Understanding Logic Analyzer Triggering - Agilent Technologies 16712A Help Manual

Chapter 1: Agilent Technologies 16712A 128K Sample Logic Analyzer
The Trigger Tab

Understanding Logic Analyzer Triggering

What is a Trigger (see page 74)
What does "Trigger Position" Mean (see page 74)
What can be Used to Specify a Trigger (see page 75)
When to use a Combination, a Branch, or a Level (see page 75)
What is a Trigger
In simplest terms, a trigger is an event that tells the logic analyzer to
finish filling its acquisition memory. The memory functions like a
conveyor belt: new samples are always coming in, and old samples
"falling off" (being overwritten). The logic analyzer has room for 128 K
samples. When this is full, the only way to fit in new data is to discard
the old.
After you specify your trigger sequence and press run, the logic
analyzer searches incoming data for events in the trigger sequence.
Using the conveyor belt metaphor again, it is like someone tending the
conveyor belt who has been told to stop the belt when a certain sample
is seen.
The trigger is not like an oscilloscope trigger. Logic analyzers trigger
only once per run, even when more than one sample matches the
trigger event. Logic analyzer trigger events are like special switches to
stop the evaluation process and just fill memory.
What does "Trigger Position" Mean
Because the logic analyzer is continually looking at data from your
target system after you select Run, and because the trigger is a single
event, you can arrange to collect data relative to it. It is like the person
running the conveyor belt is told to stop the belt when the special
sample reaches a certain position.
The default trigger position is in the middle. This means there are
74
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com