Unlike general software for plc programming only, STEP7 is a tool that can be used in PLC network systems. In the organization and management of documents, STEP7 uses the “Project†hierarchical structure system, and its architecture is shown in Figure 13-1.3. Electric Portable Juice Blender Electric Portable Juice Blender,Portable Juicer Blenders,Usb Rechargeable Juicer Blender,Rechargeable Juicer Blender Shandong Sangle Group Co.,Ltd. , https://www.sangle-group.com
1. project
The STEP7 system takes the “project†as the first level. The project is an overall control scheme for the PLC network. It can have multiple “station†nodes connected to the MPI network to form a PLC network.
For the common single PLC control occasion, only the PLC used is a "station", and there is no need to consider other nodes connected to the MPI network.
2. The station and MPI nodes are the second level of the STEP7 architecture. A station is a name of a network. In a PLC network system, a physical device that can perform data communication and connect external input/output is called a "station." A station in a PLC network system that can control a data link system is called a "master station." The master station can set parameters that control the entire PLC network. Each network system must have... a master station. In the PLC control system, the master station is generally served by the PLC host. The stations other than the primary station in the network are called secondary stations, and the secondary stations have remote I/O stations, remote device stations, local stations, and the like.
For the commonly used single PLC control, only the PLC used - "station", you only need to select the PLC serial number used, such as SIMATIC 300 or SIMATIC 400, without considering the link of other "station".
3. CPU and hardware
CPU and hardware are the third level of the STEP7 architecture. As a basic component of the PLC station, the S7-300/400 is a CPU module (CPU) and other hardware (Hardware). The model of the CPU module can be directly selected via the settings of the STEP7 software. After selecting the model of the CPU module, you can also set the main parameters of the CPU module. On this basis, you can program the functions of different CPU modules.
For the other hardware of the station, you only need to use the hardware configuration function of STEP7 to establish the actual installation of each I/O module, interface module, function module and other hardware in the PLC, and the address and management data used in the software. Correspondence, usually no further processing is required.
4. S7 program and connection object
The S7 program and connection object are the fourth level of the STEP7 architecture. The S7 program is the aforementioned PLC user program, and the connection object refers to other units connected in the PLC by means of PROPIBUS or the like.
The preparation and editing of S7 program is the main work of PLC control system design, and it is also the main function of STEP7 software. In the S7-300/400 series PLC, the S7 program consists of three parts: source file, block (Blocks) and symbol table (Symbols).
The source file (Source) is used for internal program management of STEP7 and is usually generated automatically by STEP7. Users do not need to think too much about it.
Symbols can be edited and generated by STEP7's symbol editor. They can be programmed as needed. The absolute address of the program is replaced with a meaningful symbolic address to program the program, making the program easier to read and understand.
Blocks consist of logic blocks, user-defined data types (UDTs), system data, variable tables, and so on. Among them, the logic block is the basic component of the PLC user program, which is composed of the aforementioned organization block OB, program block FC, function block FB, data block DB, system program block SFC, system function block SFB, etc., the specific meaning of the relevant block See the relevant content in Chapter 8 of this book. In the above logic block, the system program block SFC and the system function block SFB can only be called in the user program, and the user cannot edit or write it.
Like the S7-200PLC, the organization block OB, the program block FC, the function block FB, the system program block SFC, and the system function block SFB are all composed of "network". When using ladder programming, the network is composed of the most basic ladder diagram components such as contacts, coils, function command frames, and wiring. Through the program editor, different control programs can be formed.
