1984, Intel Corporation of the United States proposed a computer distributed control system-Bitbus, which mainly separated the low-speed process-oriented input and output channels from the high-speed computer multi-bus, forming the original concept of field bus. In the mid-1980s, Rosemount developed the addressable remote sensor (HART) communication protocol. A frequency signal is superimposed on the 4 ~ 20mA analog signal, and digital signal transmission is realized through twisted pair. HART protocol is the prototype of fieldbus. 1985 was initiated by Honeywell, Bailey and other big companies, which established the world FIP and formulated the FIP agreement. 1987, led by several famous companies such as Siemens, Rosemount and Yokogawa. Special Committee Interoperability System Protocol (ISP) was established, and PROFIBUS protocol was formulated. Later, the American Institute of Instrumentation also formulated the fieldbus standard IEC/ISA SP50. With the passage of time, two tit-for-tat and competing fieldbus groups have gradually formed in the world: one is the ISP group headed by Siemens, Rosemount and Yokogawa; The other is the WorldFIP Group headed by Honeywell, Bailey and other companies. 1994, the two groups announced the merger and merged into the Fieldbus Foundation (FF). Regarding the technical development and standard formulation of Fieldbus, NSFC gained the following knowledge: * * The standard formulation follows IEC/ISA SP50 protocol; Agree with the development stage schedule of fieldbus technology.