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DP83848C INITIALIZATION PROBLEM

Pravin Raut
Prodigy 40 points
Other Parts Discussed in Thread: DP83848C

Dear Sir,

We are using DP83848C ethernet PHY communicating with LPC2478.

We are connected PHY in RMII mode.

I got following results on different pins.

- PFBOUT (pin 23) connected to PFBIN1+2 (pins 18, 37) and having 1.8V
- PWR_DOWN (pin 7) is High
- MDC (pin 31) No clock
- MDIO (pin 30) shows 3.3V
- 25MHZ_OUT (pin 25) has 50 MHz (correct, because in RMII mode)
- RX_DV/RMII_MODE (pin 39) is pulled up to VCC(3.3V) by 2.2k, signal is permanetly low (plausible cause no packets received)
- RBIAS (pin 24): 1.2V
- 0V on PHYAD0 - PHYAD4

  • 0
    TI__Mastermind 31600 points
    I have moved your post to the Ethernet forum so that it will get visibility from the team.

    You have done a great job of highlighting several of the key functional parameters of the device in your application. Could you elaborate on the initialization problem? Are you able to link? Can you read registers? What is the state of the LEDs?

    Thanks,
    Patrick
  • 0 in reply to Patrick OFarrell
    Prodigy 40 points

    Thanks for your quick support.

    I attached my schematic of DP83848C for your reference.

    Suggest change if any.

    Following my steps to test DP83848C

    1. As I selected RMII mode for DP83848, so I got 50MHz frequency at Pin 25 (25MHz output).

    2. I check PFBOUT, PFBIN1, PFBIN2 are short and showing 1.8V.

    3. RBIAS is showing 1.14V.

    4.I got 0v on PHYAD0, PHYAD1, PHYAD2, PHYAD3, PHYAD4.

    5. As per datasheet it should get logical one on that pin. So I have doubt on PHY address. because address 0 is invalid, for that what i will do, can i pull up ??. 

    6. ON MDIO i am getting 0V.

    7. ON MDC i am getting 0V, where i should get CLK???

    8. I haven,t connect ethernet connector on my board.

    9. My 1st aim is to program resistors of DP83848C.

    10. When I am trying to write data on MDIO my processor is get hang.

    11. there is no clock and no data.

    12. If i try to read data, it showing only 0x0000 and that time there is no clk and no data.

  • 0 in reply to Pravin Raut
    TI__Mastermind 18425 points

    Hello Pravin,

    I cannot see the attached schematic, do you mind sending it again?

    Thank you for the detailed description and highlighting the key parameters. A few questions related to those;

    1. In your original post you mentioned that MDIO had 3.3V and in the latest post you mentioned that it was 0V. The voltage at RBIAS has also changed from 1.2V to 1.14V. What changed?

    MDIO should have 1.5Kohm pull up resistor on it and RBIAS should have 4.87Kohms 1% tolerance resistance connected to ground. You can power down the board and check the resistance across these pins.

    2. What are the strap condition of PHYAD0-PHYAD4 pins?

    -Regards,

    Aniruddha