Attention

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P4017

Code

P4017

Message

Function is not declared

This error occurs when calling a function that has not been declared.

Example

The following code will generate error P4017:

FUNCTION_BLOCK CALLER
VAR
    result : REAL;
    value : INT;
END_VAR
    result := NONEXISTENT_FUNC(value);  (* Error: Function not declared *)
END_FUNCTION_BLOCK

The function NONEXISTENT_FUNC is not declared anywhere in the code.

To fix this error, either:

1. Define the missing function:

FUNCTION NONEXISTENT_FUNC : REAL
VAR_INPUT
    input_val : INT;
END_VAR
    NONEXISTENT_FUNC := INT_TO_REAL(input_val);
END_FUNCTION

FUNCTION_BLOCK CALLER
VAR
    result : REAL;
    value : INT;
END_VAR
    result := NONEXISTENT_FUNC(value);  (* Now valid *)
END_FUNCTION_BLOCK

2. Use a standard library function if available (e.g., type conversion functions like INT_TO_REAL):

FUNCTION_BLOCK CALLER
VAR
    result : REAL;
    value : INT;
END_VAR
    result := INT_TO_REAL(value);  (* Using stdlib function *)
END_FUNCTION_BLOCK