Dynamic magnetic information storage or retrieval – General processing of a digital signal – In specific code or form
Reexamination Certificate
2000-03-01
2003-06-10
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
In specific code or form
C360S048000
Reexamination Certificate
active
06577460
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to data storage systems and, more particularly, to a system and method for improving track format efficiency in a data storage device.
BACKGROUND OF THE INVENTION
A typical data storage system includes a magnetic medium for storing data in magnetic form and a transducer used to write and read magnetic data respectively to and from the medium. A typical disk storage device, for example, includes one or more data storage disks coaxially mounted on a hub of a spindle motor. The spindle motor rotates the disks at speeds typically on the order of several thousand revolutions-per-minute (RPM).
Digital information is typically stored in the form of magnetic transitions on a series of concentric, spaced tracks formatted on the surface of the magnetizable rigid data storage disks. The tracks are generally divided into a number of sectors, with each sector comprising a number of information fields, including fields for storing data, and sector identification and synchronization information, for example.
An actuator assembly typically includes a plurality of outwardly extending arms with one or more transducers and slider bodies being mounted on flexible suspensions. The slider body lifts the transducer head off the surface of the disk as the rate of spindle motor rotation increases, and causes the head to hover above the disk on an air bearing produced by high speed disk rotation. The distance between the head and the disk surface is typically on the order of 40-100 nanometers (nm).
In a typical data storage device, such as a direct access storage device (DASD) or other magnetic or optical storage device, data is typically stored in data sectors. In addition to storing customer data, each data sector typically includes a number of fields that store specific types of information which facilitate recovery of customer data during the readback process. Such fields may include one or more synchronization fields, an error correction code (ECC) field, a cyclic redundancy code (CRC) field, and a pad field.
Conventional data channel detector implementations typically require additional data or “pad” to be written to a data sector following writing of the customer data and ECC fields in order to allow the channel's detector to decode the last bytes of data written to the sector. The purpose of the pad is to provide sample values to the channel's detector and/or parity circuits for purposes of resolving pending decisions at the end of a data read operation.
It can be appreciated that inclusion of various sync, ECC, and pad fields in each data sector reduces the available capacity for storing customer data on a data storing medium. Although necessary for recovering customer data using conventional approaches, these fields reduce the efficiency of storing customer data. Elimination or reduction of the length of these fields would result in improved format efficiency and allow more customer data to be stored to the media per unit area.
There is a need for an improved data storage formatting approach which provides for increased data sector format efficiency. There exists a further need for such an approach that provides for increased customer data storage capacity, and one that allows designers to implement more efficient coding schemes without incurring loss of format efficiency due to the requirement to add longer pad at the end of a data sector. The present invention fulfills these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus and method for transferring data between a read/write transducer and a data storage medium which provide for an improvement in track format efficiency. A track formatting methodology of the present invention involves writing, using a write current waveform developed in the read/write transducer, data to a data sector of the data storage medium. The data is typically customer data.
According to the present invention, a transition pattern is generated and used for transitioning the write current waveform from the state following writing of the data to a known state consistent with coding constraints of the channel. A predetermined data pattern associated with the known state of the write current waveform is written to a pad field of the data sector. The transition pattern and the predetermined data pattern are used to resolve detector and parity post-processor closure decisions during a sector read operation.
The generated transition pattern is used for transitioning the write current waveform to a known state consistent with coding requirements of the channel. The coding constraints typically include parity constraints and precoder constraints. The predetermined data pattern typically includes a data pattern, such as a synchronization or repeating data pattern, that facilitates detector and parity post-processor closure decisions. For example, the predetermined data pattern may constitute a pattern of all logical ones or all logical zeros.
An apparatus for transferring data to and from a data storage medium according to the present invention includes a controller coupled to an interface for receiving customer data. The apparatus further includes a data channel comprising a write circuit, and a read/write transducer coupled to the data channel.
A write coding circuit, which is coupled to the controller and the write circuit, switches write current of the read/write transducer to code the data according to a selected partial response signaling format when writing the data to a data sector of the data storage medium. The write coding circuit generates a transition pattern used for transitioning the write current from the state following writing of the data to a known state consistent with coding constraints of the channel. The read/write transducer writes a predetermined data pattern associated with the known state of the write current to a pad field of the data sector.
The write coding circuit typically codes the data according to a partial response class-4 signaling format or an extended partial response class-4 signaling format. The write coding circuit typically includes an encoder and a precoder, wherein the coding constraints are consistent with coding requirements of the encoder and precoder. The data channel also includes a parity post-processor, wherein the coding constraints are consistent with parity requirements of the parity post-processor.
The data channel may further include a detector in addition to a parity post-processor, wherein the predetermined data pattern includes a data pattern that facilitates detector and parity post-processor closure decisions. According to one embodiment, the parity post-processor and detector use the transition and predetermined data patterns to resolve block code constraints and detector decisions, respectively, at the end of a sector read operation. The predetermined data pattern is typically a synchronization data pattern or a repeating data pattern, such as a data pattern including all logical ones or all logical zeros.
According to a yet another embodiment, a data storing system includes a data storage disk, a number of transducers each supported by a support structure in proximity with the disk, and an actuator that provides relative movement between the transducers and the disk. The data storing system further includes circuitry for transferring data to and from a data storage disk. The circuitry includes a controller coupled to an interface for receiving customer data and a write circuit coupled to a read/write transducer. A write coding circuit, which is coupled to the controller and the write circuit, facilities implementation of a track formatting methodology as described above.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken
Crawford & Maunu PLLC
Hollingsworth Mark A.
Hudspeth David
International Business Machines - Corporation
Kapadia Varsha A.
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