What Channel Analysis Provides; Channel Emulation - LeCroy WaveMaster 8600A Operator's Manual

occur. Head signals for PRML channels have complex waveshapes, which are very difficult or even
impossible to analyze by visual inspection. Analysis of these signals with an oscilloscope is often
limited to looking for gross abnormalities such as significant thermal asperities or dropouts of
sufficient duration. Furthermore, because of the sophistication of PRML signal processing, even
some visible anomalies may not necessarily cause an error.
Time and Effort
Lastly, data in the sectors is complex and lengthy, and it can take significant time and effort to scroll
through and visually inspect signal locations. The problem is of data presented in a time-linear
fashion, rather than in the order of signal areas most deficient in PRML channel related signal
integrity.
In an integrated environment, the Channel Analysis feature analyzes the head signal. Designed to
overcome the obstacles just described, it combines powerful analytical tools with the ability to
capture and analyze the head signal in a synchronized way.

What Channel Analysis Provides

The DDA's Channel Analysis feature provides insight into channel data quality and errors, even
while data is being processed through the channel. It can also do the following:
•
Filter and display the head signal with automatic or selectable settings for -3dB cutoff
and boost
•
Select head signal sections to be viewed by byte number
•
Provide a display of PRML target levels annotated on the head signal trace to provide
an intuitive visual indication of head signal quality
•
Identify head signal locations of the poorest quality from a PRML standpoint, quantify
the quality of the signal at these locations, and display in order of poorest quality the
head signal location and the byte number of each error
•
Identify areas where two head signal differences are greatest and provide a
benchmark for the difference and the byte locations where these occur
The Channel Analysis feature can be operated in either of these basic modes:
•

Channel Emulation

•
Analog Compare
Because each requires a similar setup, both share the same Channel Setup menu system, which
lets you switch between modes without the need to redefine setup details.
Channel Emulation
Often when examining a partial response maximum likelihood (PRML) data signal, it may be
desirable to view those signal locations where the quality is poorest and the signal is likely to be the
most problematic for a PRML channel.
Channel Emulation enables analysis of PRML head signal quality from the point of view of the
PRML channel. This is made possible by the emulation of PRML channel processing by means of
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