Calling Functions

The Structured Text (ST) programming language enables calling functions. Function calls can be used in any expression.
Function calls
Name
Name of the called function written in IEC 61131-3 language or in C
Meaning
Calls a ST, IL, LD or FBD functions or a C function and gets its return value
Syntax
<variable> := <funct> (<par1>, ... <parN> );
Operands
The type of return value and calling parameters must follow the interface defined for the function.
Return value
Value returned by the function
When setting the value of the return parameter in the body of a function, assign the return parameter using the same name as the function:
FunctionName := <expression>;
Example
Example1: IEC 61131-3 function call
(* Main ST program *)

(* gets an integer value and converts it into a limited time value *)

dint_timeprog := SPlimit ( tprog_cmd );

appl_timer := TMR (dint_timeprog * 100);

(* Called FBD function named 'SPlimit' *)
Example2: "C" function call – same syntax as for IEC 61131-3 function calls
(* Functions used in complex expressions: min, max, right, mlen and left are standard "C" functions *)

limited_value := min (16, max (0, input_value) );

rol_msg := right (message, mlen (message) - 1) + left (message, 1);
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