Keithley 2651A Reference Manual page 119

Section 3: Functions and features
Before changing the collectsourcevalues, collecttimestamps, or timestampresolution
attributes, you must clear the buffer using the smua.nvbuffer1.clear() or
smua.nvbuffer2.clear() command.
Buffer storage control attributes: Describes buffer storage attributes
Storage attribute
appendmode
cachemode
collectsourcevalues
collecttimestamps
fillcount
fillmode
timestampresolution
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Model 2651A High Power System SourceMeter® Instrument Reference Manual
NOTE
Description
The append mode is either off or on. When the append mode is off, a new measurement
to this buffer overwrites the previous contents. When the append mode is on, the first new
measurement is stored at what was formerly rb[n+1]. This attribute is initialized to off
when the buffer is created.
When this attribute is on, the reading buffer cache improves access speed to reading
buffer data. When running successive operations that overwrite reading buffer data
without running any commands that automatically invalidate the cache, the reading buffer
may return stale cache data. This attribute is initialized to on when the buffer is created.
When this attribute is on, source values are stored with readings in the buffer. This value,
off or on, can be changed only when the buffer is empty. When the buffer is created, this
attribute is initialized to off.
When this attribute is on, timestamps will be stored with readings in the buffer. This value,
off or on, can be changed only when the buffer is empty. When the buffer is created, this
attribute is initialized to off.
The reading buffer fill count sets the number of readings to store before restarting at index
1. If the value is 0, then the capacity of the buffer is used. This attribute is only used when
the fillmode attribute is set to FILL_WINDOW.
The reading buffer fill mode controls how new data is added to the reading buffer. When
this attribute is set to FILL_ONCE, the reading buffer will not overwrite readings. If the
buffer fills up, new readings will be discarded.
When this attribute is set to FILL_WINDOW, new readings will be added after existing data
until the buffer holds fillcount elements. Once there are fillcount elements, new
data starts overwriting data starting at index 1.
The timestamp resolution, in seconds. When the buffer is created, its initial resolution is
0.000001 seconds. At this resolution, the reading buffer can store unique timestamps for
up to 71 minutes. This value can be increased for very long tests. Note: The minimum
resolution setting is 1 µs (0.000001 seconds).
2651A-901-01 Rev. A / March 2011