I347-AT4 Datasheet, PDF (43/148 Pages) Intel Corporation – Intel® Ethernet Network Connection I347-AT4 Datasheet

Device Functionality—I347-AT4
3.10.1
Maximum Peak
When register 23_5.7:6 is set to 00b, the maximum peak above a certain threshold is
reported. Pulses are sent out and recorded according to the setting of register
25_5.13:11.
There are 10 threshold settings for same channel reflections and are specified by
registers 26_5.6:0, 26_5.14:8, 27_5.6:0, 27_5.14:8, and 28_5.6:0 for positive
reflections and 26_7.6:0, 26_7.14:8, 27_7.6:0, 27_7.14:8, and 28_7.6:0 for negative
reflections.
These settings correspond to the amplitude threshold the reflected signal has to exceed
before it is counted. Any reflected signal below this threshold level is ignored. The
threshold settings are based on cable length with the breakpoints at 10 m, 50 m, 110
m, and 140 m.
There are four threshold settings for cross-channel specified by registers 25_5.6:0 and
25_5.14:8 for positive reflections and 25_7.6:0 and 25_7.14:8 for negative reflections.
The threshold settings are based on cable length with the breakpoints at 10 m.
The default values are targeted to 85 Ω to 115 Ω. However these threshold settings
should be calibrated for the desired impedance setting on the target system.
The results are stored in registers 16_5, 17_5, 18_5, and 19_5. Bits 7:0 report the
distance of the peak. The distance can be converted to using the trend line in
Figure 13. Bits 14:8 report the reflected amplitude. Bit 15 reports whether the reflected
amplitude was positive or negative. When bits 15:8 return a value of 0x80, it means
there was no peak detected above the threshold. If bits 15:8 return a value of 0x00
then the test failed.
Register 28_5.7 controls the exact distance that is reported. When set to 0b the
distance where the amplitude falls to 50% of the peak amplitude 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 is reported in bits 14:8.
In the maximum 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. Note that 24_5.8 is
ignored.
Note that the maximum peak only measures up to about 200 meters of cable.
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