DP83TD510E-EVM: External 4khz MDIO read command return wrong value

first_name Besnard

Part Number: DP83TD510E-EVM

Hi,

I am trying to read clause 22 register 0x02 on phy ID 0x00 (on DP83TD510EVM) . I use an external mdio bus running at 4khz from our microcontroller. The phy respond something but wrong value.

The read value of register 0x02 with USB-TO-MDIO software is 0x2000 (which is correct):

The read value of register 0x02 with mdio from our microntroller is 0x4003 (wich is wrong):

The only difference see is the frequency (370khz for USB-TO-MDIO).

So is the phy able to communicate on mdio bus with 4khz clock ? In the datasheet i saw only a max freq...

Thank you in adavnce for your help

over 3 years ago

0 Gokul Koraganji over 3 years ago

TI__Mastermind 19250 points

Hi Besnard,

Let me check with the team on this issue and get back to you by Tuesday.

--
Regards,
Gokul.

0 first_name Besnard over 3 years ago in reply to Gokul Koraganji

Prodigy 20 points

Hi Gokul,

I changed my MDC pin from open-drain to push pull topology and this solve my issue. I supposed it's because the rising time was too slow.

Rising time of MDC was 300ns in open drain vs 20ns in push pull .

This slow rising time may trig more than 1 rising edge on the phy side...

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DP83TD510E-EVM: External 4khz MDIO read command return wrong value