As with any perceived problem it's great if you can post some supporting screenshots that we can point Tech support to.
It's so much easier then to duplicate your findings as there's much info in a screenshot that then doesn't need mention.
I agree. In this case, though, a screenshot wouldn't help since it's a *time* effect. Instead, I'll do what the cool kids are doing these days and post some videos. Please forgive my lack of skill. In all cases, I used the internal waveform generator to produce a 1 Hz pulse, with 50 us pulse width.
Playlist with all the videos:
https://vimeo.com/album/3960396Video 1 is in Auto mode, with ~800 ms holdoff as suggested by rf-loop:
First, every pulse that's displayed has trace data at zero volts everywhere. My interpretation of this is that the scope re-arms itself almost instantly, and tries to display the trace when it's at zero volts. Even worse, the scope seems to trigger, but displays no pulse. For example, at 2 seconds, and then again at 7 seconds. This is bizarre, there should have been one trigger per second.
Video 2 is in Auto mode, with no trigger holdoff:
Here, the scope seems more eager to trigger but not display anything. You can see it happen at the 1 second mark, and then again at the 7 second mark. I couldn't catch it doing so on camera, but on occasion I would see the pulse on screen get mangled - the width would be something completely different from 50 us.
In, video 3 is with the scope in normal trigger mode:
This is what I expected to see. I found that I had to set the waveform generator frequency as high as 8 Hz before auto and normal trigger modes showed the same thing on screen. This means that the re-arm time in auto trigger mode is something less than 0.125 seconds. I think this is too short - it ought to be at least a half second so that the waveforms shown on screen in auto trigger mode can actually be seen. After all, that's the whole point of auto trigger mode - to explore around without knowing what sort of signals to look for.
Finally, here's the same signal on ye olde 54602B:
This scope had the holdoff set to 800 ms as well. It never misses any pulses, and you can clearly see the structure of the pulse. It's misshapen since the probe compensation wasn't adjusted. Due to the large dead time that its acquisition system has, it performed poorly with the holdoff turned down.
After posting I noticed I was triggering on rising edge
Just in case my point got lost - the scope behaved the same whether I was triggering on the rising or the falling edge.
Scope default holdoff need be short, other way we read thousends of negative comments how slow this scope reeact when touch probe to some potential before anything see on the screen. But user can adjust it when really need. (example if you try look AM modulated signal so that you want trig to modualtion freq, this is fast and practical way to adjust holdoff so that get stabile trig.
As I noted above, the issue at hand is not fixed by increasing holdoff.
Have you tried set trigger mode BUS and then set all trig paramaters for UART?
If you're referring to my previous post about the serial decoder, it should not matter how the scope acquisition is done. My point is that as soon as the first transition of the data is moved off-screen, the decoding fails. This prevents me from acquiring a burst of serial data, and then zooming in to look at the details.