HP 54520 Series Service Manual page 19

Trigger
Trigger Modes
Operating Characteristics
Auto Trigger Auto trigger provides an acquisition when no trigger is present. When set
to auto, if the instrument does not see a trigger within about 50 ms, it will auto- matically
start an acquisition. When set to trg'd, it will wait for the next qualified trigger.
Trigger Holdoff Trigger can be held off either by time or events over the ranges:
e time: 40 ns to 320 ms
® events: 2 to 16,000,000
An event is defined as the specified trigger condition. A separate holdoff setting (time or
events) is available for each trigger mode except delayed trigger, which is set to 40 ns.
Holdoff is not available for the auxiliary or line trigger. The maximum event counting rate is
70 MHz.
Noise Reject Reject improves triggering on noisy signals by increasing trigger hysteresis
(internal trigger only). When selected, noise reject is active for all trigger modes.
Edge Trigger
You can select a positive or negative edge for trigger on any channel, the external trigger input
(only on the HP 54520A and 54540A), or the auxiliary input. For the channel and external
trigger sources, you can set coupling to de, ac (10 Hz) , or lfrej (low frequency reject, 50 kHz).
Trigger coupling is independent of the vertical signal coupling and noise reject. Coupling for
all sources is automatically set to dc for all trigger modes except edge trigger. You can also
select line trigger in the edge trigger menu.
Pattern Trigger
You can specify a pattern using any front panel channel or external trigger input. Each input
can be specified as a high, low, or don't care with respect to the level setting in the edge
trigger menu. The trigger can be selected to occur on the last edge to enter the specified
pattern or the first edge to exit the specified pattern. The pattern must be present for more
than 1.75 ns (for the channels and external trigger), before the trigger will respond.
Time Qualified Pattern Trigger A trigger occurs on the first edge to exit a pattern
only if it meets the specified time criteria. The available time qualified modes are
(user-specified time is in brackets):
® pattern present < [time]
© pattern present > [time]
@ range: pattern present > [timel] and < [time2]
The time settings are adjustable from 20 ns to 160 ms (+3% +2 ns). The time filter recovery
time is <12 ns. In the "pattern present < [time]" mode, the pattern must be present for more
than 1.75 ns (for the channels and external trigger), before the trigger will respond.
Glitch Pattern Trigger Pattern triggering can be used to glitch trigger in conjunction
with a pattern. Using any front panel channel or external trigger input. Use "pattern
present < [time]" with [time] selected, such that it is just less than the nominal pulse width
of the signal you are analyzing. The minimum glitch width is 1 ns.
You can use the Glitch Trigger mode for glitch triggering on single sources with glitch widths
from 1 ns to 160 ms,
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