Attention

IronPLC can only run very simple programs. The steps described are accurate but many language features are not yet supported.

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