Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data clocking
Reexamination Certificate
1997-11-14
2001-02-20
Nguyen, Hoa T. (Department: 2753)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data clocking
C360S073030, C360S077040, C360S077080
Reexamination Certificate
active
06191904
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to removable storage devices for electronic information. More particular, the present invention relates to compensating for data sector timing variations due to drive eccentricity.
Consumer electronics including television sets, personal computers, and stereo or audio systems, have changed dramatically since their availability. Television was originally used as a stand alone unit in the early 1900's, but has now been integrated with audio equipment to provide video with high quality sound in stereo. For instance, a television set can have a high quality display coupled to an audio system with stereo or even “surround sound” or the like. This integration of television and audio equipment provides a user with a high quality video display for an action movie such as STARWARS™ with “life-like” sound from the high quality stereo or surround sound system. Accordingly, the clash between Luke Skywalker and Darth Vader can now be seen as well as heard in surround sound on your own home entertainment center. In the mid-1990's, computer-like functions became available on a conventional television set. Companies such as WebTV of California provide what is commonly termed as “Internet” access to a television set. The Internet is a world wide network of computers, which can now be accessed through a conventional television set at a user location. Numerous displays or “wet sites” exist on the Internet for viewing and even ordering goods and services at the convenience of home, where the act of indexing through websites is known as “surfing” the web. Accordingly, users of WebTV can surf the Internet or web using a home entertainment center.
As merely an example,
FIG. 1
illustrates a conventional audio and video configuration, commonly termed a home entertainment system, which can have Internet access.
FIG. 1
is generally a typical home entertainment system, which includes a video display
10
(e.g., television set), an audio output
20
, an audio processor
30
, a video display processor
40
, and a plurality of audio or video data sources
50
. Consumers have often been eager to store and play back pre-recorded audio (e.g., songs, music) or video using a home entertainment system. Most recently, consumers would like to also store and retrieve information, commonly termed computer data, downloaded from the Internet.
Music or audio have been traditionally recorded on many types of systems using different types of media to provide audio signals to home entertainment systems. For example, these audio systems include a reel to reel system
140
, using magnetic recording tape, an eight track player
120
, which uses eight track tapes, a phonograph
130
, which uses LP vinyl records, and an audio cassette recorder
110
, which relies upon audio cassettes. Optical storage media also have been recognized as providing convenient and high quality audio play-back of music, for example. Optical storage media exclusively for sound include a digital audio tape
90
and a compact disk
10
. Unfortunately, these audio systems generally do not have enough memory or capacity to store both video and audio to store movies or the like. Tapes also have not generally been used to efficiently store and retrieve information from a personal computer since tapes are extremely slow and cumbersome.
Audio and video have been recorded together for movies using a video tape or video cassette recorder, which relies upon tapes stored on cassettes. Video cassettes can be found at the local Blockbuster™ store, which often have numerous different movies to be viewed and enjoyed by the user. Unfortunately, these tapes are often too slow and clumsy to store and easily retrieve computer information from a personal computer. Additional video and audio media include a laser disk
70
and a digital video disk
60
, which also suffer from being read only, and cannot be easily used to record a video at the user site. Furthermore, standards for a digital video disk have not been established of the filing date of this patent application and do not seem to be readily establishable in the future.
From the above, it is desirable to have a storage media that can be used for all types of information such as audio, video, and digital data, which have features such as a high storage capacity, expandability, and quick access capabilities.
Reading and writing to magnetic disks within removable cartridges provide unique challenges not fully appreciated or addressed by fixed disk drive units. For example, the magnetic disks within removable cartridges are typically subject to greater temperature, humidity, particulate contamination, shock, mechanical stresses, etc. than magnetic disks that are sealed and protected inside fixed disk drive environments. Further, removable cartridges are repeatedly inserted and ejected from removable drive units, whereas fixed disk drives are not. As a result, removable drive units receiving such removable cartridges must be able to adapt to the greatly varying conditions of the magnetic disks.
FIG. 7
illustrates one particular difficult problem not faced by fixed disk drive units is that the variation in eccentricity between different magnetic disks.
FIG. 7
includes a magnetic disk
900
having a cylinder
910
. The geometric axis of rotation
920
of magnetic disk
900
is shown, as well as an eccentric axis of rotation
930
.
Drive eccentricity typically refers to the variation in the axis of rotation for a magnetic disks. Typically magnetic disks are rotated around geometric axis of rotation
920
and preformatted in the factory with well known servo bursts at regularly spaced intervals, for example along cylinder
910
.
FIG. 8
illustrates an ideal timing diagram of signals from a magnetic disk.
FIG. 8
includes a servo burst signal
1000
and a data sector signal
1010
. Servo burst signal
1000
includes servo bursts
1020
-
1050
, and data sector signal
1010
includes data sectors
1060
-
1110
. As illustrated, the nominal latency x between servo burst
1020
and data sector
1060
is the same as between servo burst
1040
and data sector
1090
, and the nominal latency y between servo burst
1030
and data sector
1080
is the same as between servo burst
1050
and data sector
1110
. Further the nominal timing t between servo bursts
1020
,
1030
,
1040
, etc. respectively is the same.
In this example, data sectors
1070
and
1100
are split between two servo sectors, thus preferably servo burst
1020
is used for accessing data sectors
1060
and
1070
, servo burst
1030
is used for accessing data sector
1080
, servo burst
1040
is used to access data sectors
1090
and
1100
, and servo burst
1050
is used to access data sector
1100
.
FIG. 9
illustrates a typical timing diagram of signals from an eccentric magnetic disk.
FIG. 9
includes a servo burst signal
1000
′ and a data sector signal
1010
′. Servo/burst signal
1000
′ includes servo bursts
1020
′-
1050
′, and data sector signal
1010
′ include data sectors
1060
′-
1110
′. As illustrated, the actual latency between servo burst
1020
′ and data sector
1060
′ is “x+x1”,
1120
′, the actual latency between servo burst
1030
′ and data sector
1080
′ is “y+x2”,
1121
′, the latency between servo burst
1040
′ and data sector
1090
′ is “x+x3”,
1122
′, and the latency between servo burst
1050
′ and data sector
1100
′ is “y+x4”,
1123
′. In this case x1 and x2 are positive, and x3 and x4 are negative. Further the actual timing between servo bursts
1020
′ and
1030
′ is “t+t1”,
1130
′, the time between servo bursts
1030
′ and
1040
′ is “t+t2”,
1131
′, the time between servo bursts
1040
′ and
1050
′ is “t+t3”,
1132
′, and the time between servo bursts
1050
′ and the next servo burst is “t+t4”,
1133
′. In this case t1 and t2
Drouin David
Nguyen Vien N.
Castlewood Systems, Inc.
Davidson Dan I.
Nguyen Hoa T.
Townsend and Townsend / and Crew LLP
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