I am looking at pulses of 1Mhz on multiple probes at a time which may continue for a hour. Suddenly pulses stops. I want to capture pulses just before stoppage.
Because there are multiple probes, I think you want the pattern trigger. If the pattern of no pulses (all zeros) is present for greater than the amount of time that tells you pulses have stopped, then trigger. Also specify that the horizontal time reference is at the end of captured data (rightmost) so that most of the acquisition memory has mostly pre-trigger data.
Oh, and turn off auto triggers so that only your specified pattern event will trigger the oscilloscope.
For a TRIG on one specified channel (may be use if pulses stopped on all channel in same time) :
Yes, it is possible to do this with an advanced TRIG of an oscilloscope. Here is the example with my Tektronix DPO3014, using the TIMEOUT trig mode. I used pulses at 1 MHz and 1Vpp. The setup is done so that if the low level lasts 1μs or more, the oscilloscope will trig and we will see the image of the end of the pulse train. As long as this condition is not reached the oscilloscope will not trigger, the pulse train can last for hours without problems, and will be detected at the moment that the TIMEOUT condition is encountered.
For pattern trigger is more complex. All probes to 0 (no pulse) for a trig or anyone of probe at 0 (no pulse) for a trig ? Trigger possibilities depend of your oscilloscope advanced triggering features.
Retrieving data ...