Attention

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P0015

Code

P0015

Message

Variable not defined before used

This error occurs when a variable is referenced but not declared in the current scope.

Example

The following code will generate error P0015:

FUNCTION_BLOCK LOGGER
VAR
    TRIG0 : BOOL;
END_VAR

TRIG := TRIG0;  (* Error: TRIG is not declared *)
END_FUNCTION_BLOCK

The variable TRIG is used in the assignment but is not declared in the VAR section of the function block.

To fix this error, declare the variable in the appropriate variable section:

FUNCTION_BLOCK LOGGER
VAR
    TRIG : BOOL;   (* Declare the variable *)
    TRIG0 : BOOL;
END_VAR

TRIG := TRIG0;  (* Correct: TRIG is now declared *)
END_FUNCTION_BLOCK