Create structures in a project as DUT (Data Type Unit) objects via the Add Object dialog box.
They begin with the keywords TYPE and STRUCT and end with END_STRUCT and END_TYPE.
TYPE <structurename>:
STRUCT
<declaration of variables 1>
...
<declaration of variables n>
END_STRUCT
END_TYPE
<structurename> is a type that is recognized throughout the project and can be used like a standard data type.
Nested structures are allowed. The only restriction is that variables may not be assigned to addresses (the AT declaration is not allowed).
Example for a structure definition named Polygonline:
TYPE Polygonline:
STRUCT
Start:ARRAY [1..2] OF INT;
Point1:ARRAY [1..2] OF INT;
Point2:ARRAY [1..2] OF INT;
Point3:ARRAY [1..2] OF INT;
Point4:ARRAY [1..2] OF INT;
End:ARRAY [1..2] OF INT;
END_STRUCT
END_TYPE
Example:
Poly_1:polygonline := ( Start:=[3,3], Point1:=[5,2], Point2:=[7,3], Point3:=[8,5], Point4:=[5,7], End:= [3,5]);
Initializations with variables are not possible. For an example of the initialization of an array of a structure, refer to Arrays.
Access on Structure Components
You can gain access to structure components using the following syntax:
<structurename>.<componentname>
For the previous example of the structure Polygonline, you can access the component Start by Poly_1.Start.
The data type BIT is a special data type which can only be defined in structures. It consumes memory space of 1 bit and allows you to address single bits of a structure by name.
TYPE <structurename>:
STRUCT
<bitname bit1> : BIT;
<bitname bit2> : BIT;
<bitname bit3> : BIT;
...
<bitname bitn> : BIT;
END_STRUCT
END_TYPE
You can gain access to the structure component BIT by using the following syntax:
<structurename>.<bitname>
NOTE: The usage of references and pointer on BIT variables is not possible. Furthermore, BIT variables are not allowed in arrays.
For EQ operators, it is possible to compare operands of type STRUCT (structure) if the target system supports structured data types.
