The role of transmission and comparison instructions in PLC programming - Database & Sql Blog Articles

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These data can be obtained from external devices connected to the input port, and the transfer instructions are required to read the data on these devices and send them to the internal unit; the initial data can also be programmed, that is, the immediate data is transferred to the internal unit; in addition, some The calculation data is stored somewhere in the machine, and is sent to the work unit through the initialization program when the program starts running.

(1) Access management of data in the machine

In the data operation process, the data transmission inside the machine is indispensable. The operation may involve different work units, the data needs to be transferred between them; the operation may generate some intermediate data, which needs to be transferred to the appropriate place for temporary storage; sometimes the data in the machine needs to be saved and saved, this is the place to put these The data is stored properly. In summary, data management is important for a program involving data operations.

In addition, the conversion of binary and BCD codes is also important in data management.

(2) The result of the arithmetic processing is transmitted to the output port

The result of the arithmetic processing is always to control the execution device through the output, or output data for display, or as working data of other devices. Discrete execution devices connected to the output port can be regarded as an overall data unit in a group process, and certain data can be sent according to the target state of each port, thereby realizing control of these devices.

(3) Comparison instructions are used to establish control points

The control site often has a magnitude or a change interval of a certain physical quantity as a control point. If the temperature is lower than the degree, turn on the electric heater, and the speed will be higher or lower than an interval to alarm. As a control "valve", comparison instructions often appear in industrial control programs.