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Triggering
CSA8000B & TDS8000B User Manual
3-43
Use a trigger source that is synchronized with the signal you are sampling and
displaying. Selection of your trigger source depends on your application, as
showninTable3--1.
Table 3- 1: Application-based triggering
Application Source to use
Communications (optical)
serial NRZ data si gnals
Set source t o Clock Recovery, set t he clock-recovery t ype, and
use an optical sampling module equipped with a clock-recovery
option supporti ng t he speci fic data rate of the serial optical
signal.
A custom c lock recovery rate can be def ined by the user i f the
optical module s upports a conti nuous-rate clock recovery. Refer
to Sampling Modules Supported on page 1--4 to see those
modules that support continuous-rate clock recovery.
TDR measurement using an
electric al sampling modul e
equipped with TDR
Set source t o Internal Clock t o use the internal cl ock of the
instrument (TDR clock), and select the appropriate clock
frequency. Disconnect any si gnal connected to t he External
10MHz Reference Input when usi ng the Internal cl ock.
Measurements on systems
with a synchronized pretrigger
signal
Set source t o External Direct or External Prescaler as
appropriate (see Trigger Source Connectors) and connect the
pretrigger si gnal.
Any applicati on requiring that
the input signal provide the
trigger
Set source t o External Direct or External Prescaler as
appropriate (see Trigger Source Connectors).Useasignal
splitter or power divi der to couple to both the Ext Direct or
Prescaler i nput and t he input channel, so that the sampled
signal is also the tri gger signal.
Any applicati on requiring that
you probe the trigger source
Set source t o External Direct, and use a Tektronix probe as
described in Probe-to-Trigger Source Connection on
page 3--44.
Any applicati on requiring that
you perform special measure-
ments usi ng gated t rigger.
Set source t o External Direct, and use a TTL connection to
trigger gate as described in To Use Gated Trigger on
page 3--50.
Trigger Source and ESD. Observe static precautions when coupling trigger
sources to this instrument.
CAUTION. Electrostatic-static damage can permanently degrade and damage the
inputs to this instrument, its sampling modules, and accessory probes. You must
take proper precautions; please read your sampling module user manual for
more information.