3 Using the Scope Functions  
44 Agilent U1602B/U1604B User’s and Service Guide 
Auto Trigger Mode
The Auto trigger mode displays a waveform when the trigger conditions 
are met. If the trigger conditions are not met, it forces the instrument to 
trigger. 
In Auto trigger mode, the instrument operates by first filling the 
pre- trigger buffer. It continues to flow data through this buffer while 
searching for a trigger and updates the pre- trigger buffer. After a trigger is 
found, the pre- trigger buffer will contain the events that occur just before 
the trigger. If no trigger is found, the instrument generates a trigger and 
displays the data as though a trigger had occurred. The indicator of the 
trigger mode and status are shown at the trigger status line at the right 
column of the display (refer to “Oscilloscope Display Overview   23”).
Normal Trigger Mode
The normal mode displays a waveform when the trigger conditions are 
met, otherwise the instrument does not trigger and the display is not 
updated. If you press RUN when the instrument is in Normal trigger 
mode, a trigger must be detected before an acquisition can complete.
In Normal trigger mode, the instrument must fill the pre- trigger buffer 
with data before it starts to search for a trigger event. While searching for 
the trigger, the instrument updates the pre- trigger buffer. After a trigger is 
found, the oscilloscope will fill the post- trigger buffer and display the 
acquisition memory.
In many cases, a triggered display is not needed to check for signal levels 
or activity. For these applications, use Auto Trigger mode (default setting). 
Use Normal trigger mode only if you want to acquire specific events as 
specified by the trigger settings.
Single Trigger Mode 
When you select the Single trigger mode, the instrument will fill the 
pre- trigger buffer memory. It continues to flow data through the 
pre- trigger buffer until the auto trigger overrides the searching and forces 
a trigger. At the end of the trace, the instrument will stop and display the 
results.