The difference between Modbus + and Modbus are
1.Modbus + is a peer to peer communication. Modbus is Master, Slave concept.
2.Modbus + is high speed. Modbus effective speed is 19.2kbps.
To connect BM85 with PC, firstly you have to configure one of the 4 ports in BM85 in configuration mode, then you can connect to PC through standard straight cable, i.e., (2to3, 3to2, 5to5). For programming the BM85 you can use either Hyperterminal or Modsoft package.