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Chapter 4: Concepts
Understanding Logic Analyzer Triggering
be used in place of Global Counters, if possible, because they are easier
to use and because there is a limited number of Global Counters.
Next: “Timers” on page 200
Timers
Timers are used to check the amount of time that has elapsed between
events. For example, if you want to trigger on one edge followed by
another edge that occurs within 500ns, use a timer. The most critical
point to remember in using timers is that they need to be started
before they are tested. In other words, timers do not start
automatically.
The key to setting up a timer is to identify where it should be started
and where it should be tested. Consider the example in the following
figure. The timer should be started when the rising edge on SIG1 is
detected and it should be tested when the rising edge occurs on SIG2.
An edge followed by an edge with a time limit
An example trigger sequence to set up this measurement is:
1. If there is a Rising Edge on SIG1, then
Start Timer1
Go to 2
2. If there is a Rising Edge on SIG2 AND Timer1 < 500ns then
Trigger
While the above trigger sequence seems correct, it actually has a
critical flaw. What happens if there is a rising edge on SIG1 but SIG2
doesn't occur within 500ns? The logic analyzer will never trigger,