Agilent Technologies HP 1660E Series User Manual page 122

Using the Oscilloscope
The Scope Trigger Menu
The default condition for all patterns is X, "don't care." To change the
pattern, select the Channel/Pattern field and use the pop-up menu.
A pattern of XX says to use NO channels to find the trigger.
NOTE:
Using NO channels to find the trigger does not equate to Immediate Mode
when Auto-Trig is set to Off. This event will never occur in the hardware. Do
not confuse XX with "don't care, trigger on anything."
Immediate trigger mode
Immediate trigger mode causes the oscilloscope to trigger by itself.
Immediate trigger mode can be used for dual time-base applications
where, for instance, a timing analyzer arms the oscilloscope. The
oscilloscope triggering mode must be set to Immediate in order to have
the waveforms time-correlated.
This mode is very similar to Auto-Trig On, but immediate mode does
not wait for a specified event to occur.
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