DP83867IR: MDIO level is divided after DP83867IR chip Reset pin is released!!

David Garret

Part Number: DP83867IR

Using DP83867IRPAP on a custom board with Texas TMS320DM6467TCUTD1.

The MDIO line seems to be getting pulled low by the PHY. I have a 2.2k pull-up to VDDIO, which is 3.3V. When PHY RESETN is low, MDIO is pulled high to 3.3V, as expected. Once PHY is taken out of reset, MDIO is being pulled low by something. When MAC talks, Vhigh is only about 3.27V. When the PHY responds, Vhigh is only about 1.6V. When neither the MAC nor the PHY are communicating, MDIO is pulled back low.

If I put PHY in reset and send out read requests from the MAC, then the levels are correct.

What could be pulling MDIO low?

The schematic file has been attached.

Thanks

TIQ.pdf

over 5 years ago

0 Aniruddha Khadye over 5 years ago

TI__Mastermind 18425 points

Hi David,

Can you disconnect the MDIO from the MAC by removing R154 and check if the PHY MDIO is still low? Also I noticed some connections which are not correct. Remove R351, C191, and C192 and test again.

-Regards,
Aniruddha

0 David Garret over 5 years ago in reply to Aniruddha Khadye

Prodigy 80 points

Hi Aniruddha,

Thanks for prompt reply,

I will check and get back quickly.

Thanks

0 David Garret over 5 years ago in reply to Aniruddha Khadye

Prodigy 80 points

Hi,

I removed R351, C191 and C192 but the problem did not resolved.

When I remove the R154:
-When Reset pin is Low -> MDIO is High(3.3V)
-When Reset pin is High -> MDIO is Low(0V)

I tested these on two different boards and the result was the same.

Thanks.

0 David Garret over 5 years ago in reply to Aniruddha Khadye

Prodigy 80 points

The problem is still there. Does anyone have a solution?

0 Aniruddha Khadye over 5 years ago in reply to David Garret

TI__Mastermind 18425 points

Hi David,

Is there a way to power up the DP83867 without power up that processor? If this is not possible can you try disconnecting all RGMII RX pins and COL, CRS pins of the PHY from the processor and then check if the problem persists. The RGMII RX pins are strapping pins and they need to have a specific voltage on them during power up. This can help us confirm if any unexpected voltage on pins is causing an issue.

-Regards,
Aniruddha

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DP83867IR: MDIO level is divided after DP83867IR chip Reset pin is released!!