Rigol DS1054: Can it freerun w/o trigger?

[OhhJustPeachy]

I'd like to use my Rigol DS1054 in a fashion that's better than a logic probe but worse than a logic analyzer by just setting the sweep frequency as near as I can to some integer dividend of the UUT's clock frequency and watching states flip around, i.e. with no trigger at all. I suppose I could hack this behavior by setting the time base mode to XY and feeding a sawtooth wave into the X channel and the probe into the Y channel but it seems like the scope ought to be able to do something like this on its own.

[Fungus]

Turn one channel's vertical range way down so you can see the background noise. Trigger off that.

I suppose I could hack this behavior by setting the time base mode to XY and feeding a sawtooth wave into the X channel and the probe into the Y channel but it seems like the scope ought to be able to do something like this on its own.

Or feed your "sawtooth" into one channel as a trigger and you have three more for looking at signals.

[ebastler]

You have not told us why you would want to run the scope like this. Why don't you trigger on the edge of the signal under test (or one of the signals)? That will give you one stable reference point on the horizontal axis of the screen.

If you prefer, shift the trigger time towards the left edge of the screen. You can also trigger on any (i.e. positive or negative) edge of the signal if you prefer that. If this does not work for your application, please indicate what's missing.

Edit: tpyos...

[OhhJustPeachy]

You have not told us why you would want to run the scope like this. Why don't you trigger on the edge of the signal under test (or one of the signals)? That will give you one stable reference point on the horizontal axis of the screen.

If you prefer, shift the trigger time towards the left edge of the screen. You can also trigger on any (i.e. positive or negative) edge of the signal if you prefer that. If this does not work for your application, please indicate what's missing.

What I'm wanting to do is watch a few bits' worth of something like a RAM address line that's stable in time, like show me a trace of ten sequential bits. Even if I trigger on a rising or falling edge like you suggest - which hadn't occurred to me; I was looking at the manual last night and I don't remember seeing that option but I'll look again - two zeroes or two ones in a row will move the line over. Maybe what I need to do is bring the clock in on another channel and make it trigger on that.

[ebastler]

Ah, so there is a periodic process at a sub-harmonic of the system's clock. In that case I would agree with the idea that was mentioned in the other copy of this thread -- use the trigger hold-off time, which can be adjusted quite precisely. And trigger on the system's main clock for an exact sync without drift.

[james_s]

You can absolutely trigger on a rising or falling edge, that is one of the most basic functions that every single oscilloscope made in about the last 50 years will have.