Some explanations of the upper computer and the subordinate machine

The upper computer refers to: People can directly issue control commands of computers, generally PC, the screen shows a variety of signal changes (hydraulic, water level, temperature, etc.). The lower machine is the computer which directly controls the equipment to obtain the condition of the equipment, generally is the plc/single-chip microcomputer and so on. The commands issued by the host computer are first given to the lower machine, and the subordinate machine is then interpreted as the corresponding sequential signal directly to control the corresponding equipment. The lower machine reads the device status data (general analog quantity), and translates into digital signal feedback to the upper computer. In short, the real situation varies greatly from its case. The upper and lower machine all need programming, have specialized development system.
In addition, the upper and lower computers are connected by the communication of the "physical" level of the computer, is relatively different. The general subordinate machine is responsible for the front-end "measurement, control" and other processing; The host computer is responsible for "management" processing. The lower machine is the execution unit that receives the command of the main equipment, that is, from the device, but the subordinate machine can also directly and intelligently handle the measurement and control execution, while the host computer does not participate in the specific control, only manages (data storage, display, printing ...) HMI and other aspects). Common DCs system, "centralized-decentralized (distributed) system" is the host computer centralized, sub-computer decentralized system.
Conceptually, the controller and the provider are the upper computer. The controller and the service are the lower machine. It can also be understood as the relationship between the host and the slave. But the upper computer and the lower machine can be converted.
How the two machines communicate, generally depends on the lower machine. TCP/IP is generally supported. But the lower machine generally has a more reliable unique communication protocol, buy the next machine, will bring a lot of manual CD-ROM, tell you how to use the unique protocol communication. There will be a lot of examples. It is generally a matter for programmers to look at and use some new APIs. Multi-language Support function module, generally supporting several high-level languages for the host computer programming.


Upper Machine--pc
--MC of the subordinate machine