Triggering on Waveforms
3–80 TDS 684A, TDS 744A, & TDS 784A User Manual
To understand what happens when you slew rate trigger, study Figure 3–46 as
you consider the following points:
The main menu shows the oscilloscope is set to trigger based on the slew
rate of a pulse input to the trigger source, Ch 1. It is set to monitor the
positive-polarity pulse edges of the trigger source and to trigger on any edge
with a slew rate faster than the slew rate setting.
The Trigger When side menu displays the readout Slew Rate that indicates
the slew rate setting. The slew rate setting is not the slew rate of the pulse;
instead, it is the slew rate against which the oscilloscope compares the slew
rate of pulse (see above). You set the slew rate setting indirectly by setting
the ratio of delta voltage to delta time as:
  +! 

Substituting the threshold and delta time settings for the setup in Fig-
ure 3–46:
  +!
 +ń
The trigger bar indicators (long horizontal bars) point to the upper and lower
thresholds. The pair cursors, which are aligned to threshold levels, read out a
delta voltage of approximately 4 V and a delta time of 200 ns between the
threshold levels. Therefore, the slew rate of the pulse edge triggered on is:
  +
 +
 +ń
The Trigger When side menu indicates the oscilloscope will trigger on pulses
with slew rates slower than the slew rate setting. Since the pulse edge slews
at 20 mV/ns, which is faster than the slew rate setting of 16 mV/ns, the
oscilloscope triggers.
The trigger point indicator shows where the oscilloscope triggers. For a slew
rate triggered waveform, the trigger point is always at the threshold crossed last
(the upper threshold for positive polarity settings; the lower for negative
settings).
Set the Mode and Holdoff. Mode and holdoff can be set for all standard trigger
types and classes. To set mode and holdoff, refer to Set Mode & Holdoff on
page 3–59. To learn more about trigger mode and holdoff, see Trigger Modes
and Trigger Holdoff on page 3–51.
Delayed Triggering
The TDS Oscilloscope provides a main time base and a delayed time base. The
delayed time base, like the main time base, requires a trigger signal and an input
source dedicated to that signal. You can only use delay with respect to the main