In today’s automation landscape, network structures have become a cornerstone in industrial environments across various sectors. They serve as the foundation for control systems, with their performance directly impacting the overall system efficiency. Traditional communication methods like serial ports, fieldbuses, and Ethernet have been widely adopted and refined over time. However, with the rapid advancement of IT technologies, these conventional setups are undergoing significant transformations—particularly with the growing commercialization of Ethernet in industrial settings.
Ethernet is evolving from low-level, slow-speed, non-real-time, and closed systems to high-speed, real-time, open, and flat architectures. It integrates multiple fieldbus technologies and protocols, supported by cost reductions and increased speed. Global automation leaders have successfully implemented "e-network flattening" strategies, challenging traditional control systems. As a result, Ethernet has transitioned from theoretical concepts to practical integration within industrial communication systems.
Looking ahead, the future of automation networks hinges on the standardization, versatility, and openness of application-layer protocols in the Ethernet ISO/OSI model. These factors determine whether devices from different vendors can seamlessly interact. Open and standardized protocols provide an efficient platform for interconnecting diverse devices, enabling unified management across different levels and manufacturers. Siemens’ Industrial Ethernet S7-1200, for example, aligns with these market trends, as illustrated in Figure 1.
Figure 1: S7-1200 Industrial Ethernet Architecture
The development path of S7-1200 reflects a strong emphasis on standardization, flexibility, and openness. It combines efficiency, real-time capabilities, and reliability, incorporating both standard and custom Ethernet solutions. Based on “TCP/IP + standardization (Profinet) + universality (S7/S5 compatibility, IT, ISO, etc.) + openness (Open IE),†this architecture represents one of the most advanced forms of industrial Ethernet.
S7 communication and S5-compatible communication are standard protocols used in the S7 PLC family. These protocols allow device communication without relying on specific bus systems, supporting Ethernet-based S7 stations, S5 stations, and PG/PCs. Open IE refers to communication using standard protocols like TCP, ISO on TCP, or UDP, enabling direct socket access and open communication services. This approach supports flexible, free communication with external devices using binary or ASCII formats, making it ideal for custom or proprietary protocols.
In the context of semiconductor manufacturing, where microprocessors, MCUs, ICs, and power semiconductors are produced, various third-party devices such as weighing instruments, label printers, barcode scanners, inkjet printers, and sorters are commonly used. These devices share several characteristics: they are widely distributed, require high wiring costs, use inconsistent protocols, lack physical layer uniformity, and suffer from poor networking performance and complex maintenance. Their communication needs often include low real-time requirements and uneven traffic.
Common networking solutions for these devices include analog I/O modules, USB/RS232/RS485 serial point-to-point communication, various fieldbuses, industrial tablets, and PC-based TCP/IP programs. Among these, serial communication remains the most prevalent. For instance, the S7-300 PLC may expand its serial port functionality via CP340/341 modules. However, differences in physical layers (RS232/422/485) and protocol limitations often necessitate multiple serial ports, increasing costs and complexity. Additionally, issues like low transmission rates, limited communication distances, and difficult maintenance make these solutions less efficient.
By leveraging the existing shared Ethernet infrastructure within the factory, we can achieve more obvious advantages compared to traditional approaches. First, the physical and data link layers of Ethernet follow IEEE 802.3 standards, ensuring a unified medium access layer. This simplifies the interconnection of Ethernet-enabled devices, allowing them to quickly exchange information over a common channel.
Second, the transport and network layers of Ethernet support IP-based TCP/UDP protocols. TCP offers reliable, structured communication, while UDP provides faster, connectionless data transfer. Although UDP lacks guaranteed delivery, it enables higher throughput. The "ISO-on-TCP" protocol, defined in RFC 1006, enhances reliability by supporting block transmission with acknowledgments. However, it is primarily used within the Siemens S7 product line, limiting its adoption by third-party devices. Thus, connection-oriented TCP/IP communication remains the preferred choice.
In conclusion, using a unified media access layer, standard TCP/IP transport layer, and open application layer through Ethernet is the optimal solution for connecting third-party devices in industrial automation. This approach significantly reduces equipment investment, wiring, and maintenance costs, while improving flexibility, usability, and synergy with the PLC control layer. It also simplifies the network structure, facilitates future upgrades, and aligns with the growing value proposition that manufacturers prioritize.
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