DP83848C: RMII mode: RX0, RX1, TX0, TX1 stays deat when ping

Jaka Koren

Part Number: DP83848C

Hello,

I am struggling to connect my uC (STMF4) to DP83848 PHY. I can read the registers and get the values from them, but when I try to ping it, nothing happens on either RX[0:1] or TX[0:1]. I am using the board in RMII mode. I measured PFBOUT voltages, but now I am stuck. When I connect the cable the led is ON and also pc recognize that something is connected to the board. But from here on nothing works.
I think the problem is on the PHY side, but I don't know if the PHY is broken, or I have to write some special value to some registers to start transmitting the data through?

Thank you for your help.

Regards, Jaka

over 6 years ago

0 Aniruddha Khadye over 6 years ago

TI__Mastermind 18425 points

Hi Jaka,

can you read register 0x17 to check if RMII mode is activated? Are you using 50MHz clock input and making sure that clock input for PHY and uC is synchronous?

-Regards
Aniruddha

0 Jaka Koren over 6 years ago in reply to Aniruddha Khadye

Prodigy 110 points

Hello,

Return from the 0x17 register is 0x21.
I connected the RX_CLK to uC because otherwise, uC returned that the link isn't up, and nothing worked, I assumed, that this is enough?

Regards,
Jaka

0 Ross Pimentel over 6 years ago in reply to Jaka Koren

TI__Mastermind 23675 points

Hi Jaka,

The DP83848C RX_CLK is unused when in RMII operation.

A shared reference clock between the MAC and PHY (XI pin) is required for RMII operation.

Please share the schematic so we can review the connections you have.

0 Jaka Koren over 6 years ago in reply to Ross Pimentel

Prodigy 110 points

Yes, I figure it out.
The clock was wrong, now I connected the clock out pin to the microcontroller and the connection works.

Regards, Jaka

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DP83848C: RMII mode: RX0, RX1, TX0, TX1 stays deat when ping