HP 1660CP Series User Manual page 248

System Performance Analysis (SPA) Software
SPA measurement processes
divided equally among 256 buckets. For example, if the range defined by
the low and high values is 1100, then 1100 divided by 256 equals 4.29.
This value will be rounded up to 5, each bucket will have a range of 5,
and only 220 buckets will be used (1100/5 = 220). The display grid will
be truncated on the right because only 220 buckets are displayed.
If the full range of the label or the portion of the label defined by the Low
value and High value is less than 255, then the number of buckets will be the
difference between the Low and High values.
The Low and High values can be specified as discrete values in Binary, Octal,
Decimal, or Hexadecimal. If Symbols have been defined in the Format
Specification, they can also be used for the low and high values.
Data sampling and sorting When Run is pressed, all input channels
defined in the Format Specification are sampled. Once acquired, the
sampled data is sorted into the buckets of the specified label, and the
State Overview display is updated. The acquisition is repeated until Stop
is pressed or until a display variable is changed.
Y axis scaling The display builds a vertical histogram where the
Y axis represents the relative number of occurrences in each of the
buckets. As successive acquisitions are acquired and sorted, the display
is constantly re-scaled vertically so that the upper limit of the Y axis
represents the largest number of occurrences in any bucket.
The Y axis maximum limit is displayed in Max count.
Total count The Total count field is the total number of states sampled
over the entire label range since the measurement was started.
X and O markers Markers can be placed on any bucket to determine
the number of occurrences in that bucket. The X Mark count and O Mark
count fields display the number of occurrences at the markers. The
markers move only on the bucket boundaries.
The range of each bucket can be determined by selecting the X marker or
O marker fields and noting the change in the marker value in the pop-up as
the marker is moved slowly across the display.
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