Triggering on Waveforms
3–64
TDS 684A, TDS 744A, & TDS 784A User Manual
of Figure 3–38.) The oscilloscope can then detect and trigger on violations of a
time range that occurs before or one that occurs after the clock.
NOTE. Keep hold time to at least 2 ns less than the clock period or the oscillo-
scope cannot trigger.
To quickly check if logic triggers are selected and if so, what class, check the
Trigger readout. When logic triggers are selected, the trigger readout displays the
selected logic trigger class: Pattern, State, or StlHld (Setup/Hold). (See
Figure 3–39.)
Trigger Class = State
Ch 1, 2, 3 Inputs = High, Don’t Care, High
Ch 4 Input = Rising Edge
Logic = OR
Figure 3–39: Logic Trigger Readouts — State Class Selected
NOTE. When the trigger type Logic is selected, the trigger levels must be set for
each channel individually in the Set Thresholds menu (pattern and state classes)
or the Levels (setup/hold class) menu. Therefore, the Trigger Level readout will
disappear on the display and the Trigger Level knob can be used to set the
selected level while the Main Trigger menu is set to Logic.
When you select the logic class Pattern, the oscilloscope will trigger on a
specified logic combination of the four input channels. (Pages 3–60 through
3–62 describe how pattern triggers work.) To use pattern triggering, do the
procedures that follow:
Select Pattern Triggering. Press TRIGGER MENU ➞ Type (main) ➞ Logic
(pop-up) ➞ Class (main) ➞ Pattern (pop-up).
To Check Logic
Trigger Status
To Trigger on a Pattern
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