1. Introduction The Foundation Fieldbus (FF) is a communication protocol designed specifically for process automation. The FF fieldbus initially consisted of two parts: a low-speed bus H1 (31.25 kbps) and a high-speed bus H2 (1 Mbps and 2.5 Mbps). However, with the development of multimedia technology and the improvement of industrial automation, the real-time information transmission volume of control networks has increased significantly, and the design capabilities of H2 could no longer meet the bandwidth requirements for real-time information transmission. Therefore, the Fieldbus Foundation abandoned the original H2 bus plan and replaced it with a new high-speed fieldbus—the Foundation HSE (High Speed ​​Ethernet) fieldbus—that combines fieldbus technology with mature high-speed commercial Ethernet technology. The final specification for HSE was released in March 2000. 2. Communication Structure and Network Topology HSE is a high-speed fieldbus based on the Ethernet+TCP/IP protocol and running on 100Base-T Ethernet. It supports all the functions of the low-speed bus H1 and is a supplement and enhancement to H1. 2.1 Communication Structure The HSE model adopts the physical layer, data link layer, network layer, transport layer, and application layer of the OSI reference model, and adds a user layer on top of the application layer, forming a 6-layer communication model. The correspondence between the HSE communication structure and the model layers is shown in Figure 2-1. The HSE structure is an enhanced standard Ethernet model. The bottom layer uses the latest standard Ethernet IEEE 802.3μ technology and the CS-MA/CD link control protocol for media access control. The TCP/IP protocol is an important protocol of standard Ethernet. It is located in the network layer and transport layer, realizing connection-oriented and connectionless data transmission, and providing transmission services for Distributed Host Control Protocol (DHCP), Simple Network Time Protocol (SNTP), Simple Network Management Protocol (SNMP), and Field Device Access Agent (FDAAgent). The HSE system and network management agent, function blocks, HSE management agent, and field device access agent are all located in the user layer and application layer, providing device description and access. Function blocks can directly connect to the high-speed network by adding any dedicated device, which also enhances the interoperability of HSE devices. 2.2 Network Topology HSE devices are divided into four categories: host devices, link devices, gateway devices, and Ethernet field devices. Their functions are respectively to configure, monitor, and manage the system, link H1 bus segments into the FF-HSE network, enable communication with other standard buses, and connect high-speed I/O devices or PLCs. HSE can directly use Ethernet switches, routers, etc., and connect HSE devices through twisted-pair cables or optical fibers to establish an HSE bus control network. See Figure 2-2. 3 HSE Features Besides high bandwidth and better openness, HSE's flexible network and device redundancy and flexible function block technology are two key features. 3.1 Redundancy One of HSE's features is its redundancy design. The HSE specification supports redundancy including standard Ethernet applications. HSE redundancy provides two types: communication path redundancy (redundant network) and device redundancy, allowing all ports to be connected selectively, as shown in Figure 3-1. Communication path redundancy is the physical layer media redundancy between HSE switches, link devices, and host systems, also known as media redundancy. Redundant paths are transparent to the application; if one path is interrupted, another path can be used for communication. Device redundancy is used to prevent control failure due to the failure of a single HSE device by adding multiple identical devices to the same network. As shown in the communication model structure in Figure 2-1, each HSE device has a dedicated HSE LAN Redundancy Entity (HSELRE) to provide fault tolerance. The LAN Redundancy Entity periodically sends and receives redundancy diagnostic information. Each HSE device establishes a network status table based on the diagnostic information, recording detailed status information of all HSE devices connected to the network. Based on this network status table, the LRE selects which path or port to use for information transmission. The fault tolerance method of HSE enhances the reliability and security of the control network. 3.2 Flexible Function Blocks Function blocks are one of the technical features of FF, but before the introduction of flexible function blocks, FF devices did not receive traditional discrete signals at all. HSE not only supports all standard FF function blocks but also adds flexible function blocks (FFB) to achieve discrete control, which is another feature of HSE. Flexible function blocks (FPCs) are functional modules specifically applied to hybrid, discrete control, and I/O subsystem integration. They include eight channels of multi-channel analog input/output, discrete input/output, and special application blocks, and use the standard programming language defined by IEC 61131-3, and can also be used in H1. Applications of FPCs include linkage drive, monitoring data acquisition, batch processing, and advanced I/O subsystem interfaces. They support multi-channel technology, PLCs, and gateways, providing users with a standardized enterprise-wide protocol. 4. Application Examples and Future Prospects The following is an example of using FF-HSE fieldbus for water level and temperature control. The system structure is shown in Figure 4-1. The entire system uses Smar's FF fieldbus control equipment and software. In the system, the DFI302, management computer, and monitoring station are connected to the HSE network through a 10/100M switch. The DFI302 is an FF fieldbus controller, interface, and host system that combines the functions of a link device, field device, and gateway. Its link component DF51 connects the H1 control link for temperature and water level control to the HSE network. At the upper-level monitoring station, system logic and control strategies are configured using SYSCON software; the human-machine interface is developed using AIMAX configuration software supporting OPC technology (OLE for Process Control). This network form greatly enhances the system's openness, allowing users to flexibly configure and integrate the system. We know that neither Ethernet nor TCP/IP has formed a complete communication protocol stack; application and user layers are still needed to create an open standard. HSE encompasses all these layers, making it a truly open protocol and enabling tight and concise information integration from equipment to the conference room. HSE is designed as an Internet with control functions, laying the foundation for remote operation via 3W. Its multi-layered redundancy design significantly increases the reliability of the control system, and its flexible functional blocks allow HSE to provide ideal solutions for discrete manufacturing. HSE fully embodies the concept that fieldbus is not only a communication protocol but also a programming language, enabling system configuration, equipment maintenance, and diagnostics to be implemented using a unified language. The combination of HSE and H1 allows Foundation Fieldbus to cover a wider range of control applications, providing a high-performance network architecture for industrial automation. HSE has broad application prospects. 5. Conclusion HSE provides a low-cost, high-speed process control network based on economical Ethernet hardware and software architecture. Operating at 100 Mbit/s, HSE is used in high-speed process automation, batch processing, and discrete control applications, while also providing information accumulation for plant management and MIS systems. HSE strengthens the position of Ethernet in the industrial field, enabling FF technology to cover both the field network layer and the control network layer, and fully enabling the construction of large-scale systems with hierarchical scheduling control functions and integrated instrumentation and electrical control capabilities. References: [1] Dr. Manfred Patz. Fieldbus Foundation High Speed ​​Ethernet [J]. Softing GmbH. 2000. [2] SJVincent. FOUNDATION™ Fieldbus High Speed ​​Ethernet Control System [J]. Fieldbus Inc. 2001. [3] Yang Xianhui. Fieldbus Technology and Its Application [M]. Beijing: Tsinghua University Press, 1999. [4] Feng Dongqin, et al. Development and Characteristics of Foundation Fieldbus [J]. Automation Instrumentation, 2001, 22(6). [5] Li Jia, Yang Dianfu. The Introduction of Ethernet Technology is an Inevitable Trend in the Development of Fieldbus Technology [J]. Automation Instrumentation, 2001, 22(5).