cduart_read
isr = cduart_read(sc, CDUART_ISR);
cr = cduart_read(sc, CDUART_CR);
isr = cduart_read(sc, CDUART_ISR);
sr = cduart_read(sc, CDUART_SR);
c = cduart_read(sc, CDUART_FIFO) & 0xff;
sr = cduart_read(sc, CDUART_SR);
(void)cduart_read(sc, CDUART_FIFO);
sr = cduart_read(sc, CDUART_SR);
sr = cduart_read(sc, CDUART_SR);