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Triggered Burst and Gate
Triggered Burst 7
7-5
The required count can be set by pressing the burst cnt soft-key followed by direct
entries from the keyboard, or by using the rotary control. The maximum number of
waveform cycles that can be counted is 1,048,575 (2
20
-1).
Start Phase
The start phase, i.e. the point on the waveform cy
cle at which the burst starts, can be
selected by pressing the phase soft-key followed by direct entries from the keyboard
or by
using the rotary control. Since the waveform cycle is always completed at the end
of the burst the start phase is also the stop phase.
The phase can be set with a precision of 0.1 ° but the actual resolution is limited with
so
me waveforms and at certain waveform frequencies as detailed below. To indicate
when this is the case the actual phase is shown in brackets as a non-editable field below
the programmed value.
To achieve start phase precision all waveforms are run in clock synthesis mode, i.e. as if
they
were arbitrary waveforms, when triggered burst is specified. This limits frequency
resolution to 4 digits for all waveforms although the waveforms normally generated by
DDS are still entered with 7-digit precision. Sine, cosine, haversine (etc.) waveforms are
created as if they were arbitrary waveforms with the first point of the waveform exactly
at the start phase. Each time the phase or frequency is changed the waveform is
recalculated, and this can cause a slight lag if the parameters are changed quickly using
the rotary control.
The phase resolution of true arbitrary waveforms is limited by the waveform length since
the finest resolution
is 1 clock cycle; thus waveforms with a length greater than 3600
points will have a resolution of 0.1 °, but below this number of points the maximum
resolution becomes 360° divided by the number of points.
Square waves, pulse, pulse trains and sequences have
no start phase adjustment. Their
phase is always fixed at 0°.
The start phase capabilities in triggered burst mode are summarized below:
Table 7-1. Phase Range and Resolution - Triggered Burst Mode
Waveform Maximum Waveform
Frequency
Phase Control
Range and Resolution
Sine, cosine,
haversine, havercosine
1 MHz ± 360 °, 0.1 °
Square 1 MHz 0 ° only
Triangle, Ramp, sin(x)/x 100 kHz ± 360 °, 0.1 °
Pulse, Pulse Train 10 MHz 0 ° only
Arbitrary 40 Msamples/s clock ± 360 °, 360 °divided by length or 0.1 °
Sequence 40 Msamples/s clock 0 ° only
Manual Initialization of Inter-channel Triggering
If a multi-channel instrument is set up such that all channels are triggered by
an adjacent
one it is possible to have a stable condition where all channels are waiting for a trigger
and the sequence of triggered bursts never starts. To overcome this problem any channel
can be triggered manually and independently using the force soft-key on that
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