JPH097106A - Recording and reproducing device and write current setting method - Google Patents

Abstract

PURPOSE: To reduce the power consumption by setting an optimal write current easily and inexpensively and also to improve the quality by a stable read decoding in a recording and reproducing device which records information by means of supplying a prescribed write current to a head and reproduces with the head. CONSTITUTION: An MPU 34 writes a measurement data read from a ROM 36 via an encoder 37 in a cylinder in a prescribed area of a magnetic disk by setting a prescribed number of write currents. And, a measurement signal which obtains a decoding margin from the MPU 34 at the time of reproducing is transmitted to a decoder 38 and the decoding margin such as a phase margin for every write current of read data is measured and a write current corresponding to the one among a prescribed number of write margins when saturation starts is set as an optimal write current and stored in the ROM 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for supplying a predetermined write current to a head to record information on a recording medium and reproducing the information by the head. In recent years, as an external storage device such as a computer, for example, a magnetic disk device has been miniaturized and has been installed in the computer or the like, and has low consumption in accordance with the expansion of the scale of the computer system and the demand of the personal computer. There is a demand for improved power consumption and improved recording / reproduction of information.

[0002]

2. Description of the Related Art FIG. 9 shows a plan view of an example of a conventional magnetic disk device. In a magnetic disk device 11 shown in FIG. 9, an actuator 12 has a magnetic head 14 mounted on the tip of an arm 13 via a support spring mechanism 13a, and a base of the arm 13 is rotatably supported by a pivot 15. . The arm 13 is located between a plurality of magnetic disks described later.

A rotation support portion 16 is formed on the side of the arm 13 opposite to the pivot 15, and a coil 17 wound around the rotation support portion 16 is provided. And the coil 17
The two magnets 18a and 18b are fixedly arranged below the space. This coil 17 and magnets 18a, 18b
Constitute a VCM (voice coil motor).

Such an actuator 11 has a coil 17 and a flexible printed board from a wiring board 21 for a plurality of magnetic disks 20 which are fixed and rotated on a spindle 19 of a sensorless type spindle motor (not shown). The arm 13 is rotated so as to move the magnetic head 14 in the radial direction of the magnetic disk 20 by supplying electricity via 22.

The magnetic head 14 is, for example, a thin film head, and floats by a predetermined amount as the magnetic disk 20 rotates. The thin-film type magnetic head 14 has a coil and a magnetic gap formed by a thin-film forming technique to form a write head.
A read head is formed using R (magnetoresistive) elements, and each is formed on a slider. When a predetermined current (write current) is supplied to the coil of the write head, a magnetic flux leaking due to electromagnetic conversion causes the magnetic disk 2 to move.
Writing is performed to 0, and reading is performed by the read head with a waveform (amplitude of read current) having a magnitude corresponding to the write current. In this case, the set value of the write current is supplied to each magnetic head 14 at the set constant value regardless of the magnetic head 14 or the magnetic disk 20.

FIG. 10 is a graph showing the relationship between write current and head characteristics. 9A is a graph of write current characteristics with respect to head output level, and FIG. 10B is a graph of write current characteristics with respect to overwrite (gain). Generally, the write current is the output level of the magnetic head 14 (FIG. 10A) and the overwrite gain (FIG. 10).
It is determined from the saturation characteristic of (B), and is set with reference to the magnetic head 14 which has a characteristic of being less likely to be saturated unless the write current is increased due to structural variations.

Further, the overwrite characteristic is the magnetic head 14
Is related to the flying height of the magnetic disk 20, and the overwrite characteristic deteriorates as the flying height increases. Therefore, it is set based on the characteristics of a cylinder having a high flying height (generally, an outer cylinder).

[0008]

However, if the write current is set with reference to the magnetic head 14 having a poor saturation characteristic, an excessive current is supplied to the magnetic head 14 having a good saturation characteristic or a normal saturation characteristic. Further, if the write current is set on the basis of the overwrite characteristic on the cylinder of the magnetic disk 20 having the highest flying height, the write current must be supplied more than necessary on the cylinder having a low flying height, and the power consumption is reduced. However, there is a problem in that stable read demodulation cannot be performed.

By the way, as a method for optimizing the write current, Japanese Patent Laid-Open Nos. 60-145504 and 60-1985 have been proposed.
-74102, Japanese Patent Laid-Open No. 61-156574, etc. are known. In Japanese Patent Laid-Open No. 60-145504, the optimum write current value is set at the point where the output level is saturated for each cylinder, but in order to recognize the saturation of the output level, A / D (analog / digital) is used. There is a problem that a converter is required and the cost is increased.

In Japanese Patent Laid-Open No. 60-74102, the optimum write current is set from one of the best output level of the head, the best point of the overwrite characteristic, or both. And the overwrite characteristic must be measured separately, and a component (circuit or the like) for the measurement is required, which causes a problem of cost increase.

Further, the method disclosed in Japanese Patent Laid-Open No. 61-156574 is based on a write parameter or a cylinder parameter as a method for optimally correcting a characteristic variation as a result of a combination of a head and a disk medium by using a write current or the like. The write current and the like are controlled for each head and cylinder. However, in order to set the write parameter and the cylinder parameter, when the output level of the head or the overwrite characteristic is used as a reference as in the above two publications, etc. , Corresponding components (circuits, etc.) similar to those described above
However, there is a problem in that the cost is increased due to the requirement.

Further, in the above three publications, once the write current is set as the optimum value, there is a problem that it is not possible to cope with the characteristic change of the head and the disk medium due to the environmental change after the setting. Therefore, the present invention has been made in view of the above problems, and provides a recording / reproducing device that easily and inexpensively sets an optimum write current value to achieve low power consumption and that improves quality by stable read demodulation. With the goal.

[0013]

In order to solve the above-mentioned problems, in the present invention, a write current corresponding to recording information is supplied to a predetermined number of recording heads to record information on a predetermined number of corresponding recording media. Then, in the recording / reproducing apparatus that reproduces the information on the recording medium by the reproducing head, the measurement data is written in a predetermined area of the recording medium with a predetermined number of write current values, and each of the measurement data is read. Recording having measurement means for measuring a demodulation margin, and setting means for setting, as the write current, a write current value corresponding to the value of the demodulation margin measured by the measurement means at the start of saturation A playback device is configured.

According to a second aspect, the demodulation margin according to the first aspect is a phase margin in peak detection of the read waveform of the measurement data. In the third aspect, the demodulation margin according to the first aspect is an amplitude margin in peak detection of the read waveform of the measurement data.

According to a fourth aspect, the demodulation margin according to the first aspect is a Viterbi level margin of a demodulation width in the maximum likelihood detection of the read data of the measurement data. According to a fifth aspect, the demodulation margin according to the first aspect is an offset margin due to an offset of the recording medium in the reproducing head with respect to the recording medium at the time of reading.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the demodulation margin is measured by the measuring unit for each head, and the write current is set by the setting unit for each head. Let it be done. In claim 7,
In any one of claims 1 to 6, the demodulation margin is measured by the measuring unit for each predetermined cylinder of the recording medium, and the write current is set by the setting unit for each cylinder.

According to an eighth aspect, there is provided a storage means for storing the respective values of the write currents set by the setting means according to any one of the first to seventh aspects. According to a ninth aspect, in any one of the first to eighth aspects, a cylinder for writing the measurement data is provided in a predetermined area of the recording medium.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the measurement of the demodulation margin by the measuring means and the setting of the write current by the setting means are performed at a predetermined timing and updated. . In claim 11,
Saturation is started in a recording / reproducing apparatus in which a write current corresponding to recording information is supplied to a predetermined number of recording heads to record information on a predetermined number of corresponding recording media and the reproducing head reproduces the information on the recording media. Storage means for storing the write current value determined by the measurement of the demodulation margin at the time, and when recording the information, obtain the write current value from the storage means,
A recording / reproducing apparatus is configured by including a write current supply unit that supplies a write current to the recording head.

In a twelfth aspect, the storage means according to the eleventh aspect stores a write current value for each cylinder of the recording medium and / or for each recording head. In a thirteenth aspect, a write current corresponding to recording information is supplied to a predetermined number of heads for recording / reproducing to record information on a predetermined number of corresponding recording media, and the heads store information on the recording media. In a write current setting method of a recording / reproducing apparatus for reproducing, a step of supplying a predetermined write current to the head to write measurement data in a predetermined area of the recording medium, and reading the written measurement data, A step of measuring a demodulation margin, a step of writing and reading the measurement data with different write currents a predetermined number of times, measuring a demodulation margin for each of the write currents, and a difference of a predetermined number of demodulation margins being predetermined. Calculating the number of times and setting a write current whose difference corresponds to a predetermined value as an optimum write current. Constructed.

In the fourteenth aspect, the optimum write current according to the thirteenth aspect is set for at least one of the head and the predetermined cylinder of the recording medium. Claim 1
In No. 5, the optimum write current according to claim 13 is set periodically.

[0021]

As described above, the claims 1, 2, 3, 4, 5, 9,
In the invention of 11, 12, or 13, the measuring means writes and reads the measurement data for each predetermined number of write currents in the cylinder in the predetermined region of the recording medium, the phase margin, the amplitude margin, the Viterbi level margin for each write current, or The demodulation margin such as the offset margin is measured, and the setting means sets the write current corresponding to the start of saturation from the predetermined number of demodulation margins as the optimum write current. Further, the write current value determined by the measurement of the demodulation margin is recorded in the storage means for each cylinder or each recording head, and the corresponding write current value is read and supplied from the write current supply means to the recording head. As a result, only the demodulation margin can be measured easily and inexpensively, and the necessary and minimum optimum write current can be set, and low power consumption can be achieved.

In the sixth, seventh or twelfth aspect of the invention, the optimum write current is set for at least one of the head and the predetermined cylinder. As a result, it is possible to write to each head and each cylinder with a necessary and minimum current value, and it is possible to reduce power consumption.

According to the eighth, tenth, or thirteenth aspect of the present invention, the optimum write current is set periodically, and the optimum write current is appropriately stored in the storage means and updated. As a result, it is possible to cope with changes in the characteristics of the head and the recording medium due to environmental changes, and it is possible to improve quality by stable read demodulation.

[0024]

FIG. 1 shows a configuration diagram of a first embodiment of the present invention. FIG. 1 shows a magnetic disk device 31 as a recording / reproducing device.
The main configuration of the above is shown, and is roughly divided into a controller side 32 and a drive side 33. The controller side 32 has an MPU (microprocessor) 34 as a measuring means, a data comparator 35, and a ROM as a storing means.
(Read Only Memory) 36. It should be noted that a part of the MPU 34 and the data comparator 35 constitute the setting means, and the data comparator 35 may be included in the MPU 34. Also, the drive side 32
Is composed of an encoder 37 as a modulator, a decoder 38 as a demodulator, a head IC 39, and a magnetic head 40 connected to the head IC 39 by a predetermined number.

The ROM 36 is, for example, an EEPROM (El
electrically erasable program
A mmable ROM) is used to store measurement data (worst write data) and optimum write current values corresponding to each set magnetic head (described later) and each cylinder of a magnetic disk (described later).

The MPU 34 causes the ROM 36 to read the measurement data and set and store the optimum write current. Further, the MPU 34 supplies a write current (including both measurement and recording) to the corresponding magnetic head 40 to the head IC, and at the same time, writes data (including both measurement data and recording data) to the encoder 37. And write data for measurement to the data comparator 35. Further, the MPU 34 sends a signal for measuring the demodulation margin for measuring the read demodulation margin at the time of measurement (a signal for phase-shifting the demodulation window in the first embodiment) to the decoder. The MPU 34 has a built-in clock generator.

The data comparator 35 is composed of, for example, a register or the like, and compares the measurement data (write data) from the MPU 34 with the read data of the measurement data from the encoder 37 to determine whether they match. The resulting signal is M
It is sent to the PU 34. The encoder 37 modulates write data (including measurement data and recording data) sent from the MPU 34 and sends the modulated data to the head IC 39. Based on the modulated write data, the magnetic head 40 causes the magnetic disk to drive the magnetic disk. Is recorded in a predetermined area (described later).

The decoder 38 sends the waveform of the information read by the magnetic head 40 via the head IC 39 and demodulates it. Further, the decoder 38 has a built-in clock generator, and when demodulating the read data of the measurement data, the phase shift signal from the MPU 34 as the demodulation margin measurement signal shifts the phase of the clock built in the decoder 38. (Described in FIG. 3).

Here, FIG. 2 shows an overall configuration diagram of the magnetic disk device according to the present invention. In the magnetic disk device 31 shown in FIG. 2, a magnetic disk 41, which is a predetermined number of recording media, is rotated at a predetermined rotation speed by an SPM (spindle motor) 42, and a voice coil motor (VCM) is radiated on the magnetic disk 40. 43 by the magnetic head 4
0 is moved. The magnetic head 40 includes, for example, a thin film head for recording (40a, see FIG. 8) and an MR head (40b,
(See FIG. 8) and a composite thin film magnetic head.

On the other hand, the magnetic disk device 31 is connected to a host device, and signals are exchanged with the host device by the HDC.
(Hard disk controller) 44,
The HDC 44 controls the MPU 34 with various control signals. The MPU 34, as shown in FIG.
(EEPROM) 36 is connected to the data comparison circuit 35, read / write circuit 45, and head IC 39.
Connected to The read / write circuit 45 includes the encoder 37 and the decoder 38 shown in FIG.
It is connected between the data comparison circuit 35 and the head IC 39.

Control signals from the MPU 34 (driving control signals, position signals of the magnetic head 40 on the magnetic disk 41 (analog / digital conversion not shown), etc.) are sent to the DSP 46. The DSP 46 creates a digital control signal for driving the VCM 47 from the control signal from the MPU 34, and a digital-analog converter (DAC)
Send to 47. The DAC 47 converts the analog signal and sends a control signal to the VCM drive circuit 48.
3 is driven. Incidentally, 49 is an SPM control circuit for rotating the SPM 42 at a constant speed.

The read / write circuit 45 sends the read data to the data comparison circuit 35 during measurement and to the MPU (microprocessor) 34 during normal reproduction.
On the other hand, it receives write data (including measurement data and recording data) from the MPU 34 and supplies it to the magnetic head 40 via the head IC 39.

The mechanism of the magnetic disk device 31 is similar to that shown in FIG. Therefore, FIG. 3 shows an explanatory diagram of the measurement data. The MPU 34 shown in FIG. 1 reads the measurement data recorded in the ROM 36 and sends it to the encoder 37 when setting the optimum write current.
The measurement data is set in the worst pattern as described above.

That is, the position of the read waveform peak point shown in FIG. 3B for each magnetization reversal in the write data of FIG. 3A causes a peak shift (ΔX) due to interference of adjacent waves, and this waveform interference causes Even if the data width b is the same, the peak shift differs depending on the states before and after the inversion pattern, and the inversion pattern of the write data that maximizes ΔX / b is the worst pattern. The measurement data of this worst pattern is recorded in a predetermined area of the magnetic disk 41 by the magnetic head 40 from the encoder 37 via the head IC 39.

Here, in order to set the optimum write current, the magnetic disk 41 allocates a part of the inner guard band or the outer guard band with the above-mentioned measurement data as a write area, or a predetermined radial direction on the data area. Cylinders at predetermined locations (for example, 10 locations) are assigned at intervals.

FIG. 4 shows the principle of phase margin measurement. As described above, the measurement data written in the predetermined area of the magnetic disk 41 is first transferred to the predetermined magnetic head 40.
On the other hand, a write current of a predetermined value is set and read by the MPU 34, and the read waveform is input to the decoder 38 and demodulated. In this case, one cycle of the clock (decode clock) in the decoder 38 is set as the window width and M
The window width is shifted by the phase shift signal from the PU 34.

That is, the read data shown in FIG.
As shown in FIG. 3B, the smaller the write current of the written measurement data, the smaller the amplitude and the larger the peak shift, and the larger the write current, the smaller the amplitude and the smaller the peak shift. A read error occurs when the start-up deviates from the above window. The window width is a case where the state shown in FIG. 4B is not shifted, and FIG. 4C is a case where the window width is shifted in the phase advance direction by a shift amount βns, for example.
FIG. 4D shows the case where the window width is shifted in the phase delay direction by, for example, the shift amount γns.

Therefore, with respect to the rising position of the read data shown in FIG. 4A, with reference to FIG. 4B, FIG.
The amount of shift of the sum of β ns and γ ns in FIG. 4D is measured as the phase margin. That is, when the write current of the measurement data becomes large, the peak shift of the read waveform becomes small, the phase margin becomes large, and saturation easily occurs. Then, the phase margin value is sequentially measured with respect to the measurement data written with different write currents, and the write current corresponding to the point where saturation is started is set as the optimum write current.

Therefore, FIG. 5 shows a flowchart of the optimum write current setting of the present invention. In FIG. 5, first, at the start of the optimum write current setting, as the first time (M = 1) (step (S) 1), the MPU 34 sets the write current to the head IC 39 (S2). For example (1.0
XM) Assuming that the current starts from mA, a write current of 1.0 mA is set. Subsequently, the MPU 34 reads the measurement data stored in advance in the ROM 36 and supplies the measurement data to the data comparator 35 and the encoder 37 (S
3).

Further, the MPU 34 is an arbitrary magnetic head 4
0 and the above-mentioned measurement data cylinder of the magnetic disk 41 are selected, and the encoder 37 is instructed to modulate the measurement data by the encoder 37 and write it on the cylinder (S).
4). Then, read the written measurement data,
As the first time (N = 0) to be demodulated by the decoder 38 (S
5), the MPU 34 sends to the decoder a signal for setting the phase shift amount of the demodulation window (S6). For example, the maximum shift amount SF is β in the phase advance direction as shown in FIG.
When γ is set in the phase delay direction, the phase shift amount of SFns is set to start from the phase shift amount of (SF = 0.2 × N) ms. Then, the MPU 34 makes the decoder 38
The read instruction is issued to the data comparator 35, and the result of the detection state of the rising edge of the read data in the window whose Sns phase has been shifted by the decoder 38 is sent to the data comparator 35 (S7).

The data comparator 35 compares the read data sent from the decoder 38 with the measurement data originally sent from the MPU 34 and set in the register (S
8) Then, it is determined whether or not they match correctly (S9).
The result of whether or not they match is sent to the MPU 34, and if they do not match, the MPU 34 sets the second (N = N + 1) shift amount (SF−0.2 × 2) ns in the decoder 38 (S
11), and repeat the measurement of S6 to S11 until they match.
Then, the MPU 34 holds the phase shift amount corresponding to the write current in the buffer provided in the MPU 34 as the phase margin when the coincidence is obtained (S1).
2).

Then, these steps are repeated a predetermined number of times, and at least the set number of times (for example, 5 times) are performed to hold at least five phase margin values (S13, S1).
4). The MPU 34 calculates the difference by comparing the maximum value and the minimum value of the phase margin values in the latest five measurements held. The comparison value is a predetermined value (for example, 0.2 ns or less)
Is determined (S16), and S2 and the subsequent steps are repeated until the comparison value becomes 0.2 ns or less in the latest five measurements.

Therefore, when the comparison value becomes 0.2 ns or less, it is judged that the phase margin is saturated, and M
The PU 34 sets the optimum write current value (1.0 x (M-4))
mA, the optimum write current value, the magnetic head 40, and the cylinder information are stored in the ROM 36 (S17), and the process is ended. The above (M-4) shows the saturation start point in the measurement of five times in the saturated state, whereby the necessary and minimum optimum write current can be obtained.

The MPU 34 makes this work for each magnetic head 40 and for each cylinder for measuring the magnetic disk 41, and the optimum write current value, corresponding magnetic head 40,
The information of the corresponding cylinder is sequentially stored in the ROM 36. Then, these operations are performed periodically (for example, at the time of startup, when waiting for a command, etc.) during operation of the magnetic disk device 31, and RO
The contents of M36 are updated at any time. Then, at the time of normal access, the write current value is M for the cylinder of the magnetic head 40 and the magnetic disk 41 that have been accessed.
The PU 34 will switch.

In this way, each magnetic head 40 is automatically
Also, a necessary and minimum optimum write current value corresponding to the position of each cylinder of the magnetic disk 41 can be obtained, and low power consumption can be achieved. Also, since the write current value is updated to a new value periodically using the measuring cylinder,
The characteristics of the magnetic head 40 and the magnetic disk 41 due to environmental changes can be dealt with, stable data demodulation is possible, and quality is improved.

Next, FIG. 6 shows a waveform diagram in the second embodiment of the present invention. FIG. 6 shows that the measurement signal sent from the MPU 34 to the decoder 38 is a signal for obtaining an amplitude margin in peak detection of read data, in order to obtain the demodulation margin in FIG.
In this case, a pulse shaper is provided in the decoder 38. That is, the MPU 34 sends to the decoder 38 a signal that changes the slice level for generating a rectangular wave from the analog read waveform by the pulse shaper.

Now, in the read waveform shown in FIG. 6A, for example, as shown in FIG. 6B, read data in which a rectangular wave pulse generated at a slice level of 50% by an instruction from the MPU 34 matches the measured data. 6C, a read error occurs when the slice level is close to 0% as shown in FIG. 6C, and a read error occurs even when the slice level is close to 100% as shown in FIG. 6D. At this time, the range of the slice level at which the read error does not occur is the amplitude margin, which is the demodulation margin value of the present invention.

The setting of the optimum write current by the amplitude margin can be similarly performed by replacing the phase margin in the first embodiment with the amplitude margin. Next, FIG. 7 shows a waveform diagram in the third embodiment of the present invention. FIG. 7 is similar to the first and second embodiments,
The Viterbi level margin is used instead of the phase margin and the amplitude margin, and the maximum likelihood detection circuit is provided in the decoder 38. Maximum likelihood detection detects a waveform peak with respect to the read waveform shown in FIG. 7 (A) with the width of the Viterbis threshold window W being constant. For example, a waveform having a threshold level equal to or higher than the threshold level in the initial + level direction. Detection (Fig. 7
(B) and FIG. 7 (D) are performed, the window W is slid to the peak value, and the detection of the threshold level waveform in the next − direction (FIG. 7 (C)) is performed in the − level direction. Slide the window W to the peak value of. Subsequently, when a waveform in the + direction should be detected but a waveform in the − direction is detected (FIG. 7 (C)), it is determined that a read error has occurred, and the detected waveform only at the back is detected as normal data. (FIG. 7 (D)).

Then, the width of the Viterbi threshold window W is instructed to be changed from the MPU 34 to the decoder 38 to obtain a Viterbi level margin. The Viterbi level margin is used to execute the first and second embodiments. The optimum write current value is set for each magnetic head 40 and each cylinder of the magnetic disk 41 by the same method as the phase margin and amplitude margin of the example, and is updated periodically.

Next, FIG. 8 shows an explanatory diagram of the offset margin in the fourth embodiment of the present invention. The fourth embodiment is
The optimum write current is set by using an offset margin instead of the phase margin, the amplitude margin and the Viterbi level margin. Now, as shown in FIGS. 8A and 8B, the magnetic head 40 is replaced by a thin film head 40a for recording.
And an MR head 40b for reproduction, a MP for the measuring cylinder 40n of the magnetic disk 41
U34 receives VCM through the VCM drive circuit 48 shown in FIG.
By driving 43 to sequentially offset the magnetic head 40 and detecting a read error with respect to the offset amount OF, an offset amount OF that does not cause a read error is measured as an offset margin.

Even if this offset margin is used, the optimum write current value is set for each magnetic head 40 and each cylinder of the magnetic disk 41 by the same method as the above phase margin and is updated periodically. As a result, it is possible to reduce power consumption and improve quality.

[0052]

As described above, according to claims 1, 2, 3, 4,
According to the fifth, ninth, eleventh, twelfth, or thirteenth aspect, the measurement means writes and reads measurement data for each predetermined number of write currents in the cylinder in the predetermined region of the recording medium, and the phase margin and the amplitude margin for each write current. , A Viterbi level margin, or a demodulation margin such as an offset margin is measured, and the setting means sets the write current corresponding to the saturation start from the predetermined number of demodulation margins as the optimum write current, and the write determined by the demodulation margin measurement. A current value is recorded in the storage means for each cylinder or / and for each recording head, and a corresponding write current value is read and supplied to the recording head from the write current supply means.
Only the demodulation margin can be measured easily and inexpensively, and the necessary and minimum optimum write current can be set, and low power consumption can be achieved.

According to the invention of claim 6, 7 or 12,
By setting the optimum write current for at least one of the head and the predetermined cylinder, it is possible to write with a necessary and minimum current value for each head and each cylinder, thus achieving low power consumption. You can

According to the eighth, tenth, or thirteenth aspect of the present invention, the characteristics of the head and the recording medium due to environmental changes are set by periodically setting the optimum write current, storing it in the storage means and updating it appropriately. It is possible to cope with the change, and it is possible to improve the quality by stable read demodulation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a magnetic disk device according to the present invention.

FIG. 3 is an explanatory diagram of measurement data.

FIG. 4 is a diagram illustrating the principle of phase margin measurement.

FIG. 5 is a flowchart for setting an optimum write current according to the present invention.

FIG. 6 is a waveform diagram in the second embodiment of the present invention.

FIG. 7 is a waveform diagram in the third embodiment of the present invention.

FIG. 8 is an explanatory diagram of an offset margin according to a fourth embodiment of this invention.

FIG. 9 is a plan view of an example of a conventional magnetic disk device.

FIG. 10 is a graph showing the relationship between write current and head characteristics.

[Explanation of symbols]

 31 magnetic disk device 32 controller side 33 drive side 34 MPU 35 data comparator 36 ROM (EEPROM) 37 encoder 38 decoder 39 head IC 40 magnetic head 41 magnetic disk 42 SPM 43 VCM 44 HDC 45 read / write circuit 46 DSP 47 DAC 48 VCM drive circuit 49 SPM drive circuit

Claims (15)

[Claims] 1. A recording / reproducing method in which a write current corresponding to recording information is supplied to a predetermined number of recording heads to record information on a predetermined number of corresponding recording media, and the reproducing head reproduces the information on the recording media. In the apparatus, a measuring unit that writes measurement data in a predetermined area of the recording medium with a predetermined number of write current values, reads out each measurement data and measures a demodulation margin, and a demodulation margin measured by the measurement unit. And a setting means for setting a write current value corresponding to the respective values at the start of saturation as the write current among the respective values. 2. The recording / reproducing apparatus according to claim 1, wherein the demodulation margin is a phase margin in peak detection of a read waveform of the measurement data. 3. The recording / reproducing apparatus according to claim 1, wherein the demodulation margin is an amplitude margin in peak detection of a read waveform of the measurement data. 4. The recording / reproducing apparatus according to claim 1, wherein the demodulation margin is a Viterbi level margin of a demodulation width in maximum likelihood detection of read data of the measurement data. 5. The recording / reproducing apparatus according to claim 1, wherein the demodulation margin is an offset margin due to an offset of the reproducing head with respect to the recording medium at the time of reading. 6. The method according to claim 1, wherein the demodulation margin is measured by the measuring unit for each head, and the write current is set by the setting unit for each head. Recording / reproducing apparatus characterized by. 7. The method according to claim 1, wherein the demodulation margin is measured by the measuring unit for each predetermined cylinder of the recording medium, and the write current is set by the setting unit. A recording / reproducing apparatus characterized in that it is performed every time. 8. The recording / reproducing apparatus according to claim 1, further comprising a storage unit that stores a value of each write current set by the setting unit. 9. The recording / reproducing apparatus according to claim 1, wherein a cylinder for writing the measurement data is provided in a predetermined area of the recording medium. 10. The method according to claim 1, wherein
A recording / reproducing apparatus characterized in that the demodulation margin is measured by the measuring means and the write current is set by the setting means at a predetermined timing and updated. 11. A recording / reproducing method in which a write current according to recording information is supplied to a predetermined number of recording heads to record information on a predetermined number of corresponding recording media, and the reproducing head reproduces the information on the recording media. In the device, a storage unit that stores a write current value determined by measuring a demodulation margin at the start of saturation; and, when recording information, obtains a write current value from the storage unit and supplies the write current to the recording head. A recording / reproducing device, comprising: 12. The recording / reproducing apparatus according to claim 11, wherein the storage means stores a write current value for each cylinder of the recording medium and / or for each recording head. 13. A write current according to recording information is supplied to a predetermined number of recording / reproducing heads to record information on a predetermined number of corresponding recording media, and the heads record information on the recording media. In a write current setting method of a recording / reproducing apparatus for reproducing, in a predetermined area of the recording medium, a step of supplying a predetermined write current to the head to write measurement data, and reading the written measurement data, Measuring a demodulation margin, writing and reading the measurement data with different write currents a predetermined number of times, measuring a demodulation margin for each write current, and determining a difference between the predetermined number of demodulation margins. A step of calculating the number of times and setting a write current whose difference corresponds to a predetermined value as an optimum write current. Ito current setting method. 14. A write current setting method for a recording / reproducing apparatus, wherein the optimum write current is set for at least one of the head and a predetermined cylinder of the recording medium. 15. A write current setting method for a recording / reproducing apparatus, wherein the optimum write current according to claim 13 or 14 is set periodically.