LeCroy SDA, Operator'S Manual

Page: 317 / 397

SDA Operator’s Manual
SDA-OM-E Rev H
317
The default value of 1667 is the industry standard for a "Golden PLL" and equals the ratio of
the Bit Rate to the PLL Cutoff frequency. The
PLL Cutoff frequency control reads the
frequency corresponding to the Cutoff Divisor. Alternatively, the PLL Cutoff frequency may
be entered and the nearest cutoff divisor will be computed from this entry.
4. Settings for the Custom PLL: Touch inside the Number of Poles control to select the order
of the PLL. The number of poles can be 1 or 2. Touch inside the Natural Frequency control
to set the natural frequency of the loop filter. The Damping factor control allows a damping
factor setting between 2 and 0.5.
Summary
This is a quad-grid view of your signal: eye diagram, bathtub [The bathtub curve can be thought
of as the "tails" of the TIE histogram, or the integral of the histogram. It is a logarithmic
representation of bit error rate (BER). The greater the degree of separation between the sides of
the bathtub curve, the better the BER. Deterministic jitter dominates the shape of the bathtub
curve near the edges of the graph where the curves are at their highest amplitude, while random
jitter determines the shape of the curve near the middle.], TIE trend [This is a trend of the time
interval error measurements between the data transitions and the reference clock. This is the
time record of the information contained in the TIE histogram.], and TIE histogram [A histogram of
the time interval error for all bits in the waveform. Note that while the eye diagram and mask are
displayed, mask hits are not detected in this view.].
Note: The Summary screen does not allow mask testing.
To access the "Summary" dialog, do the following:
1. Press the SDA front panel button; or, touch
Analysis in the menu bar, then Serial Data in the
drop-down menu. The display will default to the "Scope" dialog, which enables you to set up
SDA measurements while you continue to view currently displayed waveforms.
2. Touch the Summary button.
Mask Test
Press the SDA front panel button; or, touch Analysis in the menu bar, then Serial Data in the
drop-down menu. The display will default to the "Scope" dialog, which enables you to set up SDA
measurements while you continue to view currently displayed waveforms. See the Basic Setup
and PLL Setup sections for details on setting up the clock recovery.