Teledyne LeCroy WavePro Automation Command - Manual (Page 313)

Automation Command and Query Reference Manual - Control Reference
FindPattern Action
Forces pattern analysis to be run. If AutoFindPattern is True, as it is by default, then it probably will
not be necessary to use this action control.
Description
' Visual Basic Script
Set app = CreateObject("LeCroy.XStreamDSO")
app.SDA2.JitterMeasure.Pattern.FindPattern
Example
HexPattern String
Any number of characters Range
This string is shown on the Jitter Measure menu's Pattern Analysis right side dialog "Pattern" tab. If
the pattern is a recognized, nameable pattern then this string will contain that name, for example
"PRBS7" or "PRBS7 inverted". If the pattern is not a known, nameable pattern then the hex for the
pattern is shown. The hex is formatted such that the lsb is used. Since hex characters represent four
bits, some of the bits represented by the leftmost hex character may not be used. The length of the
identified pattern, in bits, is put into PatternLength (see PatternLength, below). This string cvar s just
text to be read.
Description
ISINumBits Integer
From 3 to 12 step 1 Range
This control sets the number of bits considered for display of the ISI Plot. It is accessible on SDA2's
Jitter Measure menu "Pattern" tab on the right side diallog, when ISIPlot is displayed. For the ISI Plot
SDA2 sorts groups of bits by pattern, and averages together segments of the input waveform that
have the same pattern. This control specifies how many bits are considered together. Default value
for this control is 6, which means the SDA2 must keep track of 2^6 = 64 six UI long patterns. The ISI
plot shows the next to last UI of each pattern, all overlapped. After a sufficient number of occurances
of each pattern random noise has been greatly attenuated by averaging, leaving thin lines whose
placement is due to ISI. The ISI Plot is only for display, it is informational; no jitter measurements are
derived from the ISI plot. A somewhat similar algorithm of sorting patterns is used to determine DDJ
in non-repetetive pattern mode, see NumberOfBits, below.
Description
IsRepeating Bool
This controls which algorithm is used to identify DDJ. You, the user, should set this as appropriate.
When a precisely repeating pattern is expected this control should be set to True, which is its default
value. When the data pattern does not repeat within one acqusition, then this control should be set to
False. Note that some standards use very long patterns such as PRBS 23 which may require us to
treat them as non-repeating data. With no added overhead, PRBS 23 is 2^23-1 = 8388607 UI long; at
a reasonable sample rate of 5 samples per UI that requires 41,943,035 samples to capture one
complete pattern; to see a repetition therefore would require a 100MS acquisition. After fifty 100MS
acqusitions the default "MinAverages" of 100 would be satisfied and other jitter results, that depend on
DDj being known, would appear. Clearly, use of such a long pattern is meant to resemble the
absence of a repating pattern, even if your scope can do 100MS acquisitions there is a more
reasonable approach: in such a case use a reasonable length acqusition and set "IsRepeating" to
False. See ISINumBits, above.
Description
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