Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1998-11-16
2002-05-14
Decady, Albert (Department: 2784)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S762000
Reexamination Certificate
active
06389571
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to error detection and correction devices, and more particularly to devices and methods for determining erasure locations for interleaves from thermal asperity events.
2. Description of the Related Art
Modem computer systems generally include one or more hard disk drives to store data and programs. Hard disk drives typically store information in sequence using magnetic technology. Like most recording technology, reading the sequential data bits from a hard disk often generates errors due to noise, manufacturing imperfections of the physical medium, dust, etc.
To detect and correct such errors, hard disk drives typically implement an error correction code (ECC) scheme in writing to and reading from magnetic disk drives such as a hard disk drive. These magnetic disk drives generally include error detection ad correction circuitry that implement ECC schemes using well known codes such as Reed-Solomon code to encode user data for reliable recovery of the original data through an ECC decoder. This helps to achieve a higher areal density.
Prior Art
FIG. 1
illustrates a block diagram of a conventional computer system
100
including a hard disk drive
102
and a host computer
104
. The host computer
104
receives user data from a hard disk drive
102
. A hard disk
106
in the hard disk drive
102
contains data laid out in a plurality of sectors along a plurality of tracks. When reading data from the hard disk
106
, the hard disk drive
102
rotates the hard disk
106
by means of a motor
122
and employs an actuator
120
to search for a track and sectors that contain the desired data. Upon finding the desired sectors, the read/write head
116
attached to the actuator
120
sequentially reads the data from the disk
106
to generate analog read signal (e.g., analog data signal). An amplifier
108
is coupled to the read/write head
116
to receive the read signal. The amplifier
108
amplifies the received analog read signal and transmits the amplified read signal to a read channel circuitry
110
.
The read channel circuitry
110
includes an analog-to-digital converter (ADC)
112
. The read channel circuitry
110
uses the ADC
112
to convert the amplified read signals into digital data bits. The read channel circuitry
110
then transmits the digital data to a deserializer
116
. The deserializer
116
receives the sequential data and converts the data into a series of blocks called sectors, each of which is typically 512 bytes of user data and ECC bytes appended to the user data bytes. The deserializer
116
sequentially transmits the sectors to an error detection and correction (EDAC) circuitry
118
. The EDAC circuitry
118
detects errors in the received sector and, if correctable, corrects the detected errors using an ECC scheme. Typically, the EDAC circuitry
118
employs conventional Reed-Solomon code in its ECC scheme to encode user data for reliable recovery of the original data. The EDAC circuitry
118
then transmits the error corrected user data to the host computer
104
.
In reading from the hard disk
106
however, the read/write head
116
often encounters an asperity on the surface of the hard disk
106
. In such an event, the asperity typically causes a sudden shift (e.g., rise in voltage) in the base line of the read signal, which decays exponentially. To detect such thermal asperity (TA) event, the read channel circuitry may include a TA detector
114
, which detects a TA event when the read signal deviates from a predetermined signal voltage by a specified amount.
Additionally, modern ECC schemes typically implement interleaving to break up error bursts. In a typical ECC scheme, a conventional ECC decoder decodes errors on an interleave basis. For example in an i-way (i.e., i degree) interleave, the ECC decoder decodes errors on ith data bytes independent of other non-ith data bytes.
Thus, what is needed is a method and apparatus that can record thermal asperity erasure pointer information for interleaved ECC codes. In addition, what is needed is a a method and apparatus that can efficiently extract thermal asperity erasure pointer information for interleaved ECC decoding.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing an apparatus and method for generating erasure locations of interleaves, which are being decoded. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, or a computer readable medium. Several inventive embodiments of the present invention are described below.
In one embodiment, the present invention provides a thermal asperity pointer processing apparatus for processing apparatus for generating erasure locations from a thermal asperity signal. The thermal asperity signal indicates an error burst in an interleaved data sector. The apparatus includes a thermal asperity pointer recorder, a storage unit, and a thermal asperity pointer processing unit. The thermal asperity pointer recorder is adapted to receive a thermal asperity signal and is configured to generate a thermal asperity event information associated with the thermal asperity signal. The thermal asperity event information includes a thermal asperity duration, a starting interleave number, and a starting interleave address of the thermal asperity signal in the interleaved data sector. The storage unit is configured to receive the thermal asperity event information from the thermal asperity pointer recorder and is configured to store the thermal asperity duration, starting interleave number, and starting interleave address associated with the thermal asperity signal. The thermal asperity pointer processing unit is coupled to receive the thermal asperity event information from the storage unit and is adapted to generate the erasure locations for interleaves corresponding to the error burst in the data sector.
In another embodiment, the present invention provides a method for generating erasure locations from a thermal asperity signal that indicates an error burst in a data sector having a plurality of interleaved data bytes. The method includes: (a) receiving a thermal asperity signal; (b) determining a thermal asperity event information that characterizes the received thermal asperity signal; (c) storing the thermal asperity event information; (d) accessing the stored thermal asperity event information; and (e) determining erasure locations for the interleaved data bytes from the stored thermal asperity event information.
In yet another embodiment, an apparatus for generating erasure locations from a thermal asperity signal is disclosed. The thermal asperity signal indicates an error burst in a data sector having a plurality of interleaved data bytes. The apparatus includes means (a) means for receiving a thermal asperity signal; (b) means for determining a thermal asperity event information that characterizes the received thermal asperity signal; (c) means for storing the thermal asperity event information; and (d) means for determining erasure locations for the interleaved data bytes from the stored thermal asperity event information.
The apparatus and method of the present invention advantageously employs thermal asperity signals to generate and record thermal asperity event information including a starting interleave number, a starting interleave address, and a length of the signal. In addition, the present invention accesses the stored thermal asperity event information to generate interleave erasure locations for associated data bytes being decoded on-the-fly. The use of the thermal asperity signal to generate interleave erasure locations as described herein allows efficient processing of interleaved sector data bytes by utilizing the conventional thermal asperity signals. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrati
Gill, III John T.
Yang Honda
Adaptec, Inc.
Amanze Emeka J.
De'cady Albert
Martine & Penilla LLP
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