CR6_FDM
db->cr6_data |= CR6_FDM; /* Set Full Duplex Bit */
db->cr6_data &= ~CR6_FDM; /* Clear Full Duplex Bit */
db->cr6_data |= CR6_FDM; /* Set Full Duplex Bit */
db->cr6_data &= ~CR6_FDM; /* Clear Full Duplex Bit */