SR_RXR
if (!ISSET(sr, SR_TXR | SR_RXR))
if (ISSET(sr, SR_RXR)) {
if (!ISSET(sr, SR_RXR))
while (ISSET(bus_space_read_4(iot, ioh, IXPCOM_SR), SR_RXR)
while(!(bus_space_read_4(iot, ioh, IXPCOM_SR) & SR_RXR))