Table 1: IO Signal Table
In linear programming, all programs are in OB1, as shown in Figure 1:
▲ Figure 1 Linear Programming
In modular programming, the two assembly lines are called in different sub-programs, as shown in Figures 2 and 3:
▲ Figure 2 Main Program Calling Sub-Program
▲ Figure 3 Assembly Line 1 Executing Program
▲ Figure 4 Assembly Line 2 Executing Program
Structured programming is achieved by establishing FB program blocks, with internal functions implemented within the FB. This FB block can be reused, and when calling the FB program block, the corresponding DB data block is automatically generated. When controlling the program, only specific pins need to be defined. The specific structured programming is shown in the figure below:
▲ Figure 5 OB1 Program Call
▲ Figure 6 Assembly Line 1 Program
▲ Figure 7 Assembly Line 2 Program
▲ Figure 8 Background Block of Assembly Line Function
In the previous text, the start/stop control of two assembly lines was illustrated using different programming methods.
Each programming method has been understood to a certain extent. Since the example programs are relatively simple, the advantages and disadvantages of the programs are not so obvious. However, as the complexity of the project increases, the workload of programming becomes larger, and the advantages of structured programming become more apparent. Its readability and reusability can improve work efficiency. In the process of PLC programming, it is recommended to use a hybrid programming method of structured and modular programming.
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