Hello dolby;

You seem to have been given a very interesting task, and you have tried to describe it with good details.

But there is a basic problem: to my knowledge 2 masters cannot exchange data over Profibus-DP except if connections are established between CP 342-5 (one on each CPU rack) or if a DP/DP coupler is connected between them. You have provided enough information so we can eliminate these possibilities, so I do not see how data is exchanged in the old project.

Could you open Netpro, and check if any connections have been created for each CPU: click on each CPU's Profibus interface, and if any connections are configured they will be listed in the table that appears below the project topography.

Another possibility: you do not mention if HMIs are present in the project, and if they are configured for communications to more than one CPU at a time. But in certain projects we have used operator panels as data collectors:  you write a value from CPU1 to a tag in the HMI panel, and read it from CPU2 (for example), and in that way exchange data between CPUs. But unless the program comments are very well done it will be difficult to determine which of these values serve to read/write to the CPU masters.

So basically your problem is to discover which values are actually written from one CPU to another; possibly some documentation exists in te project documents or in the comments. Once you identify them, we can help you uincover the exchange mechanism used in the old project, and see if it can be duplicated with the new CPU.

Hope this helps,

Daniel Chartier

Hello dolby;

First, Navnag's suggestion will work well for short distances between CPUs; MPI transmissions are limited to 50 m max. because the MPI ports are by definition non-isolated, so port power is low. Repeaters could be used to extend the MPI network (by segments of 50 m, if there are MPI partners on the segment; by a length of 1000 m , if there are no MPI partners between 2 repeaters.

Second, there is lot of information on the DP/DP coupler in the Siemens Product Support pages, just use the search box at the right of this page to look for it.

These documents will concentrate the most important details;

DP/DP Coupler

https://support.industry.siemens.com/cs/ww/en/view/1179382

What are the special features of input/output addressing with the DP/DP coupler?

https://support.industry.siemens.com/cs/ww/en/view/22327981

Configuration of the I/O Data on DP/DP Coupler

https://support.industry.siemens.com/cs/ww/en/view/19281019

Next, try this test on the MP you will use to transfer data between CPUs: Create 2 tags of the same type in the tag list of the MP, one attached to CPU1, the other to CPU2; if you have many such tags to transfer, identify them properly, for example MotSpeed_CPU1 and MotSpeed_CPU2. Then use a global script to transfer

MotSpeed_CPU2:= MotSpeed_CPU1.

In the program of CPU1, write the value of the motor speed to the address linked to MotSpeed_CPU1. Then in CPU2 read the value in the address linked to MotSpeed_CPU2.

Once one value has been transferred from CPU1 to CPU2, repeat the process for all the tags ypu want to transfer. Use the longest cycle possible for the global script so as not to slow down the MP program with the tag transfers.

Hope this helps,

Daniel Chartier

Helo dolby;

Best of luck!

Remember, if you need help in your project, we are always here with a helping hand.

Regards,

Daniel Chartier