1. Foundation Fieldbus (FF) This was established in September 1994 by the collaboration of American Fisher-Rousemount, Yokogawa, ABB, Siemens, Invensys, and over 80 other companies to create the ISP protocol, along with Honeywell and over 150 companies in Europe to create the WorldFIP protocol. This bus has been widely used in the field of process automation and has a promising development outlook. The Foundation Fieldbus adopts the simplified model of the International Organization for Standardization (ISO) Open System Interconnection (OSI) model (layers 1, 2, and 7), which includes the physical layer, data link layer, application layer, and an additional user layer. FF is divided into low-speed H1 and high-speed H2 communication rates, with the former having a transmission rate of 31.25 Kbit/s and a communication distance of up to 1900m, supporting bus power and intrinsically safe explosion-proof environments. The latter has transmission rates of 1 Mbit/s and 2.5 Mbit/s, with communication distances of 750m and 500m, supporting twisted pair, optical fiber, and wireless transmission, with protocol symbol IEC 1158-2 standard. The physical medium of FF uses Manchester encoding for signal transmission.2. Controller Area Network (CAN) Originally introduced by the German company Bosch, it is widely used in discrete control fields, and its bus specifications have been established as international standards by the ISO. The CAN protocol consists of two layers: the physical layer and the data link layer. CAN signal transmission uses a short frame structure, allowing for quick transmission times and automatic shutdown features, as well as strong anti-interference capabilities. CAN supports a multi-master operating mode and employs non-destructive bus arbitration technology to avoid conflicts by setting priorities. The maximum communication distance can reach 10KM at 5Kbps/s, with a maximum communication rate of 40M/1Mbp/s, and the actual number of network nodes can reach 110. Many companies have developed communication chips compliant with the CAN protocol.3. LonWorks
It was introduced by the American company Echelon and jointly advocated by Motorola and Toshiba. It uses the full 7-layer communication protocol of the ISO/OSI model, employing an object-oriented design approach that simplifies network communication design into parameter settings through network variables. It supports various communication media, including twisted pair, coaxial cable, optical fiber, and infrared, with communication rates ranging from 300 bit/s to 1.5 M/s, and a direct communication distance of up to 2700m (78 Kbit/s). LonWorks technology utilizes the LonTalk protocol, which is encapsulated in Neuron chips, making it widely used in building automation, home automation, security systems, office equipment, transportation, and industrial process control.4. DeviceNet DeviceNet is a low-cost communication connection and a simple networking solution with an open network standard. The direct interconnectivity of DeviceNet not only improves communication between devices but also provides significant device-level functionality. DeviceNet is based on CAN technology, with transmission rates from 125 Kbit/s to 500 Kbit/s, and a maximum of 64 nodes per network, operating in a Producer/Consumer communication mode using multi-channel broadcast information transmission. Devices on the DeviceNet network can be freely connected or disconnected without affecting other devices on the network, and the installation wiring costs are relatively low. The organizational structure of the DeviceNet bus is managed by the Open DeviceNet Vendor Association (ODVA).5. PROFIBUS PROFIBUS is the fieldbus standard of Germany (DIN19245) and Europe (EN50170). It consists of the PROFIBUS-DP, PROFIBUS-FMS, and PROFIBUS-PA series. DP is used for high-speed data transmission between decentralized peripherals, suitable for the field of process automation. FMS is applicable in textiles, building automation, programmable controllers, and low-voltage switches. PA is a bus type for process automation, compliant with the IEC 1158-2 standard. PROFIBUS supports several transmission modes, including master-slave systems, pure master systems, and mixed systems with multiple masters and slaves. The transmission rate of PROFIBUS ranges from 9.6 Kbit/s to 12 Mbit/s, with a maximum transmission distance of 1200m at 9.6 Kbit/s and a minimum of 200m at 12 Mbit/s, extendable to 10km using repeaters, with twisted pair or optical fiber as the transmission medium, supporting up to 127 stations.6. HART HART stands for Highway Addressable Remote Transducer, originally developed by Rosemount. Its characteristic is to achieve digital signal communication over existing analog signal transmission lines, serving as a transitional product from analog systems to digital systems. Its communication model consists of three layers: physical layer, data link layer, and application layer, supporting point-to-point master-slave response and multi-point broadcast modes. Due to its mixed analog and digital signal nature, it is difficult to develop universal communication interface chips. HART can utilize bus power, meeting intrinsic safety and explosion-proof requirements, and can be used in a dual-master device system with handheld programmers and management system hosts as master devices.7. CC-Link CC-Link stands for Control & Communication Link, launched in November 1996 by Mitsubishi Electric and several other companies, experiencing rapid growth and holding a significant market share in Asia. In its system, control and information data can be transmitted to the field network at high speeds of 10 Mbit/s, offering excellent performance, ease of use, wide application, and cost savings. It not only solves the complex wiring issues in industrial settings but also boasts excellent anti-noise performance and compatibility. CC-Link is primarily a device-layer network but can also cover higher-level control layers and lower-level sensor layers. In July 2005, CC-Link was approved as a guiding technical document for national standards by the Chinese National Standards Committee.8. WorldFIP After the North American portion of WorldFIP merged with ISP to form FF, the European portion of WorldFIP remains independent, headquartered in France. It holds an important position in the European market, especially with a market share of about 60% in France. The characteristic of WorldFIP is its single bus structure suitable for different application field needs, and it does not require any gateways or bridges, solving high-speed and low-speed connections through software. WorldFIP can achieve ‘transparent connection’ with FFHSE and has technically expanded the H1 of FF, such as speed, etc. In terms of connections with the first type of IEC 61158, WorldFIP excels and leads the world.
In addition, other notable fieldbuses include P-Net proposed by the Danish company Process-Data A/S, mainly used in agriculture, forestry, water conservancy, and food industries; the SwiftNet fieldbus mainly used in aerospace; and several other fieldbuses that will not be elaborated here.
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