DP83867IS: How to optimize clock skew

Koji Ikeda

Part Number: DP83867IS

Hello support team,

My customer ask clock skew setting. Datasheet table 8-7 and 8-8 have clock skew option. Could you advise how to optimize the clock skew? Do you have any application note?

Thanks,

Koji Ikeda

over 2 years ago

0 Gokul Koraganji over 2 years ago

TI__Mastermind 19250 points

Hi Koji,

Clock Data skew needs to be optimized to meet the stringent RGMII timing requirements.

The optimization involves selecting the delay such that we meet setup and hold requirements according to RGMII specification.

We don't have an app note, but I guess the below E2E thread might help. https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1096129/rgmii-timing---align-and-shift-mode

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Regards,
Gokul.

0 Koji Ikeda over 2 years ago in reply to Gokul Koraganji

TI__Expert 6295 points

Gokul-san,

Thank you for your support. Please let me confirm the link,

DP83867 can add delay during shift mode only. Align mode on DP83867 is used only when MAC add delay, is their understanding correct?

Thanks,

Koji Ikeda

+1 Gokul Koraganji over 2 years ago in reply to Koji Ikeda

TI__Mastermind 19250 points

Hi Koji,

Yes, that is correct.

DP83867 adds delay during transmission on RX_* pins when in RX Shift mode. It adds delay during sampling of TX_D* pins when in TX shift mode.
Align mode should be used when MAC adds these delays.

--
Regards,
Gokul.

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DP83867IS: How to optimize clock skew