RB_TBREAK
tbreak = bus_space_read_4(rambo->sc_bst, rambo->sc_bsh, RB_TBREAK);
bus_space_write_4(rambo->sc_bst, rambo->sc_bsh, RB_TBREAK, tbreak);
bus_space_write_4(sc->sc_bst, sc->sc_bsh, RB_TBREAK, sc->sc_hzticks);