DP83867IS: Reading bogus data from chip over MDIO/MDC Interface

Katie Morris

Part Number: DP83867IS

After startup we read what appears to be bogus data from all the standard registers. The only register we seem to be able to read and write successfully are REGCR (0x00Dh) and ADDAR (0x00Eh). Using those registers as described in the datasheet to do an indirect register access we get the same bogus value as we got from the standard set of registers. This value only appears to change after resetting the device. We have read values such ac 0xdffc and 0xfffc back. We have verified that that the 3.3VDC, 2.5VDC and 1.0VDC supplies come up with reset asserted. When reset is released MDIO is pulled high and held high for the time specified in the datasheet.

over 5 years ago

0 Aniruddha Khadye over 5 years ago

TI__Mastermind 18425 points

Hi Katie,

Is it possible that the PHY is not getting strapped to the address that you intend to use? Can you check the address strap pin RX_D)0 and RX_D2 to see that it has the correct voltage?

-Regards

Aniruddha

0 Katie Morris over 5 years ago in reply to Aniruddha Khadye

Prodigy 20 points

We have RX_D0 and RX_D2 left open intended for an address of 0x00. And like I mentioned above we are able to write and read the two registers REGCR (0x00Dh) and ADDAR (0x00Eh) as expected. But when we do a direct access of the standard registers or an indirect register access we read back the same bogus value. The value only seems to change upon a reset but remains the same during runtime. We also have scoped the MDIO and MDC lines and found that after a read or write the phy is responding with a valid turn around and along with the bogus data.

0 Aniruddha Khadye over 5 years ago in reply to Katie Morris

TI__Mastermind 18425 points

Hi Katie,

Would it be possible to share the schematics?

-Regards

Aniruddha

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DP83867IS: Reading bogus data from chip over MDIO/MDC Interface