reventing a gigabit link or affecting
performance.

Agere Systems has developed a cable analysis application using a combination of PHY features and software. Cable
analysis uses two distinct methods for evaluating the cable: link analysis and time domain reflectometry (TDR)
analysis.

Link analysis evaluates the cable while maintaining a link. Link analysis provides a coarse length estimate and can
detect faults that are not detectable using TDR analysis. These faults include polarity reversals and pair swaps. TDR
Analysis cannot be performed with a link; the cable must be disconnected from the remote PHY, or the remote PHY
must be powered down. TDR analysis provides an accurate length estimate and can detect faults that are not
detectable using link analysis. These faults include opens and shorts.

2 Cable Analysis Migration
Table 1 describes the cable analysis migration with respect to silicon generations. The ET1010 uses 0.18 µm process
technology. The ET1011, ET1310, and ET1081 use 0.13 µm process technology. The ET1010 and ET1011 are
single port PHYs. The ET1310 is an integrated MAC/PHY. The ET1081 is an octal PHY.

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Table 1: Cable Analysis Specifications
Feature Description 10 100 1000 Term
Unterm
ET1010
ET1011/
ET1310/
ET1081
Cable open


X X
Cable short


X X
Indicate distance
to fault



± 2 m
± 2 m

Pattern
Generator/
Sub-
Sampler/
Software
Line
Probing
Module/
Software
Detection of
cable fault
on any pair
Pair swaps
X
X
X


Link
Analysis
Link
Analysis
Detect
Polarity
Reversal
X
X

Link
Analysis
Link
Analysis
Good Cable
w/Link
Indicate length

± 5 m
± 5 m


Link
Analysis
Link
Analysis
Good Cable
w/o Link
Indicate length


±
5
m
1
±
2
m
Pattern
Generator/
Sub-
Sampler/
Software
Line
Probing
Module/
Software
Pair Skew
w/Link
Detect excessive,
>50 ns

X

Link
Analysis
Link
Analysis
Pair Skew
w/o Link
Detect excessive,
>50 ns



X
1
X
Pattern
Generator/
Sub-
Sampler/
Software
Line
Probing
Module/
Software
Excessive
Crosstalk
Cable quality or
split pairs


X X
Pattern
Generator/
Sub-
Sampler/
Software
Line
Probing
Module/
Software

1.
If the magnitude of the peak reflection is greater than 15% of an open circuit.

The ET1010 contains two important features that are used for TDR. The first feature is the pattern generator, which
allows a specific digital sequence to be transmitted on one of the four cable pairs. The second feature is the
subsampler, which allows data to be captured and processed on one of the four cable pairs. Software algorithms
developed by Agere Systems uses these two features to determine the cable characteristics.

The ET1011, ET1310, and ET1081 contain a line probing module that greatly reduces the software task of capturing
and processing TDR samples. The line probe module contains two important features that are used for TDR. The
first feature is the pulse generator, which allows a digital pulse to be transmitted on one of the four cable pairs. The
second feature is the thresholder, which extracts key features of the TDR signal on one of the four cable pairs
without the additional software burden and memory resources associated with capturing and processing all of the
TDR samples. Software algorithms developed by Agere Systems uses these two features to determine the cable
characteristics.

Table 2 shows the time required to perform TDR analysis with respect to silicon generations.

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Table 2: TDR Analysis Execution Time
Device ET1010
ET1011/
ET1310/
ET1081
Execution Time
6 s
< 1s

Page 4 of 16
3 Cable Analysis Software
The cable analysis software consists of two main libraries:

Silicon Debug Features Support Library (SDF)
IntelliSupport Library (INL)

SDF is a low-level library that contains API functions for reading and writing the proprietary registers of the PHY.
INL is a high-level library that makes use of SDF to control these registers and process them in order to perform
cable analysis. The API functions for these two libraries are discussed in detail in the Cable Analysis API
application note.

The top-level INL routine, which is the main entry point for cable analysis used by TruePHY Evaluation System
software, performs the processing shown in Figure 1.

Start
Link is up?
Yes
Perform Link Analysis
(except coarse cable
length and coarse pair
skew estimation)
No
Link is down or forced
TDR analysis?
Prompt user to disconnect
cable from remote device
or power down remote
device
Perform Link Analysis
coarse cable length and
coarse pair skew
estimation
Yes
No
End
Perform TDR Analysis

Figure 1: Processing for top-level INL routine

Page 5 of 16
3.1 Link Analysis
Link Analysis acquires the following cable analysis information:
Basic link information: Link speed, master/slave setting, and MDI/MDI-X setting
Wire map: crossover and polarity inversion detection
Signal-to-noise ratio (SNR)
Frequency offset error
Coarse cable length estimation
Coarse pair skew estimation

The link speed, master/slave setting, and MDI/MDI-X setting are retrieved using MI registers in the PHY. The
master/slave setting is only applicable for a 1000Base-T link.

The wire map is deduced based on the MDI/MDI-X setting and proprietary PHY registers. Polarity inversion cannot
be determined for a 100Base-TX link since 100Base-TX is polarity insensitive.

The SNR is a measure of the quality of the receive signal. It is determined using an internal diagnostics block called
the Diagnostic ALU, which allows simple operations to be performed on internal signals of the PHY. The SNR is
calculated using the energy at the input and output of the slicer. The SNR can only be determined for a 1000Base-T
and 100Base-TX link.

The frequency offset error indicates the difference in frequency between the master and slave clocks for a 1000Base-
T link. For the master PHY, the offset will always be zero since the master PHY provides the timing for the slave
PHY. For a 100Base-TX link, the frequency offset error indicates the difference in frequency between the clocks of
the remote and local PHYs. Frequency offset error is determined using proprietary PHY registers and is not
applicable for a 10Base-T link.

Coarse cable length estimation indicates the overall length of the cable and the length of each individual pair. The
length estimation accuracy is ± 5 m with a 1000Base-T or 100Base-TX link. The cable length cannot be determined
for a 10Base-T link. The length estimate is calculated based on equalizer coefficients and proprietary PHY registers.

Coarse pair skew indicates the time difference between the shortest length pair and the other pairs with 8ns
resolution. Coarse pair skew is only applicable for a 1000Base-T link.

3.2 TDR Analysis
TDR Analysis acquires the following cable analysis information:
Cable length estimation
Distance to cable faults
Pair skew estimation

For the ET1010, TDR analysis is accomplished using the pattern generator and subsampler. The pattern generator
transmits periodic pulses on each cable pair. These periodic pulses are reflected (echo) or coupled back (NeXT) to a
receiver on each cable pair. The subsampler samples the signal on each cable pair for each transmit/receive
combination. The software reads the samples and performs an analysis to estimate cable length, distance to fault (if
any), and pair skew.

For the ET1011, ET1310, and ET1081, TDR analysis is accomplished using the line probing module. This module
transmits one or more pulses on each cable pair. These pulses are reflected (echo) or coupled back (NeXT) to a
receiver on each cable pair. The thresholder extracts the key features of the TDR signals for each transmit/receive
combination. The software reads the thresholder and performs an analysis to estimate cable length, distance to fault
(if any), and pair skew.

The cable length is based on time difference between the transmitted pulse and the peak reflection in the echo signal.
The distance to cable faults is based on the time difference between the transmitted pulse and significant reflections
in the echo signals or coupling in the NeXT signals. The type of faults is based on the amplitude and polarity of the
significant reflections in the echo signals or the amplitude and polarity of the coupling in the NeXT signals. The pair
Page 6 of 16
skew estimations are calculated based on the cable length of the shortest pair and all other pairs. The cable length
and distance to cable fault accuracy is ± 2 m for an unterminated link (i.e., the cable has been disconnected from the
remote device), and ± 5 m for a terminated link (i.e., the remote device has been powered down) provided that the
magnitude of the peak reflection is greater than 15% of an open circuit.


Page 7 of 16
4 Screen Shots
This section contains screen shots taken from the TruePHY Evaluation System software. It is used to illustrate the
capabilities of the Cable Analysis software for both Link Analysis and TDR Analysis.


4.1 Link Analysis
Link analysis consists of the following pages: Summary, Echo, NeXT, and Channel Response. These pages are
discussed in detail in subsequent sections.

4.1.1 Summary
Figure 2 (a) illustrates the