Chapter 7 Function Block and Library 7.1.2 Characteristics and Advantages of Function Blocks Owing to the fact that function blocks present characteristics and advantages that traditional programming of a PLC does not have, function blocks are supported by IEC 61131-3, and are widely used by users. Modular design A large program is divided into several subroutines, and the subroutines are created as function blocks. The function blocks are arranged and called by POUs of the program type.
Different function blocks can be created by means of different programming languages such as a ladder Highly independent diagram, an instruction list, a structured text, and a function block diagram according to the characteristics of the function blocks or a programmer’s habit. Besides, when a POU calls a function block, the programming language by which the program in the function block is written does not need to be considered. For example, if a complex operation has to be performed in a part of a ladder diagram, users can create the part of the ladder diagram as a function block by means of a structured text, and the function block can be called by the original ladder diagram.
Reusable Once a function block is created, it can be used repeatedly as long as users conform to the rule of using the function block. Highly portable After a function block is created, it can be used in the original project. Besides, after the function block is exported, it can be imported into another project. As a result, users can gradually create their own function blocks. 7-3