Dual-surface self-servo writing for storage devices

Abstract

The present disclosure relates to dual-surface self-servo writing (SSW) for a storage device. A method for self-servo writing (SSW) of a storage device includes: detecting an SSW spiral signal from a first track on a first storage medium surface using a first read head; processing the SSW spiral signal from the first track using a first read channel to generate a first control signal for positioning the first read head relative to the first track; detecting an SSW spiral signal from a second track on a second storage medium surface using a second read head; processing the SSW spiral signal from the second track using a second read channel to generate a second control signal for positioning the second read head relative to the second track; positioning the first write head relative to the first track using the first control signal via a single write channel, and positioning the second write head relative to the second track using the second control signal via the single write channel.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims the benefit of commonly assigned, pending U.S. Provisional Patent Application No. 63 / 076,272, filed September 9, 2020, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present disclosure relates to self-servo write operations in storage devices such as disk drives. More particularly, the present disclosure relates to performing self-servo write operations simultaneously on two surfaces of a multi-surface storage device. Background Art

[0004] The background description provided herein is intended to generally present the context of the present disclosure. The work of the inventors, to the extent described in this background section and in respect of what was defined as prior art at the time of filing, is neither expressly nor impliedly admitted to be prior art with respect to the subject matter of the present invention.

[0005] In magnetic recording, as an example, reading and writing are performed by one or more heads that move relative to the surface of the storage medium. For example, a disk drive includes one or more individual disks or "platters," which may be double-sided—that is, each platter can store data on each of its two sides. Thus, such a disk drive has at least two heads per platter. In practice, there is typically at least one write head and at least one separate read head for each platter, so such a disk drive typically has at least four heads per platter.

[0006] In a common configuration, all heads in a given disk drive are mounted on an arm connected to a common actuator that controls the radial position of the heads (the angular, tangential, or circumferential components of motion are provided by the rotation of the disk platter relative to the heads). This is true whether there is one or more disks, and whether each disk has one or more heads. Each arm may include one or more articulated sections, called "microactuators," at the end of the arm that carries the heads (away from the common actuator). If there are multiple microactuators, the microactuator farthest from the common actuator carries the heads.

[0007] To control the radial position selected by the actuator, position information known as "servo" data is distributed across each surface of each platter. The servo data is typically distributed in servo "wedges" spaced (usually equiangularly spaced) across the platter surface. By reading the servo data as each servo wedge passes under the read head, the disk drive controller can determine the precise radial (and angular) position of the head and can feed back this determination to control the position of either the read head or the write head, depending on the desired operation.

[0008] Servo wedge information is typically recorded on the storage medium during manufacture. One technique for recording servo wedge information is "self-servo writing" (SSW), in which the storage device's own read / write mechanism, including a data channel controller and read / write head, possibly under the control of an external processor, is used to write the servo wedge information.

[0009] A self-servo write operation typically begins with the writing of an initial or "coarse" reference spiral. The coarse reference spiral is a collection of timing data written as a highly inclined spiral between the outer and inner diameters of the disk by rapidly scanning the disk read / write head at a relatively high rate as the disk rotates. The coarse reference spirals are either irregularly or evenly spaced. After the coarse reference spiral has been written, the read / write mechanism reads and "learns" the position of the coarse reference spiral. The coarse reference spiral is then positionally referenced to allow for finer position data as an "intermediate" reference spiral. The intermediate reference spiral is less inclined than the coarse spiral and contains more precise timing data. After the intermediate spiral has been written, the read / write mechanism reads and "learns" the intermediate position spiral. Based on this finer position data, the read / write mechanism writes the final servo control signal pattern as a "servo wedge" along concentric arcs (i.e., in-track) at varying radii.

[0010] As described above, self-servo write operations utilize the disk drive's read data channel (RDC) and write data channel (WDC), and both the RDC and WDC are typically limited to operating on only one disk surface at any given time. In a typical disk drive with multiple platters, each with hundreds of thousands of tracks, but only one RDC and one WDC, self-servo write operations performed during disk drive manufacturing can take days or weeks to complete, increasing the time and cost of manufacturing the disk drive. In fact, 40% of the time required to manufacture a high-performance disk drive is consumed by the self-servo write process. Summary of the Invention

[0011] In an implementation of the subject matter of the present disclosure, a self-servo writing method in a storage device includes: detecting, using a first read head of the storage device, a self-servo write spiral signal from a first track on a first storage medium surface of the storage device, processing the self-servo write spiral signal from the first track using a first read channel of the storage device to generate a first control signal for positioning the first read head relative to the first track; detecting, using a second read head of the storage device, a self-servo write spiral signal from a second track on a second storage medium surface of the storage device, processing the self-servo write spiral signal from the second track using the second read channel of the storage device to generate a second control signal for positioning the second read head relative to the second track, positioning the first write head relative to the first track using the first control signal via a single write channel of the storage device; and positioning the second write head relative to the second track using the second control signal via the single write channel of the storage device.

[0012] A first implementation of the method may further include determining, based on a position of a corresponding one of the first and second read heads during consecutive passes through a location on a corresponding one of the first and second storage medium surfaces, a phase difference between data written by the corresponding one of the first and second write heads during a first pass of the consecutive passes and data written by the corresponding one of the first and second write heads during a second pass of the consecutive passes; using the phase difference to adjust servo wedge data of a second pass in the consecutive passes relative to servo wedge data of the first pass in the consecutive passes; and writing the adjusted servo wedge data of the first track to the first track and the adjusted servo wedge data of the second track to the second track using a single write data channel of the storage device.

[0013] The first aspect of the first implementation may further include adjusting timing of at least one of writing servo wedge data of the first track to the first track and writing servo wedge data of the second track to the second track to compensate for the phase difference.

[0014] In a second aspect of the first implementation, servo wedge data of a first track is written to the first track, and servo wedge data of a second track is written to the second track using a single write data channel of a storage device, including: providing a write data signal including the servo wedge data of the first track and the servo wedge data of the second track to both the write head of the first track and the write head of the second track; and triggering a write select signal to write the servo wedge data in the write data signal to a correct one of the first track and the second track.

[0015] In one example of the second aspect, triggering can be performed to compensate for phase differences.

[0016] A second implementation of the method may further include processing the self-servo write spiral signal from the first track to generate a frequency control signal for adjusting a rotational speed of a storage medium of the storage device.

[0017] In a third implementation of the method, positioning the first readhead relative to the first track and positioning the second readhead relative to the second track includes rotating a common actuator having a first arm carrying the first readhead and a second arm carrying the second readhead.

[0018] According to the first aspect of the third implementation, positioning the first read head relative to the first track and positioning the second read head relative to the second track further includes adjusting a microactuator on at least one of the first arm and the second arm.

[0019] According to a first example of the first aspect, adjusting the microactuator on at least one of the first arm and the second arm includes independently adjusting a first microactuator on the first arm and a second microactuator on the second arm.

[0020] A storage device according to an implementation of the disclosed subject matter includes a storage medium having a plurality of storage medium surfaces on which servo data is written using a self-servo write method, a first read head for detecting a self-servo write spiral signal from a first track on a first storage medium surface of the storage device, the first write head corresponding to the first read head and configured to write the self-servo write data to the first track, a second read head configured to detect a self-servo write spiral signal from a second track on a second storage medium surface of the storage device, the second write head corresponding to the second read head and configured to write the self-servo write data to the second track, first read data channel circuitry configured to process the self-servo write spiral signal from the first track to generate a first control signal for positioning the first read head and the first write head relative to the first track, second read data channel circuitry configured to process the signal from the self-servo write spiral from the second track to generate a second control signal for positioning the second read head relative to the second track, and actuator control circuitry responsive to the first control signal and configured to control the positioning of the first write head relative to the first track, and responsive to the second control signal and configured to control the positioning of the second write head relative to the second track.

[0021] The first implementation of such a storage device may further include: a channel increment control circuit system configured to determine, based on a position of a corresponding one of the first and second read heads during consecutive passes through a position on a corresponding one of the first and second storage medium surfaces, a phase difference between the following data: data written by the corresponding one of the first and second write heads during a first pass of the consecutive passes and data written by the corresponding one of the first and second write heads during a second pass of the consecutive passes, wherein the actuator control circuit system is configured to use the phase difference to adjust the servo wedge data of the second pass of the consecutive passes relative to the servo wedge data of the first pass of the consecutive passes; and a single write data channel configured to write the servo wedge data of the first track to the first track and the servo wedge data of the second track to the second track.

[0022] According to the first aspect of the first implementation, the single write data channel may be further configured to adjust timing of at least one of writing servo wedge data of a first track to the first track and writing servo wedge data of a second track to the second track to compensate for the phase difference.

[0023] According to a second aspect of the first implementation, a single write data channel is configured to write servo wedge data of a first track to the first track and to write servo wedge data of a second track to the second track by: providing a write data signal including the servo wedge data of the first track and the servo wedge data of the second track to both the write head of the first track and the write head of the second track; and triggering a write select signal to write the servo wedge data in the write data signal to a correct one of the first track and the second track.

[0024] According to an example of the second aspect, a single write data channel is configured to perform triggering to compensate for the phase difference.

[0025] The second implementation of the storage device may further include a disk lock control circuit system configured to process the self-servo write spiral signal from the first track to generate a frequency control signal for adjusting a rotational speed of a storage medium of the storage device.

[0026] The third implementation of such a storage device may further include a common actuator configured to position a first arm carrying the first read head relative to the first rail, and to position a second arm carrying the second read head relative to the second rail.

[0027] According to the first aspect of the third implementation, the common actuator may be configured to rotate to position the first arm and the second arm.

[0028] The second aspect of the third implementation may further include: a microactuator on at least one of the first arm and the second arm, the microactuator configured to position at least one of: positioning the first read head relative to the first track, and positioning the second read head relative to the second track.

[0029] In a first case of the second aspect, the microactuator on at least one of the first arm and the second arm includes a first microactuator on the first arm and a second microactuator on the second arm.

[0030] In a second example of the second aspect, one of the first arm and the second arm is adjacent to two different storage medium surfaces; and one of the first arm and the second arm includes: a microactuator carrying a head for one of the two different storage medium surfaces, and another microactuator carrying a head for the other of the two different storage medium surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Further features of the present disclosure, its nature and various advantages will become apparent from the following detailed description considered in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout, and wherein:

[0032] Figure 1 and Figure 2 A disk drive is shown as an example of a storage device that may incorporate the presently disclosed subject matter;

[0033] Figure 3 is similar to Figure 1 s shows a disk drive having an arm including two microactuators;

[0034] Figure 4 is a schematic diagram of a hard drive controller that may incorporate the presently disclosed subject matter;

[0035] Figure 5 is a diagram illustrating how head position may be controlled using microactuators in a memory device that may incorporate the subject matter of the present disclosure;

[0036] Figure 6 is a diagram illustrating how phase errors between different heads that may occur in a storage device are corrected according to the presently disclosed subject matter;

[0037] Figure 7 is a diagram of a storage device control system according to an implementation of the presently disclosed subject matter;

[0038] Figure 8 is a timing diagram illustrating write signals according to an implementation of the subject matter of the present invention; and

[0039] Figure 9is a flow chart illustrating a method of implementing the subject matter of the present disclosure DETAILED DESCRIPTION

[0040] As described above, self-servo write operations utilize the disk drive's read data channel (RDC) and write data channel (WDC), and both the RDC and WDC are typically limited to operating on only one disk surface at any given time. A typical disk drive has multiple double-sided platters, each with hundreds of thousands of tracks (e.g., 200,000-400,000 tracks), but only one RDC and one WDC. In such a disk drive, a self-servo write operation can take days or weeks to complete, increasing the time and cost of manufacturing the disk drive.

[0041] By increasing the number of RDCs and WDCs in a disk drive, the time required to complete a self-servo write operation can be reduced. However, adding an RDC or WDC is costly. However, disk drives using two-dimensional magnetic recording (TDMR) have been developed and include a second RDC (but only one WDC).

[0042] Therefore, in an implementation according to the subject matter of the present disclosure, for a disk drive equipped with TDMR, the time required to complete a self-servo write operation can be almost halved by using two RDCs so that the self-servo write can be operated simultaneously on two different disk surfaces (which can be both sides of the same disk, or the surfaces of two different disks).

[0043] Although all the read / write arms carrying the read / write heads of the disk drive assembly can be mounted on a single actuator and therefore theoretically move together to the same position on each disk surface, in practice vibration and inertial forces may cause different read / write arms to move to slightly different positions. However, in addition to the two RDCs, some disk drives also have a microactuator at the end of each read / write arm. That is, in addition to each read / write arm pivoting around the main pivot point defined by the aforementioned actuator, each read / write arm should be hinged near its tip so that the tip can rotate around a second pivot point to finely adjust the position of the head, and in some cases, each read / write arm can have three or more stages, that is, at least three pivot points (including a common actuator and two microactuators). According to an implementation of the disclosed subject matter, self-servo writing can be achieved on both surfaces of a disk drive in which each arm is equipped with at least one microactuator.

[0044] In an implementation of the disclosed subject matter, the read head on one arm is locked to the servo spiral signal of the track on its corresponding surface, which can be considered the "primary" surface for the self-servo write operation. On the second surface on which the self-servo write operation is to be performed simultaneously, the microactuator of the arm for that surface is used to radially move the head, as necessary, so that it can also lock to the servo spiral signal of its corresponding track. With the heads on both surfaces aligned with their corresponding tracks, the self-servo write pattern generator can be used to write a self-servo write pattern to each corresponding track on each corresponding surface.

[0045] However, because the microactuator motion is rotational, it includes not only a radial or lateral track component for properly positioning the head on the track, but also a circumferential or angular component to move the head down-track (i.e., along the track). If more than one pass is required to write servo data to a particular track of a particular servo wedge, it is possible that the microactuator will be positioned differently during two different passes to keep the head on track. The result may be that the head may be at slightly different locations on the down track in two (or more) different passes, and phase differences may occur between the segments of the self-servo write pattern that were written during the different passes. Therefore, it is also within the subject matter of the present disclosure to track the amount of rotation of the corresponding microactuator on each of the two arms involved in the self-servo write so that the down track difference amount can be calculated and appropriate compensation can be applied.

[0046] Although the microactuators on both arms involved in self-servowriting a particular pair of surfaces can be adjusted, in simplifications of some implementations of the disclosed subject matter, one arm can be kept straight (i.e., the centerline of the microactuator remains aligned with the centerline of the main arm), and only the microactuator on the other arm is used to adjust the cross-track position of the corresponding head. However, for a particular servo wedge on a particular track, the microactuator can be in different positions on different meridians.

[0047] As described above, a storage device incorporating implementations of the presently disclosed subject matter can have only a single WDC for writing servo data. Thus, according to implementations of the presently disclosed subject matter, writing servo data to two different surfaces can be accomplished by triggering the WDC between writing to the first surface and writing to the second surface, as described below. Because each servo wedge is a short burst of data written at relatively long, fixed intervals, the duration that the WDC is actively writing servo data is significantly shorter than the disk's rotation to the next servo wedge position. Thus, triggering the WDC allows servo patterns to be written to both surfaces in a single pass without slowing down the operation of the storage device.

[0048] The subject matter of the present disclosure may be referred to by reference Figure 1 and Figure 2 Better understanding.

[0049] Figure 1 and Figure 2 A disk drive 100 is shown as an example of a storage device that may use the subject matter of the present disclosure. In this particular example, the disk drive 100 has three disks 101, 102, 103, but any number of disks may be included in a disk drive that may use the subject matter of the present disclosure. As shown, each disk 101, 102, 103 has a coating 110 on each of its upper and lower surfaces 111, 112, the coating 110 being made of a material that can store data, for example, magnetically. The present disclosure also relates to a disk drive in which one or more disks include a coating 110 on only one surface thereof, but such a disk drive stores less data in the same volume than a disk drive with double-sided disks. The disks 101-103 are mounted on a rotatable spindle 104. A motor 105 rotates the spindle 104 to rotate the disks 101-103 in the direction of arrow A ( Figure 2 Although the motor 105 is shown as being directly connected to the spindle 104, in some cases the motor 105 may be located off-axis from the spindle 104 and connected to the spindle 104 via a belt or gears (not shown).

[0050] Read / write head assembly 120 includes an actuator 121 carrying arms 122-125, one of which is positioned adjacent each surface 111 and 112 of disks 101, 102, 103 having a memory storage coating 110. In this example, there are heads on two surfaces of each of arms 123, 124, for a total of four arms 122-125, but in the example of a single-sided disk described above, there would be only three arms. In other examples, the number of arms would increase or decrease depending on the number of disks.

[0051] Each arm 122-125 carries a plurality of read heads / sensors and write heads at or furthest from the end of the actuator 121 and, in the case of arms 123, 124, on both the upper and lower surfaces. In this case, two sensors 131, 132 are shown, which may represent read and write sensors, respectively, although in some applications, each arm 123, 124 may carry more than one read head / sensor and more than one write head (not shown). Figure 1 and Figure 2 In the configuration shown, the arms 122-125 are aligned along the radius of the disks 101-103 to carry the heads 131, 132 as close as possible to the spindle 104. Figure 1 and Figure 2 This is a schematic diagram only and is not drawn to scale. Typically, for example, the spindle diameter will be larger relative to the disk diameter. Additionally, arms 122-125 will typically not point directly at the center of the disk.

[0052] Motor 126, commonly referred to as a "voice coil motor," moves along arrow B ( Figure 2 ) to move heads 131, 132 along the path indicated by dashed arrow 201. The movement of actuator 121 thus changes both the radial and circumferential positions of heads 131, 132, but the change in circumferential position is relatively insignificant with respect to disk rotation. Therefore, the movement of actuator 121 is used to control the radial position of heads 131, 132.

[0053] The position of the wedge on the surface 111 of the disk 101 (other surfaces are similar) is shown in FIG. Figure 4 Each servo wedge 200 includes data 104 identifying the servo wedge by a wedge index, track index, or sector number (to give angular, tangential, or circumferential position), and by data representing the distance from the spindle at each point along the radius of the disc.

[0054] Each arm 122-125 may include a microactuator 202 ( Figure 2 ). That is, in addition to the actuator pivot point 121, the second pivot point 203 can allow the tip 204 of the arm 122-125 to rotate relative to the arm 122-125 so that the centerline 214 of the tip 204 is no longer collinear with the centerline 141 of the arm 122-125. An electric motor (not shown) similar to the voice coil motor 126 can control the rotation of the microactuator. The size of the microactuator 202 is Figure 2 Typically, the microactuator 202 is proportionally much smaller than the body of the arms 122-125. As noted above, in some implementations, any of the arms 122-125 may include a third actuator segment (not shown).

[0055] If a particular one of the arms 122-125 is between two disks and has heads on its upper and lower surfaces for reading and writing to the respective lower and upper surfaces of two different disks, there may be two separate microactuators 301, 302, such as Figure 3 As shown ( Figure 3 (The disk drive controller 400 is omitted to avoid cluttering the drawing.) Again, the size of the microactuators 301, 302 is exaggerated relative to the body of each arm 122-125. Because each microactuator 301, 302 controls the position of a respective head on a different respective surface, the microactuators 301, 302 are controlled independently of each other.

[0056] Each of the read heads 131, 132 is connected to one of a pair of read channels 401 (there is a corresponding write channel 402) of the hard disk drive controller 400 ( Figure 4). The hard drive controller 400 also includes a processor 410 and a memory 411, as well as a connection 412 to a host processor (not shown). During normal disk operation, the memory 411 can be used to store position error sensor (PES) data indicating track position deviation. The servo control loop in the hard drive controller 400 uses the PES data and the servo wedge data to keep the heads 131, 132 on track.

[0057] As part of the drive manufacturing process, or later but before the drive is used for the first time, in one implementation, servo data is written to the servo wedges 200 on each surface of each disk platter, such as using a self-servo write process as described in commonly assigned U.S. Patent 8,027,117, the entire contents of which are incorporated herein by reference. As described above, in a drive equipped with TDMR, two RDCs may be used, which allows the self-servo write process to be performed on both disk surfaces simultaneously, allowing the servo spiral data to be read from both surfaces simultaneously, with microactuators 202 / 301 / 302 controlled separately to keep both heads on track. However, using microactuators 202 / 301 / 302 to keep both heads on track may introduce phase errors in the servo wedges. Implementations of the disclosed subject matter can be used to avoid phase errors by maintaining tracking and compensating for position differences when writing servo data as described below.

[0058] The potential sources of phase error are Figure 5 5 , wherein arm 501 has a pivot point 511 about the axis of actuator 121, shown as 510, carrying an on-track read head 521 on rail 531, without having to rotate microactuator 202 about axis 551 to a position out of alignment with body 541 of arm 501. Simultaneously, arm 502, having a pivot point 512 about the axis of actuator 121, carries an off-track read head 522 relative to rail 532, shown as 520, and microactuator 202 is maintained aligned with body 542 of arm 502.

[0059] like Figure 6As shown in FIG630 , the microactuator 202 of the arm 502 can be rotated about an axis 652 to move the head 522 into alignment with the track 532. However, while the rotation of the microactuator 202 about the axis 652 provides a cross-track component of motion that moves the head 522 into alignment with the track 532, the rotation also introduces a down-track component 662 of motion. If the writing of particular servo wedge data cannot be completed in a single pass of the head 522, this may occur before the next pass, and adjustment of the microactuator 202 may be required to keep the head 522 on track. The resulting change in down-track component 662 may produce a phase difference between the portions of the servo wedge data written on two separate passes. For the same reason, phase differences between the portions of the servo wedge data written on two separate passes of the head 521 are also possible. Implementations of the disclosed subject matter detect and maintain a record of any such phase differences so that compensation can be applied when writing servo data to either of the tracks 531 and 532.

[0060] In short, two read channels are used to read the servo spiral signals from two read heads to control the positions of the two read heads, including by utilizing the motion of microactuators to control these positions, allowing the corresponding write heads to write finer servo wedge data. The motion of the microactuators used to control these positions is tracked to allow for compensation during the writing process for phase differences between warp lines. A single write channel is sufficient to process the signals from both write heads, and because the amount of servo wedge data to be written is small, both heads can write corresponding servo wedge data within one disk rotation.

[0061] Figure 7 7 is a control system 700 according to an implementation of the disclosed subject matter. The control system 700 reads the servo spiral data from both disk surfaces, tracks the down-track component of the motion 762, and controls triggering of write data channels to be written to both disk surfaces, respectively.

[0062] Figure 7 A control system 700 is depicted coupled to two sets 701, 702 of read and write heads 703, 713, each including a respective read head and a respective write head 704, 714. As depicted, the two sets 701, 702 of read / write heads service opposing surfaces 715, 725 of a single disk platter 705. However, this is merely an example, and the control system 700 can be used to process any two surfaces in a multi-platter disk drive, even on different disks.

[0063] In addition to processing read and write signals in the manner described below, the control system 700 also controls the movement of the read / write heads 701, 702. Specifically, the control system 700 controls the voice coil motor 126 (shown schematically here) to move all heads, as described above, and the individual microactuator controlled motors 706 (shown schematically here), each of which operates by moving the microactuator 202 ( Figure 7 The head position on the corresponding arm is fine-tuned by the corresponding individual in the (not shown) figure.

[0064] like Figure 7 As shown, control system 700 includes a respective preamplifier 707, 717 that interfaces with each respective group 701, 702 of read / write heads. Control system 700 may include as many preamplifiers (not shown) as there are groups of read / write heads in the disk drive being controlled (i.e., as many preamplifiers as there are disk surfaces). Alternatively, because there are only two RDCs in the disk drive, there may be only two preamplifiers 707, 717 that are shared by all groups of read / write heads in the disk drive using, for example, a multiplexer (not shown) to selectively couple the read / write heads to the preamplifiers.

[0065] Each respective preamplifier 707, 717 is capable of directing the signal from its respective read head 703, 713 to either read data channel 0 (R0) 718 or read data channel 1 (R1) 728 in the read / write control unit 708. The disk surface corresponding to one of the read heads 703, 713 is designated as the "primary" surface. The choice of which of the two disk surfaces is "primary" is arbitrary. One of the two read channels 718, 728 to which the designated "primary" surface is coupled is used to demodulate the spiral signal from the primary surface. The demodulated output of the primary surface spiral signal is used to lock a counter (not shown) that is used for timing in a self-servo write system and is used to adjust the disk rotation of a frequency generator in the read / write control unit 708 to match the disk rotation frequency. For example, as shown, a phase-locked loop (PLL) 738 can be used for the frequency generator.

[0066] The disk lock control 719, which may be implemented, for example, in firmware 709, may use the primary surface spiral signal to control the frequency of a PLL 738, which may be used to regulate the rotational speed of the storage medium of the storage device, in a manner similar to the self-servo write operation described in the above-incorporated U.S. Patent 8,027,117. The disk lock control 719 may also use the primary surface spiral signal to command the primary voice coil motor control 720 to maintain the radial position of the read head (703 or 713) for the primary surface aligned with the data track being processed.

[0067] The other of the read heads 703, 713, i.e., the read head not used on the primary surface, is used for the secondary surface, and the secondary surface spiral signal from the other of the read heads 703, 713 is directed by a respective one of the preamplifiers 707, 717 to the other of the read channels 718, 728, i.e., the signal not coupled to the primary surface spiral signal. Figure 7 In the illustrated implementation, the primary surface is coupled to a read channel 718 by a preamplifier 707 , while the secondary surface is coupled to a read channel 728 by a preamplifier 717 .

[0068] "Increment Control" 729 uses the output of the secondary surface spiral signal demodulation, e.g. Figure 7 The output of the read channel 728 in the illustrated implementation is used to command the microactuator-2 control 722 to keep the secondary surface read head aligned with the track being read. The incremental control 729 can use the outputs of the two read channels 718, 728 to determine any phase differences in the primary surface signal between successive passes, as well as any phase differences in the secondary surface signal between successive passes.

[0069] Regarding head positioning, it is usually sufficient to keep the microactuator of the arm carrying the main read head (controlled by microactuator-1 control 721) in a neutral position (i.e., aligned with the body of the arm). However, in some cases, it may be necessary to adjust the microactuators of both heads using microactuator-1 control 721 and microactuator-2 control 722 to keep both heads on their respective tracks.

[0070] As described above, the output of the incremental control 729 is also used to determine any phase differences in the primary surface signal between successive processes and the secondary surface signal between successive processes. As described in the previous paragraph, normally, the head microactuator on the primary surface is maintained in a neutral position, and the microactuator moves only on the head on the secondary surface, which means that normally, phase differences will only occur between the weld beads on the secondary surface. However, as described in the previous paragraph, if the two microactuators are moved so that the two heads remain on their respective tracks, respective phase differences may occur between the weld beads on the primary and secondary surfaces. In any case, the self-servo write pattern generator 748 (in this embodiment, part of the self-servo write finite state machine 758) can use the result 739 of determining the phase difference for either surface by the incremental control 729 to adjust the self-servo write pattern for that surface to take into account the phase difference, for example, as described in commonly assigned U.S. Patent No. 10,971,187, which is incorporated herein by reference in its entirety.

[0071] As mentioned above, there is only one write data channel. The self-servo write data is output as signal W0 to the two preamplifiers 707717. Figure 8As shown in the timing diagram of FIG, when the data to be written is present on W0 at 801, 802, 803, the write gate signal WG is asserted at 811, 812, 813 to enable writing. When WG is asserted, the write select signal WS determines which of the preamplifiers 701, 717 will be actively written to and therefore which of the primary or secondary surfaces will be written to. In the example shown, when WS is high, the first head 703 ("head 0") on the primary surface is active, and when WS is low, the second head 713 ("head 1") on the secondary surface is active. As described above, the two surfaces can share a write channel in this manner because the write time is much shorter than the time required to move from one servo wedge to the next. Therefore, the secondary surface may be written at a later time than the primary surface with the same disk rotation. The timing of the WDC switching to a particular channel can also be used to compensate for the phase difference described above.

[0072] Figure 9 is a flow chart illustrating a method 900 for simultaneously performing self-servo write operations on two surfaces of a multi-surface memory device according to an embodiment of the present invention.

[0073] At 901, a first read head of a storage device detects a self-servo write spiral signal from a first track on a first storage medium surface of the storage device. At 902, the self-servo write spiral signal from the first track is processed using a first read channel of the storage device to generate a first control signal for positioning the first read head relative to the first track. At 904, a second read head of the storage device detects a self-servo write spiral signal from a second track on a second storage medium surface of the storage device. At 905, the self-servo write spiral signal from the second track is processed using a second read channel of the storage device to generate a second control signal for positioning the second read head relative to the second track. At 906, the first write head is positioned relative to the first track using the first control signal. At 907, the second write head is positioned relative to the second track using the second control signal. At 908, a phase difference between a first stroke of one of the first read head and the second read head and a second stroke of one of the first read head and the second read head is determined based on the positions of the first read head and the second read head. At 909, the servo wedge data for the second pass is adjusted using the phase difference relative to the servo wedge data for the first pass. At 910, for the current pass, the servo wedge data for the first track is written to the first track, and the servo wedge data for the second track is written to the second track using a single write data channel of the storage device, and method 900 ends.

[0074] It can be seen that a method of performing self-servo write operations simultaneously on two surfaces of a multi-surface memory device, and a multi-surface memory device configured for such a method are provided.

[0075] As used herein and in the following claims, the structure "one of A and B" shall mean "A or B."

[0076] It should be noted that the above is merely illustrative of the principles of the present invention, and that the present invention may be practiced through other implementation examples than the described implementation examples, which are presented for illustrative rather than limiting purposes, and that the present invention is limited only by the following claims.

Claims

1. A self-servo writing method in a storage device, the method comprising: detecting, using a first pickup head of the storage device, a self-servo write spiral signal from a first track on a surface of a first storage medium of the storage device; processing the self-servo write spiral signal from the first track using a first read channel of the storage device to generate a first control signal for positioning the first read head relative to the first track; detecting, using a second pickup head of the storage device, a self-servo write spiral signal from a second track on a surface of a second storage medium of the storage device; processing the self-servo write spiral signal from the second track using a second read channel of the storage device to generate a second control signal for positioning the second read head relative to the second track; positioning a first write head relative to the first track using the first control signal via a single write channel of the storage device; positioning a second write head relative to the second track using the second control signal via the single write channel of the storage device; as well as The servo wedge data for the first track is written to the first track, and the servo wedge data for the second track is written to the second track using the single write data channel of the storage device by: providing a write data signal including the servo wedge data of the first track and the servo wedge data of the second track to both a write head of the first track and a write head of the second track; and A write select signal is triggered to write the servo wedge data in the write data signal to a correct one of the first track and the second track.

2. The method according to claim 1, further comprising: determining, based on a position of the corresponding one of the first and second read heads during consecutive passes over a position on a corresponding one of the first and second storage medium surfaces, a phase difference between data written by the corresponding one of the first and second write heads during a first pass of the consecutive passes and data written by the corresponding one of the first and second write heads during a second pass of the consecutive passes; as well as The phase difference is used to adjust servo wedge data of a second one of the consecutive lines relative to servo wedge data of a first one of the consecutive lines, wherein: Writing the servo wedge data in the write data signal to a correct one of the first track and the second track includes writing the adjusted servo wedge data for the first track to the first track and writing the adjusted servo wedge data for the second track to the second track using the single write data channel of the storage device.

3. The method according to claim 2, further comprising: The timing of at least one of: writing of the servo wedge data of the first track to the first track and writing of the servo wedge data of the second track to the second track is adjusted to compensate for the phase difference. The method of claim 2 , wherein the triggering is performed to compensate for the phase difference.

5. The method according to claim 1, further comprising: The self-servo write spiral signal from the first track is processed to generate a frequency control signal for adjusting a rotational speed of a storage medium of the storage device.

6. The method of claim 1 , wherein positioning the first read head relative to the first track, and positioning the second read head relative to the second track comprises: A common actuator is rotated having a first arm carrying the first readhead and a second arm carrying the second readhead.

7. The method of claim 6, wherein positioning the first read head relative to the first track, and positioning the second read head relative to the second track, further comprises: A microactuator on at least one of the first arm and the second arm is adjusted.

8. The method of claim 7 , wherein adjusting a microactuator on at least one of the first arm and the second arm comprises: A first microactuator on the first arm and a second microactuator on the second arm are independently adjusted.

9. A storage device comprising: a storage medium having a plurality of storage medium surfaces on which servo data is written using a self-servo writing method; a first pickup head configured to detect a self-servowritten spiral signal from a first track on a surface of a first storage medium of the storage device; a first write head corresponding to the first read head and configured to write self-servo write data to the first track; a second pickup head configured to detect a self-servowritten spiral signal from a second track on a second storage medium surface of the storage device; a second write head corresponding to the second read head and configured to write self-servo write data to the second track; first read data channel circuitry configured to process the self-servo write spiral signal from the first track to generate first control signals for positioning the first read head and the first write head relative to the first track; second read data channel circuitry configured to process the self-servo write spiral signal from the second track to generate second control signals for positioning the second read head and the second write head relative to the second track; Actuator control circuit system: responsive to the first control signal and configured to control positioning of the first write head relative to the first track, and responsive to the second control signal and configured to control positioning of the second write head relative to the second track; as well as A single write data channel is configured to write servo wedge data for the first track to the first track and servo wedge data for the second track to the second track by: providing a write data signal including the servo wedge data of the first track and the servo wedge data of the second track to both a write head of the first track and a write head of the second track; and A write select signal is triggered to write the servo wedge data in the write data signal to a correct one of the first track and the second track.

10. The storage device according to claim 9, further comprising: channel increment control circuitry configured to determine, based on a position of a corresponding one of the first and second read heads during successive passes over a location on a corresponding one of the first and second storage medium surfaces, a phase difference between data written by the corresponding one of the first and second write heads during a first pass of the successive passes and data written by the corresponding one of the first and second write heads during a second pass of the successive passes, wherein the actuator control circuitry is configured to use the phase difference to adjust servo wedge data of the second pass of the successive passes relative to servo wedge data of the first pass of the successive passes; as well as A single write data channel is configured to write servo wedge data for the first track into the first track and to write servo wedge data for the second track into the second track.

11. The storage device of claim 10 , wherein the single write data channel is further configured to adjust the timing of at least one of the following items to compensate for the phase difference: writing of the servo wedge data of the first track to the first track, and writing of the servo wedge data of the second track to the second track. 12 . The memory device of claim 10 , wherein the single write data channel is configured to perform the triggering to compensate for the phase difference.

13. The storage device of claim 9, further comprising disk lock control circuitry configured to process the self-servo write spiral signal from the first track to generate a frequency control signal for adjusting a rotational speed of a storage medium of the storage device.

14. The storage device of claim 9, further comprising a common actuator configured to position a first arm carrying the first read head relative to the first rail and to position a second arm carrying the second read head relative to the second rail.

15. The storage device of claim 14, wherein the common actuator is configured to rotate to position the first arm and the second arm.

16. The storage device of claim 14, further comprising a microactuator on at least one of the first arm and the second arm, the microactuator configured to perform at least one of: positioning the first read head relative to the first track, and positioning the second read head relative to the second track.

17. The storage device of claim 16, wherein the microactuator on at least one of the first arm and the second arm comprises: A first microactuator is on the first arm and a second microactuator is on the second arm.

18. The storage device according to claim 16, wherein: One of the first arm and the second arm is adjacent to two different storage medium surfaces; and The one of the first arm and the second arm includes: a microactuator carrying a head for one of the two different storage medium surfaces, and another microactuator carrying a head for the other of the two different storage medium surfaces.

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