Part Number: DP83822I
Hi I am using DP83822 PHY and implemented TDR functionality as per www.ti.com/.../snla253.pdf . I am facing following issues.
I am using 10M cable for this.
1. While boot up, I get Cable fault location Length as 9 M and fault location result polarities is not zero value. (this indicate short circuit). [Sometimes]
2. While unplug and plug the cable, observed following behavior. I am using same Cat 6 cable(10M) for below scenarios
some times
Cable Length as zero
or
Cable Length as 9 and fault location result polarities value is zero.
or
Cable Length as 9 and fault location result polarities value is non zero. (this indicate short circuit)
Note:
How to use the TDR Feature of DP83822 expected self-reflectionvvalue should be set to 0x0C. Cables are causing self-reflections which means that some of the values need to be discarded because of that. 0x0C means that values from 0 to about 3 meters are ignored. In case the peak is inside the ignored range, TDR function will report fault location as the configured value which then should be ignored when calculation the location. However, with some cables the location value has been oscillating between 0x0C and 0x0D when the other end is disconnected causing unncessary connector short circuit occurrences with cables that are not broken. To compensate this, the self-reflection value is increased to 0x0D which means values from 0 to about 3.8 meters are ignored but should prevent false positives from short circuit detection.
