SNLA246D October   2015  – May 2026 DP83867CR , DP83867CS , DP83867E , DP83867IR , DP83867IS

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1DP83867 Application Overview
  5. 2Troubleshooting the Application
    1. 2.1 Schematic and Layout Checklist
    2. 2.2 Device Health Checks
      1. 2.2.1 Voltage Checks
      2. 2.2.2 Probe the RESET_N Signal
      3. 2.2.3 Probe RBIAS
      4. 2.2.4 Probe the XI Clock
      5. 2.2.5 Probe the Strap Pins During Initialization
      6. 2.2.6 Probe the Serial Management Interface (MDC, MDIO)
        1. 2.2.6.1 Read and Check Register Values
    3. 2.3 MDI Health Checks
      1. 2.3.1 Magnetics
      2. 2.3.2 Probe the MDI Signals
      3. 2.3.3 Check the Link Quality
        1. 2.3.3.1 Improving Short Cable Link Margin
        2. 2.3.3.2 Improving Inter-channel Link Margin
      4. 2.3.4 PMA Compliance
    4. 2.4 MII Health Checks
      1. 2.4.1 MII Check
      2. 2.4.2 GMII Check
      3. 2.4.3 RGMII Check
      4. 2.4.4 SGMII Check
    5. 2.5 Loopback and PRBS
      1. 2.5.1 Loopback Modes
      2. 2.5.2 Transmitting and Receiving Packets with the MAC
      3. 2.5.3 Transmitting and Receiving Packets with BIST
  6. 3Application Specific Debugs
    1. 3.1 Link up in 100Mbps Full Duplex Force Mode
    2. 3.2 Unstable Link Up Debug in 1Gbps communication
    3. 3.3 DP83867PHY and DP83867PHY Cannot Link Up in 1Gbps
    4. 3.4 EMC Debug
    5. 3.5 Packet Errors in Links with Low IPG
    6. 3.6 10Base-Te TP_IDL Failure
    7. 3.7 Slow RGMII Rise/Fall Times
  7. 4Tools and References
    1. 4.1 Extended Register Access
  8. 5Conclusion
  9. 6References
  10. 7Revision History

3.5 Packet Errors in Links with Low IPG

If packet errors are observed in ethernet links with inter-packet gaps (IPG) equal to or less than 12 idle symbols, it may be necessary to tune the Viterbi threshold within DP83867. This threshold can be tuned in the VTM_IDLE_CHECK_CNT_THR register (0x0053[3:0]) where the default value of 0x5 is intended for IPGs greater than or equal to 12 symbols.

If the application expects an IPG less than 12 symbols, the Viterbi threshold can be tuned lower to 0x4 or 0x3. If errors are observed with an IPG of exactly 12 symbols, this threshold can be tuned lower as a debug step to ensure the errors are not a result of IPG.