In extension to the IEC operators, there are several possibilities to disambiguate the access to variables or modules if the variables or module name is used multiple times within the scope of a project.
The following scope operators can be used:
global scope operator
global variable list name
enumeration name
library namespace
global node operator
An instance path starting with dot (.) opens a global scope (namespace). Therefore, if there is a local variable with the same name <varname> as a global variable, then .<varname> refers to the global variable.
You can use the name of a global variable list as a namespace for the variables enclosed in this list. Thus, it is possible to declare variables with identical names in different global variable lists and, by preceding the variable name by <global variable list name>., it is possible to access the desired one.
Syntax
<global variable list name>.<variable>
Example
The global variable lists globlist1 and globlist2 each contain a variable named varx. In the following line, varx out of globlist2 is copied to varx in globlist1:
globlist1.varx := globlist2.varx;If a variable name declared in more than one global variable lists is referenced without the global variable list name as a preceding operator, a message will be generated.
You can add the library namespace to a POU as a prefix separated by a dot to make the access to the POU unique. By default, the namespace of a library is identical to the library name.
Example: LIB_A.FB_A
Syntax
<library namespace>.<library POU>
Example
If a library which is included in a project contains the POU FB_A and there is also a POU FB_A defined locally in the project, then you can assign the name LIB_A.FB_A to the function block of the library in order to differentiate from the POU.
var1 := FB_A(in := 12); // Call of the project function block FB_A
var2 := LIB_A.FB_A(in := 22); // Call of the library function block FB_AYou can define another name for the namespace either in the when creating a library project in the (by default in the menu), or later in the dialog box of an included library in the .
You can use the type name of an enumeration to disambiguate the access to an enumeration constant. Therefore, it is possible to use the same constant in different enumerations.
The enumeration name has to precede the constant name, separated by a dot (.).
Syntax
<enumeration name>.<constant name>
Example
The constant Blue is a component of enumeration Colors as well as of enumeration Feelings.
color := Colors.Blue; // Access to enum value Blue in type Colors
feeling := Feelings.Blue; // Access to enum value Blue in type Feelings