User manual

Publication No. 980935 Rev. M 3152B User Manual
Astronics Test Systems Programming Reference 5-103
When locking the 3152B to an external source applied to the
TRIG/
PLL IN connector, the auto-detection circuit sets up the lock-
in
range and prepares the PLL circuits
for a final phase lock. After
phase
lock
has been achieved, the 3152B duplicates the
frequency and start
phase of the
external source. A front-
panel LED illuminates when the
external
source signal is valid and the instrument has locked onto it.
When phase locking to a signal on the TRIG/PLL IN connector,
p
hase
adjustment commands
allow phase shifting of the locked signal
from
-
180° to +180° referenced to the input signal.
In addition, the phase
can
be shifted by applying a signal to the front-panel PM
IN
connector
, where DC to 10 KHz voltage levels can phase-
modulate
the locked instrument.
The ECLTrig bus in the VXI chassis allows synchronizing multiple
3152Bs inside
the same VXIbus chassis without external connections
.
T
he ECLT0 and ECLT1 lines provide the necessary signals
to achieve
lock between modules. Using this method, one instrument is
configured as master and the rest of the instruments are configured
as slaves.
They do not need to be in adjacent chassis slots.
When
synchronized, the slave instruments are initially locked to the start
phase
of
the master but later can be configured to have phase offsets
relative to the master. Phase offset is programmable from 0
° to 360°.
Although
signals synchronized through the ECLTrig bus are
limited in
frequency
to 60 MHz maximum, this method is included
for backward
compatibility with the legacy 3152A.
When synchronizing through the ECLTrig bus or
TTLTrig bus, p
hase
offset is programmable
from 0° to 360°.
Phase offset resolution
depends on the number of waveform samples. For instance, if there
are
1,000 waveform samples, the phase offset is adjustable in
0.36°
increments
, since 360° / 1,000 samples = 0.36° per sample.
As another example, if
there are only ten
waveform samples, the
smallest
phase offset increment is 360° / 10 samples, or 36°.
The phase offset discussed above is known as the coarse phase
offset. To improve
the
resolution for waveforms having fewer samples,
a separate
fine phase adjustment takes the resolution down to 0.01°
.
The fine phase adjustment
and can be used in conjunction with
any
valid
coarse phase offset setting.
S
ynchronization commands are summarized in Table 5-14.