VR_CR1_FULLDUPLEX
CSR_WRITE_1(sc, VR_CR1, VR_CR1_FULLDUPLEX | VR_CR1_TX_NOPOLL);
mfdx = (cr1 & VR_CR1_FULLDUPLEX) != 0;
cr1 |= VR_CR1_FULLDUPLEX;
cr1 &= ~VR_CR1_FULLDUPLEX;