SNLA334 june   2023 DP83867CR , DP83867CS , DP83867E , DP83867IR , DP83867IS , DP83869HM

 

  1.   1
  2.   DP83867 and DP83869 TDR
  3.   Trademarks
  4. 1Time Domain Reflectometry
    1. 1.1 Example Connections
      1. 1.1.1 Open Circuit Cable
      2. 1.1.2 Short Circuit Cable
  5. 2DP83867 and DP83869 TDR Implementation
    1. 2.1 TDR Configuration
    2. 2.2 TDR Algorithm
      1. 2.2.1 TDR Algorithm Example Flow
      2. 2.2.2 TDR Algorithm Matlab Example
  6. 3Summary
  7. 4References

1 Time Domain Reflectometry

TDR only works for twisted pair connections. TDR involves sending a pulse on TX and RX pair and observing results on either pair. By measuring voltage amplitude, polarity, and the time interval, the PHY can determine the nature and position of the fault. The DP83867/DP83869 TDR generator sends pulse on the TX and RX channel, then monitors both channels to observe reflections. It sends a pulse one channel at a time, and if reflections are observed on the other channel, then the PHY TDR realizes that the wires have been crossed. The DP83867/DP83869 can detect one peak for each transmit and receive channel. TDR can be used for the following:

  • Cable Open
  • Cable Short
  • TX/RX pair cross-wired
  • Impedance discontinuity

TDR can be used only when the Link is down.