Foundation fieldbus (FF,Foundation Fieldbus) is the most promising, one of the most competitive field bus. Led by the Fisher-Rosemount company, ISP organization composed of 80 companies and jointly led by Honeywell Corporation, joint WorldFIP North America comprising 150 companies in Europe, the two groups merged in 1994, established the Fieldbus Foundation, is committed to developing integrated fieldbus standards. FF now has more than 120 members, including the world‘s major supplier of automation equipment: A-B, ABB, Foxboro, Honeywell, Smar, FUJI Electric etc.
FF communication model based on the ISO/OSI model of open systems, the physical layer, data link layer and application layer, and adds the user layer on, manufacturers of the products at the user level based on. FF bus token is used in communication, communication and non-communication can be divided into periods. FF now has high speed and low speed two rates, low H1 bus protocol has been published in 1996, has now applied to the job site, high-speed protocols intended for H2, but H2 has been supplanted by HSE. H1 transfer rate of 31.25 Kbps, transmission distance of up to 1900m, repeaters can be used to extend the transmission distance, and support for bus powered, intrinsically safe explosion-proof environment support; HSE‘s current communication rate for 10 m bps, higher-speed Ethernet in the pipeline. FF may use the bus type, tree, daisy chain network topology, network bandwidth, communications equipment will depend on the bus number, power supply and communications media specifications and other factors. FF support twisted pair, coaxial cable, fiber optic cable and transmission media such as radio, physical transport agreements comply with IECll57-2 standards, coding uses Manchester encoding. FF fieldbus has very good interoperability, that is FF uses function modules and device description language (DDL, Device Description Language) such that can accurately and reliably exchange information between nodes.