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User Manual 3155
Sequenced Wav e-
forms
SEQuence:ADVance{AUTOmatic|STEP|SINGle|MIXed}
Purpose
This command selects sequence advance mode. The way the instrument advances through the sequence
can be specified by the user.
•
AUTOmatic - specifies continuous advance where the generator steps continuously to the end of the
sequence table and repeats the sequence from the start. For example, if a sequence is made of three
segments 1, 2 and 3, the sequence generates an infinite number of 1,2,3,1,2,3,1,2,3...waveforms. Of
course, each link (segment) can be programmed with its associated loop (repeat) number. AUTO is the
default sequence advance mode.
•
In STEP advance mode, the sequence is advanced to the next waveform only when a valid trigger is re-
ceived. The output of the 3155 generates the first segment continuously until a trigger signal advances
the sequence to the next segment. If repeats were selected for a segment, the loop counter is executed
automatically.
•
In SINGle advance mode, the generator idles between steps until a valid trigger signal is sensed. This
mode operates with trigger mode only. An attempt to select the SING advance mode when the 3155 is
in continuous operating mode generates an error. After trigger, the generator outputs one waveform cy-
cle. Then, the output level idles at a DC level equal to the last point of the last generated waveform. If
loops (repeats) were programmed, the output repeats this segment every time a trigger is received.
Only after executing all of the programmed loops will the sequence step to the next assigned segment.
•
MIXed mode is a special mode, which combines continuous step advance with single step advance in a
sequence. There are three conditions for the sequence generator to operate in this mode:
Sequenced waveforms are made of a number of arbitrary waveforms,
which can be linked and looped in user-programmable order. Se-
quenced waveforms are generated from waveforms stored in the
3155 as memory segments. Therefore, before a sequence can be
used, download waveform segments to the arbitrary memory using
TRAC# or DMA methods. Information on how to partition the memory
and how to download waveforms is given in the section entitled
Downloading Arbitrary Waveforms.
An example of how sequenced waveforms work is demonstrated in
figure 1-1a through 1-6d. The sequence generator lets you link and
loop segments in user-defined order. Figure 1-6d shows a sequence
of waveforms that were stored in three different memory segments.
There are a number of tools that you can use to build a sequence ta-
ble. The easiest way is of course to use the WaveCAD program. I n -
formation how to use the WaveCAD program is given in a later
chapter. In other cases, SCPI programming allows low-level pro-
gramming of sequence tables.
Use the information below to understand sequence commands and
how to implement them in your application.
Programming Reference 4-61
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