I want to capture a square wave drop out on my scope

[Chris Wilson]

I have a Si5351a synthesiser chip that is supposed to give out 180 degree out of phase 137kHz square waves from pins CLK9 and CLK1. I believe the firmware that runs it may have a bug as I see the occasional drop out, very brief and random. I THINK there may be a higher frequency, lower amplitude signal showing during these glitches. My scopes are quite basic, a Dataman 526  150 MHz USB scope and a Philips PM3380   100 MHz "combiscope" that can be switched from analogue to digital. My knowledge of their usage is pretty rudimentary OI am afraid, although I know the basics.


I also have an elderly HP scope a HP 54501A 100MHz 4 channel jobbie. 

https://www.dataman.com/downloads/dl/file/id/40/product/35/dataman_520_series_manual.pdf

https://dam-assets.fluke.com/s3fs-public/pm33xx__umeng0200.pdf

http://ftb.ko4bb.com/manuals/82.70.254.222/HP_54501A_Digitizing_Oscilloscope_Front_Panel_Operation_Reference.pdf

I have never attempted to catch a dropped waveform, could anyone suggest if any of these scopes are capable of showing what happens during these glitches please? thanks.

[jmelson]

Look for missing pulse triggering.  Possibly your scope in digital mode has such a trigger option.  This is something that the fancier logic analyzers can usually do.
Or, set up a trigger requirement where if it has a pulse on one input but no complementary pulse on the other, it triggers.  I think I know how to do this on a Tek logic analyzer, not sure on anything else.

Jon

[tautech]

A Period trigger should do this.