Find Symbol Sequence
In Oscilloscope and Eye modes, use the Find Symbol Sequence dialog to find all occurrences of a specific sequences of symbols within a pattern waveform. For example, this feature allows you to observe how your device under test responds to a 1110 symbol sequence. Symbols in the symbol sequence are identified by the waveform levels shown in the drawings in this topic for NRZ, PAM4, PAM6, and PAM8 waveforms.
Enter the symbol sequence to find in the Sequence field. The dialog's Source field identifies 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 includes a Symbol Rate field if pattern lock is not turned on. An external pattern trigger must be is connected to the oscilloscope.
| Waveform | Available Symbols (Levels) |
|---|---|
| NRZ | 0, 1 |
| PAM4 | 0, 1, 2, 3 |
| PAM6 | 0, 1, 2, 3, 4, 5 |
| PAM8 | 0, 1, 2, 3, 4, 5, 7 |
Symbol Levels Identified in Scope Mode
Symbol Levels Identified in Eye Mode
FlexDCA
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. In the same dialog, 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. 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.