:S7-1200 PLC collecting data from 4 LOGO’s. Therein the application example (LOGO! - S7 Connection with LOGO! Client and S7-1200/1500 Server) was given to you for study.

The application example uses "S7 communication" and direct/absolute addressing. The configuration on the S7-1200 side is made only in hardware configuration. A resource identity is created and the device responsible for making the connection is selected.

The LOGO! side the configuration is done via configuration and an assignment table. In the assignment table the absolute addressing is listed for LOGO! against the S7-1200. This reminds of an i-device configuration. The PUT and GET functionality is within the LOGO! and timing regulated by the LOGO!

The S7-1200 reacts by background processes to the requests as poled by the assigned resource. Each resource is poled (time slicing) as the CPU chooses. Note that the CPU has a limit to the count of communication resources that it will handle. This limitation ensures that each device can be serviced in a timely manner.

One important point: The S7-1200 DBs linked to the LOGO! must not be of an optimized structure.

You are welcome to use the "Support Request" link to speak to Siemens directly if this topic does not meet your requirements.

Best health.