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AM2612: Regarding RGMII TX Delay

Lawrence Wang
Prodigy 560 points
Part Number: AM2612

Tool/software:

Hi experts,

I would like to ask about the RGMII TX delay.

  1. Is the minimum fixed TX delay for RGMII 1.2ns? This is the setup time and is unrelated to ID MODE.

  2. If ID MODE is enabled, additional delay is introduced. From the TRM manual, it is mentioned that this value is fixed, but what is the exact value?

    If ID MODE is disabled, no additional delay is introduced.

Currently, the customer is experiencing issues with RGMII TX delay. It has been observed that when ID MODE is disabled, the delay is 2.7ns, and when ID MODE is enabled, the measured delay is 2.9ns. It seems only 0.2ns difference, i don't know if it is correct. 

The customer requires the TX delay to be between 1ns and 2.6ns to meet system requirements. How can this be achieved?

  • 0
    TI__Expert 4660 points

    Apologies for the delay,

    The minimum delay listed in the datasheet is the minimum skew needed between the data and clock. With original RGMII (ID_MODE disabled), this delay had to be achieved by the PCB design and layout. With RGMII_ID, the skew can be generated by the MAC. 
    I am trying to get confirmation on the exact fixed ID_MODE delay time from our design owner.

    As for meeting the customer system requirements, signal propagation delay and the PHY configuration can all affect the delay time.
    What EVM's are they using for testing?
    Regards,

    Susan