User`s guide
2 Targets and Scopes in the MATLAB Interface
2-16
Note The difference between setting TriggerSample = (N + P - 1), where
N and P are the parameters of the triggering scope (Scope 1) and
TriggerSample = -1 is that in the former case, the first sample of Scope 2 will
be at the same time as the last sample of Scope 1, whereas in the latter, the
first sample of Scope 2 will be one sample after the last sample of Scope 1.
This means that in the former case both scopes acquire simultaneously for one
sample, and in the latter they will never simultaneously acquire.
Acquiring Gap-Free Data Using Two Scopes
With two scopes, you can acquire gap-free data. Gap-free data is data that two
scopes acquire consecutively, with no overlap. The first scope acquires data up
to N, then stops. The second scope begins to acquire data at N+1. This section
provides guidelines for setting up two scopes for gap-free data. This is
functionality that you cannot achieve through pre- or posttriggering.
• Set the
TriggerSample property for both scopes to -1. For example,
sc1.TriggerSample = -1
sc2.TriggerSample = -1
• Set the TriggerScope property for each scope so that each is triggered by the
other. For example,
sc1.TriggerScope=2
sc2.TriggerScope=1
• Set the NumSamples property for each scope. For example,
sc1.NumSamples=500
sc2.NumSamples=500
• Set the TriggerMode property for one of the scopes to 'Software'. You must
do this to start the data acquisition. Otherwise, each scope waits for the other
to finish acquiring data, and never starts. In “Acquisition of Gap-Free Data”
on page 2-17, the
TriggerMode property of Scope 1 is set to 'Software'. This
allows Scope 1 to be software triggered to acquire data when it receives the
command
sc1.trigger.
• Both the scopes receive exactly the same signals, in other words, the signals
you want to retrieve.