The term Program Organizational Unit (POU) is used for all programming objects (programs, function blocks, functions, etc.) which are used to create a controller application.
As defined in the IEC 61131 standard, a POU is a program, a function block, or a function. However, in this document the term POU is used for programming elements in general that can contain IEC code, such as methods, properties, interfaces etc. Whenever this document refers to POUs in the more restricted sense as defined in IEC 61131, the term POU object is used.
POUs which are managed in the Global node of the Applications tree are not device-specific but they can be instantiated for the use on a device (application). For this purpose, program POUs must be called by a task of the respective application.
But POU also is the name of a certain sub-category of these objects in the Add Object menu. At this place, it just comprises programs, function blocks, and functions.
Therefore, a POU object in general is a programming unit. It is an object which is managed either non-device-specifically in the Global node of the Applications tree or directly below an application in the Applications tree. It can be viewed and edited in an editor view. A POU object can be a program, function, function block.
It is possible to set certain Properties (such as build conditions, etc.) for each particular POU object.
For a description on how to create a POU object, refer to the section Adding POU Objects to an Application. The POU objects you have created are added to the Assets view of the Software catalog.
You can add a POU object available in the Assets view to the project in 2 different ways:
oSelect a POU object in the Assets view and drag it to the suitable node in the Applications tree.
oSelect a POU object in the Assets view and drag it to the logic editor view.
Besides the POU objects, there are device objects used for running the program on the target system (Resource, Application, Task Configuration etc.). They are managed in the Applications tree.
