TCTL_COLD
sc->sc_tctl &= ~TCTL_COLD(0x3ff);
TCTL_COLD(TX_COLLISION_DISTANCE_FDX);
TCTL_COLD(TX_COLLISION_DISTANCE_HDX);
sc->sc_tctl &= ~TCTL_COLD(0x3ff);
sc->sc_tctl |= TCTL_COLD(TX_COLLISION_DISTANCE_FDX);
sc->sc_tctl |= TCTL_COLD(TX_COLLISION_DISTANCE_HDX);
sc->sc_tctl &= ~TCTL_COLD(0x3ff);
TCTL_COLD(TX_COLLISION_DISTANCE_FDX);
TCTL_COLD(TX_COLLISION_DISTANCE_HDX);
| TCTL_COLD(TX_COLLISION_DISTANCE_FDX);