Upper computer and lower computer working principle - Database & Sql Blog Articles

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The upper computer refers to a computer that can directly issue control commands, usually a PC, and displays various signal changes (hydraulic, water level, temperature, etc.) on the screen. The lower computer is a computer that directly controls the device to obtain the condition of the device, and is generally a plc/microcontroller or the like. The command issued by the upper computer first gives the lower computer, and the lower computer interprets the corresponding timing signal according to this command to directly control the corresponding device. The lower computer reads the device status data (usually analog quantity) from time to time, and converts it into a digital signal to feed back to the host computer. In short, the actual situation is very different, but it does not change from the other: the upper and lower machines need to be programmed, and there are special development systems. Conceptually, the controller and the provider are the host computer. The controller and the server are the lower-level machines. It can also be understood as the relationship between the master and the slave. However, the upper and lower computers can be converted.

Working principle How to communicate between the two machines depends on the lower position machine. TCP/IP is generally supported. However, the lower computer generally has a more reliable unique communication protocol. When purchasing the lower computer, it will bring a large number of manual CDs, telling you how to use the unique protocol communication, which will give a lot of examples, generally for the programmers. So, let's use some new APIs. Multi-language support function module, generally supports several high-level languages ​​for upper computer programming. Usually, the communication between the upper computer and the lower computer can use different communication protocols. It can have RS232 serial communication or RS485 serial communication. When using computer and PLC communication, not only can traditional D-type serial communication be used, but also The two-wire PROFIBUS-DP communication, which is more suitable for industrial control, can realize the communication between the PLC and the host computer by using the packaged program development tool. Of course, you can write the interface protocol of the driver class to control the communication between the host computer and the lower computer. Usually, the industrial computer, workstation, touch screen as the upper computer, communication control PLC, single-chip microcomputer and other lower-level machines, thereby controlling the related equipment components and driving devices.