PHY_CNTL2_100M
val = PHY_CNTL2_AUTONEG | PHY_CNTL2_100M | PHY_CNTL2_FDX;
val = PHY_CNTL2_100M | PHY_CNTL2_FDX;
val = PHY_CNTL2_100M;
new = old & ~((PHY_CNTL2_AUTONEG | PHY_CNTL2_100M | PHY_CNTL2_FDX)