Stanford Research Systems DS345, Manual

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Introduction
This section describes the DS345's arbitrary waveform capabilities, and how
to edit those waveforms from the front panel. The DS345 can store arbitrary
waveforms in two formats: point and vector. In
point
format the DS345
stores only a list of amplitude values to load into the waveform RAM. This list
can be up to 16,300 points long, with each memory point representing a point
in the output waveform. In
vector
format the data stored is a list of
vertices–
x,y pairs of values (up to 6144 pairs). Each data pair specifies an address in
waveform RAM (the x value), and the amplitude at that point (the y value).
The waveform RAM locations between successive vertices are automatically
filled in by connecting the vertices with straight lines.
Note:
Front panel editing can be very tedious. Large or complex waveforms
are easily created using the Arbitrary Waveform Composer Software.
Sampling Rate
When the function is set to ARB the displayed frequency is the arbitrary
waveform sampling frequency. This number is not related to the normal
waveform frequency, but is the time that the DS345 dwells at each point in
the arbitrary waveform. This sampling frequency must be an integer submulti-
ple of the the 40 MHz clock frequency. That is, 40 MHz/N where N = 1,2,3...
2
34 -1 (for example 40 MHz, 20 MHz, 13.3333 MHz, 10 MHz,...). The DS345
will spend 1/Fsample on each point (40 MHz = 25 ns, 20 MHz = 50 ns, etc.).
When a new sampling frequency value is entered the DS345 will round the
value to the nearest integer submultiple of 40 MHz. The time needed to re-
peat a complete waveform is simply: # points in waveform/Fsample.
SYNC Output
During arbitrary waveform generation the front-panel SYNC output generates
a negative going (5V to 0V) 25ns pulse at the start of the arbitrary waveform.
EDIT MENU
Pressing [SHIFT][ARB EDIT] repeatedly cycles through the three lines of the
EDIT menu.
Storage Format
The first menu line allows selecting the ARB waveform storage mode. Simply
select POINT or VECTOR using the MODIFY up/down keys. The arbitrary
waveform must be cleared before the storage mode can be changed (see be-
low).
Clearing Current Waveform
The third line of the EDIT menu allows the current ARB waveform to be
cleared. Pressing any of the UNITS keys with this line displayed clears the
current waveform.
EDITING
The second line of the EDIT menu allows editing of actual waveform data.
The editing process is interactive, the waveform RAM is updated any time an
editing operation takes place. Displaying the FUNCTION output on an oscillo-
scope allows the user to see the waveform change as the data is modified.
ARBITRARY WAVEFORM EDITING
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