Could you please inform me  about the max distance in line topology at profibus?

I have a master device (s7-400) and every 400m there are slave devices (s7-300).
So,  for 8km I have 20 slave devices (nodes), like below:

[s7-400]    - 400m-     [s7-300,id=3]    -400mm-    [s7-300,id=4]   -400mm-   ......    [s7-300,id=22]
                                                        

In this wiring, I will need PROFIBUS repeaters or the DP slots of slave devices are simultaneously repeaters? 

Hi,

See the Acceptable line length in PROFIBUS-DP networks.

For that distance.... Maybe you could have a look at the option of Fiber Optics. See SIMATIC NET PROFIBUS Networks under chapter  "3.2 Configuring Optical Networks".

I hope I could help!

Thanks for your quick response.