If the only thing that matters is sample speed, then with the 800Ms/s of the digital discovery I could measure a 200Mhz square wave without any problem, or even an higher frequency signal, if I want to trade off precision.
What do you mean "measure a 200MHz square wave" and "trade off precision"? I think you are completely misunderstanding what a logic analyser will do.
I suggest you physically draw a 200MHz signal on a piece of paper (1), i.e. with a period of 5ns, 2.5ns high, 2.5ns low.
On a separate piece of paper(2) draw a series of dots with a period of 1.25ns (to the same scale, of course!) along the edge of the paper. This is the logic analyser's clock.
Put the piece of paper (2) on top of the piece of paper (1).
Wherever you see a dot, note whether the corresponding 200MHz signal is high or low; that is what the logic analyser will display.
Slide the piece of paper (2) along the 200MHz signal, and repeat.
So far, so boring.
Now repeat the above, except draw the signal so that it is the same period (5ns), but 1.5ns high and 3.5ns low. That is typical "200MHz" digital signal.
Pay particular attention to the pattern of highs/lows you record when the paper (2) is in differing horizontal positions. The pattern will vary.
Now reconsider what you might mean by "measure" and "precision".
English is not my first language, I know that sometimes i may seem a bit confusing and confused, I'm sorry.
I know what logic analyzers do, I've debugged many microcontroller project with one. When I'm talking about square wave, I always mean a square wave with 50% duty cycle,i should have said that.
That is because the only rule of thumb I could find for logic analyzers is that for a square wave with 50% duty cycle, if you want a somewhat precise visualization, you need at least a sampling frequency 4 times that of the wave. That's why I was talking about a 200MHz square wave: the digital discovery has a max sampling rate of 800Ms/s.
I know that if one pulse is so short that it's between two samples, then I will totally miss it.
So, let me ask again the starting question in a (I hope) more clear way.
Does the 100MHz bandwidth of the digital discovery means that I can reliably visualize a 100MHz square wave at 50% duty cycle?
My doubt started from the thought that to view a 100MHz square wave on an oscilloscope, you need at least a bandwidth of 500MHz, but that's to see the actual wave, not the logic state.
Inviato dal mio Moto G (5S) Plus utilizzando Tapatalk