User manual

CANbus Trigger, Decode, and Measure
38
CANbus-TD-TDM-OM-E RevB
2. Optimize your Sample Rate or Memory Length by accessing the Horizontal Dialog in your
oscilloscope and selecting either Set Max Memory mode or Fixed Sample Rate mode.
3. Touch Set Maximum Memory to decrease the memory usage in order to not sample at
rates you specify as being too high (high sample rates can slow down the decoding
algorithm). Then adjust your time timebase setting to the length needed to capture the
event.
Note: Make sure your combined timebase and memory length settings do not result in
too low of a sample rate. Otherwise, adequate capture and decode is not performed.
4. Touch Fixed Sample Rate to specify a fixed rate. It's common to fix the sample rate to a
specified value so you have the necessary oversampling to capture your Serial Data
messages (at least 4X the bit rate). This also allows for a high enough sample rate to
capture transients you may want to see on your Serial Data and analog signals (at least 2X
the frequency of any expected transients, preferably 10X).
Reference your oscilloscope’s Online Help for more information on these common settings.
Trigger Repeatedly, Save Data to a Hard Drive
You may want 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, there is
significant trigger “dead time” when using this method. To minimize dead time, use the method
described inTrigger Repeatedly, Store all Triggers (Sequence Mode).
1. Set up your desired serial data (or other) trigger condition.
2. Choose File →Save Waveform from the menu bar. A dialog is shown where you can set
Save Waveform conditions as follows:
 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