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Calling Functions and Function Blocks in ST

In ST, a function call basically has the following syntax:

OutVariable := functionName(InVar1, InVar2);

The names of the required input variables are noted in parentheses after the function name. The function's return value (result) has to be assigned to an output variable.

A function block call in ST basically has the following syntax:

instance(invar1:=1, invar2:=2);
a:= instance.outvar1;

Alternative syntax:
instance(invar1 := 1, invar2:=2, outvar1 => a);

In this example, an FB with the instance name 'instance' is called with its input parameters 'invar1' and 'invar2' (each with assigned value). The FB returns a result in form of the output variable 'outvar1'. In our sample call, the result value is written to the variable 'a'.

Further Info When calling an FB with InOut formal parameters, some rules have to be observed. Refer to the topic "InOut Variables: Rules and Specific Characteristics" for details.

Note EN/ENO allows an optional conditional execution of functions and function blocks according to the IEC 61131-3 standard. EN is an enable input, ENO an enable output formal parameter. Refer to the help topic "Execution Control: EN/ENO" for details.