How to initialize a structured type variable

[George]

My question is about the way in LogicLab (v10.0.0) when I declare a variable of structure type to set initial values to the elements of a structure that are structure type.

For example:

sX: STRUCT
    a : INT;
    b : REAL;
END_STRUCT;

sY: STRUCT
    c : BOOL;
    d : DWORD;
END_STRUCT;

str: STRUCT
    x : sX;
    y : sY;
END_STRUCT;

sVar:str

[Sergio Bertana]

Following your example in the Init value field of the sVar declation you must define the init values as reported

VAR
    sVar : str := (
x:=(a:=100, b:=1.7),
y:=(c:=TRUE, d:=16#12345678)
);
END_VAR

In the screenshot you can see the program with the declaration and during the program execution the values on watch window.

As you see I used the variable sVar in the program to enable LogicLab to init it. If not used in the program it has not initialized. The variable sVar.x.a is increased at first program loop execution so it init value of 100 has becomed 101.

[George]

Thank you very much. this was the information I was missed. It was not so clear in the LogicLab manual (6.6.7 SETTING VARIABLES INITIAL VALUE).

[George]

Is it possible to declare a CONSTANT variable of structured data type?

When I try to declare I get compilation error without error code.

[Sergio Bertana]

Yes, it is possible. The error you mentioned is probably this:

MyProgram.MS – warning G0290: MS => Constant without initial value

It has no reference number, but the description indicates that the constant doesn’t have any initial value. To declare a structured data type, you must also assign it a value.

• You can initialize values in the data structure definition as follows:

  MYSTRUCT: STRUCT
      V1 : BOOL := TRUE;
      V2 : UINT := 20;
  END_STRUCT;

• Or you can initialize the value directly when you instantiate the data structure variable in the program, like this:

  VAR CONSTANT
      MS : MYSTRUCT := (V1:=FALSE, V2:=30);
  END_VAR

[George]

In my project have a structure like:

MYSTRUCT: STRUCT
    V1 : BOOL;
    V2 : ARRAY[0..3] OF UINT;
END_STRUCT;

If I intitialize in a program it:

VAR CONSTANT
    MS : MYSTRUCT := (V1:=FALSE, V2:=[10,20,30,40]);
END_VAR

VAR
    myS : MYSTRUCT;
END_VAR

    myS:= MS;
    myS.V1:= MS.V1;

// [End of file]

I get errors

MyProgram(2) - error G0291:  MS => Invalid constant value
MyProgram(3) - error G0291:  MS.V1 => Invalid constant value

I think this error has to do with constant variable instantiation of structure data type containing array element.

[Sergio Bertana]

Errors are generated only if you declare the MS data structure as CONSTANT.

VAR CONSTANT
    MS : MYSTRUCT := (V1:=FALSE, V2:=[10,20,30,40]);
END_VAR

Without the CONSTANT attribute, the program works correctly.
I have informed Axel about this problem and I am still waiting for their response.

[Sergio Bertana]

Axel has just informed me that this behaviour is a bug. They have opened ticket:

LL-3790: Invalid constant value for structured types.

A fix will be available in future versions of LogicLab.

[Autore]

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