private Register SelectIndexRegister() {
        
        Register Rselected;
		
         switch (getXF().Index) {
            case 1:
                Rselected = getIX1();
                break;
            case 2:
                Rselected = getIX2();
                break;
            case 3:
                Rselected = getIX3();
                break;   
            default:
                 Rselected = null;
                 break;
         }
         
         return Rselected;
         
    }