SNLA452 August   2025 DP83TD510E

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Troubleshooting the Application
    1. 2.1 Schematic and Layout Checklist
    2. 2.2 Component Checklist
    3. 2.3 Device Health Checks
      1. 2.3.1 Check Voltage Supply Pins
      2. 2.3.2 Probe the RST_N Pin
      3. 2.3.3 Probe the CLKOUT Pin
      4. 2.3.4 Probe the SMI Pins
    4. 2.4 Read and Check Register Values
    5. 2.5 Verifying Strap Configuration
    6. 2.6 Loopbacks
    7. 2.7 MDI Health Checks
      1. 2.7.1 Link Up Common Issues
      2. 2.7.2 Transmit Level
        1. 2.7.2.1 Change Transmit Level
      3. 2.7.3 Time-Domain Reflectometry
      4. 2.7.4 Signal Quality Check
      5. 2.7.5 MDI Test Modes
    8. 2.8 MII Health Checks
      1. 2.8.1 RGMII
      2. 2.8.2 RMII
      3. 2.8.3 MII
  6. 3Summary
  7. 4References

2.7.4 Signal Quality Check

After confirming the link up by reading register 0x0010, the signal quality of the link can be verifying by using the built in Signal Quality Indicator (SQI) Function. Poor link quality can be caused by layout or cable imperfections, and can also lead to packet loss or errors, or even link drops.

While TDR can provide information about the existence and location of cable faults, this real-time monitoring of the signal quality can provide valuable information before a fault occurs by measuring the Signal to Noise Ratio (SNR) at periodic intervals after link is achieved.

This MSE value is stored in the memory register 0x0A85. These values can be compared to Table 2-5 to evaluate the health of the link.

Table 2-5 SQI Link Health
SQI Link Health MSE SNR (dB)
Poor MSE > 0660h SNR < 17.29
Marginal 0660h ≥ MSE > 0320h 17.29 < SNR < 20.38
Good MSE ≤ 0320h SNR > 20.38

For more information about the cable diagnostic toolkit of the DP83TD510, please refer to the Cable Diagnostic Toolkit, application note