7.3.2. RX MAC Avalon ST Client Interface with Enabled Passthrough and RX CRC Forwarding
When you turn on Preamble Passthrough in the parameter editor, the IP cores with Ethernet Mode set to 100GE data rate presents the preamble received on the first eight bytes of the o_rx_data signal; specifically, o_rx_data[511:448]. The IP cores with Ethernet Mode set to 40GE or 50GE data rates present preamble received on the o_rx_preamble port with each packet, while the o_rx_startofpacket signal is high.
The IP cores with Ethernet Mode set to 10GE or 25GE data rates present the preamble data received on the first cycle, o_rx_data[63:0].