Normal outbound frame transfer timing is illustrated in This Figure . This figure shows that an Ethernet frame is proceeded by an 8-byte preamble field (inclusive of the Start of Frame Delimiter (SFD), and completed with a 4-byte Frame Check Sequence (FCS) field. This frame is created by the MAC connected to the other end of the GMII. The PCS logic does not recognize the different fields within a frame and treats any value placed on gmii_txd_chx[7:0] within the gmii_tx_en_chx assertion window as data.
