C++ passing an object to a function, the operator= is not called

C++ passing an object to a function, the operator= is not called

So here is the code snippet:
class MyClass { public: MyClass(char chIn) { std::cout << "Constructor!"
<< std::endl; }
MyClass & operator= (char chIn) { std::cout << "Assigment operator!" <<
std::endl; } } ;
void Func(MyClass objIn) { return; }
int _tmain(int argc, _TCHAR* argv[]) { Func('T'); system("PAUSE"); return
0; }
In the upper example the constructor of the object is called!!!! Why is
this behavior? Shouldn't the assigment operator be called? Because we're
assigning a value to the function parameter, aren't we?