Non-Streaming TX Data

For Ethernet applications, tx_axis_mac_tdata must be streaming and continuous throughout a frame. This requires that tx_axis_mac_tstrb be fully asserted (all 1’s) on every cycle, except the final cycle of the frame indicated by tx_axis_mac_tlast.
  • 8-bit AXI data width;
    • tx_axis_mac_tstrb is always 1’b1 until the tx_axis_mac_tlast cycle.
  • 16-bit AXI data width;
    • tx_axis_mac_tstrb is 2’b11 on all cycles except the tx_axis_mac_tlast cycle, where it may be 2’b01 or 2’b11 depending on whether the frame ends on an odd or even byte boundary.
  • 32-bit AXI data width;
    • tx_axis_mac_tstrb must be 4’b1111 on all cycles except the tx_axis_mac_tlast cycle. On the final cycle, it must indicate the valid bytes as a contiguous sequence starting form the Least Significant Bytes (i.e., 4’b0001, 4’b0011, 4’b0111). Sparse byte enables are not supported.

If non-streaming TX data is detected (for example, if tx_axis_mac_tstrb is not fully asserted during a non-tlast cycle), the Triple Speed Ethernet MAC core terminates the transmission with an error frame and discards the remaining data. This event increments the aTxIncontinuityFramesErrors counter.