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Communication Triggering (Option)
Communication (Comm) triggers are one type of trigger. Comm triggers are designed to work
with communication masks and standards. When you select a mask to test, it is associated with a
specific communication standard. The mask you select determines the comm trigger needed for
that standard.
Note
Option SM must be installed for communication triggering.
Eye diagrams that are set up with an external clock use a time base position value large enough to
guarantee the edge is always before the acquisition record starts. This forces all comm triggers to
disable the B-Trigger.
Even though comm triggers are designed to work with masks, you can set up comm triggering
without using a mask. You can also set up your own mask to use with comm triggers.
Limit Testing Concepts
Limit testing is the ability to compare an active signal with a template waveform. The following
figure shows an active waveform (dark sine wave) being compared to a template waveform
(shaded area).
Any part of the active waveform that exceeds the template waveform's envelope is a limit test
waveform violation, which the instrument highlights. You can set the instrument to respond to a
limit test violation by stopping limit testing, emitting a beep, and so on. The following figure
shows the highlighted (black) part of the active waveform that exceeds the limit test envelope.
A template is an envelope waveform that consists of minimum/maximum (min/max) pairs of
sample points. Template envelope waveforms created from 500 point source waveforms contain
250 min/max pairs; Template envelope waveforms created from10K point waveforms contain
5000 min/max pairs.
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