Information
-
Patent Grant
-
6421193
-
Patent Number
6,421,193
-
Date Filed
Tuesday, January 26, 199925 years ago
-
Date Issued
Tuesday, July 16, 200221 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Hudspeth; David
- Davidson; Dan I.
Agents
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
A method and apparatus for compensating for multiple thermal asperity events in a sector. The present invention provides for the detection, recording and recovery from errors caused by multiple thermal asperities occurring in a single sector. The method includes detecting thermal asperity events in a sector, setting a flag indicating each occurrence of a thermal asperity event in the sector, maintaining a count of the detected thermal asperity events in the sector and recording a byte location for each of the detected thermal asperity events in the sector. The method further includes performing a data recovery procedure in response to the detected thermal asperity events. The data recovery procedure is performed using the flag settings and a location corresponding to the detected thermal asperity events. The data recovery procedure is performed using the count of the detected thermal asperity events. The setting of a flag includes setting a bit in a register. The setting of a bit indicates a start byte location for a thermal asperity event. The maintaining a count of the detected thermal asperity events in the sector includes the setting of a bit in the register for each detected thermal asperity event, the count being equal to a number of bits set in the register. The recording a location for each of the detected thermal asperity events in the sector includes setting a bit in a register, the bit position being associated with the location of the asperity event. The maintaining a count of the detected thermal asperity events in the sector includes setting a bit in a register for each detected thermal asperity events, the count being equal to a number of bits set in the register.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention relates in general to storage systems, and more particularly to a method and apparatus for compensating for multiple thermal asperity events in a sector.
2. Description of Related Art.
Computers often include auxiliary memory storage units having media for data storage and retrieval. Disk drives are the most common example of such auxiliary memory storage units. Disk drives typically include stacked, commonly rotated rigid magnetic disk for magnetically recording data thereon. Data is recorded in concentric, radially spaced data information tracks arrayed on the surfaces of the disks. Transducer heads driven in a path toward and away from the drive axis write data to and read data from the disks. A slider supports one or more magnetic heads. The slider is lightly biased to cause the heads to move toward the recording surface when the disk is stationary; but as the disk is brought up to operating speed, an air bearing is generated which moves each slider and hence the heads away from the recording surface toward a preselected flying height. Achievement of a higher data density on magnetic disks has imposed increasingly narrow transducing gaps.
Magneto-resistive (MR) heads have substantially improved the areal bit densities of hard disk drives. However, this improvement is not without complications. More specifically, MR heads have been associated with an increased sensitivity to thermal asperities. Contact with debris or media bumps can heat up MR heads, causing disturbances in the read-back signal. Near contacts with mounts on the media can cool down MR heads, causing disturbances in the read-back signal. Unless properly compensated for, these disturbances can produce unrecoverable errors.
A heating thermal asperity occurs when a head contacts a disk asperity or collides with a foreign particle. A cooling thermal asperity occurs when a head has a near contact with a disk asperity which causes a heat transfer out of the MR element. While thermal asperities can occur with inductive heads, they are a more serious problem in MR heads. For example, thin-film heads generate current based on changes in the magnetic flux. The inductance value is not significantly affected by temperature, and the change in series resistance is a second-order effect.
In contrast, the fundamental read-back mechanism of an MR head is inherently sensitive to changes in temperature. MR heads are resistive sensors, which generate resistive variations, and corresponding voltage or current variations, in response to changes in the magnetic field of the media. MR head stripes are made of permalloy. Like most metals, the resistivity of permalloy is proportional to temperature. Unfortunately, this change in resistance resulting from a thermal asperity has similar characteristics to the read-back signal the sensor is designed to detect.
Asperity problems are further compounded by efforts to push areal densities higher and to maintain adequate signal-to-noise ratios. Such trends have led to lower flying heights, creating additional problems for disk-drive manufacturers. This is true even though significant improvements have been made in media smoothness and contamination control.
Many approaches have been developed for detecting and compensating for thermal asperity transients. In fact, these thermal asperity techniques have made single thermal asperity occurrence per sector in a hard disk drive with MR heads a non-event. However, up to now, thermal asperity handling techniques have not been able to fully compensate for multiple thermal asperity events occurring in a single sector, and hard error events are still a common incident.
It can be seen that there is a need for a method and apparatus that compensates for multiple thermal asperity events occurring in a sector.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for compensating for multiple thermal asperity events in a sector.
The present invention solves the above-described problems by providing for the detection, logging and recovery from errors caused by multiple thermal asperities occurring in a single sector.
A method in accordance with the principles of the present invention includes detecting thermal asperity events in a sector, setting a flag indicating occurrence of a thermal asperity event in the sector, maintaining a count of the detected thermal asperity events in the sector and recording a location for the detected thermal asperity event in the sector.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the method further includes performing a data recovery procedure in response to the detected thermal asperity event.
Another aspect of the present invention is that the data recovery procedure is performed using the flag settings and a location corresponding to the detected thermal asperity events.
Another aspect of the present invention is that the data recovery procedure is further performed using the count of the detected thermal asperity events.
Another aspect of the present invention is that the setting of a flag includes setting a bit in a register.
Another aspect of the present invention is that the recording further comprises setting a selected bit in a register, the selected bit's position in the register being determined by the location of the detected thermal asperity event.
Another aspect of the present invention is that the maintaining a count of the detected thermal asperity events in the sector includes the setting of a bit in the register for each detected thermal asperity event, the count being equal to a number of bits set in the register.
Another aspect of the present invention is that the recording of the location for the detected thermal asperity event in the sector includes setting a bit in a register, the bit being associated with the asperity event.
Another aspect of the present invention is that the maintaining a count of the detected thermal asperity events in the sector includes setting a bit in a register for each detected thermal asperity events, the count being equal to a number of bits set in the register.
In another embodiment, the present invention includes a controller for processing multiple asperity events in a sector of a storage device, the controller including a processor for receiving indications of thermal asperity events in a sector and a register for storing an indication representing each occurrence of a thermal asperity event in the sector.
In another embodiment, the present invention includes a disk drive, the disk drive including a storage medium including sectors of recorded data, a motor for moving the storage medium relative to a magneto-resistive head and a control unit, the control unit controlling the motor and the position of the magnetic head relative to the data storage medium and a controller for processing multiple asperity events in a sector of the storage medium, the controller further including a processor for receiving indications of thermal asperity events in a sector and a register for storing an indication representing each occurrence of a thermal asperity event in the sector.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings in which like reference numbers represent corresponding parts throughout:
FIG. 1
illustrates a disk drive embodying the present invention;
FIG. 2
is a side cross-sectional schematic illustration of the merged MR head;
FIG. 3
depicts an example of a spin valve sensor upon which the invention may be practiced;
FIG. 4
illustrates the threshold detection of a heating thermal asperity event;
FIG. 5
illustrates a fast mode asperity compensation circuit in a current sensing preamplifier;
FIG. 6
illustrates a circuit for performing a fast recovery from a thermal asperity in a read channel;
FIG. 7
illustrates a circuit that detects, records and provides error recover for multiple thermal asperities in a single sector; and
FIG. 8
is a flow chart of the method for compensating for multiple thermal asperity events in a sector according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following description of the exemplary embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration the specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention.
The present invention provides a method and apparatus for compensating for multiple thermal asperity events in a sector. The present invention provides for the detection, recording and recovery from errors caused by multiple thermal asperities occurring in a single sector.
FIG. 1
illustrates a disk drive
100
embodying the present invention. As shown in
FIG. 1
, at least one rotatable magnetic disk
112
is supported on a spindle
114
and rotated by a disk drive motor
118
. The magnetic recording media on each disk is in the form of an annular pattern of concentric data tracks (not shown) on disk
112
.
At least one slider
113
is positioned on the disk
112
, each slider
113
supporting one or more magnetic read/write heads
121
where the head
121
incorporates the MR sensor of the present invention. As the disks rotate, slider
113
is moved radically in and out over disk surface
122
so that heads
121
may access different portions of the disk where desired data is recorded. Each slider
113
is attached to an actuator arm
119
by means of a suspension
115
. The suspension
115
provides a slight spring force which biases slider
113
against the disk surface
122
. Each actuator arm
119
is attached to an actuator means
127
. The actuator means as shown in
FIG. 1
may be a voice coil motor (VCM). The VCM comprises a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by controller
129
.
During operation of the disk storage system, the rotation of disk
112
generates an air bearing between slider
113
and disk surface
122
which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension
115
and supports slider
113
off and slightly above the disk surface by a small, substantially constant spacing during normal operation.
The various components of the disk storage system are controlled in operation by control signals generated by control unit
129
, such as access control signals and internal clock signals. Typically, control unit
129
comprises logic control circuits, storage means and a microprocessor. The control unit
129
generates control signals to control various system operations such as drive motor control signals on line
123
and head position and seek control signals on line
128
. The control signals on line
128
provide the desired current profiles to optimally move and position slider
113
5
o the desired data track on disk
112
. Read and write signals are communicated to and from read/write heads
121
by means of recording channel
125
.
The above description of a typical magnetic disk storage system, and the accompanying illustration of
FIG. 1
are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders.
FIG. 2
is a side cross-sectional schematic illustration of the merged MR head
200
. The merged MR head
200
includes a read head portion and a write head portion which are lapped to an air beating surface (ABS), the air bearing surface being spaced from the surface of the rotating disk by the air bearing as discussed hereinabove. The read head portion includes an MR sensor which is sandwiched between first and second gaps layers G
1
and G
2
which, in turn, are sandwiched between first and second shield layers S
1
and S
2
. The write head portion includes a coil layer C and insulation layer
12
which are sandwiched between insulation layers
11
and
13
which in turn are sandwiched between first and second pole pieces P
1
and P
2
. A gap layer G
3
is sandwiched between the first and second pole pieces at their pole tips adjacent the ABS for providing a magnetic gap. When signal current is conducted through the coil layer C, signal flux is induced into the first and second pole layers P
1
and P
2
causing signal fringe flux across the pole tips of the pole pieces at the ABS. This signal fringe flux is induced into circular tracks on the rotating disk
116
, shown in
FIG. 1
, during a write operation. During a read operation, recorded magnetic flux signals on the rotating disk are induced into the MR sensor of the read head causing a change in the resistance of the MR sensor which can be sensed by a change in potential across the MR sensor responsive to a sense current (not shown) conducted through the MR sensor. These changes in potential are processed by the drive electronics not shown. The combined head illustrated in
FIG. 2
is a merged MR head in which the second shield layer S
2
is employed as a first pole piece P
1
for the combined head. In a piggyback head (not shown) the second shield layer S
2
and the first pole piece P
1
are separate layers.
FIG. 2
illustrates the overall physical arrangement of the layers used in forming a merged MR head
200
. However,
FIG. 2
does not show the leads to the MR sensor. As mentioned above, the leads required significantly larger area than the area required of the MR sensor. Furthermore, the gap coverage at the edge of the leads is poor and potential for shield-to-lead shorts for high density (thin gap) heads increase significantly. However, since most of the shorts are from the leads to the shields, the leads should be designed to prevent shield-to-lead shorts.
FIG. 3
illustrates, with respect to GMR heads, how the leads are attached to the sensors.
FIG. 3
depicts an example of a spin valve sensor
300
upon which the invention may be practiced. The view of
FIG. 3
depicts a plan view of the air bearing surface of a substrate
301
containing the spin valve
300
. The substrate's air bearing surface normally rides upon a cushion of air, which separates it from a magnetic data storage medium such as a disk or tape.
The sensor
300
includes a plurality of substantially parallel layers including an
302
, a ferromagnetic pinned layer
303
, a conductive layer
304
, and a ferromagnetic free layer
305
. The sensor
300
also includes hard bias layers
315
-
316
, the operation of which is discussed in greater detail below. The sensor
300
is deposited upon an insulator
307
, which lies atop the substrate
301
. Adjacent layers preferably lie in direct atomic contact with each other.
The antiferromagnetic layer
302
comprises a type and thickness of antiferromagnetic substance suitable for use as a pinned layer in spin valves, e.g., a 400 Å layer of NiO. The ferromagnetic pinned layer
303
comprises a type and thickness of ferromagnetic substance suitable for use in spin valves, e.g., about 10-40 Å of Co. The conductor layer
304
comprises a type and thickness of conductive substance suitable for use in spin valves, e.g., about 20-30 Å of Cu. The ferromagnetic free layer
305
comprises a type and thickness of ferromagnetic substance suitable for use as a free layer in spin valves, e.g., about 30-150 Å of NiFe. The hard bias layers
315
-
316
provide the free layer
305
with a desired quiescent: magnetization. The hard bias layers
315
-
316
preferably comprise a magnetic material with high coercivity, such as CoPtCr.
Despite the foregoing detailed description of the sensor
300
, the present invention may be applied using many different sensor arrangements in addition to this example. For example, ordinarily skilled having the benefit of this disclosure will recognize various alternatives to the specific materials and thickness described above.
The sensor
300
exhibits a predefined magnetization. Magnetization of the sensor
300
, including the ferromagnetic layers
303
/
305
and the antiferromagnetic layer
302
, is performed in accordance with the invention. The sensor
300
may be magnetized. prior to initial operation, such as during the fabrication or assembly processes. Or, the sensor
300
may be magnetized after some period of operating the sensor
300
, where the sensor
300
loses its magnetic orientation due to a traumatic high temperature event such as electrostatic discharge. A process for magnetization of the sensor
300
is discussed in greater detail below.
Whether magnetized before or after initial operation of the sensor
300
, the magnetized components of the sensor
300
are ultimately given the same magnetic configuration. In particular, the antiferromagnetic layer
302
has a magnetic orientation in a direction
310
. For ease of explanation, conventional directional shorthand is used herein, where a circled dot indicates a direction coming out of the page (like an arrow's head), and a circled x indicates a direction going into the page (like an arrow's tail). The neighboring ferromagnetic pinned layer
303
has a magnetic moment pinned in a parallel direction
311
, due to antiferromagnetic exchange coupling between the layers
302
-
303
.
Unlike the pinned layer
303
, the free layer
305
has a magnetic moment that freely responds to external magnetic fields, such as those from a magnetic storage medium. The free layer
305
responds to an external magnetic field by changing its magnetic moment, which in turn changes the resistance of the spin valve
300
. In the absence of any other magnetic fields, the free layer
305
orients itself in a direction
313
, which is oriented 90° to the directions
310
-
311
. This quiescent magnetization direction is due to biasing of the free layer
305
by the hard bias layers
315
-
316
.
The sensor
300
may also include various accessories to direct electrical current and magnetic fields through the sensor
300
. A small but constant sense current, for example, is directed through the sensor
300
to provide a source of scattering electrons for operation of the sensor
300
according to the GMR effect. At different times, a relatively large current pulse or waveform is directed through the sensor
300
to establish the magnetization direction of the sensor
300
.
FIG. 3
also depicts the sensor
300
in relation to the various features that help direct current through the sensor
300
.
The sensor
300
is attached to a pair of complementary leads
308
-
309
to facilitate electrical connection to a sense current source
312
. The leads
308
-
309
also facilitate electrical connection to a pulse current source
323
. The leads
308
-
309
preferably comprise 500 Å of Ta with a 50 Å underlayer of Cr, or another suitable thickness and type of conductive material. The attachment of leads to magnetoresistive sensors and spin valves is a well known technique, familiar to those of ordinary skill in the art.
A technique for establishing a predetermined magnetic orientation of spin valve sensor or GMR head has been developed and is disclosed in copending, and commonly owned U.S. patent application Ser. No. 08/855,141, herein incorporated by reference. This technique will be explained with reference to FIG.
3
.
Via the leads
308
-
309
, the pulse current source
323
directs an electrical pulse current through the layers
303
-
305
. Chiefly, the pulse current heats the antiferromagnetic layer
302
past its blocking temperature. For an additional measure of magnetization biasing, the pulse current source
323
may be configured to provide pulse current in an appropriate direction to enhance biasing of the antiferromagnetic layer
302
in the direction
310
. The pulse current flows from the lead
309
to the lead
308
. To satisfy the foregoing purposes, the current source
323
comprises a suitable device to provide a current pulse of sufficient amplitude and duration to bring the antiferromagnetic layer
302
past its blocking temperature, thereby freeing the magnetic orientations of this layer as well as the associated ferromagnetic pinned layer
303
.
In addition to heat, the current pulse also provides a magnetic field that magnetically orients the antiferromagnetic layer
302
in accordance with the well known right-hand rule of electromagnetics. The pulse current lasts sufficiently long to both remove any magnetic orientation of the antiferromagnetic layer and also to reorient the layers in accordance with the magnetic field created by the flowing current.
The magnetic orientation of the antiferromagnetic layer
302
has the effect of pinning the magnetization directions of the ferromagnetic pinned layer
303
. This occurs because of the strong exchange coupling between the antiferromagnet-ferromagnet pair
302
/
303
. More particularly, the antiferromagnetic layer
302
pins the ferromagnetic pinned layer
303
in a direction parallel to its own direction. The pulse current source
323
then applies a bias current to orient the magnetic field of ferromagnet layer
305
.
As suggest above, there are may ways to detect and compensate for thermal asperity events. However, the detection and compensation techniques may be broadly characterized as preamplifier and read channel techniques.
FIG. 4
illustrates the threshold detection of a heating thermal asperity event
400
. A thermal asperity
410
causes a rapid change in the resistance of a MR head followed by a slow decay
412
. Detection of the signal excursion above a threshold level
414
produces a “fault” pulse
420
that can be used for compensation. Contact with a disk asperity causes a rapid rise in head temperature. The flash temperature of an MR element may be 50° C. to 125° C. higher than the nominal temperature. As a result, resistance can change from 1% to 2.5%. Since the typical resistance variation during readback is around 0.5%, the thermal asperity event can result in a signal transient with an amplitude that is two to five times the normal signal amplitude.
FIG. 5
illustrates a fast mode asperity compensation circuit in a current sensing preamplifier
500
. The fast mode asperity compensation circuit
500
of
FIG. 5
includes a first-gain stage reader
510
, a second-gain stage reader
512
and a transconductance feedback amplifier
520
. The transconductance feedback amplifier
520
maintains the DC balance of the preamplifier
500
. As a result of feedback, the input stage
510
has a low-frequency pole associated with the transconductance feedback amplifier
520
and capacitor C1
530
. This pole removes low-frequency components, while allowing the signal to pass through to the second stage
512
. The pole frequency is defined by:
F
p
=A
v
·g
m
/2pC1
where A
v
is the first-stage gain
510
, g
m
is the transconductance of the feedback amplifier
520
and C1 is the value of the feedback loop compensation capacitor
530
.
A threshold detector
540
monitors the preamplifier output
542
to respond to thermal asperity events. If the thermal asperity threshold is exceeded, a fault flag
550
is generated. Under normal conditions, the baseline is restored at a rate governed by the normal low-corner frequency. However, the threshold detector
540
may, optionally, enable a “fast mode”
560
wherein the low-corner frequency of the amplifier input is moved from a nominal value to a higher frequency. This value may be programmable. The movement of the low-corner frequency is accomplished by increasing the gain of the transconductance feedback amplifier
520
used to maintain the amplifier's DC balance.
When fast mode
560
is enabled, the read-back baseline is restored at a faster rate. Fast mode compensation may be invoked automatically after detection or it can be invoked by the controller during a retry via a Fast-mode input
570
.
FIG. 6
illustrates circuit
600
for performing a fast recovery from a thermal asperity in a read channel
602
. In
FIG. 6
, a threshold detector
610
is connected in parallel with the input
612
to the automatic gain control (AGC)
614
in a partial response, maximum likelihood (PRML) channel
600
. Upon detection of a thermal asperity event, the threshold detector
610
switches in a resistor
620
among the differential read signal inputs
612
. These inputs
612
are capacitively coupled
630
. The shunt resistor
620
, in conjunction with the input capacitors
630
, form a high pass filter. The baseline is then restored as dictated by the low-corner frequency.
Accordingly, the thermal asperity detection circuit
600
for read channels
602
as shown in
FIG. 6
works much like that used in preamplifiers. Generally, a thermal asperity threshold is set outside the normal dynamic data range. However, in addition to a fault flag, the channel may generate an erasure pointer
650
. This signal
650
indicates the portion of the read data stream that may have been corrupted by the thermal asperity event. Unlike the fault signal generated by the preamplifier, the channel's signal needs to be synchronized to that of the data detection path. The erasure pointer
650
can be used as part of the procedure for handling thermal asperity events.
Still, the above methods do not prevent hard error events when there are multiple thermal asperities in a single sector.
FIG. 7
illustrates a circuit
700
that detects, records and provides error recover for multiple thermal asperities in a single sector. A threshold detector
710
is used to generate a signal
712
that is sent to the controller
720
. Those skilled in the art will recognize that the invention is not meant to be limited to any single location, but rather the controller may be disposed in the channel
125
or control unit
129
as illustrated in FIG.
1
.
A processor
730
is configured or programmed to processes the thermal asperity signal
712
. The processor
730
sets a thermal asperity detected flag
740
. A counter
750
in the controller counts the number of thermal asperity events as indicated by the thermal asperity detected flag
740
. The counter
750
may be reset after each sector so that a count of the number of thermal asperity events occurring in a sector may be monitored. A register
760
is used to record the location of each of the flagged thermal asperity events in the current sector.
For example, in a
512
byte sector format, a 64 byte register
760
will give a complete picture of the thermal asperity events occurring in the sector, i.e., one predetermined bit in the 64 byte register
760
is set for each byte in the
512
byte sector that experiences a thermal asperity event. Those skilled in the art will recognize that even if a thermal asperity event is more than a byte wide, then a 64 byte register has
512
bits will suffice to indicate the location and number of the detected thermal asperity events. The bits in register
760
are reset between sectors. By identifying the location of each thermal asperity event, the corrupted data will be more likely recovered by the erasure error correction coding. Further, file error logs can reflect a more accurate picture of the thermal asperity event, and a drive's predictive failure analysis can use the log information to detect impending problems when the thermal asperity count starts to climb, e.g., from debris buildup, pressure/temperature change, and take appropriate actions.
FIG. 8
is a flow chart
800
of the method for compensating for multiple thermal asperity events in a sector according to the present invention. First, each thermal asperity event in a sector is detected
810
. Then a flag is set indicating the occurrence of the thermal asperity event
820
. A counter for maintaining a count of the thermal asperity events is incremented
830
. Each thermal asperity event is recorded with a byte location
840
. Next, a determination is made as to whether the end of a sector has been reached
850
. If not
860
, the process recycles to detect and record any additional thermal asperity events. Otherwise
870
, the thermal asperity event is processed using the indication of the thermal asperities in the sector, their corresponding location and the thermal asperity count
880
.
Those skilled in the art will recognize that setting a bit high in the 64 byte register
760
as illustrated in
FIG. 7
may be used as a flag and as an indication of the start byte for the thermal asperity. The number of bits that are set high represents the number of the byte in the sector that experienced a thermal asperity event.
The information on the number and location of the thermal asperities in the sector is made available to the ECC unit or function in the controller to enhance the error correction and detection power. The information on the thermal asperities is not meant to replace prior art ECC techniques, but rather to be be used in addition to those techniques. The additional information provided by the invention is compatible with a variety of prior art ECC techniques, but the details of the ECC system are beyond the scope of the present invention.
The foregoing description of the exemplary embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.
Claims
- 1. A method for processing asperity events in a sector of a storage device, comprising:detecting thermal asperity events while reading a sector; setting a flag indicating occurrence of a thermal asperity event in the sector; maintaining a count of the thermal asperity events in the sector; and recording a byte location for each of the thermal asperity events in the sector.
- 2. The method of claim 1 further comprising performing a data recovery procedure in response to the thermal asperity event.
- 3. The method of claim 2 wherein the data recovery procedure is performed using the flag setting and a location corresponding to the thermal asperity event.
- 4. The method of claim 3 wherein the data recovery procedure is further performed using the count of the thermal asperity events.
- 5. The method of claim 1 wherein the setting of a flag comprises setting a bit in a register.
- 6. The method of claim 1 wherein the recording further comprises setting a selected bit in a register, the selected bit's position in the register being determined by the location of the thermal asperity.
- 7. The method of claim 6 wherein the maintaining a count of the thermal asperity events in the Sector comprises the setting of a bit in the register for each thermal asperity event, the count being equal to a number of bits set in the register.
- 8. The method of claim 1 wherein the recording of the location for the thermal asperity event in the sector comprises setting a bit In a register, the bit being associated with the asperity event.
- 9. The method of claim 1 wherein the maintaining a count of the thermal asperity events In the sector comprises setting a bit in a register for each thermal asperity event, the count being equal to a number of bits set in the register.
- 10. A controller for processing multiple asperity events in a sector of a storage device, comprising:a processor for receiving information of thermal asperity events in a sector and for recording a byte location for each of the thermal asperity events in the sector; and a register for storing an indication representing each occurrence of a thermal asperity event in the sector.
- 11. The controller of claim 10 further comprising a counter for maintaining a count of the thermal asperity events in the sector.
- 12. The controller of claim 10 wherein the processor sets a flag indicating each occurrence of a thermal asperity event in a sector.
- 13. The controller of claim 12 wherein the processor initiates a data recovery procedure in response to the thermal asperity events.
- 14. The controller of claim 13 wherein the data recovery procedure is performed using the indication corresponding to the thermal asperity events.
- 15. The controller of claim 14 wherein the data recovery procedure Is further:performed using a count of the thermal asperity events.
- 16. The controller of claim 10 wherein the indication comprises a bit being set in the register.
- 17. The controller of claim 16 wherein the bits set in the register indicate a start byte location for thermal asperity events.
- 18. The controller of claim 17 wherein a count of the thermal asperity events in the sector is represented by the bits set in the register for each thermal asperity event, the count being equal to a number of bits set in the register.
- 19. The controller of claim 17 wherein each bit set in the register identifies a location of the thermal asperity events in the sector.
- 20. A disk drive, comprising;a storage medium comprising sectors of recorded data; a magneto-resistive head; a motor for moving the storage medium relative to the magneto-resistive head; and a control unit, the control unit controlling the motor and the position of the magnetic head relative to the data storage medium; and a controller for processing asperity events in a sector of the storage medium, the controller comprising: a processor for receiving information of thermal asperity events occurring while reading a sector and for recording a byte location for each of the thermal asperity events; and a register for storing an indication representing each occurrence of a thermal asperity event.
- 21. The disk drive of claim 20 further comprising a counter for maintaining a count of the thermal asperity events.
- 22. The disk drive of claim 20 wherein the processor sets a flag indicating each occurrence of a thermal asperity event.
- 23. The disk drive of claim 22 wherein the processor initiates a data recovery procedure using the indications of at least two thermal asperity events.
- 24. The disk drive of claim 23 wherein the data recovery procedure is performed using the flag settings and a location corresponding to the thermal asperity events.
- 25. The disk drive of claim 24 wherein the data recovery procedure is further performed using a count of the thermal asperity events.
- 26. The disk drive of claim 20 wherein the indication comprises a bit being set in the register.
- 27. The disk drive of claim 26 wherein the bits set in the register indicate a start byte location for thermal asperity events.
- 28. The disk drive of claim 27 wherein a count of the thermal asperity events in the sector is represented by the bits set in the register for each thermal asperity event, the count being equal to a number of bits set in the register.
- 29. The disk drive of claim 27 wherein each bit set in the register identifies a location of the thermal asperity events in the sector.
- 30. The disk drive of claim 20 wherein the magneto-resistive head comprises a anisotropic magneto-resistive sensor.
- 31. The disk drive of claim 20 wherein the magneto-resistive head comprises a spin valve sensor.
- 32. The disk drive of claim 20 wherein the register contains at least one bit corresponding to each byte in a sector.
US Referenced Citations (8)