CoDeSys on CCP XS for Bromma Conquip - Research

Student
Joel Ek
Supervisor at CC-Systems
Fredrik Löwenhielm
Dok Nr
1.0
Date
2006-08-08
Rev
PA1
Säk klass
F
Filname
Thesis.doc
CODESYS ON CCP XS FOR BROMMA CONQUIP
Figure 20: Showing the declaration of structs and functions in ANSI C
The thing we need to focus on is the code representing the classes and the structure of a class
(fig. 21). A class can hold functions and variables; these functions and variables are a part of the
class and are called class members. When an instance is created from a class it can access its
own member variables and can use its class functions to alter its variables.
Figure 21: Showing the structure of a class in C++
The counterpart to the object oriented C++ class is in ANSI C the Structure abbreviated to Struct.
The Struct is a way to combine simple data types into a complex one. Compared to the class it
does not hold any functions only the variables types that that is part of the Struct. The format of
the Struct is generated automatically when we produce an external library in <strong>CoDeSys</strong> (fig. 20).
The member functions must instead be normal functions that can be called by anyone, this leads
to some changes:
- The name of the function, if all components have a function called calculate that now is open
for everyone to use, the program will not know which calculate belongs to which Struct.
- Variables in the function, a member function have direct access to the member variables.
The names of the functions have got to change, preferably to the name of the specific component
represented by the class appended with the member-function name.
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