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DM648 Ethernet Tx Packet Max Lenth

SP
Prodigy 200 points

Hello,

As per the Transmit Buffer Descriptor Format mentioned in SPRUF57B, the PACKET_LENGTH is 11 bits and so i assume it should take a value up to 2047. But when i try to increase the packet length beyond 1518 bytes (including headers), i don't see any Ethernet packets transmitted from DM648. Could you please tell me why this happens? I am using Wireshark to capture the packets..

SP

  • 0
    TI__Guru** 116100 points
    Hi,
    If packet size exceeds >=1500 then you need JUMBO packet support.

    processors.wiki.ti.com/.../Network_Developers_Kit_FAQ
  • 0 in reply to Titusrathinaraj Stalin
    Prodigy 200 points

    Hello Titus,

    I am not using NDK as mine is a legacy code without NDK integrated..

    The link you have given tells that: "However, the hardware does not support Jumbo Frames (typically around 9000 bytes but can assume any value), since the DM648 EMAC peripheral has a limitation to receive frames up to 2047 bytes (headers included). This is still above the standard value of 1518 bytes"

    It tells that "receive up to 2047 bytes". Is the same applicable for Transmit too? I think the parameter to change is PACKET LENGTH in the Tx Buffer Descriptor. But whenever I configure a value of greater than 1518 bytes in this field, the packet is not captured in wire shark. I do hope that there is no specific register configuration to allow packet transmission beyond 1518 bytes..

    SP