PSC_READ_2
isr = PSC_READ_2(sc, PSC_ISR);
sr = PSC_READ_2(sc, PSC_SR);
sr = PSC_READ_2(sc, PSC_SR);
sr = PSC_READ_2(sc, PSC_SR);
while (sc->sc_tbc > 0 && (PSC_READ_2(sc, PSC_SR) & SR_TXRDY)) {