CDUART_SR
sr = cduart_read(sc, CDUART_SR);
sr = cduart_read(sc, CDUART_SR);
sr = cduart_read(sc, CDUART_SR);
sr = cduart_read(sc, CDUART_SR);
CDUART_SR) & CDUART_SR_RXEMPTY)
CDUART_SR) & CDUART_SR_TXFULL)