JP2002216422A - Apparatus and method for reproducing magnetic data, recording medium, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of waveform equalization in the preceding stage of a PLL(phase locked loop). SOLUTION: The waveform equalization of the data of a magnetic recording medium 11 read by a magnetic head 12 is performed by an equalizer 41. A phase frequency detecting part 18 and a VCO(voltage controlled oscillator) 19 constitutes a so-called PLL. A CPU 42 calculates an optimum tap coefficient by using an LMS(least mean square) algorithm on the basis of the output of an A/D conversion part 15, and outputs it to a digital equalizer 16. Based on the calculated tap coefficient, the CPU 42 produces further a control signal for optimizing the equalization characteristics of waveform equalization of the equalizer 41, and outputs it to the equalizer 41. The digital equalizer equalizes a reproducing signal by using the tap coefficient inputted from the CPU 42. The equalizer 41 applies waveform equalization to the inputted signal on the basis of the control signal inputted from the CPU 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic data reproducing apparatus, a magnetic data reproducing method, a storage medium, and a program, and more particularly, to optimizing an equalization process executed before a signal extraction point of a PLL. The present invention relates to a magnetic data reproducing apparatus, a magnetic data reproducing method, a storage medium, and a program capable of avoiding deterioration of a reproduction signal output without increasing cost.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram showing a configuration of a conventional magnetic data reproducing apparatus.

For example, a magnetic recording medium 1 such as a magnetic tape
The data recorded in 1 is converted into an analog electric signal by the magnetic head 12, amplified by the reproduction amplifier 13, and input to the equalizer 14. The amplified signal is equalized in waveform by the equalizer 14 to such an extent that the clock can be reproduced, and is output to the A / D converter 15. The A / D converter 15 converts analog data that has been equalized to some extent into digital data, and outputs the digital data to the digital equalizer 16, the CPU 17, and the phase frequency detector 18.

[0004] A phase frequency detector 18 detects time information of a signal to be reproduced. The detected time information is VCO
(Voltage Controlled Oscillator)
19, the phase frequency of the reproduced clock is controlled. In the magnetic data reproducing apparatus 1, the A / D converter 15 samples data using the clock reproduced here, a so-called PLL (Phase Locked Loop).
A phase-locked loop).

The digital data input to the digital equalizer 16 is further equalized. A / D converter 15
In the analog equalizer 14 provided at the preceding stage, since there is a limit of the circuit and it is practically impossible to perform the optimal equalization, the digital equalizer 1 provided at the subsequent stage
6 allows higher-precision equalization to be performed. In the magnetic data reproducing device 1, P
It is desirable to extract a signal for detecting the phase frequency of LL after higher-precision equalization is performed.
If a signal is taken out at the subsequent stage of the digital equalizer 16, the PLL loop becomes longer, which affects the characteristics of the PLL. .

[0006] The CPU 17 calculates an optimum coefficient based on an output of the A / D converter 15 by, for example, an LMS (Least Mean Square) algorithm and outputs the coefficient to the digital equalizer 16. The digital equalizer 16 has a CPU
Automatic equalization is performed using the coefficient input from 17 to absorb changes in the characteristics of the tape and changes in the magnetic recording and reproduction characteristics due to the temperature characteristics of the apparatus.

For example, in the case where the phase characteristics of the recording / reproducing waveform differ depending on the tape, or the phenomenon that the F characteristic of the reproduced signal drops due to continuous reproduction at high temperature or the like occurs, the digital equalizer 16 uses Operates to compensate for the characteristics. The data subjected to equalization with higher precision by the digital equalizer 16 is output to the signal detection unit 20. For example, the data is detected by a signal detection method using Viterbi decoding or the like, and output to the signal processing unit 21. You. The signal processing unit 21 performs reproduction signal processing such as various packet data detection and error correction. When the magnetic data reproducing device 1 is used, for example, in a reproducing unit of a digital VTR, the signal processing unit 21 outputs an image signal and an audio signal.

[0008]

In the case where an F characteristic shift occurs, the quality of the reproduced signal can be improved to some extent by the equalization processing of the digital equalizer 16, but it is better to optimize the equalizer 14 at the preceding stage. Experiments have shown that the quality of the reproduced signal is greatly improved. This is because if an equalization error remains in the output of the equalizer 14, the equalization error remains in the output signal of the A / D conversion unit 15 that is the extraction of the signal of the PLL that performs clock recovery. (Subtle shaking / distortion).

As described above, if a signal equalization error remains at the signal extraction point of the reproduction PLL, the quality of the signal deteriorates, for example, when the reproducing apparatus is operated at a high temperature, and the digital VTR or the like is degraded. In the device, problems such as the sound being interrupted on the way and the image sticking (the reproduced image is frozen) occur.

[0010] In a digital VTR or the like, it has been observed that the frequency characteristics of a reproduced signal are greatly reduced (about 3 to 6 dB) when an adhering substance is attached to the magnetic head 12 while the tape is running. In such a case, as shown in FIG. 1, even if filters are provided at the front and rear stages of the PLL and the filter at the subsequent stage is controlled, if the equalization process with high accuracy is not performed in the signal extraction of the PLL, PL
In some cases, jitter increases due to L, and good reproduction signal output may not be obtained.

As a method of avoiding these inconveniences, for example, in order to secure an error rate margin, the specifications of each component such as the magnetic head 12 may be strict, but if the specifications are strict, As the cost of parts increases, the cost of the magnetic data reproducing device 1 increases.

The present invention has been made in view of such a situation. For example, by optimizing an equalization process performed before a signal extraction point of a PLL without increasing costs, for example, digital It is intended to avoid deterioration of the reproduction signal output, such as sticking of an image or interruption of sound, due to F characteristic deterioration due to a substance attached to a magnetic head while the VTR is running.

[0013]

According to the present invention, there is provided a magnetic data reproducing apparatus comprising: first equalizing means for equalizing a reproduced signal from a magnetic recording medium; and a signal equalized by the first equalizing means. A clock recovery means for recovering a clock by using the clock recovery means; a conversion means for converting a signal equalized by the first equalization means into digital data based on the clock recovered by the clock recovery means; A second equalizer for further equalizing the digital data obtained by the first equalization, and a controller for controlling the first equalizer and the second equalizer, wherein the controller is provided by the first equalizer. Based on the equalized signal,
It is characterized in that control information for controlling the second equalizing means is generated, and the first equalizing means is controlled based on the generated control information.

The second equalizing means may include three or more tap coefficient multiplying means, and the control information may be tap coefficients.

The control means includes a tap coefficient multiplying means which, among the tap coefficient multiplying means, uses two tap coefficient multiplying means which are in contact with the largest coefficient, based on the sum of the first tap coefficient and the second tap coefficient used respectively. , The first equalizing means can be controlled.

[0016] The control means may control the first equalizing means so that the sum of the first tap coefficient and the second tap coefficient becomes zero.

According to the magnetic data reproducing method of the present invention, a first equalizing step of equalizing a reproduced signal from a magnetic recording medium;
A clock recovery step of recovering a clock using the signal equalized by the processing of the first equalization step, and a processing of the first equalization step based on the clock recovered by the processing of the clock recovery step. A conversion step of converting the equalized signal into digital data, a second equalization step of further equalizing the digital data converted by the processing of the conversion step, a first equalization step and a second equalization And a control step of controlling the processing of the step. In the processing of the control step, control information for controlling the processing of the second equalization step is based on the signal equalized in the first equalization step. In addition to the generation, the processing of the first equalization step is controlled based on the generated control information.

The program recorded on the recording medium of the present invention includes a first equalizing step for equalizing a reproduced signal from a magnetic recording medium and a signal equalized by the processing of the first equalizing step. A clock recovery step of recovering a clock, and a conversion step of converting a signal equalized by the processing of the first equalization step into digital data based on the clock recovered by the processing of the clock recovery step; A second equalization step for further equalizing the digital data converted by the processing of the conversion step; and a control step for controlling the processing of the first equalization step and the second equalization step. In the processing, based on the signal equalized in the first equalization step, control information for controlling the processing in the second equalization step is generated and generated. Based on the control information, and controls the processing of the first equalizing step.

A program according to the present invention reproduces a clock using a first equalization step for equalizing a reproduction signal from a magnetic recording medium and a signal equalized by the processing of the first equalization step. Based on the clock recovered by the clock recovery step and the clock recovered by the clock recovery step,
A conversion step of converting the signal equalized by the processing of the equalization step into digital data, a second equalization step of further equalizing the digital data converted by the processing of the conversion step, and a first equalization And a control step for controlling the processing of the second equalization step. In the processing of the control step, the processing of the second equalization step is performed based on the signal equalized in the first equalization step. It is characterized in that control information for control is generated, and the processing of the first equalization step is controlled based on the generated control information.

In the magnetic data reproducing apparatus, the magnetic data reproducing method, and the program according to the present invention, a reproduced signal from a magnetic recording medium is equalized, and the equalized signal is used.
The clock is regenerated, the equalized signal is converted to digital data based on the regenerated clock, the converted digital data is further equalized, and the pre-stage and post-stage equalization processes are controlled. , Based on the signal equalized in the previous stage,
Control information for controlling the subsequent equalization is generated, and the processing of the preceding equalization step is controlled based on the generated control information.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing a configuration of a magnetic data reproducing apparatus 31 to which the present invention is applied. Parts corresponding to those in the conventional case are denoted by the same reference numerals, and description thereof will be omitted as appropriate (hereinafter the same).

That is, in the magnetic data reproducing apparatus 31, the equalizer 41 is replaced by the CPU 17 instead of the equalizer 14.
CPU 42 is provided in place of
Has the same configuration as the magnetic data reproducing apparatus 1 of FIG. The CPU 41 generates a control signal for optimizing the equalization of the waveform of the equalizer 41 based on the tap coefficient output to the digital equalizer 16 and outputs the control signal to the equalizer 41. Drive 43 is
Connected to the CPU 41 and the magnetic disk 4
6, an optical disk 47, a magneto-optical disk 48, and a semiconductor memory 49 are mounted to exchange data.

The equalizer 41 performs waveform equalization on the input signal based on a control signal input from the CPU 41. FIG. 3 shows a more detailed block diagram of the equalizer 41. Here, a case in which the CPU 41 generates and outputs a control signal for optimizing waveform equalization to the analog cosine equalizer 53 will be described.

The signal input to the equalizer 41 is substantially equalized by a calculus equalizer 51 having a characteristic almost similar to the inverse characteristic of the magnetic recording / reproducing characteristic. Next, the phase equalizer 52 compensates for the equalization of the phase characteristics, that is, the rotation of the phase due to the orientation of a medium such as a tape in magnetic recording. FIG. 4 shows typical phase characteristics of the phase equalizer 52. The phase characteristic of the phase equalizer 52 is flat over the entire frequency range. Although not shown here, the gain characteristics of the phase equalizer 52 are flat.

The data subjected to the phase equalization by the phase equalizer 52 is input to an analog cosine equalizer 53. The analog cosine filter shown in FIG. 5 is used for the analog cosine equalizer 53.

The analog cosine filter shown in FIG. 5 includes delay units 61-1 and 61-2, tap coefficient multiplying units 62-1 to 62-3, and an adding unit 63. The delay units 61-1 and 61-2 delay the input data by one sample. Tap coefficient multipliers 62-1 and 62-3 multiply input data by tap coefficient C. The characteristics of the analog cosine filter are determined by the tap coefficient C. The tap coefficient multiplying unit 62-2 multiplies the input data by 1 (that is, outputs the input data as it is). The adder 63 adds the data input from the tap coefficient multipliers 62-1 to 62-3 and outputs the result.

The data input to the analog cosine filter is supplied to a delay unit 61-1 and a tap coefficient multiplication unit 62-
1 is input. The tap coefficient multiplying unit 62-1 multiplies the undelayed data by the tap coefficient C, and
Output to 3. The delay unit 61-1 delays the input data by one sample and outputs the delayed data to the tap coefficient multiplying unit 62-2 and the delay unit 61-2.

The tap coefficient multiplying unit 62-2 outputs the input data delayed by one sample to the adding unit 63 as it is. The delay unit 61-2 delays the input data by one sample and outputs the delayed data to the tap coefficient multiplying unit 62-3. That is, the data input to tap coefficient multiplying section 62-3 is data delayed by two samples. Tap coefficient multiplying section 62-3 multiplies the data delayed by two samples by tap coefficient C and outputs the result to adding section 63.

The adder 63 multiplies the tap coefficient C by
And receiving input of undelayed data, data not multiplied by a tap coefficient and delayed by one sample, and data multiplied by a tap coefficient C and delayed by two samples, These data are added and output.

FIG. 6 shows an analog cosine equalizer 53.
5 shows the gain characteristics of the first embodiment. Analog cosine equalizer 53
Works to raise or lower the gain frequency characteristic for the purpose of absorbing the change in the frequency characteristic due to the state of the magnetic data reproducing system. The phase characteristic of the analog cosine equalizer 53 is flat. Therefore, the phase equalizer 5
2 and the analog cosine equalizer 53 can be optimally adjusted independently.

The equalizer 41 converts the equalized data into A
/ D conversion unit 15. The A / D converter 15 converts the input analog signal into a digital signal. One of the digitized reproduction data is supplied to the phase frequency detection unit 18.
And the time information of the signal to be reproduced is detected. The detected time information is output to the VCO 19, and the phase frequency of the reproduced clock is controlled. A so-called PLL, in which the A / D converter 15 samples data based on the clock reproduced here, is configured.

The other digitized data is output to the digital equalizer 16 and further equalized. The digital equalizer 16 uses a FIR (Finite Response) digital filter shown in FIG. Since the FIR digital filter is acyclic, stability is always ensured. Therefore, since the coefficient can be freely changed without considering the stability, it is suitable for adaptive filtering and various construction methods (for example, direct type, vertical tangent type, lattice type, etc.) according to the purpose. Can be selected.

The FIR digital filter shown in FIG. 7 includes delay units 71-1 to 71-6, a tap coefficient multiplying unit 72-1.
To 72-7 and an adder 73. The delay units 71-1 to 71-6 delay the input data by one sample. Tap coefficient multiplying unit 72-
1 to 72-7 indicate that the input data has a tap coefficient K
1 to K7 are respectively multiplied. The characteristics of the FIR digital filter are determined by the tap coefficients K1 to K7. The adder 73 includes tap coefficient multipliers 72-1 to 72-1.
The data input from 2-7 is added and output. FIG.
Shows an example of a 7-tap FIR digital filter, but the number of taps may be larger than this.
It may be less than this.

The data input to the FIR digital filter is supplied to a delay unit 71-1 and a tap coefficient multiplying unit 72-1.
Is input to The tap coefficient multiplying unit 72-1 multiplies the undelayed data by the tap coefficient K1, and
Output to 3. The delay unit 71-1 delays the input data by one sample and outputs the delayed data to the tap coefficient multiplying unit 72-2 and the delay unit 71-2.

Hereinafter, the same processing is executed in the delay units 71-2 to 71-6 and the tap coefficient multiplying units 72-2 to 72-7. The result is multiplied and output to the adder 73. The adder 73 adds the input data and outputs the result.

The adaptive design algorithm is an algorithm for controlling a difference between a desired characteristic and the current characteristic as an error in a direction in which the error decreases based on an error gradient (slope). An adaptive algorithm using the value of the root mean square error as the gradient estimated value is the LMS (Least Mean Square) algorithm. The tap coefficients K1 to K7 are set to L
It is determined based on the MS algorithm so that the S / N ratio after passing through the filter is maximized. This method has a high convergence speed and can sufficiently follow changes in the magnetic recording / reproducing system.

However, for example, when the gain frequency characteristic of the input signal changes greatly, the equalizer 4
1 increases the equalization error. In such a case, an equalization error at a signal extraction point for phase frequency detection becomes large, and jitters remain in a clock reproduced by a PLL composed of the phase frequency detection unit 18 and the VCO 19, and a digital equalizer is used. Even if equalization is performed in step 16, the quality of the reproduced signal may be degraded. It is also conceivable that the extraction point of the signal for detecting the phase frequency is set as the output of the digital equalizer 16, but the loop of the PLL becomes longer, which is not preferable.

That is, the CPU 41 controls the values of the tap coefficients K1 to K7 of the digital equalizer 16 and generates and outputs a control signal for controlling the equalizer 41 by referring to the coefficients. As a result, the deviation of the equalization characteristics of the equalizer 41 is compensated, and deterioration of signal quality due to jitter can be prevented.

As a specific example, a case will be described in which a shift in the equalization characteristic of the equalizer 41 such that the frequency characteristic rises to the right due to a shift in the equalization by the analog cosine equalizer 53 will be described.

When the equalizer 41 is performing almost correct equalization, the tap coefficient of the digital equalizer 16 at the subsequent stage is, as shown in FIG.
A large coefficient appears only at 4, and the other tap coefficients remain at small values. However, when the equalization of the analog cosine equalizer 53 is shifted and the frequency characteristic is rising to the right, the digital equalizer 16 shows the frequency characteristic of falling to the right, and as shown in FIG. Large values appear in the coefficients K3 and K5 of both side taps.

That is, the CPU 41 estimates the deviation of the analog cosine equalizer 53 by referring to the values of the tap coefficients K3 and K5 which are both side taps with respect to the center tap among the tap coefficients output to the digital equalizer 16. can do. C
The PU 41 can execute optimal equalization by changing the frequency characteristics of the analog cosine equalizer 53 as necessary based on the values of the tap coefficients K3 and K5 on both sides.

Referring to the flowchart of FIG. 9, a process for controlling the frequency characteristic of the analog cosine equalizer 53 will be described.

In step S1, the CPU 41 substitutes zero for a variable A for detecting a shift of the analog cosine equalizer 53.

In step S2, the CPU 41 sets L
The values of the tap coefficients K3 and K5 are extracted from the tap coefficients K1 to K7 determined by the MS algorithm, and K3 + K5 is added to the variable A.

In step S3, the CPU 41 compares the value of the variable A with a predetermined positive threshold value and determines whether or not the variable A> the positive threshold value. Here, the positive threshold is
This is a threshold for determining whether or not the frequency characteristic of the analog cosine equalizer 53 is shifted in a lower direction, and is obtained in advance by an experiment.

If it is determined in step S3 that the variable A> the positive threshold value, the process proceeds to step S6. If it is determined in step S3 that the variable A is not greater than the positive threshold, the process proceeds to step S4 where the CPU 41
Compares the value of variable A with a predetermined negative threshold,
<It is determined whether or not a negative threshold value is set. Here, the negative threshold is a threshold for determining whether or not the frequency characteristic of the analog cosine equalizer 53 is shifted in a higher direction, and is obtained in advance by an experiment.

If it is determined in step S4 that the variable A is smaller than the negative threshold value, the process proceeds to step S8.

If it is determined in step S4 that the variable A is not smaller than the negative threshold value, it is not necessary to correct the frequency characteristic of the analog cosine equalizer 53. Therefore, in step S5, the CPU 41 operates the LMS (ie, , The tap coefficients K1 to K7 are determined by the LMS algorithm and output to the digital equalizer 16), the process returns to step S1, and the subsequent processes are repeated.

If it is determined in step S3 that the variable A is larger than the positive threshold value, the program proceeds to step S6 where CP
The U 41 generates a control signal for changing the frequency characteristic of the analog cosine equalizer 53 by one step in a direction of increasing the frequency characteristic, and outputs the control signal to the analog cosine equalizer 53 of the equalizer 41. Analog cosine equalizer 53
Changes the frequency characteristic according to the input control signal.

In step S7, the same processing as in step S5 is performed, and thereafter, the processing returns to step S1, and the subsequent processing is repeated.

If it is determined in step S4 that the variable A is smaller than the negative threshold value, the program proceeds to step S8 where CP
The U 41 generates a control signal for changing the frequency characteristic of the analog cosine equalizer 53 by one step in a direction of lowering the frequency characteristic, and outputs the control signal to the analog cosine equalizer 53 of the equalizer 41. Analog cosine equalizer 53
Changes the frequency characteristic according to the input control signal.

In step S9, the same processing as in step S5 is executed, and thereafter, the processing returns to step S1, and the subsequent processing is repeated.

In this case, the control loop becomes double (the tap coefficients K1 to K1 for controlling the digital equalizer 16 determined by the output of the equalizer 41).
7 is used to control the equalizer 41), so care must be taken in selecting a time constant and the like. For example, during processing,
By providing an appropriate waiting time, the equalizer 41
May be controlled correctly.

In this description, the case where the analog cosine equalizer 53 is controlled by using the tap coefficient of the FIR filter in the digital equalizer 16 has been described as an example.
The estimation of the deviation of 2 may be performed.

That is, when a phase shift occurs in the output of the equalizer 41, the tap coefficients (tap coefficients K1 to K3 and tap coefficients K5 to K7) on both sides with respect to the center tap are respectively inverted. A large value appears in the direction. The CPU 41 may calculate a correction value for correcting the shift of the phase equalizer 52 based on those values, and output the correction value to the phase equalizer 52.

The above-described series of processing can be executed by software. The software is a computer in which a program constituting the software is built in dedicated hardware, or a general-purpose personal computer that can execute various functions by installing various programs. For example, it is installed from a recording medium.

This recording medium, as shown in FIG.
Apart from the computer, a magnetic disk 46 (including a floppy (registered trademark) disk) on which the program is recorded and an optical disk 47 (CD-ROM (Compact Disk-Read On), which are distributed to provide the program to the user.
ly memory), a DVD (including a digital versatile disk), a magneto-optical disk 48 (including an MD (Mini-Disk)), or a package medium including a semiconductor memory 49 or the like.

In this specification, the step of describing a program recorded on a recording medium is not limited to processing performed in chronological order in the order described, but is not necessarily performed in chronological order. This also includes processing executed in parallel or individually.

[0060]

According to the magnetic data reproducing apparatus, the magnetic data reproducing method, and the program of the present invention, a reproduced signal from a magnetic recording medium is equalized, and a clock is reproduced and reproduced by using the equalized signal. Based on the clock, the equalized signal is converted into digital data, the converted digital data is further equalized, and the equalization in the former stage and the latter stage are controlled, and the equalization in the former stage is performed. The control information for controlling the subsequent equalization is generated based on the signal, and the processing of the preceding equalization step is controlled based on the generated control information. Since the equalization processing executed in the earlier stage is optimized, it is possible to avoid the deterioration of the reproduction signal output without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a conventional magnetic data reproducing device.

FIG. 2 is a block diagram showing a configuration of a magnetic data reproducing apparatus to which the present invention is applied.

FIG. 3 is a block diagram showing a more detailed configuration of the equalizer shown in FIG. 2;

FIG. 4 is a diagram for explaining characteristics of the phase equalizer in FIG. 3;

FIG. 5 is a block diagram illustrating a configuration of an analog cosine filter used in the analog cosine equalizer of FIG. 2;

FIG. 6 is a diagram for explaining characteristics of an analog cosine filter.

FIG. 7 is a block diagram showing a configuration of an FIR digital filter of the digital equalizer in FIG. 2;

FIG. 8 is a diagram for explaining a tap coefficient of FIR.

FIG. 9 is a flowchart illustrating a process of controlling a frequency characteristic of an analog cosine equalizer.

[Explanation of symbols]

11 magnetic recording medium, 12 magnetic head, 15 A
/ D converter, 16 digital equalizer, 18 phase frequency detector, 19 VCO, 41 equalizer,
42 CPU, 51 Integral equalizer, 52 Phase equalizer, 53 Analog cosine equalizer

Claims (7)

[Claims] 1. A magnetic data reproducing apparatus for reproducing data from a magnetic recording medium, comprising: a first equalizing unit for equalizing a reproduction signal from the magnetic recording medium; A clock recovery unit for recovering a clock using the signal, and converting the signal equalized by the first equalization unit to digital data based on the clock recovered by the clock recovery unit. Conversion means; second equalization means for further equalizing the digital data converted by the conversion means; and control means for controlling the first equalization means and the second equalization means. The control unit generates control information for controlling the second equalization unit based on the signal equalized by the first equalization unit, and generates the control information based on the generated control information. Before A magnetic data reproducing apparatus for controlling a first equalizing means. 2. The magnetic data reproducing apparatus according to claim 1, wherein the second equalizer includes three or more tap coefficient multipliers, and the control information is a tap coefficient. 3. The first tap coefficient and the second tap coefficient respectively used by two tap coefficient multiplying means which are in contact with the tap coefficient multiplying means having the largest coefficient among the tap coefficient multiplying means. 3. The magnetic data reproducing apparatus according to claim 2, wherein the first equalizing means is controlled based on the sum of 4. The controller according to claim 3, wherein the controller controls the first equalizer so that a sum of the first tap coefficient and the second tap coefficient becomes zero.
3. The magnetic data reproducing device according to claim 1. 5. A magnetic data reproducing method for a magnetic data reproducing apparatus for reproducing data from a magnetic recording medium, wherein: a first equalizing step of equalizing a reproduction signal from the magnetic recording medium; and the first equalizing. A clock regeneration step of regenerating a clock using the signal equalized by the processing of the step; and a processing of the first equalization step based on the clock reproduced by the processing of the clock regeneration step. A conversion step of converting the converted signal into digital data; a second equalization step of further equalizing the digital data converted by the processing of the conversion step; a first equalization step and the second And a control step of controlling the processing of the equalization step of 2. In the processing of the control step, the equalization is performed by the first equalization step. Generating control information for controlling the processing of the second equalization step based on the signal, and controlling the processing of the first equalization step based on the generated control information. A magnetic data reproducing method characterized by the above-mentioned. 6. A program for a magnetic data reproducing apparatus for reproducing data from a magnetic recording medium, wherein the first equalizing step equalizes a reproduction signal from the magnetic recording medium, and the first equalization. A clock regeneration step of regenerating a clock using the signal equalized by the processing of the step; and a processing of the first equalization step based on the clock reproduced by the processing of the clock regeneration step. A conversion step of converting the converted signal into digital data; a second equalization step of further equalizing the digital data converted by the processing of the conversion step; a first equalization step and the second And a control step of controlling the processing of the equalization step of 2. In the processing of the control step, the equalization performed by the first equalization step Generating control information for controlling the processing of the second equalization step based on the signal; and controlling the processing of the first equalization step based on the generated control information. Recording medium on which a computer-readable program is recorded. 7. A computer-executable program for controlling a magnetic data reproducing apparatus for reproducing data from a magnetic recording medium, comprising: a first equalizing step of equalizing a reproduction signal from the magnetic recording medium; A clock recovery step of recovering a clock using the signal equalized by the processing of the first equalization step; and the first and the like based on the clock recovered by the processing of the clock recovery step. A conversion step of converting the signal equalized by the processing of the equalization step into digital data, a second equalization step of further equalizing the digital data converted by the processing of the conversion step, and the first A control step of controlling the processing of the equalization step and the second equalization step. In the processing of the control step, the first equalization step is performed. Generating control information for controlling the processing of the second equalization step based on the signal equalized in the equalization step, and generating the first equalization step based on the generated control information. A program characterized by controlling the processing of.