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Logic Triggering

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Logic Triggering

Postby justfreese » Wed Apr 12, 2017 10:02 pm

Should be a simple question. I just got this scope on Monday and I'm at a critical point.

I am using all 16 digital channels and the 2 analog channels on a 2206B MSO.

I need to trigger when one of the digital channels are low, and when another channels falling edge or another channels falling edge.

Basically:

D0 = 0 and (D1 = falling edge or D2 = falling edge)
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Re: Logic Triggering

Postby Martyn » Thu Apr 13, 2017 5:40 am

WIth a trigger enabled in the trigger toolbar, repeat/auto/single, select the advanced triggers button and then digital. This will give you the digital trigger pattern editor. Each active digital line one can be monitored for a low or high level or a rising or falling edge, or ignored. Any number of levels can be specified, but no more than one transition (edge).

In your example you have (D1 = falling edge or D2 = falling edge) which is not possible as this contains two edge transitions.
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Re: Logic Triggering

Postby justfreese » Thu Apr 13, 2017 9:04 pm

Thanks for the reply. I'm going to need to do something different then.

The problem is that I am monitoring 2 error pins that are active low.
But the system only monitors the error pins when the H bridge controller is enabled.
D0=0 and D1 or D2=0

So if I just trigger off of either being low, I will get a ton of triggers and then will have to go back and find the one that showed an error.


Another thing I am trying to figure out, if I trigger at 50ms/div I can see the signals perfectly, but I can't go far enough back to see what was going on before the trigger. If I change my time base to 1 sec/div I can see more of what happens before the trigger, but what will happen to the resolution and accuracy of the reading? I am trying to find a race condition in software that is down to the microseconds.

Thanks!
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Re: Logic Triggering

Postby Martyn » Thu Apr 13, 2017 9:43 pm

How many channels do you have enabled, analog and digital, and how much time before and after the trigger do you need to see ?
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Re: Logic Triggering

Postby justfreese » Fri Apr 14, 2017 1:01 pm

I have 13 digital channels and 2 analog channels. I need to see about 2 seconds before the trigger.
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Re: Logic Triggering

Postby Martyn » Sat Apr 15, 2017 8:45 am

If you goto to Tools->Preferences-> Sampling and change the sampling transition time to 2s/div, and then use a timebase of 500ms/div, it will collect 5 seconds of data to the scope memory, rather than streaming to the PC. If you also select number of samples to the maximum at the top (2GS), you should get the detail back. Please note you can't collect 2GS it is just the quick way to set the scope to the fastest rate with the chosen active channels.

The final option is to select Single trigger, as this will use all the scopes memory for one capture. Repeat trigger will half the memory so that it has somewhere to write new data to, whilst preserving captured data.

It is always worth opening the properties dialogue, right click on display and select view properties, as this will show you how the scope is actually set up.
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