Chapter 7 Function Block and Library 7.2 Structure of the Function Blocks in ISPSoft Please refer to the following figure. The internal structure of a function block and function is similar to that of a POU of the program type. It is composed of a local symbol table and a program. A function block is edited in a way in which a POU of the program type is edited. The programming languages that users can make use of to create the function blocks in ISPSoft are ladder diagrams, instruction lists, structured texts, and function block diagrams, but are not sequential function charts. Besides, a function block can call another function block.
When a function block is called, the programming language by which program in the function block is written does not need to be considered. 7.2.1 En Pin of Function Block A superior POU (caller) calls a function block in a way similar to the way in which an applied instruction is executed. Whether a function block is executed depends on the logic state sent to the En pin of the function block. If the logic state sent to the En pin of a function block is ON, the function block will be executed. If the logic state sent to the En pin of a function block is OFF, the function block will not be executed.
The Eno pin of a function block functions to send the logic state sent to the En pin of the function block. Besides, if a function block is used in a structured text, the function block does not have an En pin. Please refer to chapter 11 for more information. 7-5