DVP-ES3 Series Programming Manual Tasks manage the execution order of the programs. Tasks help you manage large-scale program _1 development. 1.2.2 Program Organization Units and Tasks The Program Organization Units (POUs) are the basic elements that constitute the PLC program. Unlike the traditional PLC program, the program framework introduced by IEC 61131-3 allows you to divide a large program into several small units. These small units are called POUs. The POUs can be classified into three types. 1. Program (PROG): The program POU is the main program in the PLC.
You can define the execution of this POU t to be cyclic scan or interrupt driven, and arrange the scan order in the task list for program POUs. 2. Function block (FB): The function block (FB) POU is similar to a subroutine. The instructions in the function block are executed after a program POU calls the function block with the related parameters. 3. Function (FC): The function (FC) POU in similar to a macro instruction. That is, you can write many operation instructions or functions into a function-type POU, and then use then in a program POU or a function block POU. Tasks are functions that control the order of program execution or according to certain interrupt conditions.
The task provides each program POU with a specific execution task, and specifies the execution order for the program POUs or the way to enable them. Normally, only some of the program POUs in a project take part in the actual execution. The task controls whether to execute the program POU or not, and how to execute it. If the POU of the program type is not assigned in the task, the program POU is saved as ordinary source code with the project instead of being compiled into the execution code for the PLC. In addition, only the program POU needs to be assigned to the 1-10