When the length of client frame is less than 64 bytes and greater than eight bytes, the TX MAC module inserts pad bytes after the payload to create a frame length equal to the minimum size of 64 bytes. If the i_tx_skip_crc or i_tx_mac_skip_crc signal is asserted while writing frame data, the core does not insert PAD bytes even if the frame is shorter than 64 bytes long.
When using the MAC segmented interface, if the Enable preamble passthrough parameter and the i_tx_mac_skip_crc signal are both disabled, the payload length must not be less than 9 bytes. However, if the Enable preamble passthrough parameter and the i_tx_mac_skip_crc signal are both enabled, the entire frame, including Preamble and CRC, must not be less than 9 bytes. You must ensure that such frames do not reach the TX client interface as the F-Tile Ethernet Intel FPGA Hard IP discards them.