The PHY asserts the Collision detected signal ( phy_col ) to indicate the detection of a collision on the bus. The PHY asserts phy_crs while the collision condition persists. The PHY also drives phy_col asserted when operating at 10 Mb/s for signal_quality_error (SQE) testing.
The signal phy_col is not synchronous to either the phy_tx_clk or the phy_rx_clk . The phy_col signal is not used in full-duplex mode. The phy_col signal is used by both the AXI Ethernet Lite MAC core transmit and receive circuitry and is double-synchronized to the processor clock as it enters the AXI Ethernet Lite MAC . This Figure shows the behavior of phy_col during frame transmission with a collision.
