private Register SelectNextRegister() {

        Register Rselected;

        switch (getRF().Index) {
            case 0:
                Rselected = getGPR1();
                break;

            case 2:
                Rselected = getGPR3();
                break;

            default:
                Rselected = null;
                break;
        }

        return Rselected;

    }