Non-Compliant tx_axis_mac_tlast

An Ethernet frame should consist minimally of the Ethernet header, which includes the following:
  • Destination address
  • Source address
  • Optional VLAN tag
  • Ethernet type/length

If tx_axis_mac_tlast is asserted within the Ethernet header, it is known as a non-compliant tx_axis_mac_tlast.

When tx_axis_mac_tlast is asserted at the first cycle for the following configurations:
  • AXI Data Width = 8 (all supported PHY interfaces)
  • AXI Data Width = 16 (SGMII mode)

The frame is dropped silently, and there is no indicator of the dropped frame. No statistic counter is incremented in this case.

However, if tx_axis_mac_tlast is asserted from the 2nd cycle onwards but still within the header, the header is considered incomplete. In this condition, the Triple Speed Ethernet MACcore terminates the frame and asserts the corresponding PHY error signal (e.g., gm_tx_err for SGMII or GMII interface).