I347-AT4 Datasheet, PDF (44/148 Pages) Intel Corporation – Intel® Ethernet Network Connection I347-AT4 Datasheet

I347-AT4—Device Functionality
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Register 16_5, 17_5, 18_5, and 19_5 (Decimal)
Figure 13. Cable Fault Distance Trend Line
3.10.2
First Peak
When register 23_5.7:6 is set to 01b, the first peak above a certain threshold is
reported. The first peak operates in exactly the same way as the maximum peak except
that there has to be some qualification as to what constitutes a peak since the first
peak is not necessarily the maximum peak. The first peak is defined as the maximum
amplitude seen before the reflected amplitude drops by some value below this peak.
This hysteresis value is defined by register 23_5.5:0.
For example, in Figure 14, if Pa is greater than the hysteresis value in 23_5.5:0 and Va
is above the threshold value, then Va and Da are reported since it is the first peak that
is above the threshold.
If Pa is less than the hysteresis value in 23_5.5:0, then Va and Da are not reported as
the first peak. Vb and Db will be reported as the first peak if Pb is greater than the
hysteresis value in 23_5.5:0 and Vb is above the threshold value.
If Pa is greater than the hysteresis value in 23_5.5:0 but Va is below the threshold
value then Va and Da are not reported as the first peak. Vb and Db will be reported as
the first peak if Pb is greater than the hysteresis value in 23_5.5:0 and Vb is above the
threshold value.
Register 28_5.7 controls the exact distance that is reported. When set to 0b the
distance where the amplitude falls below the peak amplitude minus the hysteresis level
as defined in register 23_5.5:0 is reported. When set to 1b the distance where the peak
amplitude actually occurs is reported. In either case, the magnitude of the maximum
amplitude of the first peak is reported in bits 14:8.
In the first peak mode register 24_5.7:0 is used to set the starting distance of the
sweep. Normally, this value should be set to 0b. If this value is set to a non-zero value,
any reflection below the starting distance is ignored. This may be useful to ignore
reflections at the transformer that are reported as the first peak. Note that 24_5.8 is
ignored.
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