Structures

Overview

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.

Syntax

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

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

Initialization of Structures

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.

Bit Access in Structures

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>