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Packet Accelerator Minimum Transmission bytes [60] ?

RCReddy
Genius 3575 points


Hi Ti Folks,

                   In my investigations, i found that i am not able to push 59 bytes length packet, whereas 60 bytes length packet i was able to push. From this i can conclude that

1. 59 bytes of packet + 4 bytes of crc = 63 bytes CANNOT be pushed to-network direction.

2. 60 bytes of packet + 4 bytes of crc = 64 bytes CAN be pushed to-network direction.

please confirm both statements.

Is there any PA/GbE register setting/configuration by which i can achieve X bytes length packet [x < 60 bytes], please let me know on it. By any chance [no transmission possible for packet length < 60 bytes] is this practical limitation on hardware?

Ofcourse, i understand that Ethernet standard specifices minimum packet length to be 64 bytes.

Thanks

RC Reddy

  • 0
    TI__Intellectual 2810 points

    Hi, RC:

    The CPSW does not support automatic padding, it is up to the application to padd small-size packet.
    However, if you use PASS in the egress direction, you can configute the nextRoute command to perform autonomous L2 padding:

    /**
     *  @def  pa_NEXT_ROUTE_TX_L2_PADDING
     *        Control Info -- Set: Perform MAC padding for packet with size smaller than 60
     *                        Clear: Do not perform MAC padding
     *  @note: This option is only valid in the transmit (to-network) direction     
     */
    #define pa_NEXT_ROUTE_TX_L2_PADDING              0x0008

    Best regards,

    Eric

     

  • 0 in reply to Eric Ruei
    Genius 3575 points

    Hi,

        Thanks for your quick reply. So there is no way i can transmit X bytes [X < 60 bytes] [i mean without using padding at all]. 

    Thanks

    RC Reddy