Data storage device for data storage system

Abstract: The present invention relates to a data storage device comprising a circular disc (30), a data storage medium on at least one surface of the disc, a spiral track extending within the storage medium about the axis of the disc, and a plurality of data storage sectors formed on the track. According to the invention the storage device is characterised in that the storage medium is formed with a reference mark (100) extending radially from the axis of the disc, and the data storage sectors are arranged in groups extending along the spiral track, one end of each group of sectors being located adjacent to one of the points of intersection of the reference mark with the spiral track.

Description: The present invention relates to data storage devices for data storage systems and particularly to a format for storing data on recording disks that increases data storage capacity while enabling a relatively simple addressing structure to be used in accessing data stored in areas of the disk. Data-storing circular-disk devices, such as optical or magnetic disks, have used either concentric or spiral data storing tracks on the storage medium. Typically, so-called magnetic hard disks and flexible diskettes have used concentric tracks while optical disks have used a single spiral track on each disk. It has been a long felt need to provide a data storing format for a disc device that has increased data-storage capacity and simple addressing. Several attempts at banding a storage medium into a plurality of different data storage track lengths having different lineal and angular data densities have complicated the addressing so that it is cumbersome to manage. Known disk data storage devices have track lengths keyed or based upon one disk revolution angular length, i.e. either one or more tracks completely occupy one disk revolution (also termed tracks in the literature). Often disk revolutions are colloquially equated to tracks. This constraint unduly limits the data storage capacities and restricts flexibility in designing data storage formats. In particular, formats for so-called banded disks for increased capacities have been limited to one track, an integral number of sectors, as well as tracks, per spiral track revolution. That is, track lengths are always tied to the length of a disk revolution (the length of a single track extending in a circle around the centre of the disk). This discussion relates to addressable physical tracks on disk data storage media. Such physical tracks should not be confused with so-called logical or virtual tracks which merely map data onto physical tracks of a disk data storage medium. Because known types of addressable tracks were co-extensive with each spiral track revolution or one revolution of a concentric set of revolutions, the term track has been used colloquially to denote a revolution. As used herein, the term "addressable track" means an identifiable addressable entity that may contain data and which is separate and distinct from a revolution of a spiral track or one revolution of a disk having concentric revolutions. The term "revolution", as used herein, defines one circuit of a spiral track equal to 360 ° of the spiral track. As applied to concentric revolutions, the term "revolution" means the entirety or 360 °of each track. The term "addressable entity" is intended to mean any addressable track or any one of a plurality of addressable sectors or records in each such addressable track. As will become apparent, the size and capacity of an addressable track is totally independent of the extent of a revolution. It is a desire of disk manufacturers to comply with the American National Standards Institute (ANSI) and International Standards Organization (ISO) standards on interchange data storage media, i.e. removable data storage media. Such standards apply not only to magnetic tape, but also to removable data-storing disks. In particular, optical disks are the subject of pending, proposed and issued standards of ANSI and ISO. In making advances in the recording arts, it is also desirable for cost and marketing reasons to provide compatibility with existing standards and industry practices. This compatibility is often referred to as "backward compatibility". Current interchange standards for optical disks, inter alia, provide for either 512 byte or 1024 byte data-storing sectors in a single spiral track of each disk medium. Each optical disk revolution, also termed a track in the known arrangement, contains either seventeen of the 1024 byte sectors or thirty-one of the 512 byte sectors. Combining the desires for greater disk capacity while maintaining linear addressing with backward compatibility creates substantial problems in the conflicting requirements. It is also desired to directly access a data-storing area without extensive computation or scanning a disk being accessed. In banded disks, such direct accessing can be complicated and burdensome. Accordingly, addressing of tracks and sectors should be straightforward and consistent over the address space of the data-storing sectors and tracks. The sectors and tracks are addressable entities on a disk. Usually a single spiral track is not separately addressed, no limitation to that exclusion from addressing is intended. US -A- 4,016,603 shows a banded or zoned data storing disk using Count Key and Data (CKD) formatted tracks. The track lengths and capacities in the various zones or bands are different. While disk capacity is greatly increased, addressing and data management are complicated by the different track lengths. This patent teaches that the radially outermost zone should have the greatest number of tracks, i.e the greatest number of disk revolutions, as well as tracks having the greatest disk storing capacity. This patent also teaches that a disk supporting spindle has an index or tachometer disk for use in rotationally or angularly addressing data-storing areas on the data-storing disks. A sector servo is employed in the arrangement described for enabling a transducer to faithfully and accurately scan any track on the data-storing disks. All track lengths are keyed to and based upon the circumferential length of disk track revolutions. Concentric tracks are shown. The IBM Technical Disclosure Bulletin, Vol. 29, No. 4, September 1986 on pages 1867-8 discloses a magnetic hard disk having sectors that are angularly offset at different radii. The purpose of the offsetting is to reduce latency time. The offset-ting allows for the elapsed time necessary for seeking from one concentric track to an adjacent concentric track. US -A- 4,750,059 shows a banded magnetic hard data storing disk having concentric tracks in zones that increase in radial extent with increasing radius. The largest zone is the radially outwardmost zone, similar to the Otteson teaching. US -A- 4,422,110 teaches using two radially spaced-apart transducers for use in banded data storing media. Each of the transducers is in a different radial band. US -A- 4,015,285 shows a video data storing disk having track lengths equal to disk revolution lengths. The tracks are circumferentially offset by one sector of track. US -A- 4,814,903 shows locating spare sectors at the end of a track on a data storing disk. One track is one revolution of a single spiral track on the disk. The spare sectors are placed in a usual or desired area where stop-motion jumping is to occur. Since the spare sectors may not contain data, such jumping usually does not detract from data transfer rates. US -A- 4,873,679 shows a data storing disk having constant linear recording density. Successive track revolutions of a spiral track in the radially outward direction have an increasing number of sectors. There are always an integral number of sectors in each revolution of one spiral track. US-A-4 873 679 appears to represent the closest prior art to the present invention. US -A- 4,839,877 shows using a disk support spindle index or tachometer disk for assisting in rotationally or angularly addressing data-storing areas on a removable data-storing disk. FR-A-2649527 discloses an information recording disk with a ring-shaped recording region divided into a plurality of concentric, annular blocks. Each of the blocks is divided in a circumferential direction into a plurality of equal sectors, and a recording track and a pit train for generating a header signal are previously formed in the recording region. The recording density of blocks nearer to the outer circumference of the recording region is greater than blocks closer to the centre of the disk. The recording region of the disk has a portion where blocks are pre-formatted so that the pit pitch of the header-signal generating pit train formed on the innermost recording track of the outer one of two adjacent blocks is greater than the pit pitch of the header-signal generating pit train formed on the innermost recording track of the inner block. Figure 1 of FR-A-2649527 shows sectors within annular blocks which are keyed to (i.e. each annular block is required to start and end at) the pre-pit train. US-A- 4,432,025 shows a banded data storing disk with different length tracks. Each track is contained in and its length in bytes is determined by the disk revolution in which it is positions. The object of the present invention is to provide an improved data storage device for a data storage system. The present invention relates to a data storage device comprising a circular disk, a data storage medium on at least one surface of said disk, a spiral track extending within said storage medium for a plurality of revolutions about the axis of said disk, a plurality of data storing addressable entities disposed on said track, a reference angular position extends radially from the axis of said disk, and said data storing addressable entities are arranged in groups extending along said spiral track, characterised in that the addressable entities have physical lengths independent of the length of a revolution of the spiral track such that at least one addressable entity in at least one of said groups spans the reference angular position, and wherein a first end of each group is located adjacent to a point of intersection of said reference angular position with said spiral track. According to one embodiment of the invention, a single base format enables using either the 512 or 1024 byte sectors to be used without change in the base format; only the physical size of the sectors are changed. Other sector capacities may also be used in the single base format. The addressing methodology is unchanged, that is, the number of sectors in an addressable track is not changed. For 512 byte sectors there always are 31 sectors per addressable track and for 1024 byte sectors there are always 17 sectors per track. In accordance with another embodiment of the invention, the addressable entities on a disk have data-storing capacities and angular extents that are independent of a data-storing capacity of one of the revolutions and of the angular extent of one revolution. That is, neither sectors nor addressable tracks need be and preferably are not selected to be an integral submultiple of a spiral track revolution nor an integral multiple of a spiral track revolution. In some embodiments there may be an integral number of sectors per revolution but not an integral number of addressable tracks per revolution nor does a single addressable track need to have an integral number of revolutions. In accordance with a further embodiment of the invention, addressable data-storing tracks on a data storing disk have lengths independent of the individual length of revolutions of the disk. Each addressable track has a plurality of fixed-size (preferably like-sized) addressable data-storing sectors. Each revolution of the disk need not have an integral number of the data-storing sectors. Anchor sectors are provided that precisely locate all sectors between two radial spaced-apart anchor sectors by being precisely located with respect to a single radially-extending circumferential or angular reference position. Such reference position is determined by a spindle index mark in manufacturing equipment used to format the disk. The anchoring by the spindle index mark removes and limits cumulative angular position errors individually addressable sectors or tracks. Each disk has one or more revolution groups, each group beginning at one of the anchor sectors. The sector locations intermediate the anchor sectors in any one revolution group are based upon circumferential displacement from said anchor sectors. As such, the relative location of the intermediate sectors depends only on the anchor sector location. Such relative location is independent of any one revolution of the disk. A band of a plurality of revolution groups has one angular density for recorded control indicia and data. Each successively radially outward band has increasing angular density of recording and a greater number of addressable tracks. It is preferred that each group and each band on any one data storing medium have identical radial extents. Such preference provides a lineal progression of number of addressable tracks in each band and in the increase in angular recording density. It is further preferred that the number of bands be a number 2n, where n is a positive integer. This selection facilitates generating a separate frequency of operation for each band in devices or drives that record or read data to and from the disk medium. In an alternative embodiment of the invention, within each band, all sectors are circumferentially aligned. In yet another embodiment of the invention, a spiral track defined on one medium surface by a spiral groove or a spiral set of sector servo indicia is imposed on co-axial co-rotating data-storing disks. The format of revolution groups and bands is imposed on all of the co-axial co-rotating data-storing disks. The format defined in the invention is useable on any type of disk data storing medium, preferably one that has a single spiral track either formed or recorded thereon or imposed thereon from a co-axial co-rotating disk. In order that the invention may be more readly understood an embodiment will now be described with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of an optical disk data recorder/readback device with which the embodiment to be described is advantageously employed, Fig. 2 is a diagrammatic illustration of optical disk data storing apparatus constructed in accordance with the embodiment to be described and which may be used by the Fig. 1 illustrated device, Fig. 3 diagrammatically illustrates the revolution band format of a plurality of revolution groups of the Fig. 2 illustrated disk data storing apparatus including the format of a data-storing sector, Fig. 4 diagrammatically illustrates the format of a revolution group in any revolution band of the Fig. 2 illustrated disk data storing apparatus, Fig. 5 diagrammatically illustrates the revolution format of three revolutions having an integral and non-integral number of data-storing sectors shown in Fig. 3, Fig. 6 diagrammatically illustrates an addressing mechanism usable with the Fig. 2 illustrated data-storing disk, Fig. 7 diagrammatically illustrates the format of sectors abutting a boundary between two radially adjacent ones of the revolution bands shown in Figs. 2 to 4, Fig. 8 is a machine operations flow chart showing the operation of seeking from a current track to a target track by counting disk revolutions, Figs. 9 and 10 show, respectively, read and write circuits usable with the Fig. 1 illustrated apparatus for implementing the embodiment to be described, Figs. 11 and 12 illustrate manufacturing one of the disks in the Fig. 2 illustrated disk data storing apparatus, Fig. 13 diagrammatically illustrates applying the embodiment to be described to a count-key-data (CKD) formatted disk, Fig. 14 is a simplified machine operations chart showing certain operations related to the control of scanning addressable tracks using the Fig. 1 illustrated device for control of jump back and traversing band boundaries, and Fig. 15 diagrammatically illustrates a so-called control area of a data-storing disk implementing the embodiment to be described. Referring now more particularly to the appended drawing, like numerals indicate like parts and structural features in the various figures. Before going into the details of how the procedures and criteria are effected in accordance with the embodiment now being described, an environment in which the embodiment is advantageously implemented is shown in Fig. 1. A device similar to the Fig. 1 illustrated magneto-optical drive may be used in generating a master data storing disk for creating stamped replicas using the format of the embodiment being described. Such mastering is described in the description of Figs. 11 and 12. In Fig. 1, magneto-optic record disk 30 is mounted for rotation on spindle 31 by motor 32. Optical signal processing portion 33 is mounted on frame 35. A head-arm carriage 34 moves radially of disk 30 for moving an objective lens 45 from disk revolution to disk revolution for accessing any one of a large plurality of addressable tracks on the disk 30. The frame 35 of the device suitably supports carriage 34 for reciprocating radial motions relative to the disk 30. The radial motions of carriage 34 enable access to any one of a plurality of concentric revolutions or circumvolutions of a spiral track for recording and recovering data on and from the disk. Linear actuator 36, suitably mounted on frame 35, radially moves carriage 34 for enabling addressable track accessing. The device is attached to one or more host processors 37. Such host processors may be control units, personal computers, large system computers, communication systems, image signal processors, or the like. Attaching circuits 38 provide the logical and electrical connections between the optical recording device and the attaching host processors 37. Microprocessor 40 controls the recording device including the attachment to the host processor 37. Control data, status data, commands and the like are exchanged between attaching circuits 38 and microprocessor 40 via bidirectional bus 43. Included in microprocessor 40 is a program or microcode-storing, read-only memory (ROM) 41 and a data and control signal storing random-access memory (RAM) 42. The optical system of the MO recording device includes an objective or focusing lens 45 mounted for focusing and radial tracking motions on head-arm 33 by fine actuator 46. This actuator includes mechanisms for moving lens 45 towards and away from disk 30 for focusing and for moving the lens radially parallel to carriage 34 movement; for example, for changing tracks within a range of 100 tracks so that carriage 34 need not be actuated each time a track adjacent to a track currently being accessed is to be accessed. Numeral 47 denotes a two-way light path between lens 45 and disk 30. In magneto-optic recording, a magnetic bias field generating coil 48 generates a magnetic steering or bias field for erasing from and recording on disk 30. Electromagnet coil 48 provides a weak magnetic steering or bias field for directing the remnant magnetization direction of a small spot on disk 30 illuminated by laser light from lens 45. A laser light heats the illuminated spot on the record disk to a temperature above the Curie point of the magneto-optic layer (not shown, but can be an alloy of rare earth and transitional metals as described in US -A- 3,949,387). This heating enables the magnet coil 48 generated bias field to direct the remnant magnetization to a desired direction of magnetization as the spot cools below the Curie point temperature. For writing /recording data on disk 30, magnet coil 48 supplies a bias field oriented in the "write" direction, i.e., binary ones recorded on disk 30 normally are "north pole remnant magnetization". To erase data on disk 30, magnet coil 48 supplies a magnetic bias field such that the field's south pole is adjacent to disk 30. Magnet coil 48 control 49 is electrically coupled to magnet coil 48 over line 50 to control the write and erase directions of the coil 48 generated magnetic field. Microprocessor 40 supplies control signals over line 51 to control 49 for effecting reversal of the bias field magnetic polarity. It is necessary to control the radial position of the beam following path 47 such that a track or circumvolution on disk 30 is faithfully followed and that a desired track or circumvolution is quickly and precisely accessed. To this end, focus and tracking circuits 54 control both the coarse actuator 36 and fine actuator 46. The positioning of carriage 34 by actuator 36 is precisely controlled by control signals supplied by circuits 54 over line 55 to actuator 36. Additionally, the fine actuator 46 control by circuits 54 is exercised through control signals travelling to fine actuator 46 over lines 57 and 58 for effecting focus and track following and seeking actions. Sensor 56 senses the position of fine actuator 46 relative to head-arm carriage 33 to create a relative position error (RPE) signal. The RPE signal travels over line 53 to focus and tracking circuits 54 for servo control during track seeking and track following. Line 57 consists of two signal conductors, one conductor for carrying a focus error signal to circuits 54 and another conductor for carrying a focus control signal from circuits 54 to the focus mechanisms in fine actuator 46. Line 58 also represents a plurality of electrical conductors respectively for carrying control and sensed signals between circuits 54 and fine actuator 46. The focus and tracking position sensing is achieved by analyzing laser light reflected from disk 30 over path 47, thence through lens 45 and through one-half mirror 60 to be reflected by half-mirror 61 to a so-called "quad detector" 62. Quad detector 62 has four photoelements which supply signals respectively on four lines, collectively denominated by numeral 63, to focus and tracking circuits 54. Aligning one axis of the detector 62 with a track centre line, track following operations are enabled. Focusing operations are achieved by comparing the light intensities detected by the four photoelements in the quad detector 62. Focus and tracking circuits 54 analyze the signals on lines 63 to control both focus and tracking. Recording or writing data onto disk 30 is next de-scribed. It is assumed that coil 48 bias field is oriented for recording data. Microprocessor 40 supplies a control signal over line 65 to laser control 66 for indicating that a recording operation is to ensue. This control signal means that laser 67 is energized by control 66 to emit a high-intensity laser light beam for recording. In contrast, for reading, the laser 67 emitted laser light beam is at a reduced intensity for not heating the laser illuminated spot on disk 30 above the Curie point. Control 66 supplies its control signal over line 68 to laser 67 and receives a feedback signal over line 69 indicating the laser 67 emitted light intensity. Control 68 adjusts the light intensity to the desired value. Laser 67, a semiconductor laser such as a gallium-arsenide diode laser, can be modulated by data signals so the emitted light beam represents the data to be recorded by intensity modulation. In this regard, data circuits 75 (later described) supply data indicating signals over line 78 to laser 67 for effecting such modulation. This modulated light beam passes through polarizer 70 (linearly polarizing the beam) and thence through collimating lens 71 towards half mirror 60 for being reflected towards disk 30 through lens 45. Data circuits 75 are prepared for recording by the micro-processor 40 supplying suitable control signals over line 76. Microprocessor 40, in preparing circuits 75, is responding to commands for recording received from a host processor 37 via attaching circuits 38. Once data circuits 75 are prepared, data is transferred directly between host processor 37 and data circuits 75 through attaching circuits 38. Data circuits 75, also ancillary circuits (not shown), relate to disk 30 format signals, error detection and correction and the like. Circuits 75, during a data read or recovery action, strip the ancillary signals from the read-back signals before supplying corrected data signals over bus 77 to host processor 37 via attaching to 38. Reading or recovering data from disk 30 for transmission to a host processor requires optical and electrical processing of the laser light beam from the disk 30. That portion of the reflected light (which has its linear polarization from polarizer 70 rotated by disk 30 recording using the Kerr effect) travels along the two-way light path 47 and through lens 45 and half-mirrors 60 and 61 to the data detection portion 79 of the head-arm 33 optics. Half-mirror or beam splitter 80 divides the reflected beam into two equal intensity beams both having the same reflected rotated linear polarization. The half-mirror 80 reflected light travels through a first polarizer 81 which is set to pass only that reflected light which was rotated when the remnant magnetization on disk 30 spot being accessed has a "north" or binary one indication. This passed light impinges on photo-cell 82 for supplying a suitable indicating signal to differential amplifier 85. When the reflected light has been rotated by a "south" or erased pole direction remnant magnetization, then polarizer 81 passes no or very little light resulting in no active signal being supplied by photocell 82. The opposite operation occurs in polarizer 83 which passes only "south" rotated laser light beam to photocell 84. Photocell 84 supplies its signal indicating its received laser light to the second input of differential amplifier 85. The amplifier 85 supplies the resulting difference signal (data representing) to data circuits 75 for detection. The detected signals include not only data that is recorded but also all of the so-called ancillary signals as well. The term "data" as used herein is intended to include any and all information-bearing signals, preferably of the digital or discrete value type. The rotational position and rotational speed of spindle 31 is sensed by a suitable tachometer, index or emitter sensor 90. Sensor 90, preferably of the optical-sensing type that senses dark and light spots on a tachometer wheel (not shown) of spindle 31, supplies the "tach" signals (digital signals) to RPS circuit 91 which detects the rotational position of spindle 31 and supplies rotational information-bearing signals to microprocessor 40. Microprocessor 40 employs such rotation information signals for controlling access to data storing segments on disk 30 as is widely practiced in the magnetic data storing disks. An example of such rotationally controlled accessing of data-storing tracks is shown in US -A- 4,839,877. Additionally, the sensor 90 signals also travel to spindle speed control circuits 93 for controlling motor 32 to rotate spindle 31 at a constant rotational speed. Control 93 may include a crystal-controlled oscillator for controlling motor 32 speed, as is well known. Microprocessor 40 supplies control signals over line 94 to control 93 in the usual manner. While the preferred usage of the embodiment being described is in an optical disk, such as magneto optical disk 30, the embodiment is applicable to any data-storing disk. Such disks include read-only optical disks, magnetic hard disks, magnetic or optical floppy diskettes, as well as other types of data-storing disks. Also included in appropriate media for implementing the embodiment being described are any write-once disks, as well as other forms of read-only, write-once or rewriteable (also termed erasable) data-storing disks having diverse types of signal-storing layers for retentively or temporarily storing data or other information-bearing signals. While an emphasis of the embodiment being described is for interchangeable data storing media, the embodiment is equally useful for disks fixed in a disk drive or device. Any size of disk, track pitch, linear density and radial extent of a recording area of a disk may be used. While it is preferred that a continuous spiral track on each medium be used, other arrangements may also be used. Fig. 2 shows a simplified diagrammatic plan view of a disk 30 formatted in accordance with the embodiment being described. Beginning at inner diameter ID 319 and extending radially outward toward outer diameter OD of disk 30, a so-called control area, having a phase-encoded part PEP area 96, a standard format part SFP area 97 and a manufacturing MFG area 98, enables the Fig. 1 illustrated device to determine the operating parameters of disk 30. The details of this control area are explained later with respect to Fig. 16. Not shown in Fig. 2 is a replication of the MFG area 98 and SFP area 97 at the outer diameter OD of disk 30. In this OD replication, the replicated MFG area is positioned radially inward of the replicated SFP area. A so-called lead out spiral track revolution may be disposed radially outward of the replicated SFP area replica. MFG area 98 is an extension of band 0 (101) in that the same frequency of operation is used for reading of data in MFG area 98 as is used for reading of data in band 0. Likewise, the MFG area replica is a radial outward extension of band 106 in that the frequency of operation used for reading data in both the MFG area replica and band 106 is the same. Radial line 100 represents a fiducial or reference circum-ferential position on disk 30. Such position corresponds to the usual index line embossed or recorded on known types of disks. Disk 30 does not have such an index line be-cause, as will become apparent, many later-described data-storing sectors span reference position 30 while so-called "anchor" sectors each have one end aligned with reference position 30. Disk 30 has a single spiral track extending between an outer radial extremity and an inner radial extremity in a usual manner. The present description assumes that scanning the spiral track proceeds radially outwardly, no limitation thereto being intended. The single spiral track is divided into radial bands 101-106, each band having a like number of revolutions of the single spiral track. Ellipses 104 signify that a plurality of such bands of spiral track revolutions exist between bands 103 and 105. In magneto-optical disk 30, such a spiral track is represented by a continuous spiral groove (not shown) in the surface of the disk. The actual spiral track may be either in the spiral groove or on a land area contiguous with the spiral groove. Each band has a number of equal-data-storing-capacity addressable tracks which is greater than the number of spiral track revolutions in each band. The number of addressable tracks in each band increases with radius of the band. In early embodiments, each successive radially outward band had a fixed number of additional addressable tracks than its adjacent radially inward band of either seventeen 1024 byte data-storing sectors or thirty-one 512 byte data-storing sectors. The fixed number of additional tracks is based upon a number of later-described revolution groups in each of the bands. Each revolution group comprises a predetermined number of addressable tracks. The described embodiment shows 99 of the revolution groups in each band. Each of the revolution groups in the radially outer band had one additional addressable track as compared with each revolution group in the next radially inner band. Hence, each radially outer band had an additional 99 addressable tracks. To maximize the capacity of disk 30 for implementing the embodiment being described, the ratio of the outer diameter OD of the recording area and the inner diameter ID 319 of the recording area equals (1 + n), where n is the number of bands 101-106. The above statement is true for implementing the embodiment being described for a disk having a given minimum angular density of the radially innermost band, where each band includes a plurality of spiral track revolutions and where the addressable tracks are not based upon nor keyed to one disk revolution of 360o. Also diagrammatically shown in Fig. 2 is the implementation of the the embodiment being described to a stack of co-rotating co-axial disks 30, 107 and 108 that rotate about axis 109 that is co-axial to spindle 31. In this arrangement, a usual "comb" head may be used to access the surfaces of the three disks 30, 107 and 108. A spiral track on disk 30, the spiral track being identified by a spiral groove or a spiral set of sector servo marks, has identifications of addressable tracks embossed or otherwise recorded on disk 30. In this sense, disk 30 has a servo positioning surface, in addition to storing data, for guiding transducers (not shown) that access recording surfaces on disks 107 and 108 respectively in the same manner that magnetic "hard" disks use a single servo surface for positioning a set of transducers on respective recording surfaces. The reference position 100 is imposed on both of the disks 107, 108 by timing control in the same manner that a radial index line recorded on a servo surface of magnetic hard disks. This one servo surface and associated servo control (part of focus and tracking circuits 54) are for simultaneously positioning 17 transducers on 17 recording surfaces. The recording surfaces of disks 107 and 108 are preferably smooth so that the recording thereon indicates the tracks. The positioning is actually controlled by the servo position circuits 75 of Fig. 1 using the spiral groove of disk 30 in a usual manner. It is to be understood that the reference position 100 on each of the recording surfaces of disks 30, 107, 108 can be precisely aligned for synchronizing the operation of all of the recording surfaces. Such precise alignment is not required if the surfaces are accessed independently of each other. Further, the timing and positioning of the later described anchor sectors, anchor tracks and precessing ones of the sectors and tracks is controlled by the servo operation of the servo surface. That is, only one of the disks 30, 107 and 108 needs to have a servo positioning recording. In another disk apparatus arrangement, a single disk 30 has recordings on both surfaces. The illustrated upper recording surface 30U (Fig. 1) has a recording coating (not shown) and a spiral track indicating groove. The arrangement of the spiral groove and its indicated single spiral track provides for scanning from ID 319 to OD of disk 30. There are two arrangements that may be used for achieving two-sided recording. A first arrangement is to make the lower surface 30L smooth and having an MO coating. Instead of a single lens 45 that focusses a beam on surface 30U, an additional optical system (not shown) focuses a second laser beam on surface 30L. Both optical systems are supported as a so-called comb head wherein both beams are moved simultaneously with the carriage 34 while each will have a separate fine actuator. The illustrated fine actuator 46 is controlled by following the spiral groove whereas a second fine actuator (not shown) has a servo control slaved to fine actuator 46 movement for positioning the second laser beam on surface 30L identically to the actuator 46 movement. In this arrangement the spiral tracks on surfaces 30U and 30L are axially superposed. In a second arrangement, both surfaces 30U and 30L have a spiral groove, the spiral groove on surface 30U is arranged to provide for scanning from ID 319 to OD of disk 30 while the spiral groove on surface 30L has a reversed direction of scanning from OD to ID 319. The reverse direction of scanning is required for maintaining one direction of rotation of disk 30 for scanning both surfaces 30U and 30L. A separate and independent optical bias field generating and positioning system as described for supplying and modulating a laser beam on path 47 (Fig. 1) is replicated for scanning, recording, reading and erasing operations on surface 30L. Fig. 3 illustrates the addressable-track arrangement in each of the revolution bands 101-106. Note that there is no reference to revolutions because the addressable track arrangement is independent of revolutions. The arrangement is such that an integral number of sectors and addressable tracks exist in each of the revolution bands. Each revolution group has an established absolute angular or circumferential position for preventing accumulation of angular errors in sector locations from extending beyond each revolution group. The size of each revolution group is preferably selected based upon the accuracy of a so-called mastering machine as described with respect to Figs. 11 and 12. All addressable tracks have the same length and data storage capacity as measured in number of data-storing sectors (either 17 or 31) and data storage capacity (either 17,408 or 15,872 data bytes plus sector marks 117). Therefore, from a programmed addressing systems and accessing point of view, all addressable tracks have the same length and are backward compatible with many known addressing and disk formats. The circumferential length of these constant-length addressable tracks varies with radius as is known. The two mentioned addressable track sizes correspond to the above mentioned ANSI and ISO prescribed track capacities and extents. Such tracks are respectively co-extensive with revolutions of a single spiral track. Returning now to Fig. 3, a plurality of revolution groups 110, 111, 113 and 114 are shown. Ellipses 112 represent a plurality of further revolution groups which are disposed between revolution groups 111 and 113. All of the revolution groups 110-114 constitute one revolution band. All revolution bands 101-106 have an identical number of revolution groups (no limitation thereto intended) and every revolution group has an identical number (14) of spiral track revolutions (no limitation thereto intended). This choice of identity in the sizes of the revolution groups and bands facilitates constructing devices to operate with each disk, as will become apparent. Every revolution group in each respective revolution band has an identical number of addressable tracks. The number of addressable tracks in successive radially outward bands increases by a constant number (no limitation thereto intended). In an early embodiment, each revolution group in a succeeding radially outward band has one additional addressable track as compared with the preceding band. If each band has fifty revolution groups, then each succeeding radially outward band has an additional fifty addressable tracks. As set forth in Table 1 below, in the embodiment being described each band has 99 revolution groups resulting in an additional 99 tracks per successive radially outward band. Table 1 below shows the addressable track numbers (addresses) and the spiral track revolution numbers in sixteen bands numbered 0-15. The table was computed using the equation TBn = N + (Bn*K) wherein TB is the number of addressable tracks in a band, n indicates the number of the band (0-15), K is the number of tracks added to each successive radially outward band, as set forth above, and Bn is the band number. In this early version of the embodiment being described for a 130 mm disk having a single spiral track, each of sixteen (24) revolution bands had addressable tracks each having seventeen 1024 byte data-storing sectors. The table shows the lineal progression of increasing numbers of addressable tracks per bands having an increasing inner radius, respectively. Each radially outward band has 99 additional tracks. This number will be better understood later. Band Numbers Band Radii Addressable Track Numbers Disk Revolution Numbers 0 30.00 mm - 31.87 mm 0 to 1,583 0 to 1,385 1 31.87 mm - 33.74 mm 1,584 to 3,266 1,386 to 2,771 2 33.74 mm - 35.61 mm 3,267 to 5,048 2,772 to 4,157 3 35.62 mm - 37.48 mm 5,049 to 6,929 4,158 to 5,543 4 37.48 mm - 39.36 mm 6,930 to 8,909 5,544 to 6,929 5 39.36 mm - 41.23 mm 8,910 to 10,988 6,930 to 8,325 6 41.23 mm - 43.10 mm 10,989 to 13,166 8,316 to 9,701 7 43.10 mm - 44.97 mm 13,167 to 15,443 9,702 to 11,087 8 44.97 mm - 46,84 mm 15,444 to 17,819 11,088 to 12,473 9 46.84 mm - 48,71 mm 17,820 to 20,294 12,474 to 13,859 10 48.72 mm - 50.58 mm 20,295 to 22,868 13,860 to 15,24 11 50.58 mm - 52.45 mm 22,869 to 25,541 15,246 to 16,631 12 52.45 mm - 54.32 mm 25,542 to 28,313 16,632 to 18,017 13 54.32 mm - 56.20 mm 28,314 to 31,184 28,018 to 19,403 14 56.20 mm - 58.07 mm 31,185 to 34,154 29,404 to 20,789 15 58.07 mm - 59.94 mm 34,155 to 37,223 20,790 to 22,175 One of the functions of the embodiment being described is to provide linear step sizes in frequency changes from one revolution band to the next radially-outward revolution band of the frequency of operation to be used. The frequencies of operation for data recording and reading in the early embodiment being described are listed below. A later described binary digital control changes frequency division ratios of a source clock to obtain the frequencies in each of the bands listed below. Figs. 9 and 10 illustrate a digital control system for implementing the below listed frequencies. The frequency changes are linear with respect to the inner radial locations of each of the bands 0-15 (there are 24 bands); therefore, the linear frequency changes can be achieved by a digital to analog converter (DAC). Nominal Clock Frequencies Band Number Clock Frequency Mhz PEP (radially in) 9.864 PEP Transition 9.864 SFP Control Track 9.864 Manufacturing Area 11.274 Band Number 0 11.274 1 11.978 2 12.682 3 13.387 4 14.092 5 14.797 6 15.501 7 16.206 8 16.910 9 17.615 10 18.320 11 19.024 12 19.729 13 20.434 14 21.138 15 21.843 Manufacturing Area 21.843 SFP Control Track 9.864 Lead Out Track outer disk diameter 9.864 Table 2 shows that the manufacturing MFG area 98 requires the same frequency of operation as band 0 while the outer diameter replica of MFG area 98 replica requires the same frequency of operation as band 15. The SFP area 97 and PEP area 96 require frequencies of operation not related to the band structure of the embodiment being described. Returning to Fig. 3, each revolution group 110-114 has an anchor sector 115. Each anchor sector has one end aligned with the reference position as represented by line 100 (Fig. 2). Such reference position is essential to prevent accumulation of angular position errors during fabrication of a master disk, as described later with respect to Figs. 11 and 12. That is, the precise absolute determined positioning of anchor sectors 115 eliminates accumulated errors of sector angular positions to one revolution group. In the early version of the embodiment, each revolution group has an integral number of addressable tracks. Such integral number of addressable tracks in each revolution group is not a limitation of the embodiment being described. Each revolution group may include one or more intermediate anchor sectors, such as anchor sector 116. Anchor sector 116 can be located at a midpoint of an addressable track which is a middle addressable track in the revolution group; two such intermediate anchor sectors can be located respectively at one-third points of a revolution group, etc. If intermediate anchor sectors are employed, then precession of the frequencies of operation occurs, and the number of addressable tracks per band is changed and may not be maximized. Further, construction of devices to operate with such formatted disks may be more complex. Every sector on disk 30 has an identical internal format. The internal format of anchor sector 115 of revolution group 110 is shown. A so-called sector field 117 identifies each sector. The first portion C of field 117 is a clock synchronizing field having embossed signals of a known arrangement. The frequency of operation enabled by each portion C varies with bands as shown in Table 2. Second scanned portion T contains an embossed indication of the addressable track number or address. Third scanned portion S contains an embossed indication of the sector number within the addressable track (either 0-17 or 0-31, for example). Not shown for brevity are error detection redundancies. The second field 118 of each sector is the data storing field. On writable disks, field 118 is not embossed. On read only disks or portions of disks, field 118 contains data represented by embossed indicia. An intra-record gap (unnumbered) separates fields 117 and 118. An interrecord gap (unnumbered) is adjacent field 118 for separating the illustrated field 118 from the sector field (not shown) of the next adjacent sector. As will become more apparent, all addressable tracks have a track length independent of the revolution length. In each revolution group, a first number of addressable tracks fit into a second number of spiral track revolutions. The illustrated embodiment shows the constant length addressable tracks always occupying less than one revolution. In this embodiment, all revolution groups have 14 revolutions. The number of addressable tracks in any revolution group in any band can be calculated from Table 1 by dividing the number of addressable tracks in each band by 99. On smaller radius disks, one addressable track may occupy more than one spiral track revolution, at least in radially inward ones of the bands. By coincidence, one of the bands on a disk may have an integral number of tracks per revolution, i.e. 1, 2 etc. addressable tracks per revolution. Other bands, as contemplated by the early version of the embodiment, have a non-integral number of addressable tracks per spiral track revolution. In the illustrated embodiment, each spiral track revolution has a non-integral number of sectors. This arrangement means that the sector angular or circumferential locations within each revolution group precess around the disk. Fig. 13, later described, shows an alternative embodiment having an integral number of sectors per spiral track revolution for enabling the use of radially aligned sector fields 117 within each band. The number of sectors in each such spiral track revolution may be less than, the same as or more than constitute one of the addressable tracks. In a banded disk medium, each band has a different number of addressable tracks and portions thereof in each spiral track revolution. Making the addressable track a constant length in terms of number of sectors and storage capacity (bytes) and independent of the spiral track revolution lengths enables maximizing data storage capacity of the disk while maintaining track address-ability used in the known arrangements -- backward compatibility. Fig. 4 illustrates, in greater detail, the relationship of the sectors in each revolution group with respect to the spiral track revolutions. Again, one revolution band is shown. Revolution groups GO through GK (K is an integer having no relationship to the constant K used in later described equation (1)) are shown. Each revolution group contains a large number of sectors as indicated by ellipses 125. The illustrated revolution band has a large number of revolution groups as indicated by ellipses 120. N spiral track revolutions 121 (N is an integer that has no relation to the symbol N used in equation (1)) constitute one revolution group. An integral number of addressable tracks 124 are in each revolution group. The track and sector precession is illustrated in group GO, it being understood that groups G1-GK are identical. An anchor sector 115 defines the beginning of each revolution group and is circumferentially aligned with reference position 100. Numeral 122 denotes reference position 100 within each of the revolution groups. Addressable track 128 of GO begins at reference position 100 as an anchor sector 115. The second addressable track in GO is addressable track 129. Addressable track 129 begins at the ending of first addressable track 128. Line 122 shows that reference position 100 (end of a spiral track revolution) dissects second addressable track 129. The angular position of second addressable track 129 is dependent on the angular position of first addressable track 128. Each succeeding addressable track in GO is similarly angularly or circumferentially located. As such, circumferential positioning errors may accumulate as explained in the description of the mastering process. Similarly, at the end of revolution group GO, last addressable track 131 ends approximately at reference line 100. The penultimate addressable track 130 of GO is dissected by, i.e. spans, the reference position 100 as indicated by line 122. As mentioned above, with the exception of the anchor sectors 115 and 116, the angular positions of all the sectors also precess circumferentially. Because of this circumferential precession, some of the sectors span, i.e. are dissected by, reference position 100. Sectors 135 and 138 shown in addressable tracks 129 and 130 span reference position 100, and hence are dissected by line 122 and reference position 100. Fig. 5 illustrates a variation on tracks and sectors per spiral track revolution. Portions of three spiral track revolutions 140-142 are diagrammatically shown. Revolution 140 has 17 sectors 144 and contains one addressable track. Second revolution 141, in a band that is radially outward from spiral track revolution 140, has 18.2 sectors or one addressable track of 17 sectors plus 1.2 sectors from a second addressable track. Third spiral track revolution has P.K sectors (P is an integer and K is a fraction which is not related to any other K in this application) for storing J addressable tracks. J may be any number from 0 (stores only a partial track) to several addressable tracks plus a portion of another addressable track. Spiral track revolution 142 is generalized to show flexibility implementing the embodiment being described. Fig. 6 shows a logical to real address translation scheme that enables full advantage of implementing the embodiment being described. This addressing scheme is based upon the logical addressing found for known types of optical disk. The attaching host processor 37 addresses data on disk 30 using a logical block address (LBA) 149. LBA 149 determines which of the addressable entities, such as sectors, are spare sectors and their respective locations on disk 30. LBA 149 is managed by either one of two algorithms. A first one has been used for optical disks. In this algorithm, the number of entries in LBA 149 is constant for each disk and is based upon the number of addressable entities in the disk designated for storing data. Spare entities are not included in LBA 149. Later described secondary pointers enable addressing spare sectors via LBA 149. A second algorithm for addressing using LBA 149 is used in magnetic flexible diskettes. In this second algorithm, the address range of LBA 149 varies with the number of demarked or unusable sectors and the number of spare sectors. LBA 149 identifies for addressing only the tracks and sectors that are designated for storing data. In the event one of the sectors identifiable by the illustrated address translation becomes unusable, then a later described pointer points to a spare sector that replaces the sector gone bad. Such substitution is well known. All of the addressable tracks on disk 30 are identified in the column 166 labelled "tracks". Dashed line 150 represents that the first LBA address points to a first sector (not shown) in first track 151. Succeeding LBA addresses point to higher numbered sectors in track 151. The translation continues through track boundaries into tracks 152, each lower positioned track in Fig. 6 representing a track having a higher or larger address value. Defective sectors 153 cannot be addressed by LBA addresses. Dashed line 154 shows a given LBA address pointing to a last good sector adjacent a first one of the unusable sectors 153. Similarly, dashed line 155 represents an LBA address value one greater than the LBA address value represented by dashed line 154 pointing to a first good sector immediately adjacent the bad sectors 153 and having a sector number one greater than the highest bad sector number. Therefore, the LBA addressing is continuous. As a result of many bad sectors, the actual addressable track address space is constant. In some applications (first algorithm), such as found in optical disks, the LBA extent remains constant. When so-called floppy magnetic disks are used (second algorithm), the LBA extent decreases as the number of bad sectors increase with time. Other bad sector areas 157 and 161 similarly cause a skipping of the bad sectors for maintaining a continuous LBA address space. Dashed lines 158 and 162 respectively indicate an adjacent good sector immediately adjacent a lowest numbered bad sector in defects 157 and 161. Numerals 159 and 163 respectively indicate a first good sector adjacent a highest numbered bad sector in defects 157 and 161. All spare sectors can be located at the radially outermost track of the disk 30, such as spare sectors 343 in the last portion indicated by dashed line 344 in the radially outermost addressable track. If a sector 341 goes bad during data processing operations, then LBA 149 is updated such that the original pointer 340 to sector 341 is modified. This modification includes adding secondary pointer 342 that points to one of the spare sectors 343. In this manner the pointed to spare sector stores the data originally intended for sector 341. Once an LBA address is identified with sectors in the addressable tracks, track to revolution convertor 164 identifies the spiral track revolution having the addressed sectors and addressable tracks (see Fig. 8). The revolution number is supplied to seek control 165 that generates a seek operation based upon the number of spiral track revolutions needed to be crossed from a currently addressed track being scanned to a target track identified by an LBA address range received from host processor 37. Details of the generated seek operation are described later. A part of the addressing structure includes redirection apparatus for redirecting access requests from a bad or defective sector to an alternative sector. Primary and secondary defect lists 167 and 168 are lists relating to bad sectors. In one algorithm for identifying defective sectors, at the time of disk initialization detected defective sectors are listed in a primary defect list 167. List 167 may include pointers to spare sectors assigned to record or store data intended for the defective sectors. As shown in Fig. 6 such defective sectors can be removed entirely from the address space. Secondary defect list 168 is like the primary defect list but is generated during data-to-day usage of the disk. That is, defects can be detected after shipment of the disk from a factory and placed in the secondary defect list. While separate addressable areas on disk 30 have been used for lists 167 and 168, the two lists can be combined or can remain separate and still be stored in the same addressable area (such as a sector) on disk 30. Different types of medium, e.g. ROM, MO etc, can be handled differently. In a so-called slip mode of formatting, bad sectors are taken out of the LBA 149 address space. In a so-called replace mode of formatting, an alternative sector pointer replaces the pointer to the defective sector or can be in a table wherein the alternative sector pointer is associated with the original defective sector pointer. An important aspect of the embodiment being described is the control of the scanning over the single spiral track across a boundary between two radially adjacent revolution bands. Fig. 7 illustrates the problems and the solutions to such boundary 170 crossing. The radially outward direction is indicated by arrow 169. Reference position 100 is indicated by the vertical line 100 that also indicates the precise boundary 170 between a band "N" and the next radially outward band N+1. The band "N" corresponds to Bn used in later-described equation (1). The track scan is from left to right as viewed in Fig. 7. It is understood that the illustrated portions of spiral track revolutions 173 (having illustrated sectors 178-180), 174 (having illustrated sectors 187-191) and 175 (having illustrated sector 193) are a part of the Archimedes spiral track; the portions of the three spiral track revolutions are shown as being linear only for convenience in making the illustration. In a disk having 16 bands, radially inwardmost revolution 173 (band N) requires a frequency of operation that is about 6-7% lower than the frequency of operation required for band N+1. For bands having identical radial extents, as the number of bands increase, the frequency change decreases. Likewise, as the number of bands decrease, the frequency change increases. Each sector includes the aforedescribed sector portion or field following an intersector gap S 177 and indicated as being adjacent to sector mark M 178. M 178 is constructed as shown in Fig. 3 by sector field 117. M 178 contains the address of the current addressable track being scanned and the number of the sector currently being scanned. Intrasector gap 179 separates the sector field 178 from the data field or portion 180. Sectors 187 and 188 are the last sectors to be scanned in band N before the band boundary 170 has been crossed. Sectors 189, 190 and 191 are the first three sectors to be scanned after the band boundary 170 has been crossed. Sector 188 of band N requires a device operation frequency that is about 6% (see Table 2 for illustrative band frequencies) lower than the device operation frequency required for reading and recording in first sector 189 of band N+1. Such frequency shifting is achieved while traversing inter-sector gap S 186. Gap 186 is also termed an inter-band gap. In an alternative embodiment, inter-band gap 186 may subtend a greater angle than the inter-sector gaps 181 that are not inter-band gaps. Such greater angle requires a greater scan time than required for gap 181. Therefore, after scanning last-sector 188 of band N a greater elapsed time occurs before M field of first sector 189 of band N+1 is reached. This increase in elapsed time between sectors 188 and 189 provides a longer time for the Fig. 9 and 10 illustrated circuits to change frequency. If disk 30 is used in so-called real-time operations, extending the inter-band gap has to be accommodated in signal processing circuits beyond the present description. For reading data recorded in sector 189 (first sector of band N+1), the read-back circuits of each device are adjusted while traversing inter-sector gap 186, so that the circuits are frequency and phase synchronized in field M of sector 189. Traversing intra-sector gap G of sector 189 allows more settling of the readback circuits before the frequency and phase clock synchronization occur for reading data stored in the data field of sector 189. Recording into sector 189 requires a similar procedure as described later with respect to Fig. 10. One alternative approach for inter-band frequency changing is to either denominate sectors 187 and 188 as being spare sectors such that both sectors are scanned over without data transfers. The principles set forth in US -A- 4,814,903 apply in that the spare sectors are used for two different purposes. Yet another alternative approach is to denominate the last sector 188 in each band as not being usable. Then, while scanning an empty data field in last sector 188, more time is provided for shifting the frequency of operation of the device clocks (later described) before accessing first sector 189 of band N+1 at an increased device circuit frequency of operation. Circuits are available to shift the frequency of device circuit operations quickly. Effecting inter-band frequency changing while traversing inter-band gap 186 (Fig. 7) is a best mode of this portion of the embodiment being described. In this latter regard, known readback and recording circuits in high performance magnetic tape drives are rapidly synchronized as the magnetic tape is moving at a speed resulting in a frequency deviation from a required frequency of operation of up to about 20%. Another alternative approach to handle the band boundary 170 crossing is to denominate first sector 189 as being unavailable (spare or not usable). If the fast frequency shifting is not to be employed for any reason it is preferred that the last few sectors, such as sectors 187 and 188 of a band, be denominated as spare sectors. Of course, all spare sectors for each band can be contiguously located near boundary 170 (Fig. 7). In this instance the number of spare sectors can vary between bands. Since radially outer bands having a greater number of addressable tracks and sectors, such radially outer bands may have a greater number of spare sectors. The number of spare sectors in each band can be a constant percentage of the number of sectors in each respective band. The determination of a desired percentage for spare sectors is beyond the teachings of the present description. Fig. 8 illustrates the sequence of steps of a seek operation from a current addressable track to a target addressable track that counts revolution (spiral track groove) crossings to effect the seek operation. The description of the revolution-counting effected addressable-track seek operation is based upon a spiral grooved medium or disk 30 as found in optical disks. Other forms of spiral track revolution indications may be employed. Track to revolution converter (also see Fig. 6) consists of a microprocessor executed set of machine steps 200-205 as next described. In machine step 200 the address of the current track being scanned is converted into a spiral track revolution number. This conversion is effected by microprocessor 40 solving the equations below. First, the band number in which the current addressable track is located (band number is 0-15) is determined: B n = integer of {(1-2N+SR)/2K} wherein B n is the band in which the current addressable track is located. B indicates band and "n" is the number of band in which the current addressable track is located, e.g. numbered from 0-15 in sixteen bands on the disk. N is the number of addressable tracks n band 0 (radially inwardmost band 101 in Fig. 2). K is a constant that indicates the integer increase in number of addressable tracks per band. That is, the increase in number of addressable tracks in a radially outer band as compared to its adjacent radially inner band, e.g. the change in number of tracks from band 101 to 102. As shown in Fig. 7, the increase K is the number of additional addressable tracks found in band N+1 over the number of addressable tracks found in band N. SR is a square root factor defined as: SR is the square root of (2N-1) 2 + (8*T*K) In (2), * signifies multiplication, T is the track number of the current addressable track as set forth in Table 1 above. Next, microprocessor 40 determines the relative addressable track number "t" of track T in band B n , that is, starting with an addressable track in band B n having the lowest addressable track number Tn: t = T - T n + 1 where T n = B n {N + K[(B n - 1)/2]} In calculating the spiral track revolution number, microprocessor 40 computes a revolution factor RF and a band factor BF. Using RF and BF, microprocessor 40 calculates the angular location of the sector S in the revolution of the current addressable track and the revolution number in which the current addressable track resides. First, the calculation of RF is shown as: RF = R [(T*M)+S] where R is the number of spiral track revolutions in band Bn and M is the number of sectors in one addressable track. Band factor BF is calculated as: BF = M[N+(Bn * K)] Then R n = integer {[RF/BF ]+ (B n * R)} where R t is the revolution in which the current addressable track resides, the revolution is in band B n and R is the number of spiral track revolutions per band. As next calculated in machine step 201, the spiral track revolution in which the current addressable track resides is: R t = integer { (R * RF)/(M + BF) + (B n * R) R t is the spiral track revolution in which the current addressable track resides. The other terms are defined above. Machine steps 202 and 203 solve the equations set forth above for the target addressable track. These calculations identify the target band and target revolution on disk 30. Machine step 204 finds the difference between the target revolution and the current revolution, i.e. the radial seek distance expressed in spiral track revolutions. A positive number indicates a radially outward seek while a negative number indicates a radially inward seek. Machine step 205 also modifies the number of revolutions in the radial seek distance to accommodate the circumferential positions of the current and target addressable tracks and the speed of the seek operation as it relates to subtracting or adding revolution counts. This accommodation is a known seek adjustment control for spiral tracks. The pitch of the spiral track versus the speed of the seek determines the accommodation value. Machine step 205 also determines the accommodation of the circumferential positions of the current sector and target sector. Such determination includes solving the other factors of the equations, all as set forth below. The circumferential location of the current and target sectors are first calculated. In the equations below, sector S denotes the current and target sectors in two successive calculations, one for the current sector and one for the target sector. The successive calculations determine circumferential location of the current and target sectors respectively as measured from reference line 100 as an angle expressed in degrees. The circumferential position is expressed as angle A, expressed in degrees: A = 360 {RF/BF} - integer {RF/BF} The determined angles are then used in the above-described accommodation in calculating a true seek distance. Another factor in determining the true seek distance is an extended length inter-band gap 186. If the extension is small, then the extension is ignored. If the extension is long, then the circumferential angle is adjusted to accommodate the inter-band gap length being longer than other inter-sector gaps. The total extra circumferential displacement is determined by multiplying the extended length of inter-band gap (i.e. the added length) by the number of band boundaries 170 crossed in the seek operation yielding a gap product value. The angle of the radially outward sector, either the current or target sector, is increased by the gap product value. Then, in machine step 165, the actual seek operation to the target addressable track using spiral track revolutions is effected. Fig. 9 illustrates a read back circuit, a part of data circuits 75 (Fig. 1), usable with the embodiment being described. In particular, the Fig. 9 illustrated circuit is adapted for efficiently traversing band boundaries 170 (Fig. 7). Table 2 (see above) lists the band frequencies required to be used by the Fig. 9 illustrated read back circuit. This change in frequency between bands is about 6%. Referring now to Fig. 9, lens 45 (Fig. 1) transmits reflected laser light from disk 30 to detector 79 (also shown in Fig. 1). In reading, the disk 30 reflected light is modulated by the stored data. The modulation is a block coded signal that carries information as to its timing, e.g. it is self-timing or self-clocking. Variable gain power amplifier (PA) 210 amplifies the detector 79 supplied electrical signal. Equalizer (EQUAL) 211 processes the amplified signal in a usual manner. A feedback signal is fed back by EQUAL 211 through automatic gain control (AGC) feedback element 212 to PA 210 for automatically adjusting the VGA gain to optimize operation, as is known. The equalized signal also travels from EQUAL 211 to data detector 213 for detecting data from the self-timed or self-clocked readback signal, as is known. Data detector 213 supplies its detected signal to electronic synchronizer 214 for separating the data and clock signals that are respectively supplied over lines 215 and 216 to other usual data and clocking circuits, not shown. Frequency synthesizer 223 times the operation of synchronizer 214 in a known manner. Multiple frequency PLL (phase locked loop) 224 receives a reference frequency signal from oscillator OSC 225. PLL 224 supplies the usual timing signals to synchronizer 214 for timing its operation for separating data from the detected readback signal received from detector 213. The above described read back circuit is a usual read back circuit for optical disks. In accordance with the embodiment being described, a revolution band indication signal is received from microprocessor 40 over line 220, said line 220 which is part of line 76 of Fig. 1. In this regard, microprocessor 40 has programming that effects the calculations set forth herein plus monitors device operation with respect to bands being scanned on disk 30. The band, revolution group, addressable track and sector number being scanned are logged and updated on a real time basis, as is usual practice in peripheral data storage devices of all types. In any event, the band indicating signal (binary 0-15 or 4 bits) drives digital-to-analog (DAC) convertor 221 for adjusting operation of EQUAL 211 to the frequencies shown in Table 2. The digital control signal on line 220 may be a coded control value derived by calculations in microprocessor 40 (not described) in a usual manner from the actual band number. In any event, the value on line 220 drives DAC 221 to produce an analog output signal that varies in accordance with the particular design points of EQUAL 211. If the actual band number is supplied, then circuitry (not shown) in EQUAL 211 and DAC 221 convert the band number signal to a control signal for adjusting EQUAL 211. Equalizer circuits (filter) 211 that are changeable for passing different frequency bands of signals are known and are not described for that reason. Micro-processor 40, upon determining that the scan of a last sector 188 has been completed, switches the line 220 band number signal to the next band N+1 frequency of operation. Whenever the last sector 188 has been denominated as a spare sector (which spare is not storing data) or as an unusable sector, then completion of the data reading in last sector 188 is completed upon reading field M of sector 188. Then EQUAL 211 and DAC 221 have the elapsed time of scanning the last sector 188 data field plus gap 186 to adjust the frequency of operation to band N+1, Microprocessor 40 preferably anticipates circuit delays in operation of DAC 221 and EQUAL 211 by sending the band indicating signal over line 220 before the completion of reading last sector 188. Since read back circuits have frequency tolerances such anticipatory control change enhances the operation of the Fig. 9 illustrated circuit transitions from one band to another band. The shortest elapsed time for changing frequency at band transition 170 is scanning inter-sector or inter-band gap 186 (Fig. 7). DAC 221 continuously supplies its analog control signal to EQUAL 211 such that EQUAL 211 operates in a band of frequencies that PA 210 is supplying. Also during a seek operation, microprocessor 40, before the seek operation has been completed, supplies a band signal on line 220 that is for the band in which the target sector/track resides. Write or record and erase circuit shown in Fig. 10 effects transition from one band N to the next band N+1 over band transition 170 similarly to the Fig. 9 illustrated read circuit. Frequency synthesizer 223 of Fig. 9 also times the operation of the Fig. 10 illustrated write or recording circuit. Microprocessor 40 supplies the appropriate band signal over line 220 to frequency synthesizer 223 at all times. Therefore, frequency synthesizer 223 always generates signals having the correct frequency for a band being scanned. Frequency synthesizer 223 times the operation of write modulator 234 to generate a laser modulating signal on line 78 based upon the data-to-be-recorded received over line 235, such as receiving user data from attaching circuits 38, control and ECC data generated internally by data circuits 75 in a usual manner and in some low end recorders control and ECC data from microprocessor 40. Figs. 11 and 12 illustrate fabrication of an optical disk 30. It is to be appreciated that in fabricating masters and replicas use the known and widely employed mastering and stamping process for making replicas such as disk 30 is used. At step 270 the sector size, spiral track revolutions per radial unit (inches or centimeters) TPI is determined, size of addressable track, the inner and outer radial limits of the recording area of disk 30 (represented by bands 101-106 and in Tables 1 and 2), number of bands (preferably a number to the base 2), number of revolution groups in each band and the extent of each revolution group are all selected. It is assumed in this design step that the preferred embodiment of equal sized bands and revolution groups is being selected, no limitation thereto intended. The radial extents of bands and revolution groups may vary with radius, and the number of revolution groups in a band may vary from band to band. An important part of the design is to set the anchor sectors 115,116 in design step 271. This design step requires consideration of the capabilities of a mastering machine 250 (Fig. 11) to be used in making a master disk from which replica disks can be fabricated. An important aspect of fabricating disk 30 is to limit cumulative tolerances in circumferentially locating sectors on the disk. Such tolerance limiting is achieved by establishing anchor sectors 115, 116 to be precisely circumferentially located at reference position 100. Such precise circumferential location is a part of the design of known mastering machines as next described. Mastering machine 250 includes a precisely mounted and rotated platter 251 upon which a precision glass disk 252 is placed. The platter 251 is mounted on shaft 254 for rotation by a synchronous motor 253. Gearing may separate platter 251 from motor 253 for enabling the use of a more precise bearing support. Spindle 254 has an accurately located index mark 256 (illustrated in an alternative representation 255 of spindle 254) used in the fabrication process to accurately identify circumferential reference position 100 and to accurately locate each anchor sector 115, 116. Mastering machine 250 includes a laser master system 257 that includes precision optics for emitting a master disk ablating laser beam over light path 258. Gearing, not shown, precisely relatively moves system 257 and platter 251 for precisely creating a spiral groove in master disk 252 along with undulations in the groove that precisely identify the sectors, i.e. fields C, T and S of sector field 117 (Fig. 3). The precise locations of sector field 117 of sectors other than anchor sectors 115, 116 are determined by accurately measuring the angular displacement of platter 251 rotation, such as by RPS system 260. Mastering program control 259 is programmed with the design information generated in steps 270 and 271, in a known manner, and in performing machine step 272 responds to RPS system 260, including the critical index mark 256, to actuate laser master system 257 to create the spiral groove with sector marks for creating a master disk 252 usable to create disk replicas having a format as used in the embodiment being described. Once master disk 252 has been created in machine step 272, the quality and completeness of the master disk is verified in testing step 273. Once the master disk is verified, then at fabrication step 274 the Fig. 11 illustrated fabrication continues. Master disk 252 is used in make stamper step 265 to make so-called stampers or dies from which disk replicas can be moulded. Such stampers are usually created by vapour depositing or sputtering a metallic coating on the grooved face of master disk 252. More than one stamper may be made in one session of vapour deposition. The stampers are removed from the master disk, verified and then indicated as being suitable for making replicas. In the make replica step 266, replicas are preferably injection moulded to faithfully reproduce the mirror image of the stamper, i.e. the true image of master disk 252. The mastering machine accuracy in creating sector marks based on angular displacement of the mastering disk provides a format having an anchor sector every seventeen spiral disk revolutions, for example. The circumferential precession of sectors and addressable tracks being linear is precisely controlled by the mastering machine. Either single-sided or two-sided disks can be fabricated. Such two-sided disks may have reversed spiral grooves on opposite recording sides, such as discussed above with respect to Fig. 2. The mastering machine need not be optical. A magnetic servo surface can be recorded using known servo writing techniques. In this instance no replicas are made, except if magnetic printing is employed. In this latter instance, the remanent magnetic field of the master disk supplies a field intensity sufficient for magnetically printing the format on the magnetic disk replicas. Fig. 13 illustrates applying the principles of the embodiment being described to CKD (Count Key Data) formatted addressable tracks. A portion 290 of a single spiral track on a data-storing disk is shown. The circumferential reference position 100 is indicated by two lines enumerated 100. The constant length CKD addressable track has the same size as the addressable track described above for fixed block architecture (FBA) disks having constant capacity addressable sectors. Known CKD tracks are formatted on a disk (not virtual tracks) as one of a large plurality of concentric disk revolutions, also termed tracks. CKD disks utilize a single radially extending index line (usually recorded only on the so-called servo surface of a stack of co-axial co-rotating data storing disks) precisely indicating the disk's circumferential position, and commonly referred to as "index". The single radially-extending index line indicates the beginning and end of each of the CKD tracks. As shipped from a factory, the only indicium on a CKD track is the single index line recorded on the servo surface. Initialization of a CKD disk includes a surface analysis and writing a control record, termed "home address" or HA, on each data recording surface. Every HA is recorded to be immediately circumferentially adjacent the index line of the servo surface as that index is imposed on the data disks via the comb head assembly. Index of each CKD track on all data recording surfaces is determined by the servo surface index line. The placement of HA is such that HA is the first record to be read from any CKD track on the data recording surfaces after scanning the index line on the servo surface. For backward compatibility with the known CKD formatted disks, each addressable CKD track 295 is indicated by a single embossed or recorded pseudo index mark 291. As shown in Fig. 13, one of the addressable CKD tracks 295 has its pseudo index mark aligned with circumferential reference line 100. As such, this CKD track 295-A is an anchor addressable CKD track. HA in such anchor addressable CKD track is termed an anchor HA. Such anchor HA may include a recorded indication that it is an anchor HA. Since in a CKD formatted track there are no sectors, there can be no anchor sectors. As a substitute for the CKD track, an entire track is the above-described anchor HA or anchor addressable CKD track. The CKD required HA record 292 is recorded immediately circumferentially adjacent respective ones of the pseudo index marks. A gap 293 preferably separates each HA from its respective pseudo index mark location. The formatting of the rest of each addressable CKD track area 296 uses the known CKD format. A host processor addressing the addressable CKD tracks finds such addressing to be identical to addressing identical capacity CKD tracks. The circumferential locations of the pseudo index marks precess as described for the sector precessing. Fig. 13 illustrates the circumferential reference position 100 dissecting a second addressable CKD track 295-B in the same manner as described for the FBA formatted addressable tracks and sectors. In a multiple recording surface assembly of co-axial co-rotating disks, the recorded or embossed pseudo index marks are only on the servo surface. Reading the pseudo surface index marks identifies the beginning of each CKD track in the same cylinder of tracks, i.e. CKD tracks having the same radial position. Each revolution group GO-GK (Fig. 4) has an integral number of the addressable CKD tracks. The pseudo index mark at 297 is a full equivalent of the sector field 177 of each anchor sector 115 and 116. The bands 101-106 are the same as for the described FBA formatted addressable tracks. The above described activity for efficiently crossing band boundaries and the mastering processes for CKD formatted addressable tracks are the same as for the FBA formatted tracks. Therefore, the embodiment being described is not limited to any particular track format. Fig. 14 shows scanning sectors on the spiral track. Dashed line box 300 represents microprocessor 40 monitoring the scanning operation. Such scanning can be in connection with searching for an addressable track or a sector of an addressable track, reading, erasing or recording operations or diagnostic/calibrating functions beyond the scope of the present description. In the described FBA formatted disk, the sector numbers indicate end of an addressable track (EOT). With 17 sectors per addressable track, sector 16 is a last sector in each addressable track. As microprocessor 40 detects reading of any sector field 117, microprocessor 40 in machine step 301 checks whether or not the sector to be scanned is sector 16. If the sector being scanned is not sector 16, then EOT is not "near" the current scanning circumferential position. In this instance, microprocessor continues monitoring scanning the spiral track. If at machine step 301 the sector being scanned is sector 16, then EOT is near. If EOT is "near", then microprocessor 40 in machine step 302 checks whether or not one of the addressable tracks is being repeatedly scanned. Such repeated scanning of one addressable track is similar to the stop motion function in spiral track video disk players. It is remembered that in the illustrated embodiment, each addressable track has a smaller angular extent than one revolution of the spiral track. The jump back of lens 45 to scan the revolution having the addressed track being scanned occurs immediately at EOT of such track. The scanning of the remainder of this revolution toward the addressed track is monitored by microprocessor 40. As scanning approaches the addressed track the Fig. 1 illustrated device prepares for reading the addressed track in a usual manner. If a jump back is indicated at machine step 302, then jump back is set to occur at EOT, i.e. at end of the current sector being scanned. Otherwise, microprocessor 40 proceeds to machine step 305 for determining whether or not a band boundary is being approached, i.e. end of the current band (EOB). Note, if there is a jump back at EOT, then the band boundary is never crossed. EOB is detected by microprocessor 40 by comparing the addressable track number with all of the last addressable tracks to be scanned in each of the bands 101-106 in last sector table 308. Last sector table 308 is generated before scanning of the spiral track occurs. Table 1, supra, identifies each last addressable track in each band, i.e. the highest numbered addressable tracks for the bands are last sector table 308 for identifying the last addressable track in the respective bands. As an alternative, microprocessor 40 can calculate the last addressable track in each band on a real time basis. If EOB is being approached, microprocessor 40 at machine step 306 determines which mode (timer or circumferential scan position) of initiating traversal of the band boundary 170 is to be used. Determination of mode selection is beyond the scope this description. If the selected mode requires a time out from the beginning of last sector 188 (Fig. 7) of a band's last addressable track 174, then micro-processor 40 in machine step 311 sets a software time out timer (not shown) for timing the scanning of the last sector 188. Upon the timer timing out in machine step 312, the line 220 signal is changed in machine step 310 for indicating the next band being scanned. From machine step 310, microprocessor continues monitoring the scanning in machine step 300. If the circumferential position mode is detected in machine step 306, then microprocessor 40 monitors for the end of the current sector 188. The detected end of the data field in sector 188 indicates the onset of scanning inter-band gap 186. At this time, microprocessor 40 executes machine step 310. As pointed out above, last sector 188 may be denominated as a non-data-recording sector. In this instance, upon detection of sector field 117 of last sector 188, microprocessor 40 sends a new band signal over line 220. Referring next to Fig. 15, exemplary effects of implementing the embodiment being described on control areas 96-98 of disk 30 are described. Phase-Encoded Part (PEP) area 96 is a usual low density extra wide radially inner-most revolution of the single spiral track. All disk players or drives read PEP area 96 for making an initial evaluation a disk 30 received into a disk receiver (not shown) that places a disk 30 in the Fig. 1 illustrated play or read back position. PEP area 96 has three sectors having embossed or moulded identical disk describing data. Such disk describing data includes capacity, laser related parameter data (power levels, disk reflectivity, type of disk, e.g. ROM, MO etc), and sector size (data storing capacity, e.g. 512 or 1024 bytes). The next radially outer revolutions contain a Standard Format Part (SFP) area 97 having recorded disk describing data (data is recorded by moulding to create embossed recording) at a standard (ISO/ANSI) format and density. The SFP area disk describing data repeats the PEP area 96 stored data plus more detailed data (not required). Each addressable SFP area track is co-extensive with each spiral track revolution, i.e. uses known format. As such, the first sector 320 in each SFP track (not separately shown) has one end circumferentially aligned with reference position 100. As such, each sector 320 identifies the location of reference position 100. The angular extent of the SFP area 97 sectors is usually greater than the sector angles used in the illustrated embodiment, no limitation thereto intended. SFP area 97 has a preset number of SFP area track-revolutions. SFP area 97 is also often used for calibrating laser 67 to each received disk 30. In accordance with the embodiment being described, later-identified linear precessing/ progression format-parameter data is stored in parameters area 325. Such parameter data includes data indicating how to perform a seek operation as set forth in Fig. 8. That is, the linear progression parameter data that indicate circumferential precession of the addressable entities (tracks and/or sectors), linear progression of the number of addressable entities in successively radially outer bands 101-106 on the disk, linear progression of changes in frequency of operation of the device in the respective radial bands, the number of bands, configuration data relating to revolution groups and the like. Relating the above statement to the equations describing the Fig. 8 illustrated seek operation, the symbols N, K, S, B, n, T, t, M, R, RF, SR, BF, etc. are listed in the linear precessing/progression format parameter data area 325. In the event that in implementing the embodiment being described in a manner that results in any non-linear precession or progression in format with disk circumference or radius, then such non-linear parameter data are also includ-ed in parameters area 325. PEP area 96 and SFP area 97 have revolution pitches and formats in accordance with known arrangements. Manufacturing (MFG) area 98 is preferably constructed in accordance with the embodiment being described. The addressable track enumeration uses negative numbers for distinguishing the control area 96-98 from the data storing areas in bands 101-106. The number of addressable tracks in MFG area 98 are preset such that a continuous set of track addresses with increasing negative track numbers extends radially inward to PEP area 96. MFG area 98 has an integral number of revolution groups, one such group is shown as comprising MFG area 98. The data-storing capacity of the sectors, if any, in MFG area 98 can be different from the data-storing capacity of sectors in other areas of disk 30. It is preferred that the data-storing capacity of sectors in MFG area 98 be identical to that used in bands 101-106. Anchor sector 115-M anchors the sectors and addressable tracks of MFG area 98 to reference position 100. Immediately radially outward of MFG area 98 is band 101, numbered 0, having anchor sector 115 as sector 0 of addressable track 0 of all bands 101-106. The interband transition between MFG 98 and band 101 is as described in Fig. 7 for band transition 170.

Claims: A data storage device comprising a circular disk (30), a data storage medium on at least one surface of said disk, a spiral track extending within said storage medium for a plurality of revolutions about the axis of said disk, a plurality of data storing addressable entities disposed on said track, a reference angular position (100) extending radially from the axis of said disk, and said data storing addressable entities being arranged in groups (110-114) extending along said spiral track, characterised in that the addressable entities have physical lengths independent of the length of a revolution of the spiral track such that at least one addressable entity in at least one of said groups spans the reference angular position (100), and wherein a first end of each group is located adjacent to a point of intersection of said reference angular position with said spiral track. A data storage device according to claim 1, wherein the data storing addressable entities are addressable tracks including a plurality of data storage sectors and wherein all of the data storage sectors have the same data storage capacity. A data storage device according to claim 1 or claim 2, wherein the data storing addressable entities include a plurality of data storage sectors and wherein at least one group of addressable entities includes two data storage sectors (115,116) located adjacent to points of intersection of said reference angular position with said spiral track. A data storage device as claimed in any one of the preceding claims wherein the data storing addressable entities include data storage sectors and operations can be performed on the data stored within said data storage sectors using a predetermined frequency of operation wherein the data storage density is such that the frequency of operation required to perform operations on all the data storage sectors in a group is the same. A data storage device according to any one of the preceding claims wherein the data storing addressable entities include data storage sectors and said groups of data storage sectors are arranged in bands (101-108) extending circumferentially relative to the axis of the disk, each group of addressable entities within a given band comprising an equal number of addressable data storage sectors. A data storage device as claimed in claim 5 as dependent on claim 4, wherein the data storage density in different bands is such that a different frequency of operation is required for performing operations on the data in the groups in different bands. A data storage device as claimed in any one of the preceding claims wherein said circular disc is formed with a storage medium on both surfaces of said disc, a spiral track extending within each storage medium about the axis of said disc, and a plurality of data storage sectors formed on each of said tracks. A data storage system comprising at least one data storage device as claimed in any one of the preceding claims and means for performing operations on data stored within said data storage device.

Inventors: JAQUETTE GLEN ALAN, KULAKOWSKI JOHN EDWARD, MCDOWELL JUDSON ALLEN, MEANS RODNEY JEROME, JAQUETTE, GLEN ALAN, KULAKOWSKI, JOHN EDWARD, MCDOWELL, JUDSON ALLEN, MEANS, RODNEY JEROME
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1993
Main classification: G11B20
IPC codes: G11B7, G11B27, G11B20