MICROMINIATURE DISK DRIVE WITH CLAMP HAVING FINGERS FOR RADIALLY POSITIONING A PAIR OF DISKS AND A SPINDLE MOTOR PROVINDING A REDUCED DISK DRIVE HEIGHT.

Abstract: A rigid disk drive information storage device (1, 4) includes a rigid disk (10) having an outside diameter of about 33-34 mm, with a housing having a footprint with a width of about 35 mm and utilizing a rotary actuator (15) for positioning read/write recording elements (5) across the surface of the disk (10). The disk storage devices (1, 4) includes a footprint with length of about 50.8 mm, and includes in one embodiment dynamic head loading apparatus for loading the read/write recording elements (5) into operative relationship with the disk (10). In another embodiment the rigid disk drive (1, 4) utilizes contact start stop loading and unloading of the read/write recording elements (5). An inertial latch (16) prevents rotation of the actuator (15) when the drive (1, 4) is subjected to a rotational force. Back electromotive force generated by spin motor windings is used during power down to unload the read/write recording elements (5) from the disk surface and latch the actuator (15) in parked position.

Description: MICROMINIATURE HARD DISK DRIVE BACKGROUND OF THE INVENTION 10 Field of the Invention This invention relates generally to rigid disk drives, and more particularly to rigid disk drives for pocket, palm-top, and laptop computers. Description of Prior Art 15 The continuing trend toward smaller portable computers has created the need for a new class of miniature information storage devices. Portable applications for information storage devices have resulted in increasingly severe environmental and physical 20 requirements. Small size, low power consumption, environmental endurance, low cost and light weight are characteristics that must co-exist in these applications; they cannot be met by simple extensions of previous technology. 25 Many examples of miniaturized reduced "footprint" disk drives have been described in patents such as U.S. Patent 4,568,988 to McGinley, et al, issued February 4, 1986, Reexa ination Certificate (953rd), United States Patent B14,568,988, certificate issued November 29, 1988, 30 United States Patent 4,933,785, issued June 12, 1990 to Morehouse, et al. The rigid magnetic recording disk utilized in the device, described in McGinley, et al., had a diameter of approximately 3.5 inches. In the Morehouse, et al. device described in that patent, the rigid disks 35 utilized in the drive had a nominal diameter of 2.5 inches. The "footprint" (width by length measurement) of the drive described in the above-noted Morehouse, et al. patent was described as being 2.8 inches by 4.3 inches. That is, the housing used to enclose the rigid disk drive was 2.8 inches wide and 4.3 inches long. A rigid disk drive of that size is generally applicable to computers having a size of 8.5 inches by 11 inches by 1 inch. Another patent describing a relatively small diameter disk was issued June 18, 1991 to Stefansky, U.S. Patent 5,025,335. Stefansky describes a 2-1/2" form factor disk drive utilizing a single rigid disk having a diameter of approximately 2.6 inches. However, these products do not provide the combination of features needed for "pocket," "palm-top" and laptop computers. History has shown that as disk drives become smaller and more efficient, new applications and uses for disk storage become practical. For example, using the disk drive as a circuit board assembly component requires further reduction in the physical size of the storage device as well as unique mounting strategies, issues addressed by this invention. Use of disk drive storage devices in palm-top computers and small electronic devices, such as removable font cartridges for laser printers, require a level of vibration and shock resistance unobtainable with present large disk drives. These new applications require equipment to survive frequent drop cycles that result in unusually high acceleration and shock. It is well known that the force on an object is directly proportional to its mass, therefore reducing mass is an essential strategy for improving shock resistance. Portable equipment also makes stringent demands on the durability and stability of the storage equipment under extreme dynamic, static, temperature and humidity stress. A device of small dimensions by its nature experiences less absolute temperature induced physical dimensional displacements. High humidity, especially during storage conditions, can aggravate a phenomenon known as "stiction" that occurs with conventional disk drives; the transducer head clings to the smooth disk surface, which can stall the spin motor and damage the heads. The greater the power consumption, the larger and Ii 5 heavier the battery pack becomes. Hence, for a given % operating time, power consumption is a primary and unavoidable design consideration for portable devices. In fact, the weight of a portable device is dependent on the total energy required to meet operational mission time. 10 For disk drive equipment energy use is especially important during what is known as standby or power-down modes. Low power consumption also reduces parasitic heat, an important consideration in compact electrical equipment. Reducing the diameter and thickness of the 15 information disk(s) can also provide significant reduction in power consumption during spin up. Modern disk drive power management methods use intelligent decision strategies, evaluating disk drive usage patterns to sequence power saving shut down features. 20 SUMMARY OF THE INVENTION An object of the present invention is to provide a rigid disk drive having reduced physical dimensions, but retaining the storage capacity of larger disk drives, with minimized power consumption and providing extreme 25 resistance to shock and vibration. A further object of the invention is to provide a disk drive having a 1 1/4 inch form factor. In accordance with the invention, a rigid disk drive information storage device is provided which has a base and cover, utilizes 30 one or more information storage disks having a diameter of i approximately 33.5 mm (1 1/4 inches) provides an information storage capacity of at least 20 Megabytes. A disk drive in accordance with one embodiment of the present invention has a length of approximately 51 mm, a 35 width of approximately 35 mm and a height of approximately 10 mm in a stacked configuration with an associated printed circuit board positioned beneath the disk drive. Included is a disk spin motor internal to the housing, and a rotary actuator for positioning read/write transducer elements over the surface of the disk for the recording and play-back of digital information. In accordance with another feature of the invention, in one embodiment the transducer support arm of the disk storage device includes a lift tab which, when operated with a cam, provides a means to load or unload the head from the spinning surface of the recording disk as described in copending, commonly assigned U.S. Patent Application Serial No. 07/629,957 filed December 19, 1990 by James H. Morehouse et al. , entitled "Rigid Disk Drive with Dynamic Head Loading Apparatus", which is incorporated herein by reference in its entirety. In addition, a small form factor disk drive may not be able to produce enough torque to overcome stiction because of the low supply voltage and miniature spin motor component, thus making it impossible to start the disk rotating. Other configurations may use conventional contact start-stop head/disk interface methods. In accordance with yet another feature of the invention, the disk drive includes sampled servo fields pre-recorded on each data track of the disk, which when read back uniquely determine track position and address information as disclosed in U.S. Patent Application Serial No. 07/630,475, filed December 19, 1990 by John H. Blagaila et al. entitled "Servo Field Scheme For High Sampling Rate and Reduced Overhead Embedded Servo System in Disk Drives", and assigned to the assignee of present invention and incorporated herein by reference in its entirety. Further, the disk drive in accordance with the present invention incorporates improvements disclosed in co-pending, commonly assigned U.S. Patent Application (SERVO II) Serial No. 07/765,348 filed on September 25, 1991 by Stephen Cowen entitled "Embedded Servo System With Reduced Overhead", which serves to increase the number of track following and spin motor servo samples which may be taken per unit time, while allowing increased information storage on a track without increased format overhead. The Cowen application is incorporated herein by reference in its entirety. A further object of the invention is to incorporate an improved track following servo system to minimize the effect of mechanical resonances while permitting very high track densities. This servo system, which is described in copending and commonly assigned U.S. Patent Application Serial No. 07/766,478, filed September 25, 1991, by Thomas B. Andrews entitled "Adaptive Runout Compensation for Miniature Disk Drives", incorporates feed-forward run-out compensation by microprocessor control. This application is incorporated by reference herein in its entirety. A further object of the invention is to provide a rigid disk storage system which includes an inertia actuated latch mechanism to prevent the actuator and magnetic transducers from being moved from their parked position resulting from subjecting the disk drive to severe non-operating shocks in the plane of the disk. The inertially operated latch described in copending, commonly assigned U.S. Patent Application Serial No. 07/629,929, filed December 19, 1990, by James H. Morehouse et al. , entitled "Rotary Inertial Latch for Disk Drive Actuator" or the latch described and claimed in copending, commonly assigned U.S. Patent Application Serial No. M-1491-1P, filed September 25, 1991, by James H. Morehouse et al., entitled "Rotary Inertial Latch for Disk Drive Actuator", may be utilized. Both of the foregoing applications we hereby incorporated by reference in their entirety. In accordance with yet another feature of the present invention, the disk drive apparatus has a spin motor which includes a stator having a plurality of windings and a rotor having a plurality of magnetic poles. Stator windings consist of two types, a first type for normal running of the motor and a second winding type used during starting to increase torque and further used during power down sequencing to act as an electromotive force generator providing power to the rotary actuator to unload the transducer elements from the disk surface. When a disk drive operates in a continuous start stop configuration, the electromotive force may be used to park the heads in the landing zone and provide rapid electrodynamic braking of the spin motor to reduce wear and damage to the head disk interface. This feature is disclosed in copending, commonly assigned U.S. Patent Application Serial No. 07/630,110, filed December 19, 1990, by James H. Morehouse et al., entitled "Spin Motor For A Hard Disk Assembly", which is incorporated herein in its entirety. An alternative spin motor is described hereinafter in detail. A further object of the present invention is to provide a disk drive with a spin motor control system that includes a back electromotive force commutation circuit using digital techniques to generate commutation pulses, a start up circuit for starting the spin motor, and a monitor circuit for determining the motor spin direction and making corrections of direction if necessary after a commutation occurs. The spin motor control system preferred for use with the disk drive system described herein is described in copending, commonly assigned U.S. Patent Application Serial No. 07/630,470, filed December 19, 1990 by Michael R. Utenick et al., entitled "Spin Motor Control System for a Hard Disk Assembly", which is incorporated herein by reference in its entirety. Yet another object of the present invention is to provide methods to reduce errors caused by spin motor induced electromagnetic high frequency noise that causes interference with track position sampled data and read back signals. A further object of the present invention is to provide a low profile rigid disk drive having higher storage capacity per volume of the housing than previously available. This feature is disclosed in copending, commonly assigned U.S. Patent Application Serial No. 07/765,352, filed September 25, 1991, by James H. Morehouse et al., entitled "Architecture For Low Profile Rigid Disk Drive", which is incorporated herein in its entirety. Another object of the present invention is to provide a rigid disk drive with increased packaging density and decreased height by placing electronic circuitry in the interior free-volume of the disk drive housing, not swept by elements of the actuator/transducer assembly. A further object of the present invention is to reduce the power consumed by the rigid disk drive by operating the disk drive from a single low voltage supply, such as 3.0 volts DC, rather than 5.0 volts or 12 volts, as is customarily required, thereby allowing improved efficiency when used as a battery powered device. In accordance with another feature of the invention, a digital electronic signal interface is provided for the head disk assembly (HDA) whereby any analog disk drive signals, such as track position servo and read/write signals, are processed within the HDA and converted to digital form, thereby eliminating low level analog signals, minimizing effects of electrical interference and providing an ideal connection means when the disk drive is used as a circuit board component. Another object of the present invention is to provide a removable disk drive storage system which includes an improved shock mounting means as disclosed in copending commonly assigned U.S. Patent Application Serial No. 07/765,349, filed September 25, 1991, by James H. Morehouse et al., entitled "Shock Absorbent Mounting for Disk Drive or Other Component" which is incorporated herein by reference in its entirety. In accordance with another feature of the present invention, a disk drive is provided which includes an improved disk clamp for retaining the disks securely mounted to the spindle. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent from a study of the specification and drawings in which: Figure 1 is an exploded perspective view of a rigid disk drive in accordance with the present invention; Figure 2A is a top-plan view of one embodiment of a rigid disk drive in accordance with the present invention; Figure 2B is a view taken along the lines of 2B-2B in Figure 2A; Figure 2C is a view taken along the lines of 2C-2C of Figure 2A; Figure 2D is a top-plan view of an alternative embodiment of a rigid disk in accordance with the present invention which utilizes a resilient cover and a pluggable connector; Figure 2E is a view taken along the lines 2E-2E of Figure 2D; Figure 2F is a view taken along the lines 2F-2F of Figure 2D; Figure 3A is a top-plan view of a dynamic head loading version of a disk drive in the course of the present invention; Figure 3B is a top-plan view of a contact start-stop version of a rigid disk drive in accordance with the present invention; Figure 3C is a top-plan, highly enlarged view of the inner crash stop for a rigid disk drive in accordance with the present invention; Figure 4 is a cross-sectional view taken along the lines 4-4 of Figure 3B; Figure 5A is an exploded perspective view of the rotary actuator portion of a version of the disk drive in accordance with the present invention which utilizes dynamic loading and unloading and includes an inertial latch; Figure 5B is an exploded, enlarged perspective view of the rotary actuator portion of a rigid disk drive which utilizes the contact start/stop head technology; Figure 5C is a perspective view of cam assembly 18; Figure 6A is a plan view of a load beam utilized in the dynamic head-loading version of a disk drive in accordance with the present invention; Figure 6B is a view taken along lines 6B-6B in Figure 6A; Figure 6C is a view taken along lines 6C-6C in Figure 6A; Figure 6C 1 is a top plan view of a portion of a load beam used in the present invention; Figure 6C" is a cross sectional view taken along lines 6C"-6C" in Figure 6C; Figure 6D is a cross-sectional view taken along lines 6D-6D in Figure 6A; Figure 6E is a cross-sectional view taken along lines 6E-6E in Figure 6A; Figure 6F is a cross-sectional view taken along lines 6F-6F in Figure 6A; Figure 6G is a top-plan view of a load beam used in the dynamic head-load version of drive in accordance with the present invention; Figure 6H is a view taken along lines 6H-6H in Figure 6G showing the load beam in the loaded position; Figure 61 illustrates the load beam in Figure 6H, but in an unloaded position; Figure 6J illustrates the flexure utilized to support the read/write magnetic recording head on the load beam; Figure 6K illustrates in plan view of the underside of a load beam in the contact start/stop version of the disk drive in accordance with the present invention; Figure 6L is a view taken along the line 6L-6L of Figure 6K; Figure 7A is a combined electrical block diagram and partial structural diagram of one embodiment of a disk drive in accordance with the present invention; Figure 7B is a combined electrical block diagram and " partial structural diagram of a disk drive in accordance with an alternative embodiment of the present invention; Figure 8 is a block diagram level circuit for the spin control and drivers; Figure 9 is a circuit diagram of a spin motor drive circuit utilized with one version of the present invention; Figure 10 is a block diagram of the read/write circuitry utilized with the present invention; Figure 11 is a block diagram of the actuator driver and power-off unload circuit utilized with the present invention; Figure 12A is an illustration of a typical sector utilized on a magnetic recording disk of the head disk assembly in accordance with one version of the present invention; Figure 12B is a timing diagram of the window signals produced by the programmable low-power timer circuit of the gate array illustrated in Figure 13; Figure 12C is a timing diagram of the window signals produced by the digital demodulator & Gray code address separator of the gate array circuit of Figure 13; Figure 12D is a timing diagram of the window signals produced by the digital demodulator & Gray code address separator of the gate array circuit of Figure 13; Figure 13 is a block diagram of a gate array circuit which may be used with one embodiment of the present invention; Figure 14 is a block diagram of the A/D & D/A circuitry; and Figure 15 illustrates in block-diagram form the gate array circuit utilized in conjunction with the alternative servo system, the servo pattern of which is illustrated in Figure 12D. DETAILED DESCRIPTION OF THE INVENTION Development and production of miniature laptop and hand held computers is constrained by available disk drives that are either too large, consume excessive battery power (limiting computer operating mission time) or are not rugged enough to withstand the demanding shock and vibration requirements of portable operation. The disk drive described in this invention, combining several unique features, provides a solution to the need for a miniature rigid disk drive information storage device with the performance and capacity previously available only in larger form factors. Present 2 1/2", 3 1/2" or even 1.8" form factor disk drives do not provide the reduced power consumption or the shock and vibration durability of the disk drive described herein. Microminiature hard disk drive 1 in accordance with one embodiment of the present invention is illustrated in Figures 1 and 2A-2C. A portion of the electronics for the rigid disk drive is included internally of the case (or HDA) and a second portion of the electronics is included on the printed circuit board 2, best illustrated in Figure 1. Referring to Figure 2A, the approximate width of rigid disk drive l is 35 mm (measured from peripheral edge 32 to peripheral edge 33) and the depth of rigid disk drive 1 is approximately 50.8 mm (measured from peripheral edge 34 to peripheral edge 35) . Thus, the footprint of rigid disk drive 1 is 35 mm by 50.8 mm. Various heights of the rigid disk drive may be utilized to conform to desired standards, such as, for example, 6.3 mm, 10 mm, 12.7 mm, or 15 mm. Rigid disk drive l may be utilized in a stacked configuration with printed circuit board 2, this configuration being illustrated in Figures 2A through 2C. In this stacked arrangement, the combined depth from the top of rigid disk drive 1 to the bottom of printed circuit board 2 is approximately 10 mm. The head disk assembly portion of rigid disk drive l weighs less than 50 grams, has a sealed conductive housing and cover, enclosing a single (as shown in Figure l) or multiple rigid disks clamped to a combined spin motor and spindle bearing assembly. The spin motor uses flexible circuit interconnect means. Also enclosed in the housing is a rotary actuator mechanism comprising a bearing assembly, magnetic read/write transducers mounted on load beams, a flexible circuit interconnect means, an actuator coil and permanent magnet structure. The disk drive has operating shock limits of 10 G and non-operating shock limits of 200 G. Table 1 below indicates the specifications for micro¬ miniature rigid disk drive 1 in a version utilizing a single platter of magnetic media. The information in parenthesis in the following table are for the translate mode (also known as the emulation mode) for the drive. Table 1 Capacity Formatted Functional Performance Reliability Power +3 VDC + 5V+ 5% Startup Current 0.3 Amps +5 VDC + 5V+ 5% Startup Current 0.5 Amps Typical Heat Dissipation Spin-up 2.5 watts Idle 0.8 watts Read/Write/Seek 1.75 watts Power Savings Mode 0.4 watts Standby Mode 0.030 watts Sleep mode 0.010 watts Environmental Temperature Operating +5°C to +55°C Nonoperating -40°C to +70°C Relative Humidity 10% to 90% non- condensing Maximum Wet Bulb 30°C Shock (11ms) Operating 10 G Nonoperating 200 G Vibration (0 to peak) Operating 2 G Nonoperating 10 G Altitude Operating -1,000 to 10,000 feet Nonoperating (maximum) 40,000 feet Physical Stacked Configuration (HDA & PCB) 10mm x 41mm x 50.8mm Low Profile Configuration: Head Disk Assembly (HDA with one disk) 6.3mm x 35mm x 50.8mm Electronics Card (PCBA) 5mm x 41mm x 50.8mm Weight < 50 grams Preliminary Disk specifications An inertial latch, wh ch s descr bed and cla med in co-pending and commonly assigned U.S. Patent Application Serial No. 07/629,929, filed December 19, 1990, by J. Morehouse entitled "Rotary Inertial Latch For Disk Drive Actuator", which is incorporated herein by reference in its entirety, is used to prevent the actuator/head assembly from becoming dislodged while parked due to high in-plane shock and vibrational forces. This latch provides a locking mechanism that does not increase actuator frictional forces or require additional power to maintain the actuator in the parked position. Hard disk drive 1 operates with a single supply voltage of 3.0 volts or 5.0 volts, with the following 3 volt power specifications: Spin-up 2.5 watts Idle 0.8 watts Read/Write/Seek 1.75 watts Power Saving Mode 0.4 watts Standby Mode 0.030 watts Sleep Mode 0.010 watts Referring to Figure 1, spin motor 3 is of a low power design, and is optimized for low voltage operation. A major problem that must be solved relates to voltage head-room, which is defined as: V_headroom = ( V_supply - RPM x Ke ) where Ke is in units of Volts/1000 RPM. In practice V_supply is less than the power supply voltage because of intrinsic and irreducible switching transistor voltage losses and other parasitic voltage drops, and required RPM is an independent variable, given by elements related to information transfer rates, access time and acceptable power dissipation considerations. Since the only available element design variable is Ke, motor optimization must concentrate on this element. Disk drive 1 employs spin motor 3 that incorporates a stator having two sets of windings. The first set is used in normal running and is optimized to have maximum operating efficiency with the available voltage overhead. The second set of windings is used for two purposes, first to obtain sufficient starting torque with the limited voltage overhead, the second winding is operated in parallel with the first allowing the effective ampere-turns to be increased without increasing Ke, allowing rapid spin up from power saving sleep mode. In the second configuration the first and second coils are connected in series, to provide a back EMF generator during power down to unload the magnetic heads from the surface of the disk and latch the actuator in the parked position. Spin motor 3 may take the form of the spin motor described and claimed in co-pending and commonly assigned U.S. Patent Application Serial No. 07/630,110 of J. Morehouse et al. filed December 19, 1990, entitled "Spin Motor for a Hard Disk Assembly", which is incorporated herein by reference in its entirety. A spin motor control system as illustrated and described in co-pending and commonly assigned U.S. Patent Application Serial No. 07/630,470 of M. Utenick et al. filed December 19, 1990 entitled "Spin Motor Control System for a Hard Disk Assembly", which is also incorporated herein by reference in its entirety is desirably used in conjunction with the above-described spin motor. The complex motor switching task is incorporated in a unique motor commutating integrated circuit. Further motor optimization can be accomplished by increasing the diameter of the rotors and stator which allows reducing the motor thickness as well as achieving lower stator coil resistance. Close proximity of the spin motor to the read-write heads is inevitable because of the small dimensions of the disk drive. Switching noise generated by the commutating of the windings is a major source of high frequency interference. When induced into the transducer heads, this noise results in servo and information errors by interfering with demodulation of the servo and information read signals. This problem is partially addressed by using ferrite shielding members, having high permeability in the region of servo and read signal frequencies, employed on the transducer heads and at critical locations in the HDA. Other methods such as sine wave excitation, synchronous commutation and variable slew rate excitation and synchronous servo demodulation with precisely timed commutation also can be used to minimize the generation unwanted noise spikes. Jitter, or rotational speed variation, is an important design consideration caused by the reduced angular momentum of the miniaturized recording disk. To minimize cogging the number of motor phases can be increased to greater than three or the number of poles can be increased, to 16 rather than 12 for example. Other methods for reducing jitter include closing the spin motor control loop with signals derived from track following sampled sector servo data. Methods which require increased servo sample rates are undesirable if they reduce the disk drive formatted capacity, significantly increase the complexity of the sampling system or require the microprocessor controller to operate beyond its available bandwidth. This invention employs an innovative servo system, described in detail below, which increases the number of samples per second, providing improved error immunity without increasing the servo overhead. Reducing spin motor power consumption is a complex problem. Three factors affect motor power efficiency. First, the motor spindle bearing assembly must have very low non-repeatable run-out, this generally requires the use of a pre-loaded ball bearing cartridge. Friction in this type of bearing is dependent on the amount of pre-load and the type of non-migrating lubricant used. A second element of power consumption is due to electrical losses in the motor. These losses can be minimized by using of high energy, rare earth, magnets and a low loss magnet and pole structure along with low resistance stator windings. A third type of power loss is due to windage losses caused by the spinning disk itself resulting in heat generation by the Joule effect. This source of loss can be minimized by using a single disk of reduced diameter, such as about 1 1/4" disk instead of a 2.5" disk, rotating at the lowest practical speed. Another method to reduce motor starting torque requirements is to implement a method of dynamic loading and unloading the magnetic transducers from the surface of the rotating disk whereby friction due to head disk contact, found in conventional contact start-stop disk drives, is eliminated. A further advantage of this method is elimination of head disk "stiction" that can occur when the heads cling to the disk surface stalling the spin motor or causing damage to the head disk interface. Further, in order to minimize battery power in portable computing equipment, disk drives are subject to many more power-down and parking cycles are experienced than is typically expected in larger systems. Dynamic head loading and unloading provides increased longevity of the head/disk interface by allowing more than 1 million power down cycles without degradation due to friction and wear of the transducers and disk information surface, compared with 20 thousand cycles for conventional contact start-stop configurations. Rigid disk drive 1 may utilize the dynamic head load/unload structure of the type described and claimed in co-pending and commonly assigned U.S. Patent Application Serial No. 07/629,957 of J. Morehouse et al. filed December 19, 1990 entitled "Rigid Disk Drive With Dynamic Head Loading Apparatus", which is incorporated herein by reference in its entirety. An alternative dynamic head loading structure, which is fully described hereinafter in Figures 6A through 61, may also be utilized in hard disk drive 1. In an alternative embodiment of the present invention, microminiature hard disk drive 4 (illustrated in top plan view in Figure 3B) utilizes the contact start/stop technique in which the heads are parked on a portion of the disk surface, which ideally is not used for information storage, and which also may be textured in order to minimize the clinging of the heads to the disk. Implementations of this type are known as contact start/stop operation whereby the transducer heads land, take off and are parked on the disk surface as previously mentioned. Rigid disk drives 1 (Figs. 1 and 3A) and 4 (Fig. 3B) utilize embedded servo and a track following sampled servo system designed to withstand increased shock and vibration while making possible increased information track densities, for example 3,000 tracks per inch, required to obtain the information storage capacity found in larger disk drives. Further, while more servo samples per second are required to improve servo performance, increased servo overhead cannot be allowed to significantly reduce usable storage capacity. As previously mentioned, an improved servo pre-recorded pattern and demodulation scheme is employed that increases the number of servo fields and information sectors from 48 to 72 per revolution without increasing the relative overhead. These and other improvements are possible by using unique multi-function servo field mapping used in an embedded servo system, which is described and claimed in portions of the servo pattern layout illustrated herein in Figures 12D. The entire servo system is described and claimed in the above- mentioned U.S. Patent Application Serial No. 07/765,348, which is co-pending and commonly assigned, which application is incorporated by reference in its entirety. Alternatively, the servo system described and claimed in co-pending and commonly assigned U.S. Patent Application Serial No. 07/630,475 of J. Blagaila et al. filed December 19, 1990 entitled "Servo Field Scheme For High Sampling Rate", which is also incorporated herein by reference in its entirety, may be utilized in practicing the present invention. Another problem with track following servo systems employed in high density disk drives is what is known as settling time, defined as the time after arrival on track when the transducer head position is centered on the track. Common practice has been to use a fixed timer to delay the onset of writing until a time greater than the worst case settling time has elapsed. Since many track seeking operations use short seeks resulting in rapid servo settling time, unnecessary delays can occur when reading or writing information. This problem is particularly severe when the disk drive is subjected to severe shock while reading or writing information resulting in unacceptably slow recovery time. This problem is addressed by incorporation of an adaptive method whereby the servo system determines, by way of preset limit conditions, if the transducer is on-track and settled within acceptable limits. Further advantages of this method are that the position servo stiffness, which is determined by the servo gain and bandwidth, can be reduced in order to avoid excitation of mechanical resonances that occur in conventional systems. Other adaptive means to improve track following without requiring increased servo bandwidth and sample rate are run-out and thermal compensation by microprocessor control. Disk drives that employ an embedded sampled servo system cannot read or respond to track position information while writing contiguous sectors of information without significant overhead. The present invention incorporates staggered servo patterns, a dual read channel, and provisions for a head on another disk surface to read and supply data to the track following servo system. This method results in improved track following accuracy, noise immunity and spin motor velocity control. Rigid disk drives 1 and 4 utilize miniature read/write transducers 5, known as 50% heads, which have mean dimensions approximately one-half those of the previously known thin-film heads. Read/write transducers 5 may be ferrite monolithic or composite type devices employing various writing and reading gap structures such as metal-in-gap (MIG) . Other types of heads such as thin-film ring or magneto-resistive types may be employed. Advantages of 50% sliders are decreased foot print, allowing more information tracks to be placed on a disk, lower susceptibility to EMI, and less than one-eighth the mass of conventional sized heads proportionately reducing displacement forces when accelerations due to external shocks and impacts are encountered. In order to maintain high recording density from inner to outer tracks, heads with nearly constant flying height are used, employing modified air-bearing designs such as TPC, cross slot designs and negative pressure methods, allowing mapping of additional information sectors at outer radii to achieve increased areal storage efficiency. Read/write transducers 5 are illustrated in Figures 1, 5A, 5B, 6H, 61, 6K and 6B. Improvements in VLSI semiconductor technology, combined with other benefits derived from using a disk having a diameter of about 33.5 mm (1 1/4 inches), have reduced component count and power requirements. This has made it possible for servo, read/write and spin motor control electronics to be incorporated within the housing of rigid disk drives 1 and 4 as part of the internal disk drive assembly flexible circuit interconnect. Using TAB or COB (Chip On circuit Board) techniques automated assembly methods and higher circuit densities are practical at reduced cost. Increasing the number of electronic components in the disk drive assembly housing reduces the number of external components, resulting in greater effective volumetric packaging density, reduced spin motor noise pickup, shielding of critical analog circuits from interference from external noise sources, and reduction in the required number of external interconnects. This feature is described in detail in conjunction with Figure 7B. An important object of this feature is to eliminate external analog signals by digital signal processing within the disk drive enclosure, thereby providing for an all digital interface between the components within the disk drive enclosure and the disk drive components which are external of the disk drive housing. The computer system interface to disk drives 1 and 4 may be any of a number of industry standard types such as low power SCSI or AT Bus. One implementation of the digital disk drive assembly interface such as illustrated in Figure 7b allows direct circuit board interconnection to the host computer, providing smaller disk drive package volume, fewer electrical interconnections, and reduced power consumption by the elimination of complex bus interface. System physical interconnect means for such a small disk drive have become a major problem as the size of available connectors approaches that of the disk drive. One solution is to use flexible circuit connection means, where the terminating end is either soldered directly to the host or to a zero insertion force flex circuit connector. As disk drives have been reduced in size their physical mounting has become a problem. Present methods require special mounting hardware, such as the miniature screws employed in making watches, which are impractical to use in mass produced electronic assemblies. This invention anticipates methods such as clam-shell or trapped mounting thereby entirely eliminating the need for conventional mounting means. This invention also incorporates features described and claimed in co-pending and commonly assigned U.S. Patent Application Serial No. 07/630,136 of J. Morehouse et al. filed December 19, 1990, entitled "Shock Absorbent Mounting Arrangement For Disk Drive or Other Component", which is incorporated herein by reference in its entirety. Referring to Figure 1, microminiature hard disk drive 1 is illustrated in exploded perspective in view, along with printed circuit board 2 which is positioned beneath hard disk drive 1. Rigid disk drive 1 includes baseplate 6 which may be comprised of cast aluminum material. Baseplate 6 is a solid unitary structure which it includes an opening 7 which is, after assembly, closed by the mounting of spin motor 3, the peripheral edge of which extends slightly beyond the edge of opening 7. In addition to opening 7, an opening 8 is provided to permit air flow between the interior of the enclosure and the exterior. A suitable air filter 9, having an external diameter larger than the internal diameter of opening 8 is sealed to baseplate 6 to filter the air which enters the enclosure to prevent contaminating the interior of the disk drive. A substantially flat magnetic disk 10 is supported on spindle 11 for rotation. Magnetic disk 10 is suitably attached to spindle 11 to the use of a disk clamp 12. Although various forms of clamping mechanisms may be utilized to securely attach magnetic disk 10 to spindle 11 of spin motor 3, a particularly advantageous disk clamp is described and claimed in copending and commonly assigned U.S. Patent Application Serial No. 07/765,358 of James Dunckley, filed September 25, 1991, entitled "Clamp for Data Storage Disk", which is incorporated herein by reference in its entirety. Spin motor 3 may take the form of, for example, the spin motor which is described ai.d claimed in copending and commonly assigned U.S. Patent Application Serial No. 07/630,110, filed December 19, 1990, further details of which are described above. Magnetic recording disk 10 comprises a thin film surface, with coercivity greater than 1500 Oe, coated with materials such as Co-Ni or Co-Cr-Ta alloys, applied to both sides of a rigid substrate by methods such as RF sputtering or plating. The substrate used with magnetic recording disk 10 is preferably about 0.445 mm thick, with very flat, smooth, surfaces and with good mechanical rigidity. Examples of suitable substrate materials are aluminum alloys, glass and ceramic materials. Disk 10 has an outer diameter of about 33.5 mm, a center hole 13 with a diameter of about 10 mm. The data zone utilized is positioned between the radii of 9.4 mm and 15.5 mm. Magnetic read/write transducers 5, one supported on load beam 14-1 and one on 14-2, are positioned above the recording and playback surface of rigid disk 10 utilizing rotary actuator assembly 15, which will be described more fully during the detailed description of that assembly in connection with the drawing Figure 5A. A rotary inertial latch assembly as described and claimed in U.S. Patent Application Serial No. 07/629,929, more fully identified above, may be utilized to prevent the unwanted movement of the magnetic heads across the surface of the disk when the drive is bumped or jarred. In Figure 1, an alternate construction of an inertial latch mechanism is illustrated. Inertial latch assembly 16 in Figure 1 will be more fully described and illustrated in connection with other figures. Rotary inertial latch assembly 16 is fully described in U.S. Patent Application Serial No. 07/765,353 referred to above. Read/write transducers 5 which are supported on the ends of load beams 14-1 and 14-2 are dynamically loaded and unloaded from the surfaces of magnetic disk 10 through the use of a load tab 17 which is integrally formed at the free end of load beams 14-1 and 14-2. The details of load beams 14-1 and 14-2 and load tab 17 are described more fully hereinafter in connection with Figures 6A-6I. Cam assembly 18, in conjunction with load tab 17, on each of the load beams provide for the dynamic loading and unloading of write/read transducers 5. As pointed out above, an alternative to the dynamic head loading illustrated in the figures herein is the use of the dynamic head load structure in the above described U.S. Patent Application Serial No. 07/629,957, as well as using contact start stop techniques. Feedthrough connector 19 mounted on baseplate 6 includes a plurality of terminals 20 which extend through baseplate 6 and provide connection between the electronics internal of the HDA portion of disk drive 1 and those external to the HDA. For example, printed circuit board 2 includes various electrical circuitry, which will be more specifically described hereinafter in connection with Figures 7A and 7B. Within the housing of microminiature hard disk drive 1, read/write preamp circuitry is included on read/write integrated circuit chip 21, and the signals to and from read/write preamp IC chip 21 are provided to the external portion of hard disk drive 1 utilizing connector 22 which interfaces with pins 20 on feedthrough connector 19. Signals to and from spin motor 3 are provided via flat cable 23, one end of which is connected to spin motor 3 and the other end of which connected to connector 24. Connector 24 plugs onto some of pins 20 of feedthrough connector 19 to pass signals to and from the exterior of the housing of miniature hard disk drive 1. Included in rotary actuator assembly 15 is an inner crash stop assembly 25 which provides the crash stop function to prevent read/write transducer heads 5 from crashing into the inner portion of the rotary disk and spindle and thereby damaging the heads and/or the magnetic recording surface. Inner crash stop assembly 25 is illustrated in detail in Figure 3C which will be described later herein. The interior of hard disk drive 1 is enclosed utilizing top cover 26, a suitable gasket (not shown in Figure 1). Top cover 26, which is composed of die cast aluminum, is held securely in place on baseplate 6 utilizing suitable mounting screws, not shown. In a stacked configuration, printed circuit board 2 is supported beneath baseplate 6 utilizing suitable fastening means (not shown) . Gasket 27 is illustrated in the cross- sectional view of microminiature hard disk drive 4, shown in Figure 4. Female connector 28 on printed circuit board 2 is positioned directly beneath the lower portions (not shown) of pins 20 to couple signals from the interior of hard disk drive 1 to the printed circuit board 2. Male connector 29 provides direct connection from the HDA of disk drive 1 and the electronics located on printed circuit board 2 to the system with which rigid disk drive 1 and its associated electronics are connected. The interface between hard disk drive 1 and the system in which it will be used may take various forms, such as SCSI, microchannel or AT Bus. In Figure 1, integrated circuits 30 and 31 on printed circuit board 2, as well as others not shown, implement the external drive electronics which is illustrated in block diagram form in Figure 7B. Referring to Figure 2A, a top plan view of hard disk drive 1 stacked above printed circuit board 2 is illustrated. The width of hard disk drive 1 is measured from peripheral edge 32 to peripheral edge 33 is approximately 35 mm. The length of hard disk drive 1, as measured from peripheral edge 34 to rear peripheral edge 35 is approximately 50.8 mm. In Figure 2A, hard disk drive and its associated printed circuit board 2 are illustrated in a stacked configuration in which printed circuit board 2 is directly beneath hard disk drive 1. As pointed out earlier herein, the side to side rear dimensions in the stacked version, as measured from rear peripheral edge 33 of hard disk drive 1 to left edge 36 of printed circuit board 2 is approximately 41 mm. Figure 2B is a view taken along lines 2B-2B of Figure 2A. The height of hard disk drive 1 and printed circuit board 2 mounted in the stacked relationship, with the height measured from top surface 37 of hard disk drive 1 to the lower surface 38 of printed circuit board 2 is approximately 6.3 mm. Tall electrical components can be placed on printed circuit board 2 to take advantage of cavities or pockets in baseplate 6, thereby facilitating the low profile packaging. Figure 2C is a view taken along lines 2C-2C of Figure 2A. Referring to Figure 2D, a top plan view of an alternative embodiment of the present invention is illustrated. In Figure 2D, a disk drive in accordance with the present invention is enclosed within a resilient cover 39 which encases and provides shock mount protection for the hard disk drive included within resilient cover 39. Resilient cover 39 includes gripping surface 40 to facilitate easy insertion and removal of the package into a plug relationship with a host computing device. For example, as illustrated in Figure 2F, which is a view taken along lines 2F-2F in Figure 2D, electrical connector 41 which includes a plurality of pins, and extends from one edge of the disk drive included within resilient cover 39, provides electrical connection between the hard disk drive included within the cover and the host computing device which communicates with the removable disk drive enclosed within cover 39. Figure 2E is a view taken along lines 2E-2E of Figure 2D, and illustrates in side view the hard disk drive which is enclosed within cover 39. The resilient cover 39 and the pluggable feature of the disk drive are described and claimed in U.S. Patent Application Serial No. 07/M-1490-1P of J. Morehouse et al. filed September XX, 1991, and entitled "New Shock Mount And Removable Storage Device Incorporated Therein", which is incorporated herein by reference in its entirety. Microminiature hard disk drive 1 is illustrated in Figure 3A in the top plan view, with the top cover 26 removed for illustration of the components. In Figure 3A, load beam 14-1 and its associated read/write transducer is illustrated in a parked position off the disk and in its innermost position of travel. In the hard disk drive 1 structure dynamic head loading is utilized and therefore when the disk drive is powered down and, i.e., not rotating, load beams 14 and 14-1 and 14-2 (not shown) one moved to the position illustrated where lift tab 17 is in a parked position on cam assembly 18 to prevent the read/ rite transducer heads from interfering with or damaging the disk surface. As will be appreciated by referring to the drawing, when the actuator has moved the heads to the unloaded position, projection 42 from coil support extension 43 is positioned for engagement with the free end of inertial latch 16' in the event of a shock to the drive. In the event of a shock, inertial latch 16' will move such that its free end will engage with projection 42 on actuator coil support extension 43 and prevent the actuator, and accordingly the read/write heads, from moving across the surface of the disk. The details of the rotary actuator and body are described and disclosed more fully hereinafter with respect to Figure 5A for the dynamic head loading version and Figure 5B for the contact start/stop version of the drive. It will also be appreciated by viewing Figure 3A that inner crash stop assembly 25 (which will be described fully hereinafter in the explanation of Figure 3C) prevents the actuator from moving more fully then the most inwardly disclosed position in Figure 3A. Also illustrated in Figure 3A is read/write analog integrated circuit 21 and connector 22 which is positioned over feed through connector 19 (not shown since it is beneath connector 22) . In the same general area, it will also be recognized that flat cable 23 and connector 24, which provides electrical connection from the spin motor to the pins on feed through connector 19, is also illustrated. Flex cable 44 is utilized to transmit the signals from the read/write recording head to read/write preamp chip 21 is illustrated in the lower left-hand corner of drive 1. Also included in the HDA housing is recirculating filter 150 to filter the air within the interior of the housing. Details of the rotary actuator mechanism will best be appreciated by reference to Figure 5A which is an exploded view of the corner portion of hard disk drive 1 where the rotary actuator is positioned. Rotary actuator assembly 15 is of the moving coil type, that is a magnet is maintained in a stationary position and the movable portion of the actuator includes coil 45 which is supported on coil support extension 43 of actuator body 46. Included in actuator body 46 is a bearing assembly 47 for rotatably supporting actuator body 46 about pin 47 which is connected to base plate 6. Also illustrated in Figure 5A is upper load beam 14-1 and lower load beam 14-2 5 which are rigidly supported on actuator body 46 for rotation and positioning of read/write transducers 5 above the surface of disk 10. It will also be noted that load tabs 17 extend from the free ends of load beams 14-1 and 14-2. The flux field is established through actuator coil 10 45 through the use of magnet 48, which is supported on top plate 49 to position the magnet 48 above the top surface of actuator 45. Lower plate 50 of the magnet assembly provides the lower portion of the flux path in conjunction with the down turned portion 51 of top plate 49. Inner 15 crash stop assembly 25 with preload pin 52 is positioned between top plate 49 and lower plate 50. As pointed out above, the inner crash stop prevents the rotation of rotary actuator beyond a predetermined inner travel to prevent the read/write transducer heads from travelling 0 into an unburnished portion of the disk surface or hitting HDA components. Inertial latch 16' is supported for rotation on base plate 6 by inertial lock sleeve 53, the inner portion of which is supported on pin 54 and the outer portion of which is fitted within the aperture of 5 inertial latch 16'. Further details of the rotary latch mechanism are found in the above-identified patent applications of Morehouse et al. U.S. Serial No. 07/629,929 and U.S. Patent Application Serial No. 07/765,353. 0 Better appreciation of the cam assembly 18 will be gained by reference to Figure 5C. Referring concurrently to Figures 3A and Figure 5C, it will be appreciated that load tabs 17 in cooperation with cam surface 18-1 cooperate to move the load beams, and accordingly the 5 read/write transducer heads, above the surface of the disk when the rotary actuator is moved into the unloaded position as illustrated in Figure 3A where load tab 17 is at a rest position above surface 18-1 of cam assembly 18. The lower cam surface (not shown) of cam assembly 18 is substantially identical to the upper cam surface 18-1, and therefore in cooperation with load tip 17 on load beam 14- 2 moves the lower read/write transducer away from the lower surface of disk 10. Inner crash stop assembly 25 is illustrated in a highly enlarged scale drawing in Figure 3C. For this illustration, top plate 49 is not shown in Figure 3C, and additionally a portion of the top of inner crash stop block 55 has been removed. Inner crash stop assembly 25 includes inner crash stop spring 56 which is positioned between legs 57 and 58 of inner crash stop block 55 and the inner peripheral surface of preload pin 52. As will be appreciated by reference to Figure 3C, inner crash stop spring 56 is preloaded by the inner peripheral surface of pin 52 in combination with legs 57 and 58. As illustrated in Figure 3C, actuator body 46 includes inner crash stop contact tab 59 which extends from the edge of actuator body 46 and as illustrated by the arrows in Figure 3C comes into contact with contact inner crash stop spring 57 when the actuator is moved to position the heads toward the innermost portion of magnetic disk 10. The contact between inner crash stop contact tab 59 and inner crash stop spring 56 cushions and stops the inner travel of the actuator to prevent the heads from hitting other HDA structural elements. Referring to Figure 3B, microminiature hard disk drive 4, which is implemented in the contact start/stop version, is illustrated in top plan view. By comparing Figure 3B with 3A, it will be appreciated that a number of common structural elements exist in the dynamic head loading version illustrated in Figure 3A and the contact start/stop version illustrated in Figure 3B. Of course, in contact start/stop version the load tabs in the cam assembly is not required since the read/write transducers take off and land on the surface of a recording disk 60. Recording disk 60 differs from recording disk 10 used in hard disk drive 1 in that a take off and landing zone, bounded by dashed lines 64 and 62 (3B) on the surface of recording disk 60, is provided. Other portions of hard disk drive 4 which are also commonly used in hard disk drive 1 includes inner crash stop assembly 25, flat cable 23 which is coupled between connector 24 in the spin motor, connector 22 and read/write pre-amp integrated circuit chip 21. Also illustrated in flex cable 44. A rotary latch may also be utilized with this embodiment, although one is not shown in this figure. In Figure 5B a highly exploded and enlarged view of the actuator assembly 15 used in microminiature hard disk drive 4 is illustrated. As will be appreciated by reference to the figure, various common elements are used in this actuator assembly which are in common with actuator assembly illustrated in Figure 5A for the dynamic headload versions. Common structural elements are indicated by the same reference characters as used in previous figures. By reference to Figure 5B, it will of course be appreciated that upper load beam 63-1 and lower load beam 63-2 do not include loading tabs since none are required for the contact start-stop version. Load tabs may be used in the contact start-stop version during initial assembly head loading operation. However, the read/write recording heads 5 could be different than those utilized in the dynamic head loading version. To better appreciate the explanation of the structural characteristics of hard disk drive 4, concurrent reference with Figure 3B and Figure 4 (which is a cross-sectional view of hard disk drive 4 taken along the lines 4-4 in Figure 3B) will be helpful. Rigid disk 60 is supported for rotation in baseplate 6 by a brushless DC spin motor. A detailed description of one brushless DC spin motor suitable for use with this disk drive is included in copending above-described U.S. Patent Application Serial No. 07/630,110. Portions of this motor will also be described herein for the purposes of illustration with regard to hard disk drive 4. Referring to Figures 3B and 4, the brushless DC motor includes a stator portion having three lamination portions 64, each of which has windings 65. The stator portion is supported on baseplate 6. Rotor 66 is rigidly affixed to shaft 11 which is supported in baseplate 6 utilizing a bearing assembly, the bearings of which are indicated at 67. Permanent magnet ring 68 is supported in operative relationship to the plurality of lamination portions 64 and windings 65, with permanent magnet ring 68 being supported on lower portion 69 of rotor 66. Rigid disk 60 is supported on rotor 11 for rotation therewith by clamp ring 12 which is pressfit onto rotor 11. The details of the start-up commutation as well as direction detection for the spin motor fully described in the above referenced U.S. Patent Application Serial No. 07/630,470. Load beams 63-1 and 63-2 of actuator assembly 65 pivots about center of rotation 70. Load beam 63-1 supports at its free end, adjacent to disk 60, in this Figure, read/write transducer 5. Referring to Figure 4, this cross-sectional view illustrates the utilization of down load beam 63-1 which supports read/write transducer 5 which is positioned above the upper surface of hard disk 60. Also illustrated in Figure 4 is up load beam 63-2 which supports read/write transducer 5 which is positioned adjacent to the lower surface of rigid disk 60. The respective terms "up" and "down" with regard to the load beams are utilized to indicate the operative orientation of the read/write transducer associated with the load beam. For example, down load beam 63-1 is so named because the read/write transducer associated with that load beam is facing downwardly as viewed from the position of hard disk drive 4 in Figure 3B. Similarly, up load beam 63-2 is so denominated because the read write transducer included on up load beam 63-2 is facing upwardly. As is best illustrated in Figure 4, upper load beam 63-1 and lower load beam 63-2 are supported for rotation about center of rotation 70 by actuator body 46. Actuator body 46 is rotatably supported on baseplate 6 by a suitable bearing assembly 47 which includes actuator bearings 71. It will of course be recognized by those skilled in the art that the head positioning mechanism used in hard disk drive 4 is of the moving coil rotary actuator type. Actuator coil 45 is provided with appropriate driving signals to position the read-write recording elements over the appropriate track based on commands received from actuator driver circuits which will be described hereinafter. Permanent magnet 48 in conjunction with lower plate 50 and upper plate 49 provide a magnetic flux field across actuator coil 45. To reduce the height of head disk assembly 1, a single permanent magnet (permanent magnet 48) is utilized in conjunction with upper plate 49 and return plate 50. The physical size and shape of actuator coil 45 is determined in part by the available clearance and space within baseplate 6, and will be appreciated by reference to Figures 3B, 4 and 5B. From an electrical standpoint, the number of turns and the gauge of the wire used in actuator coil 45 are provided such that the resistance of actuator coil 45 is approximately the same as the resistance of the spin motor. It is important that this relationship be established since during power down the back EMF of the spin motor in dynamic head load-unload version of hard disk drive 1 is used to drive the actuator coil and move the head gimbal assembly into the unloaded position as illustrated in Figure 3A. This equal resistance relationship is also important because for a given coil geometry the unload torque generated is at a maximum when the wire size and number of turns produces a coil resistance equal to the resistance of the series combination of the two spin motor windings plus circuit and trace resistances. To protect the components in hard disk drive 1 and hard disk drive 4 from contamination by particles which could among other things, cause a head crash, top cover 26 is sealed to baseplate 6 by providing appropriate interfitting relationship between top cover 26, baseplate 6 and the utilization of a resilient gasket 27 (Figure 4) . Gasket 27 extends around the periphery of baseplate 6 as illustrated in Figures 6 and 8. Referring to Figure 4, it will be noted that peripheral edge 72 of top cover 26 extends around the periphery at top cover 26 fits with peripheral edge 73 of baseplate 6. To reduce the electrical interference from spin motor 3 to lower read/write transducer, shield 74 is positioned on baseplate 6 as illustrated in Figure 4. Shield 74 is preferably composed of a high permeability ferrite material which shunts the EMI at the frequency of the pass band of the recording channel. Cover 7 is secured to baseplate 6 using suitable fastening means. The above-described spin motor is controlled by spin control and driver circuit 74 which is illustrated in block diagram form in Figure 8. Spin control and driver circuit 74 may be implemented an Allegro Micro Systems Inc. , part number ULM 8902 denominated "three phase brushless DC motor drive with back-EMF sensing", which is illustrated in Figure 8 in block diagram form. Alter¬ nately, the spin control and driver circuit 74 may be implemented as described in copending and commonly assigned U.S. Patent Application Serial No. 07/630,470 filed December 19, 1990. As an alternative to the spin motor described in the above-identified patent application, a parallel wound spin motor may be utilized. In a parallel wound spin motor there are two windings on the stator, both wound in the same direction. With the parallel wound motor, spin motor drive circuit 75, illustrated in Figure 9, is utilized to start and run the motor. A description of the operation of spin motor drive circuit 75 is as follows. START MODE : During start mode more torque is required. The six motor windings are connected such that 3 motor phases are made with each phase having two windings in parallel. Also, bipolar drive is used so that two phases are energized at one time. If desired unipolar drive can be used. Bipolar Mode: In start mode transistors Q7,8,10,11,13,14 are conducting. This places motor windings Phase Al, A2 in parallel, Phase B1,B2 in parallel and Phase C1,C2 in parallel. Transistors Q9,12,15,16,17,18 are non¬ conducting. Transistors Ql,2,3,4,5 and 6 are toggled in the normal six step sequence to rotate the motor. The sequence is: Step l: Ql and Q4 are conducting while Q2,3,5 and 6 are non-conducting. Current flows from V cc through Ql, Phase A1,A2, Phase B1,B2 and Q4 causing a positive torque to be generated. Step 2: Ql and Q6 are conducting while Q2,3,4 and 5 are non-conducting. Current flows from V cc through Ql, Phase A1,A2, Phase C1,C2 and Q6 causing a positive torque to be generated. Step 3: Q3 and Q6 are conducting while Ql,2,4 and 5 are non-conducting. Current flows from V cc through Q3, Phase A1,A2, Phase C1,C2 and Q6 causing a positive torque to be generated. Step 4: Q3 and Q2 are conducting while Ql,3,4 and 6 are non-conducting. Current flows from V cc through Q3, Phase A1,A2, Phase C1,C2 and Q2 causing a positive torque to be generated. Step 5: Q5 and Q2 are conducting while Ql,3,4 and 6 are non-conducting. Current flows from V cc through Q5, Phase A1,A2, Phase C1,C2 and Q2 causing a positive torque to be generated. Step 6: Q5 and Q4 are conducting while Ql,2,3 and 6 are non-conducting. Current flows from V cc through Q5, Phase A1,A2, Phase C1,C2 and Q4 causing a positive torque to be generated. This sequence is used 6 times per revolution. Unipolar Mode: In start mode transistors Q7,8,10,11,13,14 and 16 are conducting. This places motor windings Phase A1,A2 in parallel, Phase B1,B2 in parallel and Phase C1,C2 in parallel. Transistors Q2,4,6,9,12,15,17,18 are non¬ conducting. Transistors Ql,3 and 5 are toggled in the normal three step sequence to rotate the motor. The sequence is: Step 1: Ql and Q16 are conducting while Q3 and 5 are non-conducting. Current flows from V cc through Ql,Phase A1,A2, Phase B1,B2 and Q16 causing a positive torque to be generated. Step 2: Q5 and Q16 are conducting while Ql and 3 are non-conducting. Current flows from V cc through Q5, Phase A1,A2, Phase C1,C2 and Q16 causing a positive torque to be generated. Step 3: Q3 and Q16 are conducting while Ql and 5 are non-conducting. Current flows from V cc through Q3, Phase Al, A2, Phase C1,C2 and Q16 causing a positive torque to be generated. This sequence is repeated six times per revolution. RUN MODE: During run mode very little torque is required to run the motor. Only one winding is used per phase. Since little torque is used, very little back EMF is generated thus allowing 3 volts to drive the motor with adequate headroom. Phase A2,B2 and C2 are not used to deliver torque to the motor. They are, however, connected in series so that a back EMF voltage greater than that generated by a single winding is developed. Thus transistors Q7,8,10,11,13,14, 16,17 and 18 are off during normal operation. Transistors Q9, 12 and 15 are on all the time. Thus Al and A2 are connected in series, Bl and B2 are connected in series and Cl and C2 are connected in series. Bipolar Mode: Step 1: Transistors Ql and Q4 are conducting while Q2,3,5 and 6 are non-conducting. Current flows from V cc through Ql, Phase Al, Phase Bl and Q4 causing a positive torque to be generated. Step 2: Transistors Ql and Q6 are conducting while Q2,3,4 and 5 are non-conducting. Current flows from V cc through Ql, Phase Al, Phase Cl and Q6 causing a positive torque to be generated. Step 3: Transistors Q3 and Q6 are conducting while Ql,2,4 and 5 are non-conducting. Current flows from V cc through Q3, Phase Al, Phase Cl and Q6 causing a positive torque to be generated. Step 4: Transistors Q3 and Q2 are conducting while Ql,3,4 and 6 are non-conducting. Current flows from V cc through Q3, Phase Al, Phase Cl and Q2 causing a positive torque to be generated. Step 5: Transistors Q5 and Q2 are conducting while Ql,3,4 and 6 are non-conducting. Current flows from V cc through Q5, Phase Al, Phase Cl and Q2 causing a positive torque to be generated. Step 6: Transistors Q5 and Q4 are conducting while Ql,2,3 and 6 are non-conducting. Current flows from V cc through Q5, Phase Al, Phase Cl and Q4 causing a positive torque to be generated. This sequence is used 6 times per revolution. Unipolar Mode: Step 1: Transistors Ql and Q16 are conducting while Q3 and 5 are non-conducting. Current flows from V cc through Ql, Phase A1,A2, Phase B1,B2 and Q16 causing a positive torque to be generated. Step 2: Transistors Q5 and Q16 are conducting while Ql and 3 are non-conducting. Current flows from V cc through Q5, Phase A1,A2, Phase C1,C2 and Q16 causing a positive torque to be generated. Step 3: Transistors Q3 and Q16 are conducting while Ql and 5 are non-conducting. Current flows from V cc through Q3, Phase A1,A2, Phase C1,C2 and Q16 causing a positive torque to be generated. This sequence is repeated six times per revolution. Power Down Unload Mode: During power down with the disk spinning and the data still on the disk, the spindle motor must furnish the power to drive the actuator which unloads the heads. Transistor Ql,2,3,4,5,6,7,8,10,11,13,14,16 are turned off by the power down detection circuitry. Transistors Q9,12,15 are turned on so that Phase A1,A2 are in series, B1,B2 are in series and C1,C2 are in series so that a greater back EMF voltage is generated than is possible with single winding (because of headroom considerations) . Diodes Dl,2,3,4,5 and 6 form a fullwave bridge rectifier. The full potential of the rectified voltage appears at the cathodes of D2,4, and 6. Q17 and 18 are also turned on and the rectified voltage is applied to the actuator, which causes the heads to unload from the disk. A better appreciation of the construction of the load beams utilized in the dynamic head load version and the contact short stop versions of the drives of the present invention would be obtained by reference to Figures 6A-6L. Referring to Figure 6A, load beam 14-1 is shown in plan view with the underside, that is the side on which the read/write recording transducer will be mounted, facing upward in this figure. Load beam 14-1 is referred to as the down load beam. Load beam 14-1 is unitary in construction and is preferably made from Type 302 non¬ magnetic stainless steel, having a thickness of approximately 0.0025 inches. As illustrated in Figure 6A, load beam 14-1 includes load tab 17 which is semicircular in cross section at its free end 80 as will be appreciated by reference to Figures 6C and 6C". Figure 6B illustrates load beam 14-1 in a side view taken along lines 6B-6B of Figure 6A. In the view of Figure 6B, the load beam 14-1 is shown in a flat and unloaded orientation. Tabs, denominated 76, are utilized to secure the electrical wiring which extends to the free end of the load beam for connection to the read/write transducer head to be mounted at that location. The cross-section of load beam 14-1 taken along lines 6E-6E is illustrated in Figure 6E. The hat-shaped configuration of load beam 14-1 illustrated in Figure 6E provides stiffening to the load beam. The configuration of load beam 14-1 changes from a generally flat orientation (with the exception of tabs 76 and stiffening channels 83 along the outer edge of the load beam) as shown in Figure 6F, the cross-section taken along lines 6F-6F, to the configuration illustrated in Figure 6E, and near the free end of load beam 14-1 the load tab 17 is generally semi-circular as is illustrated in Figure 6C which shows the view of load beam 14-1 taken along the line 6C-6C in Figure 6A. As will be appreciated by a reference to Figure 6A, the center line of load beam 14-1 is at the position indicated by the dashed line denominated 77. It will also be appreciated by reference to Figure 6A that the curved end portion of lift tab 17 is not symmetrical with respect to center line 77. This is also further illustrated in Figure 6C where the center line of load beam 14-1 is indicated by dashed line denominated 77. The lowest point on lift tab 17 as measured from the center of radius 78' is indicated in Figure 6C by reference line 78 which extends to the lower surface 79 of lift tab 17. A better appreciation of the offset relationship between the free end of load tab 17 and the centerline 77 of down load beam 14-1 will be obtained by reference to Figures 6C and 6C". Figure 6C is a top plan view of down load 14-1 showing the end portion thereof and a portion of flexure 84. For simplicity, cam assembly 18 and disk 10 are not shown in Figure 6C. In Figure 6C", which is a view taken along 6C"-6C", it will be appreciated that the centerline 77 of load beam 14-1 is to the left of the lowest point of tab 17 (indicated by 78) to provide an offset distance 77/78. The free end of load tab 17 is offset toward the center of disk 10 to provide symmetrical lifting of load beam 14-1 as it contacts cam surface 18-2. In Figure 6C", load tab 17 is illustrated at the position where first contact is made with cam surface 18-2. The amount of the offset 77/78 is determined based on the angular slope θ, which is measured between cam surface 18-2 and surface 10' of disk 10, along with the radius of lift tab 17, the radius being measured from center of radius 78• and the lower surface 79. The lowest point of tab 17 is indicated at 78. The centerline offset may be calculated by the formula Centerline Offset = R sine θ where θ = angle between disk surface and cam surface R = radius of curvature of load tab contacting the cam surface With this offset, the lifting force on load beam 14-1 will be applied symmetrically along the centerline of load beam 14-1. In the preferred embodiment, the angle θ is 12°, and the radius of lift tab 17 at the point of contact with cam surface 18-2 is 0.46 mm. This results in offset 77/78 being 0.095 mm. Similarly, the up load beams have their tab ends offset, also toward the center of the disk, thereby ensuring that the first surface of the load tab to contact its corresponding cam surface does so along the center line of the load beam. This centerline contact eliminates any twisting forces on the load beam. Referring to Figure 6D, a cross-sectional view taken along the line 6D-6D of Figure 6A, it will be appreciated that the free end 80 of load 17 is offset downwardly (with respect to the surface of the disk with which the load beam interfaces) from the plane of the flat surface of load beam 14-1 indicated by reference character 81 in Figure 6D. This offset is provided to maximize the clearance between load beams when the read/write heads are unloaded. Referring to Figure 6G, swage plate is 82 illustrated. Swage plate 82 is utilized in connecting the load beam to the actuator body. Also illustrated in Figure 6G is flexure 84, only a portion of which is illustrated in this figure. Flexure 84, which is preferably constructed from stainless steel having a thickness in the range of about 0.0015 inches to 0.002 inches, is utilized to support the read/write transducer head in a flexible manner below the underside of its respective load beam. A perspective view of flexure 84 is illustrated in Figure 6J. A side view of load beam 14-1 with its swage plate 82 is illustrated in Figure 6H which is a view taken along the lines 6H-6H in Figure 6G. In Figure 6H the load beam, flexure and associated read/write transducer are illustrated in loaded position. Figure 61 illustrates load beam 14-1 with associated read/write transducer and flexure in the unloaded position. As illustrated in Figure 61, there is a normal downward positioning of the free end of load beam 14-1 which is by bending load beam 14-1 to provide a predetermined pre-tensioning. Referring to Figure 6K, load beam 63-1 with its associated read/write transducer 5 and flexure 84 are illustrated in a plan view taken from the underside of load beam 63-1. Also illustrated in Figure 6K is wiring leads 85 which extend within tubing 86 which is supported in place by tabs 76 along the edge of load beam 63-1 to provide electrical connection to read/write transducer 5. Although not illustrated in the figures for the dynamic load beam version, a similar wiring arrangement is utilized for that structure as well. A side view of load beam 63-1 and its associated structure is illustrated in Figure 6L which is taken along the lines of 6L-6L in Figure 6K. Load beam 63-1 is constructed of the same type of material and same thickness is that used for load beams 14-1 and 14-2 in the dynamic head load version. Figure 7A is a combined electrical block diagram and partial structural diagram illustrating, from a circuit standpoint the drive and controller electronics included on printed circuit board 2, and in addition the read/write analog integrated circuit 21 which is included within the enclosure of hard disk drive 1 (Figure 1) . In Figure 7A, rigid disk 10 is illustrated in conjunction with lami¬ nation portions 64 of spin motor 3. The spin-up and control of the drive of the spin motor is under the electrical control of spin control and drivers circuitry 74, an expanded block diagram of which is illustrated in Figure 8. In the embodiment illustrated in Figure 1, spin control circuitry 74 is included on circuit board 2. As indicated above, spin control circuitry 74 may be implemented using an Allegro Microsystems, Inc. , part no. ULM 8902 denominated Three Phase Brushless DC Motor Drive With Back-EMF Sensing (illustrated in Figure 8 in block diagram form) . Alternatively, the spin control and drivers circuitry described in the above identified U.S. Patent Application Serial No. 07/630,470 could be used to control and drive the spin motor. As also noted above, an alternative spin motor and associated drive circuit may be used. In Figure 7A, upper load beam 14-1 is illustrated as positioned over a read/write area of disk 10, positioning read/write transducer 5 to a desired, addressed track location. Electrical conductors in a cable (not shown) provide analog information from the read/write recording element to read/write preamp 21, which in the present embodiment is located in baseplate 6 (as illustrated in Figures 1, 3A and 3B) . Read/write preamp 21 may be implemented, for example, by a Silicon Systems Incorporated, of Tustin, California, part no. 32R2030, or equivalent amplifier. Read/write preamp 21 provides the functions well known to those skilled in the art to facilitate the recording and playback of digital information from the surface of rigid disk 10. Signals from read/write preamp 21 are provided to and received from read/write combined function circuit 87, which in the present embodiment of Figure 7A is included on circuit board 2. Figure 10 illustrates in functional block form the circuits included in read/write combined function circuit 87. Read/write combined function circuit 87 may be implemented by, for example, a National Semiconductor part no. DP8491 denominated Hard Disk Data Path Electronics Circuit. Control signals to actuator coil 45 of the rotary actuator control the position of the read/write recording elements supported on their respective load beams. In the present embodiment, actuator driver and power off unload circuit 88 (Figure 7A) provides control signals to position the read/write recording elements to the desired location. A detailed block diagram of actuator driver and power off unload circuit 88 is illustrated in Figure 11. The portion of actuator driver and power off unload circuit 88 of Figure 11 illustrated within dashed line denoted by reference character 15-1 may be implemented by, for example, Allegro Microsystems, Inc. , Worchester, Mass., part no. 8932, denominated as a voice coil motor driver. The control signal to actuator coil 45 is analog and is provided by actuator driver and power off unload circuit 88. Also, as is well known to those skilled in the art, the feedback signals from the embedded servo (which will be described hereinafter) are provided in analog form. The seek control signals issued by host computing device 87 when the host computing device 89 desires that the read/write recording element be positioned over a designated track, are provided in digital form. To convert the analog signals returned from the embedded servo loop to digital signals and to convert the digital signals required for addressing a particular track to analog signals, actuator A/D & D/A circuit 90 is utilized. A detailed block diagram of the circuitry utilized in actuator A/D & D/A circuit 90 is illustrated in Figure 14. This circuit may be conveniently implemented utilizing a generally available part from Analog Devices, Norwood, Mass., their part no. ADC 7773, which is denominated as a complete embedded servo front end for hard disk drive. Returning to Figure 7A, disk controller 91 is coupled between read/write combo circuit 71, data bus 92, RAM buffer 93, and also provides signals to and receives signals from interface connector 39 (Figure 1) for communication outside of the drive and controller electronics board 2. Disk controller 91 may be conveniently implemented using Cirrus Logic, Inc. of Milpitas, CA, Integrated PC Disk and Controller part no. CL-SH 265. RAM buffer 93 may be any digital storage device having a capacity of 32K addressable storage locations, each of 8 bits in width, and is preferably for convenience a semiconductor type random access memory device. Drive and controller electronics board 2 further includes microprocessor 94 which is coupled to data bus 92, read only memory 95 and gate array 96. Microprocessor 77 may be implemented by, for example, a Motorola micro¬ processor model no. 68HC11 or an Intel Corporation micro¬ processor part no. 80C196, or similarly functional micro¬ processors from other sources. Read only memory 95 may be any suitable memory device having 32,000 storage locations, each 8 bits wide, and in the present implemen¬ tation, for reduction of size, is preferably a semiconductor memory device. Figure 13 is a block diagram of gate array 96 (which is used with spin motor in prior application Serial Number 07/630,110) illustrating the blocks utilized therein. A description of the operation of gate array 96 will follow hereinafter. Gate array circuit 97 (Figure 15) is utilized with the above-described alternative spin motor. An embedded servo system is utilized in hard disk drive 1 of the present invention, the embedded servo system being implemented with the use of electronics which is illustrated in Figure 7A (which includes other circuitry) . As illustrated in Figure 7A, rigid disk 10 includes a plurality of circular tracks, for example tracks 121-i and 121-(i+l). If both sides of rigid disk 10 are used for data, corresponding tracks on the disk surfaces are approximately cylindrically aligned. Each track is segmented into one or more sectors SCT-01, SCT-02, ... , SCT-n by prerecorded information in embedded servo field regions 120-1 through 120-n. Each servo field region 120-j, where j = 1, 2, ..., n, includes m concentric servo fields, where m is the number of concentric circular data tracks on the disk, that is, one servo field in each data track at position j (a total of nm servo fields per surface) . The particular embedded servo system utilized with hard disk drives 1 or 4 may be of the type described in copending and commonly assigned U.S. Patent Application Serial No. 07/630,475 describe above. Alternatively, the servo system described in the above-described copending commonly assigned U.S. Patent Application 07/765,348 may be utilized. Attention is directed to Figure 13, which is a block diagram of gate array 96 of Figure 7A. As will be appreciated by reference to Figures 7A and Figure 13, multiplexed low address and data bus 92 is coupled to gate array 96 for the bidirectional flow of information between microprocessor 94 and gate array 96. Throughout the drawing figures, lines with arrows on both ends indicate that there is a bidirectional flow of information over the lines in contrast to lines with an arrow on a single end which indicates that information passes in the direction of the arrow only. As will also be appreciated by reference to Figures 7A and 13, address information is provided from microprocessor 94 to gate array 96 as inputs to gate array 96. In addition, gate array 96 provides information to and receives information from other circuitry in Figure 7A and for convenience for understanding lines entering and leaving gate array 96 in Figure 13 have labels adjacent thereto to indicate the circuitry from which or to which the line is coupled. Referring to Figure 13, address latch 98 is coupled to multiplexed low address and data bus 92 from which it receives and holds the lower order address information received from multiplexed low address and data bus 92. Address latch 98 receives an address strobe from microprocessor 94 which establishes the timing when the address is valid. All outputs from address latch 98 are provided over bus 99 to read only memory 95 and additionally low order address information is also provided from address latch 98 to actuator A/D & D/A circuit 90. The low order address from address latch 98 is also provided to address decoder 100 over bus 101. Address latch 98 is equivalent to any available 8 bit latch, such as a 74LS373 latch. Address decoder 100 receives the high order address information from microprocessor 94 via bus 186. Address decoder 100 uses the external high order address bits, the latched low order address bits from address latch 98 and the timing signal, denominated DATASTROBE, received over line 80 from microprocessor 94 to decode the address for the gate array registers as well and for external chip select lines. More particularly, EXTERNAL CHIP SELECTS signals are provided over line 187 to the serial port select of read/write combined function circuit 87, the select port for spin control circuit 74, as well as for the chip select inputs to actuator A/D & D/A circuit 90. Internally within gate array 96 the decoded address information is used to select memory mapped control/status registers for all of the blocks in gate array 96. Address decoder 100 may take the form of a well known circuit such as a group 74LS138 decoders. Clock logic memory mapped register 188 generates all of the required clock signals for programmable low power timer circuit 189, programmable word length serial port 190, digital demodulator & Gray code address separator 191, pulse width modulated timer 192, pulse width modulated timer 193 and encoder/decoder 194. Crystal 195, which is provided externally of gate array 96, is used to provide a stable frequency of oscillation for clock logic memory mapped register 188. The memory mapped register portion of clock logic memory mapped register 188 functions to insure that minimum power is used or dissipated by enabling only the required clocks for the operation in progress at the time the clock signal is required. Programmable low power timer circuit 189 generates timing signals which are provided to read/write preamp 21, over line 106, a timing signal on line 107 to read/write combined function circuit 87, a plurality of timing signals (which will be fully described hereinafter) over bus 108 to digital demodulator & Gray code address separator 191 and, a timing signal over line 109 to integrity checks & address comparator 110. Digital demodulator & Gray code address separator 191 generates windows for the pulse detector included in read/ rite combined function circuit 87, over bus 111. To aid in understanding the operation of the various circuits and timing windows, attention is directed to Figure 12A which illustrates the servo field utilized on the disk 10 in conjunction with the servo system in U.S. Patent Application Serial No. 07/630,475, along with Figure 12B which illustrates the windows produced by programmable low power timer circuit 189 and Figure 12C which illustrates the windows produced by digital demodulator & Gray code address separator 191. As will be appreciated by reference to Figures 12B and 12C, the timing of the respective windows have been illustrated in timed relationship to the servo field of Figure 12A. A detailed description of the servo field in Figure 12A along with the circuitry involved is found in U.S. Patent Application Serial No. 07/630,475 referred to above and the explanation therefore will not be repeated. As an aid to understanding the windows generated by programmable low timers circuit 189 and digital demodulator & Gray code address separator 191, the following table is provided which in the left hand column lists the window acronym designation illustrated in Figures 12B and 12C, in the center column provides a descriptive title for the windows function and in the far right column indicates the circuit o which the window signal is provided. TABLE Integrity checks & address comparator 110 compares the integrity check pattern which is created from reading the servo field information (which is described in detail from the above-referenced M-1470 U.S. Patent Application Serial No. 07/630,475) with the expected pattern stored in a memory mapped register in integrity check & address comparator 110. In addition, the track address is selectively compared with the expected track address during track following (ON track MODE) . If either of these comparisons do not match, an error condition stored in a status register is assumed and is sent to microprocessor 94 over data line 112 as status information. Returning to digital demodulator & Gray code address separator 191 which was briefly referred to above, the output of this circuit is provided over bus 111 as windows for the pulse detector in read/write combo chip 87. Digital demodulator & Gray code address separator 191 receives, over line 113, the transition pulse and polarity signals from read/write combo chip 87. Using this information, digital demodulator & Gray code address separator 191 determines the track address and provides this track address information to microprocessor 94, as well as to integrity checks & address comparator 110. Pulse width modulated timer 192 has an input coupled to multiplexed low address and data bus 92 through which the microprocessor programs the frequency and the duty cycle of the output. This data is stored in two memory registers which are included in pulse width modulated timer 192 which generates at its output a control signal to set the level of the read threshold, this control signal being provided to read/write combined function circuit 87 over line 123. Pulse width modulated timer 193 also receives an input from multiplexed low address and data bus 92 and provides at its output a write current control signal which is provided to read/write analog circuit 21 over line 114. The outputs of timers 192 and 193 are filtered by suitable RC networks (not shown) to provide an appropriate voltage for the above two functions. The time constant of the RC network for the output of these two timers is a function of the device being driven and is determined by well known techniques. Programmable word length serial port 190 is utilized to program read/write combined function circuit 87, actuator driver 88 and spin control circuit 74. Serial clock output from programmable word length serial port 190 is also provided to each of the foregoing chips. The programming information to be provided to read/write combined function circuit 87, actuator driver 88 and spin control and driver circuit 74 is loaded into programmable word length serial port 90 from microprocessor 94 over 5 multiplexed low address and data bus 92. The designated address for this programming is set by the microprocessor through address decoder 100, and the data contents and length is set by a microprocessor through the memory map register included in programmable word length serial port 10 190. Power management circuit 119 is a memory mapped set of registers which controls the activation of each functional block of the drive. Only the blocks requiring to be active at a given time are activated and therefore 15 the minimum overall power required by the drive is utilized. Encoder/decoder 194 receives NRZ write data and clock signals from disk controller 91 and generates from these signals write code data which is provided over line 120 to 0 read/write combined function circuit 87. Encoder/decoder 194 receives RDGATE and WRGATE signals as enable signals from disk controller 91. Encoder/decoder 194 receives read code data and clock signals from read/write combined function circuit 87 and generates NRZ read data and NRZ 5 read clock signals which are provided to disk controller 91 over lines 121 and 122 respectively. Encoder decoder circuit 194 may be implemented by using standard 1,7 encoding circuitry well known to those skilled in the art. Figure 12D illustrates the servo field utilized in 0 conjunction with the servo circuitry described and claimed in the above-identified U.S. Patent Application Serial Number 07/M-1785. In the terminology used in the rigid disk drive and other computer peripheral storage device art, the term 5 head disk assembly, also sometimes abbreviated HDA, refers to the head and disk structures and other apparatus and circuitry included within the enclosure which houses the head and disk mechanism. For example, in Figure 1, the components included in the housing which is bounded on the lower side by base plate 6 and on the upper side by top cover 26 be considered the HDA for hard disk drive 1. An advantage to housing circuitry within the HDA is that since the base plate and top cover are both electrically conductive, there is a sealed housing which prevents external electrical interference from entering the housing and affecting circuitry within the HDA. External electrical interference is normally only a problem with circuits and conductors which carry analog signals. It has been discovered that a very advantageous disk drive system can be constructed by including within the HDA all of the analog circuitry and signal lines, while including exterior of the HDA signal lines and circuits which process only digital information. Digital circuitry could of course also be included within the HDA housing, however doing so may result in a size penalty for the HDA which may not be desirable. Referring to Figure 7B, an embodiment of the present invention is disclosed in which the above-identified advantageous result of reduced interference to electrical signals in the system is achieved. In Figure 7b, the dashed line indicated by reference character 125 demarks the above-described separation of the analog and digital circuitry for accomplishing the separation to provide the advantageous result of reduced susceptibility to noise interference from external sources. As it will be appreciated by, referring to Figure 7B, the circuitry to the right of, and below, line 125 process analog signals and converts them into digital form before those signals are sent to the circuitry in the blocks to the left of line 125. More particularly, the read/write preamp 21, read/write combined function circuit 87, actuator driver and power off unload circuit 88, spin control and driver circuity 74 and the actuator A/D and D/A circuitry 90 all process analog data, however the analog data is converted into digital data before that data is transferred to the other circuit blocks within the disk drive system. Structurally, implementing the invention described above is achieved by placing the aforementioned analog circuitry within the HDA housing and sending to the exterior of the housing via suitable connectors digital information to the remaining portions of the system. In this manner, only digital information is transferred from the interior of the HDA to the outside circuitry and any electrical interference which may be present in the area would be less likely to affect the digital signals since they are less susceptible electrical noise than other types of signals. As mentioned previously, the gate array circuitry utilized with the present invention is a function of which spin control and driver circuit, and which spin control motor previously described will be utilized in the drive. Figure 15 illustrates gate array 97, in high level block diagram form, which is utilized with the spin motor and drive circuitry discussed above with respect to spin motor drive circuit 75 and the modified spin motor described in connection therewith. Internal decoder circuitry 151 receives address and data signals from microprocessor 94. Internal decoder circuitry 151 contains the memory map for the entire system as well as address latches and data read or write state. The address may map to an internal, on- chip, function or may be an external location. A digital decoder determines the routing and sends all external address commands out to either the address and data lines output multiplex circuitry 161 or output control lines 162. Peripheral chip control circuitry 152 receives commands from input control lines 163 (connections not illustrated in the figure) or internally written ASIC registers and sends commands to output control lines 162 (connections not illustrated in the figure) to control the read/write integrated circuit 21 in the HDA. Serial communication port circuitry 153 is similar in operation to an RS-232 interface. It is used to load other chips with serial data from microprocessor 94, such as the frequency synthesizer, D/A converter, R/W pulse detector and filter used in the encoder decoder logic. Signals from this port appear at output control lines 162. Spin control circuitry 154 selects the spin motor logic control clock from either the external spin motor generated clock or an internally generated clock derived from sector pulses. The output clock is placed on output control lines 162. Encode decode circuitry 155 provides encoding and decoding of the 1,7:2,3 coded read/write data signals from the input control lines 163 to the output control lines 162. PWM control ports circuitry 156 generates three pulse-width modulated bit streams which are placed on output control lines 162. The first signal is used to control the magnetic head write current, the second to control the read channel amplitude threshold and the third to control the spin motor voltage. Servo sequencer circuitry 157 reads the track position servo information. It acts to detect index and cylinder address information and derives timing signals from the synchronization signals, and further steers analog position information to the peak detection circuitry to obtain exact position information. Information is received from input control lines 163 and after processing appears at output control lines 162. Clock generation and control circuitry 158 enables and disables the crystal oscillator (not shown) which is connected to clock generation and control circuitry 158. Programmable dividers provide variable clock signals for spin motor control, buffer control and frequency synthesizing. Address trigger circuitry 159 is comprised of a programmable 16 bit register and digital comparator which examines address information from the internal decoder circuitry 151 and can be used for diagnostic purposes. Output signals appear at output control lines 162. Internal registers 160 are used to store index address, cylinder address, status information and bit mapped error codes from the servo sequencer and to drive the peripheral control lines. Output multiplex circuitry 161 allows internal data registers and input control lines to be read by the microprocessor.

Claims: CLAIMS We claim: 1. A disk drive information storage device comprising: a substantially rigid disk having a diameter in range of from about 33 mm to about 34 mm; a housing having a footprint that includes a width of about 35 mm; a spin motor supported by said housing for rotating said rigid disk, said spin motor including a rotor for receiving said rigid disk and rotating said rigid disk about an axis; actuator means including an actuator having a body portion rotatably supported on said housing for rotation about an axis, said actuator means including an actuator drive motor coupled to said actuator body for providing rotary motion to said actuator and a transducer support arm connected to said actuator body for rotation therewith, said transducer support arm including a free end and a transducer means supported adjacent to said free end. 2. A storage device according to Claim 1, wherein said footprint includes a length of about 50.8 mm. 3. A storage device according to Claim 1. wherein said transducer support arm includes a lift tab extending from said free end, a cam assembly supported by said housing and positioned in operative relationship with said lift tab whereby when said transducer arm is pivoted to an outer peripheral zone of said disk said lift tab contacts said cam assembly and moves said transducer away from said surface of said disk. 4. A storage device according to Claim 1, wherein said actuator drive motor includes a coil coupled to said actuator body, said coil having first and second sides, said actuator drive motor further including a permanent magnet positioned on said first side of said coil and a flux plate having a first portion coupled to said magnet on said first side of said coil and a second portion which extends adjacent to said second said of said coil. 5. A storage device according to Claim 1, wherein said spin motor includes a stator and a rotor, one having a plurality of magnetic poles and the other having at least one winding, the winding comprising a first winding portion and a second winding portion; means for providing that only the first winding portion of the winding is used in driving the rotor relative to the stator when drive current is applied to the winding; and means for providing that both the first and second winding portions of the winding are used to generate back electro-magnetic force when drive current is cut off from the winding. 6. The storage device of Claim 5, wherein the first and second winding portions are connected in series when drive current is cut off from the winding. 7. The storage device of Claim 6 and further comprising means for applying the generated back electro¬ magnetic force to said actuator means. 8. The storage device of Claim 5, wherein said actuator drive motor includes a coil having a predetermined electrical resistance and wherein the combined electrical resistance of said first and second winding portions is substantially equal to said predetermined electrical resistance. 9. The storage device of Claim 6, wherein said actuator drive motor includes a coil having a predetermined electrical resistance and wherein the combined electrical resistance of said first and second winding portions is substantially equal to said predetermined electrical resistance. 10. A method to reduce external signal interference with signals in a computer disk storage system including a disk drive having at least one disk for storing information on a surface of said disk, said system further including analog circuitry for positioning a read/write transducer with respect to a surface of said disk for reading information from and writing information on said disk, digital signal processing circuitry for processing digital data in said system, comprising the steps of: enclosing said disk drive and associated analog circuitry in an electrically conductive housing; including in said housing signal conversion circuitry to convert signals within said housing which are in analog form and which are to exit said housing into digital signal form prior to transmission out of said housing. 11. A storage device according to Claim 3, wherein said transducer support arm is supported for rotation about a centerline of said transducer support arm and said lift tab is positioned such that a centerline of said lift tab is offset from said centerline of said transducer support arm. 12. A storage device according to Claim 11, wherein the portion of said lift tab which contacts the cam surface is curvilinear about a center of radius and has a radius R, and wherein the surface of the cam is inclined at an angle θ with respect to said surface of said disk, the amount of said offset is determined by the formula: Offset = R sine θ 13. A storage device according to Claim 11, wherein said lift tab is semicircular in the region where said lift tab contacts the cam surface of said cam. AMENDED CLAIMS [received by the International Bureau on 18 February 1993 (18.02.93); original claims 2-5 and 11-13 cancelled; original claims 1,6 and 8 amended; new claims 14-22 added; other claims unchanged (4 pages)] 1. A disk drive information storage device comprising: a substantially rigid disk having a diameter in range of from about 33 mm to about 34 mm; a housing having a footprint that includes a first dimension of about 35 mm; a spin motor supported by said housing for rotating said rigid disk, said spin motor including a rotor for receiving said rigid disk and rotating said rigid disk about an axis, wherein said spin motor includes a stator and a rotor, one having a plurality of magnetic poles and the other having at least one winding, the winding comprising a first winding portion and a second winding portion; means for providing that only the first winding portion of the winding is used in driving the rotor relative to the stator when drive current is applied to the winding; means for providing that both the first and second winding portions of the winding are used to generate back electro-magnetic force when drive current is cut off from the winding; actuator means including [an actuator having] a body portion rotatably supported on said housing for rotation about an axis, said actuator means including an actuator drive motor coupled to said body portion for providing rotary motion to said body portion and a transducer support arm connected to said body portion for rotation therewith, said transducer support arm including a free end and a transducer means supported adjacent to said free end. 2. The storage device of Claim 1, wherein the first and second winding portions are connected in series when drive current is cut off from the winding. 3. The storage device of Claim 2 and further comprising means for applying the generated back electromotive force to said actuator means. 4. The storage device of Claim 1, wherein said actuator drive motor includes a coil having a predetermined electrical resistance and wherein the combined electrical resistance of said first and second winding portions is substantially equal to said predetermined electrical resistance. 5. The storage device of Claim 2, wherein said actuator drive motor includes a coil having a predetermined electrical resistance and wherein the combined electrical resistance of said first and second winding portions is substantially equal to said predetermined electrical resistance. 6. A method to reduce external signal interference with signals in a computer disk storage system including a disk drive having at least one disk for storing information on a surface of said disk, said system further including analog circuitry for positioning a read/write transducer with respect to a surface of said disk for reading information from and writing information on said disk, digital signal processing circuitry for processing digital data in said system, comprising the steps of: enclosing said disk drive and associated analog circuitry in an electrically conductive housing; including in said housing signal conversion circuitry to convert signals within said housing which are in analog form and which are to exit said housing into digital signal form prior to transmission out of said housing. 7. The storage device according to any of Claims 1, or 2-5, wherein said disk drive comprises a contact start/stop disk drive. 8. The storage device according to any of Claims 1, or 2-5, wherein said disk drive comprises a dynamic head loading disk drive. 9. A disk drive information storage device comprising: a housing having a footprint that includes a first dimension of about 35 mm; a substantially rigid disk supported on said housing for rotation, said rigid disk having a diameter in range of from about 33 mm to about 34 mm; an elongated actuator arm including a load beam, said actuator arm being pivotally supported about a center of rotation on said housing, for rotation of one end of said load beam in a plane substantially parallel to a surface of said rigid disk, said load beam including at its outermost end a lift tab, said lift tab being positioned such that a centerline of said lift tab is offset from a centerline of said load beam; a slider body including a read/write recording element; means connected to said load beam and said slider body for supporting said slider body at a position intermediate said center of rotation and said lift tab; and a cam assembly supported on said housing adjacent to said lift tab and the edge of said rigid disk, said cam assembly including a cam surface positioned in operative relationship with said lift tab, said lift tab contacting said cam surface and in cooperation with said cam surface providing a lifting force along the centerline of said load beam. 10. A disk drive information storage device according to Claim 9, wherein said cam surface includes a contour which permits rotational movement of said actuator arm in a direction opposite to the direction of rotation of said actuator arm during positioning of said slider body over the surface of said disk and in an amount sufficient to permit installation of said rigid disk without interference with said actuator arm. 11. A disk drive information storage device according to Claim 9, wherein the portion of said lift tab which contacts the cam surface is curvilinear about a center of radius and has a radius R, and wherein the surface of the cam is inclined at an angle θ with respect to said surface of said disk the amount of said offset is determined by the formula: Offset = R sine θ. 12. A disk drive information storage device according to Claim 9, wherein said lift tab is semicircular in the region where said lift tab contacts the cam surface of said cam assembly. 13. A storage device according to any of Claims 1, 2-5, or 9-12, wherein said footprint includes a second dimension of about 50.8 mm. 14. A storage device according to Claim 7, wherein said footprint includes a second dimension of about 50.8 mm. 15. A storage device according to Claim 8, wherein said footprint includes a second dimension of about 50.8 mm.

Inventors: ALT ROBERT A, COWEN STEPHEN R, EMO BRUCE D, FURAY DAVID M, MOREHOUSE JAMES H, THOMPSON RICHARD K, UTENICK MICHAEL R, ALT, ROBERT, A., COWEN, STEPHEN, R., EMO, BRUCE, D., FURAY, DAVID, M., MOREHOUSE, JAMES, H., THOMPSON, RICHARD, K., UTENICK, MICHAEL, R.
Applicants: INTEGRAL PERIPHERALS INC, INTEGRAL PERIPHERALS, INC.
Application year: 1992
Main classification: G11B5
IPC codes: G11B5, G11B19, G11B25, G11B33