What is the difference between Ethernet and serial communication?
As the earliest communication method between electronic equipment and computers and electronic equipment, RS-232 serial port is now widely used in the field of industrial control. The RS-485 bus is used to make up for the short communication distance of RS-232 serial port communication technology and can only support point-to-point data. Communication technology resulting from communication and other shortcomings is also widely used in the field of industrial control. As the information society's requirements for industrial automation continue to increase, and the degree of industrial automation continues to deepen, since the RS-232 serial port supports point-to-multipoint communication, the communication distance is less than 15 meters, while the communication distance of RS-485 bus technology is 1200 meters. , due to the one-master-multi-slave communication mode, the slave device needs to wait for instructions from the control host to receive and send data. The baud rate of RS-485 bus technology for long-distance communication cannot be higher than 110Kbps. For large amounts of data and real-time Communication tasks with high sexual requirements are difficult to meet the needs. The original industrial control system based on RS-232/485 serial communication is increasingly unable to meet the actual needs of the industrial control field.
With the development of Ethernet technology and the Internet in various fields of social life, industrial Ethernet technology is now gradually penetrating into the field of industrial field control. The original industrial control network was basically dominated by field buses. Now due to Ethernet technology With the popularization and application of office systems and the continuous development of Internet technology, industrial Ethernet technology has gradually penetrated into the information layer and control layer of industrial control networks. However, the equipment layer of industrial control networks still basically uses fieldbus technology as the main communication method. , so the industrial control network is still in the process of mixed use of fieldbus technology and industrial Ethernet technology. It is very necessary to connect these devices that use fieldbus technology to communicate to industrial Ethernet, and the RS-485 bus in the field of industrial control Equipment and RS-232 serial port devices have a considerable share, and connecting serial port devices to industrial Ethernet is of considerable importance.
Using industrial Ethernet technology as a communication method has the following advantages compared to RS-232/485 serial communication technology:
1. The configuration of Ethernet devices is more flexible and convenient. The communication between multiple RS-232 serial devices and the computer is generally achieved by connecting a multi-serial card on the PCI slot of the computer or a USB-to-serial hub through a USB serial port to realize the expansion of the RS-232 serial port. Each computer has a certain number of PCI slots or USB interfaces, which limits the number of RS-232 serial devices that can communicate with the computer. Although the RS-485 serial ports bus has simple wiring, many load devices, and the communication distance can reach 1200 meters, its wiring must adopt a hand-in-hand daisy chain topology. Adding equipment to the RS-485 bus requires laying out the lines or adding 485 Repeaters or 485 hubs are used to solve wiring problems, but Ethernet is different. As long as there is a network information port, the relevant Ethernet devices can be directly connected to the Ethernet, and the number of access devices is basically There is no limit.
2. Supports hot-swappable work and can configure related devices while the system is working without stopping the system. For example, when the computer needs to add a multi-serial port card to expand the number of RS-232 serial ports, the computer needs to be shut down and the chassis is opened before the multi-serial port card can be added. The same principle applies when adding the corresponding 485 device to the RS-485 bus. The line needs to be interrupted before the corresponding equipment can be added. To add the corresponding Ethernet equipment on the Ethernet, you only need to connect the Internet cable to the nearby information port, and then configure it through the relevant software on the computer to work normally.
3. It is simple and easy to use, and the later maintenance is convenient and simple. Whether it is RS-232 device or RS-485 bus communication, it usually only communicates with a single computer. It is difficult to form a dual-server redundant hot backup system. However, it can be very easy to use on Ethernet. Easily configure a dual-server redundant hot backup system. In the same way, redundant links cannot be formed based on RS-232 serial communication or RS-485 bus communication. Once a problem occurs, the entire system may collapse, especially the RS-485 bus. Problems occur on the RS-485 bus ( Such as short circuit), it is easy to cause the entire system to be unusable, and it is very difficult to find the fault point on the RS-485 bus, and it needs to be checked one by one. Based on industrial Ethernet as a means of communication, similar problems can be avoided. Industrial networks using industrial Ethernet switches to lay out ring redundant links can self-heal within 20ms and provide timely alarm prompts for maintenance once a link has a problem.
4. High scalability and expansibility, very suitable for flexible wiring. As mentioned above, Ethernet equipment uses hot-swappable work and is flexible and convenient to configure. Using Ethernet as a communication method can have no restrictions on distance or quantity. The RS-485 bus communication distance is 1200 meters, which can be achieved by adding a 485 repeater. Or it can be converted into optical signals through optical fiber modem and transmitted through optical fiber to extend the communication distance. However, the transmission distance always has certain limitations. Ethernet can be connected to the Internet, and through the Internet, it can be anywhere in the world with a network connection. For data exchange, similarly, the maximum rate of long-distance communication on the RS-485 bus is 110Kbps, and now Fast Ethernet (100M) has been basically popular, and Gigabit Ethernet is gradually entering the industrial control field, so the communication capacity of Ethernet And there is basically no limit to the number of devices that can communicate on an Ethernet network.
5. Realizing true "management and control integration" through Ethernet communication, with the deepening of industrial control automation and office system automation, the goal of "management and control integration" in the field of industrial control is now proposed, that is to say, industrial control systems and office automation The system can be closely integrated, and information exchange can be seamlessly connected. Since office systems are now based on Ethernet for data exchange, all software runs on Ethernet, and there is no need to make any modifications to communicate with Ethernet devices. They can communicate directly with them, and can quickly integrate Ethernet in industrial control networks. Equipment-related data is integrated into the office automation system.
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Post time: Dec-27-2023