188.8.131.52. Length/Type Field Processing
This two-byte header represents either the length of the payload or the type of MAC frame.
- Length/type < 0x600—The field represents the payload length of a basic Ethernet frame. The MAC RX continues to check the frame and payload lengths.
- Length/type >= 0x600—The field represents the frame type. The following frame types are possible:
- Length/type = 0x8100—VLAN or stacked VLAN tagged frames. The MAC RX continues to check the frame and payload lengths.
- Length/type = 0x8808—Control frames. The next two bytes are the Opcode field that indicates the type of control frame. For pause frames (Opcode = 0x0001) and PFC frames (Opcode = 0x0101), the MAC RX proceeds with pause frame processing.
Note: The 50G Ethernet IP core passes these frames to the RX client interface and updates the appropriate l2_rxstatus_data bits. However, the IP core does not implement flow control.
- For other field values, the MAC RX forwards the receive frame to the client.
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