Publication No. 980935 Rev. A
3152B User Manual
EADS North America Test and Services
Introduction 1-21
start of the next signal and programmed from 100 ns to 20 seconds
with a resolution of 20 ns.
Modulation Run
Modes
As previously mentioned, the 3152B has four run modes:
Continuous, Triggered, Gated, and Burst. However, the 3152B
behaves differently when generating modulated waveforms.
While the modulated and non-modulated run modes are similar, the
modulated run mode offers two start options for the output signal
during idle. Idle is the period of time before the output is triggered
or gated to generate a modulated waveform.
The first option is where the 3152B, before receiving a trigger
event, outputs continuous, non-modulated waveforms. When the
trigger or gate occurs, the 3152B outputs the modulated waveform.
When that waveform has completed, the instrument resumes
outputting non-modulated waveforms.
The second option is where the 3152B, before receiving a trigger or
gate, outputs a DC level. When triggered or gated, the 3152B
outputs the modulated waveform. When that waveform has
completed, the instrument resumes outputting a DC level.
Synchronization of
Multiple 3152B
Modules
A single or dual waveform generator in a single slot, no matter how
advanced, may become a limiting factor for applications requiring
multiple simultaneous waveforms.
Various techniques exist to synchronize the outputs of multiple
waveform generators, but none are simple because real
synchronization requires sharing of the reference and sample
clocks, as well as signals that control the starting phase of the
waveform. The 3152B uses the VXIbus Local Bus (LBUS0-7) to
synchronize adjacent modules. The Local Bus lines are short and
can tolerate high-frequency signals, but modules must be placed in
the VXIbus chassis in a fixed master/slave configuration.
Alternatively, the ECLTrg0 and ECLTrg1 lines may be used to
synchronize multiple modules if position independence or legacy
3152A compatibility is required.
In either case, the slave instrument(s) are locked to the frequency
and starting phase of the master module. After lock has been
achieved, the starting phase of the slave modules may be shifted
with respect to the master module to create a multi-phase system.
The starting phase is programmable from 0
°
to 360
°
.
PLL
Synchronization
PLL synchronization is another technique for synchronizing multiple
waveform generators. In this case, synchronization is not between
pairs of 3152B modules, but between the 3152B and an external
device, which could be anything that generates signals stable
enough to satisfy the PLL input requirements. When placed in this
mode, the 3152B measures the profile of the input signal and
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