UARTDR
data = bus_space_read_4(iot, ioh, UARTDR);
bus_space_write_1(iot, ioh, UARTDR,
bus_space_write_multi_1(iot, ioh, UARTDR, sc->sc_tba, n);
bus_space_read_1(iot, ioh, UARTDR);
ch = WMCOM_CNREAD_4(UARTDR);
WMCOM_CNWRITE_1(UARTDR, c);