Siemens S7 series of CPUs come with a lot of different communication possibilities. There are PROFINET only CPUs, DP only CPUs and PROFIBUS/PROFINET CPUs. If you have a PROFIBUS capable CPU (Siemens or anyone else’s), it can be connected to PROFIBUS DP networks. To connect DP to PA requires a media changer, often called a “coupler”, to go from the PROFIBUS DP (RS-485) to the PA (MBP-IS). Siemens sells them, Pepperel+Fuchs sells them, ABB and others as well. The PROFIBUS(not only Siemens) way of going between DP to PA is standardized on the use of a coupler, so the Siemens PLCs way to connect to PA is the way it is done.