SNLA437 December   2023 DP83822H , DP83822HF , DP83822I , DP83822IF , DP83825I , DP83826E , DP83826I

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1DP83822 Application Overview
  5. 2Troubleshooting the PHY Application
    1. 2.1  Schematic and Layout Checklist
    2. 2.2  Verify Successful Power-up of PHY
    3. 2.3  Read and Check Register Values
    4. 2.4  Peripheral Pin Checks
      1. 2.4.1 Probe the RESET_N Signal
      2. 2.4.2 Probe the RBIAS pin
      3. 2.4.3 Probe the Serial Management Interface (MDC, MDIO) Signals
      4. 2.4.4 Probe the MDI Signals
    5. 2.5  Verifying Strap Configurations During Initialization
    6. 2.6  Debugging Link Quality
    7. 2.7  Built-In Self Test With Various Loopback Modes
    8. 2.8  Debug the Fiber Connection
    9. 2.9  Debug the MAC Interface
    10. 2.10 Debug the Start of Frame Detect
    11. 2.11 Tools and References
      1. 2.11.1 DP83822 Register Access
      2. 2.11.2 Extended Register Access
      3. 2.11.3 Software and Driver Debug on Linux
        1. 2.11.3.1 Common Terminal Outputs and Solutions
  6. 3References

2.4.3 Probe the Serial Management Interface (MDC, MDIO) Signals

If a register read and write is successful, then this section can be skipped as there's no need to verify correct operation for the Serial Management Interface.

MDIO should pull up to the I/O supply when undriven. Probe MDIO to confirm the default voltage. Before probing make sure a 2.2k Ω pullup resistor is connected on the MDIO line, if it is an extended register make sure to follow Extended Register Access. If seeing an abnormal value that is not expected probe MDC and MDIO for further debugging.

Attempt to write and read the registers. Verify the MDIO data sequence with the data sheet to make sure the MDIO read access timing is correct.

Table 2-3 SMI Protocol Structure
SMI Protocol <idle><start><op code><device addr><reg addr><turnaround><data><idle>
Read Register <idle><01><10><AAAAA><RRRRR><Z0><XXXX XXXX XXXX XXXX><idle>
Write Register <idle><01><01><AAAAA><RRRRR><10><XXXX XXXX XXXX XXXX><idle>
GUID-64096FAD-9030-4B3A-AB9F-1765BAAEC632-low.png Figure 2-2 MDC/MDIO Write Example
GUID-76626B00-DAC8-494C-B992-EE3804EF1FA0-low.png Figure 2-3 MDC/MDIO Read Example