Download 3172-W2 VXIbus Arbitrary Waveform Generator User Manual

3172 User Manual
Multiple 3172-W2
Modules
Publication Number 980949 Rev. H
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 3172 can use 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, and local
bus jumpers must be installed. Details are provided in Chapter 2 in
the Local Bus Configuration section..
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
(W2 only)
PLL synchronization is another technique for synchronizing multiple
waveform generators. In this case, synchronization is not between
pairs of 3172-W2 modules, but between the 3172-W2 and any
external device that generates signals stable enough to satisfy the
PLL input requirements. When placed in this mode, the 3172-W2
measures the frequency stability of the input signal and determines
whether or not it is valid. Then, the built-in counter/timer circuit
measures the frequency of the signal and centers its lock-in range
on this frequency. The 3172-W2 thus locks automatically onto the
frequency of the external signal. Note that there is no need for
manual initiation or operator intervention for the PLL function to find
and lock onto an external reference. The PLL range is 500 Hz to
10 MHz.
After phase locking has been established, the start phase of the
3172-W2 waveform can be shifted with respect to the start phase of
the external reference within the range of -180° to +180°, with
phase increments as low as 0.01° (fine phase control). The
reference signal is applied to the front-panel TRIG IN connector. In
this way, the same reference can be applied to multiple modules to
generate multi-phase signal patterns. The TRIG IN input has a
programmable trigger level and programmable slope.
Phase
Modulation
(W2 only)
When the 3172-W2 is placed in PLL mode, there are two ways to
control the phase offset. The first way is to modify the phase offset
setting using SCPI commands. This method is quite accurate, and
allows phase offset adjustments in increments of 0.01°.
The second way is to apply a voltage to the PM IN port of the 3172W2. This changes the start phase of the synthesizer, proportional
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Astronics Test Systems