What are the dark rectangles on the logic analyzer waveform?

[herbkanis]

Hi,
Has anyone seen dark rectangles like the ones in the waveform capture I’ve attached?
The logic is from an Epson Printer and I’m using a Diligent Discovery 2 to get the waveforms.

Thanks for any help,

[MarginallyStable]

I'm not sure if relevant for your analyzer, but may be glitch detection. Some analyzers have circuitry to detect glitches that are smaller than the instrument's sample period. 

[Paul Rose]

Yes.

https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/reference-manual

The online Waveforms manual section 4 ( Main Plot ) point  12:

Noise band indicating glitch or higher frequency components than the sampling frequency. See Real
channels options.

On figure 4.1, the corresponding label 12 shows a dark background for a portion of the plot

[herbkanis]

Both answers are correct. I did a search for "Wavegen" and "Glitch" on marginallystable's suggestion and found the reference that Paul gave.
Thanks to you both!
Cheers