LeCroy DDA 7 Zi series, Operator'S Manual

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WavePro 7Zi
229
WP700Zi-OM-E-RevA
oversampling you need to capture your Serial Data messages
(at least 4x the bit rate) and also allow you to have a high
enough sample rate to capture any transients that you may
want to see on your Serial Data and analog signals (at least
2x the frequency of any expected transients, preferably 10x).
Reference SMART Memory for more information on these common settings.
Saving Data
You may wish to set up your oscilloscope to capture a short or long memory acquisition for a certain trigger
condition, then save data to a hard drive or memory stick whenever the trigger condition is met. This can be easily
done in most LeCroy oscilloscopes. However, you must realize that there is significant trigger “dead time” when
using this method. To minimize dead time, use the method described under
Storing Triggers (Sequence Mode).
1. First, set up your desired serial data (or other) trigger condition.
2. Then, from the menu bar, choose File , Save
Waveform . This will open a dialog that allows you to
set up the Save Waveform conditions. You can choose
to have this OFF (no Auto Saving occurs), WRAP (Auto
Save occurs until the hard drive is filled, then discards
the oldest data to write the newest data), or FILL (Auto
Save occurs until the hard drive is filled).
3. Be sure to choose a Binary file format if you wish to
recall the traces into a LeCroy oscilloscope for later
analysis.
Even though the LeCroy oscilloscope hard drives are very large, it is a good idea to make sure that your trigger
condition is set correctly before beginning your acquisitions.
Note: This method is not guaranteed to capture all of your trigger events, since there will be a large amount of
“dead time” between triggers as the acquisition is captured, displayed, and stored to the hard drive before the
scope is re-armed for a new trigger. To minimize dead time, use Sequence Mode.
Storing Triggers
LeCroy oscilloscope’s have a powerful capability called Sequence Mode that allows you to store all triggered
events by minimizing the dead time between triggers to < 800 nanoseconds. This is ideal for finding repetitive
causes of problems on your serial data buses or associated signals.
Sequence Mode uses long acquisition memory that is divided into “segments.” As triggered events are acquired,
they are stored in acquisition “segments” to be recalled at a later date. The length of each sequence mode
acquisition segment and the total number of segments allowed is roughly determined by the total acquisition
memory in the oscilloscope. For instance, for a WaveRunner Xi with VL memory, you can get 10,000 segments
that are each a maximum of 625 samples long, or 10 segments that are each a maximum of 1.25 megasamples
long, or something in between. Different acquisition memory lengths have different ranges of segments and
segment lengths. You can define any number of segments from 2 to the maximum for that memory length, and
any length of segment (so long as there is sufficient acquisition memory). After acquisition of all segments is
complete, you can recall them one-by-one and view them in decoded format on the oscilloscope screen.
Acquisition dead time is kept to a minimum because there are no operations performed during the acquisition. All
data for each triggered event is written only into high-speed acquisition memory. Until the entire sequence is
completed, there is no updating of the oscilloscope display, or other operations that cause unnecessary dead
time. This is ideal for situations when you cannot take a chance on losing data.
In the example shown below, we have only acquired Channel 1 (the CAN signal) in sequence mode. We could
also acquire additional analog or other signals as desired or as necessary to do a proper analysis.
1. Touch the Timebase descriptor label to open
the
Timebase dialog.