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DP83848Q Minimum Packet length

Mark Rae
Intellectual 320 points
Other Parts Discussed in Thread: DP83848Q-Q1

We are using the  DP83848Q-Q1  for a low level data communications port in an embedded design.

we are not using an Ethernet  stack, just sending proprietary data directly tot he PHY and reading it from another PHY on the other end.

What is the minimum packet size that can be sent?

We understand JK and TR will get transferred with the rising and falling edge  of TX_EN.

Is it possible to send a packet without the Preamble and SFD? 

We would like to be able send a packet with out this header information.

Do we have to allow time between packets for the interpacket gap? is this effected by MII vs RMII interface?

Thank you 

Mark Rae

  • 0
    TI__Mastermind 18425 points

    Hello Mark,

    The minimum packet size is defined by IEEE standard and it is 64 bytes (including 4 bytes of CRC). For sending packets without preamble, DP83848Q-Q1 supports Preamble Suppression mode and this can be controlled through the BMSR register (address 0x01). Please refer to "Serial Management Preamble Suppression" section in the datasheet for more information. SFD and interpacket gap are again defined by the IEEE spec and DP83848Q-Q1 does not have the ability to supress/bypass them.

    -Regards,

    Aniruddha