The SDI-12 communication standard, a kind of serial data communication interface protocol, is widely used in environment monitoring in Euro-American countries.

And it USES asynchronous serial communication technology based on RS-485 electric interface as communication means. The process of sending data frames are analyzed and communication protocol was made.

In dealing with the communication between host computer and CNC system in FMS, EIA RS-232C serial interface and HDLC data link are used.