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DP83867IS: DP83867 timing budget

Part Number: DP83867IS


Hi,

I would like you to confirm which method is better for DP83867.


* According to following URL, there is description about timing budget of DP83867.


www.ti.com/.../snla243.pdf


I read overview of above, and I understand there is description about how we can set delay in this document.
But I'm not sure which method is better to set delay.


A. At first, we do not add delay and just measure clock and data.
    After that, we should add delay based on this result.

B. There is general delay value(Ex 2.0ns) which we should apply and we should set this delay value at first.

If user can not achive timing requirement, even though they set certain delay value, user should set additional setting.
The difference b/w above two is that this delay setting is "mandatory" or "option".

In RGMII mode, we would like to know whether this setting is mandatory or not.

Best Regards,

  • Hi machida-san,

    It depends on the MAC. If there is a delay implemented in the MAC side as well, I would recommend disabling it and implementing the delays only in the DP83867.

    Then I would suggest method B, where you take the general delay value of 2.0 ns... then measure the clock and data to see if this value needs to be changed.

    Most designs are OK with the default 2.0 ns delay as this is ideal.

    Best Regards,