External variables - VAR

External variables are global variables that are imported into a block.

You declare these variables between the keywords ‎VAR_EXTERNAL‎ and ‎END_VAR‎. If the global variable does not exist, then an error message is printed.

NOTICE

CODESYS does not require you to declare a global variable as external in order to use it in a POU. The keyword exists only for maintaining compliance with IEC 61131-3.

Syntax

<POU keyword> <POU name> 
VAR_EXTERNAL
	<variable name> : <data type>;
END_VAR

Initialization is not permitted.

Example

FUNCTION_BLOCK FB_DoSomething 
VAR_EXTERNAL
	iVarExt1 : INT; (* 1st external variable *)
END_VAR