1. Even when it has nothing to transmit, the AXI Ethernet Lite MAC monitors the bus for traffic by watching the carrier sense signal ( phy_crs ) from the external PHY. Whenever the bus is busy ( phy_crs = 1), the AXI Ethernet Lite MAC defers to the passing frame by delaying any pending transmission of its own.
2. After the last bit of the passing frame (when carrier sense signal changes from TRUE to FALSE), the AXI Ethernet Lite MAC starts the timing of the interframe gap.
3. The AXI Ethernet Lite MAC resets the interframe gap timer if the carrier sense becomes TRUE.