QMC_BD_TX_UB
qmc_write16(&bd->cbd_sc, ctrl & ~(QMC_BD_TX_UB | QMC_BD_TX_R));
if (ctrl & (QMC_BD_TX_R | QMC_BD_TX_UB)) {
ctrl |= (QMC_BD_TX_R | QMC_BD_TX_UB);
if (!(ctrl & QMC_BD_TX_UB))
qmc_write16(&bd->cbd_sc, ctrl & ~QMC_BD_TX_UB);