Find Symbol Sequence
In Oscilloscope and Eye mods, use the Find Symbol Sequence dialog box to find all occurrences of a specific sequences of symbols within a pattern waveform. This feature allows you, for example, to observe how your device under test responds to a
1110 symbol sequence.
For NRZ signals, you can search for symbols 0 and 1. For PAM4 signals, you can search for symbols 0, 1, 2, or 3. Enter the symbol sequence to find in the Sequence field.The dialog box's Source field shows the source waveform on which the search is performed. If more that one waveform is available, the source icon is a button. Click on the button to select a different waveform.
Each time you click Find Next, the relative position of the next sequence matching your criteria is shown in the pattern bar which is shown just under FlexDCA's menu. It is identified by a black bar which is pointed out in the above picture. The time scale is automatically adjusted to zoom in on the symbol sequence. A maximum sequence of 128 symbol can be entered.
The dialog box's Symbol Rate field is only displayed if pattern lock is not turned on as shown in the following picture. In this case, an external pattern trigger is assumed to be connected to the oscilloscope.
The following information applies to FlexDCA. It does not apply when FlexRT is enabled in FlexDCA. Pattern Lock is not needed or used in FlexRT.
In FlexDCA, pattern lock must be turned on or a external pattern trigger connected to the DCA-Xs front panel.
It is recommended that the entire pattern be acquired. Find Symbol Sequence only works on that data that has already been acquired. If Acquire Entire Pattern is not enabled, the search only includes the signal that is displayed on the screen. To select Acquire Entire Pattern, click Acquisition > Acquisition Setup and make the selection in the Waveform tab of the Acquisition Setup dialog box. In the same dialog box, turn off Wrap Waveform in eye mode to display the individual bits as shown in the above picture.
If pattern lock is not turned on, the pattern lock message is displayed as shown in the above picture. Because the Find Symbol Sequence only works on a single-valued waveform, as opposed to an eye diagram, ensure that the trigger setup results in a single-valued waveform. To achieve this, turn on pattern lock or use an external pattern trigger. Ignore this notice, if you are using an external pattern trigger.