US 5,477,103 A · Sequence, timing and synchronization technique for servo system controller of a computer disk mass storage device

Abstract

A servo system controller for a disk drive device which includes a rotating mass storage disk incorporates a timing error determining circuit for determining rotational speed variations in the disk from information contained in a servo field recorded in a track. A timing error signal is supplied when the speed variation exceeds a threshold, thus indicating an unacceptable level of speed variation. A digital synchronizer responds to asynchronous servo data signals from the disk to establish a cell clock signal occurring about a normal frequency, a cell during which only one servo data signal will occur, and a cell data signal which occurs during the cell. The cell clock signal clocks logical operations on a synchronous basis, and servo data signals are reliably captured. A concurrence determining circuit determines the degree of concurrence between the predetermined series of cell data signals and an actual pattern of signals derived from the servo field, and recognizes the servo control information from less than complete concurrence of the derived pattern and the actual expected pattern. Normal operation is permitted even through slight inconsistences may be detected, improving data throughput while still achieving an adequate level of error tolerance.

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Claims43

Dependent claims

A servo system controller for a disk drive device including a rotating mass storage disk with a plurality of tracks having data field and servo field information recorded therein, a head to read information recorded in the servo and data fields, and a read/write channel for supplying servo data signals related to the information read by the head, said servo system controller comprising:

a timing error determining circuit responsive to servo data signals derived from corresponding information in sequential servo fields and operative to determine any variation in speed of movement of the information recorded on a track relative to the head between sequential servo fields, and to supply a timing error signal when the amount of variation is equal to or greater than a predetermined threshold timing value;
a digital synchronizer responsive to the servo data signals delivered asynchronously about a normal frequency and operative to establish a regularly occurring cell clock signal occurring at the normal frequency, to establish a cell during which only one servo data signal will occur and during which at least one cell clock signal occurs, and to establish a cell data signal which is related to the servo data signal and which occurs during the cell, the cell clock signal clocking logical operations associated with the cell data signal in said servo system controller;
and
a concurrence determining circuit, including a majority vote detector, responsive to a predetermined series of cell data signals related to servo data signals derived from information within the servo field and operative to determine the degree of concurrence between the predetermined series of cell data signals and an actual pattern of signals corresponding to the same information within the servo field, and to supply a threshold met signal when the degree of concurrence is equal to or greater than a predetermined threshold concurrence value less than complete concurrence;
and wherein:
the timing error signal and the threshold met signal contribute to establishing an operative condition by which to evaluate the accuracy of cell data signals clocked from reading of the data field between sequential servo fields.

3 more elements

A servo system controller for a disk drive device having a rotating mass storage disk with a plurality of tracks having data field and servo field information recorded therein, a head to read information recorded in the servo and data fields, and a read/write channel to supply servo data signals related to the information read by the head, said servo system controller comprising:

a servo decoder responsive to a synch mark signal obtained from corresponding information contained in each sequential servo field of a track and operative to supply a synch mark found signal in response to the occurrence of the information recorded in the track defining the synch mark;
and
a timing error determining circuit responsive to the synch mark signals and operative to count an actual time duration between sequential synch mark signals, to compare the actual time duration to a predetermined normal time duration between sequential synch marks at desired rotation of the storage disk during normal expected operation of the disk drive device, and to develop a timing error signal related to the difference between the actual time duration and the normal time duration, said timing error determining circuit further including:
a counter operative to count a time duration between predetermined corresponding points in sequential servo fields and operative to supply an output count signal related to the absolute value of the amount of difference between the predetermined normal time duration and the value counted between the predetermined corresponding points in sequential servo fields, the predetermined corresponding points in the sequential servo fields having a predetermined relationship to the synch marks in the sequential servo fields;
and
a comparator responsive to the output count signal and a predetermined threshold signal which is related to a predetermined maximum threshold amount of time variation between sequential synch marks to obtain reliability in reading and writing data in the data fields, the comparator operative to supply the timing error signal upon the output count signal exceeding the predetermined threshold signal.

3 more elements

In a disk drive device having a rotating mass storage disk with a plurality of tracks having servo field information recorded therein, a head to read information recorded in the servo field, and a read/write channel to supply servo data signals related to the information read by the head;

an improvement of a digital synchronizer responsive to the servo data signals delivered asynchronously but substantially about a predetermined normal frequency at which the servo data signals would be delivered during desired rotation of the storage disk, comprising:
a clock for supplying a servo clock signal at a frequency which is greater than the predetermined normal frequency of the servo data signals;
and
a servo data synchronizer responsive to the servo data signals and the servo clock signals and operative to establish a cell data signal related to each servo data signal;
a count value determining circuit responsive to a predetermined number of servo clock signals which constitute a cell, the cell being a predetermined time interval at the predetermined normal frequency for obtaining reliable servo data signals corresponding to the servo field information, the count value determining circuit operative to determine a terminal count value related to the number of servo clock signals which occur until the end of the cell and a load count value related to the number of servo clock signals which occur until the end of the cell from the occurrence of the cell data signal;
a window counter responsive to the servo clock signal, the cell data signal, the terminal count value and the load count value and operative to supply a window signal defining the end of a window during which the servo data signals are reliably accepted;
a parameter determining circuit responsive to the window signal, the terminal count value, the load count value, the number of servo clock signals per cell, and the occurrence of the cell data signal, the parameter determining circuit operative to determine a cell end signal describing the end of the cell;
and
a cell clock circuit responsive to the servo clock signal and the cell end signal for deriving a cell clock signal which occurs during the cell data signal and during the window and which terminates at least as early as the end of the cell.

6 more elements

A servo system controller for a disk drive device having a rotating mass storage disk with a plurality of tracks, each track having at least one data field with data field information recorded therein and at least one servo field having servo field information recorded therein, the servo field information including at least one field represented by a predetermined pattern of information, a head to read information recorded in the servo and data fields, and a read/write channel to supply servo data signals related to the information read by the head, said servo system controller comprising:

a first register operative to hold a first value corresponding to a first pattern of servo data signals actually detected from reading the servo field information contained in each servo field;
a second register operative to hold a second value corresponding to a second predetermined pattern of signals corresponding to the servo field information actually contained in each servo field recorded on the mass storage disk;
a detection circuit responsive to the first and second values and operative to compare the first and second values and to determine a degree of concurrence between the first and second values compared and to supply a threshold met control signal upon the degree of concurrence exceeding a predetermined threshold.

A servo system controller for a disk drive device including a rotating mass storage disk with a plurality of tracks having servo field information recorded therein, the servo field including a track number code which is defined by a predetermined pattern of Gray code transitions, a head to read information recorded in the servo field, and a read/write channel for supplying servo data signals related to the information read by the head, said servo system controller comprising:

a digital synchronizer responsive to the servo data signals and operative to establish a regularly occurring cell clock signal, to establish a cell of a time interval for obtaining servo data signals corresponding to the track number code and during which only one servo data signal will occur and in which at least one cell clock signal occurs, and to establish a cell data signal which is related to the one servo data signal and which occurs during the cell, the cell clock signal clocking logical operations associated with the cell data signal in said controller;
a pattern decoder responsive to the cell data signals from the digital synchronizer which relate to servo data signals derived from the track number code and operative to determine a Gray code data signal from the servo data signals corresponding to the information in the track number code;
a track number decoder responsive to the Gray code data signal and operative to establish a track number signal therefrom;
and wherein:
the pattern decoder is selectively programmable to respond to a selected one of a plurality of different Gray code schemes:
the pattern decoder includes a divider circuit for determining the number of cells per Gray code unit in accordance with the selected one of the Gray code schemes;
and
the pattern decoder is responsive to the servo data signals derived from the track number code to supply the Gray code data signals in accordance with the selected one of the Gray code schemes.

5 more elements

Dependencies are inferred from the claim text.

Description18,393 words

Summary1,772 words

#This invention relates to computer mass storage devices having rotating computer disks with servo field control information recorded on the disk, such as by imbedding it in a track on the disk. More particularly, the present invention relates to controlling the timing, sequence of operations and synchronization of a servo system controller associated with a rotating disk mass storage device, thereby enabling improvements in performance associated with reading data from and writing data to the disk. More particularly still, the present invention relates to an integrated circuit implementation of a new and improved servo system controller which allows selection of a plurality of different operational functions associated with controlling a rotating disk computer mass storage device.

#The present invention is related to those described in U.S. patent applications Ser. No. 08/071,773 for INTEGRATED CIRCUIT AND METHOD FOR SERVO SYSTEM CONTROL IN A COMPUTER MASS STORAGE DEVICE, filed concurrently herewith; and Ser. No. 08/071,472 for BURST COMPARISON AND SEQUENTIAL TECHNIQUE FOR DETERMINING SERVO CONTROL IN A MASS STORAGE DISK DRIVE DEVICE, filed concurrently herewith. These related applications are assigned to the assignee hereof. These related applications are incorporated herein by this reference.

#In a rotating disk computer mass storage device, data and control information is typically recorded on concentric tracks on the disk. One type of arrangement imbeds the control information in servo fields. The servo fields are spaced periodically along the length of each track. The servo fields include information which describes the track number, the position on the track, synchronization information, and other information. Between each of the servo fields, data is recorded in a data field. Each servo field is utilized to identify the following data field and to position accurately a head or transducer which reads or writes the data field, among other functions. This type of arrangement is referred to as an imbedded servo field and control system because the servo field is imbedded in each of the tracks, rather than other arrangements which record the servo and control information on separate tracks from those which contain data.

Brief description of the drawings21 figures

#FIG. 1 is a generalized block diagram of a typical rotating disk drive computer mass storage device, including a head disk assembly, a servo system controller, a read/write channel and a connected computer or micro-controller.

#FIG. 2 is an illustration of a disk of the head disk assembly shown in FIG. 1 illustrating recording tracks on the disk.

#FIG. 3 is an illustration of servo and data fields within each recording track of the disk shown in FIG. 2.

Detailed description16,079 words

#A rotating disk drive computer mass storage device 50 incorporating the present invention is shown in FIG. 1. The disk drive device 50 includes a servo system controller 52 which operates in conjunction with a head disk assembly ("HDA") 54. Depending on the architecture of the computer system in which the disk drive device 50 is employed, ultimate control over the device 50 is either from a computer 56, or is from a microcontroller 58 which is in turn controlled by the computer 56. A significant portion of the present invention relates to a servo micro-sequencer and servo decoder, which are incorporated in the servo system controller 52, both of which are discussed in detail below.

#The HDA 54 comprises one or more conventional magnetic disks 60 upon which data may be written to, or read from, by means of a series of magnetic transitions, reversals or dibits recorded on a hard magnetic surface of each disk 60. The magnetic reversals are written (recorded) and read by transducers or read/write heads 62. A spindle motor 64 rotates the disks 60 with respect to the heads 62 while a voice coil motor ("VCM") 66 moves an actuator 68 to position the heads 62 on the disks 60 for reading information from or writing information to the disks 60.

#The magnetic reversals are recorded on the disks 60 in curvilinear concentric patterns known as tracks 70, as shown in FIG. 2. The concentric tracks 70 extend from an inner diameter ("ID") 73 to an outer diameter ("OD") 74 of the recording surface on the disk. The actuator 68 and VCM 66 (FIG. 1) accurately position the heads 62 (FIG. 1) over the tracks 70. Without adequate positioning, it is impossible to achieve reliability in reading data from or writing data to the disk.

Facts

Application

08/072,135Filed 4 Jun 1993

Granted

19 Dec 1995

Term ended

4 Jun 2013

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification3 codes

G11B 19/28
Driving; Starting; Stopping; Control thereof: speed controlling, regulating, or indicating
G11B 19/12
Control of operating function, e.g. switching from recording to reproducing: by sensing distinguishing features of or on records, e.g. diameter…
G11B
Information storage based on relative movement between record carrier and transducer

Description18,393 words

Summary1,772 words

Brief description of the drawings21 figures

#FIG. 2 is an illustration of a disk of the head disk assembly shown in FIG. 1 illustrating recording tracks on the disk.

#FIG. 3 is an illustration of servo and data fields within each recording track of the disk shown in FIG. 2.

Detailed description16,079 words

Sequence, timing and synchronization technique for servo system controller of a computer disk mass storage device

Life of this patent

Sequence, timing and synchronization technique for servo system controller of a computer disk mass storage device

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims43

Description18,393 words

Drawings

Classification3 codes

Life of this patent

Description18,393 words