Embedded header for split data sectors in zoned bit recorded dis

Details Embedded header for split data sectors in zoned bit recorded dis Embedded header for split data sectors in zoned bit recorded dis

1994-11-22

1998-05-19

Psitos, Aristotelis M.

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Data in specific format

360 51, G11B 0509

Patent

active

057543518

DESCRIPTION:

BRIEF SUMMARY
The present invention relates generally to hard magnetic disc drives, and in particular, to locating data sectors on the magnetic discs of the magnetic disc drive.
In rotating media mass. storage devices, data is stored on magnetic, or magnetooptic discs, in a series of concentric tracks of differing diameters. The concentric tracks are each divided into sectors extending over the angles between two disc radii along the tracks. In particular, in rotating disc magnetic data storage devices, the discs have magnetizable surface coatings in which small portions, or cells, can have the magnetization therein varied from one to the next Data is written and subsequently read by transducer heads that are suspended over the surfaces of the disc to magnetize cells of the surface coating, for writing, or responding to differences in magnetization of the adjacent cells for reading. Both the read and write operations are controlled by a read/write controller that provides encoded data to the transducer head during writing and receives magnetically caused voltage pulses from the transducer heads during reading. For such a system to operate, the sectors in which cells are grouped must be located prior to reading or writing. It is common practice to encode some cells ahead of a data sector to serve as a header that identifies a following group of sectors. Some means must be provided to supply sector location pulses to the controller indicating the location of sector boundaries to enable writing or reading of the header information on the track as a transducer head approaches alignment with the header. Once the appropriate sector is reached and identified, reading or writing of data from or to the disc can proceed.
A soft sector scheme is a common scheme used to provide sector location information. In a soft sector scheme, sector boundaries are identified by address marks formed as a part of the sector. The address mark is such that it will not be mistaken for data, such as by having the address marks on the discs violate the code used in writing the data and the headers. A circuit is used to search for the address marks, which the controller places at the beginning of the sector. Such a circuit then provides sector location pulses to the read/write controller. The soft sector scheme has a known disadvantage of being susceptible to noise and media defects. The address marks on a disc can be lost becase of flaws in the magnetic medium in which data is written or by accidentally turning on a write gate, used to enable writing, as a transducer head passes over an address mark. In this last case, the data stored on the sector for that address mark can never be retrieved because a controller will never receive the pulses necessary for locating the sector. A more common problem results through read errors while searching for the address mark, which causes a sector to be missed and lowers the throughput of the data storage device.
A preferred alternative to the soft sectoring scheme has been the use of a hard sectoring scheme. In a hard sectoring scheme, the disc data storage device generates sector location pulses at the required interval without writing or recovering any special data from the data portion of the disc media itself. Instead, the transducer head detects servo patterns which are embedded in the rotating data storage disc itself. Alternatively, a separate servo head in alignment with the transducer head detects servo patterns written on the surface of a separate dedicated servo disc. The sector location pulses are usually generated with a simple circuit which counts out a desired time or number of bytes in a sector before issuing the next sector location pulse. This type of simple hard sectoring scheme has proven adequate for many years because the interval between sector location pulses was identical on every track of the disc storage device.
The desire to store as much data on a disc as possible lead to the recording of data at different frequencies for different tracks of the disc. A problem with the simple hard s

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