阅读说明：本技术 用于磁存储介质的恒定密度写入 (Constant density writing for magnetic storage media ) 是由 S·卡切玛尔特 于 2020-03-10 设计创作，主要内容包括：本公开描述了用于磁存储介质的恒定密度写入的各方面。在一些方面,恒定密度写入器延迟写入数据内的位之间的转变以实现恒定密度写入。写入数据具有基于恒定时钟信号的初始位周期,该恒定时钟信号是基于介质磁盘的旋转而被生成的。恒定密度写入器修改写入数据以生成相位延迟写入数据,相位延迟写入数据的位周期大于或等于初始位周期。为了实现这个位周期,恒定密度写入器改变写入数据内的位转变的写入相位。恒定密度写入器还可以插入拉伸位,过滤单位转变,并且减轻相位延迟写入数据内的故障。(The present disclosure describes aspects for constant density writing of magnetic storage media. In some aspects, a constant density writer delays transitions between bits within write data to achieve constant density writing. The write data has an initial bit period based on a constant clock signal that is generated based on the rotation of the media disk. The constant density writer modifies the write data to generate phase-delayed write data having a bit period greater than or equal to the initial bit period. To achieve this bit period, a constant density writer changes the write phase of the bit transitions within the write data. Constant density writers may also insert stretch bits, filter unit transitions, and mitigate failures within phase-delayed write data.)

1. A method, comprising:

accepting write data from a host;

determining respective bit periods for concentric tracks of a plurality of concentric tracks of a disk of a magnetic storage medium, each of the respective bit periods associated with a particular concentric track of the plurality of concentric tracks, the respective bit periods varying based on respective radii of the plurality of concentric tracks; the respective bit periods are configured to maintain a particular bit density across the plurality of concentric tracks;

for the write data, selecting a concentric track from the plurality of concentric tracks, the concentric track associated with a bit period of the respective bit periods;

delaying transitions between bits of the write data based on the bit periods associated with the concentric tracks to generate phase-delayed write data, the delay of the transitions effective to cause bits of the phase-delayed write data to have the bit periods associated with the concentric tracks; and

writing the bits of the phase-delayed write data along the concentric tracks such that the concentric tracks have the particular bit density.

2. The method of claim 1, further comprising:

generating a clock signal having a clock period associated with a rotation of the disk; and

generating the write data to have an initial bit period based on the clock period of the clock signal,

wherein the respective bit periods associated with the plurality of concentric tracks are greater than or equal to the initial bit period.

3. The method of claim 2, further comprising:

defining phases of the clock cycle, the phases including a first phase and a second phase, wherein:

the clock signal comprises a first clock cycle and a second clock cycle;

the bits of the phase-delayed write data include a first bit, a second bit, and a third bit; and

the delay of the transition causes a transition between the first bit and the second bit to occur at the first phase of the first clock cycle, and the delay of the transition causes another transition between the second bit and the third bit to occur at the second phase of the second clock cycle.

4. The method of claim 3, wherein:

the first clock cycle and the second clock cycle are consecutive clock cycles of the clock signal; or

The first clock cycle is separated from the second clock cycle by one or more other clock cycles of the clock signal.

5. The method of claim 3, wherein the bit period associated with the concentric tracks is equal to a sum of an integer multiple of the clock period and one of the phases.

6. The method of claim 1, further comprising:

generating initial phase data based on the bit period and the write data prior to delaying the transition, the initial phase data indicating a starting phase of the bit within the write data based on a phase of a clock period; and

generating stretched write data based on the initial phase data by inserting at least one stretched bit between a first one of the bits of the write data and a second one of the bits of the write data, the insertion of the at least one stretched bit effective to shift the starting phase of the second bit by a multiple of the clock period,

wherein the delaying of the transitions between the bits of the write data comprises delaying transitions between bits of the stretched write data based on the initial phase data.

7. The method of claim 6, further comprising:

generating filtered write data by filtering unit transitions within the bits of the stretched write data prior to delaying the transitions,

wherein delaying the transitions between the bits of the stretched write data comprises delaying transitions between bits of the filtered write data based on the initial phase data.

8. The method of claim 1, further comprising:

determining respective start phases for the concentric tracks of the concentric tracks, each of the respective start phases associated with another particular concentric track of the plurality of concentric tracks; the respective start phases are configured to align bits across the plurality of concentric tracks.

9. An apparatus, comprising:

an interface for receiving write data from a host;

a disk of magnetic storage media for storing said written data, said disk comprising a plurality of concentric tracks;

a magnetic media writer configured to write the write data as data bits to the magnetic storage media; and

a constant density writer configured to:

determining respective bit periods of concentric tracks of the plurality of concentric tracks, each of the respective bit periods associated with a particular concentric track of the plurality of concentric tracks, the respective bit periods varying based on respective radii of the plurality of concentric tracks; the respective bit periods are configured to maintain a particular bit density across the plurality of concentric tracks;

for the write data, selecting a concentric track from the plurality of concentric tracks, the concentric track associated with a bit period of the respective bit periods;

delaying transitions between bits of the write data based on the bit periods of the concentric tracks to generate phase-delayed write data, the delay effective to cause bits of the phase-delayed write data to have the bit periods associated with the concentric tracks; and

transmitting the phase-delayed write data to the magnetic media writer to enable the concentric tracks to have the particular bit density.

10. The apparatus of claim 9, wherein:

the write data has an initial bit period based on a rotation of the disk; and

the respective bit periods associated with the plurality of concentric tracks are greater than or equal to the initial bit period.

11. The apparatus of claim 10, wherein the constant density writer is configured to:

generating initial phase data based on the bit period and the write data prior to delaying the transition, the initial phase data indicating a starting phase of the bit within the write data based on a phase of the initial bit period;

generating stretched write data based on the initial phase data by inserting at least one stretch bit between a first one of the bits of the write data and a second one of the bits of the write data, the inserting of the at least one stretch bit effective to shift a starting one of the starting phases associated with the second bit by a multiple of the initial bit period; and

delaying transitions between bits of the stretched write data based on the initial phase data.

12. The apparatus of claim 11, wherein the constant density writer is configured to:

generating filtered write data by filtering unit transitions within the bits of the stretched write data prior to delaying the transitions; and

delaying transitions between bits of the filtered write data based on the initial phase data.

13. The device of claim 9, wherein the respective bit periods of two consecutive concentric tracks of the plurality of concentric tracks differ by a fraction of a nanosecond.

14. The apparatus of claim 9, wherein:

the write data comprises another write data;

the magnetic medium writer is configured to write the other written data as other data bits to the magnetic storage medium;

the constant density writer is configured to:

for the other write data, selecting another concentric track of the plurality of concentric tracks, the other concentric track associated with another bit period of the respective bit periods;

delaying transitions between bits of the other write data based on the other bit period of the other concentric track to generate other phase-delayed write data, the delay effective to cause the bits of the other phase-delayed write data to have another bit period associated with the other concentric track; and

transmitting the other phase-delayed write data to the magnetic media writer to enable the other concentric track to have the particular bit density;

the disk of the magnetic storage medium is configured to rotate at an angular velocity when the magnetic media writer writes the write data and the other write data; and

based on the particular bit density, a significance period of the data bits written along the concentric track is approximately equal to a significance period of the other data bits written along the other concentric track.

15. A system on a chip (SoC), comprising:

an interface to a host from which write data is received for writing to a magnetic storage medium;

an interface to a media writer of the magnetic storage media; and

a constant density writer implemented at least partially in hardware, the constant density writer configured to:

determining respective bit periods for concentric tracks of the plurality of concentric tracks, each bit period of the respective bit periods being associated with a particular concentric track of the plurality of concentric tracks, the respective bit period varying based on respective radii of the plurality of concentric tracks; the respective bit periods are configured to maintain a particular bit density across the plurality of concentric tracks;

for the write data, selecting a concentric track from the plurality of concentric tracks, the concentric track associated with a bit period of the respective bit periods;

delaying transitions between bits of the write data based on the bit periods of the concentric tracks to generate phase-delayed write data, the delay of the transitions effective to cause bits of the phase-delayed write data to have the bit periods associated with the concentric tracks; and

transmitting the phase-delayed write data to the magnetic media writer to enable the concentric tracks to have the particular bit density.

16. The SoC of claim 15, wherein:

the write data has an initial bit period based on a rotation of the disk; and

the respective bit periods associated with the plurality of concentric tracks are greater than or equal to the initial bit period.

17. The system-on-chip of claim 16, wherein at least one of the respective bit periods is not a multiple of the initial bit period.

18. The SoC of claim 16, wherein the constant density writer is configured to:

generating initial phase data based on the bit period and the write data prior to delaying the transition, the initial phase data indicating a starting phase of the bit within the write data based on a phase of the initial bit period;

generating stretched write data based on the initial phase data by inserting at least one stretch bit between a first one of the bits of the write data and a second one of the bits of the write data, the inserting of the at least one stretch bit effective to shift a starting one of the starting phases associated with the second bit by a multiple of the initial bit period; and

delaying transitions between bits of the stretched write data based on the initial phase data.

19. The SoC of claim 18, wherein the constant density writer is configured to:

generating filtered write data by filtering unit transitions within the bits of the stretched write data prior to delaying the transitions; and

delaying transitions between bits of the filtered write data based on the initial phase data.

20. The SoC of claim 15, wherein the respective bit periods of two consecutive concentric tracks of the plurality of concentric tracks differ by a fraction of a nanosecond.

Background

Electronic devices provide many services to modern society. These services enable electronic devices to provide entertainment, aid in scientific research and development, and provide many modern conveniences. Many of these services create or use data stored by the electronic device. The data may include digital media such as books or movies, algorithms to perform complex simulations, personal user data, applications, and the like. To avoid exceeding data storage limits, it is beneficial to increase the data storage capacity of the electronic device and avoid deleting data, limiting services or purchasing additional external storage devices.

Many electronic devices use media drives to store data on magnetic disks, such as hard disk drives. Typically, the data for each disk is organized along concentric tracks of the magnetic medium of individual bits (bits) in which the data is written. To accommodate the larger amount of user data, the data density of each media disk has increased substantially, thereby shrinking the physical geometry of both the written tracks and bits on the magnetic media. To accommodate larger amounts of user data, it is beneficial to efficiently utilize the area of the media disk.

Disclosure of Invention

This summary is provided to introduce a selection of subject matter that is further described in the detailed description and the drawings. Accordingly, this summary should not be used to limit the scope of the claimed subject matter.

This disclosure describes apparatus and techniques for constant density writing of magnetic storage media that delay delayed transitions between bits within a data stream. In particular, a constant density writer accepts write data having an initial bit period based on a fixed clock signal. The clock signal is generated based on the rotation of the media disk. The constant density writer modifies the write data to generate phase-delayed write data having a bit period greater than or equal to the initial bit period. To achieve a bit period, a constant density writer changes the write phase of the bit transitions within the write data. Constant density writers can also insert stretch bits, filter unit-bit transitions, and mitigate glitches (glitch) in phase-delayed write data.

In some aspects, a constant density writer for a magnetic storage medium implements a method of accepting written data from a host. The constant density writer determines respective bit periods of concentric tracks of a plurality of concentric tracks of a disk of a magnetic storage medium. Each bit period is associated with a particular concentric track. The respective bit periods vary based on respective radii of the plurality of concentric tracks and are configured to maintain a particular bit density across the plurality of concentric tracks. The constant density writer selects a concentric track from a plurality of concentric tracks for writing data. The constant density writer delays transitions between bits of write data based on bit periods associated with the concentric tracks to generate phase-delayed write data. In this manner, the bits of phase-delayed write data have a bit period associated with the concentric tracks. The bits of phase-delayed write data are written along the concentric tracks such that the concentric tracks have a particular bit density.

In other aspects, an apparatus includes an interface to receive write data from a host, a magnetic disk of a magnetic storage medium to store the write data, a magnetic medium writer configured to write the write data as data bits to the magnetic storage medium, and a constant density writer. The constant density writer is configured to determine respective bit periods of concentric tracks of the plurality of concentric tracks. Each bit period is associated with a particular concentric track. The respective bit periods vary based on respective radii of the plurality of concentric tracks and are configured to maintain a particular bit density across the plurality of concentric tracks. The constant density writer is further configured to select a concentric track from the plurality of concentric tracks for writing data. The concentric tracks are associated with bit periods of the respective bit periods. To generate the phase-delayed write data, the constant density writer delays transitions between bits of the write data based on a bit period of the concentric tracks to effectively cause the bits of the phase-delayed write data to have a bit period associated with the concentric tracks. The constant density writer is further configured to transmit phase-delayed write data to the magnetic media writer to enable the concentric tracks to have a particular bit density.

In other aspects, a system on a chip (SoC) is described that includes an interface to a host from which write data is received, an interface to a magnetic media writer of a magnetic storage medium, and a constant density writer implemented at least in part in hardware. The constant density writer is configured to determine respective bit periods of concentric tracks of the plurality of concentric tracks. Each bit period is associated with a particular concentric track. The respective bit periods vary based on respective radii of the plurality of concentric tracks and are configured to maintain a particular bit density across the plurality of concentric tracks. The constant density writer is further configured to select a concentric track from the plurality of concentric tracks for writing data. The concentric tracks are associated with bit periods of the respective bit periods. To generate the phase-delayed write data, the constant density writer delays transitions between bits of the write data based on a bit period of the concentric tracks to effectively cause the bits of the phase-delayed write data to have a bit period associated with the concentric tracks. The constant density writer is further configured to transmit phase-delayed write data to the magnetic media writer to enable the concentric tracks to have a particular bit density.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

Drawings

The details of one or more implementations for constant density writing of magnetic storage media are set forth in the accompanying drawings and the description below. In the drawings, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference symbols in different instances in the description and the figures indicates similar elements:

FIG. 1 illustrates an example operating environment with a device having magnetic storage media implemented therein according to one or more implementations.

FIG. 2 illustrates an example configuration of the hard disk drive shown in FIG. 1.

FIG. 3 shows an example configuration of a read/write channel.

Fig. 4 illustrates an exemplary graph of the write data and the phase-delayed write data of fig. 3.

FIG. 5 illustrates an example implementation of the constant density writer of FIG. 1.

FIG. 6 shows an example plot of data generated by the constant density writer of FIG. 5.

FIG. 7 depicts an example method for implementing constant density writing of a magnetic storage medium using the constant density writer of FIG. 5.

FIG. 8 illustrates an example system-on-chip (SoC) environment for implementing aspects of constant density writing of the magnetic storage media of FIG. 2.

FIG. 9 illustrates an example storage media controller configured to implement aspects of constant density writing in the magnetic media of FIG. 2 associated with the controller.

Detailed Description

To accommodate larger amounts of user data, it is beneficial to efficiently utilize the area of the media disk. For example, as described in this disclosure, constant density writing enables media disks to have similar bit densities across different concentric tracks having different radii. Instead of writing data using a single frequency, data may be written at a higher frequency along concentric tracks located toward the outside of the media disk relative to data written along other concentric tracks located toward the center of the media disk. In this manner, constant density writing efficiently utilizes the area of the media disk and enables additional data to be written to the media disk.

However, some conventional media drives generate write patterns based on a fixed clock frequency that is determined based on the rotation of the media disk. In some media drives, the clock frequency may be adjusted relative to the rotation of the media disk. However, these adjustments may be relatively large and not small enough to achieve constant density writing. Thus, the media drive generates multiple regions with different bit densities across the media disk, which is less efficient than constant density writing.

This disclosure describes apparatus and techniques for constant density writing of magnetic storage media. Rather than adjusting the clock frequency relative to the rotation of the media disk, the described apparatus and techniques achieve constant density writing that delays transitions between bits within the data stream. In particular, a constant density writer accepts write data having an initial bit period based on a fixed clock signal. The clock signal is generated based on the rotation of the media disk. The constant density writer modifies the write data to generate phase-delayed write data having a bit period greater than or equal to the initial bit period. To achieve a bit period, a constant density writer changes the write phase of the bit transitions within the write data. Constant density writers may also insert stretch bits, filter unit transitions, and mitigate failures within phase-delayed write data.

The following discussion describes an operating environment, techniques employed in the operating environment, and a system on chip (SoC) in which components of the operating environment are embodied. In the context of the present disclosure, reference is made to an operating environment by way of example only.

Operating environment

FIG. 1 illustrates an example operating environment 100, with the operating environment 100 having a computing device 102 capable of storing or accessing various forms of data or information. Examples of computing device 102 include laptop 104, desktop 106, and server 108, any of which may be configured as part of a storage network or cloud storage. Other examples of computing device 102 (not shown) include a tablet computer, a set-top box, a data storage device, a wearable smart device, a television, a content streaming device, a high-definition multimedia interface (HDMI) media bar, a smart appliance, a home automation controller, a smart thermostat, an internet of things (IoT) device, a Mobile Internet Device (MID), a Network Attached Storage (NAS) drive, a converged storage system, a gaming console, an automobile entertainment device, an automobile computing system, an automobile control module (e.g., an engine or powertrain control module), and so forth.

In general, computing device 102 provides, communicates, or stores data for any suitable purpose, such as to enable functionality of a particular type of device, provide a user interface, enable network access, implement a gaming application, play back media, provide navigation, edit content, provide data storage, and so forth. Alternatively or additionally, the computing device 102 can store various data, such as databases, user data, multimedia, applications, operating systems, and so forth. One or more computing devices 102 may be configured to provide remote data storage or services, such as cloud storage, archiving, backup, client services, record keeping, and the like.

Computing device 102 includes a processor 110 and a computer-readable storage medium 112. The processors 110 are implemented as any suitable type or number of processors (single core or multi-core (e.g., ARM or x86 processor cores)) for executing instructions or commands of an operating system or other program of the computing device 102. The computer-readable storage media 112(CRM 112) includes memory media 114 and media drives 116. The memory medium or system memory of computing device 102 includes any suitable type or combination of volatile or non-volatile memory. For example, volatile memory of the computing device 102 includes various types of Random Access Memory (RAM), dynamic RAM (dram), static RAM (sram), and the like. The non-volatile memory may include Read Only Memory (ROM), electrically erasable programmable ROM (eeprom), or flash memory (e.g., NOR flash memory or NAND flash memory). These memories, alone or in combination, store data associated with applications and/or operating systems of the computing device 102.

The media drive 116 of the computing device 102 comprises one or more media drives or is implemented as part of a data storage system associated with the computing device 102. In this example, media drive 116 includes a hard disk drive 118(HDD 118), HDD 118 being capable of storing data and described with reference to various aspects of constant density writing. Alternatively or additionally, media drives 116 may be configured as any suitable type of data storage drive or system, such as a storage device, storage drive, storage array, storage volume, or the like. Although described with reference to the computing device 102, the media drive 116 may also be implemented as a standalone device alone or as part of a larger storage complex, such as a data center, server farm, or virtualized storage system (e.g., for cloud-based storage or services) in which aspects of constant density writing are implemented.

In the depicted configuration, computing device 102 also includes I/O ports 120, a graphics processing unit (unit) (GPU, not shown), and a data interface 122. In general, the I/O ports 120 allow the computing device 102 to interact with other devices, peripherals, or users. For example, the I/O ports 120 may include or be coupled to a universal serial bus, a human interface device, an audio input, an audio output, and the like. The GPU processes and renders graphics-related data of the computing device 102, such as user interface elements of an operating system, applications, and so forth. In some cases, the GPU accesses a portion of local memory to render graphics, or includes dedicated memory (e.g., video RAM) for rendering graphics for the computing device 102.

The data interface 122 of the computing device 102 provides connectivity to one or more networks and other devices connected to the networks. The data interface 122 may include a wired interface, such as an ethernet or fiber optic interface, for data transfer over a local network, an intranet, or the internet. Alternatively or additionally, data interface 122 may include a wireless interface that supports communication over a wireless network, such as a wireless LAN, a wide area wireless network (e.g., a cellular network), and/or a Wireless Personal Area Network (WPAN). In accordance with one or more aspects of constant density writing of magnetic storage media, any data transferred through the I/O ports 120 or the data interface 122 can be written to or read from a storage system of the computing device 102.

Returning to media drive 116, computing device 102 includes a hard disk drive 118 as shown and/or other types of storage media having constant density writing implemented thereon. Although not shown, other configurations of the media drive 116 are also contemplated, such as tape drives, optical media drives, HDD/SSD hybrid drives, and other storage systems that write data to a storage medium (e.g., magnetic or optical storage medium). Alternatively or additionally, the computing device 102 may include an array of media drives, or a media drive aggregation device or host that functions as a plurality of media drives in which aspects of constant density writing are implemented.

In this example, disk drive 118 includes a head disk assembly 124(HDA 124) and a drive control module 126 to implement or enable functions of hard disk drive 118, which may include self-servo writing. In some cases, the drive control module 126 is implemented as a Printed Circuit Board Assembly (PCBA) with semiconductor devices, logic, or other circuitry. The HDA 124 includes one or more media disks 128 mounted on an integrated spindle and motor assembly 130. The spindle and motor assembly 130 rotates the media disk 128 under (or over) a read/write head 132 coupled to a head assembly (not shown) of the HDA 124. The media disk 128 may be coated with a hard magnetic material (e.g., a granular surface or a thin film surface) and may be written to or read from a single side or both sides.

The read/write head 132 is operatively coupled to a preamplifier/writer module 134 (preamplifier/writer 134) of the HDA 124 that includes a preamplifier circuit. The preamplifier/writer 134 receives or stores head selection, amplification, or sense current values useful for writing data to the magnetic media 202 or reading data from the magnetic media 202.

As shown in FIG. 1, the example drive control module 126 of the hard disk drive 118 includes a storage medium controller 136, a servo control unit 138, and a read/write channel 140(R/W channel 140). In some aspects, the read/write channel 140 includes a constant density writer 142, the constant density writer 142 for generating, managing or modifying various signals or data to achieve the features of constant density writing of magnetic storage media. The constant density writer 142 is further described with reference to fig. 3-6. In general, the drive control module 126 directs or uses the servo control unit 138 to control mechanical operations, such as positioning the read/write head 132 via the HDA 124 and controlling rotational speed via the spindle and motor assembly 130. The drive control module 126 or its components may be implemented as one or more IC chips, a system on a chip, a system in a package, or a microprocessor provided with or implementing a hard disk drive controller. The drive control module 126 may also include drive electronics (not shown), and/or include various interfaces, such as a host bus interface, a storage medium interface, a spindle interface, or a preamplifier/writer interface.

By way of example, considering FIG. 2, FIG. 2 provides an example configuration of hard disk drive 118, shown generally at 200. As shown in fig. 2, the HDA 124 of the hard disk drive 118 includes an integrated spindle and motor assembly 130, with the media disks 128 of the magnetic media 202 supported and/or operated by the spindle and motor assembly 130. The arm 204 may manipulate the read/write head 132 (or multiple read/write heads 132) and thus position it over a desired track 206 of the magnetic media 202 on the media disk 128. In various aspects, the read/write head 132 includes various numbers of head elements with combined or separate functions (e.g., dedicated R/W functions). For example, the read/write head 132 includes one or more readers (read heads/elements) and one writer (write heads/elements). In other cases, the read/write head 132 includes a dedicated write head (element) and one or more separate additional dedicated read heads (elements). Alternatively or additionally, although multiple arms 204 are shown in FIG. 2, the HDA 124 or spindle and motor assembly 130 may be implemented with a single arm 204 or other suitable structure for positioning the read/write head 132. The HDA 124 and the drive control module 126 may be implemented separately, on separate substrates, and/or as separate PCBA's of the media drives. Signals or data transmitted between the HDA 124 and the drive control module 126 may be transmitted via a flexible printed cable or other suitable connection structure (such as traces, connectors, bond wires, solder balls, etc.).

FIG. 2 also includes an illustration of an example magnet 208 of the magnetic media 202 written to the media disk 128. One or more of the read/write heads 132 write magnets 208 to respective ones of the tracks 206 of the media disks 128, with sectors provided for each of the tracks (e.g., sectors of the track 206). For purposes of illustration, top media disk 128 is shown to include track 206, e.g., after being written by read/write head 132 with magnet 208. Generally, during a write operation, the read/write head 132 is driven by a write current provided by the preamplifier/writer 134, thereby using an electrical signal to generate and/or transmit a magnetic field having an associated polarity to the media disk 128. In response to application of a magnetic field or write field, the read/write head 132 forms a plurality of magnets 208 in the magnetic grains of the tracks 206 of the media disk 128. The HDA 124 of the hard disk drive 118 is configured to perform write operations according to any suitable recording technique, such as Perpendicular Magnetic Recording (PMR), Shingled Magnetic Recording (SMR), Heat Assisted Magnetic Recording (HAMR), Microwave Assisted Magnetic Recording (MAMR), and so forth.

As shown at 210, the magnetic medium 202 includes a first concentric track 206-1 and a second concentric track 206-2. The first concentric track 206-1 is located near an inner portion of the magnetic medium 202, while the second concentric track 206-2 is located near an outer portion of the magnetic medium 202. Thus, the first concentric track 206-1 has a small radius and circumference relative to the second concentric track 206-2. As the magnetic medium 202 rotates, the first concentric track 206-1 has a linear velocity 214-1, which linear velocity 214-1 is less than the linear velocity 214-2 of the second concentric track 206-2 due to the difference in radius. To achieve a constant density across the magnetic medium 202, the constant density writer 142 generates phase-delayed write data having different bit periods (e.g., different magnet periods or different magnetic write periods) for different concentric tracks 206. The difference in bit periods causes the preamplifier/writer 134 to write across the first concentric track 206-1 at the first write frequency 216-1 and across the second concentric track 206-2 at the second write frequency 216-2. The second write frequency 216-2 is higher than the first write frequency 216-1 to compensate for the difference in linear velocities 214-1 and 214-2. By using the appropriate write frequency 216, the preamplifier/writer 134 writes magnets having approximately the same effective bit period 212 along the first concentric track 206-1 and the second concentric track 206-2. In this manner, the constant density writer 142 enables data bits to have a constant density across the media disk 128 in order to efficiently utilize the area of the media disk 128.

FIG. 3 illustrates an example configuration of a read/write channel 140 implemented in accordance with one or more aspects for constant density writing of magnetic storage media. In this example, a constant density writer 142 is operatively coupled to the read/write channel 140.

In this example, the host interface 302 provides write data 304 or other information to the read/write channel 140 or a storage medium controller on which the read/write channel 140 is embodied. In general, the read/write channel 140 provides phase-delayed write data 306 to the preamplifier 134 of the media drive, and the phase-delayed write data 306 may include signals corresponding to a data pattern intended for writing on the media. In aspects of constant density writing, the constant density writer 142 varies the phase delay write data 306 sent to the preamplifier 134, such as by adjusting the bit period based on the selected concentric track 206, inserting stretch bits, filtering unit transitions, or any combination of similar operations. The constant density writer 142 may also generate or cause the read/write channel 140 to generate a control signal 308 for the preamplifier 134 to enable or disable operation of the preamplifier 134.

In general, the preamplifier 134 or preamplifier circuitry 310 generates or provides a write current to the write head 132 of the media drive 116 having a polarity or pattern of transitions corresponding to the phase-delayed write data 306 (modified or unmodified) and/or the control signal 308 for constant density writing. Based on the data and/or control signal patterns provided by the read/write channel 140 and the constant density writer 142, the preamplifier 134 generates a pulse or changes the polarity of the write current sent to the write head 132.

The write current 312 generated by the preamplifier 134 is provided to the corresponding write head 132 of the magnetic medium 202. Based on the write current 312, the write head 132 generates a magnet write field 314 to form a magnet corresponding to the phase-delayed write data 306 or any suitable form of signaling or encoding for data received from the host interface 302. For example, the magnet write field 314 generates a pulse when the phase delays transitions of the write data 306 to write or form a corresponding magnet of a corresponding polarity in the magnetic media 202.

As an example, considering fig. 4, fig. 4 illustrates an example time diagram of the write data 304 and the phase-delayed write data 306 according to various aspects of constant density writing at 400. The graph or waveform of FIG. 4 also includes a clock signal 402, and the clock signal 402 may be generated or derived by a Phase Locked Loop (PLL) or other suitable oscillator of the read/write channel 140. Generally, the clock period 404 (or frequency) of the clock signal 402 is determined based on the rotation of the media disk 128 and remains constant. The clock cycle 404 forms a time base that sets an initial bit period 406 of the write data 304. In other words, the initial bit period 406 is equal to the clock period 404.

To perform constant density writing, the constant density writer 142 (FIG. 3) identifies a set of phases 408, the phases 408 dividing the clock cycle 404. In FIG. 4, the set of phases 408 includes phases 410-1 through 410-N, where N represents a positive integer. As an example, the number of phases 410 (e.g., N) may be on the order of tens, hundreds, or thousands, and is selected to enable the constant density writer 142 to shift the phase of the data bits 412 within the write data 304 in sufficiently small increments to achieve a particular bit period for constant density writing. In general, clock cycle 404 may be an integer number of time units, and the interval between phases 410 may include any fraction of a time unit 404. For example, the least significant bit of phase 410 may be one tenth of a nanosecond, one hundredth of a nanosecond, or picoseconds.

The data bits 412 of the write data 304 are represented in FIG. 4 as B1 through B7. The write data 304 has an initial bit period 406 such that each data bit 412 occurs at a particular clock cycle 404 (e.g., clock cycles 404-1 through 404-7) of the clock signal 402.

To achieve constant density writing, the constant density writer 142 modifies the initial bit period 406 associated with the data bits 412 to generate the phase-delayed write data 306. The phase-delayed write data 306 includes data bits 412 associated with the write data 304 and has a concentric track based bit period 414 greater than or equal to the initial bit period 406. The constant density writer 142 sets the bit period 414 based on the selected concentric track 206 used to write the write data 304 to compensate for the linear velocity associated with the selected concentric track 206.

To achieve the bit period 414, the constant density writer 142 adjusts the phase of the data bits 412 by various amounts. Consider a simplified example in which the clock period 404 is 10 nanoseconds (ns), the number of phases is equal to 8 (e.g., N is equal to 8), and the bit period 414 is 13.75 ns. The phase 410 is incremented by the clock period 404 divided by the number of phases (1.25 ns in this example). In other words, the first phase 410-1 occurs at the beginning of the clock cycle 404, the second phase 410-2 occurs at 1.25ns from the beginning of the clock cycle 404, the third phase 410-2 occurs at 2.5ns from the beginning of the clock cycle 404 (e.g., 1.25ns from the second phase 410-2), and so on. In this case, bit period 414 is equal to the sum of clock period 404 and third phase 410-3. In general, bit period 414 may be equal to the sum of any multiple of clock period 404 and any phase 410.

To generate the phase-delayed write data 306, the constant density writer 142 delays the start of data bit B1 from phase 410-1 of clock cycle 404-1 to phase 410-2 of clock cycle 404-2. The delay may be based on previous data bits not shown. In addition, the constant density writer 142 delays the start of data bit B2 from phase 410-1 of the second clock cycle 404-2 to phase 410-5 of clock cycle 404-3. In this manner, data bits B1 and B2 have the same concentric track based bit period 414. The delay process continues for the other data bit 412 such that data bit B3 begins at phase 410-1 of clock cycle 404-5, data bit B4 begins at phase 410-4 of clock cycle 404-6, and data bit B5 begins at phase 410-7 of clock cycle 404-7. By delaying the start of writing data bits 412 within the data 304, the constant density writer 142 can adjust the bit period of different concentric tracks 206 in sufficiently small increments to efficiently utilize the area of the media disk 128. The constant density writer 142 is further described with reference to FIG. 5.

FIG. 5 illustrates an example implementation of a constant density writer 142. In the depicted configuration, the constant density writer 142 includes a write phase preprocessor 502, a unit filter 504, a final phase generator 506, and a selectable delay circuit 508. The write phase preprocessor 502 is coupled to inputs of the constant density writer 142, the unit filter 504, and the final phase generator 506. An input of the constant density writer 142 may be coupled to other modules within the read/write channel 140 of FIG. 3, such as a write pattern generator (not shown). A selectable delay circuit 508 is coupled between the final phase generator 506 and the output of the constant density writer 142. The output of the constant density writer 142 is coupled to the input of the preamplifier 134 (FIG. 3).

The write phase preprocessor 502 determines the bit periods 414 associated with different concentric tracks 206 of the media disk 128. The bit period 414 varies based on the radius of the concentric tracks 206 to maintain a particular bit density 206 across the concentric tracks. The bit periods 414 of successive concentric tracks 206 may differ by a fraction of a nanosecond. The write phase preprocessor 502 also selects the concentric tracks 206 for writing data to or receives a selection from another component of the drive control module 126, such as the read/write channel 140. The write phase preprocessor 502 may be implemented as a half rate clock, a quarter rate clock, or any symbol rate clock. Write phase preprocessor 502 generates initial phase data 510, stretched write data 512, and control signal 308 based on write data 304, bit periods 414, and clock signal 402, as further described below with respect to fig. 6.

The unit filter 504 is an optional component that may be used to mitigate failures within the phase-delayed write data 306. The unit filter 504 removes unit transitions within the write data 304. For example, the unit filter 504 searches the write data 304 for a bit pattern 010 and replaces it with another bit pattern 000. As another example, the unit filter 504 searches the write data 304 for the bit pattern 101 and replaces it with another bit pattern 111. In some cases, the modulation or coding scheme implemented by the read/write channel 140 reduces the likelihood of a single-bit transition occurring within the write data 304. However, sometimes this pattern occurs at the boundary of the Position Error Signal (PES), or in response to a high speed Alternating Current (AC) erasure. The unit transitions at the boundaries of the PES field may be removed and this mode in high speed AC erasure may be allowed without affecting the performance of the media disk 128. The unit filter 504 generates filtered write data 514 based on the stretched write data 512.

The final phase generator 506 adjusts the timing of the initial phase data 510 relative to the filtered write data 516 to provide the selectable delay circuit 508 with sufficient time to apply the appropriate phase delay for each data bit 412 and avoid introducing a fault. The final phase generator 506 generates pre-phase delayed write data 516 and final phase data 518. The final phase generator 506 may also pass the control signal 308 from the write phase preprocessor 502 to a selectable delay circuit 508.

In some cases, the pre-phasing delay write data 516 is based on the filtered write data 514 in order to write the write data 304 to the media disk 128. However, to erase previously written data, the pre-phased delayed write data 516 may be derived from the erase mode. The write phase preprocessor 502 may use an Alternating Current (AC) erase control signal 520 to control whether the final phase generator 506 generates the pre-phase delayed write data 516 based on the filtered write data 514 or the erase pattern.

To write the data bits 412, final phase data 518 is generated based on the initial phase data 510, as described further below. To erase previously written data, final phase data 518 may be generated such that final phase data 518 specifies a constant phase (or constant delay) of the data bits associated with the erase mode.

In some aspects, selectable delay circuit 508 applies the phase delay identified within final phase data 518 to data bits 412 within pre-phase delayed write data 516 to generate phase delayed write data 306. The selectable delay circuit 508 provides the phase delayed write data 306 and the control signal 308 to the preamplifier 134 of fig. 3. Operation of the constant density writer 142 is further described with respect to FIG. 6.

As an example, considering fig. 6, fig. 6 illustrates an example time diagram of data according to various aspects of constant density writing at 600. The graph or waveform of fig. 6 includes clock signal 402 and write data 304 (fig. 4). Further, the graph or waveform includes initial phase data 510, stretched write data 512, filtered write data 514, final phase data 518, and pre-phase delayed write data 516, which may be generated by the constant density writer 142 of FIG. 5.

During operation, the write phase preprocessor 502 accepts write data 304 from the host interface 302 (FIG. 3) or the read/write channel 140. In some cases, the read/write channel 140 modulates or encodes the write data 304 before providing the write data to the write phase preprocessor 502. Generally, the write data 304 includes data bits 412 associated with the initial bit period 406, as shown in FIG. 4. The initial bit period 406 is determined based on the clock period 404 of the clock signal 402, the clock period 404 being generated based on the rotation of the media disk 128.

The write phase preprocessor 502 generates initial phase data 510 based on the clock signal 402 and the bit periods 414 of the selected concentric tracks 206. The initial phase data 510 includes a start phase 410 associated with a corresponding data bit 412 of the write data 304. The starting phase 410 is denoted as P1 through P8, which are associated with bits B1 through B8, respectively.

Write phase preprocessor 502 also generates stretch write data 512 based on write data 304. The stretched write data 512 is similar to the write data 304, except that a stretch bit 602 is added, the stretch bit 602 being denoted as SB in FIG. 6. Where the initial phase data 510 causes the start of the data bit 412 to occur later at one or more intervals of the clock cycle 404, a stretch bit 602 is added. In some cases, continuous stretch bits 602 are added to enable bit transitions to occur at specific time intervals relative to the clock cycle 404. By including the stretch bits 602, information associated with the data bits 412 is preserved during the delay.

The unit filter 504 generates filtered write data 514 based on the stretched write data 512. In this example, the unit filter 504 changes the value of the data bit B6 from 0 to 1 to change the 101 mode between bits B5 through B7 in the stretched write data 512 to the 111 mode in the filtered write data 514.

The final phase generator 506 generates pre-phase delayed write data 516, the pre-phase delayed write data 516 being filtered write data 514. The final phase generator 506 also generates final phase data 518 based on the initial phase data 510. In particular, final phase generator 506 removes phase 410 that is not associated with a transition between 0 and 1. For example, the final phase data 518 does not include the phase P2 associated with data bit B2, the phase P4 associated with data bit B4, or the phases P6 and P7 associated with data bits B6 and B7, respectively. The final phase generator 506 also advances the timing of the phase 410 so that the phase occurs at least one clock cycle 404 before the corresponding data bit.

The selectable delay circuit 508 generates the phase-delayed write data 306 based on the pre-phase-delayed write data 516 and the final phase data 518. In particular, the selectable delay circuit 508 delays transitions between the data bits 412 within the pre-phase delayed write data 516 according to the final phase data 518. Due to this delay, the data bits 412 within the phase-delayed write data 306 have a bit period 414, the bit period 414 being different from the initial bit period 406 (e.g., different from the clock period 404).

The constant density writer 142 can also determine a starting phase (or starting position) for starting writing the phase-delayed write data 306 on the concentric track 206. Each starting phase may be selected to align data bits 412 across multiple concentric tracks 206 (e.g., to align data bits 412 between a concentric track 206 and an adjacent concentric track 206).

Constant density write technique

The following discussion describes constant density writing techniques for magnetic storage media that can improve writing efficiency. The techniques may be implemented using any of the environments and entities described herein, such as the read/write channel 140 or the constant density writer 142. These techniques include the method 700 illustrated in fig. 7, the method 700 being illustrated as a set of operations performed by one or more entities.

The method is not necessarily limited to the order of operations shown in the figures. Rather, any of the operations may be repeated, skipped, replaced, or reordered to achieve the various aspects described herein. Further, the methods may be used in whole or in part in conjunction with each other, whether performed by the same entity, separate entities, or any combination thereof. For example, aspects of the described methods may be combined to achieve constant density writing of magnetic media by a combination of adjusting bit periods, inserting stretch bits, filtering unit transitions, and mitigating failures. In portions of the following discussion, reference will be made to the entities of operating environment 100 of FIG. 1, FIG. 2, FIG. 3, and FIG. 5. Such references should not be taken as limiting the described aspects to the operating environment 100, entities, configurations or implementations, but rather as an illustration of one of various examples. Alternatively or additionally, the operations of these methods may also be implemented by or through entities described with reference to the system-on-chip of fig. 8 and/or the storage medium controller of fig. 9.

FIG. 7 depicts an example method 700 for implementing constant density writing of a magnetic storage medium, the method 700 including operations performed at least in part by the constant density writer 142.

At 702, write data is accepted from a host. For example, the host interface 302 accepts write data 304 from the host, as shown in FIG. 3. The read/write channel 140 may modulate and encode the write data 304 before providing the write data 304 to the constant density writer 142.

At 704, respective bit periods associated with a plurality of concentric tracks of a magnetic disk of a magnetic storage medium are determined. The respective bit periods vary based on respective radii of the plurality of concentric tracks to maintain a particular bit density across the plurality of concentric tracks. For example, the constant density writer 142 determines respective bit periods 414 associated with a plurality of concentric tracks of the media disk 128. The respective bit periods 414 vary based on respective radii of the plurality of concentric tracks 206 to maintain a particular bit density across the plurality of concentric tracks. In this manner, the respective bit periods 414 may compensate for differences in linear velocity associated with the plurality of concentric tracks 206 and enable data written to the media disk 128 to have the same valid bit period 212, as described above with respect to FIG. 2.

At 706, a concentric track of the plurality of concentric tracks is selected for the write data. The concentric tracks are associated with bit periods of the respective bit periods. For example, the constant density writer 142 or the read/write channel 140 selects the concentric track 206 associated with one of the bit periods 414 for the write data 304.

At 708, transitions between bits of the write data are delayed based on bit periods associated with the concentric tracks to generate phase-delayed write data. The delay of the transition effectively causes the phase-delayed write data bits to have a bit period associated with the concentric tracks. For example, the constant density writer 142 delays transitions between bits of the write data 304 based on the bit periods 414 associated with the concentric tracks 206 to generate the phase-delayed write data 306. Thus, the phase-delayed write data has a bit period 414 associated with the concentric tracks, as shown in FIG. 4.

At 710, bits of write data are phase-delayed along the concentric tracks such that the concentric tracks have a particular bit density. For example, the preamplifier 134 and the write head 132 write the phase-delayed write data 306 along the concentric track 206 such that the concentric track 206 has a particular bit density.

System on chip

FIG. 8 illustrates an exemplary system on a chip (SoC)800 that implements aspects of constant density writing of magnetic storage media. SoC 800 can be implemented in any suitable device, such as a smartphone, netbook, tablet, access point, network attached storage, camera, smart appliance, printer, set-top box, server, Solid State Drive (SSD), tape drive, Hard Disk Drive (HDD), storage drive array, memory module, storage media controller, storage media interface, head disk assembly, magnetic media preamplifier, automotive computing system, or any other suitable type of device (e.g., other devices described herein). Although described with reference to a SoC, the entities of fig. 8 may also be implemented as other types of integrated circuits or embedded systems, such as an Application Specific Integrated Circuit (ASIC), a memory controller, a communication controller, an Application Specific Standard Product (ASSP), a Digital Signal Processor (DSP), a programmable SoC (psoc), a System In Package (SiP), or a Field Programmable Gate Array (FPGA).

SoC 800 can be integrated with electronic circuitry, microprocessors, memory, input-output (I/O) control logic, communication interfaces, firmware, and/or software for providing the functionality of a computing device or magnetic storage system, such as any device or component (e.g., hard disk drive) described herein. SoC 800 may also include an integrated data bus or interconnect fabric (not shown) that couples the various components of the SoC for data communication or routing between the components. The integrated data bus, interconnect fabric, or other components of SoC 800 may be exposed or accessed through an external port, parallel data interface, serial data interface, peripheral component interface, or any other suitable data interface. For example, components of SoC 800 may access or control an external storage medium or magnetic write circuit system through an external interface or off-chip data interface.

In this example, SoC 800 is shown with various components including input-output (I/O) control logic 802 and a hardware-based processor 804 (processor 804), such as a microprocessor, processor core, application processor, DSP, and so forth. SoC 800 also includes memory 806, which memory 806 may include any type and/or combination of RAM, SRAM, DRAM, non-volatile memory, ROM, one-time programmable (OTP) memory, Multiple Time Programmable (MTP) memory, flash memory, and/or other suitable electronic data storage. In some aspects, the processor 804 and code (e.g., firmware) stored on the memory 806 are implemented as part of a storage medium controller or storage medium interface to provide various functions associated with pulse-based writing of magnetic storage media. In the context of the present disclosure, the memory 806 stores data, code, instructions or other information via non-transitory signals and does not include carrier waves or transitory signals. Alternatively or additionally, SoC 800 includes a data interface (not shown) for accessing additional or stretchable off-chip storage media, such as magnetic memory or solid-state memory (e.g., flash memory or NAND memory).

SoC 800 also includes firmware 808, applications, programs, software, and/or an operating system, which may be embodied as processor-executable instructions maintained on memory 806 for execution by processor 804 to implement the functionality of SoC 800. SoC 800 may also include other communication interfaces, such as a transceiver interface for controlling or communicating with a local on-chip (not shown) or off-chip communication transceiver component. Alternatively or additionally, the transceiver interface may also include or implement a signal interface to communicate Radio Frequency (RF), Intermediate Frequency (IF), or baseband frequency signals off-chip to support wired or wireless communication through a transceiver, physical layer transceiver (PHY), or Media Access Controller (MAC) coupled to the SoC 800. For example, SoC 800 includes a transceiver interface configured to enable storage on a wired or wireless network, such as to provide a burst-based write feature for a Network Attached Storage (NAS) device.

SoC 800 also includes a read/write channel 140 and a constant density writer 142, which may be implemented separately as shown or combined with a memory component or data interface. Alternatively or additionally, SoC 800 can include interfaces to preamplifiers and spindle/motor components of the magnetic media disk drive. As described herein, the constant density writer 142 may insert a phase delay between bit transitions to achieve aspects of constant density writing of a magnetic storage medium. Any of these entities may be embodied as different or combined components, as described with reference to various aspects presented herein. Examples of these components and/or entities or corresponding functionality are described with reference to corresponding components or entities of environment 100 of fig. 1 or the corresponding configurations shown in fig. 2 and/or 3. The constant density writer 142 may be implemented, in whole or in part, as digital logic, circuitry, and/or processor-executable instructions maintained by the memory 806 and executed by the processor 804 to implement various aspects or features of constant density writing of magnetic storage media.

Constant density writer 142 may be implemented independently or in combination with any suitable components or circuitry to implement aspects described herein. For example, constant density writer 142 can be implemented as part of a DSP, processor/memory bridge, I/O bridge, graphics processing unit, memory controller, Arithmetic Logic Unit (ALU), or the like. The constant density writer 142 may also be provided integrally with other entities of the SoC 800, such as integrated with the processor 804, memory 806, storage medium interface, or firmware 808 of the SoC 800. Alternatively or in addition, the constant density writer 142 and/or other components of the SoC 800 may be implemented as hardware, firmware, fixed logic circuitry, or any combination thereof.

As another example, consider FIG. 9, FIG. 9 illustrates an example storage medium controller 900 in accordance with one or more aspects for pulse-based writing of magnetic storage media. In general, the storage media controller 900 enables the computing device 102 to access the contents of the magnetic storage media, such as an operating system, applications, or data for applications or other services. The storage media controller also writes and reads data of the computing device 102 to and from magnetic storage media associated with the controller.

In various aspects, the storage media controller 900, or any combination of its components, may be implemented as a storage drive controller (e.g., a HDD controller or HDD chipset), a storage media controller, a NAS controller, a storage media interface, a storage media endpoint, a storage media target, or a storage aggregation controller for magnetic storage media, solid state storage media, etc. (e.g., a hybrid SSD/HDD storage system). In some cases, the storage medium controller 900 is implemented similarly to the SoC 800 described with reference to fig. 8, or is implemented with components of the SoC 800. In other words, an instance of SoC 800 can be configured as a storage media controller, such as storage media controller 900 for managing magnetic storage media. In this example, storage medium controller 900 includes input/output (I/O) control logic 902 and a processor 904, such as a microprocessor, microcontroller, processor core, application processor, DSP, or the like. Storage media controller 900 also includes a host interface 906 (e.g., a SATA, PCIe, NVMe, or Fabric interface) and a storage media interface 908 (e.g., a magnetic media interface or Head Disk Assembly (HDA) interface) that enable access to a host system (or Fabric) and storage media, respectively. In this example, storage medium interface 908 comprises a separate instance of spindle interface 910 and preamplifier interface 912 to enable communication with a head disk assembly of a media drive.

In some aspects, the storage media controller 900 implements aspects of constant density writing of magnetic storage media when managing or enabling access to a storage media coupled to the storage media interface 908. The storage media controller 900 provides a storage interface for a host system via the host interface 906, through which storage access commands, such as data to be written to a magnetic storage medium, may be received from the host system. As shown in FIG. 9, the storage medium controller 900 further includes a servo control unit 138, a read/write channel 140, and a constant density writer 142. The servo control unit 138 is operably coupled to the spindle interface 910 and provides spindle or voice coil control for the magnetic media drive. In this example, the read/write channel 140 and the constant density writer 142 are operably coupled to the preamplifier interface 912 and provide the phase delayed write data 306 and/or the pulsed write control signal to the preamplifier circuitry of the media drive. In some aspects, the firmware or logic of the processor 904 and the storage medium controller 900 is implemented to provide various data writing or processing functions associated with pulse-based writing of magnetic storage media.

The constant density writer 142 of the storage medium controller 900 may be implemented alone as shown or in combination with the processor 904, the read/write channel 140, or the storage medium interface 908. According to various aspects, the constant density writer 142 inserts a phase delay between bit transitions to achieve various aspects of constant density writing of a magnetic storage medium. Examples of these components and/or entities or corresponding functionality are described with reference to corresponding components or entities of environment 100 of fig. 1 or the corresponding configurations shown in fig. 2 and/or 3. The constant density writer 142 may be implemented, in whole or in part, as processor-executable instructions maintained by a memory of a controller and executed by the processor 904 to implement various aspects and/or features of pulse-based writing of magnetic storage media.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific examples, features, or acts described herein, including the order of their execution.