61
At any time, pressing the
view
soft
−
key gives a graphical view of the master
−
slave set
−
up,
see below for an example.
CH
→
1 2 3 4
indep - - -
Υ
master
Υ
- - -
slave -
ΥΥ
- exit
◊
Channel locking is turned on or off with the
status
soft
−
key. Any illegal setting combinations
will result in an error message when an attempt is made to turn status on. Any of the following
conditions will cause an error (see also the Synchronising Principles section for a discussion of
the set
−
up constraints):
1. More than one master channel is enabled.
2. No master channel is enabled.
3. The locked channels contain a mixture of DDS and PLL generated waveforms.
4. Frequency tracking is enabled (mode: master/freq) but the frequencies are not the same on
all channels. If PLL waveforms are locked the mode will be forced to frequency tracking.
5. A locked channel is not set to continuous mode.
6. An attempt is made to turn on phase lock with a frequency set too high. Note that the
maximum frequency for phase
−
locked DDS operation is 10MHz.
7. An attempt is made to set the frequency too high during phase lock. This error does not set
phase lock to off, the system simply inhibits the setting of the incorrect frequency.
In addition to the illegal setting combinations there are further considerations which affect the
phase resolution and accuracy between channels, see below.
Phase-setting between Channels
The inter
−
channel set
−
up screen also has a field for setting up the phase of the slaves with
respect to the master.
mode: indep
◊
phase: +000.0
°
(actual: +000.0
°
)
◊
status: off view
◊
Selecting the phase soft
−
key allows the phase to be set by direct keyboard entry or by rotary
control. Setting the phase of a slave positive advances the waveform of the slave with respect to
the master; setting it negative delays the slave with respect to the master. The phase of each
slave channel can be set independently. The phase of the master can also be set; this is
intended primarily for use in phase
−
locking between two generators. If both the master and the
slaves are set to +90
°
, say, on the same generator then the waveforms will all be in phase again;
if the master is set to +90
°
and the slaves set to
−
90
°
the master and slave wavefoms will be
180
°
out of phase.
DDS
−
generated waveforms can be phase
−
locked with 0.1
°
resolution up to their maximum
available frequency; sine, cosine, haversine and havercosine are limited to 10MHz in
phase
−
locked mode.
The phase
−
locking resolution of arbitrary waveforms will be less than 0.1
°
for waveforms of less
than 3600 points. The phase is fixed at 0
°
for pulses, pulse
−
trains and sequences.