The following figure illustrates an
unsuccessful frame reception (for example, a fragment frame or a frame with an incorrect
FCS). In this case, the rx_axis_mac_tuser signal is asserted
to you at the end of the frame. It is your responsibility to drop the data already
transferred for this frame.
Figure 1. Frame Reception with Error
The following conditions cause the assertion
of rx_axis_mac_tuser :
- Occurrence of FCS errors.
- Packets are shorter than 64 bytes (undersized or fragment frames).
- Jumbo frames are received when jumbo frames are not enabled.
- VLAN frames of length 1,519-1,522 are received when VLAN frames are not enabled.
- A frame above the programmed Maximum Frame Size is received when Maximum Frame Length checking is enabled.
- A value of 0x0000 to 0x002D is in the type/length field. In this situation, the frame should be padded to minimum length. If it is not padded to exactly minimum frame length, the frame is marked as bad (when length/type checking is enabled).
- A value of 0x002E to 0x0600 is in the type/length field, but the real length of the received frame does not match this value (when length/type checking is enabled).
- Any control frame that is received is not exactly the minimum frame length (unless control frame length checks are disabled: see Receiving a Pause Control Frame).
- An error is indicated on the PHY interface at any point during frame reception.
- An error code is received in the 1 Gb frame extension field.
- A valid pause frame addressed to the MAC, is received when flow control is enabled. See Flow Control Overview.
- A frame does not match against any of the enabled frame filters, if present.
- A valid Priority Flow Control (PFC) frame addressed to the Ethernet MAC, is received when PFC is enabled. This frame is only marked as an error because it has been used by the MAC PFC logic and has now served its purpose.