wait_intr
wait_intr(sc, IG4_INTR_TX_EMPTY);
error = wait_intr(sc, IG4_INTR_STOP_DET);
error = wait_intr(sc, IG4_INTR_TX_EMPTY);
error = wait_intr(sc, IG4_INTR_RX_FULL);
error = wait_intr(sc, IG4_INTR_TX_EMPTY);
error = wait_intr(sc, IG4_INTR_STOP_DET);