MPI is short for Multipoint Interface! MPI doesn't need software support! It can only achieve a small amount of data exchange in PLC! The physical layer of the MPI is Rs 485. MPI and DP are both PROFIBUS, the bottom layer is 485, but MPI is not open, DP is open. MPI is used between PC, computer programming,cabinets and cabinets.Profibus DP. This is the Siemens Fieldbus . Field I/O module! If you are a novice and want to learn, I recommend a book, "Easy access to Siemens S7-300 plc" PROFIBUS D P is not unique to Siemens Communication, is an open communication standard, there are many manufacturers support, with long transmission distance, the communication is reliable, the network is simple and so on the merit, is convenient and practical.
But MPI is a kind of communication way which Siemens uses exclusively, only Siemens internal equipment uses, does not have the openness, needs the special communication cable and the interface, other manufacturers basic does not support.
DP Connector, with a multimeter can be measured, usually 3 feet is a + , 8 feet is B-. You can check that there is a red dial switch ON the DP head. If the device is in the middle of the communication bus, the switch should be in the OFF position. If the device is at the end of the bus, the switch should be in the ON position. The same is true for other inverters.