User`s guide

Reconstructing a Trace
The simplest SDF file defines a single trace. A trace consists of a series of discrete points, each defined
by an X-axis value and a Y-axis value. This section tells you how to locate or calculate a single trace’s
X-axis and Y-axis values.
X-axis Values
A trace’s X-axis values are stored in one of two SDF records: the Data Header record, or the X-axis Data
record. The location used depends on whether or not consecutive points are evenly spaced along the
X-axis:
Evenly-spaced points: X-axis values are stored in the Data Header record.
Unevenly-spaced points: X-axis values are stored in the X-axis Data record.
Field 11 of the Data Header record (xResolution_type) is an indicator of X-axis spacing. Consecutive
points are evenly spaced if xResolution_type has value of 0 or 1; they are unevenly spaced if it has a
valueof2,3,or4.
When consecutive trace points are evenly spaced along the X-axis (xResolution_type = 0, or 1), the SDF
file does not include an X-axis Data record. Instead, the X-axis values of these points are completely
defined by three fields in the Data Header record:
abscissa_firstX: tells you the X-axis value of the first point.
abscissa_deltaX: tells you the X-axis spacing between points.
num_of_points: tells you how many discrete points the trace is composed of.
You can calculate X-axis values this way when xResolution_type is 0 (linear resolution):
x0 = abscissa_firstX
x1 = x0 + abscissa_deltaX
x2 = x0 + abscissa_deltaX * 2
x3 = x0 + abscissa_deltaX * 3
.
.
.
xn = x0 + abscissa_deltaX * n (where n = num_of_points −1)
Standard Data Format (SDF)
B-27