DBGU_SR_TXRDY
if (ISSET(sr, DBGU_SR_TXRDY) && sc->sc_tbc > 0) {
while (DBGUREG(DBGU_SR) & DBGU_SR_TXRDY) {
while ((DBGUREG(DBGU_SR) & DBGU_SR_TXRDY) == 0) { \