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