JPH0453005A - System for adjusting time margin - Google Patents

Abstract

PURPOSE:To improve time margin by finding the time margin according to a synchronous signal as a peak signal and changing the constant of an equalizer circuit so that the time margin can be maximum. CONSTITUTION:A magnetic head 13 is designated, and the waveform of a data read from a magnetic recording medium 11 is equalized by an equalizer circuit 15. The peak signal detected by a peak holding circuit 20 is inputted to an MPU 29 after being converted by an A/D converter 28B and on the other hand, the synchronous signal is inputted from a synchronous signal generating circuit 22 to the MPU 29 after being converted by an A/D converter 28A. According to these peak signal and synchronous signal, the MPU 29 calculates the time margin and reads the predicted maximum time margin of the correspondent magnetic head 13 from a ROM 30. Then, a control value is calculated for obtaining the maximum time margin and applied to the equalizer circuit 15 after being converted by a D/A converter 31, and the constant of the equalizer circuit 15 is changed.

Description

[Detailed Description of the Invention] [Summary] Regarding a time margin adjustment method in a magnetic recording/reproducing circuit, the purpose of this invention is to provide a time margin adjustment method that improves the time margin by equalizing input waveforms. a peak hold circuit that detects and holds a peak signal, a synchronization signal generation circuit that generates a synchronization signal, and a time margin calculation means that calculates a time margin based on the peak signal and the synchronization signal; 18th storage means for storing a maximum time margin for each head; control value calculation means for determining a control value for changing a constant of the equalizer circuit to obtain the maximum time margin; and second storage means for storing the time margin, and is configured to adjust the time margin to a maximum value.

[Industrial Application Field] The present invention relates to a time margin adjustment method in a magnetic recording/reproducing circuit.

Magnetic recording/reproducing circuits are widely used in magnetic disk devices, magnetic drum devices, and the like. In recent years, as the recording density of magnetic recording media has increased, the magnetization reversal interval has become extremely narrow. Although a read analog signal has a peak at the time of magnetization reversal, a peak shift phenomenon occurs in which the time position of the peak shifts due to the influence of adjacent magnetization reversals. For this reason, the time margin has decreased, but it is necessary to improve the time margin.

[Prior Art] As a conventional magnetic recording/reproducing circuit, there is one shown in FIG. 5, for example.

In FIG. 5, write data is amplified by a write amplifier 1 and then written by a magnetic head 2 onto a magnetic recording medium 3 such as a magnetic disk. The data written on the magnetic recording medium 3 is read by the magnetic head 2, amplified by the preamplifier 4, and then the AGC (automatic gain control) circuit 5 reads the data written on the magnetic recording medium 3 and the inner/outer periphery of the medium. Vibration fluctuations due to non-uniformity are corrected.

In a magnetic disk device, when the interval between recorded information is narrowed and the magnetization reversal density is increased, when the recorded information is read out, the reproduced signal waveform changes due to the so-called pattern effect phenomenon, resulting in level fluctuation and peak shift. It is well known that this occurs.

For this reason, an equalizer circuit (equalization circuit) 6 is used to correct level fluctuations and peak shifts. Equalizer circuit 6
The high frequency components contained in the equalized signal output by the filter 7 are cut by the filter 7, and the peak is detected and held by the peak hold circuit 8. The peak signal from the peak hold circuit 8 is sent to a synchronization signal generation circuit 9 and a discriminator 10.
The synchronizing signal generating circuit 9 and the discriminator 10 create discrimination data.

[Problems to be Solved by the Invention] However, in such conventional magnetic recording and reproducing circuits, the constants of the equalizer circuit are fixed to a constant value, so the optimum constants cannot be determined for each head with different electromagnetic conversion characteristics. There was a problem in that it was not possible to set the time margin, and it was not possible to avoid a decrease in time margin due to peak shift.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a time margin adjustment method that improves the time margin.

[Means to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

In FIG. 1, 15 is an equalizer circuit that equalizes an input waveform, 20 is a peak hold circuit that detects and holds a peak signal, 22 is a synchronization signal generation circuit that generates a synchronization signal, and 29A is a synchronization signal generation circuit that generates a synchronization signal. Time margin calculating means for calculating a time margin based on a synchronization signal; 30 is a first storage means for storing the maximum time margin for each head; 29B is a constant for the equalizer circuit for obtaining the maximum time margin; A control value calculation means for determining a control value to be changed is a second storage means 32 for storing the control value for each head.

[A time margin is calculated by the time margin calculation means based on the peak signal from the action copy brake circuit and the synchronization signal from the synchronization signal generation circuit, and the calculated time margin and the maximum time stored in the first storage means are calculated. In order to obtain the maximum time margin by calculating the difference from the margin, the control value for changing the constant of the equalizer circuit is calculated by the control value calculation means, and the obtained control value is used for the second Stored in storage means.

In this way, even if there are variations in electromagnetic conversion characteristics for each head, the equalizer constant is set to an optimal value, so it is possible to improve the time margin.

As a result, data can be read accurately and read accuracy can be improved.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 to 4 are diagrams showing an embodiment of the present invention.

In FIG. 2, 11 is a magnetic recording medium such as a magnetic disk, 2A is a write amplifier that amplifies written data, and 13 is a magnetic head that writes data to the magnetic recording medium 11 by the operation of the write amplifier 1.2A. be.

Write data written on the magnetic recording medium 11 is read by the magnetic head 13. 12B is a preamplifier, and the preamplifier 12B amplifies the read analog signal from the magnetic head 13. 14 is AGC (＾ulomati
The AGC circuit 14 adjusts the gain of the read analog signal to keep the amplitude constant.

Reference numeral 15 denotes an equalizer circuit, which is composed of, for example, a reflective cosine equalizer.

The equalizer circuit 15 adjusts the tie l-margin using the delay time τ and the equalization constant (gain factor) K.

FIG. 3 shows an example of the configuration of the equalizer circuit 15.

In FIG. 3, the equalizer circuit 15 includes a delay circuit 16 having a delay time τ, an attenuation gain circuit 17 having a gain factor K (0≦≦1), and a differential amplifier 18.

The read analog signal f (t) from the magnetic head 13 is
The delay circuit 16 delays the signal f' by a time τ and outputs it to the positive terminal of the differential amplifier 18 as a signal f' (10τ). Further, the attenuation gain circuit 17 outputs the signal Kf (t) to the negative terminal of the differential amplifier 18, and further multiplies the signal f (t+2τ) reflected from the positive terminal of the differential amplifier 18 to the differential amplifier 18.
input to the negative terminal of A resistor (not shown) is for terminating the reflected signal from the differential amplifier 18. The differential amplifier 18 connects the signal f (t+τ) and Kf(t)
+2τ), the magnetic head 13
Sharpen the analog signal read from.

19 is a filter that removes high frequency noise from the equalized signal from the equalizer circuit 15, and 20 is a peak hold circuit that detects the peak of the output signal of the filter 19 and holds the peak.

The peak signal from the peak hold circuit 20 is transmitted to the discriminator 2
1 and is also input to the synchronization signal generation circuit (PLL circuit) 22. Synchronous signal generation circuit 22 and discriminator 21
Discrimination data is created, A/D converted, and then sent to the host device.

The synchronization signal generation circuit 22 includes a phase comparator 23 that compares the phases of the peak signal and the synchronization signal and outputs a phase difference, and a charge pump 2 that generates a control voltage based on the phase difference.
4, an amplitude clamp circuit 25 that clamps the amplitude level of the control voltage, a filter 26 that cuts unnecessary high frequency noise, and a voltage controlled oscillator 27 that generates a synchronized clock having a frequency corresponding to the control voltage.

The synchronization signal from the synchronization signal generation circuit 22 is sent to the A/D converter 2.
The peak signal from the peak hold circuit 20 is converted into a digital value by the A/D converter 28B and then input to the MPU 29.

30 is a ROM as a first storage means;
The maximum time margin measured for each head at the time of shipment is stored in advance.

The MPU 29 calculates the time margin based on the difference between the peak signal and the synchronization signal, and calculates the difference between the maximum time margin read from the ROM 30 and the time margin obtained by the calculation, and calculates the time margin such that the maximum time margin is obtained. It has a function as a control value calculation means 29B that calculates a control value (control signal) for changing the constant of the equalizer circuit 15. After the control signal from the MPU 29 is converted into an analog value by the D/A converter 31-, it is applied to the equalizer circuit 15, and its constant is adjusted.

32 is a RAM as a second storage means;
A control value that provides the maximum margin is stored for each head.

Next, the operation will be explained.

FIG. 4 is a flowchart for explaining the operation.

In FIG. 4, first, in step S1, after power is turned on, the magnetic head 13 is designated to read data from the magnetic recording medium 11. Next, in step S2, the read data is amplified by the preamplifier 12B, and then in step S3, the amplitude is made constant by the AGC circuit 14, and in step S4, the equalizer circuit 15 performs waveform equalization.

Next, the peak signal detected by the peak hold circuit 20 in step S5 is input to the MPU 29 after being converted into a digital value by the A/D converter 28B, and
In step S6, the synchronization signal from the synchronization signal generation circuit 22 is converted into a digital value by the A/D converter 28A and then input to the MPU 29. In step S7, the MP'U 29 calculates a time margin using the peak signal and the synchronization signal,
In step S8, the corresponding magnetic head 13 is read from the ROM 30.
The pre-measured maximum time margin is read out, and in step S9, a control value for obtaining the maximum time margin is calculated, converted into an analog value by the D/A converter 31, and then given to the equalizer circuit J5. Change the constant. Next, in step SIO, by such feedback control, a control value that provides the maximum time margin is determined for each magnetic head 13 and stored in the RAM 32.

In this way, the constants of the equalizer circuit 15 are set to optimal values so that the time margin is maximized, so the time margin can be improved, even if there are variations in the electromagnetic conversion characteristics for each head. , data can be read accurately.

[Effects of the Invention] As described above, according to the present invention, the time margin is determined using the peak signal and the synchronization signal, and the constants of the equalizer circuit are changed so that the time margin is maximized. Therefore, even if there are variations in head characteristics, data reading accuracy can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a diagram showing an embodiment of the present invention, Fig. 3 is a diagram showing an equalizer circuit, Fig. 4 is a flowchart, and Fig. 5 is a diagram showing a conventional example. It is. In the figure, 11... Magnetic recording medium, 12A... Write amplifier, 12B... Preamplifier, 13... Magnetic head, 14... AGC circuit, 15... Equalizer circuit, 16. ...Delay circuit, 17...Attenuation circuit, 18...Differential amplifier, 19...Filter, 20...Peak hold circuit, 21...Discriminator, 22...Synchronizing signal generation circuit, 23... Phase comparator, 24... Charge pump, 25... Amplitude clamp circuit, 26... Filter, 27... Voltage controlled oscillator, 28A, 28B... A/D converter, 29 ...MPU. 29A...Timer margin calculation means, 29B...Control value calculation means, 30...ROM (first storage means), 31...D/
A converter, 32...RAM (second storage means).

Claims (1)

[Claims] An equalizer circuit (15) that equalizes an input waveform;
A peak hall F circuit (20) that detects and holds a peak signal, and a synchronization signal generation circuit (20) that generates a synchronization signal.
2), and time margin calculation means (29A) for calculating a time margin based on the peak signal and the synchronization signal.
), a first storage means (30) for storing the maximum time margin for each head, and a control value calculation means (29B) for calculating a control value for changing the constant of the equalizer circuit to obtain the maximum time margin. and second storage means (32) for storing the control value for each head, and adjusting the time margin to a maximum value.