An error-free Control frame is a received frame matching the format of Figure 1. It must pass all standard receiver frame checks (for example, FCS field checking). In addition, the control frame received must be exactly 64 bytes in length (from destination address through to the FCS field inclusive). This is minimum legal Ethernet MAC frame size and the defined size for control frames.
Any Control frame received that does not conform to these
checks contains an error, and it is passed to the RX AXI4-Stream as an errored
packet (rx_axis_mac_tuser
asserted).