Hi all,

I have this project with 4 axis baumueller servo drive with USS protocol and i want to use s7300 PLC  with CP340.

Now my question is whether i can make a master (Cp340 in this case) to communicate to 4 slave drives (Baumueller drives).

Searching for support in siemens site i found that with  s71200 it is possible to add a CM1241 module but can i achieve the same with s7300 and CP340?

BR

Hello Dren;

The USS protocol was originally offered as an (external) library for the S7-200 CPUs, so that they could control Siemens drives without being Profibus-DP masters. In Siemens' corporate vision of the time, Siemens drives should communicate through Profibus whenever possible.

So the USS protocol was never developed for the S7-300, as Modbus was. I know there were some attempts in developing it for CP 341, you can search fr them on the forum, but I am not sure any of them were successful.

For all later families (S7-1200, S7-1500), the USS protocol is available. And also for the ET 200S 1SI serial modules.

What changes do you have to make in the sample program 'USS Protocol' in order to operate multiple slaves on the ET 200S 1SI module?

https://support.industry.siemens.com/cs/ww/en/view/26513380

If you want to communicate with a Baumueller drive with a S7-300, you can either choose one of their Profibus-DP modules 9if your CPU is a Profibus master) or you could place a small ET 200S coupler (over Profibus) or CPU , including a 1SI module, and implement USS on that unit, as suggested in the FAQ above

Hope thos helps,

Daniel Chartier

Hi Daniel,

In the HW config of Step 7 there are dosen of  1SI module to choose of like in the pict.

Which is the best preformer for my application.

Thanks for sharing,

Warm regards,

Dreni

Hello Dren;

First of all, notice in your screenshot that the protocols supported by each version of the 1SIO modules is not the same; there are only 4 that support USS, and they give you a choice of 4 or 8 bytes interface.

The choice between the 4/8 byte interface is explained in the following document, and shown in my attachment below:

Operating instructions:SIMATIC ET 200S Serial interface modules

https://support.industry.siemens.com/cs/ww/en/view/9260793

Basically, selecting 4 or 8 bytes interface determines how many bytes are transferred over USS at every transmission cycle;  this is a choice that involves a compromise for your project: 8 bytes interface is faster (larger "throughput" per transmission) but requires more I/O space when you configure your ET 200S rack. This is your own choice, based on your requirements and the number of I/O modules in the rack.

Hope this helps,

Daniel Chartier