Dear Experts , 

I have :

-CPU 314 with CP 342-5 Profibus module .

-G120 CU 240B-2..

paramatizition from g120 side is done..  

I want to communicate over uss protocol ..what blocks should I use in tia portal ?

are db_send and dp_recive will be suitable >? 

if someone provides me with an application example similar to my case, that will more than appreciated ..

Hello fahad;

The CU 240B-2 has a RS-485 interface for USS or Modbus RTU interface.

Using Modbus RTU would be easier (sample function blocks have been designed by Siemens for a CP 341) but comes out more expensive since you need to purchase the loadable driver.

https://support.industry.siemens.com/cs/ww/en/view/1220184

Note that our friend TIBI68 has developped his own blocks for Modbus RTU that you can freely download here:

https://support.industry.siemens.com/tf//ww/en/posts/modbus-rtu-master-for-cp340-341-441-x-no-dongle-required/111091/?page=0&pageSize=10

Specifically for your initial enquiry: Have a look at the reply from our friend Late in the following discussion on USS protocol using a CP 340:

https://support.industry.siemens.com/tf//ww/en/posts/uss-protocol-with-plc-s7-300/30439/?page=0&pageSize=10

Hope this helps,

Daniel Chartier 

Dear Chartier ,

Thanx for your contribution,

My CP is 342-5 and not 341 ...the manual above talking about enabling mudbus in cp 341 and didnot mentioned cp 342-5..also the developed block is about cp 341

Is it the same using with cp 342-5? 

Hello fahad;

A CP 342-5 is a Profibus-DP comminication processor, and it can act as a Profibus master or slave on the network. If your drive can act as a Profibus slave, then you can use the CP 342-5 as a Profibus master to control and monitor it. 

Your drive seems to communicate over serial RS-485 with protocols USS or Modbus RTU.

https://support.industry.siemens.com/cs/products/6sl3244-0bb00-1ba1/sinamics-g120-cu240b-2?pid=229662&mlfb=6SL3244-0BB00-1BA1&mfn=ps&lc=en-WW

These protocols require a serial CP, such as a CP 340 or CP 341, as shown in the links in the preceding answer.

Although the Profibus protocol is based on RS-485, on the physical level, you cannot use a CP 342-5 for other protocols such as USS or Modbus RTU.

Hope this helps,

Daniel Chartier 

Hello Chartier ,

Now its clear..I though its possible to use *uss* protocol with 342-5 CP..so now i have to replace the g120 CU with one that support profibus ...

Thanx for help ..hope the best for you ..

Fahad