Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1999-05-20
2003-02-11
Beausoleil, Robert (Department: 2184)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S769000, C360S053000
Reexamination Certificate
active
06519715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal processing method for a magnetic disk drive, an optical disk drive, and the like, and in particular, to a signal processing method capable of improving data reliability in data recovery.
2. Description of the Related Art
Signal processing apparatuses such as a disk drive recently utilize a partial response maximum likelihood (PRML) data detecting method, which makes it possible to obtain a desired data error rate with a low signal-to-noise ratio. A representative PRML data detecting method for a magnetic disk drive has been described in pages 454 to 461 of “Viterbi Detection of Class IV Partial Response on a Magnetic Recording Channel” written by Roger W. Wood in “IEEE Transactions on Communications, Vol. Com-34, No. 5, May 1986. Additionally, as described in JP-A-7-201135 and JP-A-8-116275, an Extended PRML (EPRML) data detecting method has been adopted to reproduce signals with a lower signal-to-noise ratio. To sample signal waveforms in the PRML signal detection method, a phase locked loop circuit is used as described in JP-A-1-143447 and JP-A-2-2719. Recently, an interpolated timing recovery (ITR) circuit as described in JP-A-9-231506 has been proposed to produce synchronized target sample data from asynchronously sampled data.
FIG. 38
shows an example of structure of a general magnetic disk drive employing the PRML data detection method. A magnetic recording media
54
is a circular rotating magnetic recording media and is used to record data from host processor. In the media
54
, data track information and sampled servo information are located in order to achieve appropriate date recording and reproducing processing, as shown in FIG.
39
. Data track information stores data from host processor. Data recording and reproducing processor is carried out for each block called “sector” on tracks concentrically formed on the media
54
. Sampled Servo information, which follow the head
53
to appropriate track, is recorded on the media
54
in a fixed interval. To follow the head
53
on rotating track, a servo control circuit
52
positions head
53
in accordance with servo information. The other constituent components of
FIG. 38
are disposed for the recording/reproducing of data from host processor and operate as following.
Recording process is started by a write instruction from host processor. The instruction is received by a microprocessor
55
through a controller
51
. Microprocessor
55
issues write control command to controller
51
and servo controller
52
. Controller
51
temporarily stores record data following the write instruction in a random access memory (RAM)
56
. Servo controller
52
moves head
53
to a predetermined track, which is assigned in the write instruction. After head
53
is completely positioned to the track, the data temporarily recorded in RAM
56
is sent to a recorder circuit
58
together with a sync signal necessary for reproduction of the data and an error correction code (ECC) generated by an ECC generating and correcting circuit
57
. Recorder circuit
58
modulates the write data stream based on a PRML data detection method. Resultantly, the write data stream is written via a read/write (RW) amplifier
59
and head
53
in a sector of the predetermined track.
On the other hand, reproducing of data from a magnetic disk drive is commenced by a read instruction of host controller. On receiving the read instruction, microprocessor
55
issues a read control command to servo controller
52
and controller
51
. Servo controller
52
moves head
53
to a track in which specified data is recorded. When head
53
is positioned to the specified track, controller
51
instructs a reproducer circuit
60
to initiate reading data. A read data stream of the target sector recorded on media
54
is transmitted as reproducing signals via head
53
and RW amplifier
59
to reproducer circuit
60
. In accordance with the sync signal added to the data in the recording thereof, reproducer circuit
60
produces read data synchronized with the reproducing signals. Using sampled signals synchronized with the reproducing signals, a PRML data detection circuit demodulates read data. The read data is temporarily stored in RAM
56
. ECC circuit
57
checks and corrects errors of the read data. When the data has no errors or correctable errors by using ECC circuit
57
, the data is transferred as reproduced data to the host processor. When ECC circuit
57
cannot correct all errors, microprocessor
55
retries read operation while using variable control parameters until the data can be correctly reproduced. Finally, the trusted data in RAM
56
is transferred via controller
51
to the host processor. Otherwise, a reproduction error is notified thereto. In addition to the recording and reproducing of data, the system conducts a dropout detecting operation to detect a position and length of dropout on media. And also, the system conducts optimization of circuit parameters to change characteristics of recorder and reproducer circuits
58
and
60
.
Magnetic recording and reproducing apparatuses of the conventional technology achieves data recording and reproducing operations in the configuration described above.
In the recording and reproducing operations, when read data has correctable errors by using ECC circuit
57
, the corrected data is immediately transferred to the host processor. However read data has uncorrectable errors exceeded correction capability of the ECC circuit
57
, magnetic recording and reproducing apparatuses retries read operation from the sector on media
54
. Therefore, it needs a wait time to start reread target sector operation, called read latency. This leads to a problem of disadvantageous elongation in the data access time.
Moreover, a partial missing of record information due to, for example, dropout of a magnetic film of media
54
may cause a miss-lock of phase locked loop circuit. In such a situation, the retry of data reproduction usually fails and hence additional latency is required. Resultantly, the data access time is conspicuously elongated.
In addition, optimization of circuit parameters of the signal processing circuit and surface check of a disk are repeatedly carried out in accordance with reproducing signals from the disk while changing circuit parameters. Resultantly, time for optimization and testing of the magnetic recording and reproducing apparatuses is increased.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a signal processing apparatus capable of reducing the latency due to data errors.
A second object of the present invention is to provide a signal processing apparatus capable of reducing a data burst error related to an erroneous operation of the phase locked loop circuit.
A third object of the present invention is to provide a signal processing apparatus capable of minimizing the time required for the optimization of circuit constants and/or for the testing of the magnetic recording and reproducing apparatus.
In accordance with the present invention, the first object can be achieved by providing a storage method for storing reproduction signals. The stored reproduction signals are conducted by data reproduction using different control parameters.
In accordance with the storage method, the reproducing operation can be repeatedly conducted with different control parameters without latency.
Additionally, the first object can be achieved by providing a storage unit for storing signals obtained by reproducing an identical sector several times, and an average unit for averaging the reproduced signals. Since the storage and the average unit improve the signal-to-noise ratio, reliability of the second and subsequent data reproducing operations is increased.
The second object of the present invention can be achieved by providing a storage device to store reproduction signals, and a sampling data generator to reproduce sampling phase locked data from the reproduction signa
Mita Seiichi
Saito Atsushi
Takashi Terumi
Beausoleil Robert
Bonzo Bryce P.
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