POUs (program organization units)

Program Organization Units, or POUs for short, are components of a Control FPWIN Pro7 program. They contain the PLC control program. A Control FPWIN Pro7 program consists itself of several sub-programs. Each sub-program is complete in itself and performs a specific task. Depending on which task is concerned, the corresponding type of POU is selected.

The names of the POUs are listed under POUs in the navigator. We differentiate between three different types of POUs (program classes):

• Programs (PRG)

• Functions (FUN)

• Function blocks (FB)

Each POU, regardless of what type it is, is divided into a POU header and a POU body, both appear in the common programming window.

1.  (1) POU
2.  (2) Header
3.  (3) Body

The two parts (header and body) come from the IEC philosophy which maintains that variables should be declared in a list, whereby these declarations (symbolic names) are used in the program instead of physical addresses.

The advantage of this is that the compiler takes care of address administration and that you only have to make address changes in the POU header once (as long as you have defined a variable which is assigned to an address). The programs remain unchanged.

In the POU header, local variables are declared. Local variables are variables which are only used in the accompanying POU body.

The POU body contains the program logic which can be written in several programming languages:

● available