EXUART_UINTM_TXD
EXUART_UINTM_TXD | EXUART_UINTM_MODEM);
if (ISSET(sc->sc_uintm, EXUART_UINTM_TXD)) {
CLR(sc->sc_uintm, EXUART_UINTM_TXD);
if (!ISSET(sc->sc_uintm, EXUART_UINTM_TXD)) {
SET(sc->sc_uintm, EXUART_UINTM_TXD);