Racal Instruments 3162A/B, User Manual

Page: 73 / 144

User Manual 3162A/B
Using The Instrument 3-39
PLL Commands
To operate the PLL, set the trigger level and trigger slope and apply your
reference signal to the trigger input. Trigger level and trigger slope settings are
extremely important, especially if your reference signal has a slow slew rate.
This is because the Model 3162B locks to the phase of the reference signal at
the trigger point.
Use the following command to program the Model 3162B to lock to a front-
panel reference signal:
PHASe:LOCK ON
This command places the Model 3162B in PLL mode. If no valid reference
signal is applied to the trigger input, the PLL ON LED remains off. If you feel
that the 3162B should lock and it does not, make sure that trigger level is
adjusted correctly.
Make sure that the 3162B’s frequency setting permits phase lock in the
required range. Two graphs, one for fixed mode and the other for user mode
are given in Appendix A. The graphs show the lock range relationship between
the reference and the internal frequency settings.
The command:
PHASe:ADJust <value>
applies phase offset between the reference signal and the main output. The
default value is 0
E
. Phase offsets can be adjusted between 0
E
and +360
E
. The
resolution of this parameter is 1 waveform point, which is lowest (22.5
°
) with 16
point waveforms.
The command:
PHASe:STEP {POINt | DEGRee}
sets the phase offset adjustment units to either waveform points or degrees.
The default option is DEGR. The advantage of using units of POINts is that
phase offset of long waveforms may be adjusted with extremely fine resolution
limited only by the number of waveform points.
The command:
PHASe:SOURce {EXTernal | TTLTrg<0-3> | ECLTrg0}
selects the reference source for the PLL function. EXT selects the front-panel
trigger input. If you select this option, make sure that you also set the trigger
level and trigger slope. TTLT<n> and ECLT0 are the options to use if your
reference signal can be routed through the VXIbus backplane trigger lines.
Trigger level and trigger slope cannot be adjusted for these trigger lines.
The query:
PHASe:LOCK?