Tektronix TDSDDM1, User Manual, Page: 84 / 102

Measurement Descriptions
3–42
TDSDDM1 Disk Drive Measurement Application User Manual
The vertical asymmetry measurement is defined as follows:
Vert asym
+
ǒ
TAA
) )
TAA–
TAA
Ǔ
Where: TAA is the TAA measurement for a given sector, as
defined on page 3–13
TAA+ is the TAA+ measurement for a given sector, as
defined on page 3–16
TAA– is the TAA– measurement for a given sector, as
defined on page 3–16
The timing asymmetry measurement, A, measures the ability of the head/media
combination to process positive and negative transitions identically.
The timing asymmetry measurement is not available as an individual measure-
ment. It is available only in the TAA and PW50 snapshot displays and is not
available over the GPIB bus.
The timing asymmetry measurement is based on timing between pulse peaks,
calculated as follows:
A
+
1
4N
ȍ
(i
+
1...N)
( | T
1
– T
2
| )
Where: i indexes negative pulses
N is the number of measured time intervals
T
1
is the time from the prior positive pulse to the current pulse
T
2
is the time from the current pulse to the next positive pulse
These measurements operate as other measurements in the sense that a range of
sectors is defined and the measurement average and standard deviation calcu-
lated. The range of the measurement within each sector is determined by the
cursors.
A constant frequency sequence is written onto a track.
Timing Asymmetry, A